STUDIO COMBINATO DELLA STABILITA’ DI COLORE E DELLA DUREZZA VICKERS DI DIFFERENTI MATERIALI DA RESTAURO ESTETICI

Purpose: Two crucial properties of esthetic restorative materials are their long-term color stability and their resistance at erosion. The aim of this study was to evaluate the color stability of esthetic restorative materials after surface roughening with cola and exposure to different staining solutions (coffee and red wine), and to investigate their Vickers microhardness (VK) after exposure to acidic drink. Material and Methods: All materials (one nanofilled composite, one nanoceramic composite, one microfilled hybrid composite and one nanohybrid Ormocer based composite) were polymerized into silicon rings to obtain specimens identical in size. To analyze the discoloration, Specimens of group A were first exposed to Cola for 24 h, and then immersed in coffee or red wine over a 28-day test period; Specimens of group B were not exposed to Cola, but only to coffee or red wine. A spectrophotometric evaluation according to the CIE L*a*b* system was performed at 7, 14, 21, 28 days. To analyze microhardness, specimens of group 1 were used as control, specimens of group 2 were immersed in 50 ml of acidic drink for 1 day, specimens of group 3 were immersed in 50 ml of acidic drink for 7 days. Then, their VK was determined with a microhardness tester, using a Vickers diamond indenter and a 100g load applied for 20 seconds. Results: Specimens of group A showed higher variations when compared with group B's specimens (P < 0.05). After 28 days the immersion protocols caused a clinically perceivable color change for all materials tested (P < 0.05). Each material showed lower micro-hardness values after immersion in acidic solution (P < 0.05), and significant changes were registered for all restorative materials after immersion in acidic solution for 1 day and 7 days (P < 0.05). Conclusions: As regards discoloration, staining beverages caused significant discolorations for all the materials tested. The first exposure to Cola enhanced the subsequent staining with coffee or red wine. Nanohybrid composites reported the lowest color variations. As regards microhardness, the nanofilled composite, and the nanohybrid Ormocer based composite, showed the best behavior. The nanoceramic composite although reached lower hardness values than the previous materials, but resisted well to the 1 week immersion in soft-drink. Finally, the micro filled hybrid composite has the lowest microhardness values