Novel Biometric Guide to Position Artificial Teeth in Prosthodontics

Objective: To investigate the three dimensional (3D) relationship between intra-oral anatomical landmarks and the position of maxillary anterior teeth in dentate subjects. Method: Maxillary casts of 70 Malaysian adults (19-32 years) with well aligned teeth in Class-I dental relationship with no or minimal teeth attrition were studied. They were digitally scanned (Maestro 3D dental-scanner) to produce 3D dental images. The images were then downloaded to a 3D image analysis programme (Vectra-3D, Canfield Scientific Inc.) to be measured. Intra-oral landmarks studied on the images were the left and right hamular notches (LHN, RHN), incisive papilla (IP), the mid-point of third rugae lines (R), midpoints  of the incisal-edges of the left central and lateral incisors (LCI, LLI), right ones (RCI, RLI) and tips of  left and right canines (LC, RC) . The 3D images were geometrically standardized in the Cartesian system before collecting the 3D coordinates. The palatal vault measurements: IP-R, RHN-R, LHN-R, the depth of R from IP-LHN-RHN plane (HT) and the 6 anterior teeth positions in relation to R: LC-R, LLI-R, LCI-R, RCI-R, RLI-R, RC-R were calculated by coordinates in Microsoft excel 2013. Multivariate linear regression analysis was performed to predict each anterior tooth position based on the palatal vault dimensions IP-R, HT, LHN-R and RHN-R. The coefficient of determination R² and the significance of the relationship were tested at 5% level of significance. Result: Six regression equations showed statistically significant strong relationships between each anterior tooth position and palatal vault measurements. R² values were 0.9849, 0.9768, 0.9888, 0.99741, 0.9995, and 0.9918 for left canine to right canine positions respectively (p <0.001). Conclusion: The regression models revealed strong relationship between the intra-oral landmark measurements and the position of the natural anterior teeth in dentate individuals.