A multivariate approach to analyzing the relation between occlusion and craniofacial morphology.

This study examined the association between occlusion and craniofacial morphology using univariate and multivariate statistical methods. Data were obtained from study casts and lateral cephalometric radiographs of 164 children in the early permanent dentition. The following multiple features of occlusion were assessed: molar relation, overjet, overbite, and anterior crowding. Angular skeletal measures assessed cranial base flexure, maxillary horizontal and vertical positions, mandibular horizontal and vertical positions, horizontal and vertical maxillary-mandibular relations, and positions of the incisors. The relation between the Occlusal Index, which is a malocclusion severity index, and skeletal morphology was also investigated. Associations were examined by use of linear correlation, stepwise multiple regression, and canonical correlation analyses. Individually and in combination, occlusal features were poorly associated with individual skeletal measures (r2 less than or equal to 0.35). The strongest association occurred between a linear combination of occlusal features and a linear combination of skeletal measures (R2 = 0.66, p = 0.0001). A malocclusion severity index did not aid in the identification of craniofacial morphology. The results suggested that combinations of certain occlusal characteristics may be associated with specific skeletal types; however, a generalized statement of this concept could not be supported.

Skeletal changes associated with extraoral appliance therapy: an evaluation of 200 consecutively treated cases.

Questions exist concerning the degree to which orthodontic treatment alters facial form. This study has attempted to discern changes in several measures of vertical facial form which might be influenced by varying vectors and amounts of extraoral force. The data were collected from pre- and posttreatment lateral cephalograms of 200 children treated consecutively with full edgewise orthodontic appliances. The sample was divided into three pretreatment groups based on the type of extraoral force delivered; cervical, "combi," and no-headgear. All groups showed a wide range of variation in treatment response, but did not demonstrate significant differences. While the extraoral forces predictably improved horizontal maxillo-mandibular discrepancies, there was too much variation in response to predict vertical changes.

Clinical validity of the relationship between TMJ signs and symptoms in children and youth.

Cross-sectional data on subjective symptoms and clinical signs of TMJ dysfunction were collected from 1342 subjects ranging in age from 6 to 17 years old. Statistically significant associations existed between certain symptoms and signs (p less than .0001); however, these associations lacked correspondence as indicated by the sensitivity (from 2 percent to 40 percent) and false-positive rates (52 percent to 77 percent) of the symptom-related interview questions. These findings do not support drawing valid clinical conclusions from cross-sectional sign and symptom studies of TMJ dysfunction in children.

Imprecision and bias in orthodontic treatment results.

Imprecision in treatment response has been defined as inconsistent unpredictable results from the same treatment. Bias has been defined as systematic failure to achieve defined treatment goals. Concepts of imprecision and bias are applied to the results of a study of soft-tissue response to Class II treatment with edgewise and Herbst appliances.

Associations between occlusal characteristics and signs and symptoms of TMJ dysfunction in children and young adults.

Cross-sectional data were obtained from 1,342 subjects 6 to 17 years of age and analyzed for the prevalence of (1) specific types of occlusion, and (2) subjective symptoms and clinical signs of TMJ dysfunction. The results, as they pertained to occlusion and clinical signs, were as follows: functional shift was negatively associated with TMJ and muscle tenderness; open bite was positively associated with TMJ and muscle tenderness; excessive or negative overjets were more likely to have joint tenderness; older subjects with a cusp-to-cusp or a Class II molar relationship were more likely to experience TMJ and muscle tenderness, and restricted opening; and buccal crossbites had a significantly higher prevalence of joint sounds in older children. Results pertaining to occlusion and subjective symptoms were as follows: Class II molar relationship was positively associated with joint noise in the 6 to 8 and 15 to 17-year age groups; and subjects with negative overjet were more likely to report joint noise. Our conclusions were that (1) statistical associations exist between certain features of occlusion and TMJ signs/symptoms, and (2) such associations are greater in the older groups tested.

Differential diagnosis of class II malocclusions. Part 1. Facial types associated with class II malocclusions.

By means of computer-based statistical methods, several types of Class II malocclusion have been discovered with defining horizontal and vertical characteristics. Of the six horizontal types, four are severe syndromes, one is a loose, ill-defined grouping of cases with mild skeletal features, and one has only the dental features of Class II. Five vertical types associates with Class II were also revealed, although each vertical is not associated with all horizontal types. A simplified simulation of the computerized procedures has been developed for routine use in clinical practice.

Growth of the maxillary complex in the rhesus monkey (Macaca mulatta).

The growth of the maxillary complex of 36 rhesus monkeys (Macaca mulatta) was analyzed quantitatively and qualitatively during four defined stages of postnatal development (i.e., infant, juvenile, adolescent, young adult). At each stage, growth was observed during a 24 week period. Since some animals were observed during two successive stages of development, 47 periods of growth were studied. The incremental growth data were collected by superimposing serial cephalograms on cranial base implants and on maxillary implants. The largest increments of growth were observed in the infant animals and were successively less during the other periods studied. The horizontal growth component was more more prominent than the vertical component in all age groups. The contribution of sutural growth to the vertical displacement of the maxilla was greater posteriorly, leading to a rotation of the maxillary complex during growth. The occlusal relationship was maintained by selective bone remodeling in conjunction with dentitional migration.