Relationships between dental arch forms and basal bone morphology

Objectives: The purposes of this study were to examine the association between automatically classified human dental arch forms using the vector quantization algorithm and neighboring dentoskeletal morphology. Methods: Dental casts taken from 79 Japanese adults with normal occlusion. Dental casts were laser-scanned with a computer-assisted stereotaxic device. Each dental arch form was expressed as a vector having positional elements and categorized into 4 codes according to the quantized vector patterns. We determined the frequency of paired upper and lower codes and proportions of each code. Also, we measured the coronal and basal arch widths, the depths of the curves of dental arch in the sagittal plane, the mesio-distal crown widths of each individual tooth and the coronal arch length for each of the upper and lower dental arches. Results: The code numbers in the upper arch did not correspond to the code having the same number in the lower arch. The differences between the upper and lower dental arches did not vary by greater than 0.3mm, but showed consistent lateral gaps of about 4.3mm for the opposing canines and 2.8mm for the molars. The code having the narrowest arch width exhibited the longest coronal arch length (p<0.01). The inter-premolar and inter-molar basal arch widths determined for the code showing the widest arch width were greater than those for the code having the narrowest width (p<0.01). Conclusions: The code numbers in the upper arch did not correspond to the code having the same number in the lower arch. We determined that the lateral gaps between the upper and lower dental arches did not show a large variance. The inter-premolar and inter-molar basal arch widths determined for the code with the widest dental arch width were significantly greater than those-having the narrowest width.