Estevam Barbosa de Las Casas

Avaliação objetiva das forças axiais produzidas pela língua de crianças respiradoras orais

ABSTRACT Purpose: To quantify and to compare the forces produced by the tongues of pre-surgical mouth-breathing children, oral-breathingchildren enrolled in therapy and nasal-breathing children, and also to compare the findings of objective and clinical evaluations. Methods: Transversal study with 15 children of both genders with ages between eight and 12 years: five pre-surgical mouth breathers(Group 1), five mouth breathers enrolled in speech therapy (Group 2) and five nasal-breathing children (Group 3). A clinicalassessment of each child’s tongue characteristics was carried out, followed by the objective evaluation of the axial centre line forceof the tongue using the instrument created at Federal University of Minas Gerais. The results were descriptively analyzed usingmeasures of central tendency and dispersion. Results: The average of the force values found in Groups 1, 2 and 3, respectively,were 5.6, 6.0 and 7.3N. The average values of maximum force were 8.2, 9.2 and 10.4N. The individuals with adequate tonguetension in the clinical evaluation were the ones with highest values of average (7.0N) and maximum force (10.3N). The lowestvalues (3.5N and 2.0N) were obtained by the subjects whose subjective evaluation showed hypotension of the tongue. Statisticalanalysis indicated heterogeneous data in Groups 1 and 2, tending towards homogeneous in Group 1.

Comparison of the Mechanical Behavior between Controlled Memory and Superelastic Nickel-Titanium Files via Finite Element Analysis

INTRODUCTION The aim of this study was to evaluate the flexibility and torsional stiffness of a controlled memory (CM) nickel-titanium (NiTi) file and compare its mechanical responses with those of a superelastic NiTi file with the same geometry using finite element simulation. METHODS A commercially available instrument with a tip size of 30 and a 0.06 taper was selected for this study. The geometric model for finite element analysis was generated by micro-computed tomographic scanning, and the data for the constitutive model of controlled memory NiTi were obtained from the literature. The numeric analysis was performed in ABAQUS (SIMULIA, Providence, RI) with boundary conditions that were based on the ISO 3630-1 specification. RESULTS The CM NiTi file exhibited the least bending moment and maximum stress value (523 MPa) under 45° bending simulation. However, the least torsional stiffness was calculated for this same instrument. CONCLUSIONS The higher flexibility and potential fatigue resistance of the CM NiTi files were confirmed, indicating that this new technology represents an improvement in the mechanical behavior of the rotary NiTi files.

Abfraction and anisotropy-effects of prism orientation on stress distribution

This work discusses the effect of enamel anisotropy in the stress concentration at the cement-enamel junction (CEJ), a probable cause of fracture in enamel leading to abfraction. Usual simplifications when developing computer models in dentistry are to consider enamel isotropic, or that the direction of the prisms is orthogonal to either the dentine-enamel interface or the tooth outer surface. In this paper, a more refined model for the material behavior is described, based on laboratory observation and on the work of Fernandes and Chevitarese [1] . The material description is used in a two-dimensional (2D) finite element model of the first upper premolar, and the analysis is performed for two different situations: vertical loads, typical of normal mastication and horizontal loads, dominant in bruxism. The analyses were performed using a unit load, which under the hypothesis of linear response of the tooth, allows the combinations described in the text to simulate different functional and parafunctional loads. The results indicate that a realistic enamel description in terms of mechanical properties and spatial distribution of its prisms alters significantly the resulting stress distribution. For all cases included in this study, the detailed description of prism orientation and resulting anisotropy led to improved response in terms of stress distribution, even when loading was horizontal.

Sistemas osso-implante ex vivo utilizando haste intramedular polimérica para imobilização de fraturas femorais em bovinos jovens

The development of new devices using available and low cost materials may be an useful alternative for the treatment of long bone fractures in large animals. The aim of this study was to evaluate the mechanical strength of young bovine femur with diaphyseal fracture fixed with different polymeric intramedullary nails. Bending and compression tests using a universal machine were carried out in 4 distinct groups of 6 femurs from young calves. In one of the groups bones were intact while in the other three fractured bones were fixed using an intramedullary nail made of polypropylene, polyacetal or polyamide (one for each group). Considering bending and compression tests together, none of the used polymers offered strength to the fractured bones similar to the intact ones. The agreement of this findings with those from previous published in vivo results indicates that the employed ex vivo methods for mechanical assays may be useful in the search of stronger materials to be used in development of new devices.

Non-invasive methods of computer vision in the posture evaluation of adolescent idiopathic scoliosis

PURPOSE Reviewing techniques for non-invasive postural evaluation of adolescent idiopathic scoliosis (AIS) based on information extraction from images based on computer methods. METHODS The Scopus, Web of Science, MEDLINE, ScieLo and PubMed databases were used, for the period 2011-2015. RESULTS 131 articles were found based on keyword of which 15 articles met the established eligibility criteria. Of these, 4 were based on photogrammetry, and 11 based on laser, structured light, ultrasound, and Moiré projection. In these studies, the methodological quality varied from low to high. CONCLUSIONS The findings indicated diversity in methodologies; 14/15 articles reviewed were limited to the evaluation of the topography of the posterior back. A study, using two-dimensional photogrammetry, presented a whole body postural evaluation. As the asymmetry in AIS can be extended to the whole body, more attention should be given to develop full body assessment techniques to provide important additional data to aid in treatment decisions.

Desenvolvimento de um sistema protótipo para medição objetiva das forças linguais em humanos

This work presents the development of a system for the measurement of the axial forces produced by the human tongue. A prototype was developed which reproduces the underlying principles of the methods normally adopted in clinical procedures, with the advantage that it allows the phonoaudiologist to obtain objective measurements of these forces. This work also presents an analysis based on the repeatability and the reproducibility of the forces in an attempt to select which of these forces can be employed as parameters for diagnosis and as success indicators of therapies. Preliminary results indicate the mean force as the most reliable parameter.

Determination of tangential and normal components of oral forces

Oral forces applied to human teeth during biting and mastication are normally described in the literature only in terms of their axial components. The purpose of this study was to fully determine the spatial characteristics of the oral resultant force – its normal and tangential components - for a given individual. A load cell was especially manufactured to measure oral force and was temporarily implanted as a prosthetic device in the dental arch of a volunteer, replacing his missing upper first molar. The mastication and occlusion tests were carried out in such a way the cell should withstand the loads applied to the molar, and its state of strain was recorded by strain gauges attached to it. Based on the results of these tests and using balance equations, normal and tangential components of the resultant oral force were determined. For direct occlusion, without interposition any obstacle between cusps, a peak normal force of 135 N was recorded simultaneously to a tangential force of 44 N. For mastication of biscuits, a peak normal force of 133 N and a tangential force of 39 N were obtained.

Mechanical behavior of three nickel-titanium rotary files: A comparison of numerical simulation with bending and torsion tests

AIM To assess the flexibility and torsional stiffness of three nickel-titanium rotary instruments by finite element analysis and compare the numerical results with the experiment. METHODOLOGY Mtwo (VDW, Munich, Germany) and RaCe (FKG Dentaire, La-Chaux-de-Fonds, Switzerland) size 25, .06 taper (0.25-mm tip diameter, 0.06% conicity) and PTU F1 (Dentsply Maillefer, Ballaigues, Switzerland) instruments were selected for this study. Experimental tests to assess the flexibility and torsional stiffness of the files were performed according to specification ISO 3630-1. Geometric models for finite element analysis were obtained by micro-CT scanning. Boundary conditions for the numerical analysis were based on the specification ISO 3630-1. RESULTS A good agreement between the simulation and the experiment moment-displacement curves was found for the three types of instruments studied. RaCe exhibited the highest flexibility and PTU presented the highest torsional stiffness. Maximum values of von Mises stress were found for the PTU F1 file (1185MPa) under bending, whereas the values of von Mises stress for the three instruments were quite similar under torsion. The stress patterns proved to be different in Mtwo under bending, according to the displacement orientation. CONCLUSIONS The favorable agreement found between simulation and experiment for the three types of instruments studied confirmed the potential of the numerical method to assess the mechanical behavior of endodontic instruments. Thus, a methodology is established to predict the failure of the instruments under bending and torsion.

Falhas na utilização de poliacetal e poliamida em forma de haste intramedular bloqueada para imobilização de fratura femural induzida em bovinos jovens

In spite of the expressive development of veterinary orthopedics in the last years, long bone fractures in large animals remains a challenge for veterinary surgeons. This study is part of a proposal for development of a low-cost and easy-to-use polymeric interlocking nail designed to be used in newborns and young cattle. The objectives were to evaluate, in vivo, polyacetal and polyamide nails for immobilization of femoral fractures in calves. Five calves were submitted to general anesthesia and the left femur was fractured and then fixed using polyacetal or polyamide rods (nails) interlocked with four cortical screws (stainless steel) equally applied to the distal and proximal fracture line. In the postoperative period, calves were clinically assessed during 60 days by clinical and radiographic exams. Fractures occurred in four of the five polyacetal nails implanted in the first time and in two of the four polyamide nails implanted after the polyacetal nail failures. All failures occurred in the first 14 days after implantation. No rejection signs against the polymers were observed. In conclusion, polyacetal and polyamide did not have enough resistance to be used as intramedullary interlocking nails in this system designed to promote early femoral fractures immobilization in young calves.

Experimental and numerical analysis of large ferrocement water tanks

Abstract In the current work the ferrocement construction technique is revisited with the purpose of applying the material in civil engineering structures, particularly in large water tanks for water treatment stations. Although it is not a new technology, ferrocement continues to be an attractive alternative. The plastic potential, the unsophisticated construction techniques and the low cost justify its use, especially suitable for developing countries. However, modelling studies of this material are rare in the literature; this is what justifies the studies currently being conducted to improve current practices of design, as well as to further advance the understanding of the material. This work describes experimental and numerical tests for large ferrocement tanks, part of the water treatment facility in Divinopolis, Brazil. Different finite element models have been used in the analyses in order to evaluate the effect of some adopted simplifications. Some comparisons of the investigated approaches with the experimental data are also included, as well as remarks on the use of different constitutive models, homogenisation techniques and accuracy of the modelling data.