SILVA, Maria Goreti da; PRATES, Luiz Henrique Maykot    CHAIN, Marcelo Carvalho. Fracture resistance of teeth with MOD restorations: effect of the resin matrix and the photoactivation method.. Arq. Odontol. []. 2013, 49, 4, pp. 162-168. ISSN 1516-0939.

Aim: To evaluate the effect of two composite resins of different polymeric matrices and the photoactivation technique as regards fracture resistance by, compression of maxillary pre-molars with Class II restorations. Materials and Methods: MOD cavities were prepared in 56 premolars, simulating endodontic treatments. The teeth were divided into four groups (n=14): G1: conventional photoactivation, restoration with Filtek Z350XT (3M ESPE) and adhesive Adper Single Bond 2 (3M ESPE); G2: Pulse delay photoactivation, restoration with Filtek Z350XT and adhesive Adper Single Bond 2; G3: conventional photoactivation, restoration with Filtek P90 (3M ESPE) and self-adhesion of Filtek P90 (3M ESPE); and G4: pulse delay photoactivation, restoration with Filtek P90 and self-adhesion of Filtek P90. In G1 and G3 (conventional photoactivation), the composite resin was applied at 2 mm increments, each of which was light cured for 40 seconds, using a LED unit, at an intensity of 500 mw/cm2, measured with a radiometer (Demetron). In G2 and G4 (pulse delay photoactivation), the composite resin was also applied at 2 mm increments; however, each increment was initially photoactivated for 5 seconds at 300 mw/cm2. After a period of 5 minutes, a new photoactivation was performed for 40 seconds at an intensity of 500 mw/cm2. The photoactivation was repeated for each increment. After 24 hours, the specimens were polished and tested for compression, with cylindrical/round active tip (Instron - 0.5 mm/ min). The ANOVA 2 and Tukey tests were used for statistical analyses (p > 0.05). Results: Mean values (Newtons) were as follows: G1: 1157.98 (±444.62); G2: 1404.14 (±391.82); G3: 1255.30 (±422.34); and G4: 1213.76 (±419.95). The resistance to fracture by compression of the pre-molars with MOD restorations proved to be statistically similar in the four evaluated groups. Conclusion: No significant differences could be observed regarding the two composite resins with different polymeric matrices and the different photoactivation methods.

: Resinas compostas.; Força compressiva.; Polimerização.; Composite resins.; Compression strength.; Polymerization..