Influence of 3D printed and milled zirconia on the adhesion and viability of keratinocytes: An in vitro study.

STATEMENT OF PROBLEM

The biocompatibility and cell response of additively manufactured ceramics, important for long-term clinical success, require additional investigation.

PURPOSE

The purpose of this in vitro study was to compare the biocompatibility and cell response of human gingival keratinocytes with 3-dimensionally (3D) printed and conventionally milled zirconia.

MATERIAL AND METHODS

Cylindrical specimens of 3D printed and milled zirconia were prepared, and immortalized human gingival keratinocytes (IHGKs) were cultured on specimens of these materials. Cells cultured only in growth medium were the control. Cell adhesion, viability, and morphology were assessed by using water-soluble tetrazolium (WST-1) assays and scanning electron microscopy (SEM) of the disks after culturing. Eluates from the zirconia specimens were collected and tested to assess potential cytotoxicity over time and surface roughness measured by laser scanning microscopy. For cell adhesion, an independent t test for 2-samples with unequal variances (Welch t test) was performed. For the cytotoxicity tests, differences between groups were analyzed using the post hoc test for multiple comparisons with the Bonferroni correction (α=.05).

RESULTS

After 24 hours, no significant difference in keratinocyte adhesion was found between 3D printed and milled zirconia (P>.05). Cell viability assays showed that, while both materials exhibited lower viability compared with the control, 3D printed zirconia displayed significantly reduced cell viability after 96 hours compared with milled zirconia (P<.001). Average surface roughness (Ra) was significantly higher (P=.001) for printed (0.26 ±0.04 µm) than milled (0.08 ±0.02 µm) zirconia. SEM images confirmed good cellular adhesion and spreading on milled zirconia, with similar attachment on 3D printed zirconia.

CONCLUSIONS

Both 3D printed and milled zirconia demonstrated good biocompatibility with human gingival keratinocytes. However, under extended direct surface contact, cells on 3D printed zirconia showed lower cell viability compared with milled zirconia. While 3D printed zirconia is promising for dental applications, further refinement of its surface properties and biocompatibility may be needed.