Inhibition of demineralization adjacent to tooth-colored restorations in primary teeth after 2 in vitro challenges

As clinical diagnosis of secondary caries is the most common reason for restoration replacement, fluoride-releasing restorative materials have been developed to address this problem. The purposes of this study were to verify demineralization inhibition produced by 5 restorative materials submitted to two methods of in vitro cariogenic challenge and verify whether these methods influence material behavior by means of polarized light microscopy and microhardness.

Class V cavities were prepared on buccal surfaces of 100 extracted primary molars and randomly restored with 1 of the 4 fluoride-releasing materials, Fuji IX, Vitremer, Dyract, Tetric Ceram, and Filtek Z250 as control material (N=10). Specimens were submitted to in vitro caries induction by two different methods, acid gel immersion, and pH cycling. Teeth submitted to gel were then sectioned and prepared for polarized light microscopy in water, while teeth cycled were prepared for microhardness evaluation.

Polarized light microscopy: Means of demineralization areas (microm(2)) differed significantly, depending on the restorative material. Tukey's test revealed the smallest demineralization areas adjacent to Fuji IX and Vitremer restorations, with no difference between them (P>.05). The greatest demineralization area mean values were verified using Dyract and Filtek Z250, without differences between them (P>.05). Microhardness: Glass ionomer cements (GICs) performed better on the area of great cariogenic challenge, closer to the surface, than other materials indicating minor mineral loss during pH cycling. The compomer Dyract presented similar performance to GICs and composite resin Tetric Ceram, but it was better than Filtek Z250.

The experimental model of caries lesion induction may influence material performance. GICs, however, are superior in preventing in vitro demineralization independently of the method.