Microleakage in class V composite resin restorations treated with CO2 laser: an in-vitro study

摘要

Various materials and techniques have been investigated in order to minimize or eliminate microleakage in composite restorations. The CO$-2$/ laser (10.6 micrometer) removes the smear layer and creates an irregular surface able to promote micromechanical retention for adhesive restorative materials. Forty Class V cavities were performed with high-speed drill in 20 extracted human molar and randomly divided into 4 different groups: Group 1 -CO$-2$/ laser (3 W, 2 Hz, 50 ms) and after 37% phosphoric acid etching on dentin and enamel surface; Group 2 - 37% phosphoric acid etching and after CO$-2$/ laser; Group 3 -CO$-2$/ laser; Group 4 - 37% phosphoric acid etching. The cavity restored with composite resin (Z-100) and thermally stressed (700 cycles, 5 - 55 degree Celsius). After the samples were impermeabilized, immersed in 50% silver nitrate solution for 8 hours and sectioned with Isomet saw. The teeth were exposed to Photoflood light (G.E.) for 5 minutes to reveal the dye. Leakage was observed under stereomicroscope and evaluated with scores. Results were analyzed with ANOVA (p greater than 1%) and Tukey's test (p equals 5%) and showed significant lower microleakage in the group treated only with CO$-2$/ laser and phosphoric acid etching alone (group 3 and 4) than groups treated with phosphoric acid and CO$-2$/ laser together (group 1 and 2).