A flow cytometric analysis of the biodefensive response of deciduous tooth pulp to carious stimuli during physiological root resorption

Changes of Oral Flora, Inflammatory Factors, and Immune Function Indicators in Patients with Chronic Periodontitis and Their Clinical Significance

This research focuses on investigating the changes of oral flora, inflammatory factors, and immune function indicators in patients with chronic periodontitis (CP) and their clinical significances. Clinical indices such as gingival index (GI) and sulcus bleeding index (SBI) of the study subjects were recorded. The levels of oral flora, inflammatory factors and T lymphocyte subsets in gingival crevicular fluid (GCF) of the study subjects were measured. To analyze the correlation between GI and gingival SBI and oral flora, inflammatory factors, and immune function indicators, Pearson correlation analysis was performed. Porphyromonas gingivalis, Streptococcus digestiveis, Prevotella intermedia, Veronococcus, tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), IL-8, CD3+, CD4+, and CD4+/CD8+ had a positive correlation with GI and SBI, while IL-10 and CD8+ were negatively correlated with GI and SBI. Oral flora, inflammatory factors and immune function indicators levels are largely elevated in patients with CP and they are correlated with CP clinical indicators.

The Alpha 7 Nicotinic Acetylcholine Receptor of Deciduous Dental Pulp Stem Cells Regulates Osteoclastogenesis During Physiological Root Resorption

The physiological root resorption of deciduous teeth is a normal phenomenon, but the mechanisms underlying this process are still unclear. In this study, deciduous dental pulp stem cells (DDPSCs) and permanent dental pulp stem cells (DPSCs) were derived from deciduous teeth and normal permanent teeth at different stages of resorption. In the middle stage of root resorption, DDPSCs exhibited an increase in the ability to induce osteoclast differentiation. Activation of the alpha 7 nicotinic acetylcholine receptor (α7 nAChR) by secretory mammalian Ly-6 urokinase-type plasminogen activator receptor-associated protein 1 (SLURP-1) caused a significant increase in the expression levels of NF-κB, receptor activator of nuclear factor-kappa B ligand (RANKL), and the ratio of RANKL/osteoprotegerin (OPG). These effects were inhibited by alpha-bungarotoxin (α-BTX). Furthermore, the expression levels of RANKL/OPG were significantly reduced following inhibition of NF-κB. High-strength, dynamic positive pressure increased the expression of SLURP-1 and α7 nAChR in DDPSCs in the stable stage. These data indicated that mechanical stress stimulated the expression of SLURP-1 and α7 nAChR in DDPSCs. Additionally, SLURP-1 activated α7 nAChR, thereby upregulating the expression of NF-κB and enhancing its activity, thus regulating RANKL/OPG expression and affecting the ability of DDPSCs to influence osteoclastogenesis, which likely enhances root resorption and leads to the physiological loss of deciduous teeth.

Phenotypic analysis of immunocompetent cells in healthy human dental pulp

INTRODUCTION

Like other tissues in the body, the human dental pulp is equipped with a network of immune cells that can be mobilized against pathogens when they invade the tooth. Very little data, mostly obtained with classic histologic methods, have reported their quantities and relative percentages. The objective of this study was to characterize and precisely quantify immunocompetent cells in healthy human dental pulp by using fluorescence-activated cell sorting, together with identifying specific cell subsets in the leukocyte (CD45(+)) cells.

METHODS

Healthy human third molars were collected from 42 young patients. Dental pulps were separated from the hard tissues and prepared for flow cytometry or immunostaining analyses.

RESULTS

CD45(+) cells represented 0.94% ± 0.65% of cells obtained from the enzymatic digestion of whole dental pulps (n = 34). CD16(+)CD14(+) granulocytes/neutrophils (50.01% ± 9.08%, n = 7) were found to represent the major subpopulation in CD45(+) cells followed by CD3(+) T lymphocytes (32.58% ± 11%, n = 17), CD14(+) monocytes (8.93% ± 5.8%, n = 7), and HLA-DR(high) Lin1(-) dendritic cells (4.51% ± 1.12%, n = 7). Minor subpopulations included CD3(-)CD56(+) natural killer cells (2.63% ± 1.15%, n = 7) and CD19(+) B lymphocytes (1.65% ± 0.89%, n = 17). We further identified cells harboring a phenotype compatible with Foxp3/CD25-expressing regulatory T lymphocytes (CD45(+)CD3(+)CD4(+)CD127(low)). Fluorescence-activated cell sorting analysis and confocal microscopy also revealed expression of HO-1 in HLA-DR(+) cells.

CONCLUSIONS

For the first time, this study identifies and precisely quantifies the relative proportion of immunocompetent cells potentially involved in tissue homeostasis of healthy human dental pulp.

Pulpal status of human primary molars with coexisting caries and physiological root resorption

AIM

This study sought to investigate the effect of caries, in association with physiological root resorption, on the pulpal status of human primary molars.

DESIGN

Fifty-three mandibular primary molars were obtained from children requiring extractions under general anaesthesia. Following extraction, teeth were split longitudinally and placed in Zamboni's fixative. Teeth were categorised according to i) the depth of caries (less than or greater than halfway through dentine thickness) and ii) the degree of physiological root resorption (<33%, 34-66% or >67% of the root length). Ten-micrometre pulp sections were subject to indirect immunofluorescence using a combination of PGP 9.5 (a general neuronal marker), CD45 (a general neuronal marker), and Ulex europaeus agglutinin I (a marker of vascular endothelium). Image analysis was used to determine the percentage area of staining (PAS) for innervation and immune cells.

RESULTS

Marked differences were seen between different samples, but there were no significant differences in mean PAS for PGP 9.5 or CD45 according to the degree of caries or extent of physiological root resorption (two-way anova, P > 0.05).

CONCLUSION

Findings suggest that even if primary molars are undergoing exfoliation, they show comparable caries-induced changes to teeth without physiological root resorption, thus retaining potential for healing and repair.

Deciduous dental pulp stem cells are involved in osteoclastogenesis during physiologic root resorption

Multipotent mesenchymal stem cells are derived from the dental pulps of permanent teeth and exfoliated deciduous teeth, and are known to induce bone and dentin generation. However, the role of deciduous dental pulp stem cells (DDPSCs) in physiologic root resorption remains unclear. In this study, dental pulp stem cells (DPSCs) in permanent teeth (P) were retrieved and compared to DDPSCs from deciduous incisors at different root resorption stages: stable (S), middle (M), and final (F). Decalcified teeth sections showed that osteoclasts and resorption lacunae were most prevalent in the M resorption stage. DDPSC proliferation rate was also highest in the M stage. DDPSCs in the F stage produced more calcified nodules than those in the S or M stages. Alkaline phosphatase (ALP) expression was highest in the F stage, indicating that DDPSCs promote mineralization. In addition, the ratio of receptor activator of nuclear factor kappa B ligand (RANKL) and osteoprotegerin (OPG) expression was significantly higher in the M stage, indicating that DDPSCs promote resorption. Dickkopf 1 (Dkk1) expression was remarkably higher in the F and P groups, suggesting that the Wnt pathway is inhibited during the resorption process. Interestingly, despite the fact that Wnt3a down-regulated OPG in osteogenic induction medium and up-regulated RANKL in medium with 1,25-dihydroxy vitamin D3 (VD(3) ), the RANKL/OPG ratio was reduced only with VD(3) . Collectively, our data indicate that DDPSCs influence osteoclastogenesis during the physiologic root resorption process, and that the canonical Wnt pathway can change the RANKL/OPG expression ratio in DDPSCs.

Apoptosis in pulp elimination during physiological root resorption in human primary teeth

Pulp samples of 50 healthy human teeth with indication for extraction were examined to evaluate the role of apoptosis in pulp elimination during physiological root resorption. Two groups were formed: a test group (n=30) composed of pulp samples of primary teeth with physiological root resorption and a control group (n=20) composed of pulp samples of permanent maxillary third molars. Morphological evidence of apoptosis as well as in situ detection of cellular DNA fragmentation by TUNEL assay and detection of internucleosomal pattern of fragmentation of the genomic DNA by electrophoresis were observed. The apoptotic index of the primary tooth group was significantly higher than that of the permanent tooth group (51.01 +/- 0.52 versus 25.32 +/- 0.68) (p<0.001). TUNEL reaction showed intense and diffuse labeling in the pulp samples of primary teeth, which were discrete in the controls. Intense DNA internucleosomal fragmentation, a specific pattern for apoptosis, was observed in primary tooth pulps DNA by electrophoresis, in the permanent tooth pulps this pattern fragmentation of the genomic DNA for apoptosis were not present. These results seem to indicate a role of apoptosis in pulp elimination during the physiological root resorption of human primary teeth.

Pulpal status of human primary teeth with physiological root resorption

OBJECTIVE

The overall aim of this study was to determine whether any changes occur in the pulpal structure of human primary teeth in association with physiological root resorption.

METHODS

The experimental material comprised 64 sound primary molars, obtained from children requiring routine dental extractions under general anaesthesia. Pulp sections were processed for indirect immunofluorescence using combinations of: (i) protein gene product 9.5 (a general neuronal marker); (ii) leucocyte common antigen CD45 (a general immune cell marker); and (iii) Ulex europaeus I lectin (a marker of vascular endothelium). Image analysis was then used to determine the percentage area of staining for each label within both the pulp horn and mid-coronal region. Following measurement of the greatest degree of root resorption in each sample, teeth were subdivided into three groups: those with physiological resorption involving less than one-third, one-third to two-thirds, and more than two-thirds of their root length.

RESULTS

Wide variation was evident between different tooth samples with some resorbed teeth showing marked changes in pulpal histology. Decreased innervation density, increased immune cell accumulation, and increased vascularity were evident in some teeth with advanced root resorption. Analysis of pooled data, however, did not reveal any significant differences in mean percentage area of staining for any of these variables according to the three root resorption subgroups (P > 0.05, analysis of variance on transformed data).

CONCLUSIONS

This investigation has revealed some changes in pulpal status of human primary teeth with physiological root resorption. These were not, however, as profound as one may have anticipated. It is therefore speculated that teeth could retain the potential for sensation, healing, and repair until advanced stages of root resorption.

The effect of sodium hypochlorite application on the success of calcium hydroxide pulpotomy in primary teeth

OBJECTIVE

The aim of this study was to evaluate the effects of 3% sodium hypochlorite (NaOCl) used as a hemostatic agent on the outcome of calcium hydroxide pulpotomies of primary teeth.

STUDY DESIGN

A total of 18 primary molars with advanced caries and root resorption of approximately half the root length were randomly placed into 2 groups. Conventional calcium hydroxide pulpotomies were performed on teeth in both groups; however, a cotton pellet saturated with 3% sodium hypochlorite was applied to teeth in the treatment group for 30 seconds before the pulpotomy to control hemorrhage. After the extraction of the teeth, they were examined histologically.

RESULTS

In the histologic evaluation it was found that none of the specimens in the control group showed necrosis and 1 specimen in the treatment group showed partial necrosis.

CONCLUSION

It was found that the use of 3% NaOCl as a hemostatic agent had no effect on the outcome of calcium hydroxide pulpotomies with the given concentration and timing of the NaOCl treatment and the given observation period.