Approximal secondary caries lesion progression, a 20-week in situ study.

There is no consensus about the definition and progression of outer and wall lesions in secondary caries. In this study we investigated whether lesion progression is influenced by an adjacent composite restoration and whether wall lesions develop at the composite-tooth interface. In order to study the appearance and progression of approximal primary caries lesions and lesions next to composite restorations, 16 samples were placed in a full denture of each of 8 subjects. Each denture housed 4 restored and 4 unrestored enamel samples and similarly 8 dentin samples. All samples were distributed over 2 sample holders, in each of which 4 approximal spaces were simulated. Every 4 weeks the sample holders were microradiographed using transversal wavelength independent microradiography and lesion depth was measured. At the end of the study, after 20 weeks, the lesion depth of the outer lesions was 0-350 microm for enamel and 0-750 microm for dentin. The estimated difference in progression between secondary and primary lesions (1.1 microm/4 weeks, 95% CI: -9.2 to 11.4 microm) was not statistically significant (p = 0.83). Secondary outer lesions appeared and progressed as primary caries lesions. No clear wall lesions were found next to composite, but they were observed next to acrylic resin.