Korean J Orthod.  2025 May;55(3):224-233. 10.4041/kjod24.236.

A comparison of soft tissue outcomes in skeletal Class II malocclusion: Anterior segmental osteotomy vs. non-surgical orthodontic treatment

• Choo H
• Kim YH
• Hong P
• Choi YJ
• Kim R
• Chae HS

• KMID: 2568345
• DOI: http://doi.org/10.4041/kjod24.236

Abstract

Objective
Temporary anchorage devices (TADs) have considerably reduced the need for anterior segmental osteotomy (ASO) in patients with Class I malocclusion. Most previous studies have been published before the widespread use of TADs, thus warranting new guidelines for determining the optimal approach for surgery and orthodontic treatment. This study aimed to establish guidelines on the choice between ASO and non-ASO (NASO) based on soft tissue considerations.
Methods
Sixty-seven patients diagnosed with skeletal Class II malocclusion were divided into the ASO (n = 31) and NASO (n = 36) groups. Cephalometric analyses were used to compare the initial and final records to assess the effect of treatment on soft tissues. The interlabial gap, upper lip anterior to the E-line, lower lip anterior to the E-line, H-angle, upper lip to the nasion-perpendicular line, and nasolabial angle were evaluated. In particular, a proportional difference indicator between the upper and lower lips relative to the pogonion angle between the facial plane and CK line was presented, followed by statistics analyses. Statistical significance was set at P < 0.05.
Results
Both groups demonstrated normal proportions of the upper and lower lips; however, significant differences favoring ASO over NASO in terms of soft tissue changes were observed for several variables.
Conclusions
ASO is advised if the required adjustment for the upper and lower lips is –4.0 mm and –5.0 mm, respectively. For modifications of –2.0 mm, NASO is preferred. This study provides clinical guidelines on the choice between ASO and NASO based on the required lip movement measurements.

Keyword

Soft tissue paradigm; Bimaxillary protrusion; Anterior segmental osteotomy (ASO); Extraction

Figure

• 

  Figure 1 Landmarks and reference lines used in the cephalometric analysis. A, Axes of coordinates: Frankfort horizontal (FH) line for X-axis; nasion-perpendicular line (N-perp) for Y-axis. B, For soft tissue: subnasale (Sn), soft tissue A point (A’), upper lip anterior (UL), lower lip anterior (LL), soft tissue B point (B’), and soft tissue pogonion (Pog’).

• 

  Figure 2 Soft tissue measurements. A, H-angle (angle between facial plane and H-line); CKA (angle between the facial plane and CK line); CKHA (difference between H-angle and CKA). B, SAL depth (distance between A’ and Sn-LS); PBL depth (distance between B’ and Li-Pg’). C, SAL angle (angles between Sn-A’ and A’-LS); PBL angle (angles between Li-B’ and B’-Pg’). See Figure 1 for definitions of each landmark or measurement.

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  Figure 3 A, Superimposition of patient undergoing anterior segmental osteotomy (ASO)-initial (black line), final (red line); B, Superimposition of non-ASO patient-initial (black line), final (red line); C, Superimposition of initial (black line), before-ASO (blue line), and final (red line). In the treatment plan, although a full-arch distalization of the mandible was planned for additional improvement of the protrusion after ASO, the treatment was finished without any changes in the sagittal plane of the mandible as the patient wished to maintain the position of the lips.

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