A Pilot Study on Developing Quantitative Indices for Age-Related Changes in Maxillary Primary Molar Root Canal Morphology

Abstract Objectives To elucidate age-related changes in the root canal morphology of primary molars and determine new indices to detail the root canal anatomy by cone-beam computed tomography (CBCT).Materials and Methods CBCT data of primary molars from 57 children aged 3–8 years without systemic diseases that affect tooth development were collected. The following indices were defined and calculated using Mimics 17.0, 3-Matic 9.0, and ImageJ software: (i) the cross-sectional area of the root canal; (ii) R.15: the proportion of the lateral canal wall with an inner diameter less than 0.15 mm; (iii) LC/LR: the ratio between the canal length and root length; and (iv) Ndis: the discontinuous canal count. Correlation analysis and binary logistic regression were performed to assess the variants and age-related changes in canal morphology.Results On CBCT analysis, the cross-sectional area of the root canals for mesiobuccal (MB) roots, palatal (P) roots and distobuccal (DB) roots was negatively correlated with age (P<0.05), with a correlation coefficient of -0.41, -0.42, and -0.26, respectively. The R.15 of MB roots was positively correlated with age (P<0.05, rs=0.39). The value of LC/LR for MB, DB, and P roots decreased with age, with a correlation coefficient of -0.39, -0.42, and -0.29, respectively (P<0.05). The risk of discontinuous canals (Ndis) for MB, DB, and P roots increased with age (P<0.05), with an odds ratio of 1.61, 1.48, and 1.60 respectively.Conclusions The new indices developed in the study based on CBCT successfully demonstrate age-related changes in the root canals of primary molars.