Surface Modification of Zirconia with Fibronectin by Using Glow Discharge Plasma

BACKGROUND: Titanium dental implants with non-treated surfaces or treated surfaces have been used for many years. However, it has been discovered that titanium has several drawbacks, such as grey and non-esthetic color, metallic allergy, and increased tendency to plaque adhesion when exposed to the oral cavity. Therefore, a similar material with comparable strength to titanium but improving drawbacks of titanium material is being researched and developed by many scientists worldwide. Usage of zirconia material as a metal replacement is widely popular lately in the field of prosthetic dentistry and begin trying to use as an implant abutment and pontic crown and obtain successful results. One downside of zirconia material is its bioinert smooth surface, leading to poor cell-material interaction. So, using a GDP to modify its surface with allylamine and attached biologic fibronectin proteins to improve its surface properties. Creating a biomimetic environment can increase the reaction with the extracellular matrix proteins and cells attachment, which will lead to improve the cell material interaction and stimulate the osteogenesis. Therefore, in this paper, we analyzed the biological and physical properties of the zirconia surface to study whether it could be a better option to use as a dental implant material with improved surface properties.

OBJECTIVE OF THE STUDY: To obtain a zirconia dental implant material with improved biological and physical properties. Enhanced surface properties may promote the adhesion, proliferation and differentiation of osteoblast-like cells on the zirconia implant material and stimulate the osteogenesis.
MATERIALS AND METHODS: Zirconia disk surfaces treated with GDP-Argon first with three different watts (50W,75W and 85W): “Ar-GDP 50W, Ar-GDP 75W and Ar-GDP 85W” and followed by GDP-Allylamine: “GDP-AA 50W, GDP-AA 75W and GDP-AA 85W”. Then, they were immersed in fibronectin solution with 2 different concentrations (5µg/ml and 10µg/ml) to get our final samples: “AA50W+Fib 5, AA50W+Fib 10 and AA75W+Fib 5, AA75W+Fib 10 and AA85W+Fib 5, AA85W+Fib10”. They have undergone the analysis of physic to check the surface properties and biologic to analyze the viability, differentiation and osteogenic properties after the surface modification.
RESULTS: From surface topography evaluation, irregular folding proteins were in fibronectin grafted disks, and a rough irregular raised granular pattern was observed for allylamine grafted samples. According to EDS and XPS data, carbon and nitrogen elements were increased with increasing allylamine wattage for both allylamine and fibronectin grafted samples while oxygen component was decreased. Average surface roughness (Ra) becomes higher with higher fibronectin concentration (Ra value- Fib10µg/ml > Fib5µg/ml) and allylamine energy. For surface wettability, the contact angle becomes higher with increasing allylamine concentration. However, fibronectin grafted samples show higher hydrophilicity with lower contact angle and higher surface energy than their allylamine counterparts and control sample.
Cell viability analysis data obtained on day5 showed that AA75W+Fib5, AA85W+Fib10, AA50W+Fib5, and AA50W+Fib10 had higher OD values compared to other samples groups and were statistically significant with other groups. ALP activity assay demonstrated that AA85W+Fib10, AA50W+Fib10, and AA85W+Fib5 groups had higher ALP activity in Day5. AA50W+Fib10 group had the highest upregulation of OC, DLX5 and SP7 gene while AA85W+Fib10 group showed highest expression for OPG gene.
CONCLUSION: From the above findings of this study, it can be concluded that fibronectin grafted disks showed significant improvement in both physical and biological analysis. It overcome the genuine bio-inert properties and enhanced the osteoblast-like cell response of adhesion, proliferation and differentiation which is a key aspect of bone formation and remodeling. In addition, osteogenic related gene expression also higher after fibronectin grafting and the best and optimal conditions to be used were AA85W+Fib10 and AA50W+Fib 10. However, further in vivo studies should be conducted to confirm the result obtained in this in vitro study and the efficacy of fibronectin protein coating on the implant surface.