Non-extraction treatment in borderline class III malocclusion]

To evaluate the effect of non-extraction treatment protocol combined with rapid palatal expansion and lower molar distalization in borderline Class III malocclusion in adolescents.Nine borderline Class III patients (average age: 13.4 ± 0.7 years) with average (6.7 ± 2.8)mm crowding in maxilla and (2.6 ± 0.4) mm crowding in mandible received the treatment described above. The lateral cephalograms of these patients were analyzed. All patients had a pretreatment ANB angle greater than -3°. The difference before and after treatment was analyzed with paired t test using SPSS11.0 software package.Evaluation of cephalometric measurements revealed forward movement of the maxilla, indicated by 1.69 mm forward positioning of A-point (P < 0.05), and an increase in SNA by 1° (P = 0.054). The mandible was inhibited from growing forward with slight retrusion evidenced by a decreased B-point (-1.88 mm, P < 0.05), and a decrease in SNB by 0.69° (P < 0.05). The combined maxillary and mandibular changes resulted in an increase in ANB angle (1.69°, P < 0.05). A clockwise rotation of the mandible was found, with an increase in Y-axis (0.88°,P < 0.05) and SN-MP (1.50°,P<0.05). Significant change was also found in the forward movement of maxillary incisors (+3.44 mm, P < 0.05), and the slight retrusive positioning of mandibular incisors (-0.5 mm, P > 0.05). An increase in U1-SnPg' (1 mm, P < 0.05) and a decrease in L1-SnPg' (0.63 mm, P > 0.05) resulted in the improvement of upper and lower lips relationship (1.88 mm, P < 0.05).This treatment protocol can improve the sagittal jaws and upper-lower lip relationship.