Use of Three-Dimensional Medical Modeling Methods for Precise ...
Use of Three-Dimensional MedicalModeling Methods for Precise Planningof Orthognathic SurgeryMehmet Emin Mavili, MD,* Halil Ibrahim Canter, MD,* Banu Saglam-Aydinatay, DDS, PhD,1Soner Kamaci, DDS,1 Ilken Kocadereli, DDS, PhD1Ankara, TurkeyStereolithographic (medical rapid prototyping) uated on models preoperatively. The same surgeonbiomodeling allows three-dimensional computed had a role in both model cutting preoperatively andtomography to be used to generate solid plastic as an instructor preoperatively. The same bonyreplicas of anatomic structures. Reports in the relation was observed both in preoperativeliterature suggest that such biomodels may have a models and in the perioperative surgical field inuse in maxillofacial surgery, craniofacial surgery, all patients. Condylar malpositioning was notorthopedics, neurosurgery, otology, vascular, and observed in any of the patients. Studying pre-nasal research. A prospective trial to assess the operative planned movements of osteotomizedusefulness of biomodeling in orthognathic surgery bone segments and observing relations of osteoto-has been performed. In 12 patients with mandibu- mized segments of mandibula and maxilla inlar prognathism and/or maxillary retrusion, in orthognathic surgery increased the intraoperativeaddition to routine preoperative cephalometric accuracy. Limitations of this technology wereanalysis, preoperative high-resolution (cutting manufacturing time and cost.slice thickness of 1 mm) three-dimensional com-puted tomography scan of the patients was Key Words: Orthognathic surgery, precise preopera-obtained. Raw data obtained from computed tive planning, three-dimensional medical modelingtomography scanning was processed with a Mimics9.22 Software (Materialise’s Interactive Medical TImage Control System, Belgium). Fabrication of he complexity of craniomaxillofacial anat- omy combined with the variation encoun-three-dimensional medical models was obtained tered by the reconstructive surgeon makesthrough a process called powder depositional surgery a conceptually difficult task inmodeling by use of a Spectrum Z 510 3D Color explanation, planning, and execution.1 The need forPrinter (Z Corporation, Burlington, MA). Alveolar clear images of cranial morphology played a largearches of the maxilla and mandibula of the models part in the development of three-dimensional (3D)were replaced with orthodontic dental cast models. imaging and more recently solid anatomic modeling.Temporomandibular joints of the models were Improvements in computer hardware and softwarefixed with Kirschner wire. Maxillary and mandib- have not only made 3D images more realistic andular bony segments were mobilized according to detailed, but also allowed shape analysis and thepreoperative orthodontic planning done by analy- measurement of distance and volume.1 With the usesis of cephalometric plain radiographs. The relation of 3D medical modeling, it became possible to obtainbetween proximal and distal mandibular segments an exact copy of the patient’s skull and facialafter bilateral sagittal split osteotomies were eval- structures for preparation of implants to fit defective areas. Additionally, recent developments in software technology not only enabled simulation of osteo- From the *Department of Plastic and Reconstructive Surgery, tomies and movement of bony fragments, but alsoFaculty of Medicine; and the 1Department of Orthodontics, Faculty allowed soft tissues to be assessed after the under-of Dentistry, Hacettepe University, Ankara, Turkey. lying bony architecture has been manipulated. Address correspondence and reprint requests to Dr. Mehmet Effectiveness and safety of using computer-Emin Mavili, Department of Plastic and Reconstructive Surgery,Faculty of Medicine, Hacettepe University Sihhiye Ankara 06100, generated alloplastic (hard tissue replacement)Turkey; E-mail: firstname.lastname@example.org implants for the reconstruction of craniofacial region,740 Copyright @ 2007 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
THREE-DIMENSIONAL BIOMODELING IN ORTHOGNATHIC SURGERY / Mavili et aluse of medical modeling technology in craniofacial Spectrum Z 510 3D Color Printer (Z Corporation,surgery and use of such biomodels compared with Burlington, MA).standard imaging modalities have already been Preoperative bracket application on teeth madeevaluated.1Y4 However, effectiveness of preoperative interference with computed tomography scanninguse of life-sized, 3D models in orthodontic surgery and alveolar arches of the maxilla and mandibula ofhas not been well evaluated yet. all models had artifacts, which reduced the accu- An acrylic splint is used to transfer the pre- racy of the models. Additionally, teeth are com-operative treatment plan to the operating room, posed of enamel and dentin with differentallowing for accurate intraoperative positioning of radiologic densities, which also contributes decreas-the maxilla relative to the mandible or of the ing the accuracy of 3D medical modeling of themandibula relative to the maxilla depending on teeth.5 Therefore, alveolar arches of all models werepreoperative planning in single jaw surgery. When replaced with orthodontic dental cast models torepositioning of both the maxilla and the mandible is increase the details of dental anatomy on theplanned, an intermediate splint in addition to the fabricated model, which is important in exact fittingfinal splint is fabricated. This intermediate splint is of dental splints to the fabricated model. Mandib-used to align the osteotomized maxilla to the ular condyles were attached to the glenoid fossaenonoperated mandible, and a final splint is used to with Kirschner wire to make sure that the condylesposition the mandible to the repositioned maxilla. were kept in exact position during preoperative Although use of an acrylic splint may help adjust model surgery. Maxillary and mandibular bonythe anteroposterior positioning of the maxillary segments were osteotomized and mobilized accord-alveolar arch by stabilizing the dental casts of both ing to preoperative orthodontic planning done bymaxillary and mandibular teeth in their final position analysis of cephalometric plain radiographs. Bothin Le Fort I surgery, it is the surgeons’ task to the relation between proximal and distal mandibu-determine amount of impaction or downfracture of lar segments after bilateral sagittal split osteotomiesthe maxillary alveolar arch to adjust the vertical and the relation between mandibular and maxillarylength of the face. In the same way, although acrylic alveolar segments were evaluated on models pre-splints are useful in adjusting the anteroposterior operatively. Dental splints, used in preoperativepositioning of the distal mandibular segment in model surgery, were also used in operations of thebilateral mandibular osteotomies, they cannot help same patients.either adjusting the amount of rotational movement Acrylic dental splints of the patients wereof distal mandibular segment on x-axis or stabiliza- fabricated by using dental casts of patients adaptedtion of proximal mandibular segments in the glenoid on semiadjustable articulators. To simulate thefossae in bilateral sagittal split osteotomies. planned operative procedures, a model surgery is In this particular study, we aimed to demon- performed based on clinical assessment and cephalo-strate the increase of accuracy in orthodontic surgery metric prediction tracings. The models are mountedand prevention of condylar malpositioning and on a semiadjustable articulator and the relativecondylar sag by using life-sized, 3D models of our position of the dentition within the facial form ofpatients preoperatively. the patient is simulated. When the dental casts are in their final position, an acrylic splint is fabricated.PATIENTS AND METHODS This acrylic splint is used to transfer the treatment plan to the patient in the operating room, allowingT he study was designed as a prospective trial to assess the usefulness of biomodeling in ortho-gnathic surgery. Six male and six female patients 18 for accurate intraoperative positioning of the maxilla relative to the mandible or of the mandibula relative to the maxilla. The acrylic splint ideally containsto 29 years of age (mean, 29.4 years) were evaluated indentations of the incisal edges and cusps of thewith 3D BT in addition to routine preoperative teeth, and it is trimmed on the buccal surfaces tocephalometric analysis. Mean follow up was 12.66 allow good hygiene and permit visual verification ofmonths (range, 6Y15 months). proper seating at the time of surgery.6 When Raw data obtained from computed tomography repositioning of both the maxilla and the mandiblescanning was processed with a Mimics 9.22 Software is planned, an intermediate splint in addition to the(Interactive Medical Image Control System, Materi- final splint is fabricated. This intermediate splint isalise, Inc., Leuven, Belgium). Fabrication of 3D used to align the osteotomized maxilla to a non-medical models was obtained through a process operated mandible, and the final splint is used tocalled powder depositional modeling by use of a position the mandible to the repositioned maxilla. 741 Copyright @ 2007 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
THE JOURNAL OF CRANIOFACIAL SURGERY / VOLUME 18, NUMBER 4 July 2007 Technically, standard bilateral sagittal split paid to keep the gapping between mandibularosteotomies were performed on patients. The prox- fragments after planned movements to preventimal segment of the mandibula was stabilized with an applying load to the temporomandibular joints andAllice clamp. Then the anterior aspects of the bone grafts were used when necessary. The orienta-proximal segments of the patient’s mandibula were tions of condylar positions of each patient in glenoidshortened the same amount observed to juxtapose the fossa were checked by both opening the maxilloman-margins of the proximal and distal fragments on the dibular fixation intraoperatively to observe thepreoperative model in mandibular prognathism or occlusion patterns of the patients and obtaining thedistal segments were advanced until the same Panorex of the patients postoperatively.amount of gap as developed on the preoperative Because of routine use of semirigid fixation ofmodel developed between the margins of the prox- the mobilized alveolar segments with anteriorlyimal and distal fragments of the patient’s mandibula applied two plates to only nasomaxillary buttress ofin mandibular retrusion before fixation of the maxilla after Le Fort I osteotomy (instead of use ofmandibular segments. First, the bicortical mandibu- four plates to nasomaxillary and pterygomaxillarylar screw was always applied to the point where the buttresses) and with only two bicortical screws toproximal and distal mandibular segments came in each side of the mandibula after bilateral sagittalcontact with each other after planned movements of split osteotomy (instead of three screws to eachdistal mandibular fragment unless this point targets side), maxillomandibular fixation with elastics wasthe inferior alveolar nerve and highly increase the applied to all patients for 15 days in the post-likelihood of nerve damage. Before application of the operative period. Maxillomandibular fixation wassecond screw for fixation, meticulous attention was done 48 hours after surgery.Fig 1 Preoperative appearance of the maxillomandibular discrepancy of the patient on model (A) from the anterior view,and (B) from the right lateral view. (C) Appearance of the left side of the mandibula after 4-mm mandibular setback (linearbackward movement) in z axis and for 3-mm rotational movement to the right side in the y axis to correct both themandibular prognathism and midline shift of mandibular incisive teeth. It seems as if the mandibula was advanced forwardon that side because of the simultaneous rotational movement of the mandibular segment to the opposite side. (D)Appearance of the right side of the mandibula after the same movements. Mandibular segments seem to be in much closercontact with each other when compared with the opposite side. (E) Intraoperative view of the left side of the mandibula of thesame patient. Almost the same relationship between the proximal and distal mandibular segments can be observed that hasbeen seen on the model before. (F) Intraoperative view of the right side of the mandibula of the same patient. Almost the samerelationship between proximal and distal mandibular segments can be observed that has been seen on the model before.742 Copyright @ 2007 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
THREE-DIMENSIONAL BIOMODELING IN ORTHOGNATHIC SURGERY / Mavili et alPatient No. 1 relations between the right and left sides of the patient were observed intraoperatively (Fig 1E, F).A 26-year-old female patient was scheduled to havebilateral sagittal split osteotomies for 4-mm mandib- Patient No. 2ular setback (linear backward movement) in the zaxis and for 3-mm rotational movement to the right A 21-year-old male patient was scheduled to have Leside in y axis to correct both the mandibular Fort I osteotomy for 4-mm advancement and 2-mmprognathism and midline shift of mandibular inci- impaction of the maxillary alveolar process andsive teeth (Fig 1A, B). bilateral sagittal split osteotomies for 4-mm mandib- There was asymmetric posterior movement on ular setback (linear backward movement in z axis)the right and left side of the distal mandibular and for 4-mm rotational movement to the left side insegment because of the rotational movement of the the y axis to correct both the mandibular progna-distal segment in addition to the linear set back thism and midline shift of mandibular incisive teethmovement. Since the rotation was done to the right (Fig 2A, B).side, it was reflected as if the right side was moved There was asymmetric posterior movement onmore posteriorly when compared with the left side the right and left sides of the distal mandibular(Fig 1C, D). Additionally, there was a gap between segment because of the rotational movement of theproximal and distal mandibular segments on the left distal segment in addition to the linear setbackside (on the opposite side of rotation) and the movement. Since the rotation was done to the leftproximal and distal segments of the mandibula side, it was reflected as if the left side was movedwere in close contact with each other on the right more posteriorly when compared with the right side.side (on the same side of the rotation). The same Additionally, there was a gap between proximal andFig 2 (A) Preoperative maxillomandibular discrepancy in the anteroposterior direction. (B) Preoperative midline shift inthe frontal plane. (C) Angulation between proximal and distal segments of the mandibula on the opposite side of therotation. Note the bones are in touch with each other posteriorly and a gap develops in between them anteriorly so thatangulation faces anteriorly. (D) Intraoperative view of the right side of the mandibula of the same patient. Note that theoverlapping segments of the bones resulting from mandibular setback are compensated by the rotational movement to theleft side and it is only the anterior gapping (marked with white line) apparent after planned movements on the left side. (E)Intraoperative view of the left side of the mandibula of the same patient. Note that the overlapping segments of the bonesseems to be more that one expects because of the additive effect of mandibular setback and rotational movements on thesame side of rotational movement. 743 Copyright @ 2007 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
THE JOURNAL OF CRANIOFACIAL SURGERY / VOLUME 18, NUMBER 4 July 2007distal mandibular segments on the right side (on the addition to the linear setback movement (Fig 3C, D).opposite side of rotation) and the proximal and distal Since the rotation was done to the right side, it wassegments of the mandibula were in close contact with reflected as if the right side was moved moreeach other on the left side (on the same side of the posteriorly when compared with the left side.rotation) (Fig 2C). Same relations between right and Additionally, there was a gap between proximalleft sides of the patient were observed intraopera- and distal mandibular segments on the left side (ontively (Fig 2D, E). the opposite side of rotation) and the proximal and distal segments of the mandibula were in closePatient No. 3 contact with each other on the right side (on theA 24-year-old male patient was scheduled to have same side of the rotation) (Fig 3E). Moreover, becausebilateral sagittal split osteotomies for 6-mm mandib- of rotational movement around the z axis, there wasular setback (linear forward movement in the z axis) also coronal triangular gapping between distal andto correct the class III malocclusion for 3-mm proximal segments of osteotomized mandibula inrotational movement to the right side (rotational such a way that the angulation between bonemovement in the y axis) to correct the midline shift of segments develops at the superior part of themandibular incisive teeth and for 2-mm rotational osteotomized bones (leading to gapping inferiorly)movement in clockwise direction (rotational move- on the left side (ie, the side of downward rotation) andment in z axis) to correct the asymmetric closure at the inferior part of the osteotomized bones (leadingpattern of molar teeth (Fig 3A, B). There was to gapping superiorly) on the side of upward rotationasymmetric posterior movement on the right and (ie, the side of upward rotation). The same relationsleft side of the distal mandibular segment because of between the right and left sides of the patient werethe rotational movement of the distal segment in observed intraoperatively (Fig 3F, G).Fig 3 Preoperative appearance of maxillomandibular discrepancy of the patient on model (A) from the anterior view and(B) from the right lateral view. (C) View of the right side of the mandibula after preoperative movements of distalmandibular segment done on the model. Note that the mandibular setback and rotational movements increase the amountof overlapping bone segments. (D) View of the left side of the mandibula after preoperative movements of distalmandibular segment done on the model. Although the mandibula was setback, instead of bony overlap, one observes bonesare split over each other on left side as if it was seen in mandibular advancement. (E) Appearance on mandibula frombottom after rotation to right. On the side of rotation (right side), the bones are in touch with each other anteriorly and a gapdevelops in between them posteriorly, so that angulation faces posteriorly; whereas on the opposite side (left) of rotation,the bones are in touch with each other posteriorly and a gap develops in between them anteriorly so that angulation facesanteriorly. (F) Intraoperative view of the left side of the mandibula, showing the anteriorly located gapping. (G)Intraoperative view of the right side of the mandibula showing posteriorly located gapping (line between two arrowheads)and angulation (white solid lines).744 Copyright @ 2007 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
THREE-DIMENSIONAL BIOMODELING IN ORTHOGNATHIC SURGERY / Mavili et alRESULTS Sagittal split osteotomy is the most frequently used osteotomy for correction of skeletal problems inS ame bony relation was observed both in pre- operative models and in the perioperativesurgical field in all patients. None of the patients the mandible, because it provides better bone contact for bone healing and bicortical screwing for better fixation, therefore, reduces the risks of nonunion.12,13had infection at the maxillary osteotomy side. Sliding the mandibular segments over each otherUnilateral local infection at the osteotomy side was enables to keep the bone contact between theseen in only one patient after double jaw surgery. It osteotomized mandibular segments.was treated with oral antibiotics and follow up of that In a simple anteroposterior linear displacementpatient was uneventful otherwise. operation, one may easily guess the amount of bone Condylar malpositioning was not observed in any that should be removed from the anterior aspect ofof the patients. Although postoperative maxilloman- the proximal segment juxtaposing the margins of thedibular fixation with elastics was applied routinely to proximal and distal fragments in mandibular prog-all patients for 15 days, none of the patients had nathism or the gap developing between the proximalcomplaint related with temporomandibular joint dis- and distal fragments in mandibular retrusion. Addi-comfort such as pain, restricted joint motion, and so on. tionally, simple anteroposterior linear displacement operation does not lead to any angulation betweenDISCUSSION the osteotomized mandibular segments. The clinical situations, however, are not that simple in most of theT he critical point in performing mandibular osteotomies in orthognathic surgery is thestabilization of the condyles in glenoid fossae, cases. In addition to simple linear anterior posterior movements, rotational movements for correction of deviations from midline and/or the occlusion pat-whereas the distal segment of the mandibula is tern are necessary.repositioned over proximal segments according to Deviations of mandibular incisive teeth frompreoperative orthodontic planning before fixation of midline can be corrected by a linear movement ofthese segments. One of the most common technical distal mandibular segment on the x axis or acomplications of mandibular surgery is inability to rotational movement of distal mandibular segmentorient and maintain condylar position with precision around the y axis.14 Because the osteotomized distalin the glenoid fossa, namely condylar malposition- segment of the mandibula stays between two lateraling. There is evidence that condylar positioning after mandibular segments (ie, ramus and the condyles),bilateral sagittal split osteotomy of the mandible any linear movement on the x axis will lead to lateralinfluences postoperative skeletal stability.7Y11 angulation of the condyle on the same side of Several different types of rigid condylar fixation movement and either medial angulation of thetechniques have been reported. The primary intent of contralateral condyle or gapping between the prox-each of these techniques is to determine a proper imal and distal segments of the mandibula. In othercondylar position before surgery and obtain a bite words, it is not possible to move the medianregistration in this position. At the time of surgery, osteotomized segment of the mandibula on the xbefore creating the osteotomy cuts, the ramus is axis without applying load to the temporomandibu-oriented in its proper position with the presurgical lar joints. Therefore, skeletal deformities of thebite, and a rigid fixation appliance is attached to mandibula, leading to deviation of mandibularsome stable landmark. This procedure fixates the incisive teeth from midline are preferred to beramus in a predetermined position. Next the rigid corrected by rotational movement of distal mandib-fixation appliance is removed, the osteotomy is ular segment around the y axis. Isolated rotationalcompleted, and the appliance is reapplied, placing movement of the distal mandibular segment aroundthe condyle in the proper position. The proximal the y axis leads to development of axial triangularsegment is then fixated to the repositioned distal gapping between distal and proximal segments ofsegment of the mandible. Long-term effectiveness of osteotomized mandibula in such a way that the an-these techniques, however, is somewhat limited. gulation between bone segments develops at the dis-Additionally, another drawback of all of these tal part of the osteotomized bones (leading totechniques is the increased operation time. More- gapping posteriorly) on the same side of rotationover, surgical fixation techniques that necessitate an (Fig 4A) and at the proximal part of the osteotomizedintervention to the temporomandibular joint may bones (leading to gapping anteriorly) on the oppositelead to temporomandibular joint dysfunction in the side of rotation (Fig 4B). Additionally, proximalpostoperative period. segment juxtapose over the distal segment on the 745 Copyright @ 2007 Mutaz B. Habal, MD. 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THE JOURNAL OF CRANIOFACIAL SURGERY / VOLUME 18, NUMBER 4 July 2007Fig 4 In addition to rotation around the y axis, the distal mandibular segment can be rotated around the x and z axes inspace. (A) Angulation between proximal and distal segments of the mandibula on the same side of the rotation around the yaxis. Note the bones are in touch with each other anteriorly and a gap develops in between them posteriorly (gap betweentwo red arrowheads) so that angulation faces posteriorly. (B) Angulation between proximal and distal segments of themandibula on the opposite side of the rotation around the y axis. Note the bones are in touch with each other posteriorlyand a gap develops in between them anteriorly (gap between two red arrowheads) so that angulation faces anteriorly. Incase of rotation around the z axis, the angulation will face either up or down, rather than anteriorly or posteriorly,depending on the direction of the movement. In case of rotation in the clockwise direction around the z axis (ie, rotation ofthe right side of the distal mandibular segment up and rotation of the left side of the distal mandibular segment down); (C)on the right side, the distal and proximal segments of the mandibula are in touch with each other inferiorly and a gapdevelops in between them superiorly (gap between two red arrowheads) so that angulation faces superiorly. (D) On the leftside, the segments of the mandibula are in touch with each other superiorly and a gap develops in between them inferiorly(gap between two red arrowheads) so that angulation faces inferiorly. In case of rotation around the x axis, the anglebetween the ramus and body of mandibula changes. (E) Neutral position without any rotation around the x axis. (F)Downward rotation of the distal mandibular segment (to correct the overbite deformity of incisive teeth) increases the anglebetween the ramus and the body of the mandibula. (G) Upward rotation of distal mandibular segment (to correct theanterior open bite) decreases the angle between the ramus and the body of the mandibula.same side of rotation, whereas gapping develops inferior part of the osteotomized bones (leading tobetween proximal and distal segments as if the distal gapping superiorly) on the side of upward rotationsegment had anterior advancement on the opposite (Fig 4C) and at the superior part of the osteotomizedside of rotation. bones (leading to gapping inferiorly) on the side of Distal mandibular segment may be rotated downward rotation (Fig 4D).around the z axis in accordance with maxillary To correct an open bite deformity, the distalsegment to correct the occlusional plane in patients mandibular segment may be needed to be rotatedwith facial asymmetry as a result of disparity of the around the x axis. Although this movement does notvertical heights of each sides of the face such as cause any gapping between proximal and distalhemifacial microsomia. Isolated rotational move- mandibular segments, it still changes the angle ofment of distal mandibular segment around the z fixation (Fig 4EYG).axis leads to development of coronal triangular Such rotational movements of the distal man-gapping between distal and proximal segments of dibular fragment does not only make the intraopera-osteotomized mandibula in such a way that the tive planning more difficult, but also make theangulation between bone segments develops at the preoperative interfragmental relationship estimation746 Copyright @ 2007 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
THREE-DIMENSIONAL BIOMODELING IN ORTHOGNATHIC SURGERY / Mavili et alof mandibular segments almost impossible. If ante- acquainted with the anatomy of the region. Addi-roposterior advancement and the rotational move- tionally, surgical models are inestimable tools forment around the y axis are required in the same surgical training of the residents.patient, rotational movement will increase the effectof linear movement on one side while hiding its effecton the other side. As an example, in a 4-mm The authors thank Kutsal Tuac for her contributions in evaluationmandibular setback operation, one may expect to of raw 3D BT data of the patients with Mimics 9.22 Softwareobserve approximately 4-mm proximal bone juxta- (Interactive Medical Image Control System, Materialise, Inc., Leuven, Belgium) and in fabrication of three-dimensional medicalpose over the distal segment. In addition to this linear models with Spectrum Z 510 3D Color Printer (Z Corporation,movement, if 4-mm rotational movement to the right Burlington, MA).side is planned in this patient, then one may observejust an angulation without any gapping on the rightside and approximately 8-mm gapping with reverse REFERENCESangulation on the left side. 1. D’Urso PS, Atkinson RL, Lanigan MW, et al. Stereolitho- Prevention of naturally developing interfrag- graphic (SL) biomodelling in craniofacial surgery. Br J Plastmental positional relationships (angulations) after Surg 1998;51:522Y530rotational movements around the z and y axes 2. Eppley BL, Kilgo M, Coleman JJ 3rd. Cranial reconstruction with computer-generated hard-tissue replacement patient-during mandibular bone fixation is important not matched implants: indications, surgical technique, and long-to apply load to the temporomandibular joints. To term follow-up. 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Philadelphia: WB Saunders Co, 1980:effects of soft tissues cannot still be simulated on the 844Y1013medical models, we experienced that there is nothing 13. Ochs MW. Bicortical screw stabilization of sagittal splitlike a model in your hands preoperatively, no matter osteotomies. J Oral Maxillofac Surg 2003;61:1477Y1484 14. Mavili ME, Canter HI, Aydinatay BS, et al. Tridimensionalhow good the 3D graphics are. Performing osteo- evaluation of maxillary and mandibular movements intomies on the models makes the surgeon more orthognathic surgery. J Craniofac Surg 2007;18:792Y799 747 Copyright @ 2007 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.