Effects of decontamination protocols on the aesthetic, morphological, and material composition of preformed...

Preformed crowns (PCs) are exposed to potentially infectious bodily fluids during the trial fit; however, whether they can be safely re-used remains uncertain. This study determined the effects of decontamination methods on various PCs. The key criteria examined were aesthetic, morphological, and elemental characteristics.

This is a laboratory-based experimental study. Stainless steel, pre-veneered stainless steel, and zirconia PCs underwent either: (a) ultrasonic cleaning with EmPower^® followed by steam sterilisation, (b) thermal disinfection in an instrument washer with Asepti^® Neutraliser/Asepti^® followed by steam sterilisation, or (c) immersion in an ortho-phthalaldehyde (OPA) instrument-level disinfectant. The methods were performed for 1, 5, or 10 cycles, and scanning electron microscopy (SEM); red, green, and blue (RGB) value; and luminosity value were tracked (using a histogram of individual colour reference chips in Adobe Photoshop^® ) to assess colour changes, and energy-dispersive X-ray (EDX) spectroscopy to characterise the material composition.

Pre-veneered stainless steel crowns showed isolated zones of darkening with loss of luminosity and variations in green and blue values after ultrasonic or thermal washer disinfection combined with steam autoclaving at 5 and 10 cycles. No changes occurred with OPA. Both SEM imaging and EDX analysis identified no changes to crown materials from any of the three reprocessing methods.

Reprocessing protocols need to reflect the differing responses of various types of PCs. Repeated steam sterilisation causes slight aesthetic alterations by way of colour instability and loss of luminosity to pre-veneered stainless steel crowns, but no issues with stainless steel or zirconia PCs.