Cytotoxic effects of cyanoacrylates used as retrograde filling materials: an in vitro analysis

Advances in the development and optimization strategies of the hemostatic biomaterials

Most injuries are accompanied by acute bleeding. Hemostasis is necessary to relieve pain and reduce mortality in these accidents. In recent years, the traditional hemostatic materials, including inorganic, protein-based, polysaccharide-based and synthetic materials have been widely used in the clinic. The most prominent of these are biodegradable collagen sponges (Helistat^®, United States), gelatin sponges (Ethicon^®, SURGIFOAM^®, United States), chitosan (AllaQuixTM, ChitoSAMTM, United States), cellulose (Tabotamp^®, SURGICEL^®, United States), and the newly investigated extracellular matrix gels, etc. Although these materials have excellent hemostatic properties, they also have their advantages and disadvantages. In this review, the performance characteristics, hemostatic effects, applications and hemostatic mechanisms of various biomaterials mentioned above are presented, followed by several strategies to improve hemostasis, including modification of single materials, blending of multiple materials, design of self-assembled peptides and their hybrid materials. Finally, the exploration of more novel hemostatic biomaterials and relative coagulation mechanisms will be essential for future research on hemostatic methods.

Minimal Intervention Dentistry: Biocompatibility and Mechanism of Action of Products for Chemical-Mechanical Removal of Carious Tissue

Conventional method for removal of carious tissue using low speed drills usually induce noise and vibration, in addition to thermal and pressure effects that can be harmful to the pulp tissue and cause fear in children. Therefore, several alternative methods are being developed to try to minimize the unpleasant perception of the patient during caries removal. Chemical-mechanical removal of carious tissue goal is to selectively remove the carious lesion, which reduces the amount of bacteria inside the cavity without removing the tissue susceptible to remineralization. This method is also able to minimize the tactile perception by the patient during the manipulation of the lesion compared to the conventional method, and, therefore, it has been widely accepted among phobic patients, children and special needs patients. Due to the close relationship between dentin and pulp tissue, all injuries imposed on this dentin may have repercussions on the underlying pulp connective tissue. The morphological aspects of remaining dentin favor the diffusion of chemical components of dental materials, which can be toxic to the pulp tissue or even negatively interfere in the reparative process. Thus, considering the proximity between the applied material and the underlying pulp tissue, especially in deep cavities, there is a need to assess the biological behavior of dental materials against pulp cells, since aggressions to the pulp tissue can be caused not only by metabolites from microorganisms involved in dental caries but also by components that are released from these products. This subject was explored in this narrative literature review.

Short-chain cyanoacrylates and long-chain cyanoacrylates (Dermabond) have different antimicrobial effects

Objective

To compare the antimicrobial effect in vitro of a short-chain cyanoacrylate with a long-chain cyanoacrylate (Dermabond, Ethicon, Johnson and Johnson, USA) against bacterial strains.

Methods and analysis

The following bacterial strains were analysed: Staphylococcus aureus, Escherichia coli, Klebsiella pneumonia and Pseudomonas aeruginosa. For each microorganism, standardised sterile discs (6 mm) containing 10 µL of ethyl-cyanoacrylate and 2-octyl cyanoacrylate were applied to the plate. All plates received a blank filter-paper disc with no adhesive (control). All plates were incubated for 24 hours, after which the bacterial inhibitory halos, if present, were measured in millimetres in its greater length.

Results

Inhibitory halos were observed for both adhesives for S. aureus. Inhibition halos were observed only for ethyl-cyanoacrylate for K. pneumoniae and E. coli. No inhibition halo was observed for P. aeruginosa in any sample. The relationship between the total size of the inhibition halos and the diameter of the paper filter for S. aureus was statistically significant compared with 2-octyl cyanoacrylate.

Conclusion

Data shown conclude that ethyl-cyanoacrylate showed in vitro bacteriostatic activity for S. aureus, E. coli and K. pneumoniae. 2-Octyl cyanoacrylate showed in vitro lower bacteriostatic activity only against S. aureus when compared with ethyl-cyanoacrylate. No in vitro bactericidal activity of ethyl-cyanoacrylate or 2-octyl cyanoacrylate was observed.

Evaluation of Regular Market Ethyl Cyanoacrylate Cytotoxicity for Human Gingival Fibroblasts and Osteoblasts

Background: The aim of this study was to evaluate the cytotoxicity of cyanoacrylate adhesives in an indirect contact assay in human gingival fibroblast (FGH) and oral osteoblasts (GO) lineages. Methods: Cover glasses were glued with adhesives following the ISO 10993-2012 protocol. The groups were: C (control with cells and regular Dulbecco Modified Eagle Medium; LC (liquid ethyl-cyanoacrylate); GC (ethyl-cyanoacrylate gel); EGC (easy gel [ethyl-cyanoacrylate]); and D (Dermabond [octyl-cyanoacrylate]). Each cell linage was plated in the sixth passage using 10⁴ cells. Cell viability was measured by the MTT test at 24, 48, 72, and 96 hours. Data were analyzed by two-way analysis of variance complemented by the Tukey test, with p < 0.05 being significant. Results: Dermabond stimulated osteoblast viability at 72 h (p < 0.05). All other groups were similar to the control cells (p > 0.05). For the fibroblasts, there was no difference in the groups, including the control except that EGC was cytotoxic for these cells (p < 0.05). Conclusions: Ethyl-cyanoacrylate gel and liquid forms available on the general chemical market were not cytotoxic for oral osteoblasts and fibroblasts in most cases. However, the easy gel form was cytotoxic for fibroblasts.

Laser Processing of Electrospun PCL Fiber Mats for Tissue Engineering

Purpose

Processing technologies for cutting and joining electrospun fiber mats are required to produce complex three-dimensional (3D) structures, like a scaffold for heart valve tissue engineering. The ability to bond very thin porous sheets, thus forming a stable 3D geometry, offers completely new design strategies such as organ-shaped scaffolds with void chambers inside. In this study, solvent, glue and laser bonding are compared with regard to their retention force and practicability.

Methods

For this purpose, samples were prepared by applying each bonding technique. In addition, two different ways of preparing the bonding site were investigated: a portion of mats were bonded by an L-joint and the others by a T-joint; then tensile testing was performed until tearing of the bonding occurred. Additionally, the edges of laser cut fiber mats were investigated in order to evaluate the influence of thermal effects of the laser beam and ongoing changes in pore structure.

Results

It was found that laser cut fiber mats were slightly deformed due to thermal effects, but still had an open, porous structure at the site of the cut. Results also show that joining of fiber mats by laser led to the best bonding result with highest retention force. Application of solvent and glue led to a nonuniform and noncontinuous bonding with lower retention forces.

Conclusions

A first proof of concept for a heart valve-shaped scaffold was created by laser bonding. Thus, the laser is an advantageous tool for post-processing fiber mats and produce complex 3D structures for different applications.

Demineralization of the contacting surfaces in autologous onlay bone grafts improves bone formation and bone consolidation

BACKGROUND

Autologous bone grafts are usually well consolidated after 4 to 5 months but can be incompletely interlocked with the native bone. This study investigated the effect of acid demineralization of the graft-bed interface on graft consolidation.

METHODS

Onlay bone grafts were performed on the calvaria of 36 guinea pigs. Half of the animals had the graft-bed contacting surfaces demineralized with 50% citric acid (pH 1.0) for 3 minutes (test group). The other half received no demineralization (control group). The bone grafts were immobilized by a resorbable membrane glued to the recipient bed with cyanoacrylate. After 7, 30, and 90 days, specimens (n = 6) were obtained for light microscopy. Data from qualitative analysis and computerized histomorphometry were statistically processed at a significance level of 5%.

RESULTS

Osteogenesis was not seen at the interface after 7 days. After 30 days, the test group showed 34.39% ± 13.4% of the interface area filled with mineralized tissue, compared to 17.14% ± 8.6% in the control group (P = 0.026). After 90 days, the mean percentages of mineralized tissue at the interface in the test and control specimens were 54.00% ± 11.23% and 38.65% ± 7.76% (P = 0.041), respectively. Within groups, a higher percentage of the area filled with mineralized tissue was seen at 90 days compared to 30 days (P = 0.004 for control and 0.041 for test).

CONCLUSIONS

Demineralization of the contacting surfaces between autologous bone graft and bone bed improved new bone formation and bone consolidation. These data need to be confirmed in humans.

The modification experimental study in vivo of nano-bone gelatin

OBJECTIVE

To study the feasibility of therapy using nano-bone gelatin to comminuted fracture by animal experiment.

METHODS

The animal models of transverse fracture were made on bilateral ulnas of 45 New Zealand white rabbits, which were divided into experimental group (repair with nano-bone gelatin), control group (repair with traditional medical glue), and blank group (unrepaired) randomly. The reconstruction effect in each group was evaluated using X-ray examination, MicroCT scanning, histopathology observation, and biomechanical test postoperation regularly.

RESULT

On 12th week, the fractures in experimental and blank group get the marrow cavity completely unobstructed and good bone union; however, in control group, the fracture line slightly blurred with the marrow cavity not fully unobstructed; 6 weeks later, observation of bony calluses through MircoCT: experimental group, 68.5 ± 2.71%; blank group, 69.19 ± 2.3%; and control group, 49.35 ± 3.56%, there were no significant difference between the two groups (P > 0.05). The control group obviously showed worse bone union than the former two (P < 0.05). The histopathological examination shows that the bony calluses of experimental group are similar to those of the blank group; however, gelatin degraded slowly in control group with delayed union; on the 12th week, biomechanical test shows that the blank and experiment groups had basically same average bending strength values which had no significant difference (P > 0.05) and obviously were higher than those of the control group (P < 0.01).

CONCLUSION

The nano-bone gelatin won't lead to delayed union of fractures and may be beneficial to it, and so may be an ideal gelatin for fixing small fractures.

Use of cyanoacrylate in the coaptation of edges of surgical wounds

Cyanoacrylate has been used in several fields of different surgical specialties as an adhesive for closure of gingival flaps and in mucous and cutaneous lacerations. One of its advantages is that it has an excellent immunological response. In view of aesthetic needs, cyanoacrylate has been applied with satisfactory results, when compared with sutures. It presents better coaptation of edges of cutaneous and mucosal lesions, smaller residual scars, and biocompatibility. However, it is limited to areas of little tissue tension. This work attempts to provide a literature review with the aim of revealing the advantages of using tissue adhesives, especially cyanoacrylates, in wound coaptation in comparison with conventional methods.

Cytotoxicity evaluation of Curcuma zedoaria (Christm.) Roscoe fluid extract used in oral hygiene products

OBJECTIVE

This in vitro study evaluated the cytotoxic effects of the Curcuma zedoaria (Christm.) Roscoe (popular name: zedoary) fluid extract, as used in preparations for oral hygiene, mostly for anti-septic purposes.

MATERIALS AND METHODS

The cell viability and cell growth were assessed by Trypan blue dye exclusion assay using the LMF cell line derived from oral mucosa. Cell viability (short-term assay) was measured 0, 6, 12 and 24 h after contact with the fluid extract. Cell growth (long-term assay) was analyzed in 1, 3, 5 and 7 days. The experimental groups were those testing the fluid extract obtained from the zedoary rhizome and the extractor liquid (ethanol 70° GL) in the concentrations of 0.01-0.0001% v/v. Fresh DMEM were used in the control cultures.

RESULTS

Short-term assay-all studied cultures maintained stable cell viability; Long-term assay-there was progressive cell growth in all studied cultures.

CONCLUSION

According to the results, the zedoary fluid extract presents low cytotoxicity and probably can be used in the oral hygiene products.

Hypernociception and wound healing after application of cyanoacrylate ester as a tissue adhesive in rats

OBJECTIVE

The present study assessed and compared postoperative hypernociception and skin healing after cyanoacrylate and classic suture as well as analyzed morphologic features of the tissue repair.

STUDY DESIGN

The intensity of hypernociception was measured with an electronic pressure-meter test. Rats were given an incised wound in the middle of the palms of the right and left paws. The left side was treated with a silk suture, and the right with cyanoacrylate. Control groups were treated locally with dipyrone or received a systemic pretreatment with valdecoxib.

RESULTS

Cyanoacrylate was associated with less inflammation (first week), and the healing wound site was rich in collagenous extracellular matrix and neovascularization. Dipyrone in combination with cyanoacrylate greatly increased the antinociceptive effect. These results were not repeated after systemic treatment with valdecoxib, suggesting that the antinociceptive effect seen in the tissue adhesive was due to formation of a physical barrier.

Analysis in vitro of direct bonding system with cyanoacrylate ester and orthodontic wires

The aim of this study was to evaluate the tensile strength of orthodontic wires bonded onto the enamel with cyanoacrylate ester. To obtain the specimens, 120 human premolars (extracted for orthodontic or periodontal reasons) were included in acrylic blocks of rapid polymerization with three teeth each. Four groups were formed with ten specimens each. In the specimens, a dental splint model was made with cyanoacrylate ester and round stainless steel wire. In groups I, II and III, cyanoacrylate ester was used with round steel wires, with variation in diameter: 0.014 inches; 0.016 inches and 0.018 inches, respectively. In group IV, round steel wire 0.018 inches was used with photo polymerizing resin composite with previous acid etching. The adhesive force of the materials was measured in two points under the action of the tensiometer (ETM-USA). The number of loose wires was counted along with those that remained fixed according to the different levels of force applied because of the direction of the tensile force (vertical or horizontal) and the diameter of the wire used. The data obtained were first submitted to a descriptive analysis and then submitted to a statistical analysis (Friedman's Test and Dunn's Test of Multiple Comparison - Epi-info 3.2). Within the limitations of the experimental conditions presented, the cyanoacrylate ester or 'Super Bonder' maintained bonded to enamel and steel wires (0.016 and 0.018 inches) during the tensile strength tests under different levels of applied forces.

In vivo qualitative analysis of the biocompatibility of different cyanoacrylate-based adhesives

Cyanocrylates have been widely used in the medical and dental fields for several years. In Dentistry, cyanoacrylates have been used for suturing, pulp capping, as retrofilling material in endodontic surgeries, and as cervical plug for pulpless teeth bleaching. The biocompatibility of these adhesives has been the topic of many researches and subcutaneous implantation is an effective methodology for these studies. The present study evaluated the biocompatibility of three different cyanoacrylate-based adhesives. Thirty-six Wistar rats were used, divided into four groups of 9 animals each: A (control)--distilled water, B--cyanoacrylate ester (Super Bonder), C - n-butyl-cyanoacrylate (Histoacryl) and D--alpha-cyanoacrylate (Three Bond). The materials were dispensed in sponges of polyvinyl chloride, the animals were incised and the sponges were inserted in the subcutaneous tissue and sutured. Each group was sub-divided according to the time of sacrifice of the animals: 7, 21 and 45 days. Subjective analysis of the histologic material showed that all groups presented some degree of irritability, but the inflammatory reaction decreased with the experimental time in all groups. Group D showed an inflammatory reaction which was closer to that of the control group and was considered to have good biocompatibility. Groups B and C were similar and presented more aggressive inflammatory reactions when compared to the control group. Based on the results, it was concluded that alpha-cyanoacrylate (Three Bond) was the most biocompatible adhesive because it caused the lowest levels of inflammation.

Hemostatic agents injected directly into hepatic injury sites for liver trauma hemorrhage under the guidance of contrast-enhanced ultrasound: an animal experiment

We investigated whether direct injection of hemostatic agents into injury sites under the guidance of contrast-enhanced ultrasound (CEUS) can decrease blood loss from liver trauma. Twelve adult healthy dogs underwent laparotomy, and a hepatic wound (6.0 x 4.5 cm) was created in each dog. All animals were divided randomly into two groups: the treatment group and the control group. In the treatment group, hemocoagulase Atrox (Solco Basle Ltd., Birsfelden, Switzerland) and absorbable cyanoacrylate were injected directly into the liver injury sites, and 0.9% normal saline was injected into the injury sites in the control group. Resuscitation volume in the treatment group was less than that in the control group (55 +/- 12 mL vs. 105 +/- 23 mL, p < 0.001). The control group presented bleeding from liver injury sites. Times of bleeding at the injury site in the treatment groups were 6 +/- 1 s. Both groups presented an-echo and/or hypo-echo contrast regions, with contrast material pooling in the injury sites before the therapy. After the injection, the contrast material pooling disappeared in the treatment group observed by CEUS. Gross examination of liver tissue revealed that the injury site that had been treated was covered by clot and glue membrane. Histopathologic examination showed that there was hemostitic glue embolizing the microvessels and inflammatory cell infiltration among hepatocytes. Direct injection of hemocoagulase Atrox and cyanoacrylate into the liver injury sites guided by CEUS can effectively reduce blood loss from liver trauma within a short time. This experimental study may suggest a possible treatment for liver trauma hemorrhage and provide an experimental evidence for treating blunt abdominal parenchyma organs trauma under the guidance of CEUS.

Percutaneous injection therapy for blunt splenic trauma guided by contrast-enhanced ultrasonography

OBJECTIVE

The purpose of this study was to investigate the application of contrast-enhanced ultrasonography (CEUS) in managing blunt splenic trauma and the effectiveness of CEUS-guided percutaneous injection therapy.

METHODS

Six patients with grade 3 or 4 splenic injuries as determined by CEUS and contrast-enhanced computed tomography were given hemocoagulase atrox and absorbable cyanoacrylate percutaneously, which were injected into the injury region and active bleeding site, respectively, under CEUS guidance. Immediately after the procedure and 1 and 3 days, 1 and 2 weeks, and 1 and 6 months after the procedure, follow-up CEUS up was performed in all patients.

RESULTS

Among the 6 patients, 4 cases of CEUS-guided hemostatic injection were successful without complications. Rehemorrhage occurred in 1 patient, and a traumatic arteriovenous fistula occurred in another; repeated injection therapy in these 2 patients was effective. During the follow-up, there were no complications, and spleen perfusion recovered gradually.

CONCLUSIONS

Contrast-enhanced ultrasonography can be used to guide percutaneous injection therapy and therefore achieve the goal of using interventional ultrasonography in managing splenic trauma.

Cytotoxic effects of four different endodontic materials in human periodontal ligament fibroblasts

The purpose of this study was to compare the cytotoxicity, induced apoptosis and/or necrosis, and apoptotic mechanisms in human periodontal ligament (PDL) fibroblasts treated with four different endodontic materials: White ProRoot mineral trioxide aggregate (MTA) (MTA/Dentsply; Tulsa Dental, Memphis, TN), Diaket (ESPE, Seefeld, Germany), Endion (VOCO, Cuxhaven, Germany), and CYMED 8410 (NANO, Kaohsiung, Taiwan). The effects of these four materials on the viability of PDL fibroblasts were determined by MTT (3-(4,5-dimethyl-thiazoyl)-2,5-diphenyl-SH-tetrazolium bromide) assay. Apoptotic pathways were evaluated via several mechanisms. Exposure to MTA for 24, 48, and 72 hours resulted in no significant differences in MTT reduction and viable cell number compared with controls. However, treatment of PDL fibroblasts with Diaket, Endion, and CYMED 8410 for 24, 48, and 72 hours resulted in cytotoxicity with MTT and a reduction of viable cell number with trypan blue dye exclusion test compared with controls (from p < 0.05 to p < 0.001). Annexin V-FITC/PI staining showed that Diaket, Endion, and CYMED 8410 induced higher percentages of apoptosis and/or necrosis than in controls (45.6%, 25.5%, and 6.3%, respectively). Results of cell-cycle analyses were concordant with annexin V-FITC/PI staining findings. These results suggest that MTA is a very biocompatible filling material. However, Diaket, Endion, and CYMED 8410 are toxic to PDL fibroblasts in vitro. The main form of cell death induced by these filling materials was determined to be apoptosis and/or necrosis.

Experimental comparative study in rabbits of three different ways of cartilage graft fixation: suture, gelatin-resorcin-formaldehyde and butyl-2-cyanoacrylate

CONCLUSION

The compound gelatin-resorcin-formaldehyde (GRF) was a better stabilizing material for cartilage grafts in rabbits than butyl-2-cyanoacrylate. GRF was also better than the suture when comparing fixation of cartilage to the periosteum and inflammatory reaction.

OBJECTIVE

Cartilage grafting is an interesting option for refinements on rhinoplasties. The objective of this study was to compare butyl-2-cyanoacrylate to GRF and suture to determine the efficacy of these methods in restraining grafted cartilage in rabbits.

MATERIALS AND METHODS

Fifteen male adult New Zealand rabbits underwent surgery with the aim of collecting six auricular cartilage grafts from each animal. Two of these grafts in each animal were glued together with butyl-2-cyanoacrylate, two were glued together with compound GRF, and two were sewn together with nylon suture. These sandwich grafts were then glued or sutured to the periosteum of the glabella. After 2, 6, and 12 weeks, groups of five animals were sacrificed and histological analysis for inflammation was performed. Cartilage graft migration, adhesion, and deformities of the grafts were also evaluated.

RESULTS

There was less migration of the cartilages glued with GRF than with cyanoacrylate and suture. GRF showed statistically less inflammatory reaction and angiogenesis than the other two methods. The three methods showed a tendency to decrease of fibrosis, inflammation, and angiogenesis as weeks passed. There was no detachment or deformity in the cartilage sandwiches sutured to the glabella's periostium. The majority of detached and deformed cartilages were those glued with cyanoacrylate. The number of detached cartilages was directly related to the number of deformed cartilages. The data were statistically significant (p<0.05).

Cytotoxicity evaluation of sodium alendronate on cultured human periodontal ligament fibroblasts

External root resorption processes are usually associated with dental trauma, mainly avulsion and intrusion. In such cases endodontic therapy aims to prevent this process by using medications that can inhibit osteoclastic activity, such as bisphosphonates. However, these drugs must be biocompatible to the periapical tissues. The aim of this study was to analyze the cytotoxicity of a bisphosphonate (sodium alendronate) on human periodontal ligament fibroblasts (PDL cells). Cells were plated in a density of 1 x 10(3) cells per dish. The experimental groups were GI (control) no sodium alendronate, and GII, GIII, and GIV with sodium alendronate at the concentrations of 10(-5), 10(-6), and 10(-7) M, respectively. The experimental times were 1, 6, 12, and 24 h (short-term) for viability and 2, 4, 6, and 8 days (long-term) for cell survival. Data in triplicate were statistically analyzed. Cultures treated with the highest alendronate concentration (GII) showed cell viability percentages significantly lower (P < 0.01) than those of the other groups (GI, GIII, and GIV), at 12 and 24 h. Cell growth on GII and GIII groups was similar. GII presented smaller growth than the other groups (P < 0.05). We concluded that sodium alendronate, on direct contact with human periodontal ligament fibroblasts, is cytotoxic in concentrations higher than of 10(-6) M.

Histologic evaluation of pulpotomy performed with ethyl-cyanoacrylate and calcium hydroxide

The aim of this study was to evaluate histological aspects of the pulp-dentin complex of dogs submitted to pulpotomy and capped with ethyl-cyanoacrylate and calcium hydroxide. Thirty dog teeth were divided into 2 groups of 15 as follows: Group 1 - ethyl-cyanoacrylate; Group 2 - calcium hydroxide. The pulpotomies were carried out following all of the treatment precautions recommended for dogs. After 30 days the specimens were submitted to histological preparation and were then blindly evaluated by a histologist. Data were analyzed statistically by the Fisher exact test, comparing the two groups. After 30 days, the presence of a hard tissue barrier was observed in 83.3% of Group 1, and in 100% of Group 2 (p = 0.478). A continuous hard tissue barrier was observed in 50% of the ethyl-cyanoacrylate group and 75% of the calcium hydroxide group (p = 0.652). It can be concluded that both materials induced hard tissue barrier formation, but Group 2 had a higher percentage than Group 1, with no significant statistical differences; the differences observed between the different barriers (continuous/non-continuous) were not significant between groups and there was no pulpal necrosis in either group.

Cytotoxicity analysis of alendronate on cultured endothelial cells and subcutaneous tissue. a pilot study

The use of alendronate, a bisphosphonate which is able to inhibit bone resorption, in order to prevent dental root resorption after tooth replantation would be of clinical relevance. However, this drug must be biocompatible to the periapical tissues. The aim of this study was to analyze the effect of an alendronate paste in polyethyleneglycol (2 g ml(-1)) on endothelial cells in culture (in vitro) and on rat subcutaneous tissue (in vivo). For the in vitro study the paste was applied on round glass coverslips that were immersed into confluent cell cultures (clone Cips). The cell viability percentages of these cultures were obtained 0, 6 and 12 h after contact with the substance. As control, cultures that received plain coverslips were used. This analysis was carried out in triplicate using the Trypan blue dye exclusion assay. For the in vivo study the paste was introduced into polyethylene tubes that were placed into the rat subcutaneous tissue. The rats were killed 7 and 14 days later; then, the tissue sections stained with hematoxylin-eosin were analyzed. In vitro, the alendronate caused a significant decrease in the cell viability in 6 h (P < 0.05) and 12 h (P < 0.01), when compared with the control cultures. In vivo the tissue response was exuberant and similar at the two experimental times. There was a necrosis in a comprehensive area in contact with the open end of the tube. Presence of micro-abscesses and intense inflammatory infiltrate in the hypoderm permeating the muscle fibers and fat lobules were observed. In conclusion, the alendronate paste in polyethylene glycol as used showed to be highly cytotoxic in vitro as well as in vivo.

In vitro evaluation of the cytotoxic effects of acid solutions used as canal irrigants

Solutions of EDTA and citric acid have been used as canal irrigants. These substances must be compatible with apical periodontal tissue. The aim of this study was to evaluate comparatively the cytotoxicity of a 17% EDTA solution and that of three solutions with different concentrations of citric acid (10, 15, and 25%) on cultured fibroblasts. The solutions were diluted to 0.1% and 0.5% in culture medium and then applied to NIH 3T3 cells. After 0, 6, 12, and 24 h (short-term assay; viability) and 1, 3, 5, and 7 days (long-term assay; survival), the cells were counted. The data were compared by ANOVA. In the short-term experiments, all solutions presented a percentage of cell viability similar to that of control cells, except for the 17% EDTA solution diluted to 0.5%. After the long-term assay, all groups presented a continuous and progressive cell growth except for the 17% EDTA solution and for the 25% citric acid solution at a 0.5% dilution. The citric acid solution did not impair cell growth and viability, proving to be noncytotoxic in vitro.