Evaluation of Viability and Adhesion of Human Gingival Fibroblast and the Adhesion of Oral Microflora on Thermally Aged Zirconia and BioHPP Abutment Surfaces: An In Vitro Study

Background: The objective of the study is to evaluate the effect of thermal aging of zirconia and BioHPP abutment surfaces on the viability and adhesion of human gingival fibroblasts (HGFs) and multispecies biofilm formation of Escherichia coli (E. coli) and Streptococcus mutans (S. mutans). Materials and Method: The study utilized circular disks of zirconia oxide (ZrO₂) and BioHPP measuring 8 × 2 mm. The surface roughness was evaluated for both nonaged and aged specimens. The HGF viability was evaluated by using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, adhesion using scanning electron microscopy (SEM). Multispecies biofilms were analyzed quantitatively by using a software ImageJ and qualitatively by SEM. One-way ANOVA was used paired with post hoc Tukey test for the statistical analysis. Results: The surface roughness of BioHPP was significantly more than that of zirconia, and aged zirconia had significantly more surface roughness than nonaged zirconia. In terms of cell viability, zirconia showed higher viability of HGF compared to BioHPP where aged specimens had lesser cell viability than nonaged specimens. BioHPP had a higher adhesion rate of S. mutans and E. coli in comparison to zirconia, and aged specimens had a higher adhesion rate compared to nonaged specimens. Conclusion: Surface roughness affects the bioactivity of the cells. Therefore, for the longevity of implants, a smoother surface is preferred. Even though zirconia showed better results in terms of HGF viability and microbial adhesion in comparison to BioHPP, the smaller differences between the two show that BioHPP can be used as an alternate to zirconia in esthetically driven cases. But both the materials show that aging affects the physicochemical properties and bioactivity of the surrounding cells.