pterygoid muscle in order to maintain the blood supply to the fractured mandibular condylar head. We believe that this minor modification may minimize the risk of resorption of the fractured mandibular condylar head. In this article, we introduce this technique in detail, and report on two cases.]]>
Head ; Neck ; Pterygoid Muscles

PURPOSE: To compare the size of the masseter and lateral pterygoid muscle between the affected and the unaffected side of the patients who have the chief complaints of the mandibular asymmetry. MATERIALS AND METHODS: Twenty two patients (male: 4, female: 18, average age: 21.3 year-old) were radiographed using posterior-anterior (P-A) cephalography and computed tomography (CT). On P-A cephalography, the degree of deviation was determined by the distance from the mentum to the vertical reference line through the crista galli and the anterior nasal spine. On the scanned tracing papers of the maximum cross-sectional area of the masseter and lateral pterygoid muscle using axial CT images, the pixel number was measured. The ratio of the affected : unaffected sides were obtained. For the masseter and lateral pterygoid muscle, the relationship between the muscular volume and degree of skeletal hypoplasia was studied. RESULTS: The half cases showed no skeletal asymmetry. The lateral pterygoid muscle of the affected side was larger significantly than unaffected side (p.0.05). However, there was no significant difference between two sides in the cases of skeletal asymmetry. There was only significant difference in the cases without skeletal asymmetry (p.0.05). CONCLUSIONS: To some extent, the slight mandibular hypoplasia could affect the growth of some masticatory muscles.
Chin ; Facial Asymmetry ; Female ; Humans ; Masticatory Muscles* ; Pterygoid Muscles ; Spine

The purpose of this study was to evaluate the resistant force of medial pterygoid muscles against the mandibular advancement and distraction to anterior, and inquire into the relationship between medial pterygoid muscles and cephalometric variables. Sixty six patients with class III malocclusion underwent bilateral sagittal splitting of ramus with intraoralvertico-sagittal ramus osteotomy for mandibular set-back. The spring scale was used to measure the resistance of medial pterygoid muscles after splitting of ramus. Skeletaldental cephalometric analysis was made and statistic package was used for correlation between resistance and cephalometric variables. The resistant force of the right medial pterygoid muscle was greater than the left one in Koreans with class III malocclusion, and the force had a linear regression relationship with facial depth. The results suggested that facial depth has significant correlation with the resistance of medial pterygoid muscle, which can be acquired from patient's cephalometric analysis.
Humans ; Linear Models ; Malocclusion ; Mandibular Advancement ; Osteotomy ; Pterygoid Muscles*

The aim of this study is to introduce a surgical technique that can maintain blood supply to prevent condylar resorption in the extracorporeal reduction of condylar fracture. Neither the medial pterygoid muscle on the ramal bone nor the lateral pterygoid muscle on the condylar fragment was detached after vertical ramal osteotomy. Thus, reduction was performed in the intracorporeal state. Therefore, blood supply was expected to be maintained to the fragments of both the condylar and ramal bones. On postoperative radiographs, the anatomical outline of the fractured condyle was well restored, and the occlusion was stable. In the unilateral case, there were no signs of mandibular condylar resorption until postoperative 3 weeks. In the 2 bilateral cases, condylar displacements with plate fractures and screw loosening were observed at postoperative 1 month or 5 months, but radiodensity at the displaced fracture site increased during the follow-up period. Finally, complete remodeling of the condylar fragments with restored anatomic appearance was observed on 8-month or 2-year follow-up radiographs. All cases exhibited good healing aspects with no signs or symptoms of mandibular condylar dysfunction during the postoperative remodeling period after intracorporeal reduction of condylar fracture.
Follow-Up Studies ; Mandibular Fractures ; Osteotomy* ; Pterygoid Muscles

The aim of this study is to introduce a surgical technique that can maintain blood supply to prevent condylar resorption in the extracorporeal reduction of condylar fracture. Neither the medial pterygoid muscle on the ramal bone nor the lateral pterygoid muscle on the condylar fragment was detached after vertical ramal osteotomy. Thus, reduction was performed in the intracorporeal state. Therefore, blood supply was expected to be maintained to the fragments of both the condylar and ramal bones. On postoperative radiographs, the anatomical outline of the fractured condyle was well restored, and the occlusion was stable. In the unilateral case, there were no signs of mandibular condylar resorption until postoperative 3 weeks. In the 2 bilateral cases, condylar displacements with plate fractures and screw loosening were observed at postoperative 1 month or 5 months, but radiodensity at the displaced fracture site increased during the follow-up period. Finally, complete remodeling of the condylar fragments with restored anatomic appearance was observed on 8-month or 2-year follow-up radiographs. All cases exhibited good healing aspects with no signs or symptoms of mandibular condylar dysfunction during the postoperative remodeling period after intracorporeal reduction of condylar fracture.
Follow-Up Studies ; Mandibular Fractures ; Osteotomy* ; Pterygoid Muscles

The aim of this study is to identify the species characteristics of the dog mastication compared to the human by analyzing 8 landmarks on the heads from seven beagle dogs. The masticatory unit of the dog was relatively located posterior than the human. The predominance of horizontally-oriented fibers of the temporalis of the dog was shown in spite of vertical mandibular movement. The biomechanics of the coronoid process and the temporalis of the dog revealed but not superiorly-elevating like the human backward rotating the coronoid process. The masseter was also obliquely -oriented and the temporalis was observed in distinct two-layers. In the dogs, the higher coronoid process compared to the condyle was observed; the vertical difference of them was larger than human. The temporalis performs stronger action than masseter and related with marked horizontal action of the temporalis. These morphologies indicated that the mastication of the dog needs strengthened horizontal stability and it was taken by the cervical muscles attached backwardly to the skull. Thickened temporalis is adapted in feeding. The dentition of dog was longer and farther from the condyle and the pterygoid muscles were not well-developed than human, indicated unfavourable lateral movement. These findings were consistent with evolutionary tendency, feeding without hands and narrow skull.
Animals ; Biomechanics ; Dentition ; Dogs ; Hand ; Head ; Humans ; Mastication ; Muscles ; Pterygoid Muscles ; Skull ; Stomatognathic System

PURPOSE: The purpose of our study was to evaluate the volume of pre- and post operative masseter muscle and bite force in mandibular prognathic patients treated with SSRO with the use of the 3D CT imaging technique and occlusal force meter. MATERIALS AND METHODS: The study group consisted of 12 patients with mandibular prognathism (5 males and 7 females) who underwent mandibular setback surgery (BSSRO) in the Department of Oral and Maxillofacial Surgery, Samsung medical center. Bite force was measured at pre op, post op 3, 6 and 12 months by occlusal force meter(GM10, Nagano Keiki, Japan) The preoperative CT examination of subjects was performed between one month prior to operation and one year after to operation. And muscle volume was measured. RESULT: As compared to preoperative measurements at 1 year postoperatively the masseter and internal pterygoid muscle volume were diminished (p<0.05) The bite force steadily recovered, so at postoperatively 6 months reached the preoperative level. And at 1 year after operation, the maximum bite force was significantly greater than preoperative levels. No significant correlation was presented between masseter muscle and bite force (p>0.05), internal pterygoid muscle and bite force (p>0.05). CONCLUSION: In this study, the results showed that volume and bite force of the masticatory muscles decresed significantly immediate after orthognathic surgery for mandibular set-back. However, reduction of maximum bite force disappears within 6 months after surgery.
Bite Force ; Bites and Stings ; Humans ; Male ; Masseter Muscle ; Masticatory Muscles ; Muscles ; Orthognathic Surgery ; Prognathism ; Pterygoid Muscles ; Surgery, Oral

Fifteen young pigs were used in this study. The animals were divided into three groups; 1. Group for removal of the temporal muscle, 2. Group for removal of the masseter muscle, 3. Group for removal of masseter and internal pterygoid muscles. The animals were anesthetized with 3.5% chloral hydrate intraperitoneaily. In the right side the head was shaved. The masticatory muscle was removed. The animals were sacrificed four .months later. The head was separated from trunk and cleaned by boiling in a solution of potassiumm hydroxide. The results were as follows; 1. In the group for removal of the temporal muscle, the Coronoid process of the mandible was resorbed. 2. In the group for removal of the masseter muscle, there was produced asymmetrical growth of the mandible, attrition of the molar teeth in the control side, and resorption of the mandibular angle. 3. In the group for removahof the Masseter and Internal muscles, the changes were more severe than that of the group for removal of the masseter muscle. The mandibular angle was completely absent. 4. The growth of the bone seems definitely related to the presence of the muscular tissue actively pulling upon it.
Animals ; Chloral Hydrate ; Guinea Pigs* ; Guinea* ; Head ; Mandible* ; Masseter Muscle ; Masticatory Muscles* ; Molar ; Muscles ; Pterygoid Muscles ; Swine ; Temporal Muscle ; Tooth

PURPOSE: The purpose of this study was to propose finite element (FE) modeling methods for predicting stress distributions on teeth and mandible under chewing action. MATERIALS AND METHODS: For FE model generation, CT images of skull were translated into 3D FE models, and static analysis was performed considering linear material behaviors and nonlinear geometrical effect. To find out proper boundary and loading conditions, parametric studies were performed with various areas and directions of restraints and loading. The loading directions are prescribed to be same as direction of masseter muscle, which was referred from anatomy chart and CT image. From the analysis, strain and stress distributions of teeth and mandible were obtained and compared with experimental data for model validation. RESULTS: As a result of FE analysis, the optimized boundary condition was chosen such that 8 teeth were fixed in all directions and condyloid process was fixed in all directions except for forward and backward directions. Also, fixing a part of mandible in a lateral direction, where medial pterygoid muscle was attached, gave the more proper analytical results. Loading was prescribed in a same direction as masseter muscle. The tendency of strain distributions between the teeth predicted from the proposed model were compared with experimental results and showed good agreements. CONCLUSION: This study proposes cost efficient FE modeling method for predicting stress distributions on teeth and mandible under chewing action. The proposed modeling method is validated with experimental data and can further be used to evaluate structural safety of dental prosthesis.
Dental Prosthesis ; Finite Element Analysis ; Mandible ; Masseter Muscle ; Mastication ; Pterygoid Muscles ; Skull ; Sprains and Strains ; Tooth

It has been known that the medial pterygoid muscle influences the mandibular functions related to mandibular movements. In addition, the muscle bundle of the medial pterygoid muscle influences the stability of a complete denture. Therefore, the topography of this muscle is clinically important. However, researches on the clinical anatomy related to the insertion area, and innervation, of this muscle were rare. Therefore, authors investigated the morphological and topographic characteristics of the medial pterygoid muscle by dissection of 31 Korean cadavers. The following are the results:The middle portion of the medial pterygoid muscle was the longest with the length of 59.4 degrees +/-7.1mm, and upper one third of the total length of the muscle was composed of tendon. When comparing the morphology of the insertion area of the medial pterygoid muscle and the masseter muscle in the mandibular angle region, there was no difference of the length of the insertion from the gonion to the superior margin of the insertion on the ramus. However, the length from gonion to the anterior margin of the insertion on the ramus in the masseter case was twice as long as the medial pterygoid muscle case. Insertion of the medial pterygoid was morphologically classified into six groups based on the insertion pattern and the mylohyoid groove. Type V, which the muscle fibers in the insertion of the medial pterygoid muscle were divided and did not invade the mylohyoid groove, were found the most (26.6%). Most of pterygoid branch of trigeminal nerve entered the medial pterygoid muscle through the posterior one third area or the posterior marginal area. The average length between hamulus and the region where the pterygoid branch of mandibular nerve entered the medial pterygoid muscle was 10.1mm. In conclusion, the anatomical relationship between the medial pterygoid muscle and the surrounding structures will be able to provide useful data for clinical applications.
Cadaver ; Denture, Complete ; Mandible ; Mandibular Nerve ; Masseter Muscle ; Pterygoid Muscles* ; Tendons ; Trigeminal Nerve