Stepwise advancement using fixed functional appliances: Experimental perspective

Abstract

This study was designed to identify the pattern of bone formation in the temporomandibular joint in response to the stepwise mandibular advancement compared to single step advancement with fixed functional appliances. Two hundred fifty 35-day-old female Sprague-Dawley rats were randomly divided into 20 experimental and 10 control groups. Appliances were fitted to position the mandible forward in the experimental groups. Veneers were added to achieve movement. The rats were then sacrificed at different time points. Sections were cut and stained with periodic acid and Schiff's reagent for evaluation of new bone formation. Newly formed bone was measured by a computer-assisted image analyzing system. The results showed that, during the first advancement, bone formation in the condyle and glenoid fossa was less than that of 1-step advancement. In response to the second advancement, new bone formation was significantly higher when compared with single advancement with a maximum increase of 50% and 100% in the condyle and glenoid fossa, respectively. In conclusion, the stepwise advancement produces more skeletal effects than single advancement and a more prominent effect with stepwise advancement was found in the glenoid fossa compared with the condyle.