Pterygomaxillary Junction Research Articles

Evaluation of Treatment Protocols in Surgically Assisted Rapid Maxillary Expansion by Finite Element Analysis.

Background and Objectives: Transverse maxillary deficiency is an important maxillary anomaly that is very common in society and remains current in orthodontics. The maxillary expansion has been used in treatment for a long time. While maxillary expansion can be performed with rapid maxillary expansion in young adults, it is performed with surgically assisted rapid maxillary expansion (SARME) in individuals who have reached skeletal maturity. No consensus has been reached on the most successful surgical technique or the ideal appliance for treating transverse maxillary deficiency. Accordingly, we aimed to evaluate various surgical techniques and orthodontic appliances for treating transverse maxillary deficiency using the finite element method (FEM) to identify the treatment protocol that minimizes stress on the maxillary bone and teeth. Materials and Methods: On the virtual models obtained from the cone beam computed tomography of a patient, two different incisions (the pterygomaxillary junction is separated and not separated) were made and combined using three different orthodontic appliances (tooth, bone, and hybrid assisted). Then, stresses over the maxillary bone and maxillary teeth were calculated by FEM. Results: Our results showed that when the pterygomaxillary plates were separated, fewer stresses were observed on the bone and teeth. Although hybrid-supported appliances created less stress on the teeth than tooth-supported appliances and no difference was found between bone-supported appliances, it was found that hybrid-supported appliances created less stress on the bone than the other appliances. Conclusions: The separation of the pterygomaxillary junction in the SARME operation and the use of a bone-supported or hybrid-supported appliance would place less stress on the bone and teeth.

Le fort I osteotomy with or without concomitant removal of upper third molars: A prospective cohort study of intraoperative findings, related complications, and level of pterygomaxillary separation after down-fracture

The main objective of our study was to assess the clinical implications of concomitant intraoperative removal of maxillary third molars (M3M) with the Le Fort I osteotomy ‘twist’ technique (LF1twist). A prospective comparative study was carried out regarding the necessity of bone trimming around the pedicle, intra- and postoperative complications, surgery time, and the level of pterygomaxillary junction (PMJ) separation following LF1twist with concomitant intraoperative removal of M3M (test group) versus LF1twist alone (control group). Outcome parameters were assessed from clinical and radiographic measurements. In total, 100 surgery sites were included (50 in each group). The mean surgery time was 53.4 ± 7.8 min, with nonsignificant differences between groups. The frequency of intraoperative complications was negligible, with no significant differences between groups — though all bleeding events (n = 4) occurred when M3M was not removed concomitantly. No postoperative complications were recorded. Percentages of disarticulations occurring at the PMJ were similar in both groups. In conclusion, the results demonstrate that removal of M3M in conjunction with LF1twist does not imply additional surgery time, or differences regarding the level of PMJ separation or perioperative complications. Furthermore, the concomitant procedure reduces the amount of maxillary and palatal bone in the disjunction area, which facilitates down-fracture and field clearing for maxillary repositioning.

Comparison of the effects of different rapid maxillary expansion techniques on craniofacial structures: a finite element analysis study

AimTo compare the effects of three different maxillary expansion appliances with five different types of expansion modalities on stress distribution and displacement on the maxilla and its adjacent craniofacial structures using the finite element method (FEM).Materials and methodsCone-beam computed tomography data of a patient with maxillary transverse deficiency were rendered into a three-dimensional model of craniomaxillary structures. The expansion appliances included tooth-borne, hybrid, and bone-borne expanders. Five different expansion modalities were applied to each expander [conventional Rapid Maxillary Expansion (RME) (type 1), midpalatal suture cortico-puncture-assisted RME (type 2), LeFort l cortico-puncture-assisted RME (type 3), surgically assisted RME (SARME) without pterygomaxillary junction (PMJ) separation (type 4), and SARME with bilateral PMJ separation (type 5)]. The numerical and visual data were analyzed.ResultsThe highest amount of stress accumulation on teeth was found in the tooth-borne and hybrid groups. On the other hand, more stress concentration on the maxilla was observed in the bone-borne group. SARME cuts with PMJ separation increased total movement by reducing the stress on the midpalatal suture in all groups. While types 1, 2, and 3 were similar in terms of the amounts of displacement, types 4 and 5 increased the total amount of displacement in all groups. The total amounts of displacements from the highest value to the lowest value for the anterior and posterior maxilla were in the bone-borne, tooth-borne, and hybrid groups.ConclusionsSARME cuts were effective in reducing stress on the teeth, but the cortico-puncture application affected neither the stress values on the teeth nor the transverse displacement in the tooth-borne expanders. Surgical procedures such as SARME and corticotomy should be used with bone-borne devices to improve the outcomes of maxillary expansion procedures.

Radiological examination of the relationship between the pterygomaxillary junction and fracture pattern.

Le Fort 1 (LF1) osteotomies are widely used to correct midface deformities. To move the maxilla freely, the ptery-gomaxillary junction (PMJ) must be separated. When performing this osteotomy, the pterygoid plate must remain intact. The objective of this study was to evaluate relationship between the anatomical features of the PMJ and fracture patterns in LF1 osteotomy. Pre-operative and post-operative cone-beam computed tomography images of 41 patients (82 samples) who have undergone LF1 osteotomy surgery were radiologically evaluated. Morphologic measurements of the pterygomaxillary fissure area and pterygoid plate were carried out. Moreover, pterygomaxillary separation was divided into the clean-cut, maxillary sinus, and pterygoid plate fracture types. Statistically significant difference was observed between clean-type fracture and pterygoid plate fracture groups' thickness of the pterygoid process and thickness of the pterygomaxillary region. Anatomical variations make it difficult to separate the PMJ properly. Low thickness of PMJ increases the risk of unwanted fractures; however, according to our experience, the use of an osteotome with an incorrect angle, excessive force, and inexperienced surgeons can also cause undesirable pterygoid plate fractures.

Radiological analysis of maxillary artery relationships to key bony landmarks in maxillofacial surgery

The maxillary artery (MA) is a key structure at risk of injury in numerous oral and maxillofacial surgical (OMS) procedures. Knowledge of safe distances from this vessel to surgically familiar bony landmarks could improve patient safety and prevent catastrophic haemorrhage. Distances between the MA and bony landmarks on the maxilla and mandible were measured using CT angiograms on 100 patients (200 facial halves). The vertical height of the pterygomaxillary junction (PMJ) was mean (SD) measurement of 16 (3) mm. The MA enters the pterygomaxillary fissure (PMF) a mean (SD) distance of 29 (3) mm from the most inferior point of the PMJ. The mean (SD) shortest distance between the MA and medial surface of the mandible was 2 (2) mm (with the vessel directly contacting the mandible in 17% of cases). The branchpoint (bifurcation of the superficial temporal artery (STA) and MA) was directly in contact with the mandible in 5% of cases. The mean (SD) distances between this bifurcation point and the medial pole of the condyle were 20 (5) mm and 22 (5) mm, respectively. A horizontal plane through the sigmoid notch perpendicular to the posterior border of the mandible is a good approximation of the trajectory of the MA. The branchpoint is usually within 5 mm of this line and inferior in 70% of cases. Surgeons should take note that both the branchpoint and the MA contact the surface of the mandible in a significant number of cases.

Sinus mucosal healing pattern according to pterygomaxillary disjunction type after Le Fort I osteotomy.

During Le Fort I osteotomy, the separation of the pterygomaxillary junction (PMJ) is a difficult procedure for most surgeons because it is invisible. In this process, damage to the posterior structures constituting the sinus or those adjacent to it, including the maxillary sinus posterior wall and pterygoid plate, may occur. We would like to investigate the effects of this on the inside of the maxillary sinus after surgery and whether there are complications. One-hundred patients who underwent Le Fort I osteotomy from 2013 to 2020 using cone-beam computed tomography images were classified into two groups (clean-cut type and fractured type) according to the PMJ cutting pattern. In addition, the mucosal thickness in the maxillary sinus was divided into preoperative, postoperative three months, one year, and the change over the course of surgery was evaluated retrospectively. Of the total 100 cases, the clean-cut type numbered 28 cases and the fractured type totaled 72 cases. Among the fracture types, part of the sinus wall and the pterygoid plate were broken in 69 cases, and the maxillary sinus posterior wall was detached in three cases. There was no statistically significant difference in sinus mucosal thickening between the clean-cut type and fractured type of the PMJ, three months and one year after surgery between the two groups. However, there was a significant difference in sinus mucosal thickness at postoperative one year in the case where a partial detachment of the maxillary sinus posterior wall occurred compared to not. Even if there is some damage to the structures behind the PMJ, it may not be reasonable to spend some time on the PMJ separation process considering the overall postoperative complications, if there is no significant difference inside the sinus, or increased probability of postoperative complications.

Surgically assisted rapid palatal expansion: is the pterygomaxillary disjunction necessary? A finite element study

Transverse discrepancy is an important factor in determining facial esthetics. It has been shown there is an inverse correlation between the buccal corridor width and the intercanine and intermolar widths. Despite the fact midpalatal expansion is the treatment of choice for growing subjects, for skeletally mature subjects the rapid palatal expansion has limited orthopedic effects, and surgically assisted rapid palatal expansion (SARPE) is preferred. SARPE has shown inconsistencies depending on the surgical technique and/or expander device design. Some authors suggest that median and lateral osteotomies are sufficient to achieve the desired transverse dimensions using the SARPE procedure, while others recommend additional surgical separation of the pterygomaxillary junction. There are still controversies regarding the pterygomaxillary sutures (PMS) disjunction effect. Therefore, this study aimed to evaluate the displacement and stress distribution of the craniofacial structures resulting from SARPE, either with or without PMS osteotomy, using two different expander design (tooth-borne and tooth-bone-borne) using finite element method and finite element analysis (FEM/FEA). Regardless of the maxillary expander device type, both SARPE surgical techniques effectively produced maxillary expansion. SARPE with PMS osteotomy presented parallel maxillary expansion, and reduced stress values in the craniofacial and maxillofacial structures.

Pattern of pterygomaxillary disarticulation associated with Le Fort I maxillary osteotomy

Pterygomaxillary disarticulation (PMD) contributes to surgical complications of Le Fort 1 osteotomy and is associated with undesirable fractures of the pterygoid plates. The aim of this paper was to investigate the patterns of PMD in Le Fort I osteotomies using Rowe's disimpaction forceps, and to evaluate correlations with age and anatomical measurements. Cone-beam computed tomography (CBCT) scans of 70 consecutive orthognathic patients were retrospectively evaluated to study four patterns of PMD: Type 1 - PMD at, or anterior to, the pterygomaxillary junction (PMJ); Type 2 - PMD posterior to the PMJ; Type 3 - PMJ separation with comminuted fracture of the pterygoid plates; Type 4 - disarticulation of the maxilla involving the pterygoid plates above the level of the osteotomy line. The preoperative anteroposterior and mediolateral thicknesses of the PMJ and the length of the medial and lateral pterygoid plates were assessed. Satisfactory PMD was achieved in all cases and no severe complications were reported, including vascular, dental, mucosal, or neural damage. The most common PMD was Type 1 (54.3%), followed by Type 2 (40%). Comminuted fracture of the pterygoid plates was limited to 5.7% of cases, and no Type 4 was detected. A weak correlation was detected between PMJ thickness and PMD pattern (p = 0.04). No statistically significant correlation was detected between patients’ age and type of PMD. PMD of Le Fort I maxillary osteotomy using a Smith spreader and Rowe's disimpaction forceps proved safe, with minimal damage to the pterygoid plates.

Transmucosal pterygomaxillary disjunction using a piezoelectric device, in the context of the minimally invasive Le Fort I osteotomy protocol

The aim of this study was to assess the accuracy and clinical implications of pterygomaxillary junction (PMJ) disjunction with a transmucosal PMJ osteotomy using a piezoelectric hand-piece device, in the context of Le Fort I osteotomy, by evaluating the level of PMJ disarticulation and the need for bone trimming around the pedicle. An ambidirectional 1-month follow-up cohort study was designed involving consecutive patients undergoing minimally invasive maxillary Le Fort I osteotomy through the twist technique. Two cohorts were defined according to whether or not the transmucosal PMJ osteotomy was performed. The site of PMJ disjunction was analysed radiographically. A total of 114 patients were included in the study, 57 in each group. The overall accuracy of the PMJ disjunction path was higher in the test group (43.9%) than in the control group (15.8%). Multiple logistic regression analysis identified the need for bone trimming (odds ratio 0.02; P < 0.001) and removal of the upper third molar (odds ratio 0.17; P < 0.001) as relevant factors. In conclusion, compared with the originally described twist technique, combination of the latter with the PMJ osteotomy increased its accuracy at the level of the PMJ. As a result, there is a decrease in resistance during down-fracture and decrease in the need for bone trimming around the pedicle, with preservation of the minimally invasive concept.

A Radiographic Study on Pterygoid Implants with Hamulus as a Landmark for Engaging the Pterygoid Plate - A Retrospective Study.

Rehabilitating the posterior maxilla with pterygoid implants can be quite challenging as the area entails many hindrances for implant placement. Although few studies have reported the three-dimensional angulations according to various planes (Frankfort horizontal (FH), sagittal plane, occlusal or maxillary planes), no anatomical landmarks have been identified to guide their placement. This study aimed at analysing the three-dimensional angulation of pterygoid implants using the hamulus as an intraoral guide. Pre-operative cone-beam computed tomography scans (axial and parasagittal sections) of 150 patients rehabilitated with pterygoid implants were retrospectively analysed to determine the horizontal and vertical angulations in relation to the hamular line and FH plane, respectively. The results showed horizontal buccal and palatal safe angulations of 20.8° ± 7.6° and -20.7° ± 8.5° in relation to the hamular line. Maximum and minimum vertical angulations of 61.6° ± 7.0° and 37.2° ± 10.3° were observed, with a mean of 49.8 ± 8.1 in relation to FH plane. The post-operative scans showed that around 98% of the implants placed along the hamular line were successfully engaging the pterygoid plate. Comparing with the results of previous studies, this study concludes that when implants are placed along the hamular line, they are more likely to engage the centre of the pterygomaxillary junction resulting in an excellent prognosis of pterygoid implants.

Surgically assisted rapid palatal expansion for transverse maxillary discrepancy in adults - Case report.

Introduction and importanceTransverse maxillary deficiency is one of the most detrimental problems to midfacial growth and the integrated dentoalveolar structures. Early diagnosis and proper treatment of such cases is most important to maintain the balance between the basal bones and stable occlusion.Case presentationIn our case, a 17-year-old male had irregular upper front teeth with an unpleasant smile. Detail examination revealed a symmetrical face with an orthognathic profile, mild malar deficiency, competent lips, asymmetrical arches, Class I molar and canine relationships bilaterally. Crowding was present in the upper anterior arch with 2 mm of anterior open bite and posterior cross bite present in the premolar region and molar region bilaterally. Lefort-1 osteotomy, midpalatal split, pterygomandibular disjunction without down fracture was done. The HYRAX appliance was cemented. Distraction started after four days of surgery. One mm distraction per day was done for 10 days. The patient was transferred to fixed orthodontic treatment to relive the anterior crowding. Records were taken after 1 year of follow up and analyzed. Skeletal relationships were in harmony. Dental crowding, anterior open bite and posterior crossbite were corrected.Clinical discussionThe zygomatic buttress and the pterygomaxillary junction are considered as the critical areas of resistance for maxillary expansion. Literature claims lefort-1 osteotomy in combination with palatal distraction results in more displacement and less stress in the maxilla.ConclusionSARPE has proved to be clinically effective and stable for the correction of transversely deficient maxilla after cessation of growth in adult patients.

Evaluating Morphology of the Pterygomaxillary Junction and Its Association With the Orbit in Different Facial Skeletal Relationships

The etiology for blindness after Le Fort I osteotomy is poorly understood. The authors propose that a study of the morphology and anatomical relationship of the pterygomaxillary junction to orbital vital structures may be crucial for understanding the possible etiology. This retrospective observational study involved analysis of data procured from computed tomography scans of individuals who were categorized into 4 groups based on their skeletal characteristics: skeletal Class I, II, and III and cleft lip and palate (CLP). The outcome variables included i) the height, width, and thickness of the pterygomaxillary junction (PTMJ) which represent its morphology and ii) distance of the PTMJ to the superior orbital fissure and optic canal, to demonstrate its proximity to orbital vital structures. Primary outcome measures were to i)compare variance of the outcome variables across groups, ii) determine association between PTMJ morphology and its proximity to the orbit, and iii) determine association between skeletal morphology and the outcome variables. Data were analyzed using descriptive and inferential statistics to study variance and association. Forty patients (80 sides) were divided into 4 groups. The CLP group demonstrated maximum height and thickness of the PTMJ, whereas the Class II group demonstrated the minimum (P<.001 and P=.001, respectively). The CLP group demonstrated the closest proximity of the PTMJ to orbital vital structures (P<.001), with Class II being the farthest (P<.001). There was a weak positive correlation between the PTMJ height and its thickness and width, whereas a moderate negative correlation was seen between the PTMJ height and its distance from the optic canal and superior orbital fissures (P<.001). Morphology of the PTMJ varies with facial skeletal relationship and also influences the relationship of the PTMJ with the orbital vital structures. This may be critical in understanding the pathophysiology of blindness after Le Fort I osteotomies.

Characteristics of the Sphenoid Bone in Crouzon Syndrome.

The goal of this study is to analyze the safety of reconstructive surgeries for Crouzon syndrome, and to understand the deformities and complications related to the surgical procedure. Thirty-nine subjects underwent preoperative computed tomographic scans were included (Crouzon, n = 19; controls, n = 20) in this study. Craniofacial cephalometric measurements were analyzed by Materialise software. The overall average distance from the pterygoid junction to the coronal plane in the patients with Crouzon syndrome was 21.34 mm (standard deviation [SD] 5.13), which was deeper than that in the controls by 35% (P = 0.000).The overall average distances between the left and right foramen ovale and pterion on the sphenoid bone in the subjects were 64.93 mm (SD 7.56) and 67.83 mm (SD 8.57), which were increased by 13% (P = 0.001) and 14% (P = 0.001) compared with those in the controls.The overall distances between the most inferior point of the left and right lateral pterygoid plate and the medial pterygoid plate in the subjects were 51.09 mm (SD 6.68) and 51.51 mm (SD 10.98), which was not statically different from the controls (P = 0.887, P = 0.991, respectively). This study characterized the surgically relevant anatomy of the sphenoidal bone. The pterygomaxillary junction is located in the posterior of the skull. Though there are some anatomical differences due to age, it is well known that the cranial cavity of the sphenoid side is likely to be enlarged in Crouzon syndrome, which may contribute to the other complications of the disease.

Vascular Complications in Le Fort I Osteotomy: Incidence, Reasons, and Management of the Intraoperative Hemorrhage.

The aim of this study was to investigate the incidence, types, and reasons for the intraoperative hemorrhage during Le Fort I osteotomy. The study sample was composed of the population of the patients who underwent orthognathic surgery from April 2011 to February 2017. The vascular complications of the patients who underwent Le Fort I osteotomy during the surgery were identified. Type of the bleeding, suspected vessel, amount of the intraoperative blood loss, cause, and management of the bleeding were specified and investigated. Descriptive statistics were computed for each study variable. A total of 200 patients underwent Le Fort I osteotomy. The sample's mean age was 22.4 ± 5.8 and 55.5% of patients were female. The intraoperative vascular complication was seen in only 10 (5%) samples. The suspected source of the hemorrhage was the descending palatine artery (DPA) in 8 (4%) cases, while the pterygoid venous plexus in the other 2 (1%) cases. The cause of the bleeding was suspected down-fracture in 8 cases, while pterygomaxillary junction (PMJ) separation in the other 2 cases. DPA was ligated with ligation clips and cauterized in arterial injury cases. The hemorrhage was taken under control using a hemostatic matrix with thrombin (Surgiflo, Ethicon, USA) in the venous bleeding cases. The down-fracture of the maxilla was found to be more related to the occurrence of vascular complications. Severe bleeding was managed by the use of the hemostatic matrix with thrombin and this hemostatic agent can be used to control this type bleedings in orthognathic surgery.

Evaluation of Lefort I Osteotomy Line and Pterygomaxillary Junction Region in Patients With Cleft Lip and Palate.

This study aimed to evaluate the Le Fort I osteotomy line and pterygomaxillary junction via cone-beam computed tomography in individuals with cleft lip and palate (CLP). Retrospective study. Patients and Methods: The study included individuals older than 16 years with CLP, who were scheduled for repositioning of the maxilla by Le Fort I osteotomy, and those with class III malocclusion with maxillary hypoplasia, who were scheduled for Le Fort I osteotomy. The measurements made in the area of the cleft of individuals with CLP were compared with both the side with no cleft and those with class III malocclusion with maxillary hypoplasia. A total of 11 measurements were made on the axial section parallel to the Frankfurt Horizontal plane, corresponding to the lower 1/5 of the distance between the infraorbital foramen and the anterior nasal spine. There were significant differences both in the comparisons made between the individuals with CLP and those without CLP in terms of the canal-anterior alveolar crest (G) and sinus-anterior alveolar crest (L) measurements (P < .05). The mean measurement values showed that the measurement results were higher in individuals with CLP in general. In conclusion, we believe that there might be difficulties both in osteotomy and down fracture stages during Le Fort I osteotomies performed in individuals with CLP.

CBCT study on the positional relationship between marginal points of pterygomaxillary junction and anterior nasal spine.

This study aimed to locate the inferior end (Pti) and the superior end (Pts) of pterygomaxillary junction (PMJ) relative to anterior nasal spine (ANS) so as to provide references for pterygomaxillary separation. The study was based on CBCT images of 109 Chinese patients. We projected Pti and Pts to the frontal plane and measured the distance as well as the positional relationship between the projection points and ANS via three-dimensional reconstruction image. On average, the ANS was 5.18mm above the Pti and the horizontal distance between the Pti and ANS was 21.86mm. The horizontal and vertical distances between Pts and ANS was 20.41mm and 10.91mm, respectively. The vertical height of PMJ was 16.09mm. Scatter plots diagrammatic centered on ANS showed that 73% (160/218) Pti and 64% (140/218) Pts appeared in a 45° fan shape ranged from 20 to 25mm radius in bilateral inferior and superior quadrant, respectively. There was no significant difference in the distance between both sides (P > 0.05). During the pterygomaxillary disjunction, it exists a risk of injuring neurovascular bundle of the pterygopalatine fossa 16.09mm above the lowest border of the pterygomaxillary junction. The region within a 45° fan shape ranged in 20-25mm radius in inferior quadrant centered on ANS might be suitable for the osteotome position. The positional relationship especially between the ANS and Pti found in this study provides a reference for surgeons during pterygomaxillary disjunction.

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.

Evaluation of the Pterygomaxillary Separation Pattern in Le Fort I Osteotomy Using Different Cutting Instruments

Pterygomaxillary separation (PMS) is considered the main reason for serious complications associated with Le Fort I osteotomy. The aim of this study was to evaluate whether a piezo surgery, ultrasonic bone scalpel, or conventional bur used in Le Fort I osteotomy has an influence on PMS patterns. Using a retrospective cohort study design, we enrolled a sample composed of patients who underwent orthognathic surgery. The primary predictor variables were the cutting instruments (ultrasonic bone scalpel, piezo surgery, and Lindeman bur) used to perform Le Fort I osteotomy. Other variables were demographic and anatomic parameters. The outcome variable was the type of PMS pattern, classified as follows: type 1, PMS at the pterygomaxillary junction (ideal PMS); type 2, PMS at the greater palatine foramen; type 3, PMS from the posterior wall of the maxillary sinus; and type 4, PMS with lateral or medial pterygoid fracture. Anatomic parameters, that is, the thickness and width of the pterygomaxillary junction and distance of the greater palatine foramen, were measured on preoperative cone-beam computed tomography images. The pattern of PMS was evaluated on postoperative cone-beam computed tomography. Data were analyzed using analysis of variance and the Pearson χ2 test. P<.05 was considered statistically significant. This study sample was composed of 96 PMSs in 48 patients. The most common type of PMS was type 1 (58), followed by type 4 (21), type 2 (10), and type 3 (7). A statistically significant relation was found between the cutting instrument and the ideal separation (type 1 PMS) pattern (P=.032), and the highest rate of the ideal separation pattern was seen in the ultrasonic bone scalpel group, at 24 of 32, compared with 22 of 38 in the piezo surgery group and 12 of 26 in the conventional bur group. According to the study, the ultrasonic bone scalpel is safer than other cutting instruments in terms of the ideal separation of the pterygomaxillary junction.

Computed Tomography Scan Assessment of the Anatomy of the Pterygomaxillary Junction and Its Relevance in Le Fort I Osteotomy.

Knowledge of the morphometry and types of pterygomaxillary junction (PMJ) during Le-Fort I osteotomy is an important consideration in the reduction of intraoperative complications. The PMJ is known to display population variations and with the recent increase in these surgical interventions in Kenya, a detailed description of the PMJ is warranted. Computed tomography scan images of PMJ obtained from 63 patients were analyzed at the level of the posterior nasal spine to assess types and the morphometry of the PMJ. A fissure type of PMJ was present in 65.9% (83/126 sides) while a synostosis type was present in 34.1% (43/126). Bilateral fissures were found in 58.73% (37/63), bilateral synostosis in 26.98% (17/63), and an asymmetric PMJ in 15.25% (9/63). The average height, width, and thickness of the PMJ were 17.45 ± 5.26 mm, 10.24 ± 1.97 mm, and 6.40 ± 1.97 mm respectively. Males had a significantly greater height (P = 0.003) and width (P = 0.000). The average width was greater in cases with a synostosis as compared with those with a fissure (P = 0.019). Average distance of greater palatine canal was 40.41 ± 2.28 mm and 7.19 ± 2.20 mm from the piriform rim and the pterygoid fossa respectively. The PMJ among Kenyans is characterized by a higher occurrence of synostosis, greater height, and thickness compared with previous findings from other populations. The results of this study can be helpful for surgeons in selecting the most appropriate techniques to achieve successful pterygomaxillary disjunction and minimize avoid attendant complications such as vascular and nerve injuries.

Changes of Stress Distributions Around Pterygomaxillary Junction With Different Osteotome Angulations.

The aim of this study was to investigate how the alteration of the angulation of osteotome at pterygomaxillary junction affects lateral pterygoid plate, maxillary tuberosity, palatal surface of maxilla, palatine bone and body of sphenoid bone. Following reconstruction of 3D modelling of maxilla, Osteotomes' tip was angulated 45 and 90 to sagittal plane to simulate pterygomaxillary osteotomy. Finite element analyses (FEA) was performed and Von Misses stress distributions were analyzed for two different angulations. Independent sample t test was used to compare differences between 45 and 90 angulations. Von Misses stress values on lateral pterygoid plate were higher in 45 angulation (0.71 ± 0.21 MPa) than 90 angulation (0.54 ± 0.28 MPa). This difference was statistically significant (P < 0.01). Placement of osteotome's tip with 90 angulation had higher stress value than 45 angulation on maxillary tuberosity region. However; difference wasn't significant (P = 0.44). Stress values on body of sphenoid bone were 0.45 ± 0.17MPa for the case of 90 angulation and 0.19 ± 0.09MPa for 45 angulation. Difference between these values were statistically significant (P < 0.01). Possible risk of unfavourable lateral pterygoid plate fracture and complications related with body of sphenoid bone during pterygomaxillary osteotomy was remarkably increased in case of narrow angulation (45). Keeping osteotome at right angle with sagittal plane may avoid these complications.