Efeito de um protocolo de polimento mecânico para o controle das alterações de superfície de resina acrílica para base de prótese dentária

Abstract

Introduction: The surface of dental prostheses must be smooth enough in order to provide not only comfort to the patient but also to preserve the health of oral tissues, reducing the accumulation of microorganisms and helping maintain important characteristics such as color stability. Objective: The purpose of this study was to evaluate the effect of a frequent mechanical polishing protocol on the surface characteristics of a denture base acrylic resin on dental prosthesis submitted to mechanica l brushing and immersion in sodium hypochlorite (NaOCl) 1%. Materials and method: Sixty acrylic resin specimen were made and divided into three groups (n = 20) randomly: ESC - brushing; HIP - immersion in 1% NaOCl; ADh - immersion in distilled water with the same immersion time as 1% NaOCl (HIP group control). Each group was subsequently divided into two subgroups (n = 10): A- samples only exposed to the proposed conditions; B- samples submitted to an association of simulated fortnight ly mechanical polishing. The mechanical polishing was carried out using aluminum oxide paste and felt wheel coupled to a manual motor at 3000 rpm. The roughness, mass, hardness and color stability before exposures (T0) and after simulated periods of 12 (T1) and 24 (T2) months, totaling three evaluations were evaluated. Results: Both brushing and immersion in NaOCl 1% significantly increased the surface roughness of the material (p<0,05), however, the association with mechanical polishing led to a significa nt reduction of the roughness values (p<0,05) and the maintenance of these values over time. The polishing technique tested prevented the significant increase of mass observed after the immersions in the solutions (p<0,05), when compared to the effect pattern of these solutions on the surface hardness of the acrylic resin. The magnitude of the total color difference (ΔE) accomplished by brushing was lower after polishing was added. Conclusion: The mechanical polishing technique tested was effective in controlling the alterations in acrylic resin properties when submitted to brushing and immersion in 1% NaOCl, exerting minimal, controlled and clinically acceptable wear without compromising the surface properties nor the color stability.