Comparison of posttreatment stability after total mandibular arch distalization with mini-implants and mandibular setback surgery

Abstract

Objectives: To compare posttreatment stability in skeletal Class III patients between those treated by total mandibular arch distalization (TMAD) with buccal mini-implants and those by mandibular setback surgery (MSS).

Materials and methods: The samples included 40 Class III adults, 20 treated by TMAD using buccal interradicular mini-implants and 20 treated with MSS. Lateral cephalograms were taken at pretreatment, posttreatment, and at least 1-year follow-up, and 24 variables were compared using statistical analysis.

Results: Mandibular first molars moved distally 1.9 mm with intrusion of 1.1 mm after treatment in the TMAD group. The mandibular incisors moved distally by 2.3 mm. The MSS group exhibited a significant skeletal change of the mandible, whereas the TMAD group did not. During retention, there were no skeletal or dental changes other than 0.6 mm labial movement of the mandibular incisors (P < .05) in the MSS group. There was 1.4° of mesial tipping (P < .01) and 0.4 mm of mesial movement of the mandibular molars and 1.9° of labial tipping (P < .001) and 0.8 mm of mesial movement of the mandibular incisors in the TMAD group. These dental changes were not significantly different between the two groups.

Conclusions: The TMAD group showed a slightly decreased overjet with labial tipping of the mandibular incisors and mesial tipping of the first molars during retention. Posttreatment stability of the mandibular dentition was not significantly different between the groups. It can be useful to plan camouflage treatment by TMAD with mini-implants in mild-to-moderate Class III patients.

Keywords: Mandibular arch distalization; Mandibular setback surgery; Mini-implants; Stability.

Figure 1.

(A) Total mandibular arch distalization (TMAD) group. (B) Mandibular setback surgery (MSS) group. Interdental mini-implants were placed temporarily during surgery, and a surgical stent was used for intermaxillary fixation.

Figure 2.

(A) Landmarks, skeletal and soft-tissue measurements: 1. SNA (°), 2. SNB (°), 3. ANB (°), 4. Wits appraisal (mm), 5. FMA (°), 6. PFH/AFH (%), 7. SN to occlusal plane angle (°), 8. upper lip to E-line (mm), 9. lower lip to E-line (mm). (B) Dental measurements: 1. U1C to VRL (mm), 2. U1C to FH (mm), 3. U6C to VRL (mm), 4. U6C to FH (mm), 5. L1C perp to MP (mm), 6. L1R perp to MP (mm), 7. L1C to MP (mm), 8. L6C perp to MP (mm), 9. L6R perp to MP (mm), 10. L6C to MP (mm), 11. L6 to MP (°), 12. U1 to FH (°), 13. IMPA (°), 14. overjet (mm), 15. overbite (mm).

Figure 3.

Schematic drawings showing the changes in mandibular dentition after treatment and during retention in the TMAD group. (A) At the end of treatment, the mandibular first molars displayed 1.9 mm of distalization and 1.1 mm intrusion with distal tipping of 4.7°. The mandibular incisors showed 2.3 mm of distalization and 0.3 mm of extrusion with lingual tipping of 4.2°. (B) During posttreatment retention, the mandibular first molars displayed mesial movement of 0.4 mm and extrusion of 0.6 mm with mesial tipping of 1.4°. The mandibular incisors showed labial movement of 0.8 mm with 1.9° of labial tipping. *Significant change.