The effect of newly developed root canal sealers on rat dental pulp cells in primary culture

Cytotoxicity, Biocompatibility, and Calcium Deposition Capacity of 45S5 Bioglass Experimental Paste and Bio-C Temp: In Vitro and In Vivo Study Using Wistar Rats

The evolution of biomaterials engineering allowed for the development of products that improve outcomes in the medical-dental field. Bioglasses have demonstrated the ability to either compose or replace different materials in dentistry. This study evaluated the cytotoxicity, biocompatibility, calcium deposition, and collagen maturation of 45S5 bioglass experimental paste and Bio-C Temp, compared to calcium hydroxide (Ca(OH)2) paste. The 45S5 bioglass and Ca(OH)2 powder were mixed with distilled water (ratio 2:1); Bio-C Temp is ready-for-use. Dental pulp cells were exposed to the materials' extracts (1:2 and 1:4 dilutions; 24, 48, and 72 h) for MTT and live/dead analyses. Polyethylene tubes filled with the pastes, or left empty (control), were implanted on the dorsum of 16 rats. After 7 and 30 days (n = 8/period), the rats were euthanized and the specimens were processed for hematoxylin-eosin (H&E), von Kossa (vK), and picrosirius red (PSR) staining, or without staining for polarized light (PL) birefringence analysis. A statistical analysis was applied (p < 0.05). There was no difference in cell viability among Ca(OH)2, 45S5 bioglass, and the control, across all periods and dilutions (p > 0.05), while Bio-C Temp was cytotoxic in all periods and dilutions compared to the control (p < 0.05). Regarding biocompatibility, there was a reduction in inflammation from 7 to 30 days for all groups, without significant differences among the groups for any period (p > 0.05). The fibrous capsules were thick for all groups at 7 days and thin at 30 days. All materials showed positive structures for vK and PL analysis. At 7 days, the control and 45S5 bioglass showed more immature collagen than the other groups (p < 0.05); at 30 days, 45S5 bioglass had more immature than mature collagen, different from the other groups (p < 0.05). In conclusion, Bio-C Temp presented cytotoxicity compared to the other materials, but the three pastes showed biocompatibility and induced calcium deposition. Additionally, the bioglass paste allowed for marked and continuous collagen proliferation. This study contributed to the development of new biomaterials and highlighted different methodologies for understanding the characteristics of medical-dental materials.

Evaluation of apical microleakage of teeth sealed with four different root canal sealers

Objectives:

to compare the apical sealing ability of four root canal sealers. Materials and methods: forty extracted human maxillary canines were instrumented 1 mm short of the anatomical apex and randomly assigned to four groups (n=10), according to the root canal sealer used for obturation: Endofill, AH Plus, EndoREZ and Epiphany. Root canals were obturated with guttapercha points, except for the Epiphany group, in which resin points (Resilon) were used. The teeth were immersed in India ink for seven days and clarified using methyl salicylate. The extent of apical dye penetration was measured with a measuroscope in all aspects of the canal.

Results:

AH Plus (0.02 mm ± 0.07), Epiphany (0.00 mm ± 0.00) and EndoREZ (0.32 mm ± 0.62) did not differ statistically to each other (p>0.01). EndoFill presented the highest dye penetration mean (0.83 mm ± 0.73) and was statistically different from the other sealers (p<0.01).

Conclusions:

the resin-based root canal sealers presented lesser apical microleakage than the zinc oxide and eugenol based sealer. No statistical differences were observed among resin based sealers.

Cytotoxicity of a New Root Canal Filling Material on Human Gingival Fibroblasts

This study evaluated the cytotoxicity of the root canal sealing materials Resilon and Epiphany versus gutta-percha, Grossman's sealer, Thermaseal, and Sealapex. Using human gingival fibroblasts the fibroblasts cultures were incubated for either 1 or 24 h to test the cytotoxicity after freshly mixing or after 24 h of setting. Fibroblasts were then stained with trypan blue, to determine number of dead cells. Data were analyzed using ANOVA and t tests. Resilon was similar to gutta-percha and the control. Epiphany was less cytotoxic than Grossman's sealer at both the 1 and 24 h time periods. Epiphany was more cytotoxic than Sealapex at the 1-h time period but less cytotoxic at the 24 h time period. These results indicated that Resilon had a lower cytotoxicity and that Epiphany was more cytotoxic than conventional materials.

Comparison of the Intraosseous Biocompatibility of AH Plus, EndoREZ, and Epiphany Root Canal Sealers

To evaluate the intraosseous biocompatibility of AH Plus, EndoREZ, and Epiphany root canal sealers as recommended by the Technical Report #9 of the Fédération Dentaire Internationale (FDI). Thirty guinea pigs, 10 for each material, divided into experimental periods of 4 and 12 weeks, received one implant on each side of the lower jaw symphysis. At the end of the observation periods, the animals were killed and the specimens prepared for routine histological examination. After analyzing both periods, the inflammatory tissue reaction to EndoREZ was considered severe. In the AH Plus group, the reaction changed from severe to moderate, while it was observed biological compatibility to Epiphany with bone formation and none to slight inflammatory reaction. It was concluded that Epiphany root canal sealer was the only material that presented intraosseous biocompatibility within the two analyzed periods.

Evaluation of cytotoxicity of two endodontic cements in a macrophage culture

Compared to gutta-percha, the endodontic cements are used in small quantity to seal root canals, but are indispensable to achieve hermetically sealed margins, where its biocompatibility depends on the sum of responses of each cell present in the periapical region. The object of this study was to evaluate the cytotoxicity of two endodontic cements, one based on epoxy resin (Sealer 26) and the other containing zinc oxide eugenol (Endofill) by using cultured peritoneal macrophages from Swiss mice to measure the induced production of nitric oxide. After solidification and pulverization, aliquots of 100mul of suspension containing 18mg/mL of the respective cements were added to 96-well tissue culture plates containing the tissue culture of macrophages at a concentration of 5.0X10(6) cells/ml. In the positive control group the cell culture was treated with 10mg/mL of lipopolyssaccharide from Escherichia coli 026:B6 and the cell culture alone represented the negative control. After 48 hours of incubation, at 37ºC, in 5% CO2, the cultures were placed in an ELISA automatic reader to evaluate the release of nitric oxide. The production of nitric oxide for cement Sealer 26 was between 36.1 and 313.0 mumols, with a mean of 143.82±111.03mumols, while for the Endofill these values were significantly less (p=0.01), varying from 50.8 to 125.7mumols, with a mean of 80.33±28.42 mumols. In the positive and negative control groups the mean release of nitric oxide was of 162.75mumols and 4.42mumols, respectively. There was no significant difference between the positive control group and cement Sealer 26 (p>0.05). Therefore, the cement Sealer 26 caused significantly greater toxicity to the macrophages, possibly due to the components from the epoxy resin and formaldehyde release during polymerization.

The cytotoxicity of RoekoSeal and AH plus compared during different setting periods

The aim of this study was to evaluate the cytotoxicity of the root canal sealers RoekoSeal Automix (RSA) and AH Plus in vitro on human cervical carcinoma (HeLa) cells and mouse skin fibroblasts (L929). The sealers were covered with a 3 x 10(4) cell suspension 1 h, 24 h, 48 h, 7 days and 1 month after mixing. Four samples and respective controls without sealer were prepared. After 5 days of incubation, the number of cells was determined using an electronic counter; the number of viable cells was determined under light microscopy following the addition of nigrosin dye. The experiment was repeated twice for each sealer and each period. AH Plus was significantly more cytotoxic after 1 h, 24 h, and 48 h, compared to the 7 day and 1 month setting period on both cell lines. RoekoSeal had no cytotoxic effect on either cell line at any setting time.

A comparison of the in vitro cytotoxicity of two root canal sealers

The purpose of this study was to compare the cytotoxicity of an epoxy resin-based sealer (AH Plus) and a silicone-based sealer (Roeko Seal Automix, RSA). Cytotoxicity was assessed using the MTT assay for mitochondrial enzyme activity and haemocytometer viable cell counting after 24, 48 and 72-h exposure to L929 cells. AH Plus and RSA showed no statistically significant difference in the degree of toxicity. Both sealers had a low toxic influence on the cells during the experimental period. This study indicates that epoxy resin-based sealer AH Plus and the silicone-based sealer RSA have similar levels of cytotoxicity to mouse fibroblasts.

Biocompatibility of dental materials used in contemporary endodontic therapy: a review. Part 1. Intracanal drugs and substances

Irrigation solutions and intracanal medicaments are used within the root canal to clean and aid in disinfecting the dentinal walls. Although these materials are intended to be contained within the root canal, they invariably contact the periapical tissues, either through inadvertent extrusion through the apex or leaching. This paper is a review on the methodology involved in biocompatibility testing followed by a discussion on biocompatibility of contemporary intracanal drugs and substances used in endodontics.

The hemolytic and cytotoxic properties of a zeolite-containing root filling material in vitro

OBJECTIVE

This in vitro study characterized the hemolysis and cytotoxicity of ZUT, an experimental glass ionomer cement (GIC) sealer with an added antimicrobial-containing zeolite (0.2% Zeomic w/w).

STUDY DESIGN

ZUT, Ketac-Cem (GIC component of ZUT), Ketac-Endo, and two AH 26 sealer formulations were tested at various times after mixing. Hemolysis produced by standardized specimens was determined spectrophotometrically (n = 6/material). Cytotoxicity was assessed by using a Millipore Filter test with a HeLa cell monolayer (n = 10/material). Tests were repeated, and results were analyzed with a one-way analysis of variance (alpha = .05).

RESULTS

Disks of AH 26 containing silver produced the most hemolysis of all test groups (P < .0001). Compared to controls, GICs and AH 26 formulations were noncytotoxic at 1 and 6 hours after mixing, respectively (P > .05). Addition of Zeomic did not increase the cytotoxic and hemolytic activity of Ketac-Cem (P > .05).

CONCLUSION

Overall results suggest ZUT is less cytotoxic than AH 26 and possesses characteristics similar to the other GIC formulations tested.

The cellular compatibility of five endodontic sealers during the setting period

The purpose of this study was to evaluate the cellular compatibility of five endodontic sealers in the first 24 h after mixing. Specimens of N2, Endomethasone, Apexit, AH Plus, and Ketac Endo were extracted with cell culture medium 0, 1, 5, and 24 h after mixing. Eluates were tested for cytotoxicity with immortal 3T3 cells and primary human periodontal ligament fibroblasts using XTT-assays. Data were analyzed for statistically significant differences by means of Dunnett's t tests (p < 0.05). All extracts of N2 completely inhibited cell metabolism (p < 0.05). Similar effects were provoked by the first three eluates of Endomethasone, but the 24-h extract irritated cells significantly less (p < 0.05). Severe cytotoxicity was also observed with all Ketac Endo extracts (p < 0.05). A significant inhibition of mitochondrial activity was induced by the first (3T3) or the first and second eluate (periodontal ligament fibroblasts) of AH Plus (p < 0.05). The subsequent eluates of this sealer and all extracts of Apexit did not reveal any cytotoxic potency.

Cytotoxicity of resin-, zinc oxide-eugenol-, and calcium hydroxide-based root canal sealers on human periodontal ligament cells and permanent V79 cells

AIM

The purpose of this study was to determine the cytotoxicity of three different types of root canal sealer on human periodontal ligament (PDL) cells and a permanent hamster cell line (V79 cells).

METHODOLOGY

Set specimens from two resin based sealers (AH26 and AHPlus), three zinc oxide-eugenol-based sealers (Canals, Endomethasone and N2) and one calcium hydroxide-based sealer (Sealapex) were eluted with culture medium for 1, 2, 3 and 7 days. Cytotoxicity was judged using tetrazolium bromide reduction assay on human primary PDL cells and V79 cells derived from a Chinese hamster.

RESULTS

The results showed that elutes from resin-based, zinc oxide-eugenol-based, and calcium hydroxide-based sealers were cytotoxic to primary human PDL cultures and V79 cells. Calcium hydroxide-based sealer was the least toxic sealer amongst the chemicals tested in both cultures. The cytotoxic response decreased in an order of N2 > Endomethasone > AH26 > AHplus > Canals > Sealapex.

CONCLUSIONS

The sensitivity of toxicity depended on the materials tested and the cell culture system used. Thus, the use of both permanent and primary cells is recommended for screening of the cytotoxic effects of root canal sealers. In addition, the results confirmed that root canal sealers constantly dissolve when exposed to an aqueous environment for extended periods, possibly causing moderate or severe cytotoxic reactions. Use of calcium hydroxide-based material as a root canal sealer initially may result in a more favourable response to periradicular tissues.

Cytotoxic evaluation of root canal filling materials on primary human oral fibroblast cultures and a permanent hamster cell line

To date there has been very little data on the cytotoxic response of different cell lines to root canal sealers. The objective of this study was to determine the cytocompatibility of three different extracts of root canal sealers and to compare the cytotoxic response of these materials on two different primary human oral fibroblasts (derived from gingiva and buccal mucosa) and one permanent hamster cell line (V79 cells). Cytotoxicity was judged using an assay of tetrazolium bromide reduction. The results showed that root canal sealers (AH plus, Canals, and N2) were cytotoxic to primary human oral fibroblast cultures and V79 cells. It was found that N2 was the most toxic root canal sealer among those tested in all cultures. The toxicity decreased in an order of N2 > AH plus approximately = Canals. The sensitivity of toxicity depended on the materials tested and the cell culture system used.

Biocompatibility of root canal filling materials

Results of in vitro and in vivo studies clearly indicate that some endodontic sealers may cause local and systemic adverse effects. Though occasionally contradictory data has been reported from various authors, it may be concluded that zinc-oxide-eugenol sealers possess a marked cytotoxic and tissue-irritating potency. Most Ca(OH)2-based materials, however, were biocompatible. Genotoxic effects have been observed with sealers releasing paraformaldehyde or containing mutagenic substances, such as bisphenol-A-diglycidyl-ether or its derivatives. It cannot be excluded that these materials may pose a systemic risk because formaldehyde is rapidly distributed systemically following its application into the pulp cavity. Furthermore an increasing number of cases with an aspergillosis of the maxillary sinus have been observed which were mainly caused by zinc-releasing endodontic sealers. Overall, it is recommended that for endodontic practice, sealers that have been found to be biocompatible in a "mixed bag" of various in vitro and in vivo tests, be selected. From this point of view, ZnOE-sealers should no longer be used for root canal fillings. This recommendation applies also to sealers containing paraformaldehyde or generating this substance during their setting reaction. More experimental and clinical studies are necessary to elucidate whether new materials, such as mineral trioxide aggregate (MTA) or calcium phosphate cement, will be biocompatible alternatives in the future.

Root canal sealers cause cytotoxicity and oxidative damage in hepatocytes

Elutable substances and degradation products from root canal sealers may gain access to periodontal tissue in many ways. The aim of this study was to investigate damage and oxidative stress caused by treatment with root canal sealers in primary cultured rat hepatocytes. Four root canal sealers were used: Canals, Sealapex, AH 26, and AH Plus. Toxicity was detected by assessing lactate dehydrogenase (LDH) leakage, and oxidative stress was determined by analysis of glutathione (GSH) levels. One-way analysis of variance was performed on the data. As the concentrations of sealer were increased, LDH leakage increased (p < 0.01). Increased GSH depletion accompanied LDH leakage increase. GSH levels were reduced to zero at a concentration of 0.05% for Canals and 0.10% for AH 26. These results confirmed the hypothesis that root canal sealers can cause cytotoxicity in hepatocytes. The Canals and AH 26 sealers can also cause oxidative stress in hepatocytes.

Lactate dehydrogenase leakage of hepatocytes with AH26 and AH Plus sealer treatments

Numerous root canals filling materials are available in the field of dentistry, based on various formulas that contain a variety of different and partly mutagenic components, such as epoxy resin sealers, Ca(OH)2-based materials, and zinc oxide-eugenol cements. AH Plus root canal sealer will not release formaldehyde according to the manufacturer, although AH26 does. The purpose of this study was to analyze the leakage of lactate dehydrogenase (LDH) from rat hepatocytes after treatment with AH26 and AH Plus root canal sealers in vitro. Hepatocytes from male Sprague-Dawley rats were used to test the cytotoxicity of AH26 and AH Plus. The root canal sealers were mixed and then dissolved in the dimethyl sulfoxide to final concentrations of 0.01%, 0.04%, and 0.1% (wt/vol), with a dimethyl sulfoxide concentration of < 0.05%. Dosage-dependent and time-dependent lactate dehydrogenase leakage values were measured and tested by one-way ANOVA. The results showed that both AH26 and AH Plus are toxic to rat hepatocytes. At a low concentration, AH26 had a higher toxicity than AH Plus to rat hepatocytes.

Evaluation of cell culture cytotoxicity of five root canal sealers

The cytotoxicity of four calcium hydroxide-based root canal sealers (Sealapex, CRCS, Apexit, and Sealer 26) and one zinc oxide-eugenol-based sealer (Fill Canal) was evaluated microscopically for morphological changes in rat peritoneal macrophages. The least cytotoxic sealer was Fill Canal, followed in increasing order of cytotoxicity by CRCS, Sealer 26, Apexit, and Sealapex.

Calcium hydroxide pastes: classification and clinical indications

REVIEW ARTICLE: Calcium hydroxide has been used in endodontology for many years. The aim of this paper is to review the various formulations of calcium hydroxide that have been described, with specific reference to the vehicle used to carry the compound. The requirements for a vehicle are described, and ex vivo and in vivo studies reviewed. Vehicles can be classified into aqueous, viscous and oily, the clinical properties of calcium hydroxide changing depending on the vehicle. The review also describes the use of various active components that have been added to calcium hydroxide, including antimicrobial and anti-inflammatory agents. This review will help clinicians to make informed judgements about which formulations of calcium hydroxide should be used for specific endodontic procedures.

Tissue response to an epoxy resin-based root canal sealer

The objective of the present study was to evaluate two different types of root canal sealers: AH Plus (an epoxy resin-based sealer) and Fill Canal (a zinc oxide-eugenol based sealer). A total of 34 root canals with vital pulp from dogs' premolars were used. After instrumentation, the root canals were filled with gutta-percha and AH Plus or gutta-percha and Fill Canal sealers using a classical technique of lateral condensation. After histological processing, the sections were stained with hematoxylineosin or Mallory's trichrome stain. Inflammatory cells or areas of necrosis were not associated with AH Plus. Hard tissue formation apically to the material was observed in 14 specimens. The Fill Canal sealer presented an inflammatory response of moderate intensity in the periapical region, mainly adjacent to the material.

Cytotoxicity of three resin-based root canal sealers: an in vitro evaluation

The cytotoxicity of three resin-based root canal sealers (AH26, AH-Plus, Topseal) was evaluated in vitro. The experiments included two cell lines, L929 mouse skin fibroblasts and RPC-C2A rat pulp cells. The cytotoxicity was assessed by sulforodamine B (SRB) colorimetric assay and hemocytometer viable cell counting after 24- and 48-h exposure. AH26 had a severe cytotoxic effect whilst Topseal and AH-Plus showed a markedly lower toxic influence on the cells during the experimental period.

Cytotoxicity of four root canal sealers in permanent 3T3 cells and primary human periodontal ligament fibroblast cultures

OBJECTIVES

The purposes of this study were to determine the cytocompatibility of four endodontic sealers and gutta-percha using various extracts and to compare the cellular injuries resulting from these materials in permanent 3T3 monolayers and primary human periodontal ligament fibroblasts.

STUDY DESIGN

Set specimens from four sealers (AH26, Apexit, Sealapex, N2) as well as gutta-percha were eluted with cell culture medium for 24 hours, 5 days, 5 days, and 24 hours, respectively. Cytotoxic effects due to these extracts were evaluated by determining proliferation of permanent 3T3 cells and primary human periodontal ligament fibroblasts by means of the fluorochrome propidiumiodide.

RESULTS

No statistically significant cellular alterations were induced by gutta-percha and Apexit, whereas various extracts of AH26 and Sealapex caused significant moderate or severe growth inhibition. Severe cellular damage was documented for all extracts of N2, which was statistically significantly different from the other materials in both cell lines (p < 0.05).

CONCLUSIONS

Our results confirm that various root canal sealers constantly segregate substances after being exposed to an aqueous environment for extended periods, possibly causing moderate or severe cytotoxic reactions and possibly contributing to failure.

Physical properties of CH61, a newly developed root canal sealer

This study was performed to evaluate the physical properties (sealing, flow, radio-opacity, working time, and solubility) of a newly developed root canal sealer, CH61. It was compared with Canals, Sealapex, and AH26, which are typical commercially available root canal sealers. The sealing ability was evaluated by dye penetration. The flow was evaluated by two methods. One was flow in the vertical dimension, and the other was disk diameter. Radio-opacity, working time, and solubility were performed in accordance with the standards of the International Organization for Standardization. No dye penetration after immersion for 24 h was noted. In CH61, and there were significant differences between the values for CH61 and Canals, Sealapex, or AH26 (p < 0.001). For flow, the results differed from method to method. The radio-opacity decreased in the following order: AH26, Canals, CH61, and Sealapex. The solubility was the lowest for CH61. This study showed that CH61 had excellent sealing properties and low solubility.

Histopathological study of a newly developed root canal sealer containing tetracalcium-dicalcium phosphates and 1.0% chondroitin sulfate

We studied the possibility of the clinical use of a calcium phosphate-type newly developed sealer composed of tetracalcium phosphate, dicalcium phosphate dihydrate, and a modified McIlvain's buffer solution (TDM). Another sealer using the buffer solution, to which 2.5% chondroitin sulfate was added to promote wound healing (TDM-S), was also studied. TDM and TDM-S were histopathologically compared with another type of calcium phosphate sealer (ARS), which is commercially available in Japan, in the dorsal subcutaneous tissue and in the periapical tissue of rats. TDM and TDM-S caused no inflammatory reactions in the subcutaneous tissue. The periapical tissue reacted mildly to them. ARS caused severe inflammatory reactions in both the subcutaneous and the periapical tissue. These results indicate that TDM-S has excellent histocompatibility and potential as a root canal sealer.

In vitro evaluation of the cytotoxicity of calcium hydroxide-based root canal sealers

The cytotoxicity of three calcium hydroxide-containing root canal sealers (Sealapex, CRCS and Apexit) was tested by using L929 and BHK 21/C13 cells. After setting for 24 h, the sealers were covered with cell suspension. Cytotoxicity was determined by a quantitative technique at 24 h, 48 h and 72 h. All the sealers were found to be cytotoxic. Sealapex showed the highest cytotoxicity, causing a significant decrease in cell density. CRCS was less toxic than Sealapex and more toxic than Apexit. Apexit proved to be the least toxic material.

Experimental study of the biocompatibility of four root canal sealers and their influence on the zinc and calcium content of several tissues

Four root canal sealers (AH-26, Roth 811, CRCS, and Sealapex) were tested for tissue biocompatibility in rat connective tissue. Each sealer was placed in Teflon tubes and implanted subcutaneously in Wistar-Furth rats. The implants were removed after 7, 14, and 21 days, fixed, and histologically prepared for microscopical evaluation. Brain, liver, kidneys, and uterus were removed from the animals killed at the first experimental period (7 days) and analyzed for zinc and calcium concentration by flame atomic absorption spectrophotometry. In total, 100 specimens were examined. At the seventh day, the most irritant material was seen to be AH-26, but this inflammatory reaction decreased with time. Roth 811 and Sealapex caused moderate-to-severe inflammatory reaction, whereas CRCS caused mild to moderate. CRCS and Roth 811 induced redistribution of zinc, whereas AH-26 induced changes in calcium content in some organs.

Evaluation of calcium hydroxide-containing root canal sealers with an improved rabbit ear chamber

An improved rabbit ear chamber was used to evaluate calcium hydroxide-containing root canal sealers on their potential to induce dystrophic calcification in connective tissue. Four sealers and two control materials were introduced into the chambers and the effects of these materials on the living vascular tissue were observed continuously under a biomicroscope up to 9 weeks. Conventional histopathological investigation and examinations with a scanning electron microscope and an X-ray microanalyzer were done to supplement the results. Sealapex and Calvital (Ca(OH)2 + iodoform) revealed almost the same tissue reaction as calcium hydroxide-saline paste; they rapidly made a precipitate-barrier of calcium phosphate in the connective tissue, inducing calcification. However, Dentalis KEZ (ZnO-Ca(OH)2 + eugenol) caused mild disorders of microcirculation without calcification, as well as Canals (ZnO + eugenol). New A (Ca(OH)2 + fatty acid) had good compatibility with microvessels as well as New B (ZnO + fatty acid), however they induced no calcification and disintegrated rapidly in the tissue. These sealers were reclassified according to what they actually bring about in the tissue, not according to what they include.

Depth of penetration and appearance of Grossman sealer in the dentinal tubules: an in vivo study

Five teeth extracted after chemomechanical preparation (group A) and 11 extracted 1 to 7 yr after endodontic treatment (group B) were selected for this study. A 1% NaOCl was used for irrigations and a lateral condensation technique with a Grossman-type sealer was used for obturation. The teeth were fractured and prepared for and viewed by a scanning electron microscope equipped with an electron dispersive spectrometer. All root canal walls of group A were covered with a thick smear layer. Sealer, either rod-like or granular in appearance and barium free, was present in the majority of the dentinal tubules of group B usually at a distance up to 200 microns from the root canal walls; in two cases up to 900 microns. Sealer was found deepest in the middle third of the root. The smear layer did not stop sealer from entering the dentinal tubules. The differences in the depth of penetration or in the appearance of the sealer cannot be attributed to the different time periods the teeth remained in the arch after endodontic treatment.

In vitro evaluation of dental materials

Biocompatibility has been described as the ability of a material to perform with an appropriate host response in a specific application. Appropriate host response means no (or a tolerable) adverse reaction of a living system to the presence of such a material. An adverse reaction may be due to the toxicity of a dental material. Therefore toxicity may be regarded as one reason for nonbiocompatibility of a dental material. The toxicity of a dental material can be evaluated by in vitro tests, animal experiments and clinical trials. There exists a variety of different in vitro test methods. The most widely used biological systems for toxicity screening of dental materials are cell cultures. Cell cultures for toxicity screening of dental materials are valuable tools for understanding their biological behavior, if the limitations of the methods are taken into consideration, especially concerning the interpretation of the results. Further research should concentrate on better simulations of the in vivo situation in cell cultures. In this review the applications of various cell culture methods to evaluate the cytotoxicity of a wide range of dental materials, e.g. metals, alloys, polymers and cements, are described.

Reduced cytotoxicity of a root canal sealer through eugenol substitution

The cytotoxicity of two zinc oxide root canal sealers was investigated in vitro. The sealers were freshly mixed and set for 24 and 168 h. The sealers had identical powders but different liquid components. One (Canals) used eugenol, while the other (Canals-N) used fatty acids. L929 cells were incubated for 4 and 24 h in direct contact with the materials or with an eluate of the materials. The toxicity was evaluated using the radiochromium release assay. In the direct exposure assay, both sealers were cytotoxic when freshly prepared or after 24 h of setting. After 1 wk of setting, Canals was still toxic, while Canals-N was not significantly different from the control in the 4-h assay. In the elution assay the materials showed very low cytotoxicity. Only the eluate from freshly prepared Canals was clearly cytotoxic after 24 h. The liquid of Canals-N was clearly less cytotoxic than liquid from Canals. The results showed that the cytotoxicity of a root canal sealer can be reduced by replacing eugenol with fatty acids.

Quantitative radioactive analysis of microleakage of four different retrograde fillings

Sealing properties of four different retrograde filling materials were investigated in vitro. Radioactive isotopes were applied in the root canal, and leakage into an extraradicular fluid was measured at regular intervals. The method permitted repeated observation of the specimens over prolonged periods of time. Forty single-rooted human teeth were biomechanically instrumented and obturated using calcium-hydroxide paste. Following obturation, an apicectomy was performed and retrograde cavities were filled with four different materials: group 1, non gamma 2 amalgam (Amalcap); group 2, glass ionomer cement (Ketac Silver); group 3, calcium-hydroxide-based root canal sealer (Sealapex); group 4, composite resin (Palfique Light-S). After removal of the calcium hydroxide, the teeth were immersed in a fluid. An isotope solution was then placed in the root canals. Samples were taken from the fluid at 0, 3, 7, 28, 56, 105, 210, 285 and 376 days to determine the radioactivity. It was found that Sealapex and Palfique Light-S showed significantly less leakage than amalgam and glass ionomer cement, which had the highest apical leakage.

Toxicity of root canal sealers on rat bone cells in primary culture

The cytotoxic effects on cultured rat bone cells of newly-developed root canal sealers and commercially available sealers were compared. Various root canal sealers were applied to cultured bone cells obtained from rat calvaria by the enzyme digestion method. Measurement of [3H]-thymidine incorporation, alkaline phosphatase activity, and calcium release were performed after 24 and 48 h. No significant difference was found in cellular DNA synthesis and alkaline phosphatase activity between cells exposed to New B-1, New B-5 and controls after exposure for 24 and 48 h. Cells in contact with Tubliseal, Diaket and AH-26 demonstrated a significant difference from controls in DNA synthesis and alkaline phosphatase activity. Calcium release at 24 h was significantly different in the cells treated with New B-1 and New B-5 than in controls. No appreciable difference was found, however, between New B-6, Sealapex and controls. At 48 h, cells treated with New B-1, New B-5 and New B-6 showed differed significantly difference from controls, but the cells exposed to Sealapex did not. The newly-developed root canal sealers had lower toxicity in vitro than five types of commercially available root canal sealers.

Experimental oral foreign body reactions. Commonly employed dental materials

Foreign bodies and tissue reactions to foreign materials are commonly encountered in the oral cavity. The more common lesions include apical deposition of endodontic materials, mucosal amalgam and graphite tattoos, myospherulosis, oil granulomas, and traumatically introduced dental materials and instruments. Since many foreign materials are unidentifiable histologically, commonly used dental materials were experimentally implanted subcutaneously in rats to assess local host responses and characterize the nature of these materials microscopically. The histologic characteristics of these foreign body reactions are detailed herein. The implanted materials corresponded to reactions seen in human subjects.