Background: Screw loosening remains a common mechanical complication in implant-supported restorations; however, the combined effect of sealing and superstructure materials on abutment screw stability warrants further investigation. Methods: This study evaluated the influence of access channel sealing material and superstructure material on abutment–implant screw stability after thermomechanical cyclic loading. Forty-eight Straumann analog–abutment assemblies restored with monolithic zirconia or resin nano-ceramic (Cerasmart) crowns were assigned to two sealing protocols: Polytetrafluoroethylene (PTFE) + composite or polyvinyl siloxane (PVS) putty (n = 12). After 750,000 off-axis cycles, reverse torque values (RTV) were analyzed using two-way analysis of variance (ANOVA) and Tukey’s HSD, with effect sizes calculated (α = 0.05). Results: A significant interaction between restorative material and sealing protocol was observed (p = 0.0170; η² = 0.116). Superstructure material showed no significant influence on RTV (p = 0.8368), whereas sealing protocol had a significant main effect (p = 0.0499). RTVs were highest for zirconia + PVS putty (36.33 ± 4.53 Ncm) and lowest for zirconia + PTFE (29.32 ± 6.30 Ncm), while the Cerasmart groups showed intermediate values. Post hoc analysis confirmed higher RTV for zirconia + PVS compared with zirconia + PTFE (p = 0.0138). Conclusions: Access channel sealing materials showed a material-dependent influence on abutment screw stability. Silicone-based sealing improved torque maintenance in zirconia, indicating that rigid restorative materials may be more sensitive to sealing material selection. In contrast, Cerasmart showed comparable RTV regardless of sealing protocol, suggesting that resilient restorative materials may reduce the influence of sealing on preload maintenance.

Background: Abutment screw joint stability is essential for the long-term success of implant-supported restorations. However, the effects of antimicrobial agents on implant–abutment screw mechanics remain unclear. This in vitro study evaluated the effects of chlorhexidine and silicone-based sealing gels on reverse torque values (RTVs) following thermomechanical loading. Methods: Forty-five Straumann implant analog–abutment assemblies were allocated to three groups (n = 15 per group): untreated control, 2% chlorhexidine gel, and a silicone-based gel (Flow.sil) applied to the abutment screw threads prior to tightening. Cemented standardized monolithic zirconia crowns were subjected to thermomechanical aging (750,000 cycles, 100 N, 2 Hz, 5–55 °C). The mechanical performance of the screw joint was assessed using RTVs, whereas calculated torque loss percentages were reported as a complementary outcome to facilitate the clinical interpretation of the reverse torque findings. Data were analyzed using Shapiro–Wilk and Levene’s tests, one-way analysis of variance (ANOVA), and Tukey’s HSD test (α = 0.05). Results: Significant differences among groups were observed for post-aging RTVs (p < 0.001). The control group exhibited the highest RTVs (33.03 ± 6.57 Ncm), suggesting the most favorable post-aging reverse torque performance. RTVs were lower in the chlorhexidine (25.29 ± 4.78 Ncm) and Flow.sil (23.16 ± 7.39 Ncm) groups. Although the sealing agents did not differ significantly, chlorhexidine yielded numerically higher RTVs than Flow.sil. Conclusions: Under the present experimental conditions, direct application of antimicrobial and silicone-based sealing agents to the abutment screw threads was associated with lower RTVs than the untreated control condition. Accordingly, the potential mechanical effects of these materials should be considered when selecting screw-sealing protocols.

Background and Objectives: Soft denture lining materials improve stress distribution and patient comfort but can lose mechanical stability under routine chemical cleansing. This study aimed to evaluate the time-dependent effects of two alkaline peroxide-based denture cleansing tablets (i.e., Efferdent and Protefix) on Shore A hardness and weight change of three soft lining materials (i.e., Ufi Gel P, Ufi Gel SC, and Visco-gel) at days 1, 7, and 30. Materials and Methods: Ninety specimens (n = 10/group) were assigned to a 3 × 3 factorial design. Specimens were immersed in cleansing solutions for 8 h daily and stored in artificial saliva for 16 h; controls remained solely in artificial saliva. Shore A hardness was measured using a durometer, and weight was recorded with a precision scale. Data were analyzed by mixed-design ANOVA and linear regression (α = 0.05). Results: Material type significantly affected hardness and weight change (p < 0.001). Visco-gel showed a marked increase in Shore A hardness (from about 15–16 to 26–27 HA) and greater weight loss (approximately 0.04–0.06 g), whereas silicone-based materials (Ufi Gel P and Ufi Gel SC) demonstrated more stable hardness values (from about 24–25 to 31–32 HA) with minimal weight variation (generally below about 0.02 g). The type of cleansing tablet had a smaller but significant effect (p = 0.004), with Protefix causing greater alterations. Weight change was negatively correlated with hardness increase (R² = 0.33, p < 0.001). Conclusions: Within the limitations of this in vitro study, material composition was identified as the main determinant of degradation resistance, with silicone-based liners demonstrating greater durability under the tested conditions, while Efferdent may be considered a milder option for long-term cleansing.

Background: Given their intraoral service for clinically relevant periods, it is important to clarify whether additive manufacturing parameters influence the surface characteristics of 3D-printed provisional restorations and thereby affect microbial colonization. Methods: This study evaluated the effects of printing orientation and layer thickness on surface roughness, wettability, and Streptococcus mutans biofilm formation of LCD-printed provisional restorations. Disk-shaped specimens were fabricated from a methacrylate-based provisional resin at two orientations (0° and 90°) and two layer thicknesses (50 and 100 µm) (n = 7 per group). Surface roughness (Ra) was measured by contact profilometry, wettability by sessile-drop contact angle analysis, and biofilm formation by crystal violet staining after 72 h. Results: Data were analyzed by two-way ANOVA, aligned rank transform (ART) ANOVA, and correlation analysis (α = 0.05). Orientation alone did not affect Ra (p = 0.992), whereas layer thickness (p = 0.012) and the orientation × layer thickness interaction (p = 0.002, η² = 0.339) were significant. At 50 µm, 90° oriented specimens showed higher Ra than 0° (p = 0.021); this pattern reversed at 100 µm (p = 0.020). Neither parameter significantly affected contact angle or biofilm formation (p > 0.05). Conclusions: Both printing orientation and layer thickness altered the surface microtopography of the specimens; however, no significant differences were observed in short-term S. mutans biofilm formation among the tested groups. Within the limitations of the present single-species 72 h in vitro model, the findings suggest that material-related characteristics may have contributed more prominently to the observed biofilm behavior than the printing-induced surface differences evaluated in this study.

Background: Post–core bonding plays a critical role in restoration longevity, and both the post surface treatment and core composite polymerization mode may influence interfacial performance. Methods: This in vitro study evaluated the effect of the post surface condition (no treatment vs. airborne-particle abrasion combined with an MDP-containing primer) and the composite polymerization mode (dual-, light-, and chemical-cure) on the pull-out bond strength and failure behavior of prefabricated metal post–core systems. A 3 × 2 factorial design was applied to 72 specimens (n = 12). After thermocycling, bond strength and failure modes were analyzed using two-way analysis of variance (ANOVA) and chi-square tests (p < 0.05). Results: The surface treatment significantly increased bond strength (p < 0.001; η² = 0.49) and shifted failure modes toward predominantly non-adhesive patterns (p = 0.011). Although the core type also showed a significant effect (p < 0.001), its influence was comparatively smaller. The bond strength was ranked as light-cure > chemical-cure > dual-cure under both surface conditions. Conclusions: Within the limitations of this study, post surface treatment was the primary determinant of bond strength and failure behavior. Clinically, effective surface modification appears to be more decisive than core composite selection, while differences among core materials become more apparent after establishing a stable bonding substrate.