Comparison of the Effect of Saliva on the Mechanical Properties and Microscopic Profile of Cad/Cam and Conventional Resins: Experimental Study

Introduction: For a long time now, the majority of conventional complete denture bases have been made from acrylic resins. Conventional PMMA-based acrylic resins have remained firmly established in our practice because of their many qualities. Dentistry's entry into the era of computer-assisted design and manufacture (CAD/CAM) has offered prosthetic solutions adapted to a wide range of situations and has led to gains in precision, reproducibility and time. This work is an experimental study that investigates the microscopic structure and mechanical behaviour of two groups of acrylic resin intended for the manufacture of total dentures, while focusing on the salivary action on both types. Materials & Methods: The experiment was carried out in 3 successive stages: The first stage involved analysing the samples under a scanning electron microscope and evaluating their mechanical behaviour in terms of hardness and tensile strength. The second stage consisted of soaking the samples in artificial saliva according to a protocol described in the literature. The third stage involved carrying out the same types of analysis (SEM and mechanical) on the soaked samples. Results: Scanning electron microscope images of conventional PMMA were marked by the presence of black dots of different intensities and diameters ranging from 1 to 10 μm. They are of considerable number and occupy a large surface area in the observed sample. The image revealed spots of high opacity in places. The images were clustered and the domains are randomly oriented. The CAD/CAM images were characterised by the presence of a few black dots of varying intensities, most of which were no more than 3 μm in diameter. Other scattered dots show high opacity with band-like texturing. In the mechanical tensile test, we can say that PMMA - Conventional has better elongation and better plastic deformation, and is therefore better able to absorb external stresses, due to its high elongation capacity. On the other hand, the mechanical strength is lower than that of PMMA - CAD/CAM. The latter has higher mechanical strength but low elongation. Conclusion: This study highlights the potential benefits of CAD/CAM resins in terms of microscopic quality and mechanical strength, suggesting their advantageous use in dental prosthetics. However, long-term clinical studies are needed to validate their clinical suitability and durability.