Dental compensation for moderate Class III with vertical growth pattern by extraction of the lower second molars

Analysis of the effects and side effects of treatment of patients with moderate skeletal Class III and vertical growth pattern by means of extraction of the second molars in the lower jaw.

A total of 20 patients with a mean age of 12.9 years were examined retrospectively. Inclusion criteria consisted of a Wits value of 0 to -5, a posterior growth pattern of the mandible (Hasund analysis), an overjet of -2 to 1 mm, and an overbite of 0 to -3 mm. Treatment was performed using a straight-wire appliance. As part of the treatment, the lower second molars were extracted and Class III elastics attached. Cephalograms and orthopantomograms taken before and after treatment were used for evaluation.

Treatment resulted in a significant change in the mean overjet from 0.5 mm to 2.1 mm and the attainment of a positive mean overbite of -1.0 mm to 0.9 mm. The occlusal plane rotated anteriorly from 18.8° to 13.7°. The skeletal parameters showed a change in the Wits value from -3.3 mm to -1.4 mm and an anterior mandibular rotation (ML-NSL 35.5° vs. 32.0°). The soft tissues revealed an increase in the distance between the lower lip and the "esthetic line" to the posterior (-2.0 mm vs. -3.9 mm).

Dental compensation of moderate skeletal Class III with a tendency to an anterior open bite with vertical growth pattern by extracting the lower second molars, combined with Class III elastics, resulted in an anterior rotation of the occlusal plane and mandible. Eighteen of 20 patients achieved a physiological overjet and positive overbite. A prerequisite for this therapy is the presence of lower wisdom teeth; a potential side effect is elongation of the upper second molars.