CDEN0109

10 I I case study _ tooth whitening Inordertoobtainafavourableresultinarelatively short time, the patient preferred a combination of home and power whitening. An alginate impression wastakenpriortothefirstin-officewhiteningsession (Fig. 3). While the patient received whitening of the upperarchfor40minutes,amodelwaspouredanda customised tray was fabricated. Thus, it was possible to deliver the upper tray and the home whitening kit onthedayoftreatment. Routineexplanationsonthepossibilityofsensitiv- ity to cold, irritation to the gingiva, and limitation of whitening in the cervical area were given to the patient. The patient was scheduled for her second in- office whitening session with an interval of three to fourdays.Duringthattime,homewhiteningwasper- formedformaximumefficacyofthetreatment.After the third in-office whitening session, a remarkable differencewasobservedbetweentheupperandlower teeth(Fig.4).Althoughthedecalcificationareaonthe leftlateralincisorwasslightlymorenoticeableatthis stage, the patient was very happy about the distinct colourdifferencebetweentheupperandlowerteeth. Treatment on the lower teeth was conducted in the same manner as the upper teeth. She received three in-officewhiteningsessionsonthelowerarchwithan interval of three to four days combined with home whitening. Aesthetic re-contouring was cautiously per- formedwith12-flutedcarbideburstoreducethetips ofthecuspids.TheClassVcompositeresinfillingwas placed two weeks after whitening to allow for colour stabilityandrecoveryofbondstrengthoftheenamel. At this stage, the decalcification area finally blended innaturallywiththewhitenedteeth(Fig.5). A smile analysis after treatment revealed the efficacy of tooth whitening and confirmed that the treatment had been completed successfully (Fig. 6). Shade changes can be measured as shade guide units on a value-oriented, classic vita shade guide or as E values defined by the Commission Inter- nationale de l’Éclairage (CIE) L*a*b* colour system. E is the shortest distance in the CIE L*a*b* colour space between the colours being compared and is determined using the equation E= ( L*2 + a*2 + b*2)1 /2 where L* represents lightness, a* corre- sponds to the red–green axis (positive value indi- cates red, negative indicates green), and b* corre- sponds to the yellow–blue axis (positive value indi- cates yellow, negative value indicates blue). The shade change as indicated by E was obtained by overlapping the image of the same tooth before and after tooth whitening (Fig. 7), using the Spec- troshade analysis software (Version 2.41). An increase in E after tooth whitening is usu- ally attributed to an increase in L* values and a de- crease in b* values. It is interesting to note that E values varied according to the teeth although all teethweretreatedwiththesameconcentrationand same exposure time. This suggests that each tooth has its own degree of whitening, which is a very Fig. 5_Intra-oral view after whitening. Fig. 6_Smile analysis after whitening. cosmeticdentistry 1_2009 Tooth number #13 #12 #11 #21 #22 #23 Shade guide units 10 5 10 11 8 10 E 16.32 9.05 13.68 14.64 10.19 16.01 Summary of the shade changes of the six anterior teeth in terms of shade guide units and E values. Fig. 6