Combined and independent cytotoxicity of sodium hypochlorite, ethylenediaminetetraacetic acid and chlorhexidine.

AIM: To evaluate the capacity of commonly used root canal irrigants to induce cytotoxic effects, when applied singly or in combination. The hypothesis tested was that the irrigants were less cytotoxic when applied in combination than independently. METHODOLOGY: MRC5 cells were grown as monolayer cultures at 37 °C in an atmosphere containing 5% CO2 in air and 100% relative humidity. Cells were exposed to sodium hypochlorite (NaOCl), ethylenediaminetetraacetic acid (EDTA), chlorhexidine (CHX) and their combinations (NaOCl/EDTA, NaOCl/CHX, EDTA/CHX) in serial dilutions. Growth medium was Dulbecco's modified Eagle's medium supplemented with 10% foetal bovine serum and antibiotics and was used as control. The effect on cell survival was estimated after 6 and 24 h of exposure by means of the sulforhodamine B assay, in reference to controls. Dose-response curves were plotted, and 50% inhibitory doses (IC50 ) were subjected to statistical analysis (anova and post hoc comparison test; P < 0.05). Analysis of cell survival and interaction of the irrigants was performed using CalcuSyn dose effect analyzer software to calculate a combination index (CI). RESULTS: The tested irrigants were cytotoxic in dose- and time-dependent manner. CHX was the most cytotoxic irrigant tested, followed by NaOCl, whilst EDTA was the least cytotoxic irrigant tested. The difference between CHX and NaOCl was significant (P < 0.05) as well as between NaOCl and EDTA (P < 0.05). Based on CalcuSyn modelling, a mainly antagonistic effect was recorded with NaOCl/CHX and NaOCl/EDTA combinations. The combination EDTA/CHX had an additive to antagonistic effect. CONCLUSIONS: CHX was significantly more cytotoxic than NaOCl and EDTA. NaOCl was significantly more cytotoxic than EDTA. The combined action of irrigants did not produce a significant increase in their cytotoxicity.

In vitro cytotoxicity of six dentin bonding agents.

The cytotoxicity of six dentin bonding agents (Syntac, Solobond, Bond 1, Scotchbond 1, Heliobond and F-2000) was tested against an established cell line, L929. Under aseptic conditions 3, 5 and 10 microL dentin bonding agents were placed in the centre of Petri dishes. Each dish was covered with a 5-mL suspension of fibroblasts at a concentration of 40 000 cells mL(-1). The cultures were incubated at 37 degrees C and cytotoxicity was assessed by a quantitative technique at 24 and 72 h. All the dentin bonding agents were found to be cytotoxic. Scotchbond 1 and F-2000 showed the highest cytotoxicity followed by Solobond and Bond 1. Heliobond and Syntac were the least toxic materials.

Cytotoxic effects of different concentrations of neutral and alkaline EDTA solutions used as root canal irrigants.

The cytotoxic effects of neutral and alkaline EDTA solutions were evaluated and compared with those of sodium hypochlorite solution using an established cell line: L929. Cytotoxicity was assessed by a quantitative technique at five observation periods (1, 3, 6, 12, and 24 h). All tested agents showed moderate to severe cytotoxicity in the present experimental model in a concentration-dependent manner.

In vitro release of hydroxyl ions from calcium hydroxide gutta-percha points.

In endodontic practice, calcium hydroxide is widely used for a number of reasons associated with its high pH. The purpose of the present study was to determine in vitro the alkalizing potential of newly introduced calcium hydroxide gutta-percha points that are proposed for temporary filling of root canals. The materials tested were: calcium hydroxide gutta-percha points; chemical pure calcium hydroxide powder mixed with distilled water; and Reogan rapid, a nonsetting calcium hydroxide preparation. The materials were placed into dialysis tubing and transferred into plastic vials containing bidistilled water. Measurements were taken by a digital pH meter after 10, 20, and 30 s; 1, 15, and 30 min; and 1, 2, 3, 24, 48, 72, 96, and 120 h. The calcium hydroxide containing gutta-percha points showed a significantly lower alkalizing potential than Reogan rapid and calcium hydroxide mixed with distilled water (p < 0.05).

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.

In vitro evaluation of the cytotoxicity of a bleaching agent.

Cell cultures of L929 and BHK21/C13 cells were used to evaluate the toxicity of a newly introduced bleaching agent (Colgate Platinum) compared to hydrogen peroxide, an established bleaching agent. The cell reaction was determined by a quantitative technique at 24 h and 72 h. Both bleaching materials had a dose-dependent effect on cell viability. Concentrations of hydrogen peroxide causing a 50% decrease in cell number (50% inhibition dose-ID50) were calculated as 0.00034% after 24 h and 0.00001% after 72 h in L929 cells. The ID50 of hydrogen peroxide was found to be 0.00016% after 24 h and 0.00007% after 72 h in BHK21/C13 cells. The ID50 of Colgate Platinum was 0.00074% after 24 h and 0.00045% after 72 h in L929 cells and 0.00055% after 24 h and 0.00024% after 72 h in BHK21/C13 cells. The results showed that, in vitro, both bleaching agents were cytotoxic to fibroblasts and the new bleaching agent was less toxic than hydrogen peroxide.

In vitro release of hydroxyl ions from six types of calcium hydroxide nonsetting pastes.

The role of intracanal medication in root canal treatment is very important. Calcium hydroxide (Ca(OH)2) is considered to fulfill many of the properties of an ideal root canal dressing mainly due to its alkalizing pH. It is bacteriocidal and neutralizing to the remaining tissue debris in the root canal(s) and through the continuous release of OH- ions it promotes an alkalizing osteogenic environment for the surrounding tissues. The purpose of this study was to examine the pH values of various Ca(OH)2 based on compounds used as intracanal medicaments over a period of 5 days. The following materials were tested: Calasept, Calcicur, Calxyl blue, Calxyl red, Reogan rapid, and Tempcanal. After a fast OH- release period (2 h) each compound reached an asymptotic pH state. The results showed that all materials exhibited alkalizing pH with Reogan rapid, Calxyl Red, and Calcicur being the most potent (p = 0.05). The final pH of each compound correlated positively with the Ca(OH)2 mass fraction contained in it.

In vitro evaluation of the cytotoxicity of two glass-ionomer root canal sealers.

The cytotoxicity of two glass-ionomer root canal sealers (Ketac-Endo and Endion) was tested by using an established cell line, BHK21/C13. Under aseptic conditions, the sealers were prepared according to the manufacturers' directions, and 0.1 ml of each material was placed in petri dishes. After setting for 6 h, the sealers were covered with 20 x 10(4) cells per dish. The cultures were incubated at 37 degrees C for 24 h, 48 h, and 72 h. Cytotoxicity was assessed by a quantitative technique at three observation periods. Endion was highly cytotoxic, causing a significant decrease in cell density. Ketac-Endo proved to be a very biocompatible material.

Role of cementoenamel junction on the radicular penetration of 30% hydrogen peroxide during intracoronal bleaching in vitro.

Intracoronal bleaching of nonvital, teeth with 30% hydrogen peroxide is occasionally associated with external cervical root resorption. The exact mechanism by which bleaching induced root resorption occurs is not yet fully understood. The relationship of cementum to the enamel at the cementoenamel junction may have clinical significance. Seventeen single rooted human mandibular premolars extracted atraumatically for orthodontic reasons were used. The radicular hydrogen peroxide penetration in each tooth was measured in vitro by an indirect colorimetric method. Thereafter, the teeth were examined with a scanning electron microscope to determine the type of the cementoenamel junction. It was found that the radicular penetration of 30% hydrogen peroxide was related to the type of cementoenamel junction.

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.