EFFECT OF REMINERALIZATION ON COLOR CHANGE OF BLEACHED TOOTH

Abstract

The aim of this in vitro study was to investigate the effect of remineralization and time on the color and microhardness change of teeth bleached using 10% carbamide peroxide (10%CP) or 40% hydrogen peroxide (40%HP). Seventy-two 6x6x2 mm3 enamel slabs were prepared from human premolars. The specimens’ color and Vickers’ microhardness were recorded at baseline (T0). The specimens were divided into six groups, two groups were treated with 10%CP with or without casein phosphopeptides and amorphous calcium phosphate (CPP-ACP) (10%CP and 10% CP/CPP-ACP, respectively), two groups were treated with 40% HP with or without CPP-ACP (40%HP and 40%HP/CPP-ACP, respectively), one group received no bleaching (CON) and another group received only CPP- ACP treatment without bleaching, (CON/CPP-ACP). The CPP-ACP groups were treated with CPP-ACP twice daily for 5 minutes for seven days after completing their respective protocol. The color change and Vickers’ microhardness were recorded at three time points after treatment; 1 day (T1), 2 weeks (T2), and 1 month (T3). After 1 month, tooth color changed (∆E) in all groups at every time point, however, significant ∆E was found only at T3 for the 10% CP and the CON/CPP-ACP groups (p<0.05). Microhardness tended to decrease from the baseline (T0) value at each time point. There were significant differences between time points in microhardness (∆VHN) in the 40%HP, CON, and CON/CPP-ACP groups. A relationship between ∆E and ∆VHN was found in the 10%CP and 10%CP/CPP-ACP groups. In summary, bleached teeth whiteness decreased in the 10%CP group from T1 to T3. The CPP-ACP can prevent color relapse in 10%CP/CPP-ACP and CON/CPP-ACP groups. Microhardness improved in the 10%CP/CPP-ACP group compared with 10%CP group at T3. Both tooth whiteness and microhardness were stable for at least one month when CPP-ACP was used as an intervention in 10% CP/CPP-ACP group.