Occlusal morphology 1 year after orthodontic and surgical-orthodontic therapy

To evaluate morphologic characteristics of occlusion (contact points, contact areas, and frequency of contact) in clinically successful patients 1 year after orthodontic and surgical-orthodontic therapy followed by passive retention.

Twenty-two orthodontic and 18 surgical-orthodontic patients were analyzed. All patients were treated with standard edgewise technique by the same orthodontist. Contact points and areas were evaluated using a new method of digital image analysis of occlusal impressions. Polivinylsyloxan impressions were taken, scanned, and turned into gray-scale images. The physic relationship of light absorbance through the polivinylsyloxan for known thickness was calculated to determine contact areas (less than 50 microm of thickness) and near contact areas (less than 350 microm of thickness).

The contact area was significantly larger in the orthodontic than in the surgical-orthodontic patients (Student's t-test, P < .05). The surgical-orthodontic group had significantly fewer contact points than the orthodontic group only at 150 microm of thickness. In both groups of patients, the first molar had the largest contact surface. Occlusal support was distributed mainly in the posterior regions with an important role involving the first molars.

Surgical-orthodontic patients appear to have smaller contact surfaces and fewer contact points than orthodontic patients do. However, there were no differences in the number of teeth in contact with opposing teeth.