Comparison on polymerization of bulk-fill composite resins in different marginal thickness of tunnel restoration

Abstract

Bulk-fill composite resins (BCR) was introduced with the advantage of 4-5mm depth of cured, thus an applicable material for a tunnel restoration. The study aimed to assess the polymerization of BCR with different marginal ridge thickness in tunnel restoration technique. Fifteen extracted teeth categorized into; G1=conventional proximal restoration (n:5), G2=tunnel 1.5mm marginal ridge thickness (n:5) and G3=tunnel 3.0mm marginal ridge thickness (n:5). Samples received the designated cavity preparation design and restored with BCR, embedded in resin and sectioned into halves. Each sample was tested with Vickers micro-hardness at the top (TP), middle (MP) and bottom part (BP) to get the micro-hardness value (VH). Data were statistically analyzed with 1-way ANOVA to compare means between groups and repeated measured ANOVA to compare means between the different areas. The mean micro-hardness (VH) value for top part (TP) G1=79.1, G2=77.3 and G3=74.9.; middle part (MP) G1=79.0, G2=73.3 and G3=74.9 and bottom part (BP) G1=71.1, G2=64.4 and G3=62.7. A decrease pattern of VH noted TP>MP>BP. No significant difference (p>0.05) VH for all groups for TP. For MP, significant difference (p<0.05) noted among the 3 groups and for BP, significant differences (p<0.05) between G1 to G2 and G3 only. In the same group, no statistical mean differences (p>0.05) were noted in Group 1 for all three parts of the tested restoration (TP, MP and BP). However, for Group 2 and Group 3, statistical mean differences (p<0.05) were reported between TP and BP, and between MP and BP. The thickness of marginal ridge in tunnel technique did affect the polymerization of BCR within the recommended depth, however the VHR of >80% in all areas indicate the material did receive adequate polymerization from light irradiation and clinically acceptable to be used.