Evaluation of continuous arch and segmented arch leveling techniques in adult patients--a clinical study

The purpose of this study was to compare the efficacy of overbite correction achieved by a conventional continuous arch wire technique and the segmented arch technique as recommended by Burstone. The sample comprised 50 adult patients (age 18 to 40 years) with deep bites. Twenty-five patients were treated with a continuous arch wire technique (CAW); in the second half of the sample, the segmented arch technique (Burstone) was used for correction of the vertical malocclusion. Lateral cephalograms and plaster cast models taken before and immediately after treatment were evaluated. Statistical analysis was performed on the collected data. The results showed that both techniques produced a highly significant overbite reduction (CAW: -3.17 mm, p < 0.001; Burstone: -3.56 mm, p < 0.001). The CAW group showed an extrusion in the molar area with subsequent posterior rotation of the mandible (6occl-ML: +1.30 mm; 6occl-NSL: +1.63 mm; ML/NSL: +1.94 degrees, all p < 0.001). The Burstone group, however, showed overbite reduction by incisor intrusion without any substantial extrusion of posterior teeth (upper 1-NSL: -1.50 mm; lower 1-ML: -1.72 mm; both p < 0.001). As a consequence, no significant posterior rotation of the mandible took place (ML/NSL: +0.52 degrees, n.s.). It is concluded that in adult patients the segmented arch technique (Burstone) can be considered as being superior to a conventional continuous arch wire technique if arch leveling by incisor intrusion is indicated.