Detection of incipient caries on crown margins

Patients with numerous crowns and bridges are at risk of developing secondary decay. Caries usually occurs cervically, is a frequent cause of failure in fixed prosthodontics and accounts for nearly 60% of the reasons for the replacement of restorations. Early detection and treatment of these lesions is important to prevent cavitation. In a study by Coogan et al (Caries Research, 1995, 29, 295) an alginate impression material was used to isolate cariogenic bacteria from teeth with established carious lesions. Objectives: This impression technique was used to investigate the early colonization of the cervical margins of crowns and teeth in caries prone patients and caries free subjects. Methods: Twenty caries free subjects and 20 caries prone patients with at least 10 crowns and bridges were studied. The DMFS was measured. Impressions were taken of the teeth using hydrocolloid impression material mixed with culture broth, incubated and examined for S. mutans and Lactobacilli colonies in the cervical areas. The results were compared using a chi-squared test. Results: The mean DMFS of the caries prone patients was 129 and the caries free subjects 16. S. mutans and Lactobacilli were cultured in higher numbers from the margins of the teeth in the caries prone patients than caries free subjects (p < 0.001). Fifty four percent of the anterior teeth and 82% of the posterior teeth were restored in the caries prone patients. This difference was significant(p=0.002). Furthermore S. mutans and Lactobacilli were isolated in significantly higher numbers from the margins of posterior than anterior teeth in these patients (p = 0.016 and 0.047 respectively). Conclusion: The impression technique shows that S. mutans and Lactobacilli accumulate on the posterior cervical margins especially in patients with prosthodontic restorations which suggest these sites may have incipient caries and could be at risk of developing secondary decay.