CRANIOMAXILLOFACIAL DEFORMITIES/COSMETIC SURGERY
Stability of Mandibular Setback Surgery With and Without Presurgical Orthodontics Chin-Soo Kim, DDS, PhD,* Sang-Chang Lee, DDS, MSD,y Hee-Moon Kyung, DDS, PhD,z Hyo-Sang Park, DDS, PhD,x and Tae-Geon Kwon, DDS, PhDk Purpose:
The purpose of this study was to compare stability after mandibular setback surgery in patients with skeletal Class III malocclusion with and without presurgical orthodontics.
Materials and Methods:
This retrospective cohort study included consecutive patients with skeletal Class III malocclusion who underwent only mandibular surgery. Patients treated with the surgery-first approach without presurgical orthodontics (SF group) were compared with a control group (conventional surgery with presurgical orthodontics; CS group) using lateral cephalograms taken preoperatively, immediately postoperatively, and at the time of debonding. Predictor variables (group and timing), outcome variables (cephalometric measurements over time), and other variables, such as baseline characteristics, were evaluated to determine the difference in stability of mandibular positions such as the B point.
Results:
Sixty-one patients were enrolled in this study (CS group, n = 38; SF group, n = 23). Baseline demographic variables were similar in the 2 groups except for orthodontic treatment period. The mean setback of the mandible at the B point was similar (CS group, 8.7 mm; SF group, 9.1 mm; difference, P > .05), but the horizontal relapse in the SF group (2.4 mm) was significantly greater than in the CS group (1.6 mm; P < .05). Patients with a horizontal relapse greater than 3 mm comprised 39.1% of the SF group compared with 15.8% of the CS group (P < .05).
Conclusion:
Mandibular sagittal split ramus osteotomy without presurgical orthodontic treatment was less stable than conventional orthognathic surgery for mandibular prognathism. Before performing a surgery-first approach, skeletal stability needs to be considered. Ó 2014 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg 72:779-787, 2014
To maximize stable postoperative occlusion, conventional surgical and orthognathic treatment (CS) includes preoperative orthodontics for dental decompensation. Anteroposterior, vertical, and transverse dental positions are determined during the presurgical orthodontic period. However, worsening of the facial profile during long-term presurgical orthodontics and poor patient compliance are limitations of CS.
Recently, surgery-first orthognathic treatment (SF) without or with minimal presurgical orthodontic treatment was introduced.1 It has been widely popularized, especially in East Asian patients with mandibular prognathism. Because the SF approach corrects the skeletal problem from the beginning, esthetic concerns during the decompensation period and total treatment time can be minimized. Indications for the SF approach have been proposed as follows: 1) moderate or
Received from the School of Dentistry, Kyungpook National University, Daegu, Korea.
by the Ministry of Education, Science and Technology (20120009330) and by the Kyungpook National University Research
*Professor, Department of Oral and Maxillofacial Surgery.
Fund, 2012.
yResident, Department of Oral and Maxillofacial Surgery.
Address correspondence and reprint requests to Dr Kwon: Cen-
zProfessor, Center for Orthognathic Surgery, Department of
ter for Orthognathic Surgery, Department of Oral and Maxillofacial
Orthodontics.
Surgery, School of Dentistry, Kyungpook National University, Daegu
xProfessor, Center for Orthognathic Surgery, Department of
700-421, Republic of Korea; e-mail: [email protected]
Orthodontics.
Received August 8 2013
kProfessor, Center for Orthognathic Surgery, Department of Oral and Maxillofacial Surgery.
Ó 2014 American Association of Oral and Maxillofacial Surgeons
Accepted September 21 2013
Dr Kim and Dr Lee contributed equally to this work.
0278-2391/13/01225-1$36.00/0
This research was supported by the Basic Science Research Pro-
http://dx.doi.org/10.1016/j.joms.2013.09.033
gram through the National Research Foundation of Korea funded
779
780 minimal crowding and adequate inclination of mandibular anterior teeth, 2) at least 3 stable occlusal stops between the upper and lower arches, 3) little or no transverse discrepancy, and 4) adequate curve of Spee.2-4 Although there have been many case series showing favorable results after the SF approach, the concepts for postsurgical orthodontic treatment in this approach vary according to individual institutes. Because dental occlusion cannot be used as a guide to establish treatment, there is a fundamental limitation in accurately predicting postsurgical results. Moreover, postsurgical occlusion is unstable and its influence on relapse has not been fully investigated. Most previously published reports on the SF approach have used 2-jaw surgery,2-9 and many reports have used multisegment Le Fort I osteotomy,2,3,6,7,9 which can be another factor influencing mandibular relapse. However, the stability of the skeletal position after surgery has rarely been documented by a comparative study with a control group. In addition, although the surgical change in maxillary position can influence the mandibular position, previous reports have not considered this effect carefully. Therefore, the skeletal relapse pattern of the SF approach needs to be compared with a control group with similar skeletal movement. It is still unclear whether the SF approach can ensure maximum skeletal stability under unstable postoperative occlusion. To answer this question, the following features were analyzed: 1) the difference in presurgical condition between patients who undergo CS and those who undergo SF, 2) the difference in patterns between the surgical and postsurgical changes of these 2 groups, and 3) the factors related to relapse in these 2 groups. The authors hypothesized there would be a difference in skeletal stability in these 2 groups because eliminating presurgical orthodontics results in more unstable occlusion immediately after surgery, which can influence the final skeletal position. The purpose of this study was to determine whether mandibular setback surgery using the recently introduced SF approach has acceptable mandibular skeletal stability comparable to conventional orthognathic surgery with presurgical orthodontics.
Materials and Methods STUDY DESIGN AND SUBJECTS
The authors designed a retrospective cohort study consisting of consecutive patients with mandibular prognathism who underwent bilateral sagittal split ramus osteotomy (BSSO) at the authors’ affiliated hospital from January 2010 to December 2011. The study group was composed of adult patients who under-
SURGERY-FIRST APPROACH IN MANDIBULAR SETBACK
went BSSO without presurgical orthodontics (SF group). The control group was composed of patients who underwent BSSO with conventional presurgical orthodontics (CS group). Patients were excluded as study subjects if they underwent simultaneous maxillary surgery or had cleft lip and palate, significant mandibular chin deviation (pogonion [Pog]) greater than 4 mm from the facial midline, a history of facial trauma or infection, a hemifacial microsomia, or congenital muscular torticollis. This study was approved by the institutional review board of Kyungpook National University Hospital (Daegu, Korea; KNUH_2013-01-018). SURGICAL AND ORTHOGNATHIC TREATMENT
For patients in the SF group, orthodontic brackets were positioned without any active orthodontic force before surgery. Patients who had at least 3 stable occlusal stops in the maxillomandibular dental casts and the absence of a transverse discrepancy after determining mandibular setback underwent SF in the authors’ department. Presurgical orthodontic treatments, namely orthodontic leveling, alignment, and elimination of crowding, were performed for all patients in the CS group to achieve stable occlusion after surgery. Orthodontic treatment was carried out by 2 experienced orthodontists (H.-M.K. and H.-S.P.) at the same orthodontic department. A thin, removable, interocclusal acrylic resin splint was fabricated on a maxillomandibular dental cast mounted on an articulator to reposition the mandible to the desired position during the operation. Each operation consisted of BSSO using the same protocol by 1 surgeon (T.-G.K.). The position of the proximal segment of the mandible was secured with the mandibular condyle positioning system. The osteotomized mandible was fixed with 4hole miniplates in a monocortical fashion. After the operation, the patients used intermaxillary elastics and an interocclusal splint for 4 to 6 weeks for occlusal stabilization. The CS and SF groups received the same postoperative management. CEPHALOMETRIC ANALYSIS
Skeletal changes after surgery and stability were evaluated with lateral cephalograms taken 1 month before surgery (T1), 2 to 3 days after surgery (T2), and at the time of debonding (T3; 6 to 22 months after surgery). Postoperative change was defined as T2 minus T1 and relapse as T3 minus T2. The lateral cephalograms were digitized using V-ceph 6.0 (Osstem, Seoul, Korea) by 2 observers who were blinded to the clinical status of the patients. The traced cephalograms were overlapped at the sella (S), nasion (N), porion, and orbitale. Then, reference lines (Frankfurt horizontal [FH] plane and SN line) were drawn based
781
KIM ET AL
FIGURE 1. Cephalometric landmarks and measurements of the study. The FH plane was the horizontal reference plane. Then, reference lines (FH plane and SN line) were drawn based on the reference point. The S line perpendicular to the FH plane became the vertical reference plane. Positive values indicate forward and inferior movements. The angle of the FH plane to the maxillary occlusal plane angle (FH-OP), the mandibular plane angle (FH-MP), upper incisor inclination (FH-U1), IMPA, interincisal angle, overjet, overbite, and the horizontal (x) and vertical (y) positions of the B point and Pog were measured. A, A point; B, B point; FH, Frankfort horizontal; IMPA, mandibular incisor inclination to mandibular plane angle; L1, lower incisor; MP, mandibular plane; N, nasion; Pog, pogonion; S, sella; U1, upper incisor. Kim et al. Surgery-First Approach in Mandibular Setback. J Oral Maxillofac Surg 2014.
on the reference point. The angle of the FH plane to the maxillary occlusal plane (FH-OP), the angle of the FH plane to the mandibular plane (FH-MP), upper incisor (U1) inclination in relation to the FH plane (FHU1), mandibular incisor inclination in relation to the MP (IMPA), interincisal angle, overjet, overbite, and horizontal (x) and vertical (y) positions of the B point (B) and Pog were measured (Fig 1).
STUDY VARIABLES
The primary predictor variable in the present study was the presence or absence of presurgical orthodontics and timing (each time point for radiographic examination). Outcome variables were cephalometric measurements. The third category of variables
consisted of demographic variables, such as age (years) and gender (male vs female). DATA ANALYSIS
The reproducibility test was evaluated by comparing measurements from the original and repeat examinations of randomly collected cephalometric data from 7 patients in a P 1-week interval. The method error was calculated as ( d2/2n), where d is the difference between double measurements and n is the number of paired double measurements.10 The method error of the linear measurements ranged from 0.42 to 0.87 mm and from 0.5 to 0.9 , which was not statistically significant. Paired t test was used to compare operative changes (T2 minus T1) and postsurgical relapse (T3 minus T2). Statistical differences
782
SURGERY-FIRST APPROACH IN MANDIBULAR SETBACK
Table 1. PATIENTS’ BASELINE VALUES
Demographic variables n Age (yr), mean SD (range) Women, % (n) Presurgical orthodontics or preparation period (mo), mean SD (range) Postsurgical orthodontic period (mo), mean SD (range) With reduction genioplasty, % (n) With perioral augmentation, % (n) Cephalometric variables, mean SD Angular measurements ( ) SNA SNB ANB FH-OP FH-MP FH-U1 IMPA Interincisal angle Linear measurements (mm) B(x) Pog(x) B(y) Pog(y) Overjet Overbite
CS Group
SF Group
P Value
38 21.6 3.5 (1735) 50 (19) 12.9 3.9 (421)
23 23.0 6.3 (1744) 60.9 (14) 1.1 0.7 (0.43)
.308 .417*
Stability of Mandibular Setback Surgery With and Without Presurgical Orthodontics Chin-Soo Kim, DDS, PhD,* Sang-Chang Lee, DDS, MSD,y Hee-Moon Kyung, DDS, PhD,z Hyo-Sang Park, DDS, PhD,x and Tae-Geon Kwon, DDS, PhDk Purpose:
The purpose of this study was to compare stability after mandibular setback surgery in patients with skeletal Class III malocclusion with and without presurgical orthodontics.
Materials and Methods:
This retrospective cohort study included consecutive patients with skeletal Class III malocclusion who underwent only mandibular surgery. Patients treated with the surgery-first approach without presurgical orthodontics (SF group) were compared with a control group (conventional surgery with presurgical orthodontics; CS group) using lateral cephalograms taken preoperatively, immediately postoperatively, and at the time of debonding. Predictor variables (group and timing), outcome variables (cephalometric measurements over time), and other variables, such as baseline characteristics, were evaluated to determine the difference in stability of mandibular positions such as the B point.
Results:
Sixty-one patients were enrolled in this study (CS group, n = 38; SF group, n = 23). Baseline demographic variables were similar in the 2 groups except for orthodontic treatment period. The mean setback of the mandible at the B point was similar (CS group, 8.7 mm; SF group, 9.1 mm; difference, P > .05), but the horizontal relapse in the SF group (2.4 mm) was significantly greater than in the CS group (1.6 mm; P < .05). Patients with a horizontal relapse greater than 3 mm comprised 39.1% of the SF group compared with 15.8% of the CS group (P < .05).
Conclusion:
Mandibular sagittal split ramus osteotomy without presurgical orthodontic treatment was less stable than conventional orthognathic surgery for mandibular prognathism. Before performing a surgery-first approach, skeletal stability needs to be considered. Ó 2014 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg 72:779-787, 2014
To maximize stable postoperative occlusion, conventional surgical and orthognathic treatment (CS) includes preoperative orthodontics for dental decompensation. Anteroposterior, vertical, and transverse dental positions are determined during the presurgical orthodontic period. However, worsening of the facial profile during long-term presurgical orthodontics and poor patient compliance are limitations of CS.
Recently, surgery-first orthognathic treatment (SF) without or with minimal presurgical orthodontic treatment was introduced.1 It has been widely popularized, especially in East Asian patients with mandibular prognathism. Because the SF approach corrects the skeletal problem from the beginning, esthetic concerns during the decompensation period and total treatment time can be minimized. Indications for the SF approach have been proposed as follows: 1) moderate or
Received from the School of Dentistry, Kyungpook National University, Daegu, Korea.
by the Ministry of Education, Science and Technology (20120009330) and by the Kyungpook National University Research
*Professor, Department of Oral and Maxillofacial Surgery.
Fund, 2012.
yResident, Department of Oral and Maxillofacial Surgery.
Address correspondence and reprint requests to Dr Kwon: Cen-
zProfessor, Center for Orthognathic Surgery, Department of
ter for Orthognathic Surgery, Department of Oral and Maxillofacial
Orthodontics.
Surgery, School of Dentistry, Kyungpook National University, Daegu
xProfessor, Center for Orthognathic Surgery, Department of
700-421, Republic of Korea; e-mail: [email protected]
Orthodontics.
Received August 8 2013
kProfessor, Center for Orthognathic Surgery, Department of Oral and Maxillofacial Surgery.
Ó 2014 American Association of Oral and Maxillofacial Surgeons
Accepted September 21 2013
Dr Kim and Dr Lee contributed equally to this work.
0278-2391/13/01225-1$36.00/0
This research was supported by the Basic Science Research Pro-
http://dx.doi.org/10.1016/j.joms.2013.09.033
gram through the National Research Foundation of Korea funded
779
780 minimal crowding and adequate inclination of mandibular anterior teeth, 2) at least 3 stable occlusal stops between the upper and lower arches, 3) little or no transverse discrepancy, and 4) adequate curve of Spee.2-4 Although there have been many case series showing favorable results after the SF approach, the concepts for postsurgical orthodontic treatment in this approach vary according to individual institutes. Because dental occlusion cannot be used as a guide to establish treatment, there is a fundamental limitation in accurately predicting postsurgical results. Moreover, postsurgical occlusion is unstable and its influence on relapse has not been fully investigated. Most previously published reports on the SF approach have used 2-jaw surgery,2-9 and many reports have used multisegment Le Fort I osteotomy,2,3,6,7,9 which can be another factor influencing mandibular relapse. However, the stability of the skeletal position after surgery has rarely been documented by a comparative study with a control group. In addition, although the surgical change in maxillary position can influence the mandibular position, previous reports have not considered this effect carefully. Therefore, the skeletal relapse pattern of the SF approach needs to be compared with a control group with similar skeletal movement. It is still unclear whether the SF approach can ensure maximum skeletal stability under unstable postoperative occlusion. To answer this question, the following features were analyzed: 1) the difference in presurgical condition between patients who undergo CS and those who undergo SF, 2) the difference in patterns between the surgical and postsurgical changes of these 2 groups, and 3) the factors related to relapse in these 2 groups. The authors hypothesized there would be a difference in skeletal stability in these 2 groups because eliminating presurgical orthodontics results in more unstable occlusion immediately after surgery, which can influence the final skeletal position. The purpose of this study was to determine whether mandibular setback surgery using the recently introduced SF approach has acceptable mandibular skeletal stability comparable to conventional orthognathic surgery with presurgical orthodontics.
Materials and Methods STUDY DESIGN AND SUBJECTS
The authors designed a retrospective cohort study consisting of consecutive patients with mandibular prognathism who underwent bilateral sagittal split ramus osteotomy (BSSO) at the authors’ affiliated hospital from January 2010 to December 2011. The study group was composed of adult patients who under-
SURGERY-FIRST APPROACH IN MANDIBULAR SETBACK
went BSSO without presurgical orthodontics (SF group). The control group was composed of patients who underwent BSSO with conventional presurgical orthodontics (CS group). Patients were excluded as study subjects if they underwent simultaneous maxillary surgery or had cleft lip and palate, significant mandibular chin deviation (pogonion [Pog]) greater than 4 mm from the facial midline, a history of facial trauma or infection, a hemifacial microsomia, or congenital muscular torticollis. This study was approved by the institutional review board of Kyungpook National University Hospital (Daegu, Korea; KNUH_2013-01-018). SURGICAL AND ORTHOGNATHIC TREATMENT
For patients in the SF group, orthodontic brackets were positioned without any active orthodontic force before surgery. Patients who had at least 3 stable occlusal stops in the maxillomandibular dental casts and the absence of a transverse discrepancy after determining mandibular setback underwent SF in the authors’ department. Presurgical orthodontic treatments, namely orthodontic leveling, alignment, and elimination of crowding, were performed for all patients in the CS group to achieve stable occlusion after surgery. Orthodontic treatment was carried out by 2 experienced orthodontists (H.-M.K. and H.-S.P.) at the same orthodontic department. A thin, removable, interocclusal acrylic resin splint was fabricated on a maxillomandibular dental cast mounted on an articulator to reposition the mandible to the desired position during the operation. Each operation consisted of BSSO using the same protocol by 1 surgeon (T.-G.K.). The position of the proximal segment of the mandible was secured with the mandibular condyle positioning system. The osteotomized mandible was fixed with 4hole miniplates in a monocortical fashion. After the operation, the patients used intermaxillary elastics and an interocclusal splint for 4 to 6 weeks for occlusal stabilization. The CS and SF groups received the same postoperative management. CEPHALOMETRIC ANALYSIS
Skeletal changes after surgery and stability were evaluated with lateral cephalograms taken 1 month before surgery (T1), 2 to 3 days after surgery (T2), and at the time of debonding (T3; 6 to 22 months after surgery). Postoperative change was defined as T2 minus T1 and relapse as T3 minus T2. The lateral cephalograms were digitized using V-ceph 6.0 (Osstem, Seoul, Korea) by 2 observers who were blinded to the clinical status of the patients. The traced cephalograms were overlapped at the sella (S), nasion (N), porion, and orbitale. Then, reference lines (Frankfurt horizontal [FH] plane and SN line) were drawn based
781
KIM ET AL
FIGURE 1. Cephalometric landmarks and measurements of the study. The FH plane was the horizontal reference plane. Then, reference lines (FH plane and SN line) were drawn based on the reference point. The S line perpendicular to the FH plane became the vertical reference plane. Positive values indicate forward and inferior movements. The angle of the FH plane to the maxillary occlusal plane angle (FH-OP), the mandibular plane angle (FH-MP), upper incisor inclination (FH-U1), IMPA, interincisal angle, overjet, overbite, and the horizontal (x) and vertical (y) positions of the B point and Pog were measured. A, A point; B, B point; FH, Frankfort horizontal; IMPA, mandibular incisor inclination to mandibular plane angle; L1, lower incisor; MP, mandibular plane; N, nasion; Pog, pogonion; S, sella; U1, upper incisor. Kim et al. Surgery-First Approach in Mandibular Setback. J Oral Maxillofac Surg 2014.
on the reference point. The angle of the FH plane to the maxillary occlusal plane (FH-OP), the angle of the FH plane to the mandibular plane (FH-MP), upper incisor (U1) inclination in relation to the FH plane (FHU1), mandibular incisor inclination in relation to the MP (IMPA), interincisal angle, overjet, overbite, and horizontal (x) and vertical (y) positions of the B point (B) and Pog were measured (Fig 1).
STUDY VARIABLES
The primary predictor variable in the present study was the presence or absence of presurgical orthodontics and timing (each time point for radiographic examination). Outcome variables were cephalometric measurements. The third category of variables
consisted of demographic variables, such as age (years) and gender (male vs female). DATA ANALYSIS
The reproducibility test was evaluated by comparing measurements from the original and repeat examinations of randomly collected cephalometric data from 7 patients in a P 1-week interval. The method error was calculated as ( d2/2n), where d is the difference between double measurements and n is the number of paired double measurements.10 The method error of the linear measurements ranged from 0.42 to 0.87 mm and from 0.5 to 0.9 , which was not statistically significant. Paired t test was used to compare operative changes (T2 minus T1) and postsurgical relapse (T3 minus T2). Statistical differences
782
SURGERY-FIRST APPROACH IN MANDIBULAR SETBACK
Table 1. PATIENTS’ BASELINE VALUES
Demographic variables n Age (yr), mean SD (range) Women, % (n) Presurgical orthodontics or preparation period (mo), mean SD (range) Postsurgical orthodontic period (mo), mean SD (range) With reduction genioplasty, % (n) With perioral augmentation, % (n) Cephalometric variables, mean SD Angular measurements ( ) SNA SNB ANB FH-OP FH-MP FH-U1 IMPA Interincisal angle Linear measurements (mm) B(x) Pog(x) B(y) Pog(y) Overjet Overbite
CS Group
SF Group
P Value
38 21.6 3.5 (1735) 50 (19) 12.9 3.9 (421)
23 23.0 6.3 (1744) 60.9 (14) 1.1 0.7 (0.43)
.308 .417*
