Staining drinks effect on colour and microhardness of Z250 composite

Objective: Aim of this study was the colour and microhardness analysis of a microhybrid composite after immersion in hot staining drinks.

Methods: Ninety-six Filtek Z250 (3M ESPE) samples (4x4x2 mm) were photopolymerized on both sides (30+30 sec). Half samples were polished with Soflex Pop-on disks (3M ESPE). Six groups of 16 samples were identified per immersion drink and type of polishing: G1=coffee-mylar, G2=coffee-disks, G3=tea-mylar, G4=tea-disks, G5=water-mylar, G6=water-disks. Colorimetric analysis was performed by means of a spectrocolorimeter: CIELab parameters lightness (L), chroma (C) and hue (h) were considered. Hardness evaluation was performed with a Vickers microdurometer. Samples were analysed before the treatment (t0), after one day (t1) and after three days (t2) of immersion in the beverages at a temperature of 55°C. Statistical analysis was carried out with one-way ANOVA, Scheffe post hoc test, and paired-samples Student T test.

Results: Vickers test showed a general hardness increase after immersion in hot beverages: p<0,05 t0-t1, p=0,000 t0-t2 and t1-t2 for G1; NS for G2; p<0,01 t0-t2 for G3; p=0,000 t0-t1 and t0-t2 for G4; p<0,01 t0-t2 for G5; p<0,05 t0-t2 for G6.

Colorimetric analysis, a part from G5 and G6, showed a general decrease of L (p=0,000 for G1, G2 and G4 at each immersion time; p<0,01 t0-t1 and t0-t2, p=0,000 t1-t2 for G3), increase of C (p=0,000) and decrease of h (p=0,000 for G1 and G2; p=0,000 t0-t1 and t0-t2, p<0,05 t1-t2 for G3; p<0,05 t0-t1, p=0,000 t0-t2 and t1-t2 for G4). Major colour variations were revealed for coffee rather than tea and for mylar rather than disks groups at t1 and t2 (p=0,000).

Conclusions: Immersion in hot staining drinks caused hardness increase and discoloration of Filtek Z250. It is convenient to know patients diet and oral hygiene to plan a follow-up and surface polishing of restorations.