Efficacy of Cleaning Methods for the Trans-Mucosal Parts of Zirconia Monolithic Crowns

Background

Dental crowns have surface pollutants after their manufacturing. We know that these pollutants can be a source of peri-implant inflammation for some cases. This study aimed to compare two dental crowns cleaning methods that are simple and quick to apply in the dental lab.

Objectives

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

Material and Methods

Eighteen customized zirconia monolithic crowns were divided into two groups of 9 crowns receiving a different cleaning protocol. The first group was treated with steam cleaning, 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, sterile water, and 70% ethanol. The presence and nature of the contaminants were investigated by BSE-SEM and energy-dispersive X-ray spectroscopy microanalysis.

Results

Organic (e.g., paint, sweat) and inorganic (e.g., zirconia fragments, silica, and metals) were identified on the surface of the zirconia crown before the cleaning treatments. At baseline, pollutants cover 0.51% ± 0.26% of the total area. This percentage dropped, respectively, to 0.02% ± 0.03% after steam cleaning (p < 0.0001) and to 0.02% ± 0.01 after the ultrasonic cleaning protocol (p = 0.0026). No difference was observed between the two decontamination techniques (p > 0.9999), but the variance in the steam group was higher compared to the ultrasound group (p = 0.0042).

Conclusions

Both protocols allowed the cleaning of the transmucosal parts of the zirconia crowns to an extent of 99.98% of the studied surface. However, the ultrasound technique displayed less variability in the removal of residual pollutants and therefore should be preferred.