Danillo Costa Rodrigues

Mechanical and photoelastic analysis of four different fixation methods for mandibular body fractures

OBJECTIVE The aim of the present study was to compare four methods of fixation in mandibular body fractures. STUDY DESIGN Mechanical and photoelastic tests were performed using polyurethane and photoelastic resin mandibles, respectively. The study groups contained the following: (I), two miniplates of 2.0 mm; (II) one 2.0 mm plate and an Erich arch bar; (III) one 2.4 mm plate and an Erich arch bar, and (IV) one 2.0 mm plate and one 2.4 mm plate. The differences between the mean values were analyzed using Tukeys test, the Mann-Whitney test and the Bonferroni correction. RESULTS Group II recorded the lowest resistance, followed by groups I, IV and III. The photoelastic test confirmed the increase of tension in group II. CONCLUSION The 2.4 mm system board in linear mandibular body fractures provided more resistance and the use of only one 2.0 mm plate in the central area of the mandible created higher tension.

Clinical, radiographic, and histological analyses of calcium phosphate cement as filling material in maxillary sinus lift surgery

BACKGROUND The installation of dental implants in the posterior maxilla is often faced with resorbed alveolar processes, resulting from a combination of pneumatization of the maxillary sinus, the effects of periodontal disease, and physiological bone resorption. The sinus lift surgery has been practiced since 1980 with the aim to increase bone height in this region for an implant supported prosthetic rehabilitation, and various filling materials have been used for such. OBJECTIVES This study aimed to clinically, radiographically, and histologically evaluate a preparation of calcium phosphate cement (Bone Source(®), BS) used as filling material in maxillary sinus elevation surgery. METHODS Ten patients were operated requiring maxillary sinus graft for future placement of osseointegrated implants. After a period ranging from 9 to 16 months, a clinical evaluation and biopsy of the grafted area in the region adjacent to the axis of the implant to be inserted were performed. RESULTS Clinically and radiographically, no evidence of resorption/substitution of BS was noticed. Although no patients have had postoperative complications and the material presented fully biocompatible characteristics with woven bone in intimate contact with BS, it was not possible to place any implants due to minimal bone formation and friability of the material. CONCLUSION It was concluded that despite the osteoconductive capacity of BS, this conventional calcium phosphate preparation does not support sufficient amount of new bone formation that could allow its use as filling material for maxillary sinus floor lift and subsequent dental implant placement.

Development plates for stable internal fixation: Study of mechanical resistance in simulated fractures of the mandibular condyle

OBJECTIVE To develop Y-shaped plates with different thicknesses to be used in simulated fractures of the mandibular condyle. Ten plates were developed in Y shape, containing eight holes, and 30 synthetic polyurethane mandible replicas were developed for the study. MATERIAL AND METHODS The load test was performed on an Instron Model 4411 universal testing machine, applying load in the mediolateral and anterior-posterior positions on the head of the condyle. Two-way ANOVA with Tukey testing with a 5% significance level was used. RESULTS It was observed that when the load was applied in the medial-lateral plate of greater thickness (1.5 mm), it gave the highest strength, while in the anteroposterior direction, the plate with the highest resistance was of the lesser thickness (0.6 mm). A plate with a thickness of 1.5 mm was the one with the highest average value for all displacements. In the anteroposterior direction, the highest values of resistance were seen in the displacement of 15 mm. CONCLUSION After comparing the values of the biomechanical testing found in the scientific literature, it is suggested that the use of Y plates are suitable for use in subcondylar fractures within the limitations of the study.

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.

Perception of oral and maxillofacial surgeons, orthodontists and laypersons in relation to the harmony of the smile

OBJECTIVE Harmony is one of the main objectives in surgical and orthodontic treatment and this harmony must be present in the smile, as well as in the face. The aim of the present study was to assess the perceptions of professionals and laypersons in relation to the harmony of the smile of patients with or without vertical maxillary alterations. MATERIALS AND METHODS Sixty observers (oral and maxillofacial surgeons, orthodontists and laypersons) reported the degree of harmony of six smiles using an objective questionnaire and the participants indicated if there was a need for corrective surgery or not. The classification of observers was recorded on a Likert scale from 1 to 5. Mixed regression was used to determine differences between the three groups. RESULTS Statistically significant differences were found only for the harmony of the smile between the oral and maxillofacial surgeons and laypersons, with laypersons being more critical when assessing the smile. There was no statistical difference between the other groups for the harmony of the smile or the indication of corrective surgery. The patterns of greater or lesser harmony determined by observers during the smile were similar to those found in the literature as the ideal standard in relation to vertical maxillary positioning. CONCLUSIONS Laypersons had a tendency to be more critical in relation to facial harmony than surgeons, although no statistical differences were found in the other groups in relation to the harmony of the smile or indication for the corrective surgery. In addition, the patterns of greater or lesser harmony of the smile determined by the participants were similar to those found in the literature as the ideal standard in relation to vertical maxillary positioning. Overall, the present study demonstrates that adequate interaction between surgeons, orthodontists and laypersons is essential in order to achieve facial harmony with orthodontic and/or surgical treatment. CLINICAL RELEVANCE Opinion of specialists and laypersons about the smile in relation to the vertical positioning of the maxilla.

Evaluation of cyclic and linear mechanical resistance of prebent and manually-bent plates used for maxillary advancement in orthognathic surgery

The aim of the present study was to compare prebent and manually-bent plates used in maxillary advancement. The prebent plates were fixed in polyurethane blocks for the linear test and aluminium blocks for the cyclic test, and the manually-bent plates were fixed in polyurethane and aluminium blocks. The linear load tests were done using an Instron® 4411 mechanical testing machine and the cyclic test with an Instron® E3000 testing machine. The linear mechanical test showed that there was no significant difference between the plates. In the cyclic test the prebent plates reached the limit of 500000 cycles without fracturing whereas the manually-bent plate group fractured before reaching the limit of cycles (p=0.008). The decision to use prebent or manually-bent plates during operations should be influenced by the production of the bends and their consequent brittleness.