Tooth whiteners are used widely to recover the original color of tooth. There , is no doubt these products work as whiteners, at least on mild to moderate stains, but the safety of these_ products are unclear. Abrasive agents in the tooth whitener remove attached stains on the tooth surface or bleaching agents in the tooth whitener change the organic material within the tooth. Free radicals released from tooth whiteners can change the surface properties including color of restorative materials or can accelerate the corrosion of dental appliances made of metal.
In this experiment, the effect of tooth whitener application on the color and microhardness of seven esthetic restorative materials was determined in vitro. RMS, NWT and MTD were used as tooth whiteners and tooth paste(DTQ) was used as control. g
Specimens were made according to the manufacturer´s instructions and wei;e polished. Initial color and Vickers hardness were measured. The tooth whiteners and control agents were-appied according to the manufacturers´ instructions or clinically simulated procedures for eight weeks. Color difference was measured using Differential Colorimeter(N-lodes TC-6FX, Denshoku Co.. Japan), and microhardness was measured using microhardness tester(Mitsuzawa Seiki Co. Japan). The results of CIELAB L`, CIELAB AE" and Vickers hardness were anal.VW1
The results were as follows
1.,-CIELAB L´ values after tooth whitener application were changedsignificantly depending on three variables, those were material type, tooth whitener type and application penod(p<0.01). Five kinds of materials showed the highest
CIELAB L* values after RMT application, but the difference of values among the materials was small. t
2. DTQ applied group showed the smallest color difference(CIELAB 8E* value) after application for four or ei0i weeks, and 1\``<´:´T applied group showed the highest color difference during first four week period. NITI) applied; group showed the highest color difference during four to eight week period, and resultantly showed the highest color difference after, eight week application. 2
3. Vickers hardness numbers were generally increased after whitener application. In the same material, the change ratios of VIL1s were not different regardless of the applied agents, and VHNs of glass ionomers were increased h
significantly higher than those of composite resins.
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