A retrospective comparison of functional appliance treatment of Class III malocclusions in the deciduous and mixed dentitions.

This retrospective study compared the effectiveness of treatment of Class III malocclusions with the removable mandibular retractor in the deciduous and mixed dentitions. A group of 20 children with Class III malocclusions started treatment at a mean age of 5 years 1 month +/- 7 months (deciduous dentition), while a group of 18 children with Class III malocclusions started treatment at a mean age of 8 years 2 months +/- 9 months (mixed dentition). The mean observation period was 2 years 3 months +/- 6 months for the first group, and 2 years 4 months +/- 7 months for the second group. Matched control groups of children with untreated Class III malocclusions in the deciduous and in the mixed dentition (16 subjects and 15 subjects, respectively) were used. The cephalometric analysis was based on a stable basicranial reference system appropriate for longitudinal studies that begin at early developmental ages. The results showed that treatment of Class III malocclusions in the deciduous dentition produced a more significant anterior morphogenetic rotation of the mandible, due to a more upward and forward direction of condylar growth (P < 0.01). This leads to significantly smaller increments in mandibular total length (Co-Pg) in children with Class III malocclusions under-going very early treatment (P < 0.01). On the contrary, maxillary dento-alveolar protrusion induced by therapy was greater in Class III subjects treated in the mixed dentition (P < 0.01). The optimum timing to improve skeletal relationships in Class III malocclusions by means of a functional appliance appears to be in the deciduous dentition.