Nightguard vital bleaching and its effect on enamel surface morphology

Influence of using different toothpaste during bleaching with violet LED light (405 nm) on the colour and roughness of dental enamel: an in vitro study

This in vitro study aimed to investigate potential changes in the color and roughness of dental enamel resulting from the use of different toothpaste formulations during bleaching with violet LED light (405 nm). Sixty specimens of bovine incisors, each measuring 6 × 6 × 3 mm, were segregated into six distinct experimental groups based on their respective treatments (n = 10): C + VL: Brushing with Colgate® Total 12 + bleaching with violet LED; LB + VL: Brushing with Colgate® Luminous White Brilliant + bleaching with violet LED; LI + VL: Brushing with Colgate® Luminous White Instant + violet LED bleaching; C: Brushing with Colgate® Total 12; LB: Brushing with Colgate® Luminous White Brilliant; LI: Brushing with Colgate® Luminous White Instant. The examined variables included alterations in color (∆L*, ∆a*, ∆b*, ∆Eab, and ∆E00), surface roughness (Ra), and scanning electron microscopy observations. No statistically significant distinctions emerged in total color variations (∆E00 and ∆E) among the groups under scrutiny. Notably, the groups that employed Colgate® Luminous White Instant displayed elevated roughness values, irrespective of their association with violet LED, as corroborated by scanning electron microscopy examinations. It can be concluded that whitening toothpastes associated to violet LED do not influence the color change of dental enamel in fifteen days of treatment. Toothpastes with a higher number of abrasive particles showed greater changes in enamel roughness, regardless of the use of violet LED.

Evaluation of pH Levels and Surface Roughness After Bleaching and Abrasion Tests of Eight Commercial Products

OBJECTIVE

This in vitro study evaluated the effect of different bleaching protocols and the variation of pH levels of bleaching gels regarding roughness and wear of bovine enamel, after in-office bleaching protocols and brushing.

MATERIALS AND METHODS

Ninety fragments were randomly divided into nine groups: C, control; WHP15, 35% hydrogen peroxide (HP) (Whiteness HP, FGM) three gel applications of 15 min each, three sessions with 1 week intervals; WHP45, 35% HP (Whiteness HP) one application/45 min, three sessions with 1 week intervals; LPS, 35% HP (Lase Peroxide, DMC) plus hybrid light (HL) [light-emitting diode (LED)/diode laser], four applications/7 min 30 sec (6 min of HL activation), one session; LPSII, 25% HP (Lase Peroxide II, DMC) plus HL, four applications/7 min 30 sec (6 min of HL activation), one session; LPL, 15% HP (Lase Peroxide Light, DMC) four applications/7 min 30 sec (6 min of HL activation), one session; WO, 35% HP (Whitegold Office, Dentsply) three applications/15 min, three sessions with 1 week intervals; WBC40, 35% HP (Whiteness HP Blue Calcium, FGM) one application/40 min, three sessions with 1 week intervals; and WBC50, 20% HP (Whiteness HP Blue Calcium) one application/50 min, three sessions with 1 week intervals. The median pH values were determined utilizing a pH meter during the initial and final gel applications. A rugosimeter was utilized to evaluate the surface roughness (Ra) before and after bleaching and brushing (100,000 strokes), and the surface wear after brushing.

RESULTS

For the results of the pH values, there was a decrease in the pH levels from the initial to the final bleaching time, except for the WBC50. The WO and WBC40 groups exhibited higher pH values. For the results of roughness and wear, there was an increase in surface roughness and wear among the groups.

CONCLUSIONS

The pH values tended to decrease from the initial to the final bleaching. After tooth brushing, bleaching procedures with lower pH products provided a significant increase in enamel wear and surface roughness.

Shear Bond Strength of Orthodontic Brackets to Tooth Enamel After Treatment With Different Tooth Bleaching Methods

Background:

Bleaching treatments decrease shear bond strength between orthodontic brackets and teeth; although definite results have not been reported in this regard.

Objectives:

This study determined the effects of different bleaching protocols on the shear bond strength of orthodontic brackets to teeth.

Materials and Methods:

This experimental study was performed in Iran. Forty-eight extracted human premolars were randomly assigned into four groups. In the control group, no bleaching treatment was performed. In groups 2 - 4, the bleaching procedures were performed using carbamide peroxide 45%, carbamide peroxide 20% and diode laser, respectively. Two weeks later, brackets were bonded to teeth and thermocycled. The shear bond strengths of the brackets to the teeth were measured. Data was analyzed by one-way ANOVA and Dunnett post-hoc test.

Results:

Shear bond strength of the brackets to the teeth were 10.54 ± 1.51, 6.37 ± 0.92, 7.67 ± 1.01 and 7.49 ± 1.19 MPa, in groups 1 - 4, respectively. Significant differences were found between control group and all other groups (P < 0.001); and also between groups 2 and 3 (P < 0.05). No significant differences were found between the other groups.

Conclusions:

The bleaching procedures using 20% carbamide peroxide and 45% carbamide peroxide and diode laser significantly decreased shear bond strength of brackets to the teeth. 45% carbamide peroxide had a more significant effect on bond strength compared to 20% carbamide peroxide. The difference in bond strength was not significant between laser group and either carbamide peroxide groups.

Aesthetic Rehabilitation of Discoloured Nonvital Anterior tooth with Carbamide Peroxide Bleaching: Case Series

Discolouration of teeth, especially the anteriores, can result in considerably cosmetic impairment in person. Combine effects of intrinsic and extrinsic colour determines the appearance of teeth. Whitening of teeth with bleaching is a more conservative therapeutic method than full crowns, veneers or composite restorations which is more invasive and expensive. Among bleaching techniques, in office bleaching with carbamide peroxide provide superior aesthetic result in short period of time with no adverse effects. This paper presents case series of tooth discolouration in non-vital tooth which was successfully bleached using 35 % carbamide peroxide. After 1 year follow up the prognosis was good with no reversal of tooth discolouration. This case report allows the better understanding of the concept of nonvital tooth bleaching with carbamide peroxide which gives a non-invasive alternative for aesthetic purpose in preserving the natural tooth structure.

Histomorphologic alterations of human enamel after repeated applications of a bleaching agent

The objective of the study was to analyse the histomorphology of enamel after repeated applications of a professional bleaching regimen. Enamel specimens were obtained from buccal surfaces of 20 extracted human incisors. Two specimens were obtained for each tooth. Half of each tooth was maintained in distilled water and served as control; the other part was treated with a 38 percent hydrogen peroxide professional bleaching agent. The treated specimens were divided in four groups: in group 1, the professional bleaching protocol suggested by the manufacturer was applied once; in group 2, the same protocol was repeated twice; in group 3, three times; in group 4, four times. Between bleaching applications and before SEM evaluation, enamel specimens were maintained in artificial saliva for 1 week. Enamel specimens for each group were submitted to a qualitative scanning electron microscopy (SEM) analysis (200X, 500X, 1000X, 3000X), comparing the treated specimens with the related control enamel. Results of the SEM analysis showed no relevant alteration on the enamel surfaces, when the bleaching protocol was applied once or twice. However, significant changes of enamel surface morphology were SEM observed in groups 3 and 4, suggesting a predominance of depressions when bleaching procedure was repeated three or four times. From the results of this in vitro study, it is possible to state that bleaching procedures should not be carried out indiscriminately. SEM analysis showed important alterations of the prismatic structure of the enamel when the bleaching protocol was applied three and four times.

Effect of intracoronal bleaching agents on ultrastructure and mineral content of dentin

Aim:

The purpose of this in vitro study was to evaluate the ultrastructural changes of dentin induced after exposure to different intracoronal tooth bleaching agents.

Materials and Methods:

Dental discs of 1 mm thickness were prepared from coronal dentin of sixty-four human maxillary premolars. Experimental specimens were divided into four subgroups: 45% carbamide peroxide, 35% hydrogen peroxide, sodium perborate + 30% hydrogen peroxide, sodium perborate + water. The specimens were then evaluated under scanning electron microscope to determine diameter of dentinal tubules and chemical analysis.

Results:

There was significant difference between dentinal tubule diameter of all test and control groups with the exception of sodium perborate + water. Chemical analysis revealed that there was no significant difference between experimental subgroups regarding calcium and sulfur wt%.

Conclusions:

All bleaching agents increased dentinal tubule diameter and promote alterations in mineral content of dentin with the exception of Sodium perborate mixed with water.

One-year clinical evaluation of the efficacy of a new daytime at-home bleaching technique

The aim of this study was to compare the clinical efficacy and side effects of a new daytime at-home bleaching technique (28% carbamide peroxide [CP] gel) with the overnight application of 10% CP and to determine the change of tooth color 1-year post-treatment. Twenty healthy volunteers were assigned to one of two sample groups of 10. All participants employed one of the two at-home bleaching systems: (1) the new daytime at-home bleaching system including 28% CP gel with a non-custom-fit tray (Meta Tray, Remedent, Deurle, Belgium) for 20 minutes, and (b) the conventional overnight at-home bleaching system with a 10% CP gel and a custom-fit tray (Opalescence PF, Ultradent, South Jordan, UT, USA) for 6 to 8 hours. Digital images and CIE (International Commission on Illumination) L*, a*, and b* spectrophotometric measurements were taken at baseline, after the bleaching treatment and 1-year post-treatment. Tooth and gingival sensitivity was measured with a specially designed 4-point scale. Significant differences were found in L*, a*, and b* values, between initial and post-treatment, for both bleaching systems (p < 0.05). However, no significant difference was detected between post-treatment and 1-year follow-up. The bleaching effectiveness of Opalescence PF was found to be superior to that of Meta Tray, considering the color parameter of DeltaE (p < 0.05). Meta Tray provoked less tooth sensitivity (p < 0.05), however gingival sensitivity appeared more in this group (p < 0.05). Within the limitations of this study, it can be concluded that the new daytime at-home bleaching system tested (Meta Tray) produced significant bleaching effects. However, the clinical efficacy of the overnight bleaching system was found to be superior to the daytime at-home bleaching system evaluated in this study. The whitening effect remained similar 1-year after the bleaching treatment for both at-home bleaching systems. CLINICAL SIGNIFICANCE Although the new daytime at-home bleaching system tested exhibited significant bleaching effects, overnight bleaching with a 10% CP gel resulted in a higher bleaching effectiveness than this new system. Although the participants using the new bleaching system exhibited less tooth sensitivity probably because of the reduced contact time of bleaching gel with tooth surfaces, the application of the bleaching agent with a non-customized tray provoked more gingival sensitivity in this group.

Effect of carbamide peroxide-based bleaching agents containing fluoride or calcium on tensile strength of human enamel

Objective:

The aim of this study was to evaluate the effects of carbamide peroxide-based bleaching agents (CPG) containing fluoride (CF) or calcium (CCa) on the ultimate tensile strength of enamel (UTS).

Method:

A "cube-like" resin composite structure was built-up on the occlusal surface of twenty-two sound third molars to facilitate specimen preparation for the micro-tensile test. The restored teeth were serially sectioned in buccal-lingual direction in slices with approximate 0.7 mm thickness. Each slice was trimmed with a fine diamond bur to reduce the buccal, internal slope enamel of the cusps to a dumb-bell shape with a cross-sectional area at the "neck" of less than 0.5 mm². The samples were randomly divided into 12 groups (n=11). The control groups were not submitted to the bleaching regimen. Specimens were treated with 10% CPG gel or with 10% CPG formulations containing CF (0.2% and 0.5%) or CCa (0.05% and 0.2%). Bleached groups received the application of the 10% CPGs for 6 hours/day at 37° C, during 14 consecutive days and were stored in artificial saliva (AS) or 100% relative humidity (RH) among each application. After bleaching, specimens were tested with the microtensile method at 0.5 mm/min. Data were analyzed by two-way ANOVA and Tukey test (5%).

Results:

No significant difference was observed between groups stored in AS or RH. Specimens treated with CF or CCa presented similar UTS as unbleached control groups.

Conclusion:

Either 10% CPG formulations containing CF or CCa can preserve the UTS after bleaching regimen.

Effect of two in-office whitening agents on the enamel surface in vivo: a morphological and non-contact profilometric study

This study evaluated the morphological effects produced in vivo by two in-office bleaching agents on enamel surface roughness using a noncontact profilometric analysis of epoxy replicas. The null hypothesis tested was that there would be no difference in the micromorphology of the enamel surface during or after bleaching with two different bleaching agents. Eighteen subjects were selected and randomly assigned to two treatment groups (n=9). The tooth whitening materials tested were 38% hydrogen peroxide (HP) (Opalescence Xtra Boost) and 35% carbamide peroxide (CP) (Rembrandt Quik Start). The bleaching agents were applied in accordance with manufacturer protocols. The treatments were repeated four times at one-week intervals. High precision impressions of the upper right incisor were taken at baseline as the control (CTRL) and after each bleaching treatment (T0: first application, T1: second application at one week, T2: third application at two weeks and T3: fourth application at three weeks). Epoxy resin replicas were poured from impressions, and the surface roughness was analyzed by means of a non-contact profilometer (Talysurf CLI 1000). Epoxy replicas were then observed using SEM. All data were statistically analyzed using ANOVA and differences were determined with a t-test. No significant differences in surface roughness were found on enamel replicas using either 38% hydrogen peroxide or 35% carbamide peroxide in vivo. This in vivo study supports the null hypothesis that two in-office bleaching agents, with either a high concentration of hydrogen or carbamide peroxide, do not alter enamel surface roughness, even after multiple applications.

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.

Investigation of the effects of 30% hydrogen peroxide on human tooth enamel by Raman scattering and laser-induced fluorescence

The safety of tooth bleaching, which is based upon hydrogen peroxide (HP) as the active agent, has been questioned. Our aim was to investigate the effects of 30% HP on human tooth enamel. The specimens were divided randomly into three groups and treated with distilled water, HCl, and HP, respectively. Raman scattering and laser-induced fluorescence of enamel were determined before and after treatment. Microhardness testing and scanning electron microscopy were also used. The results of Raman scattering showed that the Raman relative intensity of enamel changed significantly after HP and HCl treatment. These findings were consistent with the results of microhardness testing and morphological observations. In addition, a small band at 876 cm(-1) due to O-O stretching of HP became pronounced during HP treatment, which provided direct evidence that HP has the ability to penetrate enamel. Meanwhile, the results of laser-induced fluorescence revealed that HP caused the greatest fluorescence reduction. This suggested that the organic matter in enamel might be greatly affected by HP, which was also supported by the results of microhardness. It can be concluded, therefore, that the 30% HP may have adverse effects on the mineral and the organic matter of human tooth enamel.

The effect of 24h non-stop hydrogen peroxide concentration on bovine enamel and dentine mineral content and microhardness

OBJECTIVES

Tooth bleaching agents may adversely affect tooth structure. The aim of this study was to investigate the effect of hydrogen peroxide concentration on mineral loss and microhardness of bovine teeth.

METHODS

Twenty-six freshly extracted intact bovine incisor teeth were stored in distilled water. Five teeth were sectioned and four samples (2 mm x 2 mm x 1.5 mm) each of enamel and dentine were obtained from each tooth. The samples of enamel and dentine were divided into four groups and immersed in either 0%, 3%, 10% or 30% (w/v) hydrogen peroxide solutions for 24h at 37 degrees C. Samples from the solutions were taken for ion release analysis using inductively coupled plasma mass spectrometry. The remaining 21 teeth were mounted in epoxy resin and the upper surface of the specimens were ground and polished to expose the enamel and dentine for microhardness measurements. These specimens were randomly divided into three equal groups and Vickers microhardness values were recorded on the enamel and dentine surfaces of each group before and after bleaching.

RESULTS

The differences in ion release concentration after treatment with 0% (control) and each of 3%, 10% and 30% hydrogen peroxide (w/v) were statistically significant (p<0.025). The release of calcium and phosphorous ions increased with increasing hydrogen peroxide concentrations. A significant reduction (p<0.05) in Vickers microhardness values for enamel was recorded after bleaching.

CONCLUSIONS

Ion release from both enamel and dentine increased with increasing hydrogen peroxide concentration. Microhardness of enamel decreased significantly with bleaching.

Demineralization Effects of 2 Bleaching Procedures on Enamel Surfaces With and Without Post-treatment Fluoride Application

The results of this study suggest that post-treatment fluoride application prevents mineral loss in bleached enamel surfaces.

Effect on enamel microhardness of two consumer-available bleaching solutions when compared with a dentist-prescribed, home-applied bleaching solution and a control

BACKGROUND

There exists limited data in the literature regarding the efficacy and safety of consumer-available, paint-on bleaching solutions.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of two consumer-available, paint-on bleaching products on enamel microhardness against a control and a dentist-prescribed, home-applied (DPHA) bleaching product.

MATERIALS AND METHODS

Eighty enamel slabs were obtained from extracted human teeth and randomly divided into four treatment groups: (1) control; (2) Opalescence (Ultradent Products, Inc., South Jordan, UT, USA); (3) Crest Night Effects (Procter & Gamble, Cincinnati, OH, USA); and (4) Colgate Simply White Night (Colgate-Palmolive Co., Piscataway, NJ, USA). Opalescence is a carbamide peroxide DPHA product, whereas Crest Night Effects and Colgate Simply White Night are consumer-available products. The specimens in groups 2 to 4 underwent 2 weeks of treatment for 8 h/d. Specimens were maintained in artificial saliva at 37 degrees C between treatments. Subsequently, one-half of the specimens in groups 2 to 4 (n=10) underwent an additional seven treatments for 8 h/d, while the other half were stored in artificial saliva, receiving no further treatment. Microhardness was measured as Knoop hardness numbers (KHNs) at baseline and after 1, 7, 14, and 21 treatment days. The results were analyzed for statistical significance both intra- and intergroups using analysis of variance (p=.05).

RESULTS

A statistically significant reduction in mean KHN was observed compared with baseline at 1, 7, 14, and 21 treatment days for group 4 and at 7 treatment days for group 3. When compared with the control or DPHA product, group 4 was the only treatment that resulted in significantly lower mean KHNs at 7, 14, and 21 treatment days.

CONCLUSION

When evaluating enamel microhardness, consumer available, paint-on bleaching solutions may adversely affect enamel microhardness compared to a control and 10% carbamide peroxide DPHA bleaching solution.

CLINICAL SIGNIFICANCE

With numerous consumer-available bleaching products on the market, it is crucial to be judicious in their selection and use. The results of this in vitro study showed that the consumer-available, paint-on bleaching solutions adversely affected enamel microhardness at some time during the study. Consumers should be made aware of this effect on enamel.

The effect of tooth bleaching on the shear bond strength of orthodontic brackets

INTRODUCTION

The purpose of this study was to determine the effect of enamel bleaching on the shear bond strength of orthodontic brackets bonded with a composite adhesive.

METHODS

Two protocols were used on 60 human molars. In the at-home bleaching group (n = 30), Opalescence bleaching agent (Ultradent, South Jordan, Utah), which contains 10% carbamide peroxide, was brushed onto the teeth daily for 14 days and left for 6 hours each day. Teeth in the in-office group (n = 30) were treated with Zoom! (Discus Dental, Culver City, Calif), which contains 25% hydrogen peroxide gel, and then exposed to a light source for 20 minutes; these teeth were treated twice. After bleaching, the specimens were randomly divided into equal subgroups and stored in artificial saliva at 37 degrees C for 7 or 14 days before bonding. Shear bond strength testing was performed on all teeth. The Kruskal-Wallis test for nonparametric means was used to determine whether significant differences existed between the various subgroups and an unbleached control group.

RESULTS

The mean shear bond strength for the control group was 5.6 +/- 1.8 MPa. Means for the at-home groups were 5.2 +/- 3.6 MPa and 7.2 +/- 3.2 MPa for the 7- and 14-day waiting periods, respectively. Means for the in-office groups were 5.1 +/- 5.3 MPa and 6.6 +/- 2.6 MPa for the 7- and 14-day waiting periods, respectively. The Kruskal-Wallis test (X(2) = 8.089) indicated no significant differences between the 5 subgroups (P = .088).

CONCLUSIONS

The results showed that in-office and at-home bleaching did not affect the shear bond strength of orthodontic brackets to enamel.

Flexural Strength and Modulus Properties of Carbamide Peroxide?Treated Bovine Dentin

BACKGROUND

The effects of carbamide peroxide bleach on tooth structure are uncertain.

PURPOSE

The purpose of this study was to investigate the effects of direct or indirect carbamide peroxide application on dentin flexural strength and modulus in vitro.

MATERIALS AND METHODS

Dentin bars were machined from bovine incisors and treated with 10% carbamide peroxide for 6 h/d for 14 days. Four groups were created, with eight bars in each group: group 1-direct bleach application only; group 2-indirect bleach application only; group 3-direct bleach application followed by a 2-week storage in artificial saliva; group 4-direct bleach application followed by a 2-week storage in artificial saliva and daily topical fluoride treatments. The specimens' flexural strength and modulus were tested after 24 hours, and the results were compared with water controls using independent t-tests (p < .05).

RESULTS

Flexural strength results (in megapascals) for bleached versus control dentin (1=205+/-26 vs 215+/-14, 2=257+/-25 vs 261+/-14, 3=180+/-22 vs 193+/-36, 4=157+/-18 vs 184+/-11) were significantly lower in group 4 (p=.005). Modulus results (in gigapascals) for bleached versus control dentin (1=10.7+/-1.4 vs 12.2+/-0.6, 2=14.2+/-1.7 vs 14.4+/-1.6, 3=10.0+/-2.0 vs 10.9+/-1.3, 4=9.0+/-1.2 vs 11.1+/-1.0) were significantly lower in groups 1 and 4 (p=.013 and p=.003, respectively). There were no significant differences in strength and modulus results between the bleached and control dentin in groups 2 and 3. A direct application of carbamide peroxide to bovine dentin significantly decreased some dentin mechanical properties in vitro. An indirect application of carbamide peroxide to dentin did not significantly decrease dentin strength and stiffness.

CLINICAL SIGNIFICANCE

This in vitro study suggests that a bleaching treatment, when applied to the enamel of intact teeth, does not significantly affect the mechanical properties of the underlying dentin. However, when applied directly to dentin in clinical situations such as root exposure or occlusal attrition, the bleaching treatment may result in altered mechanical properties of dentin. The clinical consequences of this observation are, however, unknown.

Effect of a carbamide peroxide bleaching gel containing calcium or fluoride on human enamel surface microhardness

This in vitro study evaluated the surface microhardness of human enamel submitted to bleaching with 10% carbamide peroxide (CP) containing calcium or fluoride. Ninety-eight dental blocks (5 x 5 mm²) with polished enamel surfaces were randomly assigned to 7 treatment groups (n=14), as follows: without bleaching and storage in artificial saliva (control); 10% CP; 10% CP + 0.05% calcium; 10% CP + 0.1% calcium; 10% CP + 0.2% calcium; 10% CP + 0.2% fluoride; and 10% CP + 0.5% fluoride. During 14 days, enamel surfaces were daily exposed to a 6-h bleaching regimen followed by storage in artificial saliva. Surface microhardness was measured before (baseline), during (7th day), immediately after bleaching (14th day) and 1 week post bleaching. Data were analyzed by two-way ANOVA and Tukey's test (p<0.05). All treatments reduced SM significantly during the bleaching cycle (7th day), immediately after bleaching (14th day) and 1 week post bleaching, compared to baseline and to the unbleached control group. In conclusion, in spite of the addition of calcium and fluoride, all bleaching treatments affected the enamel surface microhardness.

Effect of direct peroxide bleach application to bovine dentin on flexural strength and modulus in vitro

OBJECTIVES

The objective of this study was to determine the effects of carbamide peroxide (CP) and hydrogen peroxide (HP) bleaching on the flexural strength (FS) and flexural modulus (FM) of dentin.

METHODS

2x2x20mm bovine dentin specimens were immersed in the bleaching agents to simulate overnight (10 or 15% CP, 6h daily, 2 weeks), exaggerated overnight (10% CP, 6h/day, 5 days/week, 2 months), daytime (6.5 or 7.5% HP, 1h daily, 3 weeks) and in-office (35% HP, 1h/day, 2 days/week, 3 weeks) treatment protocols. Distilled water (DW) and a placebo gel acted as control immersion materials. After immersion, the specimens were rinsed and stored in DW. Mechanical testing was performed 24h after the last treatment using an Instron Universal Testing Machine with a crosshead speed of 0.75 mm/min. The results were analyzed by ANOVA and Tukey's tests (p<0.05).

RESULTS

There were significant reductions in the FS and FM of dentin after 2-week and 2-month exposures to CP. There were no significant differences in the FS or the FM of the dentin among the HP treatment and control groups.

CONCLUSIONS

Direct in vitro application of CP bleaches caused significant decreases in dentin FS and FM. Similar decreases were not observed among the HP-treated dentin groups, which were exposed to shorter treatment times. Further research is needed to determine the effect of CP and HP on dentin in vivo.

Effect of home bleaching agents on the roughness and surface morphology of human enamel and dentine

AIMS

Carbamide peroxide (CP) containing bleaching agents are now widely used in different concentrations. In this study, the effect of 10% and 15% CP containing home bleaching agents on the surface roughness and morphology of human enamel and dentine were evaluated in vitro.

METHODS

90 non-carious human mandibular incisors were divided randomly into two equal groups (enamel and dentine). The dentine group specimens were ground to expose dentine surfaces. The samples in both groups were then randomly divided into three main groups and then divided into three subgroups, according to bleaching application times (n=15). The samples in both enamel and dentine groups were treated with 10% CP at Group 1 and 4, 15% CP at Group 2 and 5 and distilled water at Group 3 and 6. The surface roughness of the samples was analysed before bleaching (1a, 2a, 3a for enamel, 4a, 5a, 6a for dentine), after 4hr (1b, 2b, 3b for enamel, 4b, 5b, 6b for dentine) and after 28hr of bleaching application (1c, 2c, 3c for enamel, 4c, 5c, 6c for dentine) using a computerised roughness tester. The surface morphologies of treated and control specimens were also examined by SEM.

RESULTS

There were no statistically significant differences between the surface roughness of untreated control specimens and the specimens treated with the bleaching materials (10% and 15% CP) for both enamel and dentine at any given measurement time (p>0.05).

CONCLUSION

Under the careful guidance of a dentist, home bleaching can be thought a reliable treatment for both stained enamel and dentine, regardless of whether 10% or 15% CP is used.

In situ effect of 10% carbamide peroxide on microhardness of human enamel: function of time

PURPOSE

This study evaluated the effect of two home bleaching regimens (1 h/day versus 7 h/day for a total of 21 days) on the microhardness of superficial enamel treated with 10% carbamide peroxide gel.

MATERIALS AND METHODS

Rectangular enamel specimens (2.5 x 2.5 x 1 mm) were obtained from human third molars and mounted on the palatal aspect of removable orthodontic retainers. Nine enamel specimens were mounted in each of 10 retainers, used by 10 volunteers during the active phase of the study. Modified 0.089 cm thick bleaching trays were fabricated for each participant. Each bleaching tray fit a participant's arch and the retainer containing the enamel specimens. Enamel specimens were treated with a 10% carbamide peroxide bleaching gel (Nite White Excel 2Z, Discus Dental, Culver City, CA, USA) for either 1 h/day (n = 30) or 7 h/day (n = 30), both for 21 days. Three enamel specimens in each retainer were never treated and served as controls. The retainers were worn by the participants whether or not they underwent bleaching. This simulated the natural action of the saliva/oral fluids on the enamel specimens. Enamel specimens were subjected to pre- and post-treatment microhardness measurements. Post-treatment Knoop hardness numbers were compared with baseline values and analyzed statistically.

RESULTS

Bleaching treatment resulted in a nonsignificant reduction in microhardness values when compared with values of the control nontreated specimens (1.7% and 2.5% reduction in hardness for 1 h/day and 7 h/day, respectively). There was no difference in microhardness between the different treatment regimens.

CONCLUSION

Home bleaching with 10% carbamide peroxide for up to 7 h/day for 21 days does not significantly affect enamel microhardness.

CLINICAL SIGNIFICANCE

Bleaching with 10% carbamide peroxide for 1 h/day or 7 h/day for a total of 21 days is safe for human enamel.

Nightguard vital bleaching of tetracycline-stained teeth: 90 months post treatment

PURPOSE

The purpose of this longitudinal whitening study was to determine the stability, post-treatment side effects, and patient satisfaction at 90 months post treatment after 6 months of active treatment of tetracycline-stained teeth with 10% carbamide peroxide.

MATERIALS AND METHODS

Fifteen of 21 participants enrolled in the study (71%) were contacted and asked to participate in a survey concerning their whitening experience. Participants were asked whether there had been any change in the shade of their teeth after treatment and if they had experienced any side effects that they believed were treatment related. Eight of the 15 participated in a clinical examination.

RESULTS

Nine participants (60%) reported no obvious shade change or only a slight darkening not noticed by others. None reported darkening back to the original shade; however, four had re-treated their teeth. Examiners were in agreement with the participants' perception of shade change upon comparing pretreatment and post-treatment photographs and Vita shade (Vita Zahnfabrik D-79713, Bad Sackingen, Germany) values. The degree of improvement over the pretreatment shade was significant for the 90-month post-treatment shade (p < .01). All respondents (n = 15) denied having to have a crown or root canal or tooth sensitivity that they believed was treatment related.

CLINICAL SIGNIFICANCE

The results of this study of nightguard vital bleaching indicate that tetracycline-stained teeth can be whitened successfully using extended treatment time and that shade stability may last at least 90 months post treatment (range 84-100 mo). Patients participating in this study were over-whelmingly positive about the procedure in terms of shade retention and lack of post-treatment side effects.

Scanning electron microscopy study of dental enamel surface exposed to 35% hydrogen peroxide: alone, with saliva, and with 10% carbamide peroxide

Several vital bleaching systems have been introduced in response to the demand in esthetic dentistry. The active agents are commonly hydrogen peroxide or carbamide peroxide used in at-home or in-office techniques. Although generally positive results have been reported concerning the whitening ability of these agents, concerns still remain as to their effects on dental tissues. The purpose of this investigation was to evaluate the effect of these bleaching agents on the enamel surface morphology. Twelve extracted teeth were used according to three experimental protocols. In experimental protocol 1, specimens were treated with 35% hydrogen peroxide. In experimental protocol 2, after treatment with 35% hydrogen peroxide the specimens were immersed in natural saliva for 1 week. In experimental protocol 3, 35% hydrogen peroxide was applied once and 10% carbamide peroxide was applied for 1 week (12 h of 10% carbamide peroxide alternating with 12 h saliva). Scanning electron microscopy evaluation revealed that regional variation in tooth morphology surface sometimes exceeded the effects of the peroxide used according to experimental protocols. Thirty-five percent hydrogen peroxide had a tendency to promote an increase in density of pits. Precipitates were observed on specimen surfaces immersed in natural saliva according to protocol 2. A smooth and shiny surface was observed in specimens treated according to protocol 3. The potential relationship between surface alterations and differences in enamel permeability is currently under investigation. CLINICAL SIGNIFICANCE The differences in various articles written on the subject cannot be reconciled because of the lac of standardization of baseline data regarding factors such as location on the tooth, type of tooth eruption or noneruption, and age in the oral cavity. This article demonstrates that, despite changes observed in the enamel surface after bleaching, normal variation in tooth morphology may exceed the effects of 35% hydrogen peroxide and 10% carbamide peroxide on the teeth. Hence, considering the morphologic features of the tooth surface, bleaching, as described in thi study, can be considered safe for enamel.

Tooth bleaching--a critical review of the biological aspects

Present tooth-bleaching techniques are based upon hydrogen peroxide as the active agent. It is applied directly, or produced in a chemical reaction from sodium perborate or carbamide peroxide. More than 90% immediate success has been reported for intracoronal bleaching of non-vital teeth, and in the period of 1-8 years' observation time, from 10 to 40% of the initially successfully treated teeth needed re-treatment. Cervical root resorption is a possible consequence of internal bleaching and is more frequently observed in teeth treated with the thermo-catalytic procedure. When the external tooth-bleaching technique is used, the first subjective change in tooth color may be observed after 2-4 nights of tooth bleaching, and more than 90% satisfactory results have been reported. Tooth sensitivity is a common side-effect of external tooth bleaching observed in 15%-78% of the patients, but clinical studies addressing the risk of other adverse effects are lacking. Direct contact with hydrogen peroxide induced genotoxic effects in bacteria and cultured cells, whereas the effect was reduced or abolished in the presence of metabolizing enzymes. Several tumor-promoting studies, including the hamster cheek pouch model, indicated that hydrogen peroxide might act as a promoter. Multiple exposures of hydrogen peroxide have resulted in localized effects on the gastric mucosa, decreased food consumption, reduced weight gain, and blood chemistry changes in mice and rats. Our risk assessment revealed that a sufficient safety level was not reached in certain clinical situations of external tooth bleaching, such as bleaching one tooth arch with 35% carbamide peroxide, using several applications per day of 22% carbamide peroxide, and bleaching both arches simultaneously with 22% carbamide peroxide. The recommendation is to avoid using concentrations higher than 10% carbamide peroxide when one performs external bleaching. We advocate a selective use of external tooth bleaching based on high ethical standards and professional judgment.