Bolton Ratios and Associated Occlusal/Arch Factors

Method: A Stereo-lithographic (STL) format using a 3 Shape three-dimensional scanner of two sets of models (T-1, 12-15 years and T-2, 18-37 years) from 44 subjects (22 males/22 females) from the Denver Growth Study (250 patients with 3,000 models) were studied.  Two different methods were used to determine the electronic arch form/arch perimeter.  Using software from ESM Digital Solutions, Bolton's ratios, overbite/overjet, crowding/spacing, and Angle's Class were recorded.  Ten casts were re-measured for error.

Result: No statistical significant correlations were found for either the anterior or the total Bolton ratios relative to the factors studied.  The highest value was r=0.59 for females T-2 anterior Bolton and mandibular crowding/spacing.   All p-values comparing Angle's Class (I and II) were greater than 0.05, confirming no statistical significance.  The greatest discrepancy in individual tooth measurements were the maxillary first premolars (14%), maxillary first molars (13%), and mandibular first molars (9.5%).  There was a 70% total discrepancy between the two different methods of measuring arch perimeter distal to the permanent canines.

Conclusion: Bolton ratios were not correlated to the occlusal factors of overbite/overjet and Angle's Class and to the dental arches with crowding/spacing. Electronic selection of points distal to canines can cause error as can measurements of selected teeth.