RESUMEN. Antecedentes: El método de elección para asegurar que la superficie no pierda humectación y evitar lesiones posteriores o recalentamiento pulpar es la utilización de elementos rotatorios diamantados con adecuado estado y corte. La información disponible en la literatura, no relaciona directamente la eficiencia de desgaste de las fresas de diamante, con la cantidad y calidad de diamantes en la superficie del instrumento rotatorio ni establece un número de usos que determine la vida media del instrumento. Objetivo: Evaluar la durabilidad de los diamantes de corte sobre la superficie activa de los instrumentos rotatorios de alta velocidad, tras realizar cierto número de desgastes en dientes naturales, y así proporcionar un margen de uso de las fresas de diamante. Métodos: Se realizó un estudio ex vivo que comparó 4 marcas comerciales de fresas de diamante, grano dentro del rango (64 -126 micras) tipo troncocónica, punta redonda (ISO 850): MDT® (ISRAEL), SWISSTECH® (COLTENE-SUIZA), POINTECH® (CHINA), JOTA® (SUIZA), tras 5 usos clínicos. Se realizaron 5 cortes, cada uno de 0.16 mm de la corona del diente. Posteriormente, las fresas de diamante, se llevaron a microscopía electrónica de barrido, para observar: a) adhesión de diamantes a substrato en cabeza y cuerpo, b) estado de los diamantes en el substrato en cabeza y cuerpo, tras los 5 cortes clínicos y c) estado final de las fresas de diamante utilizadas. Se realizó un análisis cualitativo y cuantitativo. Resultados: Todas las fresas, de las 4 marcas evaluadas, presentaron cambios tras los 5 usos realizados, tanto la cabeza y el cuerpo del instrumento, tuvieron el mismo desgaste. Pese a que todas las muestras presentaron variaciones, fue representativo que en algunas fue más evidente el desalojo y fractura de los diamantes. Conclusión: Es necesario que, tras 5 usos clínicos de los instrumentos, se realice un cambio de este, para garantizar un desgaste realizado por los diamantes y no por fricción, y así evitar daños en la pulpa, y en la adhesión de los materiales restaurativos.ABSTRACT. Background: Using elements with appropriate state and cut, is the method of choice to ensure the surface doesn’t lose the initial moisture and avoid later injuries, or pulp overheating, if a blunt or worndown tool is used. Little information is available about wear efficiency of diamond coated burs, that also relates the amount and quality of diamonds on the surface of the rotary instrument, according to the number of uses, and the deleterious effects of the diamond coated burs upon the pulp, and the influence over the dentinal sensitivity of the patient. Aim: To evaluate the durability of cut diamonds on the active surface of the high speed diamond coated burs, after making a number of wears on natural teeth, thus providing a margin of use of diamond coated burs. Methods: An ex vivo study comparing four commercial brands of rotary diamond instruments grain within the range (64 -126 microns) tapered round toe type (ISO 850) was conducted: MDT® (ISRAEL), SWISSTECH® (COLTENE-SWITZERLAND),  POINTECH® (CHINA), JOTA® (SWITZERLAND), after 5 clinical applications in dental enamel. Five cuts were made in enamel tooth crown. Subsequently, rotary instruments took scanning electron microscopy to observe: a) diamond substrate adhesion in the head and body, b) state of the diamond substrate in the head and body, after 5 cuts in enamel c) final state of the diamond rotary instrument used. Results: A qualitative and quantitative analysis was performed. The four brands tested were unchanged after 5 applications made to enamel, so that both the head and body had the same wear. Although all samples showed variations in some representative was most evident, the eviction and breaking of diamonds. Conclusion: It´s necessary to change the rotary diamond instruments, after 5 uses, to have a good coated tissue and to avoid pulp damage, or restorative materials adhesion failure.

<p><strong><span>ABSTRACT. </span></strong><em><strong><span>Background:</span></strong></em><span class="apple-converted-space"><span> </span></span><span>Biomechanical effects of occlusal loads on teeth during clenching and in mastication have been evaluated. A harmful consequence of occlusal overload is tooth fracture, which has been analyzed through methods such as electrical tests, photo elasticity, and finite elements. Although there are numerous studies linking periodontal disease and occlusion, the biomechanical role of the forces exerted on the periodontium has not been studied enough.<span class="apple-converted-space"> </span><em><strong>Objective:</strong></em><span class="apple-converted-space"> </span>To evaluate the effect of normal and harmful occlusal forces on the periodontium through finite elements.<span class="apple-converted-space"> </span><em><strong>Methods:</strong></em><span class="apple-converted-space"> </span>The finite element analysis included the following steps: specification of geometry, element type, and material properties and force magnitudes in Newton’s (from 150 N to 675 N using 25 N increments) on the longitudinal axis of the tooth.<span class="apple-converted-space"> </span><em><strong>Results:</strong></em><span class="apple-converted-space"> </span>There was a statistically significant difference between the stress distribution in periodontal ligament, cortical bone, and dentine according to tooth type (p = 0.000), but not significant differences were observed in cancellous bone (p = 0.166).<span class="apple-converted-space"> </span><em><strong>Conclusion:</strong></em><span class="apple-converted-space"> </span>The concentration of stress was located in the three teeth, incisor, premolar, and molar, in the buccal cervical area where most stress distribution was evident in all magnitudes of force applied.</span></p>