Digital analyses of Bolton tooth size ratios and their association to gender, angle class, and other occlusal traits: a study using a partially automated digital 3D model analysis

BACKGROUND

This study aims to verify Bolton's values for tooth size ratios and to evaluate possible relationships to different occlusal traits using precise digital measurement methods.

MATERIALS AND METHODS

Including 1000 consecutively selected patients from three study centres a digital, partially automated model analysis was performed utilizing the software OnyxCeph. The measurements comprised tooth width for calculation of anterior (AR) and overall ratio (OR) as a percentage, arch width, length, perimeter, overjet, overbite, space analysis in millimetre and the assessment of the angle classification.

RESULTS

AR and OR were significantly increased compared to Bolton's ratios of 77.2% (AR) and 91.3% (OR). In the gender comparison, male patients showed larger tooth size ratios, especially in the OR. Patients with Angle Class II/1 and II/2 had smaller tooth size ratios than patients with Angle Class III and I. Thus, patients with Angle Class II/1 had the largest tooth diameters in all maxillary teeth and with Angle Class II/2 the smallest tooth sizes in the mandible. The largest tooth widths in the lower jaw were observed in the Angle Class III patient group. Furthermore, a negative correlation from AR/OR to overjet, overbite, and available space in lower jaw as well as a positive correlation to available space in upper jaw was detected.

CONCLUSIONS

There is a clear correlation between the tooth size ratios and the present dysgnathia as well as other orthodontically relevant occlusal traits. This prior knowledge about our patients is extremely important to create an individualized treatment plan and enable sufficient occlusion. To achieve a functionally good occlusion with correct overjet and overbite, it is essential that the maxillary and mandibular teeth are proportional in size. Any deviation from the ideal patient in terms of tooth size, number, shape, or arch must be considered in the pre-therapeutic treatment plan in combination with the existing dysgnathia in order to be able to achieve a stable anterior and posterior occlusion with appropriate adjustments to the therapy post-therapeutically.

Digital analysis of tooth sizes among individuals with different malocclusions: A study using three-dimensional digital dental models

OBJECTIVE

It is aimed to examine the tooth sizes of digital models of patients with different malocclusions with the help of three-dimensional measurement software.

METHODS

Digital models of 252 patients aged between 13 and 25 years of age were included. According to the Angle classification, three different malocclusion groups were allocated such that there were 84 patients in each group, plaster models of patients scanned with the three-dimensional model browser 3Shape R700 3D Scanner (3Shape A/S Copenhagen, Denmark) and transferred to the digital format. 3Shape Ortho Analyzer (3Shape A/S Copenhagen, Denmark) software was used for making the necessary tooth size measurements.

RESULTS

When the measurements were evaluated, it was determined that significant changes occurred between tooth sizes of individuals with different malocclusions. Generally, higher values were observed in mesiodistal and buccolingual tooth dimensions of class II individuals compared to other groups. There was no difference between the groups in the anterior ratio values, but when the overall ratio values were evaluated among the groups, a statistically significant difference was determined. Class II malocclusion group was found to have a significantly lower overall ratio of occurrence.

CONCLUSION

Individuals with different malocclusions differ in tooth size.

Dental anomaly patterns in mixed dentition: Illustrating the role of interceptive orthodontics in the management of mandibular lateral incisor-canine transpositions and palatally displaced maxillary canines

Dental anomalies of size, number, and position have been suggested to have a genetic background and frequently complicate the orthodontic treatment. Early intervention is a paramount step in managing patients with dental anomaly patterns (DAPs) to decrease the complexity of the case during the later stages of comprehensive orthodontic care. This case report highlights the importance of the detailed diagnosis in a case with several dental anomalies (mandibular lateral incisor-canine transposition, palatally displaced canines, small-sized maxillary lateral incisors and congenitally missing second premolar), utilizing interceptive orthodontic management in the mixed dentition stage in order to minimize the complexity and complications of comprehensive orthodontic care in the permanent dentition stage.

Association between incisor positions and amount of interdental stripping in patients undergoing orthodontic treatment

INTRODUCTION

The study aimed to investigate the effect of a nonextraction treatment approach with interdental stripping (IDS) on the dentofacial structures in patients with dental and skeletal Class I, II, and III malocclusions.

METHODS

A total of 60 patients with mild-to-moderate crowding of the teeth and nonsevere skeletal malocclusion were included and divided into 3 groups: Class I, Class II, and Class III groups (n = 20 per group). In all patients, nonextraction orthodontic treatment was administered, and those who underwent IDS at the jaw quadrants as needed were evaluated. For pretreatment and posttreatment evaluation, lateral cephalometric radiography and 3-dimensional dental model scans were acquired for each patient. For statistical analysis, paired-samples t test and 1-way analysis of variance with Tukey post-hoc test were used for parametric variables, whereas the Wilcoxon paired signed rank test and Kruskal-Wallis test with Dunn post-hoc test were used for nonparametric variables.

RESULTS

An increase in the maxillary incisor angle was observed in patients with Class I and Class III malocclusions, whereas a decrease was observed in patients with a Class II malocclusion (P < 0.05). Mandibular incisor angles were significantly increased in the Class II malocclusion group (P < 0.05) but unchanged in the other groups. IDS was more frequently applied to the posterior aspect of the maxilla and mandible in patients with a Class II malocclusion than in patients with other malocclusion types, and the amount of IDS at the anterior aspect of the mandible was significantly higher in the Class III group.

CONCLUSIONS

Combined nonextraction orthodontic treatment and IDS yielded successful treatment outcomes. IDS application was localized to different jaw regions according to the different malocclusion types.

The Tooth Size Discrepancy among Orthodontic Patients and Normal Occlusion Individuals from Saudi Arabia: A Three-Dimensional Scan Analysis of Diagnostic Casts

Background/Purpose:

Tooth size discrepancy is one of the causative factors of malocclusion. This study aimed to establish the TDS among various malocclusion classes and normal occlusion subjects in a Southern Saudi population.

Materials and Methods:

The study casts of orthodontic patients from Southern Saudi Arabia (mean age: 19.6 years ± 2.45; n = 120) were randomly selected and grouped into eight equal classes based on Angle's classification and gender. An additional 30 study casts, devoid of malocclusion, having excellent intercuspation and class I occlusion, were grouped into two controls (n = 15) based on gender. The study casts were three-dimensional scanned to measure mesiodistal widths of all the teeth. The calculated anterior ratios (AR) and overall ratio (OR) were statistically analyzed with analysis of variance and t-tests.

Results:

There were no significant differences in “OR” and “AR” between the genders (P > 0.05) and among the malocclusion and control subgroups (P > 0.05). The mean “OR” (92.01 ± 0.18) and “AR” (78.60 ± 0.27) of the malocclusion group were significantly higher than that of Bolton's ratios (P > 0.05). The “AR” of the control group was significantly higher than Bolton's standards (P = 0.048). However, “OR” was no different (P = 0.105). Malocclusion patients displayed a discrepancy (±2 standard deviation) in “AR” of 22.5% and 'OR' of 6.7% from Bolton's mean (BM). Similarly, the control group displayed a discrepancy in “AR” of 20% and “OR” of 10% from BM.

Conclusion:

The mean “OR” and “AR” of the Southern Saudi population showed no sexual dimorphism and no significant difference among various malocclusion and control subgroups. The “AR” of the malocclusion and control subgroups did not comply with Bolton's standards.

Craniofacial characteristics of Syrian adolescents with Class II division 1 malocclusion: a retrospective study

Background

Malocclusion characteristics vary across different ethnic groups and populations. Limited data are available regarding the characteristics of Syrian adolescents with Class II division 1 (Class II-1) malocclusion, and the recent inflow of Syrian refugees and immigrants into Europe and many areas worldwide demonstrate the need for updated studies to discover the craniofacial characteristics of these new immigrants.

Objectives

The present compound cephalometric and tooth-size study sought to assess the dentofacial morphology, upper-airway dimensions, and tooth-size characteristics of Syrian adolescents with Class II-1 malocclusion and compare the results with established Syrian population norms.

Materials and Methods

The study sample consisted of 43 Syrian patients including 24 females and 19 males with Class II-1 malocclusion (age: 14.3 (±1.5) years, mean (±SD)). Cephalometric radiographs and orthodontic casts were analyzed using special orthodontic software (OnyxCeph3^™) and a universal digital caliper, respectively. Statistics were calculated using the SPSS software.

Results

In Syrian adolescents with Class II-1 malocclusion, the position of the mandible relative to the nasion perpendicular (mean (95% confidence interval)) was −11.01 (−12.45, −9.57) mm. Facial axis angle showed a negative value: −6.25 (−7.65, −4.85) degrees. An obtuse nasolabial angle was observed: 104.05 (101.77, 106.33) degrees. The average width of the upper pharynx was 11.50 (10.53, 12.47) mm; however, there was no prevalence of an upper-pharyngeal width of 5 mm or less. The average value of the anterior tooth-size ratio was 80.69 (79.85, 81.53) percent. In total, 39.5% of the investigated subjects had anterior ratios outside two standard deviations from Bolton’s norm, while 25.6% of the investigated subjects had anterior ratios outside two standard deviations from Syrian population norm.

Conclusions

In this study, the inter-maxillary discrepancy of Class II-1 Syrian adolescents was a consequence of their hyperdivergent facial pattern. The observed small pharyngeal widths were not clinically significant, while the anterior tooth-size discrepancy might be clinically relevant.

A systematic review and meta-analysis on Bolton's ratios: Normal occlusion and malocclusion

INTRODUCTION

The purpose of this study was to seek and summarise the Bolton overall index (OI) and anterior index (AI) regarding normal occlusion and Angle's malocclusion according to gender, and to assess if these indices support Bolton's standards as general references.

METHODS

PubMed, LILACS, Embase, CENTRAL and Google Scholar databases were searched up to June 2019 (CRD42018088438). Non-randomised clinical studies, published in English and assessing Bolton's OI and/or AI in normal occlusion and Angle's malocclusion groups, were included. OI and AI means, sample size and SDs were collected. The National Heart, Lung, and Blood Institute's Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies was used to assess the risk of bias. Pairwise random-effects and multilevel Bayesian network meta-analyses were used to synthesise available data.

RESULTS

Fifty-three observational studies were included (11,411 participants; 3746 men, 4430 women; 15 studies lacked gender information). For normal occlusion, pooled estimates for OI and AI means were 91.78% (95% confidence interval [CI] = 91.42-92.14; I² = 92.87%) and 78.25% (95% CI = 77.87-78.62; I² = 90.67%), respectively. We could identify in Angle's Class III patients meaningful OI and AI mean deviations from normal occlusion (0.76, 95% credible interval [CrI] = 0.55-0.98 and 0.61, 95% CrI = 0.35-0.87, respectively), while in Class II patients we found a meaningful mean deviation from normal occlusion only for OI (-0.28, 95% CrI = -0.52--0.05). Concerning gender impact, male patients presented higher OI (0.30, 95% CI = 0.00-0.59) and AI (0.41, 95% CI = 0.00-0.83) mean values than female patients in Class I.

CONCLUSION

Normal occlusion OI and AI mean values differ from Bolton's original values. Class II division 2, for OI mean values, and Class III, for both OI and AI, are proportionally larger than normal occlusion patients. Gender had almost no impact on teeth mesiodistal proportion.

Assessing the accuracy of two posterior tooth-size discrepancy prediction methods based on virtual occlusal setups

OBJECTIVE

To assess accuracy of the Bolton and Johnson/Bailey (JB) analyses in identifying clinically significant posterior tooth-size discrepancies using virtually constructed occlusal setups.

MATERIALS AND METHODS

Virtual models and cone-beam computed tomography data sets from 30 patients were utilized to construct 60 (two per patient) virtual posterior occlusal setups. Observed discrepancies in cusp-embrasure relationships were compared to estimated posterior interarch tooth-size discrepancies (ITSDs) calculated via Bolton and JB posterior analyses. Clinical significance for discrepancies was established at >1 mm from ideal cusp-embrasure relationships in accordance with current American Board of Orthodontics methodology. Data within groups were normally distributed, thus comparisons were completed via paired t-tests. Paired nominal data were analyzed utilizing McNemar's test, and simple linear regression was used to model the relationship of predicted to observed discrepancies.

RESULTS

McNemar's test revealed significant differences (P ≤ .05) between the Bolton and JB groups' frequencies in matching the virtual setups correctly. JB predictions matched 100% (right) and 97% (left) setups; whereas, Bolton predictions matched only 23% (right and left) setups. A positive correlation was observed between JB predictions and cusp-embrasure discrepancies, demonstrating that average posterior discrepancy values increased 0.28 mm for every 1 mm predicted via the JB analysis.

CONCLUSIONS

The JB analysis correctly characterized, but overestimated, the degree of posterior ITSDs corresponding to a clinically significant discrepancy in the virtual setups. Algebraically calculated posterior ITSDs based on the Overall and Anterior Bolton ratios were not accurate predictors of discrepancies observed in the virtual setups. Both Bolton and JB demonstrated weaknesses that limit precise identification of clinically significant ITSDs.

Comparison of Bolton ratio in normal occlusion and different malocclusion groups in Iranian population

OBJECTIVES

Bolton ratio is used as a method for diagnosis of tooth size discrepancy. Tooth size discrepancy has an important role in the stability of results of final orthodontic treatment. The aim of this study was to determine and compare Bolton ratio in normal occlusion and different malocclusion groups of Iranian population.

MATERIALS AND METHODS

This descriptive-analytic study comprises 240 orthodontic patient casts (for every malocclusion group: class I, class II division 1, class II division 2, class III, 30 males and 30 females) which have fully erupted and complete permanent dentitions from first molar to first molar, and also 60 persons (30 male-30 female) with normal occlusion. The mesiodistal tooth sizes were measured using digital caliper two times with a 4-week interval.

RESULTS

The average mesiodistal size of all teeth in the malocclusion group was significantly bigger than in the normal occlusion group. Although there was no relationship between anterior ratio and gender or malocclusion groups, but a significant relationship between total ratio in Class II division 1 and normal occlusion was seen. Furthermore, a significant difference between anterior and total ratios in the present study and original Bolton's values was found.

CONCLUSIONS

In the normal occlusion group, the anterior and total ratios were bigger than those in Bolton's original study. Also, "class II division 1" showed the lowest values of Bolton ratio among the other normal occlusion and malocclusion groups. Therefore, the original Bolton's values should be used conservatively in Iranian population.

Morphological characteristics influencing the orthodontic extraction strategies for Angle's class II division 1 malocclusions

BACKGROUND

Extraction has now been accepted widely in various malocclusions including Angle's class II division 1. However, the levels of scientific evidence in orthodontic treatment planning have been weak, and it is unlikely to systematically provide a rationale and consistent basis in decisions of extraction. This study was retrospectively designed to investigate the initial morphologic characteristics of class II division 1 subjects involving four different extraction strategies, to determine the relevant influential factors when choosing extraction strategies with the most commonly used mechanics and the principle of simplicity in orthodontic treatment based on cases diagnosed and treated by an experienced orthodontist.

METHODS

One hundred and ten samples of Angle's class II division 1 malocclusion with good facial and occlusal outcomes after orthodontic treatment were selected and divided into four groups according to different extraction patterns. For each case, pretreatment models and the lateral radiographs were analyzed. Significant variables of models and craniofacial structures of each group were identified by comparing the measurements using one-way analysis of variance (ANOVA) at a significance level of P < 0.05. Then, binary logistic regression analysis was used and a regression equation was established to quantify the correlations among the significant variables and their contributions to the extraction decisions.

RESULTS

Molar relationship, lower anterior crowding, anterior Bolton index, and anterior overjet measured from models, as well as ANS-Xi-Pm, NBa-PtGn, Li-NsPog', U1-NPog and L1-NPog measured from lateral radiographs were found to be statistically significant. Binary logistic regression analysis revealed that lower anterior crowding, molar relationship, and growth pattern were the three most relevant influential factors with a declining impact contributing to the extraction decisions for Angle's class II division 1 malocclusions.

CONCLUSIONS

Angle's class II division 1 malocclusions exhibit various morphological characteristics. Orthodontists should comprehensively consider the reciprocal impact of multiple factors when choosing different extraction strategies for Angle's class II division 1 malocclusions.

Study of variations of the Bolton index in the Moroccan population depending on angle malocclusion class

Many difficulties may arise during the finishing phase of orthodontic treatment on account of discrepancy between mandibular and maxillary tooth size. In 1958, Bolton devised the index that bears his name and enables possible tooth-size discrepancy to be diagnosed. Use of this index in practice has shown that it can vary depending on the different angle malocclusion classes. The aim of this work is to study variations of the Bolton index as a function of the malocclusion class in the Moroccan population, and to compare the results obtained with those of other populations. Ninety models were therefore selected in different groups of dental Class I, Class II and Class III malocclusions. The mesiodistal (MD) diameters of 12 maxillary and mandibular teeth were measured and the anterior and general Bolton indices were calculated. The results obtained show that there is no significant difference between the various groups of angle malocclusion classes, and that some other populations present results similar to those of the Moroccan sample.

Comprehensive intermaxillary tooth width proportion of Bangkok residents

Proper occlusion depends on the correct width ratio between upper and lower teeth, known as Bolton's ratio. In fact, this ratio can be calculated for each pair of teeth from the central incisor to the first permanent molar. This set of ratios, known as comprehensive cumulative percentage ratios (CPRs), can be used not only to determine which tooth or teeth have a tooth width discrepancy, but can also enable the partial graphical analysis of tooth width discrepancy when there is agenesis of certain permanent teeth. Although CPRs have been calculated for Caucasians, tooth width is known to vary depending on racial origin. Therefore, a test of differences between racial groups should be carried out. If these ratios of the Caucasians and Bangkokians are significantly different, the ratio of the Bangkokians is recommended. The objective of this study was to measure tooth size disproportion for Thai patients and to calculate a corresponding set of CPRs. Thirty-seven pairs of dental models were made from a group of Bangkok residents with normal occlusion. Mesiodistal tooth width was measured for each model. The intra- and inter-examiner measurement errors were ascertained as insignificant (p > 0.05). CPRs were then calculated and compared to those derived from other studies. Ten of thirteen CPRs were significantly different from corresponding values derived from Caucasians. We conclude that tooth width ratios vary between different racial groups, and therefore that these should be calculated specifically for each patient racial group.