H. N. Newman

Clinical evaluation of cervical dentine sensitivity in a population of patients referred to a specialist periodontology department: a pilot study

The prevalence of tooth sensitivity [Cervical Dentine Sensitivity (CDS)] in adult populations indicates that 8-35% of subjects reported CDS depending on the population studied and the methodology used. Few studies, however, have reported on the prevalence of CDS in periodontal patients. The aim of the study was to determine the prevalence, severity and distribution of CDS in patients referred for specialist periodontal diagnosis. Fifty-one patients [27 male, 24 female; mean age 48.5 years (standard deviation 11.63)] who gave their informed written consent were clinically evaluated for CDS using recognized methods of assessment, namely Yeaple probe, cold air blast and subjective evaluation. Other clinical variables (e.g. plaque and recession scores) were also recorded at this visit. Regression analysis and correlation coefficients were used to determine the relationship between the clinical variables. The results demonstrated a prevalence of CDS ranging between 72.5 and 98% of patients, with no significant gender difference. Results for the distribution of tooth types showed that molar teeth were mainly affected, followed by left canines and premolars. No correlation was noted between plaque, recession, response to tactile or thermal stimulation. Pain response from tactile and thermal stimulation showed no significant difference between tooth surfaces. Cold stimulation was perceived to be the dominant pain-producing stimulus as had been previously reported. The results of this investigation support those from another study, which found the prevalence of CDS to be higher in periodontal patients than has been reported elsewhere. This finding would suggest that previous periodontal treatment and/or periodontal disease may play a role in the aetiology of CDS.

Polymerase chain reaction analysis of oestrogen and androgen receptor expression in human gingival and periodontal tissue

Oestrogen and androgen receptors mediate the effects of their respective hormones by acting as ligand-activated transcription factors that control a wide range of biological processes. In order to determine whether periodontal and gingival tissues could respond to oestrogen and androgen, the specific and highly sensitive reverse-transcribed polymerase chain reaction (PT-PCR) was used to examine the presence of the mRNAs corresponding to these receptors. Expression of the androgen receptor was readily detected in periodontal and gingival tissue and in fibroblasts derived from these tissues, but transcripts for the oestrogen receptor were not detected in these samples. Moreover, treatment of the cultured fibroblasts with the oestrogen diethylstilbesterol (DES) or the androgen dihydrotestosterone (DHT) did not induce the expression of the oestrogen receptor mRNA; nor did the hormones modify the activity of the androgen receptor gene. These results suggest that, while periodontal and gingival tissues are not able to respond directly to oestrogen, they may nevertheless be highly sensitive to the anabolic effects of androgens.

THE DENTIN DISC SURFACE: A PLAUSIBLE MODEL FOR DENTIN PHYSIOLOGY AND DENTIN SENSITIVITY EVALUATION

Dentin sensitivity (DS) is a painful clinical condition which may affect 8-35% of the population. Various treatment modalities have claimed success in relieving DS, although at present there does not appear to be a universally accepted desensitizing agent. Current opinion based on Brannstroms Hydrodynamic Theory would suggest that following exposure of the dentin surface (through attrition, abrasion, or erosion), the presence of open dentinal tubules, patent to the pulp, may be a prerequisite for DS. The concept of tubule occlusion as a method of dentin desensitization, therefore, is a logical conclusion from the hydrodynamic theory. The fact that many of the agents used clinically to desensitize dentin are also effective in reducing dentin permeability tends to support the hydrodynamic theory. This paper reviews the in vitro evaluation of desensitizing agents, the techniques used to characterize their effects on the prepared dentin surface, and the ability of these agents to reduce permeability through tubule occlusion, and presents recent findings from ongoing research based on the Pashley Dentin Disc model. It can be concluded that the use of this model to determine surface characteristics, and reductions in dentin permeability through tubule narrowing or occlusion, provides a useful screening method for evaluating potential desensitizing agents. Interpreting changes observed in vitro is difficult, and extrapolation to the clinical situation must be tempered with caution.

Flow Cytometry Analysis of Gingival and Periodontal Ligament Cells

Gingival and periodontal ligament (PDL) fibroblasts are the major cellular components of periodontal soft connective tissues, but the precise differences between these cells are not yet known. In the present study, we have therefore examined the phenotypic and functional features of the cells obtained from gingival and PDL biopsy samples. Spindle-shaped cells characteristic of fibroblasts were the main cell type observed in vitro, although epithelial cells were also present in primary gingival cell cultures. Flow cytometry was used to measure the size and granularity of the cultured cells, and showed that the gingival fibroblasts were smaller and less granular compared with the PDL cells. The expression of certain key extracellular matrix (ECM) proteins, fibronectin, collagen type I, and tenascin was measured by flow cytometry. Analysis of the fluorescence profiles of these cultures showed that the majority of cells expressed fibronectin and that the average fluorescence intensity of this antigen in the PDL cells was higher than that in the gingival fibroblasts. Moreover, the fibronectin-positive PDL cells apparently comprised two subpopulations which expressed fibronectin at different levels, suggesting that the cells in the PDL cultures were functionally heterogeneous. The level of collagen type I was also found to be up-regulated in the PDL compared with the gingival cells and, as with fibronectin, was expressed at two different levels by subsets of the PDL cells. In contrast, tenascin was expressed at very similar levels by both the gingival fibroblasts and PDL cells. In addition, measurement of alkaline phosphatase, a marker enzyme for mineralized tissue-forming cells, showed that the PDL cells had higher activity than the gingival fibroblasts and that the alkaline phosphatase activity in the PDL cells was far more markedly up-regulated by dexamethasone. Our findings demonstrate that, despite their similar spindle-shaped appearance, fibroblasts derived from gingival and PDL tissues appear to display distinct functional activities which are likely to play a vital part in the maintenance of tissue integrity and regenerative processes.

Molecular identification of Capnocytophaga spp. via 16S rRNA PCR-restriction fragment length polymorphism analysis

ABSTRACT Capnocytophaga spp. have been implicated as putative periodontal pathogens associated with various periodontal diseases. Although the genus is known to contain five human oral isolates, accurate identification to species level of these organisms recovered from subgingival plaque has been hampered by the lack of a reliable method. Hence, most studies to date have reported these isolates as Capnocytophaga spp. Previous attempts at identification were based on biochemical tests; however, the results were inconclusive. Considering the differing virulence features of the respective isolates, it is crucial to identify these isolates to species level. The universal and conservative nature of the 16S rRNA gene has provided an accurate method for bacterial identification. The aim of this study was to identify Capnocytophaga spp. via restriction enzyme analysis of this gene (16S rRNA PCR-restriction fragment length polymorphism). The results (backed up by 16S rRNA gene sequencing) showed that this method reliably identifies all named Capnocytophaga spp. to species level.

Retroviral transduction of human periodontal cells with a temperature-sensitive SV40 large T antigen

The periodontal ligament (PDL) is considered to contain subpopulations of cells responsible for the development, repair and regeneration of the periodontium. Cell cultures have been used as model systems in order to understand the complex cellular and biochemical events underlying these processes. In order to obtain long-term cultures of these cells that can be cloned and characterized, primary cultures of PDL and gingival cells were infected with an amphotropic retroviral construct encoding a temperature-sensitive SV40 large T antigen (tsT). After selection for drug resistance, the cells expressed the T antigen and proliferated at 34 degrees C for more than 40 passages. However, when the T antigen was inactivated by incubation at 39 degrees C, the cultures became growth-arrested and the granularity of the cells increased, possibly as a result of differentiation. Reverse transcribed-polymerase chain reaction and flow cytometry showed that the tsT-transduced cells expressed a number of soft and hard connective-tissue antigens, including osteocalcin, osteonectin, osteopontin, collagen type I and alkaline phosphatase. Moreover, incubation of the transduced PDL cells at 39 degrees C was found to upregulate the expression of osteocalcin, osteopontin and collagen type I, but downregulate osteonectin. At this temperature, the presence of the dexamethasone downregulated type I collagen, while vitamin D3 had no effect on the expression of any of the antigens examined. Under all culture conditions, antigen expression was far higher in the transduced PDL cells than the gingival cells. The findings thus show that growth of the tsT-transduced PDL and gingival cells is temperature-dependent and that the presence of the T antigen increases their lifespan but does not ablate the expression of certain of their characteristic phenotypic and functional features.

A METHOD FOR THE IDENTIFICATION OF STREPTOCOCCUS-MUTANS IN GINGIVAL MARGIN PLAQUE BY IMMUNOFLUORESCENCE

A method was developed to identify Streptococcus mutans in natural dental plaque by indirect immunofluorescence staining, using a high-titred polyclonal antiserum raised against a serotype c strain of S. mutans followed by an FITC conjugate. Specificity was determined by staining 45 representative strains of plaque organisms, which demonstrated minimal cross-reactions. In vitro incubation of S. mutans NCTC 10449 films with a human serum containing antibodies to S. mutans and the presence of extracellular polysaccharide did not inhibit staining. The staining method enabled 98% of the streptococci to be detected in mixtures of S. mutans NCTC 10449 and Lactobacillus casei NCTC 10302. S. mutans was detected at a ratio of 1:100,000 in mixtures of pure cultures. In plaque samples, S. mutans could be distinguished from other organisms, including an unidentified cross-reacting bacillus found in some gingival plaque samples. The results suggest that immunofluorescence is a fast, practical method for identifying specific bacteria in plaque and, therefore, could be of use in microbiological studies of caries.