Ultrasonic activation of internal bleaching agents

Comparative Evaluation of Activated and Nonactivated Microbubbles on the Efficacy of Bleaching Agents

INTRODUCTION

Intracoronal bleaching serves as a conservative option for nonvital teeth that exhibit discoloration. Hydrogen peroxide (H2O2) is frequently utilized in bleaching processes owing to its capability to produce free radicals. The main drawbacks of the currently available bleaching agents are the occurrence of cervical resorption and the multiple dental visits to achieve the desired result. Therefore, in our study, to address the limitations associated with cervical resorption and extended treatment duration for badly stained teeth, an attempt was made to incorporate a whitening agent (35% H2O2) with microbubbles.

AIM

 This study aimed to compare and evaluate the effect of activated and nonactivated microbubbles on the efficacy of bleaching agents.

METHODOLOGY

 Forty-five human central incisors were collected and divided into three groups: Group I (HP), H2O2 plain (n = 15) (Control); Group II (HPM), H2O2-infused microbubbles without ultrasonic activation (n = 15) (experimental group); and Group III (HPMU), H2O2-infused microbubbles with ultrasonic activation (n = 15) (experimental group). The crowns were artificially stained. Microbubbles containing 35% H2O2 were generated using the probe sonication method. The bleaching agent H2O2 plain (0.04 mL) was syringed into the pulp chamber in group I, while H2O2-infused microbubbles (0.04 mL) were syringed into group II and group III. Group III was further activated ultrasonically. The evaluation of color shade differences was conducted using the Vita Lumin shade guide at three time points: baseline, day 7, and day 14.

RESULTS

 Data regarding color change using Vita shade were investigated for normality using the Kolmogorov Smirnov test and assessed a non-normal distribution. Intergroup comparisons at each particular time interval (baseline, day 7, and day 14) were analyzed using the Kruskal-Wallis H test followed by multiple pairwise comparisons using the Adjusted Bonferroni post hoc test. Intragroup comparisons between different time intervals were analyzed using related samples from Friedman's test followed by multiple pairwise comparisons using the post hoc Dunn test. The level of statistical significance was determined at P < 0.05. There was no statistical difference in the baseline values of all three groups. Group I (HP) exhibited an average increase of three Vita Lumin shade tabs on day 7 and day 14, respectively, whereas Group II (HPM) exhibited an average increase of six and four Vita Lumin shade tabs on day 7 and day 14, respectively, and Group III (HPMU) exhibited an average increase of 10 and 3 Vita Lumin shade tabs on day 7 and day 14, respectively.

CONCLUSIONS

 Microbubbles containing H2O2 were more efficient and faster than plain H2O2 for bleaching, and the efficacy of bleaching was enhanced when activated using ultrasonic technology.

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.

Technique for Darkening of Extracted Teeth Simulating Pulpal Necrosis Discoloration

Background

The use of discolored teeth is required to test whitening products, and it is difficult to obtain them, given their scarcity.

Objective

To present a technique for in vitro darkening of extracted teeth simulating pulpal necrosis discoloration.

Materials and Methods

Hemolysates I and II from human blood were subjected or not to laser irradiation (442 nm) for 1 h. The concentration of oxyhemoglobin (O₂Hb) was analyzed by ultraviolet/visible spectroscopy, and the conversion of O₂Hb to methemoglobin (MetHb) by transmission spectroscopy was assessed immediately and after 3 and 40 days. For darkening evaluation, bovine incisors were divided into two groups (n = 25), and their pulp chambers were filled with hemolysate solution II (HSII) and hemolysate II solution + laser (HSII+L). After storage in artificial saliva for 40 days at 37°C, color changes were measured by a colorimeter and ΔE was compared with the NBS parameters. Data were analyzed using a mixed linear model (α=5%).

Results

HSII+L presented the lowest O₂Hb and higher MetHb. The conversion of O₂Hb to MetHb in HSII+L was 42% higher than in HSII. Both groups were effective in darkening the teeth, according to the NBS. Darkening stabilized from day 35. HSII promoted a marked color difference.

Conclusion

The proposed technique was effective in darkening the extracted teeth simulating necrosis discoloration for in vitro models.

The effectiveness of in-office dental bleaching with and without sonic activation: A randomized, split-mouth, double-blind clinical trial

OBJECTIVE

This study was aimed at comparing the bleaching efficacy and bleaching sensitivity (BS) of two higher-concentration in-office bleaching gels (37% carbamide peroxide [CP] and 38% hydrogen peroxide [HP]) applied under two conditions: alone or in association with sonic activation.

METHODS

Fifty-six volunteers were randomly assigned in the split-mouth design into the following groups: CP, CP with sonic activation (CPS), HP, and HP with sonic activation (HPS). Two in-office bleaching sessions were performed. Color was evaluated using Vita Classical, Vita Bleachedguide, and digital spectrophotometer at baseline and at 30 days post-bleaching. Absolute risk and intensity of BS were recorded using two pain scales. All data were evaluated statistically (color changes [t test], BS [Chi-square and McNemar test], and BS intensity [VAS; t test; NRS; Wilcoxon; α = 0.05]).

RESULTS

Significant and higher whitening was observed for HP when compared with CP (p < 0.04). However, higher BS intensity was observed in the former (p < 0.001). No significant difference was observed in whitening effect or BS when the HP or CP bleaching gels were agitated (sonic application) compared with when they were not (p > 0.05).

CONCLUSION

The 37% CP gel demonstrated lower bleaching efficacy and lower BS compared with the 38% HP bleaching gel. The whitening effect was not influenced by the use of sonic activation.

CLINICAL SIGNIFICANCE

The use of 37% CP gel did not achieve the same whitening effect when compared to 38% HP gel used for in-office bleaching. The use of sonic activation offers no benefit for in-office bleaching.

Photon-Induced Photoacoustic Streaming Activation of the Postbleaching Antioxidant Application Rapidly Improves Bonding to Pulp Chamber Dentin

Objective: This study explored whether the erbium/yttrium/aluminum/garnet (Er:YAG) laser irradiated through the photon-induced photoacoustic streaming (PIPS) method would impact on the resin bonding to pulp chamber dentin when used to activate bleaching and/or postbleaching antioxidant treatment. Materials and methods: One hundred five dentin samples prepared from freshly extracted human incisors were randomly assigned to seven groups (n = 15): control (no bleaching/antioxidant); CB (conventional bleaching only); MB (modified bleaching only); CB-NI (conventional bleaching+antioxidant with needle irrigation); MB-NI (modified bleaching+antioxidant with needle irrigation); CB-PIPSI (conventional bleaching+antioxidant with PIPS-activated irrigation); and MB-PIPSI (modified bleaching+antioxidant with PIPS-activated irrigation). Bleaching (40% hydrogen peroxide) lasted for 20 min. Modified bleaching groups were irradiated with Er:YAG laser using the PIPS tip (2940 nm, 0.90 W, 30 Hz, 30 mJ/pulse, 50-μsec pulse duration) during the first 60 sec of the procedure. The antioxidant treatment with 10% sodium ascorbate lasted for 60 sec. PIPS-activated antioxidant groups were irradiated with Er:YAG laser using the PIPS tip (2940 nm, 0.30 W, 15 Hz, 20 mJ per pulse, 50-μsec pulse duration) throughout the procedure. After completing the composite restorations, all samples were subjected to 5000 thermocycling and the shear bond strength (SBS) test at a crosshead speed of 1 mm/min. SBS data were analyzed using the Kruskal-Wallis test with Bonferroni correction (α& 0.05). Results: No significant difference was detected among the control, CB-PIPSI, and MB-PIPSI (p > 0.05), which presented a significantly higher SBS compared with the other groups (p < 0.05). Conclusions: Irrespective of the application mode of the initial bleaching, PIPS-activated irrigation of the antioxidant improved SBS to bleached dentin to the level of the control in 1 min. Postbleaching antioxidant treatment combined with the PIPS method might be a promising approach to enable immediate resin restoration of bleached dentin.

Influence of the bleaching interval on the luminosity of long-term discolored enamel-dentin discs

OBJECTIVES

The aim of this study is to investigate the influence of changing the sodium perborate-tetrahydrate (PBS-4) at a 4-day interval versus no change after 16 days of internal bleaching.

MATERIALS AND METHODS

Two hundred and ten bovine enamel-dentin discs were discolored for 3.5 years with 14 different endodontic materials. All groups with a discoloring index of ∆E (mean) ≥ 5.5 were included in the present investigation: ApexCal (APCA), MTA white + blood (WMTA+BL), Portland cement + blood (PC+BL), blood (BL), MTA gray (GMTA), MTA gray + blood (GMTA+BL), Ledermix (LED), and triple antibiotic paste containing minocycline (3Mix). Fourteen specimens of each group were randomly assigned into two treatment groups: (1) no change of the PBS-4 (n = 7); (2) change of the PBS-4 every 4 days (n = 7). Color measurements were taken at 10 different time intervals and the L*a*b* values were recorded with a spectrophotometer (VITA Easyshade® compact).

RESULTS

In the group 3Mix, significantly better results were achieved by changing the bleaching agent every 4 days (P = 0.0049; q = 0.04), while the group WMTA+BL indicated better results by no change of the bleaching agent (P = 0.0222, q = 0.09). All remaining groups showed no statistical difference between the two treatment procedures.

CONCLUSIONS

Moderate discolorations can be successfully treated without changing the bleaching agent over a period of 16 days. Changing the sodium perborate-tetrahydrate every 4 days is preferred in case of severe discolored enamel-dentin discs only.

CLINICAL RELEVANCE

This approach may offer a reduced number of clinical appointments and a secondary cost reduction to the patient.