Effect of maxillary surgical movement on nasal cavity and maxillary sinus dimensions and function after Le Fort I osteotomy.

This study was designed to evaluate the effects of different maxillary movements performed in Le Fort I surgery on the anatomy of the nasal cavity and maxillary sinus, occurrence of rhinosinusitis, and nasal airflow. Patients were divided into three groups: group I underwent pure advancement, group II underwent advancement with yaw rotation, and group III underwent advancement with impaction movements. All evaluations were performed using pre- and postoperative computed tomography images and surveys. Twenty-eight patients were enrolled. The mean pre- and postoperative nasal air volumes in group I were 22.74 ± 6.32 cm3 and 25.17 ± 6.19 cm3, respectively, showing a significant increase (P = 0.041). The mean pre- and postoperative maxillary sinus air volumes were 33.94 ± 13.72 cm3 and 26.28 ± 14.12 cm3 in group II and 35.29 ± 9.58 cm3 and 28.65 ± 8.42 cm3 in group III, respectively, showing significant reductions (P = 0.028 and P = 0.007, respectively). For all movements, the occurrence of septum deviation and nasal airflow impairment was not statistically significant. Pure maxillary advancement movement enhanced nasal cavity air volume. The yaw rotation movement significantly increased quantitative clinical rhinosinusitis symptoms. The risk of airflow impairment following Le Fort I surgery is low.

Evaluation of the effect of mandibular length and height on the sagittal split ramus osteotomy rigid internal fixation techniques: A finite element analysis.

PURPOSE: A major concern after mandibular advancement with sagittal split ramus osteotomy surgery is postoperative stability and relapse. Currently, there is no consensus on the ideal fixation technique, or how prognosis is affected by mandibular height and length. The aim of the present study was to assess stress distribution on the fixation units and the bone after sagittal split ramus osteotomy and determine the contributions of different mandibular body heights and lengths. MATERIALS AND METHODS: Sagittal split ramus osteotomy and mandibular advancement were simulated in different height/length models prior to fixation using a miniplate, hybrid, or inverted L system using finite element analysis. The greatest and least amount of stress was generated using the miniplate, and inverted L system, respectively. RESULTS: The highest tension and compression in the bone was measured in the miniplate system. While the inverted L system generated less stress in the fixation units than the hybrid system, the hybrid system caused less stress in the bone and lower displacement values compared to other systems. An increase in length, and a decrease in height, both promoted stress, however, the difference was greatest in the former. CONCLUSION: Based on our results, when sagittal split ramus osteotomy is planned for a rather long or thin mandible, using the hybrid system for fixation is recommended.

Comparison of local and general anaesthesia for arthrocentesis of the temporomandibular joint.

Arthrocentesis of the temporomandibular joint is an effective treatment for some disorders, and is usually done under local anaesthesia. We know of few studies that have compared the ease of arthrocentesis and its outcomes under local or general anaesthesia, so we studied 32 patients (n=16 in each group). Postoperative oedema and pain, maximum mouth opening, duration of arthrocentesis, and ease of operation were assessed to compare the relative effectiveness of the two types of anaesthetic. Scores for duration of arthrocentesis (p=0.003) and ease of procedure (0.004) differed significantly, while the other results were similar in the two groups. We noticed some superior outcomes when the procedure was done under general anaesthesia, but because of its limitations, selection of patients becomes more important.

Biomechanical evaluation of a new design titanium miniplate for the treatment of mandibular angle fractures.

The optimal management of mandibular angle fractures remains controversial. The aim of this experimental study was to test the stability and resistance to mechanical force of a new titanium miniplate design. Thirty fresh sheep hemimandibles, sectioned at the angle region, were used to evaluate two plating techniques. One group received fixation via a new design single non-compression titanium miniplate and the second group via a six-hole straight non-compression titanium miniplate. A custom-made biomechanical test model was used for the samples. Each hemimandible was subjected to compressive and tensile forces using an Instron machine. The biomechanical forces (N) that caused 4-mm displacement or fixation loosening were compared. Comparison between the groups showed that fixation with the new design miniplate had more resistance to lateral compression forces than with a six-hole straight miniplate (P<0.009). Moreover, the new design miniplate fixation displayed more resistance to vertical compression and tensile forces (P>0.46 and P>0.61, respectively). The study demonstrated that mandibular fracture fixation with the new design non-compression titanium miniplate offered greater resistance to lateral displacement forces and may also provide increased resistance to vertical compressive and tensile forces than a conventional six-hole straight miniplate.

Histomorphometric evaluation of delayed changes in masseter muscle after lengthening the rabbit mandible by distraction osteogenesis.

OBJECTIVE: The aim of the study was to evaluate the delayed responses and changes of gradually lengthened masseter muscles of rabbit mandibles. STUDY DESIGN: Unilateral lengthening of rabbit mandibles was performed in 18 New Zealand rabbits for 7 days at the rate of 1 mm day(-1). Mandibles of animals were removed at months 3, 4, and 6 after distraction. Biopsy samples of distracted and contralateral side masseter muscles were histopathologically evaluated and mean area of muscle fibers (MAF) was evaluated with histomorphometric methods. Results were statistically analyzed. RESULTS: Mild to moderate atrophy of the fibers, and necrosis and myophagocytosis in some areas were the leading features at month 3 and which were decreased at month 4 in distracted side-muscle specimens, with no statistically significant differences when compared with non-distracted side muscles at the same periods. Almost completely, normal fibers were detected in distracted muscle specimens at month 6. Evidence of myopathic changes was found to disappear at month 6 and no significant difference was found in the MAF of distracted side muscles. CONCLUSION: This study showed that the masseter muscle could adapt to gradual lengthening of the mandible within 6 months. Regenerative features and some degree of atrophic changes that could be observed at months 3 and 4 disappeared at month 6, with adaptation of the fibers.