Effect of coating on the color and surface hardness of the surface of dental ceramics

Abstract

Background: The aim of this study was to investigate whether boron nitride (BN) and
BN–chromium (BN–Cr) coatings applied with the sputtering method would change the
characteristics of hardness and discoloration of the ceramic veneer surface.
Materials and Methods: In this experimental study, thirty disc‑shaped cores (10 mm in diameter
and 0.8 mm in thickness) were prepared. Three different ceramic systems, IPS Empress (E) (Ivoclar
Vivadent, Schaan, Liechntenstein), IPS e.max Press (EP) (Ivoclar Vivadent, Schaan, Liechntenstein),
and Turkom Cera (T) (Turcom‑Ceramic SDN‑BHD, Kuala Lumpur, Malaysia), were tested, each
with n = 10. The specimens were divided into two subgroups (n = 5) according to the coating on
the veneering ceramic: BN or BN–Cr. The Vickers hardness and color differences (ΔE) values were
measured before and after coating. Surface analysis was performed with X‑ray diffraction, X‑ray
photoelectron spectroscopy, and scanning electron microscopic. The Wilcoxon signed‑rank test was
performed to compare hardness values. The Kruskal–Wallis test was performed to compare ΔE
values among all groups. The post hoc tests was used after Kruskal–Wallis, with level of statistical
significance set at P ≤ 0.05.
Results: BN–Cr coating statistically significantly increased the hardness of all types of
ceramics (P < 0.05). BN coating did not change the hardness statistically significantly (P > 0.05).
The mean ΔE values indicated clinically noticeable (over the limit of 3.7) color change in all groups
except for the EP‑BN and T‑BN groups.
Conclusion: Although BN–Cr coating in this thickness had a negative effect on color, it increased
the hardness of the ceramics and could be useful in the palatal region.
Key Words: Ceramics, color, hardness, sputter coating