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  • 1. Ambré, Marcus J
    et al.
    Aschan, Fredrik
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Fracture strength of yttria-stabilized zirconium-dioxide (Y-TZP) fixed dental prostheses (FDPs) with different abutment core thicknesses and connector dimensions2013In: Journal of Prosthodontics, ISSN 1059-941X, E-ISSN 1532-849X, Vol. 22, no 5, p. 377-382Article in journal (Refereed)
    Abstract [en]

    Purpose: The aim of this study was to investigate the fracture strength and fracture mode of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) posterior three-unit FDPs with varying connector dimension and abutment core thickness. Materials and Methods: Seventy 3-unit posterior FDP cores made of Y-TZP were divided into 7 groups with varying connector dimensions and abutment core thicknesses. All the FDPs underwent a simulated aging process including veneering, firing applications, thermocycling, and cyclic preloading. Finally the FDPs were subjected to load until fracture. Results: Significant difference was seen between the different subgroups (p < 0.05). Groups with the same connector dimension showed no significant difference in fracture strength. All fractures of the specimens involved the connector. Conclusions: Within the limitations of this in vitro study, it can be concluded that the strength of an all-ceramic Y-TZP FDP beam depends more on the connector dimension than on the thickness of the abutment core. Results indicate that the minimum abutment core thickness of an all-ceramic Y-TZP FDP might be reduced, compared to the recommended thickness, without reducing the strength of the reconstruction. This indication, however, needs to be verified by further studies before being considered generally applicable.

  • 2.
    Bahat, Zdravko
    et al.
    Malmö högskola, Faculty of Odontology (OD).
    Mahmood, Deyar Jallal Hadi
    Malmö högskola, Faculty of Odontology (OD).
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Fracture strength of three-unit fixed partial denture cores (Y-TZP) with different connector dimension and design2009In: Swedish Dental Journal, ISSN 0347-9994, Vol. 33, no 3, p. 149-159Article in journal (Refereed)
    Abstract [en]

    True crystalline ceramic materials presently used in restorative dentistry are Al2O3 (alumina) and yttrium-oxide stabilised tetragonal polycrystalline zirconium-dioxide (Y-TZP). To ensure optimal clinical performance, the dimensions of the Fixed Partial Denture (FPD) framework in general and of the connectors in particular, must be adequate. Considered recommendations for connector dimensions for Y-TZP FPDs vary from 2 to 4 mm in occluso-gingival height and 2 to 4 mm in bucco-lingual width. In order to reduce the fracture probability when designing all-ceramic FPDs, the shape of the connector is an important factor to consider. The radius of curvature at the gingival embrasure plays a significant role in the load-bearing capacity. FPDs with small gingival embrasure radii are subjected to high stress concentrations in the connector area during loading, compared to FPDs with large embrasure radii. The aim of this in-vitro study was to investigate how different radii of curvature in the embrasure of the connector area and different connector dimensions could affect the fracture resistance of 3-unit all-ceramic FPDs made of Y-TZP. Forty-eight FPDs in 6 groups of 8 FPDs with different connector design were produced in Procera Zirconia Bridge material. The FPD cores were subjected to heat treatment to simulate veneering. Following cementation, the FPDs were firstly thermocycled for 5,000 cycles, then preloaded for 10,000 cycles and finally loaded to fracture. All the FPDs fractured in the connector area. All the crack propagation which led to fracture started at the gingival embrasure of the connector. Within the limitations of this in-vitro study,the recommended minimum dimension of an anterior 3-unit all-ceramic FPD of Y-TZP is 3 mm in incisal-cervical direction and 2 mm in buccal-lingual direction. By increasing the radius of the gingival embrasure from 0.6 to 0.9 mm, the fracture strength for a Y-TZP FPD with connector dimension 3 x 3 mm increases by 20%.

  • 3.
    Bakitian, Fahad
    et al.
    Malmö University, Faculty of Odontology (OD).
    Papia, Evaggelia
    Malmö University, Faculty of Odontology (OD).
    Larsson, Christel
    Malmö University, Faculty of Odontology (OD).
    Vult von Steyern, Per
    Malmö University, Faculty of Odontology (OD).
    Evaluation of Stress Distribution in Tooth-Supported Fixed Dental Prostheses Made of Translucent Zirconia with Variations in Framework Designs: A Three-Dimensional Finite Element Analysis2020In: Journal of Prosthodontics, ISSN 1059-941X, E-ISSN 1532-849X, Vol. 29, no 4, p. 315-322Article in journal (Refereed)
    Abstract [en]

    Purpose To evaluate the influence of the framework designs on the stress distribution within tooth-supported partially veneered fixed dental prostheses (FDPs) made of translucent zirconia under simulated loads using a three-dimensional finite element analysis (3D-FEA). Material and Methods For a linear 3D-FEA, simplified 3D solid models of prepared abutment teeth (first premolar and first molar) with different 3-unit FDPs were created. The models with different FDP designs-monolithic zirconia (control); semi-monolithic zirconia with 0.3 mm veneer thickness (SM0.3); semi-monolithic zirconia with 0.5 mm veneer thickness (SM0.5); semi-monolithic zirconia with 0.5 mm veneer thickness supported with cap design (SMC), and semi-monolithic zirconia with 0.5 mm veneer thickness supported with wave design (SMW)-were analyzed using 3D-FEA. The elastic properties of the components (bone, dentine, cement, translucent zirconia, and veneering porcelain) were obtained from the published data for FEA. Simulated static loading forces (300 N) were applied at 10 degrees oblique direction over six points in the occlusal surfaces of the FDPs. Maximum principal stress, shear stress, and safety factor were calculated and analyzed among the different models. Results Semi-monolithic with cap design showed the smallest maximum principal stress levels in the veneering porcelain compared to all other models (SM0.3, SM0.5, SMW). The SM0.3 had lower maximum principal stress levels in the veneering porcelain compared to SM0.5. Regarding stresses in the zirconia framework, all models had comparable results in maximum principal tensile stresses, except SMW had a lower value. Maximum principal stress levels were located in the veneer component of SM0.3, SM0.5, and SMW, whereas, such levels were observed in the cervical areas of the zirconia frameworks of SMC and control. The SM0.3 had the highest maximum shear stress levels at the zirconia-veneer interface, while SMW had the lowest shear values. The 3D-FEA models with different FDP designs showed different minimum safety factor levels. Conclusions Framework and veneer designs play a significant role in the stress distribution of the partially veneered zirconia FDPs under loading. The FDPs with zirconia frameworks with cap design minimize the maximum principal tensile stress in the veneering porcelain. The FDPs with 0.3-mm-veneering porcelain show low maximum principal tensile stress in the veneering porcelain, but highest maximum shear stress at the zirconia-veneer interface. The FDPs with wave design of zirconia frameworks minimize the maximum shear stress considerably.

  • 4.
    Bakitian, Fahad
    et al.
    Malmö University, Faculty of Odontology (OD).
    Seweryniak, Przemek
    Papia, Evaggelia
    Malmö University, Faculty of Odontology (OD).
    Larsson, Christel
    Malmö University, Faculty of Odontology (OD).
    Vult von Steyern, Per
    Malmö University, Faculty of Odontology (OD).
    Effect of different semimonolithic designs on fracture resistance and fracture mode of translucent and high-translucent zirconia crowns2018In: Clinical, Cosmetic and Investigational Dentistry, E-ISSN 1179-1357, Vol. 10, p. 51-60Article in journal (Refereed)
    Abstract [en]

    Purpose: The aim of this study was to describe different designs of semimonolithic crowns made of translucent and high-translucent zirconia materials and to evaluate the effect on fracture resistance and fracture mode. Methods: One hundred crowns with different designs were produced and divided into five groups (n=20): monolithic (M), partially veneered monolithic (semimonolithic) with 0.3 mm buccal veneer (SM0.3), semimonolithic with 0.5 mm buccal veneer (SM0.5), semimonolithic with 0.5 mm buccal veneer supported by wave design (SMW), and semimonolithic with 0.5 mm buccal veneer supported by occlusal cap design (SMC). Each group was divided into two subgroups (n=10) according to the materials used, translucent and high-translucent zirconia. All crowns underwent artificial aging before loading until fracture. Fracture mode analysis was performed. Fracture loads and fracture modes were analyzed using two-way ANOVA and Fisher’s exact probability tests (P≤0.05). Results: SM0.3 design showed highest fracture loads with no significant difference compared to M and SMW designs (P>0.05). SM0.5 design showed lower fracture loads compared to SMW and SWC designs. Crowns made of translucent zirconia showed higher fracture loads compared to those made of high-translucent zirconia. M, SM0.3, and all but one of the SMC crowns showed complete fractures with significant differences in fracture mode compared to SMW and SM0.5 crowns with cohesive veneer fractures (P≤0.05). Conclusion: Translucent and high-translucent zirconia crowns might be used in combination with 0.3 mm microcoating porcelain layer with semimonolithic design to enhance the esthetic properties of restorations without significantly decreasing fracture resistance of the crowns. If 0.5 mm porcelain layer is needed for a semimonolithic crown, wave design or cap design might be used to increase fracture resistance. In both cases, fracture resistance gained is likely to be clinically sufficient as the registered fracture loads were high in relation to expected loads under clinical use.

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  • 5.
    Bakitian, Fahad
    et al.
    Malmö högskola, Faculty of Odontology (OD).
    Seweryniak, Przemek
    Papia, Evaggelia
    Malmö högskola, Faculty of Odontology (OD).
    Larsson, Christel
    Malmö högskola, Faculty of Odontology (OD).
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Fracture strength of veneered translucent zirconium dioxide crowns with different porcelain thicknesses.2017In: Acta Biomaterialia Odontologica Scandinavica, E-ISSN 2333-7931, Vol. 3, no 1, p. 74-83Article in journal (Refereed)
    Abstract [en]

    Abstract Objective: To evaluate fracture strength of veneered translucent zirconium dioxide crowns designed with different porcelain layer thicknesses. Materials and Methods: Sixty crowns, divided into six groups of 10, were used in this study. Groups were divided according to different thicknesses of porcelain veneer on translucent zirconium dioxide cores of equal thickness (0.5 mm). Porcelain thicknesses were 2.5, 2.0, 1.0, 0.8, 0.5 and 0.3 mm. Crowns were artificially aged before loaded to fracture. Determination of fracture mode was performed using light microscope. Results: Group 1.0 mm showed significantly (p ≤ .05) highest fracture loads (mean 1540 N) in comparison with groups 2.5, 2.0 and 0.3 mm (mean 851, 910 and 1202 N). There was no significant difference (p>.05) in fracture loads among groups 1.0, 0.8 and 0.5 mm (mean 1540, 1313 and 1286 N). There were significantly (p ≤ .05) more complete fractures in group 0.3 mm compared to all other groups which presented mainly cohesive fractures. Conclusions: Translucent zirconium dioxide crowns can be veneered with minimal thickness layer of 0.5 mm porcelain without showing significantly reduced fracture strength compared to traditionally veneered (1.0–2.0 mm) crowns. Fracture strength of micro-veneered crowns with a layer of porcelain (0.3 mm) is lower than that of traditionally veneered crowns but still within range of what may be considered clinically sufficient. Porcelain layers of 2.0 mm or thicker should be used where expected loads are low only.

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  • 6.
    Bakitian, Fahad
    et al.
    Malmö University, Faculty of Odontology (OD).
    Seweryniak, Przemek
    Papia, Evaggelia
    Malmö University, Faculty of Odontology (OD).
    Larsson, Christel
    Malmö University, Faculty of Odontology (OD).
    Vult von Steyern, Per
    Malmö University, Faculty of Odontology (OD).
    Load-Bearing Capacity of Monolithic Zirconia Fixed Dental Prostheses Fabricated with Different Connector Designs and Embrasure Shaping Methods2019In: Journal of Prosthodontics, ISSN 1059-941X, E-ISSN 1532-849X, Vol. 28, no 1, p. 64-70Article in journal (Refereed)
    Abstract [en]

    Aim> To investigate the load-bearing capacity and failure mode of monolithic zirconia fixed dental prostheses (FDPs) fabricated with different connector designs and embrasure shaping methods. Materials and methods> Seventy 4-unit zirconia FDPs (with 2 premolar pontics) were fabricated and divided into 7 groups (n = 10) according to the different connector designs gained by using different embrasure shaping methods. The groups were as follows: monolithic FDPs fabricated with sharp embrasures, monolithic FDPs fabricated with blunt embrasures, monolithic FDPs fabricated with blunt embrasures and no occlusal embrasures, 2 groups of monolithic FDPs fabricated with blunt embrasures and interproximal separations made with diamond discs at the soft stage and at the fully sintered stage, and monolithic FDPs fabricated with blunt embrasures and interproximal separation accentuated by localized porcelain build-up. A final group of fully veneered traditional zirconia FDPs to be used as a control group were fabricated with default milling settings. The FDPs were artificially aged and loaded to fracture. Load to fracture and failure modes were analyzed by 1-way ANOVA, Tukey post-hoc test, and Fisher exact test (α = 0.05). Results> The FDPs fabricated with interproximal porcelain separation showed significantly the highest load to fracture (1038 N ± 82) of all groups (p < 0.001), with no significant difference compared to the FDPs with no occlusal embrasures (934 N ± 175) (p ˃ 0.29). The FDPs fabricated with blunt embrasures showed significantly higher load to fracture (873 N ± 115) compared to the FDPs in control group (689 N ± 75) and the FDPs with sharp embrasures (417 N ± 87) (p < 0.001). There were no significant differences between the FDPs with sharp embrasures (417 N ± 87) and the FDPs with interproximal discs separations (467 N ± 94; p ˃ 0.23). Failure mode of the FDPs fabricated with sharp embrasures and interproximal discs separations differed significantly compared to the FDPs in the other groups (p < 0.001). Conclusions> Sharp embrasures and interproximal separations made with diamond discs significantly decrease the load-bearing capacity of monolithic zirconia FDPs compared to FDPs made with blunt embrasures. Blunt embrasures in combination with localized porcelain build-up produce FDPs with high load-bearing capacity in relation to loads that might be expected under clinical use. This article is protected by copyright. All rights reserved.

  • 7.
    Bertl, Kristina
    et al.
    Malmö University, Faculty of Odontology (OD).
    Isidor, Flemming
    Section of Prosthetic Dentistry, Department of Dentistry, Aarhus University.
    Vult von Steyern, Per
    Malmö University, Faculty of Odontology (OD).
    Stavropoulos, Andreas
    Malmö University, Faculty of Odontology (OD).
    Does implantoplasty affect the failure strength of narrow and regular diameter implants?: A laboratory study2021In: Clinical Oral Investigations, ISSN 1432-6981, E-ISSN 1436-3771, Vol. 25, p. 2203-2211Article in journal (Refereed)
    Abstract [en]

    Objective

    To assess whether the impact of implantoplasty (IP) on the maximum implant failure strength depends on implant type/design, diameter, or material.

    Methods

    Fourteen implants each of different type/design [bone (BL) and tissue level (TL)], diameter [narrow (3.3 mm) and regular (4.1 mm)], and material [titanium grade IV (Ti) and titanium-zirconium alloy (TiZr)] of one company were used. Half of the implants were subjected to IP in a computerized torn. All implants were subjected to dynamic loading prior to loading until failure to simulate regular mastication. Multiple linear regression analyses were performed with maximum implant failure strength as dependent variable and IP, implant type/design, diameter, and material as predictors.

    Results

    Implants subjected to IP and TL implants showed statistically significant reduced implant failure strength irrespective of the diameter compared with implants without IP and BL implants, respectively. Implant material had a significant impact for TL implants and for regular diameter implants, with TiZr being stronger than Ti. During dynamic loading, 1 narrow Ti TL implant without IP, 4 narrow Ti TL implants subjected to IP, and 1 narrow TiZr TL implant subjected to IP were fractured.

    Conclusion

    IP significantly reduced the maximum implant failure strength, irrespective implant type/design, diameter, or mate- rial, but the maximum implant failure strength of regular diameter implants and of narrow BL implants remained high.

    Clinical Relevance

    IP seems to have no clinically relevant impact on the majority of cases, except from those of single narrow Ti TL implants, which may have an increased risk for mechanical complications. This should be considered for peri-implantitis treatment planning (e.g., communication of potential complications to the patient), but also in the planning of implant installation (e.g., choosing TiZr instead of Ti for narrow implants).

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  • 8. Borg, Marcus
    et al.
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Larsson, Christel
    Malmö högskola, Faculty of Odontology (OD).
    Titanium- and zirconia-based implant-supported fixed dental prostheses. A randomized, prospective clinical pilot trial2014In: Swedish Dental Journal, ISSN 0347-9994, Vol. 38, no 1, p. 23-30Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to compare porcelain-veneered implant-supported FDPs based on zirconium dioxide and titanium respectively. Sixteen patients received 18 implant-supported partial fixed dental prostheses (FDPs); 8 titanium-based and 10 zirconia-based. The FDPs were randomized between the two material groups. Follow-up of the patients was performed at 3 months and thereafter once a year. An assessment protocol based on the California Dental Association (CDA) quality assessment system was used. Results: All patients were seen at follow-up. The mean time of clinical service at follow-up was 15,2 months (range 12-24 months). All restorations were in place and all patients were satisfied with the treatment. No technical complications were noted in either group. Minor biological complications, in the form of plaque and/or mucositis, not affecting the survival of the restorations were noted for six of the titanium-based restorations and two of the zirconia-based restorations. The difference between the two material groups was not statistically significant. The outcomes of both materials were comparable. Short term data from this study suggests that porcelain-veneered implant-supported partial FDPs based on zirconia and titanium are satisfactory and equal treatment options. This conclusion is however preliminary as it is based on a small number of patients and short-term follow-up. Long-term follow-up of larger groups of patients is needed before more definite conclusions can be made.

  • 9.
    Falk, Anders
    et al.
    Malmö högskola, Faculty of Odontology (OD).
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Franssori, Håkan
    Thorén, Margareta Molin
    Reliability of the impression replica technique2015In: International Journal of Prosthodontics, ISSN 0893-2174, E-ISSN 1139-9791, Vol. 28, no 2, p. 179-180Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to evaluate the reliability of the impression replica technique with a four-unit zirconia fixed dental prosthesis (FOP). Marginal and internal fit were measured by repeatedly placing the FDP on an epoxy cast using light-body silicone material corresponding to cement. All measured marginal and internal fit points showed varying values. The greatest variations were seen at the most distal margin (33 mu m) and at the distal abutment of the FDP (77 mu m). The results showed that the technique gives moderate variations and is a useful method to evaluate marginal and internal fit.

  • 10.
    Gardell, Emma
    et al.
    Malmö University, Faculty of Odontology (OD).
    Larsson, Christel
    Malmö University, Faculty of Odontology (OD).
    Vult von Steyern, Per
    Malmö University, Faculty of Odontology (OD).
    Translucent Zirconium Dioxide and Lithium Disilicate: A 3-Year Follow-up of a Prospective, Practice-Based Randomized Controlled Trial on Posterior Monolithic Crowns2021In: International Journal of Prosthodontics, ISSN 0893-2174, E-ISSN 1139-9791, Vol. 34, no 2, p. 163-+Article in journal (Refereed)
    Abstract [en]

    Purpose: To systematically evaluate and compare the clinical performance of lithium disilicate (LDS)and zirconium dioxide (ZrO2)-based ceramic monolithic crowns in the posterior dentition. Materials and Methods: Treatment was administered by two experienced general dental practitioners in two public dental health care clinics. Forty-four patients received 60 crowns randomized to be either LDS or ZrO2 and cemented with resin cement. Evaluations were performed after 3 years using California Dental Association criteria. Results: The mean follow-up time was 40 months (range: 31 to 50). No crown fractured during the observation time, and no chip-off fractures occurred. The success rate for ZrO2 was 80%, and the survival rate was 93.3%. For LDS, the success rate was 89.7%, and the survival rate was 100%. Survival after 3 years for all crowns together was 96.6%, and success was 84.7%. There was no significant difference between the two materials. Conclusion: Crowns made of monolithic translucent ZrO2 and LDS show equal and promising clinical results from a short-term perspective. There seems to be a difference between how patients and professionals rate crowns concerning esthetics (color and shape), with patients rating the restorations more favorably.

  • 11. Gracis, Stefano
    et al.
    Michalakis, Konstantinos
    Vigolo, Paolo
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Zwahlen, Marcel
    Sailer, Irena
    Internal vs. external connections for abutments/reconstructions: a systematic review2012In: Clinical Oral Implants Research, ISSN 0905-7161, E-ISSN 1600-0501, Vol. 23, no Suppl 6, p. 202-216Article, review/survey (Other academic)
    Abstract [en]

    OBJECTIVES: The objectives of the review were (1) to evaluate the accuracy of implant-level impressions in cases with internal and external connection abutments/reconstructions, and (2) to evaluate the incidence of technical complications of internal and external connection metal- or zirconia-based abutments and single-implant reconstructions. MATERIALS AND METHODS: A MEDLINE electronic search was conducted to identify English language publications in dental journals related to each of the two topics by inserting the appropriate keywords. These electronic searches were complemented by a hand search of the January 2009 to January 2012 issues of the following journals: Clinical Oral Implants Research, The Journal of Prosthetic Dentistry, The International Journal of Prosthodontics, The International Journal of Periodontics and Restorative Dentistry, The International Journal of Oral Maxillofacial Implants, Clinical Implant Dentistry and Related Research. RESULTS: Seven in vitro studies were included in the review to evaluate the accuracy of implant-level accuracy. No clinical study was found. There was no study that directly compared the influence of internal and external implant connections for abutments/reconstructions on the accuracy of implant-level impressions. All in vitro studies reported separately on the two connection designs and they did not use same protocol and, therefore, the data could not be compared. Fourteen clinical studies on metal-based abutments/reconstructions and five clinical studies on zirconia-based abutments/reconstructions satisfied the inclusion criteria and, therefore, were included in the review to evaluate the incidence of technical complications. The most frequent mechanical complication found in both implant connection design when employing metal abutments/reconstructions was screw loosening. CONCLUSIONS: Implant-level impression accuracy may be influenced by a number of variables (implant connection type, connection design, disparallelism between multiple implants, impression material and technique employed). Implant divergence appears to affect negatively impression accuracy when using internal connection implants. Based on the sparse literature evaluating the incidence of technical complications of metal or zirconia abutments/reconstructions, it was concluded that: The incidence of fracture of metal-based and zirconia-based abutments and that of abutment screws does not seem to be influenced by the type of connection. Loosening of abutment screws was the most frequently occurring technical complication. The type of connection seems to have an influence on the incidence of the screw loosening: more loose screws were reported for externally connected implant systems for both types of materials. However, proper preload may decrease the incidence of such a complication.

  • 12. Haag, Per
    et al.
    Andersson, M
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Odén, A
    15 Years of Clinical Experience with Procera® Alumina2004In: Applied Osseointegration Research, ISSN 1651-0070, Vol. 4, p. 7-12Article, review/survey (Other academic)
    Abstract [en]

    This paper reviews the long history and background development of technical, laboratory and clinical applications of Procera® technology for the fabrication of restorations on teeth and implants. Current clinical practice is considered and long-term results presented.

  • 13.
    Haag, Per
    et al.
    Malmö University, Faculty of Odontology (OD).
    Khan, F.
    Andersson, M.
    Vult von Steyern, Per
    Malmö University, Faculty of Odontology (OD).
    Influence of firing conditions and production methods on fracture strength of titanium-based metal ceramic crowns2018In: Journal of Adhesion Science and Technology, ISSN 0169-4243, E-ISSN 1568-5616, Vol. 32, no 3, p. 225-238Article in journal (Refereed)
    Abstract [en]

    Objectives: This study evaluated the effect of argon atmosphere compared with vacuum during porcelain firing on the fracture strength of crowns made of porcelain and electron beam melted (EBM) Ti-6Al-4 V, cast commercially pure titanium or milled commercially pure titanium. Methods: Sixty crown copings of c. p. titanium, Ti-6Al-4 V alloy and porcelain were fabricated using three production techniques. The copings were fired either under vacuum or in an argon gas atmosphere. Specimens were subdivided into groups of cast c. p. titanium, milled c. p. titanium and EBM Ti-6Al-4 V which were further subdivided according to firing modes employing either vacuum or argon gas. The 60 specimens were subjected to cyclic preloading and thermocycling, and were then individually loaded until interface fractured. Differences between the group mean values were calculated using the one-way ANOVA and Tukey's range test. Two fractured samples from each group were cut with a diamond blade and examined using SEM and EDS for visualization and chemical composition analysis of the fractured interface. Results: The highest mean fracture strength values, though not significant, were recorded for the groups fired in argon atmosphere, and the lowest mean fracture strength values were recorded for the groups fired in vacuum, with one exception. Comparing the two main groups of firing atmosphere, no significant difference could be documented. SEM and EDS analysis indicated clear differences in composition and structure between the groups included in the study. Conclusions: Firing in argon atmosphere does not significantly improve the fracture strength of porcelain bonded to titanium.

  • 14.
    Heidari, Nada
    et al.
    Malmö University, Faculty of Odontology (OD).
    Amawi, Rasha
    Malmö University, Faculty of Odontology (OD).
    Seweryniak, Przemek
    Commercial Dental Laboratory, Malmö, Sweden.
    Bakitian, Fahad
    Department of Restorative Dentistry, Umm Al-Qura University, Makkah, Saudi Arabia.
    Vult von Steyern, Per
    Malmö University, Faculty of Odontology (OD).
    Fracture Resistance and Fracture Behaviour of Monolithic Multi-Layered Translucent Zirconia Fixed Dental Prostheses with Different Placing Strategies of Connector: An in vitro Study2022In: Clinical, Cosmetic and Investigational Dentistry, E-ISSN 1179-1357, Vol. 14, p. 61-69Article in journal (Refereed)
    Abstract [en]

    Purpose: To evaluate the effect of different placing strategies performed in the connector area on fracture resistance and fracture behaviour of monolithic multi-layered translucent zirconia fixed dental prostheses (FDPs).

    Materials and Methods: Thirty 3-unit monolithic FDPs were produced and divided into three groups (n = 10) based on the different strategies for placing the connector area of FDPs in multi-layered zirconia blank with varying contents of yttria ranging from 4 to 5 mol%. The groups were as follows: FDPs with connectors placed in dentin layer with 4 mol% yttria content, FDPs with connectors placed in gradient layer, and FDPs with connectors placed in translucent layer with 5 mol% yttria content. A final group (n = 10) of conventional monolithic zirconia with a monolayer of yttria content (4 mol%) has been used as a control group. The specimens were artificially aged using thermocycling and pre-loading procedures and subsequently loaded to fracture using a universal testing machine. Fracture loads and fracture behaviour were analyzed using one-way ANOVA and Fisher's exact tests and statistically evaluated (p ≤ 0.05).

    Results: There were no significant differences in fracture loads among the groups based on the placing strategies of the connector area of the FDPs in the multi-layered translucent zirconia blank (p > 0.05). There was no significant difference in fracture loads between monolithic multi-layered translucent zirconia and conventional monolithic translucent zirconia materials (p > 0.05). Fracture behaviour of FDPs with connector area placed in translucent layer differed significantly compared to FDPs with connector area placed in dentin layer and FDPs in control group (p = 0.004).

    Conclusion: The placing strategies of the connector used in the computer aided design and manufacturing procedures do not considerably affect fracture resistance of monolithic FDPs made of multi-layered translucent zirconia. Monolithic FDPs made of multi-layered translucent zirconia show comparable strength to FDPs made of conventional translucent zirconia, but with different fracture behaviour.

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  • 15.
    Johansson, Camilla
    et al.
    Malmö högskola, Faculty of Odontology (OD).
    Kmet, Gratiela
    Malmö högskola, Faculty of Odontology (OD).
    Rivera, Johnny
    Malmö högskola, Faculty of Odontology (OD).
    Larsson, Christel
    Malmö högskola, Faculty of Odontology (OD).
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Fracture strength of monolithic all-ceramic crowns made of high translucent yttrium oxide-stabilized zirconium dioxide compared to porcelain-veneered crowns and lithium disilicate crowns2014In: Acta Odontologica Scandinavica, ISSN 0001-6357, E-ISSN 1502-3850, Vol. 72, no 2, p. 145-153Article in journal (Refereed)
    Abstract [en]

    Abstract Objective. The aim of the study was to provide data on the fracture strength of monolithic high translucent Y-TZP crowns and porcelain-veneered high translucent Y-TZP crown cores and to compare that data with the fracture strength of porcelain-veneered Y-TZP crown cores and monolithic lithium disilicate glass-ceramic crowns. Materials and methods. Sixty standardized crowns divided into six groups (n = 10) were fabricated: monolithic high translucent Y-TZP crowns, brand A, monolithic high translucent Y-TZP crowns, brand B, veneered high translucent Y-TZP crown cores, brand A, veneered high translucent Y-TZP crown cores, brand B, heat-pressed monolithic lithium disilicate crowns and veneered Y-TZP crown cores. All crowns were thermocycled, cemented onto dies, cyclically pre-loaded and finally loaded to fracture. Results. The monolithic Y-TZP groups showed significantly higher fracture strength (2795 N and 3038 N) compared to all other groups. The fracture strength in the veneered Y-TZP group (2229 N) was significantly higher than the monolithic lithium disilicate group (1856 N) and the veneered high translucent Y-TZP groups (1480 N and 1808 N). Conclusions. The fracture strength of monolithic high translucent Y-TZP crowns is considerably higher than that of porcelain-veneered Y-TZP crown cores, porcelain-veneered high translucent Y-TZP crown cores and monolithic lithium disilicate crowns. The fracture strength of a crown made of monolithic high translucent Y-TZP is, with a large safety margin, sufficient for clinical use for the majority of patients. Porcelain-veneered Y-TZP crown cores show higher fracture resistance than monolithic lithium disilicate crowns.

  • 16.
    Karlsson, Linda
    et al.
    Malmö högskola, Library and IT Services (BIT).
    Kauppinen, Asko
    Malmö högskola, Faculty of Culture and Society (KS).
    Kinnberg, Therese
    Matteson, Mikael
    Malmö högskola, Faculty of Health and Society (HS).
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Introduktion med studentfokus2006In: Kvalitetsarbete på Malmö högskola då och nu: med sikte på framtiden; / [ed] Viveca Serder, Malmö högskola, 2006, p. 15-25Chapter in book (Other academic)
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  • 17. Kokubo, Yuji
    et al.
    Nagayama, Yuki
    Tsumita, Mitsuyoshi
    Ohkubo, Chikahiro
    Fukushima, Shunji
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Clinical Marginal and Internal Gaps of In-Ceram Crowns Fabricated Using the GN-I System2005In: Journal of Oral Rehabilitation, E-ISSN 1365-2842, Vol. 32, no 10, p. 753-758Article in journal (Other academic)
    Abstract [en]

    The marginal and internal gaps of ceramic crowns with alumina copings fabricated using a computer-aided design, computer-aided manufacturing system, were evaluated in vivo using silicone materials. Black and white silicone materials were used to record the marginal and internal gaps of 82 In-Ceram crowns before final cementation. The silicone materials were sectioned bucco-lingually and mesio-distally and viewed under a microscope to measure the thickness of the white silicone layer. Sixteen reference points were measured on each specimen. The mean marginal gaps were compared among the anterior, premolar and molar teeth, and the mean gaps at the reference points within the groups were compared by analysis of variance and the Dunnett T3 test. The mean marginal gap was 66.8 mum. There were no differences in marginal gaps among the three groups. In all the groups, the marginal gaps were the smallest, whereas the occlusal gaps were the largest. The mean marginal gaps of the In-Ceram crowns with the alumina copings fabricated using the GN-I system were within the range of clinically acceptable values.

  • 18. Kokubo, Yuji
    et al.
    Ohkubo, Chikahiro
    Tsumita, Mitsuyoshi
    Miyashita, Akira
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Fukushima, Shunji
    Clinical Marginal and Internal Gaps of Procera AllCeram Crowns2005In: Journal of Oral Rehabilitation, E-ISSN 1365-2842, Vol. 32, no 7, p. 526-530Article in journal (Other academic)
    Abstract [en]

    This study evaluated the marginal and internal gaps of Procera AllCeram crowns in vivo using silicone materials. Ninety Procera AllCeram crowns were evaluated before final cementation. White and black silicone materials were used to record the marginal and internal fit; then the crowns were sectioned bucco-lingually and mesio-distally to measure the thickness of the silicone layer using a microscope. Sixteen reference points were measured on each specimen. Mean marginal gaps among anterior, premolar and molar teeth, and mean gaps at the reference points within the groups were compared by analysis of variance and Dunnett T3 test. The mean values at the margins were the smallest in all tooth groups, whereas those at the rounded slope of the chamfer were the largest. There were significant differences (P < 0.001) in the mean gaps at the four reference points (margin, rounded slope of the chamfer, axial wall and occlusal surface) in each group, except for the molar teeth. The mean marginal gaps of the Procera AllCeram crowns were within the range of clinical acceptance.

  • 19. Kokubo, Yuji
    et al.
    Tsumita, Mitsuyoshi
    Ohkubo, Chikahiro
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Murata, Toshiyuki
    Fukushima, Shunji
    Clinical marginal gap of porcelain fused to electro-formed gold coping crowns2006In: European Journal of Prosthodontics and Restorative Dentistry, ISSN 0965-7452, Vol. 14, no 2, p. 85-89Article in journal (Refereed)
    Abstract [en]

    This study evaluated the marginal and internal gaps of Auro Galvano Crowns (AGC) in vivo. One hundred AGC crowns were examined using white and black silicone materials; the thickness of the silicone layer was measured at 16 reference points using a microscope. The mean marginal gaps among anterior, premolar and molar teeth, and the mean gaps within the groups were compared by analysis of variance and Dunnett T3 test. The results showed that at the margins, there were no significant differences among the four measuring points within each group, and there were no significant differences in the mean marginal gaps among the three groups. The mean marginal gaps in all groups were within the limits of clinical acceptability.

  • 20. Kokubo, Yuji
    et al.
    Tsumita, Mitsuyoshi
    Sakurai, S
    Torizuka, K
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Fukushima, Shunji
    The effect of core framework designs on the fracture loads of all-ceramic fixed partial dentures on posterior implants2007In: Journal of Oral Rehabilitation, E-ISSN 1365-2842, Vol. 34, no 7, p. 503-507Article in journal (Refereed)
    Abstract [en]

    This study evaluated the fracture loads of three-unit all-ceramic bridges on implants; the core frameworks of the bridges were made of zirconium oxide. Three core framework designs were fabricated according to the design of the bars between the retainers: (i) straight, (ii) curved in the occlusal direction, or (iii) curved in the gingival direction. A static load was applied at the centre of the pontic, and the mean initial crack and final fracture loads were measured and compared. The core framework curved in the occlusal direction had the highest final fracture loads; there were significant differences (P < 0.05) in the mean final fracture load, whereas initial fracture load, which fractured of veneered porcelain, did not show significant differences among three designs. The all-ceramic bridges on the implants made with Procera zirconium core frameworks had high final fracture load. The core framework design that curved in the occlusal direction helped the framework withstand the occlusal load, which results in reliable prostheses, especially in the molar region.

  • 21.
    Korduner, Eva-Karin
    et al.
    Malmö högskola, Faculty of Odontology (OD).
    Collin Bagewitz, I.
    Von Steyern, Per Vult
    Malmö högskola, Faculty of Odontology (OD).
    Wolf, Eva
    Malmö högskola, Faculty of Odontology (OD).
    Prosthodontic decision-making relating to dentitions with compromised molars: the perspective of Swedish General Dental Practitioners2016In: Journal of Oral Rehabilitation, E-ISSN 1365-2842, Vol. 43, no 12, p. 967-976Article in journal (Refereed)
    Abstract [en]

    The aim of this investigation was to study the clinical prosthodontic decision-making process relating to dentitions with compromised molars among Swedish general dental practitioners (GDPs). Eleven Swedish GDPs were purposively selected, and all agreed to participate. Then, in-depth, semi-structured interviews were conducted and covered treatment considerations concerning two authentic patient cases, initially with complete dental arches, and later, a final treatment based on a shortened dental arch (SDA) was discussed. The cases involved patients with compromised teeth situated mainly in the molar regions. One patient suffered from extensive caries and the other from severe periodontal disease. Qualitative content analysis was used to analyse the data. In the systematic analysis, two main categories were identified: holistic and functional approach. Among the interviewed GDPs, focus was put on patients' needs, background history and motivation for treatment as well as the preservation of molar support. Within the limitations of this study, the following can be concluded: keeping a dental arch with molars seems to be important to Swedish general dental practitioners. The SDA concept does not seem to have a substantial impact on the prosthodontic decision-making relating to dentitions with compromised molars. The dentist's experiences, as well as colleagues' or consulting specialist advice together with aetiological factors and the patient's individual situation, influence the decision-making more than the SDA concept. The conflicting results in the prosthetic decision-making process concerning the relevance of age and the need for molar support need further investigation, for example based on decisions made in the dentists own clinical practice.

  • 22.
    Korduner, Eva-Karin
    et al.
    Malmö högskola, Faculty of Odontology (OD).
    Söderfeldt, Björn
    Malmö högskola, Faculty of Odontology (OD).
    Bagewitz, Ingrid Collin
    Von Steyern, Per Vult
    Malmö högskola, Faculty of Odontology (OD).
    Wolf, Eva
    Malmö högskola, Faculty of Odontology (OD).
    The Shortened Dental Arch concept from the perspective of Swedish General Dental Practitioners: a qualitative study2016In: Swedish Dental Journal, ISSN 0347-9994, Vol. 40, no 1, p. 1-11Article in journal (Refereed)
    Abstract [en]

    The aim was to study the cognizance of and attitudes towards the Shortened Dental Arch (SDA) concept among Swedish General Dental Practitioners (GDPs) and the application of the SDA concept in their treatment planning using Qualitative Content Analysis. Eleven Swedish GDPs were purposively selected and all agreed to participate. In-depth semi-structured interviews were conducted and covered treatment considerations concerning two patient cases and the participants' reflections regarding pre-formulated statements about the SDA concept. Qualitative content analysis was used to analyze this data. The emerging theme was "the SDA concept is irrelevant" in the sense of the GDPs disregarding treatments providing dentitions with loss of posterior teeth. There was a strong reluctance to extract teeth, without consideration of the SDA concept, and a firmly patient-focused attitude towards the needs, age and financial situation of the patients. Within the limitations of this study, Swedish GDPs show little or no cognizance of the SDA concept and it does not seem to be applied in their treatment planning. The results show that the qualitative methodology can be beneficial for further understanding of cognizance and attitudes towards the SDA concept

  • 23.
    Larsson, Christel
    et al.
    Malmö högskola, Faculty of Odontology (OD).
    Drazic, Marko
    Nilsson, Eddie
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Fracture of porcelain-veneered gold-alloy and zirconia molar crowns using a modified test set-up2015In: Acta Biomaterialia Odontologica Scandinavica, E-ISSN 2333-7931, Vol. 1, no 1, p. 35-42Article in journal (Refereed)
    Abstract [en]

    Objective: to compare fracture load and fracture mode of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) and metal-ceramic (MC) molar crowns using a modified test set-up to produce fractures similar to those seen in vivo, i.e. fractures of the veneering material rather than complete fractures. Materials and methods: 13 high-noble-alloy MC and 13 Y-TZP molar crowns veneered with porcelain were manufactured. The crowns were artificially aged before final load to fracture. Load was applied using a 7mm diameter steel ball exerting force on the cusps with stresses directed toward the core-veneer interface. Fracture surface analysis was performed using light- and scanning electron microscopy. Results: The test design produced fractures of the veneering material rather than complete fractures. MC crowns withstood significantly (p>.001) higher loads (mean 2155 N) than Y-TZP (mean 1505 N) crowns yet both endure loads sufficient for predictable clinical use. Fracture mode differed between MC and Y-TZP. MC crowns exhibited fractures involving the core-veneer interface but without core exposure. One Y-TZP crown suffered a complete fracture, all others displayed fractures of the veneering material involving the core-veneer interface with core exposure. Conclusions: The test set-up produces fractures similar to those found in vivo and may be useful to evaluate the core-veneer interface of different material systems, both metals and ceramics. The study confirms suggestions from previous studies of a weaker core-veneer bond for Y-TZP compared to MC crowns.

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  • 24.
    Larsson, Christel
    et al.
    Malmö högskola, Faculty of Odontology (OD).
    El Madhoun, Sammah
    Wennerberg, Ann
    Malmö högskola, Faculty of Odontology (OD).
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Fracture strength of yttria-stabilized tetragonal zirconia polycrystals crowns with different design: an in-vitro study2012In: Clinical Oral Implants Research, ISSN 0905-7161, E-ISSN 1600-0501, Vol. 27, no 7, p. 820-826Article in journal (Refereed)
    Abstract [en]

    Abstract Objectives: The aim of this study was to evaluate the effect of different types and design of zirconia frameworks as well as the effect of different veneering ceramics on the fracture strength of crowns. The importance of different abutment materials was also evaluated. Materials and methods: Eighty cores, 40 in a fully-sintered zirconia material and 40 in a pre-sintered zirconia material were made. Twenty cores of each material were made with a core of even thickness shape (ES) and 20 were made with a core with anatomical shape (AS). The cores were divided into subgroups and veneered with one of two different veneering ceramics: a porcelain and a glass-ceramic material. In total eight groups of 10 crowns were made. They were all cemented onto abutments made of resin. One extra group of 10 AS, pre-sintered zirconia cores veneered with glass-ceramic were made and cemented onto titanium abutments. All crowns underwent thermocycling and mechanical pre-load and were finally loaded until fracture. Results: AS crowns withstood significantly higher loads than ES crowns (P-value <0.001), and crowns with titanium abutments withstood significantly higher loads than crowns supported by abutments made of inlay pattern resin (P-value <0.001). Three types of fracture were noted: minor and major fracture of the veneering ceramic, and complete fracture through core and veneer. ES crowns showed significantly more major fractures of the veneering ceramic than AS crowns. Conclusions: This in vitro study indicates that the design of the core, as well as the abutment support, significantly influences fracture load and fracture mode of yttria-stabilized tetragonal zirconia polycrystals crowns.

  • 25.
    Larsson, Christel
    et al.
    Malmö högskola, Faculty of Odontology (OD).
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Five-year follow-up of implant-supported all-ceramic FDPs. A randomized clinical trial2010In: IADR Abstract book, IADR , 2010, article id 2112Conference paper (Other academic)
    Abstract [en]

    Objectives: The purpose of this study was to evaluate the clinical performance of two- to five-unit implant-supported all-ceramic restorations and to compare the results of two different all-ceramic systems, Denzir® (DZ) and In-Ceram Zirconia® (InZ). Methods: Eighteen patients were treated with a total of 25 two- to five-unit implant-supported fixed dental prostheses. Nine patients were given restorations of the DZ system and the other nine were given restorations of the InZ system. The restorations were cemented with zinc phosphate cement onto customized titanium abutments and were evaluated after one, three and five years. Results: At the five-year follow-up, all restorations were in function; none had fractured. Superficial cohesive (chip-off) fractures were, however, observed in 9 of the 18 patients (11 of 25 restorations). Sixteen units in the DZ group (9 of 13 restorations) and 3 in the InZ group (2 of 12 restorations) had chip-off fractures. The difference between the two groups regarding frequency of chip-off fractures was statistically significant (P<0.05 at FDP level and P<0.001 at unit level). Conclusion: The results suggest that all-ceramic implant-supported fixed dental prostheses of two- to five-units may be considered a treatment alternative. The DZ system as used in this study, however, exhibits an unacceptable amount of veneering porcelain fractures and thus cannot be recommended for the type of treatment evaluated in this trial. Poor compatibility or problems with the bond mechanisms between veneer and framework could not explain the chip-off fractures. Factors concerning veneering porcelain need to be further evaluated.

  • 26.
    Larsson, Christel
    et al.
    Malmö högskola, Faculty of Odontology (OD).
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Five-year follow-up of implant-supported Y-TZP and ZTA fixed dental prostheses. A randomized, prospective clinical trial comparing two different material systems2010In: International Journal of Prosthodontics, ISSN 0893-2174, E-ISSN 1139-9791, Vol. 23, no 6, p. 555-561Article in journal (Refereed)
    Abstract [en]

    PURPOSE: The aim of this study was to evaluate the clinical performance of two- to five-unit implant-supported all-ceramic restorations and to compare the results of two different all-ceramic systems, Denzir (DZ) and In-Ceram Zirconia (InZ). MATERIALS AND METHODS: Eighteen patients were treated with a total of 25 two- to five-unit implant-supported fixed dental prostheses. Nine patients were given DZ system restorations and 9 were given InZ system restorations. The restorations were cemented with zinc phosphate cement onto customized titanium abutments and were evaluated after 1, 3, and 5 years. RESULTS: At the 5-year follow-up, all restorations were in function; none had fractured. However, superficial cohesive (chip-off) fractures were observed in 9 of 18 patients (11 of 25 restorations). Sixteen units in the DZ group (9 of 13 restorations) and 3 in the InZ group (2 of 12 restorations) had chip-off fractures. The difference between the two groups regarding frequency of chip-off fractures was statistically significant (P < .05 at the FDP level and P < .001 at the unit level). CONCLUSION: The results suggest that all-ceramic implant-supported fixed dental prostheses of two to five units may be considered a treatment alternative. The DZ system, however, exhibited an unacceptable amount of veneering porcelain fractures and thus cannot be recommended for the type of treatment evaluated in this trial. Poor compatibility or problems with the bond mechanisms between the veneer and framework could not explain the chip-off fractures. Stress distribution, as well as other factors concerning the veneering porcelain, need to be evaluated further.

  • 27.
    Larsson, Christel
    et al.
    Malmö högskola, Faculty of Odontology (OD).
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Implant-supported full-arch zirconia-based mandibular fixed dental prostheses: eight-year results from a clinical pilot study2013In: Acta Odontologica Scandinavica, ISSN 0001-6357, E-ISSN 1502-3850, Vol. 71, no 5, p. 1118-1122Article in journal (Refereed)
    Abstract [en]

    Objective. The purpose of this pilot study was to evaluate the long-term clinical performance of implant-supported full-arch zirconia-based fixed dental prostheses (FDPs). Materials and methods. Ten patients received full-arch zirconia-based (Cercon) mandibular FDPs supported by four implants (Astra Tech). Nine patients received 10-unit FDPs and one patient received a 9-unit FDP. The FDPs were cemented onto individually prepared titanium abutments and were evaluated at baseline and after 12, 24, 36 and 96 months. Results. Nine patients attended the 8-year follow-up. None of the restorations showed bulk fracture, all FDPs were in use. Fractures of the veneering porcelain were, however, observed in eight patients. A total of 36 out of 89 units (40%) showed such fractures. Patient satisfaction was excellent despite the veneering material fractures. Conclusion. Results from this 8-year pilot study suggest that implant-supported full-arch zirconia-based FDPs can be an acceptable treatment alternative.

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  • 28.
    Larsson, Christel
    et al.
    Malmö högskola, Faculty of Odontology (OD).
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Ten-Year Follow-Up of Implant-Supported All-Ceramic Fixed Dental Prostheses: A Randomized, Prospective Clinical Trial2016In: International Journal of Prosthodontics, ISSN 0893-2174, E-ISSN 1139-9791, Vol. 29, no 1, p. 31-34Article in journal (Refereed)
    Abstract [en]

    PURPOSE: The aim of this study was to evaluate the long-term clinical performance of and patient satisfaction with implant-supported all-ceramic fixed dental prostheses (FDPs) and to compare two different all-ceramic systems, Denzir (DZ) and In-Ceram Zirconia (InZ). MATERIALS AND METHODS: A total of 18 patients received 25 partial FDPs; 13 DZ, and 12 InZ. RESULTS: Of these patients, 17 attended the 10-year follow-up. None of the restorations had fractured. Fractures of the veneering porcelain were observed in nine patients; two from the InZ group and seven from the DZ group. All FDPs were in use, and all patients were fully satisfied with the treatment. CONCLUSION: Results from this long-term follow-up suggest that implant-supported all-ceramic FDPs are an acceptable treatment alternative.

  • 29.
    Larsson, Christel
    et al.
    Malmö högskola, Faculty of Odontology (OD).
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Holm, L
    Lövgren, N
    Kokubo, Yuji
    Fracture strength of four-unit Y-TZP FPD cores designed with varying connector diameter. An in-vitro study.2007In: Journal of Oral Rehabilitation, E-ISSN 1365-2842, Vol. 34, no 9, p. 702-709Article in journal (Refereed)
    Abstract [en]

    Reported clinical success rates of all-ceramic fixed partial dentures (FPDs) made of high-strength oxide ceramics range between 82.5% and 100%. The main cause of all-ceramic FPD failure is fracture in the connector area. There is, however, no consensus on what connector dimensions are adequate. The aim of this in-vitro study was, therefore, to compare the fracture strength of four-unit Y-TZP FPD cores designed with different connector diameters. A total of 40 four-unit FPD cores supported by end abutments and having two pontics were manufactured in Procera Zirconia. Five groups of FPD cores with connector dimensions of 2.0, 2.5, 3.0, 3.5 and 4.0 mm were produced. All FPD cores underwent a firing programme according to the manufacturer's recommendations for the veneering porcelain, a cyclic preload, thermocycling and finally, load until fracture. Fracture strength was significantly higher for each increase in connector diameter except for the 2.0-mm and 2.5-mm diameters where all fractures occurred during preload. All FPD cores fractured in the connector area. Within the limitations of this in-vitro study, a minimum diameter of 4.0 mm is recommended for all-ceramic zirconia-based FPDs with long spans or replacing molars. Clinical studies are, however, needed to determine adequate connector dimensions.

  • 30.
    Larsson, Christel
    et al.
    Malmö högskola, Faculty of Odontology (OD).
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Nilner, Krister
    Malmö högskola, Faculty of Odontology (OD).
    A prospective study of implant-supported full-arch yttria-stabilized tetragonal zirconia polycrystal mandibular fixed dental prostheses: three-year results2010In: International Journal of Prosthodontics, ISSN 0893-2174, E-ISSN 1139-9791, Vol. 23, no 4, p. 364-369Article in journal (Refereed)
    Abstract [en]

    PURPOSE: The development of high-strength oxide ceramic materials has led to increased interest in all-ceramic fixed dental prostheses (FDPs). Success rates reported in clinical studies for all-ceramic FDPs based on high-strength oxide ceramic materials reportedly approach those of porcelain-fused-to-metal FDPs. These reconstructions, however, are still of limited size and have mainly concerned FDPs supported by natural teeth. The purpose of this study was to evaluate the clinical performance of multiunit all-ceramic FDPs supported by dental implants. MATERIALS AND METHODS: Ten patients received mandibular yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) FDPs manufactured according to the Cercon technique and supported by four Astra Tech implants. Nine patients received 10-unit FDPs and one patient received a 9-unit FDP. The FDPs were cemented with Panavia F 2.0 onto individually prepared titanium abutments. The FDPs were evaluated at baseline and after 12, 24, and 36 months. RESULTS: At the 3-year follow-up, all FDPs were in use, and all patients were fully satisfied with their treatment. None of the reconstructions had fractured. Superficial chip-off fractures of the veneering porcelain were, however, observed in nine patients (34 of 99 units, 34%). CONCLUSION: Results from this 3-year study suggest that implant-supported full-arch Y-TZP FDPs manufactured according to the Cercon technique should be viewed as a treatment alternative cautiously. A better understanding of the factors resulting in chip-off fractures is needed, together with longer follow-up studies involving larger numbers of patients, before the material and technique can be recommended for general use.

  • 31.
    Larsson, Christel
    et al.
    Malmö högskola, Faculty of Odontology (OD).
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Nilner, Krister
    Malmö högskola, Faculty of Odontology (OD).
    All-ceramic multi-unit implant-supported fixed dental prostheses: A prospective clinical study2009In: IADR Abstract book;Abstract #242, IADR , 2009Conference paper (Other academic)
    Abstract [en]

    The development of high-strength oxide ceramic materials has led to increased interest in all-ceramic fixed dental prostheses (FDPs). Success rates reported in clinical studies on such reconstructions are close to those of porcelain fused to metal (PFM) FDPs. These reconstructions however, are still of limited size and have so far only concerned FDPs supported by natural teeth. Objectives: The purpose of this study was to evaluate the clinical performance of mutli-unit all-ceramic FDPs supported by dental implants. Methods: Ten patients received all-ceramic FDPs designed according to the Cercon® technique and supported by four AstraTech implants in the lower jaw. Nine patients received ten-unit prostheses and one patient received a nine-unit FDP. The FDPs were cemented with Panavia F2.0 onto preparable titanium abutments. The FDPs were evaluated at baseline, twelve, twenty-four and thirty-six months. The surface and marginal integrity were rated according to the California Dental Association (CDA) quality assessment system. Results: At the three-year follow up all FDPs were in use and all patients reported that they were fully satisfied with the treatment. None of the reconstructions had fractured. Superficial cohesive, chip-off, fractures of the veneering porcelain were, however, observed in nine patients. A total of 34 of 99 units (34%) showed such chip-off fractures. Corresponding results for the twelve-month and twenty-four month follow-ups were 14% and 19% respectively. Most patients were unaware of the fractures, some fractures were adjusted by polishing but no FDPs were in need of replacement. Conclusion: Results from this three-year study suggest that multi-unit all-ceramic implant-supported FDPs designed according to the Cercon® technique may be considered a treatment alternative. Better understanding of the factors behind chip-off fractures is necessary togehter with long-term follow-up studies before the material and technique can be recommended for general use.

  • 32.
    Larsson, Christel
    et al.
    Malmö högskola, Faculty of Odontology (OD).
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Sunzel, Bo
    Malmö högskola, Faculty of Odontology (OD).
    Nilner, Krister
    Malmö högskola, Faculty of Odontology (OD).
    All-ceramic two- to five-unit implant-supported reconstructions. A randomized, prospective clinical trial2006In: Swedish Dental Journal, ISSN 0347-9994, Vol. 30, no 2, p. 45-53Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to evaluate the clinical performance of two to five-unit implant-supported all-ceramic reconstructions and to compare the results of two different all-ceramic systems, Denzir (DZ) and In-Ceram Zirconia (InZ). Eighteen patients were treated with a total of 25 two- to five-unit implant-supported reconstructions. Nine patients were given reconstructions of the DZ system and the other nine reconstructions of the InZ system.The reconstructions were cemented with zinc phosphate cement onto preparable titanium abutments and were evaluated after 6 and 12 months. At the 12-month follow-up, all reconstructions were in function; none had fractured. Superficial cohesive (chip-off) fractures were, however, observed in 6 of the 18 patients (8 of 25 reconstructions). Nine units in the DZ group (in 7 of 13 reconstructions) and one in the InZ group (1 of 12 reconstructions) had chip-off fractures. The difference between the two groups regarding frequency of chip-off fractures was statistically significant (P < 0.01). Marginal integrity was rated excellent at 34 abutments (56%) and acceptable at 27 (44%). Results from this 12-month trial suggest that all-ceramic implant-supported fixed partial dentures of two- to five-units may be considered a treatment alternative. When comparing the two ceramic systems under study, however, this study concludes that the DZ system exhibits an unacceptable amount of veneering porcelain fractures and thus cannot be recommended for the type of treatment evaluated in this trial. Further studies and long-term follow-ups must be performed before the materials and technique can be recommended for general use.

  • 33.
    Lindström, Martin J R
    et al.
    Malmö University, Faculty of Odontology (OD).
    Ahmad, Marianne
    Malmö University, Faculty of Odontology (OD).
    Jimbo, Ryo
    Malmö University, Faculty of Odontology (OD).
    Ameri, Arman
    Malmö University, Faculty of Odontology (OD).
    Vult von Steyern, Per
    Malmö University, Faculty of Odontology (OD).
    Becktor, Jonas P
    Malmö University, Faculty of Odontology (OD).
    Volumetric measurement of dentoalveolar defects by means of intraoral 3D scanner and gravimetric model2019In: Odontology: official journal of The Society of the Nippon Dental University, ISSN 1618-1247, E-ISSN 1618-1255, Vol. 103, no 3, p. 353-359Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to evaluate the accuracy in volumetric measurements obtained on an experimental model using an intraoral scanner and a gravimetric method. Three identical partial dentate maxillary acrylic models with three fabricated alveolar defects, in anterior and posterior regions, were scanned using an intraoral scanner (20 scans/defects). The defects differed in terms of size and distance of neighbouring teeth. As references, replicas of each defect were created using a dimensional stable silicone impression material. After measuring the mass of each replica, the volume was calculated by dividing the mass of each replica by the density of the impression material. The defects had a volume, according to the gravimetric method, ranging from 40.5 to 143.7 mm. The scans were imported to metrology software for analyses. Accuracy was determined in terms of trueness and precision. The mean trueness for all defect types was 0.168 mm (SD 0.691, range 2.82). There was no statistical significant difference between the mean trueness for all defects measured (p = 0.910). The mean precision for all defect types was 0.147 mm (SD 0.524, range 2.86). There were no statistical significant differences between the dental models in regard to mean precision (p = 0.401), however, there were statistical significant differences between defects in position 1 and 2 (p = 0.002) and 1 and 3 (p = 0.001). Based on the findings of this study, the intraoral scanner utilized in the current study presented an acceptable level of accuracy when measuring volume of defects.

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  • 34.
    Löfroth, M
    et al.
    Malmö University, Faculty of Odontology (OD).
    Ghasemimehr, Marjan
    Malmö University, Faculty of Odontology (OD).
    Falk, Anders
    Malmö University, Faculty of Odontology (OD).
    Vult von Steyern, Per
    Malmö University, Faculty of Odontology (OD).
    Bisphenol A in dental materials: existence, leakage and biological effects2019In: Heliyon, E-ISSN 2405-8440, Vol. 5, no 5, article id e01711Article, review/survey (Refereed)
    Abstract [en]

    Objective: Recently, questions have been raised concerning the potential endocrine disrupting effects of bisphenol A (BPA). This substance is a constituent in many different products which we frequently come into contact with, such as food containers and receipts. Resin-based dental filling materials are another source of exposure, although according to previous studies the amount and potential risks are not clear. Thus, the aims of the present study were (1) to identify if direct dental filling materials are liable to leak BPA and (2) to investigate if this leakage could lead to any adverse effects on health. Materials and methods: A literature search was made with PubMed as the primary source, subsequently complemented with reference tracking. Results: A total of 26 articles were included, 24 of which were used for the first aim (leakage) and 2 for the second aim (health risks). The majority of studies, including all in vivo studies, showed leakage of BPA from dental materials in various amounts and during different time intervals. The findings showed a contradiction in results regarding the connection between dental materials and adverse health effects. Conclusions: There is leakage of BPA from some dental materials, but critical levels are not evident. Bis-DMA contents might convert to BPA in the oral cavity. There is a contradiction between in vitro and in vivo studies concerning BPA leakage and finally, there is a lack of studies investigating the association between BPA exposure and its adverse effects on human health.

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  • 35.
    Mahmood Jallal Hadi, Deyar
    et al.
    Malmö högskola, Faculty of Odontology (OD).
    Linderoth, Ewa H
    Malmö högskola, Faculty of Odontology (OD).
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    The influence of support properties and complexity on fracture strength and fracture mode of all-ceramic fixed dental prostheses2011In: Acta Odontologica Scandinavica, ISSN 0001-6357, E-ISSN 1502-3850, Vol. 69, no 4, p. 229-237Article in journal (Refereed)
    Abstract [en]

    Objective: When a new material is released, clinical studies are indicated. For the clinical studies to be defensible, in-vitro studies, as clinically relevant as possible, must be performed. The aim of the present study was to investigate how the choice of material used for supporting tooth analogues and support complexity influence test results concerning the fracture strength of FDPs made of a brittle material Y-TZP. Material and methods: Twenty-four FDPs were produced in Y-TZP. The FDP cores were subjected to heat treatment to simulate veneering and then thermocycled for 5,000 cycles to simulate ageing. The FDPs were divided into 3 groups and were cemented on tooth-supporting analogues made from aluminium, polymer and DuraLay®. The FDPs were preloaded for 10,000 cycles and finally loaded to fracture. Results: There were no significant differences in load-to- fracture and fracture mode between the groups cemented on polymer and DuraLay® tooth analogues. The FDPs cemented on aluminium tooth analogues showed a significantly higher load at fracture and a different fracture mode. Conclusions: Within the limitations of this in-vitro study the following could be concluded: to achieve mutually comparable results there is a need for a standardised, simple test set-up for in-vitro testing of all-ceramic FDPs intended for cementation upon natural teeth. Resilient, non-complex and resilient complex tooth analogues give comparable test results when the test set-up is unchanged in all other aspects. Non-resilient (with an e-modulus of aluminium or higher) tooth analogues give high and unrealistic load-at-fracture values together with adverse fracture modes compared to FDPs failing in clinical situations.

  • 36.
    Mahmood Jallal Hadi, Deyar
    et al.
    Malmö högskola, Faculty of Odontology (OD).
    Linderoth, Ewa H
    Malmö högskola, Faculty of Odontology (OD).
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Wennerberg, Ann
    Malmö högskola, Faculty of Odontology (OD).
    Fracture strength of all-ceramic (Y-TZP) three- and four-unit fixed dental prostheses with different connector design and production history.2013In: Swedish Dental Journal, ISSN 0347-9994, Vol. 37, no 4, p. 179-187Article in journal (Refereed)
    Abstract [en]

    Aims: To investigate how different default settings for connector design of two different CAD/CAM systems, i.e. to compare how different radii of curvature in the embrasure area of the connector affect the fracture strength and the fracture mode of 3-unit and 4-unit all-ceramic FDPs made from Y-TZP and to investigate how the number of pontics affect the fracture strength of Y-TZP. Material and methods: 32 all-ceramic three (3Z) and four (4Z) -unit, Y-TZP, FDP cores were made and divided in 4 groups, with 8 FDP in each group. The groups 3Z:1 and 4Z:1 were generated with a mechanical scanner, Procera® Forte and the FDPs in group 3Z:2 and 4Z:2 were generated with an optical scanner, NobelProcera® Scanner. The connector dimensions were set to 3 mm x 3 mm and core was set to 0.7 mm. The design of radius of the gingival and occlusal embrasures in the connector areas was set according to default settings and the manufacturer’s recommendations. All the FDP cores were subjected to heat treatment, thermocycled for 5,000 cycles, preloaded for 10,000 cycles to simulate ageing and finally loaded to fracture. Results: Regarding connector design a significant difference was found between group 3Z:1 and 3Z:2 (P<0.05), and group 4Z:1 (50% of the FDPs fractured during preloading 30-300N) and 4Z:2 (P<0.05). An extra pontic decreased the fracture strength up to 45%. Conclusions: The default settings of the two different CAD/CAM systems had a great impact on the fracture strength. It is important that a CAD/CAM system is equipped with possibilities to design a connector that fulfils the clinical demands of mechanical function and longevity. The most crucial factor for the load-bearing capacity is the design of the radius of the gingival embrasures. Increasing the number of pontics from three to four decreases the load-bearing capacity nearly twice.

  • 37.
    Mahmood Jallal Hadi, Deyar
    et al.
    Malmö högskola, Faculty of Odontology (OD).
    Linderoth, Ewa H
    Malmö högskola, Faculty of Odontology (OD).
    Wennerberg, Ann
    Malmö högskola, Faculty of Odontology (OD).
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Influence of core design, production technique, and material selection on fracture behavior of yttria-stabilized tetragonal zirconia polycrystal fixed dental prostheses produced using different multilayer techniques: split-file, over-pressing, and manually built-up veneers2016In: Clinical, Cosmetic and Investigational Dentistry, E-ISSN 1179-1357, Vol. 8, p. 15-27Article in journal (Refereed)
    Abstract [en]

    Aim: To investigate and compare the fracture strength and fracture mode in eleven groups of currently, the most commonly used multilayer three-unit all-ceramic yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) fixed dental prostheses (FDPs) with respect to the choice of core material, veneering material area, manufacturing technique, design of connectors, and radii of curvature of FDP cores. Materials and methods: A total of 110 three-unit Y-TZP FDP cores with one intermediate pontic were made. The FDP cores in groups 1–7 were made with a split-file design, veneered with manually built-up porcelain, computer-aided design-on veneers, and over-pressed veneers. Groups 8–11 consisted of FDPs with a state-of-the-art design, veneered with manually built-up porcelain. All the FDP cores were subjected to simulated aging and finally loaded to fracture. Results: There was a significant difference (P<0.05) between the core designs, but not between the different types of Y-TZP materials. The split-file designs with VITABLOCS® (1,806±165 N) and e.max® ZirPress (1,854±115 N) and the state-of-the-art design with VITA VM® 9 (1,849±150 N) demonstrated the highest mean fracture values. Conclusion: The shape of a split-file designed all-ceramic reconstruction calls for a different dimension protocol, compared to traditionally shaped ones, as the split-file design leads to sharp approximal indentations acting as fractural impressions, thus decreasing the overall strength. The design of a framework is a crucial factor for the load bearing capacity of an all-ceramic FDP. The state-of-the-art design is preferable since the split-file designed cores call for a cross-sectional connector area at least 42% larger, to have the same load bearing capacity as the state-of-the-art designed cores. All veneering materials and techniques tested in the study, split-file, over-press, built-up porcelains, and glass–ceramics are, with a great safety margin, sufficient for clinical use both anteriorly and posteriorly. Analysis of the fracture pattern shows differences between the milled veneers and over-pressed or built-up veneers, where the milled ones show numerically more veneer cracks and the other groups only show complete connector fractures.

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  • 38. Nakamura, Keisuke
    et al.
    Ankyu, Shuhei
    Nilsson, Fritjof
    Kanno, Taro
    Niwano, Yoshimi
    Vult von Steyern, Per
    Malmö University, Faculty of Odontology (OD).
    Ortengren, Ulf
    Critical considerations on load-to-failure test for monolithic zirconia molar crowns2018In: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 87, p. 180-189Article in journal (Refereed)
    Abstract [en]

    Application of monolithic zirconia crowns (MZCs) with reduced thickness to the molar region has been proposed, but potential complications have yet to be fully evaluated in laboratory tests. The present study aimed to develop a clinically relevant load-to-failure test in combination with fatigue treatments involving thermal and mechanical cycling (TC and MC) to evaluate the fracture resistance of molar MZCs. MZCs with a minimal thickness of 0.5mm were bonded to dies made of resin-based composite (RBC), epoxy resin (EP), or polyoxymethylene-copolymer (POM-C). The samples were either untreated (UT) or subjected to TC (5-55 degrees C for 1x 10(5) cycles) and MC (300 N for 2.4x 10(6) cycles). The stress generated by TC and MC was simulated by finite element modeling. The load-to-failure test was performed using an inverse V-shaped two-plane indenter and was followed by fractographic analysis. The median values of fracture load for MZC/RBC and MZC/EP in the TC group were significantly lower than those in the UT group. MC also decreased the median value of fracture load for MZC/RBC significantly, but not that for MZC/EP and MZC/POM-C. Fractography revealed that the fracture started in the cervical area in all groups, which is similar to clinically failed crowns. The simulation confirmed stress concentration at the cervical area in both TC and MC groups. The present study suggests that the load-to-failure test using a two-plane indenter could induce clinically relevant fracture of MZCs, the vulnerability of the MZCs depends largely on the die material employed, and MZCs are more likely to be damaged by thermal fatigue than mechanical fatigue.

  • 39.
    Nordahl, Niklas
    et al.
    Malmö högskola, Faculty of Odontology (OD).
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Larsson, Christel
    Malmö högskola, Faculty of Odontology (OD).
    Fracture strength of ceramic monolithic crown systems of different thickness2015In: Journal of Oral Science, ISSN 1343-4934, E-ISSN 1880-4926, Vol. 57, no 3, p. 255-261Article in journal (Refereed)
    Abstract [en]

    The objective of this study was to evaluate fracture strength of high-translucent (HTZ) and low-translucent (LTZ) zirconia and glass-ceramic (LDS) crowns. HTZ and LTZ crowns were made with thicknesses of; 0.3 mm, 0.5 mm, 0.7 mm, 1.0 mm, and 1.5 mm; and LDS crowns of 1.0 mm and 1.5 mm thicknesses. Each group consisted of 10 crowns. All crowns underwent artificial aging before loading until fracture. Mean fracture strengths varied from 450 N to 3,248 N in the LTZ group, 438 N to 3,487 N in the HTZ group, and 1,030 N to 1,431 N in the LDS group. The load at fracture of HTZ and LTZ crowns was equal. The load at fracture of yttria-stabilized tetragonal zirconia polycrystals crowns was significantly greater than LDS crowns (P = 0.000). Two types of fractures were recorded; complete and partial crack-like fracture. The crack type fracture occurred most frequently in all groups except in the thicker LTZ groups (1.0 mm and 1.5 mm). According to this study, there is no difference in strength between crowns made of high-translucent or low-translucent zirconia. At equal thickness, the strength of zirconia crowns was significantly greater than that of lithium-disilicate glass-ceramic.

  • 40.
    Papia, Evaggelia
    et al.
    Malmö University, Faculty of Odontology (OD).
    Arnoldsson, Pernilla
    Baudinova, Ayna
    Jimbo, Ryo
    Malmö University, Faculty of Odontology (OD).
    Vult von Steyern, Per
    Malmö University, Faculty of Odontology (OD).
    Cast, milled and EBM-manufactured titanium, differences in porcelain shear2018In: Dental materials journal, ISSN 0287-4547, Vol. 37, no 2, p. 214-221Article in journal (Refereed)
    Abstract [en]

    The objectives were to analyze the oxide layer generated between titanium and porcelain during firing and compare it in different manufacturing techniques: cast, milled and EBM-technique. Seventy two specimens were manufactured, subdivided according to surface treatment: time of passivation (P) and no time of passivation (NP) before porcelain firing. Specimens from each group were analyzed with scanning electron microscopy: one only fired once, and one subjected to six firings. Remaining specimens were subjected to shear bond strength test. The EBM-produced NP-group had highest mean value (25.0 MPa) and the milled P-group showed lowest mean value (18.5 MPa) when all factors were compared. No significant difference was detected according to time of passivation. SEM showed consistent and well-defined boundary between the different layers. Time of passivation and impact on oxide growth was not detected. The bond strength of porcelain to milled titanium is lower when compared to cast titanium and EBM-produced titanium.

  • 41.
    Papia, Evaggelia
    et al.
    Malmö högskola, Faculty of Odontology (OD).
    Jimbo, Ryo
    Malmö högskola, Faculty of Odontology (OD).
    Chrcanovic, Bruno
    Malmö högskola, Faculty of Odontology (OD).
    Andersson, Martin
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Surface structure and mechanical properties of impaction-modified Y-TZP2014In: Dental Materials, ISSN 0109-5641, E-ISSN 1879-0097, Vol. 30, no 8, p. 808-816Article in journal (Refereed)
    Abstract [en]

    Objectives The objectives of the study were to describe the surface structure and the chemical surface composition of Y-TZP ceramics produced by using the modified additive technique and to evaluate the flexural strength of Y-TZP with or without surface modification and with different pretreatments: etching before or after sintering combined with or without an adhesive cement system. Methods Y-TZP discs were used for surface analysis (n = 48) and for biaxial flexural strength testing (n = 200). The specimens were divided into groups depending on the cementation surface of Y-TZP: unmodified, sandblasted or glass-modified Y-TZP surfaces, and according to the production process: etching before or after sintering. Results The surface structure and the chemical composition of glass-modified Y-TZP differ; a rougher surface and phase transformation was identified compared to unmodified Y-TZP. The unmodified Y-TZP groups showed significantly higher flexural strength compared to the glass-modified groups (p < 0.001) and showed increased flexural strength after sandblasting (p < 0.001). Furthermore, by adding cement to the surface, the value increased even further in comparison with the sandblasted non-cemented specimens (p < 0.01). After thermocycling, however, the cement layer on the unmodified and the sandblasted surfaces had air pockets and regions with loose cement. Significance A rougher surface structure, superficial glass remnants and a higher content of m-phase was present in the cementation surface of glass-modified Y-TZP. The glass modification creates a bondable cementation surface that is durable. By etching the glass-modified Y-TZP before sintering, a more homogenous surface is created compared to one that is etched after sintering.

  • 42.
    Papia, Evaggelia
    et al.
    Malmö högskola, Faculty of Odontology (OD).
    Larsson, Christel
    Malmö högskola, Faculty of Odontology (OD).
    du Toit, Madeleine
    Malmö högskola, Library and IT Services (BIT).
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Bonding between oxide based ceramics and adhesive cement systems: a systematic review2014In: Journal of Biomedical Materials Research. Part B - Applied biomaterials, ISSN 1552-4973, E-ISSN 1552-4981, Vol. 102, no 2, p. 395-413Article, review/survey (Refereed)
    Abstract [en]

    The following aims were set for this systematic literature review: (a) to make an inventory of existing methods to achieve bondable surfaces on oxide ceramics and (b) to evaluate which methods might provide sufficient bond strength. Current literature of in vitro studies regarding bond strength achieved using different surface treatments on oxide ceramics in combination with adhesive cement systems was selected from PubMed and systematically analyzed and completed with reference tracking. The total number of publications included for aim a was 127 studies, 23 of which were used for aim b. The surface treatments are divided into seven main groups: as-produced, grinding/polishing, airborne particle abrasion, surface coating, laser treatment, acid treatment, and primer treatment. There are large variations, making comparison of the studies difficult. An as-produced surface of oxide ceramic needs to be surface treated to achieve durable bond strength. Abrasive surface treatment and/or silica-coating treatment with the use of primer treatment can provide sufficient bond strength for bonding oxide ceramics. This conclusion, however, needs to be confirmed by clinical studies. There is no universal surface treatment. Consideration should be given to the specific materials to be cemented and to the adhesive cement system to be used.

  • 43.
    Papia, Evaggelia
    et al.
    Malmö högskola, Faculty of Odontology (OD).
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Bond strength between different bonding systems and densely sintered alumina with sandblasted surfaces or as produced2008In: Swedish Dental Journal, ISSN 0347-9994, Vol. 32, no 1, p. 35-45Article in journal (Refereed)
    Abstract [en]

    The traditional zinc phosphate cementation technique for crowns and fixed partial dentures (FPDs) is based on mechanical retention where the geometry of the prepared tooth provides retention for the restoration. In clinical situations where mechanical retention is compromised or regarded insufficient, a bonding system can be used to provide retention. This study investigates whether bond strengths of different bonding systems to densely sintered high-strength alumina ceramics are sufficient. One hundred twenty pairs of industrially manufactured specimens--one block and one cylinder-shaped disc of densely sintered alumina--were used. The cementation surfaces of the blocks were sandblasted with 110-microm aluminium oxide while the cementation surfaces of the discs were left untreated, as produced. The pairs were then bonded with one of six different bonding systems. Each bonding group of 20 samples was randomly divided into thermocycled and non-thermocycled subgroups (n=10). Both subgroups were stored 1 week in distilled water (37 degrees C). During this week, the thermocycled subgroup underwent 5000 thermocycles (5 degrees C-55 degrees C). Following pre-treatment, the specimens were loaded until fracture in a universal testing machine to determine shear bond strength. Data were analysed using student's t-test and a one-way ANOVA. Fractured interfaces were examined under a light microscope to classify the failure mode of the debonded area as adhesive, cohesive, or a combination of the two. The highest bond strengths, achieved with two of the bonding systems, were significantly higher than the remaining bonding systems, irrespective of pretreatment--(p>0.001). The predominant failure mode for both treated and untreated surfaces was adhesive. Two of the six tested bonding systems achieved sufficient shear bond strength to densely sintered alumina. Furthermore, recommendations on whether to use surface-treated or as produced densely sintered alumina must be based on which bonding system is being used.

  • 44.
    Papia, Evaggelia
    et al.
    Malmö högskola, Faculty of Odontology (OD).
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Bond strengths of different adhesion systems to a sandblasted alumina core material2006Conference paper (Other academic)
  • 45.
    Papia, Evaggelia
    et al.
    Malmö högskola, Faculty of Odontology (OD).
    Zethraeus, Johan
    Ransbäck, Per-Åke
    Wennerberg, Ann
    Malmö högskola, Faculty of Odontology (OD).
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Impaction-modified densely sintered yttria-stabilized tetragonal zirconium dioxide: methodology, surface structure, and bond strength2012In: Journal of Biomedical Materials Research. Part B - Applied biomaterials, ISSN 1552-4973, E-ISSN 1552-4981, Vol. 100, no 3, p. 677-684Article in journal (Refereed)
    Abstract [en]

    The objectives of the study were to describe a novel method for producing zirconium dioxide specimens with a cementation surface that allows adhesive cementation techniques, to describe the surface structure and to evaluate the bond strength. Forty-eight pairs of specimens were fabricated and adhesively luted together. Three different surfaces were tested: impaction-modified surfaces created by using glass granules (G), impaction-modified surfaces created by using polymer granules (P) and a nonmodified control surface (C). Two bonding systems were used, Variolink(®)II (VA) or Panavia™F 2.0 (PA). During the different fabrication steps, the surfaces were examined under light microscope and analyzed with an optical interferometer. All groups were thermocycled and subjected to shear bond strength test. The groups with modified cementation surfaces showed significantly higher shear bond strength: 34.9 MPa (VA-G), 30.9 MPa (VA-P), 29.6 MPa (PA-P), and 26.1 MPa (PA-G) compared with the relevant control group: 20.5 MPa (VA-C) and 17.8 MPa (PA-C). The groups with surface modification showed a rougher surface structure and significantly fewer fractures between the cement and the zirconium dioxide surfaces compared to the control groups where all failures were adhesive. Impaction modification with an impaction medium pressed into the cementation surface of zirconium dioxide-based reconstructions can be used in combination with an additive production technique to increase bond strength. Both modification techniques described in the study result in a rougher surface structure and higher shear bond strength compared to the control groups.

  • 46. Rutkunas, Vygandas
    et al.
    Larsson, Christel
    Malmö University, Faculty of Odontology (OD).
    Vult von Steyern, Per
    Malmö University, Faculty of Odontology (OD).
    Mangano, Francesco
    Gedrimiene, Agne
    Clinical and laboratory passive fit assessment of implant-supported zirconia restorations fabricated using conventional and digital workflow2020In: Clinical Implant Dentistry and Related Research, ISSN 1523-0899, E-ISSN 1708-8208, Vol. 22, no 2, p. 237-245Article in journal (Refereed)
    Abstract [en]

    Background Long-term success of implant-supported restorations can be affected by the accuracy of the prosthodontic workflow which may differ between conventional and digital techniques. Purpose The purpose was to compare the fit of two-implant-supported restorations, fabricated using conventional and digital workflows and to assess the influence of distance and angulation between the implants on the passive fit of the prosthesis. The SR test was selected to evaluate the fit of two-implant-supported zirconia restorations. Materials and Methods Forty-eight zirconia two-implant-supported restorations were fabricated according to conventional (group C, n = 24) and digital (group D, n = 24) workflows. The SR parameter was calculated as a difference of rotation angles of each screw in passive and nonpassive situations. SR values between groups C and D were compared by performing measurements intraorally, on master and control casts. Results SR intraorally in group C (16.25 +/- 15.52 degrees) was higher than it was in group D (13.85 +/- 10.78 degrees), but the difference was not statistically significant (P = .557). While measuring SR on the master cast, group C SR (6.04 +/- 7.43 degrees) had lower values than group D (13.12 +/- 13.86 degrees) (P = .0039). No statistically significant correlations were found between SR measurements and inter-implant distance or angulation. Restorations with inter-implant angle higher than 10 degrees differed significantly from those with less than 10 degrees angulation. Conclusions Digital restorations had a better fit on the control cast, which was used as a reference in this study. Angulation of more than 10 degrees between the implants could negatively affect the passive fit of the digitally fabricated restorations intraorally.

  • 47.
    Stavropoulos, Andreas
    et al.
    Malmö University, Faculty of Odontology (OD). Med Univ Vienna, Univ Clin Dent, Div Conservat Dent & Periodontol, Vienna, Austria..
    Bertl, Kristina
    Malmö University, Faculty of Odontology (OD). Sigmund Freud Univ Vienna, Fac Med, Dept Periodontol, Dent Clin, Vienna, Austria..
    Isidor, Flemming
    Aarhus Univ, Dept Dent & Oral Hlth, Sect Prosthet Dent, Aarhus, Denmark..
    Vult von Steyern, Per
    Malmö University, Faculty of Odontology (OD). Nord Inst Dent Mat, NIOM, Oslo, Norway..
    Implantoplasty and the risk of fracture of narrow implants with advanced bone loss: A laboratory study2023In: Clinical Oral Implants Research, ISSN 0905-7161, E-ISSN 1600-0501, Vol. 34, no 10, p. 1038-1046Article in journal (Refereed)
    Abstract [en]

    Objectives: To assess the impact of implantoplasty (IP) on maximum implant failure strength of narrow diameter implants of different type/design and material, with simulated advanced bone loss.

    Materials and Methods: Narrow, parallel-walled implants (3.3 mm in diameter x 10 mm long) with an internal connection of different type/design [bone level (BL), tissue level (TL)] and material [Titanium grade IV (Ti), Titanium-Zirconium alloy (TiZr)] from one specific manufacturer were used. Half of the implants were subjected to IP in their coronal 5 mm; the remaining were used as controls (seven implants per group). Dynamic loading prior to maximum load strength testing was included.

    Results: During dynamic loading, the fracture rate of BL implants was low and independent of IP, while that of TL implants increased significantly with IP compared with controls (p = .001). Maximum implant failure strength reduction (in %) due to IP, was 1.3%-25.4%; TiZr BL implants were least affected. Implants subjected to IP compared to those without IP as well as TL implants compared to BL implants showed a significantly lower maximum implant failure strength (p < .002); implant material was not significant (p = .845).

    Conclusions: Based on data from implants of one specific manufacturer, IP has a significant negative impact on the fracture strength of narrow implants suffering from advanced peri-implantitis. TL implants have been more severely affected compared to BL implants and presented an increased risk for failure during normal chewing forces. In addition, this negative impact of IP on TL implants was independent of the implant material (i.e., Ti or TiZr).

    Clinical Relevance: Narrow single TL implants with advanced horizontal bone loss (e.g., 5 mm), when subjected to IP, appear to have an increased fracture risk during normal function.

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  • 48. Suleiman, Sozan Hama
    et al.
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Fracture strength of porcelain fused to metal crowns made of cast, milled or laser-sintered cobalt-chromium2013In: Acta Odontologica Scandinavica, ISSN 0001-6357, E-ISSN 1502-3850, Vol. 5, no 71, p. 1280-1289Article in journal (Refereed)
    Abstract [en]

    AIMS: The aim was to compare the fracture strength of porcelain fused to metal crowns with copings fabricated in Co-Cr using different manufacturing techniques (casting, milling and laser-sintering) with crowns manufactured in a high-gold alloy. METHODS: A total of 50 identical crowns were fabricated and sub-divided into five groups; cast Co-Cr, milled Co-Cr, two groups of laser-sintered Co-Cr and a control group cast in a high-gold alloy. After thermocycling (5000 cycles, 5-55°C) and pre-load (30-300 N, 10,000 cycles) the crowns were loaded until fracture. Load (N) and fracture mode were recorded. RESULTS: There was a significant difference (p < 0.05) in fracture strength between the control group and one of the laser-sintered groups. The mean values (N) for the groups were as follows: cast Co-Cr, 1560 ± 274; milled Co-Cr, 1643 ± 153; laser-sintered Co-Cr 1, 1448 ± 168; laser-sintered Co-Cr 2, 1562 ± 72; control group, 1725 ± 220. CONCLUSION: There is no difference in strength between Co-Cr crowns produced using the different production technologies: casting, milling or laser-sintering. Metal ceramic crowns made with copings fabricated in a high-gold alloy present numerically higher fracture strength than crowns made with copings fabricated in Co-Cr alloys. The difference is confirmed when analyzing the fracture surfaces, but the difference in fracture strength value is limited and is only significant with regard to one of the two laser-sintered groups.

  • 49. Tsumita, Mitsuyoshi
    et al.
    Kokubo, Yuji
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    Fukushima, Shunji
    Effect of framework shape on the fracture strength of implant-supported all-ceramic fixed partial dentures in the molar region2008In: Journal of Prosthodontics, ISSN 1059-941X, E-ISSN 1532-849X, Vol. 17, no 4, p. 274-285Article in journal (Refereed)
    Abstract [en]

    PURPOSE: The aim of the present study was to clarify the effects of the shape of the zirconium framework of implant-supported, all-ceramic fixed partial dentures (FPDs) on the fracture strength and fracture mode. MATERIALS AND METHODS: This study consisted of mechanical strength testing and 3D finite element analysis (FEA). The three framework shapes used in this study were: (1) conventional shape (control); (2) convex shape: 1.0-mm curve in the direction of the occlusal surface; and (3) concave shape: 1.0-mm curve in the direction of the gingival surface. Five frameworks were made for each condition (total: 15). A load (N) was applied until the FPD fractured. For FEA, a 3D model consisting of cortical bone, cancellous bone, implant bodies, and superstructure was constructed. RESULTS: The results of the mechanical strength test showed that fracture load was 916.0 +/- 150.1 N for the conventional shape, 1690.5 +/- 205.3 N for the convex shape, and 1515.5 +/- 137.0 N for the concave shape. The mean final fracture load for the FPDs with frameworks was the highest for the convex shape; however, a critical crack in the veneer porcelain (736.5 +/- 145.2 N) was confirmed during loading for the convex shape. Stress distribution maps for all conditions showed that tensile stress was generated at the veneer porcelain on the gingival side of the mesial and distal connectors of the pontic; however, there were differences in the maximum value and stress distribution within the framework. CONCLUSION: The shape of the framework, particularly the shape of the pontic-connector interface, affects the stress distribution, fracture strength, and fracture mode of all-ceramic FPDs, and stress concentration inside a framework may induce cracking of layering porcelain.

  • 50.
    Vennerström, Micael
    et al.
    Malmö högskola, Faculty of Odontology (OD).
    Fakhary, Mobin
    Malmö högskola, Faculty of Odontology (OD).
    Vult von Steyern, Per
    Malmö högskola, Faculty of Odontology (OD).
    The fit of crowns produced using digital impression systems2014In: Swedish Dental Journal, ISSN 0347-9994, Vol. 38, no 3, p. 101-110Article in journal (Refereed)
    Abstract [en]

    Compare the marginal and internal fit of crowns manufactured using four different digital impression systems with crowns manufactured using conventional impression technique, that served as a control group. Fifty all-ceramic crowns were fabricated using 50 standardized dies divided into five groups, each group representing one impression system. Each crown was cemented onto its respective model and sectioned into four segments. The marginal and internal fit were measured at 8 predefined points. A total of 1567 measurements were made, statistically analyzed and compared with crowns fabricated using the five systems. The following was found: (1) No significant difference was found with regard to marginal gap when comparing the control group to any of the digital systems. (2) Lava (TM) had smaller marginal gaps than CEREC (R) and iTero (R), (3) CEREC and Lava had smaller gaps in the chamfer compared to iTero and the control, (4) E4D (R) showed smaller gaps than CEREC at measuring points 4-8 and CEREC a smaller gap at point 2, (5) Lava showed smaller gaps than CEREC at measuring points 1,3 and 5-8. (6) Lava had smaller gaps than iTero at measuring points 1-4,7 and 8. All differences presented were significant. In conclusions, crowns manufactured using digital impressions present a marginal and internal fit equal to, or better than, crowns made using a conventional impression method. The marginal and internal fit of reconstructions made using digital impression techniques could improve with a lower initial setting of the spacer.

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