In vivo analysis of the presence of heme oxygenase-1, transcription factor Jun-D and CD90+/CD73+/CD105+/CD45- cells in the pulp of bleached teeth

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).

Final irrigation with bioglass solution in regenerative endodontic procedure induces tissue formation inside the root canals, collagen maturation, proliferation cell and presence of osteocalcin

AIM

To evaluate the influence of an experimental solution of cobalt-doped F18 bioactive glass (F18Co) on tissue repair following regenerative endodontic procedure (REP) in rat molars.

METHODOLOGY

The F18Co solution was prepared at a ratio of 1:5 F18Co powder to distilled water. The right or left upper first molars of 12 Wistar rats were used, where the pulps were exposed, removed, and irrigated with 2.5% sodium hypochlorite (NaOCl), followed by 17% ethylenediaminetetraacetic acid (EDTA) (5 min each). Subsequently, the molars were divided into two groups (n = 6): REP-SS and REP-F18Co, where they received a final irrigation (5 min) with saline solution (SS) or F18Co solution, respectively. Then, intracanal bleeding was induced, and the tooth was sealed. Untreated molars were used as controls (n = 3). At 21 days, the rats were euthanized, and the specimens were processed for analysis of mineralized tissue and soft tissue formation inside the root canal using haematoxylin-eosin. The presence and maturation of collagen were evaluated by Masson's trichrome and picrosirius red staining. Immunolabelling analyses of proliferating cell nuclear antigen (PCNA) and osteocalcin (OCN) were performed. The data were submitted to the Mann-Whitney U-test (p < .05).

RESULTS

There was a similar formation of mineralized tissue in thickness and length in REP-SS and REP-F18Co groups (p > .05). Regarding the presence of newly formed soft tissue, most specimens of the REP-F18Co had tissue formation up to the cervical third of the canal, whilst the REP-SS specimens showed formation up to the middle third (p < .05), and there was higher maturation of collagen in REP-F18Co (p < .05). The number of PCNA-positive cells found in the apical third of the root canal was significantly higher in the F18Co group, as well as the OCN immunolabelling, which was severe in most specimens of REP-F18Co, and low in most specimens of REP-SS.

CONCLUSION

The final irrigation with F18Co bioactive glass solution in REP did not influence mineralized tissue formation but induced soft tissue formation inside the root canals, with higher collagen maturation, and an increase in PCNA-positive cells and OCN immunolabelling.

Polydioxanone Enhances Bone Regeneration After Resection and Reconstruction of Rat Femur with rhBMP2

The aim of this study was to assess the bone regeneration potential of a polydioxanone (PDO) scaffold together with recombinant human bone morphogenetic protein-2 (rhBMP-2) for the reconstruction of large bone defect. In total, 24 male rats (6 months old) were subjected to bilateral femoral stabilization using titanium plates to create a 2 mm gap, and reconstruction using rhBMP-2 (Infuse®; 3.25 μg). The bone defects were covered with PDO (PDO group), or with titanium mesh (Ti group). Animals were euthanized on days 14 and 60. Simultaneously, 16 rats received PDO and Ti in their dorsum for the purpose of biocompatibility analysis at 3, 5, 7, and 10 days postoperatively. X-ray densitometry showed a higher density in the PDO group on day 14. On day 60, coverage of the bone defect with PDO showed a larger quantity of newly formed bone than that found for the Ti group, a lower inflammatory infiltrate value, and a more significant number of blood vessels on day 14. By immunohistochemical assessment, runt-related transcription factor 2 (RUNX2) and osteocalcin (OCN) showed higher labeling on day 14 in the PDO group. On day 60, bone morphogenetic protein-2 (BMP-2) showed higher labeling in the PDO group, whereas Ti showed higher labeling for osteoprotegerin, nuclear factor kappa B ligand-activating receptor, RUNX2, and OCN. Furthermore, biocompatibility analysis showed a higher inflammatory response in the Ti group. The PDO scaffold enhanced bone regeneration when associated with rhBMP-2 in rat femur reconstruction. Impact statement Regeneration of segmental bone defects is a difficult task, and several techniques and materials have been used. Recent advances in the production of synthetic polymers, such as polydioxanone (PDO), produced by three-dimensional printing, have shown distinct characteristics that could improve tissue regeneration even in an important bone defect. The present preclinical study showed that PDO membranes used as scaffolds to carry recombinant human bone morphogenetic protein-2 (rhBMP-2) improved bone tissue regeneration by more than 8-fold when compared with titanium mesh, suggesting that PDO membranes could be a feasible and useful material for use in guided bone regeneration. (In English, viable is only used for living creatures capable of sustaining life.

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.

Bleaching effectiveness and cytotoxicity of new experimental formulation of niobium-based bleaching gel

OBJECTIVES

The development of new bleaching agents with minimum concentration of hydrogen peroxide (HP), without adverse effects, and with bleaching effectiveness, has great clinical relevance. The aim of this study was to evaluate the bleaching efficacy and cytotoxicity of a new niobium-based bleaching gel, compared to already available HP-based gels.

MATERIALS AND METHODS

For the bleaching efficacy analysis, 40 bovine incisors were randomly divided into 4 groups according to the established bleaching protocol: control, untreated; 35HP, 35% HP bleaching gel; 6HP, 6% HP bleaching gel; NbHP, niobium gel associated with 3% HP gel. The color variation was measured in a spectrophotometer and the values of ΔL, Δa, Δb, and ΔE obtained. For the cell viability assay by MTT, MC3T3 cells were exposed to bleaching gel extracts (1:500, 1:250, 1:125 dilutions; immediately and 24 h). Statistical tests were performed (P < 0.05).

RESULTS

The color alteration for all bleaching gels was significant compared to control (P < 0.05), but the NbHP gel showed a significant ΔE than other gels, with expressive color alteration at 14 days (P < 0.05). The 35HP showed high cytotoxicity regarding control and the most groups in all periods and extracts analyzed (P < 0.05), while the NbHP showed greater cell viability than control in the immediate period, dilution of the 1:500 and superior to 6HP in the most extracts at 24 h.

CONCLUSION

The new experimental niobium-based gel has bleaching efficacy similar to that of gels with a high concentration of HP, and it has high cytocompatibility.

CLINICAL RELEVANCE

The use of this new generation of niobium-based whitening gel associated with a low concentration of hydrogen peroxide represents the possibility of a tooth whitening with lower dentin sensitivity.

A new approach for professional dental bleaching using a polymeric catalyst primer

OBJECTIVE

Evaluate the influence of a polymeric catalyst primer (PCP) on esthetic efficacy (EE), degradation kinetics of hydrogen peroxide (H₂ O₂ ), and trans-amelodentinal cytotoxicity (TC) of bleaching gels.

MATERIALS AND METHODS

The following groups were established: G1: No treatment (NC, negative control); G2: PCP; G3: 10% H₂ O₂ ; G4: PCP + 10% H₂ O₂ ; G5: 20% H₂ O₂ ; G6: PCP + 20% H₂ O₂ ; G7: 35% H₂ O₂ (positive control); G8: PCP + 35% H₂ O₂ . To determine EE, enamel/dentin discs (E/DDs) were stained and subjected or not to bleaching protocols for 45 min. To assess TC, the E/DDs were adapted to artificial pulp chambers. The extracts (culture medium + gel components diffused through E/DDs) were applied to odontoblast-like MDPC-23 cells. The viability (VB), oxidative stress (OxS), morphology (SEM), amount of H₂ O₂ diffused and the production of hydroxyl radical (OH^• ) were assessed (two-way ANOVA/Tukey/paired Student t-test; p < 0.05).

RESULTS

The highest EE was found in G8 (p < 0.05), and G4, G6, and G7 did not differ statistically (p > 0.05). In G4, the limited H₂ O₂ diffusion reduced OxS and increased cell VB (p < 0.05).

CONCLUSIONS

Coating the enamel with PCP containing 10 mg/ml of manganese oxide before applying the 10% H₂ O₂ bleaching gel maintains the EE of conventional in-office bleaching and minimizes the toxic effects of this esthetic therapy.

CLINICAL SIGNIFICANCE

Coating the enamel with a PCP before applying the bleaching gel may potentiate the EE of the conventional in-office tooth bleaching and reduce the toxicity of this professional therapy to the dental pulp.

Interleukin-6, tumor necrosis factor-α, and CD5 immunolabeling of new experimental endodontic sealer and repair material

The aim of this study was to evaluate the biocompatibility and immunoinflammatory response of the Sealepox and Sealepox-RP, based on interleukin (IL)-6, tumor necrosis factor (TNF)-α, and CD5 immunolabelling. The ProRoot MTA (PRMTA) was used for comparison. Polyethylene tubes (1.0-mm internal, 1.6-mm external diameter, and 10.0-mm length; ISO 10993) with or without (control) materials were randomly implanted in the dorsum of 35 rats (4 per rat). After 7, 15, 30, 60, and 90 days (n = 7), the tubes were removed for histological and immunohistochemical analysis. The Kruskal-Wallis and Dunn's test for non-parametric data and, ANOVA and Tukey test for parametric data were used (P < 0.05). Hematoxylin and eosin staining revealed that the concentration of inflammatory cells decreased over time with no differences between groups in all periods (P > 0.05). Regarding IL-6 immunostaining, there was no difference at 7 days (P > 0.05); all groups decreased over time, being faster for the PRMTA group and also, with no differences between groups in the last period (P > 0.05). For TNF-α, at 7 days there was no difference between groups (P > 0.05); there was an increase at 15 days for PRMTA and, at 30 and 60 days, for PRMTA and Sealepox compared to the control (P < 0.05). At 90 days, Sealepox RP showed the lowest immunostaining being similar to the control (P > 0.05). Regarding CD5 cells, at 7 days, there was high immunostaining for PRMTA compared to the control (P < 0.05); and significant reduction over time with difference for all groups at 30 and 60 days. (P < 0.05); Sealepox was similar to the control in all periods (P > 0.05). Sealepox RP showed the highest immunostaining at 15 days, being different from the control and PRMTA (P < 0.05); in the other periods it was similar to the control (P > 0.05). It can be concluded that Sealepox and Sealepox-RP were biocompatible and demonstrated similar immunoinflammatory response regarding IL-6, TNF-α, and CD5 compared to PRMTA.

Influence of Hydrogen Peroxide on Mineralization in Dental Pulp Cells: A Systematic Review

Background: Dental bleaching agents show the ability to permeate through dental hard tissues, which may lead to pulp tissue changes. This systematic review (PROSPERO register: CRD42020213767) is aimed at understanding the effects of bleaching agents on the process of mineralization of the pulp tissue.

Methods: Only in vitro studies evaluating the influence of hydrogen peroxide (HP) on mineralization in dental pulp cells were included. Studies without a non-bleached control group or cells after co-treatment with a bleaching agent other than HP and/or carbamide peroxide were excluded. The primary outcomes evaluated were alkaline phosphatase (ALP) activity and mineralized nodule deposition. The mineralization markers analysis in dental pulp cells and the cell viability were considered secondary outcomes. Two independent authors conducted a systematic search (PubMed/MEDLINE, Scopus, Embase, Cochrane Library, and OpenGrey until January 2021) with no language restrictions and performed data extraction. The quality assessment was appraised according to a modified Joanna Briggs Institute critical appraisal checklist.

Results: The search resulted in 473 studies, and 11 were considered eligible. Overall, a reduction in the process of mineralization was observed among pulp cells after bleaching. A reduction in the ALP activity was reported in the mostly bleached groups using different protocols and analysis periods of nine studies. Regarding mineralized nodule deposition, 6 studies reported a significant reduction from 7 to 21 days among bleached groups. Of those three studies that investigated other mineralization markers, two found a reduction in the expression of dentin matrix acidic phosphoprotein (DMP)-1, dentin sialophosphoprotein (DSPP), and matrix extracellular phosphoglycoprotein (MEPE) among some bleaching gel concentrations. In contrast, one study showed a greater expression of osteopontin (OPN) and osteocalcin (OCN) in 100 μmol/L HP after 5 or 10 min of exposure, and another study showed significant induction of DSPP in concentrations of up to 0.5 mmol/L HP.

Conclusion: Especially, high concentrations of bleaching gel reduce the potential of mineralization in pulp cells in in vitro studies; however, different HP concentrations, bleaching protocols, and analysis periods can influence this outcome.

Evolution of endodontic medicine: a critical narrative review of the interrelationship between endodontics and systemic pathological conditions

Endodontics has gained emphasis in the scientific community in recent years due to the increase in clinical and in animal models studies focused on endodontic medicine, which aims to evaluate the interrelationship between systemic and periapical tissues pathological conditions. These studies have shown that systemic changes can boost the pathogenesis of endodontic infection, favoring its development and progression. A contrary relationship is reported in numerous studies that affirm the potential of endodontic infection to trigger systemic damage and may lead to the worsening of pre-existing pathologies. Recently, the potential of filling materials to develop systemic changes such as neurological alterations had been evaluated, also showing that systemic diseases can negatively influence tissue responses to filling materials after endodontic treatment. Despite advances in endodontic medicine studies, there are still gaps in knowledge on the mechanisms of interactions between apical periodontitis (AP) and systemic diseases and much research to be done. In this sense, this critical narrative literature review aimed to show the evolution of studies in endodontic medicine to help the endodontist to know the role of systemic diseases in the pathogenesis of AP and the possible interference in the repair of periapical tissues after endodontic treatment, as well as to evidence the systemic complications that can be triggered or aggravated in the presence of endodontic infection.

Influence of low-level laser therapy on inflammation, collagen fiber maturation, and tertiary dentin deposition in the pulp of bleached teeth

OBJECTIVES

We evaluated the effects of low-level laser therapy (LLLT) using an infrared laser (IRL) and a red laser (RL) on the pulp of molar teeth in rats after dental bleaching to assess inflammation, collagen fiber maturation, and tertiary dentin formation.

MATERIALS AND METHODS

Eighty Wistar rats (Rattus norvegicus, albinus) were randomly divided into eight groups with 10 hemimaxillae in each of the following: control; bleached (Ble, 35% hydrogen peroxide [H₂O₂]); Ble-1IRL and Ble-1RL (one IRL [808 nm, 30 s, 3 J] or RL [660 nm, 15 s, 1.5 J] application immediately after H₂O₂); Ble-3IRL and Ble-3RL (three [immediately, 24 h, and 48 h] IRL or RL applications after H₂O₂); and 3IRL and 3RL (three IRL or RL applications without bleaching). The rats were euthanized after 2 and 30 days for histological evaluation of inflammation (hematoxylin-eosin) and maturation of collagen fibers (picrosirius red). Additionally, the dentin deposition in the specimens obtained at 30 days was quantified via microtomography of the pulp chamber volume. Statistical analyses were performed (P < 0.05).

RESULTS

Initially, severe damages to the pulp were observed in the Ble and Ble-1RL groups. Ble-1IRL and Ble-3RL groups showed lower inflammation. The bleached groups had a greater amount of mature collagen fibers than the control group. The Ble-3IRL group had a greater number of immature fibers than the Ble group. At 30 days, there was an absence of inflammation and equal proportion of mature and immature collagen fibers. All bleached groups showed a reduction in the volume of the pulp chamber.

CONCLUSION

Three consecutive applications of RL and one IRL application can minimize damage to the pulp of bleached teeth, whereas three IRL applications can minimize pulp fibrosis. However, LLLT did not prevent deposition of tertiary dentin.

CLINICAL RELEVANCE

This study describes LLLT protocols capable of minimizing inflammation and maturation of collagen fibers in pulp tissue after dental bleaching. However, the protocols proved insufficient for reducing the formation of tertiary dentin in bleached teeth.