The in-vitro evaluation of the adhesion of gingival cells to materials used for Ti-Base restorations

In implant dentistry, Ti-Base abutments are recommended to avoid aesthetic problems caused by metal abutments and inflammation resulting from intraoral cementation. In digital dentistry, the CEREC system (version 5.2.4) lists the following materials as compatible with Ti-Base: IPS e.max CAD (Ivoclar, Liechtenstein), inCoris ZI (Dentsply Sirona, USA), CEREC Tessera (Dentsply Sirona, USA), and Enamic IS (VITA Zahnfabrik, Germany). Enamic IS, a hybrid material containing both feldspathic porcelain and resin, was excluded from this study. This study aimed to investigate the interaction between gingival tissue and materials compatible with Ti-Base restorations. The materials tested were IPS e.max CAD (LD), inCoris ZI (ZR), and CEREC Tessera (ALD). Human gingival fibroblasts (HGF) were used as the cell line. Thirteen samples per group were prepared with dimensions of 5×5×1.5 ± 0.05 mm. ZR and LD samples were polished, while the ALD group received glaze application according to CEREC 5.2.4 specifications. Surface roughness was measured first. Cytotoxicity was evaluated using the MTT assay after 24, 48, and 72 hours of incubation. Cell adhesion was assessed after 7 days using ELISA to measure integrin β4 levels. SEM imaging at 24, 72, and 168 hours (100×, 500×, 1800× magnification) was used to analyze surface characteristics and changes in cell morphology. Statistical analysis was performed using IBM SPSS v29 (IBM Corporation, USA), with a significance level of p < 0.05. Shapiro–Wilk and Kolmogorov–Smirnov tests, paired samples t-test, ANOVA with post-hoc Tukey's HSD, independent median test and pairwise comparisons were used along with descriptive statistics. Polishing significantly reduced surface roughness for all materials. A significant difference was found between the polished ZR and both the polished LD and glazed ALD groups. However, no significant difference was observed between LD and ALD. All materials were non-cytotoxic at all time points according to ISO 10993-5 standards. ZR showed the highest hemidesmosomal attachment. A significant difference existed between ZR and LD, but ALD showed no significant difference compared to the other two. SEM images revealed earlier cell adhesion on ZR, though by day 7, all groups exhibited similar results. Based on the findings, using polished zirconia for gingiva-contacting surfaces of Ti-Base restorations is recommended.