Colorimetric assessment of laser and home bleaching techniques

Evaluation of tooth color change after a bleaching process with different lasers

The aim of this in vitro study was to evaluate the efficiency of diode laser-activated bleaching systems for color change of teeth. 75 extracted teeth were studied in five different bleaching protocols. Group 1: diode laser 445 nm, 320 µm fiber, 0.5W, continuous wave mode, dose 53 J/cm2. Group 2: diode laser 970 nm, 320 µm fiber, 1W, continuous wave mode, dose 106.10 J/cm2. Group 3: diode laser 940 nm, bleaching handpiece, 7W, continuous wave mode, dose 105 J/cm2. Group 4: diode laser 940 nm, 300 µm fiber, 2W, continuous wave mode, dose 47.16 J/cm2. Group 5: bleaching process without laser activation. In groups 1, 2 and 5, teeth were bleached with Perfect Bleach Office + and in groups 3 and 4, LaserWhite20 bleaching gel was used. Tooth color was determined immediately after the bleaching process using a spectrophotometer. Color change data on the CIE L * a * b* system was analyzed statistically by the one-way ANOVA and Tukey's HSD test. All bleaching procedures resulted in a change of color. All laser groups (∆E * ab > 3) have statistically larger ∆E * ab values than the control group (∆E * ab = 0.73) (p < 0.05). The diode laser 445 nm has the largest ∆E * ab value (∆E * ab = 4.65) and results in a significantly higher color difference than all other groups. In terms of color score difference in VITA Shades, all laser-activated groups lead to a lightening effect while the control group leads to only a slight lightening effect. The diode laser 445 nm produced the greatest color difference. Laser-activated bleaching is more effective than conventional bleaching without light activation. The diode laser 445 nm performs best in this in vitro study.

Effect of 1.5% potassium oxalate on sensitivity control, color change, and quality of life after at-home tooth whitening: A randomized, placebo-controlled clinical trial

OBJECTIVE

This clinical trial evaluated the effect of 1.5% potassium oxalate (PO) in controlling sensitivity and color change after at-home tooth whitening. It also evaluated the influence of PO on health-related quality of life (HRQoL) and the degree of patient satisfaction after bleaching treatment.

MATERIALS AND METHODS

Fifty volunteers were randomized into two groups (n = 25): At-home bleaching gel with 22% carbamide peroxide for 45 min + placebo gel (GP) or 1.5% PO (GPO) for 10 min. The intensity of tooth sensitivity was assessed daily through the visual analog scale. The color analysis was performed three times: baseline, 21 days, and 1 month after the last application of the whitening gel. The impact of the oral condition on the patient's quality of life (OIDP) was used to measure the impact caused by the whitening treatment in relation to the individuals' ability to carry out their daily activities and its influence on HRQOL.

RESULTS

No difference in tooth sensitivity was observed (p > 0.05). In addition, there was no difference in color change between groups (p > 0.05). However, there was an intragroup statistical difference throughout the evaluation period (p <0.05). The OIDP analysis showed a statistical difference between the groups (p > 0.05) and there was no difference between the groups regarding the degree of satisfaction with the bleaching (p > 0.05).

CONCLUSIONS

The 1.5% PO was effective in preventing sensitivity and did not interfere with tooth whitening. Desensitizing therapy had a positive impact on quality of life and patient satisfaction.

Present status and future directions - Managing discoloured teeth

Managing tooth discolouration involves a range of different protocols for clinicians and patients in order to achieve an aesthetic result. There is an increasing public awareness in the appearance of their teeth and management of tooth discolouration may be inter-disciplinary and involve both vital and nonvital teeth. Vital teeth can be easily treated with low concentration hydrogen peroxide products safely and effectively using an external approach and trays. For endodontically treated teeth, the walking bleach technique with hydrogen releasing peroxide products is popular. However, there is an association with external cervical root resorption with higher concentrations of hydrogen peroxide of 30%-35%. There are also regulatory considerations for the use of hydrogen peroxide in certain jurisdictions internationally. Prosthodontic treatments are more invasive and involve loss of tooth structure as well as a life cycle of further treatment in the future. This narrative review is based on searches on PubMed and the Cochrane library. Bleaching endodontically treated teeth can be considered a safe and effective protocol in the management of discoloured teeth. However, the association between bleaching and resorption remains unclear although there is likely to be a relation to prior trauma. It is prudent to avoid thermocatalytic approaches and to use a base/sealer to cover the root filling. An awareness expectations of patients and multidisciplinary treatment considerations is important in achieving the aesthetic result for the patient. It is likely that there will be an increasing demand for aesthetic whitening treatments. Bleaching of teeth has also become increasingly regulated although there are international differences in the use and concentration of bleaching agents.

Effect of Three Wavelengths of Diode Laser on the Efficacy of Bleaching of Stained Teeth

Objectives:

Light irradiation and heat have been used to accelerate the process of tooth bleaching. This study aimed to assess the efficacy of conventional bleaching compared to laser-bleaching using three different wavelengths of diode lasers.

Materials and Methods:

In this in-vitro experimental study, 40 extracted human central incisors were immersed in a coloring solution made of tea, coffee, and cola for 21 days. The L*, a*, and b* color parameters were measured before and after the immersion using spectrophotometry. The teeth were then randomly divided into four groups (n=10) as follows: group 1: 810-nm diode laser + Biolase Laser White 20, group 2: 940-nm diode laser + Biolase Laser White 20, group 3: 980-nm diode laser + Biolase Laser White 20, and group 4: conventional bleaching with Opalescence Boost without laser irradiation. One-way analysis of variance (ANOVA) was used to assess the effect of laser type and bleaching technique on color parameters.

Results:

The 940-nm (ΔE=28.5896) and 810-nm laser groups (ΔE=21.2382) showed the highest and the lowest bleaching efficacy, respectively; however, the groups were not significantly different in terms of bleaching efficacy (P>0.05).

Conclusion:

Laser-bleaching with 810-, 940- and 980-nm wavelengths of diode laser has an efficacy similar to that of conventional bleaching but in a shorter period. No difference was noted between different laser wavelengths in terms of bleaching efficacy.

Dental bleaching efficacy and impact on demineralization susceptibility of simulated stained-remineralized caries lesions

OBJECTIVES

To evaluate the efficacy of different bleaching systems on artificially created stained-remineralized caries lesions; and to assess the susceptibility of the bleached lesions to further demineralization.

METHODS

Human enamel specimens were sectioned, polished, demineralized, and randomly divided into six groups (n = 21) to create stained-remineralized lesions, either non-metallic (non-Met: G1, G2 and G3) or metallic (Met: G4, G5 and G6). G1 and G4 received no bleaching treatment, while G2 and G5 were treated with 15% carbamide peroxide (at-home bleaching protocol; 4 h/d×7), and G3 and G6 with 40% hydrogen peroxide (in-office bleaching protocol; 20min × 3). Susceptibility to further demineralization was tested after bleaching treatment. Lesion mineral loss and depth were measured by transversal microradiography, and color change by spectrophotometry. Outcomes were analyzed using ANOVA models followed by Fisher's PLSD tests (α = 0.05).

RESULTS

Metallic-stained lesions were significantly darker (all p < 0.001) and more resistant to bleaching (p < 0.005) than non-Met ones. For both stain types, the at-home bleaching protocol was more effective than the in-office (p < 0.005); however, it also increased the lesion susceptibility to demineralization (p < 0.05) [ΔΔZ mean ± SD ranging from 205 ± 73 to 313 ± 188 (at home) vs. 132 ± 45 to 206 ± 98 (in office); p < 0.05]. After bleaching, non-Met lesions were significantly more susceptible to demineralization (p < 0.05), with the ΔΔZ ranging from 206 ± 98 to 313 ± 188 compared to Met lesions ranging from 132 ± 45 to 205 ± 73.

CONCLUSIONS

At-home bleaching protocol presented greater bleaching efficacy compared to in-office bleaching protocol. After bleaching, metallic-stained lesions were more resistant to subsequent demineralization compared to non-metallic stained lesions.

CLINICAL SIGNIFICANCE

Bleaching stained-arrested caries lesions may improve aesthetics but also increase susceptibility to demineralization, depending on the type of stain involved and bleaching system used.

Evaluation of the Diode laser (810nm, 980 nm) on color change of teeth after external bleaching

Subject and aim: The aim of this study was to evaluate the efficiency of diode laser-activated bleaching systems for color change of teeth. Materials & Methods: 40 premolars with intact enamel surfaces were selected for five external bleaching protocols (n=8). Two different wavelengths of diode laser (810 and 980 nm) with two different hydrogen peroxide concentrations (30% and 46%) were selected for laser bleaching. Group 1 received bleaching (Heydent- Germany) with a 810 nm diode laser; Group 2 received bleaching (Heydent- Germany) with a 980 nm diode laser; Group 3 received bleaching (laser white*20- Biolase) with a 810 nm diode laser; Group 4 received bleaching (laser white*20- Biolase) with a 980 nm diode laser, with an output power of 1.5 W, in continuous wave (cw) mode for each irradiation. Group 5 as control group received 40% hydrogen peroxide (Opalescence Boost, Ultradent-USA) with no light activation. The color of teeth was scored at baseline and 1 week after bleaching with spectrophotometer. Color change data on the CIEL*a*b* system were analyzed statistically by the one-way ANOVA and Tukey's HSD test. Results: All the bleaching techniques resulted in shade change. According to ΔE values, all techniques were effective to bleach the teeth (ΔE ≥ 3). Statistically significant differences were detected among bleaching protocols (p=0.06). Regarding shade change values expressed as ΔL*, Δa*, Δb*, ΔE*, laser bleached groups were no statistically different with each other (p>0.05). Conclusion: Bleaching with different wavelengths of diode laser resulted in the same results.

Influence of Different Types and Concentrations of Chemical Catalysts on Dental Bleaching Efficiency

The objective of this study was to evaluate the effects of different types and concentrations of chemical catalysts on the efficiency of 35% hydrogen peroxide gel on dental bleaching. Enamel-dentin disks were obtained from bovine incisors and the initial color was assessed. The groups were divided according to the type and concentration of catalyst added to an experimental gel: ferrous sulphate (FS) (0.001, 0.002 and 0.003%); ferrous gluconate (Fg) (0.01, 0.02 and 0.03%); ferric chloride (FC) (0.01, 0.02 and 0.03%); manganese gluconate (MG) (0.01, 0.02 and 0.03%); and manganese chloride (MC) (0.01, 0.02 and 0.03%). The positive control (PC) group received the bleaching gel without any catalyst, while in the negative control (NC) the specimens remained in artificial saliva. Three applications of the bleaching gels were performed for 10 minutes each, repeated after 7 days. Color assessments were performed 7 days after the first session and 7 days after the second. The specimens were stored in artificial saliva and assessed again after 1 year. The data were analyzed by parametric analysis of variance and Tukey's test. Some of the chemical catalysts tested were effective in reducing the yellowish color of the samples in relation to the positive control group after 1 and 2 applications and diminished the color relapse over time. After 1 year, the FS was the most effective catalyst tested. We concluded that some chemical catalysts increased the efficiency of dental bleaching.

The effect of light-activation sources on tooth bleaching

Vital bleaching is one of the most requested cosmetic dental procedures asked by patients who seek a more pleasing smile. This procedure consists of carbamide or hydrogen peroxide gel applications that can be applied in-office or by the patient (at-home/overnight bleaching system). Some in-office treatments utilise whitening light with the objective of speeding up the whitening process. The objective of this article is to review and summarise the current literature with regard to the effect of light-activation sources on in-office tooth bleaching. A literature search was conducted using Medline, accessed via the National Library of Medicine Pub Med from 2003 to 2013 searching for articles relating to effectiveness of light activation sources on in-office tooth bleaching. This study found conflicting evidence on whether light truly improve tooth whitening. Other factors such as, type of stain, initial tooth colour and subject age which can influence tooth bleaching outcome were discussed. Conclusions: The use of light activator sources with in-office bleaching treatment of vital teeth did not increase the efficacy of bleaching or accelerate the bleaching.

Spectrophotometric evaluation of dental bleaching under orthodontic bracket in enamel and dentin

Aware of the diffusion capacity of bleaching in the dental tissues, many orthodontists are subjecting their patients to dental bleaching during orthodontic treatment for esthetic purposes or to anticipate the exchange of esthetic restorations after the orthodontic treatment. For this purpose specific products have been developed in pre-loaded whitening trays designed to fit over and around brackets and wires, with clinical efficacy proven.

OBJECTIVE

The objective of this study was to evaluate, through spectrophotometric reflectance, the effectiveness of dental bleaching under orthodontic bracket.

MATERIAL AND METHODS

Thirty-two bovine incisors crown blocks of 8 mm x 8 mm height lengths were used. Staining of tooth blocks with black tea was performed for six days. They were distributed randomly into 4 groups (1-home bleaching with bracket, 2- home bleaching without bracket, 3- office bleaching with bracket, 4 office bleaching without bracket). The color evaluation was performed (CIE L * a * b *) using color reflectance spectrophotometer. Metal brackets were bonded in groups 1 and 3. The groups 1 and 2 samples were subjected to the carbamide peroxide at 15%, 4 hours daily for 21 days. Groups 3 and 4 were subjected to 3 in-office bleaching treatment sessions, hydrogen peroxide 38%. After removal of the brackets, the second color evaluation was performed in tooth block, difference between the area under the bracket and around it, and after 7 days to verified color stability. Data analysis was performed using the paired t-test and two-way variance analysis and Tukey's.

RESULTS

The home bleaching technique proved to be more effective compared to the office bleaching. There was a significant difference between the margin and center color values of the specimens that were subjected to bracket bonding.

CONCLUSIONS

The bracket bond presence affected the effectiveness of both the home and office bleaching treatments. Key words:Tooth bleaching, spectrophotometry, orthodontics.

Color alteration, hydrogen peroxide diffusion, and cytotoxicity caused by in-office bleaching protocols

OBJECTIVES

This study evaluated the color alteration, cytotoxicity, and hydrogen peroxide (HP) diffusion associated with different in-office bleaching protocols.

MATERIALS AND METHODS

Bovine enamel/dentin disks were subjected to three bleaching sessions with 35 % HP (three 15-min applications), 35 % HP (one 45-min application), or 20 % HP (one 45-min application). The control group was not bleached. Before bleaching, the disks were adapted to artificial pulp chambers positioned in compartments containing 1 ml of acetate buffer or medium, so that the dentin remained in contact with these substances. Immediately after bleaching, the HP that diffused through the disks was stabilized by acetate buffer and was quantified (two-way repeated measures ANOVA/Fisher's protected least significant difference (PLSD) test; α = 5 %). Cells of mouse dental papilla cell-23 (MDPC-23) were incubated in this culture media for 1 h, followed by analysis of cellular metabolism (methyl tetrazolium assay) (one-way ANOVA/Tukey test; α = 5 %) and morphology (scanning electron microscopy). The specimen color alteration (ΔE) was analyzed by reflection spectrophotometry (two-way repeated measures ANOVA/Fisher's PLSD test; α = 5 %).

RESULTS

All protocols showed equal effectiveness at the end of the treatment. HP diffusion was significantly higher in the groups bleached with 35 % HP. Reapplication of 35 % HP resulted in increased diffusion only in the first session; however, the decrease in cell metabolism was similar for all studied protocols.

CONCLUSION

Despite greater peroxide diffusion in the groups treated with 35 % HP, all protocols showed the same effectiveness and were cytotoxic to MDPC-23 cells.

CLINICAL RELEVANCE

Bleaching protocols using high HP concentrations should be avoided because they exert aggressive actions on odontoblast-like cells.

Plasma in dentistry

This review describes the contemporary aspects of plasma application in dentistry. Previous studies on plasma applications were classified into two categories, surface treatment and direct applications, and were reviewed, respectively according to the approach. The current review discussed modification of dental implant surface, enhancing of adhesive qualities, enhancing of polymerization, surface coating and plasma cleaning under the topics of surface treatment. Microbicidal activities, decontamination, root canal disinfection and tooth bleaching were reviewed as direct applications with other miscellaneous ones. Non-thermal atmospheric pressure plasma was of particular focus since it is gaining considerable attention due to the possibility for its use in living tissues. Future perspectives have also been discussed briefly. Although it is still not popular among dentists, plasma has shown promises in several areas of dentistry and is now opening a new era of plasma dentistry.

Optical effects of experimental light-activated bleaching procedures

OBJECTIVE

The purpose of this study was to evaluate the efficiency of experimental light-activated bleaching procedures.

BACKGROUND DATA

The improved color effect may be attributed to the potential photochemical effect of light-emitting diode (LED405), organic LED (OLED), and femtosecond laser rather than to the photothermal effect of conventional lights used for tooth bleaching.

MATERIALS AND METHODS

Specially made pastilles of hydroxylapatite were immersed in green tea for 8 h and randomly divided into four groups (n=50) specified by the type of light source applied during a 30 min bleaching treatment: LED405, OLED, and femtosecond laser, or its absence (control group). Each group was treated with five bleaching gels: 10%, 16%, and 30% carbamide peroxide (CP), and 25% and 38% hydrogen peroxide (HP). Changes in color were determined by red-green-blue (RGB) colorimeter and ultraviolet-visible-near-infrared (UV/Vis/NIR) spectroscopy.

RESULTS

Regardless of the applied bleaching gel, LED405 produced a larger increase in the value of RGB index than did OLED and bleaching without light activation (p<0.05). Femtosecond laser also produced significantly better results in combination with 16% CP and 38% HP. Furthermore, application of a bleaching agent with a higher concentration of peroxide boosted the value of the RGB index. Spectroscopic measurements revealed similar results, although treatments with OLED were rated relatively better than in RGB analysis.

CONCLUSIONS

The mechanisms of light-activated bleaching procedures had a significant effect on the color change. The bleaching activation with LED405 and higher concentrations of peroxide in bleaching agents promoted better whitening effect.

High-efficiency tooth bleaching using non-thermal atmospheric pressure plasma with low concentration of hydrogen peroxide

Light-activated tooth bleaching with a high hydrogen peroxide (HP; H2O2) concentration has risks and the actual role of the light source is doubtful. The use of conventional light might result in an increase in the temperature and cause thermal damage to the health of the tooth tissue.

OBJECTIVE

This study investigated the efficacy of tooth bleaching using non-thermal atmospheric pressure plasma (NAPP) with 15% carbamide peroxide (CP; CH6N2O3) including 5.4% HP, as compared with conventional light sources.

MATERIAL AND METHODS

Forty human teeth were randomly divided into four groups: Group I (CP+NAPP), Group II (CP+plasma arc lamp; PAC), Group III (CP+diode laser), and Group IV (CP alone). Color changes (∆E) of the tooth and tooth surface temperatures were measured. Data were evaluated by one-way analysis of variance (ANOVA) and post-hoc Tukey's tests.

RESULTS

Group I showed the highest bleaching efficacy, with a ∆E value of 1.92-, 2.61 and 2.97-fold greater than those of Groups II, III and IV, respectively (P<0.05). The tooth surface temperature was maintained around 37°C in Group I, but it reached 43°C in Groups II and III.

CONCLUSIONS

The NAPP has a greater capability for effective tooth bleaching than conventional light sources with a low concentration of HP without causing thermal damage. Tooth bleaching using NAPP can become a major technique for in-office bleaching in the near future.

Effect of dental bleaching after bracket bonding and debonding using three different adhesive systems

OBJECTIVE

To evaluate the influence of bonding and debonding of orthodontic brackets on dental in-home bleaching, taking into account three different adhesive systems.

METHODS

Forty-four bovine incisors were divided into four groups according to the primer system used for orthodontic bracket bonding. Following the debonding of orthodontic brackets, the teeth were stored in staining solution for 96 hours. Then, teeth were whitened using 10% carbamide peroxide for two weeks at a 6-hour-a-day regime. Standardized digital photographs were taken at the following intervals: T₀ (initial); T₁ (after debonding); T₂ (after pigmentation); T₃, T₄ and T₅ representing 1, 7, and 14 days of bleaching. Repeatability and stability tests were carried out to check the method accuracy. Images were analyzed using Adobe Photoshop 7.0 software considering (L*a*b*) color coordinate values and a modified color difference total (ΔE').

RESULTS

The results of this study (ANOVA and Tukey; p < 0.01) demonstrated that after 7 days of bleaching, experimental groups showed significantly less teeth whitening compared to the control group. However, there were no significant color differences between the groups after 14 days, according to values of lightness (L*).

CONCLUSIONS

Regardless of the adhesive primer system applied, bonding and debonding of orthodontic brackets alters the outcome of tooth whitening in the first 7 days of bleaching, however it has no influence on the whitening of the dental structure after 14 days of in-home dental bleaching with 10% carbamide peroxide.

Three-Month Evaluation of Vital Tooth Bleaching Using Light Units—A Randomized Clinical Study

The aim of this study was to evaluate the color stability of vital bleaching using a halogen unit, laser, or only chemical activation up to three months after treatment. A total of 60 patients were divided into three groups, and their teeth were bleached with 38% hydrogen peroxide using three methods: acceleration of the bleaching process with halogen (eight minutes), laser (30 seconds), or chemical activation only. All teeth were bleached a maximum of four times (4 × 15 minutes) until a change of six shade tabs took place. The color was evaluated both visually and with a spectrophotometer before bleaching, immediately after bleaching, and one and three months after bleaching. Directly after bleaching, the use of halogen showed better results than laser (p≤0.05). One and three months after bleaching, no significant difference was found between the tested methods relative to the shade change, independent of the method of shade evaluation (p&gt;0.05). As far as the color stability is concerned, bleaching with halogen resulted in stable color throughout the three months (p&gt;0.05), whereas the other two methods resulted in whiter teeth after one and three months compared with the color directly after bleaching (p≤0.05). Bleaching with laser needed more time than halogen for the desired shade change (p≤0.05). Although directly after treatment bleaching with halogen resulted in better results, one and three months after bleaching the kind of acceleration used in the bleaching process did not have any effect on the esthetic results.

Comparison of Two At-home Whitening Products of Similar Peroxide Concentration and Different Delivery Methods

Purpose

This study compared the whitening efficacy, side effects, and patients' preferences/perceptions of two whitening systems of similar peroxide concentration but different formulation and delivery methods.

Methods

The tooth color change of 24 participants was measured using a shade guide (BSG) and a spectrophotometer (ES). Color difference was calculated: ΔE* = [(ΔL*)2 + (Δa*)2 + (Δb*)2]1/2. One whitening treatment was randomly applied to the right or left maxillary anterior teeth and the other was applied to the contralateral teeth, at-home with 35% carbamide peroxide in a tray (TW) or with 14% hydrogen peroxide in strips (WS). The tooth color was evaluated at baseline, 15 and 30 days (15 days postwhitening). Participants rated their tooth and soft tissue sensitivity (1–10 scale) and completed a questionnaire on their preferences. Results were analyzed by repeated measurement regression analysis/Tukey and Mann-Whitney (p&lt;0.05).

Results

At 15 days, the teeth treated with TW and WS presented ΔE* = 7 and 6, respectively (ΔBSG=3 for both), and at 30 days, they presented ΔE* = 7.5 and 6.5, respectively (ΔBSG=3 for both). There was no significant difference in tooth and soft tissue sensitivity between treatments. No participant reported tooth and gingival sensitivity at the postwhitening appointment. Of the participants, 83% preferred the TW over WS.

Conclusion

Both ΔE* and ΔBSG showed no significant difference in tooth color change between TW and SW at either time point. By the end of the study no participants reported tooth and gingival sensitivity. Participants preferred TW over SW.

Efficacy of tooth bleaching with and without light activation and its effect on the pulp temperature: an in vitro study

The aim of this in vitro study was to evaluate the colour stability of bleaching after light activation with halogen unit, laser, LED unit or chemical activation up to 3 months after treatment. Four groups of teeth (n = 20) were bleached with Opalescence Xtra Boost (38% hydrogen peroxide) using four different methods: activation with halogen, LED, laser or chemical activation only. All teeth were bleached in one session for four times (4 × 15 min) and the colour was evaluated using a spectrophotometer at the following time points: before bleaching, immediately after bleaching, 1 day, and 1 and 3 months after the end of bleaching. Between the tested time points, the teeth were stored in 0.9% NaCl solution. Additionally, the temperature increase in the pulp chamber was measured using a measuring sensor connected to a computer. Bleaching with the halogen unit showed the highest colour change. Halogen unit, laser and chemical activation resulted in whiter teeth after 1 and 3 months compared to the colour after the end of the bleaching procedure (p ≤ 0.05). Three months after the end of bleaching, the shade changes observed were-halogen: 7.1 > chemical activation: 6.2 > LED: 5.4 > laser: 5.2. Halogen showed the highest temperature increase (17.39°C ± 1.96) followed by laser (14.06°C ± 2.55) and LED (0.41°C ± 0.66) (p < 0.0001). Chemical activation did not affect the temperature in the pulp chamber. The use of light activation did not show any advantages compared to chemical bleaching. Although halogen unit showed the higher shade's change, its use resulted also in the higher pulp temperature. According to the present findings, light activation of the bleaching agent seems not to be beneficial compared to bleaching without light activation, concerning the colour stability up to 3 months after bleaching and the pulp temperature caused during the bleaching procedure.

Assessment of the effectiveness of light-emitting diode and diode laser hybrid light sources to intensify dental bleaching treatment

OBJECTIVE

To evaluate the effectiveness of the color change of hybrid light-emitting diode (LED) and low-intensity infrared diode laser devices for activating dental bleaching and to verify the occurrence of a color regression with time.

MATERIAL AND METHODS

A total of 180 specimens obtained from human premolars were immersed in a coffee solution for 15 days for darkening and then divided into eight experimental groups (n = 20 in each) as follows: G1, bleaching without light; G2, bleaching with halogen light; G3, bleaching with a blue LED (1000 mW/470 nm) and a laser device (120 mW/795 nm) simultaneously; G4, bleaching with an LED emitting blue light (1000 mW/470 nm); G5, bleaching with a blue LED (800 mW/470 nm) and a laser device (500 mW/830 nm) simultaneously; G6, bleaching with a blue LED device (800 mW); G7, bleaching with a green LED (600 mW/530 nm) and a laser device (120 mW/795 nm) simultaneously; and G8, bleaching with a green LED (600 mW). Three measurements were performed (at baseline and 14 days and 12 months after bleaching) using a Vita Easyshade spectrophotometer. The data were submitted to two-way ANOVA and a Tukey test.

RESULTS

All groups showed significantly higher ΔE values than Group G1, with the exception of Group G8. Variations in the ΔE values at 14 days were significant when compared with those obtained at baseline and after 12 months.

CONCLUSIONS

Light activation of the bleaching gel provided faster and more intense bleaching than use of the bleaching gel without light activation. Combinations of low-intensity diode lasers are ineffective as a bleaching gel activator. Color regression was observed after 12 months of storage.

Analysis of the Pulp Chamber Temperature of Teeth Submitted to Light Activation with and without Bleaching Gel

Purpose

This study evaluated the temperature of the pulpal chamber (PC) of teeth submitted to the light activation with and without bleaching gel, using different types of light sources.

Materials and methods

A digital thermometer, thermocouple K type, was located in the PC of human upper central incisors and the specimens received light activation from the following sources: G1—Laser, G2—Halogen light, G3—progressive intensity halogen lamp, G4—LED/Laser. The light was applied for 3 minutes, with and without the use of bleaching gel. The data were collected after every 30 seconds and analyzed by three-way ANOVA and Tukey's test.

Results

The mean values were: Use of the gel—with gel: 3.09a, without gel: 2.79b; Type of light source—G1: 0.60a, G2: 2.38b, G3: 4.16c, G4: 4.63d; Time of activation 30 seconds: 1.15a, 1 minutes: 2.20b, 1 minutes 30 seconds: 2.97c, 2 minutes: 3.44d, 2 minutes 30 seconds: 3.81e, 3 minutes: 4.09e.

Conclusions

The use of bleaching gel associated with light activation resulted in higher heating of the PC. LED/LASER light and progressive intensity halogen lamp showed highest levels of heating. The increase of irradiation time significantly increased the temperature.

Comparison of At-home and In-office Tooth Whitening Using a Novel Shade Guide

Five days of at-home whitening with 10% carbamide peroxide (eight hours/day) produces a similar tooth whitening result as one in-office treatment with 25% hydrogen peroxide (one hour).

In Situ Study of In-office Bleaching Procedures Using Light Sources on Human Enamel Microhardness

Regardless of the light sources used, the microhardness of human dental enamel did not present significant changes 14 days after in-office bleaching.

Influence of surfactants on the effectiveness of bleaching gels

This study evaluated the influence of surfactants on the effectiveness of 35% hydrogen peroxide (HP) and 10% carbamide peroxide (CP) bleaching gels. One hundred and forty bovine teeth were used, which were stained by immersion in a coffee, red wine, and tobacco mixture for 7 days. At the end of this process, the color measurement at baseline was taken with the Vita Easyshade spectrophotometer. The teeth were divided into seven groups: (a) negative control (NC), (b) positive control for HP (PC-35), (c) HP + Tween 20 (T20-35), (d) HP + laurel sodium sulfate (LSS-35), (e) positive control for CP (PC-10), (f) CP + Tween 20 (T20-10), and (g) CP + laurel sodium sulfate (LSS-10). Group NC was kept in artificial saliva for 21 days. Groups PC-35, T20-35, and LSS 35 received three applications of bleaching gel for 10 min; the process was repeated after 7 days. Groups PC-10, T20-10, and LSS-10 received the gel for 8 h per day for 14 days. After the bleaching process, the final color was measured. The analysis of variance and Tukey tests showed statistically significant differences for the parameters of ∆L, ∆b, and ∆E of the HP gels with surfactant and positive control group (PC-35). Within the limits of this in vitro study, the addition of surfactants to HP bleaching gel increased the bleaching effectiveness.

Effect of light-activated bleaching on the microleakage of Class V tooth-colored restorations

OBJECTIVE

In-office bleaching procedures utilizing highly concentrated 30%-35% hydrogen peroxide solutions or hydrogen peroxide releasing agents are used for tooth whitening. Some recommend that, to enhance the whitening process, light-activation of the bleaching agent should be performed. The current study evaluated the effect of plasma arc bleaching on the microleakage of Class V restorations restored with resin composite, compomer and resin-modified glass ionomer (RMGI).

MATERIALS AND METHODS

The buccal surfaces of 72 freshly extracted premolars were prepared with Class V cavities (4 x 2.5 x 1.5 mm) extended 1 mm apical to the CEJ. The prepared teethwere randomly divided into six groups. The cavities were restored with Single Bond and Z100 resin composite (Groups 1 and 2), Prompt L-Pop and F2000 compomer (Groups 3 and 4) and Vitremer RMGI (Groups 5 and 6), respectively. They were then thermocycled for 500 cycles. The samples from Groups 1, 3 and 5 were incubated at 37 degrees C and 100% humidity. Groups 2, 4 and 6 were bleached using in-office bleaching gel and the plasma arc bleaching unit, then incubated. All samples were sealed with nail varnish and immersed in 2% basic fuschin for 24 hours. The restorations were sectioned longitudinally and microleakage was evaluated using a scale ranging from 0 to 3. The data were analyzed using the Kruskal-Wallis test (alpha = 0.05).

RESULTS

No statistically significant differences between study groups were observed in both the enamel and dentinal margins (p > 0.05).

CONCLUSION

Plasma arc bleaching did not significantly affect the microleakage of existing tooth-colored restorations restored with Z100 resin composite, F2000 compomer and Vitremer RMGI.

Intrapulpal temperature variation during bleaching with various activation mechanisms

Objectives:

The aim of this study was to evaluate the intrapulpal temperature variation after bleaching treatment with 35% hydrogen peroxide using different sources of activation.

Material and Methods:

Twenty-four human teeth were sectioned in the mesiodistal direction providing 48 specimens, and were divided into 4 groups (n=12): (G1) Control - Bleaching gel without light activation, (G2) Bleaching gel + halogen light, (G3) Bleaching gel + LED, (G4) Bleaching gel + Nd:YAG Laser. The temperatures were recorded using a digital thermometer at 4 time points: before bleaching gel application, 1 min after bleaching gel application, during activation of the bleaching gel, and after the bleaching agent turned from a dark-red into a clear gel. Data were analyzed statistically by the Dunnet's test, ANOVA and Tukey's test (α=0.05).

Results:

The mean intrapulpal temperature values (°C) in the groups were: G1: 0.617 ± 0.41; G2: 1.800 ± 0.68; G3: 0.975 ± 0.51; and G4: 4.325 ± 1.09. The mean maximum temperature variation (MTV) values were: 1.5°C (G1), 2.9°C (G2), 1.7°C (G3) and 6.9°C (G4). When comparing the experimental groups to the control group, G3 was not statistically different from G1 (p>0.05), but G2 and G4 presented significantly higher (p<0.05) intrapulpal temperatures and MTV. The three experimental groups differed significantly (p<0.05) from each other.

Conclusions:

The Nd:YAG laser was the activation method that presented the highest values of intrapulpal temperature variation when compared with LED and halogen light. The group activated by LED light presented the lowest values of temperature variation, which were similar to that of the control group.

The effect of tooth bleaching on the enamel surface and the tensile force to debond orthodontic brackets

OBJECTIVE

The aim of this study was to evaluate the influence of successive tooth bleaching on the tensile force to debond orthodontic brackets and dental enamel.

DESIGN

In vitro study.

SETTINGS

Department of Orthodontics, Faculty of Dentistry, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.

MATERIALS AND METHODS

Seventy-two human premolars were divided into three groups: Group 1 was not submitted to bleaching, Group 2 was subjected to one tooth bleaching (35% hydrogen peroxide enabled by LEDs) and Group 3 was subjected to two tooth bleachings interspersed by aging. Twenty teeth from each group were subjected to tensile test, failure pattern after debonding and evaluation of resin/enamel interface. Four teeth from each group were not submitted to tensile bond testing and had their external surfaces and internal structure analyzed by SEM and polarized light microscopy.

RESULTS

The strength of the brackets decreased in Groups 2 and 3, but was not significant (P=0.635). In general, the failure pattern appeared at the resin/bracket interface or within the resin. The experimental groups showed an increase in slots and erosions on the surface of the enamel and were more pronounced in Group 3. There were no changes to the internal structure of the enamel.

CONCLUSIONS

The use of a 35% hydrogen peroxide in-office bleaching system, in vitro, seven days before bonding, does not significantly reduce the tensile force to debond orthodontic brackets, even after a second bleaching procedure. In most cases, debonding occurred at the adhesive/bracket interface or within the adhesive. Bleaching alters the enamel surface and the resin/enamel interface, but it does not influence bond strength.

Different light-activated in-office bleaching systems: a clinical evaluation

The aim of this clinical study was to evaluate the efficiency of in-office bleaching systems with different light sources for color change and possible side effects such as tooth sensitivity and gingival irritations. Forty healthy volunteers aged 18 years and older (average age 27.3 years), having all their natural healthy teeth in shade A3 or darker on the Vita shade guide, with no restorations on the buccal surfaces and no tooth sensitivity, participated in this study. Participants were randomly assigned to four groups of ten volunteers. Group 1 received bleaching without light activation (Opalescence Xtra Boost, Ultradent); group 2 received bleaching (Laser White 10, Biolase) with a diode laser (810 nm, 10 W/ Laser Smile, Biolase) activation; group 3 received bleaching treatment (Remewhite, Remedent) with a plasma arc lamp (400-490 nm, 2800 mV/cm(2), Remecure CL15), and group 4 received bleaching with a light emitting diode (LED) lamp (By White accelerator, Ensodent) according to the manufacturers' recommendations. The shade was assessed with a classical Vita shade guide (Vita Zahnfabrik) and a digital spectrophotometer (Vita Easy Shade, Vident). The color of teeth was scored at baseline and 1 week after bleaching. Any side effects on teeth or gingiva was recorded by visual analog scale. Results were analyzed statistically, by one-way analysis of variance (ANOVA), Kruskal-Wallis, and Mann-Whitney U tests with Bonferroni correction. All the bleaching techniques resulted in shade change. No significant differences were found in the color change among the four groups with shade guide assessment (P > 0.05), but spectrophotometer readings exhibited significant differences among the groups (P < 0.05). The overall shade change values expressed as DeltaL, Deltaa, Deltab, DeltaE for group 2 was significantly higher than those for the other groups (P < 0.05). Group 2 also showed lower tooth and gingival sensitivity scores than those of the other groups (P < 0.05). All techniques resulted in shade change. Although the shade guide evaluation did not exhibit any differences among the bleaching treatment groups, spectrophotometer readings showed different findings. The results obtained by the two methods of evaluation of shade change used in this study were different from each other. Bleaching with diode laser resulted in less tooth and gingival sensitivity than the other bleaching systems.

CLINICAL RELEVANCE

in-office bleaching systems used with or without light, lead to a shade change. As bleaching with diode laser resulted in less tooth and gingival sensitivity, it might be preferred among in-office bleaching systems.

Tooth bleaching with nonthermal atmospheric pressure plasma

We demonstrated that room temperature plasma could be used for tooth bleaching. A nonthermal, atmospheric pressure, helium plasma jet device was developed to enhance the tooth bleaching effect of hydrogen peroxide (H(2)O(2)). All teeth were sectioned sagittally into halves, which were assigned randomly to either the experimental group or the control group. The experimental group was treated with H(2)O(2) (28%, 20 microL every 30 seconds) plus plasma (5 W) for 10 minutes; the control group was treated with H(2)O(2) alone for the same duration. Removal of the tooth surface protein was demonstrated by scanning electron microscopy images and Ponceau staining. Production of hydroxyl radicals (.OH) was measured by using electron spin resonance spin-trapping. Combining plasma and H(2)O(2) improved the bleaching efficacy by a factor of 3 compared with using H(2)O(2) alone. Tooth surface proteins were noticeably removed by plasma treatment. When a piece of tooth was added to a solution of H(2)O(2) as a catalyst, production of *OH after plasma treatment was 1.9 times greater than when using H(2)O(2) alone. We suggest that the improvement in tooth bleaching induced by plasma is due to the removal of tooth surface proteins and to increased *OH production.

In vitro evaluation of the effectiveness of bleaching agents activated by different light sources

PURPOSE

This study evaluated the efficacy of tooth whitening and color stability at different time periods after treatment.

MATERIALS AND METHODS

Blocks obtained from human molars were divided into 15 groups (n = 5) by bleaching agents: 35% hydrogen peroxide (Whiteness HP and Opalescence Xtra) and 37% carbamide peroxide (Whiteness Super); and light sources: halogen lamp and plasma arc lamp (bleach mode), LED/diode laser, argon laser, and no light source. The efficacy of bleaching was measured using a spectrophotometer. Six bleaching sessions were performed (times 1 to 6). The specimens were submitted to another reading 7, 15, and 30 days after the end of bleaching (times 7, 8, and 9). The results were submitted to ANOVA followed by Tukey test and polynomial regression (p < 0.05).

RESULTS

Carbamide peroxide significantly differed from hydrogen peroxide, presenting low reflectance values. Activated versus non-activated bleaching did not differ significantly for any gel tested, except for Whiteness HP activated by argon laser, which presented the lowest mean reflectance values. The results obtained with hydrogen peroxide revealed a decrease in reflectance values one month after the end of treatment. For carbamide peroxide, this decrease was not observed.

CONCLUSION

The halogen lamp presented the same or higher efficacy than non-activated bleaching, which had a longer gel contact period. When hydrogen peroxide was used, a decrease in reflectance values was observed 30 days after the end of bleaching.

The efficacy of three different in-office bleaching systems and their effect on enamel microhardness

This in vitro study evaluated and compared the efficacy of three in-office bleaching systems and investigated their effect on enamel microhardness. Three groups of 12 teeth (third molars) each were bleached as follows: Group A: Opalescence Xtra Boost (38% HP), Group B: Easywhite Ready (30% HP) with plasma unit and Group C: Zoom2 system (25% HP with the Zoom2 unit). The teeth were stained with tea for 24 hours, followed by the appropriate bleaching procedure. Each bleaching cycle was conducted for 15 minutes. The bleaching procedure was repeated until a shade change of six tabs (VITA shade guide) was obtained. The shade of the teeth was evaluated before, immediately after bleaching and one month later, both visually and digitally. Additionally, the "change of shade tabs per minute" was calculated. For the digital evaluation, the photos were taken under the same circumstances and the L*a*b* values were calculated using Photoshop. Five additional enamel samples for each group were prepared, and Knoop microhardness was evaluated before and after 15 minutes of bleaching. According to the visual shade evaluation, the treatment cycles required to reach the defined level of bleaching were: 1.58 for Group A (23.7 minutes), 1.02 for Group B (16.2 minutes) and 1.25 for Group C (18.7 minutes). Immediately after bleaching, a significant difference was found between Groups A and B (p = 0.0094). However, one month after the bleaching procedure, no significant difference could be observed among the three groups. According to the digital evaluation, no significant differences were found among the three bleaching systems for each of the L*a*b* values and the three times tested (p > 0.05). No significant difference (p = 0.055) was noticed among the three groups regarding microhardness after bleaching.

Frequency doubled neodymium:yttrium-aluminum-garnet and diode laser-activated power bleaching--pH, environmental scanning electron microscopy, and colorimetric in vitro evaluations

Corrosiveness of enamel surfaces of Smartbleach, Opus White, Opalescense Xtra Boost and a gel containing titanium dioxide (TiO(2)) particles, activated either by a frequency doubled neodymium: yttrium-aluminum-garnet (Nd:YAG) laser (532 nm) or a diode laser (810 nm) was evaluated by environmental scanning electron microscopy (ESEM). Changes in teeth color shades and the pH were also evaluated. Each bleaching agent was laser activated for 30 s and removed after 1 min or 10 min. This procedure was repeated up to four times, the bleaching agent receiving a maximum application time of 40 min, with total irradiation times of 0.5 min to 2 min of laser activation. The results of the pH measurements showed that only Smartbleach was in the alkaline pH range, whereas the other three were acidic. The surface effects were unrelated to the pH of the bleaching agents. With the exception of Opus White, no severe alterations on the enamel surface were detected. Although short application times were chosen, improved changes in brightness of up to ten steps on the Vitapan classical shade guide were detected.

Nonvital tooth bleaching: a review of the literature and clinical procedures

Tooth discoloration varies in etiology, appearance, localization, severity, and adhesion to tooth structure. It can be defined as being extrinsic or intrinsic on the basis of localization and etiology. In this review of the literature, various causes of tooth discoloration, different bleaching materials, and their applications to endodontically treated teeth have been described. In the walking bleach technique the root filling should be completed first, and a cervical seal must be established. The bleaching agent should be changed every 3-7 days. The thermocatalytic technique involves placement of a bleaching agent in the pulp chamber followed by heat application. At the end of each visit the bleaching agent is left in the tooth so that it can function as a walking bleach until the next visit. External bleaching of endodontically treated teeth with an in-office technique requires a high concentration gel. It might be a supplement to the walking bleach technique, if the results are not satisfactory after 3-4 visits. These treatments require a bonded temporary filling or a bonded resin composite to seal the access cavity. There is a deficiency of evidence-based science in the literature that addresses the prognosis of bleached nonvital teeth. Therefore, it is important to always be aware of the possible complications and risks that are associated with the different bleaching techniques.

Eight in-office tooth whitening systems evaluated in vivo: a pilot study

This in vivo pilot study evaluated eight products with hydrogen peroxide (HP) concentrations ranging from 15% to 35%. The treatment contact time varied from 15 minutes to 60 minutes. Patients were evaluated for color at baseline, immediately after treatment and at one, two, four and six weeks after treatment using a colorimeter, shade guide and photos. All eight products were effective in bleaching teeth. Colorimeter data for deltaE immediately after treatment was 6.77. At one and six weeks after bleaching, there were 51% and 65% reductions in deltaE, respectively.

External bleaching therapy with activation by heat, light or laser—A systematic review

OBJECTIVE

External bleaching procedures utilizing highly concentrated 30-35% hydrogen peroxide solutions or hydrogen peroxide releasing agents can be used for tooth whitening. To enhance or accelerate the whitening process, heat-activation of the bleaching agent by light, heat or laser is described in the literature. The aim of the present review article was to summarize and discuss the available information concerning the efficacy, effects and side effects of activated bleaching procedures.

SOURCES

Information from all original scientific full papers or reviews listed in PubMed or ISI Web of Science (search term: (bleaching OR brightening OR whitening OR colour) AND (light OR laser OR heat OR activation)) were included in the review.

DATA

Existing literature reveals that activation of bleaching agents by heat, light or laser may have an adverse effect on pulpal tissue due to an increase of intra-pulpal temperature exceeding the critical value of 5.5 degrees C. Available studies do not allow for a final judgment whether tooth whitening can either be increased or accelerated by additional activation.

CONCLUSION

Therefore, application of activated bleaching procedures should be critically assessed considering the physical, physiological and patho-physiological implications.

Evaluation of dentin permeability after light activated internal dental bleaching

The aim of this in vitro study was to assess quantitatively the dentin permeability of human teeth after intracoronal bleaching therapy with 35% hydrogen peroxide activated by LEDs, halogen lamp or using the walking bleach technique. Forty human maxillary central incisors had standard access cavities performed and the cervical thirds of the canals were prepared with Gates-Glidden drills up to a size 130. Roots were resected between the coronal and middle thirds and the apical portions were discarded. A glass ionomer, 2 mm thick cervical plug was placed inside the canal, at the cement-enamel junction level. Group I received 35% hydrogen peroxide gel activated by LEDs. Group II was submitted to 35% hydrogen peroxide gel activated by halogen lamp. Group III received 35% hydrogen peroxide gel and the walking bleach technique was followed. Group IV (control) received a dry cotton pellet inside the pulp chamber with temporary restoration. Dentinal permeability was quantified by copper ion penetration. Linear measurements were obtained by analysis of digital images under x 5 magnification. Mean values and SD for the experimental groups were: I, 7.1% (+/-3.2%); II, 8.4% (+/-3.0%); III, 9.1% (+/-3.0%); IV, 1.3% (+/-2.8%). One-way ANOVA was used to analyze the results. Results showed an increase of permeability values for groups I, II and III when compared to group IV (control); however, no statistical differences were found between the three tested bleaching techniques. It can be concluded that 35% hydrogen peroxide activated by LED, halogen lamp or used following the walking bleach technique produced similar increase in dentinal permeability.

Separate Whitening Effects on Enamel and Dentin After Fourteen Days

The purpose of this study was to investigate the mechanism of action of a bleaching agent, as it relates to enamel and dentin. Twenty-six extracted human molar teeth were sectioned at the cemento-enamel junction and were randomly assigned to two groups. L*a*b* readings were taken with a spectrophotometer: on buccal surfaces of the crown, at enamel and dentin. The teeth were exposed to carbamide peroxide or placebo gel and L*a*b* scores were again recorded to determine color changes. Treatments were compared using ancova test with baseline color as the covariate. Relative to placebo, buccal surfaces exhibited the greatest Deltab* and DeltaL* color change. On buccal surfaces, the adjusted mean (SE) treatment differences were -7.8 (1.00) for Deltab* and 5.7 (0.97) for DeltaL, with groups differing significantly (p < 0.0001). On enamel surfaces, treatment differences were -3.6 (0.61) for Deltab* and 4.6 (0.80) for DeltaL* (p < 0.0001). Dentin exhibited the least color improvement. Adjusted mean (SE) treatment differences were -1.9 (0.87) for Deltab* and 2.4 (1.10) for DeltaL*, with groups differing significantly (p < 0.02) on dentin color change. The majority of color change seen on the buccal surface of tooth crowns exposed to carbamide peroxide 15% was because of the color change in enamel. As compared to enamel, dentin was less affected after 14 days.

Clinical Color Match of Porcelain Visual Shade-Matching Systems

BACKGROUND

Accuracy of the total color replication process has not been clinically evaluated for various porcelain visual shade-matching systems.

PURPOSE

The purpose of this study was to evaluate the final color replication process of three porcelain visual shade-matching systems. Subjects' natural dentition was compared with laboratory-fabricated individualized porcelain shade tabs.

MATERIALS AND METHODS

Shade matches of 10 subjects' incisors were obtained using three different porcelain visual shade-matching systems. Commercial laboratories fabricated one corresponding individualized porcelain shade tab for each incisor per visual shade-matching system selection. Color-match evaluations of the fabricated individualized porcelain shade tabs to the corresponding teeth were completed by prosthodontists' consensus and by subjects' self-evaluation using the US Public Health Service criteria. Statistical analysis was carried out on the combined evaluations with logistic regression and the Generalized Estimating Equation for repeated measures.

RESULTS

The Vitapan 3D Master/Omega 900 system (Vident Inc., Brea, CA, USA) was significantly more likely than the Vita Lumin Vacuum/VMK 68 system (Vident Inc.) to obtain a clinically acceptable color match (odds ratio [OR]=6.31; 95% CI=1.24-32.07). The likelihood of obtaining a clinically acceptable color match through subjects' self-evaluation was found to be significantly higher compared with prosthodontists' consensus (OR=2.75; 95% CI=1.27-5.94).

CONCLUSIONS

Within the limits of this preliminary study, significant differences in clinical acceptability were seen between the color matches of the fabricated individualized porcelain shade tabs from different systems and subjects' central incisors. Subjects' range of acceptability was much broader compared with that of the prosthodontists in assessing the color match of the fabricated porcelain shade tabs.

CLINICAL SIGNIFICANCE

The use of certain porcelain visual shade-matching systems may result in a clinically acceptable color match of the final restoration more readily than the use of other systems. Color-match evaluation of final restorations should be accomplished through a consensus between prosthodontists and patients, given the difference in thresholds of acceptability.

Efficacy of different whitening modalities on bovine enamel and dentin

Previous studies have shown that bleaching treatment may be efficient in both enamel and dentin, but it is still unknown how much the subsurface dentin contributes to the color change of teeth. This in vitro study evaluated the whitening effect of different external bleaching agents on enamel-dentin slabs and subsurface dentin. Ninety bovine teeth were distributed among six groups (A, Opalescence 10%; B, Opalescence PF 15%; C, Opalescence Quick; D, Opalescence Extra Boost; E, Rapid White; F, Whitestrips). Two enamel-dentin specimens were prepared from the labial surface of each teeth. In one of the specimens enamel was removed, resulting in a dentin (CD) disc of 1 mm high. The labial and the pulpal sides of the second specimen were ground until the remaining enamel and dentin layers of the enamel-dentin sample (ED) were 1 mm each. Whitening treatment of the ED specimens was performed according to manufacturers' instructions. Pre- and posttreatment Lab values of ED samples were analyzed using CIE-Lab. Baseline Lab values of dentin were analyzed by evaluation of the CD specimen. Finally, enamel of the ED specimens was removed and color change of the exposed dentin (D) was recorded. For all treatment agents significant color changes (DeltaE) were observed for enamel-dentin samples and subsurface dentin specimens compared to controls. In groups A-D DeltaE was significantly higher in dentin than enamel-dentin. Furthermore, L and b values of bleached enamel-dentin and subsurface dentin samples differed significantly from baseline. Treatment with the tested external whitening bleaching agents resulted in color change of both enamel-dentin and subsurface dentin samples. The results indicate that color change of treated teeth might be highly influenced by color change of the subsurface dentin.

Effect of light energy on peroxide tooth bleaching

BACKGROUND

Light-activated bleaching is a method of tooth whitening. The authors conducted a study to compare the whitening effects and tooth temperature changes induced by various combinations of peroxide bleaches and light sources.

METHODS

The authors randomly assigned 250 extracted human teeth halves into experimental groups (n = 10). A placebo gel (control), a 35 percent hydrogen peroxide or a 10 percent carbamide peroxide bleach was placed on the tooth surface and was irradiated with no light (control); a halogen curing light; an infrared, or IR, light; an argon laser; or a carbon dioxide, or CO2, laser. Color changes were evaluated immediately, one day and one week after treatment using a value-oriented shade guide and an electronic dental color analyzer. The outer enamel and inner dentin surface temperatures were monitored before and immediately after each 30-second application of light using a thermocouple thermometer.

RESULTS

Color and temperature changes were significantly affected by an interaction of the bleach and light variables. The application of lights significantly improved the whitening efficacy of some bleach materials, but it caused significant temperature increases in the outer and inner tooth surfaces. The IR and CO2 laser lights caused the highest tooth temperature increases.

CONCLUSIONS

Dentists performing an in-office bleaching technique with the use of an additional light source to accelerate tooth whitening should consider the specific bleaching agent being used, as well as the potential risks of heating teeth.

CLINICAL IMPLICATIONS

A specific combination of bleach and light that demonstrates good color change and little temperature rise should be selected for in-office tooth bleaching.

Light augments tooth whitening with peroxide

BACKGROUND

The authors tested the adjunctive use of light with a 15 percent peroxide gel as a single-visit, in-office tooth whitening system.

METHODS

Subject (N = 87) with stained (> shade D4, Vita Zahnfabrik, Bad Säckingen, Germany) anterior teeth were randomly assigned to test (peroxide and light), peroxide control (peroxide gel) or light control (placebo gel and light) groups and were treated for one hour. The researchers evaluated tooth shade, color and subject response at baseline and posttreatment and at three and six months posttreatment.

RESULTS

The initial shade unit reduction of combined light and peroxide treatment (8.4) was greatest compared with that of peroxide alone (5.9) and of light alone (4.9). Approximately 88 percent of these effects persisted for six months. Lightness was increased and yellowness decreased to a significantly greater extent in the test group than in either control. These findings were corroborated by subject evaluation. One week after treatment, moderate to greatly increased tooth sensitivity occurred in 20 percent of test subjects, 21.7 percent of peroxide control subjects and none of the light control subjects. Neither tooth sensitivity nor gingival redness was present at the three- and six-month visits.

CONCLUSIONS

Peroxide and light treatment significantly lightened the color of teeth to a greater extent than did peroxide or light alone, with a low and transient incidence of tooth sensitivity.

CLINICAL IMPLICATIONS

Light can increase the tooth-whitening effect of peroxide, thereby increasing the effectiveness of tooth-whitening procedures.

Enamel caries initiation and progression after argon laser irradiation: in vitro argon laser systems comparison

OBJECTIVE

The purpose of this in vitro laboratory study was to determine the effect of low-fluence argon laser (AL) irradiation delivered from two different argon laser systems on enamel caries-like lesion initiation and progression.

BACKGROUND DATA

Previous in vitro investigations and a recent in vivo pilot study have shown that AL irradiation of enamel provided a protective effect against in vitro and in vivo cariogenic challenges.

MATERIALS AND METHODS

Twenty extracted human molars were selected, and 10 teeth were assigned to the HGM argon laser group and 10 were assigned to the LaserMed argon laser group. The exposed buccal windows of sound enamel were exposed to low-fluence irradiation, while the lingual windows of enamel were not exposed to laser irradiation and served as the no-treatment (control) group. Enamel caries-like lesions were created using an acidified gel. Two longitudinal sections were taken per sample (n = 20 lesions per group) and evaluated by polarized light microscopy for body of the lesion depths after lesion initiation (8 weeks) and progression (12 weeks) periods.

RESULTS

After lesion initiation and progression, the body of lesion depths were similar for both argon-irradiated groups (p > 0.05). With the no-treatment (control) group, there were significant increases in lesion depth with a 61-78% increase for the lesion initiation period and a 50-69% increase for the lesion progression period when compared with the argon laser-treated groups.

CONCLUSION

Argon laser irradiation provides a certain degree of protection against in vitro enamel caries initiation and progression. Resistance to a continuous caries challenge was similar with either argon laser delivery systems (HGM and LaserMed). Argon laser irradiation may prove to be beneficial in reducing the caries susceptibility of sound enamel and white spot lesions in the clinical environment.