Update on the adaptive immune responses of the dental pulp.

Recent advances in immunology have disclosed the enormous complexity of the immune regulatory system. The dental pulp is equipped to mount adaptive immune responses to caries, which include at least antigen-presenting cells, lymphocytes, mast cells and their cytokines, and chemokines. The purpose of this review is to summarize our current understanding of the roles of these cellular and molecular components in the irreversibly inflamed pulp. The immunopathology of abscess formation and the mechanisms for painless pulpitis are also discussed.

Innate immune responses of the dental pulp to caries.

Various cells and inflammatory mediators are involved in the initial pulpal responses to caries. This review focuses on the cellular, neuronal, and vascular components of pulpal innate responses to caries. Discussion will include dentinal fluid, odontoblasts, neuropeptides, and neurogenic inflammation, which are not classic immune components but actively participate in the inflammatory response as the caries progress pulpally. Summaries of innate immune cells as well as their cytokines and chemokines in healthy and reversible pulpitis tissues are presented.

Relationships between caries bacteria, host responses, and clinical signs and symptoms of pulpitis.

Knowledge of caries bacteria and the inflammatory responses they elicit in the dental pulp is prerequisite to our understanding of the pathogenesis of pulpitis. Recent advances in immunology and neurophysiology can now explain some of the clinical manifestations of pulpitis. The purpose of this review is twofold. The first purpose is to review the literature of the caries microflora, the host immune responses they elicit, and how they do so. The relationship between both proinflammatory and anti-inflammatory cytokines and pulpitis is discussed. The proinflammatory properties of lipoteichoic acid, which is a common virulence factor among Gram-positive bacteria such as those found among the caries bacteria, are reviewed. The second purpose is to review how bacteria and their metabolites, as well as pulpal immune and inflammatory reactions to them, modify the pain sensation in pulpitis.

The antimicrobial effect of MTAD, sodium hypochlorite, doxycycline, and citric acid on Enterococcus faecalis.

This study compared the antimicrobial effect of MTAD, two of its components, doxycycline and citric acid, and sodium hypochlorite (NaOCl) in two in vitro models on Enterococcus faecalis. In the bovine tooth model, the lumens of 30 bovine dentin discs were infected with E. faecalis for 2 weeks before treating with either one of the experimental irrigants or saline. Bacteria in the shavings were collected with two sizes of burs and enumerated after overnight culturing. Zones of inhibition were recorded in the agar diffusion model for each irrigant. In the tooth model, NaOCl and doxycycline were more effective than control in killing E. faecalis at the shallow bur depth, but at the deeper bur depth only NaOCl was superior. In the agar diffusion model, NaOCl produced less inhibition than MTAD or doxycycline.

The effect of operational speed on the fracture of nickel-titanium rotary instruments.

The purpose of this study was to compare the number of rotations to fracture of nickel-titanium (NiTi) rotary files operated at different speeds and different angles. We used 60 Profile NiTi rotary files, size 25 (30 each of 0.04 and 0.06 taper), operated at speeds of 350 or 600 rpm at angles of 25, 28, and 33.5 degrees. The time to fracture and number of rotations to fracture were recorded and calculated. A significant (p < 0.001) difference was found in the number of rotations to fracture according to taper and angle. Files of 0.06 taper fractured more readily than files of 0.04 taper. Increasing the angle at which the file was rotated decreased the number of rotations to fracture for both tapers; 0.04-taper files were more affected by an increase in the angle than the 0.06-taper files. However, the number of rotations to fracture was not related to the speed at which the files were operated.

A quantitative comparison of the fill density of MTA produced by two placement techniques.

This study compared the fill density of mineral trioxide aggregate (MTA) produced by hand condensation with that produced by hand condensation with indirect ultrasonic (US) activation. Sixty acrylic blocks with straight or curved canals were instrumented to an apical size 45, and weighed with a digital electronic balance. In 30 randomly chosen specimens, the canal was filled with MTA by hand condensation and weighed. The MTA was removed; the canal was rinsed and dried, and refilled using hand condensation with indirect US activation. In the other 30 specimens, the procedure was carried out identically but in reverse order. The blocks were then reweighed. The weight of the MTA fill produced by the two placement methods in the two canal configurations was analyzed by a two-way ANOVA. Hand condensation with indirect US activation resulted in an MTA fill that was statistically significantly heavier, and thus denser, than that accomplished by hand condensation alone in both curved and straight canals (p < 0.0001).

Apical diffusion of calcium hydroxide in an in vitro model.

An in vitro agar model was developed to study the effect of intracanal medicaments on periapical tissues and was used to study the diffusion of three calcium hydroxide (Ca(OH)2) medicaments of varying viscosity through simulated root canals with various sizes of apical foramina. Experimental medicaments were added to pipette tips used to represent tooth roots, which were fixed in syringes containing brain heart infusion agar and calcium-reactive dye. OH and Ca concentrations were measured in the agar at 30 minutes and 24 hours. Ca concentration and pH increased with larger aperture sizes, and higher pH and Ca diffusion was produced by a 10% Ca(OH)2 solution than was produced by Pulpdent or a Ca(OH)2 paste. The results suggest that the properties of the Ca(OH)2-containing vehicle could affect the action of the medicament in the periapical tissues.

A comparison of the in vitro retentive strength of glass-ionomer cement, zinc-phosphate cement, and mineral trioxide aggregate for the retention of prefabricated posts in bovine incisors.

The purpose of this study was to compare the retentive strength of zinc-phosphate cement, glass-ionomer cement, and mineral trioxide aggregate (MTA) cement in the retention of prefabricated posts. The root canals of 60 bovine incisors were prepared and obturated with warm gutta-percha. Post space was prepared, the smear layer removed, and posts were luted with zinc-phosphate cement, glass-ionomer cement, or MTA. The specimens were stored at 37 degrees C and 100% humidity for 2 weeks, and then subjected to increasing axial tensile forces by an Instron machine until bond failure occurred. Data were analyzed by a one-way ANOVA and a Tukey-Kramer multiple comparison test. The retentive strengths of zinc phosphate and glass-ionomer cements were statistically equivalent, and significantly greater than MTA (p < 0.001), which suggests that zinc phosphate or glass-ionomer cement may be superior to MTA when used as luting agents for posts in endodontically treated teeth.

Antibacterial efficacy of calcium hydroxide, iodine potassium iodide, betadine, and betadine scrub with and without surfactant against E faecalis in vitro.

OBJECTIVE: This study investigated the ability of endodontic irrigants and medicaments to eliminate Enterococcus faecalis from infected dentinal tubules, and whether their antimicrobial action was enhanced by surfactant. STUDY DESIGN: For the study, 5-mm dentin disks were sectioned from bovine incisor roots and infected with E faecalis. Lumens were instrumented, and 1 of 7 medicaments (10% Ca(OH) 2, Betadine, or IKI, each with or without surfactant, or Betadine Scrub) was used to flush and fill each lumen. Positive controls received saline. Specimens were incubated for 15 minutes or 24 hours. Quantitative microbiology of the remaining bacteria was performed and groups were compared using a 1-way ANOVA. RESULTS: The addition of surfactant did not enhance the antibacterial action of any medicament. When used as a 24-hour medicament, Ca(OH) 2 consistently failed to eliminate E faecalis, whereas both Betadine Scrub and IKI rendered 90% of samples sterile. IKI was the only agent shown to consistently eliminate E faecalis in a 15-minute time frame. CONCLUSION: Under the in vitro conditions of this study, IKI was able to eliminate E faecalis from bovine root dentin when used with a 15-minute contact time.

Sealing ability of One-Up Bond and MTA with and without a secondary seal as furcation perforation repair materials.

This study investigated the ability of One-Up Bond alone and mineral trioxide aggregate (MTA), with and without a secondary seal of One-Up Bond or SuperEBA to seal saucer-shaped perforation defects in human molars. Cusps were removed, roots were amputated, and endodontic therapy completed on 40 extracted teeth. A cylindrical hole was made in each tooth from the furcation area to the chamber, into which a section of steel tubing was cemented. Intracoronal saucer-shaped defects were created over the perforation. The teeth were restored with MTA, One-Up Bond, or MTA with a secondary seal of One-Up Bond or SuperEBA. The integrity of the seal was evaluated by fluid filtration. MTA alone leaked significantly more than One-Up Bond or MTA with either secondary seal at 24 h. At 1 month, MTA, MTA plus One-Up Bond, and One-Up Bond alone were equivalent.

A comparison of laterally condensed gutta-percha, thermoplasticized gutta-percha, and mineral trioxide aggregate as root canal filling materials.

The purpose of this study was to evaluate the potential of using mineral trioxide aggregate as a root canal filling material by comparing its apical sealing ability with that of laterally condensed gutta-percha with sealer and high-temperature thermoplasticized gutta-percha with sealer in extracted bovine teeth. Sixty bovine incisors with single canals were prepared in a standard manner using LightSpeed instruments, randomly divided into three groups of 20 teeth, and obturated. The sealing ability of each technique was assessed by immersion in 1% methylene blue dye for 3 days. The teeth were cleared, and the linear extent of dye penetration was measured with a stereomicroscope. Data were analyzed by the Kruskal-Wallis one-way ANOVA followed by Dunn's test. Canals filled with laterally condensed gutta-percha or thermoplasticized gutta-percha showed significantly less apical dye penetration than canals obturated with mineral trioxide aggregate (p < 0.001). There was no significant difference in leakage between the laterally condensed group and the thermoplasticized group. The results suggest that gutta-percha obturation may provide an apical seal that is superior to MTA.

Effect of intracanal restorative material on the stiffness of endodontically treated teeth.

This study compared the ability of various intracanal restorative materials to restore the stiffness of endodontically treated teeth. We randomly placed bovine central incisors into six groups. We did not instrument negative control teeth, and we instrumented, but did not restore, positive control teeth. We restored teeth in the experimental groups with resin-based composite, resin-based composite plus a fiberglass post, or resin-based composite plus a cemented metal post. We subjected all teeth to nondestructive, compressive testing and recorded the stiffness of each sample. Results indicated that performing endodontic access and instrumentation alone resulted in a 24% loss in tooth stiffness. Teeth restored using an intracanal resin bonding technique alone or in combination with a post regained the stiffness lost from access and instrumentation, and teeth that were restored with bonded resin and a metal post cemented with Panavia 21 cement were significantly stiffer than the untreated negative control group (p < 0.05). Our results suggest that intracanal resin bonding techniques may reduce the need for immediate crown placement after endodontic therapy.

The effect of various intracanal oxidizing agents on the push-out strength of various perforation repair materials.

OBJECTIVE: The purpose of this study was to determine the effect of intracanal oxidizing agents on the strength of materials used to repair root perforations. STUDY DESIGN: Standardized perforations in bovine root samples were repaired with mineral trioxide aggregate (MTA), Super-EBA cement (S-EBA), or intermediate restorative material (IRM). After 7 days, 10 samples from each group were tested for push-out strength with an Instron machine (controls). The remaining samples were immersed in NaOCl, sodium perborate mixed with saline (SPB+S), Superoxol (SO), sodium perborate mixed with Superoxol (SPB+SO), or saline for 7 days to investigate the effect of irrigating and walking bleach compounds on the perforation repair materials. Push-out strength values were compared with those of the dry materials to determine whether any loss of integrity had occurred. RESULTS: MTA was statistically significantly less resistant across conditions to displacement than S-EBA or IRM. IRM was consistent across treatment conditions, whereas S-EBA lost strength when exposed to NaOCl, SPB+S, or SPB+SO. Exposure to SPB+S had the greatest effect on all 3 materials. CONCLUSIONS: IRM performed consistently as a perforation repair material despite exposure to oxidizing agents, whereas MTA was less resistant to dislodgement than either IRM or S-EBA and was more affected than IRM by sodium perborate-containing bleaching solutions.

Human periodontal ligament cell viability in milk and milk substitutes.

The purpose of this study was to determine the efficacy of several milk substitutes compared to whole milk in maintaining the viability of human periodontal ligament (PDL) cells on avulsed teeth. PDL cells were obtained from freshly extracted, healthy third molars and cultured in Eagle's minimal essential media (EMEM). The cells were plated onto 24-well culture plates and allowed to attach for 24 h. EMEM was replaced with refrigerated whole milk (positive control), reconstituted powdered milk, evaporated milk, or one of two baby formulas (Similac or Enfamil). Tap water served as the negative control. Tissue culture plates were incubated with the experimental media at 37 degrees C for 1, 2, 4, or 8 h. Cell viability was determined by a cell proliferation assay (CellTiter 96 AQ Assay), with absorbance read at 450 nM. A two-way ANOVA (p < 0.001) indicated that at 1 h there was no difference in the effect on PDL cell viability between any of the materials and whole milk. At 2 h, Enfamil and Similac performed significantly better than whole milk, whereas evaporated milk performed worse. At 4 h, Enfamil performed better than whole milk, whereas all other milk substitutes performed worse. At 8 h, all substitutes performed worse than whole milk. These results suggest that Enfamil, which is supplied in powder form that does not require special storage and has a shelf life of 18 months, is a more effective storage medium for avulsed teeth than pasteurized milk for at least 4 h.

In vitro antimicrobial activity of various medication preparations on E. faecalis in root canal dentin.

The purpose of this study was to evaluate the antimicrobial activity of several medication preparations in root canal dentin infected with Enterococcus faecalis. Roots of extracted bovine incisors were prepared to standardized cylindrical test specimens, 5 mm in height. The smear layer was removed and the samples were autoclaved and then incubated at 37 degrees C/5% CO2 for 24 h in brain-heart infusion (BHI) broth containing 7.0 x 10(4) colony forming units per ml of E. faecalis. The samples were washed in phosphate buffered saline and mounted to individual culture wells with sticky wax. Test medications were applied to fill the canal lumina; medication groups were: (a) sterile H2O (positive control); (b) a 10% mixture of 1.0 g Ca(OH)2 USP in 10 ml sterile H2O; (c) 10% Ca(OH)2 in 0.12% chlorhexidine gluconate (Peridex); (d) Peridex; and (e) uninoculated BHI (negative control). The samples were incubated at 37 degrees C/5% CO2 for 24 h. Dentin samples for quantitative microbiology were then obtained with consecutive sterile burs (ISO 029, 035, 042). All three experimental groups demonstrated significantly greater antimicrobial activity than the positive control (p < 0.001). Group 2 demonstrated significantly greater antimicrobial activity than Group 3 or Group 4 at all dentin depths (p < 0.05). These results suggest that 10% Ca(OH)2 may be more effective than Peridex or 10% Ca(OH)2 in Peridex for the elimination of E. faecalis from dentin tubules.

Secondary hyperparathyroidism: a case report.

A thorough diagnostic examination is essential before providing endodontic treatment. The sequence of diagnostic procedures must begin with a well-organized review of the medical history. In the early screening process, a health history that reveals a systemic disorder must be investigated further because it may have a significant impact on the dental diagnosis and ultimate endodontic treatment. There are a number of systemic diseases that can cause bone lesions throughout the body. Chronic renal failure is one disorder that may stimulate a secondary hyperparathyroidism that can cause a variety of bone lesions. In some instances these lesions appear in the periapical region of teeth and can lead to a misdiagnosis of a lesion of endodontic origin. The following case report of a patient referred for endodontic treatment demonstrates the importance of understanding the effects of end-stage renal disease on the dental structures.