The objective of this study was to construct three-dimensional (3D) images of premolars to measure the length, surface area and volume of crown and root and to analyze the mathematical relation among crown-to-root ratios in terms of length, surface area and volume. Twenty-five premolars were scanned using micro-computed tomography (micro CT) in vitro to build 3D models. The long axis and enamelo-cemental junction of each tooth were determined with the help of Geomagic Studio software, and the length, surface and volume of crown and root were measured. The crown-to-root ratios in terms of length, surface and volume were calculated and the relationship among length, surface area and volume of crown and root as well their ratios were analyzed using SPSS software. The interrelationship among crown length (x), surface area (y) and volume (z) could be expressed as z= -808.2 0+ 124.80x +3.35y -5.59x2- 0.14xy+3.47y 2*10-4 (R2 = 0.99) and that of root length (x ), surface area (y ) and volume (z ), as z = -207.50 +13.87x +1.75y + 5.03x 2*10-2-8.05x y *10-2+ 2.58*10-3y 2 (R2 = 0.93) . The correlation among crown-to-root ratio in length(x ), crown-to-root ratio in surface area (y ) and crown-to-root ratio in volume (z ) could be expressed in z = -4.48*10-2 -1.25x *10-2+1.20y + 3.29x22-5.05x y + 2.00y 2 (R2 = 0.96). The length, surface area and volume of crown and root of premolars share a close relationship, while, a definite mathematical relation could be observed amongst their ratios. Crown to root ratio in terms of length, surface and volume, may provide a novel multi-criterion method for evaluating tooth function.
KEY WORDS: Bicuspid; Tooth crown; Tooth root.
LIU, L.; LI, H.; ZHAO, T.; GAO, Y.; GUO, J.; WANG, X. & LI, X. Crown-to-root ratios in terms of length, surface area and volume: A pilot study of premolars. Int. J. Morphol., 34(2):465-470, 2016.
