The surgical outcomes of anterior segmental osteotomy in Asian skeletal class II patients.

PURPOSE: Anterior segmental osteotomy (ASO) following the surgery-first approach is a long-established treatment modality to resolve lip protrusion in patients with skeletal class II patterns. However, the indications and effectiveness of ASO still remain uncertain. The objective of this study is to investigate the effectiveness of ASO in Asian skeletal class II patients by evaluating the skeletal and soft tissue changes and analyzing pre-treatment variables that determine successful outcomes in occlusal as well as esthetic aspects. METHODS: The lateral cephalograms of 44 skeletal class II patients who underwent ASO and orthodontic treatment for resolving lip protrusion were retrospectively collected. Hard and soft tissue variables of two groups, normalized (NG) and unnormalized (UNG) ANB after treatment were compared and analyzed. The rotational effect of the anterior segment on the hard and soft tissue was also investigated. RESULTS: ASO was successful in correcting the skeletal class II relationship and lip protrusion (ΔANB - 2.3°, 4-5 mm lips retraction) in most cases. However, for patients with severely camouflaged skeletal class II incisors involving a large ANB and SNA, a large ANB still remained post-treatment. The study also found that rotation of the upper and lower anterior segments further augmented the amount of lip retraction. CONCLUSIONS: ASO was found to successfully correct ANB of skeletal class II patients under the following conditions (ANB 5.3° ± 1.5°, SNB 77.3° ± 4.5°, U1 to FH 115° ± 7.5, L1 to FH 48.0° ± 4.6). However, patients with larger ANB and SNA values may require bi-maxillary surgery. In addition, ASO has limitations in correcting gummy smile in cases of extreme maxillary excess. For patients requiring a large amount of lip retraction, rotation of the anterior segment may be beneficial in conjunction with bi-maxillary surgery.

Soft-Tissue Response following Genioplasty Combined with Anterior Segmental Osteotomy.

BACKGROUND: The authors' main aim was to analyze soft-tissue response of the chin following genioplasty with anterior segmental osteotomy, which enables optimal surgical planning of genioplasty. METHODS: Sixty-two patients who underwent genioplasty with concomitant anterior segmental osteotomy were divided into three groups depending on the direction of pogonion (Pog) movement: G1 (without sagittal change), G2 (advancement genioplasty), and G3 (setback genioplasty). All genioplasties included height reduction. Hard- and soft-tissue measurements with cephalometry were performed at T1 (before surgery), T2 (after surgery), and T3 (after orthodontic treatment) for the analysis of sagittal and vertical changes. Correlation and regression analyses were conducted to analyze soft- to hard -tissue movement and soft-tissue thickness changes. RESULTS: During the T1 to T2 period, the horizontal soft- to hard-tissue ratio at Pog was 0.85 in G2 and 0.80 in G3, and the vertical ratio at menton (Me) was 0.9 for all groups. The correlation coefficients were 0.64 (G2) and 0.83 (G3) at Pog and 0.9 (all), 0.85 (G1), 0.95 (G3) at Me. There was no significant correlation between initial soft-tissue thickness and soft-tissue response ratio. During the T2 to T3 period, no significant relapses were observed, which demonstrates the stability of anterior segmental osteotomy combined genioplasty. CONCLUSIONS: Clinically and statistically significant soft-tissue responses were demonstrated at Pog and Me. The higher values in G3 in particular suggest that setback genioplasty with anterior segmental osteotomy is an effective treatment alternative to conventional two-jaw surgery in some patients with bimaxillary prognathism with macrogenia. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.