Within the limitations of this study, the cements tested had different mechanical properties, while cuspid coverage did not result in improved fracture resistance of the restored teeth.

The fracture resistance of ceramic restorations is associated with the quantity of the dental structure removed. In relation to the fracture resistance, preference should be given to inlay restorations rather than to onlays; however, no restorative technique was able to attain the fracture resistance of intact teeth. SUMMARYThis in vitro study evaluated the fracture resistance of teeth restored with different designs of partial ceramic restorations using two diameters of steel ball to apply fracture stresses. One hundred and twenty sound maxillary premolars were randomly divided into three groups of 40 elements; each group was submitted to one of three indirect restoration designs: inlay, onlay with only lingual cuspal coverage and onlay with buccal and palatal cuspal coverage. Another 20 intact teeth were randomly assigned as control groups. The restorations were produced with Super Porcelain EX-3 and Vitadur Alpha ceramics and luted according to manufacturers' instructions. The specimens were subjected to compressive axial loading in a universal testing machine at 0.5 mm/minute using two steel balls (3 and 10 mm in diameter), evaluating a total of 14 groups with 10 specimens each. Peak load to fracture was measured for each specimen. The results were submitted to analysis of variance and Tukey's test. Statistical analysis revealed that the inlays showed a significantly higher fracture resistance than both onlay designs, but with fracture resistance lower than that of intact teeth. Onlay fracture strength was equivalent for both designs. The force required to cause fracture with the 10-mm diameter ball was greater than with the 3-mm diameter ball. There were no differences between the tested ceramics.

Clinical RelevanceOne of the advantages reported for indirect composite restorations is the reduction of polymerization shrinkage, which could produce better marginal sealing. Although sealing of cervical enamel margins was slightly better for the indirect systems used, no difference between indirect and direct restorations was found for cervical margins in cementum/dentin. SUMMARYThis study compared microleakage between indirect composite inlays and direct composite restorations. Forty-eight standard inlay MOD cavities, with cervical margins located either in enamel or dentin, were prepared in extracted human third molars. The specimens were randomly divided into 3 groups (n=16). In the control group, the cavities were restored with the composite Filtek Z250 (3M ESPE). For the experimental groups, indirect restorations were made with the Artglass (Heraeus-Kulzer) or Belleglass HP (Kerr Laboratories) systems and cemented with the dual curing cement RelyX ARC (3M ESPE). The adhesive system Single Bond (3M ESPE) was applied on all groups. The specimens were submitted to thermolcycling, coated with nail varnish, then immersed in 2% basic fuchsine aqueous solution for 24 hours. The teeth were then sectioned and leakage scores were evaluated (40x), based on a standard ranking. Data were submitted to statistical analysis (Mann-Whitney and Kruskal-Wallis tests) with a 95% confidence level. No statistical difference was found between substrates (p=0.595), and the materials performed similarly in dentin (p=0.482). Direct restorations showed higher leakage than indirect restorations at the enamel margins (p=0.004). Within the limitations of this experimental design, overall leakage was similar between both substrates, while the indirect systems provided a better sealing than direct composites only in enamel.

No abstract

The three resin cements had different mechanical properties. A higher flexural modulus usually resulted in improved resistance to fracture for the ceramically restored teeth.