Statement of the Problem : Dental practitioners are faced with many materials and methods commercially available
for tooth whitening. This study aims to compare the short term effectiveness and major side effects of 4 popular bleaching systems in a relatively large sample.
Materials and Methods: A sample of 300 subjects were divided equally into 4 groups and treated with ( home bleaching – Opalescence 20%, in office – Bright Smile, in office – Zoom, and in office – Zoom plus home bleaching – Day White 9.5%).
Results: The four whitening systems were significantly effective at 3 days (T1) and 3 months (T2) after the whitening treatment. At T2, there was no significant difference in whitening effectiveness among the four whitening systems. Tooth sensitivity and gingival irritation were associated with the 4 whitening systems.
Conclusion: The bleaching procedures tested in this study are equally effective with high satisfaction level and with self-limiting tooth and gingival sensitivity.
Key words: Tooth bleaching, Vital, Hydrogen Peroxide, Carbamide Peroxide,.
The shade of teeth is one of the main contributes to improve smiles 1,2..Television and magazines have influenced the general populations idea that whiter teeth are both healthier and more pleasing 3. This has led to huge demand for teeth whitening procedures. Consequently, dental practitioners are faced with a market flooded with many materials and methods catered to this demand. The main ingredient of most bleaching products is carbamide peroxide with different concentrations (up to 35%). Questions regarding the most economical, effective, and conservative teeth whitening procedures are yet to be answered.
Attempts to bleach teeth were initiated more than a century ago and has since developed new methods and materials to make the treatment procedure more effective, less time consuming and more convenient for both patient and dentist. In-office bleaching has a wide variety of methods for application and activation. Initially, heat was used in conjunction with hydrogen peroxide and ethyl ether on cotton to treat discolored teeth 4. In office teeth whitening procedures then evolved from a procedure performed over a span of multiple office visits into a technique that achieved the desired results in one or two visits. Light-activation of high concentration hydrogen peroxide in the dental office emerged as an advanced technique to whiten all teeth simultaneously and became a prescribed method of whitening teeth.5, 6 .
10% carbamide peroxide was eventually discovered to whiten teeth when placed in orthodontic positioners to help improve the health of gingival tissue 4,7. Later, custom fitting night-guard vacuform material was used to carry the carbamide peroxide while placed over teeth. This bleaching procedure is initiated without a light source because the reaction is chemical 8. This method is often used at home by the patient and thus is named at-home bleaching.
The efficacy of at-home bleaching agents has been well documented in clinical trials 9-11. However, the effectiveness of in-office bleaching has been studied with mixed and controversial results. In office bleaching using light activation versus the in-office chemically activated method have been compared with no statistical difference between the two 12. Similarly, when two in-office bleaching methods were tested, one with light and another without light, both resulted in statistically significant lighter teeth 13. Zekonis on the other hand, found that at-home bleaching resulted in significantly lighter teeth compared to in-office bleaching 14. In contrast, one study found that an in-office product resulted in a 6 shade tab difference with significantly less bleaching cycles compared to at-home 15.
In addition to the in-office bleaching method, some systems provide the patient with an extra home bleaching adjunct kit16. However, only few studies evaluated the effect of this combination on overall bleaching result in comparison with using either of the methods alone 17, 18.
The most commonly reported side effects of at home and in –office bleaching include gingival and mucosal irritation with tooth sensitivity. However, these side effects have been found to be transient 13 -15, 19-21.
Shortcomings associated with bleaching studies:
On reviewing previous studies, it was noticed that the methods used to assess the effect of bleaching varied among different bleaching studies. Some investigators used shade tabs solely to measure the effectiveness of the bleaching agents 11,19,22. When using shade tabs, it is important to calibrate the examiners to be able to measure the effectiveness of bleaching methods consistently 19, 23. This calibration is essential to minimize the effect of examiners experience, skills, and fatigue when matching shade tabs to natural teeth.
The number of subjects in a study needs to represent the targeted population. In a review of in vivo bleach studies, Buchalla 6 noted that the number of subjects in the reviewed studies ranged from 7 to 87 patients. The number of subjects in the studies of da Costa 21 and Al Omairi 24 ranged from 20 to 40 respectively. The results obtained from such small samples divided into smaller groups testing different bleaching systems may not be reliable. Larger samples are needed to minimize variation and assure representation of the general population.
The subjects also need to be void of bias that will skew the results from representing the targeted population. In one study 19 dental students were used as subjects 9. This introduces a bias in which the dental students might have been more motivated compared to the general public. Furthermore, the inclusion criteria of some studies can also become a limiting factor. Several of the previous bleaching studies included subjects with a minimum shade of D4 or darker according to the Vitapan system 5, 9, 11-15, 24, 25. (Vita Zahnfabrik, Bad Säckimgen,Germany). If the sample is skewed toward only those with darker teeth, the effectiveness of the bleaching method could be overestimated.
The aims of this study are the following:
- Report, and compare, the short term effectiveness and major side effects of 4 different bleaching systems in a relatively large sample representing the general public.
- Investigate if combination treatment ( office + home ) gives better bleaching effect than using either of the methods alone.
- To assess the patient satisfaction level of bleaching treatments.
Material and methods:
Sample: After acquiring the approval of the Ethical Committee at the Health Science Center of Kuwait University, an advertisement was placed on bulletin boards as well as the website of the Health Science Center of Kuwait University, selective private and public dental clinics, and in a local newspaper of the Kuwait University to recruit patients to participate in a prospective study testing the effectiveness of four different bleaching systems:
As a response to the advertisements, 450 persons volunteered to participate in the study. Any individual above the age of 14 who was not medically compromised or mentally challenged and willing to whiten his or her teeth by the method proposed by the researcher, was welcomed to be included in the study. Upon our initial clinical examination, 150 participants were excluded due to one or more of the following exclusion criteria:
- Subjects with active periodontal problems, carious lesion, broken/fractured teeth or restorations, missing anterior tooth, or with restoration covering more than 30% of labial surface of any anterior tooth, or exposed dentin.
- Subjects with amelogenesis, dentogenesis imperfecta, or other dental anomalies affecting the outer tooth surface.
- Subjects with history of previous bleaching treatment or active orthodontic treatment.
- Pregnant or lactating females.
The remaining 300 subjects were consecutively assigned to the following 4 groups with 75 subject in each group.
- Home bleaching (HB) group:(Opalescence 20%, Ultradent Products Inc, South Jordan, Utah USA).
- Brightsmile (BS) group: Light activated in-office bleaching systems (BRITESMILE 2000, Discus Dental, Culver city, California, USA).
- Zoom (Z) group: Light activated in-office bleaching systems ( Discus Dental, LLC., Culver city, California, USA).
- Zoom plus home bleaching (Z+HB) group: Light activated in-office bleaching systems (ZOOM 3) combined with home bleaching system (Day White 9.5%, Discus Dental LLC., Culver city, California, USA).
Dental prophylaxis and scaling were done to all subjects at least one week before starting the bleaching treatment. All available anterior teeth, premolars and first molars were bleached. All subjects signed an informed consent form before participating in the study which was approved by the Ethical clearance Committee at the Health Science Center of Kuwait University.
Custom trays with bleach reservoir were made for the home bleaching. The bleaching tray was made of 0.5mm soft plastic material. The subjects who were assigned to (HB) group were instructed to wear the bleaching tray containing the bleaching gel (Opalescence 20%) daily, for 6 hours, for a total of 2 weeks. The subjects who were assigned to (Z+HB) group were instructed to start their home bleaching treatment 1 week after finishing the in-office bleaching. They were asked to wear their bleaching tray daily for 1 hour for 4 days. All subjects were given a dated log form to register their home bleaching time. The in-office bleaching was conducted in 4 sessions by applying new bleaching material followed by exposure to light at each session, following the instructions by the manufacturers of BRITESMILE2000 and ZOOM. The session lasts 20 minutes for Britesmile and 15 minutes for Zoom. To ensure protection of the maxillary and mandibular gingiva, an isolation material (provided with the bleaching kit) was applied on the gingiva. Cheek retractor was used to hold the skin and lips away from the treatment area, and cotton rolls were placed in the cheek vestibules for moisture control. Bite blocks were used as a jaw rest. Lip balm was applied to the lips. The subject and the operatory staff wore an orange-tinted protective eyewear during the light-activated whitening procedures. The mixed peroxide gel was applied to the buccal surfaces of all the incisors, canines, premolars, and molars fully to ensure a uniform effect.
To avoid the subjective variation and bias, the clinical examination was done by two calibrated dentists (FK and JA). Prior to starting the study, our whitening effect evaluators were calibrated to use the vita shade guide in the following way:
An acceptable kappa score (substantial agreement, 0.61-0.80) was ascertained 26. Calibration for the subjective discrepancies regarding the reading of the shade guide was done by making the analyzers read the shade on 18 ceramic tooth models randomly picked. The analyzers were provided with the same models a week later and their readings were documented again. The difference between the two trail readings were analyzed and Kappa score was calculated within each examiner and between both examiners. This calibration was repeated until accepted kappa score was obtained. The intra-examiner consistency by kappa for examiner FK was 0.73 and for examiner JA was 0.98. The inter-examiner consistency kappa between the 2 examiners was 0.80.
Whitening effect: The whitening effect was assessed at the middle third of the labial surface of the upper right central incisor. The whitening effect was measured before bleaching (T0), 1 to 3 days post bleaching (T1), and 3months ( + or – 1 week) after bleaching (T2). The whitening effect was evaluated by the following methods:
1. Self-evaluation by the patient: A 10 cm long Visual analog scale divided into 1cm long segments (scaled form 0 to 10 with 10 as very dark teeth, 5 as normal or acceptable whiteness, and 0 as excellent whiteness) was presented to each subject at each evaluation interval to determine the brightness of the subject’s right upper central incisor (fig. 1).
Care was taken to ensure that subject’s lips were not covered with any lip stick at any evaluation time. The evaluation was conducted in a well lit room without use of dental chair light. The subject would evaluate the shade of his/her teeth by looking in a non-magnifying hand mirror.
2. Clinical evaluation by calibrated dentist: Vita 3D bleached shade guide was used at each evaluation interval to determine the shade of the upper right central incisor. The examination was done by two calibrated dentists (FK and JA). The lightest tab of the vita 3D bleached shade guide (0M1) was marked as 0 and the darkest tab (5M3) as 14 (fig. 2).
Patient perception regarding tooth sensitivity and gingival irritation was evaluated by questioning the subjects at T0, T1, and T2 if their teeth were sensitive at all times or sensitive to hot, cold, chewing, or brushing. The response of the patient was marked 0 if no sensitivity was present, 1 if mild sensitivity was present, 2 if moderate to severe sensitivity was present. Similarly, The subjects were asked if they experienced any gingival sensitivity. The response of the patient was marked 0 if no sensitivity was present, 1 if mild sensitivity was present, 2 if moderate to severe sensitivity was present. The responses of all questions related to sensitivity of teeth and gingiva were combined and then the mean of the overall responses was calculated
Treatment satisfaction level:
Patient satisfaction level was assessed by questioning the participants at T1 and T2 if they would repeat the bleaching procedure again and if they would recommend the bleaching procedure to a friend. The response of the subjects were marked as 0 if their answer was “no”, and 1 if their answer was “yes”.
Data management and analysis were carried out using the Statistical Package for Social Sciences Software (SPSS, version 17.0; SPSS Inc., Chicago, Ill., USA). The variables age and whitening scores were examined for normality of data with Kolmogorov-Smirnov test, and descriptive statistics presented as mean and standard error (SE). The whitening effect evaluators were calibrated to use the vita shade guide by kappa values. The differences in initial values, T0 and subsequent follow up at T1 and T2 were compared using non-parametric Mann-Whitney- or Kruskal Wallis tests. The proportional responses on sensitivity to various bleaching methods, and their severity were assessed with Chi-square or normal Z-test. The two-tailed probability p value < 0.05 was considered statistically significant.
Whitening effect: Both of the evaluation methods (visual analog and vita 3D) showed that all of the 4 whitening methods (home bleaching – Opalescence 20%, in-office – bright smile, in-office – Zoom, and in-office – Zoom plus home bleaching – Day White 9.5%) were significantly effective at T1 (Table 1). and T2 (Table 2) The p values were all significant at 0.001.
There was no significant difference among the 4 whitening methods (home bleaching – Opalescence 20%, in office bright smile, in-office – zoom, and in-office – zoom plus home bleaching – day white 9.5%) used at 3 months post bleaching (T2). The p value was more than 0.2. (Table 2).
(Table 3) shows that there was a significant increase in the teeth and gingival sensitivity at T1 (p < .03). However, this sensitivity was transient. At 3 months post bleaching (T2), there was no significant increase in teeth sensitivity and gingival irritation when compared to baseline results at T0 (p ≥ 0.425). Treatment satisfaction level: Patient satisfaction level was high in all of the 4 different bleaching methods used in this study In summary, about 76% of the patients were satisfied with the bleaching treatment and would repeat their bleaching experience in the future. And about 86% of the patients would recommend their friends to have their teeth whitened (Table 4 ).
Modern dentistry has witnessed the emergence of many bleaching methods and materials. In pursuit of better shade for vital teeth, bleaching remains one of the most preferred economically viable and conservative treatments4. The manufactures of different bleaching systems claim superior efficacy of their bleaching systems compared to others. Since the active ingredients of most bleaching systems is the same, the authors of this study attempted to report if any differences exist among 4 popular bleaching systems with regard to efficacy and major side effects in a relatively large sample.
Unlike previous studies5, 9, 11-15, 24, 25 which excluded subjects with initial tooth shade lighter than D4, this study did not exclude any patients whose initial shades were relatively lighter on the vita shade guide. We accepted all patients who walked in with dark teeth complaint or with a feeling that their teeth were not as white as they should. We believe that including such patients will make our sample more representative to the actual population. If the sample is skewed toward only those with darker teeth, the effectiveness of the bleaching methods could be overestimated.
In order to assure best reliability of the results, 2 evaluation methods were used. The patients used 10 cm long visual analog scale divided into 1cm long segments and the dentists used Vita 3D bleaching shade guide in their assessments of the whitening effects. Both evaluation methods showed that all of the four bleaching systems were equally effective at T1 and T2. Contrary to what was expected 16-18, the combination of in-office bleaching with home bleaching was not more effective than in-office bleaching alone or home bleaching alone. However, this study was limited to short term effectiveness, up to 3 months (+ or – 2 weeks) after the date of the bleaching. The sample used in this study will be followed to test if there will be any long term differences in the effectiveness among the 4 bleaching systems, which will be reported in future studies.
Confirming the results of the other studies 8, 13 -15, 19-21 there was a significant increase in the tooth and gingival sensitivity immediately after bleaching at T1. The results of this study further reinforces the fact that tooth sensitivity associated with any bleaching method is transient. The responses of the subjects to the sensitivity questions at T2 showed no significant differences than their responses to the same sensitivity questions at T0
The satisfaction level of the patients who participated in this study was assessed by their positive response to the questions about their bleaching or their recommendation bleaching to their friends. The significant increase in teeth whitening at T1 and T2 combined with relatively minor and transient tooth and gingival sensitivity seemed to make the majority of the subjects satisfied with the overall tooth whitening results. However, it should be emphasized that treatment satisfaction could be influenced by many variables such as the ambience of a dental office and behavior of the staff which could not be controlled in this study.
1) The whitening systems tested in this study are all effective (short term) with no significant difference between them.
2) There is transient increase in tooth and gingival sensitivity as a result of tooth whitening treatment.
3) The combination of home bleaching with in-office bleaching is not more effective than either alone
4) Patient satisfaction level for tooth whitening procedure is high
Dentists could choose any of the whitening systems which were tested in this study because they are equally effective with self-limiting side effects.
The authors wish to thank Fabi Koya for her assistance in clinical investigation and data collection. This work was supported by Kuwait University Research Administration grant DI 02/06.
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