Accepted Manuscript Proximal Segment changes after Bilateral Sagittal Split Ramus Osteotomy in Facial Asymmetry Patients Ji-Woon Kim, Postgraduate student, Woo-Sung Son, Seong-Sik Kim, Pprofessor, Yong-Il Kim, Assistant professor PII:
S0278-2391(15)00206-2
DOI:
10.1016/j.joms.2015.02.021
Reference:
YJOMS 56679
To appear in:
Journal of Oral and Maxillofacial Surgery
Received Date: 19 January 2015 Revised Date:
16 February 2015
Accepted Date: 19 February 2015
Please cite this article as: Kim J-W, Son W-S, Kim S-S, Kim Y-I, Proximal Segment changes after Bilateral Sagittal Split Ramus Osteotomy in Facial Asymmetry Patients, Journal of Oral and Maxillofacial Surgery (2015), doi: 10.1016/j.joms.2015.02.021. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Proximal Segment changes after Bilateral Sagittal Split Ramus Osteotomy in Facial
Ji-Woon Kim1, Woo-Sung Son1, Seong-Sik Kim1, Yong-Il Kim1
Department of Orthodontics, Dental research institute, Pusan National University Dental Hospital,
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1
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Asymmetry Patients
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Yangsan, South Korea
Running title: Proximal segment’s change in facial asymmetryl
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1st author) Ji-Woon Kim ,
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Postgraduate student, 1 Department of Orthodontics, Dental research institute, Pusan National University
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Dental Hospital, Yangsan, South Korea
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3rd author) Seong-Sik Kim ,
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Pprofessor, Department of Orthodontics, Dental research institute, Pusan National University Dental Hospital, Yangsan, South Korea
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4th author) Yong-Il Kim
Assistant professor, Department of Orthodontics, Dental research institute, Pusan National University Dental Hospital, Yangsan, South Korea
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Corresponding author) Woo-Sung Son
1
Professor, 1
Department of Orthodontics, Dental research institute, Pusan National University Dental Hospital,
Geumoro 10, Mulgeumeup, Yangsan, South Korea 626-787
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Tel: 82- 55-360-5150, Fax: 82- 55-360-5154, E-mail: [email protected]
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Yangsan, South Korea
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Acknowledgements
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This work was supported by 2-year research grant from Pusan National University.
ACCEPTED MANUSCRIPT Proximal Segment changes after Bilateral Sagittal Split Ramus Osteotomy in Facial Asymmetry Patients
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ABSTRACT Purpose: To investigate the 3-dimensional postoperative changes in the proximal segments in facial asymmetry patients according to the anteroposterior skeletal patterns.
Materials and Method: Fifty one patients with facial asymmetry who had undergone Le Fort I osteotomy and
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sagittal split ramus osteotomy (SSRO) with rigid fixation were classified according to their anteroposterior skeletal patterns. Cone-beam computed tomography (CBCT) data were obtained before (T0) and 6 months (T1)
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after surgery. The position, angulation, and distance of proximal segment were measured from CBCT superimposition.
Results: In comparison of the T0 and T1, there were almost no significant differences in the condylar head position in any of the groups (p > 0.05), except for the axial condylar head position (ACH) on the deviated side in skeletal class I group (p < 0.05) and the sagittal condylar head position (SCH) on the deviated side in skeletal
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class III group (p < 0.05). However, the changes of the coronoid process and ramus down were various (p < 0.05), and these movements were related to the changes of the ramal plane. In comparison of the deviated and non-deviated sides, there were significant differences only in skeletal class I group (p < 0.05).
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Conclusions: The most dispositive factors affecting differences between the deviated and non-deviated sides in facial asymmetry patients after BSSRO could be the direction of the surgical movement of the distal segment of
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the mandible rather than its extent.
KEY WORDS: Facial asymmetry, SSRO, CBCT, Proximal segment changes
ACCEPTED MANUSCRIPT INTRODUCTION Facial asymmetry is lack of correspondence in the size, form or arrangement of features on opposite sides of the face relative to the midsagittal reference plane.1 It manifests as differences in the length or angulation of maxilla or mandible. Lee et al.2 for example, studying condylar asymmetry, demonstrated that the condyle on the non-deviated side is larger than that on the deviated side. The correction of mandibular position by
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advancement or setback, however, can cause displacement and rotation of the proximal segment, which its postoperative changes have effects on skeletal stability and sometimes produce temporomandibular disorder
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(TMD) symptoms.3,4
Bilateral sagittal split ramus osteotomy (SSRO) is one of the most commonly employed procedures for correction of protruded, retruded or deviated mandible. Many studies have reported on changes in the positions
have focused on facial-asymmetry patients.
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of the proximal segment and condyle after mandibular advancement6,7,8 or setback surgery9,10,11, but few studies
Patients with facial asymmetry undergo complicated mandibular movement such as asymmetric mandibular setback or advancement through orthognathic surgery. This can cause different changes of the position, distance
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and angulation of the proximal segments.
Recently, several researchers have studied condylar-position changes in skeletal class III malocclusion patients with facial asymmetry.12 However, they did not give three dimensional information about the postoperative
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proximal segment changes. 3D CBCT enables accurate visualization of anatomic structures as well as precision measurement of skeletal landmarks without requiring any radiographic magnification.13,14 It could be the better
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method for evaluation of postoperative changes of the proximal segment. Therefore, the purpose of the present study were to investigate the postoperative changes in the position, angulation and distance of the proximal segments in facial asymmetry patients and to compare between the deviated and non-deviated sides according to the anteroposterior skeletal patterns
MATERIALS AND METHODS Subjects The subjects of this retrospective study comprised 51 patients with facial asymmetry (chin deviation ≥ 4.0mm) who had undergone Le Fort I osteotomy and SSRO with rigid internal fixation (RIF) at 000000 University
ACCEPTED MANUSCRIPT Dental Hospital. The patients were classified into 3 groups according to their anteroposterior skeletal patterns (Table 1). Group I comprised 18 patients (3 men, 15 women; age: 22.14 ± 2.59 years) with skeletal class I malocclusion (0.60° ≤ ANB ≤ 4.20°); group II, 15 patients (5 men, 10 women; age: 24.71 ± 2.77 years) with skeletal class II malocclusion (ANB > 4.20°); group III, 18 patients (10 men, 8 women; age: 22.07 ± 2.88 years)
Committee of 000000 University Dental Hospital (PNUDH-2013-025).
Data acquisition
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with skeletal class III malocclusion (ANB < 0.60°). This study was reviewed and approved by the Ethics
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CBCT (Zenith 3D, Vatech Co., Seoul, Korea) data were obtained for the evaluation of the proximal segment before surgery (T0; average, 0.95 ± 1.02 months) and 6 months after surgery (T1; average, 8.75 ± 3.07 months). The craniofacial region was scanned under a 20 x 19 cm field of view and by application of a 90 kVp tube
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voltage, a 4.0 mA tube current, 24 seconds of scan time and a 0.30 mm voxel size. The raw data were reconstructed as 3D images using 3D image software (Ondemand 3D; Cybermed Inc., Seoul, Korea). To evaluate the postoperative change of the proximal segments at T0 and T1 stages, 3D images were
CBCT assessment
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superimposed according to the maximized the mutual information theory.15,16
Reference points and planes. To establish the 3D coordinates of the craniofacial structures, the reference points and planes were defined as in Figure 1 and 2. The Na-parallel (Na-par) plane was drawn parallel to the Frankfort
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horizontal (FH) plane and passing through the Nasion; the midsagittal reference (MSR) plane was drawn perpendicular to the FH plane and passing through the Nasion and Basion, and the Na-perpendicular (Na-per)
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plane was drawn perpendicular to the FH and MSR planes and passing through the Nasion. Measurements of proximal segment. The postoperative change of proximal segment was assessed according to the following variables (Table 2, Figures 1, 2). Because the proximal segment is composed of the condylar head, coronoid process and ramus down, the postoperative position change of these three landmarks represented the proximal-segment position change. Therefore, we measured the distance from each landmark to the three reference planes in order to evaluate the 3D change of the proximal-segment position; also measured the distances between each of the landmarks to estimate the linear change of the extents of movement of the interproximal segments between the T0 and T1 stage. Finally, to compare the angular change of the proximal segment before and after surgery, the angulation of the ramal plane were measured in relation to the reference
ACCEPTED MANUSCRIPT plane. The deviated side (D) was defined as the location of the chin deviation relative to the MSR plane, and non-deviated side (ND) was defined as the opposite side.
Statistical analysis All of the data were analyzed using PASW Statistics 18 (IBM, New York, NY). Wilcoxon signed rank test
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was conducted to compare proximal-segment changes at T0 and T1, respectively. A Mann-Whitney U test was conducted to compare the deviated and non-deviated sides on the basis of the anteroposterior skeletal patterns. A Spearman correlation analysis was used to assess the relationship between the extent of distal-segment
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movement and the deviated/non-deviated-side difference. Differences were considered to be significant at p < 0.05. Further, to evaluate the intra-assessor reproducibility of the CBCT results, the variables of 7 randomly selected subjects were evaluated twice at 2-week intervals using the intraclass correlation coefficient (ICC). The
lowest, and that of the ICP was the highest.
RESULTS
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mean ICC was 0.965 in the 95% confidence interval (lower: 0.800, upper: 0.999). The ICC of the CRD was the
Proximal segment’s changes from T0 to T1 stages.
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The condylar head moved laterally on the deviated side in group I (ACH) and anteriorly on the deviated side in group III (SCH) after surgery (p < 0.05; Table 3, Figure 3). The coronoid process moved medially on the deviated side in groups I and III and on the non-deviated side if group III (ACP) (p < 0.05). It also moved
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posteriorly on the deviated side in group I (SCP) and superiorly on both the deviated and non-deviated sides in groups I and II (CCP) (p < 0.05; Table 3). The ramus down moved laterally on the non-deviated side in group II
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(ARD) (p < 0.05). It also moved anteriorly on the deviated side in group II and on the non-deviated side in groups I and II (SRD), as well as superiorly on the non-deviated side in group III (CRD) (p < 0.05; Table 3). The ramal plane on the axial plane rotated inwardly on the deviated side in groups I and II and the nondeviated side in groups I and III (ARP) (p < 0.05). On the coronal plane, it rotated inwardly on the deviated side in group I and outwardly on the non-deviated side in groups I and II (CRP) (p < 0.05; Table 3). Although there were no significant differences in the inter-condylar width or inter-ramus down width, the inter-coronoid process width had decreased in groups I and III (ICP) (p < 0.05; Table 3).
Comparison between deviated and non-deviated sides
ACCEPTED MANUSCRIPT There was a statistically significant difference in the mediolateral change of the condylar head in group I (ACH), which showed more lateral movement on the deviated side than on the non-deviated side (p < 0.05). There were no significant differences in the mediolateral, anteroposterior or superioinferior changes of the condylar head between the deviated and non-deviated sides of groups II and III (p > 0.05; Table 4). There were no significant differences in the mediolateral, anteroposterior or superioinferior changes of the
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coronoid process between the deviated and non-deviated sides in any of the groups (p > 0.05; Table 4). There was a statistically significant difference in the mediolateral change of the ramus down (ARD) of group I, which showed medial movement on the deviated side but lateral movement on the non-deviated side (p < 0.05). There
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were no significant differences in the mediolateral, anteroposterior or superioinferior changes of the ramus down between the deviated and non-deviated sides in group II (p > 0.05; Table 4).
There was a statistically significant difference of coronal ramal plane angle in group I (CRP), which showed
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inward rotation on the deviated side but outward rotation on the non-deviated side (p < 0.05). There were no significant differences in the axial or coronal ramal plane angles in groups II and III (p > 0.05; Table 4).
Correlation between extent of distal-segment movement and deviated/non-deviated side differences There were no statistically significant correlations in three groups, which indicated that the difference in the
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extent of distal-segment movement between the deviated and non-deviated sides was not a dispositive factor in the proximal-segment changes (p > 0.05).
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DISCUSSION
The SSRO is a commonly employed orthognathic-surgical method. There have been many reports on the
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possible factors affecting post-SSRO condylar position: for example, movement of the distal segment of the mandible, the fixation method, the anatomic shape and contours of the proximal segment, and the surgical expertise.9,17,18,19,20 Research has shown that the condylar position can be influenced by bony interferences between the proximal and distal segments, and that the characteristics of those changes vary according to the anteroposterior skeletal patterns.24,25,26 Harris et al.24 reported that, after SSRO with mandibular advancement in skeletal class II malocclusion, the condyle tends to move medially, posteriorly, and superiorly and to rotate medially. Lee et al.9 showed that, after SSRO with mandibular setback in skeletal class III malocclusion, the condyle tends to move laterally, anteriorly, and inferiorly and to rotate inward and backward. However, the focuses of these previous studies were limited to mandibular advancement and setback the same direction. There
ACCEPTED MANUSCRIPT have, in fact, been only a relative few studies that have focused on the asymmetric extent and direction of mandibular movement in facial-asymmetry patients after BSSRO.
In the present results, the facial-asymmetry patients with skeletal class I malocclusion showed distal-segment mandibular movement in the form of advancement on the deviated side and setback on the non-deviated side.
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The skeletal class II patients, by contrast, showed mandibular movement in the form of asymmetric advancement that was the greater on the deviated side than on the non-deviated side. In the case of skeletal class III malocclusion, the mandible movement was in the form of asymmetric setback that was more extensive on the
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non-deviated side than on the deviated side. In this study, the distal segments of the mandible move in different directions and to different extents according to the anteroposterior skeletal patterns (Table 5). In the comparison of the T0 and T1 stages, the condylar head maintained its original position, except for the
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lateral movement on the deviated side in group I (ACH) and the anterior movement on the deviated side in group III (SCH). Although the condylar head in skeletal class II malocclusion basically tended to move medially, posteriorly, and superiorly except for the ACH on the non-deviated side and the CCH on the deviated side, as agreed with the results of Harris et al.24 for mandibular advancement, there were no significant differences in the condylar head position 6 months after surgery (p > 0.05). And, although the condylar head in skeletal class III
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malocclusion basically tended to move laterally, anteriorly, and inferiorly, in agreement with the results of Lee et al.9 for mandibular setback, there were no significant differences in the condylar head position (p > 0.05),
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except for the SCH on the deviated side (p < 0.05) 6 months after surgery.
The reason for the lack of significant differences of condylar head position between the T0 and T1 stages may
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be due to the timing of postoperative CBCT: 1 month in Lee et al.,9 2 months in Harris et al.,24 and 6 months after surgery in the present study. Actually, some clinicians found that the condylar position had a tendency to return to the preoperative state and, after 3 months, to revert to about half of the immediate postoperative state;12 that the anteroposterior condylar position in the glenoid fossa had moved from the anterior to concentric position, tending to return slightly toward the original position, and that the skeletal changes occurring between postoperative 6 months and follow-up were insignificant.11 However, postoperative condylar change, such as condylar resoprtion, could induce the long-term changes. In contrast to the condylar head, the proximal-segment changes of the coronoid process and ramus down in each group were various. They made it possible to maintain the condylar head position by adjusting their position three-dimensionally. These movements were related to the
ACCEPTED MANUSCRIPT changes of ramal plane angulation, which moved in different directions among the groups. There were changes of the inter-proximal segment width as well. The inter-coronoid process width decreased in groups I and III (ICP) (P < 0.05; Table 3). Whereas the condylar head and ramus down tended to maintain their original position on the axial view, the coronoid process moved medially, both on the deviated side in groups I and III, and on the non-deviated side in group III (ACP). This medial movement of the coronoid process could affect the inward
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rotation of the axial ramal plane angulation in groups I and III.
A factor for possibly affecting this difference of ramal plane angulation in asymmetric setback movement of the mandible is the fixation method.19,21 With rigid internal fixation (RIF) in particular, because the gaps between the proximal and distal segments of the mandible can cause rotation of the condyle laterally or medially,
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it is important to maintain them to prevent any such rotational change.22 Notwithstanding the fact that the application of post-SSRO RIF certainly is helpful in facilitating rapid bone healing, early recovery of
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masticatory function and an increased postoperative stability; widening or narrowing of the gaps between segments can affect condylar position.5 Indeed, Kundert et al.23 reported that after surgery with RIF, there was significant displacement. Other possible factors causing differences in ramal plane angulation are the surgeon's skill level as reflected in control of the proximal and distal segments, and patients' characteristics such as the anatomic shapes of segments.17,18,20 The mandibular anatomic morphology such as U-shaped or V-shaped
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mandible could influence the postoperative proximal segment position.” Interestingly, in the comparison of the deviated and non-deviated sides, there were statistically significant differences only in skeletal class I malocclusion with facial asymmetry. Our results indicated that, on the axial
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plane, the condylar head moved more laterally on the deviated side than on the non-deviated side (p < 0.05), and that the ramus down moved medially on the deviated side and laterally on the non-deviated side (p < 0.05).
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Moreover, the ramal plane, on the coronal plane, showed inward rotation on the deviated side but outward rotation on the non-deviated side (p < 0.05). Even so, there were no significant differences between the deviated and non-deviated sides in skeletal class II or III malocclusion with facial asymmetry (p > 0.05). As already noted, it was considered that these differences were related to the different distal-segment movements of the mandible in skeletal class I malocclusion with facial asymmetry; forward on the deviated side and backward on the non-deviated side. In case of either asymmetric advancement or setback, the distal segment of the mandible moved in the same direction on both the deviated and non-deviated sides though the extent of movement differed.
ACCEPTED MANUSCRIPT Accordingly, our results suggested that one of the most influential factors with regard to differences between the deviated and non-deviated sides could be the direction of movement of the distal segment of mandible rather than its extent (Tables 5). Similarly, in the findings of two investigations, there was no correlation between the extent of mandibular advancement or setback and the change of condylar position.9,21 Correspondingly, the proximal-segment changes after mandibular asymmetric advancement or setback surgery
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for the facial-asymmetry patients with skeletal class II and III malocclusion were similar to those for the symmetric cases but different from those for the facial-asymmetry patients with skeletal class I malocclusion. Therefore, we propose that one of the most dispositive factors affecting differences between the deviated and
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non-deviated sides could be the direction of the movement of the distal segment of the mandible rather than its extent. For this reason, SSRO might be effective orthognathic-surgical modality for maintenance of the condylar position in skeletal class II and III malocclusion with facial asymmetry; in skeletal class I malocclusion with
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facial asymmetry, however, clinicians will need to consider the stabilization of the condylar position.
Conclusion
In facial asymmetry patients after SSRO, the most important factors affecting the proximal segment changes
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between the deviated and non-deviated sides could be the direction of the surgical movement of the distal segment of the mandible not its extent .
REFERENCES
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1. Peck H, Peck S: A concept of facial esthetics. Angle Orthod 40:284, 1970 2. Lee BR, Kang DK, Son WS, et al: The relationship between condyle position, morphology and chin deviation
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in skeletal class III patients with facial asymmetry using cone-beam CT. Korean J Orthod 41:87, 2011 3. Hu J, Wang D, Zou S: Effects of mandibular setback in the temporomandibular joint: a comparison of oblique and sagittal split ramus osteotomy. J Oral maxillofac Surg 58:375, 2000 4. Yamada K, Hanada K, Hayashi T, et al: Condylar bony change, disk displacement, and signs and symptoms of TMJ disorders in orthognathic surgery patients. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 91:603, 2001 5. Nishmura A, Sakurada S, Iwase S: Positional changes in the mandibular condyle and amount of mouth opening after sagittal split ramus osteotomy with rigid or nonrigid osteosynthesis. J Oral Maxillofac Surg 55:672, 1997
ACCEPTED MANUSCRIPT 6. Marden EA, Thomas D, Stephen RM, et al: Short-term changes of condylar position after sagittal split osteotomy for mandibular advancement. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 87:159, 1999 7. Jonas PB, Joe R, Karin BB, et al: Transverse displacement of the proximal segment after bilateral sagittal osteotomy. J Oral Maxillofac Surg 60:395, 2002 8. Carvalho Fde A, Cevidanes LH, da Motta AT, et al: Three-dimensional assessment of mandibular
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advancement 1 year after surgery. Am J Orthod Dentofacial Orthop 137: S53.e1, 2010
9. Lee W, Park JU: Three-dimensional evaluation of positional change of the condyle after mandibular setback by means of bilateral sagittal split ramus osteotomy. Oral Surg Oral Med Oral Pathol Oral Radiol Endod
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94:305, 2002
10. Jang JR, Choi GH, Park YJ, et al: The evaluation of the positional change of the mandibular condyle after bilateral sagittal split ramus osteotomy using three dimensional computed tomography in skeletal class III
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patients. J Kor Oral Maxillofac Surg 35:316, 2009
11. Kim YI, Cho BH, Jung YH, et al: Cone-beam computerized tomography evaluation of condylar changes and stability following two-jaw surgery: Le Fort I osteotomy and mandibular setback surgery with rigid fixation. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 111:681, 2011
12. Lee SK, Kim KW, Kim CH: Postoperative positional change of condyle after bilateral sagittal split ramus
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osteotomy associated with mandibular asymmetry. J Kor Oral Maxillofac Surg 30:359, 2004 13. Bergersen EO: Enlargement and distortion in cephalometric radiography: compensation tables for linear measurements. Angle Orthod 50:230, 1980
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14. Cavakcanti MG, Haller JW, Vannier MW: Three-dimensional computed tomography landmark measurement in craniofacial surgical planning: experimental validation in vitro. J Oral Maxillofac Surg
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57:690, 1999
15. Maes F, Collignon A, Vandermeulen D, et al: Multimodality image registration by maximization of mutual information. IEEE Trans Med Imaging 16:187, 1997 16. Choi JH, Mah J: A new method for superimposition of CBCT volumes. J Clin Orthod 44:303, 2010 17. Komori E, Aigase K, Sugisaki M, et al: Cause of early skeletal relapse after mandibular setback. Am J Orthod Dentofacial Orthop 95:29, 1989 18. Will LA, Joondeph DR, Hohl TH, et al: Condylar position following mandibular advancement: its relationship to relapse. J Oral Maxillofac Surg 42:578, 1984
ACCEPTED MANUSCRIPT 19. Van Sickels JE, Larsen AJ, Thrash WJ: Relapse after rigid fixation of mandibular advancement. J oral maxillofac Surg 44:698, 1986 20. Epker BN, Wessberg GA: Mechanism of early skeletal relapse following surgical advancement of the mandible. Br J Oral Surg 20:175, 1982 21. Hackney FL, Van Sickels JE: Condylar displacement and temporomandibular joint dysfunction following
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bilateral sagittal split osteotomy and rigid fixation. J Oral Maxillofac Surg 47:223, 1989
22. Back SH, Kim TK, Kim MJ: Is there any difference in the condylar position and angulation after asymmetric mandibular setback? Oral Surg Oral Med Oral Pathol Oral Radiol Endod 101:55, 2006
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23. Kundert M, Hadjianghelou O: Condylar displacement after sagittal splitting of mandibular rami. J Maxillofac Surg 8:278, 1980
24. Harris MD, Van Sickels JE, Alder M: Factors influencing condylar position after the bilateral sagittal split
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osteotomy fixed with bicortical screws. J Oral Maxillofac Surg 57:650, 1999
25. Yoshida K, Rivera RS, Kaneko M, et al: Minimizing displacement of the proximal segment after bilateral sagittal split ramus osteotomy in asymmetric cases. J Oral Maxillofac Surg 59:15, 2001 26. Al-Gunaid T, Yamada K, Takagi R, et al: Postoperative stability of bimaxillary surgery in class III patients
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Surg 37:992, 2008
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with mandibular protrusion and mandibular deviation: a frontal cephalometric study. Int J Oral Maxillofac
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FIGURE LEGENDS
Figure 1. Three-dimensional (3D) measurement point and reference plane in 3D CBCT images
Reference points: Cdlat, Condylion lateralis; Cdmed, Condylion medialis; CC, Center of condyle; Cor,
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Coronoid process; RD, Ramus down; Nasion (Na) was the origin (0,0,0). Reference planes: Naparallel (Na-par) plane, Parallel to FH plane and passing through Na; Midsagittal reference (MSR)
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plane, Perpendicular to FH plane and passing through Na and Basion (Ba); Na-perpendicular (Na-per) plane, Perpendicular to FH and MSR planes passing through Na
Figure 2. Reference planes and angular measurements
A. Sagittal plane: Sagittal condylar head position (SCH), Distance from center of condyle to Na-per plane
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Sagittal coronoid process position (SCP), Distance from coronoid process to Na-per plane: Sagittal ramus down position (SRD), Distance from ramus down to Na-per plane B. Coronal plane: Coronal condylar head position (CCH), Distance from center of condyle to Na-par
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plane; Coronal coronoid process position (CCP), Distance from coronoid process to Na-par plane; Coronal ramus down position (CRD), Distance from ramus down to Na-par plane; Coronal ramal plane angle
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C. Axial plane: Axial condylar head position (ACH), Distance from center of condyle to MSR plane; Axial coronoid process position (ACP), Distance from coronoid process to MSR plane; Axial ramus down position (ARD), Distance from ramus down to MSR plane; Axial ramal plane angle
D. Inter-condylar head width (ICH), inter-coronoid process width (ICP), Inter-sigmoid notch width (ISN), Inter-ramus down width (IRD)
Figure 3. Proximal changes after surgery for group I with the deviation at left side. Pre- and Post-operative 3D (A, B), sagittal (C, D), coronal (E, F) and axial (G, H) images, respectively.
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Table 1. Demographic data and criteria by subgroup
Chin deviation (mm)
7.29 (2.51)
ANB (°)
2.05 (1.39)
Chin deviation (mm)
1.03 (0.68)
ANB (°)
2.70 (1.48)
Before surgery
After surgery
Group II (N=15)
Group III (N=18)
Multiple comparison,
p-value
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Group I (N=18)
Variable
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Tables
6.27 (2.63)
7.23 (2.79)
0.338
6.17 (1.44)
-2.26 (3.44)
0.000*
1.09 (0.66)
0.85 (0.55)
0.390
3.99 (1.97)
3.00 (1.87)
0.096
group no.
II > I > III
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*p
S0278-2391(15)00206-2
DOI:
10.1016/j.joms.2015.02.021
Reference:
YJOMS 56679
To appear in:
Journal of Oral and Maxillofacial Surgery
Received Date: 19 January 2015 Revised Date:
16 February 2015
Accepted Date: 19 February 2015
Please cite this article as: Kim J-W, Son W-S, Kim S-S, Kim Y-I, Proximal Segment changes after Bilateral Sagittal Split Ramus Osteotomy in Facial Asymmetry Patients, Journal of Oral and Maxillofacial Surgery (2015), doi: 10.1016/j.joms.2015.02.021. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Proximal Segment changes after Bilateral Sagittal Split Ramus Osteotomy in Facial
Ji-Woon Kim1, Woo-Sung Son1, Seong-Sik Kim1, Yong-Il Kim1
Department of Orthodontics, Dental research institute, Pusan National University Dental Hospital,
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1
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Asymmetry Patients
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Yangsan, South Korea
Running title: Proximal segment’s change in facial asymmetryl
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1st author) Ji-Woon Kim ,
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Postgraduate student, 1 Department of Orthodontics, Dental research institute, Pusan National University
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Dental Hospital, Yangsan, South Korea
1
3rd author) Seong-Sik Kim ,
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Pprofessor, Department of Orthodontics, Dental research institute, Pusan National University Dental Hospital, Yangsan, South Korea
1
4th author) Yong-Il Kim
Assistant professor, Department of Orthodontics, Dental research institute, Pusan National University Dental Hospital, Yangsan, South Korea
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Corresponding author) Woo-Sung Son
1
Professor, 1
Department of Orthodontics, Dental research institute, Pusan National University Dental Hospital,
Geumoro 10, Mulgeumeup, Yangsan, South Korea 626-787
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Tel: 82- 55-360-5150, Fax: 82- 55-360-5154, E-mail: [email protected]
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Yangsan, South Korea
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Acknowledgements
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This work was supported by 2-year research grant from Pusan National University.
ACCEPTED MANUSCRIPT Proximal Segment changes after Bilateral Sagittal Split Ramus Osteotomy in Facial Asymmetry Patients
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ABSTRACT Purpose: To investigate the 3-dimensional postoperative changes in the proximal segments in facial asymmetry patients according to the anteroposterior skeletal patterns.
Materials and Method: Fifty one patients with facial asymmetry who had undergone Le Fort I osteotomy and
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sagittal split ramus osteotomy (SSRO) with rigid fixation were classified according to their anteroposterior skeletal patterns. Cone-beam computed tomography (CBCT) data were obtained before (T0) and 6 months (T1)
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after surgery. The position, angulation, and distance of proximal segment were measured from CBCT superimposition.
Results: In comparison of the T0 and T1, there were almost no significant differences in the condylar head position in any of the groups (p > 0.05), except for the axial condylar head position (ACH) on the deviated side in skeletal class I group (p < 0.05) and the sagittal condylar head position (SCH) on the deviated side in skeletal
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class III group (p < 0.05). However, the changes of the coronoid process and ramus down were various (p < 0.05), and these movements were related to the changes of the ramal plane. In comparison of the deviated and non-deviated sides, there were significant differences only in skeletal class I group (p < 0.05).
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Conclusions: The most dispositive factors affecting differences between the deviated and non-deviated sides in facial asymmetry patients after BSSRO could be the direction of the surgical movement of the distal segment of
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the mandible rather than its extent.
KEY WORDS: Facial asymmetry, SSRO, CBCT, Proximal segment changes
ACCEPTED MANUSCRIPT INTRODUCTION Facial asymmetry is lack of correspondence in the size, form or arrangement of features on opposite sides of the face relative to the midsagittal reference plane.1 It manifests as differences in the length or angulation of maxilla or mandible. Lee et al.2 for example, studying condylar asymmetry, demonstrated that the condyle on the non-deviated side is larger than that on the deviated side. The correction of mandibular position by
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advancement or setback, however, can cause displacement and rotation of the proximal segment, which its postoperative changes have effects on skeletal stability and sometimes produce temporomandibular disorder
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(TMD) symptoms.3,4
Bilateral sagittal split ramus osteotomy (SSRO) is one of the most commonly employed procedures for correction of protruded, retruded or deviated mandible. Many studies have reported on changes in the positions
have focused on facial-asymmetry patients.
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of the proximal segment and condyle after mandibular advancement6,7,8 or setback surgery9,10,11, but few studies
Patients with facial asymmetry undergo complicated mandibular movement such as asymmetric mandibular setback or advancement through orthognathic surgery. This can cause different changes of the position, distance
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and angulation of the proximal segments.
Recently, several researchers have studied condylar-position changes in skeletal class III malocclusion patients with facial asymmetry.12 However, they did not give three dimensional information about the postoperative
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proximal segment changes. 3D CBCT enables accurate visualization of anatomic structures as well as precision measurement of skeletal landmarks without requiring any radiographic magnification.13,14 It could be the better
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method for evaluation of postoperative changes of the proximal segment. Therefore, the purpose of the present study were to investigate the postoperative changes in the position, angulation and distance of the proximal segments in facial asymmetry patients and to compare between the deviated and non-deviated sides according to the anteroposterior skeletal patterns
MATERIALS AND METHODS Subjects The subjects of this retrospective study comprised 51 patients with facial asymmetry (chin deviation ≥ 4.0mm) who had undergone Le Fort I osteotomy and SSRO with rigid internal fixation (RIF) at 000000 University
ACCEPTED MANUSCRIPT Dental Hospital. The patients were classified into 3 groups according to their anteroposterior skeletal patterns (Table 1). Group I comprised 18 patients (3 men, 15 women; age: 22.14 ± 2.59 years) with skeletal class I malocclusion (0.60° ≤ ANB ≤ 4.20°); group II, 15 patients (5 men, 10 women; age: 24.71 ± 2.77 years) with skeletal class II malocclusion (ANB > 4.20°); group III, 18 patients (10 men, 8 women; age: 22.07 ± 2.88 years)
Committee of 000000 University Dental Hospital (PNUDH-2013-025).
Data acquisition
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with skeletal class III malocclusion (ANB < 0.60°). This study was reviewed and approved by the Ethics
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CBCT (Zenith 3D, Vatech Co., Seoul, Korea) data were obtained for the evaluation of the proximal segment before surgery (T0; average, 0.95 ± 1.02 months) and 6 months after surgery (T1; average, 8.75 ± 3.07 months). The craniofacial region was scanned under a 20 x 19 cm field of view and by application of a 90 kVp tube
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voltage, a 4.0 mA tube current, 24 seconds of scan time and a 0.30 mm voxel size. The raw data were reconstructed as 3D images using 3D image software (Ondemand 3D; Cybermed Inc., Seoul, Korea). To evaluate the postoperative change of the proximal segments at T0 and T1 stages, 3D images were
CBCT assessment
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superimposed according to the maximized the mutual information theory.15,16
Reference points and planes. To establish the 3D coordinates of the craniofacial structures, the reference points and planes were defined as in Figure 1 and 2. The Na-parallel (Na-par) plane was drawn parallel to the Frankfort
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horizontal (FH) plane and passing through the Nasion; the midsagittal reference (MSR) plane was drawn perpendicular to the FH plane and passing through the Nasion and Basion, and the Na-perpendicular (Na-per)
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plane was drawn perpendicular to the FH and MSR planes and passing through the Nasion. Measurements of proximal segment. The postoperative change of proximal segment was assessed according to the following variables (Table 2, Figures 1, 2). Because the proximal segment is composed of the condylar head, coronoid process and ramus down, the postoperative position change of these three landmarks represented the proximal-segment position change. Therefore, we measured the distance from each landmark to the three reference planes in order to evaluate the 3D change of the proximal-segment position; also measured the distances between each of the landmarks to estimate the linear change of the extents of movement of the interproximal segments between the T0 and T1 stage. Finally, to compare the angular change of the proximal segment before and after surgery, the angulation of the ramal plane were measured in relation to the reference
ACCEPTED MANUSCRIPT plane. The deviated side (D) was defined as the location of the chin deviation relative to the MSR plane, and non-deviated side (ND) was defined as the opposite side.
Statistical analysis All of the data were analyzed using PASW Statistics 18 (IBM, New York, NY). Wilcoxon signed rank test
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was conducted to compare proximal-segment changes at T0 and T1, respectively. A Mann-Whitney U test was conducted to compare the deviated and non-deviated sides on the basis of the anteroposterior skeletal patterns. A Spearman correlation analysis was used to assess the relationship between the extent of distal-segment
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movement and the deviated/non-deviated-side difference. Differences were considered to be significant at p < 0.05. Further, to evaluate the intra-assessor reproducibility of the CBCT results, the variables of 7 randomly selected subjects were evaluated twice at 2-week intervals using the intraclass correlation coefficient (ICC). The
lowest, and that of the ICP was the highest.
RESULTS
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mean ICC was 0.965 in the 95% confidence interval (lower: 0.800, upper: 0.999). The ICC of the CRD was the
Proximal segment’s changes from T0 to T1 stages.
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The condylar head moved laterally on the deviated side in group I (ACH) and anteriorly on the deviated side in group III (SCH) after surgery (p < 0.05; Table 3, Figure 3). The coronoid process moved medially on the deviated side in groups I and III and on the non-deviated side if group III (ACP) (p < 0.05). It also moved
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posteriorly on the deviated side in group I (SCP) and superiorly on both the deviated and non-deviated sides in groups I and II (CCP) (p < 0.05; Table 3). The ramus down moved laterally on the non-deviated side in group II
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(ARD) (p < 0.05). It also moved anteriorly on the deviated side in group II and on the non-deviated side in groups I and II (SRD), as well as superiorly on the non-deviated side in group III (CRD) (p < 0.05; Table 3). The ramal plane on the axial plane rotated inwardly on the deviated side in groups I and II and the nondeviated side in groups I and III (ARP) (p < 0.05). On the coronal plane, it rotated inwardly on the deviated side in group I and outwardly on the non-deviated side in groups I and II (CRP) (p < 0.05; Table 3). Although there were no significant differences in the inter-condylar width or inter-ramus down width, the inter-coronoid process width had decreased in groups I and III (ICP) (p < 0.05; Table 3).
Comparison between deviated and non-deviated sides
ACCEPTED MANUSCRIPT There was a statistically significant difference in the mediolateral change of the condylar head in group I (ACH), which showed more lateral movement on the deviated side than on the non-deviated side (p < 0.05). There were no significant differences in the mediolateral, anteroposterior or superioinferior changes of the condylar head between the deviated and non-deviated sides of groups II and III (p > 0.05; Table 4). There were no significant differences in the mediolateral, anteroposterior or superioinferior changes of the
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coronoid process between the deviated and non-deviated sides in any of the groups (p > 0.05; Table 4). There was a statistically significant difference in the mediolateral change of the ramus down (ARD) of group I, which showed medial movement on the deviated side but lateral movement on the non-deviated side (p < 0.05). There
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were no significant differences in the mediolateral, anteroposterior or superioinferior changes of the ramus down between the deviated and non-deviated sides in group II (p > 0.05; Table 4).
There was a statistically significant difference of coronal ramal plane angle in group I (CRP), which showed
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inward rotation on the deviated side but outward rotation on the non-deviated side (p < 0.05). There were no significant differences in the axial or coronal ramal plane angles in groups II and III (p > 0.05; Table 4).
Correlation between extent of distal-segment movement and deviated/non-deviated side differences There were no statistically significant correlations in three groups, which indicated that the difference in the
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extent of distal-segment movement between the deviated and non-deviated sides was not a dispositive factor in the proximal-segment changes (p > 0.05).
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DISCUSSION
The SSRO is a commonly employed orthognathic-surgical method. There have been many reports on the
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possible factors affecting post-SSRO condylar position: for example, movement of the distal segment of the mandible, the fixation method, the anatomic shape and contours of the proximal segment, and the surgical expertise.9,17,18,19,20 Research has shown that the condylar position can be influenced by bony interferences between the proximal and distal segments, and that the characteristics of those changes vary according to the anteroposterior skeletal patterns.24,25,26 Harris et al.24 reported that, after SSRO with mandibular advancement in skeletal class II malocclusion, the condyle tends to move medially, posteriorly, and superiorly and to rotate medially. Lee et al.9 showed that, after SSRO with mandibular setback in skeletal class III malocclusion, the condyle tends to move laterally, anteriorly, and inferiorly and to rotate inward and backward. However, the focuses of these previous studies were limited to mandibular advancement and setback the same direction. There
ACCEPTED MANUSCRIPT have, in fact, been only a relative few studies that have focused on the asymmetric extent and direction of mandibular movement in facial-asymmetry patients after BSSRO.
In the present results, the facial-asymmetry patients with skeletal class I malocclusion showed distal-segment mandibular movement in the form of advancement on the deviated side and setback on the non-deviated side.
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The skeletal class II patients, by contrast, showed mandibular movement in the form of asymmetric advancement that was the greater on the deviated side than on the non-deviated side. In the case of skeletal class III malocclusion, the mandible movement was in the form of asymmetric setback that was more extensive on the
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non-deviated side than on the deviated side. In this study, the distal segments of the mandible move in different directions and to different extents according to the anteroposterior skeletal patterns (Table 5). In the comparison of the T0 and T1 stages, the condylar head maintained its original position, except for the
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lateral movement on the deviated side in group I (ACH) and the anterior movement on the deviated side in group III (SCH). Although the condylar head in skeletal class II malocclusion basically tended to move medially, posteriorly, and superiorly except for the ACH on the non-deviated side and the CCH on the deviated side, as agreed with the results of Harris et al.24 for mandibular advancement, there were no significant differences in the condylar head position 6 months after surgery (p > 0.05). And, although the condylar head in skeletal class III
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malocclusion basically tended to move laterally, anteriorly, and inferiorly, in agreement with the results of Lee et al.9 for mandibular setback, there were no significant differences in the condylar head position (p > 0.05),
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except for the SCH on the deviated side (p < 0.05) 6 months after surgery.
The reason for the lack of significant differences of condylar head position between the T0 and T1 stages may
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be due to the timing of postoperative CBCT: 1 month in Lee et al.,9 2 months in Harris et al.,24 and 6 months after surgery in the present study. Actually, some clinicians found that the condylar position had a tendency to return to the preoperative state and, after 3 months, to revert to about half of the immediate postoperative state;12 that the anteroposterior condylar position in the glenoid fossa had moved from the anterior to concentric position, tending to return slightly toward the original position, and that the skeletal changes occurring between postoperative 6 months and follow-up were insignificant.11 However, postoperative condylar change, such as condylar resoprtion, could induce the long-term changes. In contrast to the condylar head, the proximal-segment changes of the coronoid process and ramus down in each group were various. They made it possible to maintain the condylar head position by adjusting their position three-dimensionally. These movements were related to the
ACCEPTED MANUSCRIPT changes of ramal plane angulation, which moved in different directions among the groups. There were changes of the inter-proximal segment width as well. The inter-coronoid process width decreased in groups I and III (ICP) (P < 0.05; Table 3). Whereas the condylar head and ramus down tended to maintain their original position on the axial view, the coronoid process moved medially, both on the deviated side in groups I and III, and on the non-deviated side in group III (ACP). This medial movement of the coronoid process could affect the inward
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rotation of the axial ramal plane angulation in groups I and III.
A factor for possibly affecting this difference of ramal plane angulation in asymmetric setback movement of the mandible is the fixation method.19,21 With rigid internal fixation (RIF) in particular, because the gaps between the proximal and distal segments of the mandible can cause rotation of the condyle laterally or medially,
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it is important to maintain them to prevent any such rotational change.22 Notwithstanding the fact that the application of post-SSRO RIF certainly is helpful in facilitating rapid bone healing, early recovery of
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masticatory function and an increased postoperative stability; widening or narrowing of the gaps between segments can affect condylar position.5 Indeed, Kundert et al.23 reported that after surgery with RIF, there was significant displacement. Other possible factors causing differences in ramal plane angulation are the surgeon's skill level as reflected in control of the proximal and distal segments, and patients' characteristics such as the anatomic shapes of segments.17,18,20 The mandibular anatomic morphology such as U-shaped or V-shaped
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mandible could influence the postoperative proximal segment position.” Interestingly, in the comparison of the deviated and non-deviated sides, there were statistically significant differences only in skeletal class I malocclusion with facial asymmetry. Our results indicated that, on the axial
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plane, the condylar head moved more laterally on the deviated side than on the non-deviated side (p < 0.05), and that the ramus down moved medially on the deviated side and laterally on the non-deviated side (p < 0.05).
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Moreover, the ramal plane, on the coronal plane, showed inward rotation on the deviated side but outward rotation on the non-deviated side (p < 0.05). Even so, there were no significant differences between the deviated and non-deviated sides in skeletal class II or III malocclusion with facial asymmetry (p > 0.05). As already noted, it was considered that these differences were related to the different distal-segment movements of the mandible in skeletal class I malocclusion with facial asymmetry; forward on the deviated side and backward on the non-deviated side. In case of either asymmetric advancement or setback, the distal segment of the mandible moved in the same direction on both the deviated and non-deviated sides though the extent of movement differed.
ACCEPTED MANUSCRIPT Accordingly, our results suggested that one of the most influential factors with regard to differences between the deviated and non-deviated sides could be the direction of movement of the distal segment of mandible rather than its extent (Tables 5). Similarly, in the findings of two investigations, there was no correlation between the extent of mandibular advancement or setback and the change of condylar position.9,21 Correspondingly, the proximal-segment changes after mandibular asymmetric advancement or setback surgery
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for the facial-asymmetry patients with skeletal class II and III malocclusion were similar to those for the symmetric cases but different from those for the facial-asymmetry patients with skeletal class I malocclusion. Therefore, we propose that one of the most dispositive factors affecting differences between the deviated and
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non-deviated sides could be the direction of the movement of the distal segment of the mandible rather than its extent. For this reason, SSRO might be effective orthognathic-surgical modality for maintenance of the condylar position in skeletal class II and III malocclusion with facial asymmetry; in skeletal class I malocclusion with
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facial asymmetry, however, clinicians will need to consider the stabilization of the condylar position.
Conclusion
In facial asymmetry patients after SSRO, the most important factors affecting the proximal segment changes
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between the deviated and non-deviated sides could be the direction of the surgical movement of the distal segment of the mandible not its extent .
REFERENCES
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1. Peck H, Peck S: A concept of facial esthetics. Angle Orthod 40:284, 1970 2. Lee BR, Kang DK, Son WS, et al: The relationship between condyle position, morphology and chin deviation
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in skeletal class III patients with facial asymmetry using cone-beam CT. Korean J Orthod 41:87, 2011 3. Hu J, Wang D, Zou S: Effects of mandibular setback in the temporomandibular joint: a comparison of oblique and sagittal split ramus osteotomy. J Oral maxillofac Surg 58:375, 2000 4. Yamada K, Hanada K, Hayashi T, et al: Condylar bony change, disk displacement, and signs and symptoms of TMJ disorders in orthognathic surgery patients. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 91:603, 2001 5. Nishmura A, Sakurada S, Iwase S: Positional changes in the mandibular condyle and amount of mouth opening after sagittal split ramus osteotomy with rigid or nonrigid osteosynthesis. J Oral Maxillofac Surg 55:672, 1997
ACCEPTED MANUSCRIPT 6. Marden EA, Thomas D, Stephen RM, et al: Short-term changes of condylar position after sagittal split osteotomy for mandibular advancement. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 87:159, 1999 7. Jonas PB, Joe R, Karin BB, et al: Transverse displacement of the proximal segment after bilateral sagittal osteotomy. J Oral Maxillofac Surg 60:395, 2002 8. Carvalho Fde A, Cevidanes LH, da Motta AT, et al: Three-dimensional assessment of mandibular
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advancement 1 year after surgery. Am J Orthod Dentofacial Orthop 137: S53.e1, 2010
9. Lee W, Park JU: Three-dimensional evaluation of positional change of the condyle after mandibular setback by means of bilateral sagittal split ramus osteotomy. Oral Surg Oral Med Oral Pathol Oral Radiol Endod
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94:305, 2002
10. Jang JR, Choi GH, Park YJ, et al: The evaluation of the positional change of the mandibular condyle after bilateral sagittal split ramus osteotomy using three dimensional computed tomography in skeletal class III
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patients. J Kor Oral Maxillofac Surg 35:316, 2009
11. Kim YI, Cho BH, Jung YH, et al: Cone-beam computerized tomography evaluation of condylar changes and stability following two-jaw surgery: Le Fort I osteotomy and mandibular setback surgery with rigid fixation. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 111:681, 2011
12. Lee SK, Kim KW, Kim CH: Postoperative positional change of condyle after bilateral sagittal split ramus
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osteotomy associated with mandibular asymmetry. J Kor Oral Maxillofac Surg 30:359, 2004 13. Bergersen EO: Enlargement and distortion in cephalometric radiography: compensation tables for linear measurements. Angle Orthod 50:230, 1980
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14. Cavakcanti MG, Haller JW, Vannier MW: Three-dimensional computed tomography landmark measurement in craniofacial surgical planning: experimental validation in vitro. J Oral Maxillofac Surg
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57:690, 1999
15. Maes F, Collignon A, Vandermeulen D, et al: Multimodality image registration by maximization of mutual information. IEEE Trans Med Imaging 16:187, 1997 16. Choi JH, Mah J: A new method for superimposition of CBCT volumes. J Clin Orthod 44:303, 2010 17. Komori E, Aigase K, Sugisaki M, et al: Cause of early skeletal relapse after mandibular setback. Am J Orthod Dentofacial Orthop 95:29, 1989 18. Will LA, Joondeph DR, Hohl TH, et al: Condylar position following mandibular advancement: its relationship to relapse. J Oral Maxillofac Surg 42:578, 1984
ACCEPTED MANUSCRIPT 19. Van Sickels JE, Larsen AJ, Thrash WJ: Relapse after rigid fixation of mandibular advancement. J oral maxillofac Surg 44:698, 1986 20. Epker BN, Wessberg GA: Mechanism of early skeletal relapse following surgical advancement of the mandible. Br J Oral Surg 20:175, 1982 21. Hackney FL, Van Sickels JE: Condylar displacement and temporomandibular joint dysfunction following
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bilateral sagittal split osteotomy and rigid fixation. J Oral Maxillofac Surg 47:223, 1989
22. Back SH, Kim TK, Kim MJ: Is there any difference in the condylar position and angulation after asymmetric mandibular setback? Oral Surg Oral Med Oral Pathol Oral Radiol Endod 101:55, 2006
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23. Kundert M, Hadjianghelou O: Condylar displacement after sagittal splitting of mandibular rami. J Maxillofac Surg 8:278, 1980
24. Harris MD, Van Sickels JE, Alder M: Factors influencing condylar position after the bilateral sagittal split
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osteotomy fixed with bicortical screws. J Oral Maxillofac Surg 57:650, 1999
25. Yoshida K, Rivera RS, Kaneko M, et al: Minimizing displacement of the proximal segment after bilateral sagittal split ramus osteotomy in asymmetric cases. J Oral Maxillofac Surg 59:15, 2001 26. Al-Gunaid T, Yamada K, Takagi R, et al: Postoperative stability of bimaxillary surgery in class III patients
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Surg 37:992, 2008
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with mandibular protrusion and mandibular deviation: a frontal cephalometric study. Int J Oral Maxillofac
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FIGURE LEGENDS
Figure 1. Three-dimensional (3D) measurement point and reference plane in 3D CBCT images
Reference points: Cdlat, Condylion lateralis; Cdmed, Condylion medialis; CC, Center of condyle; Cor,
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Coronoid process; RD, Ramus down; Nasion (Na) was the origin (0,0,0). Reference planes: Naparallel (Na-par) plane, Parallel to FH plane and passing through Na; Midsagittal reference (MSR)
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plane, Perpendicular to FH plane and passing through Na and Basion (Ba); Na-perpendicular (Na-per) plane, Perpendicular to FH and MSR planes passing through Na
Figure 2. Reference planes and angular measurements
A. Sagittal plane: Sagittal condylar head position (SCH), Distance from center of condyle to Na-per plane
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Sagittal coronoid process position (SCP), Distance from coronoid process to Na-per plane: Sagittal ramus down position (SRD), Distance from ramus down to Na-per plane B. Coronal plane: Coronal condylar head position (CCH), Distance from center of condyle to Na-par
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plane; Coronal coronoid process position (CCP), Distance from coronoid process to Na-par plane; Coronal ramus down position (CRD), Distance from ramus down to Na-par plane; Coronal ramal plane angle
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C. Axial plane: Axial condylar head position (ACH), Distance from center of condyle to MSR plane; Axial coronoid process position (ACP), Distance from coronoid process to MSR plane; Axial ramus down position (ARD), Distance from ramus down to MSR plane; Axial ramal plane angle
D. Inter-condylar head width (ICH), inter-coronoid process width (ICP), Inter-sigmoid notch width (ISN), Inter-ramus down width (IRD)
Figure 3. Proximal changes after surgery for group I with the deviation at left side. Pre- and Post-operative 3D (A, B), sagittal (C, D), coronal (E, F) and axial (G, H) images, respectively.
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Table 1. Demographic data and criteria by subgroup
Chin deviation (mm)
7.29 (2.51)
ANB (°)
2.05 (1.39)
Chin deviation (mm)
1.03 (0.68)
ANB (°)
2.70 (1.48)
Before surgery
After surgery
Group II (N=15)
Group III (N=18)
Multiple comparison,
p-value
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Group I (N=18)
Variable
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Tables
6.27 (2.63)
7.23 (2.79)
0.338
6.17 (1.44)
-2.26 (3.44)
0.000*
1.09 (0.66)
0.85 (0.55)
0.390
3.99 (1.97)
3.00 (1.87)
0.096
group no.
II > I > III
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*p
