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Biomedical subjects

G M Newcomb

Publications and source records attributed to G M Newcomb.

At least 19 recordsLinked to original sources
PubMed1991

Compliance with supportive periodontal therapy.

All new patients commencing supportive periodontal therapy (periodontal maintenance) after treatment in a specialist periodontal practice from 1983 to 1986 were identified from practice records. Based on their compliance with the recommended schedule of visits, the patients were classified as either compliant or non-compliant. The results indicated that there were no significant differences between compliant and non-compliant patients with regards to age, sex, number of missing teeth, plaque score, or periodontal disease severity. More non-compliant patients than compliant patients were smokers (P less than 0.05). By contrast, more compliant patients were covered by private dental insurance (P less than 0.01) and more had periodontal surgery during treatment (P less than 0.001). Only 36% of the initial patient sample was found to be compliant at the end of 1989, with the greatest patient loss in the first year of supportive periodontal therapy of about 42%. The annual attrition rate decreased in subsequent years to average about 10% of those remaining in each year, indicating that a patient is more likely to remain compliant if he or she attends for at least 1 year of supportive periodontal treatment. Non-compliant patients were sent a questionnaire seeking reasons for their non-compliance. Forty percent of the questionnaires were returned. The most common reason given for non-compliance was that a general dental practitioner was attending to the patient's periodontal treatment needs. Many considered supportive periodontal therapy to be too expensive, while a significant proportion considered that they no longer required treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

The effect of a single episode of chlorhexidine irrigation on the gingival response to scaling and root planing.

The adjunctive effects of subgingival chlorhexidine irrigation on gingival response following scaling and root planing were investigated. Changes in clinical parameters, and microbial composition of subgingival plaque as monitored by dark-field microscopy were assessed in 12 patients over a period of 12 weeks. Two test sites and two matched control sites with probing depth ranging from 4 mm to 7 mm were selected in each patient. Oral hygiene instruction and a single episode of scaling and root planing were carried out. In addition test sites were irrigated with one mL of 0.2% chlorhexidine solution by the operator, while control sites were either irrigated with an equal volume of physiological saline or not irrigated. There were significant improvements in the clinical parameters with little difference between test and control sites. Between the beginning and the end of the study there was a marked reduction in the proportion of spirochaetes with a concomitant increase in coccoid organisms with, again, only minor differences between the test and the control sites. It was concluded that subgingival irrigation with a single application of 0.2% chlorhexidine did not enhance gingival healing, or delay recolonization of pockets by certain micro-organisms (as monitored by dark-field microscopy), when scaling and root planing had been thoroughly carried out immediately prior to irrigation.

Bacteria↗
PubMed1990

Microbiological assays as predictors of the response to periodontal therapy.

Thirty-four patients with periodontal disease each had subgingival plaque samples collected from four sites (one from each quadrant) in their mouths. The relative proportions of spirochaetes, motile rods and cocci were determined using dark field microscopy and the proportion of anaerobic to aerobic microorganisms was calculated after culture. In addition, clinical recordings were made at these sampled sites. The patients then underwent a course of periodontal treatment and were placed on a maintenance programme. The clinical recordings were repeated and the results examined to ascertain if the original microbiological or clinical measurements could have been used to predict the response to therapy. Of the baseline recordings, the initial probing depth, the initial attachment level and the presence of suppuration all showed a positive correlation with the degree of pocket reduction or attachment gain produced by treatment. The percentage of cocci in the subgingival plaque correlated negatively with the treatment response. Suppuration seemed to be associated primarily with the original pocket depth while the percentage of cocci in subgingival plaque showed a true relationship with the amount of attachment gained after periodontal therapy. The significance of this finding is discussed.

Adult↗
PubMed1989

Ultrastructure of the tibial epiphyseal growth plate in microphthalmic (mi/mi) mice.

Osteoclasts from growth plates of affected (mi/mi) and control (mi/+) microphthalmic mice, from newborn to 15 days old, were examined. Osteoclasts from unaffected mice were generally large, multinucleated cells with distinct ruffled borders and clear zones. Osteoclasts from the mi/mi litter mates were predominantly mononucleated, lacking in ruffled borders, clear zones and an abundance of organelles, features not normally associated with a functioning resorptive cell. The lamina limitans was more distinct in mi/mi mice. By 15 days, no evidence of bone resorption was seen in mi/mi mice. The immature appearance of osteoclasts and the lack of bone marrow cavity formation in mi/mi mice may result from either a fusion defect or from a limited life span of osteoclasts.

Animals↗
PubMed1989

The relationship between microbiological assays and the clinical signs of periodontal disease.

Ninety-five patients with periodontal disease each had subgingival plaque samples collected from four sites (one from each quadrant) in their mouths. The relative proportions of spirochaetes, motile rods and cocci were determined using dark field microscopy and the proportion of anaerobic to aerobic micro-organisms calculated after culture. In addition, clinical recordings were made. The only significant correlations observed were between probing depth or attachment loss and the proportion of cocci in the plaque (negative association), probing depth or attachment loss and sites which were suppurating or displayed a radiolucent interdental crest (positive association), and the percentage of cocci and sites with a radiolucent interdental crest (negative association). Partial correlation analysis controlling for probing depth or attachment loss showed that a significant inverse association between the percentages of cocci and the presence of a radiolucent interdental crest remained. No significant associations were observed between clinical signs such as bleeding on probing or suppuration and the microbiological assays. Overall there was a poor correlation between many of the signs thought by some to indicate periodontal disease activity.

Adult↗
PubMed1988

Human gingival Langerhans cells as accessory cells in mitogen induced T cell responses.

Peripheral blood and gingival tissue was collected from patients undergoing surgery for the treatment of periodontal disease. Both unfractionated peripheral blood mononuclear cells and a T cell-enriched, monocyte-depleted lymphocyte population were isolated from the blood samples while a gingival epithelial cell suspension was prepared from the oral aspect of the gingival tissue. The blood cells (1 X 10(5)) were then co-cultured with the gingival epithelial cells (1 X 10(5) and 1 X 10(4)) in 200 microliters aliquots in microtitre trays for three days to see if the epithelial cells could act as accessory cells in the lymphocyte response to the mitogen, phytohaemagglutinin (PHA). Lymphocyte proliferation was assessed by measuring the uptake of [6-3H] thymidine during the last 18 hours of culture. Removal of monocytes from peripheral blood mononuclear cells led to a significant, but not total, reduction in the proliferative response to PHA. When gingival epithelial cells were added to the T cells they restored their response to PHA in a dose dependent fashion. As Langerhans cells were the only potentially immunocompetent cells seen in the epithelial cell suspensions, it is concluded that these cells are acting as accessory cells in the T cell response to PHA.

Adult↗
PubMed1986

The ultrastructure of human gingival Langerhans cells in health and disease.

There was a statistically significant shift towards increased proportions of type I Langerhans cells (containing many Langerhans-cell granules) and reduced proportions of both type II Langerhans cells (containing few granules) and indeterminate cells in diseased oral epithelium when compared to healthy oral epithelium. Langerhans cells and indeterminate cells were also seen in the sulcular epithelium of healthy and diseased specimens but never in junctional or pocket-lining epithelium.

Adult↗
PubMed1986

The antimicrobial and clinical effects of a single subgingival irrigation of chlorhexidine in advanced periodontal lesions.

The antimicrobial effects of subgingival chlorhexidine (CH) irrigations on the pathogenic flora in advanced periodontal lesions were assessed. Changes in the patterns of colonization within the subgingival sites were monitored by differential dark-field microscopy, in 16 patients, over a period of 10 weeks. In addition, changes in the clinical parameters of the diseased sites were also monitored. Initial base-line evaluations were made for both the clinical and microbiological parameters. 4 sites of moderate to advanced periodontal disease were selected in each patient. These were randomly irrigated with a single dose of either 0.2% CH gel, 0.2% CH solution, or physiological saline, while 1 site was left as a control. The patients were seen weekly, until the 5th week, then at the 7th and 10th weeks. At each appointment, a microbiological sample was taken from the subgingival region of each site, together with an assessment of the clinical indices. Results indicated that a single irrigation of an 0.2% solution of CH or 0.2% CH gel had a marked effect in decreasing the % of spirochaetes and, to some extent, motile bacteria. There was a concomitant shift in colonization to cocci, fusiform and filamentous organisms in pockets that were irrigated; this coincided with a reduction in the % of bleeding sites. Various patterns of colonization were observed which have been described and may assist in differential dark field (DDF) monitoring of lesions. Bleeding on blunt probing was found to be correlated with a flora dominated by spirochaetes. No other correlations were found over the 10-week period between the other parameters.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteria↗
PubMed1985

The effect of atrophy, hyperplasia, and keratinization accompanying the estrous cycle on Langerhans' cells in mouse vaginal epithelium.

The morphology and numbers of Langerhans' cells vary in epithelia with different patterns of hyperplasia and keratinization. Langerhans' cells stained for ATPase were compared at five phases of the estrous cycle in murine vaginal epithelium. The cells were more dendritic and sparsely distributed with hyperplasia and were less dendritic and more densely distributed with atrophy. Greater numbers of the cells did not accompany keratinization at estrus. Ultrastructurally, three types of Langerhans' cells were discriminated. The first type, active in protein synthesis and phagocytosis, was commonest in sloughing and atrophic epithelium. The second type, containing accumulated and dispersed, electron-dense bodies presumed to be lysosomes, predominated in hyperplastic epithelium. The third, a mature resting cell, was found only after keratinization was complete. This study shows that Langerhans' cells in murine vaginal epithelium vary in morphology and numbers with the epithelial changes of the estrous cycle which may relate to their immunological role, but does not support the contention that their distribution is important for keratinization.

Adenosine Triphosphatases↗
PubMed1984

The pulpal response to citric acid in cats.

Citric acid conditioning of dentine has been proposed as an efficacious treatment for promoting re-attachment after periodontal surgery. This study investigated the pulpal reactions to periodontal surgery combined with citric acid (pH 1) demineralization of exposed dentine for 3 min. 9 cats were used as the experimental animals, with each cat providing 1 negative and 1 positive control and 2 experimental canine teeth. Evaluation was over 3 observation periods, with 3 cats in each period being sacrificed at 4, 21 and 83 days. Positive control teeth, which underwent periodontal surgery combining the removal of approximately 3 mm2 of labial bone and vigorous root planning of the exposed root surfaces, displayed mild to moderate pulpal reactions during the short- and intermediate-term periods and only mild to no reactions in the long-term period. The addition of citric acid demineralization, however, resulted in 5 experimental teeth (28%) becoming abscessed or totally necrotic in the intermediate- and long-term periods. At 21 days, the frequency of adverse pulpal responses to surgery and citric acid conditioning was significantly (p less than 0.05) greater than to surgery alone. Although 4 experimental teeth were relatively uninflamed at the long-term period of observation, all showed irritational dentine formation. Penetration of exposed dentinal tubules by plaque bacteria was observed only in the citric acid treated teeth.

Acid Etching, Dental↗
PubMed1984

Loss of Langerhans cells from gingival tissue maintained in organ culture.

Changes occurring in a population of Langerhans cells (LC) were investigated using human gingival epithelium maintained in organ culture. The enzyme adenosine-5'-triphosphatase together with the surface antigens HLA-DR and T6 were used to identify and quantitate these cells. An exponential fall in the expression of each of these markers was seen to occur with increasing incubation time, suggesting that a true loss of these cells is in fact occurring. HLA-DR antigen is shed from LC at a rate significantly greater than that at which LC are lost. A mathematical model which simulates the behaviour of LC within organ culture is presented, and several implications and possible explanations proposed.

Adenosine Triphosphatases↗
PubMed1983

Effect of citric acid on soft tissue healing in the rat palate.

The present study was carried out to determine the effects of citric acid (pH 1) on soft tissue healing. Standardised circular wounds were created in the palates of 24 rats using a modified trephine. Test animals had citric acid (pH 1) applied to the wounds for 3 min followed by rinsing with saline. In the control animals saline alone was applied for a similar time which was again followed by rinsing. Animals were sacrificed at 0, 1, 4 and 24 h, the palates dissected out and fixed in either neutral formalin, formol-sucrose for histochemical analysis or had epithelial sheets prepared for ATPase staining of Langerhans cells. At 0, 1 and 4 h less enzyme activity (non-specific esterase and acid phosphatase) was observed in the epithelium in the edge of the citric acid treated wounds compared to the controls. This was not seen at 24 h. No morphological difference was noted between the citric acid treated wounds and the controls at any of the time intervals. The morphology and distribution of ATPase positive Langerhans cells did not differ between the test and control wounds. These results indicate that the application of citric acid (pH 1) has little effect on the short-term healing of soft tissue wounds in the rat palate.

Animals↗
PubMed1982

Focal palmoplantar and gingival hyperkeratosis syndrome: report of a family, with cytologic, ultrastructural, and histochemical findings.

An Australian family in which two members were affected by focal palmoplantar and gingival mucosal hyperkeratosis syndrome is reported. The propositus and his daughter had symptoms which suggested that esophageal lesions might be present. In view of the association of tylosis with esophageal carcinoma in other families, both patients were investigated by barium swallow or endoscopy. No esophageal lesions were found. Previously unreported paranuclear bodies were described in the keratinocytes of the spinous and granular cell layers of the finely papillated gingival epithelium of the propositus. Similar paranuclear bodies, although rare, were identified in cytologic smears from the four members of the family examined, two of whom had slight whitening of the mucosa of the retromolar pads only. By electron microscopy and histochemistry, these bodies were characterized as condensations of tonofilaments and not heteromorphic keratohyalin.

Adolescent↗
PubMed1982

An unusual form of chronic gingivitis: an ultrastructural, histochemical, and immunologic investigation.

Gingival tissue from a patient suffering from an unusual form of gingivitis, previously described as plasma cell gingivitis, has been subjected to ultrastructural, histochemical, and immunologic investigation. Macrophages and T-lymphocytes infiltrated the oral epithelium where a dissecting type of injury was produced, predominantly in the lower spinous layer. Interkeratinocyte junctions were disrupted and collections of isolated desmosomes were observed in the intercellular spaces. It is postulated that the primary lesion in this atypical gingivitis lies in the epithelium and that the plasma cell infiltrate in the connective tissue is secondary to this. No allergen could be identified, and over a period of 7 years the condition has shown a tendency to resolve spontaneously.

Child↗