Recent considerations in regenerative endodontic treatment approaches

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.

The effect of intracanal medication variations on microhardness of simulated immature root dentin

The effect of different medicaments and irrigation solutions on root dentin microhardness (MH) was evaluated depending on time. After initial measurements, MH of 60 maxillary incisors (n = 15 per group) was measured after 3 steps: irrigation with 2.5% sodium hypochlorite, exposure to medicaments [triple antibiotic (TAP) or calcium hydroxide (CH) pastes, 1 week or 1 month)] and final irrigation [20 mL of 17% EDTA or 20 mL 1% phytic acid (PA)]. The percentage of MH reduction was calculated. Data were analysed statistically at P < 0.05. Treatments caused a significant decrease in MH values compared to baseline and pre-measurements (P < 0.05). TAP significantly reduced the MH values of the samples over time (P < 0.05). Removal of TAP after 1 month with PA resulted in a significant reduction in MH compared to removing TAP after 1 week and CH removing after 1 month (P < 0.05). Considering the chemical preparation steps, the most hazardous effect on MH was observed after the first irrigation.

Effect of ethylenediaminetetraacetic acid irrigation on immune-inflammatory response in teeth submitted to regenerative endodontic therapy

AIM

To analyse longitudinally the immune-inflammatory response in teeth of mice that underwent a regenerative protocol with or without the use of ethylenediaminetetraacetic acid (EDTA) to irrigate the root canal system.

METHODOLOGY

First maxillary molars of mice were devitalized using size 10 and 15 files. Teeth were divided into the following groups: Empty - the canals were left empty; Blood Clot (BC) - the canals were filled with a blood clot; and EDTA + Blood - the canals were irrigated with 0.06 mL of 17% EDTA for 1 min and filled with a blood clot. Access cavities were restored with Coltosol^® . Animals were sacrificed at 7, 14 or 21 days after the operative procedures, and teeth were collected. RNA was extracted, mRNA expression of the cytokines IGF, NGF, IL-1α, IL-10, TGF and VEGF was assessed using real-time PCR, and the anova Kruskal-Wallis test was used.

RESULTS

IL-1 mRNA expression was significantly higher in the EDTA + BC group than in the Empty and BC groups at the 7th and 14th days of evaluation (P < 0.05). IL-10 mRNA expression was similar across the three groups at all time periods. TGF-β mRNA expression in the EDTA + BC group was significantly higher on the 7th and 21st days than on the 14th (P < 0.05); at day 21, TGF-β mRNA expression was similar between the BC and EDTA + BC groups but significantly higher than in the Empty group (P < 0.05). IGF mRNA expression was significantly higher in the EDTA + BC group than in the other groups at all time periods. VEGF mRNA expression remained unchanged throughout the experimental period in all groups (P > 0.05). NGF mRNA expression was similar amongst all groups at the 7th and 21st days (P > 0.05). At the 14th day, however, there was a significant increase in NGF mRNA expression in the EDTA + Blood group (P < 0.05) when compared with the expression in the other groups.

CONCLUSION

EDTA promoted increased expression of factors that have the potential to improve the outcome of regenerative endodontic treatment.

Regenerative Endodontic Procedures Using Contemporary Endodontic Materials

Calcium hydroxide apexification and Mineral Trioxide Aggregate (MTA) apexification are classical treatments for necrotic immature permanent teeth. The first tend to fail for lack of compliance given the high number of sessions needed; the second has technical difficulties such as material manipulation and overfilling. With both techniques, the root development is interrupted leaving the tooth with a fragile root structure, a poor crown-to-root ratio, periodontal breakdown, and high risk of fracture, compromising long-term prognosis of the tooth. New scientific literature has described a procedure that allows complete root development of these specific teeth. This regenerative endodontic procedure (REP) proposes the use of a combination of antimicrobials and irrigants, no canal walls instrumentation, induced apical bleeding to form a blood clot and a tight seal into the root canal to promote healing. MTA is the most used material to perform this seal, but updated guidelines advise the use of other bioactive endodontic cements that incorporate calcium and silicate in their compositions. They share most of their characteristics with MTA but claim to have fewer drawbacks with regards to manipulation and aesthetics. The purpose of the present article is to review pertinent literature and to describe the clinical procedures protocol with its variations, and their clinical application.

The role of stem cell therapy in regeneration of dentine-pulp complex: a systematic review

Infection of the dental pulp will result in inflammation and eventually tissue necrosis which is treated conventionally by pulpectomy and root canal treatment. Advances in regenerative medicine and tissue engineering along with the introduction of new sources of stem cells have led to the possibility of pulp tissue regeneration. This systematic review analyzes animal studies published since 2010 to determine the ability of stem cell therapy to regenerate the dentine-pulp complex (DPC) and the success of clinical protocols. In vitro and human clinical studies are excluded and only the experimental studies on animal models were included. Dental pulp stem cells constitute the most commonly used cell type. The majority of stem cells are incorporated into various types of scaffold and implanted into root canals. Some of the studies combine growth factors with stem cells in an attempt to improve the outcome. Studies of ectopic transplantation using small animal models are simple and non-systematic evaluation techniques. Stem cell concentrations have not been so far reported; therefore, the translational value of such animal studies remains questionable. Though all types of stem cells appear capable of regenerating a dentine-pulp complex, still several factors have been considered in selecting the cell type. Co-administrative factors are essential for inducing the systemic migration of stem cells, and their vascularization and differentiation into odontoblast-like cells. Scaffolds provide a biodegradable structure able to control the release of growth factors. To identify problems and reduce costs, novel strategies should be initially tested in subcutaneous or renal capsule implantation followed by root canal models to confirm results.