Colorimetric analysis and microhardness of a nanofilled composite resin after immersion in staining drinks

Background. The aim of this study was the colorimetric and microhardness evaluation of a nanofilled composite resin after immersion in hot staining drinks. Methods and materials. Sixty-four Ceram X (Dentsply) samples (4x4x2 mm) were prepared and photopolymerized on both sides (30+30 sec) under a mylar film. Half samples were polished with Soflex Pop-on disks (3M ESPE). Colorimetric analysis were performed by means of a spectrocolorimeter (CIELab parameter C); hardness evaluations were performed by means of a Vickers microdurometer. Four groups of 16 samples were identified, subdivided per type of polishing and immersion drinks: G1=mylar-coffee; G2=mylar-tea; G3=disks-coffee; G4=disks-tea. Samples were submitted to analysis before the treatment (t0), after one day immersion in the beverages at 55°C temperature (t1) and after three days immersion (t2) in the same conditions. Statistical analysis was performed (one-way ANOVA, Sheffe post hoc test, independent-samples and paired-samples Student T test). Results. Vickers tests did not show a general hardness increase after immersion in the beverages as evidenced in literature: HV=42,07±3,27 at t0 and HV=50,16±3,10 at t2 for G1 (p=0,000); HV=48,67±3,18 at t0 and HV=45,74±2,53 at t2 for G2 (p<0,005); HV=69,2±4,99 at t0 and 68,76±5,79 at t2 for G3 (NS); 71,61±7,41 at t0 and 71,05±7,5 at t2 for G4 (NS). Colorimetric analysis showed an increase of the saturation parameter C (6,87±0,16 at t0 and 15,11±0,91 at t2 for G1, p=0,000; 7,07±0,32 at t0 and 8,2±0,37 at t2 for G2, p=0,000; 7,15±0,28 at t0 and 11,47±1,47 at t2 for G3, p=0,000; 7,11±0,28 at t0 and 8,51±0,27 at t2 for G4, p=0,000). Conclusions. It is convenient to know patients diet and oral hygiene in order to plan a follow-up and the surface polishing of the restorations.