[The anatomical and physiological aspects in the treatment of temporomandibular joint disorders]

Craniofacial features of patients with Class III abnormalities: growth-related changes and effects of short-term and long-term chincup therapy

The craniofacial features of patients with Class III abnormalities, including growth-related changes and effects of short-term and long-term chincup therapy, were studied. Twenty female subjects were treated with chincups and an orthopedic force of 500 g for 31 months (short-term treatment group). Another 36 female patients were treated with chincups and a force of 250 to 300 g for 86 months (long-term treatment group). All subjects treated with chincups had lateral cephalograms taken before treatment (T0), after treatment (T1), and at retention (T2). Cross-sectional lateral films of 562 skeletal Class III girls were selected from the records of 1265 Class III patients at a public hospital and private clinics as controls. The controls were selected to approximately match the ANB angle, Wits appraisal, and chronological age of the treated groups. Short-term treatment resulted in a slight improvement in ANB angle and Wits appraisal, while long-term treatment resulted in a significant improvement in ANB angle and Wits appraisal. Such treatment also resulted in a significant inhibition of the growth of the ramus (2.2 mm) and body length (3.6 mm) of the mandible, a backward rotation of the mandible, and a reduction (8.2 degrees ) of the gonial angle. However, there was no alteration of any parameter of the maxilla and the cranial base, except the length of S-N and N-S-Ar in the long-term treatment group. Subjects who completed the long-term treatment protocol retained the changes by wearing the appliance during sleep, with a force of 200 g applied to the center of the chin.

Wear in the upper and lower incisors in relation to incisal and condylar guidance

The incisors of 85 patients were examined for tooth wear with the aim to evaluate possible association between the degree of wear and anterior guidance. Apart from clinical functional analysis electronic axiography using the system CADIAX was carried out. Anterior guidance in protrusive movement was marked on individually mounted plaster casts and scanned using a pantograph. The cephalometric analysis program CADIAS was used for the metric determination of the anterior guidance angle to the axis-orbital plane, and in order to relate the anterior guidance to the horizontal condylar inclination. The interincisal angle was included in the evaluation as a further functional angle and according to overjet and overbite there were classified typical incisor relations. Where both anterior guidance and incisor inclination and relation were in the normal range, there was an increase in incisal tooth wear in the group investigated. With reduced functional space, frequently found together with anterior deep bite, incisor wear was less extensive. While the occurrence of parafunction was shown not to be related to anterior guidance and incisor inclination and relation parafunctions were the decisive factor in the occurrence of severe incisor wear. Where anterior guidance and incisor inclination and relation are normal, the area of enamel under load is smaller and the space for bruxism larger. Parafunctional forces thus appear to result in a higher degree of wear than is found with the reduced functional space of a steep incisor position. Anterior guidance could not be evaluated as a parafunctonal inducing factor, but only as determining the wear pattern in the individual.