Avaliação da textura superficial e comportamento ao desgaste do esmalte dentário

Abstract

The search for increasing the durability of dental restorations and for dental work more similar to enamel has induced an increase in the research work centered on the physical behavior of the involved materials, bringing together efforts from professionals of differentareas, such as material sciences, engineering and dentistry. These dental materials are exposed to the diverse degrading actions present in the oral environment, among them, the dental excessive wear, commonly caused by bruxism, a parafunctional habit of grinding or pressing the teeth. This problem, which causes the loss of perfect occlusal contact and consequently a disturbance in the efficiency of stomatognathic system, has been studied by dentistry mainly focused on measuring wear rates. However, as this is considered a contact problem, it becomes important to know its superficial topography, which is relatedto the existence of asperities on a smaller scale, responsible for the interaction between opposing bodies. In this work, an attempt is made to correlate the topography of dental enamel to its behavior under wear, obtaining a mapping of the wear mechanisms involved. For this purpose, techniques of microscopic mapping were used via 3D profilometry andscanning electron microscope (SEM). These techniques provided tools for quantitative and qualitative analysis of the problem. For the implementation of the procedures, three extracted teeth of different functions in the mastication were used as samples: a canine, a premolar and a molar tooth. For each sample it was selected two areas, a seemingly wear-free and the other with typical facet of bruxism. These areas were evaluated and, through the analysis of the differences among the two surfaces, the wear mechanisms models responsible by the alterations were proposed. Replicas of two premolar teeth were made in epoxi resin (Araldite â). It was evaluated in each tooth and in its respective replica a certain area so that the results could be compared, in way to verify in which level the replica is capable to copy the tooth superficial texture. This procedure was made with the purpose of defining an in vivo method to follow the evolution of wear in bruxism patient. In a last stage a third molar, recently extracted, which was semi-included, butocclusal contact-free, was evaluated in way to characterize the surface of a tooth with the more possible preserved nature. The results indicate that the dental enamel presents a topographical profile with a symmetrical distribution, between peaks and valleys, relative to the parameters of amplitudes as well as to parameters of material concentrations. Thevalues encountered for the amplitude and densities of peaks parameters are high. It was possible to identify the pattern of enamel formation through the detection of the perikymata, so much through profilometry as SEM. It was verified in the degraded tooth the existence of mechanisms of mechanical origin added to chemical reactions, producing a type of wear called chemical wear. The existence of this phenomenon was identified from the verification in the degraded tooth of the presence of more deep valleys in relation to the peaks. The mechanism of abrasion, also present in this type of wear, significantly decreased the amplitude of the peaks.The results still showed that brittle fracture is the dominant dental wear mechanism, which is strongly associated to the displacement pattern of dental contact surfaces and tooth function. Besides, they suggest that the severity of damage is higher for posterior teeth. The evaluation methodology via profilometry 3D revealed potentially efficient for the characterization of the superficial topography and for the verification of the mechanisms of dental wear. The applicability of the replicas could be evaluated. The convenience of correlating SEM and profilometry for checking the obtained data and reaching more consistent interpretation of the results was also shown.