Abstract
Aim: The roughness and micromorphology of various surface treatments in aged metal-free crowns and the bond strength of these crowns repaired with composite resin (CR) was evaluated in vitro. Methods: A CR core build-up was confectioned in 60 premolars and prepared for metal-free crowns. Prepared teeth were molded with the addition of silicone, and the laboratory ceromer/fiber-reinforced crowns (SR Adoro/Fibrex Lab) were fabricated. Subsequently, the crowns were cemented and artificially aged in a mechanical fatigue device (1.2 X 106 cycles), then divided into 4 groups (n = 15) according to the surface treatment: 1) phosphoric acid etching (PA); 2) PA + silane application; 3) roughening with a diamond bur + PA; and 4) sandblasting with Al2O3 + PA. After the treatments, the crowns (n = 2) were qualitatively analyzed by scanning electron microscope (SEM) and surface roughness (n = 5) was analyzed before and after the surface treatment (Ra parameter). The remaining crowns (n = 8) received standard repair with an adhesive system (Tetric N-Bond) and a nanohybrid CR (Tetric N-Ceram), and the microshear bond strength (SBS) test was performed (0.5 mm/min). Roughness and SBS data were analyzed by one- and two-way ANOVA, respectively, as well as Tukey’s post-test (α = 0.05). Results: Sandblasting with Al2O3 + PA resulted in the highest final roughness and SBS values. The lowest results were observed in the PA group, whereas the silane and diamond bur groups showed intermediate values. Conclusion: It may be concluded that indirect ceromer crowns sandblasted with aluminum oxide prior to PA etching promote increased roughness surface and bond strength values.
Highlights
Known as “ceromer,” “polymeric glass porcelain,” or “second-generation laboratory CR,” are widely used in clinical practice because they minimize the adverse effects of direct restorations, such as polymerization shrinkage[1], poor marginal adaptation, and postoperative sensitivity[2] In addition, they can provide better standards of translucency and can be low-cost alternatives to all-ceramic restorations[3]
Indirect resins possess high mechanical strength, these restorations are subject to fractures as any other material
The final roughness was higher in the sandblasting group and lower in the PA group, whereas the silane and diamond bur groups showed intermediate values
Summary
Indirect resins possess high mechanical strength, these restorations are subject to fractures as any other material. This type of failure should be carefully evaluated to define the best treatment. Corroborating in vitro studies[6,7,8], clinical studies show that most cases of crown fractures are repairable[9,10]. This is advantageous because complete replacement of indirect restorations may present more disadvantages than advantages, such as the treatment complexity and expense[11]. With the evolution of adhesive techniques, adhesive repair has been widely used and can be considered beneficial, allowing good longevity in this type of dental restoration[12,13]
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