Photoelastic analysis of tension distribution in different orthodontic approaches for closing anterior open bites.

Abstract

This study aims to evaluate tension distribution in the anterior region of the mandible during two orthodontic mechanical approaches to treat anterior open bite. It was an in-vitro experimental study, that analyzed 5 models of photoelastic resin, simulating a lower dental arch. The anterior teeth underwent orthodontic forces of the Blue Elgiloy® 0.016" x 0.022" (MEAW technique) and Gummetal® 0.018"x 0.022" (GEAW technique) archwires. Tension distribution was assessed on three different points in the lower dental midline and was measured using a reflection polariscope. The archwires were evaluated with and without anterior elastic bands (6 oz, 170 g) installed between lateral incisors and lower canines, as recommended for anterior open bite. The highest magnitudes of tension generated by the archwires were observed in the cervical regions of the teeth (on average 50% higher than those at the most apical point) regardless of the technique used. Comparatively, the GEAW technique showed significantly (P<0.05) lower tension values (16 MPa) than the MEAW technique using Blue Elgiloy (24 MPa). The GEAW technique showed a more favorable tension distribution pattern than the MEAW approach. The use of elastic bands improved tension distribution, regardless of the technique. The results also suggest that the use of anterior elastic bands in both techniques reduced the tensions released by the intrusive forces generated by the archwires.