OBJECTIVES: We aimed to determine the relation between the radiographical depth of approximal lesions and the presence of bacteria in the dentine in posterior teeth in both dentitions.

MATERIAL AND METHODS: Sample 1 consisted of 34 approximal lesions in primary molars in children aged 5-7 years old. Sample 2 consisted of 48 approximal lesions in molars and premolars in adult patients aged 18-67 years old. All lesions were in need of restorative treatment according to the dentists. During the operative interventions dentine biopsies were collected with a sterile bur just pulpally of the enamel-dentin junction. Two authors evaluated the presence/absence of bacterial colonies. The lesions depth on bitewing radiographs (RSCORING) were assessed independently by two examiners twice using the ICCMS classification system: RI=initial-; RM=moderate-; RE=extensive caries.

RESULTS: In sample 1, the RSCORING was distributed as follows: RI=15; RM=12; RE = 7. In 9 cases the lesions were clinically cavitated. Bacteria were visible on the agar plates in one case (7%) of the RI lesion, 86% of the RM lesions and in all the RE lesions, (p < .001). In sample 2, RSCORING was distributed as follows RI=14; RM=23; RE=9. In 15 cases, the lesions were clinically cavitated. In 2 cases (14%), there were visible bacteria on the agar plates among the RI lesions, while this was the case in 86% of RM lesions and in 100% of RE lesions (p < .001).

CONCLUSIONS: RM and RE lesions seem to harbor bacteria in the dentine and are candidates for invasive treatment. In contrast, RI lesions should in general be managed non-invasively.