Bolton's Ratios in Normal, Spaced and Crowded Dental Arches (Iraqi Study)

Determination of mesio-distal width of human teeth is very important due to its relation to many dental fields like aesthetic dentistry, orthodontics, anthropometrics, prosthodontics, studying the differences between ethnic groups and in gender determination in forensic dentistry. So that Bolton developed an analysis to assist in establishing the discrepancy between the mesio-distal widths of the maxillary and mandibular teeth. This study was aimed to determine and compare the anterior and overall Bolton's ratios in normal, crowded and spaced dentitions.

One hundred fifty pair of dental casts belonged to 150 Iraqi individuals having class I dental relationship with normal, crowded and spaced dentition after analyzing the space in both dental arches. The mesio-distal crown widths of the maxillary and mandibular permanent teeth anterior to the second molars were measured using electronic digital vernier with 0.01mm accuracy to calculate Bolton's ratios. Unpaired t-test, one-way ANOVA and post hoc Tukey's test were used to compare the measured parameters.

The combined mesio-distal crown widths were significantly higher in crowded dentition followed by normal then spaced dentition. Bolton's ratios neither showed significant gender and group differences nor followed the same pattern of the combined mesio-distal crown widths.

The difference in Bolton's ratios was related to the difference in the mesio-distal widths and dental arch discrepancy that must be addressed in details.