Effect of metronidazole on experimental periodontitis: cell population characteristics.

Systemic administration of metronidazole during an experimental periodontitis resulted in significantly less active tissue destruction compared to drug-free animals. However, the size of the inflammatory infiltrates in both groups was similar. The present study assessed cell populations within the infiltrates of metronidazole receiving and drug-free animals. In the experimental group, metronidazole was administered orally to 4 squirrel monkeys (100 mg/kg body weight per day) for 17 days. After 3 days, marginal periodontitis was induced around maxillary and mandibular bicuspids and molars by tying silk ligatures at the gingival margins. In 4 monkeys of the drug-free control group, periodontitis was induced around similar teeth. Biopsies of the gingiva representing 3, 7 and 14 days of experimental periodontitis were taken in both groups. The total number of cells and the number of polymorphonuclear leucocytes (PMN's) were counted on one-micron sections. At 3 days after ligature placement, there were numerically less total cells and PMN's in the metronidazole receiving experimental group. At 7 and 14 days the total number of cells and the number of PMN's was significantly greater in the drug-free control group, where more active periodontal breakdown had occurred. These results emphasize the potentially destructive role of PMN's in acute bursts of tissue destruction.

Factors determining the outcome of scaling and root planing.

Scaling and root planing are the predominant and recognized forms of periodontal therapy. They have been known for centuries, and have been investigated with increasing intensity since the turn of the century. Scaling and root planing aim at therapeutic changes of the "hard tissue lesion" at the root surface, in order to render it biologically acceptable to cells capable of attaching to it. Two major components of these root surface alterations are calculus and cementum alterations. Numerous studies have shown that scaling and root planing effectively removes subgingival deposits, and that this removal is seldom complete in deeper pockets. Even though beneficial clinical effects of scaling and root planing have been shown, it is unlikely that the full potential of healing is utilized today due to technical shortcomings. Several studies have shown that the design and dimensions of curets as used today are not optimal. These instruments are for many situations too big, subject to rapid dulling, and produce a smear layer. Chemical agents have been used to remove this layer with limited success. The therapist is a virtually unknown factor in the system of delivering scaling and root planing. A recent study showed that scaling and root planing forces used by different therapists on similar root surfaces varied by factors greater than 10. In addition, higher forces were shown to remove significantly more root substance. Apparently there is a large subjective component included in the delivery of scaling and root planing therapy. Even though scaling and root planing have been shown to be effective therapeutic procedures, many aspects require more research.

Cross-sectional and longitudinal reliability for clinical measurement of attachment loss.

Progression of marginal periodontitis in humans is characterized by acute exacerbations during short periods of time followed by periods of remission. The analytical procedures used to distinguish actively progressing sites from non-progressing sites within an individual's dentition are controversial. The purpose of the present investigation was to use measurements of probing depth and attachment level from a prospective longitudinal study of episodic periodontal disease progression to examine measurement and diagnostic reliability. In 10 systemically healthy adult human subjects with untreated advanced periodontitis, probing depth and attachment levels were measured at baseline and every 30 days for 10 to 12 months. Measurements were made at 6 sites of each tooth using an acrylic onlay as a reference point and a pressure sensitive probe. Replicate measurements were made on sites showing apparent changes in attachment loss of 2 mm or more in a month, and their contralateral counterparts. Cross-sectional reliability was described by means and standard deviations for the absolute differences between replicate measurements: 0.63 +/- 0.87 mm for anterior teeth, 0.58 +/- 0.80 mm for premolars and 0.69 +/- 0.91 mm for molars. The mean differences tended to decrease with increasing time on study and tended to be greater in deeper pockets. Longitudinal reliability was described by analyzing site-specific serial attachment level measurements across the study time period. Maximum likelihood methods were used to estimate false positive and false negative diagnostic rates associated with the diagnosis of attachment loss based on minimum threshold levels of 1 and 2 mm. The use of a 1 mm threshold resulted in estimated false positive rates of 0.08 to 0.11 and false negative rates of 0.11 to 0.15.(ABSTRACT TRUNCATED AT 250 WORDS)

Correlations between periodontal tissue breakdown and cell populations.

The present study evaluated correlations between periodontal breakdown and cell populations during an experimental periodontitis. Periodontitis was induced by tying plaque retentive silk ligatures at the gingival margins of maxillary and mandibular bicuspids and molars of 4 squirrel monkeys. Periodontal destruction was evaluated at baseline, and 3, 7 and 14 days after ligature placement by measuring loss of connective tissue attachment and crestal alveolar bone. Cell populations were characterized at corresponding time points by counting polymorphonuclear leucocytes (PMNs), plasma cells and the total number of cells. At baseline, levels of connective tissue attachment and crestal alveolar bone were normal. At 3, 7 and 14 days, loss of attachment and loss of bone were statistically significant. At baseline PMNs and plasma cells were sparse. At 3, 7 and 14 days, the total number of cells and PMNs were statistically significantly increased compared to baseline. Periodontal tissue destruction was positively and strongly correlated with the number of PMNs. These correlations emphasize the potential role of PMNs during acute bursts of periodontal tissue destruction.

A combination of platelet-derived and insulin-like growth factors enhances periodontal regeneration.

The combination of platelet-derived growth factor (PDGF) and insulin-like growth factor one (IGF-1) has previously been shown to enhance repair of soft tissue wounds. Here we report initial observations following application of PDGF and IGF-1 to periodontitis-affected teeth in beagle dogs. 1 micrograms of PDGF and IGF-1 in an aqueous gel was applied to the root surfaces of test teeth following open flap debridement. Control sites received the gel alone. Block biopsies of the teeth and surrounding bone were taken 2 weeks after treatment. Histologic analyses of control specimens revealed a long junctional epithelial attachment, and no new bone or cementum formation. In contrast, growth factor treated sites exhibited significant amounts of new bone and cementum formation. A nearly continuous layer of osteoblasts lined the newly formed bone, and there was a dense cellular "front" at the coronal extent of the new bone. These preliminary results suggest that in vivo application of the combination of PDGF and IGF-1 may enhance regeneration of the periodontal structures.

Factors associated with occurrence and reversibility of connective tissue attachment loss.

Marginal periodontitis appears to be site-specific, demonstrates rapid bursts of connective tissue attachment destruction, and may, at times, repair spontaneously. The present study was undertaken to investigate associations between bacterial populations and periodontal destruction parameters within the first 14 days after induction of experimental periodontitis in animals receiving metronidazole. Metronidazole was administered orally to four squirrel monkeys for 17 days at a daily dose of 100 mg/kg body weight. After three days (baseline), marginal periodontitis was induced by tying silk ligatures at the gingival margins of maxillary and mandibular bicuspids and molars. Subgingival bacterial samples were taken and periodontal destruction evaluated at baseline, and 3, 7 and 14 days after ligature placement. Dark-field microscopy was used to quantitate motile forms, spirochetes, straight and curved rods, filaments, cocci and fusiforms. Levels of connective tissue attachment, crestal alveolar bone and the volume of bone were assessed histometrically. Bacterial and histometric parameters were analyzed using analysis of variance. The results indicated that subgingival plaque, prior to induction of periodontitis, consisted primarily of cocci. At three days after ligature placement, cocci were significantly decreased, while straight rods became the predominant bacterial group for the remainder of the study. Spirochetes and motile forms were virtually absent at all time points. Histometric analyses showed significant loss of connective tissue attachment at three and seven days, which was reversed and repaired at 14 days. Factors relating to initiation, potentiation, and reversibility of connective tissue attachment loss are discussed.

Effect of metronidazole on development of subgingival plaque and experimental periodontitis.

Active tissue destruction in experimental periodontitis has been positively correlated with subgingival spirochetes and total number of organisms. The present study was designed to inhibit spirochete populations and evaluate the effect upon periodontal destruction. Metronidazole was administered orally to four squirrel monkeys (100 mg/kg/bwt) for 17 days. After 3 days, marginal periodontitis was induced around bicuspids and molars by tying silk ligatures at the gingival margins. Subgingival plaque samples were taken baseline and 14 days after ligature placement. Dark-field microscopy quantitated motile forms, spirochetes, straight and curved rods, filament, cocci and fusiforms. Periodontal destruction was evaluated at 2 weeks by histometric analysis of connective tissue attachment, crestal alveolar bone and infiltrated connective tissue. Bacterial and histometric comparisons were made with experimental periodontitis data from four animals (control) which had not received metronidazole. Subgingival plaque prior to periodontitis induction was dominated by cocci, but fusiforms and straight rods were also present. Straight rods formed a greater proportion of the plaque which developed in metronidazole-receiving animals. The absence of spirochetes and motile rods contrasted with the control group where spirochetes were the predominant type. The total number of bacteria was also larger in the control animals. Histometric analysis showed that areas of infiltrated supracrestal connective tissue were similar in both groups. Loss of connective tissue attachment and alveolar bone was significantly less in experimental animals, and the latter values did not differ significantly from baseline dimensions. The results indicated that the subgingival bacterial populations which developed during metronidazole administration did not result in an experimental periodontitis.

Microbial populations and active tissue destruction in experimental periodontitis.

Although specific subgingival microflora are being associated with active tissue destruction in periodontitis, little information exists on the relationship between subgingival flora and histological evidence of tissue destruction. The present study was undertaken to explore these relationships during experimental marginal periodontitis in squirrel monkeys. In 4 squirrel monkeys, experimental periodontitis was induced around bicuspids and molars using silk ligatures. The buccal part of the subgingival ligature was removed for bacterial sampling 3, 7, and 14 days after ligature placement. Dark-field microscopy was used to quantify motile forms, spirochetes, straight and curved rods, filaments, cocci and fusiforms. Subgingival plaque prior to periodontitis induction was dominated by cocci, but fusiforms and straight rods were also present. Spirochetes, filaments, curved rods and motile forms were absent. 3 days after induction of periodontitis, there were marked increases in spirochetes, motile forms, filaments, curved and straight rods. The proportions of coccoids and fusiforms decreased. The bacterial proportions stayed at approximately the same levels through 7 and 14 days. Histometric quantification of periodontal destruction showed loss of connective tissue attachment and crestal alveolar bone. A positive correlation was found between periodontal tissue destruction and both total number of subgingival bacteria and spirochetes.