Planar Procrustes analysis of tooth shape

Accurate quantification of variation in tooth shape is important in studies of dental development, which typically have involved measuring distances b etween subjectively identified landmarks, key points of correspondence on t eeth. An established statistical framework now exists for the analysis of s hape when objects are represented as configurations of landmark coordinates ; allowing work with the fall geometry of objects, which is otherwise lost. This approach was introduced here to the study of tooth morphology, demons trating how after. optimally matching shapes to account for the unwanted ef fects of location, scale and rotation, most standard descriptive and infere ntial statistical techniques can be adapted and applied successfully. The t echniques are illustrated using a sample of buccal-surface images of centra l incisors from patients: with hypodontia; a significant difference is foun d in mean buccal-surface shape (Hotelling's two-sample T-2-test: P= 0.004) when compared to a corresponding control group. Successful implementation o f these methods depends on the accuracy and reliability with which the land marks are collected; issues and problems to be addressed are discussed. (C) 2001 Elsevier Science Ltd. All rights reserved.