A novel shape representation of the dental arch and its applications in some dentistry problems

Standardized digital images of maxillary dental casts of 47 subjects were analyzed using MATLAB software whereby the two hamular notches and the incisive papilla defines the Cartesian vertical and horizontal axes, as well as the origin. The angle and length of the midpoints of the anterior teeth, mesiobuccal and distobuccal cusp of the posterior teeth were measured from the origin and denoted as θ₁, ..., θ₁₈ and l₁, ..., l₁₈ respectively. These values were collectively used to represent the shape of each dental cast. Clustering and principal component analyses were employed to find possible groups of dental arches using the above measure of shape. The main result of this study is that the 3 groups of dental arch shape may be represented by the novel feature vector v_k=(θ^k₁, l^k₁, θ^k₃, l^k₃, θ^k₅, l^k₅, θ^k₁₃, l^k₁₃), k=1, 2, 3. Knowledge of v^k implies three impression trays should be sufficient in a particular prosthetic dentistry application for Malaysian patients. Further, given that v^k are accurately measured they may be potential candidates as evidence in specific application of forensic dentistry.