Effects of two matrix systems on the polymerization of composites

Aim: The aim of this in vitro study was to examine the surface microhardness of composite resins when placed in class II cavities with two different matrix systems. Material Methods: A hybrid composite (Tetric Ceram-Ivoclar Vivadent), two nanohybrid composites (Grandio- Voco, Synergy D6-Coltène/Whaledent) and a nanofil composite (Filtek Supreme XT-3M Espe) were placed in slot class II cavities in silicon molar teeth (n=80). The cavity was prepared in plastic teeth (4mm bucco-lingual x 4 mm depth x 3mm mesio-distal)( KaVo,EWL model). Cavosurface margins were not beveled. The impressions of the tooth with the cavity preparation were taken using polyvinyl siloxan(Speedy/PuttyLigth-Coltene). A silicon material (AffinisPrecious-Coltène) was injected in the impressions and a silicon mold of the teeth and the cavity were obtained. The prepared silicon teeth were mounted in plastic jaw (KaVo,EWL model) to simulate proximal contact. Metal sectional matrix (Quickmat-Polydentia) (n=40) and clear matrix system (Lucifix-HaweNeos) (n=40) were prepared for each tooth. Wedges were used to stabilize the matrix. The cavities were restored incrementally in oblique layers with all four restorative materials. And each increment was light cured for 40 s (Celalux-Voco). The restorations were then removed from the cavities and surface hardness of the proximal and axio-pulpal surfaces were immediatly measured with Microhardness Vickers Test device (Clemex CMT 7, Clemex Labs.).Data were statistically analyzed with one way ANOVA and Tukey's Multiple Comprassion test. Results: No significant differences were found between metal matrix and clear matrix (p>0.05). Microhardness of axio-pulpal surfaces were found significantly lower than proximal surfaces microhardness (p<0.05) for each restorative materials. Conclusion: Metal or clear matrix systems could be used in slot class II cavities in regard the surface microhardness of composite resins.