Andrezza Lauria

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.

Evaluation of the Use of Biomodels in Sequelae of Maxillofacial Trauma

El uso de tecnologia de prototipado rapido en Cirugia Oral y Maxilofacial se ha incrementado en la ultima decada, lo que permite la gestion de los biomodelos de procesamiento de imagenes medicas, como tomografia computarizada para obtener un modelo tridimensional con las mismas caracteristicas geometricas del virtual. El objetivo de este estudio es presentar el uso de biomodelos para el tratamiento de las secuelas de un traumatismo maxilofacial con la evaluacion de las historias clinicas en un periodo que varia entre enero de 2000 a diciembre de 2010. Para el diagnostico y la planificacion de la cirugia maxilofacial de las secuelas en este periodo, 15 prototipos fueron utilizados, lo que permite determinar la planificacion del tratamiento con mas precision y para ahorrar tiempo de quirofano.

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.

Biomechanical analysis on different fixation techniques for treatment of mandibular body fractures

Aim: To biomechanically analyze two fixation techniques in polyurethane hemi-mandibular bodyfractures, using a universal testing machine. Methods: The study employed 10 polyurethanehemi-mandible replicas, which simulated simple fractures of the mandibular body, divided into twogroups: one group comprised 5 hemi-mandibles with two 2.0 mm system plates in the tension andcompression zones, while the other group contained 5 hemi-mandibles with an Erich bar and a2.0 mm system plate in the tension and neutral zones, respectively. Data were analyzed statisticallyby the Student’s t-test (α=0.05) Results: The test results indicated that the fixation using 2.0 mmsystem plates offered significantly more resistance to the loads and presented significantly largerdisplacement compared to the fixation using just one 2.0 mm system plate and the Erich bar.Conclusions: It may be concluded that the use of two plates in the 2.0 mm system had greatermechanical strength than a single 2.0 mm plate combined with an Erich bar. Clinically, it is knownthat both techniques can provide good results, but patients receiving the combination of Erich barand one plate are required to be more cooperative during the postoperative period, especiallywith respect to the prescribed diet in order to avoid failures in this system. (AU)

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

ObjectivesThis paper aims to evaluate in vitro the mechanical and microstructural properties of internal fixation systems used in oral and maxillofacial surgeries.Materials and methodsFour 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.ResultsPlates 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.ConclusionsThe results indicate that all materials tested are adequate for use in oral maxillofacial surgeries.

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.