CDEN0210

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