Experimental gel containing bioactive glass-ceramic to minimize the pulp damage caused by dental bleaching in rats

Bioactive Glass in Tissue Regeneration: Unveiling Recent Advances in Regenerative Strategies and Applications

Bioactive glass (BG) is a class of biocompatible, biodegradable, multifunctional inorganic glass materials, which is successfully used for orthopedic and dental applications, with several products already approved for clinical use. Apart from exhibiting osteogenic properties, BG is also known to be angiogenic and antibacterial. Recently, BG's role in immunomodulation has been gradually revealed. While the therapeutic effect of BG is mostly reported in the context of bone and skin-related regeneration, its application in regenerating other tissues/organs, such as muscle, cartilage, and gastrointestinal tissue, has also been explored recently. The strategies of applying BG have also expanded from powder or cement form to more advanced strategies such as fabrication of composite polymer-BG scaffold, 3D printing of BG-loaded scaffold, and BG-induced extracellular vesicle production. This review presents a concise overview of the recent applications of BG in regenerative medicine. Various regenerative strategies of BG will be first introduced. Next, the applications of BG in regenerating various tissues/organs, such as bone, cartilage, muscle, tendon, skin, and gastrointestinal tissue, will be discussed. Finally, summarizing clinical applications of BG for tissue regeneration will conclude, and outline future challenges and directions for the clinical translation of BG.

Influence of dental bleaching on the pulp tissue: A systematic review of in vivo studies

BACKGROUND

Although several studies indicate the harmful effects of bleaching on pulp tissue, the demand for this procedure using high concentrations of hydrogen peroxide (HP) is high.

OBJECTIVES

To investigate the influence of bleaching on the pulp tissue.

METHODS

Electronic searches were conducted (PubMed/MEDLINE, Scopus, Cochrane Library and grey literature) until February 2021. Only in vivo studies that evaluated the effects of HP and/or carbamide peroxide (CP) bleaching gels on the inflammatory response in the pulp tissue compared with a non-bleached group were included. Risk of bias was performed according to a modified Methodological Index for Non-Randomized Studies scale for human studies and the Systematic Review Centre for Laboratory Animal Experimentation's RoB tool for animal studies. Meta-analysis was unfeasible.

RESULTS

Of the 1311 studies, 30 were eligible. Of these, 18 studies evaluated the inflammatory response in animal models. All these studies reported a moderate-to-strong inflammatory response in the superficial regions of pulp, characterized by cell disorganization and necrotic areas, particularly during the initial periods following exposure to 35%-38% HP, for 30-40 min. In the evaluation of human teeth across 11 studies, seven investigated inflammatory responses, with five observing significant inflammation in the pulp of bleached teeth. In terms of tertiary dentine deposition, 11 out of 12 studies noted its occurrence after bleaching with 35%-38% HP in long-term assessments. Additionally, three studies reported significant levels of osteocalcin/osteopontin at 2 or 10 days post-treatment. Other studies indicated an increase in pro-inflammatory cytokines ranging from immediately up to 10 days after bleaching. Studies using humans' teeth had a low risk of bias, whereas animal studies had a high risk of bias.

DISCUSSION

Despite the heterogeneity in bleaching protocols among studies, High-concentrations of HP shows the potential to induce significant pulp damage.

CONCLUSIONS

High-concentrations of bleaching gel increases inflammatory response and necrosis in the pulp tissue at short periods after bleaching, mainly in rat molars and in human incisors, in addition to greater hard tissue deposition over time. However, further well-described histological studies with long-term follow-up are encouraged due to the methodological limitations of these studies.

REGISTRATION

PROSPERO (CRD42021230937).

Role of induced nitric oxide synthases in orofacial nociception/discomfort after dental tooth bleaching with hydrogen peroxide

OBJECTIVE

To evaluate the role of induced nitric oxide synthase (iNOS) in nociception/orofacial discomfort in rats submitted to tooth whitening with hydrogen peroxide (H₂O₂).

DESIGN

Wistar rats were divided into three groups (n = 24/group): a sham group not submitted to whitening treatment, a saline group submitted to whitening treatment, and a test group submitted to whitening treatment and blockade of iNOS with aminoguanidine 50 mg/kg/day. After 24 and 48 h, and 7 days, the animals were euthanized to collect trigeminal ganglia and maxillae to histomorphometric analysis (size of neuronal bodies and percentage of pulp area filled by vessels) and behavior/nociception (Grimace scales, scratching and biting counting, weight loss and nociception assay). ANOVA-1- or - 2-way tests were used (p < 0.05, GraphPadPrism 5.0).

RESULTS

The aminoguanidine-treated group showed a reduction in nociceptive threshold in the masseteric region (p < 0.001), Grimace scale scores (p < 0.001), number of scratching (p = 0.011) and body mass loss (p = 0.007). After 24 and 48 h of tooth bleaching, the saline group showed a significant increase in the mean area of the blood vessels (p = 0.020) and iNOS immunostaining in odontoblasts (p = 0.002) and non-odontoblasts cells (p = 0.025). Aminoguanidine reversed both increases. Tooth bleaching reduced the mean area of neuronal bodies, and aminoguanidine significantly reversed it (p = 0.019), but an increase in GFAP immunostaining in neuronal bodies did not reduce after seven-days or after aminoguanidine treatment (p = 0.003).

CONCLUSION

iNOS blockage by aminoguanidine plays an important role in nociception and orofacial discomfort by control of inflammation in dental pulp after tooth bleaching with hydrogen peroxide (H₂O₂) 35%.

Can different agents reduce the damage caused by bleaching gel to pulp tissue? A systematic review of basic research

Objectives

This study aimed to investigate the effectiveness of different topical/systemic agents in reducing the damage caused by bleaching gel to pulp tissue or cells.

Materials and Methods

Electronic searches were performed in July 2023. In vivo and in vitro studies evaluating the effects of different topical or systemic agents on pulp inflammation or cytotoxicity after exposure to bleaching agents were included. The risk of bias was assessed.

Results

Out of 1,112 articles, 27 were included. Nine animal studies evaluated remineralizing/anti-inflammatories agents in rat molars subjected to bleaching with 35%-38% hydrogen peroxide (HP). Five of these studies demonstrated a significant reduction in inflammation caused by HP when combined with bioglass or MI Paste Plus (GC America), or following KF-desensitizing or Otosporin treatment (n = 3). However, orally administered drugs did not reduce pulp inflammation (n = 4). Cytotoxicity (n = 17) was primarily assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay on human dental pulp cells and mouse dental papilla Cell-23 cells. Certain substances, including sodium ascorbate, butein, manganese chloride, and peroxidase, were found to reduce cytotoxicity, particularly when applied prior to bleaching. The risk of bias was high in animal studies and low in laboratory studies.

Conclusions

Few in vivo studies have evaluated agents to reduce the damage caused by bleaching gel to pulp tissue. Within the limitations of these studies, it was found that topical agents were effective in reducing pulp inflammation in animals and cytotoxicity. Further analyses with human pulp are required to substantiate these findings.

Trial Registration

PROSPERO Identifier: CRD42022337192.

Fabrication and characterization of chlorhexidine gluconate loaded poly(vinyl alcohol)/45S5 nano-bioactive glass nanofibrous membrane for guided tissue regeneration applications

Polymeric barrier membranes are used in periodontal applications to prevent fibroblastic cell migration into the cavities of bone tissue and to properly guide the proliferation of tissues. In this study, the fabrication, characterization, bioactivity, and in vitro biological properties of polyvinyl alcohol-based nanofibrous membranes containing nano-sized 45S5 bioactive glass (BG) loaded with chlorhexidine (CH) gluconate with biocompatible, bioactive, and antibacterial properties for using as dental barrier membranes were investigated. Nanofibrous membranes with an average fiber diameter, pore size, and porosity of 210 nm, 24.73 μm, and 12.42%, respectively, were loaded with 1% and 2% CH, and the release profile was investigated. The presence of BG in the membranes promoted fibroblastic proliferation and the presence of CH provided antibacterial properties. Nanofibrous membranes exhibit a high ability to restrict bacterial growth while fulfilling the necessary conditions for use as a dental barrier thanks to their low swelling rates, significant surface bioactivities, and appropriate degradation levels.

Photobiomodulation reduces inflammation but does not influence the hypoxia-inducible factor-1α in pulp tissue of rats after bleaching

Objectives:

To evaluate the influence of photobiomodulation with infrared laser (IRL) in the rat pulp tissue after bleaching, considering the immunolabeling of interleukin (IL)-23 and hypoxia-inducible factor (HIF)-1α.

Methodology:

The right and left molars of forty rats were divided into groups: Control – with placebo gel and Bleached – with 35% hydrogen peroxide (H₂O₂). Half of the rats received one IRL application on both sides, establishing a split-mouth design, which resulted in 4 groups with 20 hemi-maxillae each: Control, Bleach, IRL, and Bleached-IRL. Rats (n=10) from each group were euthanized, at 2- and 30-days mark, and the pulp tissue was evaluated using inflammation and immunolabeling scores. Wilcoxon and Mann-Whitney statistical tests were performed (p<0.05).

Results:

At the 2-days mark, the Bleached group had severe inflammation and necrosis in the occlusal thirds of the pulp, and moderate to severe inflammation in cervical third, whereas the Bleached-IRL had mild to moderate inflammation (p<0.05). At the 30-days mark, there was no inflammation, but tertiary dentine formation in the bleached groups. Regarding IL-23, severe immunolabeling was observed in the Bleached group (p<0.05) at the 2-days mark; at the 30-days mark, there was a reduction in immunolabeling, in which the Bleached group had moderate and the Bleached-IRL group had mild immunolabeling (p>0.05). HIF-1α was more evident at the 2-days mark in the Bleached group, without significant difference with the Bleached-IRL (p>0.05). The difference was observed between the bleached and control groups, without immunolabeling (p<0.05); at the 30-days mark, the Bleached group had reduction in HIF-1α immunolabeling, while the Bleached-IRL had an increase; the difference remained between the bleached and the controls groups (p<0.05)

Conclusion:

Photobiomodulation using IRL minimized the inflammation and IL-23 immunolabeling in the pulp tissue of rats after dental bleaching, but did not influence significantly the HIF-1α immunolabeling.

Topical application of Otosporin® before in-office bleaching: a split mouth, triple-blind, multicenter randomized clinical trial

OBJECTIVES

To evaluate if the topical application of Otosporin® before in-office bleaching with a 35% hydrogen peroxide (HP) gel reduces the risk and intensity of tooth sensitivity (TS), as well as the bleaching effectiveness.

MATERIALS AND METHODS

Twenty participants were selected for this split mouth, triple-blind, multicenter randomized clinical trial. Before each bleaching session, the placebo was applied in the patient's hemi-arch and the other half received the Otosporin®, according to the randomization procedure. Both products were applied topically for 10 min. The 35% HP was applied in two sessions with a 1-week interval. The risk and intensity of TS were assessed using the Numerical Scale (NRS) and the Visual Analog Scale (VAS). The bleaching effectiveness were evaluated with the visual scales and with a digital spectrophotometer. The absolute risk of TS was compared by McNemar's test. To compare the intensity of TS, the Wilcoxon signed-rank test was used to evaluate the NRS, while the paired t test was used to evaluate VAS. Bleaching effectiveness (ΔSGUs and ΔE_ab, ΔE₀₀, and ΔWI_D) was compared between groups using the paired t-test (α = 0.05).

RESULTS

No significant difference at risk (p = 1.0) and intensity of TS (p > 0.59; VAS and p = 1.00 for NRS) was detected between groups. For both groups, a significant bleaching was observed after 30 days of evaluation (p < 0.39).

CONCLUSIONS

The previous application of Otosporin® in the in-office bleaching did not reduce the risk and intensity of TS and did not affect the effectiveness of the bleaching.

CLINICAL RELEVANCE

The application of Otosporin® before in-office bleaching with 35% HP was not able to reduce the risk and intensity of TS.