Flexural strength of parckable composites: influence of materials and packng force

This study evaluated the influence of packing forces on the flexural strength of three packable and one hybrid composite. A metallic stardard mold was used to prepare 12 specimens from each packable composite (ALERT, Solitaire and Surefil) and a hybrid composite (Filtek Z250), divided in two packing forces (7.4 N and 17.2 N). The specimens were light cured for 40 seconds, being immersed in distilled water for seven days. Flexural strength was measured on a testing machine; at a crosshead speed of 0.5 mm/minutes. Data were analyzed using parametric statistical tests. Materials exhibited statistically significant differences (p<0.05): Surefil = Filtek Z250 > ALERT > Solitaire. No statistical differences in flexural strength were found between the packing forces and the interaction. It was conclued that packing forces do not affect flexural strength of tested composites, and packable composites had similar or lower flexural strength than a hybrid composite.

Cervical microleakage in MOD restorations: in vitro comparison of indirect and direct composite.

This 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.

Flexural strength and modulus of elasticity of indirect composite resins

This study aimed to evaluate the flexural strength and elastic modulus of indirect composite resins compared with direct composite resin. Two indirect composite resins (Artglass, AR and Belle Glass HP, BE) and one direct composite resin (Filtek™ Z250, Z2) were tested. Fifteen standard specimens (25x2x2mm) were prepared for each material. Z2 was polymerized using a XL 3000 light curing unit with energy higher than 450 mW/cm² for 40 seconds. The AR was photopolymerized with intense pulsed visible ligth during 180 seconds, at 520 nm/20 Hz. BE was photopolymerized during 60 seconds at 500 nm and post-cured at 138°C, under pressure, in a nitrogen atmosphere for 20 minutes. The specimens were stored in distilled water at 37°C for seven days and, then, subjected to FS and EM tests, using a universal testing machine. One-way analysis of variance and Tukey's test were used. The mean flexural values (MPa) were: AR = 126.8 ± 16.8; BE = 145.2 ± 14.3; Z2 = 140.0, without significant differences (p>0.05). Significant differences (p<0.01) were observed regarding elastic modulus, as follow: BE (15.1 ± 1.7) > Z2 (9.6 ± 1.5) > AR (7.5 ± 1.0). Within the limitations of the study, it was concluded that significant differences were only observed for elastic modulus, with the direct material exhibiting lower values.