Ex vivo pilot study on the performance of ultrasonic and rotary instruments obtained by the process of chemical vapor deposition (CVD) in fixed prosthodontics

Trabalho final do 5º ano com vista à atribuição do grau de mestre no âmbito do ciclo de estudos de Mestrado Integrado em Medicina Dentária apresentado à Faculdade de Medicina da Universidade de Coimbra.Statement of the problem Recently, and attempting to overcome some limitations of the conventional tools, instruments obtained by a process of chemical vapour deposition (CVD) appeared with promising features and alleged advantages in many applications, such as preparation and finishing in fixed prosthodontics procedures. However, there is still no conclusive evidence of their superior performance. Objectives The aim of this study is to test different types of CVD-obtained instruments in crown preparations, using profilometric evaluation of surface roughness and three-dimensional form, in order to demonstrate, in a scientific manner, the advantages or disadvantages of these instruments, as well as diagnose possible flaws or confirm the accuracy of the methodology, thus being called a pilot study. Materials and methods Margin preparations were made, with the aid of a parallelometer, applying different methods of preparation and finishing in a split-tooth model. The margins were photographed with high magnification, and then a 3D profilometric evaluation was made, resulting in values for different roughness parameters, as well as three-dimensional images of the surface. Results The group prepared and finished with CVD burs achieved the lowest roughness values. The highest scores were associated to the group prepared with high-speed diamond burs and finishing made with CVD ultrasonic tips. Groups 4 and 1 achieved both median scores, whereas the latter presented greater variability. However, in a visual analysis of the three-dimensional images, groups 2 and 4 (both finished using CVD ultrasonic tips) show a more regular and smooth surface, with less relief marks, opposing to the ones corresponding to groups 1 and 3, which show a more pronounced bur path, matching its movements along the margin. Conclusion Preparations made with CVD burs present the best roughness results, conventional diamond burs presented the most variable ones and the association between conventional diamond burs and CVD ultrasonic tips presented the worst values. Nonetheless, by examining the three-dimensional images and taking in consideration a whole set of success parameters, groups finished using CVD ultrasonic tips seem to deliver better conditions for a positive outcome of fixed prosthodontic restorations by providing more precise, well-defined and sharp margins, which can enhance marginal fit, castability and aesthetics. Clinical significance Clinically, the definition, sharpness and precision on the margins are more important features than roughness, as dissected on this study. Provided that margins produced with CVD ultrasonic excel on these characteristics, this makes them a valid and important tool in the execution of a successful fixed prosthodontics restoration