CDEN0210

30 I I research _ bleaching application, the gel was removed with high volume suctionandthesampleswerewipedcleanwithcot- tongauzesaturatedindistilledwater.Therefore,the total exposure of the teeth to the bleaching agent waslimitedto45minutespersession.Sessionswere performed once a week for seven weeks. The gel applications were activated by the use of theZoom2mercurymetalhalidelightunitthat,ac- cording to the manufacturer, emits violet coloured lightwithawavelengthintherangeof350to400nm. When placed into position, the light unit is capable ofilluminatingalloftheteethsimultaneously(Fig.2). Theuseofthislightunitimpliesthataspecificwave- lengthoflightactivatessomeaspectofthewhitener and enhances the whitening effect. An infrared fil- terhelpstominimisetheamountofheatgenerated at the surface of the teeth during the treatment session. Immediately following the completion of each 45-minute session, digital images of both the buccal and lingual surfaces were recorded against a neutral grey background. The L*, C*, and H* values were also recorded with the spectrophotometer. The samples were stored in distilled water until the next session to prevent desiccation. _Results The means of the L*, C* and H* values for each of the TCN derivatives and the control as recorded by the spectrophotometer at the specified weekly intervals are listed in Table II. Tables Ia to c show the regression plots of the L*, C* and H* values for theTCNandcontrolgroups.Statisticalanalysisofthe changesinL*,C*andH*betweenbaselineandthefinal evaluation was performed. There was a significant association amongst treatment group, evaluation andinteractionterm,treatmentgroupxevaluation, and L* (two-way ANOVA; p < 0.001, p = 0.002 and p<0.001,respectively).AllgroupsexceptDoxycycline demonstrated statistically significant differences in brightness between the baseline and the final evaluation (Holm-Sidak Multiple Comparisons Test; all comparisons to baseline; p < 0.05). For the Chlortetracycline-, Doxycycline- and Minocycline- stained groups a decrease in brightness rather than an increase was observed. The control group demonstrated a significant increase in brightness (Table Ia). The mean L* for the control group was signi- ficantly higher than the Chlortetracycline, Doxy- cycline and Minocycline groups at baseline. Since cosmeticdentistry 2_2010 Figs. 3a–d_The stained teeth and control groups demonstrating progress from baseline through weeks 1, 3, 5 and 7. Chlortetracycline Baseline 1st week 3rd week 5th week 7th week Fig. 3a Control Baseline 1st week 3rd week 5th week 7th week Fig. 3b