Paulo César Borges

Experimental Force Definition System for a New Orthodontic Retraction Spring

A new geometry of orthodontic retraction spring was experimentally studied through an electronic device (platform for measuring forces), using strain gauges that were adapted to cantilever beams. The sample consisted of 36 titanium-molybdenum springs, divided into three groups of 12 springs each. The springs were produced with different cross sections of 0.016 x 0.022 inch and 0.017 x 0.025 inch and with different angles between the extremities (120 degrees and 130 degrees). The springs were adapted to the platform in three different positions so that the force system developed by them could be known (horizontal forces, vertical forces, alpha-beta moments, and moment-to-force ratio M:F). The analysis of factorial variance and the Tukey honestly significant difference test were applied to verify the differences between the averages caused by three possible variation sources and the interactions between them. Regression analysis was also performed to obtain the spring rate. The results show the interactions between the three geometric variables, force magnitudes, and also the spring rates, which are compatible with the ones mentioned in the literature related to the subject. The spring rate was within the levels that are appropriate for clinical use (varying from beta = 33.1 gf/mm to beta = 43.9 gf/mm).

Alternative methodology for flexural strength testing in natural teeth

The use of natural teeth for performing in vivo , in situ and/or in vitro studies has been widely observed in the dental field. The mechanical behavior of teeth subjected to masticatory efforts is commonly used as a variable of response. In conditions of malocclusion, the most relevant component accounting for the integrity of the dental structure is non-axial (flexural). This force, while acting on a tooth in function in the oral cavity, generates a similar situation as that of a beam in balance supporting a load concentrated on its free extremity. Based on this configuration, a methodology has been developed to investigate the behavior of teeth subjected to this kind of efforts, taking into consideration specific aspects of the tested teeth, such as the transversal section area and the moment of inertia. For determination of the transversal section area an image analysis program was used. For assessment of the other variables, a C++ language program was implemented utilizing the Borland Compiler C++ Builder, version 1.0, for Windows (Borland International, USA). The applicability of the developed methodology is illustrated in this article using bovine teeth. Our findings indicate that more accurate data can be obtained with the application of this methodology and that it is suitable for studies testing the flexural strength of extracted teeth, as a variable of response.

ANÁLISE DE UMA MOLA ORTODÔNTICA DO TIPO DELTA E SUA INFLUÊNCIA NA MOVIMENTAÇÃO DENTÁRIA: UM ESTUDO NUMÉRICO EXPERIMENTAL

Em odontologia sao frequentemente utilizados dispositivos conhecidos por alcas ortodonticas para a movimentacao dentaria em um tratamento clinico. As alcas ortodonticas sao elementos fabricados em fio metalico, cujas forcas e momentos gerados sao diretamente relacionados com os tipos de movimentos de translacao, rotacao controlada e nao controlada dos dentes para fins especificos. Este artigo alia analises de elementos finitos tridimensionais, amplamente utilizados em engenharia, com metodos experimentais para o desenvolvimento de uma alca ortodontica tipo delta. Foram avaliadas as tensoes atuantes, as forcas, os momentos e a relacao momento forca, a fim de prever alguns tipos de movimentos dentarios com o uso da alca proposta. Verificou-se forca de extrusao dentaria nula e ativacao maxima de ate 8,0 mm (tensao maxima de von Mises igual a 1.226,8 MPa), bem como a possibilidade da inducao dos movimentos dentarios de inclinacao nao controlada – controlada de raiz e inclinacao controlada de coroa com o uso desta alca. Palavras-chave: Alcas ortodonticas, metodo dos elementos finitos, analise experimental. ABSTRACT Devices known as orthodontic springs are frequently used in dentistry to provide dental movement in a clinical treatment. Orthodontic springs are, basically, elements manufactured in metallic wire which forces and moments are directly related to the types of translation movement, controlled tilt and no controlled tilt of the teeth. This article allies three dimensional finite element analysis, largely applied in engineering, with experimental methods for the development of an orthodontic delta spring, evaluating the stresses, forces, moments and the ratio moment force, in order to foresee some types of dental movements with the use of the proposed spring. It was verified null dental extrusion forces and maximum activation of up to 8.0 mm (maximum von Mises stress equal to 1,226.8 MPa) as well as the possibility of the induction of dental movements like no controlled – controlled tilt of root and controlled tilt of crown with the use of this spring. Keywords: Orthodontic springs, finite element method, experimental analysis.