Morphometric analysis of pterygomaxillary region by using cone beam computed tomography.

PURPOSE: Many complications during Le Fort I osteotomy are encountered during pterygomaxillary separation. The study aimed to evaluate the pterygomaxillary region in regards to the Le Fort I osteotomy using cone-beam computed tomography (CBCT) images. MATERIALS AND METHODS: The CBCT images of 200 patients (100 males, 100 females) aged 18-78 years were evaluated measuring the thickness and width of the pterygomaxillary region, the location of the descending palatine artery, and the length of the pterygoid plates on the axial section. RESULTS: It has been determined that the distance between the descending palatine canal and the priform rim is longer in males (P=0.037). Medial plate was longer on the right (P=0.0001) and left (P=0.025) in females. The thickness of the pterygomaxillary region was longer in females (P=0.000). The distance between the pterygomaxillary fissure and the descending palatine canal was longer on the right (P=0.001). CONCLUSION: The pterygomaxillary region may have different anatomies that predispose to specific complications associated with Le Fort I osteotomy. Therefore, before surgery, the pterygomaxillary region should be examined with CBCT, and necessary precautions should be taken preoperatively considering the possible complications.

Use of alveolar distraction osteogenesis for implant placement: a case report with eight-year follow-up.

Insufficient alveolar ridge width may impede the success of dental implants. Techniques for resolving this problem include autologous bone grafts, guided bone regeneration, bone splitting and bone spreading techniques. Recently, alveolar distraction osteogenesis has become an alternative method for alveolar augmentation. We propose the use of alveolar bone distraction for insufficient alveolar ridge width. A healthy 33-year-old female presented with missing teeth to our clinic. Clinical and radiographic examination revealed the alveolar ridge was too narrow for placement of dental implants. Therefore, horizontal distraction osteogenesis of the posterior mandibular ridge was chosen for augmentation. Two months later, two implants were placed. No significant marginal bone resorption was seen around the implants eight years after placement. Our results indicate that horizontal alveolar distraction is recommended to increase ridge width and allow placement of standard dental implants.

Comparison of biomechanical behaviour of maxilla following Le Fort I osteotomy with 2- versus 4-plate fixation using 3D-FEA: part 3: inferior and anterior repositioning surgery.

Having studied the effect of maxillary advancement and maxillary impaction in parts 1 and 2 of this research, the purpose of this study was to investigate the biomechanical behavior of different fixation models in inferiorly and anteriorly repositioned maxilla following Le Fort I osteotomy. Two separate three-dimensional finite element models, simulating the inferiorly advanced maxilla at Le Fort I level, were used to compare 2- and 4-plate fixation. Model INF-2 resulted in 247,897 elements and 53,247 nodes and INF-4 consisted of 273,130 elements and 59,917 nodes. The stresses occurring in and around the bone and plate-screw complex were computed. The highest Von Mises stresses on the plates and maximum principal stresses on the bones were found in INF-2, especially under horizontal and oblique loads, when compared with INF-4. The present biomechanical study shows that the traditionally used 4-plate fixation technique, following Le Fort I inferior and anterior repositioning surgery, without bone grafting, provides fewer stress fields on the maxillary bones and fixation materials.

Comparison of biomechanical behaviour of maxilla following Le Fort I osteotomy with 2- versus 4-plate fixation using 3D-FEA Part 2: impaction surgery.

The aim of the second part of this study was to evaluate the mechanical behaviour of 2- versus 4-plate fixation and bony structures after Le Fort I impaction surgeries using three-dimensional finite element analysis (3D-FEA). Two 3D-FEA models were created to fixate the impacted maxilla at the Le Fort I level as 2-plate fixation at the piriform rims (IMP-2 model) and 4-plate fixation at the zygomatic buttresses and piriform rims (IMP-4 model). The IMP-2 model contained 225664 elements and 48754 nodes and the IMP-4 model consisted of 245929 elements and 53670 nodes. The stresses in each maxillary model were computed. The models were loaded on one side, at the molar-premolar region, in vertical, horizontal and oblique directions to reflect the chewing process. It was concluded that the use of 4-plate fixation following Le Fort I advancement surgery provides fewer stress fields on the maxillary bones and fixation materials than 2-plate fixation from a mechanical point of view.

Comparison of biomechanical behaviour of maxilla following Le Fort I osteotomy with 2- versus 4-plate fixation using 3D-FEA. Part 1: advancement surgery.

The study aimed to calculate the location and intensity of the maximum stress fields on the fixation plates and surrounding maxilla following Le Fort I osteotomies after advancement procedures using three-dimensional finite element analysis. The models were generated using skull CT scan data. Le Fort I osteotomy simulations were made and two separate impacted maxillary models were designed. The ADV-2 model has 2 plate fixations bilaterally at the piriform rims, the ADV-4 model has 4 plate fixations at the zygomatic buttresses and piriform rims. The stress fields on bone, plate and screws were computed for each model. Posterior occlusal loads were simulated on one side in the molar-premolar region, in all three directions, reflecting the chewing forces. The increased locations of highest Von Mises stresses on the plates and highest maximum principle stresses on the bones were determined in ADV-2 models especially under horizontal and oblique loads when compared with ADV-4 models. Evaluation of the highest Von Mises stress values and maximum principal stress revealed that oblique load in the ADV-2 model received the highest values. 4-plate fixation following Le Fort I advancement surgery exerts less stress on the maxillary bones and fixation materials than 2-plate fixation.

Comparison of different fixation methods following sagittal split ramus osteotomies using three-dimensional finite elements analysis. Part 1: advancement surgery-posterior loading.

The purpose of this study was to evaluate the mechanical behavior of different fixation methods used in bilateral sagittal split ramus osteotomy (BSSRO). Part 1 comprises of the results of the analysis for mandibular advancement, four different fixation configurations of six hole fragmentation mini plates with monocortical screws and lag screws and posterior loading conditions in the molar and premolar region. The finite element analysis method (FEA) appears suitable for simulating complex mechanical stress situations in the maxillofacial region. The mechanical behavior of selected lag screws with linear or triangular configuration and double parallel or single oblique six hole mini plates with monocortical screws were compared by FEA after 5 mm BSSRO advancement procedure. Four separate three-dimensional finite element models of the mandible were created to simulate the BSSRO and corresponding fixation methods. These models consisted of 122,717 elements and 25,048 nodes. The mechanical parameters of the materials studied were adopted from the literature or were based on manufacturer's information. 500 N posterior occlusal loads were simulated on the distal segments. The commercial finite element solver MSC Marc software was utilized to calculate the stress fields on both the segments and fixative appliances. It was concluded that the use of 2.0mm lag screws placed in a triangular configuration following the BSSRO advancement surgery provides sufficient stability with any rotational movement and less stress fields at the osteotomy site, when compared with the other rigid fixation methods used in the current study.