Influence of erosive challenge on surface roughness and adhesion of microorganisms to PMMA blocks for CAD/CAM, after polishing with abrasive rubbers and surface sealants

Abstract

Currently, the exposure of temporary materials to acidic pH has become an important topic for discussion in dentistry, as the number of patients with gastroesophageal reflux disease (GERD) or eating disorders (bulimia nervosa and/or anorexia) has increased significantly. Acid erosion can increase the roughness of the provisional restoration and provide biofilm accumulation and, consequently, inflammation of the gingival tissue due to the adhesion of microorganisms, in addition to decreasing the mechanical strength of the prosthesis and staining. Surface sealants are used in order to decrease surface porosity and obtain smoothness in provisional restorations, however, mechanical and aesthetic problems have been associated with surface sealants. In view of the above, the aim of the present study will be to characterize the surface and analyze the microbiological characteristics of PMMA blocks for CAD/CAM, polished with abrasive rubbers associated with different surface sealants and subjected to the erosive challenge. The study will have four factors under analysis: (1) prefabricated polymer block (PMMA) for the CAD/CAM system; (2) Surface treatments (AT: Astropol tips, SB: Discover surface sealant, and PS: Palaseal surface sealant); (3) Erosive Challenge (EC): immersion in 5% HCl (pH 2.0) for 45 hours (CE1) and 91 hours (CE2) (4) analysis times at 3 levels (T0 - after storage in distilled water for 24 hours, after CE1, and CE2. Three response variables will be considered: (1) characterize the surface through the surface roughness (Ra); (2) Microbiological analysis of mixed biofilm of S. mutans and C. albicans by means of (2.1) Quantification of cultivable cells (CFUs), (2.2) 3D analysis of the biofilm by confocal laser microscopy (CM) and (2.3) analysis of the structure of biofilms by scanning electron microscopy (SEM). The quantitative data obtained in each analysis will be submitted to the normality test and later to the most appropriate statistical test, with a significance level of 5%. Qualitative data will visualize the biofilm structure formed, comparing the different proposed groups.(AU)