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)     

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)     

The significance of alveolar bone in periodontal disease

The present experiment was designed to study if a gingival unit with a long supraalveolar connective tissue attachment provides less resistance against progression of periodontal disease than a unit with a supraalveolar connective tissue attachment of normal length. A long supraalveolar connective tissue attachment was established at the buccal aspect of mandibular premolars and molars in dogs by surgical removal of the marginal portion of the buccal alveolar bone after elevation of a muco-periosteal flap. Attempts were made to minimize mechanical injury to the root cementum and the supraalveolar fibrous attachment during the surgical procedure. Contralateral, non-operated teeth with a supraalveolar connective tissue attachment of normal length were used as controls. Following surgery, plaque control was initiated and maintained for 3 months by topical application of 0.2% chlorhexidine digluconate solution twice daily. During the following 6 months, the oral hygiene measures were abandoned and plaque was allowed to accumulate on both groups of teeth. In order to enhance plaque formation and to promote the development of subgingival plaque, cotton floss ligatures were placed at the entrance of the gingival sulci. The dogs were sacrificed 6 months after the initiation of the plaque accumulation period. The jaws were removed and histological sections prepared of test and control teeth including their surrounding periodontal tissues. The histological analysis revealed that the plaque induced inflammatory lesion in the gingival connective tissue did not extend more apically in sites with a long supraalveolar connective tissue attachment than in sites with a supraalveolar fibrous attachment of normal length. A small but statistically significant loss of connective tissue attachment had occurred in both groups of teeth. This attachment loss, however, was similar in sites with a long supraalveolar connective tissue attachment and in sites with a supraalveolar fibrous attachment of normal length. These findings suggest that the loss of attachment in periodontal disease is unrelated to the presence or absence of the bony component of the periodontium.     

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.     

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.     

Recession in sites with inadequate width of the keratinized gingival An experimental study in the dog

Abstract The present investigation was performed to assess the inflammatory response in gingival units subsequent to the placement of restorations with subgingivally located margins. 3 beagle dogs were used. Cotton floss ligatures were placed around the neck of the mandibular third and fourth premolars of all dogs. The ligatures were exchanged once a month during the first 6 months of experiment. When 40–50% of the height of the supporting tissues had been lost in an experimental periodontitis the ligatures were removed but the animals allowed to accumulate deposits for another 60 days. The inflamed periodontal tissues were subsequently excised using either an “apically placed flap” procedure or a “gingivectomy” procedure. In the flap procedure the main part of the keratinized gingiva was preserved while in the gingivectomy procedure the keratinized part of the gingiva was removed in toto. Following scaling and root planing the animals were during a maintenance period of 4 months placed on a program involving chlorhexidine application and mechanical tooth cleaning twice daily. On Day 0 a notch was prepared in the buccal surface of each root at the level of the gingival margin. Furthermore, steel bands were placed along the buccal surface of each root of the third and fourth premolars and secured with an apical margin at the level of 1 mm apical to the notch. The bands were cemented to the root surfaces by a cement. The dogs were allowed to accumulate plaque and calculus for 6 months. Towards the end of the study a clinical examination was performed to assess the position of the steel bands in relation to the notch and the gingival margin, the presence of subgingival plaque and the condition of the gingiva. The animals were subsequently sacrificed and specimens containing' the mandibular third and fourth premolars were harvested, fixed in formalin, decalcified and embedded in paraffin. The buccolingual sections of each root were cut with a microtome set at 4 μm and stained in hematoxylin and eosin. In the biopsies the distance between the gingival margin and the most apical cells of the junctional epithelium, the distance between the junctional epithelium and the margin of the bone crest and the distance between the notch and the gingival margin were assessed. In addition, the size of the infiltrated connective tissue was calculated using a morphometric test system. The results of the experiment revealed that the placement of a “restoration” in a subgingival position in gingival sites also allowed to accumulate plaque established conditions which promoted development of moderate to severe gingival inflammation. In experimental sites characterized by the presence of an “inadequate” width of the keratinized gingiva, the inflammatory reaction was almost always accompanied by loss of gingival tissue. It is suggested that the placement of restorations in a subgingival position in sites with a narrow zone or lacking keratinized gingiva may in the presence of subgingival plaque favor the apical displacement of the soft tissue margin.     

Location of proliferating gingival cells following toothbrushing stimulation

OBJECTIVES: Mechanical stimulation by toothbrushing promotes healing of gingivitis through accelerating cell proliferation. Junctional epithelium proliferates at periodontal pocket formation. A question is arisen whether toothbrushing contributes to the repair of gingival inflammation or deterioration of pocket formation. The location of proliferating cells in gingiva stimulated mechanically by toothbrushing was investigated. MATERIALS AND METHODS: A total of 24 teeth of dogs underwent daily plaque removal with a curette (plaque removal) or both plaque removal and toothbrushing (toothbrushing). Proliferative activity of gingival cells in six individual zones was evaluated by assaying expression of proliferating cell nuclear antigen (PCNA). RESULTS: Toothbrushing increased densities of PCNA-positive basal cells in the junctional epithelium, connective tissues adjacent to the junctional epithelium, the alveolar bone of the oral epithelial side and the oral epithelium. However, the densities of PCNA-positive cells at the apical portion of the junctional epithelium, connective tissues adjacent to the cementum and the alveolar bone of the periodontal ligament side did not increase following toothbrushing. CONCLUSIONS: Toothbrushing promotes proliferation of gingival cells other than fibroblasts in periodontium and basal cells in the apical portion of the junctional epithelium. The repair of periodontal tissues might be promoted by toothbrushing within the limit of the direct mechanical stimulation.     

Effects of topical application of chlorhexidine on plaque and gingivitis in monkeys

All teeth except the lower right canine, premolars and molars, in each of 4 adult male macaque monkeys with heavy plaque deposits and severe gingivitis, were scaled and polished daily for 5 days, followed by daily topical applications of 2% aqueous chlorhexidine gluconate. Minimal amounts of simple plaque containing epithelial cells and Gram positive cocci formed on the treated teeth whereas the untreated teeth retained heavy deposits of complex plaque. In chlorhexidine treated areras the clinical level of gingivitis appeared to subside to a minimum after 15-20 days. Histomorphometric assessments of gingivitis after 42 or 52 days treatment were made on decalcified paraffin sections, by measuring the total area of gingival connective tissue and the area containing inflammatory cells and calculating the proportion of gingival tissue affected. A total of 21 teeth were assessed. Untreated teeth had from 16-40% of the gingivba inflamed, treated teeth only 0-6%. Thus daily topical application of chlorhexidine significantly inhibits plaque accumulation and maintains a significant reduction in gingivitis in these animals. No differences in the nature or degree of keratinization could be detected between treated and untreated areas, nor were there any visible side effects of the use of chlorhexidine for this period.     

Histopathologic features of the initial and early stages of experimental gingivitis in man

The pathologic alterations occurring in the gingival tissues of humans immediately following the beginning of plaque accumulation have not heen elucidated previously. Seven males, 22--31 years of age, free of clinical manifestations of dental and periodontal disease, and exhibiting a Plaque Index score of zero for the previous 28 days served as subjects. Plaque control measures were discontinued for 8 days and biopsies were taken from the buccal marginal gingiva of the first premolars on days 0, 2, 4, and 8. Paraffin- and Epon-embedded section, treated with a variety of histochemical stains were analyzed microscopically and cell counts were done on 1-micron Epon section. At 2 and 4 days following the beginning of plaque accumulation, the vessels subjacent to the juctional epithelium exhibited vasculitis and alterations in the perivascular collagen. There was a statistically significant increase in the number of neutrophils residing in the junctional epithelium. By the end of the 8-day period, the number of small mononuclear cells, mostly lymphocytes, in the connective tissues had increased by 3-fold and the area of collagen fiber alteration by 4-fold. In addition, the number of fibroblasts per unit area of connective tissue decreased significantly. Thus, within the period of 8 days following the beginning of plaque accumulation, an early lesion exhibiting many features characteristic of delayed hypersensitivity develops.     

Variability of histologic criteria in clinically healthy human gingiva

After prophylaxis, 5 dental hygienists performed optimal oral hygiene under supervision for 6 months. At months 0, 1, 4 and 6, Plaque Index, Gingival Exudate Flow Rate and Gingival Index were assessed, and a buccal biopsy of their gingiva 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 fibroblasts, polymorphonuclear neutrophilic granulocytes, lymphocytes, plasma cells and macrophages 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. All the changes inside the tissue occurred slowly. During the 6-month period there was a continuous increase of the volume density of the epithelium in the gingiva. An increase in the percentage of fibroblasts was observed between months 1 and 4 together with a decrease in the percentage of lymphocytes and in the volume density of the infiltrated connective tissue. Between months 4 and 6 an increase of the volume density of the collagen was found together with a further increase in the percentage of fibroblasts and a further decrease in the percentage of lymphocytes. After 6 months of perfect oral hygiene no more plasma cells were visible. This study has shown that, even in presence of clinically healthy gingiva, subclinical changes may take place. It appears realistic to accept the presence of a very mild gingivitis localized in an area adjacent to the attachment as compatible with gingival health.     

The effect of delmopinol rinsing on dental plaque formation and gingivitis healing

The aim of this study was to investigate a possible dose-response effect of delmopinol hydrochloride, on the development of plaque and on the healing of gingivitis. 64 healthy male volunteers, aged 18-40 years with healthy gingivae and clean teeth, participated. During a 2-week period, the participants refrained from all oral hygiene and rinsed 2x daily with a placebo solution. On day 14 of the study, they received professional toothcleaning, and were randomly assigned to 4 groups. For the following 2 weeks, they rinsed 2x daily for 1 min with 10 ml of 0.05% (15 subjects), 0.1% (17) or 0.2% (16) delmopinol, respectively. 16 subjects rinsed with 0.2% chlorhexidine. No oral hygiene procedures were performed during the test period. On days 0, 14 and 28, gingival bleeding index and the presence of stainable plaque were determined. Periodic identical photographs were used for planimetric determination of buccal plaque extension. No significant difference for the reduction in gingival bleeding index was found between 0.2% delmopinol and chlorhexidine rinsing. The mean plaque index showed its most significant reduction on lingual surfaces of both upper and lower jaws when rinsing with 0.2% delmopinol. Mean plaque extension was reduced by 23% for 0.05%, 39% for 0.1% and 55% for 0.2% delmopinol. A significant dose-response effect for 0.05%, 0.1% and 0.2% delmopinol was found for gingival bleeding index, plaque index and plaque extension. The results show that delmopinol favors the healing of gingivitis and reduces plaque formation.     

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.     

Efficacy of Listerine®, Meridol® and chlorhexidine mouthrinses on plaque, gingivitis and plaque bacteria vitality

The experimental gingivitis model was used to compare the anti-plaque, anti-gingivitis and anti-microbial efficacies of a phenolic compound (Listerine) and an amine/stannous fluoride mouthwash (Meridol), using a placebo preparation as negative control and a chlorhexidine solution as positive control in a double-blind study. After professional toothcleaning, 36 volunteers performed optimal oral hygiene for a period of 2 weeks. They then ceased all oral hygiene procedures for 21 days during which they rinsed twice daily with 1 of the 4 mouthrinses. After 3 weeks of rinsing, plaque indices remained the lowest in the chlorhexidine group, while subjects using Listerine or Meridol harbored similar indices significantly lower than that of individuals rinsing with the placebo solution. Up to that time, the gingival index scores were equal in all groups except for the chlorhexidine group in which the values only amounted to half of these encountered in the other groups. The plaque vitality scores showed a bactericidal effect in vivo of chlorhexidine during the entire time of experimental gingivitis. In contrast, the data gave no evidence of an antibacterial effect in vivo of Listerine. The efficacy of Meridol to kill micro-organisms was similar to chlorhexidine during the early stages of plaque accumulation and, with time, became insignificant. This study has demonstrated that chlorhexidine was superior to Listerine and Meridol in its ability to maintain low plaque scores and gingival health during this 3-week period of no mechanical oral hygiene. Moreover, it was also shown that Meridol was as effective as Listerine in reducing plaque accumulation and, in contrast to Listerine, possessed a remarkable but transient antibacterial effect in vivo.     

Rinsing with delmopinol 0.2% and chlorhexidine 0.2%: short-term effect on salivary microbiology, plaque, and gingivitis.

The aim of this short-term study was to compare the effect of delmopinol HCl 0.2% and chlorhexidine digluconate 0.2% rinses on the development of dental plaque, the healing of experimental gingivitis, and the salivary microbiology. As part of a larger study protocol, 45 healthy males enrolled in an oral hygiene program to upgrade their oral health. For this portion of the study, participants had their teeth professionally cleaned on day 0. The participants then abstained from standard mechanical oral hygiene procedures, but applied a placebo solution twice daily for 2 weeks. At the end of this period the subjects received a second professional cleaning and were then assigned to 2 treatment groups: Group 1 rinsed with 10 ml of delmopinol HCl 0.2% and Group 2 rinsed with 10 ml of chlorhexidine digluconate 0.2% for 1 minute twice daily for the next 2 weeks and continued to refrain from mechanical oral hygiene procedures. At the end of the placebo and active treatment periods 1) saliva samples were taken and cultivated on a series of media; 2) the degree of gingivitis was assessed with gingival crevicular fluid (GCF) and gingivitis index (GI); and 3) the plaque index was assessed and the stainable buccal plaque extension was analyzed planimetrically. No changes in the salivary microbiological counts were detected for the subjects rinsing with delmopinol. Subjects rinsing with chlorhexidine showed significant reductions of anaerobes, aerobes, and S. mutans in saliva. The amounts of GCF and GI were reduced largely to the same extent in both treatment groups. Mean plaque extension was reduced by 52% after delmopinol and 88% after chlorhexidine rinsing.(ABSTRACT TRUNCATED AT 250 WORDS)     

Carrageenan-induced inflammation and its effects on mitotic activity and keratinization of gingival epithelium. A histologic and autoradiographic study

This study was undertaken in order to: evaluate the cell population in carrageenan-induced inflammation and investigate the extent to which this inflammation modified mitotic activity, and keratinization of the sulcular epithelium induced by daily prophylaxes in monkeys. Normal-keratinized oral gingival epithelium was also evaluated for these processes in the same gingival specimens. Each of three adult Rhesus monkeys received a thorough prophylaxis 1 week prior to the experiment. Over the 10-week experimental period, each monkey received daily rubber cup prophylaxes. In addition, during the last 10 days, daily gingival injections of a 1% carrageenan saline solution and normal saline solution were given. One hour prior to sacrifice, each monkey received an intravenous injection of tritiated thymidine, 1 microCi/gram of body weight. After sacrifice and tissue processing, the histologic sections were evaluated. It was found that the carrageenan solution injected into gingival tissues produced an acute inflammatory response consisting of polymorphonuclear leukocytes PMNs (61.3%), lymphocytes (5.2%), monocytes/macrophages (23.5%), plasma cells (2.0%) and unidentified cells (3.8%). An Inflammatory Index and a Mitotic Activity Index were determined, and keratin length and widths were measured. Data were analyzed statistically using analysis of variance. Pairwise comparisons were also made using Scheffe's method of multiple comparisons. The study showed that: carrageenan solutions injected into gingival tissues elicited an acute inflammation; acute inflammation present in gingival connective tissue stimulated an increase in mitotic activity in subjacent gingival epithelium; acute inflammation within gingival tissues did not modify the induced-keratinized sulcular epithelium, or the normally-keratinized oral gingival epithelium; and acute inflammation may not necessarily affect tissue keratinization, if bacterial plaque is removed daily.     

The effect of topical application of dextran on the gingiva of the beagle dog.

Dextrans derived from Leuconostoc mesenteroides were placed on clinically healthy gingiva of Beagle dogs once a day for 21 days. Control gingival tissues received saline. Both healthy controls and dextran-treated tissues were brushed daily. Inflamed control tissues were obtained by allowing plaque to accumulate for 21 days. Tissues receiving daily application of dextran solutions developed chronic gingival inflammation but displayed no clinical signs of gingivitis. Healthy control gingival tissues showed no clinical signs of gingivitis and minor histologic inflammatory changes. Tissues exposed to dental plaque showed the typical clinical and histological inflammatory changes of gingivitis. Thus dextran, a substance similar to the extracellular polysaccharide found in dental plaque, was able to penetrate the sulcular epithelium, enter healthy gingival connective tissue and cause chronic inflammation. This connective tissue inflammation occurred without inducing any of the clinical signs of gingivitis. Therefore, it is concluded that dextran produced one component of the gingivitis response, chronic histologic inflammation, independent of another major component of the disease, clinical inflammation.     

A long junctional epithelium - A locus minoris resistentiae in plaque infection?

Abstract The present experiment was undertaken to examine whether a gingival unit with a long junctional epithelium provides a. less efficient seal against plaque infection than a unit with a junctional epithelium of normal length. Periodontal tissue breakdown was produced around 8 teeth (test teeth) in each of 4 monkeys by placing elastic ligatures around the neck of the teeth. When the periodontal pockets at the approximal tooth surfaces were 4–5 mm deep and angular bony defects had been produced, the ligatures were removed. The periodontal tissues of the test teeth were subjected to flap surgery. The exposed root surfaces were scaled and planed but no osseous surgery was carried out. Following surgery, plaque control comprising all teeth of the dentition was instituted and maintained for 4 months. Healing following this type of surgical treatment involved the establishment of a long junctional epithelium. During the final 6 months of experimentation, oral hygiene measures were abandoned and plaque was allowed to accumulate. In each animal, 4 test teeth and 3 normal control teeth were selected to study gingival inflammation resulting from undisturbed plaque accumulation. In order to enhance subgingival plaque formation, in each animal cotton floss ligatures were placed in the entrance of the gingival sulci of the remaining 4 test teeth and in 3 controls. The animals were sacrificed 10 months after surgery. The jaws were removed and histological sections of the teeth including surrounding periodontal tissues were produced. The histological analysis revealed that the inflammatory lesion in the gingival connective tissue (the ICT area) resulting from plaque infection did not extend deeper into the periodontal tissues in sites with a long junctional epithelium than in gingival units of normal height. The results were interpreted to indicate that the barrier function of a long junctional epithelium against plaque infection is not inferior to that provided by a dentogingival epithelium of normal length.     

Effect of experimental neutropenia on initial gingivitis in dogs

Abstract – The role of neutrophilic granulocytes in the loss of gingival collagen has been studied by inducing experimental neutropenia during initial gingivitis in beagle dogs. Neutropenia was induced for 4 d in three animals with normal gingiva by repeated injections of rabbit anti-neutrophil serum. During neutropenia microbial plaque was allowed to form on the teeth. Samples of junctional (crevicular) leukocytes and gingival fluid were taken on days 0 and 4. Block biopsies of buccal gingiva were obtained on day 4. Stained semi- and ultrathin sections were used for histometric and serologic tissue analysis. Gingival fluid flow increased from day 0 to day 4 in all dogs while junctional leukocytes increased in one dog only. Subgingival plaque had formed in most biopsies, and in the junctional epithelium very few neutrophilic granulocytes were present. In the coronal connective tissue subjacent to the junctional epithelium lymphoid cells, structurally abnormal neutrophilic granulocytes and monocytes/macrophages were diffusely scattered. The gingival collagen appeared mainly displaced by the inflammatory cells rather than dissolved. The data suggest that neutrophilic granulocytes may contribute to the loss of gingival collagen during initial gingivitis in dogs. The neutrophils also seem to be of importance for the limitation of subgingival plaque growth along the tooth surface.     

环孢素对大鼠牙龈组织形态影响的定量分析

目的定量分析环孢素（CsP）对大鼠牙龈组织形态影响的部位特异性和时间依赖性。方法将80只7周龄雄性Wistar大鼠随机分为实验组和对照组,每组又分为10、20、30、40 d亚组。实验组胃饲含CsP的鲜牛奶,对照组胃饲等量鲜牛奶。内固定取材后制作下颌第一磨牙颊舌向石蜡切片,HE染色,利用图像分析系统分别测量颊侧和舌侧牙龈上皮面积、结缔组织面积、最长钉突长度,行完全随机分组两因素析因设计资料的方差分析。结果实验组大鼠牙龈增厚,颊侧附着龈近膜龈联合处上皮钉突明显增生伸长。实验组大鼠颊侧和舌侧牙龈上皮面积和结缔组织面积以及颊侧最长钉突长度均显著大于对照组（颊侧P＜0.01,舌侧0.01＜P＜0.05）,2组间舌侧最长钉突长度差异无统计学意义。各时间点相比,颊侧和舌侧上皮面积、结缔组织面积以及最长钉突长度间差异无统计学意义。结论CsP对大鼠颊侧膜龈联合端附着龈上皮的影响存在部位特异性,对大鼠牙龈的影响无时间依赖性。     

Connective tissue attachment formation following exclusion of gingival connective tissue and epithelium during healing

The present investigation was designed to evaluate the potential for reformation of connective tissue attachment on exposed and planed root surfaces by preventing the dentogingival epithelium and the gingival connective tissue from interfering with healing following periodontal surgery. Following the elevation of soft tissue flaps, the buccal and proximal alveolar bone of 24 teeth (48 roots) was removed to mid-root level in 6 monkeys and the exposed root surfaces were carefully planed in order to remove the root cementum. Before the flaps were repositioned and sutured, a membrane (Millipore® filter) was placed over the denuded part of the root surfaces of 16 teeth (test teeth) in order to prevent the epithelium and the gingival connective tissue from interfering with healing. The membrane was adjusted to cover the tooth surfaces from midcrown level to approximately l mm apical to the bone crest. No membranes were placed around the remaining 8 teeth (control teeth) before flap repositioning. The animals were sacrificed 6 months after surgery. The jaws were removed and histological sections of test and control teeth including their buccal periodontal tissues were produced. Nine of the test teeth had to be excluded from examination due to technical failures in the surgical procedure or tissue preparation. New cementum with inserting collagen fibers was observed on all remaining 14 test roots. The length of this newly formed fibrous attachment corresponded to approximately 50% of the distance from the apical extension of root planing to the cemento-enamel junction. In the majority of the control teeth no new attachment had formed but a “long” junctional epithelium was lining the root surfaces to the apical extension of root planing. In 3 control roots a small amount of new cementum with inserting collagen fibers was found in the most apical area of root planing. The results showed that the reformation of a connective tissue attachment was considerably favored by the placement of membranes which prevented the dentogingival epithelium and the gingival connective tissue from interfering with healing.