Effect of soluble plaque factors on inflammatory reactions in the dental pulp

Effect of scaling on the invasion of oral microorganisms into dentinal tubules including the response of pulpal cells-an in vitro study

Objectives

To investigate how scaling affects the penetration of microorganisms into dentinal tubules, how pulpal cells seeded into the pulp cavity respond to bacterial challenge, and how penetration and inflammatory response may depend on the bacterial composition.

Materials and methods

Root canals of 102 extracted human teeth underwent shaping and cleaning. Half of the teeth were subjected to scaling and root planing, the other half remained untreated. Teeth were exposed to either Streptococcus gordonii and Actinomyces oris or S. gordonii and Porphyromonas gingivalis for 10 weeks. Bacterial invasion was assessed in a depth of 1 mm to the root surface. Human pulpal cells were seeded into the cavities to assess the expression of interleukin-8 (IL-8), monocyte chemoattractant protein-1 (MCP-1), and matrix metalloproteinase-3 (MMP-3) by real-time polymerase chain reaction and immunoassay.

Results

The percentage of teeth with bacteria detected in dentine was higher when teeth received scaling than when they were untreated: 66.6% versus 44.4% when exposed to A. oris/S. gordonii, and 50% versus 25% when exposed to P. gingivalis/S. gordonii (p = 0.043). Scaling had no impact on IL-8 and MMP-3 expression in pulpal cells. P. gingivalis/S. gordonii caused higher levels of IL-8, MCP-1, and MMP-3 than A. oris/S. gordonii (p = 0.003, p = 0.011, p = 0.037).

Conclusion

Scaling supports the penetration of bacteria into the dentine of extracted human teeth. P. gingivalis may affect the immune response in pulpal cells.

Clinical relevance

Root surface debridement with hand instruments may facilitate bacterial penetration. Other kinds of mechanical instrumentation in this experimental setting should be investigated.

Effects of Extracellular pH on Dental Pulp Cells In Vitro

INTRODUCTION

The proliferation and migration of dental pulp stem cells (DPSCs), a population comprised of dental pulp cells (DPCs), are important processes for pulp tissue repair. Dental pulp is exposed to changes in extracellular pH under various conditions, such as acidosis and exposure to caries-associated bacteria or a pulp capping agent. The objective of this study was to investigate the effects of extracellular pH on DPC proliferation and migration in vitro.

METHODS

To evaluate the proliferation potency of DPCs in various extracellular pH conditions, 2 × 10(4) cells were seeded into 35-mm dishes. The following day, we changed to NaHCO3-free medium, which was adjusted to different extracellular pH levels.

RESULTS

After 120 hours, DPCs cultured in media from a pH of 3.5 to 5.5 showed cell death, those cultured in conditions from a pH of 6.5 to 7.5 showed growth arrest or cell death, and those grown at a pH of 9.5 showed mild proliferation. The migratory activity of living DPCs was not affected by extracellular pH. For histologic analysis, human teeth possessing a small abscess in the coronal pulp chamber were sliced for histologic analysis. Proliferating cell nuclear antigen (PCNA) immunolocalization was used as an index of cell proliferation for the sections and cultured cells. Acidic extracellular pH conditions resulted in reduced numbers of PCNA-positive DPCs in the dishes. As for pulp tissue affected by a small abscess, a PCNA-negative pulp cell layer was observed in close proximity to the infectious lesion.

CONCLUSIONS

Together, these results suggest that an acidic extracellular pH condition is associated with DPC growth arrest or cell death.

Interrelationship Between Periapical Lesion and Systemic Metabolic Disorders

BACKGROUND

Periapical periodontitis, also known as periapical lesion, is a common dental disease, along with periodontitis (gum disease). Periapical periodontitis is a chronic inflammatory disease, caused by endodontic infection, and its development is regulated by the host immune/inflammatory response. Metabolic disorders, which are largely dependent on life style such as eating habits, have been interpreted as a "metabolically-triggered" low-grade systemic inflammation and may interact with periapical periodontitis by triggering immune modulation. The host immune system is therefore considered the common fundamental mechanism of both disease conditions.

METHOD

We have reviewed >200 articles to discuss the interrelationship between periapical lesions and metabolic disorders including type 2 diabetes mellitus, hypertension, and non-alcoholic fatty liver diseases (NAFLD), and their common pathological background in immunology/osteoimmunology and cytokine biology.

RESULTS

An elevated inflammatory state caused by metabolic disorders can impact the clinical outcome of periapical lesions and interfere with wound healing after endodontic treatment. Although additional well-designed clinical studies are needed, periapical lesions appear to affect insulin sensitivity and exacerbate non-alcoholic steatohepatitis.

CONCLUSION

Immune regulatory cytokines produced by various cell types, including immune cells and adipose tissue, play an important role in this interrelationship.

Infection-stimulated infraosseus inflammation and bone destruction is increased in P-/E-selectin knockout mice

Infections of the dental pulp commonly result in infraosseus inflammation and bone destruction. However, the role of phagocytic leucocytes in the pathogenesis of pulpal infections has been uncertain. In this work we used P/E-/- selectin-deficient mice, which lack rolling adhesion of leucocytes to endothelium and mimic the human syndrome, leucocyte adhesion deficiency II (LAD-II), to test the hypothesis that phagocytic leucocytes protect against pulpal infection and subsequent periapical infraosseus bone resorption. P/E-/- mice and P/E+/+ wild-type controls were subjected to surgical pulp exposure, and both groups were infected with a mixture of pulpal pathogens including Prevotella intermedia, Fusobacterium nucleatum, Peptostreptococcus micros and Streptococcus intermedius. Animals were killed after 20 days, and the extent of infraosseus bone destruction was quantified by histomorphometry. In two separate experiments, P/E-/- mice had significantly greater bone resorption than P/E+/+ controls. The increased bone destruction correlated with a twofold decrease in polymorphonuclear (PMN) infiltration into periapical inflammatory tissues of P/E-/- mice. P/E-/- mice had higher tissue levels of the bone resorptive cytokine, interleukin (IL)-1alpha. Tissue levels of IL-2, IL-4, IL-10, tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) were all higher in P/E-/- mice, but the increases were not statistically significant. Only IL-12 was higher in P/E+/+ mice, possibly reflecting a greater number of infiltrating monocytes in wild-type mice. These findings demonstrate that phagocytic leucocytes are protective in this model, and suggest that elevated expression of inflammatory cytokines is responsible for the observed bone destruction.