Objectives: The assessment of bitewing radiographs requires knowledge of radiographic anatomy and pathology, and the comprehension of possible effects of superposition which may lead to false positive diagnoses. Based on a clinical case report in which non-carious radiolucencies were discovered on the mesial surfaces of upper molars, this phenomenon, which has not been reported before, was explained. Due to the anatomical characteristics of the rhombic tooth, in particular the crown's receding mesial surface from the mesiobuccal towards the distopalatal side, which is combined with an often prominent palatal cusp and a smaller mesiodistal diameter at the cervical neck, radiolucencies - normally typical caries indicators - can sometimes be observed on the mesial surfaces of upper primary and first permanent molars on bitewings. These triangular-shaped radiolucencies (TSRs) can therefore be attributed to the effects of superposition. The aim of the present epidemiological study was to assess the radiographic frequency of TSRs.
Methods: As part of a clinical-radiographic follow-up examination involving 11-12 year old children (n = 113), both the caries status (World Health Organization (WHO) standard) and the frequency of TSRs were recorded.
Results: TSRs were most frequently present on upper second primary molars (60.3%). 35.5% of the upper first primary molars and 24.8% of the upper first permanent molars displayed TSRs. However, none of the lower primary and/or permanent molars displayed this phenomenon.
Conclusion: In the mesial surface of upper primary and permanent molars where the frequency of TSRs was fairly high, it may be essential to distinguish this change from approximal caries.