cde0210

While nightguard vital bleaching is the most used treatment modality for whitening of -discoloured teeth, in-office tooth whitening pro-cedures that use a concentration of higher than 10 % carbamide peroxide have been advocated as acceptable alternatives. Patients often choose in-office bleaching when they desire more rapid whitening of their teeth and/or when they do not desire to wear bleaching trays for at-home techniques.1 Although manufacturers indicate that most in-office bleaching agents can be used without light irradiation, studies have reported that light activation can enhance the results of the bleaching procedures.2 The light energy increases the rate of hydrogen peroxide degradation to form oxygen free radicals, leading to an enhancement of the bleaching process...

I 29 research _ bleaching I cosmeticdentistry 2_2010 would whiten in the same manner and to the same degree as non-experimental teeth. _Materials and methods Twenty extracted human molar teeth were sec- tioned approximately 2 mm above their furcations to provide the clinical crowns for this experiment. Images of the buccal and lingual surfaces were recorded with a digital camera (Canon EOS-D30, Canon) using standardised settings throughout the experiment. Each tooth was then analysed with a dental spectrophotometer (VITA Easyshade, VITA) against a neutral grey background. After baseline recordings, the pulp chambers were etched for 60 seconds with 37 % phosphoric acid gel and then thoroughly rinsed with distilled water. Saturated solutions of Chlortetracycline, Doxycycline and Minocycline were produced by mixing100to250mgofthefiverespectivemedica- ments in 5 ml of distilled water. Only the resulting supernatantwasrecoveredforuse.Fivepulpcham- bers were filled with 0.5 ml of each of the solutions. Distilled water was used as a control in the five remaining pulp chambers. Composite resin disks were used to seal the chambers of all teeth. The teeth were then placed crown first into a centrifuge tube and subjected to centrifugation at 2,800 rpm for 20 minutes. After centrifugation, the teethwerestoredindistilledwaterforoneweekbe- fore exposure to continuous light irradiation with two 60 W Xenon lamps for seven weeks. Digital im- agesofthecolourchangeofboththebuccal(B)and lingual (L) surfaces were recorded against a neutral greybackground.Thechroma(C*),brightness(L*)and hue(H*)valueswererecordedwiththespectropho- tometer, and the colour differences ( E) between baseline and seven weeks were calculated from the spectral data. Colour differences were calculated using CIE E*, using the following formula: E* = [( L*) 2 + ( C*) 2 + ( H*) 2]1/2 _In-office whitening procedure At the completion of the discolouration phase, three randomly selected samples from each group weresubjectedtoZoom2in-officetoothwhitening procedures. The Zoom 2 system uses a hydrogen- peroxide-based tooth whitener, which comes pre- packaged as two individual components: a 25 % hydrogen peroxide gel and a proprietary activator. These two components are mixed at room tem- peraturetoformaworkinggelthathasa20%con- centration of hydrogen peroxide and a pH between 7.5 and 8.5 (Figs. 1a & b). Prior to the application of thegeltothesampleteeth,thesampleswerecoated with a solution supplied by the manufacturer in the form of pre-treatment starter swabs. The treatment sessions were broken down into three 15-minute applications of the 20 % con- centration hydrogen peroxide gel. Between each Tables Ia–c_Regression plots of L*, C* and H*. Table Ia Table Ic Table Ib — Chlortetracycline — Control — Doxycycline — Minocycline — Chlortetracycline — Control — Doxycycline — Minocycline — Chlortetracycline — Control — Doxycycline — Minocycline