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Biomedical subjects

R N Powell

Publications and source records attributed to R N Powell.

At least 73 records · Page 4Linked to original sources
PubMed1982

Association between plaque accumulation and Langerhans cell numbers in the oral epithelium of attached gingiva.

After gingival health had been achieved in four subjects they were instructed to cease all oral hygiene measures. At 0, 8 and 21 days Plaque and Gingival Indices were recorded and gingival biopsies were removed from the buccal aspect of a first molar. Frozen sections of the gingival oral epithelium were stained for ATPase and 5'-nucleotidase to determine the number of Langerhans cells in a defined cross-sectional area. It was found that, as plaque accumulated, there was a statistically significant increase in the number of Langerhans cells in oral epithelium, particularly in the stratum spinosum. These results indicate that dental plaque can elicit a response in Langerhans cells located in the oral epithelium of the gingiva.

Adult↗
PubMed1982

Differing profiles of periodontal disease in two similar South Pacific island populations.

The periodontal condition of a cross-section of individuals aged between 15-59 years was characterised from clinical and radiographic observations of dental calculus, gingival inflammation, the level of the gingival attachment , alveolar bone loss, teeth missing or requiring extraction for periodontal reasons. The common characteristics of the profile in Tonga and W. Samoa were a high prevalence of the factors common to periodontal disease: calculus and gingival inflammation; a progressive apical movement of the gingival attachment; and alveolar bone loss. All these criteria showed a positive age dependency with calculus (particularly subgingival calculus) and gingival inflammation being very commonly associated with all tooth types at an early age, less than 30 years. Tooth loss observed was presumed to be previously associated with periodontal disease because the prevalence of dental caries was very low in both populations. Substantial differences were observed in the number of missing teeth between Tongan and Samoan populations, the Tongan subjects having a high rate of tooth loss. From radiographic interpretations of the periodontal conditions fewer subjects in Tonga were assessed as having no disease, and there was a higher prevalence of progressive destructive disease in Tonga than in W. Samoa. The proportion of subjects in both countries with no disease decreased rapidly with age. There was no evident explanation of the greater severity of disease in Tonga than in W. Samoa. The prevalence of microbial plaque, calculus and gingival inflammation was very high in all subjects at all ages particularly over 30 years in both populations.

Adolescent↗
PubMed1981

Disparities in gingival height in the mandibular central incisor region of children aged 6--12 years.

An investigation of disparate gingival heights of the mandibular central incisor region in 93 children aged from 6 to 12 years was undertaken. Unaffected paired teeth demonstrated an age-associated increase in clinical crown length, similar to previous reports, suggesting a gradual remodelling of soft tissues. Affected teeth displayed a rapid increase in clinical crown length suggesting that by age 10 years true recession had occurred. Significant associations with gingival inflammation (at the 0.1% level), and with anterior crowding (at the 0.2% level), occurred. Frenal involvement did not influence the position of the gingival margin.

Age Factors↗
PubMed1979

The effect of placement of cervical margins of class II amalgam restorations on plaque accumulation and gingival health.

The effects or restoring early proximal carious lesions were investigated in a series of thirty-six surfaces. In eighteen lesions the cervical margins of the restorations extended subgingivally, and in eighteen the margins were located supragingivally. Three months after restoration, plaque accumulation was not significantly different from pre-restoration levels. The degree of gingival inflammation showed a significant improvement after restoration where cervical margins were finished supragingivally (P less than 0.5). Where margins were finished subgingivally a highly significant deterioration in gingival health occurred (P less than 0.1).

Adolescent↗
PubMed1979

Conversion of a stable T-cell lesion to a progressive B-cell lesion in the pathogenesis of chronic inflammatory periodontal disease: an hypothesis.

Changes in the host's immunological response or, alternatively, changes in the oral microflora have been implicated as possible mechanisms by which a stable lesion of chronic inflammatory periodontal disease may become a progressive lesion leading to tissue destruction and tooth loss. It has recently been established that the progressive lesion in humans can be unequivocally considered as a B-cell response. Circumstantial evidence exists which suggests that the stable lesion is in fact a T-cell-mediated mechanism. An hypothesis is presented to explain the change from a stable to a progressive state in terms of a shift from a predominantly T-cell lesion to one involving large numbers of B-cells. Mechanisms of this shift in cell populations are considered together with a discussion of possible means of preventing such a shift.

Animals↗
PubMed1979

The immunopathogenesis of progressive chronic inflammatory periodontal disease.

Natural, humoral and cellular immune mechanisms have all been implicated in the pathogenesis of chronic inflammatory periodontal disease. However, confusion still exists as to the role played by each of these immunological mechanisms. Recently, characterization of the cell types within the progressive lesion has been established, in which four recognizable zones were described. Immediately subjacent to the epithelium lining the periodontal pocket both polymorphonuclear leukocytes (PMN's) and macrophages were seen, while cells deeper in the tissues had the morphological appearance of lymphocytes. The majority of these lymphocytes had a B-cell phenotype although a few T-cells and macrophages were found. On the advancing front of the lesion the cells had the morphological appearance of plasma cells, the majority of which contained IgG. Other cells found in this region had the morphology of plasma cells yet contained no cytoplasmic immunoglobulin, but they did contain substantial amounts of lysosomal enzymes. Similar cells have previously been described in periodontal disease; their frequent association with fibroblasts may suggest that they are important in the pathogenesis. Deposits of IgG and fibrin were found in the fibrous tissue band surrounding the lesion. These results are reviewed and, although the zones described were not anatomically distinct, by describing the lesion in this way it was possible to establish a convenient model to explain the immunopathogenesis of progressive chronic inflammatory periodontal disease. In this respect, progressive chronic inflammatory periodontal disease in man should be considered as a B-cell lesion.

Animals↗
PubMed1977

The reversal of localized experimental gingivitis. A comparison between mechanical toothbrushing procedures and a 0.2% chlorhexidine mouthrinse.

Twenty dental students randomly divided into four groups of five participated in this trial. Three weeks of supervised oral hygiene preceded the study in order to ensure a optimum state of gingival health. The gingival condition was assessed by means of the Gingival Index and measurements of gingival exudate. Plaque accumulation was assessed by means of the Plaque Index. Using plaque-guards, two 21-day periods were alllowed for the induction of localized experimental gingivitis around a lateral incisor and adjacent canine in each jaw. The contralateral areas served as controls. Habitual oral hygiene procedures were maintained in all other areas of the mouth throughout the experimental periods. Following 21 days of localized plaque accumulation in the mandibular experimental areas, mechanical toothcleaning procedures were introduced at intervals of once a day (Group A), once every second day (Group B), once every third day (Group C) and once every fourth day (Group D). Groups A and B regained gingival health in 10 days. The experiment was then repeated in the maxillary experimental areas. Group A, rinsing once daily with chlorhexidine solution regained gingival health in 4 days. The results obtained in the localized experimental gingivitis model were similar to those reported when totally withdrawing oral hygiene.

Adult↗