Displacements prediction from 3D finite element model of maxillary protraction with and without rapid maxillary expansion in a patient with unilateral cleft palate and alveolus
© Zhang et al. 2015
Received: 18 November 2014
Accepted: 10 August 2015
Published: 19 August 2015
Both maxillary protraction and rapid expansion are recommended for patients with cleft palate and alveolus. The aim of the study is to establish a three-dimensional finite element model of the craniomaxillary complex with unilateral cleft palate and alveolus to simulate maxillary protraction with and without rapid maxillary expansion. The study also investigates the deformation of the craniomaxillary complex after applied orthopaedic forces in different directions.
A three dimensional finite element model of 1,277,568 hexahedral elements (C3D8) and 1,801,945 nodes was established based upon CT scan of a patient with unilateral cleft palate and alveolus on the right side in this study. A force of 4.9 N per side was directed on the anatomic height of contour on the buccal side of the first molar. The angles between the force vector and occlusal plane were −30°, −20°, −10°, 0°, 10°, 20°, and 30°. A force of 2.45 N on each loading point was directed on the anatomic height of contour on the lingual side of the first premolar and the first molar to simulate the expansion of the palate.
The craniomaxillary complex displaced forward under any of the loading conditions. The sagittal and vertical displacement of the craniomaxillary complex reached their peak at the protraction degree of −10° forward and downward to the occlusal plane. There were larger sagittal displacements when the maxilla was protracted forward with maxillary expansion. The palatal plane rotated counterclockwise under any of the loading conditions. Being protracted without expansion, the dental arch was constricted. When supplemented with maxillary expansion, the width of the dental arch increased. Transverse deformation of the dental arch on affected side was different from that on unaffected side.
Protraction force alone led the craniomaxillary complex moved forward and counterclockwise, accompanied with lateral constrain on the dental arch. Additional rapid maxillary expansion resulted in a more positive reaction including both larger sagittal displacement and the width of the dental arch increase.
Cleft palate and alveolus are common congenital anomalies that are receiving much attention from stomatologists [1–4]. Children who have a cleft palate usually need surgery at around 6 months of age to repair the cleft and they often display different degrees of midfacial hypoplasia after surgery [5–7]. As patients grow, occlusion, speech, breathing, swallowing and aesthetics, among other things, may be affected if the patient did not receive appropriate treatment for long periods of time [8–10]. Orthodontists often provide maxillary protraction for children in the growing and developing periods that suffer from cleft palate and alveolus to stimulate maxillary [11, 12]. Some investigations have manifested skeletal, alveolar and dental effects from short-term maxillary protraction. Forward displacements of the maxilla, clockwise rotation of the mandible, protrusion of the upper incisors and retrusion of the lower incisors are seen [13, 14], but the skeletal effects of maxillary protraction remain controversial. There are no significant skeletal changes in some long-term follow-ups [13, 15].
In addition to the maxillary deficiency of patients with cleft palate and alveolus in the sagittal direction, bone defect and the injury of the surgery causes deficiency in the transverse direction [16–21]. Maxillary protraction therapy is commonly supplemented with rapid maxillary expansion for these patients [22–25]. Some evidence in the literature suggests that maxillary expansion alone can be beneficial in the treatment of certain types of Class III malocclusion [26, 27]. These investigations have also shown that the direction of the force is critical in controlling the rotation of the maxilla. Nanda and Hickory noted , based on the functional matrix theory, that the maxillary growth pattern was similar to the effect of maxillary protraction, and the displacement pattern of the maxillary complex can be altered by the direction of the traction force.
Finite element analysis is a mathematical method in which the shape of complex geometric objects and their physical properties are computer constructed. Interactions of various components of the model are then calculated for stress, strain, and deformation. Among which, the displacement changes of the objects is the most intuitive evaluation indicators. Three-dimensional (3D) finite element method was first used in orthodontics by Thresher and Saito  to study stresses on human teeth. Ever since, this method has proved effective in many dental fields such as simulation of tooth movement and optimization of orthodontic mechanics.
The aim of the study is to establish a 3D finite element model of the craniomaxillary complex with unilateral cleft palate and alveolus to simulate maxillary protraction with and without rapid maxillary expansion. The study also investigates the displacement changes of the craniomaxillary complex after applied orthopedic forces in different directions.
Patient data and craniomaxillary complex reconstruction
Ethical approval of this research was obtained from the ethics committee of China Medical University. The scan data was obtained from a 13-year-old boy with unilateral cleft palate and alveolus on the right side. Written informed consent was obtained from his parents. Spiral computed tomography images (SomatonLightspeed/64 plus; GE Healthcare, Waukesha, WI, USA) of the craniofacial complex region (0.5-mm layer; voxel size, 0.44 × 0.44 × 0.5 mm3) were obtained, saved as digital imaging and communications in medicine (DICOM) files, and then imported into Mimics® software (Materialise, Leuven, Belgium) for model reconstruction. A Hounsfield unit (HU) with a value range of 226–3071 was used to identify and distinguish craniomaxillary bone from other tissues. The craniomaxillary complex was segmented from the skull by using the “erase” function in the software on each slice of the data set.
Computational grid of craniomaxillary complex
The STL file was imported into MSC. Marc® (MSC Software Corporation, Santa Ana, CA, USA), which was used to generate a volume mesh from the 3D geometry of the craniomaxillary complex. The craniomaxillary complex was meshed into 1,277,568 hexahedral elements (C3D8) and 1,801,945 nodes (Fig. 1).
Material properties, boundary and loading conditions
Young’s modulus (N/mm2)
1.37 × 104
7.9 × 103
2.0 × 104
To measure the amount of displacement of the craniomaxillary complex, representative nodes in the frontal, sagittal and transverse planes were selected. First, the amount of sagittal displacement of the craniomaxillary complex, which was generally used when comparing the effect of an orthopaedic appliance following maxillary protraction [34, 35] was measured at eight marker nodes in the sagittal plane. These included four dental marker nodes and four skeletal marker nodes. Among these nodes, subspinale (A), upper incisor (U1), left first molar’s palatal cusp tip (ML1) and right first molar’s palatal cusp tip (MR1) represent the characteristics of the dentition and the alveolar bone, and nasion (N), the most concave part of the nasal bone (Cn), inferior part of the nasal bone (In) and anterior nasal spine (ANS) represent the skeletal characteristics of the craniomaxillary complex. The detailed marker location was shown in Fig. 2. Second, the vertical displacement of the complex was analyzed by measuring the vertical displacement of ANS and posterior nasal spine (PNS) in the palatal plane. Lastly, the width of the dental arch was measured. Anterior arch width was analyzed by measuring the distance between the cusps of the canine. Width of the medial dental arch was analyzed by measuring the distance between the central fossa of the first premolar. The distance between the central fossa of the fist molar was measured to analyze the width of the posterior dental arch (Fig. 3).
The sagittal displacements of 4 dental marker nodes at different protraction degrees
The sagittal displacement of 4 skeletal marker nodes at different protraction degrees
Figure 6 also shows the sagittal displacements of the dental marker nodes and the skeletal marker nodes on the anterior of the craniomaxillary complex. At the protraction degree of −10° forward and downward to the occlusal plane, the sagittal displacement of the maxilla reached the maximum. At the same time, the sagittal displacements of the selected nodes increased gradually from superior to inferior of the craniomaxillary complex.
The vertical displacement of the palatal plane at different protraction degrees
The changes of the dental arch width
Deformation of the dental arch width under different protraction degrees
Anterior arch (mm)
Medial arch (mm)
Posterior arch (mm)
In cleft palate and alveolus patients, the mandible is usually unaffected by the cleft and grows normally, however, the maxilla often does not grow as far forward and downward as the non-cleft child, resulting in a short maxilla and a Class III malocclusion . The scar contracture that occurs from the hard palate repair is thought to distort the growth of the maxilla resulting in maxillary hypoplasia [16–21]. Maxillary protraction is recommended for cleft palate and alveolus patients with skeletal maxillary deficiency [5, 28, 37, 38]. The principle of maxillary protraction is to apply tensile force on the craniomaxillary sutures and thereby stimulate bone apposition in the suture areas. Numerous animal experiments have shown that a maxillary protraction appliance with controlled force is effective on anterior displacement and bone formation at the cartilaginous suture area of the maxillary complex [39, 40].
Maxillary deficiency in patients with cleft palate and alveolus occurred in both the sagittal and the transverse direction due to the bone defect and the injury of the surgery. Therefore, maxillary protraction therapy is often supplemented with maxillary expansion to correct the insufficient maxillary arch width [16, 41]. Rapid maxillary expansion is typically used in young patient and has been shown to help correct the sagittal defect of the maxilla [42, 43]. Haas [44, 45] reported the orthopedic effect of rapid maxillary expansion, which produced a forward and downward tipping of the maxilla with concomitant downward and backward mandibular rotation. These orthopedic changes facilitated the correction of a mild deficiency of the midface. Turley  stated that palatal expansion “disarticulates” the maxilla and initiates cellular responses in these circumaxillary sutures allowing a more positive reaction to protraction forces. Melsen  confirmed these increased cellular responses to rapid maxillary expansion. The displacement of various craniofacial structures was considerably more after maxillary protraction with maxillary expansion. This agrees with Yu et al. , who showed greater displacement in the frontal, vertical and lateral directions with maxillary expansion when compared with no maxillary expansion. In this study, both with and without rapid maxillary expansion, the maxilla moved forward under any of the loading conditions. The sagittal displacement of the maxilla was greater with the help of maxillary expansion. At the protraction degree of −10° forward and downward to the occlusal plane, the sagittal displacement of the maxilla reached the maximum. At the same time, the sagittal displacements of the selected nodes increased gradually from superior to inferior of the craniomaxillary complex. Therefore, the protraction of the maxilla causes more dental than skeletal changes. For patient with flared upper incisors, the difference in the dental and skeletal displacement will affect the protrusion of the upper lip.
It is necessary to control vertical growth during maxillary protraction in patients with cleft palate and alveolus, which has been reported as difficult. Lower anterior facial height may decrease, remain the same, or even increase during maxillary protraction [48–56]. Possible changes in lower anterior facial height during maxillary protraction under forces from various directions may play an important role in the prognosis of patients with a Class III malocclusion and maxillary deficiency [57–59]. Biomechanical studies were performed to explore the relationship between the direction of applied force and the displacement of the craniomaxillary complex by using the finite element method, which is a helpful and reliable mathematical instrument in orthodontics [58–60].
Merwin et al.  and Ngan et al.  reported that the counterclockwise rotational tendency of the maxilla was the reason for contraindication of maxillary protraction therapy in Class III patients with maxillary deficiency and open bite. In this study, regardless of whether maxillary protraction was supplemented with or without rapid maxillary expansion, the palatal plane rotated counterclockwise in all loading conditions. The palatal plane rotational amplitude of the expansion group was larger than that of the non-expansion group at the same protraction degree. Therefore, maxillary protraction, especially supplemented with rapid maxillary expansion, should be used with caution for cleft palate and alveolus patients with maxillary deficiency and open bite.
The rotational amplitude peaked at −10° protraction and decreased gradually on both sides. The sagittal displacement of the anterior of craniomaxillary complex also peaked at −10° protraction. The above results show that the maximum value of the forward displacement and the counterclockwise of the palatal plane can be obtained at the protraction degree of −10°. Therefore, a protraction direction of −10° is recommended for patients with maxillary deficiency and deep bite. In addition, the supplement with rapid maxillary expansion can greatly improve the above effect.
Bone graft of the alveolus cleft would be obtained in patients during periods of growth and development when the canines are erupting . Therefore, the width alternation of the dental arch by the protraction of the maxilla is one of the main concerns of orthodontics and oral surgeons.
Lei et al.  found that the dental arch of cleft lip and palate patient tended to be constricted after maxillary protraction. As it has been shown in Table 2, the dental arch was constricted after maxillary protraction. With the supplement of maxillary expansion, the width of the dental arch increased. As it has been shown in this study, the transverse deformation of the affected side was different from that of the unaffected side. The dental arch was constricted by the protraction of the maxilla. With the supplement of maxillary expansion, the dental arch on the unaffected side was expanded while the dental arch on the unaffected side was still constricted. But, the expansion of the dental arch would greatly reduce the tendency of constriction on the affected side. With the increase of protraction degree, the tendency of constriction increased. So, an asymmetric expansion would be suitable for patients with unilateral cleft palate and alveolus. The use of a counterclockwise protraction force increases its efficiency. Lei et al.  found that the tendency for constriction at the anterior region of the dental arch was one of the most important side effects for maxillary protraction. It has also been found in this study, the deformation of the dental arch increased gradually from posterior to anterior at the same protraction degree. In all the situations, alternation of the dental arch width was more sensitive in the anterior part of the dental arch than the posterior part of the dental arch.
The anatomy of the midface is complex, as the maxilla articulates with ten other facial bones and with the anterior and middle cranial base. Therefore, a refined finite element model is needed for precise and realistic simulation. Although tetrahedral elements have commonly been used in biomechanical applications [58, 64, 65] because automated meshing techniques are available, hexahedral elements offer attractive numerical properties relative to tetrahedrons [66, 67]. Benzley et al. compared the accuracy of the hexahedral meshes with the tetrahedral meshes in their study, found that linear hexahedrons could generally deform in a lower strain energy state, thus making them more accurate than linear tetrahedrons in numerous situations . Xiulin Yan et al. reported that tetrahedral elements are not as accuracy and reliable as hexahedral elements for finite element models with complicated geometry . In this study, an element model consisting of 1,277,568 hexahedral elements (C3D8) and 1,801,945 nodes individually was established, which greatly increase the accuracy of the model. The results of this study may differ from data obtained from in vivo investigations. Additional biochemical and clinical studies, as well as animal experiments, are needed to understand the effects of maxillary protraction with and without the use of rapid maxillary expansion in more detail. Progressive research with clinical identification of dynamic modeling is also required to investigate the effects of protraction, both with and without the use of maxillary expansion on the facial musculature and other soft tissues.
The craniomaxillary complex moved forward and counterclockwise under a protraction force −30° to 30° forward and downward to the occlusal plane.
Rapid maxillary expansion provided a more positive reaction to maxillary protraction. Greater deformation was obtained by maxillary expansion when compared with no maxillary expansion.
At the protraction degree of −10° forward and downward to the occlusal plane, sagittal deformation of the maxilla reached the maximum. The palatal plane rotated counterclockwise under any of the loading conditions, and the rotational amplitude peaked at −10° protraction.
At the same protraction degree, sagittal deformation of the maxilla increased gradually from superior to inferior.
When maxilla was protracted forward without expansion, the dental arch narrowed down with the increase of the protraction degree. The transverse deformation of the arch width increased from posterior to anterior. With the supplement of rapid maxillary expansion, the dental arch was expanded. The transverse deformation of the arch width decreased gradually with the increase of the protraction degree.
The dental arch on the unaffected side was constricted by the protraction of the maxilla and would be expanded by maxillary expansion. But, the dental arch on the affected side was constricted in both of the situations. With the increased of the protraction degree, the constricted displacement increased gradually.
Maxillary protraction, especially supplemented with rapid maxillary expansion is recommended for patients with maxillary deficiency.
A protraction direction of −10° is recommended for patients with maxillary deficiency and deep bite. In addition, the supplement with rapid maxillary expansion can greatly improve the above effect.
Asymmetric expansion is recommended for patients with unilateral cleft palate and alveolus. The use of a counterclockwise protraction force may enhance its efficiency.
DZ carried out the design of the study, participated in the data analysis and drafted the manuscript. LZ carried out the establishment of the 3D-FEM models. QW participated in the data analysis and helped to draft the manuscript. LL conceived of the study, participated in its design and helped to draft the manuscript. JM participated in the design of the study and helped to draft the manuscript. All authors read and approved the final manuscript.
This study was financially supported by funds from Scientific Research Project of Shenyang (F11-262-9-42), Scientific Research Project of Liaoning Province (No. 2013021005) and Public Welfare Fund Project of Liaoning Province (No. 2012002015). We are grateful to professor Jun Xiao (School of Information Science, Northeastern University, Shenyang, China) for the technological support in conducting this study. We also thank professor Yang Zhang (School of Stomatology, China Medical University, Shenyang, China) for her contribution in polishing the manuscript.
Compliance with ethical guidelines
Competing interests The authors declare that they have no competing interests.
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
- Lei Ruoh-Lih, Chen Huey-Shys, Huang Bao-yuan, Chen Yueh Chin, Chen Philip Kou-Ting, Lee Huei-Ying, Chang Chi-Wen, Chih-Lung Wu. Population-based study of birth prevalence and factors associated with cleft lip and/or palate in Taiwan 2002-2009. PLoS One. 2013;8:e58690.View ArticleGoogle Scholar
- Kumari P, Sk Roy, Roy ID, Kumar P, Datana S, Rahman S. Stability of cleft maxilla in Le Fort I maxillary advancement. Ann Maxillofac Surg. 2013;3:139–43.View ArticleGoogle Scholar
- Scopelliti D, Fatone FM, Cipriani O, Papi P. Simultaneous options for cleft secondary deformities. Ann Maxillofac Surg. 2013;3:173–7.View ArticleGoogle Scholar
- Freitas JA, Garib DG, Oliveira TM, Lauris RC, Almeida AL, Neves LT. Rehabilitative treatment of cleft lip and palate: experience of the hospital for rehabilitation of craniofacial anomalies/USP—part 2: pediatric dentistry and orthodontics. J Appl Oral Sci. 2012;20:268–81.View ArticleGoogle Scholar
- Ross RB. Treatment variables affecting facial growth in complete unilateral cleft lip and palate. Cleft Palate J. 1987;24:5–77.Google Scholar
- Williams AC, Bearn D, Mildinhall S, Murphy T, Sell D, Shaw WC, et al. Cleft lip and palate care in the United Kingdom—the clinical standards advisory group study. Part 2: dentofacial outcomes and patient satisfaction. Cleft Palate Craniofac J. 2001;38:24–9.View ArticleGoogle Scholar
- Meazzini MC, Basile V, Mazzoleni F, Bozzetti A, Brusati R. Long-term follow-up of large maxillary advancements with distraction osteogenesis in growing and non-growing cleft lip and palate patients. J Plast Reconstr Aesthet Surg. 2015;68:79–86.View ArticleGoogle Scholar
- Kuijpers MAR, Chiu Y-T, Nada RM, Carels CEL, Fudalej PS. Three-dimensional imaging methods for quantitative analysis of facial soft tissues and skeletal morphology in patients with orofacial clefts: a systematic review. PLoS One. 2014;9:e93442.View ArticleGoogle Scholar
- Antonarakis GS, Patel RN, Tompson B. Oral health-related quality of life in non-syndromic cleft lip and/or palate patients: a systematic review. Commun Dent Health. 2013;30:189–95.Google Scholar
- EI-Kassaby MA, Abdelrahman NI, Abbass IT. Premaxillary characteristics in complete bilateral cleft lip and palate: a predictor for treatment outcome. Ann Maxillofac Surg. 2013;3:11–9.View ArticleGoogle Scholar
- Tindlund RS. Skeletal response to maxillary protraction in patients with cleft lip and palate before age 10 years. Cleft Palate Craniofac J. 1994;31:295–308.View ArticleGoogle Scholar
- Manosudprasit M, Wangsrimongkol T, Chowchuen B, Somsuk T. Growth modification in unilateral cleft lip and palate patients with face mask. J Med Assoc Thail. 2012;95:42–8.Google Scholar
- Tindlund RS. Orthopedic protraction of the midface in the deciduous dentition. Results covering 3 years out of treatment. J Craniomaxillofac Surg. 1989;17:17–9.View ArticleGoogle Scholar
- Ranta R. Orthodontic treatment in adults with cleft lip and palate. J Craniomaxillofac Surg. 1989;17:42–4.View ArticleGoogle Scholar
- So LL. Effects of reverse headgear treatment on sagittal correction in girls born with unilateral complete cleft lip and cleft palate-skeletal and dental changes. Am J Orthod Dentofacial Orthop. 1996;109:140–7.View ArticleGoogle Scholar
- Yen SL. Protocols for late maxillary protraction in cleft lip and palate patients at childrens hospital Los Angeles. Semin Orthod. 2011;17:138–48.View ArticleGoogle Scholar
- Arosarena OA. Cleft lip and palate. Otolaryngol Clin N Am. 2007;40:27–60.View ArticleGoogle Scholar
- Liao YF, Mars M. Long-term effects of clefts on craniofacial morphology in patients with unilateral cleft lip and palate. Cleft Palate Craniofac J. 2005;42:601–9.View ArticleGoogle Scholar
- Liao YF, Mars M. Long-term effects of palate repair on craniofacial morphology in patients with unilateral cleft lip and palate. Cleft Palate Craniofac J. 2005;42:594–600.View ArticleGoogle Scholar
- Liao YF, Mars M. Long-term effects of lip repair on dentofacial morphology in patients with unilateral cleft lip and palate. Cleft Palate Craniofac J. 2005;42:526–32.View ArticleGoogle Scholar
- Mars M, Houston WJB. A preliminary study of facial growth and morphology in unoperated male unilateral cleft lip and palate subjects over 13 years of age. Cleft Palate Craniofac J. 1990;27:7–10.View ArticleGoogle Scholar
- Chen Z, Pan X, Shao Q, Chen Z. Biomechanical effects on maxillary protraction of the craniofacial skeleton with cleft lip and palate after alveolar bone graft. J Craniofac Surg. 2013;24:446–53.View ArticleGoogle Scholar
- da Luz Vieira G, de Menezes LM, de Lima EM, Rizzatto S. Dentoskeletal effects of maxillary protraction in cleft patients with repetitive weekly protocol of alternate rapid maxillary expansions and constrictions. Cleft Palate Craniofac J. 2009;46:391–8.View ArticleGoogle Scholar
- Kawakami M, Yagi T, Takada K. Maxillary expansion and protraction in correction of midface retrusion in a complete unilateral cleft lip and palate patient. Angle Orthod. 2002;72:355–61.Google Scholar
- Liou EJ, Tsai WC. A new protocol for maxillary protraction in cleft patients: repetitive weekly protocol of alternate rapid maxillary expansions and constrictions. Cleft Palate Craniofac J. 2005;42:121–7.View ArticleGoogle Scholar
- Tindlund RS, Rygh P, Bøe OE. Intercanine widening and sagittal effect of maxillary transverse expansion I patients with cleft lip and palate during the deciduous and mixed dentitions. Cleft Palate Craniofac J. 1993;30:195–207.View ArticleGoogle Scholar
- Tindlund RS, Rygh P, Bøe OE. Orthopedic protraction of the upper jaw in cleft lip and palate patients during the deciduous and mixed dentition periods in comparison with normal growth and development. Craniofac J. 1993;30:182–94.View ArticleGoogle Scholar
- Nanda R, Hickory W. Zygomaticomaxillary structure adaptations incident to anteriorly directed forces in rhesus monkeys. Angle Orthod. 1984;54:199–210.Google Scholar
- Thresher RW, Saito GE. The stress analysis of human teeth. J Biomech. 1973;6:443–9.View ArticleGoogle Scholar
- Iseri H, Tekkaya AE, Oztan O, BIlgic S. Biomechanical effects of rapid maxillary expansion on the craniofacial skeleton, studied by the finite element method. Eur J Orthod. 1998;20:347–56.View ArticleGoogle Scholar
- Jafari A, Shetty KS, Kumar M. Study of stress distribution and displacement of various craniofacial structures following application of transverse orthopedic forces- a three-dimensional FEM study. Angle Orthod. 2003;73:12–20.Google Scholar
- Pan X, Qian Y, Yu J, Wang D, Tang Y, Shen G. Biomechanical effects of rapid palatal expansion on the craniofacial skeleton with cleft palate: a three-dimensional finite element analysis. Cleft Palate Craniofac J. 2007;44:149–54.View ArticleGoogle Scholar
- Lee NK, Baek SH. Stress and displacement between maxillary protraction with miniplates placed at the infrazygomatic crest and the lateral nasal wall: a 3-dimensional finite element analysis. Am J Orthod Dentofac Orthop. 2012;141:345–51.View ArticleGoogle Scholar
- Yan Xiulin, He Weijun, Lin Tao, Liu Jun, Bai Xiaofeng, Yan Guangqi, Li Lu. Three-dimensional finite element analysis of the craniomaxillary complex during maxillary protraction with bone anchorage VS conventional dental anchorage. Am J Orthod Dentofac Orthop. 2013;143:197–205.View ArticleGoogle Scholar
- Yu Hyung S, Baik Hyoung S, Sung Sang J, Kim Kee D, Cho Young S. Three-dimensional finite element analysis of maxillary protraction with and without rapid palatal expansion. Eur J Orthod. 2007;29:118–25.View ArticleGoogle Scholar
- Vargervik K. Growth characteristics of the premaxilla and orthodontic treatment principles in bilateral cleft lip and palate. Cleft Palate Craniofac J. 1983;20:289–302.Google Scholar
- Buschang PH, Porter C, Genecov E, Genecov D, Sayler KE. Face mask therapy of preadolescents with unilateral cleft lip and palate. Angle Orthod. 1995;64:145–50.Google Scholar
- Nanda R. Biomechanical and clinical considerations of a modified protraction headgear. Am J Orthod. 1980;78:125–39.View ArticleGoogle Scholar
- Dellinger EL. A preliminary study of anterior maxillary displacement. Am J Orthod. 1973;63:509–16.View ArticleGoogle Scholar
- Kambara T. Dentofacial changes produced by extraoral forward force in the Macaca irus. Am J Orthod. 1977;71:249–76.View ArticleGoogle Scholar
- Choi YK, Park SB, Kim YI, Son WS. Three-dimensional evaluation of midfacial asymmetry in patients with nonsyndromic unilaterial cleft lip and palate by cone-beam computed tomography. Korean J Orthod. 2013;43:113–9.View ArticleGoogle Scholar
- Chen ZX, Pan XG, Chen ZQ. Maxillary protraction with and without maxillary expansion on unilateral cleft lip and palate model: a finite element analysis. Shanghai Kou Qiang Yi Xue. 2012;21:287–93.MathSciNetGoogle Scholar
- Tindlund RS, Rygh P. Soft-tissue profile changes during widening and protraction of the maxilla in patients with cleft lip and palate compared with normal growth and development. Cleft Palate Craniofac J. 1993;30:454–68.View ArticleGoogle Scholar
- Haas AJ. Palatal expansion: just the beginning of dentofacial orthopedic. Am J Orthod. 1970;57:219–55.View ArticleGoogle Scholar
- Haas AJ. Treatment of maxillary deficiency by opening the midpalatal suture. Angle Orthod. 1965;65:200–17.Google Scholar
- Turley RK. Orthopedic correction of Class III malocclusion with palatal expansion and custom protraction headgear. J Clin Orthod. 1988;22:314–25.Google Scholar
- Melsen B. Palatal growth studied on human autopsy material. A histologic microradiographic study. Am J Orthod. 1975;68:42–54.View ArticleGoogle Scholar
- Cozza P, Baccetti T, Mucedero M, Pavoni C, Franchi L. Treatment and posttreatment effects of a facial mask combined with a biteblock appliance in Class III malocclusion. Am J Orthod Dentofac Orthop. 2010;138:300–10.View ArticleGoogle Scholar
- Lee JW, Park KH, Kim SH, Park YG, Kim SJ. Correlation between skeletal changes by maxillary protraction and upper airway dimensions. Angle Orthod. 2011;81:426–32.View ArticleGoogle Scholar
- Baccetti T, McGill JS, Franchi L, McNamara JA, Tollaro I. Skeletal effects of early treatment of Class III malocclusion with maxillary expansion and face-mask therapy. Am J Orthod Dentofac Orthop. 1998;113:333–43.View ArticleGoogle Scholar
- Altug Z, Arslan AD. Skeletal and dental effects of a mini maxillary protraction appliance. Angle Orthod. 2006;76:360–8.Google Scholar
- Enacar A, Giray B, Pehlivanoglu M, Iplikcioglu H. Facemask therapy with rigid anchorage in a patient with maxillary hypoplasia and severe oligodontia. Am J Orthod Dentofac Orthop. 2003;123:571–7.View ArticleGoogle Scholar
- De Clerck HJ, Cevidanes LH, Baccetti T. Dentofacial effects of bone-anchored maxillary protraction: a controlled study on consecutively treated Class III patients. Am J Orthod Dentofac Orthop. 2010;138:577–81.View ArticleGoogle Scholar
- Baek SH, Kim KW, Choi JY. New treatment modality for maxillary hypoplasia in cleft patients. Angle Orhtod. 2010;80:783–91.View ArticleGoogle Scholar
- Lee DY, Kim ES, Lim YK. Skeletal changes of maxillary protraction without rapid maxillary expansion: a comparison of the primary and mixed dentition. Angel Orthod. 2010;80:692–8.View ArticleGoogle Scholar
- Cha BK, Choi DS, Ngan P, Jost-brinkmann PG, Kim SM, Jang IS. Maxillary protraction with miniplates providing skeletal anchorage in a growing Class III patient. Am J Orthod Dentofac Orthop. 2011;139:99–112.View ArticleGoogle Scholar
- Itoh T, Chaconas SJ, Caputo AA, Matysa J. Photoelastic effects of maxillary protraction on the craniofacial complex. Am J Orthod. 1985;88:117–24.View ArticleGoogle Scholar
- Miyasaka-Hiraga J, Tanne K, Nakamura S. Finite element analysis for stress in the craniofacial sutures produced by maxillary protraction force applied at the upper canines. Br J Orthod. 1994;21:343–8.View ArticleGoogle Scholar
- Gautam P, Valiathan A, Adhikari R. Skeletal response to maxillary protraction with and without maxillary expansion: a finite element study. Am J Orthod Dentofac Orthop. 2009;135:723–8.View ArticleGoogle Scholar
- Merwin D, Ngan P, Hagg U, Yiu C, Wei SHY. Timing for effective application of anteriorly directed orthopedic force to the maxilla. Am J Orhod Dentofac Orthop. 1997;112:292–9.View ArticleGoogle Scholar
- Ngan PW, Hagg U, Yiu C, Wei SHY. Treatment response and long-term dentofacial adaptations to maxillary expansion and protraction. Semin Orthod. 1997;3:255–6.View ArticleGoogle Scholar
- Freitas JA, Garib DG, Trindade-Suedam IK, et al. Rehabilitative treatment of cleft lip and palate: experience of the Hospital for Rehabilitation of Craniofacial Anomalies-USP—Part 3: oral and maxillofacial surgery. J Appl Oral Sci. 2012;20:673–9.View ArticleGoogle Scholar
- Lei YH, Jian XC, Ren BQ. Three-dimensional finite element model of maxillary protraction of the maxilla in patients with cleft lip and palate. Zhong Nan Da Xue Xue Bao Yi Xue Ban. 2008;33:898–905.Google Scholar
- Holberg C, Rudzki-Janson I. Stresses at the cranial base induced by rapid maxillary expansion. Angel Orthod. 2007;76:543–50.Google Scholar
- Boryor A, Geiger M, Hohmann A, Wunderlich A, Sander C, Martin Sander F, Sander FG. Stress distribution and displacement analysis during an intermaxillary disjunction—a three-dimensional FEM study of a human skull. J Biomech. 2008;41:376–82.View ArticleGoogle Scholar
- Viceconti M, Bellingeri L, Cristofilini L, Toni A. A comparative study on different methods of automatic mesh generation of human femurs. Med Eng Phys. 1998;20:1–10.View ArticleGoogle Scholar
- Ji S, Ford JC, Greenwald RM, Bechwith JG, Oaulsen KD, Flashman LA, McAllister TW. Automated subject-specific, hexahedral mesh generation via image registration. Finite Elem Anal Des. 2011;47:1178–85.View ArticleGoogle Scholar
- Benzley SE, Perry E, Merkley K, Clark B. A comparison of all hexahedral and all tetrahedral finite element meshes for elastic and elastic-plastic analysis. In: Proceedings of the 4th International Meshing Roundtable; 1995. pp. 179–92.Google Scholar