Approximal morphology as predictor of approximal caries in primary molar teeth.

Objective: To evaluate the predictive power of the morphology of the distal surface on 1st and mesial surface on 2nd primary molar teeth on caries development in young children.

Sample And Methods: Out of 101 3-to 4-year-old children from an on-going study, 62 children, for whom parents' informed consent was given, participated. Upper and lower molar teeth of one randomly selected side received a 2-day temporarily separation. Bitewing radiographs and silicone impressions of interproximal area (IPA) were obtained. One-year procedures were repeated in 52 children (84%). The morphology of the distal surfaces of the first molar teeth and the mesial surfaces on the second molar teeth (n=208) was scored from the occlusal aspect on images from the baseline resin models resulting in four IPA variants: concave-concave; concave-convex; convex-concave, and convex-convex. Approximal caries on the surface in question was radiographically assessed as absent/present.

Results: Of the 52 children examined at follow-up, 31 children (60%) had 1-4 concave surfaces. In total 53 (25%) of the 208 surfaces were concave. A total of 22 children (43%) had 1-4 approximal lesions adding up to 59 lesions. Multiple logistic regression analyses disclosed that gender, surface morphology on one of the approximal surfaces (focus-surface), and adjacent-surface morphology were significantly related to caries development (p values ≤ 0.03). The odds ratio for developing caries in the focus-surface/adjacent-surface in the four IPA variants were convex-convex, 1.0; convex-concave, 5.5 (CI 2.0-14.7); concave-convex, 12.9 (CI 4.1-40.3); and concave-concave, 15.7 (CI 5.1-48.3).

Conclusion: Morphology of approximal surfaces in primary molar teeth, in particular both surfaces being concave, significantly influences the risk of developing caries.

Clinical Relevance: The concave morphology of approximal surfaces can predict future caries lesions supporting specific home-care and in-office preventive strategies.