Gingivitis In Dogs Research Articles

Effect of Ligature Placement and Dental Plaque on Periodontal Tissue Breakdown in the Dog

EXPERIMENTS REPORTED by Saxe et al. , 1 Svanberg et al., 2 and Lindhe et a l . 3 , 4 have revealed that in the presence of a plaque infection, gingivitis in dogs in most instances eventually develops into progressive periodontitis. In the studies referred to the conversion of gingivitis into progressive periodontitis required between 1 and 3 years of experiment. In order to accelerate the conversion of gingivitis into periodontitis in dogs and hence to facilitate analyses of tissue alterations related to this transition, different model systems have been utilized. 5 9 These models have involved procedures such as: (1) the raising of mucoperiosteal flaps, (2) the elimination of the cortical layer of the alveolar bone crest, and (3) the of ligatures around the neck of teeth in plaque infected dentitions. Experiments of this kind also have been carried out in rats and in monkeys. 1 0 , 1 1 A paper by Rovin et a l . 1 0 establishes the baseline for all the application studies hitherto reported. They studied the influence of bacteria on the initiation of periodontal disease in germfree and conventional rats. In order to produce gingival irritation, silk ligatures were placed at the cervical margins of the mandibular first molars. In the conventional, but not in the germfree rats, ligature placement within a few weeks resulted in a marked inflammation of the supporting tissues. This means, that the disease inducing potential of ligature placement, seemed to be the result of the combined presence of microorganisms and the ligature.

Vascular permeability during initial gingivitis in dogs.

Variations in the permeability of dento‐gingival blood vessels during initial gingivitis have been studied in four beagle dogs. On two occasions during a four‐day period of developing gingivitis, increased permeability of the dento‐gingival blood vessels was provoked by inserting filter paper strips into the dento‐gingival junction. Vessels in a state of abnorma permeability were labelled on one occasion during the four‐day period by intravascularly injected colloidal carbon and by fluorescent microspheres on the other occasion. The vascular labelling scores for each of the two tracers were determined in gingival biopsies. An experimental outline was used which allowed comparison of the permeability characteristics of the vessels on day 0 with those on day 2 and on day 2 with those on day 4 of the initial gingivitis.At each time interval (day 0, 2 and 4) the vascular labelling of the dento‐gingival blood vessels was found evenly distributed in the coronal‐apical direction of the vascular plexus. The labels were most frequently found in vessels 10–50 microns in width. In three of the dogs the vascular label scores were found to be significantly higher on day 2 compared with day 0 and on day 4 compared with day 2.The results indicate the development of a vasculitis in the dento‐gingival blood vessels during initial gingivitis involving most vessels of venular type in the vascular plexus.

Initial gingivitis in dogs.

The gingival characteristics after four days of gingivitis development have been studied in three Beagle dogs. Gingival normality was induced by regular tooth cleaning and gingivitis was provoked by abolishing oral hygiene procedures and giving the animals a soft diet. Measurements of the gingival fluid flow and the amount of crevicular leukocytes served to clinically assess the gingival condition. Semi‐ and ultra‐thin sections from contralateral biopsies of buccal gingival tissues from premolars obtained on day 0 and day 4 respectively were subjected to stereologic analysis based on morphometric point counting procedures. On day 0 of the experiment two dogs revealed minute amounts of gingival fluid and crevicular leukocytes and the gingival tissues of these dogs were normal. The third dog had somewhat higher amounts of the gingival parameters and the connective tissue adjacent to the junctional epithelium harboured a small lymphoid infiltrate occupying 8.3 ± 2.8% of the gingival tissues. On day 4 the gingival fluid flow and the amounts of crevicular leukocytes were increased in all dogs compared to their values on day 0.The coronal con nective tissue in the two dogs with initially normal gingiva revealed on day 4 an infiltrated portion which occupied 6.1 ± 2.4% of the gingival tissues. The infiltrate was predominated by neutrophilic granulocytes, monocytes, macrophages, immunoblasts and small lymphocytes. A 60% loss of the collagen density in the infiltrated fraction was noted between biopsies from day 0 and day 4 in these two dogs. The tissues of the dog which entered the experiment with a preestablished lymphoid infiltrate reacted with similar but more intense inflammatory processes on day 4 than those of the dogs with normal gingiva on day 0.The results indicate that initial gingivitis in dogs is characterized by acute exudative inflammation and immunopathological processes as well as by a marked loss of collagen fibers in the connective tissue located beneath the coronal part of the junctional epithelium. Possible mechanisms responsible for the observed alterations have been discussed.

Clinical and stereologic analysis of the course of early gingivitis in dogs

In the present investigation an attempt was made to follow the sequence of events occurring in the gingival tissues of dogs reacting to the reaccumulation of microbial plaque. The experiment was performed on 5 young dogs which twice a day during a preparatory period of 5–6 months had been treated with a 2 % chlorhexidine mouthrinse. When the eruption of the permanent teeth was in a final phase a clinical examination (Plaque Index, Gingival Index, Gingival exudate measurements) was performed, biopsies sampled from predetermined tooth regions and the chlorhexidine regimen terminated. On days 1, 3, 5, 7, 14, and 28 the clinical examinations were repeated and biopsies of buccal gingival tissues taken from incisors, canines, and premolars. The gingival tissues were subjected to a stereologic analysis based on morphometric point counting procedures. On day zero small amounts of plaque were detected on most teeth. Following the termination of the chlorhexidine regimen plaque accumulation as well as gingival exudation increased. The morphometric data revealed that (1) all biopsies contained a small portion of ICT (infiltrated connective tissue) which did not increase in size with time (2) the cellular composition of ICT fluctuated but did not change its general pattern with time (3) immunoblasts were rarely seen but an unusual lymphoid cell (X‐lymphocyte) was regularly present in ICT. The possibility was discussed that chlorhexidine not only interferes with plaque formation but also may suppress some aspects of the inflammatory and immunopathologic response of the gingiva.

Effect of anti-thymocyte serum on development of gingivitis in dogs.

The effect of repeated injections of heterologous anti‐thymocyte globulin (ATS) on the development of gingivitis has been studied in beagle dogs. Control dogs were injected with control rabbit immunoglobulin. The immunosuppressive effect of the antiserum was evaluated from the inhibition of a delayed hypersensitivity reaction in the skin towards l‐dinitro‐2.4‐chlorobenzene (DNCB). The gingival condition was determined by measurements of crevicular leukocytes, gingival fluid, acid phosphatase activity in crevicular samples and by counts of inflammatory cells in sections of gingival biopsies. Antiserum administration, but not control rabbit IgG, abolished the hypersensitivity reaction in the skin towards DNCB. The parameters of gingival inflammation increased during the 28day experimental period, both in the experimental and in the control dogs. The results indicate that cellular immunity does not play a major role for the development of gingival inflammation in beagle dogs.

Morphological changes in gingival blood vessels during developing gingivitis in dogs

Blood vessels situated at the gingival margin were studied in dogs during a 16‐day period of developing gingivitis. Morphological changes in the vessels were assessed from photographs which had been taken periodically and were identical. Two characteristic alterations were found: increased width and changes in the course of the vessels. Increases in width were observed during the first week of the experiment. Changes in the course of vessels were found during the second week.

歯肉のコラゲナーゼ活性に関する研究

The present investigations were undertaken to determine whether human gingival homogenate from patients with periodontal disease reveals collagenase activity with the use of reconstituted radioactive collagen.The results were as follows:1) Human gingival collagenase was isolated from human gingival homogenate. Specific activity of human gingival collagenase, distinct from that of bacterial collagenase, has been demonstrated by the use of paper chromatography, gel filtration and some other techniques.2) The enzyme was maximally active at neutral pH, required Ca++, and was inhibited by EDTA but not by cystein.3) In the course of experimental gingivitis in dog, gingival collagenase activity was significantly increased.