Objective: To determine the prevalence of tooth size discrepancy (TSD) in a representative orthodontics population, to explore how many millimeters of TSD is clinically significant and to determine the ability of simple visual inspection to detect such a discrepancy.
Materials and methods: The sample comprised 150 pretreatment study casts with fully erupted and complete permanent dentitions from first molar to first molar, which were selected randomly from records of the orthodontic patients. The mesiodistal diameters of the teeth were measured at contact points using digital calipers and the Bolton's analysis was carried out on them. Simple visual estimation of Bolton discrepancy was also performed.
Results: In the sample group, 24% of the patients had anterior tooth width ratios and 8% had total arch ratios greater than ±2 standard deviation (SD) from Bolton's means. For the anterior analysis, correction greater than ±2 mm was required for 24% of patients in the upper arch or 14% in the lower arch. For the total arch analysis, correction greater than ±2 mm was required for 36% of patients in the upper arch or 32% in the lower arch.
Conclusion: Bolton's analysis should be routinely performed in all orthodontic patients and the findings should be included in orthodontic treatment planning. 2 mm of the required tooth size correction is an appropriate threshold for clinical significance. Visual estimation of TSD has low sensitivity and specificity. Careful measurement is more frequently required in clinical practice than visual estimation would suggest.
Keywords: Bolton's ratios; anterior ratio; tooth size discrepancy; total arch ratio.