Applicability of Bolton's Analysis: A Study on Jaipur Population

Assessing the validity and reliability of tooth widths and bolton ratios obtained from digital models and plaster models

Aim:

The aim of the study is to compare and evaluate the validity and reliability of tooth widths and Bolton ratios measured from digital models obtained from intraoral scanners and plaster models derived from alginate and polyvinyl siloxane impression materials.

Materials and Methods:

Alginate and polyvinylsiloxane impression was taken for 40 subjects, orthokal stone was poured and grouped as Group I and Group II, respectively. Intraoral scanning was done using Trios Pod 3shape for the same patients, digital models were obtained and grouped as Group III. OrthoAnalyzer software was used for obtaining measurements in digital models and Aerospace Vernier calipers in plaster models. The validity and reliability of the three groups were quantified and compared.

Results:

Validity measurements showed significant differences between tooth widths and Bolton ratios obtained from digital models and plaster models indicating higher accuracy for plaster models whereas reliability coefficients were excellent for digital models indicating better reproducibility of values.

Conclusion:

The study shows significant differences in accuracy on measuring with vernier calipers and Orthoanalyzer software showing plaster models are still better than digital models for measuring tooth widths and bolton ratios.

Applicability of Bolton’s Analysis: A Study on Tibetan Community

Aim

This study aimed to evaluate the anterior and overall ratios of Tibetan population residing at Mundgod and to compare the obtained ratios to the ratios available from Bolton’s study.

Materials and Methods

The study consists of randomly selected 120 samples of Tibetan population ranging in age from 15 to 25 years, residing at Mundgod, Karnataka (60 males and 60 females). After measuring the width of each tooth, overall and anterior ratios were measured using formula proposed by Bolton.

Statistical Analysis

Anterior and overall tooth ratios obtained from the study were compared to standard Bolton’s ratio by one-sample t-test. The differences between males and females were compared by independent samples t-test.

Results

The overall ratio was significantly lower for both males (P = 0.03) and females (P = 0.001) at 90.20 and 88.93, respectively, when compared to the Bolton’s value of 91.3, whereas anterior ratio for males (P = 0.001) was significantly higher at 77.9 when compared to Bolton’s value of 77.2. The combined values of males and females when compared to Bolton’s value, i.e., the combined overall ratio (P = 0.001) was significantly lower at 89.5 and the combined anterior ratio (P = 0.016) was significantly higher at 78.7.

Conclusion

In the present study, significant difference was observed between the overall and anterior ratios in Tibetan population as compared to the Bolton’s value. Therefore, Bolton’s original data cannot be applied for Tibetan population.

Tooth-Size Discrepancies in Patients Requiring Mandibular Advancement Surgery

PURPOSE

Numerous studies have shown that tooth size is an important key to ideal occlusion. Bolton (Angle Orthod 28:13, 1958; 48:504, 1962) described a constant ratio between the widths of the upper and lower teeth that must be present to achieve an optimal occlusion. The purpose of this study was to determine the incidence of Bolton discrepancies in patients with Class II malocclusion scheduled for mandibular advancement surgery.

PATIENTS AND METHODS

This study included 126 patients (40 male, 86 female) with Class II malocclusion who had at least a mandibular advancement as part of their surgical treatment. The mesiodistal widths of the 6 anterior maxillary and mandibular teeth were measured on preoperative models using a caliper. The measurements were used to compute the anterior Bolton ratio.

RESULTS

Seventy-three of 126 patients (57.9%) were found to have an anterior Bolton ratio greater than the Bolton norm, indicating too much lower tooth mass compared with the upper mass or too little upper tooth mass compared with the lower mass.

CONCLUSION

Tooth-size discrepancies are common in patients requiring mandibular advancement surgery. This can make it difficult to advance the mandible into a solid Class I relation at the time of surgery. Bolton discrepancies should be considered when planning treatment with presurgical orthodontics. In addition, if necessary, the width of the lower incisors should be decreased or a space distal to the maxillary lateral incisors should be created to allow the establishment of a solid Class I canine occlusion at the time of surgery.