Comparing Soft Tissue Outcomes in Skeletal Class II Malocclusion: Anterior Segmental Osteotomy vs. Non-Surgical Orthodontic Treatment

doi:10.21203/rs.3.rs-4912693/v1

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Research Article

Comparing Soft Tissue Outcomes in Skeletal Class II Malocclusion: Anterior Segmental Osteotomy vs. Non-Surgical Orthodontic Treatment

https://doi.org/10.21203/rs.3.rs-4912693/v1

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Objectives: Temporary anchorage devices (TAD) has reduced the need for anterior segmental osteotomy (ASO) in patients with Class I malocclusion. Previous studies were mostly published before the widespread use of TADs. Therefore, new guidelines are required to determine the optimal approach between surgery and orthodontic treatment. The purpose of this study is to establish guidelines on the choice between ASO and non-ASO (NASO) based on soft tissue considerations.

Materials and Methods: Sixty-seven patients diagnosed with skeletal Class II malocclusion were divided into ASO (n = 31) and NASO (n = 36) groups. Cephalometric analyses were used to compare the initial and final records to assess the impact of treatment on soft tissue. The interlabial gap, upper lip to E-line, lower lip to E-line, H-angle, UL to N-perpendicular line, and nasolabial angle were evaluated. Specially a proportional difference indicator between the upper and lower lips relative to the Pog (CKHA) was presented, followed by statistics analyses. A P-value of less than 0.05 indicated statistical significance.

Results: Both groups showed normal proportion between the upper and lower lips, although significant differences favoring ASO over NASO in soft tissue changes were observed in several variables.

Conclusions: If the required adjustment for the upper and lower lips is -4.0 mm and -5.0 mm, respectively, ASO is advised. For modifications of -2.0 mm, NASO is preferred.

Clinical Relevance: This study provides clinical guideline for choosing between ASO and NASO treatments based on required lip movement measurements.

Soft tissue paradigm

Bimaxillary protrusion

Anterior segmental osteotomy (ASO)

Extraction orthodontic treatment

Bimaxillary protrusion, which is prevalent in the Asian and African populations, frequently occurs in orthodontic practice [1, 2]. The advent of temporary orthodontic anchorage devices (TAD) has expanded the spectrum of orthodontic treatment orthodontic treatment range by enhancing the anchorage capabilities. Despite these advantages, this orthodontic approach may lead to adverse outcomes, including limited aesthetic enhancement, root resorption, excessive retroclination of the front teeth, and diminished alveolar bone density in the anterior region [3]. To mitigate these adverse effects and effectively address lip protrusion, anterior segmental osteotomy (ASO) combined with premolar extraction was performed [4].

A systematic analysis conducted by Jayaratne et al [2] documented that the nasolabial angle (NLA) increased from 8.9° to 18° following ASO procedures. Furthermore, it was observed that the labial superius underwent posterior displacement within a span of 0.9–7.25 mm. The horizontal displacement of the maxillary incisors owing to anterior movement in the maxilla varied from 33–67%, whereas that of the mandibular incisors varied from 67–89% owing to anterior mandibular adjustments. Additionally, five studies highlighted a decrease in the interlabial gap after ASO surgery. As reported in different studies, the variability in soft tissue alterations following ASO could be attributed to ethnic variations within the studied populations. In a comparative analysis of ASO versus nonsurgical and non-extraction orthognathic approaches, Lee et al [5] observed that the group undergoing ASO exhibited greater posterior displacement of the upper incisors and more significant alterations in the NLA than the non-surgical and non-extraction orthognathic approaches did. While extensive research has been conducted on soft tissue modifications following ASO, comparative studies between ASO surgical correction and nonsurgical tooth extraction methods are limited.

The purpose of this study was to evaluate soft tissue changes after ASO versus non-ASO (NASO) orthodontic treatment using TAD with premolar extraction. By contrasting the outcomes of treatments using ASO and NASO, this study aimed to facilitate the formulation of tailored treatment plans optimized for individual patient needs and the decision-making between the two plans.

STUDY SAMPLE

The study sample size was determined using the G*Power software (version 3.1; Heinrich-Heine University, Düsseldorf, Germany). This involved conducting two independent sample t-tests, assuming a two-tailed distribution, an effect size of 0.5 (indicative of a medium effect), a significance level of 0.05, and a power of 0.8. The calculation indicated that a minimum of 63 subjects were necessary for a comparative analysis between the two groups.

This is a retrospective study. Between September 1, 2016, and September 1, 2021, 67 patients aged 19–40 years who visited the Department of Orthodontics at Aju University Dental Hospital were selected based on the study’s inclusion and exclusion criteria. Pre- and post-treatment lateral cephalometric radiographs were obtained and analyzed.

The inclusion criteria were: 1) diagnosis of skeletal class II malocclusion (ANB > 2°); 2) adults aged 18 years or older; 3) individuals who have received orthodontic treatment; 4) patients with extracted premolars; and 5) patients seeking treatment for lip protrusion. The exclusion criteria were: 1) patients with congenital dental anomalies; 2) individuals with congenital conditions, including craniosynostosis and cleft palate; 3) patients with systemic diseases affecting bone metabolism; 4) patients with severe facial asymmetry (chin displacement less than 4 mm relative to the facial midline); and 5) patients who have discontinued orthodontic treatment (Online resource 1).

This study was conducted following the approval and guidelines of the Institutional Review Board of Ajou University Hospital (IRB No: AJOUIRB-DB-2022-354).

CEPHALOMETRIC MEASUREMENT

Lateral cephalometric radiographs were obtained with the subjects in a natural head posture, and the patients were instructed to maintain their lips at rest to accurately assess lip incompetence, as outlined by Park and Burstone [6]. The cephalometric measurements and analyses were conducted by a single examiner (PR Hong) utilizing the V-ceph 8.4 software (Osstem, Seoul, Korea). The cephalometric analyses of 10 randomly chosen patients were repeated at 4-week intervals to assess the precision of the examiner’s measurements. The reproducibility of these measurements was confirmed by calculating the intraclass correlation coefficient, which exceeded 0.9, indicating a high level of measurement reliability.

Forty-one specific measurements were used to assess the facial profile changes pre- and post-treatment. These measurements were analyzed on the X-axis, defined by the Frankfort Horizontal (FH) line, and on the Y-axis, determined by the line perpendicular to point N (N-perpendicular line), facilitating both vertical and horizontal comparisons (Fig. 1). To evaluate the morphological alterations of the lips, measurements, such as SAL depth, PBL depth, SAL angle, and PBL angle, were employed [7]. Specifically, the SAL depth and PBL depth refer to the distances from A’ to Sn-Ls and from B’ to Li-Pg, respectively, whereas the SAL angle and PBL angle denote the angles formed by Sn-A’-Ls and Li-B’-Pg, respectively (Fig. 2a, b). Furthermore, to examine the nuances of the upper and lower labial angles, the CK, H, and CKH angles (where the CKH angle equals the H angle minus the CK angle) were utilized (Fig. 2c; Online resource 2) [8].

ASO was performed exclusively by a single surgeon (YJ Choi), whereas all orthodontic treatments were administered by a single ABO-certified orthodontist (HS Chae) using a 0.022 slot bracket system with an MBT prescription. In the ASO treatment group, a range of minimum to maximum anchorage was applied to both the maxilla and mandible to close the spaces remaining after the surgery. In the NASO group, maximum anchorage was achieved using TAD in the maxilla, and a moderate-to-maximum anchorage approach was adopted in the mandible.

SURGICAL PROCEDURES

ASO and/or genioplasty were performed under general anesthesia. The first premolars were extracted during surgery to facilitate the posterior translation of the anterior segment. Owing to the superior blood supply of the mandible than that of the maxilla, mandibular osteotomy was prioritized to minimize the ischemic duration in the maxillary region. The osteotomy was performed using a 4 mm diameter round burr and a reciprocating saw. For the mandible, an incision was made below the mucogingival junction, extending from canine to canine, to ensure protection of the bilateral mental nerves. In the maxilla, a minor Le Fort I incision spanning from the canine to the canine was made on the labial side. The palatal incision involved a central stab incision coupled with a crevicular incision extending from the canine to the second premolar. These specific maxillary incisions were designed to preserve blood supply to the palatal area. Following repositioning of the maxillary and mandibular segments to their intended locations, they were secured using miniplates and screws. An additional genioplasty guided by intraoperative evaluation was also performed.

STATISTICAL ANALYSIS

The data obtained were subjected to rigorous statistical analysis using SPSS software (IBM, Armonk, New York, United States, version 29.0). The Shapiro–Wilk test, for both pre- and post-treatment measurements, evaluated the data distribution for normality. An independent t-test was used to compare the measurements obtained before treatment, the changes observed from before to after treatment, and the measurements recorded after treatment between the ASO and NASO groups. A p-value of less than 0.05 indicated statistical significance.

PRE-TREATMENT COMPARISON BETWEEN ASO AND NASO

Before treatment initiation, significant differences were observed between the patients undergoing ASO and NASO across several parameters. Notably, the interlabial gap, UL-E (upper lip to E-line), LL-E (lower lip to E-line), PBL depth, H angle, distance from B' to the N-perpendicular line, UL (Upper Labial) position to N-perp, Pog' to N-perp, and lower lip thickness exhibited statistically significant differences (p < 0.05) between the ASO and NASO groups (Table 1). Additionally, the CK angle, assessing lower incisors protrusion, showed a significant difference (p < 0.1), with the ASO group presenting greater measurements of 1.87° and 2.93° for the H and CK angles, respectively. This indicated that the ASO group had more protrusion in the upper and lower lips than the NASO group had. The interlabial gap, a potential indicator of lip incompetence, was 2.05 mm larger in the ASO group than in the NASO group before treatment. The upper and lower lip protrusion relative to the E-line was approximately 2 mm more pronounced in the ASO group than in the NASO group. Regarding the N-perpendicular line, the soft tissue points A and B were 1.74 mm more anterior and 4.83 mm more posterior in the ASO group, respectively, than in the NASO group. The position of the upper lip was 2.83 mm further anterior in the ASO group, and the soft tissue pogonion (Pog') was 9.65 mm more posterior than in the NASO cohort. The SAL angle, SAL depth, PBL angle, and PBL depth demonstrated significant disparities, with the PBL depth being notably greater in the ASO group by -1.97 mm than in the NASO group. While no significant difference was noted in the thickness of the upper lip between the two groups, the lower lip thickness was significantly greater in the ASO group by 1.46 mm than in the NASO group, as delineated in Table 1.

Table 1

SOFT TISSUE MEASUREMENTS TO COMPARE ASO WITH NASO BEFORE TREATMENT
	ASO		NASO
Measurements	mean	SD	Mean	SD	difference	P
Interlabial gap	4.54	2.06	2.49	2.34	2.05	0.00**
UL-E	2.98	2.19	1.00	1.95	1.98	0.00**
LL-E	5.33	2.75	3.28	2.65	2.05	0.00**
PBL angle	130.10	12.82	137.18	75.05	-7.08	0.58
PBL depth	-5.17	1.13	-3.19	2.04	-1.97	0.00**
SAL angle	152.75	10.64	154.32	11.77	-1.57	0.57
SAL depth	-1.53	0.63	-1.34	0.54	-0.19	0.19
CK angle	28.59	5.90	25.66	7.34	2.93	0.08
H angle	21.00	2.84	19.13	3.56	1.87	0.02*
CKH angle	-7.58	4.46	-6.52	5.46	-1.06	0.39
Nasolabial angle	91.09	9.45	92.67	8.98	-1.58	0.49
A’ to N-perp	15.64	4.19	13.90	4.24	1.74	0.097
B’ to N-perp	4.92	5.72	9.75	5.36	-4.83	0.00**
UL to N-perp	20.92	4.71	18.09	4.43	2.83	0.01**
LL to N-perp	16.27	5.15	14.98	4.66	1.29	0.29
Pog’ to N-perp	2.23	6.58	11.88	4.61	-9.65	0.00**
UL thickness	12.56	2.43	12.16	2.04	0.41	0.46
LL thickness	14.49	2.06	13.03	1.74	1.46	0.00**
Independent t-test was performed to compare the variables of the two groups before treatment; p < 0.05, *p < 0.01.
ASO, anterior segmental osteotomy; NASO, non-ASO

COMPARISON OF POST-TREATMENT OUTCOMES BETWEEN ASO AND NASO

Following the treatment phase, statistically significant differences were observed in several parameters, including PBL angle, PBL depth, NLA, B' to N-perpendicular, Pog' to N-perpendicular, and lower lip thickness when comparing outcomes between patients undergoing ASO and NASO. Specifically, in the ASO group, the PBL angle decreased by an average of 18.78° in contrast to the NASO group. Additionally, the lower lip thickness in the ASO group was 1.61 mm thicker post-treatment than in the NASO group. Regarding the positional changes of the anatomical points, the B' point in the ASO group was positioned 5.90 mm more posteriorly, and the Pog' point was 8.76 mm further back than in the NASO group post-treatment. Finally, the NLA was enlarged by 5.39° in the ASO group compared with that in the NASO group (Table 2).

Table 2

SOFT TISSUE MEASUREMENTS TO COMPARE ASO WITH NASO AFTER TREATMENT
	ASO		NASO
Measurements	mean	SD	mean	SD	difference	P
Interlabial gap	3.00	1.94	2.29	2.32	0.71	0.19
UL-E	-1.11	1.92	-0.77	2.24	-0.34	0.51
LL-E	0.43	2.03	0.96	2.91	-0.54	0.39
PBL angle	132.69	9.26	151.47	10.56	-18.78	0.00**
PBL depth	-4.76	0.83	-4.08	1.10	-0.68	0.01*
SAL angle	151.44	11.71	152.15	10.85	-0.71	0.80
SAL depth	-1.62	0.59	-1.51	0.55	-0.11	0.44
CK angle	18.31	4.28	19.66	6.04	-1.35	0.30
H angle	15.97	2.21	16.31	3.42	-0.34	0.64
CKH angle	-2.34	3.10	-3.35	4.61	1.01	0.29
Nasolabial angle	102.75	8.21	97.37	9.21	5.39	0.02*
A’ to N-perp	13.29	4.19	11.21	4.51	2.09	0.06
B’ to N-perp	2.79	5.57	8.69	5.63	-5.90	0.00**
UL to N-perp	16.83	4.68	16.42	3.73	0.41	0.69
LL to N-perp	11.56	5.02	12.85	4.27	-1.29	0.26
Pog’ to N-perp	2.39	5.87	11.14	4.68	-8.76	0.00**
UL thickness	13.67	2.46	13.12	2.30	0.55	0.35
LL thickness	15.43	1.98	13.82	1.95	1.61	0.00**
Independent t-test was performed to compare the variables of the two groups after treatment; p < 0.05, *p < 0.01.
ASO, anterior segmental osteotomy; NASO, non-ASO

ANALYSIS OF PRE- AND POST-TREATMENT MODIFICATIONS IN ASO VERSUS NASO

Significant variations were identified in the alterations observed from before to after the treatment across several measurements between the patients treated with anterior ASO and NASO, with statistical significance. These measurements included changes in the interlabial gap, UL-E (upper lip to E-plane), LL-E (lower lip to E-plane), PBL depth, CK angle, H angle, NLA, UL to N-perpendicular, and LL to N-perpendicular (Table 3). A notable difference was also observed in the change from B' to N-perpendicular between the two groups (p < 0.1). Specifically, the ASO group reduced the interlabial gap by -1.54 mm, while the NASO group showed no significant change. Correlation analyses of soft tissue measurements revealed significant relationships between the change in the interlabial gap and the change in the CK angle (p < 0.05), as well as between the interlabial gap and the CKH angle (p < 0.05) across all patients. Within the ASO group, a significant correlation was found only between the change in the interlabial gap and CKH angle (p < 0.05), indicating specific patterns of facial profile adjustment in response to the respective treatments. Ricketts's E line pre- and post-treatment changes were more posterior in the ASO group than in the NASO group by -2.32 mm in the upper and − 2.58 mm in the lower lips. The change from pre- to post-treatment in the upper and lower lips relative to the N-perpendicular line was more posterior in the ASO group than in the NASO group by -2.42 mm in the upper and − 2.58 mm in the lower lips. Changes in the SAL angle, SAL depth, PBL angle, and PBL depth were analyzed to assess lip curvature. Only the change in Δ PBL depth was notably greater in the NASO group than the ASO group by -1.30 mm, indicating soft tissue B point retraction, which was unfavorable. For the CK angle, indicative of lower lip protrusion, the ASO group exhibited a more significant pre-treatment reduction of -4.28° than the NASO group did. The H angle, assessing upper lip protrusion, demonstrated a greater adjustment of -2.21° in the ASO group. The combined change in the CKH angle was 2.07° more substantial in the ASO group, reflecting different degrees of facial profile correction between the groups. The NLA change was significantly larger in the ASO group than in the NASO group, with a 6.96° increase from pre- to post-treatment, highlighting the impact of surgical intervention on the aesthetic angle between the nose and upper lip. The impact of genioplasty on outcomes was not statistically significant (Table 3).

Table 3

COMPARISON OF PRE- AND POST-TREATMENT CHANGES BETWEEN ASO AND NASO GROUPS
	(T1–T0)
Measurements	ΔASO s Mean	Δ NASO Mean	Mean difference	SD difference	P
Interlabial gap diff	-1.54	-0.20	-1.34	0.55	0.01*
UL-E diff	-4.10	-1.77	-2.32	0.46	0.00**
LL-E diff	-4.91	-2.32	-2.58	0.71	0.00**
PBL angle diff	2.59	14.29	-11.70	14.26	0.21
PBL depth diff	0.41	-0.89	1.30	0.31	0.00**
SAL angle diff	-1.30	-2.16	0.86	2.98	0.39
SAL depth diff	-0.09	-0.17	0.08	0.15	0.30
CK angle diff	-10.28	-6.00	-4.28	1.68	0.01**
H angle diff	-5.03	-2.83	-2.21	0.66	0.00**
CKH angle diff	5.24	3.17	2.07	1.21	0.05
Nasolabial angle diff	11.66	4.70	6.96	1.94	0.00**
A’ to N-perp diff	-2.35	-2.70	0.35	0.99	0.36
B’ to N-perp diff	-2.13	-1.06	-1.08	0.71	0.07
UL to N-perp diff	-4.10	-1.67	-2.42	0.63	0.00**
LL to N-perp diff	-4.71	-2.13	-2.58	0.83	0.00**
Pog’ to N-perp diff	0.16	-0.74	0.90	0.81	0.14
UL thickness diff	1.10	0.96	0.14	0.33	0.34
LL thickness diff	0.94	0.79	0.15	0.38	0.35
Independent t-test was performed to compare the variables between Δ ASO surgery and Δ MI non-surgery; p < 0.05, *p < 0.01. ASO, anterior segmental osteotomy.

Tweed [9] highlighted the significant link between the aesthetic balance of the facial profile and the positioning of the mandibular anterior teeth. Merrifield [10] later articulated that for an ideal facial appearance, a profile line extending from the soft tissue pogonion should intersect the upper lip, whereas the lower lip should either align tangentially or reside slightly posterior to this line. The aesthetic interplay and balance between the upper and lower lips have been recognized by Jang as crucial elements in defining facial attractiveness [11]. Specifically, the decision-making process must be approached with caution when considering surgical interventions because of the potential for irreversible effects on facial aesthetics. The NLA, a critical aesthetic determinant related to the appearance of the nose and lips, exhibits variability across different races, genders, and ages, with Naini et al [12] emphasizing its significance. Bernstein [13] identified the optimal NLA angle as 100° for males and 105° for females in Western populations, whereas Bae et al [14] reported an average angle of 95.80 ± 8.93° for Korean women in their 20s.

Additionally, preferences among Korean rhinoplasty patients lean towards an NLA ranging from 85° to 95°, favoring Asian aesthetic norms over Western ones [15]. In this study, no significant difference in the NLA was observed between the ASO and NASO groups before treatment. However, a notable difference was evident in the degree of change in the nasolabial angle after treatment, with the ASO group experiencing a greater alteration (6.96°) than the NASO group. This aligns with the findings by Lee et al [5], who reported that ASO led to more pronounced posterior displacement of the anterior segment of the maxilla and a significant adjustment in the NLA than nonsurgical orthodontic treatment. The ASO group showed a 6.96° greater reduction in the NLA, resulting in a post-treatment average of 102.75°, compared to 97.37° in the NASO group, indicating that normalization within the Korean aesthetic preference can be achieved through NASO. Lip incompetence, characterized by the challenge of closing the lips without strain, is recognized as a contributing element to soft tissue aesthetics [16]. The extent to which lip incompetence can be rectified is intrinsically linked to the degree of correction achievable in the underlying skeletal discrepancies or dentoalveolar configurations [8]. Nonsurgical extraction correction strategies, particularly for vertical skeletal open bites, dentoalveolar vertical excess, or anterior-posterior dentoalveolar protrusions, offer limited improvement owing to the constraints imposed by the existing skeletal or dentoalveolar framework. Thus, ASO surgery is identified as being more efficacious than nonsurgical tooth extraction correction in addressing cases associated with lip incompetence. This study demonstrated that the ASO group experienced a more significant reduction in the interlabial gap, both before and after treatment, than the NASO group. The change in interlabial gap was − 1.54 mm in the ASO group and − 0.20 mm in the NASO group. Initially, the interlabial gap measured 4.54 mm in the ASO group and 2.49 mm, which was within the normal limit in the NASO group, aligning with findings by Kim [7] that underscored the vertical and horizontal dimensions contributing to lip incompetence. Nonetheless, it is crucial to acknowledge a limitation of this comparison arising from the preexisting differences between the two groups at the outset. These initial disparities were mainly due to treatment planning and decisions made during diagnosis, which were predicated on the diagnosis of lip incompetence.

Lee et al [5] further elucidated that in patients with Class II malocclusion, the forward protrusion of the lower lip, despite a retrusive mandible, can often be attributed to lip incompetence or the forward pressure exerted by the protruding maxillary anterior teeth, which in turn displaces the lower lip downwards and forward. In the present study, the interlabial gap change was associated with the CK angle in the ASO group. Therefore, in such scenarios, addressing the protrusive aspects of the maxilla alone may suffice to facilitate the desired retraction of the lower lip, underscoring the need for a strategic approach to correct dental and skeletal discrepancies in Class II malocclusion cases. Hodges indicated that the lower incisors reflect a stronger correlation to tooth movement than the upper incisors do [17]. Kim et al [8] also reported that 1 mm of mandibular anterior movement in Class III non-extraction orthodontic patients regressed by 79% compared to soft tissue N-Pog.

For patients with Class II protrusion, a treatment approach that entails greater movement of the maxilla and minimal movement of the mandible may represent an optimal strategy for resolving maxillary and mandibular protrusions. In Class II skeletal patterns, the mandible is typically proportionally smaller than the maxilla is. Consequently, the decision to perform ASO on the mandible warrants careful consideration, as a reduction in hard tissue can lead to a corresponding reduction in soft tissue volume, which results in soft tissue B retrusion. Thus, the initial angulation of the anterior mandibular teeth and the projected extent of movement within the treatment plan are critical considerations. Deliberations over the necessity of mandibular surgery should be approached with caution. Although not explicitly analyzed in this study, an ideal aesthetic treatment plan for patients with Class II may involve comprehensive arch distalization through ASO procedures on both the maxilla and mandible (Fig. 3). This approach offers an aesthetically pleasing outcome by harmonizing the facial profile and dental alignment.

Tweed(9) highlighted the pivotal role of the position of the mandibular anterior teeth in shaping the aesthetic outcomes of orthodontic treatment. Despite this diagnostic approach being criticized for lacking soft tissue, the growing emphasis on soft tissues in contemporary orthodontic practices cannot be understated. This study reaffirms the significance of the mandibular anterior incisor angle (IMPA) as a crucial diagnostic parameter, reflecting a broader understanding of the interplay between dental positioning and soft tissue aesthetics. A notable limitation of this study is the discrepancy in the pretreatment conditions between the ASO and NASO groups. Specifically, the ASO group exhibited more pronounced Class II characteristics at the outset. Consequently, future studies should benefit from a larger sample size encompassing a wider array of borderline cases to facilitate a more nuanced understanding of the differential effects of ASO and NASO treatments on soft tissue changes.

Our findings revealed significant differences in soft tissue measurement pre- and post-treatment between the ASO and NASO, particularly in the interlabial gap and nasolabial angle, UL-E, H angle, and distance from the upper lip to the nasion perpendicular line (UL to N-perp). Notable differences related to the lower lip change were noted in the LL-E, PBL depth, CK angle, the distance from the lower lip to the nasion perpendicular line (LL to N-perp), and B' to N-perp. Based on the findings, we suggest using the required movement as a guideline for selecting between ASO and NASO. If the required adjustment for the upper and lower lips is approximately − 4.0 mm and − 5.0 mm, respectively, ASO is advised due to its effectiveness in achieving significant profile improvements. For modifications of approximately − 2.0 mm, NASO is preferred. This strategic choice allows targeted enhancements in Class II profiles through ASO for maxillary adjustments and posterior movements of the mandibular anterior teeth. We also highlight the fact that decompensation of the maxilla is critical in determining the extent of mandibular movement to prevent overreaction of the ASO segments due to the compensated, uprighted maxillary incisors. Consequently, a routine surgical-first approach is not recommended. Instead, prioritizing preoperative orthodontic correction followed by ASO is recommended.

Authors’ contributions

With the submission of this manuscript, I would like to state that

All authors of this research paper directly participated in the planning, execution, or analysis of this study.
All authors of this paper have read and approved the final version submitted.
The contents of this manuscript have not been copyrighted or published previously.
The contents of this manuscript are not under consideration for publication elsewhere.
The contents of this manuscript will not be copyrighted, submitted, or published elsewhere while acceptance by the Journal is under consideration.
This study is original in nature. No directly related manuscript has been published or is unpublished by the authors of this paper.
There is no conflict of interest to disclose for any author.

The individual roles of each author are as follows:

Hyunhee Choo: Data collection, analysis, interpretation, and manuscript construction.
Young Ho Kim: conception and design of the study, description of data results, and construction of the manuscript.
Pureum Hong: design and organization of the article.
Reuben Kim: conception and design of the article.
Young-Jin Choi: Surgical information of the article.
Hwa Sung Chae: Conception and design of the article, data analysis, data interpretation, and manuscript construction.
All the authors read and approved the final manuscript.

Compliance with Ethical Standards

Disclosure of potential conflicts of interest

The authors declare that they have no conflict of interest.

Ethical approval

All human research procedures were followed in accordance with the ethical standards of the committee responsible for human experimentation (institutional and national), and with the Helsinki Declaration of 1975, as revised in 2013. This study was reviewed and approved by the Institutional Review Board (IRB) of Ajou University Hospital (IRB no.: AJIRB-MED-MDB-2022-354).

Informed consent

Informed consent was obtained from all subjects and/or their legal guardian(s)

Funding

The authors declare that they have no funding for this research article.

Consent for publication

Not applicable

Data availability statements

The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

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No competing interests reported.

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Comparing Soft Tissue Outcomes in Skeletal Class II Malocclusion: Anterior Segmental Osteotomy vs. Non-Surgical Orthodontic Treatment

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Abstract

Figures

Introduction

Materials and Methods

STUDY SAMPLE

CEPHALOMETRIC MEASUREMENT

SURGICAL PROCEDURES

STATISTICAL ANALYSIS

Results

PRE-TREATMENT COMPARISON BETWEEN ASO AND NASO

COMPARISON OF POST-TREATMENT OUTCOMES BETWEEN ASO AND NASO

ANALYSIS OF PRE- AND POST-TREATMENT MODIFICATIONS IN ASO VERSUS NASO

Discussion

Conclusion

Declarations

References

Additional Declarations

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