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.

Mechanical and microstructural properties of fixation systems used in oral and maxillofacial surgery.

OBJECTIVES: This paper aims to evaluate in vitro the mechanical and microstructural properties of internal fixation systems used in oral and maxillofacial surgeries. MATERIALS AND METHODS: Four brands of internal fixation systems (screws and 4-hole straight plates) were selected and assigned to four groups: G1 Leibinger®, G2 Tóride®, G3 Engimplan®, and G4 Medartis®. The systems were submitted to Vickers hardness testing, metallographic and interstitial elements chemical composition analyses. Data were submitted to ANOVA and Tukey's test for statistical analysis. RESULTS: Plates in groups 1, 2, and 3 showed similar microstructure and mechanical properties, different from those in G4 revealing larger grains. In all groups, the screws showed similar microstructure, with uniform arrangement and size of grains; the screws showed higher hardness values than those observed for the plates. CONCLUSIONS: The results indicate that all materials tested are adequate for use in oral maxillofacial surgeries.

Analysis of residual stress and hardness in regions of pre-manufactured and manual bends in fixation plates for maxillary advancement.

The aim of this study was to analyze, through Vickers hardness test and photoelasticity analysis, pre-bent areas, manually bent areas, and areas without bends of 10-mm advancement pre-bent titanium plates (Leibinger system). The work was divided into three groups: group I-region without bend, group II-region of 90° manual bend, and group III-region of 90° pre-fabricated bends. All the materials were evaluated through hardness analysis by the Vickers hardness test, stress analysis by residual images obtained in a polariscope, and photoelastic analysis by reflection during the manual bending. The data obtained from the hardness tests were statistically analyzed using ANOVA and Tukey's tests at a significance level of 5 %. The pre-bent plate (group III) showed hardness means statistically significantly higher (P < 0.05) than those of the other groups (I-region without bends, II-90° manually bent region). Through the study of photoelastic reflection, it was possible to identify that the stress gradually increased, reaching a pink color (1.81 δ / λ), as the bending was performed. A general analysis of the results showed that the bent plate region of pre-bent titanium presented the best results.

Maxillofacial trauma and seat belt: a 10-year retrospective study.

INTRODUCTION: Brazil is among the countries with the highest prevalence of people injured by traffic accidents, showing that in 2008, levels reached 18.3 victims for 100,000 habitants were victims of traffic accidents. MATERIALS AND METHODS: This retrospective study involved data collected from treated patients' charts at seven different hospitals located in three different cities all in the state of São Paulo, Brazil. Information was obtained through a standardized form, which was designed to investigate the epidemiologic features of maxillofacial traumas, restricted to victims of car accidents. RESULTS: Three hundred ninety-six patients were victims of car crashes with mean age 29.75 years. The age group 18-30 years showed an association with facial trauma in 96 patients, 41.56 % of whom reported using seat belt. Le Fort I, II and III (70 %) and mandible (63.11 %) were more associated with body traumas and seat belt use. The most common soft tissue lesion was laceration with 189 cases (42.3 %). The treatment way was assessed, 93 (23 %) were treated surgically and 303 (77 %) underwent conservative treatment. DISCUSSION: Classically, it is known front seat belt use was positively correlated with back seat belt use, healthy diet, dental and general health, regular walking, adequate sleep and no smoking. Accidents involving cars occurred more frequently in age group 18-30 years, suffering more general traumas and representing the nonusers group that wore fewer seat belts, caused, perhaps, by bigger access of the youth to cars, driving in high speed and to an inefficient fiscalization of the traffic laws.

Anatomical relationship of lingual nerve to the region of mandibular third molar.

OBJECTIVES: This study evaluated the relationship of the lingual nerve with the adjacent anatomical structures of the mandibular third molar region, influencing the dentist to be aware of the variability of these relationships. MATERIAL AND METHODS: Samples of 24 human corpse half-heads were selected and divided according with the presence or absence of the mandibular third molars. The lingual nerve (LN) was explored, showing its run from the oblique line until its crossing with the submandibular gland duct. The measurements along the LN and the adjacent anatomical structures were taken at the retromolar, molar and sublingual region with the use of a digital caliper. RESULTS: The distance from the LN and the third molar socket, which represents the horizontal distance of the lingual plate to the nerve, on average, was 4.4 mm (SD 2.4 mm). The distance from the LN and the lingual alveolar rim, which represents the vertical relationship between the nerve and the lingual alveolar rim of the third molar socket, on average, was 16.8 mm (SD 5.7 mm). The LN has a varied topography that leaves it very vulnerable during any procedure executed in this region. CONCLUSIONS: Unless adequate protection of the lingual nerve is acquired by following an adequate surgical technique, the lingual nerve will always be vulnerable to damage during surgical intervention or manipulation in this region.