We certainly feel that this is a key cell in inflamed periodontal tissue and its role in periodontitis needs to be revisited.

The chronically inflamed periodontal lesions in the present study appeared with little evidence of mast cell degranulation. The results show, however, that mast cells in inflamed gingiva have the potential to degrade extracellular matrix if appropriately triggered.

Nerve growth factor beta (NGF-beta) and its precursor proNGF are important for the differentiation and survival of neurons and dermal keratinocytes. The aim of this study was to determine the role that NGF might play in the differentiation and wound healing of oral mucosa. Cultured normal human oral mucosal keratinocytes expressed mRNA for NGF-beta/proNGF and for their receptors TrkA and p75(NTR). Lysates from cultured oral mucosal keratinocytes did not contain detectable amounts of mature 14-kDa NGF-beta but did contain several NGF proforms with molecular weights between 32 and 114 kDa. Culture medium from oral mucosal keratinocytes contained 75 kDa proNGF. The addition of NGF-beta significantly enhanced the proliferation of oral mucosal keratinocyte cultures and in vitro scratch closure. Immunostaining of biopsies from normal oral mucosa showed the presence of proNGF in all epithelial layers. NGF staining was observed in the granular and upper spinous cell layers. TrkA immunoreactivity was detected in basal and parabasal cells, with weak to moderate staining in spinous and granular cell layers. p75(NTR) staining was seen in basal cell layers. These findings indicate that NGF-beta/proNGF have mitogenic and motogenic effects on oral mucosal keratinocytes and therefore may aid in the healing of oral wounds. Differential expression of NGF and NGF receptors throughout the epithelium suggests a role in epithelial differentiation.

The markedly increased cell proliferation in ERY supports the notion that this form displays a higher disease activity as compared to RET. It can therefore be important to study each disease form separately.

– When cultures of human epithelial cells were treated for 5 min at 37°C with chlorhexidine in Eagle's medium without serum added, concentrations from 0.05 mM were found to be toxic as measured by growth inhibition and differential staining. About 20 times higher concentrations were needed to obtain a toxic effect, however, when the cells were treated with chlorhexidine dissolved in calf serum. Human whole saliva collected from a single subject had no such protective effect. The intracellular activities of 5′‐nucleotidase, alkaline phosphatase, and NADPH2+ NADH2‐diaphorases decreased upon treatment of the cells with concentrations of chlorhexidine at 0.2 and 2 mM, whereas 0.02 mM had no measurable effect on these enzymes. Treatment with chlorhexidine at 10−4mM had no effect on the hypotonic hemolysis of human erythrocytes, 0.001–0.1 mM stabilized the cells, but increasing the concentration to 1 mM gave 100% hemolysis. A concentration‐dependent inhibition of the Na+–K+–ATPase activity was found when erythrocyte membranes were incubated with chlorhexidine in the range of 0.002–0.2 mM.

– The cytotoxicity of fresh and 1‐day‐old silicate cement, composite restorative material and zinc oxide‐eugenol cement (ZOE) was tested using human epithelial cells (NCTC 2544) in four different cell culture systems: (1) 5.1Cr‐release from prelabeled cells after incubation for 4 and 24 h in the presence of the materials, (2) Implanting the materials on an agar overlay and visualizing any cytotoxic effects after 24 h by neutral red vital stain. (3) Cell growth during 5 d in the presence of the materials7hellip; (4) Colony‐forming ability after exposure of the cells for 30 min to medium previously incubated with the materials for 24 h. Freshly prepared and 1‐day‐old ZOE exhibited a prominent cytotoxic effect in all four systems. A less marked effect was found for the composite material in systems 2, 3, and 4, while silicate cement appeared to be the least toxic material in these three systems. Neither silicate cement nor composite showed any cytotoxic effect in system 1 based on51Cr‐release. It is concluded that the effects obtained by the cell culture techniques did not mimic the reactions obtained when the materials are tested under conditions which reflect their clinical use.

HIV infection is associated with increased numbers of mast cells, macrophages and neutrophils in the chronic periodontal lesion. This may predispose for tissue destruction through the release of inflammatory mediators and effector molecules. The unusually heavy cell infiltrate throughout the gingival connective tissue may contribute to the diverging pattern of periodontal tissue loss in HIV-positive patients.

– The retention of alkali soluble (CaF2) and alkali insoluble (fluorapatite) fluoride in sound enamel and demineralized enamel 2 wk after application of Duraphat was investigated in a group of orthodontic patients from whom pairs of homolog premolars were to be extracted. Demineralization of the enamel was induced during a 4‐wk period prior to application of fluoride by applying orthodontic bands to the premolars. The bands also remained attached to the teeth during and after application of fluoride (2 wk) to maintain a cariogenic environment. Three consecutive enamel layers (∼5 μm) were subsequently etched off. A significant uptake of fluoride in the first and second layer of sound enamel and in all the three enamel layers of demineralized enamel was found. More fluoride was found in demineralized enamel and a higher proportion of this fluoride was found to be in an alkali insoluble form compared with the fluoride in sound enamel. The SEM study showed a rough enamel surface after three consecutive acid etchings. The etching pattern differed within the etched area. It was suggested that the variation in etching pattern might be due to differences in orientation of the crystallites and the original surface morphology.