Floating norms for the ANB angle as guidance for clinical considerations

Lateral cephalometric parameters among Arab skeletal classes II and III patients and applying machine learning models

BACKGROUND

The World Health Organization considers malocclusion one of the most essential oral health problems. This disease influences various aspects of patients' health and well-being. Therefore, making it easier and more accurate to understand and diagnose patients with skeletal malocclusions is necessary.

OBJECTIVES

The main aim of this research was the establishment of machine learning models to correctly classify individual Arab patients, being citizens of Israel, as skeletal class II or III. Secondary outcomes of the study included comparing cephalometric parameters between patients with skeletal class II and III and between age and gender-specific subgroups, an analysis of the correlation of various cephalometric variables, and principal component analysis in skeletal class diagnosis.

METHODS

This quantitative, observational study is based on data from the Orthodontic Center, Jatt, Israel. The experimental data consisted of the coded records of 502 Arab patients diagnosed as Class II or III according to the Calculated_ANB. This parameter was defined as the difference between the measured ANB angle and the individualized ANB of Panagiotidis and Witt. In this observational study, we focused on the primary aim, i.e., the establishment of machine learning models for the correct classification of skeletal class II and III in a group of Arab orthodontic patients. For this purpose, various ML models and input data was tested after identifying the most relevant parameters by conducting a principal component analysis. As secondary outcomes this study compared the cephalometric parameters and analyzed their correlations between skeletal class II and III as well as between gender and age specific subgroups.

RESULTS

Comparison of the two groups demonstrated significant differences between skeletal class II and class III patients. This was shown for the parameters NL-NSL angle, PFH/AFH ratio, SNA angle, SNB angle, SN-Ba angle. SN-Pg angle, and ML-NSL angle in skeletal class III patients, and for S-N (mm) in skeletal class II patients. In skeletal class II and skeletal class III patients, the results showed that the Calculated_ANB correlated well with many other cephalometric parameters. With the help of the Principal Component Analysis (PCA), it was possible to explain about 71% of the variation between the first two PCs. Finally, applying the stepwise forward Machine Learning models, it could be demonstrated that the model works only with the parameters Wits appraisal and SNB angle was able to predict the allocation of patients to either skeletal class II or III with an accuracy of 0.95, compared to a value of 0.99 when all parameters were used ("general model").

CONCLUSION

There is a significant relationship between many cephalometric parameters within the different groups of gender and age. This study highlights the high accuracy and power of Wits appraisal and the SNB angle in evaluating the classification of orthodontic malocclusion.

Comparative treatment outcomes after bilateral extractions of maxillary second molars or first premolars in patients with class II malocclusion: a retrospective study

BACKGROUND

This retrospective cohort study aimed to compare treatment results between bilateral extraction of upper second molars (M2) and first premolars (P1) in terms of treatment timing, cephalometry, upper third molar alignment and relapse in the long-term.

METHODS

Fifty-three consecutively treated Caucasian patients with a brachyfacial pattern, skeletal class I and dental class II requiring extraction in the maxilla due to crowding were retrospectively divided into group I (M2 extracted; N = 31) and II (P1 extracted; N = 22). Fixed appliances were inserted after extraction and after distalisation of the first molars in group I. Post-treatment lateral cephalograms were digitally analysed and compared between groups. Six to seven years later relapse and success of upper third molar alignment were clinically evaluated as well as orthodontic treatment duration, pre-treatment age and gender recorded.

RESULTS

After debonding patients with second molar extraction showed significantly smaller values for the Wits-appraisal, but higher values for index and facial axis. Extracting first premolars caused significantly more retroinclination/-position of anterior teeth and an increased profile concavity, more relapse and less successful alignment of upper third molars. Orthodontic treatment duration, pre-treatment age and gender were not significantly different between groups.

CONCLUSIONS

Bilateral extraction of upper first premolars or second molars may solve dental crowding in skeletal class I dental class II patients with a brachyfacial growth pattern. Upper second molar extraction seems to affect maxillary third molar alignment, long-term stability and dental and soft-tissue cephalometric parameters positively, but no intervention proved to be clearly superior.

Floating norms for individualising the ANB angle and the WITS appraisal in orthodontic cephalometric analysis based on guiding variables

PURPOSE

The sagittal skeletal relationship of maxilla and mandible (skeletal class) can generally be determined via lateral cephalograms (ANB angle or Wits appraisal) by comparing measurements to empirical norms based on the respective population mean. However, values differing from these empirical norms also enable a therapeutically desired, normal class I occlusion depending on individual craniofacial pattern, thus requiring floating norms based on guiding variables. As available regression equations consider only few predictor variables and are not up-to-date regarding a contemporary patient collective, the aim of this study was to establish improved and extended regression equations for individualising the ANB angle and Wits appraisal.

METHODS

This retrospective, cross-sectional multicentre study was based on 71 Caucasian male and female subjects of any age with normal dental occlusion. We cephalometrically analysed digitised pretreatment lateral radiographs and performed multiple linear regression analyses to identify suitable skeletal predictor variables for individualising the ANB angle and Wits appraisal.

RESULTS

Inter- and intrarater reliability tests showed mostly perfect measurement concordance. Both original regression equations by Panagiotidis/Witt and Järvinen could be updated for a contemporary population with new regression coefficients. The equation for individualising the ANB could be further optimised in its prediction reliability by adding the skeletal predictor variables NL-NSL, NSBa, facial axis (Ricketts) and index (Hasund), whereas the recalculated Wits equation could not be further improved by additional guiding variables.

CONCLUSIONS

The improved regression formulae for individualising the ANB angle and Wits appraisal should help to improve the assessment of sagittal skeletal class in clinical orthodontic practice.

Cephalometric Floating Norms for the β Angle and MMBP-Wits

The importance of an accurate measurement of sagittal jaw relationship, that is, skeletal class, is critical to orthodontic treatment planning. The ANB angle, β angle, and MMBP-Wits are among indices of sagittal jaw relationship. All of these indices are subjected to geometrical distortion, especially from facial divergence, making the use of floating (individualized) norms necessary. This study thus provides floating norms for the ANB angle and for the first time for the β angle and MMBP-Wits. Lateral head films were obtained from 119 subjects (74 females and 45 males; mean age, 11.2 ± 1.5 years; range, 8.2–14.0 years) with well-balanced and pleasant profile and a near-ideal occlusion. Multiple regression models were employed to quantify the association of the ANB angle, β angle, and MMBP-Wits each with other four angular cephalometric parameters including SNA, SN/PP, SN/MP, and NSBa angles. The β angle and MMBP-Wits were associated with the SNA and SN/MP angles; the ANB angle was associated with all the four other cephalometric variables. Floating norms for the β angle and MMBP-Wits (but not ANB angle) have been cross-tabulated according to the SNA angle (from 74° to 90°) and SN/MP angle (from 24° to 44°). While the ANB angle is subjected to significantly more geometrical distortion as compared to the β angle and MMBP-Wits, floating norms may be used to individualize the reference values for both the β angle and MMBP-Wits.

A network approach to orthodontic diagnosis

BACKGROUND

Network analysis, a recent advancement in complexity science, enables understanding of the properties of complex biological processes characterized by the interaction, adaptive regulation, and coordination of a large number of participating components.

OBJECTIVE

We applied network analysis to orthodontics to detect and visualize the most interconnected clinical, radiographic, and functional data pertaining to the orofacial system.

MATERIALS AND METHODS

The sample consisted of 104 individuals from 7 to 13 years of age in the mixed dentition phase without previous orthodontic intervention. The subjects were divided according to skeletal class; their clinical, radiographic, and functional features were represented as vertices (nodes) and links (edges) connecting them.

RESULTS

Class II subjects exhibited few highly connected orthodontic features (hubs), while Class III patients showed a more compact network structure characterized by strong co-occurrence of normal and abnormal clinical, functional, and radiological features. Restricting our analysis to the highest correlations, we identified critical peculiarities of Class II and Class III malocclusions.

CONCLUSIONS

The topology of the dentofacial system obtained by network analysis could allow orthodontists to visually evaluate and anticipate the co-occurrence of auxological anomalies during individual craniofacial growth and possibly localize reactive sites for a therapeutic approach to malocclusion.

Improving the concordance between various anteroposterior cephalometric measurements using Procrustes analysis

The aim of this study was to investigate a method which minimizes the effects of geometric distortion on various cephalometric measurements used to determine sagittal discrepancy, such as ANB angle, Wits appraisal, AB plane angle, projections on the palatal plane, Frankfort horizontal (FH) plane, the mandibulomaxillary bisector, and the SN line, in an attempt to optimize the correlation between them. This was accomplished by superimposing the Bolton 12-year male-female averaged template on a patient's tracing using Procrustes analysis and performing measurements while exchanging the patient's reference landmarks/planes (point N, the mandibulomaxillary bisector, FH plane, occlusal plane, palatal plane, and SN line) with those of the template. The normalized measurements were then compared with their classic counterparts using correlation coefficients. The above cephalometric analyses, classic and normalized, were applied to 71 patients [26 males: mean age 13.1 years, standard deviation (SD) 1.1 years and 45 females: mean age of 14.6 years, SD 8.2 years]. Spearman's rank correlation coefficient was calculated between the classic measurements and their normalized counterparts, resulting in a consistent increase in the correlation between the normalized measurements in comparison with the classic ones. This increase varied in absolute value from 0.052 to 0.405. All normalized measurements were highly correlated (P > 0.742, absolute value). Although correlation calculations do not represent a true measure of diagnostic performance, it is hoped that improving their correspondence heightens the possibility of the different tests agreeing on the patient's sagittal discrepancy, decreasing the possibility of differing, or even totally opposing diagnostic outcomes resulting from their application to (clear-cut) Class I, II, and III patients.

Influence of diabetes mellitus on the development and treatment of malocclusions--a case report with literature review

Diabetes mellitus is a metabolic disorder characterized by disturbed glucose regulation, manifesting primarily as chronic hyperglycemia. Today about 6% of the world's population suffers from diabetes mellitus. This metabolic disorder is known to be associated with a large number of concomitant and secondary diseases of the cardiovascular system, as well as of the joint and supporting tissue systems. It is also a recognized fact that diabetes mellitus is closely associated with diverse problems in the oral, facial and jaw regions. These facts suggest that patients with diabetes may respond to orthodontic treatment differently from those without diabetes in how the periodontium and surrounding visceral cranium react to therapy. Beginning with a clinical case report we proceed to present a general overview of the clinical features and pathophysiology of diabetes mellitus, followed by a critical discussion of the results of a systematic literature search for aspects of the disease relevant to orthodontics.

Estudo cefalométrico da correlação da anatomia da base craniana com o padrão facial e as bases apicais

OBJETIVOS: este estudo transversal foi realizado com o objetivo de avaliar cefalometricamente a correlação da anatomia da base craniana com o padrão facial e as bases apicais. METODOLOGIA: foram utilizadas 88 telerradiografias de norma lateral de jovens leucodermas brasileiros com média de idade de 10,3 anos. Utilizou-se o índice VERT de Ricketts para a determinação do padrão facial, distribuindo a amostra em: 37 para o grupo M (mesofaciais), 34 para o grupo D (dolicofaciais) e 17 para o grupo B (braquifaciais). Realizaram-se, manualmente: o desenho anatômico, a demarcação de pontos, o traçado de linhas e planos e a aferição de medidas lineares e angulares. As medidas da base do crânio utilizadas foram S-N, N.S.Ba e S-N.Po-Or, e as medidas das bases apicais foram S.N.A, S.N.B e A.N.B. RESULTADOS E CONCLUSÕES: concluiu-se que, na correlação entre a base craniana e o padrão facial, houve significância entre a variável N.S.Ba e o índice VERT. Na correlação entre a base craniana e as bases apicais, houve significância entre N.S.Ba e as variáveis S.N.A e S.N.B, e entre S-N.Po-Or e as variáveis S.N.A e S.N.B.

Influence of occlusal plane inclination on ANB and Wits assessments of anteroposterior jaw relationships

INTRODUCTION

Although assessments of anteroposterior relationships are vital for orthodontic treatment planning, they cannot be precisely achieved by current cephalometric and noncephalometric resources. ANB angle and the Wits appraisal are the most popular cephalometric measurements applied in clinical orthodontics, although they have drawbacks. Facial vertical features, especially the occlusal plane angle, play an important role in their assessment, contributing to their unreliability.

METHODS

To further understand the influence of occlusal plane inclination, ANB angle and the Wits appraisal were analyzed in cephalo-lateral radiographs of 122 finished orthodontic patients in 2 groups: high occlusal plane angle and low occlusal plane angle.

RESULTS

There was a tendency for inconsistency between ANB and Wits assessments in the high occlusal plane angle group and a tendency for consistency in the low occlusal plane angle group. Cranial base influences on ANB and Wits assessments were investigated by subdividing the groups. Any of the considered cranial base factors was decisive for lack or presence of consistency between ANB and Wits assessments.

CONCLUSIONS

The clinician should beware of possible misinterpretations when using ANB and Wits to assess the anteroposterior relationship of the jaws, especially in high occlusal plane angle patients.

Age-related changes in sagittal relationship between the maxilla and mandible

The aim of the study was to assess age-related changes in sagittal jaw relationship during pre-pubertal and pubertal development on the basis of angular [ANB, anteroposterior dysplasia indicator (APDI) and A-B plane angle] and linear (Wits, AF-BF, App-Bpp, and App-Pgpp) measurements. Lateral cephalograms of orthodontically untreated subjects were evaluated at 7, 9, 11, 13 and 15 years of age. Cephalometric standards and age-related changes were determined on the basis of Class I subjects with a good occlusion (n = 18, 10 males and 8 females). With respect to changes related to growth, the main findings were, in both genders, a statistically significant age-related decrease in ANB angle, App-Bpp and App-Pgpp, a significant increase in APDI, but no age-related change in Wits. A reduction of sagittal jaw distance during pre-pubertal and pubertal development was observed arising from a relative dominance of sagittal mandibular growth. For an evaluation of differences concerning jaw relationship in Class II subjects, a group with Class II division 1 malocclusions (n = 17) and a group with Class II division 2 malocclusions (n = 12 were compared with two control groups, i.e. the good occlusion group and a Class I group (n = 37). Conclusions about the sagittal discrepancy in Class II division 1 and Class II division 2 subjects depended on the geometric reference used in the various parameters, and further research is called for with respect to the diagnostic performance of the various measurements. Differences between Class II subjects and controls present at 15 years of age were already established at 7 years of age, but were less pronounced.

Role of cranial base flexure in developing sagittal jaw discrepancies

The aim of this longitudinal cephalometric study was to investigate skeletal features in patients with small and large cranial base angles. Two groups of untreated subjects were formed on the basis of a small and large cranial base angle N-S-Ar at the age of 5 years: the large cranial base angle group (n = 22) consisted of subjects with an N-S-Ar angle larger than 125 degrees (mean, 128.1 degrees ), and the small cranial base angle group (n = 20) included subjects with an N-S-Ar angle of less than 120 degrees (mean, 117.6 degrees ). Cephalometric data of the 2 groups were analyzed at subject ages 5 and 12 years. At both ages, the groups showed significant differences of the variables SNA, SNB, individualized ANB, and Y axis. The unadjusted ANB angle and the angle of convexity N-A-Pg were not significantly different between the 2 groups. According to the individualized norm of the ANB angle, subjects with a large cranial base angle in the primary dentition demonstrated a skeletal Class II tendency both at the initial observation and at the longitudinal follow-up. On the basis of cephalometric variables at 12 years of age, it was possible to classify 88.1% of the initial large and small cranial base angle individuals, indicating a constancy of the skeletal pattern during the longitudinal follow-up. The relationship between cranial base flexure and skeletal pattern of the jaws seems to be established before the age of 5 years.

Skeletal Class II patterns in the primary dentition

The aim of this longitudinal cephalometric study was to investigate early characteristics of favorable and unfavorable growth. Two groups of untreated subjects with skeletal Class II pattern were formed on the basis of an ANB angle at least 2.5 degrees above the individual norm, according to Järvinen, at age 5. The subjects were followed longitudinally until age 12. The favorable growth group (n = 13) consisted of subjects who exhibited a decrease in the individualized ANB angle of at least 1.5 degrees during follow-up. The unfavorable growth group (n = 10) was characterized by an increase in the individualized ANB angle during the growth period from 5 to 12 years. Early characteristics of unfavorable growth included increased mandibular plane angle (measured to the sella-nasion line and the palatal plane, P <.05), increased lower gonial angle (P <.05), and a decreased ratio of posterior-to-anterior face height (P <.05) [corrected]. At the longitudinal follow-up at age 12, the 2 groups showed significant differences in SNB (P <.01) and individualized ANB (P <.01). The improved sagittal jaw relationship in the favorable growth group was the result of changed mandibular position. Morphogenetic posterior rotation seems to occur early in patients with skeletal Class II pattern and unfavorable growth and might be part of an adaptive mechanism compensating for insufficient mandibular growth.

Comparison between cephalometric classification methods for sagittal jaw relationships

The present study evaluated how 2 widely used cephalometric sagittal analyses, ANB angle and WITS appraisal, classify skeletal classes I, II, and III in a random selection of 497 Finnish boys aged 4-20 years. This distribution was also compared with the visual inspection of cephalometric structures judged by 2 university instructors in orthodontics. The results showed remarkable differences and even sparked controversy concerning classification of the sagittal jaw relationships. The ANB angle and the WITS appraisal emphasized the role of class II based on a failure to distinguish the proportion of class I. The low-angle influence skewed the distribution of the ANB pattern in the class III direction, and the WITS pattern, conversely, towards class II. High- or low-angle influence had only minor effects on the visual inspection of cephalometric structures. This cross-sectional study showed an age-related decreasing mean value for the ANB angle and increasing mean value for the WITS appraisal, thus explaining the remarkable difference in the distribution of sagittal classes. However, the findings of age-related changes makes the use of the fixed norms questionable. For extreme or controversial cephalometric interpretations, visual inspection provides an essential aid in diagnosis and skeletal classification.

Extracranial versus intracranial references in individual cephalometric analysis

This study was undertaken to determine whether angles SNA and ANB genuinely represent both the degree of maxillary prognathism and the intermaxillary relationship in natural head position (NHP). Pearson's r correlation coefficients were used to assess the associations between these angles, and variables based on NHP and extracranial reference lines. A large sample (n = 106) was used, comprising subjects with a variety of facial patterns. This was also divided into subgroups comprising subjects with similar facial configurations, determined by natural head position parameters. For the subgroups, SNA and ANB were not associated with the variables based on NHP, and showed high variations in subjects with similar facial patterns. SNA also showed statistically significant and high correlation with the inclination of the NSL to the true vertical.

A comparison of ANB, WITS, AF-BF, and APDI measurements

In the present study, the relationships among ANB, Wits, AF-BF, and APDI measurements used in the assessment of the anteroposterior jaw disorders were examined on the cephalometric radiographs of 63 male and 82 female subjects, and high correlations were found among them. Furthermore, relationships were explored between these parameters and some measurements that were thought to have influenced them. The results of the geometric studies could not be proved on the basis of statistical evaluation.

[Evaluation of the applicability of a mathematical model in the x-ray cephalometric diagnosis of sagittal bite anomalies. A clinical test]

The mathematical model (Järvinen) for measuring the sagittal difference between the maxillary and mandibular apical bases has been clinically tested. The material for this study consisted of 30 lateral skull radiographs of orthodontically untreated children (aged seven to 15 years) with different types of skeletal and/or dento-alveolar malocclusions. A comparison of the model with two conventional and two more developed methods to measure the sagittal apical base difference showed that the correlation between the new and the older methods increased as the errors of the older methods were eliminated. The results seemed to indicate that sagittal malocclusions could be accurately diagnosed by means of the model.

Relation of the Wits appraisal to the ANB angle: a statistical appraisal

The hypothesis that the relationship between the ANB angle and the Wits appraisal can be expressed by measuring the individual variations in their reference systems and by constructing a model of regression between them and a few parameters describing the reference systems was tested with material consisting of 30 lateral cephalometric radiographs of untreated orthodontic patients with different types of skeletal and/or dentoalveolar malocclusions. The results indicated that approximately 93% of the variation of the Wits appraisal could be explained by the variation of the ANB, NSL/OL, and SNA angles. The study also showed that the results given by different measurements with different reference systems, such as the ANB angle and the Wits appraisal, cannot be directly compared. To obtain comparable interpretations, one should correct the results of both measurements in relation to the variations in their reference systems.