The biomechanical relationship between incisor and condylar guidances in deep bite and normal cases.

The purpose of this study was to investigate the biomechanical relationship between the condylar and anterior guidances in deep bite malocclusion and control groups. The subjects consisted of 18 deep bite patients and 14 normal occlusions. A four-bar mechanism was described on the lateral cephalogram films and a computer program, for which the lengths of the links measured on the films were the inputs, was developed. The computer program was used to calculate the angles of rotation of the mandible and the condyle during contact of the mandibular anterior teeth with the lingual surface of the maxillary anterior teeth as the mandible moves forward. Comparison of the mean values of the angles of rotation of the mandible and condyle in the two groups has shown that the change in the angle of rotation of the condyle is statistically significant (P < 0.05). The angles of rotation of condyle in deep bite group were found larger than the angles of normal group. Correlation between the angles of rotation of the condyle and mandible has shown that they were significantly related. The cause of temporomandibular disorders may be attributed to the large angle of rotation of the condyle in deep incisal overbite.

The influence of orthodontic extraction treatment on dental structures: a two-factor evaluation.

The purpose of this investigation was to evaluate the effects of different growth patterns and treatment types on dentoalveolar structures in patients treated with fixed Edgewise mechanics and the extraction of four first premolars. A total of 41 patients with a mean chronological age of 14 years 7 months and skeletal age of 14 years 6 months were included in the study. The type of growth pattern was assessed as mesio- or hyper-divergent, and the treatment type as the use or non-use of headgear. The results were analysed by two-way analysis of variance (ANOVA). The decrease in overbite in the mesiodivergent group was statistically significant when compared with the increase in the hyper-divergent group (P < 0.01). Extrusion of the lower molar was observed in all groups, and a statistically significant difference was found between the mesio- and hyper-divergent groups (P < 0.05). Interaction between growth pattern and treatment type was not found to be significant for any variable. It can be concluded that premolar extractions and the use of headgear with fixed appliances does not significantly change the overjet, occlusal plane angle, upper and lower anterior dentoalveolar heights, upper posterior dentoalveolar height, or the inclination of the upper and lower incisors. The only significant changes were observed in overbite as a result of treatment mechanics and in lower posterior dentoalveolar height due to the growth pattern.

Effects of an activator on the masseter and anterior temporal muscle activities in Class II malocclusions.

Effects of an activator on the temporal and masseter muscles activities were investigated in subjects with an Angle Class II division 1 malocclusions in this study. The measurements were done on 21 subjects. Twelve of these subjects were in the treatment group and 9 were in the control group. Average ages of treatment group was 11.42 +/- 0.29 years and average ages of control group was 10.68 +/- 0.52 years. Muscle activities were investigated at the beginning and at the end of this research, both with and without the activator. The increase of activities in the rest position and decrease of activities in maximum biting of both muscles with activator were found to be statistically significant at the beginning of the treatment. Activities of both muscles with the activator decreased in the rest position at the end of treatment when compared to the beginning of the treatment. No change has been observed between the activities of masseter and temporal muscles recorded at the beginning and at the end of this investigation without the activator.

The influence of extraction orthodontic treatment on craniofacial structures: evaluation according to two different factors.

The purpose of this study was to evaluate the effects of different growth pattern and treatment type factors on craniofacial structures in cases treated with fixed mechanics and premolar extractions. A total of 41 cases with a mean chronologic age of 14 years 7 months and skeletal age of 14 years 6 months was included in the study. These cases were treated with fixed Edgewise mechanics and with extraction of four first premolars. The growth pattern factor was assessed in two levels as mesiodivergent and hyperdivergent, and the treatment type factor was assessed as with and without headgear. The results were analyzed by two-way analysis of variance. In the assessment of differences between the two types of growth patterns at the end of treatment; the changes in N-ANS and N-M were found to be statistically significant (P <.05). In comparison of cases treated with and without headgear, changes in SNA and ANB angles were found to be statistically significant (P <.01). Interaction was found to be nonsignificant for all measurements. It was observed that treatment with fixed appliances and premolar extractions does not change significantly the growth pattern.