Bolton Tooth-Size Discrepancy: A Narrative Review

AbstractInterarch tooth-size harmony is an important part of achieving stable intercuspation, appropriate overjet and overbite, and satisfactory orthodontic finishing. Tooth-size discrepancy (TSD) describes a disproportion between the mesiodistal tooth widths of the maxillary and mandibular dentitions. Bolton developed a quantitative method to express this relationship as an anterior ratio and an overall ratio. The classical reference values are approximately 77.2% for the six 1,2 anterior teeth and 91.3% for the twelve teeth from first molar to first molar. Subsequent studies have shown that these ratios are useful clinical guides but are not universal constants. Differenceshave been reported among populations, malocclusion groups and study methods. Modern digital workflows have improved speed and reproducibility, yet careful clinical interpretation remains necessary. This narrative review summarizes the development, calculation, interpretation, clinical importance, measurement methods, biological and population variation, and current practical use of Bolton analysis in orthodontic diagnosis and treatment planning.