Risk assessment of the toxicity of solvents of gutta-percha used in endodontic retreatment.

Three randomly assigned groups of single-canaled extracted teeth obturated with gutta-percha were retreated using controlled application of one of three organic solvents: chloroform, xylene, or halothane. Two additional groups of teeth served as positive and negative controls. Residual volume of solvent expressed through the apical foramen during retreatment was determined by the difference of pretreatment and posttreatment weights of hermetically sealed receptacles attached to the root surface of the teeth. Results indicate that the amount of solvent that has been determined to have leached out through the apical foramen is several orders of magnitude below the permissible toxic dose. Thus, it is proposed that the use of any of the aforementioned solvents used in the retreatment of root canals would pose negligible risk to the patient.

Role of metabolism by esterase and cytochrome P-450 in cocaine-induced suppression of the antibody response.

To investigate the role of metabolism in cocaine-induced immunosuppression, diazinon and beta-ionone were administered as an esterase inhibitor and a cytochrome P-450 (P-450) inducer, respectively, to B6C3F1 female mice. When 10 or 30 mg/kg of diazinon was administered 30 min before cocaine (30 mg/kg) was administered i.p. for 7 consecutive days, the suppression of the T-dependent antibody response to sheep red blood cells was potentiated greatly when compared to the suppression by cocaine alone. Spleen and thymus weights were decreased significantly and serum glutamate-pyruvate transaminase activities were elevated dramatically when cocaine and diazinon were administered together. beta-Ionone was administered s.c. for 7 consecutive days and the P-450 activities were determined 3 days after the last administration. beta-Ionone induced cocaine N-demethylation, which is the first step in the activation of cocaine to the metabolites capable of producing hepatotoxicity, as well as P-450IA1- and P-450IIB1-specific monooxygenases. The inductive effects of beta-ionone on P-450IA1/2 and P-450IIB1/2 proteins were confirmed by using Western immunoblotting with selective monoclonal antibodies. In addition, when beta-ionone (600 mg/kg) was administered with cocaine for 7 days, the suppression of the antibody response was potentiated greatly, thymus weight was decreased significantly and serum glutamate-pyruvate transaminase was elevated. Our present results suggest that inhibition of the esterase pathway of cocaine shunts the metabolism of cocaine into an immunotoxic pathway, and that the metabolism of cocaine by P-450 may be the critical pathway for the generation of the metabolites capable of suppressing the antibody response.

Comparison of human polymorphonuclear neutrophil elastase, polymorphonuclear neutrophil cathepsin-G, and alpha 2-macroglobulin levels in healthy and inflamed dental pulps.

Polymorphonuclear neutrophils (PMNs) are found in dental pulp secondary to carious exposures, periodontal disease, or trauma. Lysosomal degranulation of these cells liberates cellular proteases, including elastase (PMN-E) and cathepsin-G (PMN-CG), which produce connective tissue degradation. However, nonspecific pulpal tissue destruction can be modified by a naturally occurring serum protease inhibitor alpha 2-macroglobulin (A2-M). This study relates the concentrations of human PMN-E, PMN-CG, and A2-M in healthy and inflamed pulpal samples. Evaluation of 21 specimens yielded statistically significant differences between healthy and moderate to severely inflamed pulps for all groups (p < 0.05). No significant correlation was detected among human PMN-E, PMN-CG, and A2-M in the healthy tissues (P > 0.05). However, in the moderate to severely inflamed pulps, there was a significant correlation between PMN-CG and A2-M (p < 0.05).

A method for producing experimental simple vertical root fractures in dog teeth.

Vertical root fractures present difficult diagnostic problems and have poor prognoses. Treatment of root fractures consists of osseous recontouring, hemisection, and root amputation or sealing medicaments into the root canal in an effort to promote defect calcification. Dogs are often used as models for root fracture studies; however, production of simple vertical fractures has been inconsistent with high rates (18 to 65%) of undesired fragmented fractures. A technique to reproducibly create simple vertical fractures with minimal trauma and low fragmentation is described. Selected posterior dog teeth were endodontically instrumented. A 60-degree beveled tip conical wedge was controllable driven apically to cause fracture. The teeth were then medicated with experimental compounds and sealed with glass ionomer cement. After 8 wk, the animals were killed and the mandibles and maxillae dissected free and serially sectioned. Light microscopic examination revealed that most of the teeth fractured (93%) were the simple vertical type.

Immunosuppression in adult female B6C3F1 mice by chronic exposure to ethanol in a liquid diet.

The overall objective of these studies was to characterize the effects of ethanol on the immunocompetence of adult female B6C3F1 mice. To obtain a significant suppression in the antibody response to SRBC, splenocytes from untreated mice had to be directly exposed to concentrations of ethanol from 0.3% to 3.0%, or to acetaldehyde at concentrations greater than 0.03%. We do not believe that these results are consistent with a role by a direct effect by either ethanol or its primary metabolite because these concentrations are higher than what could be obtained as reasonable blood levels. For in vivo exposure, we employed a pair-feeding regimen which was based on a liquid diet containing 5% ethanol (v/v) that provided 36% of the caloric intake as ethanol. Our results indicated that there was a definite temporal relationship to the consequent suppression of the antibody response to SRBC in that no effect was observed after 14 days exposure, and that the magnitude of the suppression increased from 18% after 21 days to 70% after 42 days. We also monitored the liver for histopathology and observed that the ethanol-induced liver damage was restricted to steatosis (fatty liver), which was also manifested with time and which was most pronounced after 42 days exposure. In contrast to our results with the in vivo antibody response, we saw no effect on mitogen-induced proliferation by splenocytes from ethanol-treated mice. These results prompted us to measure in vitro antibody responses by splenocytes from ethanol-treated mice. We saw no suppression of the in vitro antibody responses to SRBC, DNP-Ficoll or LPS after any length of exposure to ethanol, and speculated that the basis for the suppression of the in vivo antibody response was an indirect consequence of exposure. We subsequently determined that when normal splenocytes were cultured in 5% serum from ethanol-exposed mice (42-day group), there was a > 80% suppression relative to the serum from the pair-fed controls. As important controls for these studies, we have demonstrated that there was no difference between the responses of normal lymphocytes cultured in 5% normal mouse serum and in 5% serum taken from the pair-fed restricted controls. A determination of the ethanol content in the serum from ethanol-exposed mice (42-day group) indicated that the amount of ethanol present in these cultures was < 0.003%.(ABSTRACT TRUNCATED AT 400 WORDS)

Natural modifiers of the inflammatory process in the human dental pulp.

Concentrations of the protease inhibitors alpha 1-antitrypsin and alpha 2-macroglobulin were determined in normal and inflamed human dental pulps. Carious pulpal exposure which is associated with polymorphonuclear leukocyte infiltration and release of lysosomal enzymes was chosen as the point of verifiable inflammatory activity in the pulp. Normal samples were collected from nondiseased third molar teeth treatment planned for extraction and inflamed human pulps were collected from teeth with deep carious lesions. One half of each sample was assayed for concentration of protease inhibitors by enzyme-linked immunosorbent assay and the remaining half was examined histologically to verify the clinical diagnosis and categorize the extent of the inflammatory process. alpha 1-Antitrypsin and alpha 2-macroglobulin were detected in normal and inflamed human dental pulps in the nanogram per milliliter range. Statistically significant differences were found in the concentrations of alpha 2-macroglobulin (p less than 0.01) in moderate to severe inflammation versus normal pulp categories and between mildly inflamed pulps and moderate to severely inflamed pulps (p less than 0.05). Although differences in concentrations of alpha 1-antitrypsin were seen between inflamed and normal pulps, the differences were not statistically significant. The presence of these two protease inhibitors in the human dental pulp tissue and the increase in their concentration in acute inflammation indicates that these proteins play a role in the pathogenesis of pulpal inflammatory disease.

Human polymorphonuclear granule components: relative levels detected by a modified enzyme-linked immunosorbent assay in normal and inflamed dental pulps.

Lysosomal granules of polymorphonuclear leukocytes (PMN's) contain proteolytic enzymes and other components important in the regulation of inflammation and the elimination of bacteria or debris associated with pulp disease. However, PMN lysosomal degranulation is nonspecific and can result in destruction of healthy connective tissue adjacent to the areas of damaged or infected tissue. For this study a modified enzyme-linked immunosorbent assay was used to detect the human PMN lysosomal granule products: elastase, cathepsin G, and lactoferrin. Evaluation of 55 pulp samples yielded a statistically significant difference (p less than 0.05) among the levels of elastase and lactoferrin in normal and moderate to severely inflamed pulps. Although cathepsin G levels were increased, there was no statistical significance (p greater than 0.05) among groups. The results indicate that a modified enzyme-linked immunosorbent assay technique can be used to measure PMN lysosomal granule components in dental pulp tissues. Additionally, elastase and lactoferrin levels appear to be valid diagnostic markers of advanced dental pulp disease.

Determination and relationship of C-reactive protein in human dental pulps and in serum.

C-reactive protein (CRP), an acute phase protein synthesized by the liver, increases in serum as much as 3000 times above its normal level in response to acute inflammation. The purpose of this study was to determine whether CRP levels in dental pulps could be correlated with the histological disease status of the pulp and with systemic blood levels of CRP. Inflamed and necrotic pulps were extirpated during routine endodontic therapy. Normal pulps were removed from extracted, intact third molars. One half of each pulp specimen was placed in formalin for histological study; the other half was frozen for immunological study. A serum sample was obtained from each patient at the end of the dental visit. CRP levels were determined by the enzyme-linked immunosorbent assay. Pulps were categorized histologically as normal, inflamed, inflamed/necrotic, or necrotic. The correlation between CRP levels of pulp and serum was not significant. CRP levels of normal pulps differed significantly only from inflamed pulps (p less than 0.05, Dunnett). This increase in CRP appears to be a local phenomenon resulting from the interaction of CRP with various inflammatory mediators in the pulp.

Incomplete polymerization of Cavalite with the use of recommended photopolymerization times: a warning of possible cytotoxic effects.

As part of a study of the suitability of new materials for use as a retrofilling material, we examined the polymerization properties of Cavalite, a light-cured, hydroxyapatite and glass ionomer-containing cavity liner. By varying the time of photopolymerization, it was found that polymerization for 20 to 30 seconds according to the manufacturer's recommendations is not sufficient to ensure complete polymerization. The implications of this incomplete polymerization are discussed in terms of possible cytotoxic effects on tissues exposed to unpolymerized Cavalite, both when used in retrofilling situations and as a deep cavity liner.

Repair of surgical clefts of the hard palate in beagles.

The biological responses to the repair of palatal clefts has been evaluated principally by monitoring craniofacial growth. Little is known about the regenerative ability of the repaired palate. In the present study, 18 Beagle pups (51 to 58 days old) were assigned to one of three groups: (1) control group, having no surgery; (2) cleft group, having a surgically created cleft of the posterior hard palate (mean bony measurement: 3.1 x 11.7 mm) at 8 weeks of age; and (3) repaired group, same as group 2, and followed by soft-tissue closure at 12 weeks of age. Craniofacial growth was monitored by cephalometric and dental cast measurements. Records were taken at 6-week intervals. Animals were sacrificed either 16 or 28 weeks after time of cleft creation. Routine histologic examination and histochemical detection of alkaline phosphatase activity were performed to examine the quality and extent of soft-tissue repair and bone formation. Analysis of the cleft palate group revealed that the size of the bony cleft increased with time. The histologic examination demonstrated at 24 weeks of age (12 weeks after the repair) active reduction of medial margin of the bony palate as evidenced by osteoclastic activity. At 36 weeks of age, neither osteoblastic nor osteoclastic activity was detected. The mean dimensions of the bony cleft, in the cleft group at 36 weeks, were 7.9 x 18.8 mm. In the repaired group, partial bone repair occurred. However, no consistency was seen in predicting extent or location of repair. Histochemical detection of alkaline phosphatase activity indicated that the repaired group had greater amounts of new bone formation. In some sites, suture regeneration was seen. As with the amount of bone formation, the amount of suture regeneration was variable. This study revealed that the presence of a cleft inhibits osteoblastic activity along the margin of the cleft, and there is limited potential for regeneration of the palate subsequent to the repair.

Toxic effects of Cu implants on liver.

In an effort to identify possible systemic effects due to dissolution of Cu from the experimental use of dental amalgam, specimens of pure Cu and several dental amalgams containing various concentrations of Cu were implanted into the peritoneal cavity of rats for 4 weeks. Concentrations of Cu in the liver varied from 33.3 to 156.2 micrograms Cu/dry g of liver tissue after implantation of the Cu-containing amalgams. Histopathological changes in the liver confirmed the presence of Cu within the lysosomes of hepatocytes. The histopathological and chemical changes in the liver after implantation indicated the need for subsequent investigations of long-term systemic toxicity to the use of Cu-containing implants.

An in vivo method for the biological evaluation of metal implants.

The peritoneal cavity of the rat was used as an implantation site in order to study the quantitative, cellular response and the qualitative, histopathological response to three metals (Ag, Sn, Cu). The effects of the metals on the cells were correlated with the cellular concentrations of the metal as determined by chemical analysis. Small variations in the cell population and a minimal foreign body reaction was observed with an implanted control material (silicone polymer). Large increases in the number of cells and an intense foreign body reaction was observed with Cu implants. Decreases in the number of cells were seen with Sn and Ag implants, but only Sn elicited a foreign body reaction. Implantation of Ag failed to elicit a foreign body reaction. Significant concentrations of all three metals were detected in the retrieved cells.

The effects of periodontal therapy on the mast cell population in gingival tissues.

The histologic condition of the gingival tissues was determined prior to and 4 weeks after scaling and curettage, then 4 months after periodontal osseous surgery in a group of eight patients with chronic periodontitis. The histopathologic changes were correlated with variations in mast cell population following the different modes of periodontal therapy.