Comparison between histological and clinical parameters during human experimental gingivitis

The purpose of this investigation was to study stereologically the histopathologic alterations occurring during a human experimental gingivitis, and to establish a relationship between clinical parameters and histologic findings. Eight dental students volunteered for the study. After a prophylaxis they performed optimal oral hygiene for 3-4 weeks to reach mean plaque and gingival indices approaching zero. They then abandoned all oral hygiene procedures for a period of 21 days. At d 0, 4, 7, 14 and 21, Plaque Index (PII), Gingival Index (GI) and Gingival Exudate Flow Rate (GEFR) were assessed, and a buccal biopsy of their gingiva was taken. Point counting procedures were performed at 2 different levels of magnification to estimate the volume densities of epithelium, infiltrated and non-infiltrated connective tissue, and collagen. The percentages of polymorphonuclear neutrophilic granulocytes, lymphocytes, plasma cells, macrophages and fibroblasts were estimated by counting the number of profiles of these cells in the connective tissue area close to the apical end of the junctional epithelium. The histological picture during the entire experiment was one of an early lesion (Page & Schroeder 1976). The clinically healthy gingiva did not correspond to a histologically healthy gingiva containing only a few inflammatory cells, probably because the 3-4 wk of perfect oral hygiene were not sufficient to generate histological health. Furthermore, no chronic inflammation of the gingiva, as characterized by a predominance of plasma cells, was observed after 3 wk without oral hygiene. Thus, more than 3 wk of no oral hygiene are necessary to obtain an established gingival lesion. With increasing gingivitis scores between GI = 0 and GI = 2 there was a significant increase in the percentages of lymphocytes and a significant decrease in the percentages of fibroblasts. With increasing GEFR similar trends in percentages were observed for lymphocytes and fibroblasts. It was concluded that GI scores and GEFR reflect histologic changes in tissue and, hence, are valid indicators of gingivitis development.     

Stereological observations on long-term experimental gingivitis in man

The purpose of the present investigation was to study stereologically the histopathologic changes in the gingiva during 6 months of abolished oral hygiene and to study the development of chronic gingivitis in man. After a thorough prophylaxis procedure, 5 dental students performed optimal oral hygiene under supervision for a period of 3 weeks. At the end of this pre-experimental phase, they were asked to abolish all oral hygiene procedures for 4 (2 individuals) to 6 months (3 individuals). At day 21, and after 2, 3, 4, 5 and 6 months, the gingival exudate flow rate and the gingival index were assessed, and buccal gingival biopsies taken. Semi-thin histologic sections were stained with basic fuchsine and methylene blue. By point counting at 2 different levels of magnification, the volume densities of epithelium, infiltrated (ICT) and non-infiltrated connective tissue, and collagen were estimated. The %s of fibroblasts, PMN's lymphocytes, plasma cells and macrophages were estimated in a predetermined standardized area close to the apical termination of the junctional epithelium. With increasing time, the volume densities of the ICT rose concomitantly with a decrease in the volume densities of the collagen. In spite of great interindividual variations, a slow shift in the proportions of some cell populations was consistently observed. While the fraction of PMN's, lymphocytes and macrophages remained stable, a decrease of fibro-blasts (57 to 39%) and an increase of plasma cells (0.2 to 10%) was observed. This study has, therefore, demonstrated that, in 6 months of plaque accumulation, a chronic gingivitis with a predominance of PMN's and lymphocytes develops.(ABSTRACT TRUNCATED AT 250 WORDS)     

Observations on the initial stages of healing following human experimental gingivitis A clinical and morphometric study

The aim of the present study was to investigate stereologically the histologic alterations occurring during gingival healing after experimental gingivitis and to compare clinical parameters with histological findings. 8 dental students volunteered for the investigation. After a prophylaxis, they performed optimal oral hygiene to reach mean plaque and gingival indices approaching zero. They then abolished all oral hygiene procedures for a period of 21 days. After this experimental gingivitis phase, they again performed optimal oral hygiene for 8 days to restore gingival health. At days 0, 1, 2, 4 and 8 after experimental gingivitis, the plaque index (PlI), the gingival index (GI) and the gingival exudate flow rate (GEFR) were assessed and their buccal gingiva was biopsied. Point counting procedures were performed at 2 different levels of magnification on light microscopic sections to estimate the volume fractions of epithelium, infiltrated and non-infiltrated connective tissue, and collagen. The relative numbers of fibroblasts, polymorphonuclear neutrophils, lymphocytes, plasma cells and macrophages were estimated by counting the number of profiles of these cells in a specific connective tissue area adjacent to the apical end of the junctional epithelium. A rapid drop in the PlI was noted with increasing time after oral hygiene, followed by a slower decrease in the GI and GEFR scores. The histological picture during the entire experiment was that of an initial gingival lesion. At day 0, no chronic inflammation of the gingiva characterized by a predominance of plasma cells was observed.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Histological and clinical parameters of human gingiva following 3 weeks of chemical (chlorhexidine) or mechanical plaque control

The aim of the present study was to compare stereologically the histopathologic variations following 3 weeks of chemical (chlorhexidine) or mechanical plaque control. 18 students and dental hygienists volunteered for this investigation. After prophylaxis, they performed optimal oral hygiene to reach mean plaque and gingival indices approaching 0. Six of them then performed mechanical plaque control of 3 weeks (control), while the other 12 rinsed 3 times daily with a 0.12% chlorhexidine solution (test). At days 0 and 21, the plaque index (PlI), the gingival index (Gl) and the gingival exudate flow rate (GEFR) were assessed and biopsies were obtained from buccal sites. Point-counting procedures were performed at 2 different levels of magnification on light microscopic sections to estimate the volume fractions of epithelium, infiltrated and non-infiltrated connective tissue, and collagen. The relative numbers of fibroblasts, polymorphonuclear neutrophils, lymphocytes, plasma cells, macrophages and mast cells were estimated by counting the number of nuclear profiles of these cells in a specific connective tissue area adjacent to the apical termination of the junctional epithelium. After 21 days, the PlIs of the test subjects were significantly higher than the PlIs of the controls, but their Gl were similar. At the end of the experimental period, the various volume fractions and %s of cell profiles remained stable with the exception of an increase in the %s of lymphocytes in the test group. This study has shown that, clinically as well as histologically, the daily use of chlorhexidine for a 3-week period is equally efficient as optimal mechanical tooth cleaning in maintaining a healthy gingiva in the buccal sites investigated.     

Experimental gingivitis in young dogs

abstract — The aim of the present study was to analyze and express in quantitative terms some of the structural alterations which develop in an initially normal gingiva during a phase of continuous plaque accumulation. Four beagle dogs were used. The animals had from birth been twice daily subjected to meticulous mechanical tooth cleaning. When the dogs were 10 months of age their gingiva were in excellent health as evaluated by Gingival Index and Gingival Exudate measurements. Gingival tissues were harvested from the premolar and molar regions in the right jaws. The tooth cleanings were then terminated and plaque allowed to accumulate. Clinical examinations were performed and gingival biopsies sampled after 4, 7, 14, 21 and 28 d. The composition of the gingival biopsies was analyzed in a sampling microscope. After 4 d of plaque accumulation significant amounts of gingival exudate could be sampled. The exudation then gradually increased during the following weeks. Biopsies representing day zero did not contain any inflammatory cell infiltrates. However, after 4 d of the experiment leukocytes were found in the collagen-poor connective tissue immediately beneath the junctional epithelium. The size of the infiltrated connective tissue (ICT) gradually increased during the experiment. The volumetric density of collagen in the noninfiltrated connective tissue (NCT) was always much higher than in ICT. In ICT, however, this density parameter remained rather constant throughout the study. On days 4 and 7 neutrophilic granulocytes constituted 60–70% of the leukocyte population. On day 28, however, the infiltrate comprised mainly mononuclear leukocytes, especially plasma cells, neutrophils at that time occupying only a small fraction of the infiltrate.     

Clinical and histologic characteristics of normal gingiva in dogs

The aims of the present study were to establish normal gingiva in dogs, to characterize the clinical conditions prevailing and to stereologically describe the structural composition of the normal gingival tissues. Three beagle dogs were subjected to regular oral hygiene procedures during 15 weeks. Measurements of gingival fluid flow and the amounts of crevicular leukocytes served to clinically assess the gingival conditions. Semi-and ultrathin sections from biopsies of normal buccal gingival tissues from premolars were subjected to stereologic analysis based on morphometric point counting procedures. Gingival normality was achieved in two of the dogs. The normal gingival tissue in these dogs was characterized clinically by abscense of gingival fluid flow and by a minute amount of crevicular leukocytes. A gingival sulcus was most often absent. The junctional epithelium was without rete pegs, and the entire gingival connective tissue was densely filled by homogeneous collagen fiber bundles. A few isolated inflammatory cells were present in the junctional epithelium and the adjacent connective tissue. No clusters of inflammatory cells forming an infiltrate could be observed.
Stereologically, the gingival tissue comprised 48% epithelium and 52% connective tissue. The junctional epithelium occupied 10% of the gingival tissue and included a fraction of 2.8% occupied by leukocytes. The latter by volume comprised 50% neutrophilic granulocytes and mononuclear cells each. The connective tissue was composed of 67% collagen fibers, 14% free cells and 19% residual tissue. The composition of the connective tissue adjacent to the junctional epithelium differed somewhat from that of more central connective tissue fractions.     

Cell populations associated with conversion from bleeding to nonbleeding gingiva

The purpose of this study was to observe changes in cell populations of the interdental gingival tissue, which accompanied the conversion of a bleeding to a nonbleeding state induced by scaling and improved oral hygiene. Fifteen bleeding and 18 stopped-bleeding interproximal gingival biopsies were obtained from 33 patients and processed for light microscopic evaluation. The morphometric analysis of eight connective tissue components revealed that the percentage volume density of all inflammatory cells decreased, and the percentage of fibroblasts and collagen increased, when the gingiva changed from a bleeding to a nonbleeding state. Furthermore, the inflammatory cell infiltrate in bleeding and stopped-bleeding specimens was dominated by mononuclear cells of the lymphocyte/macrophage/monocyte group, while plasma cells and polymorphonuclear leukocytes comprised only a small fraction of the inflammatory cells present. Significant repair of gingival connective tissue had occurred in the stopped-bleeding specimens.     

Experimental gingivitis in the monkey

Rhesus monkeys receiving an oral hygiene program which included brushing, interdental cleansing and topical applications of chlorhexidine gluconate demonstrated a clinically normal gingiva for periods of up to 3 months. Wide fluctuations within individual dental units were noted with respect to histological sulcus depth, degree of connective tissue infiltration with lymphocytes and plasma cells, and total leukocyte or polymorphonuclear leukocyte (PMN) counts in the Junctional epithelium, even when the plaque and gingivitis index scores were 0. Of 18 clinically normal dental units sampled, only 6 appeared free of connective tissue inflammation. However, more than half of the tissue blocks obtained from dental units with a gingivitis and plaque index of 0 also showed scores of 0 with respect to the connective tissue inflammation (CTI) score and the number of PMNs in the Junctional epithelium. Within three days following discontinuation of oral hygiene procedures, rhesus monkeys developed a clinically noticeable gingivitis which began in the interdental papillae. Increases in CTI scores and number of leukocytes in the Junctional epithelium were evident after 2 days without oral hygiene. These values tended to increase further during the experimental period. A slight, but significant increase in sulcus depth was also noted during this time period. Regardless of the clinical state of the gingiva, a positive correlation was established between CTI scores and the number of PMNs and leukocytes in the Junctional epithelium. In early gingivitis, the plasma cells did not appear to outnumber lymphocytes, as has been reported for chronic gingivitis of longer duration.     

Stereologic study of cyclosporin A-induced gingival overgrowth in renal transplant patients

Gingival biopsies were taken from 13 renal transplant patients (mean age 26.5 yr), 11 of whom exhibited cyclosporin A (CsA)-inditced gingival overgrowth. Control material was obtained from seven volunteers (mean age 28 yr). Gingival tissue components were analyzed by quantitative microscopy (stereology) on 5-(μm-thick sections of interdental papillae. The volume density (Vv) of different tissue components and the surface density of epithelial ridges were calculated by conventional point and intersection counting. The study showed that the volume density of oral epithelium and the surface density of the epithelial ridges in the CsA-induced gingival overgrowth were significantly increased compared to normal gingival tissue. The connective tissue of the lesion exhibited a significant increase in volume density of cells, blood vessels and non-collagenous matrix with a corresponding decrease in the collagenous matrix. These results indicate that CsA-induced gingival overgrowth represents a tissue with an altered composition characterized by increased thickness of oral epithelium and relatively-increased amount of cells, vessels, non-collagenous matrix and decreased collagenous matrix in the connective tissue.     

Experimental cellular immune reactions in the gingiva of beagle dogs

Four Beagle dogs were sensitized to 1-dinitro-2.4 chlorobenzene (DNCB) during a preexperimental period of three months. The animals were fed a hard diet and subjected to plaque removal three times weekly throughout the study. During the experimental period of 75 days DNCB was applied to the gingiva three times weekly on one side of the jaws and the vehicle (Orabase) was applied on the other. Gingival biopsies were taken on day 75 of the experiment. Semithin sections were subjected to light microscopic analysis using morphometric point counting procedures. The mor0phometic data showed that the gingiva on the experimental (DNCB) side contained leukocyte inflitrates dominated by mononuclear inflammatory cells, in the marginal oral epithelium, junctional epithelium as well as in the connective tissue immediately below these epithelia. The oral epithelium was the site of severe alterations such as intercellular edema and lack of a stratum corneum. In the diseased portion of the connective tissue the establishment of a lymphocyte-macrophage dominated infiltrate was secured simultaneously with a drastic reduction of the collagen content.
The results of the study indicate that the reaction elicited in the tissues was related to delayed hypersensitivity and that the establishment of an experimental cellular immune reaction caused damage to the gingival structures.     

Histologic characteristics of clinically healthy gingiva in adolescents

Gingival biopsies from healthy buccal gingival units in 10 young individuals (12-14 yr) were analyzed morphometrically. The connective tissue was generally characterized by a dense collagenous network, apart from a well defined zone subjacent to the smooth and noninfiltrated junctional epithelium. This zone, which constituted on average 10% of the connective tissue volume, was less dense than the remaining part of the connective tissue and devoid of well defined collagen fiber bundles. This zone could also harbor clusters of inflammatory cells, mainly mononuclear cells, surrounded by non-infiltrated collagen-poor connective tissue. In the noninfiltrated collagen-dense mid-portion of the gingival connective tissue small areas of infiltrates could be found, the composition of which resembled that of the infiltrated areas subjacent to the junctional epithelium.     

Collagen degradation in the gingiva of the mouse incisor

In this study we investigated the possible role of the junctional epithelium of the mouse incisor in the degradation of collagen fibers carried during eruption from the periodontal ligament into the gingiva. To eliminate the contribution of fibroblasts to collagen breakdown the periodontal ligament was frozen in the sub-crestal region by local application of liquid nitrogen. As a result of this treatment the fibroblasts were disrupted and, with ongoing eruption, the ligament was split into two separate sets of collagen fibers, one attached to the incisor and the other to the alveolar bone. The injured connective tissue in the tooth-related compartment continued to move in the occlusal direction and made contact with the intact gingiva. Following its arrival in the sub-epithelial region, the collagen fibers were not degraded but carried further towards the incisal edge, a process resulting in a forward shift of the level of connective tissue attachment. The degree to which this occurred was inversely proportional to the number of fibroblasts which had repopulated the connective tissue adjacent to the incisor. The data suggest that degradation of collagen and maintenance of connective tissue attachment in mouse incisor gingiva cannot solely be performed by cells of the junctional epithelium but require primarily the degradative activity of fibroblasts.     

Histologic evidence for impaired growth control in diphenylhydantoin gingival overgrowth in man.

Fibroblast density and collagen content in non-inflamed gingiva from patients with gingival overgrowth due to sodium 5,5-diphenylhydantoinate therapy were measured and compared to normal tissue. Direct counting of fibroblast nuclei as well as stereologic point-counting precedures were performed using stained microtome sections. In no case were fibroblasts more numerous or collagen fibres more ubiquitous in DPH-enlarged gingiva. The mature, fibrous-type DPH gingival lesion represents neither hypertrophy, hyperplasia nor fibrosis, but is an example of uncontrolled growth of a connective tissue of apparently normal cell and fibre composition.     

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.     

Correlated morphometric and biochemical analysis of gingival tissue in early chronic gingivitis in man

Stereologic point-counting procedures were used to analyse quantitatively marginal gingival biopsies from 20 children 9 to 15 yr of age. Light and electron-microscopic random cross-sections of the tissue were subjected to multistage morphometric procedures for the characterization of volumetric and numerical parameters describing a defined simplified model of gingival tissue. The data revealed that (1) the gingival model was comprised of 31 per cent epithelium and 69 per cent connective tissue (including 5 per cent infiltrated connective tissue), (2) the infiltrated portion differed from normal tissue in that it had a markedly reduced collagen content (70 per cent) and a dense accumulation of cells, 76 per cent of which belong to the lymphocyte series, (3) the infiltrated portion contained a significant population of cells identified as immunoblasts, (4) fibroblasts were equally numerous in the infiltrated and non-infiltrated connective tissue portion, but about 3 times larger and pathologically altered in the infiltrated portion, (5) the size of fibroblasts correlated positively with the number of lymphocytes. The findings strongly suggest that the “early gingival lesion” has the characteristics of a cellular hypersensitivity reaction and that lymphocytes, possibly by means of cytotoxic factors or direct cell-to-cell interactions, affect the synthetic activity of fibroblasts, leading to alterations in connective tissue substances. The data provided the basis for the presentation of a new concept for the pathogenesis of human gingivitis.     

Morphological aspects of the gingiva in children with Down''s syndrome during experimental gingivitis

In a previous investigation, children with Down's syndrome (DS) showed an earlier, more rapid and more extensive gingival inflammation than normal healthy control children. These differences in gingival inflammation may be the result of aberrant morphology of the gingiva related to the genetic disorder in DS children. The aims of the present study were (i) to describe the structural composition of "normal" gingiva in DS compared to control children, (ii) to analyse the histological changes in the gingiva during plaque development and (iii) to investigate whether the clinical findings could be supported by morphological observations. The study was carried out in 8 DS and 8 matched control children. Their ages ranged from 5-10 years. Gingival normality was guaranteed by strict oral hygiene procedures. During a period of 21 days in which oral hygiene was abolished, gingival biopsies were taken from buccal sites of deciduous teeth following a predetermined schedule on days 0, 7, 14 and 21. Results on day 0 showed no morphological differences between the DS and control children regarding oral epithelium, junctional epithelium or connective tissue. During the experimental phase of the study, the amount of plaque accumulation in the DS children gave rise to a more extensive gingival inflammation than in the control children. The gingival inflammation in the DS group started earlier and included: (1) an acute inflammatory response, (2) an increase of the junctional epithelium area, (3) an increase of the infiltrated connective tissue area (ICT) and (4) a decrease in collagen fibre density of about 35-40% compared to day 0. The same phenomena were not seen until 7 days later in the control group. Conversely, the development of a perivascular lymphocyte infiltrate (LI) in the DS children was delayed compared to the control group. This may be caused by the impaired delayed-type hypersensitivity response in DS children. The development of 2 separate infiltrates (ICT and LI) in this age group and the different temporal development of ICT (day 7 for the DS and day 14 for the control group) and LI (day 14 for the DS and day 7 for the control group) does suggest different immunological mechanisms for both areas and both groups.     

Effects of toothbrushing frequency on proliferation of gingival cells and collagen synthesis

BACKGROUND: Mechanical stimulation by toothbrushing enhances proliferation of fibroblasts and junctional epithelium (JE). These changes in gingiva may depend on the interval between toothbrushing. The effects of toothbrushing frequency on proliferation of gingival fibroblasts and basal cells of JE were evaluated. METHODS: Twelve mongrel dogs were used. Each tooth was brushed for 20 s at 1.96 N. The subepithelial connective tissue of JE was examined for proliferating cell nuclear antigen (PCNA)-positive fibroblasts and procollagen type-I C-peptide (PIP)-positive fibroblasts. JE was examined for PCNA-positive basal cells. RESULTS: Gingiva that received brushing twice a day showed increases in the density of fibroblasts and ratio of PCNA-positive fibroblasts to total fibroblasts at 4 weeks. The ratio of PIP-positive fibroblasts increased at 8 weeks in gingiva brushed twice a day and once a day. PCNA-positive basal cell ratio increased at 4 weeks in gingiva brushed twice a day and once a day. CONCLUSIONS: A high frequency of brushing was associated with increased numbers of PCNA-positive fibroblasts, PIP-positive fibroblasts and PCNA-positive basal cells. Gingival cell proliferation increased and reached a plateau earlier in gingiva brushed twice a day than in gingiva brushed once a day.     

Histologic characteristics of clinically healthy gingiva in adolescents

Abstract – Gingival biopsies from healthy buccal gingival units in 10 young individuals (12–14 yr) were analyzed morphometrically. The connective tissue was generally characterized by a dense collagenous network, apart from a well defined zone subjacent to the smooth and noninfiltrated juncdonal epithelium. This zone, which constituted on average 10%, of the connective tissue volume, was less dense than the remaining part of the connective tissue and devoid of well defined collagen fiber bundles. This zone could also harbor clusters of infiammatory cells, mainly mononuclear cells, surrounded by non-infiltrated collagen-poor connective tissue, in the noninfiltrated collagen-dense mid-portion of the gingival connective tissue small areas of infiltrates could be found, the composition of which resembled that of the infiltrated areas subjacent to the junctional epithehum.     

Influence of experimental neutropenia in dogs with chronic gingivitis

The influence of a four day period of experimental neutropenia on the clinical state and the structural constituents of chronically inflamed gingiva has been studied in four beagle dogs. Neutropenia was induced by heterologous anti-neutrophil serum. The effects on the gingiva were evaluated by Gingival Index (GI) and Gingival Exudate measurements and by morphometric analysis of various tissue components in sections from biopsies of buccal gingiva sampled on days 2, 3, and 4. Control biopsies were obtained before induction of neutropenia. The GI did not markedly change during the observation period. The amount of Gingival Exudate, however, significantly decreased following the induction of neutropenia and remained low throughout the experiment. Neutrophilic granulocytes disappeared in the gingival tissues, while, apart from a relative increase in plasma cells, no other tissue components seemed to change. No bacterial invasion of the junctional epithelium or of the gingival connective tissue could be observed. Thus during a four day period the bacterial defense mechanisms at the dentogingival junction seem to be able to prevent penetration of microorganisms into the gingival tissues despite the absence of neutrophilic granulocytes.