Cultured Primary Osteoblast Viability and Apoptosis in the Presence of Root Canal Sealers

Biocompatibility of Root Canal Sealers: A Systematic Review of In Vitro and In Vivo Studies

(1) Aim: To perform a systematic review of the literature on the biocompatibility of root canal sealers that encompasses the various types of sealers that are commercially available as well as both in vitro and in vivo evidence. (2) Methods: This systematic review has been registered in PROSPERO (ID 140445) and was carried out according to PRISMA guidelines using the following databases: PubMed, Cochrane Library, ClinicalTrials.gov, Science Direct, and Web of Science Core Collection. Studies published between 2000 and 11 June 2019 that evaluated cytotoxicity (cell viability/proliferation) and biocompatibility (tissue response) of root canal sealers were included. (3) Results: From a total of 1249 studies, 73 in vitro and 21 in vivo studies were included. In general, studies suggest that root canal sealers elicit mild to severe toxic effects and that several factors may influence biocompatibility, e.g., material setting condition and time, material concentration, and type of exposure. Bioactive endodontic sealers seem to exhibit a lower toxic potential in vitro. (4) Conclusions: The available evidence shows that root canal sealers exhibit variable toxic potential at the cellular and tissue level. However, the methodological heterogeneity among studies included in this systematic review and the somewhat conflicting results do not allow a conclusion on which type of sealer presents higher biocompatibility. Further research is crucial to achieve a better understanding of the biological effects of root canal sealers.

In Vivo Comparative Evaluation of Periapical Healing in Response to a Calcium Silicate and Calcium Hydroxide Based Endodontic Sealers

BACKGROUND:

The composition of the root canal filling materials together with the apical limit of the root canal obturation affect the complete periapical healing after root canal therapy.

AIM:

This study was performed to evaluate and compare the periapical healing in response to calcium-silicate (iRoot SP) and calcium-hydroxide (Apexit) based-sealers.

MATERIAL AND METHODS:

Seventy-two upper premolars root canals of six dogs were used. The teeth were randomly assigned to four groups: Group one: roots were obturated using gutta-percha and Apexit-sealer; Group two: roots were obturated using gutta-percha&iRoot SP-sealer; Group three: the teeth were left open without obturation; Group four: where healthy teeth were used as a negative control. Teeth were evaluated after one, two and three months. The newly formed mineralised apical tissue and the periapical inflammatory infiltrate of the obtained photomicrographs were evaluated, and scorings were statistically-analysed.

RESULTS:

The mean percentage of the periapical inflammatory infiltrates and mineralisation scoring after one, two and three months evaluation period were not significantly different among the four groups (P > 0.05).

CONCLUSIONS:

Regardless of the sealer used, iRoot SP and Apexit promote healing of periapical tissues. IRoot SP sealer showed early insignificant more partial and almost full healing after two and three months.

Behaviour of co-cultured human osteoclastic and osteoblastic cells exposed to endodontic sealers' extracts

OBJECTIVES

Bone tissue is constantly being moulded and shaped by the coordinated action of bone-resorbing osteoclasts and bone-synthesizing osteoblasts. This study addresses the long-term effects of endodontic sealers' extracts (AH Plus™, GuttaFlow™, Tubliseal™, Sealapex™ and RealSeal™) on co-cultures of human osteoclastic and osteoblastic cells.

METHODS

The sealers were mixed according to the manufacturer's instructions, freshly extracted with culture medium (1.3 cm(2)/ml; 24 h; 37 °C, 5% CO2/air) and diluted (1:20-1:2,500). Co-cultures of osteoclastic and osteoblastic cells, established from precursors present in human peripheral blood mononuclear cells and bone marrow cells, respectively, were exposed to the extracts for 21 days. Co-cultures were characterized for the osteoclastic and osteoblastic response.

RESULTS

The sealers caused a dose-dependent decrease on TRAP and ALP activities, respectively, an osteoclastic and an osteoblastic marker. The resorbing ability of the osteoclastic cells and the expression of osteoclastic and osteoblastic genes were also decreased; in addition, the extracts affected several intracellular signalling pathways. Inhibition was higher during the two first weeks, followed by adaptive cell responses. Osteoblastic response was more sensitive to the extracts' toxicity and showed lower adaptive ability.

SIGNIFICANCE

A correlation to the clinical situation cannot be predicted; however, the results suggest that the sealers' eluents might disrupt the highly regulated interaction between osteoblastic and osteoclastic cells, compromising the local bone metabolism. Also, the higher susceptibility of the osteoblastic response might be particularly relevant in the initial stages of the healing of periapical lesions, due to the significant role of the bone formation events.

Attenuation of AH26-induced apoptosis by inhibition of SAPK/JNK pathway in MC-3T3 E1 cells

INTRODUCTION

The cytotoxicity of AH26, a resin-based sealer, induces apoptosis in osteoblast cells. However, the apoptosis pathway is not completely understood. This study examined the apoptosis pathway and its regulation of AH26 through mitogen-activated protein kinase (MAPKs), which may play a role in reducing the cytotoxicity of AH26.

METHODS

Using mouse osteoblasts cells (MC-3T3-E1), specimens of AH26 were eluted with the culture medium for 1, 3, 5, and 7 days. The cytotoxicity was tested using an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The induction of apoptosis was detected by Hoechst33258 staining and poly (ADP-ribose) polymerase (PARP) activation. The AH26-involved signal pathway was analyzed by immunoblotting with a specific antibody.

RESULTS

AH26 exhibited cytotoxicity toward MC-3T3-E1 cells, which resulted in mitochondria-mediated apoptosis, as confirmed by Bax expression and the displacement of cytochrome c from mitochondria to cytosol. As evidence of MAPKs activation, the cells treated with AH26 expressed stress-activated protein/c-jun N-terminal kinase (SAPK/JNK) and extracellular signal-regulated protein kinase (ERK1/2). SAPK/JNK activation appears to regulate apoptosis, whereas ERK activation protects cell survival.

CONCLUSIONS

From these results, the toxicity of AH26 can be decreased by controlling the apoptosis signals. This approach might have potential applications for reducing the long-term stress of periapical tissue that improves endodontic treatment.

Microleakage evaluation of roots filled with different obturation techniques and sealers

OBJECTIVE

The aim of this study was to compare the apical seal of the Single-cone ProTaper gutta-percha technique and the lateral compaction technique in combination with 3 sealers (AH-26, Apexit, and Sealite-Ultra).

STUDY DESIGN

Seventy extracted single-root teeth were used. Root canals were prepared with ProTaper rotary instruments. Six groups were formed: (I) Single-cone ProTaper gutta-percha with AH-26; (II) lateral compaction technique with AH-26; (III) Single-cone ProTaper gutta-percha with Apexit; (IV) lateral compaction technique with Apexit; (V) Single-cone ProTaper gutta-percha with Sealite-Ultra; and (VI) lateral compaction technique with Sealite-Ultra. The fluid conductance of each specimen was measured after the 7th and 30th days using a fluid filtration method.

RESULTS

When lateral compaction was performed, all sealers showed similar levels of leakage (P > .05). Using the single-cone technique, Sealite-Ultra showed more leakage than the others (P < .05). Comparing filling techniques, there was a significant difference only in the Sealite-Ultra groups (P < .05).

CONCLUSION

Single-cone ProTaper gutta-percha and lateral compaction techniques showed similar sealing effect.

New Portland cement-based materials for endodontics mixed with articaine solution: a study of cellular response

The biocompatibility of innovative tetrasilicate cements proposed for root-end filling restorations was tested. White ProRoot-MTA and AH Plus were used as control. The new cements were mixed with a local anesthetic solution (4% articaine) to form a paste. Human osteoblast-like cells Saos-2 were challenged in short-term cultures (72 hours) with solid materials and with material extracts prepared in culture medium. Cell growth and viability, cellular attachment, and morphologic features were assessed to verify cell/material interactions. No acute toxicity was exerted by the experimental cements in the assay systems. On solid samples Saos-2 adhered and proliferated on all the experimental cements and on MTA. The ultrastructural findings revealed that Saos-2 were able to adhere and to spread. The maintenance of the osteoblastic phenotype on the innovative cements was confirmed by the alkaline phosphatase assay. All experimental cements prepared with articaine supported the growth of bone-like cells, showing suitable properties to be used as canal sealers and root-end filling materials.

Self-setting properties and in vitro bioactivity of calcium sulfate hemihydrate-tricalcium silicate composite bone cements

Self-setting biomaterials are widely used for tissue repair and regeneration. Calcium sulfate hemihydrate has been used for many years as a self-setting biomaterial due to its good setting properties. However, too fast a degradation rate and lack of bioactivity have limited its application in orthopaedic field. Herein, tricalcium silicate was introduced into calcium sulfate hemihydrate (CaSO(4).1/2H(2)O) to form a calcium sulfate hemihydrate-based composite, and its behavior as a cement was studied in comparison with pure calcium sulfate hemihydrate. The results indicated that the workability and setting time of the composite pastes are higher than those of pure CaSO(4).1/2H(2)O, and the composite pastes showed much better short- and long-term mechanical properties than those of pure CaSO(4).1/2H(2)O. Moreover, the biphasic specimens showed significantly improved bioactivity and degradability compared with those of pure CaSO(4).1/2H(2)O, indicating that the composite cements might have a significant clinical advantage over the traditional CaSO(4).1/2H(2)O cement.

Mechanisms of root canal sealers cytotoxicity on osteoblastic cell line MC3T3-E1

OBJECTIVE

The cytotoxic mechanisms of root canal sealers (Sealapex, AH26, and N2 Universal) were studied in vitro with MC3T3-E1 osteoblastic cells.

STUDY DESIGN

MC3T3-E1 cells were cotreated with root canal sealers and antioxidants, and concentrations of intracellular glutathione (GSH) and reactive oxygen species (ROS) were measured. DNA fragmentation was observed after treatment with the sealers.

RESULTS

N-Acetylcysteine (NAC) prevented N2 Universal- and AH26-induced cytotoxicities. However, ascorbic acid and Trolox did not affect the cytotoxicity of the sealers. N2 Universal and AH26 significantly decreased the GSH pool within a 3-hour treatment period. Unlike GSH levels, the ROS levels were not altered by the sealers. Cytotoxicity of Sealapex was not affected by NAC, and there were no changes of GSH/glutathione disulfide levels in cells treated with Sealapex.

CONCLUSION

Cytotoxicities of N2 Universal and AH26 are caused by an intracellular GSH depletion without a burst of ROS. Sealapex may cause cytotoxicity in a way different from N2 Universal and AH26.

Cytotoxicity of new resin-, calcium hydroxide- and silicone-based root canal sealers on fibroblasts derived from human gingiva and L929 cell lines

AIM

To assess ex vivo the cytotoxic effects of five new root canal sealers (RC Sealer, Epiphany, EndoREZ, GuttaFlow and Acroseal) and three existing products (AH Plus, RoekoSeal and Apexit) using primary human gingival fibroblasts (HGF) and a mouse fibroblast cell line, L929.

METHODOLOGY

Eight samples of each sealer were fabricated in sterile cylindrical Teflon blocks, 4.4 mm diameter and 2 mm height and then divided into two groups, fresh and aged specimens. Extraction of fresh specimens was carried out after setting whilst aged specimens were placed in Petri dishes and kept in a humid chamber at 37 degrees C for 7 days before extraction in cell culture medium using the ratio 1.25 cm(2) mL(-1). Undiluted eluates were used for the dimethylthiazol diphenyltetrazolium bromide (MTT) assay with HGF and L-929. Morphology of HGF cells was also examined by an inverted microscope using undiluted eluates of the sealers. The results were analysed using a two-tailed t-test (alpha = 0.05) between groups.

RESULTS

Resin-based (Epiphany and EndoREZ) and calcium hydroxide-based (Apexit and Acroseal) sealers were significantly more cytotoxic than other sealers (P<0.05). However, L929 cells were more sensitive to Apexit and EndoREZ than HGF cells. RC Sealer showed mild cytotoxicity to HGF at both setting times. AH Plus did not exert any cytotoxic effect to HGF and aged specimens appeared to induce cellular proliferation. RoekoSeal and GuttaFlow also demonstrated mild cytotoxicity. GuttaFlow was slightly more cytotoxic to both cultures, especially when tested fresh.

CONCLUSIONS

Toxicity varied but RC Sealer and GuttaFlow were the least toxic new sealers.

An FTIR Study of the Setting Reaction of Various Endodontic Sealers

The aim of the present study was to investigate the correlation between setting time and setting conversion in endodontic sealers. The sealers tested were Roth's 811, Endion, Sealapex, and AH-26 Silverfree. The setting time was recorded according to International Standardization Organization 6876 specification, whereas the setting conversion was monitored by micro-multiple internal reflection Fourier transform infrared spectroscopy immediately after mixing, before the setting time, at the setting time, and after the setting time. In Roth's 811, which showed the longest setting time, all free eugenol was consumed at the setting time. The setting conversion of Endion, Sealapex, and AH-26 Silverfree continued after the setting time. No correlation was found between setting time and setting conversion because of the different setting mechanisms involved in the materials tested.

The Influence of Root Canal Sealer on Extended Intracanal Survival of Enterococcus faecalis With and Without Gelatinase Production Ability in Obturated Root Canals

Enterococcus faecalis can survive for extended periods in obturated root canals. In this study, the hypotheses tested were that long-term survival of E. faecalis is dependent on (1) the type of endodontic sealer and (2) the capacity for microbial gelatinase activity, a potential "virulence" trait identified previously in clinical isolates. Root canals of extracted human canines (n=95) were inoculated with either E. faecalis OG1RF or its gelatinase-negative mutant E. faecalis TX5128. After 48 hours of incubation at 37 degrees C, canals were obturated with gutta-percha and either the epoxy-resin-based AH-Plus (Dentsply, De Trey, Konstanz, Germany), the silicone-based RoekoSeal (Coltène/Whaledent, Langenau, Germany), or zinc oxide eugenol-based Roth's sealer (Root Canal Cement Type 801; Roth International Ltd, Chicago, IL). Access cavities were sealed. After 8 months of incubation at 37 degrees C, viable E. faecalis was recovered from more teeth sealed with RoekoSeal (95%) compared with AH-Plus (40%) (p=0.0004, Fisher's exact test) and Roth's sealer (45%) (p=0.0012, Fisher's exact test). In the RoekoSeal groups, viable counts of E. faecalis OG1RF were higher than E. faecalis TX5128 (p=0.03, Mann-Whitney U test) suggesting that gelatinase activity plays a role in long-term survival of E. faecalis in obturated root canals.

Initial In Vitro Biological Response to Contemporary Endodontic Sealers

The objective of this study was to evaluate the cytotoxicity of three endodontic sealers (AH Plus/Maillefer-Dentsply, Epiphany/Pentron, GuttaFlow, Coltene-Whaledent). Materials were mixed according to the manufacturer instructions and packed into Teflon molds (10 x 1 mm). For cytotoxicity testing (MTT method), the specimens were placed in contact with cultured cells, then evaluated at two subsequent time points (24 or 72 h). In addition to testing the mixed materials, 5 microl of primer liquid (GuttaFlow and Epiphany) and resin solvents (HEMA, ethanol, sterile water, or acetone) were added directly in culture for 24 and 72 h. The results showed that most materials pose significant cytotoxic risks and that cytotoxicity generally increased with time. At 72 h, GuttaFlow became significantly less toxic than AH Plus, Epiphany sealer, and Resilon. The current results support the need to continue to develop better endodontic sealers that combine the excellent sealing and bonding properties of resins with acceptable biological properties for endodontic applications.

Biologic perspectives to support clinical choices in root canal treatment

Some of the most keenly debated issues in endodontics have revolved around the where to end the root filling, as well as cleaning and shaping and obturation techniques. In some respects, original scientifically-based concepts have been abandoned in favour of clinical techniques that may provide aesthetically pleasing radiographs, but do not necessarily support tissue regeneration around the root apex following obturation. Recently advocated obturation techniques supporting the use of resin-based and bonded materials have not had the same extensive evaluation that gutta-percha, when in contact with the periradicular tissues, has had. Further studies are necessary so that evidence-based data can support the confident use of these innovative materials.