Immunomodulation Mediated by Azithromycin in Experimental Periapical Inflammation.

INTRODUCTION: The purpose of the present study was to compare the immunomodulatory effect of azithromycin (AZM), ampicillin (AMP), amoxicillin (AMX), and clindamycin (CLI) in vitro and AZM on preexisting periapical lesions compared with AMP. METHODS: The susceptibility of 4 common human endodontic pathogens (Parvimonas micra, Streptococcus intermedius, Prevotella intermedia, and Fusobacterium nucleatum) to AZM, AMP, AMX, and CLI was confirmed by agar disk diffusion assay. Preexisting periapical lesions in C57BL/6J mice were treated with AZM, AMP, or phosphate-buffered saline (PBS). Periapical bone healing and the pattern of inflammatory cell infiltration were evaluated after a 10-day treatment by micro-computed tomographic and histology, respectively. Besides, the effect of antibiotics in pathogen-stimulated nuclear factor kappa B activation and the production of interleukin 1 alpha and tumor necrosis factor alpha was assessed in vitro by luciferase assay and enzyme-linked immunosorbent assay. RESULTS: All examined endodontic pathogens were susceptible to AZM, AMP, AMX, and CLI. AZM significantly attenuated periapical bone loss versus PBS. PBS resulted in widely diffused infiltration of mixed inflammatory cells. By contrast, AZM brought about localized infiltration of neutrophils and M2 macrophages and advanced fibrosis. Although the effect of AMP on bone was uncertain, inflammatory cell infiltration was considerably milder than PBS. However, most macrophages observed seemed to be M1 macrophages. AZM suppressed pathogen-stimulated nuclear factor kappa B activation and cytokine production, whereas AMP, AMX, and CLI reduced only cytokine production moderately. CONCLUSIONS: This study showed that AZM led to the resolution of preexisting experimental periapical inflammation. Our data provide a perspective on host response in antibiotic selection for endodontic treatment. However, well-designed clinical trials are necessary to better elucidate the benefits of AZM as an adjunctive therapy for endodontic treatment when antibiotic therapy is recommended. Although both AZM and AMP were effective on preexisting periapical lesions, AZM led to advanced wound healing, probably depending on its immunomodulatory effect.

Bacteria-reactive immune response may induce RANKL-expressing T cells in the mouse periapical bone loss lesion.

INTRODUCTION: The present study investigated whether bacteria infecting the root canal can activate any infiltrating T cells to produce receptor activator of nuclear factor kappa B (NF-κB) ligand (RANKL). METHODS: Using a mouse model of periapical lesion induced by artificial dental pulp exposure, the presence of RANKL-positive T cells and osteoclasts in the periapical lesion was examined by an immunohistochemical approach. The bacteria colonizing the exposed root canal were identified by 16S ribosomal RNA (rRNA) sequence analysis. The isolated endodontic bacteria were further immunized to normal mice, and soluble activator of NF-κB ligand (sRANKL) production by the T cells isolated from the immunized mice was evaluated by ex vivo culture system. RESULTS: RANKL-positive T cells along with TRAP+ osteoclasts were identified in periapical bone resorption lesions. The gram-negative bacterium Pasteurella pnumotropica, which was most frequently detected from the root canal of exposed pulp, showed remarkably elevated serum immunoglobulin G (IgG)-antibody response in pulp-exposed mice compared with control nontreated mice. Immunization of mice with P. pneumotropica induced not only serum IgG-antibody but also primed bacteria-reactive T cells that produced sRANKL in response to ex vivo exposure to P. pneumotropica. CONCLUSIONS: T cells infiltrating the periapical region express RANKL, and the endodontic bacteria colonizing the root canal appear to induce RANKL expression from bacteria-reactive T cells, suggesting the possible pathogenic engagement of the immune response to endodontic bacteria in the context of developing bone resorptive periapical lesions.

A faculty group practice-driven credentialing and privileging infrastructure in a school of dental medicine.

Credentialing and assigning clinical privileges are well-established practices in institutions that need to verify a clinician's ability to provide direct patient care services. The credentialing process verifies a provider's credentials to practice his or her profession, while privileging authorizes the individual to perform enumerated procedures within a specific scope of practice. All clinical faculty members at Harvard School of Dental Medicine (HSDM) practice in the Faculty Group Practice (FGP). Because of the number of practitioners in the FGP, the organization instituted a more formal process of credentialing that verifies that practitioners are not only licensed to practice, but also are competent to provide direct patient care. In contrast to other dental schools that have established similar protocols, HSDM approached the process not from the academic side, but rather from the clinical practice side, explicitly taking into account whether the FGP could accommodate another practitioner when an academic department wished to appoint a new faculty member. In doing so, we had to be careful to reconcile our educational and research needs with those of the FGP. In this article, we describe how, within this framework, we established a credentialing and privileging program in which all full- and part-time faculty members, as well as advanced graduate students, were included.

Hypoxia-amplified proliferation of human dental pulp cells.

INTRODUCTION: Postnatal human dental pulp is a potentially promising source of progenitor cells. Sustaining and amplifying progenitor cell populations would be beneficial for basic science research with application in pulpal regeneration. Hypoxia has been observed to promote the undifferentiated cell state in various stem cell populations. The purpose of this study was to examine human dental pulp cells (DPCs) proliferation in normoxia and hypoxia. METHODS: Dental pulp cells were obtained from third molars of adult patients and cultured in alpha modification of Eagle's medium culture medium with 10% fetal bovine serum. For cell proliferation, DPCs were divided into two groups: (1) DPCs incubated in normoxic conditions (20% oxygen tension) and (2) DPC incubated in hypoxic conditions (3% oxygen tension). Cell proliferation assays were performed every 2 to 3 days from day 3 to day 14 by trypsinization and quantification of cells with a hemacytometer. Fluorescence-activated cell sorting analysis was completed to investigate stem cell markers, CD133, and STRO-1. RESULTS: DPCs proliferated significantly more in hypoxia than in normoxia (ie, two-fold throughout the experiment, p < 0.0001). The primitive stem cell marker, CD133, decreased in hypoxia, whereas the osteoprogenitor marker, STRO-1, increased by 8.5-fold. CONCLUSIONS: This study suggested that hypoxia is an effective treatment to amplify numbers of progenitor cells from human dental pulp.

Use of the cold test as a measure of pulpal anesthesia during endodontic therapy: a randomized, blinded, placebo-controlled clinical trial.

Soft tissue signs are inadequate to assess pulpal anesthesia during root canal therapy (RCT). The intention of this study was to determine if a negative response to cold testing is a more effective measure to assess pulpal anesthesia compared to soft tissues signs. Using a randomized, blinded, placebo-controlled design, subjects with baseline responsiveness to cold testing were enrolled. Test subjects achieved a negative response to cold testing prior to RCT. Control subjects were given a sham cold test after demonstrating soft tissue signs. Visual analog scale determined pain level. Unadjusted results showed 12% of test subjects experienced pain during RCT compared with 38% of control subjects (N = 83, p = .004, power = 84%). Multiple logistic regression controlled for confounders and effect modifiers, OR = .20 (p = .01). Subjects who achieved a negative response to the cold test were approximately 80% less likely to experience pain during RCT compared to subjects with soft tissue signs of anesthesia alone.

Neospora caninum: adoptive transfer of immune lymphocytes precipitates disease in BALB/c mice.

Neospora caninum is a recently described apicomplexan parasite first isolated from a dog in 1988 and has subsequently been shown to infect a wide range of mammals. In mice, Neospora can cause primary pneumonia, myositis, encephalitis, radiculoneuritis, and pancreatitis. Whereas, certain aspects of the host immune response to Toxoplasma gondii have been well studied, not as much is known about the full immune response to Neospora. This paper examines whether or not immune splenocytes are able to adoptively transfer protection against N. caninum infection in BALB/c mice. Mice receiving immune enriched CD8+ cells had severe neurological signs by 19 days post infection. Mice receiving immune enriched CD4+ cells had mild neurological signs on day 22 post infection. It would appear that additional immune cells can precipitate disease in the presence of circulating lymphocytes.

Determining the optimal obturation length: a meta-analysis of literature.

The purpose was to aid in determining termination of instrumentation and obturation. A meta-analysis was conducted as to success/failure of different obturation lengths. Inclusion criteria were (a) minimum follow-up of 2 yr, (b) data on obturation length, (c) definition of success/failure, (d) available data on success/failure, (e) radiographic evaluation. Correlations were made as to success/failure as related to length of obturation from the apex. When comparing group A (obturated 0-1 mm from apex) versus group C (obturated past apex) using the DerSimonian and Laird estimates, group A showed a marginally better (p < 0.10) success rate than group C by 28.8%. Group A had better success than group B (obturated >1 mm short); the difference was insignificant. The results were similar after controlling for study quality using a single random effects regression model. In conclusion, the meta-analysis indicated that a better success rate is achieved when treatment includes obturation short of the apex.

Evaluation of the whole genome DNA-DNA hybridization technique to identify bacteria in histological sections of periradicular lesions.

Whole genome DNA-DNA hybridization has been used to identify bacteria in periradicular lesions partly because there is no amplification of the bacteria, therefore, minor contaminants are not detected. There are, however, potential pitfalls with this technique, including inability to distinguish dead bacteria, cross-reactions of species within a genus, and inability to detect species present in low numbers because of loss of DNA during extraction and purification. Alternatively, inadequate extraction and purification of DNA could result in false positives. Therefore, controls are required to monitor DNA loss, DNA cross-reactions, and DNA of pure cultures mixed with bacteria-free tissue to monitor for false positives. We determined that the quality of DNA extracted from histological sections of periradicular lesions is excellent for DNA-DNA hybridization. Although lesions contain large numbers of bacteria, histological sections through lesions barely contain sufficient quantity of bacteria for such analysis. This was confirmed by histological observation of sparsely distributed bacteria within lesions. Furthermore, we found that the bacteria are not distributed evenly throughout periradicular lesions, in numbers or species.