The effect of toothpaste and thermal aging on extrinsically stained additively manufactured zirconia: A comparative study on surface roughness and stain durability.

Purpose The purpose of this in vitro study was to compare the average surface roughness (Ra) and stain durability of extrinsically stained additively manufactured zirconia, after brushing with different toothpastes and thermal cycling, with those of subtractively manufactured zirconia and lithium disilicate.Materials And Methods Forty-eight disk-shaped specimens (Ø13 × 2 mm) were fabricated from an additively manufactured zirconia (INNI Cera BCM W1000, AM-ZR), a subtractively manufactured zirconia (VITA YZ ST, SM-ZR), and a subtractively manufactured lithium disilicate (UP.CAD HT, SM-LD) (N = 16 per material). One surface of each specimen was externally stained (B4, VITA AKZENT Plus) and glazed (VITA AKZENT Plus Glaze LT), after which baseline Ra and color measurements were recorded with a laser microscope and a spectrophotometer, respectively. Specimens were then subjected to 5000 cycles of brushing with either regular (RT) or whitening (WT) toothpaste (n = 8 per subgroup), 5000 cycles of thermal cycling, and a further 10,000 brushing cycles, with Ra and color measurements repeated after each step with the same equipment. Stain durability was assessed by calculating color differences (ΔE00) between consecutive time points and between baseline and final measurements (total) using the CIEDE2000 formula. One-way analysis of variance and Tukey tests were used to compare the baseline Ra values of tested materials, while generalized linear model analysis was used to evaluate the effect of material type, toothpaste type, and time interval on Ra and ΔE00 (α = 0.05).Results SM-ZR had the lowest baseline Ra among the tested materials (p < 0.001). The three-way interaction among main factors affected the Ra and ΔE00 values (p ≤ 0.041). SM-ZR had lower Ra than SM-LD at baseline and after thermal cycling with both toothpastes, as well as after the first brushing cycle with RT and the second brushing cycle with WT (p ≤ 0.025). It also had a lower Ra than AM-ZR after thermal cycling and the second brushing with WT (p ≤ 0.016). After thermal cycling, RT-brushed SM-ZR had lower ΔE00 than RT-brushed AM-ZR and WT-brushed SM-ZR (p = 0.004). These specimens also had their lowest ΔE00 after thermal cycling (p < 0.001). RT-brushed AM-ZR and SM-LD had lower ΔE00 after thermal cycling and after the second brushing than their total ΔE00 (p ≤ 0.027). After thermal cycling, ΔE00 of AM-ZR and after the second brushing, ΔE00 of SM-LD were lower than their total ΔE00 when brushed with WT (p ≤ 0.001).Conclusions The Ra of AM-ZR was comparable to that of SM-ZR and SM-LD at all time points, in terms of the previously reported clinical acceptability threshold. The color change for all materials after aging, including two cycles of brushing with toothpaste and thermal cycling, was moderately unacceptable considering previously published thresholds.