Three-dimensional characterization of naturally developed early caries lesions using high-resolution micro-computed tomography.

Objectives: The goal of this micro-Computed-Tomography (μCT) study was to characterize the structural parameters of natural, early proximal enamel caries lesions and correlate them with two-dimensional radiographic findings.

Methods: Extracted human premolar teeth with ICDAS score 2 proximal lesions were examined using visual-tactile, μCT and simulated bitewing radiographs (BTX). Sound enamel and caries-lesions' structural and mineral density (MD) parameters were analyzed which included surface layer (SL) status and thickness, depth of lesion, and MD.

Results: Thirty-six extracted premolars with 54 proximal early enamel caries lesions were analyzed. Lesions varied notably in lesion depth and MD. SL thickness ranged between 20 and 139μm. Three teeth (5.6%) had micro-cavitations upon the μCT examination despite being "clinically" non-cavitated. Cavitation status had no significant association with μCT nor BTX radiographic depth. Depth of lesions correlated weakly but statistically significantly with mineral loss (ML) at body of lesion (r=0.301, p=0.027). SL thickness also correlated negatively with ML at SL (r=-0.501, p<0.001).

Conclusions: Early proximal enamel lesions with ICDAS 2 score as determined by visual-tactile examination exhibited a wide range of lesion parameters and cavitation status when examined by μCT. Visual-tactile examination may fail to detect micro-cavitations in enamel surface that are detectable by μCT.

Clinical Significance: Clinicians have direct access to early proximal enamel lesions during orthodontic separation, exfoliation, extraction or restoration of adjacent teeth. This study invites the clinician to consider more decisive management options in high risk individuals (e.g. micro-invasive techniques), given the finding of vast structural variability of such lesions.