Efeito da manipulação de cimentos de ionômero de vidro convencionais na microinfiltração de restaurações de classe ii em molares decíduos

Abstract

The present study was developed aiming to assess the effect of manipulation process of conventional glass ionomer cements GIC - on microleakage at the gingival margin of class II restorations, in primary molars, in vitro. Forty clinically sound primary molars were selected and stored in distilled water during the intermediary phases of theexperiment. Mesial and distal class II cavities were prepared in each tooth. The dimensions of the cavities were standardized by the diameter of the diamond bur and the gingival wall located 1 mm above the amelocemental junction. Two conventional restorative glass ionomer cements that presented both versions, in bottle and encapsulated, with the same name were chosen for evaluation. Through simpledrawing, 20 teeth were filled with encapsulated GIC: mesial cavities with Vidrion R Caps® (SS White) and distal cavities with GC Fuji IX GP FAST® (GC Corporation). The other 20 teeth were filled with GIC available in bottle: mesial cavities with Vidrion R® (SS White) and distal cavities with GC Fuji IX® (GC Corporation). All filling procedures were performed by one operator, according to the manufacturers instructions, at 41,4º+/- 2ºF. The specimens were, afterwards, made waterproof (in the pulp chamber with epoxy resin and in the other surfaces with two coats of cosmetic enamel, except for the interface ionomer/enamel along the gingival floor) and then, immersed in 0,5% methylene blue solution, pH 7,2, at 66,6ºF, during four hours. After the teeth had beenmesio-distally sectioned, microleakage was assessed by three calibrated examiners in an optical microscope with 30 times magnification, and scores ranging from 0-3 were used. The data were submitted to the statistical tests of Kruskall-Wallis and of Mann-Whitney. Although GIC present adhesion to tooth structure, coefficient of thermal expansion similar to the tooth and lower set contraction, in this research high indexes of gingival microleakage were obtained for all assessed GIC, with 68% of the total samples showing the maximum score (degree 3), 22% showing some infiltration (scores 1 and 2) and only 10% of the samples being free of microleakage. Highlysignificant difference was observed (p=0,000) between the values of gingival microleakage obtained for manually and mechanically manipulated GIC. The use of encapsulation for GIC and its manipulation in a mechanic shredder decreased the microleakage statistically, regardless of the material used. This result has beenanticipated since an improvement in the properties of the GIC has been observed when it is mechanically manipulated. When comparing two GIC of different brands, within each manipulation process, better results were anticipated for Fuji IX® since superior Summary properties are attributed to it. However, Vidrion R® presented lower scores of gingivalmicroleakage, although that difference had only been statistically significant (p=0,000) when the materials were mechanically manipulated