Bolton Tooth Size Discrepancy - OrthoCAD Digital Analysis versus Calipers

Objectives: With the increasing use of computerized digital models in orthodontics, it is important to continue studying their accuracy. The objective of this study was to measure tooth sizes and analyze Bolton tooth size discrepancy using OrthoCAD (OC) software and digital calipers (control). Methods: Dental casts in good condition were selected from 25 subjects. The plaster models were measured three times with digital calipers to the nearest 0.01 mm, and these measurements were averaged for the control. The casts were also scanned into OC system. These 3D digital models were magnified and measured using the OC software. Data were analyzed by paired t-tests at the 0.05 level of significance. Results: Means and standard deviations (n=25) for Bolton analysis are listed. Statistically equivalent results between the OC and caliper measurements were observed for 5 of 8 Bolton variables. Statistical differences were observed for Bolton overall maxillary, anterior maxillary and overall mandibular variables with differences of -0.63 to -0.87%.

                                                Gypsum Model               OC System                p-value

Bolton Overall Maxillary           94.8 (5.2) mm              95.4 (5.1) mm              0.020

Bolton Anterior Maxillary          45.7 (3.0) mm              46.1 (3.1) mm              0.011

Bolton Overall Mandibular        86.5 (5.2) mm              87.2 (4.8) mm              0.014

Bolton Anterior Mandibular      35.6 (2.1) mm              36.0 (1.8) mm              0.053 (ns)

Bolton Overall Discrepancy      -0.6 (2.3) mm               0.13 (2.0) mm              0.504 (ns)

Bolton Anterior Discrepancy     0.52 (1.8) mm              0.46 (1.8) mm              0.757 (ns)

Bolton Overall Ratio                 0.912 (0.022)               0.915 (0.019)               0.468 (ns)

Bolton Anterior Ratio                0.782 (0.032)               0.781 (0.030)               0.923 (ns)

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*ns=not significant.  Conclusions: Measurements of tooth width, Bolton discrepancy and Bolton ratio by both the OC method and digital calipers are clinically equivalent for purposes of treatment planning and diagnosis.