Bovine Pulp Research Articles

Detection of organochlorine compounds formed during the contact of sodium hypochlorite with dentin and dental pulp.

This study used gas chromatography-mass spectrometry (GC-MS) to detect the products formed during the contact of sodium hypochlorite (NaOCl) with bovine pulp and dentin. For analysis of the products formed in the volatile phase, 11 mg of bovine pulp tissue were placed in contact with 0.5%, 2.5% and 5.25% NaOCl until complete tissue dissolution occurred. The solid phase microextraction (SPME) fiber was exposed inside the container through the cover membrane and immediately injected into the GC-MS system. 30 mg of the of dentin were kept in contact with NaOCl, and then the SPME fiber was exposed inside the container through the cover membrane for adsorption of the products and injected into the GC-MS system. The same protocol was used for the aqueous phase. For analysis of the volatile compounds, the final solution was extracted using pure ethyl ether. The suspended particulate phase of the mixture was aspirated, and ether was separated from the aqueous phase of the solution. The ether containing the products that resulted from the chemical interaction of dentin and pulp with the NaOCl was filtered and then injected into the GC-MS system for analysis of the aqueous phase. The aqueous and volatile phases of both dentin and pulp showed the formation of chloroform, hexachloroethane, dichloromethylbenzene and benzaldehyde. In conclusion, organochlorine compounds are generated during the contact of dentin and pulp with NaOCl at concentrations of 0.5%, 2.5% and 5.25%.

Influence of EDTA and dentine in tissue dissolution ability of sodium hypochlorite

This study verified whether ethylenediaminetetraacetic acid (EDTA) influences the pulp tissue dissolution capability of different concentrations of NaOCl, in the presence of dentine. NaOCl and EDTA solutions were simultaneously mixed in flasks either containing a dentine disc or those not containing a dentine disc. Previously weighed bovine pulp tissues were immersed in the solutions for 5, 15 and 30 min. The weight loss was measured. The dissolution tests were performed in triplicate. Univariate analysis of variance, along with further Tukey's honestly significant difference pairwise comparisons, was used to verify the effect of EDTA, different concentrations of NaOCl, dentine and time of incubation on the tissue dissolution. Higher concentrations of NaOCl increased the tissue dissolution. EDTA reduced the capacity of NaOCl to dissolve pulp tissue, even in presence of dentine. Dentine negatively affects the capacity of NaOCl to dissolve pulp tissue. In conclusion, the presence of EDTA and dentine negatively affects the tissue dissolution ability of NaOCl.

Pulp Tissue Dissolution Capacity of Sodium Hypochlorite Combined with Cetrimide and Polypropylene Glycol

This study evaluated the influence of the addition of cetrimide and polypropylene glycol to sodium hypochlorite (NaOCl) on its capacity to dissolve pulp tissue. Bovine pulp fragments with standardized weight and volume were immersed for 5, 15 and 30 min in 2 mL of NaOCl and Hypoclean (NaOCl added with cetrimide and polypropylene glycol) solutions at 5.25%, 2.5%, 1%, 0.5% and 0.25% and afterwards re-weighted. Distilled water was used as a control. The percentage of tissue loss was considered for statistical analysis (univariate ANOVA, SPSS, v. 17.0) at 5% significance level. There was no tissue dissolution in the control group. NaOCl added with surfactants (Hypoclean) dissolved more pulp tissue (p<0.05) than NaOCl alone. Tissue dissolution was directly dependent on the concentration of solutions (p<0.05), and also on the time range (p<0.05). The combination of NaOCl at high and low concentrations with the surfactants cetrimide and polypropylene glycol increased significantly its capacity to dissolve pulp tissue.

Can the sodium hypochlorite tissue dissolution ability during endodontic treatment really be trusted? An in vitro and ex vivo study

Data were analyzed by means of the analysis of variance with Tukey test (P < 0.05). Dissolution time was analyzed by immersing bovine pulp tissue in different volumes of 2.5% and 5.25% NaOCl solution. Results: No significant difference was found between the NaOCl concentrations in the histological investigation. No substance was able to completely clean the isthmuses. Moreover, a higher dissolution rate for the bovine pulp tissue was found in NaOCl with a concentration of 5.25%, in addition to a shorter dissolution time for larger volumes. Conclusion: The NaOCl is effective for tissue dissolution when in direct contact, however, NaOCl solution, even in high concentrations, was not competent to dissolve remnants of pulp tissue in root isthmuses during endodontic treatment.

Evidence of the protein content of bovine and human dental pulps by the action of endodontic irrigation solutions through electrophoretic patterns

Background: Sodium dodecyl sulfate polyacrylamide gel electrophoresis let to show the protein content of different tissues. Dental pulp contains connective tissue which is removed during the endodontic treatment. Many studies consider bovine rather than human pulp tissue because of its size. Aim: To evidence the protein content of bovine and human dental pulps and the action of endodontic irrigation solutions through electrophoretic patterns. Materials and Methods: Extracts of human and bovine dental pulps were prepared. Sodium hypochlorite, calcium hydroxide, chlorhexidine and ethylenediamine tetraacetic acid were used as irrigating solutions. Results: Bovine and human pulps have a small difference in two bands of proteins present between 74 kDa and 80 kDa. The denaturizing capacity of sodium hypochlorite and the washing action of calcium hydroxide and chlorhexidine were evidenced. Ethylenediamine tetraacetic acid solution was shown to contain proteins continuously during the endodontic root canal washing. Conclusions: Differences in pulp tissues and the action of irrigating solutions on their protein content would help on the understanding of the biological process of the endodontic treatment.

Chlorhexidine gel associated with papain in pulp tissue dissolution.

ObjectivesThis study aimed to evaluate the capacity of 2% chlorhexidine gel associated with 8% papain gel in comparison with 5.25% sodium hypochlorite in bovine pulp tissue dissolution.Materials and MethodsNinety bovine pulps of standardized sizes were used and fragmented into 5-mm sizes. The fragments were removed from the root middle third region. They were divided into 6 experimental groups (n = 15), 1) 8% papain; 2) 2% chlorhexidine; 3) 2% chlorhexidine associated with 8% papain; 4) 0.9% saline solution; 5) 2.5% sodium hypochlorite; and 6) 5.25% sodium hypochlorite. The pulp fragments were weighed and put into immobile test tubes for dissolution for time intervals of 30, 60, 90, and 120 min.ResultsThe 5.25% sodium hypochlorite had greater dissolution potential than the pure papain, and when associated with chlorhexidine, both promoted greater dissolution than did the saline solution and 2% chlorhexidine groups (p < 0.05). The 2.5% sodium hypochlorite promoted dissolution to a lesser extent than the groups with papain within a period of 30 min (p < 0.05), but, was comparable to the saline solution and chlorhexidine. After 120 min, the 2.5% and 5.25% sodium hypochlorite promoted dissolution of 100% of the pulp fragments, and papain, 61%, while chlorhexidine associated with papain and chlorhexidine alone dissolved only 55% and 3%, respectively.ConclusionsThe 8% papain in gel, both alone and in association with chlorhexidine, was able to dissolve bovine pulp tissue, but to a lesser extent than did 5.25% sodium hypochlorite.

Efficacy and Safety of Various Active Irrigation Devices When Used with Either Positive or Negative Pressure: An In Vitro Study

IntroductionThe purpose of this in vitro study was to evaluate and compare the efficacy and safety of different devices available for canal cleansing. MethodsThe following systems were tested: passive ultrasonic irrigation, EndoVac (Discus Dental, Culver City, CA), and the irrigation ultrasonic needle (ProUltra PiezoFlow Irrigation Ultrasonic Needle; Dentsply Tulsa Dental Specialties, Tulsa, OK) used in both the injection mode (IUNI) and the aspiration mode (IUNA). In the control group, traditional irrigation with a syringe and side-vented needle was used. A resin model was used with 4 lateral canals (respectively at 2, 5, 8, and 11 mm from the apical foramen) filled with bovine pulp stained with fuchsin. The model also included a 2-mm chamber in communication with the apex, again filled with bovine pulp, which enabled the measurement of the extrusion of NaOCl beyond the apex. ResultsWith regard to efficacy, the most effective systems were found to be those using the ultrasonic needle, either in aspiration or injection modes; EndoVac was the least effective. Conversely, IUNI was found to bring the highest risk with regard to the extrusion of sodium hypochlorite beyond the apex. EndoVac was the safest but only by a slight margin compared with IUNA and passive ultrasonic irrigation. ConclusionsBased on this study, the system that best reconciles efficacy and safety appears to be IUNA.

Human and bovine pulp-derived cell reactions to dental resin cements

The objective of this study was to evaluate the cytotoxic reaction of transfected human pulp derived cells (tHPDC) and transfected bovine pulp derived cells (tBPDC) after exposure to resin cements [RelyX UnicemClicker (RX), MaxCem (MC), Panavia F 2.0 (PF), BisCem (BC), and Bistite II DC (BII)] and to compare it to the generation of reactive oxygen species (ROS). Set materials were extracted in culture medium, cell survival as a measure of cytotoxicity was determined photometrically using crystal violet after cells were exposed to the extracts for 24 h. The generation of ROS was detected by flow cytometry after cells were exposed to extract dilutions for 1 h. The ranking of the least to the most cytotoxic material was: RX < BII < PF < BC < MC for both cell lines, but for tHPDC, only MC and PF eluates were different from untreated controls. Generally, tBPDC were more susceptible to materials than tHPDC, but only for RX and BC was this difference statistically significant. All undiluted extracts increased ROS production in both cell lines but to a higher amount in tHPDC than in tBPDC. tHPDC reacted less sensitive than tBPDC in the cytotoxicity test but with the same rank order of materials. In contrast, the cellular oxidative stress reaction was more pronounced in tHPDC than in tBPDC. Depending on the residual dentine layer in deep cavities, biologically active resin monomers or additives released from resin cements may influence the dentine–pulp complex, for instance, its regenerative and reparative capacities.

Physicochemical and Pulp Tissue Dissolution Properties of Some Household Bleach Brands Compared with a Dental Sodium Hypochlorite Solution

IntroductionMany clinicians use household bleach to irrigate root canals. Sodium hypochlorite solutions are also available from dental suppliers. We compared physicochemical features of these products and investigated their impact on pulp tissue dissolution. MethodsSix different brands of household bleach were bought from drugstores. These were compared with Chlor-XTRA and technical NaOCl solutions of controlled concentration and alkalinity regarding their chlorine content (wt% NaOCl), pH, alkaline capacity, osmolarity, surface tension (Wilhelmy plate method), and price. Bovine pulp tissue (n = 10 specimens per group) dissolution at 37°C by test and control solutions adjusted to 1.0% NaOCl was assessed. Reduction in tissue weight was compared between groups by one-way analysis of variance, followed by Bonferroni correction (P < .05). ResultsThe pH of undiluted solutions ranged between 11.1 and 12.7. Batches of the same product differed in NaOCl content. No product contained more than an equivalent of 0.1 mol/L NaOH. One household bleach brand (Safeway Bleach Summit Fresh) was slightly alkalized; the other solutions under investigation were not. Osmolarity was similar between products. The surface tension of Chlor-XTRA and Safeway Bleach Summit Fresh was about half that of the other solutions. Tissue dissolution was statistically similar (P > .05) among all solutions. Price was about 100-fold higher per liter of Chlor-XTRA compared with household bleach. ConclusionsOther than its price, the Chlor-XTRA solution had no unique features. In contrast to an earlier report, reduced surface tension did not result in greater soft tissue dissolution by NaOCl.

Analysis of bovine pulp tissue dissolution ability by photodynamic therapy: an in vitro study

PURPOSE: To evaluate the bovine pulp tissue dissolution ability of photodynamic therapy. METHIDS: Twenty pieces of bovine pulp tissue were weighed and divided randomly into four groups (n=5), according to the cleaning protocol: G1 - distilled water (negative control), G2 - sodium hypochlorite 1% (positive control), G3 - photodynamic therapy, G4 - sodium hypochlorite 1% + photodynamic therapy. The observation of the events of dissolution was performed by two observers blinded in relation to the test using 2x magnification, recording time in minutes until complete tissue dissolution. The total observation time was 2 hours. The dissolution rate was calculated dividing the weight of the fragment pulp (mg) by the time of dissolution (mg/min). RESULTS: Only group 2 (NaOCl) was able to promote complete dissolution of pulp tissue. In the other groups there was no occurrence of complete dissolution of the samples. The mean dissolution time for samples from group 2 (NaOCl) was 1.26 mg/min. CONCLUSION: Only the sodium hypochlorite was able to dissolve the fragments of bovine pulp tissue and photodynamic therapy does not show ability to dissolve tissue.

Pulp tissue dissolution when the use of sodium hypochlorite and EDTA alone or associated

PURPOSE: The aim of the present study was to evaluate the tissue dissolving capacity of various concentrations of sodium hypochlorite either alone or in combination with 17% EDTA. METHODS: Eighty bovine pulp fragments were prepared, and their weight was determined using a precision balance. Each pulp fragment was immersed for 2 hours in a solution/mixture that was based on the following groups: G1 - saline solution; G2 - 0.5% NaOCl; G3 - 1.0% NaOCl; G4 - 2.5% NaOCl; G5 - 17% EDTA; G6 - 0.5% NaOCl+17% EDTA; G7 - 1.0% NaOCl+17% EDTA; and G8 - 2.5% NaOCl+17% EDTA. The final weight was measured, and the weight loss was calculated. A statistical analysis was performed using either the Student's t-test for paired samples or an ANOVA and Tukey tests (P<0.05 was considered to be significant). RESULTS: We measured a significant difference between the sample weight before and after treatment for each of the tested groups (P<0.05). The 2.5% sodium hypochlorite solution (G4) completely dissolved the pulp tissue within the test period. NaOCl+EDTA was less effective than sodium hypochlorite alone at dissolving the pulp tissue (P<0.05), and EDTA alone (G5) did not markedly dissolve the pulp tissue. CONCLUSION: Using EDTA together with NaOCl reduced the tissue dissolving properties compared with NaOCl alone, regardless of the concentration of NaOCl that was used.

Bovine pulp tissue dissolution ability of HealOzone®, Aquatine Alpha Electrolyte® and sodium hypochlorite

The aim of this study was to evaluate the bovine pulp tissue dissolution ability of HealOzone, Aquatine Alpha Electrolyte® and 0.5% sodium hypochlorite, used alone or in combination. Thirty bovine pulp fragments were weighed, divided into six groups and placed individually in Eppendorf tubes containing the tested solution until total dissolution occurred. The groups were: G1: saline (negative control), G2: Aquatine Alpha Electrolyte®, G3: 0.5% NaOCl (positive control), G4: Saline + HealOzone, G5: 0.5% NaOCl + HealOzone, G6: Aquatine Alpha Electrolyte® + HealOzone. HealOzone was activated for 2 min with a #6 cup covering the test tube opening on a fixed platform. Two blinded observers using 2× loupes magnification assessed the samples continuously for the first 2 h, and then every hour for the next 8 h. Dissolution speed was calculated by dividing pulp weight by dissolution time (mg min(-1) ). G3 (NaOCl) and G5 (NaOCl + HealOzone) dissolved the pulp tissue completely. The mean dissolution speed for G3 was 0.396 mg min(-1) (SD 0.032) and for G5 was 0.775 mg min(-1) (SD 0.2). Student's t-test showed that G5 dissolved bovine pulp tissue faster than G3 (P = 0.01). Only groups containing sodium hypochlorite dissolved pulp tissue, whilst HealOzone enhanced speed of dissolution.

Dissolution of bovine pulp tissue in solutions consisting of varying NaOCl concentrations and combined with EDTA

This in vitro study evaluated (1) the dissolution of bovine pulp tissue in solutions consisting of varying NaOCl concentrations and combined with EDTA; and (2) the pH of these solutions before and after the experiment. The independent variables were the concentration and the volume of the solution. Thirty bovine pulps were divided in equal fragments, resulting in 90 fragments of pulp tissue. Each fragment was immersed in one of the following solutions: 1% NaOCl (4 ml), 2.5% NaOCl (4 ml), 1% NaOCl + 17% EDTA (2 ml : 2 ml), 1% NaOCl + 17% EDTA (1 ml : 3 ml), 2.5% NaOCl + 17% EDTA (2 ml : 2 ml), and 2.5% NaOCl + 17% EDTA (1 ml : 3 ml). The test solutions were dichotomized as either able or not able to dissolve the tissue, the latter being attributed when the dissolution of the pulp tissue was not complete within 48 hours. When the samples were able to dissolve the tissue, the time required for complete tissue dissolution was submitted to statistical analysis. The pH of the solutions was measured before and after the experiment. The pH variable was dichotomized as either changed or unchanged. The results demonstrated that the NaOCl solutions combined with 17% EDTA were not able to dissolve the tissue. The t-test revealed that the 2.5% NaOCl solution presented a lower mean dissolution time than the 1% NaOCl solution (p < 0.001). The pH of the solutions with equal volumes of NaOCl and EDTA decreased in 48 hours.

Comparison of Organic Tissue Dissolution Capacities of Sodium Hypochlorite and Chlorine Dioxide

The organic tissue dissolution properties of irrigating solutions are important for the success of endodontic treatment. Chlorine dioxide (ClO 2) has been recently proposed as an irrigation solution in endodontics. The organic tissue dissolution property of sodium hypochlorite (NaOCl) is well-known and extensively investigated, but apparently no data have been published on tissue-dissolving properties of ClO 2. The aim of this in vitro study was to compare organic tissue dissolution capacity of NaOCl and ClO 2. In this study, 5.25% NaOCl, 13.8% ClO 2, and, as a control, isotonic saline solutions (0.9% NaCl) were used. Thirty bovine pulp specimens were previously weighed and immersed for 20 minutes in each test solution (changing the solution every 2 minutes). The pulp specimens were then blotted dry and weighed again. The percentage of weight loss was calculated and statistically analyzed by using one-way analysis of variance and post hoc Tukey honestly significant difference tests. Saline solution did not dissolve the organic tissue. Both 5.25% NaOCl and 13.8% ClO 2 dissolved the tissue pieces more effectively than saline control ( P < .05). No statistically significant difference was found between the tissue-dissolving properties of 5.25% NaOCl and those of 13.8% ClO 2 ( P > .05). Within the limitations of this in vitro study, it was concluded that ClO 2 and NaOCl are equally efficient for dissolving organic tissue.

Acoustic Hypochlorite Activation in Simulated Curved Canals

IntroductionIt was the goal of this study to compare different NaOCl activation schemes regarding a desired and an untoward outcome. Ultrasonic tips and a currently marketed sonic system were used in conjunction with a 2.5% sodium hypochlorite solution. Necrotic pulp tissue dissolution in simulated accessory canals and transportation of the main canal were assessed. MethodsEpoxy resin models (10 per group) with a curved simulated main root canal and two simulated accessory canals filled with necrotic bovine pulp tissue were irrigated passively with one of three ultrasonic setups (straight stainless steel files, prebent stainless steel files, or nickel-titanium tips) or a sonic device in conjunction with a plastic tip. Activation was performed four times for 30 seconds with replenishment of the NaOCl solution in between. All the files/tips had a 2% taper and a 0.15-mm tip diameter according to the manufacturer. Data from superimposing and analyzing digital photos before and after treatment were statistically analyzed using one-way analysis of variance followed by Bonferroni's correction for multiple comparisons (alpha < 0.05). ResultsPassive ultrasonic irrigation (PUI) in all the groups dissolved significantly more tissue than sonic activation (p < 0.05). No detectable canal transportation with sonic activation was observed. The difference in this outcome was not significant compared with ultrasonically activated nickel-titanium tips, whereas the straight stainless steel files caused significantly more ledging compared with these setups (p < 0.05). ConclusionUnder the current conditions, PUI with a nickel-titanium tip promoted superior tissue-dissolving effects over sonic irrigant activation while maintaining simulated canal anatomy.

Necrotic pulp tissue dissolution by passive ultrasonic irrigation in simulated accessory canals: impact of canal location and angulation

To evaluate whether passive ultrasonic irrigation (PUI) of 2.5% NaOCl would dissolve necrotic pulp tissue from simulated accessory root canals (SACs) better than passive placement of the irrigant, when temperature was equilibrated between the two treatments. Transparent root canal models (n = 6) were made from epoxy resin. SACs of 0.2 mm diameter were placed at defined angles and positions in the mid-canal and apical area. SACs were filled with necrotic bovine pulp tissue. PUI was performed five times for 1 min each with irrigant replenishment after every minute. Main canal temperature was measured after each minute, and a digital photograph was taken. In control experiments, mock treatments were performed with the same set-up without activation of the file using heated NaOCl to mimic the temperature created by PUI. Experiments were repeated five times. Digital photographs were analysed for the distance of dissolved tissue into the SACs in mm. Overall comparison (sum of dissolved tissue from all five accessory canals) between treatments was performed using paired t-test. Differences between SAC angulation and position after PUI were investigated using anova/Bonferroni (alpha < 0.05). Passive ultrasonic irrigation caused a rise in irrigant temperature in the main canal to 53.5 +/- 2.7 degrees C after the fifth minute. PUI dissolved a total of 6.4 +/- 2.1 mm, mock treatment controlled for heat: 1.4 +/- 0.6 mm (P < 0.05). No significant influence of SAC position or angulation was found. Passive ultrasonic irrigation promotes positive tissue-dissolving effects beyond a rise in irrigant temperature.

Use of a bottle warmer to increase 4% sodium hypochlorite tissue dissolution ability on bovine pulp

The aim of this study was to evaluate the tissue dissolution ability of 4% sodium hypochlorite at increasing temperatures with the use of a baby bottle warmer. Twenty pieces of bovine pulp tissue from freshly extracted incisors and canines were weighted and randomly distributed among four groups in accordance to the exposure to 4% sodium hypochlorite at different temperatures: group C--room temperature (20.5 degrees C--control); group T1--45 degrees C; group T2--60 degrees C; group T3--75 degrees C. The samples were placed within test tubes when the solution reached the desired temperature. Time taken for the dissolution was recorded. One-way anova with logarithmical transformation and Duncan post-hoc was used (P = 0.05). There was a statistically significant increase in speed of pulp dissolution from group T1 to group C and from groups T2 and T3 to group T1; group T2 and T3 displayed similar dissolution speeds.

Tissue dissolving ability of several endodontic irrigants on bovine pulp tissue.

A desirable characteristic of root canal irrigants is the ability of dissolving soft tissues. Sodium hypochlorite, an antibacterial and tissue solvent irrigant used in endodontic treatment is known to be toxic for periapical tissues. Chlorhexidine gluconate, an effective antimicrobial agent, is another irrigant with limited tissue dissolving ability. A mixture of a tetracycline isomer, an acid, and a detergent (MTAD), has recently been introduced as an alternative irrigant in root canal therapy. The purpose of this study was to evaluate the tissue dissolving effect of these root canal irrigants on bovine pulp tissue. Fifty pieces of bovine pulp tissue 80 mg each were treated with either normal saline, MTAD, 2% chlorhexidine gluconate, 2.6% NaOCl or 5.25% NaOCl for 10 min at 37°C. Desiccated pre-treatment and post-treatment weights of samples were compared. Using Kruskal-Wallis and Mann-Whitney U tests, data was analyzed. Tissue dissolution effect of 5.25% NaOCl (85.98%) was statistically greater than that of all other solutions (P<0.05). Chlorhexidine gluconate had the weakest dissolution effect, and dissolved only 9.36% of the sample tissue. No significant differences were observed between the dissolution effects of normal saline or MTAD. Based on the results of this study, the use of NaOCl as intracanal irrigation during instrumentation is recommended, because of its greater tissue dissolution effect.

Pulp-Dissolving Ability of Several Endodontic Irrigants: A Spectro-Photometry Evaluation

The aim of this study is to test the dissolving action of different concentrations of NaOCl (0.5%, 2.5% and 5%) and EDTA 17% on bovine pulp tissue, testing solutions at three different times (1, 5, 10 minutes), 100 mg.of dental pulp placed into a becker with 20 ml of solution was evaluated using a spectrophotometer. A solution of NaOCl 5% showed the highest solubility value. Samples treated with 2.5% NaOCl showed solubility values of 0.98 in one minute, 29.1 in five minutes and 57 in ten minutes. Groups treated with NaOCl 0.5% showed small dissolving modifications. 17% EDTA showed the lowest values of solubility. 5% NaOCl solution showed highest pulp dissolving ability, even a 2.5% solution showed high dissolving ability but in longer times.

Dissolution of pulp tissue by aqueous solution of chlorhexidine digluconate and chlorhexidine digluconate gel.

To evaluate the activity of various root canal irrigants on bovine pulp tissue. The irrigants tested were: 0.5, 1.0 and 2.5% sodium hypochlorite; 2% aqueous solution of chlorhexidine digluconate; 2% chlorhexidine digluconate gel (Natrosol); and distilled water as control. Bovine pulp fragments were weighed and placed in contact with 20 mL of each tested substance in a centrifuge at 150 r.p.m. until total dissolution. Dissolution speed was calculated by dividing pulp weight by dissolution time. Statistical analysis was performed using the Kruskal-Wallis test. Distilled water and both solutions of chlorhexidine did not dissolve the pulp tissue within 6 h. Mean dissolution speeds for 0.5, 1.0 and 2.5% sodium hypochlorite solutions were 0.31, 0.43 and 0.55 mg min(-1), respectively. The solvent ability of chlorhexidine solutions was similar to that of distilled water. The results for sodium hypochlorite solutions, chlorhexidine solutions and distilled water were statistically different (P>0.01). Both chlorhexidine preparations and distilled water were not able to dissolve pulp tissue. All sodium hypochlorite solutions were efficient in dissolving pulp tissue; the dissolution speed varied with the concentration of the solution.