Influence of Multi-cycle Infiltration on Porosity and Optical Properties of Glassinfiltrated Alumina Biocomposites for Dental Restorations

Abstract

Glass-infiltrated alumina biocomposites have been largely used in Dentistry due to their biocompatibility, high potential to mimic the natural dentition and good marginal adaptation. However, their optical and mechanical properties are jeopardized by the presence of residual porosity in the final structure. The objective of this study was to increase light transmittance of alumina-based biocomposites that are infiltrated with a lanthanum-containing aluminosilicate glass by means of increasing the number of infiltration cycles from one to three. The influence of the number of cycles on both residual porosity and optical properties was assessed. The infiltration cycles were carried out at 1200°C for 95 min. After each cycle the residual glass was removed and an additional glass layer was placed over the alumina preform. The SEM images showed that specimens infiltrated with three cycles had denser microstructure, with a residual porosity of 1.8 vol%, whereas specimens submitted to only one cycles showed residual porosity of 4.5 vol%. Transmittance increased 55% for specimens subjected to three infiltration cycles, while light scattering coefficient was reduced by 45% and the contrast ratio was reduced by 23%. These results indicate that the higher number of cycles resulted a more translucent material due to lower porosity and lower pore size (smaller than 3.2 µm). In conclusion, this work showed that multi-cycle infiltration is effective in reducing residual porosity and improving light transmittance of the biocomposite tested.