Maxillary Segment Research Articles

Protocol and Evaluation of 3D-Planned Microsurgical and Dental Implant Reconstruction of Maxillary Cleft Critical Size Defects in Adolescents and Young Adults.

Functional and esthetic final reconstruction of the cleft maxilla is still challenging. Current reconstructive and augmentation techniques do not provide sufficient bone and soft tissue support for the predictable rehabilitation with dental implants due to presence of maxillary bone critical size defects and soft tissue deficiency, scaring and poor vascularity. In this article the protocol for the use of 3D virtual surgical planning and microvascular tissue transfers for the reconstruction and rehabilitation of cleft maxilla is presented. Twenty-five patients (8 male/17 female) aged 14–41 years old with cleft-associated critical size defects were treated by 3D-virtual planned microvascular tissue transfers taken either from fibula, iliac crest, radial forearm, or medial femoral condyle. Follow-up lasted 1–5 years. No significant bone resorption (p > 0.005) nor volume loss of the graft was observed (p = 0.645). Patients received final permanent prosthetic reconstruction of the anterior maxilla based on 2–5 dental implants, depending on the defect severity. This is the first study presenting the use of virtual planning in the final restoration of the cleft maxilla with microvascular tissue transfers and dental implants. Presented protocol provide highly functional and aesthetic results.

Correction of Condylar Displacement of the Mandible Using Early Screw Removal following Patient-Customized Orthognathic Surgery.

Objective: Orthognathic surgery (OGS) is a surgical intervention that corrects dentofacial deformities through the movement of maxillary and mandibular segments to achieve adequate masticatory function, joint health, and facial harmony. However, some patients present with occlusal discrepancies, condylar sag, and/or temporomandibular disorders after OGS. Various methods have been employed to solve these problems after surgery. This study aimed to evaluate the effectiveness of early screw removal in patients with occlusal discrepancies after OGS using three-dimensional cone-beam computed tomography (CBCT). Methods: In 44 patients with dentofacial deformities, patient-customized OGSs with customized plates were performed to correct facial deformities using customized guides with computer-aided surgical simulation. Of the 44 patients, eight patients complained of occlusal discrepancies and temporomandibular disorders after OGS. These eight patients underwent screw removal under local anesthesia around four weeks. The temporomandibular joint spaces at three time points (pre-surgical, post-surgical, and after screw removal) in the sagittal and coronal planes were compared using CBCT. Results: Eight patients showed an increase in joint space on CBCT images immediately after surgery (T1), but after early screw removal (T2), these spaces almost returned to their pre-surgical state, and the temporomandibular joint problem disappeared. Conclusions: The removal of screws located in the distal segment under local anesthesia between three and four weeks post-surgically may be a treatment option for patients with post-OGS occlusal discrepancies, condylar sag, and/or temporomandibular disorder.

The Effect Of Different Force Levels for Maxillary Protraction on The Upper Inciosrs’ Position in Growing Class 3 Patients

Objective: To evaluate changes in the anterior maxillary dentoalveolar segment concomitant with different levels of force application for maxillary protraction in growing skeletal class3 patients. Subjects and Methods: The current study was conducted on 30 class 3 patients (19 boys and 11 girls) with maxillary difficieny. The age of the recrutted sample ranged from 7-10 years. The patients were randomely allocated into three equal groups. The point of protraction force application varied among the three groups; group A at the occlusal plane, group B 20 mm above the occlusal plane and group C at the infraorbital foramen. The duration of the treatment laste for 8 months, the patients were instructed to werethe appliance 16 hour/day with the applied 550gs protraction force. The analysis of the outcomes of this study was doneusing CBCT images were taken before and after maxillary protraction. Results: The average amount the upper midface projection varied significantly (p˂ 0.05) among the three studied groups as demonstrated by L&R IOF –TVP. The maximum amount of the upper midface anterior displacement was observed in group C (2.65 mm) followed by group B (1.77 mm) . the least amount of displacement was observed in group A (0.93 mm) . Conclusions: The application of the protraction force in a level higher than the occlusal plane is an efficient tool to maximized the amount of upper midface projection after protraction facemask without affecting the amount of maxillary advancement.

A Staged Expansion Screw Protocol to Retract the Premaxilla In BCLP Infants with Delayed Nasoalveolar Molding.

Currently, the treatment protocol for cleft palate at several centers around the world involves primary lip repair around 3-4 months of age, using presurgical nasoalveolar molding, which is done soon after birth. Unfortunately, in cases where treatment is delayed, the potential for repositioning the nasoalveolar apparatus is severely limited. The purpose of this paper is to illustrate a novel use of an expansion screw appliance to aid in the faster and more efficient active molding of the premaxillary and lateral maxillary segments in infants for whom the start of PNAM therapy is delayed, without the side effects commonly seen with pin-retained active molding appliances.

Maxillary Changes Following Facial Bipartition - A Three-Dimensional Quantification.

Children with Apert syndrome have hypertelorism and midfacial hypoplasia, which can be treated with facial bipartition (FB), often aided by rigid external distraction. The technique involves a midline osteotomy that lateralizes the maxillary segments, resulting in posterior cross-bites and midline diastema. Varying degrees of spontaneous realignment of the dental arches occurs postoperatively. This study aims to quantify these movements and assess whether they occur as part of a wider skeletal relapse or as dental compensation. Patients who underwent FB and had high quality computed tomography scans at the preoperative stage, immediately postsurgery, and later postoperatively were reviewed. DICOM files were converted to three-dimensional bone meshes and anatomical point-to-point displacements were quantified using nonrigid iterative closest point registration. Displacements were visualized using arrow maps, thereby providing an overview of the movements of the facial skeleton and dentition. Five patients with Apert syndrome were included. In all cases, the arrow maps demonstrated initial significant anterior movement of the frontofacial segment coupled with medial rotation of the orbits and transverse divergence of the maxillary arches. The bony position following initial surgery was shown to be largely stable, with primary dentoalveolar relapse correcting the dental alignment. This study showed that spontaneous dental compensation occurs following FB without compromising the surgical result. It may be appropriate to delay active orthodontic for 6-months postoperatively until completion of this early compensatory phase.

Effect of Le Fort I Maxillary Repositioning on Three-Dimensional Nasal Tip Rotation: A Comparative Study with Implication for the Asian Nose

Background: Le Fort I maxillary repositioning influences nasal morphology. In Asian cultures, upward nasal tip rotation with increased nostril exposure is considered aesthetically unpleasant and can have psychosocial consequences. This three-dimensional imaging–based study evaluated the effect of different Le Fort I maxillary movements on nasal tip rotation. Methods: Consecutive patients who underwent two-jaw orthognathic surgery (n = 107) were enrolled. To achieve a standard head orientation, preoperative and 1-week and 12-month postoperative cone-beam computed tomography–derived three-dimensional craniofacial models were superimposed. Tip rotation angle was calculated according to the Frankfort horizontal plane for all three-dimensional digital models. The final tip rotation angle change was defined as 12-month postoperative value minus preoperative value. Translational maxillary movement types (advancement versus setback and intrusion versus extrusion), postoperative maxillary segment locations (anterosuperior, anteroinferior, posterosuperior, or posteroinferior), and actual linear maxillary changes were noted. Results: Advancement (1.79 ± 5.20 degrees) and intrusion (2.23 ± 4.96 degrees) movements demonstrated significantly larger final tip rotation angle changes than setback (−0.88 ± 5.15 degrees) and extrusion (0.09 ± 5.44 degrees) movements (all p < 0.05). Postoperative anterosuperior location (2.95 ± 4.52 degrees) of the maxillary segment demonstrated a significantly larger final tip rotation angle change than anteroinferior (0.48 ± 5.65 degrees), posterosuperior (−1.08 ± 4.77 degrees), and posteroinferior (−0.64 ± 5.80 degrees) locations (all p < 0.05). Translational maxillary movement and actual linear maxillary change were not correlated with final tip rotation angle change. Conclusion: Effects of Le Fort I maxillary repositioning on nasal tip rotation depend on movement types and maxillary segment location. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, III.

Osteotomy of the Premaxilla in Bilateral Cleft Lip: A Useful Technique Following Failure of Primary Lip Closure.

Successful aesthetic repair of the bilateral cleft lip and palate (BCLP) is one of the most challenging cases encountered by a surgeon. This challenge is heightened when the premaxilla is anteriorly protruded in relation lateral maxillary segments. Our aim is to demonstrate a useful technique for reducing the cleft size before secondary lip repair. We use a premaxillary osteotomy to posteriorly reposition the premaxilla between the lateral segments. Six patients with BCLP underwent repositioning of the protruded premaxilla. Five patients had previous primary lip closure procedures with unsatisfactory results. The cleft size was reduced by premaxillary osteotomy from nasal septum and partial removal of the vertical vomer. The osteotomized premaxilla was then repositioned, fixed with a custom-made orthodontic appliance. Following this procedure, the lip was closed in a traditional fashion. All patients demonstrated satisfying lip closure without tension. In each case, the premaxilla was vital and exhibited partial stabilization during follow-up. In this study the authors demonstrate the usefulness of a premaxillary segment setback as an adjunct to improved function and aesthetics in bilateral lip repair. This method serves as useful technique for previously unsuccessful closure of BCLP.

Skeletal and Dental Habilitation of Residual Alveolar and Maxillary Clefts.

Management of residual clefts of the alveolus and maxilla requires the coordinated effort of multiple members of the craniofacial team including surgeon, orthodontist, and when teeth are hypoplastic or absent, the prosthodontist to achieve complete habilitation. Such cooperation among specialists begins early in the patient's life and continues through completion of care.Although numerous publications on this topic exist, few present definitive multidisciplinary reconstructive outcomes with longterm results. In this review paper, the authors present our comprehensive, multidisciplinary protocols, experience, and techniques as they have evolved with over 35 years of practice at our Craniofacial Center.Details of our updated protocols for each intervention and procedure, including our current thoughts on appropriate timing, follow up and advantages from the incorporation of current technologies are discussed. Close cooperation among specialists at all stages of care, the use of evolving technology, and adherence to, and modification where indicated, of time honored team protocols enables us to consistently achieve successful functional and esthetic outcomes, while minimizing complications.

Automated system of the determination of maxillary sinus morphometric parameters

Was to compare manual, semi-automatic and automatic methods for determining the maxillary sinus volume using cone beam computed tomography (CBCT). CBCT images from 48 patients (96 maxillary sinuses) with no history of sinus and alveolar bone surgery, who were presented to Minsk medical centers, were used in this study. Neural network training was performed on CBCT scans of 42 patients (84 maxillary sinuses).The height, depth and width of the sinus were measured manually on CBCT scans of 6 patients (12 maxillary sinuses). Maxillary sinus volume (V) was calculated by the formula: V=height´depth´1/3 width. Semi-automatic segmentation was carried out by an expert radiologist. The convolutional neural network technology was applied for maxillary sinus automatic segmentation. The largest values were revealed by using the automatic method for sinus volume measurement. These values were within the 95% confidence interval (±4.29 cm3) of the average sinus volume obtained from semi-automatic method. The data obtained using the convolutional neural network technique (artificial intelligence) has a high correlation with the results of sinus morphometric analysis acquired through manual and semi-automatic methods. Automatic maxillary sinus segmentation technique does not require special user knowledge. This method is reproducible and it is implemented in a short time interval.

Adaptive Localizing Region-Based Level Set for Segmentation of Maxillary Sinus Based on Convolutional Neural Networks.

In this paper, we propose a novel method, an adaptive localizing region-based level set using convolutional neural network, for improving performance of maxillary sinus segmentation. The healthy sinus without lesion inside is easy for conventional algorithms. However, in practice, most of the cases are filled with lesions of great heterogeneity which lead to lower accuracy. Therefore, we provide a strategy to avoid active contour from being trapped into a nontarget area. First, features of lesion and maxillary sinus are studied using a convolutional neural network (CNN) with two convolutional and three fully connected layers in architecture. In addition, outputs of CNN are devised to evaluate possibilities of zero level set location close to lesion or not. Finally, the method estimates stable points on the contour by an interactive process. If it locates in the lesion, the point needs to be paid a certain speed compensation based on the value of possibility via CNN, assisting itself to escape from the local minima. If not, the point preserves current status till convergence. Capabilities of our method have been demonstrated on a dataset of 200 CT images with possible lesions. To illustrate the strength of our method, we evaluated it against state-of-the-art methods, FLS and CRF-FCN. For all cases, our method, as assessed by Dice similarity coefficients, performed significantly better compared with currently available methods and obtained a significant Dice improvement, 0.25 than FLS and 0.12 than CRF-FCN, respectively, on an average.

Analysis of dental and basal bone arch form correlations in skeletal Class Ⅱ malocclusion

This study aimed to establish mathematical equations to describe the dental and basal arch forms in skeletal Class II malocclusion and to investigate correlations between these forms to facilitate clinical diagnosis and treatment design. Cone-beam computed tomography images of 60 patients (30 each with skeletal Class II malocclusion and normal occlusion) were subjected to 3-dimensional volume rendering, image reconstruction, and measurement. Using a computer program written in Java on the Eclipse platform (EclipseFoundation, Ottawa, Canada), a beta function was used to establish mathematical models of dental and basal bone arch forms, and model-fitting was performed. A mathematical model was developed to describe the dental and basal arch forms in skeletal Class II malocclusion. The maxillary and mandibular dental arch lengths were significantly longer in skeletal Class II malocclusion than in normal occlusion, whereas the width of the maxillary molar segment was smaller. The maxillary molar and mandibular intercranial segments in the basal arch were significantly longer in skeletal Class II malocclusion than in normal occlusion, whereas the mandibular intercranial segment width was smaller. The dental arch and basal bone arch forms in the maxilla and mandible follow individual curves, described by a beta function. In skeletal Class II malocclusion, the dental and basal arches are discrepant in horizontal and anteroposterior dimensions, which should be considered during orthodontic treatment planning to improve arch matching.

LE FORT I OSTEOTOMİSİNDE İKİ PLAK İLE MAKSİLLER FİKSASYON YÖNTEMİ :TEKNİK RAPOR VE VAKA SUNUMU

Restoring facial esthetics and occlusion while maintaining long term stability are the goals of orthognathic surgery. Le Fort I osteotomy is frequently used for the correction of dentofacial deformities and is accepted as a relatively stable procedure. Many factors affecting the stability of the mobilized maxilla have been reported. Among these, the use of a stable internal fixation method is of primary importance to postoperative stability. Most oral and maxillofacial surgeons prefer bilaterally applying titanium miniplates in both the anterior apertura piriformis region and the posterior zygomaticomaxillary buttress region to achieve the rigid fixation of the maxillary segment following Le Fort I osteotomy. In the literature, there is currently a lack of agreement on the number of plates required to adequately secure the mobilized maxilla to prevent postoperative relapse. Reducing the number of miniplates allows surgeons to reduce any potential complications, operation time, and costs. In this case report, a patient with maxillary retrognathia and mandibular prognathia, manifesting dental Class III characteristics who underwent one piece Le Fort I osteotomy at Baskent University Faculty of Dentistry, Department of Oral and Maxillofacial Surgery was presented. Under general anesthesia one piece Le Fort I osteotomy was performed. Following down fracture, mobilization of the maxillary segment was completed and 10 mm horizontal advancement movement was achieved. Surgical rigid fixation was performed under intermaxillary fixation with surgical splints. Maxillary fixation was completed with two pre-bent titanium Le Fort I plate placed bilaterally at the piriform apertura with no zygomaticomaxillary buttress fixation. Prior to extubation, intermaxillary fixation and surgical splints were released. Intermaxillary elastics were used six to eight weeks following surgery in addition to a soft, no-chew diet. The patient received both preoperative and postoperative orthodontic treatment. Digital lateral cephalometric radiographs, which were taken one week before orthognatic surgery (T1), one week postoperatively (T2), and nine months postoperatively (T3), were used to analyze skeletal movement and stability of the maxilla. Lateral cephalometric measurements were performed digitally using a computer-assisted software program. Linear and angular measurements of sagittal and vertical maxillary positions was calculated. A horizontal reference plane (HR) +7° to the SN plane at the S point and a vertical reference plane (VR) 90° to the horizontal plane at the Sella point were used in the analyses. After completion of growth and development, the SN plane remains in the same position, giving us the opportunity to measure skeletal movement with these horizontal and vertical reference planes. The difference in the A point-HR distances between the pre and postoperative radiographs indicates the horizontal movement of the maxilla, whereas the difference in the A point-VR distances indicates the vertical movement of the maxilla. The major criteria for maxillary skeletal relapse was the change in the distance from the A point to the horizontal and vertical reference planes. Significant immediate postsurgical changes were found in early postoperative lateral cephalometric radiography (T2). In 9 month follow-up lateral cephalometric measurements (T3) all landmarks in the horizontal and vertical plane showed skeletal stability. The relapse amount in maxillary movement was less than 1 mm in both horizontal and vertical planes. According to the postoperative lateral cephalometric measurements, the two plate anterior fixation method in the one piece Le Fort I ostetomy showed satisfactory results in terms of skeletal stability.

Distraction osteogenesis for management of cleft maxilla with the use of internal distraction device- A case report

Distraction osteogenesis (DO) has been used recently to correct cleft in the maxillary region with predictable and stable results. This case report describes a case with the use of DO for rapid movement of tooth-bone segments in patients with clefts of the maxilla involving palate. Both acceptable skeletal and soft tissue relationships with satisfactory occlusion were achieved. After 12 months of postoperative follow-up, the occlusal results were stable with minimal skeletal relapse. Keywords: Soft tissue, Intraoral distraction device, Distraction osteogenesis.

Dental arch relapse following midfacial bipartition: a three-dimensional semi-automated quantification

Introduction: Children with Apert Syndrome have hypertelorism and midfacial hypoplasia, which can be treated with midfacial bipartition (MB) or midfacial bipartition distraction utilising rigid external distraction (MBD-RED). These techniques involve a midline osteotomy that lateralises the maxillary segments, resulting in posterior cross-bites and midline diastema.

Cymbalcloeon gen. nov., an incredible new mayfly genus (Ephemeroptera: Baetidae) from Thailand.

The genus Cymbalcloeon gen. nov. (Ephemeroptera: Baetidae) is established for a new species Cymbalcloeon sartorii sp. nov. from Thailand, based on larval stage. This genus is unique among all of the Baetidae by the presence of three pairs of single gills on segments V–VII, ventrally oriented to cover the sterna VI–IX. Cymbalcloeon sartorii gen. nov. et sp. nov. presents unique or rare morphological characters such as a deeply concave margin between the prostheca and mola, without setae; a very large subtriangular process of the left mandible; a maxillary palp segment II with scarce and very long setae; almost completely fused labial palp segments II and III with numerous very long setae; elongate tarsal claw with two rows of teeth; a shagreen surface of the terga and paraproct; and a very reduced body size. The gills of the new genus move very quickly during respiration and present a near-synchronous protraction. Due to the very derived larval morphological character and the unknown imaginal stage, the exact phylogenetic position of the genus remains unclear; it most certainly belongs to the concept of Anteropatellata and is possibly closely related to the genus Baetopus.

Skeletal, dental and facial aesthetic changes following anterior maxillary segmental distraction by tooth-borne device in patients with cleft lip and palate

Maxillary skeletal deficiency secondary to cleft lip and palate (CLP) remains a significant challenge. The aim of this study was to present the comprehensive skeletal, dental and facial aesthetic outcomes of anterior maxillary segmental distraction osteogenesis (AMSDO) for treatment of maxillary hypoplasia in patients with CLP. Twelve patients with maxillary hypoplasia treated with AMSDO by a customized tooth-borne distractor were included. Three-dimensional changes of anterior maxillary segment, upper incisor and pharyngeal space were measured by three-dimensional reconstruction derived from cone beam computed tomography (CBCT) data. Length and width of dental arch during distraction were determined in dental casts. Nasolabial angle, soft-tissue convexity and patient’s subjective satisfaction were assessed to evaluate facial aesthetic improvements. Nasopharyngoscopic evaluation and speech assessment were also performed before and after distraction. All patients successfully received AMSDO without serious complications. Following AMSDO, the anterior maxillary segments moved forward 5.56±0.28mm and slightly upward 1.15±0.13mm. AMSDO significantly lengthened maxillary dental arch, generated new bone to relieve dental crowding and improved patients’ facial aesthetic without worsening velopharyngeal closure and speech quality. AMSDO by tooth-borne distractor is an effective surgical alternative for the advancement in patients with cleft maxillary hypoplasia.

Biomechanical Analysis of Grafted and Nongrafted Maxillary Sinus Augmentation in the Atrophic Posterior Maxilla with Three-Dimensional Finite Element Method.

This study is aimed at determining the optimal sinus augmentation approach considering the poor bone condition in the zone of atrophic posterior maxilla. A series of simplified maxillary segment models varying in residual bone height (RBH) and bone quality were established. A 10 mm standard implant combined with two types of maxillary sinus augmentation methods was applied with the RBH, which was less than 10 mm in the maxilla. The maximal equivalent von Mises (EQV) stress in residual bone was evaluated. Bone quality had an enormous impact on the stress magnitude of supporting bone. Applying sinus augmentation combined with grafts was suitable for stress distribution, and high-stiffness graft performed better than low-stiffness one. For 7 mm and 5 mm atrophic maxilla, nongrafted maxillary sinus augmentation was feasible in D3 bone. Poor bone quality was a negative factor for the implant in the region of atrophic posterior maxilla, which could be improved by grafts. Meanwhile, the choice of maxillary sinus augmentation approaches should be determined by the RBH and quality.

Type of maxillary segment mobilization affects three-dimensional nasal morphology

Surgical mobilization of the maxillary segment affects nasal morphology. This study assessed the impact of the type of maxillary mobilization on the three-dimensional (3D) nasal morphometry. Pre- and postsurgery cone beam computed tomography-derived facial image datasets of consecutive patients who underwent two-jaw orthognathic surgery were reviewed. Using preoperative 3D facial models as the positional reference of the skeletal framework, 12-month postoperative 3D facial models were classified into four types of maxillary mobilizations (advancement [n = 83], setback [n = 24], intrusion [n = 55], and extrusion [n = 52]) and four types of final maxillary positions (anterosuperior [n = 44], anteroinferior [n = 39], posterosuperior [n = 11], and posteroinferior [n = 13]). Six 3D soft tissue nasal morphometric parameters were measured, with excellent intra- and interexaminer reliability scores (ICC>0.897) for all the measurements. The 3D nasal change for each nasal parameter was computed as the difference between postoperative and preoperative measurement values. The intrusion maxillary mobilization resulted in a significantly (all p<0.05) larger 3D nasal change in terms of alar width, alar base width, and nostril angle parameters, and a smaller change in terms of the nasal tip height parameter than the extrusion maxillary mobilization; however, no significant (all p>0.05) difference was observed between advancement and setback maxillary mobilizations. The anterosuperior and posterosuperior maxillary positions had a significantly (all p<0.05) larger 3D nasal change in terms of the alar base width and nostril angle than the anteroinferior and posteroinferior maxillary positions. The type of maxillary mobilization affects the 3D nasal morphometry.

Quantitative Augmented Reality-Assisted Free-Hand Orthognathic Surgery Using Electromagnetic Tracking and Skin-Attached Dynamic Reference.

The purpose of this study was to develop a quantitative AR-assisted free-hand orthognathic surgery method using electromagnetic (EM) tracking and skin-attached dynamic reference. The authors proposed a novel, simplified, and convenient workflow for augmented reality (AR)-assisted orthognathic surgery based on optical marker-less tracking, a comfortable display, and a non-invasive, skin-attached dynamic reference frame. The 2 registrations between the physical (EM tracking) and CT image spaces and between the physical and AR camera spaces, essential processes in AR-assisted surgery, were pre-operatively performed using the registration body complex and 3D depth camera. The intraoperative model of the maxillary bone segment (MBS) was superimposed on the real patient image with the simulated goal model on a flat-panel display, and the MBS was freely handled for repositioning with respect to the skin-attached dynamic reference tool (SRT) with quantitative visualization of landmarks of interest using only EM tracking. To evaluate the accuracy of AR-assisted Le Fort I surgery, the MBS of the phantom was simulated and repositioned by 6 translational and three rotational movements. The mean absolute deviations (MADs) between the simulation and post-operative positions of MBS landmarks by the SRT were 0.20, 0.34, 0.29, and 0.55 mm in x- (left lateral, right lateral), y- (setback, advance), and z- (impaction, elongation) directions, and RMS, respectively, while those by the BRT were 0.23, 0.37, 0.30, and 0.60 mm. There were no significant differences between the translation and rotation surgeries or among surgeries in the x-, y-, and z-axes for the SRT. The MADs in the x-, y-, and z-axes exhibited no significant differences between the SRT and BRT. The developed method showed high accuracy and reliability in free-hand orthognathic surgery using EM tracking and skin-attached dynamic reference.

Does angulation of osteotome during pterygomaxillary dysjunction for a Le Fort I osteotomy influence stress transmission to the orbit? A finite element simulation in normal and cleft maxillae

Pterygomaxillary (PTM) dysjunction is a technique-sensitive step in Le Fort I osteotomy. Various studies implicate improper osteotomy techniques and anatomical variations of the midface in ophthalmic/orbital complications. The aim of this study was to assess the stress distribution and its transmission to the orbit during PTM dysjunction while using different angulations of the osteotome. The study involved the generation of two virtual models from the computed tomographic images of a non-cleft and cleft patient. Nonlinear, three-dimensional finite element analysis (3D-FEA) of the models was performed for mapping the equivalent stress (in megapascals [MPa]) and maximum principal stress (in MPa) at the PTM junction, optic canal, and superior orbital fissures. The results of our study showed that there was no significant change in the transmission of stress to the bony orbit in a normal maxilla, with variations in the angulation of the osteotome. However, the equivalent stress generated for the cleft maxilla showed an increase that could potentiate indirect globe injury. The study shows that a judicious technique for PTM dysjunction and a cautious approach in cleft maxillae could reduce incidence of ophthalmic complications in clinical practice.