Correction of facial asymmetry and maxillary canting with corticotomy and 1-jaw orthognathic surgery
2014; Elsevier BV; Volume: 146; Issue: 6 Linguagem: Inglês
10.1016/j.ajodo.2014.08.018
ISSN1097-6752
AutoresHyo‐Won Ahn, Dong Hwi Seo, Seong‐Hun Kim, Baek‐Soo Lee, Kyu‐Rhim Chung, Gerald Nelson,
Tópico(s)Dental Radiography and Imaging
Resumo•Maxillary canting correction is achieved by maxillary corticotomy combined with temporary skeletal anchorage devices.•Maxillary corticotomy and 1-jaw surgery is a good treatment option for facial asymmetry. Although 2-jaw orthognathic surgery is a typical recommendation for the treatment of facial asymmetry, another good treatment alternative is maxillary corticotomy with temporary skeletal anchorage devices followed by mandibular orthognathic surgery. The corticotomy procedure described here can achieve unilateral molar intrusion and occlusal plane canting correction with potentially fewer complications than 2-jaw orthognathic surgery. The approach allows movement of dentoalveolar segments in less time than with conventional dental intrusion using temporary skeletal anchorage devices. A 2-jaw asymmetry with occlusal plane canting might be corrected using maxillary corticotomy and mandibular orthognathics rather than 2-jaw orthognathics. Two patients with facial asymmetry are presented here. In each one, the maxillary cant was corrected over a period of 2 to 3 months with 3.5 mm of intrusion of the unilateral buccal segment. After the preorthognathic cant correction, orthognathic surgery was done to correct the mandibular asymmetry. Although 2-jaw orthognathic surgery is a typical recommendation for the treatment of facial asymmetry, another good treatment alternative is maxillary corticotomy with temporary skeletal anchorage devices followed by mandibular orthognathic surgery. The corticotomy procedure described here can achieve unilateral molar intrusion and occlusal plane canting correction with potentially fewer complications than 2-jaw orthognathic surgery. The approach allows movement of dentoalveolar segments in less time than with conventional dental intrusion using temporary skeletal anchorage devices. A 2-jaw asymmetry with occlusal plane canting might be corrected using maxillary corticotomy and mandibular orthognathics rather than 2-jaw orthognathics. Two patients with facial asymmetry are presented here. In each one, the maxillary cant was corrected over a period of 2 to 3 months with 3.5 mm of intrusion of the unilateral buccal segment. After the preorthognathic cant correction, orthognathic surgery was done to correct the mandibular asymmetry. Facial asymmetry is one reason that patients seek orthognathic surgery combined with orthodontic treatment. Common features of facial asymmetry include a mandibular deviation to the right or left that increases gradually from the upper to the lower face. This is usually associated with a cant of the maxilla and the maxillary occlusal plane.1Haraguchi S. Takada K. Yasuda Y. Facial asymmetry in subjects with skeletal Class III deformity.Angle Orthod. 2002; 72: 28-35PubMed Google Scholar Severt and Proffit2Severt T.R. Proffit W.R. The prevalence of facial asymmetry in the dentofacial deformities population at the University of North Carolina.Int J Adult Orthodon Orthognath Surg. 1997; 12: 171-176PubMed Google Scholar reported that the frequencies of facial asymmetry are 5%, 36%, and 74% in the upper, middle, and lower thirds of the face, respectively. In such cases, dramatic improvement of facial balance comes with surgery to the mandible. Correction of the maxillary cant is usually a prerequisite. Consequently, correction typically includes a combination of LeFort I osteotomy and bilateral sagittal split ramus osteotomy.3Burstone C.J. Diagnosis and treatment planning of patients with asymmetries.Semin Orthod. 1998; 4: 153-164Abstract Full Text PDF PubMed Scopus (66) Google Scholar Case reports have been published demonstrating nonorthognathic correction of the maxillary cant before orthognathic surgery.4Kang Y.G. Nam J.H. Park Y.G. Use of rhythmic wire system with miniscrews to correct occlusal-plane canting.Am J Orthod Dentofacial Orthop. 2010; 137: 540-547Abstract Full Text Full Text PDF PubMed Scopus (11) Google Scholar, 5Jeon Y.J. Kim Y.H. Son W.S. Hans M.G. Correction of a canted occlusal plane with miniscrews in a patient with facial asymmetry.Am J Orthod Dentofacial Orthop. 2006; 130: 244-252Abstract Full Text Full Text PDF PubMed Scopus (40) Google Scholar Posterior bite-blocks or high-pull headgear has been used to intrude the molars conventionally. Both of these methods require significant patient cooperation. With either method, it is difficult to control the direction and quantity of tooth movement.6Noar J.H. Shell N. Hunt N.P. The performance of bonded magnets used in the treatment of anterior open bite.Am J Orthod Dentofacial Orthop. 1996; 109: 549-556Abstract Full Text Full Text PDF PubMed Google Scholar, 7Takano-Yamamoto T. Kuroda S. Titanium screw anchorage for correction of canted occlusal plane in patients with facial asymmetry.Am J Orthod Dentofacial Orthop. 2007; 132: 237-242Abstract Full Text Full Text PDF PubMed Scopus (36) Google Scholar With the advent of temporary skeletal anchorage devices (TSADs), orthodontic molar intrusion and occlusal plane canting correction have been reported, with minimal surgical intervention.4Kang Y.G. Nam J.H. Park Y.G. Use of rhythmic wire system with miniscrews to correct occlusal-plane canting.Am J Orthod Dentofacial Orthop. 2010; 137: 540-547Abstract Full Text Full Text PDF PubMed Scopus (11) Google Scholar, 5Jeon Y.J. Kim Y.H. Son W.S. Hans M.G. Correction of a canted occlusal plane with miniscrews in a patient with facial asymmetry.Am J Orthod Dentofacial Orthop. 2006; 130: 244-252Abstract Full Text Full Text PDF PubMed Scopus (40) Google Scholar, 8Hong R.K. Lim S.M. Heo J.M. Baek S.H. Orthodontic treatment of gummy smile by maxillary total intrusion with a midpalatal absolute anchorage system.Korean J Orthod. 2013; 43: 147-158Crossref PubMed Scopus (21) Google Scholar, 9Seo Y.J. Kim S.J. Munkhshur J. Chung K.R. Ngan P. Kim S.H. Treatment and retention of relapsed anterior openbite with low tongue posture and tongue-tie: a 10-year follow-up.Korean J Orthod. 2014; 44: 203-216Crossref PubMed Scopus (15) Google Scholar Kang et al4Kang Y.G. Nam J.H. Park Y.G. Use of rhythmic wire system with miniscrews to correct occlusal-plane canting.Am J Orthod Dentofacial Orthop. 2010; 137: 540-547Abstract Full Text Full Text PDF PubMed Scopus (11) Google Scholar introduced a rhythmic arch system using TSADs and obtained a considerable amount of canting correction. Jeon et al5Jeon Y.J. Kim Y.H. Son W.S. Hans M.G. Correction of a canted occlusal plane with miniscrews in a patient with facial asymmetry.Am J Orthod Dentofacial Orthop. 2006; 130: 244-252Abstract Full Text Full Text PDF PubMed Scopus (40) Google Scholar reported correction of mandibular prognathism with mandibular surgery only, correcting the maxillary asymmetry by intrusion of the maxillary molars unilaterally using TSADs. However, the treatment times were extended, increasing the risk of side effects.10Daimaruya T. Takahashi I. Nagasaka H. Umemori M. Sugawara J. Mitani H. Effects of maxillary molar intrusion on the nasal floor and tooth root using the skeletal anchorage system in dogs.Angle Orthod. 2003; 73: 158-166PubMed Google Scholar Since Köle11Kole H. Surgical operations on the alveolar ridge to correct occlusal abnormalities.Oral Surg Oral Med Oral Pathol. 1959; 12: 515-529Abstract Full Text PDF PubMed Scopus (195) Google Scholar suggested clinical applications of corticotomy in 1959, various technical advancements have been reported.12Suya H. Corticotomy in orthodontics.in: Hosl E. Baldauf A. Mechanical and biological basics in orthodontic therapy. Huthig Buch Verlag, Heidelberg, Germany1991: 207-226Google Scholar, 13Wilcko W.M. Wilcko T. Bouquot J.E. Ferguson D.J. Rapid orthodontics with alveolar reshaping: two case reports of decrowding.Int J Periodontics Restorative Dent. 2001; 21: 9-19PubMed Google Scholar, 14Chung K.R. Mitsugi M. Lee B.S. Kanno T. Lee W. Kim S.H. Speedy surgical orthodontic treatment with skeletal anchorage in adults—sagittal correction and open bite correction.J Oral Maxillofac Surg. 2009; 67: 2130-2148Abstract Full Text Full Text PDF PubMed Scopus (21) Google Scholar, 15Chung K.R. Kim S.H. Lee B.S. Speedy surgical orthodontic treatment using temporary anchorage devices as an alternative to orthognathic surgery.Am J Orthod Dentofacial Orthop. 2009; 135: 787-798Abstract Full Text Full Text PDF PubMed Scopus (33) Google Scholar One is orthopedic force application against intraosseous anchorage after corticotomy.14Chung K.R. Mitsugi M. Lee B.S. Kanno T. Lee W. Kim S.H. Speedy surgical orthodontic treatment with skeletal anchorage in adults—sagittal correction and open bite correction.J Oral Maxillofac Surg. 2009; 67: 2130-2148Abstract Full Text Full Text PDF PubMed Scopus (21) Google Scholar, 15Chung K.R. Kim S.H. Lee B.S. Speedy surgical orthodontic treatment using temporary anchorage devices as an alternative to orthognathic surgery.Am J Orthod Dentofacial Orthop. 2009; 135: 787-798Abstract Full Text Full Text PDF PubMed Scopus (33) Google Scholar A heavier force is applied than the orthodontic force because the aim of this technique is not tooth movement through the bone but rather bony block movement by compression osteogenesis.12Suya H. Corticotomy in orthodontics.in: Hosl E. Baldauf A. Mechanical and biological basics in orthodontic therapy. Huthig Buch Verlag, Heidelberg, Germany1991: 207-226Google Scholar, 16Kanno T. Mitsugi M. Furuki Y. Kozato S. Ayasaka N. Mori H. Corticotomy and compression osteogenesis in the posterior maxilla for treating severe anterior open bite.Int J Oral Maxillofac Surg. 2007; 36: 354-357Abstract Full Text Full Text PDF PubMed Scopus (21) Google Scholar If the cortical layer of the basal and alveolar bone is removed, medullary bone can be bent by traction force.14Chung K.R. Mitsugi M. Lee B.S. Kanno T. Lee W. Kim S.H. Speedy surgical orthodontic treatment with skeletal anchorage in adults—sagittal correction and open bite correction.J Oral Maxillofac Surg. 2009; 67: 2130-2148Abstract Full Text Full Text PDF PubMed Scopus (21) Google Scholar We have called the combination of corticotomy and orthopedic force application using TSADs speedy surgical orthodontics (SSO).14Chung K.R. Mitsugi M. Lee B.S. Kanno T. Lee W. Kim S.H. Speedy surgical orthodontic treatment with skeletal anchorage in adults—sagittal correction and open bite correction.J Oral Maxillofac Surg. 2009; 67: 2130-2148Abstract Full Text Full Text PDF PubMed Scopus (21) Google Scholar, 15Chung K.R. Kim S.H. Lee B.S. Speedy surgical orthodontic treatment using temporary anchorage devices as an alternative to orthognathic surgery.Am J Orthod Dentofacial Orthop. 2009; 135: 787-798Abstract Full Text Full Text PDF PubMed Scopus (33) Google Scholar By using this protocol, correction of a significant facial asymmetry can be achieved with single-jaw surgery. Omitting the corticotomy element means slower correction and lacks the correction of the supporting bone that corticotomy allows. This report includes 2 patients who demonstrate the clinical application of correcting an occlusal plane cant with corticotomies and orthopedic force. Overerupted maxillary molars and premolars are first passively splinted with a prefabricated bondable splint. This splint consists of a 0.036-in stainless steel wire with a power arm extension, soldered to mesh-backed pads. Bonding these splints to the buccal and palatal aspects of the teeth stabilizes the teeth as 1 unit. The corticotomy procedure can be done after the teeth are stabilized. The corticotomies were performed in 2 stages to ensure a good blood supply. The first was done on the palatal side. The second was done 2 weeks later on the buccal side (Fig 1). For the palatal corticotomy, a flap was elevated in the regions of the maxillary premolars and molars after a sulcular incision. A vertical corticotomy using piezosurgery and a round bur with a slow-speed hand piece was performed between the first premolar and the second premolar with care not to damage the root apices. A horizontal corticotomy was next, 3 mm above the root apex from the premolars to the distal aspect of the second molar. A second vertical corticotomy was performed distal to the second molar up to the alveolar crest (Fig 1, A and B). The flap was closed, followed by a 2-week healing period. The buccal corticotomy was combined with placement of the TSADs and extraction of the maxillary first premolar (part of the treatment plan to resolve crowding). The palatal corticotomy outline is similar to that on the buccal aspect (Fig 1, C and D). On the midpalatal area, a miniplate with 2 horizontal arms (Jin Biomed, Bucheon, Korea) that were oriented toward the target teeth was implanted on the midpalatal area for palatal intrusion. Flap surgery was not necessary because the soft tissues on the midpalatal area were thin (Fig 1, E). On the buccal side between the first and second molar areas, we placed an I-shaped titanium C-tube plate, with 2 anchoring holes and a 0.036-in diameter tube-shaped head, to serve as the point of orthodontic force application (Fig 1, F). With elastic chain, 500 g of force was applied to intrude the posterior segment immediately after the perisegmental corticotomy. At the same time, the maxillary canine was retracted into the extraction site (Fig 1, F). A 15-year-old girl came to the Kyung Hee dental hospital in Seoul, Korea, with the chief complaint of facial asymmetry. She had a straight lateral profile, mesognathic facial type, eye-level canting (right side down), lip-line canting (right side high), chin deviation to the right, and an acceptable display of her maxillary anterior teeth (Fig 2, A). The intraoral photographs showed an Angle Class I malocclusion, severe anterior crowding, an ectopically positioned maxillary left canine, a mandibular dental midline discrepancy to the right, and transverse compensation of the maxillary and mandibular molars (Fig 2, B). The cephalometric analysis indicated a hyperdivergent skeletal pattern (FMA, 32.8°), normal relationships of the maxilla (SNA, 80.7°) and the mandible (SNB, 77.9°), maxillary occlusal plane cant (left side down), menton deviation to the right side (7.0 mm), and upright maxillary and mandibular incisors (U1-FH, 108.2°; IMPA, 81.9°) (Fig 3 and Table). Although her condyle was thin and narrow, especially on right side, there was no clinical symptom of temporomandibular disorder or a centric occlusion-centric relation discrepancy. On the axial cut of the cone-beam computed tomography (CBCT) images (Alphard Vega; Asahi Roentgen, Kyoto, Japan), the vertical height difference of the buccal cusp tips between the maxillary left and right first molars was about 3.5 mm, and both buccal cusp tips had abnormal torque because of the transverse compensation (Fig 4, A). The torque would be evaluated after the cant correction. Accordingly, the diagnosis was a Class I skeletal relationship, steep mandibular plane angle, facial asymmetry, and severe crowding.TableCephalometric survey of patient 1MeasurementMeanSDPretreatmentPosttreatmentSkeletal-horizontal SNA (°)81.63.280.780.7 SNB (°)79.23.077.976.1 ANB (°)2.51.82.84.6Skeletal-vertical PFH/AFH (%)66.84.359.958.1 FMA (°)25.44.632.836.4 SN-OP (°)17.93.821.224.6 SN To PP (°)10.23.29.810.0Dental FH-UI (°)116.05.7108.2116.5 IMPA (°)95.96.481.988.9 Interincisal angle (°)123.88.3137.0117.9 FMIA (°)59.87.265.254.5Soft tissue Nasolabial angle (°)93.28.097.296.1 UL-E plane (mm)-0.92.2-1.7-0.2 LL-E plane (mm)0.62.3-0.70.7 Open table in a new tab Fig 4Comparison between A, pretreatment and B, after-intrusion axial images of the maxillary left posterior segment of patient 1. In 3 months, 3.5 mm of intrusion of the maxillary left molars was achieved, and the molar compensation was corrected.View Large Image Figure ViewerDownload Hi-res image Download (PPT) The treatment objectives were correction of the facial asymmetry, elimination of crowding of the maxillary and mandibular dentition, and establishment of a normal occlusion. The canting extended to the orbit, correction of which was not part of the treatment plan. We set a goal to correct the facial asymmetry below the LeFort I level and initially planned 2-jaw surgery. However, the patient wanted to minimize the expense and scope of the surgical intervention. Fortunately, she had a normally positioned maxilla anteroposteriorly and a dental midline coincident with the facial midline. The alternative plan she selected was a bilateral sagittal split ramus osteotomy after SSO maxillary cant correction with a unilateral corticotomy. Because the maxillary incisors were upright and the maxillary left canine was blocked, the plan included unilateral extraction of the left first premolar. Corticotomies on both sides were performed as described, and an orthopedic intrusion force was immediately applied. In 3 months, intrusion of the maxillary left posterior segment was complete. To prevent extrusion of the opposing teeth, a resin bite-block was added on the left mandibular molars. CBCT scans and superimposition of the cephalograms confirmed 3.5 mm of intrusion of the maxillary left molars (Fig 4, B). The buccal and lingual bonded mesh appliances were removed, and brackets (Quicklear; Forestadent, Pforzheim, Germany) were placed on the maxillary teeth for further leveling and alignment. Cross elastics were used between the TSADs on the maxillary arch and the mandibular molars for transverse decompensation. After the preoperative orthodontic treatment, the midline of the maxillary dentition coincided with the facial midline, and the maxillary occlusal canting and the transverse decompensation were corrected (Figs 5 and 6). An asymmetric mandibular setback was then performed with bilateral sagittal split ramus osteotomy. Orthodontic treatment was resumed 6 weeks postsurgery and was completed after 5 months. The total active treatment period was 22 months. At debonding, the extraoral photographs showed a distinct improvement of the facial symmetry and a beautiful smile line (Fig 7, A). The single-jaw surgery alone achieved good facial symmetry even in the middle face level. In the maxilla, the facial gingival line showed mild asymmetry because of the gingival height of the maxillary left canine. The maxillary left canine was positioned higher before treatment and moved significantly both downward and in a distal direction after unilateral extraction of the first premolar; this might have been responsible for the difference in crown length. The dental midlines of the maxilla and the mandible coincided with the facial midline. A Class I functional occlusion with ideal overjet and overbite was obtained (Fig 7, B). No significant root resorption was evident in the panoramic radiograph. The posttreatment lateral cephalometric analysis and superimposition showed good inclination of the maxillary and mandibular incisors (U1-FH, 116.5°; IMPA, 88.9°) and a favorable maxillomandibular relationship (Fig 8). The occlusal plane was greater by 3° than before treatment (SN-OP, 21.2° to 24.6°). The treatment results were well maintained at 8 months after debonding (Fig 9).Fig 6Preorthognathic surgery posteroanterior cephalogram of patient 1.View Large Image Figure ViewerDownload Hi-res image Download (PPT)Fig 7Posttreatment extraoral and intraoral photographs of patient 1.View Large Image Figure ViewerDownload Hi-res image Download (PPT)Fig 8A, Posttreatment superimposition between the pretreatment and final cephalometric tracings; B, the posteroanterior cephalogram; and C, the panoramic radiograph of patient 1.View Large Image Figure ViewerDownload Hi-res image Download (PPT)Fig 9Eight-month retention extraoral and intraoral photographs of patient 1.View Large Image Figure ViewerDownload Hi-res image Download (PPT) A 21-year-old man came with a chief complaint of facial asymmetry. He had a normal skeletal relationship of the maxilla anteroposteriorly. The occlusal planes were canted down on the right side. Moderate anterior crowding was observed, with a superiorly positioned canine on the extruded side (Fig 10). Similar to the previous patient, a corticotomy of the maxillary right segment and extraction of the right first premolar were performed. The right posterior segment was successfully intruded by 3.5 mm over 2 months (Figs 10, D-F, and 11). After 10 months, the transverse dental compensation was resolved, and single-jaw surgery was done (Fig 12).Fig 11Comparison between A, pretreatment and B, after-intrusion axial images of the maxillary right posterior segment of patient 2. In 2 months, 3.5 mm of intrusion of the maxillary right molars was achieved.View Large Image Figure ViewerDownload Hi-res image Download (PPT)Fig 12Posteroanterior cephalograms: A, pretreatment, B, after intrusion, and C, after 1-jaw orthognathic surgery of patient 2. The midsagittal reference line, maxillary occlusal plane, and menton deviation are shown.View Large Image Figure ViewerDownload Hi-res image Download (PPT) The 3-dimensional morphologic variety of facial asymmetry characteristics generates many subtypes.17Miyatake E. Miyawaki S. Morishige Y. Nishiyama A. Sasaki A. Takano-Yamamoto T. Class III malocclusion with severe facial asymmetry, unilateral posterior crossbite, and temporomandibular disorders.Am J Orthod Dentofacial Orthop. 2003; 124: 435-445Abstract Full Text Full Text PDF PubMed Scopus (24) Google Scholar, 18Kim H.O. Lee W. Kook Y.A. Kim Y. Comparison of the condyle-fossa relationship between skeletal class III malocclusion patients with and without asymmetry: a retrospective three-dimensional cone-beam computed tomograpy study.Korean J Orthod. 2013; 43: 209-217Crossref PubMed Scopus (28) Google Scholar Precise and accurate diagnosis and surgical treatment planning are important to address the underlying causes of a facial asymmetry. The clinician will evaluate the asymmetry of the upper third of the face (orbital dystopia) to determine whether it will be included in treatment planning. In the mandible, one can see various degrees of menton deviation, frontal ramal inclination, gonion canted toward the midsagittal plane, and arch-form discrepancies.19Baek C. Paeng J.Y. Lee J.S. Hong J. Morphologic evaluation and classification of facial asymmetry using 3-dimensional computed tomography.J Oral Maxillofac Surg. 2012; 70: 1161-1169Abstract Full Text Full Text PDF PubMed Scopus (77) Google Scholar Skeletal asymmetry problems in the maxilla are much less frequent or complex than in the mandible, where the degree of asymmetry tends to increase with greater distance from the cranium.19Baek C. Paeng J.Y. Lee J.S. Hong J. Morphologic evaluation and classification of facial asymmetry using 3-dimensional computed tomography.J Oral Maxillofac Surg. 2012; 70: 1161-1169Abstract Full Text Full Text PDF PubMed Scopus (77) Google Scholar Case selection is critical when considering a maxillary corticotomy (SSO) combined with single-jaw surgery in patients with facial asymmetry. The maxillary deformity should be limited to canting. If sagittal, transverse, and bilateral vertical maxillary skeletal corrections are necessary, then SSO would not be an option. After the corticotomy is completed, the outcome should be a normal orientation of the occlusal plane and an acceptable mandibular function. The goals of the orthodontic-corticotomy phase before orthognathic surgery are to correct the cant, eliminate the transverse dental compensation, and align the teeth to their proper positions.20Sekiya T. Nakamura Y. Oikawa T. Ishii H. Hirashita A. Seto K. Elimination of transverse dental compensation is critical for treatment of patients with severe facial asymmetry.Am J Orthod Dentofacial Orthop. 2010; 137: 552-562Abstract Full Text Full Text PDF PubMed Scopus (23) Google Scholar For the cant correction, the clinician will analyze the differential force applications between the buccal and palatal sides. With careful planning, torque control can be achieved simultaneously with intrusion. Without such precise treatment planning of the SSO phase, the result can be an extended treatment time. What are the benefits of SSO when compared with 2-jaw surgery? After 2-jaw orthognathic surgery, the patient may experience a longer and more uncomfortable healing period, a change in the alar base, and a period of restricted nasal breathing. The corticotomy procedure presented here requires 2 in-office surgical approaches, under local anesthesia, and takes about 30 minutes. Postsurgical healing is less eventful. Corticotomy has been used as an alternative method to orthognathic surgery or conventional orthodontics in borderline cases of adults.11Kole H. Surgical operations on the alveolar ridge to correct occlusal abnormalities.Oral Surg Oral Med Oral Pathol. 1959; 12: 515-529Abstract Full Text PDF PubMed Scopus (195) Google Scholar, 14Chung K.R. Mitsugi M. Lee B.S. Kanno T. Lee W. Kim S.H. Speedy surgical orthodontic treatment with skeletal anchorage in adults—sagittal correction and open bite correction.J Oral Maxillofac Surg. 2009; 67: 2130-2148Abstract Full Text Full Text PDF PubMed Scopus (21) Google Scholar By removing the cortical layer, tooth movement is faster, and less root resorption is expected compared with conventional orthodontic intrusion.21Hwang H.S. Lee K.H. Intrusion of overerupted molars by corticotomy and magnetics.Am J Orthod Dentofacial Orthop. 2001; 120: 209-216Abstract Full Text Full Text PDF PubMed Scopus (50) Google Scholar As Suya12Suya H. Corticotomy in orthodontics.in: Hosl E. Baldauf A. Mechanical and biological basics in orthodontic therapy. Huthig Buch Verlag, Heidelberg, Germany1991: 207-226Google Scholar explained in "corticotomy-facilitated orthodontics," the tooth has a role as a handle when bands of medullary bone move as a block. Tooth movement after corticotomy is primarily bony block movement rather than individual tooth movement. Histologic study with dogs showed that the appearance of necrotic tissue that was called "hyalinization" was restricted to 1 week in the corticotomy group, instead of lasting 4 weeks in the orthodontic movement–only control group.22Iino S. Sakoda S. Ito G. Nishimori T. Ikeda T. Miyawaki S. Acceleration of orthodontic tooth movement by alveolar corticotomy in the dog.Am J Orthod Dentofacial Orthop. 2007; 131: 448.e1-448.e8Abstract Full Text Full Text PDF PubMed Scopus (144) Google Scholar This quick removal of hyalinization tissue can be explained by the regional acceleratory phenomenon. Corticotomy is associated with a reduced chance of root damage during surgery. Note that the amount of canting correction is not limited to the width of corticotomy. It is preferable to remove the cortical layer as much as the planned intrusion to facilitate compressive osteogenesis. However, intrusion up to 6 mm has proved to be clinically acceptable.14Chung K.R. Mitsugi M. Lee B.S. Kanno T. Lee W. Kim S.H. Speedy surgical orthodontic treatment with skeletal anchorage in adults—sagittal correction and open bite correction.J Oral Maxillofac Surg. 2009; 67: 2130-2148Abstract Full Text Full Text PDF PubMed Scopus (21) Google Scholar, 16Kanno T. Mitsugi M. Furuki Y. Kozato S. Ayasaka N. Mori H. Corticotomy and compression osteogenesis in the posterior maxilla for treating severe anterior open bite.Int J Oral Maxillofac Surg. 2007; 36: 354-357Abstract Full Text Full Text PDF PubMed Scopus (21) Google Scholar Two-jaw surgery achieves impaction without additional dental intrusion, but there is a limit to how much impaction is possible. With a corticotomy, not only does a wide path of cortical plate removal provide bone block, but also the additional dental intrusion allows for more cant correction than orthognathics could achieve. The TSAD anchors include a C-tube in the buccal posterior maxilla or zygomatic buttress and a miniplate in the midpalatal suture. These devices work together to provide compression osteogenesis and intrude the posterior fragment.23Seo K.W. Ahn H.W. Kim S.H. Chung K.R. Nelson G. Miniplate with a bendable C-tube head allows the clinician to alter biomechanical advantage without physically moving the skeletal anchorage device.J Craniofac Surg. 2014; 25: 686-689Crossref PubMed Scopus (6) Google Scholar Orthopedic intrusion with a corticotomy (SSO) permits rapid repositioning of the dental segments.24Choo H. Heo H.A. Yoon H.J. Chung K.R. Kim S.H. Treatment outcome analysis of speedy surgical orthodontics for adults with maxillary protrusion.Am J Orthod Dentofacial Orthop. 2011; 140: e251-e262Abstract Full Text Full Text PDF PubMed Scopus (19) Google Scholar The regional accelerated phenomenon during compression accelerates the completion of the treatment. Many studies of orthodontic intrusion with TSADs have reported complications such as root resorption or extended treatment time.21Hwang H.S. Lee K.H. Intrusion of overerupted molars by corticotomy and magnetics.Am J Orthod Dentofacial Orthop. 2001; 120: 209-216Abstract Full Text Full Text PDF PubMed Scopus (50) Google Scholar, 22Iino S. Sakoda S. Ito G. Nishimori T. Ikeda T. Miyawaki S. Acceleration of orthodontic tooth movement by alveolar corticotomy in the dog.Am J Orthod Dentofacial Orthop. 2007; 131: 448.e1-448.e8Abstract Full Text Full Text PDF PubMed Scopus (144) Google Scholar Corticotomy-induced compression osteogenesis by orthopedic traction produced faster tooth movement and consequently a reduced risk of root resorption.21Hwang H.S. Lee K.H. Intrusion of overerupted molars by corticotomy and magnetics.Am J Orthod Dentofacial Orthop. 2001; 120: 209-216Abstract Full Text Full Text PDF PubMed Scopus (50) Google Scholar, 25Moon C.H. Wee J.U. Lee H.S. Intrusion of overerupted molars by corticotomy and orthodontic skeletal anchorage system.Angle Orthod. 2007; 77: 1119-1125Crossref PubMed Scopus (50) Google Scholar In the patients presented here, 3.5 mm of intrusion was achieved in 2 to 3 months. The root lengths of the maxillary first and second premolars and the first molar were evaluated between pretreament and after-intrusion with CBCT (Invivo5 software; Anatomage, San Jose, Calif). The palatal root of the first molar was shortened by 2.4 mm in patient 1. All other root lengths were shortened less than 1 mm. A significant amount of intrusion was achieved during a relatively short time without notable root resorption. The miniplate is more suitable than the mini-implant for SSO because of the heavier force requirements (250 g per each side). For the palatal area, implantation of the miniplate in the midpalatal area is recommended. The thinner soft tissue layer and thicker cortical bone depth provide better initial stability than would the palatal slope. No nerves or vessels pass through this area. On the buccal side, the skeletal anchorage is positioned at least 2 to 3 mm above the horizontal corticotomy line to avoid the area of active bone remodeling and obstacles such as dilacerated roots, an expanded maxillary sinus, or a severe alveolar ridge resorption.26Kim G.T. Kim S.H. Choi Y.S. Park Y.J. Chung K.R. Suk K.E. et al.Cone-beam computed tomography evaluation of orthodontic miniplate anchoring screws in the posterior maxilla.Am J Orthod Dentofacial Orthop. 2009; 136: 628.e1-628.e10Abstract Full Text Full Text PDF Google Scholar The miniplate can also be used for distalization of the whole dentition or canine retraction, without the need of additional TSADs. One important issue regarding occlusal canting correction is stability. Proffit et al27Proffit W.R. Turvey T.A. Phillips C. The hierarchy of stability and predictability in orthognathic surgery with rigid fixation: an update and extension.Head Face Med. 2007; 3: 21Crossref PubMed Scopus (286) Google Scholar demonstrated that vertical asymmetry correction by surgery of the maxilla is quite stable. Others also reported that maxillary stability after LeFort I osteotomy for cant correction does not differ from that for maxillary advancement.28Ueki K. Hashiba Y. Marukawa K. Yoshida K. Shimizu C. Nakagawa K. et al.Comparison of maxillary stability after Le Fort I osteotomy for occlusal cant correction surgery and maxillary advanced surgery.Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2007; 104: 38-43Abstract Full Text Full Text PDF PubMed Scopus (10) Google Scholar There have been no long-term studies about the stability of orthodontic intrusion with TSADs for the treatment of canted occlusal planes. There are limited data on the correction of anterior open bite. Lee and Park29Lee H.A. Park Y.C. Treatment and posttreatment changes following intrusion of maxillary posterior teeth with miniscrew implants for open bite correction.Korean J Orthod. 2008; 38: 31-40Crossref Scopus (54) Google Scholar reported a 10.4% relapse rate for the intruded maxillary molars and an 18.1% relapse rate for overbites at 1 year posttreatment. Baek et al30Baek M.S. Choi Y.J. Yu H.S. Lee K.J. Kwak J. Park Y.C. Long-term stability of anterior open-bite treatment by intrusion of maxillary posterior teeth.Am J Orthod Dentofacial Orthop. 2010; 138: 396.e1-396.e9Abstract Full Text Full Text PDF PubMed Scopus (54) Google Scholar also reported a 22.9% relapse rate for intruded maxillary molars and a 17.0% relapse rate for overbites at 3 years posttreatment. There are no long-term data on the stability of maxillary posterior impaction with corticotomy. Corticotomy is expected to be more stable than conventional orthodontic intrusion because it is considered bony block movement rather than individual tooth movement only. Further studies will be useful on the effects of various force intervals after corticotomy and its long-term stability. Maxillary corticotomy combined with TSADs (SSO) achieved unilateral molar intrusion and occlusal plane canting correction. It is a potentially less expensive, in-office alternative to cant correction with 2-jaw orthognathic surgery. In selected patients with facial asymmetry, maxillary cant correction with maxillary corticotomy combined with TSADs can allow a 1-jaw surgery treatment plan that would otherwise require 2-jaw orthognathic surgery.
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