Comparative in vitro mechanical evaluation of techniques using a 2.0 mm locking fixation system for simulated fractures of the mandibular body.

PURPOSE: To perform a comparative evaluation of the mechanical resistance of simulated fractures of the mandibular body which were repaired using different fixation techniques with two different brands of 2.0 mm locking fixation systems. MATERIALS AND METHODS: Four aluminum hemimandibles with linear sectioning simulating a mandibular body fracture were used as the substrates and were fixed using the two techniques and two different brands of fixation plate. These were divided into four groups: groups I and II were fixed with one four-hole plate, with four 6 mm screws in the tension zone and one four-hole plate, with four 10 mm screws in the compression zone; and groups III and IV were fixed with one four-hole plate with four 6 mm screws in the neutral zone. Fixation plates manufactured by Tóride were used for groups I and III, and by Traumec for groups II and IV. The hemimandibles were submitted to vertical, linear load testing in an Instron 4411 servohydraulic mechanical testing unit, and the load/displacement (3 mm, 5 mm and 7 mm) and the peak loads were measured. Means and standard deviations were evaluated applying variance analysis with a significance level of 5%. RESULTS: The only significant difference between the brands was seen at displacements of 7 mm. Comparing the techniques, groups I and II showed higher mechanical strength than groups III and IV, as expected. CONCLUSION: For the treatment of mandibular linear body fracture, two locking plates, one in the tension zone and another in the compression zone, have a greater mechanical strength than a single locking plate in the neutral zone.

Assessment of the fixation of mandibular symphysis fractures using conical cannulated screws: mechanical and photoelastic tests.

OBJECTIVE: The aim of this study was to use mechanical and photoelastic tests to compare the performance of cannulated screws with other fixation methods in mandibular symphysis fractures. STUDY DESIGN: Ten polyurethane mandibles were allocated to each group and fixed as follows: group PRP, 2 perpendicular miniplates; group PLL, 1 miniplate and 1 plate, parallel; and group CS, 2 cannulated screws. Vertical linear loading tests were performed. The differences between mean values were analyzed with the Tukey test. The photoelastic test was carried out using a polariscope. RESULTS: The results revealed differences between the CS and PRP groups at 1, 3, 5, and 10 millimeters of displacement. The photoelastic test confirmed higher stress concentration in all groups close to the mandibular base, whereas the CS group showed it throughout the region assessed. CONCLUSIONS: Conical cannulated screws performed well in mechanical and photoelastic tests.

Fractographic analysis of 2.0-mm plates with a screw locking system in simulated fractures of the mandibular body.

PURPOSE: The purpose of the present study was to analyze the fractured plates from 2 brands of 2.0-mm locking fixation systems submitted to axial linear load testing. MATERIALS AND METHODS: Four aluminum hemimandibles with linear sectioning to simulate a mandibular body fracture were used as a substrate and fixed with 2 fixation techniques from 2 national brands: Tóride and Traumec. The techniques were as follows: one 4-hole plate, with four 6-mm screws in the tension zone, and one 4-hole plate, with four 10-mm screws in the compression zone; and one 4-hole plate, with four 6-mm holes in the neutral zone. The hemimandibles were submitted to vertical linear load tests using an Instron 4411 mechanical test machine. The system was submitted to the test until complete failure had occurred. Next, a topographic analysis of the surface of the plates was performed using a stereomicroscope and an electronic scanning microscope. The samples were evaluated using different magnifications, and images were obtained. RESULTS: The surface of the fracture analyzed in scanning electron microscopy demonstrated a ductile-type fracture, usually found in the traction test bodies of ductile materials, such as titanium. No evidence of failure was observed in any fracture surface from a change in the structure or composition of the material. CONCLUSIONS: The plates were fractured by a ductile rupture mechanism, as expected, suggesting that the manufacturing of the national brand name plates used in the present study has been under adequate quality control, with no structural changes produced by the manufacturing process that could compromise their function.

Comparison of postoperative stability of three rigid internal fixation techniques after sagittal split ramus osteotomy for mandibular advancement.

INTRODUCTION: The aim of this investigation was to compare the skeletal stability of three different rigid fixation methods after mandibular advancement. MATERIAL AND METHODS: Fifty-five class II malocclusion patients treated with the use of bilateral sagittal split ramus osteotomy and mandibular advancement were selected for this retrospective study. Group 1 (n = 17) had miniplates with monocortical screws, Group 2 (n = 16) had bicortical screws and Group 3 (n = 22) had the osteotomy fixed by means of the hybrid technique. Cephalograms were taken preoperatively, 1 week within the postoperative care period, and 6 months after the orthognathic surgery. Linear and angular changes of the cephalometric landmarks of the chin region were measured at each period, and the changes at each cephalometric landmark were determined for the time gaps. Postoperative changes in the mandibular shape were analyzed to determine the stability of fixation methods. RESULTS: There was minimum difference in the relapse of the mandibular advancement among the three groups. Statistical analysis showed no significant difference in postoperative stability. However, a positive correlation between the amount of advancement and the amount of postoperative relapse was demonstrated by the linear multiple regression test (p < 0.05). CONCLUSION: It can be concluded that all techniques can be used to obtain stable postoperative results in mandibular advancement after 6 months.

TMJ total joint prosthesis for condylar fracture malunion / Prótesis articular total de ATM para malunión de fractura condilar

In the international literatura exist some information related to temporomandibular joint (TMJ) involvement in condylar fracture malunion; the treatment is variated being executed with a bone reconstruction, ramus vertical osteotomy or condilar plate. This case demonstrates that TMJ replacement with prosthetic joint is technically possible and appropriate in the case of malunion of condylar fracture.

La literatura internacional presenta información asociada a la mal unión de fracturas condilares de laarticulación temporo mandibular; el tratamiento es variado siendo ejecutado con reconstrucciones óseas, osteotomía vertical de rama mandibular o instalación de placas con forma condilar. Este caso demuestra que el reemplazo de ATM con prótesis articular es técnicamente posible y apropiado en casos de malunion de fracturas condilares.

Comparative study between 2 methods of mounting models in semiadjustable articulator for orthognathic surgery.

PURPOSE: Compare the traditional method of mounting dental casts on a semiadjustable articulator and the new method suggested by Wolford and Galiano, 1 analyzing the inclination of maxillary occlusal plane in relation to FHP. MATERIALS AND METHODS: Two casts of 10 patients were obtained. One of them was used for mounting of models on a traditional articulator, by using a face bow transfer system and the other one was used to mounting models at Occlusal Plane Indicator platform (OPI), using the SAM articulator. After that, na analysis of the accuracy of mounting models was performed. The angle made by de occlusal plane and FHP on the cephalogram should be equal the angle between the occlusal plane and the upper member of the articulator. RESULTS: The measures were tabulated in Microsoft Excell(®) and calculated using a 1-way analysis variance. Statistically, the results did not reveal significant differences among the measures. CONCLUSION: OPI and face bow presents similar results but more studies are needed to verify its accuracy relative to the maxillary cant in OPI or develop new techniques able to solve the disadvantages of each technique.

Efficacy of eminectomy in the treatment of prolonged mandibular dislocation

Surgery of the temporomandibular joint is indicated for different clinical situations, including internal derangements,hipomobility, hipermobility, pathology and trauma. Mandibular dislocation is an acute painful condition that causes severe functional limitation. Manual reduction, with or without pharmacological assistance, is the treatment of choice and should be performed as early as possible. On rare situations mandibular dislocation maynot be perceived by the patient and remain undiagnosed or misdiagnosed for a long period. This may include severe illness, neurological diseases and prolonged intensive care hospitalization with oral intubation and sedation.Treatment of prolonged mandibular dislocation is different. Morphological changes of the joint and associated structures will prevent successful manual reduction even with the patient under general anesthesia. Basically, two types of surgery may be indicated: elimination of the articular eminence (eminectomy) or reestablishment of a new condyle - ramus relationship, that can be achieved by condilotomy. This article reports a case of prolonged mandibular dislocation that was treated surgically with success. A review of the literature is performed by authors and advantages and disadvantages of each type of treatment are discussed (AU)

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Efficacy of eminectomy in the treatment of prolonged mandibular dislocation.

Surgery of the temporomandibular joint is indicated for different clinical situations, including internal derangements, hypomobility, hypermobility, pathology and trauma. Mandibular dislocation is an acute painful condition that causes severe functional limitation. Manual reduction, with or without pharmacological assistance, is the treatment of choice and should be performed as early as possible. On rare situations mandibular dislocation may not be perceived by the patient and remain undiagnosed or misdiagnosed for a long period. This may include severe illness, neurological diseases and prolonged intensive care hospitalization with oral intubation and sedation. Treatment of prolonged mandibular dislocation is different. Morphological changes of the joint and associated structures will prevent successful manual reduction even with the patient under general anesthesia. Basically, two types of surgery may be indicated: elimination of the articular eminence (eminectomy) or reestablishment of a new condyle-ramus relationship, that can be achieved by condilotomy. This article reports a case of prolonged mandibular dislocation that was treated surgically with success. A review of the literature is performed by authors and advantages and disadvantages of each type of treatment are discussed.