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: Restoring extensively damaged, endodontically treated molars with an indirect restoration that both preserves and protects the remaining tooth structure is a significant challenge. Overlays and endocrowns offer a less invasive alternative compared to conventional crowns. Purpose: The aim of this study was to evaluate the fracture resistance and fracture patterns of molars restored with different materials and designs. Materials and Methods: This study involved 40 extracted human molars, which underwent endodontic root canal treatment and were divided into four groups: composite core build-up with pressed lithium disilicate overlay (OL) (n = 10); composite core build-up with milled composite overlay (OC) (n = 10); pressed lithium disilicate endocrown (EL) (n = 10); milled composite endocrown (EC) (n = 10). The teeth were subjected to thermocyclic loading (10,000 cycles between 5 and 55°C), followed by chewing simulation (0–50 N at 1.6 Hz for 600,000 cycles with a 10° inclination), another round of thermocyclic loading (10,000 cycles between 5 and 55°C), and finally, a fracture strength test (5 mm steel ball at a 10° inclination with a load rate of 0.5 mm/min). Afterwards methylene blue was used to stain any cracks or fracture lines in the teeth for microscopic evaluation. Results: The findings suggest that while the material type may not significantly impact fracture resistance or catastrophic fracture likelihood, the type of restoration (endocrown vs., overlay) is a crucial factor to consider. Conclusions: Clinicians should weigh the higher risk of catastrophic fractures associated with endocrowns when selecting restorative options for endodontically treated teeth. Clinical Implications: Overlays and endocrowns offer similar overall tooth fracture resistance, making both viable options for restoring endodontically treated molars. However, OLs may better withstand chewing forces and posed no risk of catastrophic tooth fractures, unlike ECs, which carry a higher tooth fracture risk.

Background: Inter-implant distance (IID) plays a crucial role in maintaining peri-implant bone stability and osseointegration. Narrower IIDs (< 3 mm) have been associated with increased bone loss, but the threshold varies with implant connection type. The undersized preparation protocol, which induces static strain in the bone, enhances primary stability but may lead to microstructural damage, remodelling, or necrosis. The effect of this technique on osseointegration in adjacent implants with varying IIDs is not well documented. This study investigates the impact of undersized and non-undersized preparation protocols on osseointegration at different IIDs.

Methods: The study utilized eight sheep, with 64 implants placed in the mandibles following two surgical protocols: undersized preparation (UP) and non-undersized preparation (NUP). Implants were positioned at two IIDs (2 mm and 4 mm). Biomechanical, histomorphometric, and micromorphometric analyses were performed five weeks post-surgery. Bone-to-implant contact (BIC), bone volume fraction (BVTV), and bone mineral density (BMD) were measured in the regions of interest (inner and outer portions relative to the IID). A linear mixed model approach was applied to analyse the data with statistical significance set at p < 0.05.

Results: The analyses showed no statistically significant differences between the surgical protocols or IIDs for the evaluated parameters ( p >0.05). Nevertheless, trends were observed, with higher BIC and increased bone remodelling in the inner regions at 2 mm IID, particularly when using the undersized preparation protocol. Additionally, BVTV values were higher in the inner portions at 4 mm IID, suggesting reduced bone remodelling compared to 2 mm IID. These results indicate that while mechanical stress influenced trends in bone response, the overall resilience of peri-implant bone healing was evident.

Conclusions: No significant differences in osseointegration were observed between surgical protocols or IIDs. However, the trend of increased remodelling and higher BIC at 2 mm IID highlights the mechanical impact of undersized preparation in close implant spacing. These findings emphasize the complexity of peri-implant bone response to mechanical forces, necessitating further clinical studies to validate these results in human models.

OBJECTIVES: This study aimed to evaluate potential differences in biofilm accumulation on three different implant surfaces: turned surface (TS), modified surface (MS), and modified surface treated with implantoplasty (IPS), using a within-subject comparison.

MATERIAL AND METHODS: Ten volunteers wore individualized splints containing three titanium implants with different surfaces (TS, MS, and IPS) on each buccal side of the splint. The implant position (anterior, central, and posterior) was randomly assigned among the three implants on each side. Volunteers were instructed to wear the splint for 72 h and to remove it only for eating, drinking, and performing standard oral hygiene; the splint itself was not cleaned. After 72 h, the implants were carefully removed from the splint, and the accumulated biofilm was assessed using a crystal violet assay by measuring intensity/absorbance at 570 nm.

RESULTS: All volunteers reported no deviations from the instructions. The lowest mean amount of biofilm (0.405 ± 0.07) was detected on implants of the IPS group, followed by implants of the MS (0.463 ± 0.06) and TS group (0.467 ± 0.07). A multilevel mixed-effects linear regression analysis confirmed that implants of the IPS group accumulated a significantly lower amount of biofilm than the other surfaces (p < 0.001); however, no significant difference was detected between implants of the TS and MS groups (p = 0.806).

CONCLUSIONS: Implantoplasty can generate a surface significantly less conducive to biofilm accumulation in the short term compared to pristine implants with turned or modified surfaces.

TRIAL REGISTRATION: clinicaltrials.gov identifier: NCT06049121.

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.

Introduction

Different materials and restorative concepts have been proposed over the years to restore endodontically treated teeth (ETT). Monolithic ceramic and composite restoration can be lute to the tooh, without the use of a post. However, little is known how the material stiffness and presence of a composite core will affect the survival and failure mode.

The objective of this in-vitro study was to evaluate the fracture strength and failure mode of endodontically treated molars, restored with ceramic or hybrid composite monolithic restoration, in the presence of absence of a composite core.

Materials and Methods

Sixty depulped molars were restored with a lithium-disilicate (e.max CAD) or hybrid composite (Cerasmart) restoration. Both materials were used in a monolithic approach, but with 3 different designs: (a) monolithic endocrown, (b) crown with a separate composite core, and (c) overlay without core buildup or pulpal extension. Ten sound teeth were used as control group. All groups were thermocycled (10,000 cycles), subsequently loaded in a chewing simulator (100,000 cycles) and finally loaded until fracture.

Results

Peak fracture loads and failure modes were registered. No significant differences were seen between the groups in terms of fracture load. Failure modes were statistically significantly different among groups with significant correlation between restoration type and material. (p < 0.001 and p = 0.033, respectively). No group presented significantly higher fracture resistance. Although ceramic crowns and overlays presented the highest repairability, all restored ETT were within the range of the intact tooth' fracture strength.

Conclusion

No restoration presented significant different fracture loads. However, the type of restoration and material choice were correlated to the fracture mode.

OBJECTIVE: To evaluate the clinical outcome of different designs of zirconia dental implants.

DATA: This systematic review adhered to the PRISMA checklist and followed the PICO framework. The protocol is registered in PROSPERO (CRD42022337228).

SOURCES: The search was conducted in March 2023 through four databases (PubMed, Web of Science, Cochrane Library, and Google Scholar) along with a search of references in the related reviews. Three authors reviewed on title, and abstract level and analysed the risk of bias, and all authors reviewed on a full-text level.

STUDY SELECTION: Clinical studies excluding case reports for patients treated with different designs of zirconia dental implants were included. From a total of 2728 titles, 71 full-text studies were screened, and 27 studies were included to assess the risk of bias (ROBINS-I tool) and data extraction. After quality assessment, four studies were included, and the remaining 23 excluded studies were narratively described.

RESULT: The included prospective studies with moderate risk of bias reported success and survival rates of one-piece implants that ranged between 95 and 98.4 % with no difference between different lengths and diameters. The acid-etched roughened surface showed higher clinical outcomes compared to other surface roughness designs.

CONCLUSION: Promising 5-year clinical outcomes were found for one-piece zirconia implants with no difference between different diameters and lengths. Concerning surface roughness, better outcomes were found when using the acid-etched implant surface. However, due to the limited available studies, further high-quality clinical studies comparing zirconia one-piece and two-piece implants with different diameters, lengths, and surface roughness are needed.

CLINICAL SIGNIFICANCE: Based on this systematic review, under suitable clinical situations, the one-piece zirconia implants with diameters of 4.0 mm, 4.5 mm, or 5.5 mm and lengths of 8 mm, 10 mm, 12 mm, or 14 mm have similar promising clinical outcomes. Additionally, the acid-etched roughened implant surface may be preferable.

Purpose: To assess and compare the clinical outcomes of three different types of all-ceramic posterior monolithic tooth-supported crowns. Materials and Methods: A total of 71 patients received 90 all-ceramic crowns randomized to be either high-translucency zirconia (ZC), high-translucency zirconia with a partial buccal veneer (ZC-V), or lithium disilicate glass-ceramic (LDS). All treatments were performed by four general dentists. Choice of material was blinded. Baseline and subsequent annual evaluation were based on modified California Dental Association (CDA) criteria. A questionnaire was used to include patient-reported outcomes and to compare them to the crown quality rating performed by dentists. Results: A total of 66 patients with 84 crowns were examined after 3 years. The survival rate was 98.8%. No crowns fractured during the observation period. One ZC-V crown failed due to loss of retention, and three complications were noted: loss of retention occurred in one ZC crown, and two ZC crowns needed to be endodontically treated. There was no significant difference between the different crowns regarding marginal integrity, surface, or anatomical form. Both patients and examining dentists rated the crowns favorably regarding esthetics, patients more than dentists. Conclusion: Posterior lithium disilicate glass-ceramic crowns and translucent zirconia crowns with or without a partial buccal veneer show excellent and promising clinical outcomes from a short-term perspective. Patients and dentists rate the restorations favorably concerning esthetics and function.

Purpose: To determine the biologic and biomechanical effects of two implant drilling protocols on the cortical bone around implants subjected to immediate loading. Materials and Methods: A total of 48 implants were inserted into the mandibles of six sheep following one of two drilling protocols: undersized preparation (US; n = 24) and nonundersized preparation (NUS; n = 24). Immediately after implant insertion, an abutment was placed on each implant and 36 implants were subjected to 10 sessions of dynamic vertical loads (1,500 cycles, 1 Hz) of 25 N or 50 N. Insertion torque value (ITV) was recorded at implant installation. Resonance frequency analysis (RFA) was measured at implant insertion and at each loading session. Fluorochrome was administered at day 17, and the animals were euthanized after 5 weeks. The removal torque values (RTVs) were measured, and samples underwent histomorphometric, mu CT (microcomputed tomography), and fluorescence image acquisition analyses. The bone volume density (BV/TV), bone-to-implant contact (BIC), bone area fraction occupancy (BAFO), and fluorochrome stained bone surface (MS) were calculated. A linear mixed model analysis was performed, and Pearson paired correlation was calculated. Results: Five implants from the NUS group failed, with a mean ITV of 8.8 Ncm and an RFA value of 57. The mean ITVs for US group and NUS group were 80.5 (+/- 14) Ncm and 45.9 (+/- 25) Ncm, respectively (P < .001). No differences were noted in the RFA values from the time of implant insertion until the end of the study. No differences in RTV, BV/TV, BAFO, or MS were observed between the groups. Intense new bone formation took place in the NUS group implants that were subjected to load. Conclusions: Undersized preparation of cortical bone ensured a greater BIC compared to a nonundersized preparation. Moreover, this study demonstrated that immediate loading did not interfere with the osseointegration process, but loading induced intense new bone formation in the NUS group. It is not recommended to immediately load the implants when the clinically perceived primary stability is lower than an ITV of 10 Ncm and an RFA value of 60.