Wear and Marginal Gap of Direct Composites on Endodontically Treated Teeth.

Purpose: The aim of this in vitro study was to evaluate the effect of different direct restoration techniques on endodontically treated anterior teeth, with or without fiber posts, analyzing interfacial adaptation, wear, and fracture resistance. Materials and Methods: 36 extracted single-rooted anterior teeth were selected. Endodontic treatment was carried out in all samples. After 24 h of storage in water at 37°C, samples were divided into 3 groups according to the cavity design: 1) endodontic access; 2) endodontic access + 1 class-III cavity; 3) endodontic access + 2 class-III cavities. Samples were then divided into 3 subgroups (n = 4) according to the restoration technique: SB1) direct composite restoration (DCR); SB2) DCR supported by a fiber post (Rebilda Post, Voco); SB3) DCR supported by vertical fibers (Rebilda Post GT, Voco). All specimens were scanned with x-ray computed microtomography (micro-CT Skyscan, Bruker), with the following parameters: 100 kV, 100 μA, Al-Cu filter, 10 μm pixel size, rotation step 0.1 degree, 6 h total scan duration. Then, specimens of each group were subjected to mechanical fatigue testing in a dual-axis masticatory simulator (CS4.4, SD Mechatronik). A force of 50 N was applied using a ceramic steatite ball with a diameter of 4 mm as an antagonist for 100,000 cycles at a frequency of 1 Hz, downward speed 16 mm/s, 2-mm sliding movement starting from the palatal cingulum towards the incisal edge, with an initial angle of 45 degrees. After fatigue testing, micro-CT scanning was performed again to evaluate the interfacial behavior and wear resistance. Micro-CT images before and after cyclic loading were analyzed with Mimics (segmentation) and Geomagic Software (alignment and analysis) to evaluate composite wear and interface gap progression before and after mechanical loading. Finally, a static fracture test with a universal testing machine (Instron) was performed to measure the fracture resistance of the samples after fatigue tests (4-mm-diameter metal cone at a constant speed of 0.5 mm/min and an angle of 30 degrees). Statistical analysis was performed with two-way ANOVA to evaluate the effect of cavity configuration and restoration of wear, interfacial gap, and fracture resistance. Results: Gap progression and volume are significantly related to the build-up technique (p < 0.001) as well as to the cavity configuration (p = 0.032). Two-way ANOVA showed that both the variable cavity (p = 0.0020) and the variable material (p = 0.0013) significantly influence the fracture resistance. No other significant interactions were shown by ANOVA (p = 0.5130). Conclusion: Endontically treated anterior teeth should be restored with composite restorations supported by fiber structures, especially in the case of loss of both marginal ridges. Further studies are needed to better understand the influence of fiber post on interfacial adaptation, wear, and fracture resistance over time. [ABSTRACT FROM AUTHOR]