Abstract
Objectives
To investigate the effectiveness of two home bleaching modalities on whitening of tetracycline-stained teeth (TST).
Methods
A randomized controlled trial on the bleaching effect of 15% carbamide peroxide gel loaded in tray and 6.5% hydrogen peroxide strip in subjects with TST was performed. Eligible subjects were judged independently by two assessors, and randomly assigned into the tray or the strip group. Lightness (L*), redness (a*) and yellowness (b*) were measured with colorimeter at baseline, one, two and three months. Any adverse reaction associated with bleaching were also recorded. Overall colour changes (ΔE) were analysed by one-sample and independent t -test/Wilcoxon test at significance level α = 0.05.
Result
Twelve and fourteen participants were allocated to the tray and the strip group respectively. Both groups experienced noticeable and significant L*a*b* improvement at the end of the trial in comparison to the baseline (p < 0.05). Significant improvement was observed in the first month for the tray group (p < 0.05) and in the first two months for the strip group (p < 0.05). While greater lightness improvement was observed in the tray group over the s trip group in the first month (p = 0.02), the reverse was noticed in the second month (p = 0.01). There was no difference between two groups at the end of this trial (p < 0.05) and no significant adverse reactions were observed.
Conclusion
Over a three-month period, 6.0% hydrogen peroxide strip performed equally well as the 15% carbamide peroxide tray delivery system in TST.
Clinical significance
Home bleaching systems produce noticeable tooth whitening effect in subjects with tetracycline-stained teeth.
1
Introduction
Tetracyclines are broad-spectrum antibiotics used for treatment of a range of common infections . However, they may incorporated into developing tooth tissue and are discoloured by light induced oxidization and may deteriorate dental aesthetics significantly . The prevalence of tetracycline stained teeth (TST) has been estimated to be 3–6% and up to 23% in one national survey . This can be generalized or localized and range in colour from mild yellow to grey and dark brown. The clinical presentation is dependent on the type of tetracycline, its dose, length of medication, and period of development of the tooth tissue .
Clinical management of TST includes the use of bleaching , composite resin/porcelain laminate veneers or full coverage metal-ceramic/all ceramic crowns to improve the aesthetic appearance. Bleaching is the most conservative treatment option without sacrifice of sound tooth substances and subjects’ satisfaction and oral health related quality of life has been improved after bleaching . Moreover, bleaching systems based on carbamide peroxide and hydrogen peroxide have been shown to be clinically safe with no irreversible side effects and have minimum biological cost . Bleaching agents may be administered professionally or by patients at home .
The quinone rings in tetracyclines that are responsible for red discoloration can be altered to less coloured molecules . Tray based peroxide home bleaching systems have been shown to lighten the appearance of TST when used for prolonged periods. Using 10% carbamide peroxide gel for a 6-month period in a tray delivery system, Haywood et al. found that the tooth whitening effects were long lasting up to 90 months and that patients gave positive feedback . They also observed that severe discoloration in the gingival third of the tooth gave a poor prognosis for total tooth whitening. In a similar design study, Matis et al. compared the effects of different concentrations of carbamide peroxide (10%, 15% and 20%) on tetracycline stained teeth also for a 6-month period . They showed that most rapid whitening occurred in the first month. There was some relapse of the tooth whitening effects after bleaching, mostly 3 months after bleaching. However, improvements in the redness and lightness are still observed at 5 years . Supporting the observation of Haywood et al . , they found that the darker the teeth at baseline, the more difficult it was to lighten them.
Polyethylene strips have been used for delivery of bleaching peroxide and their direct contact with teeth may reduce overall peroxide dose and treatment time . These strips may be easier to use by the patients compared to other delivery systems and eliminate the need of fabricating a custom tray . Hydrogen peroxide bleaching strips used for six months has been shown to significantly whiten teeth with tetracycline staining . Bleaching strips have been compared to 10% carbamide peroxide tray delivery system (equivalent to 3.6% hydrogen peroxide) in non-TST and the strips produced a comparable (strips with 5.3% hydrogen peroxide) or even greater (strips with 6.5% hydrogen peroxide) whitening effect when compared to the tray system. For TST, Kugel et al. found that the 6.5% hydrogen peroxide strip system demonstrated significantly greater tooth whitening at 1- and 2-month and experienced a more rapid whitening effect in comparison to 10% carbamide peroxide tray delivery system . Effects of increased tooth whitening with higher concentrations of bleaching agents have been reported on both non-TST and TST .
Tetracycline staining has been a significant issue in Hong Kong and China . Our hypothesis was both the tray and strip systems are effective in bleaching teeth with tetracycline staining and the objectives of this study are to prove this hypothesis and as a pilot study to compare the tooth whitening effect of a strip system (6.0% hydrogen peroxide) and a tray system (15% carbamide peroxide equivalent to 5.4% hydrogen peroxide) of similar hydrogen peroxide concentration in subjects with TST in a randomized clinical trial.
2
Materials and methods
A randomized controlled trial was performed on the tooth whitening effects of two bleaching modalities, a tray based system using 15% carbamide peroxide and a strip based system using 6.0% hydrogen peroxide, on tetracycline stained teeth (TST). This trial was approved by the Ethics committee of the Faculty of Dentistry, the University of Hong Kong. Snowball sampling was used to recruit subjects, which was performed by word of mouth and written notices via staff and students of the University teaching hospital, Prince Philip Dental Hospital (PPDH) over a 6-month period. Participants’ selection and data collection were all performed in PPDH.
2.1
Selection criteria and participants
Potential participants were invited for a clinical examination and were screened for eligibility according to the inclusion and exclusion criteria ( Table 1 ). The presence of tetracycline staining teeth in the maxillary anterior region were judged independently by two assessors (MB and AC) and where inconsistent opinion was found, third assessor (PN) opinion was sought . Those who did not meet the selection criteria or refused to participate this trial were offered other treatment as appropriate. Written consents were obtained from all selected participants after verbal and written explanation of the trial.
| Inclusion criteria | Exclusion criteria |
|---|---|
|
|
2.2
Intervention and trial design
Enrolled participants received a dental prophylaxis and an alginate impression (Aroma Fine Plus, GC Corporation, Tokyo, Japan) of the maxillary arch were made and poured in dental stone (Dentstone KD, Saint-Gobain formula, France). From this a clear maxillary positioning jig (Biocryl ® , 3 mm thickness, Great Lakes Orthodontics, Tonowanda, NY, USA) was fabricated so that the disposable tube of colorimeter (ShadeVision System, X-Rite Inc. Grandville, MI, USA) could be accurately re-positioned into the location cone of the jig to measure the labial middle third tooth colour of a selected tooth . Baseline colour of the maxillary right central incisor and if this was restored the maxillary left central or lateral incisor was measured by a colorimeter which adopted the Commission Internationale de l’É clairage (International Commission on Illumination, CIE) L*a*b* three dimensional colour space. Axis L* is a measure of the lightness of an object and range from zero (perfect dark) to 100 (perfect reflecting diffuser). Axis a* is a measure of redness (positive) or greenness (negative) while axis b* is a measure of yellowness (positive) or blueness (negative). In CIELAB (1976) ’s definition, the overall colour changes delta E (ΔE) can be calculated by the square root of the changes in L*a*b* (ΔE = [(ΔL*) 2 + (Δa*) 2 + (Δb*) 2 ] 1/2 ) .
Participants were then randomly assigned to either the tray group or the strip group by a research assistant tossing a coin (allocation ratio 1:1). At this time the clinicians instructed the participants on the bleaching product, how it should be used and what adverse symptoms they may expect. For the participants assigned to the tray group, a full maxillary arch bleaching tray (Drufosoft 1.5 mm thickness, Dreve-Dentamid GMBH, Unna, Germany) was fabricated on the stone model. Gel reservoir was painted on the labial surface of the anterior teeth 1 mm terminated from the attached gingiva on the stone cast using two layers of spacer (Pink Rubber Sep, Kerr Corporation, Orange, CA, USA). The tray has gingival scalloping extended 2 to 3 mm past the attached gingiva but they did not engage undercuts or terminate on the top of the rugae. Participants were instructed to inject 15% carbamide peroxide bleaching gel in a syringe (Nupro White Gold™, Dentsply Professional, York, USA) into the labial surface of maxillary incisors and canines and wear the tray up to 2 h or overnight during the 3-month trial period. For the strip group, participants were instructed to place the gel side of the maxillary strips containing 6.0% hydrogen peroxide (Crest Whitestrips™, Procter & Gamble, Cincinnati, USA) against the labial surface of maxillary incisors and canines twice daily for 30 min during the 3-month trial period. All participants were requested to report any adverse reaction associated with bleaching that they experienced and were addressed accordingly. Participants were advised avoid tobacco use and consume staining foods and drinks such as curry and coffee etc. during the trial period.
Participants were clinically reviewed by one reviewer who was blinded to their treatment group at one-, two- and three-months ( Fig. 2 ). The primary outcome measures were the changes in L*a*b* (i.e. adjusted colorimeter values) and the calculated overall colour changes ΔE compared to baseline. Three colorimeter readings were taken and averaged. The colorimeter was calibrated for each subject’s measurement. The secondary outcome was any significant adverse reaction associated with bleaching reported by the participants and assessed clinically by the reviewer.
2.3
Sample size calculation
Recruiting adult subjects with untreated tetracycline stained teeth (TST) was recommended however was anticipated to be difficult, therefore the objective of this clinical trial was to determine the effectiveness of strip and tray based bleaching modalities on TST. ΔE value (just noticeable difference) more than 2 will normally be noticeable to an experienced observer . The standard deviation of TST at baseline were around 2 . The effect size is therefore equivalent to 1.0. For one sample t -test with α = 0.05 and 80% power, 10 subjects will be needed. Twenty percent more subjects were recruited for potential drop-out.
2.4
Statistical analysis
Continuous variables were tested for normality by Kolmogorov–Smirnov test. For normal distributed variables, means were analysed using two-sided parametric one sample t -test and independent t -test for intra- and inter-group comparison respectively. For non-normally distributed variables, means were either log converted to normal distribution or medians were analysed using two-sided non-parametric one-sample Wilcoxon test and Mann-Whitney U test for intra- and inter-group comparison respectively. Categorical variables were analysed by Fisher’s exact test. Significance level was set at α = 0.05. All data were analysed using Statistical Package for Social Science (SPSS) 23.0 (IBM, New York, USA).
2
Materials and methods
A randomized controlled trial was performed on the tooth whitening effects of two bleaching modalities, a tray based system using 15% carbamide peroxide and a strip based system using 6.0% hydrogen peroxide, on tetracycline stained teeth (TST). This trial was approved by the Ethics committee of the Faculty of Dentistry, the University of Hong Kong. Snowball sampling was used to recruit subjects, which was performed by word of mouth and written notices via staff and students of the University teaching hospital, Prince Philip Dental Hospital (PPDH) over a 6-month period. Participants’ selection and data collection were all performed in PPDH.
2.1
Selection criteria and participants
Potential participants were invited for a clinical examination and were screened for eligibility according to the inclusion and exclusion criteria ( Table 1 ). The presence of tetracycline staining teeth in the maxillary anterior region were judged independently by two assessors (MB and AC) and where inconsistent opinion was found, third assessor (PN) opinion was sought . Those who did not meet the selection criteria or refused to participate this trial were offered other treatment as appropriate. Written consents were obtained from all selected participants after verbal and written explanation of the trial.
| Inclusion criteria | Exclusion criteria |
|---|---|
|
|
2.2
Intervention and trial design
Enrolled participants received a dental prophylaxis and an alginate impression (Aroma Fine Plus, GC Corporation, Tokyo, Japan) of the maxillary arch were made and poured in dental stone (Dentstone KD, Saint-Gobain formula, France). From this a clear maxillary positioning jig (Biocryl ® , 3 mm thickness, Great Lakes Orthodontics, Tonowanda, NY, USA) was fabricated so that the disposable tube of colorimeter (ShadeVision System, X-Rite Inc. Grandville, MI, USA) could be accurately re-positioned into the location cone of the jig to measure the labial middle third tooth colour of a selected tooth . Baseline colour of the maxillary right central incisor and if this was restored the maxillary left central or lateral incisor was measured by a colorimeter which adopted the Commission Internationale de l’É clairage (International Commission on Illumination, CIE) L*a*b* three dimensional colour space. Axis L* is a measure of the lightness of an object and range from zero (perfect dark) to 100 (perfect reflecting diffuser). Axis a* is a measure of redness (positive) or greenness (negative) while axis b* is a measure of yellowness (positive) or blueness (negative). In CIELAB (1976) ’s definition, the overall colour changes delta E (ΔE) can be calculated by the square root of the changes in L*a*b* (ΔE = [(ΔL*) 2 + (Δa*) 2 + (Δb*) 2 ] 1/2 ) .
Participants were then randomly assigned to either the tray group or the strip group by a research assistant tossing a coin (allocation ratio 1:1). At this time the clinicians instructed the participants on the bleaching product, how it should be used and what adverse symptoms they may expect. For the participants assigned to the tray group, a full maxillary arch bleaching tray (Drufosoft 1.5 mm thickness, Dreve-Dentamid GMBH, Unna, Germany) was fabricated on the stone model. Gel reservoir was painted on the labial surface of the anterior teeth 1 mm terminated from the attached gingiva on the stone cast using two layers of spacer (Pink Rubber Sep, Kerr Corporation, Orange, CA, USA). The tray has gingival scalloping extended 2 to 3 mm past the attached gingiva but they did not engage undercuts or terminate on the top of the rugae. Participants were instructed to inject 15% carbamide peroxide bleaching gel in a syringe (Nupro White Gold™, Dentsply Professional, York, USA) into the labial surface of maxillary incisors and canines and wear the tray up to 2 h or overnight during the 3-month trial period. For the strip group, participants were instructed to place the gel side of the maxillary strips containing 6.0% hydrogen peroxide (Crest Whitestrips™, Procter & Gamble, Cincinnati, USA) against the labial surface of maxillary incisors and canines twice daily for 30 min during the 3-month trial period. All participants were requested to report any adverse reaction associated with bleaching that they experienced and were addressed accordingly. Participants were advised avoid tobacco use and consume staining foods and drinks such as curry and coffee etc. during the trial period.
Participants were clinically reviewed by one reviewer who was blinded to their treatment group at one-, two- and three-months ( Fig. 2 ). The primary outcome measures were the changes in L*a*b* (i.e. adjusted colorimeter values) and the calculated overall colour changes ΔE compared to baseline. Three colorimeter readings were taken and averaged. The colorimeter was calibrated for each subject’s measurement. The secondary outcome was any significant adverse reaction associated with bleaching reported by the participants and assessed clinically by the reviewer.
2.3
Sample size calculation
Recruiting adult subjects with untreated tetracycline stained teeth (TST) was recommended however was anticipated to be difficult, therefore the objective of this clinical trial was to determine the effectiveness of strip and tray based bleaching modalities on TST. ΔE value (just noticeable difference) more than 2 will normally be noticeable to an experienced observer . The standard deviation of TST at baseline were around 2 . The effect size is therefore equivalent to 1.0. For one sample t -test with α = 0.05 and 80% power, 10 subjects will be needed. Twenty percent more subjects were recruited for potential drop-out.
2.4
Statistical analysis
Continuous variables were tested for normality by Kolmogorov–Smirnov test. For normal distributed variables, means were analysed using two-sided parametric one sample t -test and independent t -test for intra- and inter-group comparison respectively. For non-normally distributed variables, means were either log converted to normal distribution or medians were analysed using two-sided non-parametric one-sample Wilcoxon test and Mann-Whitney U test for intra- and inter-group comparison respectively. Categorical variables were analysed by Fisher’s exact test. Significance level was set at α = 0.05. All data were analysed using Statistical Package for Social Science (SPSS) 23.0 (IBM, New York, USA).
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