The association between clinical and radiographic findings in carious primary molar teeth

AIM This project undertook two cross-sectional studies involving the primary dentition. The aim was: Study A: to characterise the relationship between the radiographic appearance of early approximal carious lesions and cavitation threshold in primary molar teeth. Study B: to correlate the radiographic and histological measurements of the Remaining Dentine Thickness (RDT) beneath deep caries lesions in primary molar teeth. MATERIALS AND METHODS Patients requiring extraction under general anaesthesia at the Leeds Dental Institute were asked to participate in the study. For Study A, teeth were examined visually (both in-vivo and in-vitro) for presence/absence of cavitation and radiographically according to two radiographic criteria (i) ICDAS radiographic scoring system and (ii) the extent of the lesion as < or > 0.5mm from the enamel-dentine junction (EDJ) into dentine. For Study B, RDT was measured radiographically and histologically (in mm). RESULTS For Study A, 72 primary molars with approximal carious lesions extending radiographically into enamel, outer and inner dentine were included. Teeth showed a mixture of first and second primary molars (30 and 42 respectively), maxillary and mandibular teeth (36 teeth each), and mesial and distal lesions (34 and 38 respectively). Regarding radiographic ICDAS, no cavitation was associated with score 0 and 1. For score 2, 3 and 4, cavitation was reported in 11%, 45% and 86% of the cases respectively. According to the radiographic extension from EDJ, there was a statistically significant increase (p<0.05, chi-square) in the probability of cavitation (92%) with the radiographic lesions extended >0.5mm beyond the EDJ compared to the lesions extended < 0.5mm (29%). For study B, 50 primary molars were collected. Teeth showed a mixture of 21 first and 29 second primary molars of which 23 were maxillary and 27 were mandibular teeth with approximal and occlusal lesions (28 and 22 respectively). Radiographic RDT overestimated the histologic RDT by approximately 0.4 (0.2) mm. The overestimation was consistent across all primary molars and both proximal and occlusal lesions. CONCLUSION This study has given an additional insight into the radiographic interpretation in the primary dentition. It identified noticeable increase in the probability of cavitation when carious lesions extend >0.5mm beyond EDJ. In addition, it showed that digital bitewing radiographs overestimate the remaining dentine thickness in carious primary molars. These are significant findings when considering different treatment options for both early and deep carious lesions in primary molars.