Measurement of root surface area of permanent teeth in a Chinese population

Objectives: The aim of this study was to investigate the relation between the remaining area of periodontal attachment and the attachment levels for each type of permanent teeth in a Chinese population by using micro computed tomography (micro-CT) scans. Design: A total of 440 extracted permanent teeth (including each tooth type except for the third molars) were collected from a Chinese population and scanned using a micro-CT. The CT data were input into Mimics 15.01 to generate 3D tooth models. To simulate various attachment levels, the roots were virtually cut at 0, 2, 4, 6, 8, and 10 mm from the cemonto-enamel junction (CEJ). The net and percent remaining root surface area (RSA) were measured and calculated, and the data corresponding to attachment level were fitted to a linear function. Results: A Linear function can perfectly fit in relating the simulated attachment level to the net and percent remaining RSA (R-2 > 0.99, and p < 0.001 for each tooth type). For net remaining RSA, the slope of the linear function was steepest for maxillary first molars (b(1) = -39.32) and least steep for mandibular central incisor (b(1) = -13.08); whereas for the percentage of remaining RSA, the slopes (b(1)) were relatively within a narrow range, from -7.40 (maxillary canine) to -9.64 (maxillary first molars). Conclusion: Micro-CT offers simple and precise technique for quantitative analysis of the RSA. The total amount and vertical distribution of the RSA varied by tooth type. Linear formulas can perfectly describe the relation between the attachment level and the net and percent remaining RSA.