Effect of stannous fluoride and dilute hydrofluoric acid on early enamel erosion over time in vivo.

Recent experimental in vivo studies have shown that aqueous solutions of stannous fluoride (SnF(2)) and hydrofluoric acid (HF) can reduce enamel solubility after 5 min. The aim of this study was to evaluate the longer-term protective effect of SnF(2) (0.78%, pH 2.9) and HF (0.2%, pH 2.0) (both approximately 0.1 mol/l F) using the same experimental model. Labial surfaces of healthy anterior teeth (all four surfaces when possible, otherwise a pair of surfaces) in 103 subjects (n = 399 teeth) were exposed to citric acid (0.01 mol/l, pH 2.7). The acid was applied using a peristaltic pump (5 ml, 6 ml/min) and was collected in coded test tubes (etch I). The test solutions were then applied to the same surfaces of the teeth (1 min, 6 ml/min). After either 1, 7, 14 or 28 days, citric acid was again applied to the same surfaces and subsequently collected (etch II). Enamel solubility was examined by assessment of calcium concentration in etch I and etch II solutions using atom absorption spectroscopy. Median values were calculated for all time periods and statistical analysis was carried out using the Wilcoxon signed-ranks test. Results showed that HF reduced enamel solubility by 54 and 36% after 1 and 7 days, respectively. After 14 and 28 days, there was no longer any effect. SnF(2) showed no protective effect after the first day. Given these results, repeated application of HF and especially SnF(2) may be necessary to improve the protective effect of these fluorides, and this requires further testing.

The effects of acidic fluoride solutions on early enamel erosion in vivo.

Acidic fluoride solutions may reduce dental erosion. The aim of this study was to compare the effect of different acidic fluoride solutions on enamel dissolution using an established in vivo model. When possible 4 anterior teeth (255 teeth in a total of 67 subjects) were isolated and exposed to 0.01 M citric acid. The acid was collected in test tubes before (etch I) and 5 min after (etch II) application of test fluoride preparations. Acidic fluoride solutions (pH range 1.5-2.9), i.e. SnF(2), TiF(4) and hydrogen fluoride (HF) (all approx. 0.1 M F), HF (0.027, 0.055, 0.082 M F) and neutral NaF solution (0.1 M F) as control were applied to the labial surfaces of the teeth for 1 min (6 ml/min). Enamel dissolution was examined by chemical analysis of calcium content in the citric acid etch solutions using atom absorption spectrometry. The change in calcium concentration (DeltaCa) and the percentage of mean calcium reduction were calculated from the difference in calcium loss between etch I and etch II. Statistical analysis was carried out using the Wilcoxon signed rank test and Kruskal-Wallis tests with Dunn's multiple comparison. Results showed a mean DeltaCa of 0.671 mg/l (SD 0.625) for SnF(2), and ranged from 0.233 mg/l (SD 0.248) for the weakest HF solution to 0.373 mg/l (SD 0.310) for the strongest HF solution. This represented a 67% reduction in enamel dissolution for SnF(2) and a 40-76% reduction for the HF solutions. No reduction was observed for TiF(4) or NaF. The types of metal, pH and fluoride concentration are all important for the in vivo effect.

A novel interpretation of immune redundancy and duality in reperfusion injury with important implications for intervention in ischaemic disease.

The majority of ischaemia related injury occurs upon tissue reperfusion. Knock-out mouse models have recently shed light on the underlying molecular mechanisms, and suggest that this may be the result of an innate autoimmune response. Based on these new findings we present a novel model of immune redundancy and duality in reperfusion injury. Natural antibody, mannan-binding lectin and toll-like receptor 4 are three pre-formed innate immune receptors that recognise pathogenic molecular patterns. Removing either significantly ameliorates reperfusion injury. We propose that these three receptors serve as key parallel recognition elements that respond to the same or similar ischaemic neo-antigens, of which at least one may have a lipopolysaccharide-like motif. This would fit both with the ligand preference of the three receptors, and the observation that giving monoclonal antibody to lipopolysaccharide reduces reperfusion injury. The consequent injury caused by receptor activation appears to be mainly related to the complement anaphylatoxins, and less to phagocytes, oxidative radicals, and the membrane attack complex. C5a levels in particular are predictive of overall injury, and we suggest this anaphylatoxin causes most of reperfusion injury via both direct toxic effects and a generalised immune activation. The former is illustrated by the recent observation that excess C5a alone can cause cardiac dysfunction. As for the latter, there is evidence that adaptive immunity (especially CD4+ cells) and other serum cascades (coagulation and kallikrein) are involved, and may have been recruited by complement. Furthermore, excess C5a can cause innate immune overactivation that paralyses neutrophils, reduces complement lytic function, and leads to systemic inflammation. This is analogous to what happens in sepsis, and would explain the passive role in IRI of normal immune effectors. Finally, there is a duality complement's function in reperfusion, as some elements are conductive of damage, whilst others may help inflammatory resolution. Most important among the latter are the opsonins, like C3b and apparently C1q, which help macrophages clear apoptosing cells before they undergo secondary necrosis. This model has important implications for clinical interventions. Firstly, redundancy means that inhibiting multiple receptors may achieve a larger mortality reduction than the small and inconsistent one seen in the published monotherapy trials. Secondly, duality means that a non-specific inhibition of complement would reduce both injury and resolution. Therefore, a specific inhibition of the lectin pathway and/or an inhibition of the downstream effectors upon which the receptors converge (e.g. C5a) seem to be a better interceptive strategy.

Effects of hippocampal lesioning on experimental periodontitis in Wistar rats.

The hippocampus, which is a brain structure involved in learning and memory processes, plays a key role in the feedback regulation of the hypothalamic-pituitary-adrenal (HPA) axis and autonomic sympathetic nervous system, and the subsequent secretion of immuno-modulatory hormones in response to pathogenic microorganisms. Dysregulation of these brain-neuroendocrine-immune regulatory networks, which act in concert to maintain homeostasis, is found to be of critical importance to the host defence against pathogens, as well as susceptibility to diseases, including periodontal disease. The present study was designed to determine the effects of hippocampal lesioning on the progression of periodontitis. Experimental ligature-induced periodontitis was induced in 16 Wistar rats, which were bilaterally lesioned in their hippocampal region with an aspiration technique that is well documented to impair learning and memory, as well as in 15 sham-operated control rats. The disease progression was evaluated radiographically and histometrically. The results revealed that the hippocampal lesioned rats developed significantly more destruction of the periodontium than did the sham-operated controls. This finding supports recent studies that indicate that inappropriate brain-neuroendocrine regulation of inflammatory responses to infectious agents may play an important role in disease susceptibility and progression.

Postnatal glutamate-induced central nervous system lesions alter periodontal disease susceptibility in adult Wistar rats.

BACKGROUND: Inability to mount a suitable brain-neuroendocrine response to bacterial or other antigenic challenges has been found to play an important rôle in infectious and inflammatory disease susceptibility and progression, including periodontal disease. OBJECTIVE: The present study was designed to determine the effects of glutamate administration to new-born Wistar rats on the development and progression of naturally occurring and ligature-induced periodontal disease in the rats as adults. Postnatal glutamate administration is known to permanently damage neurones in the hypothalamic arcuate nucleus. METHOD: New-born rats were treated 1x daily subcutaneously with 2 mg/g of monosodium-L-glutamate (MSG) for 5 days from day 3 to 6. Control animals were injected with similar amounts of saline. Experimental ligature-induced periodontal disease was induced in the rats at the age of 12 weeks at maxillary right 2nd molar teeth. The contralateral maxillary left 2nd molars served as control teeth, and for assessment of naturally occurring periodontal disease. Disease progression was evaluated histometrically. RESULTS: The results revealed that the glutamate-lesioned rats developed significantly more periodontal tissue destruction compared to sham-lesioned control rats in both the ligated and non-ligated teeth. CONCLUSIONS: This study supports our recent findings indicating that inappropriate brain-neuroendocrine-immune regulation may play a rôle in periodontal disease susceptibility and progression.

Hypothalamic-pituitary-adrenal axis activation by experimental periodontal disease in rats.

Organisms respond to inflammatory conditions by mounting a co-ordinated complex series of adaptive responses involving the immune, nervous and endocrine systems that are aimed at restoring the homeostatic balance. We have recently shown in a rat model that inappropriate hypothalamic-pituitary-adrenal (HPA) axis regulation and a subsequent inability to mount a suitable glucocorticoid response to gingival inflammation may influence susceptibility to periodontal disease. This study was designed to investigate whether ligature- and bacterial lipopolysaccharide (LPS)-induced inflammation in the gingival connective tissues may activate this physiological axis, and to further explore the significance of HPA regulation in periodontal disease. Experimental periodontal disease was induced in major histocompatibility complex (MHC)-identical but HPA low (LEW) and high (F344) responding rat strains. We tested (1) whether ongoing periodontal disease activates the HPA axis as measured by corticosterone levels, and (2) whether genetic differences in HPA regulation modulate periodontal disease progression. In the F344 strain. the periodontal tissue destruction was more severe. This observation was associated with a significant increase of corticosterone levels in F344 rats only. Addition of LPS at the gingival inflammatory site led to a further increase of corticosterone levels and disease severity in F344 rats. These findings illustrate a positive feedback loop between the HPA axis and periodontal disease: the disease activates the HPA axis, and a genetically determined high HPA responsivity further increases disease susceptibility.

Glucocorticoid receptor antagonist RU 486 treatment reduces periodontitis in Fischer 344 rats.

Inappropriate hypothalamic pituitary adrenal (HPA) axis regulation of immune responses to bacterial challenges has been found to play an important role in infections and inflammatory disease susceptibility and progression. In the present study we investigated the tissue effects of experimental periodontitis in Fischer 344 rats, which were subcutaneously (s.c.) injected with 20 mg/kg of the glucocorticoid receptor antagonist and active antiglucocorticoid agent RU 486 every second day over a period of 14 d. Periodontitis was induced by placing a bacterial plaque retentive silk ligature in the gingival sulcus around the neck of maxillary right 2nd molar teeth 1 d after the first injection in 10 RU 486-treated and 10 vehicle (1,2-propanediol)-treated control animals. The contralateral maxillary left 2nd molars served as internal control teeth for naturally occurring periodontitis. Disease progression was evaluated radiographically and histometrically. The average level of corticosterone in blood at sacrifice was significantly lower in the RU 486-treated animals as compared to controls. The experimental animals also developed significantly less periodontal breakdown at both experimental and control teeth compared to the vehicle-treated control animals. The results support our recent findings showing that HPA hyper-reactivity, either genetically determined or experimentally induced, stimulates periodontal disease susceptibility. These findings suggest that central nervous regulation of inflammatory responses to dental plaque microorganisms in the gums may modulate periodontal disease susceptibility and progression.

Effects of hypothalamic-pituitary-adrenal axis reactivity on periodontal tissue destruction in rats.

The aim of this study was to test the hypothesis of an association between hypothalamic-pituitary-adrenal (HPA) axis reactivity and progression of periodontal disease. Histocompatible Lewis and Fischer 344 rats respond to stressful stimuli with low and high HPA axis reactivity, respectively. Experimental periodontitis was induced by tying a silk ligature around the neck of maxillary 2nd right molar teeth in 10 Lewis and 10 Fischer 344 rats with contralateral non-manipulated teeth as controls. Twenty non-manipulated animals were included. Also, experimental periodontitis was induced in 10 adrenalectomized Wistar rats and in 10 sham-operated rats. Furthermore, corticosterone pellets were subcutaneously implanted in 9 Lewis rats, while placebo pellets were implanted in 8 animals. Disease progression was evaluated histometrically and radiographically. The low-responding Lewis rats developed significantly less periodontal breakdown than did the high-responding Fischer 344 rats. Administration of corticosterone increased the disease development. while adrenalectomy reduced the disease severity. Our findings demonstrate the importance of genetic factors in the development of periodontal disease, and suggest that HPA axis hyper-activation is one mechanism by which periodontal disease susceptibility may be increased.

Emotional stress effects on immunity, gingivitis and periodontitis.

Gingivitis and periodontitis are thought to result from an imbalance between those oral microorganisms which normally colonize tooth surfaces in close contact with the gingival margin, and the nature and efficiency of the host response. The bacteria are the triggering agents, but host defence mechanisms within the gingival/periodontal tissues seem to be responsible for most of the tissue damage and for the outcome and progression of the diseases. It has recently been shown that emotional or psychological load (stress) may influence immune activities directly via nerve messenger substances (neurotransmitters and neuropeptides) and/or indirectly via neuroendocrine (hormone) substances. This review discusses how emotional stressors and nervous and neuroendocrine responses to psychological stressors may modulate the immune response to bacteria, and thus be expected to influence the progression and course of gingivitis and periodontitis.

Severe dental aberrations in familial steroid dehydrogenase deficiency: a new association.

Severe numerical dental aberrations are rare, and are most often seen as a part of certain syndromes. We here report on a Saudi Arabian family where first-cousin marriages have caused numerical and structural dental abnormalities linked to autosomal recessively inherited liver diseases. The two latest affected children in this family have had their liver defect successfully treated with fat-soluble vitamins and chenodeoxycholic acid, enabling us to study their dental development. One boy exhibits 11 supernumerary teeth, a general hypomineralisation and enamel hypoplasia, while an affected cousin successfully diagnosed at an early age, so far, only suffers from structural enamel defects. The children are otherwise healthy. There is no resemblance to any known syndromes. We suggest that the supernumerary teeth and the liver disease are caused by the same genetic defect, and represent a new association. The hypomineralisation, however, is most likely to result from vitamin deficiency secondary to malabsorption during the first years of life, before successful treatment was instituted.

[Cancer metastasis]. / Spredning av kreftsvulster.

Despite increasing insight into the biology of tumour development, the number of cancer deaths has not been subsequently reduced. This may be because approximately half of the cancers have metastasized already at the time of initial diagnosis. It seems important therefore, to learn more about the complex metastatic process. This process includes several linked sequential steps, and depends on an intimate interaction between the metastatic cells and the environment. In this review, we discuss these steps with emphasis on recent studies of the various cellular interactions that take place. Understanding these factors should result in diagnostic improvements and more effective treatment of cancer metastasis.

On the genetics of hypodontia and microdontia: synergism or allelism of major genes in a family with six affected members.

Familial severe hypodontia of the permanent dentition is a rare condition. The genetics of this entity remains unclear and several modes of inheritance have been suggested. We report here an increase in the number of congenitally missing teeth after the mating of affected subjects from two unrelated Norwegian families. This condition may be the result of allelic mutations at a single gene locus. Alternatively, incompletely penetrant non-allelic genes may show a synergistic effect as expected for a multifactorial trait with interacting gene products. This and similar kindreds may allow identification of genes involved in growth and differentiation of dental tissues by linkage and haplotype association analysis. Brittle nails, delayed growth of the hair, and delayed teething in the probands support the grouping of these conditions among the ectodermal dysplasias.

A synthetic, chemically modified ribozyme eliminates amelogenin, the major translation product in developing mouse enamel in vivo.

Ribozymes are small RNA structures capable of cleaving RNA target molecules in a catalytic fashion. Designed ribozymes can be targeted to specific mRNAs, blocking their expression without affecting normal functions of other genes. Because of their specific and catalytic mode of action ribozymes are ideal agents for therapeutic interventions against malfunctioning or foreign gene products. Here we report successful experiments to 'knock out' a major translation product in vivo using synthesized, chemically modified ribozymes. The ribozymes, designed to cleave amelogenin mRNA, were injected close to developing mandibular molar teeth in newborn mice, resulting in a prolonged and specific arrest of amelogenin synthesis not caused by general toxicity. No carriers were required to assist cellular uptake. Amelogenins are highly conserved tissue-specific proteins that play a central role in mammalian enamel biomineralization. Ultrastructural analyses of in vivo ribozyme-treated teeth demonstrated their failure to develop normally mineralized enamel. These results demonstrate that synthesized ribozymes can be highly effective in achieving both timed and localized 'knock-out' of important gene products in vivo, and suggest new possibilities for suppression of gene expression for research and therapeutic purposes.

Retrograde axonal cytokine transport: a pathway for immunostimulation in the brain inducing hypoxia and sudden infant death?

The etiology and pathogenesis of sudden infant death syndrome (SIDS) remain unknown. A hypothesis for SIDS should explain three characteristic findings: (a) an age distribution peaking at 2-4 months; (b) frequent association with respiratory tract infections; and (c) occurrence during sleep. The diagnosis of SIDS is applied when death cannot be explained, and this syndrome therefore probably includes various underlying causes. Based on recent observations, however, we suggest a pathogenic pathway that might be common to most SIDS victims.

Up-regulated epithelial expression of HLA-DR and secretory component in salivary glands: reflection of mucosal immunostimulation in sudden infant death syndrome.

Human parotid glands from 55 forensic autopsy subjects, 1-12 mo of age, were examined by immunohistochemistry without knowledge about the cause of death. Various combinations of monoclonal or polyclonal antibody reagents of the following specificities were applied in two-color immunofluorescence analyses: HLA class I or II (DR, DP, or DQ); pan-T cell (CD3); leukocyte common antigen (CD45); and secretory component (poly-Ig receptor). Sudden infant death syndrome victims (n = 17) were shown to have significantly increased numbers of CD45+ stromal leukocytes and intensified epithelial expression of HLA-DR and secretory component as well as increased endothelial expression of both HLA class I and II (DR, DP, and DQ) determinants compared with controls (n = 31) who had died from noninfectious causes. Seven overtly infectious subjects (bronchopneumonia) showed still more up-regulated expression. This result suggested that enhanced stimulation of the local immune system exists in sudden infant death syndrome, with release of certain cytokines that are known to up-regulate epithelial expression of HLA-DR and secretory component.

Increased epithelial expression of HLA-DQ and HLA-DP molecules in salivary glands from patients with Sjögren's syndrome compared with obstructive sialadenitis.

Salivary gland specimens from 10 patients with primary Sjögren's syndrome (pSS) were examined by two-colour immunofluorescence with various combinations of monoclonal and polyclonal antibody reagents of the following specificities: human leucocyte antigen (HLA) class I and II (DR, DP and DQ), CD3, CD45 (leucocyte common antigen), various cytokeratins, and factor VIII-related antigen. Tissue specimens from 10 normal glands and 10 glands with obstructive sialadenitis (no known autoimmunity) served as controls. Only some intercalated ducts and scattered acini of the normal major glands expressed HLA class II determinants (< 5% of total epithelial area); the relative proportion of positive elements indicated differential expression (DR > DP > DQ). SS glands contained substantial T cell infiltrates and increased numbers of activated (DR+) T cells; adjacent epithelium showed extensive differential expression of HLA class II determinants (DR > DP > DQ). Glands with obstructive sialadenitis showed similarly increased epithelial expression of HLA-DR but with surprisingly small amounts of concomitant HLA-DP and -DQ expression. Epithelial HLA class II expression probably depends on cytokines as an inductive event, which is not unique for SS but particularly prominent in this disorder. Our results suggest that epithelial expression of HLA-DP or -DQ, rather than -DR, might be a prerequisite for the autoimmune process of SS to develop in genetically susceptible individuals.

Distribution of blood-group-related carbohydrate antigens on oral endothelial cells.

Recent studies indicate that carbohydrate structures are involved in various endothelial functions such as inflammatory processes, adhesion of metastatic cells to endothelium and endothelial differentiation. In this paper we report the endothelial expression of various blood-group-related carbohydrate structures in normal oral mucosa using 15 different monoclonal antibodies reacting with type 1, 2 or 3 carbohydrate chains. Twenty biopsies, including normal oral mucosa, from secretor individuals comprised nine blood group O, nine A, one B and one AB. Endothelial staining was compared with epithelial staining in the same biopsies. Five blood-group-related carbohydrate antigens were detected on endothelial cells. The H type 2 antigen, which is the precursor of A, B and AB antigens, has previously been believed to be a universal marker for endothelial cells. All blood group O individuals (n = 9) showed strong H antigen staining in the endothelium of most vessels. However, of blood group A, B and AB individuals (n = 11), four showed heterogenous H antigen staining. In addition, we found that six out of ten blood group A or AB individuals, who expressed A or A and B antigens on spinous squamous cells and glandular epithelium, showed either heterogenous or no staining for these structures on their endothelial cells. It is concluded that there are differences between the biosynthesis of blood-group-related carbohydrate antigens in oral endothelium and epithelium.

Development of immune response markers in the trachea in the fetal period and the first year of life.

Immunoglobulin (Ig)-producing cells, T cells (CD3) and epithelial expression of secretory component (SC) and HLA class II determinants (DR, -DP, -DQ) were studied by immunohistochemistry in 16 fetal and 15 postnatal specimens from the tracheal wall. Small amounts of secretory component (SC) was present in the tracheal surface and gland epithelium in the fetal period and increased towards term. A few IgM-, IgD- and IgG-producing cells were present in some fetal specimens but no IgA- and IgE-producing cells were found. Only very few CD3+ T-cells were present in fetal specimens and intraepithelial T-cells were virtually absent until after birth. Premature infants that lived for 1 week had less SC epithelial expression than mature infants of the same age. The density of CD3+ T-cells, IgA-, IgM-producing cells as well as the epithelial SC expression increased rapidly after birth. Epithelial MHC class II expression was absent in fetal specimens. HLA-DR was detected on the apical border of the surface epithelium one week after birth and was extensively expressed throughout the remaining postnatal period. Epithelial DP and PQ expression were virtually absent during this same period. These features probably reflect local activation of the immune system in response to environmental factors.