Effect of Ageing, Staining and Polishing on the Colour Stability of a Single, a Group Shade and Nano Fill Dental Composite: An In-vitro Study

Abstract

Introduction: With the increase in aesthetic requirements, more people are requesting tooth coloured fillings. An anterior restoration is deemed unacceptable if its colour changes significantly. Aim: To assess the colour stability of a single shade, a group shade and a nano fill dental resin composite which comes in multiple shades. Materials and Methods: This in-vitro study was conducted in the month of August 2021 at the Advanced Technology Dental Research Laboratory at the King Abdul Aziz University, Jeddah, Western region, Saudi Arabia. Three composites were tested; a single shade (Omnichroma), a group shade (Optishade Light (OL) and Optishade Medium (OM)) and a conventional nano fill (Z350) 40 cylindrical discs (10 mm in diameter and 2 mm in depth) were fabricated in total. Each material and shade to be tested had 10 samples per group (n=10). The materials were aged in a thermocycler for 5000 cycles then stained with either green tea or coffee for six days. Upon completion of the staining protocol, they were then polished with soflex diamond polishing system. Colour measurements were taken at each stage, calculated and compared. Mixed model repeated Analysis Of Variance (ANOVA) was performed to determine significance of the colour change (ΔE00) between materials and treatments and Bonferroni test was used for multiple comparison between groups. Results: The effect of ageing varied according to individual material; Z350 had lower ΔE00 when compared to other materials. After staining with tea, it was found that Z350 and Omnichroma exhibited a significant change (p<0.05) in ΔE00 when compared to OL. Polishing improved the ΔE00 in all the materials. All green tea-stained materials with the exception of Omnichroma returned to a clinically acceptable E00 after polishing. After polishing coffee stained samples, OL and OM remained above the clinically acceptable threshold while Z350 and omnichroma were returned to a clinically acceptable level. Conclusion: All the materials showed a change in ΔE00 after ageing, with OM and Z350 being the only materials to exhibit a clinically acceptable change. While polishing decreased ΔE00 in all the materials, it did not return them all to a clinically acceptable level. Thus, polishing helps improve the appearance of stained restorations but may not be enough to completely remove stains, even in newly introduced direct aesthetic dental materials.

Keywords

• aesthetic dental filling
• discolouration
• omnichroma
• optishade