Adaptive calcified matrix response of dental pulp to bacterial invasion is associated with establishment of a network of glial fibrillary acidic protein+/glutamine synthetase+ cells.

We report evidence for anatomical and functional changes of dental pulp in response to bacterial invasion through dentin that parallel responses to noxious stimuli reported in neural crest-derived sensory tissues. Sections of resin-embedded carious adult molar teeth were prepared for immunohistochemistry, in situ hybridization, ultrastructural analysis, and microdissection to extract mRNA for quantitative analyses. In odontoblasts adjacent to the leading edge of bacterial invasion in carious teeth, expression levels of the gene encoding dentin sialo-protein were 16-fold greater than in odontoblasts of healthy teeth, reducing progressively with distance from this site of the carious lesion. In contrast, gene expression for dentin matrix protein-1 by odontoblasts was completely suppressed in carious teeth relative to healthy teeth. These changes in gene expression were related to a gradient of deposited reactionary dentin that displayed a highly modified structure. In carious teeth, interodontoblastic dentin sialo-protein(-) cells expressing glutamine synthetase (GS) showed up-regulation of glial fibrillary acidic protein (GFAP). These cells extended processes that associated with odontoblasts. Furthermore, connexin 43 established a linkage between adjacent GFAP(+)/GS(+) cells in carious teeth only. These findings indicate an adaptive pulpal response to encroaching caries that includes the deposition of modified, calcified, dentin matrix associated with networks of GFAP(+)/GS(+) interodontoblastic cells. A regulatory role for the networks of GFAP(+)/GS(+) cells is proposed, mediated by the secretion of glutamate to modulate odontoblastic response.

[Isolation, cultivation and initial identification of Nanobacteria from dental pulp stone].

OBJECTIVE: To isolate Nanobacteria from dental pulp stone and perform culturing and the identification of Nanobacteria. METHODS: Freshly collected 27 dental pulp stones were divided into nine samples. Each sample contained three dental pulp stones. All samples were used for the isolation and culture of Nanobacteria. The shape and the growth characteristics of the cultured bacteria were observed. Nanobacteria were identified by von Kossa staining, immunohistochemical staining and indirect immunofluorescence staining, double staining including Hoechst staining and von Kossa staining. RESULTS: The characteristics growth and morphology of the bacteria detected in seven samples were similar to Nanobacteria. von Kossa staining, immunohistochemical staining, indirect immunofluorescent staining were positive for Nanobacteria. In double staining method, Hoechst staining of the samples was negative for Nanobacteria, but von Kossa staining was positive. Hoechst staining of the dental pulp cells was positive. No Nanobacteria was found in the other two samples. CONCLUSIONS: The bacteria isolated from dental pulp stone in this study was similar to Nanobacteria in terms of growth rate, morphology and staining properties. These unusual properties of the bacteria may play an important role in the formation of pulp stone.

Microorganisms in closed periapical lesions.

The purpose of this study was to investigate the microorganisms of strictly selected closed periapical lesions associated with both refractory endodontic therapy and pulpal calcification. Definitive criteria were established that assured complete clinical isolation of the periapical lesion from the oral and periodontal environment. A total of 13 criteria-referenced lesions were selected from 70 patients with endodontic surgical indications. A well controlled culturing method was used in all cases and samples were taken by one clinician at three separate sites during each surgery. Samples taken at the surgical window and within the body of the lesion served as controls, whilst a third sample was taken at the apex. In all 13 cases, samples taken from the apex yielded microorganisms comprising 63.6% obligate anaerobes and 36.4% facultative anaerobes. Prevalence of the isolated species was 31.8% for Actinomyces sp., 22.7% Propionibacterium sp., 18.2% Streptococcus sp., 13.6% Staphlyococcus sp., 4.6% Porphyromonas gingivalis, 4.6% Peptostreptococcus micros and 4.6% Gram-negative enterics. The results of this investigation indicate that closed periapical lesions associated with calcified teeth or those resistant to root canal treatment harbour bacteria. The inability to eradicate all root canal microorganisms during root canal treatment, along with anatomical factors, may allow further bacterial colonization of the root apex and surrounding periapical tissues, and consequently prevent healing.