Efficacy of cleaning methods for the trans-mucosal parts of zirconia monolithic crowns

Objectives: To characterize quantitatively and qualitatively the pollution of transmucosal parts of zirconia monolithic crown after supra-mucosal glazing in the lab, and to compare the efficacy of steam versus ultrasonic cleaning protocols.

Material and methods: 18 customized zirconia monolithic crowns fixed on an angulated screw channel titanium base were divided into two groups of 9 crowns receiving a different cleaning protocol. The first group was treated with steam whereas the second group was initially rubbed with a sterile compress soaked in a detergent and then cleaned in three successive ultrasonic baths containing a detergent, pure water, and 70° ethanol. The presence of pollutants was quantified by scanning electron microscopy and the nature of the contaminants was investigated by an energy-dispersive X-ray spectroscopy analysis.

Results: The percentage of pollutants at baseline was 0.51 ± 0.26. This percentage dropped respectively to 0.02 % ± 0.03 after the steam cleaning process (p < 0.0001) and to 0.02 % ± 0.01 when applying the ultrasonic cleaning protocol (p = 0.0026). No difference was observed between the two techniques (p > 0.9999) but the variance in the S group was higher compared to the US group (p = 0.0042). Some components were detected on crowns surfaces before cleaning methods.

Conclusions: Both cleaning protocols allowed to clean the transmucosal parts of the zirconia crown to an extend of 99. 98% of the studied surface. However, the US technique displayed less variability in the removal of the residual pollutants and therefore might be preferred.