A new in vitro model to study the relationship of gap size and secondary caries

Objectives: To investigate the relationship of gap size and secondary caries in a newly developed secondary caries microbial model that permits adjustment of the gap between the tooth and a restoration. Methods: Tooth-resin-matrix composite specimens were mounted on gap-model stages with a gap size of 50 or 500 mu m in experiment 1, and 0, 25, 250, or 1,000 mu m in experiment 2. They were attached to plastic Petri plates, gas-sterilized and then incubated in a microbial caries model ( with Streptococcus mutans TH16 in 1% sucrose tryptic soy broth for 1 h, 4 times/day, and with a buffer solution for the rest of the day). After 8 days of incubation, tooth specimens were sectioned and stained overnight with a rhodamine B solution. Digital images taken under a confocal microscope were analyzed for lesion size at the outer surface lesion and wall lesion (WL). Results: Gap size was found to affect the development of dentin WL area in experiment 1 and enamel and dentin WL areas in experiment 2, with bigger lesions being observed in the wider gap group (p < 0.05). Conclusion: The findings of this study suggest that the size of the gap between tooth and restoration affects the development of secondary caries along the cavity wall. Copyright (c) 2007 S. Karger AG, Basel.