The efficacy of laser-assisted in-office bleaching and home bleaching on sound and demineralized enamel

Internal bleaching with calcium oxalate and laser irradiation for managing discolorations induced by mineral trioxide aggregate

AIM

This in vitro study investigated the effects of incorporating 1%, 3%, and 5% calcium oxalate into 15% hydrogen peroxide (H2O2), with and without laser activation, on the whitening of teeth discolored by mineral trioxide aggregate (MTA).

METHODS

The pulp tissue of 80 bovine incisors was removed, and an MTA plug was placed at 2 mm below the cementoenamel junction. After nine months, the samples were randomly divided into eight groups (n = 10). Groups 1 to 4 were treated with 15% H2O2 gel containing 0, 1, 3, or 5% calcium oxalate, respectively. The same gels were applied in groups 5 to 8 but activated with an 810 nm diode laser (2 W, continuous wave). The teeth were incubated for five days, followed by the second gel application. Tooth color was evaluated at baseline (T1), after MTA discoloration (T2), and after the first (T3) and second (T4) gel applications, using the CIELAB system to measure color changes (ΔE).

RESULTS

The mean ΔE2 - 3 and ΔE2 - 4 differed significantly between groups (P = 0.002 and P = 0.040, respectively). After the first and second gel applications, ΔE values were significantly higher in groups 2 (H2O2 + 1% calcium oxalate) and 6 (H2O2 + 1% calcium oxalate + laser) than in groups 1 (H2O2), 5 (H2O2 + laser), and 8 (H2O2 + 5% calcium oxalate + laser) (P < 0.05).

CONCLUSIONS

Incorporating 1% calcium oxalate into 15% H2O2 can enhance the whitening of teeth discolored by white MTA. Laser activation did not further improve the outcome of internal bleaching in teeth with MTA discoloration.

Effects of microabrasion and bleaching on color and shear bond strength of simulated stained-remineralized caries lesions

Purpose

This study investigated the effects of bleaching and microabrasion on the color and shear bond strength (SBS) of stained-remineralized caries-like lesions (s-RCLs).

Methods

Human enamel specimens were demineralized, stained (coffee/tea), then remineralized (2% NaF and artificial saliva [AS]) to create s-RCLs. Specimens were randomly divided into five groups (n = 18): G1, demineralized/AS; G2, s-RCLs/AS; G3, s-RCLs/at-home bleaching (15% carbamide peroxide [CP)], 6 h/d×7)/AS; G4, s-RCLs/microabrasion (6.6% hydrochloric acid, [1min/3cycles]/AS; and G5, s-RCLs/microabrasion and at-home bleaching/AS. Color was spectrophotometrically measured at baseline, after demineralization, after staining, and after treatment. After two weeks, the SBS was tested using a universal testing machine. Outcomes were analyzed using ANOVA models followed by Tukey's test (α = 0.05).

Results

The mean colors (ΔE) for demineralization and staining were significant (ΔE ≤ 5.9 and ≤14.4, respectively). G3 (ΔE 23.9) and G5 (ΔE 25.2) were significantly improved compared to G4 (ΔE 12.3). The SBS in G5 had the highest significant value (25.2 MPa), followed by G4 and G3 (21.5-20.6 MPa), which were significantly higher than G2 (16.8 MPa). G2, in turn, was more significant than G1 (10.9 MPa).

Conclusion

At-home bleaching (15% CP) for seven days eliminated and improved organic stains on RCLs. Faster results were achieved when combined with microabrasion. All surface treatments resulted in high SBS.

Comparison of various methods of restoring adhesion to recently bleached enamel

AIM

This study compared the effectiveness of several techniques in restoring compromised bonding to recently bleached enamel.

METHODS

Seventy-five healthy bovine incisors were divided into five groups (n = 15). Fifteen teeth (Group 1) remained intact, whereas 60 (Groups 2 to 5) underwent at-home bleaching with 16% carbamide peroxide. The bonding procedures were as follows: Group 1: Bonding of resin composite to unbleached enamel; Group 2: Bonding immediately after bleaching; Group 3: Application of a 10% sodium ascorbate solution for 10 min before bonding; Group 4: Enamel removal to the depth of 0.5 mm; and Group 5: Increased curing time of the bonding agent to 80 instead of 20 s. After 24 h, the specimens were subjected to micro-shear testing, and the failure mode was determined.

RESULTS

ANOVA revealed a significant difference in bond strength among the groups (P < 0.001). The mean bond strength was significantly lower in group 2 than in other groups (P < 0.05), which showed comparable bond strength to each other (P > 0.05). Adhesive failure was the most predominant failure type in all groups. The mixed failure occurred with a frequency of 26.7% in groups 3 and 5. The Fisher's exact test revealed a significant difference in failure modes among the groups (P = 0.047).

CONCLUSIONS

The three experimental procedures used in this study, including the application of 10% sodium ascorbate before bonding, enamel removal to the depth of 0.5 mm, and increasing the curing time of the bonding agent to 80 s, were effective in restoring the compromised bonding to recently bleached enamel.

Exploring the efficacy of laser-assisted in-office tooth bleaching: A study on varied irradiation times and power settings utilizing a diode laser (445 nm)

The aim of this study was to evaluate the effectiveness of a laser-assisted in-office tooth bleaching treatment, employing a diode laser (445 nm) using different power and time settings. Two hundred human incisors were collected for evaluating tooth color change (ΔΕ00) and whiteness index in dentistry (ΔWID) following laser-assisted tooth bleaching treatment. The specimens were distributed into 25 groups (n = 8) according to laser output power (0.5-2 W) and duration of irradiation (10-60 s) that was applied. ΔΕ00 and ΔWID were evaluated using a spectrophotometer at three points of time (24 h, 1 week and 1 month after treatments). Three-way ANOVA revealed that power, duration of laser irradiation, and time of measurement after bleaching treatments significantly affected both ΔΕ00 and ΔWID(p < 0.05). Furthermore, laser irradiation increased ΔΕ00 and ΔWID at all applied powers compared to the control group (p < 0.05), but this increase was dependent on the duration of irradiation. Laser irradiation significantly increased ΔΕ00 when the duration of operation was 50-60 s at 0.5-1 W, while at 1.5-2 W was significantly increased when the duration was 30-60 s. ΔWID was significant higher in the laser groups compared to the control group at all powers, except for 0.5 W where it was significant higher when the duration was 50-60 s. The outcomes of the study can help in selecting the suitable power settings and duration of laser exposure to achieve the optimal whitening results while ensuring the safety of the tooth pulp.

Antimicrobial photodynamic therapy against Lactobacillus casei using curcumin, nano-curcumin, or erythrosine and a dental LED curing device

This study aimed to investigate the photodynamic effects of curcumin, nanomicelle curcumin, and erythrosine on Lactobacillus casei (L. casei). Various concentrations of curcumin (1.5 g/L, 3 g/L), nano-curcumin (3 g/L), and erythrosine (100 µM/L, 250 µM/L) were tested either alone or combined with light irradiation (PDT effect) against L. casei in planktonic and biofilm cultures. The light was emitted from a light-emitting diode (LED) with a central wavelength of 450 nm. A 0.12% chlorhexidine digluconate (CHX) solution served as the positive control, and a solution containing neither photosensitizer nor light was the negative control group. The number of viable microorganisms was determined using serial dilution. There was a significant difference in the viability of L. casei in both planktonic and biofilm forms (P < 0.05). In the planktonic culture, the antibacterial effects of CHX and PDT groups with curcumin 3 g/L and erythrosine 250 µM/L were significantly greater than the other groups (P < 0.05). For L. casei biofilms, the greatest toxic effects were observed in CHX and PDT groups with curcumin 3 g/L, erythrosine 250 µmol/L, erythrosine 100 µmol/L, and nanomicelle curcumin 3 g/L, with a significant difference to other groups (P < 0.05). The antibacterial effects of all photosensitizers (except erythrosine 250 µmol/L at planktonic culture) enhanced significantly when combined with light irradiation (P < 0.05). PDT with curcumin 3 g/L or erythrosine 250 µmol/L produced comparable results to CHX against L. casei at both planktonic and biofilm cultures. Alternatively, PDT with erythrosine 100 µmol/L or nanomicelle curcumin 3 g/L could be suggested to kill L. casei biofilms.

The Use of Diode Low-Power Laser Therapy before In-Office Bleaching to Prevent Bleaching-Induced Tooth Sensitivity: A Clinical Double-Blind Randomized Study

INTRODUCTION

The present study aimed to investigate the effectiveness of low-level laser therapy (LLLT) use before in-office bleaching to prevent an increase in the risk and intensity of tooth sensitivity.

METHODS

Thirty patients were selected. Before bleaching with 38% hydrogen peroxide, the participants were randomly divided into two groups of 15 subjects. Test group: the patients' teeth were subjected to a preliminary LLLT procedure by an 810 nm diode laser with 0.5 W for 30 s for an energy density of 15 J/cm² and a group placebo. All patients were instructed to report their cold sensitivity experiences immediately, 1 h, 24 h, and 48 h after the end of bleaching via a VAS score.

RESULTS

The results obtained show an increase in VAS values for both groups (290 and 490 vs. 224 and 234 of baseline time of test and placebo group, respectively); afterward, the VAS value seemingly decreases at 1 h after the end of bleaching, approaching the baseline VAS for the test group (274) in comparison to the placebo group.

CONCLUSIONS

The use of preliminary diode LLLT could represent a valid possibility to reduce the occurrence of tooth sensitivity post-whitening and shorten recovery time in cases where tooth sensitivity occurs.

Evaluation of the laser wavelength role on tooth bleaching in terms of color change, roughness, and microhardness with pulpal rapid temperature monitoring: an in vitro study

This in-vitro study evaluates the efficacy of the teeth bleaching approach using different laser wavelengths (405 nm blue diode, 940 nm infrared diode, and Er,Cr:YSGG 2780 nm lasers) in comparison to the conventional method using light-emitting diode (LED) sources (420-480) nm. Eighty caries-free sound human premolars were randomly divided into four groups (N=20). Each group received a different bleaching procedure. Then each group was further subdivided into two subgroups (N=10) stained with different solutions. The pulp chamber temperature rise was recorded using an optical fiber sensor with a novel design and fabrication. The color was analyzed using a digital spectrophotometer. Five samples of each subgroup were tested for surface roughness, while the others were tested for Vickers microhardness. The bleaching process with a short wavelength 405 nm blue diode laser showed the best results for the shade, with a minimum pulpal temperature increase indicating no possible necrosis and hence maintaining tooth vitality. Additionally, a remarkable reduction in bleaching time was achieved compared to the conventional approach. This process also yielded the highest color change (Δ E) and increased microhardness, with no noticeable change to the tooth roughness. The 405 nm blue diode laser applied for bleaching showed the best bleaching activity against tested stains and negligible pulpal temperature rise with a noticeable reduction in the bleaching time. The proposed novel method to measure temperature change could be used to develop a promising smart sensor for quick, effective, repeatable, and in-situ monitoring of human body temperature.

Does the application of whitening dentifrices during at-home bleaching affect the bond strength of resin composite to dentin?

AIM

This study aimed to evaluate the effect of using whitening dentifrices during at-home bleaching on the shear bond strength (SBS) of resin composite to dentin, and investigate whether the increased polymerization time would improve SBS.

METHODS

Ninety-six bovine incisors were divided into 4 groups of 24, according to the whitening treatment applied as follows: group 1, at-home bleaching + brushing with a regular dentifrice; group 2, at-home bleaching + brushing with a whitening dentifrice containing ozone; group 3, at-home bleaching + brushing with a commercial whitening dentifrice; and group 4 (control), no whitening/brushing treatment. Each group was divided into two subgroups (n = 12) to assess the effect of curing time (20 versus 80 s) on SBS. A self-etch adhesive was bonded to dentin, and after 2-day water storage, SBS was determined.

RESULTS

SBS was significantly affected by the whitening treatment (P = 0.03), but increasing the curing time had no significant effect on SBS (P = 0.137). Bond strength in group 1 was comparable to the control group (P > 0.05). The specimens in group 3 displayed significantly lower SBS than either group 4 or group 1 (P > 0.05). No significant difference was observed between the SBS of group 2 compared to any other group (P > 0.05). There was no significant association between the treatment group and failure type (P > 0.05).

CONCLUSION

The bonding interface was not negatively influenced by the at-home bleaching procedure. However, using a commercial whitening dentifrice during at-home bleaching produced a significant detrimental effect on SBS. Extending the curing time would have no beneficial effect on adhesion to a whitened dental substrate.

Clinical and radiographic effectiveness of mineral trioxide aggregate (MTA) partial pulpotomy with low power or high power diode laser irradiation in deciduous molars: a randomized clinical trial

This study investigated the clinical and radiographic effectiveness of MTA partial pulpotomy with low power or high power diode laser irradiation in primary molars. In this randomized single-blind clinical trial, 63 mandibular second molars were assigned into three groups (n = 21). After pulp amputation and achieving hemostasis, MTA was placed over pulp stumps in group 1 (MTA). The patients in groups 2 (LLLT-MTA) and 3 (DL-MTA) underwent low level (660 nm, 200 mW) and high power (810 nm, 1 W) diode laser radiation prior to MTA placement, respectively. The occurrence of clinical failure (spontaneous pain, tenderness upon percussion, swelling, fistula, mobility) and radiographic failure (periodontal ligament widening, external or internal root resorption, periapical or furcal radiolucency) was recorded up to 18 months after therapy. MTA and LLLT-MTA groups showed clinical success rate of 100% throughout the experiment. The clinical success rate of DL-MTA group was 95.2%, 95.2%, and 87.5% after 6, 9, and 18 months. The radiographic success rates were 90.5%, 90.5%, and 87.5% in the MTA group; 100%, 95.2%, and 88.2% in the LLLT-MTA group, and 85.7%, 76.2%, and 68.7% in the DL-MTA group, at 6-, 9-, and 18-month follow-ups, respectively. No significant differences were found in the frequency of clinical or radiographic failure among the groups at any interval (p > 0.05). MTA partial pulpotomy was a suitable technique for vital pulp therapy in deciduous teeth. The addition of low power or high power diode laser radiation to the procedure did not cause a significant difference in success rate values.

Effectiveness of an 810-nm Diode Laser in Addition to Non-surgical Periodontal Therapy in Patients With Chronic Periodontitis: A Randomized Single-Blind Clinical Trial

Introduction: This study evaluated the effectiveness of an 810-nm diode laser as an adjunct to scaling and root planning (SRP) in improving periodontal parameters in patients with chronic periodontitis. Methods: This randomized clinical trial consisted of 36 patients (16 females and 20 males) with chronic periodontitis and pocket depths of 4-6 mm. The quadrants were randomly divided into two sides; one side of each patient was selected as the laser group (SRP + laser) and the other side served as the control group (SRP alone). An 810-nm diode laser was applied in the laser side to remove the outer gingival epithelium (1.5 W, CW) as well as the inner epithelium of the periodontal pockets (1 W, CW). The clinical parameters including bleeding on probing (BOP), probing depth (PD), plaque index (PI), and clinical attachment level (CAL) were measured at baseline and 6 and 18 weeks after therapy. Results: In both groups, there was a significant improvement in BOP, PD, PI and CAL over the course of the experiment (P < 0.001). Significantly lower BOP was found in the SRP + laser group than the SRP alone group after 6 and 18 weeks of intervention (P < 0.05). The difference in other parameters was not significant between the two groups, neither at 6 nor at 18 weeks after the treatment (P > 0.05). Conclusion: Within the limitations of this study, the association of the diode laser with standard non-surgical periodontal therapy (SRP) provided minimal additional benefits for patients with moderate chronic periodontitis.

Bleaching Stained Arrested Caries Lesions: In vivo Clinical Study

Objective  Conservative approaches to esthetically treat stained arrested caries lesions (s-ACLs) have not been explored in clinical studies. This study aims to investigate the efficacy of in-office dental bleaching agent, as a conservative approach, to esthetically treat s-ACLs.

Materials and Methods  Twelve patients ( n = 46) presented with s-ACLs were treated with 40% hydrogen peroxide (in-office bleaching protocol; 20 minutes × 3). Color values were measured using a spectrophotometer (CIE L*a*b*), aided with digital photography to assess visual color change clinically. Measurements were taken for each specimen at baseline and immediately after bleaching.

Statistical Analysis  The color change calculated before and after bleaching for each dental substrate was analyzed using paired t -test (α = 0.05).

Results  The bleached s-ACLs had a significant increase in L * values ( p < 0.001), and a significant decrease in both a * ( p = 0.001) and b * ( p = 0.007) values, indicating lighter color improvement (bleaching efficacy). The baseline mean of L *, a *, and b * values were 61.5, 2, and 15.4, respectively, and after bleaching were 67.7, 1.4, and 13.3, respectively, with a mean increase in ∆ E of >7.9, which resulted in a visible clinical stain improvement as orange/light brown stains were removed completely, while gray/black stains improved to a lesser extent.

Conclusion  Significant color improvement was observed when the in-office bleaching protocol (40% hydrogen peroxide) was used in orange/brown s-ACLs. However, it showed lesser improvement in gray/black s-ACLs.

Bleaching of simulated stained-remineralized caries lesions in vitro

OBJECTIVE

Non-invasive esthetic treatment options for stained arrested caries lesions have not been explored. This study aimed to develop laboratory models to create stained-remineralized caries-like lesions (s-RCLs) and to test the efficacy of bleaching on their esthetic treatment.

MATERIALS AND METHODS

One hundred twelve enamel/dentin specimens were prepared from human molars, embedded, and had their color measured spectrophotometrically at baseline and after demineralization. They were randomly divided into four groups (n = 14) based on the staining/remineralization protocols for a total of 5 days: G1, no staining/no remineralization; G2, no staining/remineralization in artificial saliva (AS); G3, non-metallic staining/remineralization with sodium fluoride/AS; and G4, metallic staining/remineralization with silver diamine fluoride/AS. The lesion mineral loss (ΔZ) and depth (L) were measured using transverse microradiography along with color change (ΔE). Specimens were bleached and color was re-evaluated. Data were analyzed using ANOVA models followed by Fisher's PLSD tests (α = 0.05).

RESULTS

s-RCLs in G4 were significantly (p < 0.001) darker than G3, G2, and G1 regardless of substrate type and condition. s-RCLs in G2, G3, and G4 showed significantly lower ΔZ and L than G1 (all p < 0.001), confirming occurrence of remineralization. G4 exhibited significantly lower ΔZ and L compared to G2 (p < 0.001). Bleaching was more effective in non-metallic than in metallic stained lesions regardless of substrate type (p < 0.001).

CONCLUSION

The proposed models created distinct s-RCLs. Non-metallic s-RCLs were lighter and more responsive to bleaching compared to metallic s-RCLs.

CLINICAL RELEVANCE

The developed experimental models allow the further investigation of the efficacy and safety of different clinical strategies for the esthetic management of s-RCLs.

Effectiveness of sodium bicarbonate combined with hydrogen peroxide and CPP-ACPF in whitening and microhardness of enamel

Background

This study investigated the effects of sodium bicarbonate (NaHCO3) combined with 1.5% hydrogen peroxide (H2O2) and casein phosphopeptide amorphous calcium phosphate fluoride (CPP-ACPF) on color and microhardness of enamel.

Material and Methods

Seventy-five bovine incisors were immersed in a tea solution for 7.5 days. The specimens were randomly divided into five groups according to the whitening agent applied: 1) 94% NaHCO3, 2) a blend of 94% NaHCO3 and CPP-ACPF, 3) a blend of 94% NaHCO3 and 1.5% H2O2, 4) a blend of 94% NaHCO3, 1.5% H2O2 and CPP-ACPF, 5) control. The whitening procedure was performed for 10 times over 10 days. At each day, the buccal surfaces were covered with whitening agents for 5 minutes and then brushed for 30 seconds. After the 10 days, the teeth were again immersed in a tea solution for 10 minutes. Color assessment was performed at baseline (T1), after the first staining process (T2), after the whitening procedure (T3), and after the second staining process (T4). Finally, the specimens were subjected to microhardness test.

Results

There was a statistically significant difference in the color change between T2 and T3 stages among the study groups (p<0.05), with the greatest improvement observed in group 4. Microhardness was significantly greater in groups 2 and 4, as compared to the other groups (p<0.05).

Conclusions

The combination of 94% NaHCO3, 1.5% H2O2 and CPP-ACPF was effective in improving color and microhardness of teeth with extrinsic stains and could be recommended in the clinical situation.

Comparison of Tooth Discoloration Induced by Calcium-Enriched Mixture and Mineral Trioxide Aggregate

Introduction:

The aim of this in vitro study was to evaluate the tooth discoloration induced by calcium-enriched mixture (CEM) cement and mineral trioxide aggregate (MTA).

Methods and Materials:

Forty five endodontically treated human maxillary central incisors were selected and divided into three groups (n=15) after removing the coronal 3 mm of the obturating materials. In the MTA group, white MTA plug was placed in pulp chamber and coronal zone of the root canal. In CEM cement group, CEM plug was placed in the tooth in the same manner. In both groups, a wet cotton pellet was placed in the access cavity and the teeth were temporarily sealed. After 24 h the teeth were restored with resin composite. In the negative control group the teeth were also restored with resin composite. The color change in the cervical third of teeth was measured with a colorimeter and was repeated 3 times for each specimen. The teeth were kept in artificial saliva for 6 months. After this period, the color change was measured again. Data were collected by Commission International de I'Eclairage's L*a*b color values, and corresponding ΔE values were calculated. The results were analyzed using the one-way ANOVA and post-hoc Tukey’s test with the significance level defined as 0.05.

Results:

There was no significant differences between CEM group and control group in mean discoloration. The mean tooth discoloration in MTA group was significantly greater than CEM and control groups (P<0.05).

Conclusion:

According to the result of the present study CEM cement did not induce tooth discoloration after six months. Therefore it can be used in vital pulp therapy of esthetically sensitive teeth.