Tissue reaction to endodontic materials: methods, criteria, assessment, and observations

Laboratory study of tissue repair of resin-based endodontic sealers in critical surgical defects

Filling materials should be restricted to the root canal space. However, sometimes it is impossible to control the apical extrusion, in this case, the fate of the filling material and the result of the treatment will depend on its physicochemical properties and biocompatibility.

The fate of overfilling in root canal treatments with long-term follow-up: a case series

This study describes 6 cases of endodontic overfilling with successful clinical outcomes during long-term (up to 35 years) radiographic follow-up. Successful endodontic treatment depends on proper shaping, disinfection, and obturation of root canals. Filling materials should completely fill the root canal space without exceeding the anatomical apex. Overfilling may occur when the filling material extrudes into the periapical tissues beyond the apex. The present case series describes 6 root canal treatments in which overfilling of root canal sealer and gutta-percha accidentally occurred. Patients’ teeth were periodically checked with periapical radiographs in order to evaluate the outcomes during long-term follow-up. All cases showed healing and progressive resorption of the extruded materials in the periapex. The present cases showed that if a 3-dimensional seal was present at the apical level, overfilling did not negatively affect the long-term outcomes of root canal treatment.

A Review of Medicolegal Considerations of Endodontic Practice for General Dental Practitioners

Treating a live human being to their health has been considered as a noble profession since the ancient times. Doctors are duty bound by their professional ethics to provide the best treatment to their patients. Endodontics is the specialty branch of the dental science of saving natural teeth in the oral cavity. During endodontic procedures, a mishap can occur any time in a day-to-day practice and may be treated as negligence which in turn ends into some legal complications. To prevent and tackle such future medicolegal issues related to endodontic treatment, the knowledge of the legal aspect of such clinical situation is necessary.

Iatrogenic Damage to the Periodontium by Chemicals and Dental Materials

The toxicity and tissue reactions to dental materials are receiving more attention as a wide variety of materials are used and as federal agencies demonstrate more concern in this area. A further indication of the importance of the interaction of materials and tissues is the development of recommended standard practices and tests for the biological interaction of materials.

Ability of new obturation materials to improve the seal of the root canal system: a review

New obturation biomaterials have been introduced over the past decade to improve the seal of the root canal system. However, it is not clear whether they have really produced a three-dimensional impervious seal that is important for reducing diseases associated with root canal treatment. A review of the literature was performed to identify models that have been employed for evaluating the seal of the root canal system. In vitro and in vivo models are not totally adept at quantifying the seal of root canals obturated with classic materials. Thus, one has to resort to clinical outcomes to examine whether there are real benefits associated with the use of recently introduced materials for obturating root canals. However, there is no simple answer because endodontic treatment outcomes are influenced by a host of other predictors that are more likely to take precedence over the influence of obturation materials. From the perspective of clinical performance, classic root filling materials have stood the test of time. Because many of the recently introduced materials are so new, there is not enough evidence yet to support their ability to improve clinical performance. This emphasizes the need to translate anecdotal information into clinically relevant research data on new biomaterials.

Clinical negligence or endodontic mishaps: A surgeons dilemma

Complications may occur during and after endodontic treatment, which may be due to negligence of the operator. The surgical treatment of a case presenting pain and persistent pus discharge and swelling due to the extrusion of the root canal filling to the base of the nasal floor between left maxillary lateral and canine teeth is presented in this report. First, carelessness was during root canal treatment that was over obturated and second time during extraction in which overextended gutta-percha remained in the bone, caused the complications like pain, persistent pus discharge, and headache. Clinicians should be aware of the fact that endodontic instruments and filling materials (solid or liquid) can be extended in such a degree that can lead to neurological or sinus complications.

Subcutaneous connective tissue reaction to methacrylate resin-based and zinc oxide and eugenol sealers

INTRODUCTION

An evaluation was made of the connective tissue reaction in rats after subcutaneous implantation of methacrylate resin-based sealers (EndoREZ [Ultradent Products, Inc, South Jordan, UT] with a polymerization accelerator and RealSeal [Sybron Dental Specialties, Orange, CA]) and Pulp Canal Sealer (Sybron Dental Specialties), a zinc oxide and eugenol-based sealer used as the control.

METHODS

Silicone tubes containing the test materials were implanted in 24 Wistar rats. Solid silicone rods of the same size served as the negative controls. After 10, 30, and 90 days, the animals (n = 8 per period) were euthanized and the implants with surrounding tissues dissected and processed for routine histological evaluation. A four-category evaluation system was used to measure and record the microscopic observations according to the thickness of a fibrous capsule, the vascular changes, and the various types of inflammatory cells.

RESULTS

Initially, a severe inflammatory reaction was observed of the soft tissues in direct contact with both EndoREZ/Accelerator and Real Seal. The severity decreased over time and was resolved at the end of the experiment. Pulp Canal Sealer showed a severe tissue reaction for all observation periods. The negative controls showed an initial mild to moderate inflammatory reaction. After 30 days, healthy fibrous connective tissue was observed, which increased over time. After 10 days, no statistically significant differences between the experimental groups were observed. After 90 days, EndoREZ and RealSeal were statistically significantly less toxic than Pulp Canal Sealer (p > 0.05).

CONCLUSIONS

After 90 days, both methacrylate resin-based sealers were considered biologically acceptable when implanted in subcutaneous connective tissues of the rat. Pulp Canal Sealer remained toxic for the duration of the study.

Periapical repair in dog teeth: root canal adhesive filling by using the Resilon System

INTRODUCTION

New filling biomaterials with better physicochemical properties would create a favorable biologic environment for the healing of periapical tissues. The aim of this study was to evaluate periapical repair after biomechanical preparation and root filling with an adhesive system compared with the gold standard material (gutta-percha+sealer) in dog teeth.

METHODS

The pulp of 25 root canals was removed. The apical cementum layer was perforated, and the root canals were prepared up to size #60 K-file followed by step-back shaping with the #90 K-file and filled by the lateral condensation technique. In the experimental group (n=15), the Resilon System (Pentron Clinical Technologies, Wallingford, CT) was used. As a control material (n=10), gutta-percha cones and pulp canal sealer were used. After 60 days, the animals were killed, and 10 histologic parameters were evaluated. Differences among the groups were analyzed by using the Mann-Whitney and Fisher exact tests.

RESULTS

In radiographic and histologic evaluations, most fillings were slightly short of the apex. Progressive regenerative stages were observed; however, there was a reduced prevalence of biologic foraminal closure. No significant differences were observed between the 2 biomaterials with regard to any of the parameters evaluated (P>.05).

CONCLUSIONS

The Resilon System shows periapical biocompatibility equivalent to the gold standard material.

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The Authors describe two cases of alleged malpractice due to overfilling. The aim of this article is to underline some medico-legal aspects regarding the quantity of extruded material which may be considered acceptable and the consequent damage to the patient.

Two cases are presented here: In the first case, the dentist’s liability is clear due to excessive extrusion of endodontic material beyond the apical region combined with incomplete obturation of the canals. In the second case however, because two different dentists were involved, establishing the connection of causality between their work and the damage reported by the patient was not easy. This situation makes it difficult to establish the limits of potential responsibility, coupled with the complete absence of radiographic signs of periapical rarefaction and the small quantities of material beyond the apex. From a medico-legal point of view, a dentist may be held responsible for compensation and financial expenses of a patient for restoration of damage resulting from a dental procedure.

Italian guidelines offer no indications as to when overfilling should be considered the result of a procedural error, or if it fits within the range labelled as “acceptable” and this gap offers extremely subjective interpretations of legal consultants. So, it would therefore be useful to adopt more precise qualitative/dimensional parameters, keeping in mind that the guidelines offer therapeutic recommendations and are not rigid protocols.

Radiographic evaluation of periapical healing of permanent teeth with periapical lesions after extrusion of AH Plus sealer

The aim of this study was to clinically and radiographically examine the effects of extrusion of AH Plus sealer on the healing of permanent teeth with apical periodontitis. A total of 87 root canals radiographically detected with apical periodontitis were included in the study. Posttreatment radiographs indicated sealer extrusion into 49 canals (Group 1) and no sealer extrusion into 38 canals (Group 2). Periapical treatment was judged as complete healing (CH), incomplete healing (IH) and no healing (NH) at the end of a 4-year follow-up period. Amounts of extraradicular sealer were recorded as "unchanged," "reduced," "almost absent," or "absent." The t test was used for the statistical analyses. In Group 1, CH was detected in 41 canals, IH in 4 canals, and NH in 4 canals. Differences between CH and both IH and NH were statistically significant (P < .001). In Group 2, CH was detected in 34 canals and NH in 4 canals. The difference between CH and NH was statistically significant (P < .001). A statistically significant difference (P < .05) between treatment groups was observed for CH at the 6-month follow-up appointment only; other than that instance, there were no statistical differences for CH or NH between the groups. In conclusion, extruded AH Plus does not prevent periapical healing, but can be a delaying factor for healing in children.

In vivo comparison of the biocompatibility of two root canal sealers implanted into the subcutaneous connective tissue of rats

OBJECTIVE

To evaluate the subcutaneous biocompatibility of 2 root canal sealers.

STUDY DESIGN

The subcutaneous implant technique recommended by the Fédération Dentaire International (FDI) was used to test Endométhasone and EndoREZ root canal sealers. These materials were placed in Teflon tubes, 1 mm in diameter and 10 mm in length, and implanted into 2 pockets created in the back of 40 Calomys callosus rodents, 20 for each material. Tissue biopsies were collected and histologically examined 15, 30, 60, and 90 days after the implantation procedure. The overall level of the inflammatory tissue response was graded as none, slight, moderate, or severe on the sealer-connective tissue interface at the opening ends of the tubes. The connective tissue response along the lateral wall outside of each tube served as a negative control.

RESULTS

The tissue reaction to the Endométhasone diminished with time. The EndoREZ sealer was highly toxic during all experimental periods.

CONCLUSION

Endométhasone root canal sealer presented biocompatibility within the analyzed periods, whereas EndoREZ showed no biocompatible behavior and caused late hypersensitive reaction.

The immuno cross-reactivity of gutta percha points

OBJECTIVE

The purpose of this study is to test the postulated immuno cross-reactivity between proteins derived from raw gutta percha (RGP), gutta percha point (GPP) and natural rubber latex (NRL).

METHODS

Antigenicity and cross-reactivity of proteins were determined by the FITkit (FITBiotech, Finland) and ELISA inhibition assays.

RESULTS

Antigenicity of proteins derived from RGP or GPP was not demonstrated. Except for NRL glove extracts, neither extracts from RGP or GPP were reactive in ELISA inhibition assay.

SIGNIFICANCE

There is no immunologic cross-reactivity in vitro between proteins derived from RGP or GPP, and from NRL gloves. Thus, therapeutic use of GPP is unlikely to initiate adverse immuno-reactivity in individuals previously sensitized to NRL proteins.

Pulp cell cultures obtained with two different methods for in vitro cytotoxicity tests

AIM

To describe two different protocols for obtaining primary pulp cell cultures, one derived from explants and the other following dissociation into single cell suspension by enzyme digestion.

METHODS

Human pulp tissue was obtained from three healthy premolars. The harvested pulp tissue was prepared for culture using physical methods (one of the premolars) and enzyme, type XI collagenase, (the two remaining premolars).

RESULTS

In the case of explant based culture, only limited growth was observed in some cases. However, by enzyme digestion, after two weeks cell growth was evident, and differences in cell type were observed according to the tooth involved.

CONCLUSION

It has been possible to obtain abundant biological material using an enzyme digestion-based protocol for testing purposes, with low experimental variability, as all cells originated from the same individual.

Short-Term Cytotoxicity Assessment of Components of the Epiphany Resin-Percha Obturating System by Indirect and Direct Contact Millipore Filter Assays

The Epiphany Resin-Percha Obturating System was assessed for cytotoxicity, compared with gutta-percha and AH-Plus sealer. Specimen disks (Resilon, gutta-percha), filled glass rings (sealers), or imbibed cellulose disks (primer, thinning resin) were placed over Millipore filters in direct or indirect contact with HeLa cell monolayer, incubated for 2 hours, and stained with tetrazolium blue. Cytotoxicity was rated by the surrounding unstained zone: none (0 mm), mild (</=7 mm), moderate (7-12 mm), or marked (>12 mm). Data were analyzed with one-way ANOVA and post hoc pairwise t tests. Unstained zones indicating moderate cytotoxicity were significantly larger (p < 0.05) for Epiphany primer than for thinning resin and for freshly mixed AH-Plus than for Epiphany sealer. Set sealers (24 and 48 hours), gutta-percha, and Resilon elicited noncytotoxic responses. In conclusion, cytotoxicity of set Epiphany sealer and Resilon was comparable with that of set AH-Plus and gutta-percha. Cytotoxicity of freshly mixed Epiphany sealer, primer, and thinning resin did not exceed that of freshly mixed AH-Plus.

Bone level around endodontically treated teeth in periodontitis patients

OBJECTIVES

This retrospective study compared the marginal bone level of teeth with root canal fillings with contra-lateral teeth without.

METHODS

Of 286 consecutive patients (> or =35 years), referred to practice for periodontology in the Netherlands, 67 full sets of radiographs contained > or =1 endodontically treated tooth and its contra-lateral tooth without root canal treatment. Bone level at the mesial and distal of these teeth was scored from the CEJ. In multi-rooted teeth, the presence of interradicular radiolucency was assessed. The presence of posts, and periapical radiolucencies was assessed. Analysis for differences between treated teeth and contra-laterals was controlled for tooth surface, presence of a post and tooth type.

RESULTS

The mean distance from the root filling to the apex was 2.6 mm. Periapical radiolucencies were found in 14%. The mean bone level was at 4.3 mm for endodontically treated teeth and at 3.7 mm for contra-laterals. Significantly more bone loss (0.6 mm) was found at the endodontically treated teeth. No difference was found between mesial and distal, teeth without and with posts and different tooth types. The presence of interradicular radiolucency was more frequent in endodontically treated teeth (OR 2.1, p(McNemar test)=0.039).

CONCLUSION

In periodontitis patients, teeth with endodontic treatment had more bone loss as compared with untreated contralaterals.

Observations on healing following endodontic surgery in nonhuman primates (Macaca fascicularis): Effects of rhBMP-2

OBJECTIVES

The potential of recombinant human bone morphogenetic protein-2 (rhBMP-2) to enhance bone healing following endodontic surgery was tested. The pattern and timing of de novo bone formation and cementum regeneration, and the potential for root resorption and ankylosis to accompany bone formation were evaluated.

STUDY DESIGN

Pulpal infections were induced in maxillary and mandibular incisor teeth in young adult Cynomolgus monkeys. The teeth received conventional endodontic treatment immediately followed by surgical root resection. In a randomized split-mouth design, contralateral apical bone defects received rhBMP-2 in absorbable collagen sponge (ACS) carrier or served as sham-surgery controls to provide histological and radiographic evaluations following 1 (mandibular incisors) and 4.5 (maxillary incisors) month(s) postsurgery.

RESULTS

At 1 month postsurgery trabecular bone filled the apical bone defects. The newly formed bone appeared considerably more mature and had assumed characteristics of the contiguous resident bone at 4.5 months postsurgery. The resected root tips were almost completely covered by new cementum with a maturing functionally oriented periodontal ligament. Localized inflammatory infiltrates were associated with the filled root canals and extruded root-filling material. Root resorption and ankylosis were not observed. There were no apparent differences in healing patterns between sites implanted with rhBMP-2/ACS and those serving as sham-surgery controls.

CONCLUSIONS

Under conditions where the influence of infectious elements and irritation caused by root filling material are minimized, bone formation and cementum regeneration appears rapid following endodontic surgery. rhBMP-2/ACS did not offer an obvious benefit above and beyond that of the native osteogenic potential in this animal model.

Do procedural errors cause endodontic treatment failure?

BACKGROUND

This article reviews the effect of endodontic procedural errors, such as underfilling, overfilling, root perforations and separated instruments, on the outcome of endodontic therapy.

TYPES OF STUDIES REVIEWED

Filling the root canal more than 2 millimeters from the radiographic apex (underfilling) or beyond the radiographic apex (overfilling), perforations of the root canal system and instrument separation are possible complications of endodontic therapy. Although these procedural errors may have different causes, they all may affect the outcome of treatment.

RESULTS

Endodontic procedural errors are not the direct cause of treatment failure; rather, the presence of pathogens in the incompletely treated or untreated root canal system is the primary cause of periradicular pathosis. Procedural errors typically are due to several factors. Among them is a lack of understanding of the root canal anatomy, the principles of mechanical instrumentation and tissue wound healing.

CLINICAL IMPLICATIONS

Procedural errors impede endodontic therapy, thus increasing the risk of treatment failure, especially in teeth with necrotic pulps and periradicular lesions. However, procedural errors often are preventable.

Expression of MHC Class II, CD70, CD80, CD86 and pro-inflammatory cytokines is differentially regulated in oral epithelial cells following bacterial challenge

Oral epithelium may play a regulatory role in local immune responses when interacting with bacteria. The present study was undertaken to investigate the effects of selected bacterial pathogens found in periodontal and endodontic infections on oral epithelial cells. Expression of cell surface molecules (major histocompatibility complex (MHC) Class II, CD54, CD70, CD80 and CD86) and secretion of inflammatory cytokines (interleukin (IL)-1beta, IL-6, and tumor necrosis factor (TNF)-alpha) in response to selected bacterial challenge were examined on an immortalized oral epithelial cell line, HOK-18A and a skin epithelial cell line, HaCaT. Actinomyces viscosus, Actinomyces israelii, Fusobacterium nucleatum lipopolysaccharide (LPS) or primary human periradicular exudate from a granuloma were co-cultured with epithelial cells for 4 or 24 h. Subsequently, cell surface expression of MHC Class II, CD54, CD70, CD80 and CD86, along with pro-inflammatory cytokine levels were determined using flow cytometry, ELISA and RT-PCR. Results indicated that the selected oral bacteria have greater effects on oral versus skin epithelial cells. F. nucleatum increased MHC Class II and CD54 (ICAM-1) cell surface expression on HOK-18A and HaCaT cells. A. israelii also had enhancing effects on the expression of CD54 and MHC Class II. A. israelii and LPS induced a 2.8-fold (P < 0.001) and 4.4-fold (P < 0.005) TNF-alpha secretion, respectively, while F. nucleatum and LPS induced a 10-fold (P < 0.0004) and 6-fold (P < 0.01) IL-1beta secretion, respectively by HOK-18A. Interestingly, CD70, CD80, and CD86 were generally decreased upon bacteria and LPS challenge on HOK-18A. The effects of increased MHC Class II and decreased CD70 were also evident with challenge of human periradicular exudate on HOK-18A. The implications of the study are unique in that oral epithelial cells may play both activating and inhibitory roles in the host immune response towards infection by oral bacteria. We introduce a concept of 'dormancy' where the differential expression of key cell surface antigens on oral epithelial cells may keep the recruited immune effector cells in a state of unresponsiveness, thus contributing to the long term quiescent period observed in many periodontal and endodontic lesions.

Periapical inflammation affecting coronally-inoculated dog teeth with root fillings augmented by white MTA orifice plugs

Placement of orifice plugs has been suggested to augment the seal of conventional root canal fillings. This study assessed in vivo the efficacy of white mineral trioxide aggregate (MTA) plugs in preventing periapical inflammation subsequent to coronal inoculation of root-filled teeth. The two-rooted mandibular premolars of six beagle dogs were conventionally prepared and filled with gutta-percha and sealer. A white MTA orifice plug was placed into one canal in each tooth. Pulp chambers were inoculated with plaque except for 12 teeth (negative control), and restored. Radiographs were taken at regular intervals. At 10 months, dogs were killed and jaw blocks processed for histology. None of the roots revealed radiographic or histologic evidence of severe inflammation. Mild inflammation was observed in 17% and 39% of the roots with and without an orifice plug, respectively (McNemar, p > 0.05). Without development of severe inflammation, the seal augmentation efficacy of MTA orifice plugs could not be determined.

Tissue reaction initiated by different sealers

AIMS

To analyse the type and degree of inflammatory reaction initiated by four sealers.

METHODOLOGY

Twenty-four root canals of Macaca mulatta monkeys were filled within the canal and eight were overfilled with AH26, Apexit, Endomethasone or Grossman's sealers. The result of the treatment was evaluated after 6 months by histological assessment of the periapical tissues.

RESULTS

In the group of root canals filled within the root, no inflammatory reaction was detected in specimens of Apexit and Grossman's sealers, but the other two sealers initiated different degrees of lymphocytic/plasmocytic tissue reactions. Endomethasone initiated a mild lymphocytic/plasmocytic reaction in three of the nine cases and AH26 caused mild lymphocytic/plasmocytic infiltration in two of the seven cases. In the group of overfilled root canals, all four sealers initiated inflammatory reactions. The periapical tissue reactions of overfilled root canals were similar to reactions detected in cases filled within the canal. However, additional histological features developed in specimens of Endomethasone and AH26: Endomethasone initiated a foreign body-type granulomatous reaction around the sealer particles and AH26 particles were engulfed by macrophages. The overfilled root canals of Apexit and Grossman's sealers initiated only lymphocytic/plasmocytic reactions.

CONCLUSIONS

This study suggests that sealers with different chemical compositions initiate different histological reactions. It also emphasizes the importance of confining root filling to the canal system because all sealers initiate inflammatory reactions when they are present in the apical tissues

Biocompatibility of dental materials used in contemporary endodontic therapy: a review. Part 2. Root-canal-filling materials

Root-canal-filling materials are either placed directly onto vital periapical tissues or may leach through dentine. The tissue response to these materials therefore becomes important and may influence the outcome of endodontic treatment. This paper is a review of the biocompatibility of contemporary orthograde and retrograde root-canal-filling materials.

Long-term cytocompatibility of various endodontic sealers using a new root canal model

It was the purpose of our study to determine the cytotoxicity of several types of root canal sealers in vitro over the period of 1 yr by using a new test model. Roots of extracted human teeth were filled with N2, Apexit, Roekoseal, AH Plus, Ketac Endo, Endomethasone, and one gutta-percha point. In addition, roots filled with laterally condensed gutta-percha/N2. Teeth filled with one gutta-percha point only were controls. All specimens were consecutively extracted with distilled water for a total period of 1 yr. Extracts were investigated for cytotoxicity by using immortalized 3T3 fibroblasts and primary human periodontal ligament fibroblasts. Results were statistically analyzed with Dunnett's t tests (p < 0.05). Pronounced cytotoxic effects were only caused by N2-extracts in both cell cultures (p < 0.05). Furthermore, statistically significant cytotoxic alterations were also induced by 10-week eluates of Endomethasone (p < 0.05). All other investigated materials did not significantly alter cell metabolism.

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.

The induction of micronuclei in V79 cells by the root canal filling material AH plus

The in vitro micronucleus test (MNT) is an alternative to the chromosomal aberration assay for the detection of chromosomal mutations. Here, the epoxy resin-based root canal filling material AH Plus, the compounds paste A and paste B were tested for cytotoxicity and the induction of micronuclei in V79 cells. Paste A is the epoxy-resin-containing compound. AH Plus was tested immediately after mixing and after a setting time of 24 h. The materials were eluted in dimethyl sulfoxide (DMSO) and physiologic saline for 24 h. DMSO eluates of the mixed material, paste A and paste B clearly reduced the viability of V79 cells, but eluates prepared with physiological saline were at least 10-100-fold less toxic. Likewise, freshly mixed AH Plus was mutagenic in a dose-dependent manner in V79 cells after elution in dimethyl sulfoxide only. The numbers of micronuclei were about 7-fold higher in treated cell cultures compared with untreated controls. No mutagenicity was observed with DMSO and physiological saline eluates of mixed AH Plus set for 24 h. DMSO eluates of paste A induced effects similar to the freshly mixed AH Plus, and paste B was not effective. Therefore, we provide evidence for the induction of chromosomal mutations by freshly mixed AH Plus under experimental conditions.

Cytotoxic and mutagenic potencies of various root canal filling materials in eukaryotic and prokaryotic cells in vitro

Cytotoxic and mutagenic effects of root canal filling cements of various chemical composition were determined in vitro. Materials set for 24 h and 1 wk were eluted for 24 h in cell culture medium (cytotoxicity testing) and dimethyl sulfoxide or physiological saline (mutagenicity testing). The differences between cytotoxic potencies of eluates of the endodontic materials on L-929 cells were quantified colorimetrically (MTT test). Eluates of Traitement SPAD were about 5- to 30-fold more toxic than silver-free AH26, Tubli-Seal, CRCS, and Endomethsone N. The rank order of the toxic effects depended on the setting time of mixed materials. Dimethyl sulfoxide and saline eluates of Traitement SPAD, Tubli-Seal, Endomethasone N, CRCS, and Ketac-Endo were not mutagenic in the Ames test. Both eluates of silver-free AH26 set for 24 h were weakly mutagenic in Salmonella typhimurium TA100. Weak mutagenicity of saline eluates of the material was also observed in TA97a and TA102. These results point to the possibility that mixed silver-free AH26 might contain small amounts of two mutagenic substances: bisphenol A diglycidyl ether and formaldehyde.

The protective effect of zinc on rosin and resin acid toxicity in human polymorphonuclear leukocytes and human gingival fibroblasts in vitro

Combinations of rosin and zinc are used in dentistry as components of periodontal dressings and cements and as root canal sealers. The composition and properties of rosins differ largely depending on source and refinement processes. Rosin (colophony) is composed of approximately 70% resin acids. In order to study the toxic effects of different natural rosins and purified resin acids and the detoxifying effects of zinc, these compounds were analyzed and tested on human polymorphonuclear leukocytes (PMN cells) and human gingival fibroblasts using the radiochromium release method. The rosins and the pure resin acids showed a strong dose-related cytotoxicity, which was inhibited by increased zinc concentrations. The purified resin acids (isopimaric, levopimaric, and neoabietic acid) were more toxic than the natural rosins. The contents of these resin acids might explain the difference in toxicity of the rosins tested. It is concluded that rosin and zinc are not to be considered inert compounds and that the cytoprotective effects of zinc and its role in dentistry products merit further investigations.

Periradicular curettage

Periradicular curettage is a part of the treatment procedure of periradicular surgery. Its main purpose is to remove pathological periradicular tissues for visibility and accessibility to facilitate the treatment of the apical root canal system, or sometimes for the removal of harmful foreign materials present in the periradicular area. Inflammatory periradicular lesions (granuloma and cysts) are the responses of the periradicular tissues to irritants from the root canal and not from the periradicular area unless medicaments and/or filling materials have been forced through the apical foramina or perforations into the periodontium. Histologically, the inflammatory periradicular lesion is similar to healing granulation tissue, which is composed of cells which have natural and specific immunological defence capability and cooperate by means of cytokines to amplify the protective mechanisms of the host. Accordingly, it is not necessary to completely curette out all the inflamed periradicular tissues during surgery, since this granulation-like tissue will be incorporated into the new granulation tissue as part of the healing process. To control the source of irritants in the root canal is far more important than to remove all periradicular tissues affected by the irritants. The successful removal of all irritants from the root canal system results in resolution of pulpally induced periradicular lesions. In the case where the periradicular lesion is caused by endodontic instruments or cytotoxic filling materials placed in the periradicular tissues, removal of these foreign objects is required for resolution of the lesion.

Tissue reaction to gutta-percha particles of various sizes when implanted subcutaneously in guinea pigs

Tissue reaction to gutta-percha was studied using subcutaneously implanted Teflon cages in guinea pigs. Gutta-percha was tested in three forms: (i) as large particles prepared by dividing gutta-percha cones into pieces, (ii) as fine particles prepared by ball-milling of gutta-percha, and (iii) as particles produced by dissolving gutta-percha in rosin-chloroform. Gutta-percha evoked two distinct types of tissue response. The large pieces were well encapsulated and the surrounding tissue was free of inflammation. The fine particles evoked an intense, localized tissue response, characterized by the presence of macrophages and multinucleated giant cells. The rosin-chloroform treated gutta-percha induced a similar tissue reaction to that observed with the fine particles of gutta-percha. In addition, cell remnants were present in association with the material, which indicates an initial toxicity to rosin-chloroform treated gutta-percha. These results show that the size and surface character of gutta-percha can determine the type of tissue reaction to the material. The accumulation of macrophages around gutta-percha may be an important factor in the impairment of healing of periapical lesions when teeth are root filled with excess material.

Mutagenicity of AH26 in an in vitro mammalian cell mutation assay

The mutagenic activity of the root canal sealer AH26 was tested in the V79/hprt mammalian cell mutation assay. AH26 was mixed and eluted immediately after mixing or after setting times of 24 h or 7 days. Different amounts of dimethyl sulfoxide or physiological saline eluates were then tested for mutagenicity. Eluates of mixed AH26 were toxic and mutagenic, and both effects strongly depended on the setting time. The number of mutants after exposure to eluates of unset AH26 was enhanced approximately 7- to 10-fold. However, the mutagenic activity of the mixed material was clearly reduced after a setting time of 1 wk. Physiological saline eluates of the mixed AH26 were toxic at higher doses, but were not found to be mutagenic. Dimethyl sulfoxide eluates of the liquid component of AH26 elicited mutagenic effects similar to the freshly mixed material; eluates made in physiological saline were barely mutagenic at a 10-fold higher concentration. In accordance with recommendations of international guidelines, the V79/hprt mammalian cell mutation assay will be routinely used for the evaluation of the mutagenicity of dental materials in further investigations.

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.

Reaction of inflamed periapical tissue to intracanal medicaments and root canal sealers

The effects of different intracanal medicaments and zinc oxide-eugenol based root canal sealers on an experimentally induced apical periodontitis were studied histologically in mesial roots of lower molars of Wistar rats. After root canal instrumentation each canal was filled either with an intracanal medicament twice for 3 days each time or with a sealer for 21 days. The intracanal medicament chlorophenol caused periapical tissue damage. P-chloroxylenol-camphor lead to periapical improvement as did 5% sodium-hypochlorite. 12% sodium-hypochlorite gave tissue damage. After intracanal medication with an aqueous suspension of calcium hydroxide periapical repair was clearly visible. A combination of a corticoid and an antibiotic appeared to induce damage of the periapical tissues. The root canal sealers Endomethasone and N2 essentially impaired periapical repair. The results were acceptable for Aptal-Zink-Harz root canal fillings after 21 days as well as after 56 days.

A histological comparison of periapical inflammatory and neural responses to two endodontic sealers in the ferret

Previous studies have shown that there is a proliferation of nerves beneath the apices of pulpectomized teeth. This may be due to the inflammation induced after the procedure, resulting, perhaps, from the irritant nature of the materials used to fill the root canal. The experiment reported here was conducted to determine whether this inflammation was induced by the sealer rather than arising as a result of tissue damage and whether, if inflammation is eliminated or reduced, the neural changes are also reduced. In 12 young adult ferrets under general anaesthesia the pulps of the lower canine teeth were removed and replaced with gutta percha and sealer. A sealer of Grossman's formulation with eugenol as the liquid phase was used on one side and a calcium hydroxide sealer that contained no eugenol on the other. Three months later the animals were, again under general anaesthesia, perfused with a fixative mixture. The mandibles were removed and the presence and size of any periapical inflammatory lesions and the density of periapical innervation determined histologically. All 12 teeth sealed with the Grossman's sealer had inflammatory lesions at their apices. Three of the 12 teeth treated with the calcium hydroxide sealer showed similar lesions. In all the teeth with inflammatory lesions the normal arrangement of nerves in a periodontal 'plexus' was disrupted but there was no statistically significant difference between the overall innervation density in inflamed and non-inflamed periapical areas nor between areas beneath teeth sealed with Grossman's sealer and with calcium hydroxide. The incidence of periapical inflammation is related to the nature of endodontic sealer used.(ABSTRACT TRUNCATED AT 250 WORDS)

Metal deposition in post-surgical granulomas of the urinary tract

Fourteen cases of post-surgical granulomatous inflammation of the urinary tract were studied to investigate the possible deposition in the tissues of metals derived from the diathermy instruments used. The granulomas showed central necrosis, palisaded histiocytes and giant cells. On electronmicroscopy both amorphous material and electrondense particles were seen in the granulomas. The former appeared to be necrotic tissue. The particles were metallic in nature. Energy dispersive analysis of X-rays showed the presence of tungsten, iron, copper, nickel, chromium, zinc and vanadium. Tungsten particles were always pure. Other single particles contained two or more of the remaining elements, indicating the presence of alloy metals. Analysis of the diathermy instruments showed the cutting loops to be pure tungsten and the 'rollerballs' to be nickel silver containing copper, zinc, nickel, manganese and iron. Both the loops and balls are supported on stainless steel wires containing iron, chromium, nickel, manganese, molybdenum, copper and vanadium. It is proposed that metallic fragments from the instruments were deposited in the tissues during the surgical procedures and elicited an immunological reaction with granuloma formation. Tungsten is probably inert but nickel, chromium, copper and zinc are immunogenic. Under certain circumstances both nickel and chromium may also be carcinogenic.

Healing of induced periapical lesions in ferret canines

A previous study showed that the ferret canine is an appropriate model for inducing periapical lesions. Ferret canines were used in this study to study changes in periapical lesions after root canal treatment (RCT). After periapical pathosis was induced in the maxillary and mandibular canines of six ferrets, RCT was performed on three of the four canines in each animal. Each ferret received periodic intraperitoneal injections of Procion red dye. Two animals were killed at each of 4, 8, and 12 wk after RCT. Apices and surrounding lesions were evaluated radiographically, histologically, and by fluorescent microscopy. Periapical radiolucencies increased in size during induction but showed no changes after RCT. Lesions in untreated teeth showed features of granulomatous inflammation, mainly the presence of macrophages and lymphocytes. After RCT, there was histological evidence of healing in the form of cementum deposition, increased vascularity, and increased fibroblastic and osteoblastic activity. Fluorescent staining showed cementum deposition of variable thickness in the treated specimens.

Biologic properties of eugenol and zinc oxide-eugenol. A clinically oriented review

Eugenol-containing dental materials are frequently used in clinical dentistry. When zinc oxide-eugenol (ZOE) is applied to a dentinal cavity, small quantities of eugenol diffuse through the dentin to the pulp. Low concentrations of eugenol exert anti-inflammatory and local anesthetic effects on the dental pulp. Thus use of ZOE temporary filling may facilitate pulpal healing; on the other hand, high eugenol concentrations are cytotoxic. Direct application of eugenol to pulp tissue may result in extensive tissue damage. The ability of ZOE-based endodontic sealers to influence periapical tissue healing is considered in view of eugenol's anti-inflammatory and toxic properties.