One goal of orthodontic treatment is to maintain

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1 Original article Soft-tissue changes after maxillomandibular advancement surgery assessed with cone-beam computed tomography Michael S. Ryckman, a Steven Harrison, b Don Oliver, b Christian Sander, c ndrew. oryor, d nsgar. Hohmann, d Fatih Kilic, d and Ki eom Kim e Dayton, Ohio, St. Louis, Mo, and Ulm, Germany Introduction: The purpose of this study was to quantify anteroposterior and transverse facial soft-tissue changes with respect to underlying skeletal movements after maxillomandibular advancements by using cone-beam computed tomography. Methods: Thirty white patients were treated by maxillomandibular advancements after LeFort I osteotomies and bilateral sagittal split osteotomies. The patients were scanned by using cone-beam computed tomography within 1 week before the surgery, within 1 week after the surgery, and a minimum of 8 weeks postsurgery. We measured the differences between the first and last images and calculated ratios for anteroposterior and transverse soft-to-hard tissue movements. Changes in the greatest interalar width were also measured. Results: There was a statistically significant difference in the greatest interalar width change between patients receiving maxillary advancements greater than 4 mm and those having advancements less than or equal to 4 mm (P <0.023). Mean ratios of anteroposterior soft-to-hard tissue movements were 84.9% ± 38.0% in the malar region, 96.1% ± 15.5% in the chin, and 101.1% ± 27.3% in the subcommissural region. Mean ratios of transverse soft-to-hard tissue movements were 39.4% ± 19.7% in the malar region and 82.5% ± 56.7% in the subcommissural region. Conclusions: The amount of maxillary advancement most likely plays a role in the postsurgical increase in interalar width. In addition, facial soft tissues appear to respond more to anterior movement of the jaws than to an increase in transverse dimensions after maxillomandibular advancements. (m J Orthod Dentofacial Orthop 2010;137:S86-93) One goal of orthodontic treatment is to maintain or improve a patient s facial balance. When orthognathic surgery is performed in conjunction with orthodontics, the capacity to alter facial appearance is increased. Even with the ability to optimally reposition the jaws through orthognathic surgery, however, a patient s final soft-tissue appearance might not reflect the exact movements of the jaws. ecause of factors such as soft-tissue thickness and elasticity, the facial soft-tissue drape does not always follow the movement of the underlying skeleton at a 1:1 ratio. thorough a Private practice, Dayton, Ohio. b Clinical assistant professor, Department of Orthodontics, Saint Louis University, St. Louis, Mo. c ssistant professor, University of Ulm, Ulm, Germany. d Scientific staff, Department of Orthodontics, University of Ulm, Ulm, Germany. e ssistant professor, Department of Orthodontics, Saint Louis University, St Louis, Mo. The authors report no commercial, proprietary, or financial interest in the products or companies described in this article. Reprint requests to: Ki eom Kim, Department of Orthodontics, Saint Louis University, 3320 Rutger St, St. Louis, MO 63104; , kkim8@slu.edu. Submitted, ugust 2008; revised and accepted, March /$36.00 Copyright 2010 by the merican ssociation of Orthodontists. doi: /j.ajodo understanding of the soft-tissue response to underlying skeletal movement is necessary for treatment planning, prediction, patient education, and informed consent. Numerous studies have attempted to quantify facial soft-tissue changes after orthognathic surgery. consistent finding was that the alar base width and the greatest interalar width of the nose generally increase after maxillary advancements and impactions. 1-9 ecause of this potentially undesirable side effect, most surgeons place an alar base cinch suture to aid in controlling the final width of the alar base, and several studies suggest that this procedure is helpful. 3,4,6 nother frequently studied soft-tissue region is that overlying the chin. y measuring the differences between presurgical and postsurgical lateral cephalograms, several studies have shown that the soft-tissue chin region advances at about 100% of the amount of mandibular advancement Using 3-dimensional (3D) laser-scanning techniques, McCance et al 14 observed a 125% average for the soft-to-hard tissue ratio of the chin. Few studies have attempted to quantify postsurgical soft-tissue changes in facial regions lateral to the midline because these structures are usually not identifiable on traditional 2-dimensional cephalograms. 15,16 S86

2 Ryckman et al merican Journal of Orthodontics and Dentofacial Orthopedics Volume 137, Number 4, Supplement 1 S87 E C D F C D Fig 1. Frontal view of superimpositions (T0, yellow; T1, blue; T2, pink)., Malar implant;, alar base; C, gonial angle; D, subcommissure; E, maxillary incisor; F, -point. Furthermore, repeatedly identifying nonmidline softtissue landmarks is difficult even with newer 3D imaging techniques because these tissues are broad and curved.2,17 Nonetheless, by superimposing 3D laser facial scans, McCance et al14 found a soft-to-hard tissue response of 150% in the paranasal regions after maxillary advancements, but Soncul and amber18 reported findings closer to 75% for similar measurements. In another laser facial-scanning study, McCance et al19 showed progressively decreasing soft-tissue responses to maxillary advancements as the location of measurement moved away from the midline. nother region of the face that few studies have attempted to quantify is the soft tissue covering the lateral aspects of the mandible, particularly after mandibular advancements. McCance et al14 demonstrated smaller softto-hard tissue movement ratios lateral to the midline in the mandible. The soft tissues overlying the chin, mentalis, and canine regions advanced 125% of the amount of mandibular advancement, whereas the soft tissues over the body of the mandible approached only a 100% ratio. Most studies quantifying soft-tissue profile changes after orthognathic surgery have been comparisons of presurgical and postsurgical lateral cephalograms, but these studies largely neglect nonmidline structures and facial shapes. In the past few decades, several techniques have been developed to analyze patients 3-dimensionally, but most of these methods include only soft-tissue information. Cone-beam computed tomography (CCT), on the other hand, gives clinicians high-resolution images with both soft-tissue and hard-tissue information. dditional S86-93_OPRG_3052.indd 87 benefits include lower costs and less radiation exposure to patients than conventional computed tomography The purpose of this study was to quantify both anteroposterior and transverse facial soft-tissue changes with respect to underlying skeletal movements after maxillomandibular advancements by using CCT. Material and methods The records of 30 white patients were collected from a private practice in oral surgery. The average patient age was 27.9 years (range,16-63 years); the sample included 10 male and 20 female subjects. The patients had received maxillary and mandibular advancements with rigid fixation, all performed by 2 oral surgeons using the same protocol. Eleven patients with malar deficiency also received malar augmentations in the form of Interpore-200 (Nobel iocare, Yorba Linda, Calif) and vitene (C. R. ard, Woburn, Mass) heat-treated grafts. These grafts are moldable mixes of porous hydroxyapatite and microfibrillar collagen, and were also used to augment the antegonial notch regions when necessary. Ten patients received advancement genioplasties. ll patients received alar base cinches, and V-Y advancement mucosal closures were performed as necessary for patients requiring more upper lip fullness. lar base cinches were tightened at the surgeon s discretion. ll patients received comprehensive orthodontic treatment before and after surgery. ll patients had 3 CCT scans: within 1 week presurgery (T0), within 1 week postsurgery (T1), and at 3/24/10 12:11 PM

3 S88 Ryckman et al merican Journal of Orthodontics and Dentofacial Orthopedics pril 2010 E C D F C D Fig 2. Profile view of superimpositions (T0, yellow; T1, blue; T2, pink)., Malar implant;, alar base; C, gonial angle; D, subcommissure; E, maxillary incisor; F, -point. least 8 weeks postsurgery (T2). The range for the T2 scans was 8 to 17 weeks, with a mean of 10 weeks. ll scans were taken with the patient in centric relation, without a splint. The scans were made with an i-ct CCT scanner (Imaging Sciences International, Hatfield, Pa) and required 40 seconds each. Voxel size was set at 0.25, and each scan contained 555 slices, sufficiently encompassing the region of interest. Each data set was imported directly into mira (version 4.1.1, Mercury Computer Systems, Chelmsford, Mass). The scans were superimposed by using skeletal structures unaffected by the surgeries: outer surfaces of the frontal and sphenoid bones, and the superior regions of the outer surfaces of the zygomas. fter selecting these regions, the automatic affine registration tool of mira was used for stepwise superimposition. This tool uses Hounsfield-value distribution to calculate a measurement describing a distance between 2 data sets to be superimposed. This measurement is automatically minimized during registration, and the original shape of the data is preserved with rigid transformation (Figs 1 and 2). ll data were acquired by using mira. ll hardtissue changes were measured at 500 Hounsfield units (HU); soft-tissue changes were recorded at 900 HU. Cross-sectional reference planes were established to ensure that all measurements were recorded similarly for each patient (Fig 3). In the T0 image, the horizontal plane was created first and rotated until it was parallel with the Frankfort horizontal plane. Next, the sagittal plane was created, S86-93_OPRG_3052.indd 88 Fig 3. Cross-sectional reference planes. oriented perpendicular to the horizontal plane, and rotated until it was parallel to the midsagittal plane (determined by nasion and sella in this study). Last, the coronal plane was generated and oriented perpendicular to both of the other planes. The orientations of the planes were then locked, but the planes could still be moved in the third dimension, always remaining parallel to their initially established orientations. Planes were moved to each region of interest, and all measurements were recorded along the intersections of the planes to ensure consistency with the direction of measurement. 3/24/10 12:11 PM

4 Ryckman et al merican Journal of Orthodontics and Dentofacial Orthopedics Volume 137, Number 4, Supplement 1 Fig 4. nteroposterior hard-tissue change of a malar implant. Point indicates the intersection of the horizontal and sagittal planes with the most anterior projection of the implant (T2). Point indicates the intersection of the planes with the T0 image. Fig 5. Soft-tissue changes over a malar implant. Point indicates the intersection of the horizontal and sagittal planes with the T2 image, and Point indicates the intersection of the planes with the T0 image. Surgical advancement of the maxilla was determined by measuring the change between the T0 and T1 images at the mesio-incisal edge of the maxillary right central incisor. lthough using -point to measure maxillary advancement might have been more ideal, this point was unidentifiable on the CCT scan because of an overlying fixation plate. dvancement of the mandible was measured at -point. ll softtissue changes were measured between the T0 and S86-93_OPRG_3052.indd 89 S89 Fig 6. Inferior view of the nose for measurement of greatest interalar width. Points and were selected to measure the interalar width. T2 images. nteroposterior and transverse changes over malar implants were measured at the point of maximum anterior and transverse projection of the implant, respectively. To measure the anteroposterior hard-tissue change of a malar implant, the horizontal and sagittal planes were placed over the point of maximum anterior projection of the implant, and a measurement was taken between the 2 images along the intersection of the 2 planes (Fig 4). Then, without moving the planes, the Hounsfield units were adjusted to view the soft tissues, and a measurement was taken between the 2 soft-tissue images along the intersection of the 2 planes (Fig 5). In this manner, soft-tissue changes were compared with the directly underlying hard-tissue changes. The soft-to-hard tissue movement ratios (percentages) were calculated by dividing the value of the soft-tissue change by the value of the hard-tissue change. Transverse changes at the malar implants were recorded in the same manner, but using the coronal plane in place of the sagittal plane and measuring at the point of maximum lateral projection of the implant. y using this same method, measurements were recorded for anteroposterior changes at pogonion, both anteroposterior and transverse changes at the subcommissural regions, and transverse changes at the gonial regions. oth anteroposterior and transverse measurements in the subcommissural regions were recorded from points just anterior to the rims of the mental foramina. The location of the transverse measurement in the gonial regions was constructed by setting the horizontal plane at the level of the maxillary central incisors, whereas the coronal plane was set at the level of the most inferior projection of the articular eminence. 3/24/10 12:11 PM

5 S90 Ryckman et al merican Journal of Orthodontics and Dentofacial Orthopedics pril 2010 Table. Descriptive statistics Measurement n Minimum Maximum Mean SD Maxillary advancement (mm) Mandibular advancement (mm) Greatest interalar width increase (mm) nteroposterior malar change (%)* Transverse malar change (%)* Change at pogonion (%)* nteroposterior subcommissural change (%)* Transverse subcommissural change (%)* Transverse gonial change (%)* *Percentage change indicates the soft-tissue change relative to the underlying hard-tissue change. Negative values indicate soft-tissue movement in the opposite direction to the hard-tissue movement. Measurements were not recorded if the planes intersected over a fixation plate or screw on the T2 image. Right and left sides were not compared; all bilateral measurements were combined for all calculations. Measurements were not recorded if the planes intersected over a fixation plate or screw on the T2 image because this might have produced a misleadingly large measurement of hard-tissue change. The right and left sides were not compared; all bilateral measurements were combined for all calculations. The only measurements not recorded parallel to the reference planes were the greatest interalar widths, because the greatest interalar width is unlikely to exist parallel to these planes. These measurements were first recorded while viewing the noses from the inferior aspect (Fig 6) and then verified by rotating the images and viewing the noses from several angles. Statistical analysis Descriptive statistics were calculated for all softto-hard tissue movement ratios and for the changes in greatest interalar width. The Mann-Whitney test was used to test for significant differences in the greatest interalar width change between patients who received maxillary advancements less than 4.0 mm and those who received advancements greater than or equal to 4.0 mm. T tests for equality of means or Mann-Whitney tests (for calculations in groups with fewer than 20 patients) were also used to test for significant differences in all mandibular measurements between patients who received genioplasties and those who did not. Finally, t tests for equality of means or Mann-Whitney tests were used to test for significant differences in the mandibular measurements between patients who received mandibular advancements less than 10.0 mm and those who received advancements greater than or equal to 10.0 mm. Ten percent of the sample was remeasured to test for reliability with an intraclass correlation coefficient. ll statistics were calculated by using SPSS software for Windows (version 14.0, SPSS, Chicago, Ill) on a personal computer. Results The intraclass correlation coefficient showed the measurements to be reliable. The lowest of the Cronbach s alpha measurements was.972, for maxillary advancement. Descriptive statistics for all measurements are listed in the Table. For patients who received maxillary advancements less than 4.0 mm, the mean increase in greatest interalar width was 1.7 ± 1.0 mm. Patients who received maxillaryadvancements greater than or equal to 4.0 mm, on the other hand, had a mean increase of 2.8 ± 1.1 mm. statistically significant difference was found for the change in greatest interalar width between these 2 groups (Z = 2.266, P <0.023). statistically significant difference was also found in the anteroposterior subcommissural changes between patients who received genioplasty and those who did not (t = 2.486, P <0.016). The mean ratios of anteroposterior soft-to-hard tissue movements in the subcommissural region were 95.1% ± 25.3% for patients without genioplasties and ± 27.7% for patients who received genioplasties. There were no significant differences for the ratios of soft-to-hard tissue movement in the anteroposterior chin region, transverse subcommissural region, or transverse gonial region between patients who received genioplasties and those who did not (P >0.050). For patients who received mandibular advancements less than 10.0 mm, the mean ratio for transverse softto-hard tissue movement in the subcommissural region was 95.2% ± 66.4%. Patients who received advancements greater than or equal to 10.0 mm, on the other hand, had a mean ratio of 57.0% ± 4.6%. statistically

6 merican Journal of Orthodontics and Dentofacial Orthopedics Ryckman et al S91 Volume 137, Number 4, Supplement 1 significant difference was found for the transverse softto-hard tissue movement in the subcommissural region between these 2 groups (Z = 1.960, P <0.050). There were no significant differences for the ratios of soft-tohard tissue movement in the anteroposterior chin region, anteroposterior subcommissural region, or transverse gonial region between patients who received mandibular advancements less than 10.0 mm and those who received advancements greater than or equal to 10.0 mm (P >0.050) Discussion The average increase in greatest interalar width of 2.3 ± 1.2 mm for all patients in this study supports the findings of previous studies that most anterior movements of the maxilla result in increased transverse nasal dimensions. 1-6,8,9 No patient had a decrease in greatest interalar width after the LeFort I osteotomy. It is not possible to determine the effect of the alar base cinch sutures used in this study because all patients received the sutures, and differential tension was placed on the sutures at the surgeon s discretion. lso, because of the differential tension on the sutures depending on the presurgical alar base width, it is not possible to determine whether narrow presurgical noses experienced a greater increase in transverse dimensions than did wide presurgical noses, as was the case in studies by etts et al 2 and Chung et al. 9 Patients who received maxillary advancements greater than or equal to 4.0 mm experienced a larger increase in the greatest interalar width than did those with maxillary advancements less than 4.0 mm. The increase in transverse nasal dimensions is probably multifactorial, because several authors have suggested that the increases are primarily due to muscle shortening and lateral retraction associated with the transection of perioral and perinasal musculature during surgery etts et al 2 suggested that the location of the LeFort I soft-tissue incision and technique used for wound closure contributed more to the final nasolabial results than did the actual hard-tissue changes. However, our results demonstrate that the amount of maxillary advancement is an important factor in determining the final transverse dimensions of the nose. Conversely, the amount of mandibular advancement did not prove to be a significant factor in the soft-tohard tissue movement ratios for most measurements. The only measurement that had a statistically significant difference between mandibular advancements less than 10.0 mm and advancements greater than or equal to 10.0 mm was the transverse subcommissural change. The additional anterior pull of the soft tissues in patients with the larger advancements probably stretched the tissues more tightly, preventing the mean transverse subcommissural soft-to-hard tissue movement ratio (57.0% ± 4.6%) from reaching that of the patients with smaller mandibular advancements (95.2% ± 66.4%). The mean soft-to-hard tissue movement ratio of 96.1% ± 15.5% for the tissues overlying pogonion agrees with several studies that investigated this measurement after mandibular advancements The difference between patients with and without genioplasties was not statistically significant for this measurement, so both groups were included in the ratio listed above. Patients with genioplasties had a significantly different anteroposterior subcommissural change (112.9% ± 27.7%) than did patients without genioplasties (95.1% ± 25.3%), so the results for patients without genioplasties probably indicate the true soft-tissue response in this region. The location of measurement for anteroposterior subcommissural change was usually slightly superior to the osteotomy used for chin advancement. The forward movement of the chin most likely pulled the soft tissue overlying the subcommissural regions even more anteriorly in patients with genioplasties, accounting for their greater soft-tissue response. lthough other authors noticed a trend toward smaller soft-to-hard tissue movement ratios lateral to the midline, the ratios overlying the chin and subcommissural regions were nearly identical in this study. 14,19 This study is the first to report nonmidline soft-tohard tissue movement ratios while calculating the hardtissue changes directly beneath the point of soft-tissue measurement. Previous studies calculated lateral softtissue changes but compared them with measurements of midline skeletal advancement. ut if there is any rotational component to the advancement, the actual hard-tissue advancement varies at different regions of the bone. In both the malar and subcommissural measurements, the soft tissues responded less to transverse skeletal changes than to anteroposterior changes. The mean anteroposterior malar soft-to-hard tissue movement ratio was 84.9% ± 38.0%, whereas the transverse ratio was only 39.4% ± 19.7%. The mean subcommissural anteroposterior ratio was 101.1% ± 27.3%, and the transverse ratio was only 82.5% ± 56.7%. possible explanation for these lower transverse ratios is the anterior pull of the tissues resulting from the advancements. Since the primary goal of advancement surgery is anterior movement, the soft tissues might have been stretched enough anteriorly that they slightly compressed over the lateral parts of the face, preventing the full expression of transverse soft-tissue movement that might have otherwise been observed.

7 S92 Ryckman et al merican Journal of Orthodontics and Dentofacial Orthopedics pril 2010 The mean anteroposterior malar soft-to-hard tissue ratio reported in this study (84.9% ± 38.0%) was between those reported by McCance et al 14 (150%) and Soncul and amber 18 (about 75%) for the paranasal regions. The anteroposterior subcommissural ratio in this study for patients without genioplasties (95.1% ± 25.3%) was also similar to that of McCance et al, 14 who reported ratios close to 125% for the canine regions and close to 100% for tissues over the body of the mandible. The soft tissues of the gonial regions showed the greatest variability, ranging from 700.0% to % of the transverse hard-tissue movement at the gonial angles. The average ratio of movement was 8.1% ± 156.6%. No previous studies have reported findings for this region of the face after mandibular advancement. This small ratio could be attributed to the anterior pull of soft tissues after the maxillomandibular advancements. The gonial angles are a posterior part of the face, and they should experience much of any lateral compression resulting from anterior pull of the facial soft tissues. One problem with this study was that many postsurgical CCT scans might have been taken too soon after the surgeries (average 10 weeks). ecause of the time required for postsurgical swelling to subside, most studies involving postsurgical soft-tissue changes used images that were at least 3 months postsurgical, and many even extended that to 6 months or 1 year. 2,4-9,12,14,18,19 Some studies suggested that soft-tissue stability is not reached until 1 year or even longer postsurgically. 10,26,27 On the other hand, Moss et al 28 described little facial soft-tissue change from 3 months to 1 year postsurgery. Hernandez-Orsini et al 11 saw comparable results when calculating soft-to-hard tissue ratios for patients at early and late postsurgical times. The first point was between 15 days and 8 months postsurgery, and the second was at least 8 months postsurgery. They found no statistically significant differences between ratios at the different times, suggesting that any changes in soft tissue between the 2 times were related to underlying skeletal changes rather than postsurgical swelling. It might be impossible to know exactly when postsurgical swelling is completely gone, because several other processes could be altering the soft-tissue appearance at the same time that swelling is subsiding. ccording to Day and Lee, 29 the changes in facial soft tissues after the initial inflammation from the orthognathic surgery are combinations of soft tissue remodeling, tissue relocation, hard tissue relapse, weight loss, and weight gain. In spite of this, our study could be strengthened by repeating it with a sample with more long-term follow-up CCT scans to eliminate concerns about postsurgical swelling. The method of measuring postsurgical soft-tissue change in this study proved to be an effective way to calculate changes in any direction while directly relating soft-tissue movements to underlying skeletal changes. With the increasing popularity of CCT, opportunities to further explore postsurgical soft-tissue changes in 3 dimensions should be abundant. Conclusions 1. the amount of maxillary advancement most likely plays a role in the postsurgical increase in greatest interalar width. 2. after maxillomandibular advancements, facial soft tissues appear to respond more to the anterior movement of the jaws than they do to increased transverse dimensions. We thank G. William rnett and Michael J. Gunson for providing the surgical sample for this study. References 1. Collins PC, Epker N. The alar base cinch: a technique for prevention of alar base flaring secondary to maxillary surgery. Oral Surg Oral Med Oral Pathol 1982;53: etts NJ, Vig KW, Vig P, Spalding P, Fonseca RJ. Changes in the nasal and labial soft tissues after surgical repositioning of the maxilla. Int J dult Orthod Orthognath Surg 1993;8: Guymon M, Crosby DR, Wolford LM. The alar base cinch suture to control nasal width in maxillary osteotomies. Int J dult Orthod Orthognath Surg 1988;3: Westermark H, ystedt H, Von Konow L, Sallstrom KO. Nasolabial morphology after Le Fort I osteotomies. Effect of alar base suture. Int J Oral Maxillofac Surg 1991;20: Rosen HM. Lip-nasal aesthetics following Le Fort I osteotomy. Plast Reconstr Surg 1988;81: Honrado CP, Lee S, loomquist DS, Larrabee WF Jr. Quantitative assessment of nasal changes after maxillomandibular surgery using a 3-dimensional digital imaging system. rch Facial Plast Surg 2006;8: Phillips C, Devereux JP, Tulloch CJF, Tucker MR. Full-face soft tissue response to surgical maxillary intrusion. Int J dult Orthod Orthognath Surg 1986;1: Stewart, McCance M, James DR, Moss JP. Three-dimensional nasal changes following maxillary advancement in cleft patients. Int J Oral Maxillofac Surg 1996;25: Chung C, Lee Y, Park K, Park S, Park Y, Kim K. Nasal changes after surgical correction of skeletal Class III malocclusion in Koreans. ngle Orthod 2008;78: Quast DC, iggerstaff RH, Haley JV. The short-term and longterm soft-tissue profile changes accompanying mandibular advancement surgery. m J Orthod 1983;84: Hernandez-Orsini R, Jacobson, Sarver DM, artolucci. Short-term and long-term soft tissue profile changes after mandibular advancements using rigid fixation techniques. Int J dult Orthod Orthognath Surg 1989;4: Lines P, Steinhauser WW. Soft tissue changes in relationship to movement of hard structures in orthognathic surgery: a preliminary report. J Oral Surg 1974;32: Mommaerts MY, Marxer H. cephalometric analysis of the long-term, soft tissue profile changes which accompany the

8 merican Journal of Orthodontics and Dentofacial Orthopedics Ryckman et al S93 Volume 137, Number 4, Supplement 1 advancement of the mandible by sagittal split ramus osteotomies. J Craniomaxillofac Surg 1987;15: McCance M, Moss JP, Fright WR, James DR, Linney D. three-dimensional analysis of bone and soft tissue to bone ratio of movements in 17 skeletal II patients following orthognathic surgery. Eur J Orthod 1993;15: Hajeer MY, youb F, Millett DT, ock M, Siebert JP. Threedimensional imaging in orthognathic surgery: the clinical application of a new method. Int J dult Orthod Orthognath Surg 2002;17: Grayson, Cutting C, ookstein FL, Kim H, McCarthy JG. The three-dimensional cephalogram: theory, technique, and clinical application. m J Orthod Dentofacial Orthop 1988;94: Guest E, erry E, Morris D. Novel methods for quantifying soft tissue changes after orthognathic surgery. Int J Oral Maxillofac Surg 2001;30: Soncul M, amber M. Evaluation of facial soft tissue changes with optical surface scan after surgical correction of Class III deformities. J Oral Maxillofac Surg 2004;62: McCance M, Moss JP, Wright WR, Linney D, James DR. three-dimensional soft tissue analysis of 16 skeletal Class III patients following bimaxillary surgery. r J Oral Maxillofac Surg 1992;30: Kau CH, Richmond S, Palomo JM, Hans MG. Three-dimensional cone beam computerized tomography in orthodontics. J Orthod 2005;32: Mah JK, Danforth R, umann, Hatcher D. Radiation absorbed in maxillofacial imaging with a new dental computed tomography device. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2003;96: Swennen GRJ, Schutyser F, Hausamen JE. Three-dimensional cephalometry. erlin: Verlag Springer; Schendel S, Williamson LW. Muscle reorientation following superior repositioning of the maxilla. J Oral Maxillofac Surg 1983;41: Schendel S, Carlotti E Jr. Nasal considerations in orthognathic surgery. m J Orthod Dentofacial Orthop 1991;100: ltman JI, Oeltjen JC. Nasal deformities associated with orthognathic surgery: analysis, prevention, and correction. J Craniofac Surg 2007;18: ailey LJ, Collie FM, White RP Jr. Long-term soft tissue changes after orthognathic surgery. Int J dult Orthod Orthognath Surg 1996;11: Lee DY, ailey LJ, Proffit WR. Soft tissue changes after superior repositioning of the maxilla with Le Fort I osteotomy: 5-year follow-up. Int J dult Orthod Orthognath Surg 1996;11: Moss JP, McCance M, Fright WR, Linney D, James DR. three-dimensional soft tissue analysis of fifteen patients with Class II, Division 1 malocclusions after bimaxillary surgery. m J Orthod Dentofacial Orthop 1994;105: Day CJ, Lee RT. Three-dimensional assessment of the facial soft tissue changes that occur postoperatively in orthognathic patients. World J Orthod 2006;7:15-26.