| Research Abstract |
We have previously reported that the insertion of Beta Quartz Glass Ceramic inserts into a composite resin greatly reduced the polymerization shrinkage and the coefficient of thermal expansion in vitro. But, The megafiller has to be inserted completely inside the composite resin to avoid exposing megafiller on the surface of the restoration clinically. The purpose of this study was to determine the coefficient of thermal expansion of three different types of composite resins inserted with the spherical ceramic megaffiler (φ1 mm) of alumina or zirconia ceramics using a thermomechanical analyzer (Thermofirex, Rigaku Co.). Three cylindrical specimen (φ4 mm×10 mm) of each of the composite resins were prepared. The composite resins used in this study were Clearfil AP-P as highly loaded type composite, Palfique Estelite as submicrofilled composite and Heliomolar Rediopaque as microfilled composite. The specimen was kept in 37℃ water for 48 hours and dried in oven at 37℃. Once, the specimen g
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radually heated up to 90℃ and gradually cooled down to 20℃. Again, the specimen uniformly raised up to 90℃ in the thermomechanical analyzer. The coefficient of thermal expansion was measured at the range of 35℃〜80℃ with a straight line. Results are as follows. Clearfil AP-X with 10% alumina showed 25.3×10, 30% alumina was 23.3.×10, 50%-22.4×10, whereas 0% showed 36.7×10. Palfique Estelite with 10% alumina showed 54.8, 30%-49.2, 50%-43.4, whereas 0% showed 64.2. Heliomolar Radiopaque with 10% alumina showed 73.8, 30%-66.2, 50%-62.2, whereas 0% showed 76.0. Clearfil AP-X with 0% zirconia showed 36.7, 10%-57.3, 30%-43.0, 50%-33.4. Heliomolar Radiopaque with 0% zirconia showed 76.0, 10%-67.5, 30%-58.1, 50%-47.1. The coefficient of thermal expansion reduced as increasing amount of spherical ceramic megafillers, and zirconia ceramics was more effective than alumina ceramics. Surface gloss was measured using a gloss meter (VG-2000, Nippon Denshoku Co.). Surface gloss measurement was undertaken with 60 of the angle of incidence and 60 of the acceptance. Surface gloss of the composites were given as same as the gloss of composites without megafillers. When we applied clinically, we have no problem on the cavity deeper more than 1.5 mm. The cavity floor was laid thinner with composite resin paste beforehand. Several particles of megafillers sticked once at the tip of filling instrument inserted into the composite resin without use of tweezers. Megafillers treated with silance coupling agent well bonded to composite. It was concluded that the reinforced composite restoration by inserting with spherical ceramic magafillers was very useful clinically. Less
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