The effect of dental bleaching on pulpal tissue response in a diabetic animal model

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.

Influence of systemic antibiotic therapy on the development and progression of induced apical periodontitis in Wistar rats

The aim of this study was to investigate the influence of systemic antibiotic therapy on the development and progression of induced apical periodontitis (AP) in Wistar rats. Fifty-six rats were submitted to pulp exposure of the lower left first molar for the induction of AP. On the same day, intraperitoneal antibiotic therapy was administered once a day, for 15 days, until euthanasia. The groups were formed according to the different treatments (n = 8): C-control; GEN-treated with gentamicin (10 mg/Kg); AC-treated with amoxicillin (100 mg/Kg); MZ-treated with metronidazole (40 mg/Kg); AMP-treated with ampicillin (100 mg/Kg); AMC group-treated with amoxicillin + clavulanic acid (100 mg/kg); CLI-treated with clindamycin (60 mg/kg). After euthanasia, the jaws were collected and processed for (1) histological and histometric analysis using hematoxylin and eosin staining, (2) analysis of collagen fibers using Picrosirius Red staining and (3) bacteriological analysis using Brown-Brenn staining. The data were analyzed statistically (p < 0.05). AP induction was confirmed in all groups. The AMC group had the lower intensity of inflammatory infiltrate (p = 0.028) and less periapical bone resorption compared to control (p = 0.006). Regarding collagen maturation, PSR staining revealed a predominance of mature collagen fibers in all groups. The AC and AMC groups had the lower amount of mature fibers and the highest amount of immature fibers, compared to all other groups (p < 0.001). All groups showed bacterial contamination; however, the AC and AMC groups showed a lower extent of bacterial contamination compared to the control (p < 0.001). It can be concluded that systemic antibiotic therapy influences the development and progression of induced AP.

Effects of diabetes mellitus on dental pulp: A systematic review of in vivo and in vitro studies

OBJECTIVES

This systematic review (PROSPERO CRD42021227711) evaluated the influence of diabetes mellitus (DM) on the response of the pulp tissue and in the pulp cells behaviour.

MATERIALS AND METHODS

Searches in PubMed/MEDLINE, Embase, Web of Science and OpenGrey were performed until March 2022. Studies evaluating the effects of DM in the pulp tissue inflammation and in the cell behaviour were included, followed by risk of bias assessment (Methodological Index for Non-Randomized Studies and SYRCLE's RoB tools). The meta-analysis was unfeasible, and a narrative synthesis for each outcome was provided.

RESULTS

Of the 615 studies, 21 were eligible, mainly with in vivo analysis (16 studies). The pulp inflammation (10 studies) was analysed mainly by haematoxylin-eosin stain; DM increased pulp inflammation/degeneration in 9 studies, especially after dental procedures. The cell viability (5 studies) was analysed mostly using MTT assay; DM and glycating agents decreased cellular viability in 3 studies. DM reduced collagen in all of three studies. There were controversial results regarding mineralization; however, increased alkaline phosphatase was reported in three of four studies.

CONCLUSIONS

DM seems to increase inflammation/degeneration and mineralization in the pulp tissue while reducing cell proliferation. Further analyses in human pulp are important to provide stronger evidence.

Influence of photoactivation on tissue response to different dyes used in photodynamic therapy and laser ablation therapy

Laser ablation therapy (LA) uses Indocyanine Green dye (ICG) which efficiently absorbs laser energy and the increased temperature results in an instantaneous flame that chars tissue and microbes. Photodynamic therapy (PDT) uses different dyes that are activated by light to kill bacteria. This study evaluated the biocompatibility of the dye Curcumin (CUR), Methylene Blue (MB), and Indocyanine Green (ICG) before and after laser activation (ACT). Polyethylene tubes containing one of the dyes were implanted in the subcutaneous tissue of 32 rats (4 tubes per rat) which were divided into 8 groups: C - control (saline solution); C + ACT (Red Laser 660 nm); CUR; CUR + ACT (480 nm blue LED); MB; MB + ACT (Red Laser 660 nm); ICG; ICG + ACT (810 nm Infrared Laser). After 7 and 30 days (n = 8/time), the rats were euthanized and the tubes with the surrounding tissue were removed and processed for histological analysis of inflammation using H&E stain, and collagen fiber maturation using picrosirius red (PSR). A two-way analysis of variance statistical test was applied (p < 0.05). At 7 days, regardless of laser activation, the CUR group showed a greater inflammatory infiltrate compared to the ICG and control groups, and the MB group had a greater inflammation only in relation to the control (p < 0.05). At 30 days, CUR and MB groups showed a greater inflammatory infiltrate than the control (p < 0.05). ICG group was equal to the control in both periods, regardless of the laser activation (p > 0.05). Laser activation induced the proliferation of collagen immature fibers at 7 days, regardless of the dye (p < 0.05). The CUR group showed a lower percentage of immature and mature fibers at 7 days, compared to ICG and control (p < 0.05) and, at 30 days, compared to control (p < 0.05). Regardless of laser activation, the ICG showed the results of collagen maturation closest to the control (p > 0.05). It was concluded that all dyes are biocompatible and that laser activation did not interfere with biocompatibility. In addition, the maturity of collagen was adequate before and after the laser activation. These results demonstrate that the clinical use of dyes is safe even when activated with a laser.

The Role of Cellular Metabolism in Maintaining the Function of the Dentine-Pulp Complex: A Narrative Review

The cellular metabolic processes ensure the physiological integrity of the dentine-pulp complex. Odontoblasts and odontoblast-like cells are responsible for the defence mechanisms in the form of tertiary dentine formation. In turn, the main defence reaction of the pulp is the development of inflammation, during which the metabolic and signalling pathways of the cells are significantly altered. The selected dental procedures, such as orthodontic treatment, resin infiltration, resin restorations or dental bleaching, can impact the cellular metabolism in the dental pulp. Among systemic metabolic diseases, diabetes mellitus causes the most consequences for the cellular metabolism of the dentine-pulp complex. Similarly, ageing processes present a proven effect on the metabolic functioning of the odontoblasts and the pulp cells. In the literature, several potential metabolic mediators demonstrating anti-inflammatory properties on inflamed dental pulp are mentioned. Moreover, the pulp stem cells exhibit the regenerative potential essential for maintaining the function of the dentine-pulp complex.

Influence of ethylenediaminetetraacetic acid irrigation on the regenerative endodontic procedure in an immature rat molar model

AIM

To analyse the influence of ethylenediaminetetraacetic acid (EDTA) on the repair process in immature rat molars after a regenerative endodontic procedure (REP).

METHODOLOGY

The lower first molars of 12 4-week-old Wistar rats underwent pulpectomy in the mesial root and were divided into the following groups: sodium hypochlorite (NaOCl; n = 6) - the mesial canals were irrigated with 2.5% NaOCl for 5 min, and NaOCl-EDTA (n = 6) - the canals were irrigated with 2.5% NaOCl, followed by 17% EDTA for 5 min each. After evoking bleeding using a size 10 K-file, the cavities were sealed. Three molars on the untreated side were randomly used as control (control-15 d; n = 3), and three molars from the other three rats untreated were used as immediate control (n = 3). After 15 days (NaOCl, NaOCl-EDTA and control-15 d groups) or immediately (control-immediate), the animals were euthanized, and the teeth were subjected to histologic evaluation of tissue regeneration and presence of collagen fibres. Mann-Whitney U-test was used (p < .05).

RESULTS

The experimental groups had newly formed cementum-like tissue and increased root length and thickness. Half of the specimens in NaOCl-EDTA group showed apical foramen closure, whilst the NaOCl group had partial apical closure. The experimental groups showed inflammatory infiltrate extending mainly to the medium third of the root canal. These parameters were similar between experimental groups (p > .05). Newly formed connective tissue in the pulp space was significantly higher in the NaOCl-EDTA group than in NaOCl group (p < .05). Regarding the collagen fibres, the NaOCl-EDTA group had more collagen fibres in the root tip, but there was no significant difference compared to NaOCl group, and both groups showed greater amount of immature fibres in this area; in the centre of the apical third of root canal, there was equivalence between mature and immature fibres from both groups (p > .05).

CONCLUSIONS

Ethylenediaminetetraacetic acid irrigation improved newly formed intracanal connective tissue after REP in immature molars of rats; however, EDTA did not influence cementum-like tissue formation, apical closure, inflammatory infiltrate and maturation of collagen fibres.

Influence of supplement administration of omega-3 on the subcutaneous tissue response of endodontic sealers in Wistar rats

AIM

Natural substances such as omega-3 have been used in the medical field due to their numerous properties and, in particular, modulating effect on the systemic and local inflammatory processes. Thus, this study evaluated the influence of omega-3 supplementation on the subcutaneous tissue response of endodontic sealers in Wistar Rats.

METHODOLOGY

Polyethylene tubes were implanted in the subcutaneous tissue of 48 animals (one empty for control and three filled with Sealapex, AH Plus or Endofill). The animals were treated with omega-3 (TO) or water (TW). Treatments started 15 days before implantation until euthanasia. After 5, 15 and 30 days (n = 8), animals were euthanized and polyethylene tubes and surrounding tissue were removed and processed for histological analysis. The inflammatory reaction was analysed by Haematoxylin and Eosin stain and immunolabelling for IL-6 and TNF-α. The collagen maturity was analysed by picrosirius red stain and calcium deposition by von Kossa stain and polarized light. Results were statistically analysed (p < .05).

RESULTS

Amongst TW sealer groups, Endofill evoked a more intense inflammatory infiltrate compared with AH Plus and control in the 30-day period (p = .009). However, in TO sealer groups, there was no difference amongst the sealers and control in all periods (p > .05). Comparing each sealer as a function of the supplementation with water or omega-3, there are differences for Endofill (p = .001) and Sealapex (p = .005) in the 30-day period, presenting lower inflammatory infiltrate in the animals treated with omega-3. A higher percentage of immature fibres was observed at 15 and 30 days in the TO group, compared with the TW group (p < .05). The deposition of calcium particles was observed only by Sealapex in all periods, despite the supplementation procedure.

CONCLUSIONS

Omega-3 supplementation influence the tissue reactions of endodontic sealers, modulating inflammation, the immunolabelling of IL-6 and TNF-α, the repair process and it does not interfere with calcium deposition.

Influence of violet LED associated or not with peroxide gel on inflammation, mineralization, and collagen fiber maturation in dentin and pulp tissue

OBJECTIVES

To evaluate the influence of violet LED, associated or not with a 17.5% hydrogen peroxide (HP) bleaching gel, on inflammation, mineralization in pulp tissue, and collagen fiber maturation in dentin and pulp tissue.

MATERIALS AND METHODS

The maxillary molars of eighty Wistar rats were distributed into four groups (n = 10): CONT - without treatment; HP - 30-minute application of 17.5% HP; LED - 20-minute application of violet LED; and HP+LED - application of PH and violet LED. Rats were euthanized and jaws were processed for histologic and immunohistochemical evaluation (IL-17, IL-23, and osteocalcin) and picrosirius red immediately after (T0), and at 7 (T1), 15 (T2), and 30 days (T3) post-treatment, with Wilcoxon, Mann-Whitney, paired T-test, and T-test (α = 0.05).

RESULTS

HP and HP+LED presented necrosis and severe inflammatory infiltrate. When compared to CONT group, LED presented severe osteocalcin (OCN) immunostaining in T2 and less immature fibers in T2 and T3.

CONCLUSION

The violet LED caused no severe damage to the pulp tissue, increased IL-17 and IL-23 expression in T0 when associated with HP, and had no influence on pulp tissue mineralization, besides accelerating the maturation of collagen fibers of dentin.

CLINICAL RELEVANCE

Violet LED therapy induced no inflammation in the pulp tissue of rats and played no role in pulp tissue fibrosis, besides accelerating the maturation of dentin collagen fibers.

Effects of Remineralizing Agents Based on Calcium Phosphate, Sodium Phosphate, or Sodium Fluoride on Eroded Cervical Dentin

OBJECTIVES

To evaluate the effect of remineralizing agents on collagen matrix pattern, precipitate formation, and dentinal tubule obliteration in eroded cervical dentin.

METHODS AND MATERIALS

One hundred bovine cervical dentin specimens were previously eroded (0.6% hydrochloric acid, pH 2.3, 5 minutes) and then randomized into five groups (n=20): G1, control (without treatment); G2, Desensibilize Nano P (FGM); G3, MI Paste Plus (Recaldent); G4, Regenerate (NR-5); and G5, Desensibilize KF 2% (FGM). These treatments were applied in four sessions with 7-day intervals. During this period, the samples were subjected to an erosive challenge with orange juice (pH 3.8, 5 minutes). The specimens were analyzed by polarized light microscopy with picrosirius red staining, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX).

RESULTS

The G3 showed a higher concentration of type I collagen than G2 and G5 (p<0.05). The G3 showed greater formation of surface precipitates than that of G1 and G5 (p<0.05). In addition, G4 and G5 showed a greater number of open dentinal tubules than that of G3 (p<0.05).

CONCLUSIONS

Calcium phosphate-based remineralizing agents have shown to be a promising alternative treatment for preventing deleterious effects on the eroded dentin collagen matrix. In addition, they promoted precipitate formation and dentinal tubule obliteration on the eroded dentin.

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.

Biocompatibility, Biomineralization, and Maturation of Collagen by RTR®, Bioglass and DM Bone® Materials

This study evaluated the biocompatibility, biomineralization, and collagen fiber maturation induced by Resorbable Tissue Replacement (RTR®; β-tricalcium phosphate [TCP]), Bioglass (BIOG; bioactive glass), and DM Bone® (DMB; hydroxyapatite and β-TCP) in vivo. Sixty-four polyethylene tubes with or without (control group; CG) materials (n=8/group/period) were randomly implanted in the subcutaneous tissue of 16 male Wistar rats (four per rat), weighting 250 to 280 g. The rats were killed after 7 and 30 days (n=8), and the specimens were removed for analysis of inflammation using hematoxylin-eosin; biomineralization assay using von Kossa (VK) staining and polarized light (PL); and collagen fiber maturation using picrosirius red (PSR). Nonparametric data were statistically analyzed by Kruskal-Wallis and Dunn tests, and parametric data by one-way ANOVA test (p<0.05). At 7 days, all groups induced moderate inflammation (p>0.05). At 30 days, there was mild inflammation in the BIOG and CG, and moderate inflammation in the RTR and DMB groups, with a significant difference between the CG and RTR (p<0.05). The fibrous capsule was thick at 7 days and predominantly thin at 30 days in all groups. All materials exhibited structures that stained positively for VK and PL. Immature collagen fibers were predominant at 7 and 30 days in all groups (p>0.05), although DMB exhibited more mature fibers than BIOG at 30 days (p<0.05). RTR, BIOG, and DMB were biocompatible, inducing inflammation that reduced over time and biomineralization in the subcutaneous tissue of rats. DMB exhibited more mature collagen fibers than BIOG over a longer period.

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

Objectives

This study evaluated if the use of a bioactive glass-ceramic-based gel, named Biosilicate (BS), before, after or mixed with bleaching gel, could influence the inflammation of the dental pulp tissue of rats’ molars undergoing dental bleaching with hydrogen peroxide (H₂O₂).

Methodology

The upper molars of Wistar rats (Rattus norvegicus, albinus) were divided into Ble: bleached (35% H₂O₂, 30-min); Ble-BS: bleached and followed by BS-based gel application (20 min); BS-Ble: BS-based gel application and then bleaching; BS/7d-Ble: BS-based gel applications for 7 days and then bleaching; Ble+BS: blend of H₂O₂ with BS-based gel (1:1, 30-min); and control: placebo gel. After 2 and 30 days (n=10), the rats were euthanized for histological evaluation. The Kruskal-Wallis and Dunn statistical tests were performed (P<0.05).

Results

At 2 days, the Ble and Ble-BS groups had significant alterations in the pulp tissue, with an area of necrosis. The groups with the application of BS-based gel before H₂O₂ had moderate inflammation and partial disorganization in the occlusal third of the coronary pulp and were significantly different from the Ble in the middle and cervical thirds (P<0.05). The most favorable results were observed in the Ble+BS, which was similar to the control in all thirds of the coronary pulp (P>0.05). At 30 days, the pulp tissue was organized and the bleached groups presented tertiary dentin deposition. The Ble group had the highest deposition of tertiary dentin, followed by the Ble-BS, and both were different from control (P<0.05).

Conclusion

A single BS-based gel application beforehand or BS-based gel blended with a bleaching gel minimize the pulp damage induced by dental bleaching.

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.

Influence of Pregnancy on the Inflammatory Process Following Direct Pulp Capping: a Preliminary Study in Rats

The purpose of this study was to evaluate the inflammatory process following direct pulp capping during pregnancy. This experimental study involved 48 maxillary first molars of female Wistar rats. The procedures were performed in pregnant and non-pregnant animals (n =20 each). Direct pulp capping with mineral trioxide aggregate (MTA) and restoration with a light-cured resin composite was performed in half of exposed pulp specimens. In the other half of specimens, light-cured composite was placed directly on the exposed pulp. In the control groups (n=4 each), no intervention was performed. Animals were euthanized at 3 and 7 days. All sections (three per slide) were viewed under an optical microscope. One previously calibrated pathologist performed descriptive analysis and assigned scores for inflammatory response and tissue organization adjacent to the pulp exposure. The Kappa value for intra-examiner variability was 0.91. At 3 days, in animals treated with MTA, inflammatory infiltrate was absent in non-pregnant animals while mild inflammatory infiltrate was observed in some pregnant animals. The inflammatory response ranged from mild to severe in both groups treated with composite alone. At 7 days, the inflammatory response was more intense in pregnant than in non-pregnant animals treated with MTA; while this difference were not evident in animals treated with composite alone. In conclusion, pregnancy may not influence the inflammatory process following direct pulp capping with light-cured resin composite, which was always harmful to the pulp; while the tissue response after the direct pulp with MTA were more favorable in non-pregnant animals.

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

AIM

To investigate hydrogen peroxide (H₂ O₂ )-induced responsiveness in pulp cells using heme oxygenase-1 (HO-1) immunolabelling, Jun-D immunolabelling to study the effects of H₂ O₂ on odontoblastic differentiation and CD90+/CD73+/CD105+/CD45- cell counting for in vivo identification of mesenchymal stem cells in the pulp.

METHODOLOGY

The maxillary molars of 50 rats were treated with a bleaching gel (35% H₂ O₂ , 1 × 30 min) or placebo gel (control groups). At 2, 3, 7, 15 and 30 days after the treatment (n = 10), inflammation in pulp tissue was analysed by haematoxylin-eosin staining, HO-1- and Jun-D-immunolabelled cells were counted in each third of the pulp chamber, and the number of CD90+/CD73+/CD105+/CD45- cells was quantified by immunofluorescence. The results were assessed using the Paired t-test or Wilcoxon signed-rank test (P < 0.05).

RESULTS

Significant H₂ O₂ -induced inflammation was noted at 2 and 3 days (P < 0.05), with tertiary dentine formation occurring from 7 days. The bleached specimens had greater HO-1 immunolabelling in the middle and cervical thirds of the coronal pulp at 2 and 3 days, in all thirds at 7 days, and in the occlusal third at 15 days (P < 0.05), and significant nuclear Jun-D immunolabelling in the cervical third at 2 and 3 days and in the occlusal and middle thirds at 7 days (P < 0.05). Bleached and control groups had low numbers of CD90+/CD73+/CD105+/CD45- cells in the pulp at all periods (P > 0.05).

CONCLUSIONS

Pulp cells responded to oxidative stress by expressing HO-1 during the post-bleaching inflammation phase until the beginning of the repair phase. Jun-D expression occurred during the reduction of inflammation and the beginning of tertiary dentine production. The presence of oxidative stress did not influence the number of CD90+/CD73+/CD105+/CD45- cells identified in vivo in the dental pulp.

Bleaching gel mixed with MI Paste Plus reduces penetration of H2O2 and damage to pulp tissue and maintains bleaching effectiveness

OBJECTIVES

MI Paste Plus remineralizer (Rem) strengthens dental structures after bleaching. We investigated the effect of Rem on the penetration of hydrogen peroxide (H₂O₂), bleaching effectiveness, and pulp inflammation after bleaching.

MATERIALS AND METHODS

Bovine disks were grouped as follows (n = 10): control (untreated), bleached (Ble; 35% H₂O₂, 30 min), Ble-Rem (H₂O₂ followed by Rem, 30 min), Rem-Ble (Rem followed by H₂O₂), Rem-Ble-Rem (Rem before and after H₂O₂), and Ble+Rem (mixture of Rem with H₂O₂, 1:1, 30 min). The penetration of H₂O₂ was quantified and bleaching efficacy was analyzed. Upper rat molars (n = 10) received the same treatments at random. The rats were euthanized after two days and 30 days, and their jaws were removed for histological analysis. Statistical tests were performed (P < 0.05).

RESULTS

The bleached groups, except Ble+Rem (P > 0.05), showed significant H₂O₂ penetration compared with control (P < 0.05). Color alteration analysis showed that ΔL and ΔE were significantly higher in the bleached groups than those in control (P < 0.05); the Δb of the bleached groups differed from that of control at 24 h (P < 0.05). At two days, necrosis or inflammation was observed in the bleached groups compared with control (P < 0.05), except Ble+Rem, which was similar to control (P > 0.05). At 30 days, tertiary dentin formation was significant in the bleached groups (P < 0.05), except Ble+Rem (P > 0.05).

CONCLUSION

The mixture of MI Paste Plus and bleaching gel reduces H₂O₂ penetration and pulp damage and maintains bleaching effectiveness.

CLINICAL RELEVANCE

Because bleaching can damage dental tissues, we studied a new bleaching protocol that reduces damage to the pulp tissue while maintaining bleaching efficiency: a single application of 30 min of MI Paste Plus mixed with 35% H₂O₂ bleaching gel (1:1).

In Vivo Study of the Action of a Topical Anti-Inflammatory Drug In Rat Teeth Submitted To Dental Bleaching

Bleaching gel containing hydrogen peroxide (H2O2) cause damages in pulp tissue. This study investigated the action of a topical anti-inflammatory, the Otosporin®, in rats' bleached teeth with the null hypothesis of which the Otosporin® is no able to minimize the pulp inflammation that bleaching gel generates. The rat's molars were divided into groups: BLE: bleached (35% H2O2 concentration /single application of 30 min); BLE-O: bleached followed by Otosporin® (10 min); and control: placebo gel. In the second day after dental bleaching, the rats were killed, and the jaws were processed for hematoxylin-eosin and immunohistochemistry analysis for tumor necrosis factor alpha (TNF-α), interleukin (IL)-6 and IL-17. The data collected were subjected to Kruskal-Wallis and Dunn statistical tests with at a 5% level of significance (p<0.05). The BLE group had moderate to strong inflammation in the occlusal third of the coronary pulp, with necrotic areas; and BLE-O, mild inflammation (p<0.05). There was a significant difference in the occlusal and middle thirds of the coronary pulp between the BLE with BLE-O and control groups (p<0.05). There was no difference in the cervical third (p>0.05). The BLE group had a high immunoexpression of TNF-α than BLE-O and control groups (p<0.05), with moderate and mild immunoexpression, respectively. Regarding IL-6 and IL-17, the BLE group had higher immunoexpression than control (p<0.05); the BLE-O was similar to the control (p>0.05). The topical anti-inflammatory Otosporin® can reduce pulp inflammation after dental bleaching in the rat teeth.

Pulp response of rats submitted to bleaching and the use of different anti-inflammatory drugs

This study aimed to evaluate neuropeptide expression after bleaching treatment using histopathological and immunohistochemical analyses and the effects of hydrocortisone and acetaminophen on pulp inflammation, sine dental bleaching and inflammation first occur, and only then, the treatmentt. Sixty-three rats were divided into three groups (n = 21) according to the pain-relieving therapy used: I-control; II-topical application of Otosporin for 10 min after the bleaching treatment; III-oral administration of paracetamol 30 min before whitening and then every 12h. In all the study groups, placebo gel was applied to the left upper jaw (control) and a 35% H2O2-based whitening gel was applied to the right upper jaw for 45 min. Seven animals from each group were euthanized at different time points: 0h after treatment, 24h, and 48h. After euthanasia, the first molar on each side was analyzed by histology and immunohistochemistry to assess the degree of inflammation and verify the presence of the neuropeptides, substance P (SP) and calcitonin gene-related peptide (CGRP). The data were analyzed using the statistical nonparametric Kruskal-Wallis test followed by Dunn's test for individual comparisons. Extensive areas of necrosis were observed in the groups that received bleaching treatment only, whereas reduced damage were obtained in the group treated with Otosporin. The immunohistochemical analysis showed positive immunolabeling in all groups, including the control, but this was stronger in the groups that received bleaching treatment. The best results were obtained in the group that received treatment with Otosporin. The use of Otosporin after dental bleaching minimized the side effects of this treatment.

The presence of osteocalcin, osteopontin and reactive oxygen species-positive cells in pulp tissue after dental bleaching

AIM

To analyse the influence of H₂ O₂ on pulp repair through osteocalcin and osteopontin immunolabelling and in cellular defence by using the antireactive oxygen species (ROS) antibody.

METHODOLOGY

The maxillary molars of 50 rats were treated with 35% H₂ O₂ (Ble groups) or placebo gel (control groups). At 0 h and 2, 7, 15 and 30 days (n = 10 hemimaxillae), the rats were killed and pulp tissue was evaluated using inflammation and immunolabelling scores (osteocalcin/osteopontin); ROS-positive cells were counted. Paired t-test and Wilcoxon signed-rank test were used (P < 0.05).

RESULTS

The Ble group had necrosis in the coronal pulp at 0 h and in the occlusal third of the coronal pulp at 2 days; at 7, 15 and 30 days, no inflammation was noted similar to the controls (P > 0.05). Osteocalcin was absent in the Ble at 0 h, moderate at 2 days and increased thereafter, differing from the controls at all two periods (P < 0.05). Osteopontin was higher principally at 7 and 15 days in Ble groups, but differing with control groups from 2 days after bleaching (P < 0.05). The Ble group had more ROS-positive cells in the pulp at 7 and 15 days (P < 0.05). Tertiary dentine was observed at 7 days, increasing thereafter (P < 0.05).

CONCLUSIONS

Post-bleaching pulp repair was associated with increased osteocalcin over time. Osteopontin also participated in this process, and anti-ROS was involved in cellular defence against H₂ O₂ .

Human Dental Pulp Stem Cells Exhibit Different Biological Behaviours in Response to Commercial Bleaching Products

The purpose of this study was to evaluate the diffusion capacity and the biological effects of different bleaching products on human dental pulp stem cells (hDPSCs). The bleaching gel was applied for 90, 30 or 15 min to enamel/dentine discs that adapted in an artificial chamber. The diffusion of hydrogen peroxide (HP) was analysed by fluorometry and the diffusion products were applied to hDPSCs. Cell viability, cell migration and cell morphology assays were performed using the eluates of diffusion products. Finally, cell apoptosis and the expression of mesenchymal stem cell markers were analysed by flow cytometry. Statistical analysis was performed using analysis of variance and Kruskal⁻Wallis or Mann⁻Whitney tests (&alpha; < 0.05). Significant reductions of approximately 95% in cell viability were observed for the 3 &times; 15 min groups (p < 0.001), while 1 &times; 30 min of PerfectBleach and 1 &times; 90 min of PolaNight resulted in reductions of 50% and 60% in cell viability, respectively (p < 0.001). Similar results were obtained in the migration assay. Moreover, the 3 &times; 15 min group was associated with cell morphology alterations and reductions of >70% in cell live. Finally, hDPSCs maintained their mesenchymal phenotype in all conditions. Similar concentrations of carbamide peroxide (CP) and HP in different commercial products exhibited different biological effects on hDPSCs.

Concentration-dependent effect of bleaching agents on the immunolabelling of interleukin-6, interleukin-17 and CD5-positive cells in the dental pulp

AIM

To evaluate lymphocyte-like cell activation (CD5-positive cells) and the expression of interleukin (IL)-6 and IL-17 in the pulp after tooth bleaching with two concentrations of hydrogen peroxide (H₂ O₂ ).

METHODOLOGY

The right and left maxillary molars from 40 rats were treated randomly with bleaching gel with 20% H₂ O₂ (BLUE group, 1 application of 50 min), 35% H₂ O₂ (MAXX group, three applications of 15 min), or placebo gel (control). After 2 and 30 days, the rats were killed (n = 10), and the jaws were processed for histological and immunohistochemistry analysis of the pulp tissue. The scores of inflammation and immunolabelling (IL-6/IL-17) were submitted to Mann-Whitney and Kruskal-Wallis followed Dunn tests, respectively; anova tests were used for comparisons of number of CD5-positive cells and pulp chamber area values (P < 0.05).

RESULTS

At 2 days, 60% of specimens of the BLUE group were associated with moderate inflammation in pulp horns, and in the MAXX group with necrosis (P < 0.05). At 30 days, the pulp was organized, and tertiary dentine was formed. The MAXX group had superior immunolabelling of IL-17 at 2 days differing significantly from other groups (P < 0.05). At 2 days, 90% of the specimens of the BLUE group had moderate immunolabelling of IL-6, and 50% of the MAXX group had severe immunolabelling, both significantly different from the control (P < 0.05). There was no significant difference between the groups at 30 days (P > 0.05). CD5-positive cells were present at 2 and 30 days, particularly in the bleached groups (P < 0.05), without significant difference between time periods (P > 0.05).

CONCLUSIONS

IL-6 and IL-17 participated in inflammation in the pulp tissue of rats after tooth bleaching, particularly at 2 days. The immunolabelling was greater with increasing H₂ O₂ concentration. This process was accompanied by the prolonged activation of CD5-positive cells.

Influence of different types of light on the response of the pulp tissue in dental bleaching: a systematic review

OBJECTIVES

This systematic review (PROSPERO register: CRD42016053140) investigated the influence of different types of light on the pulp tissue during dental bleaching.

MATERIALS AND METHODS

Two independent authors conducted a systematic search and risk of bias evaluations. An electronic search was undertaken (PubMed/Medline, Embase, The Cochrane Library, and other databases) until May 2017. The population, intervention, comparison, outcomes (PICO) question was: "Does the light in dental bleaching change the response of the pulp to the bleaching procedure?" The intervention involved pulp tissue/cells after bleaching with light, while the comparison involved pulp tissue/cells after bleaching without light. The primary outcome was the inflammation/cytotoxicity observed in pulp after bleaching.

RESULTS

Out of 2210 articles found, 12 articles were included in the review; four were in vivo studies (one study in dogs/others in human), and eight were in vitro studies (cell culture/with artificial pulp chamber or not). The light source used was halogen, light-emitting diode (LED), and laser. Only one in vivo study that used heat to simulate light effects showed significant pulp inflammation. Only two in vitro studies demonstrated that light influenced cell metabolism; one using halogen light indicated negative effects, and the other using laser therapy indicated positive effects. Given that animal and in vitro studies have been identified, there remain some limitations for extrapolation to the human situation. Furthermore, different light parameters were used.

CONCLUSIONS

The effects of dental bleaching on the pulp are not influenced by different types of light, but different light parameters can influence these properties.

CLINICAL RELEVANCE

There is insufficient evidence about the influence of different types of light on inflammation/cytotoxicity of the pulp.

The effect of dental bleaching on pulpal tissue response in a diabetic animal model: a study of immunoregulatory cytokines

AIM

To evaluate the influence of tooth bleaching on immunoregulatory cytokines production (IL-6, Tumour necrosis factor (TNF)-α and IL-17) in the pulp tissue of normoglycaemic and diabetic rats.

METHODOLOGY

Twenty-eight rats were divided into normoglycaemic and diabetic rats (n = 14). Diabetes mellitus (DM) was induced with a single dose of alloxan diluted in citrate buffer via intramuscular injection. After DM confirmation, all rats were sedated and tooth bleaching was performed using 35% hydrogen peroxide on the right maxillary molars for 30 min. Left molars were used as controls. Bleaching resulted in four hemimaxillae groups: normoglycaemic (N), N-bleached (NBle), diabetic (D) and D-bleached (DBle). After 2 and 30 days, rats were euthanized and hemimaxillae processed for analysis by haematoxylin and eosin and immunohistochemistry. Results within and between animals were submitted to Wilcoxon signed-rank and Mann-Whitney tests (P < 0.05).

RESULTS

At 2 days, the NBle group had mild, and the DBle had severe inflammatory infiltration in the pulpal tissue (P < 0.05). TNF-α and IL-6 cytokines were associated with increased immunolabelling in the bleached groups compared to nonbleached (P < 0.05). However, IL-17 had increased immunolabelling in the NBle compared to the N and DBle group (P < 0.05). At 30 days, reactionary dentine was observed in the coronal pulp of all bleached teeth and no inflammation was present (P > 0.05). TNF-α cytokines had increased immunolabelling in the DBle group compared to the D group (P < 0.05). However, for IL-6 and IL-17, no difference was observed in this period (P > 0.05).

CONCLUSIONS

Tooth bleaching increased IL-6 and TNF-α in the pulp tissue regardless of diabetes mellitus; however, diabetic rats had higher TNF-α levels for longer periods. Tooth bleaching influenced the increase in IL-17 in the early periods in normoglycaemic rats.