RELIABILITY OF THE BOLTON TOOTH-SIZE ANALYSIS WHEN APPLIED TO CROWDEDDENTITIONS

The Bolton tooth-size analysis is widely taught and used in orthodonti cs. However, its reliability has not been documented. The purpose of t his study was to evaluate the reliability of the analysis when perform ed with needle-pointed dividers and a Boley gauge. Four clinicians mea sured the teeth on 15 sets of casts with two instruments at two sessio ns. The measurements were used to calculate tooth-size excess. To eval uate the measurement error, the difference between the two analyses ma de by the same investigator on the same set of casts was calculated. M ore of the same-investigator analyses were significantly correlated wh en the Boley gauge was used than when the needle-pointed dividers were used. Between-investigator analyses revealed significant correlations for each measurement session with both instruments. Every investigato r was found to have at least one measurement error for each analysis a nd with each instrument that was as large as a clinically significant result of a Bolton analysis. The results of this study demonstrate tha t clinically significant measurement errors can occur when the Bolton tooth-size analysis is performed on casts with at least 3 mm of crowdi ng. The Boley gauge demonstrated a higher frequency of significantly c orrelated repeated measures and thus may be somewhat more reliable for this analysis than the needle-pointed dividers.