This study assessed the bond strength of prefabricated post systems at different root levels of endodontically treated teeth. One-rooted human premolars (N = 70; n = 10) were cut to 2 mm above the cement-enamel junction. Root canals were treated and randomly assigned to one of the seven post systems: T: Titanium (Mooser), ZrO: Zirconia (Cosmopost), G: Fiber (FRC Postec Plus), E1: Fiber (Direct) (Everstick post), E2: Fiber (Indirect) (Everstick post), PP: Fiber (PinPost), and LP: Injectable Resin/Fiber composite (EverX Posterior). All posts were luted using a resin cement (Variolink II), and the roots were sectioned at the coronal, middle, and apical root levels. Push-out tests were performed in the Universal Testing Machine (0.5 mm/min). Data (MPa) were analyzed using two-way ANOVA and Tukey’s tests (α = 0.05). The results showed that the bond strength (mean ± SD) of E2 posts were highest (5.3 ± 2.7) followed by PP (4.1 ± 2.0); G (4.0 ± 1.6); LP (2.6 ± 1.9): T (2.2 ± 1.5) and ZrO (1.9 ± 1.0) posts systems. No significant differences were found in bond strength of all post systems. The bond strength in the coronal root level was the highest with 3.6 ± 2.2 MPa. The bond strength of FRC post systems was significantly higher than those of rigid posts of titanium or ZrO₂. Bond strength results were the highest in the coronal root level for all tested post systems but did not differ significantly from the other two root levels.

To assess the mechanical durability of monolithic zirconia implant-supported fixed dental prostheses (iFDP) design on one implant, with a distal and a mesial extension cantilever bonded to a titanium base compared to established designs on two implants. Roxolid Tissue level (TL), and tissue level x (TLX) implants were used to manufacture screw-retained 3-unit iFDPs (n = 60, n = 10 per group), with following configurations (X: Cantilever; I: Implant, T: Test group, C: Control group): T1: X-I-X (TL); T2: X-I-X (TLX); T3: I-I-X (TL); T4: I-I-X (TLX); C1: I-X-I (TL); C2: I-X-I (TLX). The iFDPs were thermomechanically aged and subsequently loaded until fracture using a universal testing machine. The failure load at first crack (F_initial) and at catastrophic fracture (F_max) were measured and statistical evaluation was performed using two-way ANOVA and Tukey's post-hoc tests. The mean values ranged between 190 ± 73 and 510 ± 459 N for F_initial groups, and between 468 ± 76 and 1579 ± 249 N for F_max, respectively. Regarding F_initial, neither the implant type, nor the iFDP configuration significantly influenced measured failure loads (all p > 0.05). The choice of implant type did not show any significant effect (p > 0.05), while reconstruction design significantly affected F_max data (I-I-X^a < X-I-X^b < I-X-I^c) (p < 0.05). The mesial and distal extension groups (X-I-X) showed fractures only at the cantilever extension site, while the distal extension group (I-I-X) showed one abutment and one connector fracture at the implant/reconstruction interface. Results suggest that iFDPs with I-X-I design can be recommended regardless of tested implant type followed by the mesial and distal extension design on one implant abutment (X-I-X).

To investigate the effect of resin-based cements, thermocycling and dynamic loading on the marginal and internal fit of inlays made from two different monolithic zirconia materials. Sixty-four caries-free extracted maxillary premolar teeth were embedded in acrylic resin molds and prepared for mesial occlusal distal inlays by one operator. They were randomly divided into two groups based on inlay material; Zolid Gen-X (n = 32) and IPS e.max ZirCAD Prime (n = 32). Each group was subdivided into two subgroups according to cement type: RelyX Unicem (n = 16) and Panavia F 2.0 (n = 16). Half of the specimens were incubated at 37 °C for 24hr while the other half underwent a thermomechanical aging protocol consisting of 1,200,000 dynamic loading cycles at 5 and 55 °C. Occlusal and proximal marginal fit were measured at 20 locations using a stereomicroscope at 20x magnification. Internal fit was assessed at seven locations using scanning electron microscopy (SEM) at 200x. Data were analyzed using three-way ANOVA and multivariate tests at a significance level of P < 0.05but comprom. The marginal gap of the monolithic zirconia inlays remained within clinically acceptable ranges (50-120 μm) regardless of the type of zirconia material. However, the choice of resin cement had a significant effect as RelyX cement produced smaller gaps compared to Panavia at both occlusal and proximal surfaces (P < 0.05). Simulated aging, including thermocycling and dynamic loading, significantly increased marginal gaps (P < 0.05), indicating its impact on long-term performance. In contrast, internal fit values ranged from 111.95 to 163.16 μm and showed no statistically significant differences between zirconia material, resin cement, or aging conditions (P > 0.05). These findings highlight the importance of selecting appropriate cement systems and considering aging effects to optimize the marginal integrity of zirconia inlays while confirming the stability of their internal fit. This study found no significant difference in marginal fit between Zolid Gen-X (4Y-TZP) and IPS e.max ZirCAD Prime (3Y-TZP/5Y-TZP gradient) under tested conditions. Both materials achieved clinically acceptable fit. However, RelyX cement provided significantly better marginal integrity than Panavia, and aging significantly increased marginal gaps. Internal fit was unaffected by material, cement, or aging, but exceeded ideal values. Cement choice and aging are crucial factors for marginal seal longevity.