PURPOSE: To evaluate how laboratory polishing and glazing and clinical adjustments, i.e., by grinding and polishing affect the biaxial flexural strength and surface characterization of multilayer zirconia.

METHODS: Specimens of KATANA™ Zirconia YML, containing Enamel-Body 1 or Body 2-3 layers, and UTML were divided into 18 groups (n = 11) according to material/layer and finish treatment: laboratory polishing, glazing, or both, or followed by clinical adjustments. The surface roughness, surface structure and elemental composition were evaluated. Thermocyclic-mechanical cyclic loading and biaxial flexural strength test were performed. Three- and two-way ANOVA were used (α = 0.05).

RESULTS: The yttrium amount decreased in the order UTML, YML Enamel-Body 1, and YML Body 2-3. Body 2-3 showed higher flexural strength than Enamel-Body 1 and UTML, in that order. Flexural strength after clinical adjustments was higher in Body 2-3 but lower in Enamel-Body 1 and UTML. Finish treatments had indistinguishable impact on Enamel-Body 1. Body 2-3 had higher strength after polishing, polishing and glazing, and glazing, in that order. UTML displayed the highest strength after polishing and glazing or glazing. The surface roughness was lowest after polishing regardless of material/layer.

CONCLUSIONS: Laboratory treatments and clinical adjustments of multilayer zirconia affect the flexural strength and surface roughness differently depending on the zirconia type. Composition-gradient zirconia should be polished, and shade-gradient zirconia (≥ 5 mol% yttria) should be polished and glazed. Clinical adjustments of zirconia with higher yttria content are detrimental for the flexural strength and should be performed with caution.

STATEMENT OF PROBLEM: The fit of implant-supported prostheses plays an important role in their mechanical and biological stability. Clinically, the prosthetic fit is typically assessed radiographically, but this method relies on the operator's subjective evaluation. Whether available digital tools could optimize the evaluation of the prosthetic fit is uncertain.

PURPOSE: The purpose of this in vitro study was to evaluate the influence of an image processing program on the radiographic detection of discrepancies in the active and passive fit of implant-supported prostheses. Two-implant-supported screw-retained prostheses were analyzed by simulating the vertical and horizontal misfits of 3 different implant abutment configurations.

MATERIAL AND METHODS: Seven casts were fabricated using 2 internal-connection titanium implants: 1 control; 3 with vertical (V) misfit of 50 µm, 100 µm, 150 µm; and 3 with horizontal (H) misfit of 35 µm, 70 µm, 100 µm. Thirty bar-shaped zirconia frameworks were fabricated and divided into 3 groups (n=10) according to their attachment to 2 engaging (E-E), 2 nonengaging (NE-NE), and engaging and nonengaging (E-NE) titanium bases. Digital parallel periapical radiographs were made of each specimen in the passive and active fit situation on each cast (1-screw test), except for the E-E specimens, which were only seated on the control, H35, and H70 casts because the fit on the remaining casts was poor. The mean gray value (MGV) was measured at the chosen regions of interest on the second implant (side B) using the ImageJ software program. Differences in the MGV measurements between the passive and active conditions were tested using a t test (α=.05) and compared the different misfit levels using analysis of variance (1-way ANOVA), followed by the Tukey HSD test (α=.05).

RESULTS: The highest values for the differences between passive and active fit were found for the V150 and H100 misfit simulations (P<.05). Statistical differences between the MGVs were found with some exceptions: the smallest simulated misfits (H35 and V50) revealed statistically significant MGV differences from the highest simulated misfits (V150, H100) and from the H70 in the groups where an engaging component was present (P>.05). In the horizontal misfit group of NE-NE abutment configuration, H70 revealed no significant difference from the control group cast (P>.05).

CONCLUSIONS: Measuring MGV differences between passive and active fit could be a promising alternative for detecting 70- to 150-µm gaps in the implant-abutment connection that result from the misfit. However, the procedure was not adequate for detecting <50 µm gaps, cannot be uniformly applied to all types of implant-abutment connections, and requires 2 exposures to X-radiation.

The aim of this long-term follow-up study was to investigate the relationship between bite force, bruxism, and fractures of teeth and veneer porcelain of fixed dental prostheses. Patients previously assessed as probable bruxers (n = 30) and non-bruxers (n = 21), all rehabilitated with dental implant-supported restorations, underwent a clinical examination and measurement of maximum bite force. A univariate general linear model was used to compare regression lines showing the relationship between fractures and bite force. Bruxers had significantly higher maximum bite force (p = 0.023) and higher proportion of tooth/veneer porcelain fractures per total number of tooth/prosthetic units (p = 0.045). There was no significant difference in the relationship between frequency of tooth/veneer porcelain fractures and maximum bite force between probable bruxers and non-bruxers (p = 0.054). However, there was a significant difference between probable bruxers and non-bruxers when the percentage of fractures in relation to the total number of units was considered instead of the frequency of fractures (p = 0.035). Higher maximum bite force in probable bruxers was related to higher prevalence of fractures of teeth and veneer porcelain, emphasizing the potential benefits of pre-treatment assessment of bruxism as well as bite force. Easy-to-use reliable clinical methods for bite force measurement should be tested and implemented in dental practice.

Purpose: To investigate the shear bond strength of composite resin in five different ceramic repair systems for three different ceramic materials. Materials and Methods: A total of 225 monolithic zirconia (Zr), lithium disilicate (LDS), and cobalt-chromium (CoCr) specimens with feldspathic porcelain (FP) veneer were fabricated (N = 75 per material). The specimens underwent thermocycling and were randomly divided into five groups for the following intraoral repair systems (n = 15): (1) Clearfil Ceramic Primer Plus, Kuraray Noritake; (2) iBond Intraoral Repair Kit, Kulzer; (3) VOCO Cimara, VOCO Dental; (4) Ceramic Repair System Kit, Ivoclar Vivadent; and (5) Ultradent Porcelain Repair Kit, Ultradent Products. After surface conditioning, composite was applied using a cylindrical mold, and a second round of thermocycling was performed. Each specimen was then subjected to shear load until failure. Microshear bond strength was compared using one-way ANOVA ( Tukey test, alpha < .05). Results: The type of porcelain repair kit significantly affected the shear bond strength. For Zr, the repair systems from Kulzer and VOCO had significantly higher shear bond strength than the other systems (P < .001), without significant difference between Kulzer and VOCO. For the LDS and CoCr with FP, hydrofluoric acid had the highest shear bond strength (P < .001). Conclusions: For zirconia, a 10- methacryloyloxydecyl dihydrogen phosphate (10-MDP) system should be used. The results also suggest that a cleaning bur may be beneficial. For glass-based ceramics and FP, etching with hydrofluoric acid remains the method of choice.

STATEMENT OF PROBLEM: Prosthesis fit is 1 of the main factors influencing the success and survival of an implant-supported screw-retained restoration. However, scientific validation of the performance of engaging and nonengaging components in a fixed partial denture (FPD) and the effect of their combinations on the fit of FPDs is lacking. The screw resistance test has been used for the fit assessment of screw-retained FPDs. However, objective assessments by using analog and digital devices are now available.

PURPOSE: The purpose of this in vitro study was to investigate the effect of engaging and nonengaging components on the fit of screw-retained frameworks, supported by 2 conical connection implants with simulated vertical and horizontal misfits, by performing 2 different screw resistance tests (analog and digital).

MATERIAL AND METHODS: Thirty 2-implant-supported bar-shaped zirconia frameworks cemented on two 2-mm titanium bases were fabricated and divided into 3 groups (n=10) according to different abutment combinations: both engaging, engaging and nonengaging, both nonengaging. The fit of each framework was tested on the control cast and on 6 definitive casts simulating 50-, 100-, and 150-μm vertical and 35-, 70-, and 100-μm horizontal misfit levels. The abutment screws were tightened on each implant, and the screw rotation angle was measured both digitally, with a custom-made digital torque wrench and a computer software program, and conventionally, with an analog torque wrench and protractor. Clearly ill-fitting specimens were excluded. The data were statistically analyzed by 1-way analysis of variance (ANOVA) and the Tukey post hoc test (α=.05).

RESULTS: Both engaging specimens on the 100-μm horizontal misfit group and on all vertical misfit groups were clearly ill-fitting and excluded. Statistically significant differences among groups with different combinations of abutments were found (P<.05). The engaging abutments had a higher angle of rotation than the nonengaging abutments on all casts. In the horizontal misfit group, both engaging specimens had the highest angle of rotation, followed by engaging and nonengaging and both engaging specimens. In the vertical misfit group, the engaging and nonengaging specimens had the highest angle of rotation on the side of the engaging abutment. The angle of rotation increased with the increasing level of misfit.

CONCLUSIONS: Both nonengaging frameworks showed superiority in misfit tolerance, as the angle of rotation was lower than that of the engaging and nonengaging and both engaging frameworks. Conventional and digital torque wrenches showed similar results.

PURPOSE: To evaluate the survival rate of full-coverage tooth-supported fixed prosthetic restorations, single crowns (SCs), and fixed dental prostheses (FDPs), taking into consideration the potential influence of tooth-vitality, presence and type of post, and type of prosthetic restoration material.

MATERIALS AND METHODS: In October 2022, two authors independently conducted a search in PubMed, Web of Science, and Scopus electronic databases as well as a hand search to identify clinical human studies on full-coverage SCs and FDPs supported by vital and/or non-vital abutments and/or a combination of both, with a minimum observation period of 24 months.

RESULTS: Out of 4198 studies identified through the database search and 22 through hand searching, 26 studies fulfilled the inclusion criteria and were included in the analysis of the present systematic review. Included studies scored six points and more according to Newcastle-Ottawa Scale (NOS). The highest estimated 5-year survival rate was observed for (metal-ceramic and all-ceramic) SCs on vital teeth (98.3%; 95% CI [98.1, 98.6%]) and all ceramic SCs on non-vital teeth with fiber post (95.0%; 95% CI [94.5-95.4%]). Metal-ceramic SCs on vital teeth (97.1%; 95% CI [95.6-98.7%]) showed a statistically significant higher estimated 5-year survival rate compared to metal-ceramic SCs with cast metal post (90.7%; 95% CI [87.4-94.0%], P < 0.001), fiber post (91.3%; 95% CI [90.9-91.6%], P < 0.001) and without post (85.7%; 95% CI [80.7, 90.6%], P < 0.032). All-ceramic SCs with fiber post had a statistically significant higher estimated 5-year survival rate (95.0%; 95% CI [94.5-95.4%]) compared to metal-ceramic SCs on non-vital teeth with fiber post (91.3%; 95% CI [90.9-91.6%], P < 0.001). SCs (all-ceramic and metal-ceramic) with fiber post had a statistically significantly higher estimated 5-year survival rate of (92.7%; 95% CI [92.4-92.9%]) than SCs made of metal-ceramic and retained by cast metal post (90.7%; 95% CI [87.4-94.0%], P < 0.001). For FDPs, the 5-year survival rate was significantly higher for FDPs on vital abutments (84.9%; 95% CI [75.9, 93.9%]) compared to FDPs retained by non-vital abutment/s (81.3%; 95% CI [80.3, 82.2%], P = 0.049) irrespective to presence, type of post, and FDPs material. The results are limited by the limited number of studies and the presence of uncontrolled confounding clinical variables.

CONCLUSIONS: Within the limitations of the study, tooth vitality is suggested to contribute positively to the survival of SCs and FDPs.

OBJECTIVE: The aim of this study was to evaluate the influence of combining primers and cements from two different resin cement systems on the microtensile bond strength (muTBS) between zirconia and human dentin.

MATERIALS AND METHODS: A total of 120 specimens of zirconia cemented to dentin were allocated into eight groups based on cement type (RelyX Ultimate or Panavia V5) and primers (Tooth Primer, Clearfil Ceramic Primer and Scotchbond Universal Adhesive) combinations, applied to dentin or ceramic surfaces. Following artificial aging with 5000 thermocycles, muTBS tests were conducted. Statistical analysis was performed using One-way ANOVA and Tukey's post hoc tests (p </= 0.05), and failure modes were assessed.

RESULTS: The Panavia V5 cement system demonstrated the highest bond strength (19.4 +/- 4.4 MPa), significantly higher than the other groups except when RelyX cement was used with Panavia primers (16.9 +/- 3.7 MPa). Cohesive fractures within the cement layer were the predominant failure mode.

CONCLUSIONS: The combination of primers from different adhesive cement system brands may significantly affect the bonding effectiveness. Therefore, using products from a single product line of the same adhesive cement system, and following the manufacturer's recommendations for indications and use, is crucial for a more predictable clinical outcome.

Aim: This study aimed to evaluate the bond strength of adhesively cemented lithium disilicate restorations to dentin by applying different pretreatments and cleaning methods.

Material and Methods: Twenty-five human posterior teeth were mounted in an acrylic mold, flattened to expose mid-coronal dentin, and divided into five groups based on different pretreatments and cleaning methods prior to adhesive cementation. After cementation, the teeth were sectioned to obtain 1 mm² specimens, yielding 15 specimens in each group that were subjected to aging and thermocycling process, followed by a microtensile bond test and failure mode assessment.

Results: The highest bond strength values were in the control group and in the group that was treated with fluoride and where the temporary cement was removed using pumice, whereas the lowest values were in groups that were cleaned by excavator irrespective of whether they were treated with fluoride or not. However, all groups showed mainly cohesive failure without any statistically significant differences.

Conclusions: To eliminate any possible negative impact of eugenol on adhesion to dentin, surface cleaning by rotational brush and pumice is recommended prior to cementing lithium disilicate restorations.

Background: The aim of this study was to investigate how different scanning protocols affect the accuracy (truenessand precision) of intraoral scanning of complete arches with implant cylinders.Material and Methods: A master model was designed with five cylinders. One scanner, TRIOS2 (3shape), was usedto scan the model with four different scan protocols: ROCK (wavelike scanning in a pendulum movement), ZIG-ZAG (wavelike scanning technique), OBP (occlusal, buccal, and palatal), and OWBP (occlusal, wiggling, buccal,and palatal). A total of 30 scans were performed using each of the four protocols. The master model was digitizedwith an industrial ISO-certified ATOS scanner. GOM inspect software was used to compare the scans to the mastermodel and evaluate any deviation between the scan protocols and the master model. The data was analyzed usingthe One Sample t-test (p=0,05).Results: The precision (standard deviation) ranged from 23-83μm for protocol ROCK, 22-147μm for ZIGZAG,21-170μm for OBP, and 23-116μm for OWBP. The trueness (mean deviation from master model) was 5-41μm forROCK, 7-97μm for ZIGZAG, -21-29μm for OBP, and 1-24μm for OWBP. All protocols showed statistically signi-ficant differences to the master model in multiple distances, except OWBP, which had a single significant differencein comparison to the master model.Conclusions: Protocol OWBP has a higher trueness than other tested protocols. All tested protocols have highertrueness and precision when scanning smaller distances than inter-arch measurement. Clinical significance;Thetrueness and precision of intraoral scanning is generally better in smaller spans due to less deviation. The protocolOWBP, that is recommended by the manufacturer, has the least deviating trueness in comparison to the mastermodel.