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Postoperative Stability of Patients Undergoing Orthognathic Surgery with Orthodontic Treatment Using Clear Aligners: A Preliminary Study

Postoperative Stability of Patients Undergoing Orthognathic Surgery with Orthodontic Treatment... applied sciences Article Postoperative Stability of Patients Undergoing Orthognathic Surgery with Orthodontic Treatment Using Clear Aligners: A Preliminary Study 1 , 2 , 3 4 5 1 , 2 , 3 , Chiho Moon , George K. Sándor , Edward Chengchuan Ko and Yong-Deok Kim * Department of Oral and Maxillofacial Surgery, School of Dentistry, Pusan National University, Geumo-ro 20, Mulgeum, Yangsan 50612, Korea; mch2875@naver.com Dental and Life Science Institute, School of Dentistry, Pusan National University, Yangsan 50612, Korea Dental Research Instutite, Pusan National University Dental Hospital, Yangsan 50612, Korea Department of Oral and Maxillofacial Surgery, Oulu University Hospital, University of Oulu, 90220 Oulu, Finland; sandor_george@hotmail.com Department of Oral and Maxillofacial Surgery, Kaohsiung Medical University, Kaohsiung 80708, Taiwan; ko.edward.kaseizen@gmail.com * Correspondence: ydkimdds@pusan.ac.kr; Tel.: +82-55-360-5116; Fax: +82-55-360-5104 Abstract: Backgrond: Until now, there have been many studies on the postoperative stability of orthognathic patients treated with traditional fixed orthodontic appliances. Recently, the use of clear aligners as orthodontic appliances has increased in orthodontic treatment for aesthetic and patient convenience. The aim of this preliminary study was to investigate the stability and characteristics of patients undergoing orthognathic surgery using clear aligners. Patients and Methods: This study was performed on patients who underwent orthognathic surgery by one surgeon at Pusan National Citation: Moon, C.; Sándor, G.K.; Ko, University Dental Hospital from April 2017 to August 2021. A comparative study was conducted E.C.; Kim, Y.-D. Postoperative on five patients treated with clear aligners during orthodontic treatment and ten patients treated Stability of Patients Undergoing with traditional fixed appliances as a control group. Postoperative skeletal changes and recurrence Orthognathic Surgery with were evaluated by cone beam computed tomography and lateral cephalometric radiographs taken Orthodontic Treatment Using Clear two days postoperatively and six months postoperatively. Several measurement variables were Aligners: A Preliminary Study. Appl. used to confirm the presence or absence of recurrence, preoperative and postoperative orthodontic Sci. 2021, 11, 11216. https://doi.org/ treatment period, and the number of extracted teeth. Results: Postoperative stability for six months 10.3390/app112311216 after surgery was not significantly different between the clear aligner group and the traditional Academic Editors: Gabriele Cervino fixed appliance group. The preoperative orthodontic treatment period was also shorter in the clear and Dorina Lauritano aligner group, and the number of extracted premolar teeth and impacted teeth were also fewer in the clear aligner group, but there was no significant difference. Conclusions: Orthodontic treatment Received: 2 November 2021 using clear aligners continues to develop, and it is believed that there is no limit to what can be Accepted: 24 November 2021 accomplished during orthodontic surgery accompanied by clear aligners. Published: 25 November 2021 Keywords: orthognathic surgery; clear aligner; Invisalign; stability; preoperative orthodontic treat- Publisher’s Note: MDPI stays neutral ment; CAD-CAM; 3D printer with regard to jurisdictional claims in published maps and institutional affil- iations. 1. Introduction Since Kesling first invented the aligner in 1946, an aligner for tooth alignment has been developed [1]. Recently, patient demand has increased for more orthodontic treatments Copyright: © 2021 by the authors. with esthetic appliances [2]. In line with this, Align Technology Inc. (San Jose, CA, USA) Licensee MDPI, Basel, Switzerland. launched the Invisalign system in 1999, which enables esthetic orthodontic treatment This article is an open access article because traditional braces are not invisible. This was the first CAD (computer-aided distributed under the terms and design) and CAM (computer-aided manufacturing)-based orthodontic appliance, which conditions of the Creative Commons can be digitally scanned, and made as a series of aligners using a single impression [3,4]. Attribution (CC BY) license (https:// The approximate digital manufacturing process of a clear aligner is as follows. First, a creativecommons.org/licenses/by/ digital image is obtained by scanning a plaster model taken either by direct impression 4.0/). Appl. Sci. 2021, 11, 11216. https://doi.org/10.3390/app112311216 https://www.mdpi.com/journal/applsci Appl. Sci. 2021, 11, x FOR PEER REVIEW 2 of 10 Appl. Sci. 2021, 11, 11216 2 of 9 The approximate digital manufacturing process of a clear aligner is as follows. First, a digital image is obtained by scanning a plaster model taken either by direct impression of the patient’s dentition with a three-dimensional (3D) scanner or by directly scanning of the patient’s dentition with a three-dimensional (3D) scanner or by directly scanning the patient’s dentition with an intraoral scanner. When the digital model is created in this the patient’s dentition with an intraoral scanner. When the digital model is created in this way, the file can be loaded in the setup program to start making the clear aligner [4,5]. way, the file can be loaded in the setup program to start making the clear aligner [4,5]. Following the setup program, the crown, root, and long axis are set, and the teeth are Following the setup program, the crown, root, and long axis are set, and the teeth are moved to the desired position, which is the final arrangement. After that, a series of clear moved to the desired position, which is the final arrangement. After that, a series of clear aligners suitable for the treatment period is designed. At this stage, it is recommended aligners suitable for the treatment period is designed. At this stage, it is recommended that that the tooth rotation is within 2.5 degrees and the movement distance confined to 0.3 the tooth rotation is within 2.5 degrees and the movement distance confined to 0.3 mm at mm at each stage [6]. After that, a 3D printer is used to make a model for step-by-step each stage [6]. After that, a 3D printer is used to make a model for step-by-step changes changes and then make a series of progressive clear aligners to move the misaligned teeth. and then make a series of progressive clear aligners to move the misaligned teeth. Recently, increasing numbers of patients are receiving orthodontic treatment with Recently, increasing numbers of patients are receiving orthodontic treatment with clear aligners, including those patients undergoing orthognathic surgery. Although there clear aligners, including those patients undergoing orthognathic surgery. Although there have been many studies showing that the postoperative stability of orthodontic patients have been many studies showing that the postoperative stability of orthodontic patients treated with conventional fixed orthodontic devices is good [7,8], there have been no stud- treated with conventional fixed orthodontic devices is good [7,8], there have been no ies on postoperative stability of orthodontic patients treated with clear aligners. In this studies on postoperative stability of orthodontic patients treated with clear aligners. In this preliminary study, the stability and characteristics of patients using clear aligners after preliminary study, the stability and characteristics of patients using clear aligners after orthognathic surgery were investigated. orthognathic surgery were investigated. 2. Materials and Methods 2. Materials and Methods 2.1. Patients 2.1. Patients This retrospective study was exempt from review by the Institutional Review Board This retrospective study was exempt from review by the Institutional Review Board at Pusan National University Dental Hospital (Approval No.: PNUDH-2021-038). A total at Pusan National University Dental Hospital (Approval No.: PNUDH-2021-038). A to- of 15 patients who underwent orthognathic surgery by one surgeon at PNUDH between tal of 15 patients who underwent orthognathic surgery by one surgeon at PNUDH be- April 2017 and August 2021 were included in this study. Of the 15 patients, 5 patients tween April 2017 and August 2021 were included in this study. Of the 15 patients, received preoperative orthodontic treatment with clear aligners, and the remaining 10 pa- 5 patients received preoperative orthodontic treatment with clear aligners, and the re- tients received orthodontic treatment with traditional fixed appliances. maining 10 patients received orthodontic treatment with traditional fixed appliances. 2.2. Study Methods 2.2. Study Methods For all patients, cone beam computed tomography (CBCT), and lateral cephalometric For all patients, cone beam computed tomography (CBCT), and lateral cephalometric radiographs were taken postoperatively on day 2 and month 6 to confirm skeletal changes radiographs were taken postoperatively on day 2 and month 6 to confirm skeletal changes (Figures 1 and 2). Postoperative stability was evaluated and analyzed by measuring several (Figures 1 and 2). Postoperative stability was evaluated and analyzed by measuring sev- measurement variables (L1 to NB, Pog. to NB, A-Pog., angle of facial convexity (AFC), SN eral measurement variables (L1 to NB, Pog. to NB, A-Pog., angle of facial convexity (AFC), vertical, and 0-merdian) (Table 1). The duration of each patient’s preoperative orthodontic SN vertical, and 0-merdian) (Table 1). The duration of each patient’s preoperative ortho- period, the number of premolar extractions, and the number of impacted teeth were also dontic period, the number of premolar extractions, and the number of impacted teeth compared and analyzed. were also compared and analyzed. (a) (b) (c) Figure 1. Orthognathic surgery patient with clear aligners. (a) Before surgery; (b) 2 days after surgery; (c) 6 months post- Figure 1. Orthognathic surgery patient with clear aligners. (a) Before surgery; (b) 2 days after surgery; (c) 6 months operative radiograph image. Braces attached to teeth were not observed on radiographs. postoperative radiograph image. Braces attached to teeth were not observed on radiographs. Appl. Sci. 2021, 11, 11216 3 of 9 Appl. Sci. 2021, 11, x FOR PEER REVIEW 3 of 10 (a) (b) (c) Figure 2. Orthognathic surgery patient with conventional fixed appliance. (a) Before surgery; (b) 2 days after surgery; (c) Figure 2. Orthognathic surgery patient with conventional fixed appliance. (a) Before surgery; (b) 2 days after surgery; 6 months postoperative radiograph image. The bracket attached to teeth was not observed on radiographs. (c) 6 months postoperative radiograph image. The bracket attached to teeth was not observed on radiographs. Table 1. Measurement variables. Table 1. Measurement variables. L1 to NB (linear) (mm): Distance from [Mandible 1 crown] to Line [B-point]-[Nasion] L1 to NB (linear) (mm): Distance from [Mandible 1 crown] to Line [B-point]-[Nasion] Pog. to NB (mm): Distance from [Pogonion] to Line [B-point]-[Nasion] Positive for right Pog. to NB (mm): Distance from [Pogonion] to Line [B-point]-[Nasion] Positive for right side of Line side of Line A-Pog. (mm): Distance from [Mandible 1 crown] to Line [A-Point]-[Pogonion] Positive for right side of Line A-Pog. (mm): Distance from [Mandible 1 crown] to Line [A-Point]-[Pogonion] Positive Angle of facial convexity (AFC) (deg): Angle of line [Subnasale]-[Glabella] and [soft tissue Pogonion]-[Subnasale] for right side of Line SN Vr. (mm): Subtract distance of [Subnasale] from distance of [soft tissue Pogonion], parallel to line [Porion]-[Orbitale] Angle of facial convexity (AFC) (deg): Angle of line [Subnasale]-[Glabella] and [soft tis- sue Pogonion]-[Subnasale] 0-Med. (mm): Subtract distance of [soft tissue Nasion] from distance of [soft tissue Pogonion], parallel to line [Porion]-[Orbitale] SN Vr. (mm): Subtract distance of [Subnasale] from distance of [soft tissue Pogonion], parallel to line [Porion]-[Orbitale] 2.3. Statistical Analysis 0-Med. (mm): Subtract distance of [soft tissue Nasion] from distance of [soft tissue Pogo- All measurements were statistically analyzed using a statistical program (SPSS 14.0; nion], parallel to line [Porion]-[Orbitale] IBM SPSS Statistics, Chicago, IL, USA). All landmarks were analyzed using a cephalometric analysis program (Vceph 6.0; Osstem implant Co., Seoul, Korea) 2.3. Statistical Analysis 2.4. The Manufacturing Process of Clear Aligners by CAD/CAM All measurements were statistically analyzed using a statistical program (SPSS 14.0; IBM SPSS Statistics, Chicago, IL, USA). All landmarks were analyzed using a cephalo- In our hospital, the patient’s dentition is obtained directly from the oral cavity us- m ing etran ic an intraoral alysis pscanner rogram ((Figur Vcephe 6. 30; O ). Following sstem imp this, lant the Co., S digital eoul, K model orea) is called from the setup program. Common programs include Maestro 3D Ortho Studio (Age solutions, 2.4. T Pontedera, he Manu Italy facturin ), Ortho g Proc Analyzer ess of Clear (3Shape, Aligners Copenhagen by CAD/CAM K, Denmark), Orchestrate 3D (Orchestrate 3D, Rialto, CA, USA) [5], and Autolign (Dorico, Yongin, Korea). In this study, In our hospital, the patient’s dentition is obtained directly from the oral cavity using the Autolign (Dorico, Yongin, Korea) program was used. Each tooth number is marked an intraoral scanner (Figure 3). Following this, the digital model is called from the setup on the imported digital model, and the most mesial and distal points of each tooth are program. Common programs include Maestro 3D Ortho Studio (Age solutions, marked (Figure 4). After that, the cutting line of the crown is corrected to accurately mark Pontedera, Italy), Ortho Analyzer (3Shape, Copenhagen K, Denmark), Orchestrate 3D the clinical crown (Figure 5). Next, when the tooth axis and root are formed, the model (Orchestrate 3D, Rialto, CA, USA) [5], and Autolign (Dorico, Yongin, Korea). In this study, setup is completed (Figure 6). After that, the teeth are moved to the desired final occlusion the Autolign (Dorico, Yongin, Korea) program was used. Each tooth number is marked (Figure 7). At this time, each tooth can move not only in parallel but also by rotation on the imported digital model, and the most mesial and distal points of each tooth are (Figure 8). When the final occlusion is set, the movement amount (within 0.3 mm) [5] and marked (Figure 4). After that, the cutting line of the crown is corrected to accurately mark rotation of each step is set within 2.5 degrees [6], and after deciding how many steps to the clinical crown (Figure 5). Next, when the tooth axis and root are formed, the model make for the clear aligners (Figure 9), the series of models are printed using a 3D printer. setup is completed (Figure 6). After that, the teeth are moved to the desired final occlusion After that, clear aligners are manufactured using a pressure molding machine for each (Figure 7). At this time, each tooth can move not only in parallel but also by rotation (Fig- model in the series. ure 8). When the final occlusion is set, the movement amount (within 0.3 mm) [5] and rotation of each step is set within 2.5 degrees [6], and after deciding how many steps to make for the clear aligners (Figure 9), the series of models are printed using a 3D printer. Appl. Sci. 2021, 11, x FOR PEER REVIEW 4 of 10 Appl. Sci. 2021, 11, x FOR PEER REVIEW 4 of 10 Appl. Sci. 2021, 11, x FOR PEER REVIEW 4 of 10 After that, clear aligners are manufactured using a pressure molding machine for each After that, clear aligners are manufactured using a pressure molding machine for each model in the series. model in the series. Appl. Sci. 2021, 11, 11216 4 of 9 After that, clear aligners are manufactured using a pressure molding machine for each model in the series. Figure 3. Photo taken directly from intraoral dentition using an intraoral scanner. First, each member Figure 3. Photo taken directly from intraoral dentition using an intraoral scanner. First, each mem- Figure 3. Photo taken directly from intraoral dentition using an intraoral scanner. First, each mem- Figure 3. Photo taken directly from intraoral dentition using an intraoral scanner. First, each mem- of the dentition of the maxilla and mandible is scanned, then the patient is occluded, and then the ber of the dentition of the maxilla and mandible is scanned, then the patient is occluded, and then ber of the dentition of the maxilla and mandible is scanned, then the patient is occluded, and then ber of the dentition of the maxilla and mandible is scanned, then the patient is occluded, and then current occlusion is also scanned. the current occlusion is also scanned. the current occlusion is also scanned. the current occlusion is also scanned. (a) (b) (a) (b) Figure 4. (a) The screen where the digital model is loaded into the setup program. One can see the dentition of the upper (a) (b) and lower jaws and the patient’s current occlusion status. (b) A photograph showing the most mesial and distal parts of Figure 4. (a) The screen where the digital model is loaded into the setup program. One can see the dentition of the upper Figure 4. (a) The screen where the digital model is loaded into the setup program. One can see the dentition of the upper Figure 4. each tooth w (a) Tih th e screen where the digita green dots after each tooth l model marked to is loade distingu d i ish and di nto the setup program. One can see the d splay the teeth in the digital model. entition of the upper and lower jaws and the patient’s current occlusion status. (b) A photograph showing the most mesial and distal parts of and lower jaws and the patient’s current occlusion status. (b) A photograph showing the most mesial and distal parts of and lower jaws and the patient’s current occlusion status. (b) A photograph showing the most mesial and distal parts of each tooth with green dots after each tooth marked to distinguish and display the teeth in the digital model. each tooth with green dots after each tooth marked to distinguish and display the teeth in the digital model. each tooth with green dots after each tooth marked to distinguish and display the teeth in the digital model. (a) (b) (a) (b) (a) (b) Figure 5. (a) In order to more accurately realize the crown of each tooth, the screen is curved by placing additional dots between the markings of each tooth performed in Figure 4b. The degree of curvature is also freely adjustable. The gingival margin and the boundaries between the teeth are precisely marked. (b) The screen of (a) viewed from the front. Appl. Sci. 2021, 11, x FOR PEER REVIEW 5 of 10 Appl. Sci. 2021, 11, x FOR PEER REVIEW 5 of 10 Appl. Sci. 2021, 11, x FOR PEER REVIEW 5 of 10 Appl. Sci. 2021, 11, 11216 5 of 9 Figure 5. (a) In order to more accurately realize the crown of each tooth, the screen is curved by placing additional dots Figure 5. (a) In order to more accurately realize the crown of each tooth, the screen is curved by placing additional dots between the markings of each tooth performed in Figure 4b. The degree of curvature is also freely adjustable. The gingival Figure 5. (a) In order to more accurately realize the crown of each tooth, the screen is curved by placing additional dots between the markings of each tooth performed in Figure 4b. The degree of curvature is also freely adjustable. The gingival margin and the boundaries between the teeth are precisely marked. (b) The screen of (a) viewed from the front. between the markings of each tooth performed in Figure 4b. The degree of curvature is also freely adjustable. The gingival margin and the boundaries between the teeth are precisely marked. (b) The screen of (a) viewed from the front. margin and the boundaries between the teeth are precisely marked. (b) The screen of (a) viewed from the front. (a) ( b) (a) (b) (a) (b) Figure 6. (a) A step in which a virtual root is formed by marking the major axis of each tooth. At this time, it is possible to Figure 6. (a) A step in which a virtual root is formed by marking the major axis of each tooth. At this time, it is possible to Figure 6. (a) A step in which a virtual root is formed by marking the major axis of each tooth. At this time, it is possible to rotate in mesio-distal, bucco-palatal (bucco-lingual), and clockwise/counterclockwise rotation of the teeth when viewed Figure 6. (a) A step in which a virtual root is formed by marking the major axis of each tooth. At this time, it is possible to rotate in mesio-distal, bucco-palatal (bucco-lingual), and clockwise/counterclockwise rotation of the teeth when viewed rotate in mesio-distal, bucco-palatal (bucco-lingual), and clockwise/counterclockwise rotation of the teeth when viewed from the occlusal plane. (b) A step in which both the crown and root are set up. The patient’s existing dentition has been rotate in mesio-distal, bucco-palatal (bucco-lingual), and clockwise/counterclockwise rotation of the teeth when viewed from the occlusal plane. (b) A step in which both the crown and root are set up. The patient’s existing dentition has been from the occlusal plane. (b) A step in which both the crown and root are set up. The patient’s existing dentition has been accurately implemented. from the occlusal plane. (b) A step in which both the crown and root are set up. The patient’s existing dentition has been accurately implemented. accurately implemented. accurately implemented. (a) ( b) (a) (b) (a) (b) Figure 7. (a,b) Screen for moving each tooth to the final occlusion. It is possible to check the amount of movement of each Figure 7. (a,b) Screen for moving each tooth to the final occlusion. It is possible to check the amount of movement of each Figure tooth when the teeth are 7. (a,b) Screen for moving moved from the exi each tooth tosthe ting dental final occlusion. state to the final occlusion. It is possible to check the amount of movement of each Figure 7. (a,b) Screen for moving each tooth to the final occlusion. It is possible to check the amount of movement of each tooth when the teeth are moved from the existing dental state to the final occlusion. tooth when the teeth are moved from the existing dental state to the final occlusion. tooth when the teeth are moved from the existing dental state to the final occlusion. (a) ( b) (a) (b) (a) (b) Figure 8. (a) Photograph showing that each tooth can rotate and move parallel to the bucco-palatal (bucco-lingual) and Appl. Sci. Figure 8. 2021, 11 (, x FO a) Photograph showing that each R PEER REVIEW tooth can rotate and move parallel to the bucco-palatal (bucco-lingual) an6 of d 10 mesio-distal. (b) A photograph of overlapping existing occlusion (green) and final occlusion (white). Figure 8. (a) Photograph showing that each tooth can rotate and move parallel to the bucco-palatal (bucco-lingual) and Figure 8. (a) Photograph showing that each tooth can rotate and move parallel to the bucco-palatal (bucco-lingual) and mesio-distal. (b) A photograph of overlapping existing occlusion (green) and final occlusion (white). mesio-distal. (b) A photograph of overlapping existing occlusion (green) and final occlusion (white). mesio-distal. (b) A photograph of overlapping existing occlusion (green) and final occlusion (white). (a) (b) Figure 9. (a) A screen with a rotation of 2 degrees within one step, a movement distance of 0.2 mm, and tooth movement Figure 9. (a) A screen with a rotation of 2 degrees within one step, a movement distance of 0.2 mm, and tooth movement planned in 23 steps. (b) If necessary, an attachment can be added to the tooth. planned in 23 steps. (b) If necessary, an attachment can be added to the tooth. 3. Results Of the 15 patients (11 males, 4 females, mean age: 22.6 ± 4.36), 5 patients (5 males, 0 females, mean age: 22.2 ± 1.33) received preoperative orthodontic treatment with clear aligners, and the remaining 10 patients (6 males, 4 females, mean age: 24.0 ± 7.86) received orthodontic treatment with traditional fixed appliances as a control group. Only one pa- tient in the clear aligner group underwent Le Fort I osteotomy and mandibular bilateral sagittal split osteotomy surgery, and the remaining 14 patients had only mandibular bi- lateral sagittal split osteotomy surgery. There was no significant difference between the two groups, although the preopera- tive orthodontic period was longer in those who received orthodontic treatment with clear aligners than those who received orthodontic treatment with traditional fixed appliances (e.g., braces) (Table 2). The number of extractions of premolars and the number of im- pacted teeth was also smaller in the group treated with clear aligners, but there was no significant difference between the two groups (Table 2). To evaluate postoperative stability, six measurement variables were compared be- tween the two groups, but no significant difference was found (Table 3). Table 2. Preoperative orthodontic period, number of premolar extraction teeth, and number of im- pacted teeth between clear aligner group and traditional fixed appliance (e.g., bracket) group. Clear Aligners (n = 5) Braces (n = 10) p-Value * Mean SD Mean SD Preoperative orthodontic treatment 11.6 3.01 15.4 7.86 0.206 period (month) Extracted premolar teeth (ea.) 0.4 0.8 1.6 1.50 0.206 Impacted teeth (ea.) 0 0 0.8 1.32 0.371 * Fisher’s exact test. If p-value < 0.05, there is a significant difference between the two groups. Table 3. Postoperative stability measurement between the clear aligner group and the traditional fixed appliance (e.g., bracket) group on the 2nd day and 6th month postoperatively. Clear Aligners (n = 5) Braces (n = 10) △T2-T1 p-Value * Mean SD Mean SD L1 to NB 0.29 0.75 0.07 1.46 0.690 Pog. to NB −0.26 1.03 −0.12 0.77 0.440 A-Pog. −0.52 1.51 0.41 1.74 0.310 AFC −2.18 1.70 −0.92 1.50 0.440 SN Vr. 2.68 1.31 2.00 4.90 1 0-Med. 2.21 2.47 3.74 7.98 0.768 Appl. Sci. 2021, 11, 11216 6 of 9 3. Results Of the 15 patients (11 males, 4 females, mean age: 22.6  4.36), 5 patients (5 males, 0 females, mean age: 22.2  1.33) received preoperative orthodontic treatment with clear aligners, and the remaining 10 patients (6 males, 4 females, mean age: 24.0 7.86) received orthodontic treatment with traditional fixed appliances as a control group. Only one patient in the clear aligner group underwent Le Fort I osteotomy and mandibular bilateral sagittal split osteotomy surgery, and the remaining 14 patients had only mandibular bilateral sagittal split osteotomy surgery. There was no significant difference between the two groups, although the preoperative orthodontic period was longer in those who received orthodontic treatment with clear aligners than those who received orthodontic treatment with traditional fixed appliances (e.g., braces) (Table 2). The number of extractions of premolars and the number of impacted teeth was also smaller in the group treated with clear aligners, but there was no significant difference between the two groups (Table 2). Table 2. Preoperative orthodontic period, number of premolar extraction teeth, and number of impacted teeth between clear aligner group and traditional fixed appliance (e.g., bracket) group. Clear Aligners (n = 5) Braces (n = 10) p-Value * Mean SD Mean SD Preoperative orthodontic 11.6 3.01 15.4 7.86 0.206 treatment period (month) Extracted premolar teeth (ea.) 0.4 0.8 1.6 1.50 0.206 Impacted teeth (ea.) 0 0 0.8 1.32 0.371 * Fisher ’s exact test. If p-value < 0.05, there is a significant difference between the two groups. To evaluate postoperative stability, six measurement variables were compared between the two groups, but no significant difference was found (Table 3). Table 3. Postoperative stability measurement between the clear aligner group and the traditional fixed appliance (e.g., bracket) group on the 2nd day and 6th month postoperatively. Clear Aligners (n = 5) Braces (n = 10) p-Value * 4T2-T1 Mean SD Mean SD L1 to NB 0.29 0.75 0.07 1.46 0.690 Pog. to NB 0.26 1.03 0.12 0.77 0.440 A-Pog. 0.52 1.51 0.41 1.74 0.310 AFC 2.18 1.70 0.92 1.50 0.440 SN Vr. 2.68 1.31 2.00 4.90 1 0-Med. 2.21 2.47 3.74 7.98 0.768 T1: 2nd day after surgery, T2: 6th month after surgery. * Mann—Whitney test. p-value < 0.05 indicates a significant difference between the two groups. 4. Discussion There have been many studies on stability after orthognathic surgery [7,8]. However, there are no studies to identify the characteristics of patients who underwent orthognathic surgery after preoperative orthodontic surgery with clear aligners. There have been few reports of patients who underwent orthognathic surgery with preoperative correction with clear aligners. For example, when searching for ““clear aligner$” and “orthognathic$”” in PubMed, there were only five papers. Among these studies, two [9,10] were on the use of a stent as a clear aligner during surgery, and one [11] was on the surgery-first technique. A similar search on PubMed for ““invisalign$” and “orthognathic$”” only yielded four papers. Appl. Sci. 2021, 11, 11216 7 of 9 According to the results of the study, the number of extracted premolars was fewer in the group that received preoperative orthodontic treatment with clear aligners compared to the group that had been corrected preoperatively with conventional orthodontic devices. There was no significant difference in the period of orthodontic treatment. Referring to Table 4, the average mandibular setback amount of the patients in the clear aligners group was 7.9 mm, which showed that preoperative orthodontic treatment with clear aligners was possible even during orthognathic surgery with a relatively large setback. Table 4. Information on five patients with clear aligners. Preoperative Extracted Orthodontic Impacted Amount of Surgical Sex Age Premolar Plate Removal Treatment Period Teeth (ea.) Movement Teeth (ea.) (Months) Vertical reduction (3.5 mm) Was performed 1 Male 24 8 0 0 Le Fort I osteotomy, 23 months Mn. setback BSSO after surgery. (Rt.: 10 mm, Lt.: 9 mm) Was performed Mn. setback BSSO 2 Male 20 11 0 0 5 months (Rt.: 12 mm, Lt.: 5 mm) after surgery. Was performed Mn. setback BSSO 3 Male 23 12 2 0 11 months (Rt.: 6 mm, Lt.: 1 mm) after surgery. Was performed Mn. setback BSSO 4 Male 22 10 0 0 4 months (Rt.: 9 mm, Lt.: 11 mm) after surgery. Was performed Mn. setback BSSO 5 Male 22 17 0 0 8 months (Rt.: 9 mm, Lt.: 7 mm) after surgery. (Mn.: mandible, BSSO: bilateral sagittal split osteotomy, Rt.: right, Lt.: left). For maxillomandibular fixation using elastics after orthognathic surgery in our hospi- tal, from immediately after surgery to one week after surgery, it is not possible to open the mouth at all while occluded with 4.6 mm (170.1 g) elastic. Up to one month, it is possible to open the mouth with a 9.5 mm (170.1 g) elastic. This protocol was equally applied to all patients participating in this study, and there were no differences between the clear aligner group and the traditional orthodontic device group in elastic guide postoperatively. Even though the clear aligner was developed in 1999, it has evolved considerably, and many patients are receiving orthodontic treatment using the clear aligner approach [3,12]. A systematic review on orthodontic treatment using clear aligners found no significant difference in stability and occlusal characteristics compared to conventional orthodontic appliances [13]. Orthodontic treatment with clear aligners has the following advantages, including aesthetics, patient convenience, reduction in the number of visits to the dental clinic, decreased chair time, removable device, convenience in oral hygiene management, saving time required for wire replacement or bracket installation, and ease of taking im- pressions [2,14]. In addition, the patient is well accustomed to maintaining the device after surgery because they have experience with the device. In addition, there is no interference from braces during surgery (Figure 10), so there is no hindrance during surgery, and there is no risk of the bracket falling off during surgery. Another advantage of orthodontic treatment using clear aligners is that the brackets physically interfere with tooth brushing, making oral hygiene management difficult, but clear aligners do not. These removable clear aligners can also reduce the incidence of white spot lesions on teeth [15]. In a similar vein, according to Sfondrini et al., there was no significant difference in periodontal and Appl. Sci. 2021, 11, x FOR PEER REVIEW 8 of 10 Even though the clear aligner was developed in 1999, it has evolved considerably, and many patients are receiving orthodontic treatment using the clear aligner approach [3,12]. A systematic review on orthodontic treatment using clear aligners found no signif- icant difference in stability and occlusal characteristics compared to conventional ortho- dontic appliances [13]. Orthodontic treatment with clear aligners has the following ad- vantages, including aesthetics, patient convenience, reduction in the number of visits to the dental clinic, decreased chair time, removable device, convenience in oral hygiene management, saving time required for wire replacement or bracket installation, and ease of taking impressions [2,14]. In addition, the patient is well accustomed to maintaining the device after surgery because they have experience with the device. In addition, there is no interference from braces during surgery (Figure 10), so there is no hindrance during surgery, and there is no risk of the bracket falling off during surgery. Another advantage of orthodontic treatment using clear aligners is that the brackets physically interfere with tooth brushing, making oral hygiene management difficult, but clear aligners do not. These removable clear aligners can also reduce the incidence of white spot lesions on teeth [15]. In a similar vein, according to Sfondrini et al., there was no significant difference in Appl. Sci. 2021, 11, 11216 8 of 9 periodontal and microbiological parameters in patients undergoing correction with a clear aligner for two months compared with patients who did not receive orthodontic treatment [16]. According to Kankam et al., there was no significant difference in postoperative microbiological parameters in patients undergoing correction with a clear aligner for two edema in orthodontic patients treated with clear aligners [17]. On the other hand, disad- months compared with patients who did not receive orthodontic treatment [16]. According vantages include the need to install a screw to anchor the elastics during surgery [18], and to Kankam et al., there was no significant difference in postoperative edema in orthodontic patients treated with clear aligners [17]. On the other hand, disadvantages include the need the patient’s cooperation during orthodontic treatment is important. According to a large to install a screw to anchor the elastics during surgery [18], and the patient’s cooperation cohort of clear aligner therapy patients, 45.5% of patients wore the aligner for 22 h or more during orthodontic treatment is important. According to a large cohort of clear aligner a day, while 25.7% wore it for less than 11 h [19]. Since orthodontic treatment is required therapy patients, 45.5% of patients wore the aligner for 22 h or more a day, while 25.7% after surgery [20], the dentist and the patient must communicate in order to cooperate wore it for less than 11 h [19]. Since orthodontic treatment is required after surgery [20], the dentist and the patient must communicate in order to cooperate with the patient, and with the patient, and sometimes the doctor must induce the patient to show better com- sometimes the doctor must induce the patient to show better compliance [21]. It must be pliance [21]. It must be replaced with the next device according to the requirements, and replaced with the next device according to the requirements, and there is a risk of losing there is a risk of losing the orthodontic device. Furthermore, braces may be attached dur- the orthodontic device. Furthermore, braces may be attached during the postoperative ing the postoperative orthodontic period. orthodontic period. (a) (b) Figure 10. Figure (a) In10. traoperative c (a) Intraoperative linica clinical l pictu pictur re of e orthognathic of orthognathic sur surgery patient with gery patient with clearclear aligners. aligners. This p This photo shows hoto shows th the e maxillomandibular fixation using wire as a final occlusion state after three mini screws were placed in each segment before maxillomandibular fixation using wire as a final occlusion state after three mini screws were placed in each segment before fixing the miniplate to the mandible. There are no fixed braces or metal wires attached to the teeth. (b) Clinical pictures of fixing the miniplate to the mandible. There are no fixed braces or metal wires attached to the teeth. (b) Clinical pictures of patients who received orthodontic treatment with brackets. The photographing method is the same as in (a). patients who received orthodontic treatment with brackets. The photographing method is the same as in (a). When asked about the expected disadvantages of orthognathic surgery using clear When asked about the expected disadvantages of orthognathic surgery using clear aligners, surgeons expect the preoperative period to be long, that the extraction cases will be difficult, with the possibility of using conventional fixed appliances for postoperative aligners, surgeons expect the preoperative period to be long, that the extraction cases will correction. However, in this study, there were no significant differences in the preoperative be difficult, with the possibility of using conventional fixed appliances for postoperative correction period in the clear aligner group. There was a case with tooth extraction and correction. However, in this study, there were no significant differences in the preopera- where no braces were used for postoperative correction, just clear aligners. As time goes tive correction period in the clear aligner group. There was a case with tooth extraction by, orthodontists will develop orthodontic treatments using clear aligners, overcoming the limitations of orthodontics. It is thought that almost all the shortcomings can be overcome and where no braces were used for postoperative correction, just clear aligners. As time even during orthognathic surgery accompanying this clear aligner approach. For future studies, it will be necessary to study greater numbers of patients regarding the applicability of transparent aligners to complex preoperative orthodontic treatment. 5. Conclusions Even when using preoperative orthodontic treatment with clear aligners, there was no difficulty in combining clear aligners with orthognathic surgery cases. It is thought that similar results can be obtained using the combination of clear aligners with orthognathic surgery as compared with conventional surgery. The sample size of this preliminary study was, however, limited; thus, further studies with greater numbers of cases are needed to define the role of orthognathic surgery using clear aligners. Appl. Sci. 2021, 11, 11216 9 of 9 Author Contributions: C.M. and E.C.K. contributed to the acquisition, analysis, and interpretation of data for the work, and Y.-D.K., to the conception and design of the work, and to the analysis and interpretation. G.K.S. contributed to the interpretation of data and linguistic aspects of the manuscript. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Institutional Review Board Statement: The study was conducted according to the guidelines of the Declaration of Helsinki, and approved by the Institutional Review Board (or Ethics Committee) of Pusan National University Dental Hospital (PNUDH-2021-0238, 17-09-21). Informed Consent Statement: Not applicable. Conflicts of Interest: The authors declare no conflict of interest. References 1. Kesling, H.D. Coordinating the predetermined pattern and tooth positioner with conventional treatment. Am. J. Orthod. Oral Surg. 1946, 32, 285–293. [CrossRef] 2. Rosvall, M.D.; Fields, H.W.; Ziuchkovski, J.; Rosenstiel, S.F.; Johnston, W.M. Attractiveness, acceptability, and value of orthodontic appliances. Am. J. Orthod. Dentofacial Orthop. 2009, 135, 276 e271-212; discussion 276–277. [CrossRef] [PubMed] 3. Hennessy, J.; Al-Awadhi, E.A. Clear aligners generations and orthodontic tooth movement. J. Orthod. 2016, 43, 68–76. [CrossRef] [PubMed] 4. Kasper, F.K. 3D Printing applications in clear aligner fabrication. In Proceedings of the Forty-sixth Annual Moyers Symposium and the Forty-fourth Annual International Conference on Craniofacial Research The University of Michigan, Ann Arbor, MI, USA, 1–3 March 2019; pp. 7–21. 5. Lim, S.-H. Digital fabrication and application of clear aligner after alignment with NiTi archwires. J. Korean Dent. Assoc. 2016, 54, 551–562. 6. Hahn, W.; Engelke, B.; Jung, K.; Dathe, H.; Fialka-Fricke, J.; Kubein-Meesenburg, D.; Sadat-Khonsari, R. Initial forces and moments delivered by removable thermoplastic appliances during rotation of an upper central incisor. Angle. Orthod. 2010, 80, 239–246. [CrossRef] [PubMed] 7. Proffit, W.R.; Turvey, T.A.; Phillips, C. Orthognathic surgery: A hierarchy of stability. Int. J. Adult. Orthodon. Orthognath. Surg. 1996, 11, 191–204. [PubMed] 8. Bailey, L.; Cevidanes, L.H.; Proffit, W.R. Stability and predictability of orthognathic surgery. Am. J. Orthod. Dentofac. Orthop. 2004, 126, 273–277. [CrossRef] 9. Border, M.; Strait, R.; Vega, L. Clear Aligner Orthognathic Splints (CAOS) and Custom Maxillary Fixation Plates for Surgery-First or Surgery-Only Cases. J. Oral Maxillofac. Surg. 2021, 79, e6–e11. [CrossRef] [PubMed] 10. Caminiti, M.; Lou, T. Clear Aligner Orthognathic Splints. J. Oral Maxillofac. Surg. 2019, 77, 1071 e1071–1071 e1078. [CrossRef] [PubMed] 11. Kook, M.S.; Kim, H.M.; Oh, H.K.; Lee, K.M. Clear Aligner Use Following Surgery-First Mandibular Prognathism Correction. J. Craniofac. Surg. 2019, 30, e544–e547. [CrossRef] [PubMed] 12. Kravitz, N.D.; Kusnoto, B.; BeGole, E.; Obrez, A.; Agran, B. How well does Invisalign work? A prospective clinical study evaluating the efficacy of tooth movement with Invisalign. Am. J. Orthod. Dentofac. Orthop. 2009, 135, 27–35. [CrossRef] [PubMed] 13. Zheng, M.; Liu, R.; Ni, Z.; Yu, Z. Efficiency, effectiveness and treatment stability of clear aligners: A systematic review and meta-analysis. Orthod. Craniofac. Res. 2017, 20, 127–133. [CrossRef] 14. Ke, Y.; Zhu, Y.; Zhu, M. A comparison of treatment effectiveness between clear aligner and fixed appliance therapies. BMC Oral Health 2019, 19, 24. [CrossRef] [PubMed] 15. Buschang, P.H.; Chastain, D.; Keylor, C.L.; Crosby, D.; Julien, K.C. Incidence of white spot lesions among patients treated with clear aligners and traditional braces. Angle. Orthod. 2019, 89, 359–364. [CrossRef] [PubMed] 16. Sfondrini, M.S.; Butera, A.; Michele, P.D.; Luccisano, C.; Ottini, B.; Sangalli, E.; Gallo, S.; Pascadopoli, M.; Gandini, P.; Scribante, A. Microbiological Changes during Orthodontic Aligner Therapy: A Prospective Clinical Trial. Appl. Sci. 2021, 11, 6758. [CrossRef] 17. Kankam, H.; Madari, S.; Sawh-Martinez, R.; Bruckman, K.C.; Steinbacher, D.M. Comparing Outcomes in Orthognathic Surgery Using Clear Aligners Versus Conventional Fixed Appliances. J. Craniofac. Surg. 2019, 30, 1488–1491. [CrossRef] [PubMed] 18. Lou, T.; Caminiti, M. Orthognathic Surgery Combined with Clear Aligner Therapy. J. Clin. Orthod. 2021, 55, 44–58. [PubMed] 19. Timm, L.H.; Farrag, G.; Baxmann, M.; Schwendicke, F. Factors Influencing Patient Compliance during Clear Aligner Therapy: A Retrospective Cohort Study. J. Clin. Med. 2021, 10, 3103. [CrossRef] [PubMed] 20. Dowling, P.A.; Espeland, L.; Krogstad, O.; Stenvik, A.; Kelly, A. Duration of orthodontic treatment involving orthognathic surgery. Int. J. Adult Orthodon. Orthognath. Surg. 1999, 14, 146–152. [PubMed] 21. Sahm, G.; Bartsch, A.; Witt, E. Reliability of patient reports on compliance. Eur. J. Orthod. 1990, 12, 438–446. [CrossRef] [PubMed] http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Applied Sciences Multidisciplinary Digital Publishing Institute

Postoperative Stability of Patients Undergoing Orthognathic Surgery with Orthodontic Treatment Using Clear Aligners: A Preliminary Study

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applied sciences Article Postoperative Stability of Patients Undergoing Orthognathic Surgery with Orthodontic Treatment Using Clear Aligners: A Preliminary Study 1 , 2 , 3 4 5 1 , 2 , 3 , Chiho Moon , George K. Sándor , Edward Chengchuan Ko and Yong-Deok Kim * Department of Oral and Maxillofacial Surgery, School of Dentistry, Pusan National University, Geumo-ro 20, Mulgeum, Yangsan 50612, Korea; mch2875@naver.com Dental and Life Science Institute, School of Dentistry, Pusan National University, Yangsan 50612, Korea Dental Research Instutite, Pusan National University Dental Hospital, Yangsan 50612, Korea Department of Oral and Maxillofacial Surgery, Oulu University Hospital, University of Oulu, 90220 Oulu, Finland; sandor_george@hotmail.com Department of Oral and Maxillofacial Surgery, Kaohsiung Medical University, Kaohsiung 80708, Taiwan; ko.edward.kaseizen@gmail.com * Correspondence: ydkimdds@pusan.ac.kr; Tel.: +82-55-360-5116; Fax: +82-55-360-5104 Abstract: Backgrond: Until now, there have been many studies on the postoperative stability of orthognathic patients treated with traditional fixed orthodontic appliances. Recently, the use of clear aligners as orthodontic appliances has increased in orthodontic treatment for aesthetic and patient convenience. The aim of this preliminary study was to investigate the stability and characteristics of patients undergoing orthognathic surgery using clear aligners. Patients and Methods: This study was performed on patients who underwent orthognathic surgery by one surgeon at Pusan National Citation: Moon, C.; Sándor, G.K.; Ko, University Dental Hospital from April 2017 to August 2021. A comparative study was conducted E.C.; Kim, Y.-D. Postoperative on five patients treated with clear aligners during orthodontic treatment and ten patients treated Stability of Patients Undergoing with traditional fixed appliances as a control group. Postoperative skeletal changes and recurrence Orthognathic Surgery with were evaluated by cone beam computed tomography and lateral cephalometric radiographs taken Orthodontic Treatment Using Clear two days postoperatively and six months postoperatively. Several measurement variables were Aligners: A Preliminary Study. Appl. used to confirm the presence or absence of recurrence, preoperative and postoperative orthodontic Sci. 2021, 11, 11216. https://doi.org/ treatment period, and the number of extracted teeth. Results: Postoperative stability for six months 10.3390/app112311216 after surgery was not significantly different between the clear aligner group and the traditional Academic Editors: Gabriele Cervino fixed appliance group. The preoperative orthodontic treatment period was also shorter in the clear and Dorina Lauritano aligner group, and the number of extracted premolar teeth and impacted teeth were also fewer in the clear aligner group, but there was no significant difference. Conclusions: Orthodontic treatment Received: 2 November 2021 using clear aligners continues to develop, and it is believed that there is no limit to what can be Accepted: 24 November 2021 accomplished during orthodontic surgery accompanied by clear aligners. Published: 25 November 2021 Keywords: orthognathic surgery; clear aligner; Invisalign; stability; preoperative orthodontic treat- Publisher’s Note: MDPI stays neutral ment; CAD-CAM; 3D printer with regard to jurisdictional claims in published maps and institutional affil- iations. 1. Introduction Since Kesling first invented the aligner in 1946, an aligner for tooth alignment has been developed [1]. Recently, patient demand has increased for more orthodontic treatments Copyright: © 2021 by the authors. with esthetic appliances [2]. In line with this, Align Technology Inc. (San Jose, CA, USA) Licensee MDPI, Basel, Switzerland. launched the Invisalign system in 1999, which enables esthetic orthodontic treatment This article is an open access article because traditional braces are not invisible. This was the first CAD (computer-aided distributed under the terms and design) and CAM (computer-aided manufacturing)-based orthodontic appliance, which conditions of the Creative Commons can be digitally scanned, and made as a series of aligners using a single impression [3,4]. Attribution (CC BY) license (https:// The approximate digital manufacturing process of a clear aligner is as follows. First, a creativecommons.org/licenses/by/ digital image is obtained by scanning a plaster model taken either by direct impression 4.0/). Appl. Sci. 2021, 11, 11216. https://doi.org/10.3390/app112311216 https://www.mdpi.com/journal/applsci Appl. Sci. 2021, 11, x FOR PEER REVIEW 2 of 10 Appl. Sci. 2021, 11, 11216 2 of 9 The approximate digital manufacturing process of a clear aligner is as follows. First, a digital image is obtained by scanning a plaster model taken either by direct impression of the patient’s dentition with a three-dimensional (3D) scanner or by directly scanning of the patient’s dentition with a three-dimensional (3D) scanner or by directly scanning the patient’s dentition with an intraoral scanner. When the digital model is created in this the patient’s dentition with an intraoral scanner. When the digital model is created in this way, the file can be loaded in the setup program to start making the clear aligner [4,5]. way, the file can be loaded in the setup program to start making the clear aligner [4,5]. Following the setup program, the crown, root, and long axis are set, and the teeth are Following the setup program, the crown, root, and long axis are set, and the teeth are moved to the desired position, which is the final arrangement. After that, a series of clear moved to the desired position, which is the final arrangement. After that, a series of clear aligners suitable for the treatment period is designed. At this stage, it is recommended aligners suitable for the treatment period is designed. At this stage, it is recommended that that the tooth rotation is within 2.5 degrees and the movement distance confined to 0.3 the tooth rotation is within 2.5 degrees and the movement distance confined to 0.3 mm at mm at each stage [6]. After that, a 3D printer is used to make a model for step-by-step each stage [6]. After that, a 3D printer is used to make a model for step-by-step changes changes and then make a series of progressive clear aligners to move the misaligned teeth. and then make a series of progressive clear aligners to move the misaligned teeth. Recently, increasing numbers of patients are receiving orthodontic treatment with Recently, increasing numbers of patients are receiving orthodontic treatment with clear aligners, including those patients undergoing orthognathic surgery. Although there clear aligners, including those patients undergoing orthognathic surgery. Although there have been many studies showing that the postoperative stability of orthodontic patients have been many studies showing that the postoperative stability of orthodontic patients treated with conventional fixed orthodontic devices is good [7,8], there have been no stud- treated with conventional fixed orthodontic devices is good [7,8], there have been no ies on postoperative stability of orthodontic patients treated with clear aligners. In this studies on postoperative stability of orthodontic patients treated with clear aligners. In this preliminary study, the stability and characteristics of patients using clear aligners after preliminary study, the stability and characteristics of patients using clear aligners after orthognathic surgery were investigated. orthognathic surgery were investigated. 2. Materials and Methods 2. Materials and Methods 2.1. Patients 2.1. Patients This retrospective study was exempt from review by the Institutional Review Board This retrospective study was exempt from review by the Institutional Review Board at Pusan National University Dental Hospital (Approval No.: PNUDH-2021-038). A total at Pusan National University Dental Hospital (Approval No.: PNUDH-2021-038). A to- of 15 patients who underwent orthognathic surgery by one surgeon at PNUDH between tal of 15 patients who underwent orthognathic surgery by one surgeon at PNUDH be- April 2017 and August 2021 were included in this study. Of the 15 patients, 5 patients tween April 2017 and August 2021 were included in this study. Of the 15 patients, received preoperative orthodontic treatment with clear aligners, and the remaining 10 pa- 5 patients received preoperative orthodontic treatment with clear aligners, and the re- tients received orthodontic treatment with traditional fixed appliances. maining 10 patients received orthodontic treatment with traditional fixed appliances. 2.2. Study Methods 2.2. Study Methods For all patients, cone beam computed tomography (CBCT), and lateral cephalometric For all patients, cone beam computed tomography (CBCT), and lateral cephalometric radiographs were taken postoperatively on day 2 and month 6 to confirm skeletal changes radiographs were taken postoperatively on day 2 and month 6 to confirm skeletal changes (Figures 1 and 2). Postoperative stability was evaluated and analyzed by measuring several (Figures 1 and 2). Postoperative stability was evaluated and analyzed by measuring sev- measurement variables (L1 to NB, Pog. to NB, A-Pog., angle of facial convexity (AFC), SN eral measurement variables (L1 to NB, Pog. to NB, A-Pog., angle of facial convexity (AFC), vertical, and 0-merdian) (Table 1). The duration of each patient’s preoperative orthodontic SN vertical, and 0-merdian) (Table 1). The duration of each patient’s preoperative ortho- period, the number of premolar extractions, and the number of impacted teeth were also dontic period, the number of premolar extractions, and the number of impacted teeth compared and analyzed. were also compared and analyzed. (a) (b) (c) Figure 1. Orthognathic surgery patient with clear aligners. (a) Before surgery; (b) 2 days after surgery; (c) 6 months post- Figure 1. Orthognathic surgery patient with clear aligners. (a) Before surgery; (b) 2 days after surgery; (c) 6 months operative radiograph image. Braces attached to teeth were not observed on radiographs. postoperative radiograph image. Braces attached to teeth were not observed on radiographs. Appl. Sci. 2021, 11, 11216 3 of 9 Appl. Sci. 2021, 11, x FOR PEER REVIEW 3 of 10 (a) (b) (c) Figure 2. Orthognathic surgery patient with conventional fixed appliance. (a) Before surgery; (b) 2 days after surgery; (c) Figure 2. Orthognathic surgery patient with conventional fixed appliance. (a) Before surgery; (b) 2 days after surgery; 6 months postoperative radiograph image. The bracket attached to teeth was not observed on radiographs. (c) 6 months postoperative radiograph image. The bracket attached to teeth was not observed on radiographs. Table 1. Measurement variables. Table 1. Measurement variables. L1 to NB (linear) (mm): Distance from [Mandible 1 crown] to Line [B-point]-[Nasion] L1 to NB (linear) (mm): Distance from [Mandible 1 crown] to Line [B-point]-[Nasion] Pog. to NB (mm): Distance from [Pogonion] to Line [B-point]-[Nasion] Positive for right Pog. to NB (mm): Distance from [Pogonion] to Line [B-point]-[Nasion] Positive for right side of Line side of Line A-Pog. (mm): Distance from [Mandible 1 crown] to Line [A-Point]-[Pogonion] Positive for right side of Line A-Pog. (mm): Distance from [Mandible 1 crown] to Line [A-Point]-[Pogonion] Positive Angle of facial convexity (AFC) (deg): Angle of line [Subnasale]-[Glabella] and [soft tissue Pogonion]-[Subnasale] for right side of Line SN Vr. (mm): Subtract distance of [Subnasale] from distance of [soft tissue Pogonion], parallel to line [Porion]-[Orbitale] Angle of facial convexity (AFC) (deg): Angle of line [Subnasale]-[Glabella] and [soft tis- sue Pogonion]-[Subnasale] 0-Med. (mm): Subtract distance of [soft tissue Nasion] from distance of [soft tissue Pogonion], parallel to line [Porion]-[Orbitale] SN Vr. (mm): Subtract distance of [Subnasale] from distance of [soft tissue Pogonion], parallel to line [Porion]-[Orbitale] 2.3. Statistical Analysis 0-Med. (mm): Subtract distance of [soft tissue Nasion] from distance of [soft tissue Pogo- All measurements were statistically analyzed using a statistical program (SPSS 14.0; nion], parallel to line [Porion]-[Orbitale] IBM SPSS Statistics, Chicago, IL, USA). All landmarks were analyzed using a cephalometric analysis program (Vceph 6.0; Osstem implant Co., Seoul, Korea) 2.3. Statistical Analysis 2.4. The Manufacturing Process of Clear Aligners by CAD/CAM All measurements were statistically analyzed using a statistical program (SPSS 14.0; IBM SPSS Statistics, Chicago, IL, USA). All landmarks were analyzed using a cephalo- In our hospital, the patient’s dentition is obtained directly from the oral cavity us- m ing etran ic an intraoral alysis pscanner rogram ((Figur Vcephe 6. 30; O ). Following sstem imp this, lant the Co., S digital eoul, K model orea) is called from the setup program. Common programs include Maestro 3D Ortho Studio (Age solutions, 2.4. T Pontedera, he Manu Italy facturin ), Ortho g Proc Analyzer ess of Clear (3Shape, Aligners Copenhagen by CAD/CAM K, Denmark), Orchestrate 3D (Orchestrate 3D, Rialto, CA, USA) [5], and Autolign (Dorico, Yongin, Korea). In this study, In our hospital, the patient’s dentition is obtained directly from the oral cavity using the Autolign (Dorico, Yongin, Korea) program was used. Each tooth number is marked an intraoral scanner (Figure 3). Following this, the digital model is called from the setup on the imported digital model, and the most mesial and distal points of each tooth are program. Common programs include Maestro 3D Ortho Studio (Age solutions, marked (Figure 4). After that, the cutting line of the crown is corrected to accurately mark Pontedera, Italy), Ortho Analyzer (3Shape, Copenhagen K, Denmark), Orchestrate 3D the clinical crown (Figure 5). Next, when the tooth axis and root are formed, the model (Orchestrate 3D, Rialto, CA, USA) [5], and Autolign (Dorico, Yongin, Korea). In this study, setup is completed (Figure 6). After that, the teeth are moved to the desired final occlusion the Autolign (Dorico, Yongin, Korea) program was used. Each tooth number is marked (Figure 7). At this time, each tooth can move not only in parallel but also by rotation on the imported digital model, and the most mesial and distal points of each tooth are (Figure 8). When the final occlusion is set, the movement amount (within 0.3 mm) [5] and marked (Figure 4). After that, the cutting line of the crown is corrected to accurately mark rotation of each step is set within 2.5 degrees [6], and after deciding how many steps to the clinical crown (Figure 5). Next, when the tooth axis and root are formed, the model make for the clear aligners (Figure 9), the series of models are printed using a 3D printer. setup is completed (Figure 6). After that, the teeth are moved to the desired final occlusion After that, clear aligners are manufactured using a pressure molding machine for each (Figure 7). At this time, each tooth can move not only in parallel but also by rotation (Fig- model in the series. ure 8). When the final occlusion is set, the movement amount (within 0.3 mm) [5] and rotation of each step is set within 2.5 degrees [6], and after deciding how many steps to make for the clear aligners (Figure 9), the series of models are printed using a 3D printer. Appl. Sci. 2021, 11, x FOR PEER REVIEW 4 of 10 Appl. Sci. 2021, 11, x FOR PEER REVIEW 4 of 10 Appl. Sci. 2021, 11, x FOR PEER REVIEW 4 of 10 After that, clear aligners are manufactured using a pressure molding machine for each After that, clear aligners are manufactured using a pressure molding machine for each model in the series. model in the series. Appl. Sci. 2021, 11, 11216 4 of 9 After that, clear aligners are manufactured using a pressure molding machine for each model in the series. Figure 3. Photo taken directly from intraoral dentition using an intraoral scanner. First, each member Figure 3. Photo taken directly from intraoral dentition using an intraoral scanner. First, each mem- Figure 3. Photo taken directly from intraoral dentition using an intraoral scanner. First, each mem- Figure 3. Photo taken directly from intraoral dentition using an intraoral scanner. First, each mem- of the dentition of the maxilla and mandible is scanned, then the patient is occluded, and then the ber of the dentition of the maxilla and mandible is scanned, then the patient is occluded, and then ber of the dentition of the maxilla and mandible is scanned, then the patient is occluded, and then ber of the dentition of the maxilla and mandible is scanned, then the patient is occluded, and then current occlusion is also scanned. the current occlusion is also scanned. the current occlusion is also scanned. the current occlusion is also scanned. (a) (b) (a) (b) Figure 4. (a) The screen where the digital model is loaded into the setup program. One can see the dentition of the upper (a) (b) and lower jaws and the patient’s current occlusion status. (b) A photograph showing the most mesial and distal parts of Figure 4. (a) The screen where the digital model is loaded into the setup program. One can see the dentition of the upper Figure 4. (a) The screen where the digital model is loaded into the setup program. One can see the dentition of the upper Figure 4. each tooth w (a) Tih th e screen where the digita green dots after each tooth l model marked to is loade distingu d i ish and di nto the setup program. One can see the d splay the teeth in the digital model. entition of the upper and lower jaws and the patient’s current occlusion status. (b) A photograph showing the most mesial and distal parts of and lower jaws and the patient’s current occlusion status. (b) A photograph showing the most mesial and distal parts of and lower jaws and the patient’s current occlusion status. (b) A photograph showing the most mesial and distal parts of each tooth with green dots after each tooth marked to distinguish and display the teeth in the digital model. each tooth with green dots after each tooth marked to distinguish and display the teeth in the digital model. each tooth with green dots after each tooth marked to distinguish and display the teeth in the digital model. (a) (b) (a) (b) (a) (b) Figure 5. (a) In order to more accurately realize the crown of each tooth, the screen is curved by placing additional dots between the markings of each tooth performed in Figure 4b. The degree of curvature is also freely adjustable. The gingival margin and the boundaries between the teeth are precisely marked. (b) The screen of (a) viewed from the front. Appl. Sci. 2021, 11, x FOR PEER REVIEW 5 of 10 Appl. Sci. 2021, 11, x FOR PEER REVIEW 5 of 10 Appl. Sci. 2021, 11, x FOR PEER REVIEW 5 of 10 Appl. Sci. 2021, 11, 11216 5 of 9 Figure 5. (a) In order to more accurately realize the crown of each tooth, the screen is curved by placing additional dots Figure 5. (a) In order to more accurately realize the crown of each tooth, the screen is curved by placing additional dots between the markings of each tooth performed in Figure 4b. The degree of curvature is also freely adjustable. The gingival Figure 5. (a) In order to more accurately realize the crown of each tooth, the screen is curved by placing additional dots between the markings of each tooth performed in Figure 4b. The degree of curvature is also freely adjustable. The gingival margin and the boundaries between the teeth are precisely marked. (b) The screen of (a) viewed from the front. between the markings of each tooth performed in Figure 4b. The degree of curvature is also freely adjustable. The gingival margin and the boundaries between the teeth are precisely marked. (b) The screen of (a) viewed from the front. margin and the boundaries between the teeth are precisely marked. (b) The screen of (a) viewed from the front. (a) ( b) (a) (b) (a) (b) Figure 6. (a) A step in which a virtual root is formed by marking the major axis of each tooth. At this time, it is possible to Figure 6. (a) A step in which a virtual root is formed by marking the major axis of each tooth. At this time, it is possible to Figure 6. (a) A step in which a virtual root is formed by marking the major axis of each tooth. At this time, it is possible to rotate in mesio-distal, bucco-palatal (bucco-lingual), and clockwise/counterclockwise rotation of the teeth when viewed Figure 6. (a) A step in which a virtual root is formed by marking the major axis of each tooth. At this time, it is possible to rotate in mesio-distal, bucco-palatal (bucco-lingual), and clockwise/counterclockwise rotation of the teeth when viewed rotate in mesio-distal, bucco-palatal (bucco-lingual), and clockwise/counterclockwise rotation of the teeth when viewed from the occlusal plane. (b) A step in which both the crown and root are set up. The patient’s existing dentition has been rotate in mesio-distal, bucco-palatal (bucco-lingual), and clockwise/counterclockwise rotation of the teeth when viewed from the occlusal plane. (b) A step in which both the crown and root are set up. The patient’s existing dentition has been from the occlusal plane. (b) A step in which both the crown and root are set up. The patient’s existing dentition has been accurately implemented. from the occlusal plane. (b) A step in which both the crown and root are set up. The patient’s existing dentition has been accurately implemented. accurately implemented. accurately implemented. (a) ( b) (a) (b) (a) (b) Figure 7. (a,b) Screen for moving each tooth to the final occlusion. It is possible to check the amount of movement of each Figure 7. (a,b) Screen for moving each tooth to the final occlusion. It is possible to check the amount of movement of each Figure tooth when the teeth are 7. (a,b) Screen for moving moved from the exi each tooth tosthe ting dental final occlusion. state to the final occlusion. It is possible to check the amount of movement of each Figure 7. (a,b) Screen for moving each tooth to the final occlusion. It is possible to check the amount of movement of each tooth when the teeth are moved from the existing dental state to the final occlusion. tooth when the teeth are moved from the existing dental state to the final occlusion. tooth when the teeth are moved from the existing dental state to the final occlusion. (a) ( b) (a) (b) (a) (b) Figure 8. (a) Photograph showing that each tooth can rotate and move parallel to the bucco-palatal (bucco-lingual) and Appl. Sci. Figure 8. 2021, 11 (, x FO a) Photograph showing that each R PEER REVIEW tooth can rotate and move parallel to the bucco-palatal (bucco-lingual) an6 of d 10 mesio-distal. (b) A photograph of overlapping existing occlusion (green) and final occlusion (white). Figure 8. (a) Photograph showing that each tooth can rotate and move parallel to the bucco-palatal (bucco-lingual) and Figure 8. (a) Photograph showing that each tooth can rotate and move parallel to the bucco-palatal (bucco-lingual) and mesio-distal. (b) A photograph of overlapping existing occlusion (green) and final occlusion (white). mesio-distal. (b) A photograph of overlapping existing occlusion (green) and final occlusion (white). mesio-distal. (b) A photograph of overlapping existing occlusion (green) and final occlusion (white). (a) (b) Figure 9. (a) A screen with a rotation of 2 degrees within one step, a movement distance of 0.2 mm, and tooth movement Figure 9. (a) A screen with a rotation of 2 degrees within one step, a movement distance of 0.2 mm, and tooth movement planned in 23 steps. (b) If necessary, an attachment can be added to the tooth. planned in 23 steps. (b) If necessary, an attachment can be added to the tooth. 3. Results Of the 15 patients (11 males, 4 females, mean age: 22.6 ± 4.36), 5 patients (5 males, 0 females, mean age: 22.2 ± 1.33) received preoperative orthodontic treatment with clear aligners, and the remaining 10 patients (6 males, 4 females, mean age: 24.0 ± 7.86) received orthodontic treatment with traditional fixed appliances as a control group. Only one pa- tient in the clear aligner group underwent Le Fort I osteotomy and mandibular bilateral sagittal split osteotomy surgery, and the remaining 14 patients had only mandibular bi- lateral sagittal split osteotomy surgery. There was no significant difference between the two groups, although the preopera- tive orthodontic period was longer in those who received orthodontic treatment with clear aligners than those who received orthodontic treatment with traditional fixed appliances (e.g., braces) (Table 2). The number of extractions of premolars and the number of im- pacted teeth was also smaller in the group treated with clear aligners, but there was no significant difference between the two groups (Table 2). To evaluate postoperative stability, six measurement variables were compared be- tween the two groups, but no significant difference was found (Table 3). Table 2. Preoperative orthodontic period, number of premolar extraction teeth, and number of im- pacted teeth between clear aligner group and traditional fixed appliance (e.g., bracket) group. Clear Aligners (n = 5) Braces (n = 10) p-Value * Mean SD Mean SD Preoperative orthodontic treatment 11.6 3.01 15.4 7.86 0.206 period (month) Extracted premolar teeth (ea.) 0.4 0.8 1.6 1.50 0.206 Impacted teeth (ea.) 0 0 0.8 1.32 0.371 * Fisher’s exact test. If p-value < 0.05, there is a significant difference between the two groups. Table 3. Postoperative stability measurement between the clear aligner group and the traditional fixed appliance (e.g., bracket) group on the 2nd day and 6th month postoperatively. Clear Aligners (n = 5) Braces (n = 10) △T2-T1 p-Value * Mean SD Mean SD L1 to NB 0.29 0.75 0.07 1.46 0.690 Pog. to NB −0.26 1.03 −0.12 0.77 0.440 A-Pog. −0.52 1.51 0.41 1.74 0.310 AFC −2.18 1.70 −0.92 1.50 0.440 SN Vr. 2.68 1.31 2.00 4.90 1 0-Med. 2.21 2.47 3.74 7.98 0.768 Appl. Sci. 2021, 11, 11216 6 of 9 3. Results Of the 15 patients (11 males, 4 females, mean age: 22.6  4.36), 5 patients (5 males, 0 females, mean age: 22.2  1.33) received preoperative orthodontic treatment with clear aligners, and the remaining 10 patients (6 males, 4 females, mean age: 24.0 7.86) received orthodontic treatment with traditional fixed appliances as a control group. Only one patient in the clear aligner group underwent Le Fort I osteotomy and mandibular bilateral sagittal split osteotomy surgery, and the remaining 14 patients had only mandibular bilateral sagittal split osteotomy surgery. There was no significant difference between the two groups, although the preoperative orthodontic period was longer in those who received orthodontic treatment with clear aligners than those who received orthodontic treatment with traditional fixed appliances (e.g., braces) (Table 2). The number of extractions of premolars and the number of impacted teeth was also smaller in the group treated with clear aligners, but there was no significant difference between the two groups (Table 2). Table 2. Preoperative orthodontic period, number of premolar extraction teeth, and number of impacted teeth between clear aligner group and traditional fixed appliance (e.g., bracket) group. Clear Aligners (n = 5) Braces (n = 10) p-Value * Mean SD Mean SD Preoperative orthodontic 11.6 3.01 15.4 7.86 0.206 treatment period (month) Extracted premolar teeth (ea.) 0.4 0.8 1.6 1.50 0.206 Impacted teeth (ea.) 0 0 0.8 1.32 0.371 * Fisher ’s exact test. If p-value < 0.05, there is a significant difference between the two groups. To evaluate postoperative stability, six measurement variables were compared between the two groups, but no significant difference was found (Table 3). Table 3. Postoperative stability measurement between the clear aligner group and the traditional fixed appliance (e.g., bracket) group on the 2nd day and 6th month postoperatively. Clear Aligners (n = 5) Braces (n = 10) p-Value * 4T2-T1 Mean SD Mean SD L1 to NB 0.29 0.75 0.07 1.46 0.690 Pog. to NB 0.26 1.03 0.12 0.77 0.440 A-Pog. 0.52 1.51 0.41 1.74 0.310 AFC 2.18 1.70 0.92 1.50 0.440 SN Vr. 2.68 1.31 2.00 4.90 1 0-Med. 2.21 2.47 3.74 7.98 0.768 T1: 2nd day after surgery, T2: 6th month after surgery. * Mann—Whitney test. p-value < 0.05 indicates a significant difference between the two groups. 4. Discussion There have been many studies on stability after orthognathic surgery [7,8]. However, there are no studies to identify the characteristics of patients who underwent orthognathic surgery after preoperative orthodontic surgery with clear aligners. There have been few reports of patients who underwent orthognathic surgery with preoperative correction with clear aligners. For example, when searching for ““clear aligner$” and “orthognathic$”” in PubMed, there were only five papers. Among these studies, two [9,10] were on the use of a stent as a clear aligner during surgery, and one [11] was on the surgery-first technique. A similar search on PubMed for ““invisalign$” and “orthognathic$”” only yielded four papers. Appl. Sci. 2021, 11, 11216 7 of 9 According to the results of the study, the number of extracted premolars was fewer in the group that received preoperative orthodontic treatment with clear aligners compared to the group that had been corrected preoperatively with conventional orthodontic devices. There was no significant difference in the period of orthodontic treatment. Referring to Table 4, the average mandibular setback amount of the patients in the clear aligners group was 7.9 mm, which showed that preoperative orthodontic treatment with clear aligners was possible even during orthognathic surgery with a relatively large setback. Table 4. Information on five patients with clear aligners. Preoperative Extracted Orthodontic Impacted Amount of Surgical Sex Age Premolar Plate Removal Treatment Period Teeth (ea.) Movement Teeth (ea.) (Months) Vertical reduction (3.5 mm) Was performed 1 Male 24 8 0 0 Le Fort I osteotomy, 23 months Mn. setback BSSO after surgery. (Rt.: 10 mm, Lt.: 9 mm) Was performed Mn. setback BSSO 2 Male 20 11 0 0 5 months (Rt.: 12 mm, Lt.: 5 mm) after surgery. Was performed Mn. setback BSSO 3 Male 23 12 2 0 11 months (Rt.: 6 mm, Lt.: 1 mm) after surgery. Was performed Mn. setback BSSO 4 Male 22 10 0 0 4 months (Rt.: 9 mm, Lt.: 11 mm) after surgery. Was performed Mn. setback BSSO 5 Male 22 17 0 0 8 months (Rt.: 9 mm, Lt.: 7 mm) after surgery. (Mn.: mandible, BSSO: bilateral sagittal split osteotomy, Rt.: right, Lt.: left). For maxillomandibular fixation using elastics after orthognathic surgery in our hospi- tal, from immediately after surgery to one week after surgery, it is not possible to open the mouth at all while occluded with 4.6 mm (170.1 g) elastic. Up to one month, it is possible to open the mouth with a 9.5 mm (170.1 g) elastic. This protocol was equally applied to all patients participating in this study, and there were no differences between the clear aligner group and the traditional orthodontic device group in elastic guide postoperatively. Even though the clear aligner was developed in 1999, it has evolved considerably, and many patients are receiving orthodontic treatment using the clear aligner approach [3,12]. A systematic review on orthodontic treatment using clear aligners found no significant difference in stability and occlusal characteristics compared to conventional orthodontic appliances [13]. Orthodontic treatment with clear aligners has the following advantages, including aesthetics, patient convenience, reduction in the number of visits to the dental clinic, decreased chair time, removable device, convenience in oral hygiene management, saving time required for wire replacement or bracket installation, and ease of taking im- pressions [2,14]. In addition, the patient is well accustomed to maintaining the device after surgery because they have experience with the device. In addition, there is no interference from braces during surgery (Figure 10), so there is no hindrance during surgery, and there is no risk of the bracket falling off during surgery. Another advantage of orthodontic treatment using clear aligners is that the brackets physically interfere with tooth brushing, making oral hygiene management difficult, but clear aligners do not. These removable clear aligners can also reduce the incidence of white spot lesions on teeth [15]. In a similar vein, according to Sfondrini et al., there was no significant difference in periodontal and Appl. Sci. 2021, 11, x FOR PEER REVIEW 8 of 10 Even though the clear aligner was developed in 1999, it has evolved considerably, and many patients are receiving orthodontic treatment using the clear aligner approach [3,12]. A systematic review on orthodontic treatment using clear aligners found no signif- icant difference in stability and occlusal characteristics compared to conventional ortho- dontic appliances [13]. Orthodontic treatment with clear aligners has the following ad- vantages, including aesthetics, patient convenience, reduction in the number of visits to the dental clinic, decreased chair time, removable device, convenience in oral hygiene management, saving time required for wire replacement or bracket installation, and ease of taking impressions [2,14]. In addition, the patient is well accustomed to maintaining the device after surgery because they have experience with the device. In addition, there is no interference from braces during surgery (Figure 10), so there is no hindrance during surgery, and there is no risk of the bracket falling off during surgery. Another advantage of orthodontic treatment using clear aligners is that the brackets physically interfere with tooth brushing, making oral hygiene management difficult, but clear aligners do not. These removable clear aligners can also reduce the incidence of white spot lesions on teeth [15]. In a similar vein, according to Sfondrini et al., there was no significant difference in Appl. Sci. 2021, 11, 11216 8 of 9 periodontal and microbiological parameters in patients undergoing correction with a clear aligner for two months compared with patients who did not receive orthodontic treatment [16]. According to Kankam et al., there was no significant difference in postoperative microbiological parameters in patients undergoing correction with a clear aligner for two edema in orthodontic patients treated with clear aligners [17]. On the other hand, disad- months compared with patients who did not receive orthodontic treatment [16]. According vantages include the need to install a screw to anchor the elastics during surgery [18], and to Kankam et al., there was no significant difference in postoperative edema in orthodontic patients treated with clear aligners [17]. On the other hand, disadvantages include the need the patient’s cooperation during orthodontic treatment is important. According to a large to install a screw to anchor the elastics during surgery [18], and the patient’s cooperation cohort of clear aligner therapy patients, 45.5% of patients wore the aligner for 22 h or more during orthodontic treatment is important. According to a large cohort of clear aligner a day, while 25.7% wore it for less than 11 h [19]. Since orthodontic treatment is required therapy patients, 45.5% of patients wore the aligner for 22 h or more a day, while 25.7% after surgery [20], the dentist and the patient must communicate in order to cooperate wore it for less than 11 h [19]. Since orthodontic treatment is required after surgery [20], the dentist and the patient must communicate in order to cooperate with the patient, and with the patient, and sometimes the doctor must induce the patient to show better com- sometimes the doctor must induce the patient to show better compliance [21]. It must be pliance [21]. It must be replaced with the next device according to the requirements, and replaced with the next device according to the requirements, and there is a risk of losing there is a risk of losing the orthodontic device. Furthermore, braces may be attached dur- the orthodontic device. Furthermore, braces may be attached during the postoperative ing the postoperative orthodontic period. orthodontic period. (a) (b) Figure 10. Figure (a) In10. traoperative c (a) Intraoperative linica clinical l pictu pictur re of e orthognathic of orthognathic sur surgery patient with gery patient with clearclear aligners. aligners. This p This photo shows hoto shows th the e maxillomandibular fixation using wire as a final occlusion state after three mini screws were placed in each segment before maxillomandibular fixation using wire as a final occlusion state after three mini screws were placed in each segment before fixing the miniplate to the mandible. There are no fixed braces or metal wires attached to the teeth. (b) Clinical pictures of fixing the miniplate to the mandible. There are no fixed braces or metal wires attached to the teeth. (b) Clinical pictures of patients who received orthodontic treatment with brackets. The photographing method is the same as in (a). patients who received orthodontic treatment with brackets. The photographing method is the same as in (a). When asked about the expected disadvantages of orthognathic surgery using clear When asked about the expected disadvantages of orthognathic surgery using clear aligners, surgeons expect the preoperative period to be long, that the extraction cases will be difficult, with the possibility of using conventional fixed appliances for postoperative aligners, surgeons expect the preoperative period to be long, that the extraction cases will correction. However, in this study, there were no significant differences in the preoperative be difficult, with the possibility of using conventional fixed appliances for postoperative correction period in the clear aligner group. There was a case with tooth extraction and correction. However, in this study, there were no significant differences in the preopera- where no braces were used for postoperative correction, just clear aligners. As time goes tive correction period in the clear aligner group. There was a case with tooth extraction by, orthodontists will develop orthodontic treatments using clear aligners, overcoming the limitations of orthodontics. It is thought that almost all the shortcomings can be overcome and where no braces were used for postoperative correction, just clear aligners. As time even during orthognathic surgery accompanying this clear aligner approach. For future studies, it will be necessary to study greater numbers of patients regarding the applicability of transparent aligners to complex preoperative orthodontic treatment. 5. Conclusions Even when using preoperative orthodontic treatment with clear aligners, there was no difficulty in combining clear aligners with orthognathic surgery cases. It is thought that similar results can be obtained using the combination of clear aligners with orthognathic surgery as compared with conventional surgery. The sample size of this preliminary study was, however, limited; thus, further studies with greater numbers of cases are needed to define the role of orthognathic surgery using clear aligners. Appl. Sci. 2021, 11, 11216 9 of 9 Author Contributions: C.M. and E.C.K. contributed to the acquisition, analysis, and interpretation of data for the work, and Y.-D.K., to the conception and design of the work, and to the analysis and interpretation. G.K.S. contributed to the interpretation of data and linguistic aspects of the manuscript. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Institutional Review Board Statement: The study was conducted according to the guidelines of the Declaration of Helsinki, and approved by the Institutional Review Board (or Ethics Committee) of Pusan National University Dental Hospital (PNUDH-2021-0238, 17-09-21). Informed Consent Statement: Not applicable. Conflicts of Interest: The authors declare no conflict of interest. References 1. Kesling, H.D. Coordinating the predetermined pattern and tooth positioner with conventional treatment. Am. J. Orthod. Oral Surg. 1946, 32, 285–293. [CrossRef] 2. Rosvall, M.D.; Fields, H.W.; Ziuchkovski, J.; Rosenstiel, S.F.; Johnston, W.M. Attractiveness, acceptability, and value of orthodontic appliances. Am. J. Orthod. Dentofacial Orthop. 2009, 135, 276 e271-212; discussion 276–277. [CrossRef] [PubMed] 3. Hennessy, J.; Al-Awadhi, E.A. Clear aligners generations and orthodontic tooth movement. J. Orthod. 2016, 43, 68–76. [CrossRef] [PubMed] 4. 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Journal

Applied SciencesMultidisciplinary Digital Publishing Institute

Published: Nov 25, 2021

Keywords: orthognathic surgery; clear aligner; Invisalign; stability; preoperative orthodontic treatment; CAD-CAM; 3D printer

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