Using of low modulus of elasticity base in high c-factor resin composite restoration: an in vitro study

Abstract

This in vitro study aims to investigate whether or not using a resin modified glass ionomer as a base or intermediate layer would improve marginal integrity of a high C-factor class V resin composite restoration. Eighty non-carious human third molars were used. A box-shaped, 5x3x2.5 mm3, Class V cavity preparation was placed on buccal surface at the cementoenamel junction. Teeth were then randomly assigned to 8 experimental groups (n=10): group 1, Resin composite (FiltekTM Z350 XT); group 2, FiltekTM Bulkfill; groups 3 and 4, resin composite with FiltekTM Z350 XT Flowable as base; groups 5 and 6, resin composite with Fuji II LC as base; groups 7 and 8, resin composite with Fuji II LC as base with use of Cavity Conditioner. In groups 1 – 4 the prepared cavities were etched, with selective enamel etching, and the adhesive (Scothbond Universal, 3M ESPE, USA) were then applied according to manufacturer's instructions, then restored with resin composite (FiltekTM Z350 XT, 3M ESPE, USA) while in groups 5 – 8 the same bonding procedures were done after placement of RMGI base. The restorations were finished and polished, thermocycled (10,000×, 5-55°C) and stained with a 50% silver nitrate solution. After being sectioned bucco-lingually, 6 surfaces of measurement per tooth were obtained, and depth of dye penetration recorded. Microleakage data were analyzed using Kruskal-Wallis non-paramatric independent analysis and a Mann-Whitney U test. Kruskal-Wallis test indicated significant differences among 8 experimental groups for gingival (P < 0.001) scores. For Mann-Whitney U test, significant difference was found between group using low modulus of elasticity base and group without using low modulus of elasticity base only gingival margin (P < 0.001). Mann-Whitney U test also revealed significant difference between group using dentin conditioner and group without uses of dentin conditioner at gingival margin. In conclusion, based on our findings, the use of low modulus of elasticity materials does not result in better marginal seal for high C-factor Class V resin composite. The use of dentin conditioner may improve marginal integrity for resin composite restoration when RMGI is used as base.