Abstract:
Objective : The objective of this study was to investigate the influence of cement film thickness, cement type, and substrate (enamel or dentin) on fracture resistance of ceramic. Materials and Methods : One hundred extracted human third molars were polished to obtain fifty enamel and fifty dentin samples. To these samples 1-mm thick lithium disilicate ceramic plates were cemented with different cement film thicknesses (100 and 300 µm) using metal strips as spacers. The cements used were etch-and rinse (RelyX Ultimate) and self-adhesive (RelyX U200) resin cements. Compressive load was applied on ceramic plates using a universal testing machine and fracture loads were recorded in Newton (N). Statistical analysis was performed by multiple regression (P < .05). The representative specimens were evaluated by scanning electron microscopy (SEM) in order to control the cement film thickness. Results : The group with a cement thickness of 100-µm cemented to enamel with Rely X ultimate showed the highest mean fracture load (MFL; 1591 ±172.59 N). Higher MFL significantly related to RelyX Ultimate comparing to RelyX U200 and thinner film cement (P < .05). Bonding to dentin resulted in lower MFL comparing to enamel (P < .001). Conclusion : The Higher fracture loads were related to thinner cement film thickness and RelyX Ultimate resin cement. Bonding to dentin resulted in lower fracture loads than bonding to enamel.
