The identification of Class III malocclusions by discriminant analysis

Using networks to understand medical data: the case of Class III malocclusions

A system of elements that interact or regulate each other can be represented by a mathematical object called a network. While network analysis has been successfully applied to high-throughput biological systems, less has been done regarding their application in more applied fields of medicine; here we show an application based on standard medical diagnostic data. We apply network analysis to Class III malocclusion, one of the most difficult to understand and treat orofacial anomaly. We hypothesize that different interactions of the skeletal components can contribute to pathological disequilibrium; in order to test this hypothesis, we apply network analysis to 532 Class III young female patients. The topology of the Class III malocclusion obtained by network analysis shows a strong co-occurrence of abnormal skeletal features. The pattern of these occurrences influences the vertical and horizontal balance of disharmony in skeletal form and position. Patients with more unbalanced orthodontic phenotypes show preponderance of the pathological skeletal nodes and minor relevance of adaptive dentoalveolar equilibrating nodes. Furthermore, by applying Power Graphs analysis we identify some functional modules among orthodontic nodes. These modules correspond to groups of tightly inter-related features and presumably constitute the key regulators of plasticity and the sites of unbalance of the growing dentofacial Class III system. The data of the present study show that, in their most basic abstraction level, the orofacial characteristics can be represented as graphs using nodes to represent orthodontic characteristics, and edges to represent their various types of interactions. The applications of this mathematical model could improve the interpretation of the quantitative, patient-specific information, and help to better targeting therapy. Last but not least, the methodology we have applied in analyzing orthodontic features can be applied easily to other fields of the medical science.

3D soft tissue analysis--part 2: vertical parameters

INTRODUCTION

The increasing relevance of 3D methods in orthodontic diagnostics and treatment planning calls for the development of new analysis methods and the definition of three-dimensional mean values.

OBJECTIVE

The aim of this study was to develop a reliable three-dimensional (3D) analysis of facial soft tissues. Our objectives were to determine vertical 3D mean values and define the relationship between vertical skeletal parameters and digitally-recorded 3D soft tissue parameters.

PATIENTS AND METHODS

A total of 100 adult patients (female symbol = 53, male symbol = 47) of Caucasian ethnic origin were included in the study. Patients with syndromes, cleft lip and palate, noticeable asymmetry or anomalies in the number of teeth were excluded. Arithmetic means for three vertical 3D soft tissue parameters were calculated. The parameters were analyzed biometrically in terms of their reliability and gender-specific differences. Furthermore, the 3D soft tissue values were analyzed with regard to any correlations with vertical cephalometric values. In addition, we employed stepwise discriminant analysis, a multivariate statistical method, to examine the extent to which correct assessment of craniofacial morphology is possible by referring to those 3D parameters.

RESULTS

We successfully defined reproducible 3D mean values for the 3D soft tissue parameters, demonstrating highly significant correlations between the vertical 3D soft tissue measurements and cephalometric measurements. 89.8% of the patients could be correctly assigned to a vertical or horizontal craniofacial morphology according to the 3D soft tissue values.

CONCLUSION

3D soft tissue analysis provides information about vertical skeletal parameters, allowing assessment of vertical craniofacial morphology. Further investigation will be required so that 3D soft tissue diagnosis can be integrated into treatment planning and assessment as a supportive diagnostic tool in the future.

Treatment decision in adult patients with Class III malocclusion: orthodontic therapy or orthognathic surgery?

Class III malocclusion is one of the most difficult anomalies to understand. Because not all Class III patients are candidates for surgical correction, patient assessment and selection remain main issues in diagnosis and treatment planning. The purpose of this study was to separate Class III patients who can be properly treated orthodontically from those who require orthognathic surgery. A large sample size was a necessary to obtain a sufficiently robust model. Thus, a multicentric study design was chosen (Orthodontic Departments of the Universities of Frankfurt, Heidelberg, and Würzburg, Germany). The cephalograms of 175 adult patients with Class III malocclusions were analyzed. The orthodontic group comprised 87 patients, and the surgery group, 88 patients. Twenty linear, proportional, and angular measurements were made. Stepwise discriminant analysis was applied to identify the dentoskeletal variables that best separate the groups. The discriminant function model was highly significant (P <.0001); 92% of the patients were correctly classified. The following variables were extracted: Wits appraisal, length of the anterior cranial base, maxillary/mandibular (M/M) ratio, and lower gonial angle. The resulting equation was: Individual score = -1.805 + 0.209. Wits + 0.044. S-N + 5.689. M/M ratio - 0.056. Go(lower). By means of discriminant analysis, correct classification of adult Class III malocclusion patients succeeded to a very high degree. Of all the variables, the Wits appraisal was the most decisive parameter.

Evaluation of the profile line in prognathic patients in the Saxony-Anhalt region of Germany

The aim of the present study was to investigate the soft-tissue morphology and profile line of prognathic patients in the Saxony-Anhalt region of central Germany. To this effect, the profile photographs and lateral cephalograms taken at treatment start for 34 adults (17 female patients, mean age: 22.6 years; 17 male patients; mean age: 23.2 years), Class III subjects who had not undergone orthodontic treatment, were measured and, by means of statistical analysis, the findings were compared with those of an age-matched control group (17 female subjects, mean age: 21.4 years; 17 male subjects, mean age: 23.8 years). Patients with Class III anomalies had a significantly longer and thinner lower lip and a smaller lower subnasal angle than the control subjects. The lower face was markedly enlarged. Furthermore, the osseous profile line was significantly flatter and the soft-tissue convexity was considerably reduced compared with the control group. Hence the prognathic patients of central Germany manifested typical features of the prognathic profile line. To elucidate typical regional features, further comparative studies are required.

[The differential diagnostic value of skeletal, dental and soft-tissue analyses in the planning of orthodontic-oral surgical therapy. A retrospective study of treated patients with skeletal Angle class III]

The study evaluated the orthodontic documentation gathered in the course of conducting combined surgical-orthodontic therapy on 45 skeletal angle class III patients. In 15 of the patients Le Fort I osteotomy of the maxilla was performed, in 15 sagittal split osteotomy of the mandible, and in the last 15 patients bimaxillary surgery. The purpose of the study was to evaluate by means of a retrospective analysis of cephalograms taken prior to surgery the role hard tissue, soft tissue, and dental cephalometric variables play in the choice of the type of surgery to be performed. Discriminate analysis was used to determine the ability of the individual parameters to predicate accurately the type of the surgery that had been carried out. The study revealed that the skeletal relationship diagnosed in the x-rays was suitable primarily in the differentiation of the monomaxillary and bimaxillary patients who had undergone surgery. Using discriminate analysis the accuracy to predict group membership was 75.6% for the skeletal parameters of the McNamara analysis and 67.5% for those of the Bergen analysis. Differentiation between the cases where surgery had been performed solely in the maxilla and those where surgery had been performed only in the mandible was most successful using the soft tissue parameters describing the position of the subnasale and the position of the lower lip in relation to the aesthetic line according to Ricketts. In addition, the arrangement of the lower incisors was more retrusive in the cases with isolated surgery in the maxilla. Discriminate analysis applying a combination of skeletal, dental, and soft tissue parameters had a capability to predict accurately in 93.3% of the patients the form of the chosen surgical procedure.