Potential pathways for bone resorption in human periodontal disease

Two novel SNPs in genes involved in immune response and their association with mandibular residual ridge resorption

“Residual ridge resorption” (RRR) is a multifactorial condition involving bone resorption of the residual ridge. We investigated 10 single nucleotide polymorphisms (SNPs) in seven genes with the aim of identifying the genetic factors associated with RRR susceptibility. The study group included 96 RRR patients and 96 controls. Age at first edentulism, duration of edentulism, and bone height were recorded. Saliva was collected from the subjects for DNA extraction. Genotype analysis was performed on the ‘SequenomMassARRAYiPLEX’. The genotype and allele frequencies calculated in patients and controls were compared. We found that rs1800896 in the IL10 gene and rs5743289 in NOD2 gene showed significant association with RRR. Within the RRR group, genotypes for each SNP were separated, and we observed that the age at first edentulism and bone height showed variations in the different genotypes of the ten studied SNPs. This study showed an association between SNPs in IL10 and NOD2 genes. It also revealed that the genotypes of the different SNPs influence bone resorption and health. Additionally, age at first edentulism and bone height were much lower in some genotypes. This study demonstrates the need for larger multicenter trials to confirm these findings. Finally, we suggest that the results of this study may be utilized for developing novel genetic diagnostic tests and for identifying Saudi individuals who may be more susceptible to RRR development following dental extraction.

Genotype is an important determinant factor of host susceptibility to periodontitis in the Collaborative Cross and inbred mouse populations

Background

Periodontal infection (Periodontitis) is a chronic inflammatory disease, which results in the breakdown of the supporting tissues of the teeth. Previous epidemiological studies have suggested that resistance to chronic periodontitis is controlled to some extent by genetic factors of the host. The aim of this study was to determine the phenotypic response of inbred and Collaborative Cross (CC) mouse populations to periodontal bacterial challenge, using an experimental periodontitis model. In this model, mice are co-infected with Porphyromonas gingivalis and Fusobacterium nucleatum, bacterial strains associated with human periodontal disease. Six weeks following the infection, the maxillary jaws were harvested and analyzed for alveolar bone loss relative to uninfected controls, using computerized microtomography (microCT). Initially, four commercial inbred mouse strains were examined to calibrate the procedure and test for gender effects. Subsequently, we applied the same protocol to 23 lines (at inbreeding generations 10–18) from the newly developed mouse genetic reference population, the Collaborative Cross (CC) to determine heritability and genetic variation of control bone volume prior to infection (CBV, naïve bone volume around the teeth of uninfected mice), and residual bone volume (RBV, bone volume after infection) and loss of bone volume (LBV, the difference between CBV and RBV) following infection.

Results

BALB/CJ mice were highly susceptible (P<0.05) whereas DBA/2J, C57BL/6J and A/J mice were resistant. Six lines of the tested CC population were susceptible, whereas the remaining lines were resistant to alveolar bone loss. Gender effects on bone volume were tested across the four inbred and 23 CC lines, and found not to be significant. Based on ANOVA analyses, broad-sense heritabilities were statistically significant and equal to 0.4 for CBV and 0.2 for LBV.

Conclusions

The moderate heritability values indicate that the variation in host susceptibility to the disease is controlled to an appreciable extent by genetic factors. These results strongly support the possibility of using the Collaborative Cross, as well as developing dedicated F2 (resistant x susceptible inbred strains) resource populations, for future dissection of genetic factors in periodontitis.

Radiographic absorptiometry method in measurement of localized alveolar bone density changes

OBJECTIVE

The objective of this study was to measure the accuracy and precision of a radiographic absorptiometry method by using an occlusal density reference wedge in quantification of localized alveolar bone density changes.

STUDY DESIGN

Twenty-two volunteer subjects had baseline and follow-up radiographs taken of mandibular premolar-molar regions with an occlusal density reference wedge in both films and added bone chips in the baseline films. The absolute bone equivalent densities were calculated in the areas that contained bone chips from the baseline and follow-up radiographs. The differences in densities described the masses of the added bone chips that were then compared with the true masses by using regression analysis.

RESULTS

The correlation between the estimated and true bone-chip masses ranged from R = 0.82 to 0.94, depending on the background bone density. There was an average 22% overestimation of the mass of the bone chips when they were in low-density background, and up to 69% overestimation when in high-density background. The precision error of the method, which was calculated from duplicate bone density measurements of non-changing areas in both films, was 4.5%.

CONCLUSIONS

The accuracy of the intraoral radiographic absorptiometry method is low when used for absolute quantification of bone density. However, the precision of the method is good and the correlation is linear, indicating that the method can be used for serial assessment of bone density changes at individual sites.

Endotoxin affinity for orthodontic brackets

Endotoxin, cell envelope lipopolysaccharide produced by gram-negative bacteria can activate an immune response through a variety of pathways. In addition, it can stimulate bone resorption and reduce the periodontal tissue's healing capacity. Previous studies have documented the affinity of lipopolysaccharide for restorative materials. This study evaluated the affinity of lipopolysaccharide for commercially available orthodontic brackets. Stainless steel, ceramic, plastic, and "gold" brackets were exposed to 10 EU/mm2radiolabeled Porphyromonas gingivalis or Escherichia coli lipolpoysaccharide in water and incubated for 24 hours at 37 degrees C. Brackets were then transferred to fresh lipopolysaccharide-free water and incubated for 24 hours at 37 degrees C to evaluate elution. This elution transfer was continued up to 96 hours total incubation. Lipopolysaccharide adherence and elution levels were calculated after treatment, and elution solutions were evaluated through liquid scintillation spectrometry. Mean initial lipopolysaccharide adherence ranged from 2.42 +/- 0.26 EU/mm2(E. coli, plastic) to 6.75 +/- 0.34 EU/mm2 (P. gingivalis, stainless steel). P. gingivalis lipopolysaccharide adherence was significantly greater than E. coli lipopolysaccharide adherence for all bracket types. Moreover, for each lipopolysaccharide type, stainless steel brackets exhibited significantly greater lipopolysaccharide adherence. Regarding elution, only the P. gingivalis lipopolysaccharide-exposed ceramic and plastic brackets at 24 hours and the stainless steel and ceramic brackets at 48 hours eluted measurable lipopolysaccharide. Results from this study demonstrate that P. gingivalis and E. coli LPS exhibit a high affinity for orthodontic brackets. In vivo, this affinity could affect the concentration of LPS in the gingival sulcus, thereby contributing to inflammation in tissues adjacent to the brackets.

A review of residual ridge resorption and bone density

Residual ridge resorption is a common and often incapacitating problem, particularly for persons with edentulous mandibles. Several studies suggest a correlation between ridge resorption and osteoporosis. Recent radiologic studies indicate that the mineral density of the cortex and the bone mass in the mandible are correlated with skeletal bone density. Most resorption occurs in the alveolar process, whereas the basal portion remains relatively intact. On the other hand, radiologic measurements of bone density primarily yield information after the basal portion, where the bone mass of the mandible is greatest and functional stresses of mastication may affect bone density. Ironically, radiologic measurements may not accurately indicate the effect of osteoporosis on alveolar resorption. Apparently, excessive occlusal force can also produce extensive atrophy without systemic impact. Not until muscular function decreases does real osteoporosis develop in edentulous jaws. Not only does the volume of the ridge decrease, but also the density of the basal portion decreases as a result of diminished function. This article reviews the literature on residual ridge resorption and components that may affect the rate of resorption.

Scanning electron microscopic observations of apical root surfaces of teeth with apical periodontitis

The aim of this study was to observe apical root surfaces of teeth with chronic periapical lesions. Five premolars and three molars with radiographically demonstrable periapical lesions were extracted and fixed in 2.5% phosphate-buffered glutaraldehyde solution for 9 days. The apical 3-mm portion of 17 roots was removed and prepared for scanning electron microscope. Lacunar resorption zones were frequently observed on the root surfaces. Bacteria and yeast cells were detected in some of the lacunae. Periapical bacterial plaque with a smooth structure was present mostly around the main apical foramen. Cementum-like tissue deposits indicative of repair were seen adjacent to some resorption areas. Clastic cells tightly attached to crater-like depressions with finger-like projections were observed laterally on the specimens. Current research should be focused on new procedures to eliminate extraradicular microrganisms and periapical bacterial plaque in persistent periapical infections.

Resistance of the maxillary ridge to occlusal trauma

Histories and clinical evaluations were obtained from 230 postmenopausal women aged 48 to 56 years to determine whether the alveolar height in the edentulous anterior region of the maxillae is adversely affected by the presence of mandibular incisors. Many of these women lost their teeth in early adulthood. When all subjects were included, the height of the ridge in the anterior region of the maxillae was not significantly altered by presence of mandibular incisors. When the ridge height was compared among those who had been edentate in the maxillae for less than 30 years, the difference between dentate and edentate subjects was significant. This study indicates that the alveolar ridges in the anterior region of the maxillae where teeth were extracted early in life during the rapid phase of bone metabolism are less disposed to bite trauma caused by the presence of the mandibular incisors than are individuals who lost their teeth in middle or old age.

Detection of Porphyromonas gingivalis in oral plaque samples by use of the polymerase chain reaction

Periodontitis is believed to be caused by bacteria which inhabit periodontal pockets. The identification of these periodontal pathogens by currently available methods requires considerable time and expertise. In this study, we have used a polymerase chain reaction (PCR) assay that is quick, relatively simple, and can detect low numbers of a putative periodontal pathogen. Primers specific for the fimbrial gene of Porphyromonas gingivalis were selected from the published sequence and used for amplification of a 131-basepair sequence of genomic DNA. The PCR detected as few as 100 P. gingivalis cells obtained from pure cultures. Three other bacteria (Actinobacillus actinomycetemcomitans, Prevotella intermedia, and Capnocytophaga gingivalis) that are also putative periodontal pathogens yielded no PCR product at any of the cell concentrations used. This assay was also used for detection of P. gingivalis in subgingival plaque. Five of 13 subgingival bacterial plaque samples obtained from four advanced adult periodontitis patients and two samples from a prepubescent child with advanced periodontitis contained P. gingivalis. The protocol developed is relatively simple and can be completed within four hours of the time of sample acquisition.

Gingivitis/stomatitis in cats

Any alteration in the balance of bacterial challenge versus the host's ability to resist and repair will result in oral lesions that are similar in appearance. The bacterial cause of gingivitis and periodontitis in humans and in all other animals in which it has been studied is firmly established, and specific species of predominantly gram-negative anaerobes have been implicated. Naturally occurring or acquired immunopathologies are likely to result in premature dental disease. When oral disease is associated with the accumulation of plaque, a positive response can be achieved by reducing the bacterial challenge to the host through the maintenance of oral hygiene by timely professional dental prophylaxis and home care. Disease that is the result of atypical immune responses, however, can be much more difficult to manage. Such oral disease can occur with either immune deficiencies or exaggerated immune responses, and it is likely that multiple mechanisms are active concurrently. In any case, gram-negative anaerobes present in plaque are likely to be a major contributing factor. Therefore patients with chronic refractory gingivitis-stomatitis must be considered to be plaque intolerant. Only with a frequent regimen of aggressive and thorough professional dental treatment plus meticulous oral home care on a daily basis can one expect to keep these cases in remission. Because this is often unrealistic, the only other way to keep these patients free of disease is by total dental extraction. The tissues that are colonized by the causative organisms must be eliminated. All root tips and bony sequestra must be removed and healing with intact epithelium accomplished before these cases will go into remission. Edentulous feline patients that continue to have signs of gingivostomatitis have been found to have an area of nonhealed bony sequestrum and chronic osteomyelitis. Once effective debridement has been accomplished and epithelial healing completed, nonresponsive cases can be expected to go into remission (Color Plate 2, Figure 7). It is hoped that as more is learned about this frustrating problem, the many factors influencing feline oral disease will be scientifically documented. In the future, actual diagnoses can be systematically made early on in disease, and treatment will be more than just symptomatic.

Effect of lipoteichoic acid on proliferation and differentiation of keratinocytes

Bacterial infection is always found to be associated with cholesteatoma. Accumulation of keratin debris is one of the crucial factors for the growth of cholesteatoma. The effects of lipoteichoic acid, a cell wall component of gram-positive bacteria, on the proliferation and differentiation of keratinocytes were studied. Various concentrations of lipoteichoic acid (0 to 100 micrograms/ml) were added to keratinocytes. DNA synthesis and protein synthesis were inhibited by decreasing the incorporation of 3H-thymidine and 3H-leucine into keratinocytes. The effects of lipoteichoic acid on terminal differentiation were then studied by measuring the number of sodium dodecyl sulfate-insoluble cornified cell envelopes and the transglutaminase activity (a marker of terminal differentiation) determined by incorporation of 3H-putrescine into cornified envelopes. These studies showed that lipoteichoic acid stimulated the formation of cornified cell envelopes and transglutaminase activity. These findings suggest that lipoteichoic acid stimulated the terminal differentiation and accumulation of keratin debris and that lipoteichoic acid might have stimulatory effects on the development of cholesteatoma.

Effect of fibronectin on healing of replanted teeth in monkeys: a histologic and autoradiographic study

The purpose of this study was to evaluate the effect of fibronectin application on healing of replanted teeth. Three rhesus monkeys were used. Maxillary and mandibular incisors and premolars were extracted and replanted. Teeth were extracted with forceps and placed in saline solution. After 5 minutes, each tooth was returned to its socket and immobilized by interproximal acid-etch splints, which were removed after 1 week. Of the forty-eight teeth replanted, twenty-four control teeth were replanted as described. On each of the remaining teeth, the root surface and the inner walls of the socket were bathed with 1 ml of fibronectin in saline solution (400 micrograms/ml) during the 5-minute interval between tooth extraction and its replantation. Replanted teeth and animal killings were scheduled to provide observations 1, 3, 7, 14, 28, and 45 days after replantation. Each monkey received an intravenous injection of tritiated thymidine, 1 microCi/g body weight, 1 hour before it was killed. Tissue specimens were processed for histologic and autoradiographic evaluation following standard procedures. For each of the six points of time, four pairs of contralateral teeth were available for evaluation; four teeth were treated with fibronectin and four without it. The findings of this study indicate that fibronectin use resulted in enhanced healing by early replacement of the fibrin clot, increased connective tissue cell proliferation, reduction of the inflammatory response, and inhibition of both cementum resorption and dentoalveolar ankylosis.

Some biological activities of Eikenella corrodens major outer membrane proteins

Major outer membrane proteins of Eikenella corrodens, an organism frequently isolated from patients with periodontal disease, were tested for some biological activities. Mouse peritoneal macrophages, exposed at low concentrations of the above-mentioned proteins (between 0.05 and 5 micrograms/ml), showed evident and marked morphological modifications consisting of increases in the size and vacuolation of the cells. Higher concentrations showed a toxic effect. Low concentrations resulted in a selective release of lysosomal enzymes without any significant release of lactatedehydrogenase, and cytoplasmic marker; while concentrations of 25-50 micrograms/ml, which were toxic in trypan-blue exclusion test, increased LDH release. Eikenella corrodens major proteins increased the platelet aggregation of ADP and thrombin. The residual complement activity of serum samples incubated with various amounts of proteins at 37 degrees C for 30 minutes appeared strongly reduced with respect to controls, thus showing a consumption of the complement components. These results suggested that Eikenella corrodens major proteins may play a role in the development of periodontal lesions.

Identity of limulus amoebocyte lysate-active root surface materials from periodontally involved teeth

A new approach has been developed to circumvent the problems of false positive reactions in the Limulus Amoebocyte Lysate (LAL) assay for lipopolysaccharide (LPS) in root surface materials. These LAL-reactive materials include thrombin, thromboplastin, ribonuclease, ribonucleic acid, lipoteichoic acid and peptidoglycan fragments. In the present study, hot phenol/water extraction of these substances followed by ultracentrifugation of the resulting aqueous phases reduced their concentrations to very low levels. Furthermore, the application of Polymyxin B/Sepharose 4B affinity chromatography to these extracts enabled their intrinsic LAL-activity to be determined. Use of these techniques to assay root surface materials has identified LPS as being the major LAL-reactive material present. The mean LPS yield for the periodontally involved teeth was 4.13 micrograms/tooth, representing 2.82 micrograms/root. In contrast, the mean yield of LPS for the periodontally uninvolved teeth was 3.12 ng/tooth.

Kinin generation in the gingival inflammatory response to topically applied bacterial lipopolysaccharides

A water-soluble lipopolysaccharide from Salmonella enteritidis and a phenol-soluble lipopolysaccharide from Leptotrichia buccalis were applied topically to the healthy marginal gingivae of beagle dogs. Saline was applied to contralateral areas as an internal control. Increases in vascular permeability were monitored by measurement of gingival fluid, and the collected gingival fluid samples were assayed for kininogenase and kinin activities. Both lipopolysaccharides induced an inflammatory response, as indicated by increased gingival fluid flow. Kininogenase-kinin activities paralleled the increases in gingival fluid flow, with the highest values being associated with peak increases in gingival fluid. The results indicate that both lipopolysaccharides, although different in lipid solubility, penetrate healthy sulcular epithelium and initiate an inflammatory response which is mediated in part by the kallikrein-kinin system. Interrelationships between this system and other inflammatory mediators suggest that kinin generation not only plays a role in the early phases of acute gingival inflammation, but may also contribute to the activation of other mediators appearing later in the response and in chronic inflammatory lesions.

Effect of endotoxin on keratin production of keratinocytes in vitro

The rate of keratin protein accumulation appears to be a crucial factor in the pathogenesis of middle ear cholesteatoma. The effect of endotoxin on keratin production of keratinocytes was studied. Endotoxins are lipopolysaccharides contained within the cell wall of gram-negative bacteria. Various concentrations of endotoxin were added to keratinocytes derived from newborn rats. Syntheses of keratin proteins were studied by incorporation of 3H-leucine into each protein fraction. Extraction of keratin proteins with various salt solutions showed that endotoxin stimulated keratinocytes to produce keratohyalin granules and its related proteins as well as proteins in the stratum corneum (keratin proteins). These findings suggest that accumulation of keratin debris in cholesteatoma may result from the effect of infection in the epithelial cells.

Lactate dehydrogenase activity in gingival crevicular fluid collected with filter paper strips: analysis in subjects with non-inflamed and mildly inflamed gingiva

A previous study of lactate dehydrogenase (LDH) in gingival crevicular fluid (GCF) suggested that the concentration is 10 to 25 times that of serum (means = 2300 international units/1 versus 100 IU/1 for serum). That study used capillary tubes to collect microliter amounts of GCF. Since invasive collection techniques can influence GCF flow, we evaluated LDH activity in GCF collected by filter strips. GCF was collected in a standardized fashion from 10 subjects with mild inflammation (GI = 0.5-1.0) and 10 subjects without evidence of gingival inflammation (GI = 0). Our results indicate that LDH volume activity was greater for subjects with GI = 0 (means = 105,529 IU/1) than for subjects with GI = 0.5-1.0 (means = 77,661 IU/1), but the difference was not significant. LDH total unit activity was significantly greater in subjects with GI = 0.5-1.0 versus GI = 0 (means = 0.048 IU versus means = 0.0242 IU, P less than 0.0001). The relationship of LDH volume activity to GCF volume, the regression lines fit to the data, and calculation of LDH total unit activity were important for analysis of enzyme activity in GCF.

The pathogenesis of atrophic rhinitis in pigs induced by toxigenic Pasteurella multocida

The pathogenesis of atrophic rhinitis was studied in an experiment in which piglets were infected with a toxigenic type D Pasteurella multocida strain in the right half of the nasal cavity. Two days before inoculation the nasal mucosa on the right side had been subjected to mild irritation by intranasal instillation of a weak solution of acetic acid. The untreated (left) half of the nasal cavity served as an intrinsic control. Macroscopically, changes in the turbinates were already appreciable at 3 days p.i., and pronounced turbinate atrophy was noted at 7 days p.i. At 14 days p.i. deviation of the snout and almost complete turbinate atrophy was observed. The turbinates in the untreated half of the nasal cavity developed normally. Histologically, the changes were initially characterized by bone resorption mediated by an increased number of osteoclasts. Later osteoclasts were sparse, and there was an apparent disruption of osteoid synthesis. Ultrastructurally, the osteoblasts showed nuclear indentations and dilatation of the endoplasmic reticulum. Since no inflammatory reaction was observed, the hypothesis is advanced that atrophic rhinitis in pigs is caused by a P. multocida-produced factor which will stimulate bone resorption and suppress osteoid synthesis.

The origin of osteoclasts: evidence, clinical implications and investigative challenges of an extra-skeletal source

Recent evidence for an extraskeletal origin of osteoclasts and the historical record of the genesis of osteoclasts are examined critically. Reviews of the structure, function and development of osteoclasts from mononuclear precursors, the local regulation of bone resorption and the coupling of bone formation to preceding resorption are presented as a background for discussing the clinical implications for management of osteolytic bone diseases. The roles of osteoclasts and macrophages as phagocytes are compared and contrasted, and recent evidence for macrophage heterogeneity resulting from site-specific monoblastic precursors is reviewed. The implications of these recent developments in macrophage biology are extrapolated to osteoclasts and the existence of site-specific, extraskeletal osteoclast precursors is proposed. Finally, the investigative challenges inherent in these perspectives are discussed.

Butyrate: a cytotoxin for Vero cells produced by Bacteroides gingivalis and Bacteroides asaccharolyticus

Culture filtrates of B. gingivalis and B. asaccharolyticus are cytotoxic for Vero cells. It is shown that the cytotoxic effect is due to the butyrate concentrations present in the culture filtrates of these strains. This cytotoxic effect proved to be reversible. Strains of the B. melaninogenicus subspecies intermedius and melaninogenicus did not produce butyrate and did not show cytotoxic activity towards Vero Cells. The significance of the production of toxic concentrations of butyrate for the etiology of especially periodontal diseases is discussed.

Influence of optimal and excluded oral hygiene on early formation of dental plaque on plastic films. A quantitative and descriptive light and electron microscopic study

The influence of oral hygiene on early plaque formation has been studied. The amount and structure of dental deposits formed on plastic films were determined at two occasions with or without a preceding period of effective oral hygiene. Six human subjects developed plaque during 4 hours on plastic films applied to the buccal surfaces of premolars and cuspids. The plastic films with adhering deposits were processed for electron microscopy. In presence of healthy gingiva, the plastic films were covered by a surface coating of acellular material in or on which bacteria, epithelial cells and leukocytes were observed. The microorganisms were almost exclusively Gram-positive cocci. When plaque formation was preceded by a week of excluded oral hygiene, the deposits collected on the same teeth exhibited a threefold increase in the number of bacteria. The relative composition of the flora was altered, as evidenced by a higher number of Gram-negative cells as well as the occurrence of rods and filamentous organisms. The results indicate that neglect of oral hygiene favors an earlier establishment of a complex bacterial flora at the dento-gingival region of the buccal surfaces of premolars and cuspids.

Bacterial endotoxin: a role in chronic inflammatory periodontal disease?

A review of current information was undertaken examining suggested roles for bacterial endotoxin in periodontal disease. Evidence for the presence of endotoxin in plaque, gingival crevicular fluid and periodontally involved cementum is discussed. The biological effects of endotoxin are numerous, and its abilities to induce tissue inflammation, resorb rat foetal bone, activate the complement pathway, stimulate macrophages and activate immune responses are examined in relation to the suggestion that endotoxin is an important factor in the pathogenesis of periodontal disease.

The immunopathogenesis of progressive chronic inflammatory periodontal disease

Natural, humoral and cellular immune mechanisms have all been implicated in the pathogenesis of chronic inflammatory periodontal disease. However, confusion still exists as to the role played by each of these immunological mechanisms. Recently, characterization of the cell types within the progressive lesion has been established, in which four recognizable zones were described. Immediately subjacent to the epithelium lining the periodontal pocket both polymorphonuclear leukocytes (PMN's) and macrophages were seen, while cells deeper in the tissues had the morphological appearance of lymphocytes. The majority of these lymphocytes had a B-cell phenotype although a few T-cells and macrophages were found. On the advancing front of the lesion the cells had the morphological appearance of plasma cells, the majority of which contained IgG. Other cells found in this region had the morphology of plasma cells yet contained no cytoplasmic immunoglobulin, but they did contain substantial amounts of lysosomal enzymes. Similar cells have previously been described in periodontal disease; their frequent association with fibroblasts may suggest that they are important in the pathogenesis. Deposits of IgG and fibrin were found in the fibrous tissue band surrounding the lesion. These results are reviewed and, although the zones described were not anatomically distinct, by describing the lesion in this way it was possible to establish a convenient model to explain the immunopathogenesis of progressive chronic inflammatory periodontal disease. In this respect, progressive chronic inflammatory periodontal disease in man should be considered as a B-cell lesion.

Gingival inflammation and bone loss in periodontal disease

Fifty subjects between 27 and 43 years of age were studied to determine the relationship between the severity of gingival inflammation, the amount of bone loss and the plaque score in interproximal sites. The results indicate moderately good correlations between Gingival Index or Plaque Index and percentage bone loss. However a low correlation was found between the amount of crevicular fluid and percentage loss. Gingival Index and Plaque Index were well correlated. It was also found that when patients were divided into two age groups, younger and older than 35 years, the older individuals studied had more bone loss interproximally compared with the younger despite comparable amounts of plaque or gingival inflammation. The data suggest that both severity and longevity of the inflammation may play a role in determining the rate of alveolar bone resorption.

The angular bone defect and its relationship to trauma from occlusion and downgrowth of subgingival plaque

Sixty-four sets of human teeth were collected with the aim of evaluating the role of trauma from occlusion in the etiology of destructive periodontal disease. Before the jaws were taken out, a careful bite analysis was carried out. After fixation of the jaws, impressions were taken and plaster of Paris models were made. Finally, a set of 14 radiographs were taken. On the basis of the "clinical" records postmortem, the study models and the radiographs, the jaws were sectioned. Only mesio-distal sections were included in the present analysis. The total number of interdental spaces examined was 106. The following observations were made: 1. Before any loss of periodontal fiber attachment has taken place, the configuration of the interdental septum is entirely dependent on the location of the cemento-enamel junction (CEJ) of the two neighboring teeth. The alveolar crest does not approach the apical border of the junctional epithelium closer than about 1 mm. Thus, if the CEJ is located at different levels on two neighboring teeth, the marginal termination of the interdental septum will be oblique, forming an acute angle with the "lowest" tooth. 2. Loss of periodontal fiber attachment could invariably be related to the apical growth of subgingival plaque, and downgrowth of plaque was always associated with an inflammatory process which involved lysis of the attachment fibers within a distance varying between 0.2 and 1.8 mm from the apical border of the plaque. Subsequently, the JE proliferated down to cover the denuded root surface. 3. Reduction in height of the alveolar crest could also be related to the downgrowth of plaque. The distance from plaque to bone was never found to be less than 0.5 mm and never more than 2.7 mm. The configuration of the interdental septum always seemed to be determined by the level of the plaque on the two neighboring tooth surfaces. Thus, if the plaque had reached the same level on both sides, the crest of the interdental septum assumed a horizontal outline; if plaque had proliferated down to different levels, the crest of the interdental septum was oblique and an angular defect hereby established. 4. In the present material no evidence was found to indicate that functional (traumatic) forces can act as a co-factor in the causation of angular defects. In fact, such defects were found equally often adjacent to "nontraumatized" as to "traumatized" teeth. 5. Infrabony pockets were invariably associated with downgrowth of subgingival plaque.

Pore size measurements and some age-related changes in human alveolar bone and rat femur

Bone pore volume of pores ranging from 0.1 to 77 mum in diameter was unchanged in alveolar bone from patients with periodontal disease compared with control subjects, a finding that is inconsistent with the involvement of systemic factors in alveolar bone loss in this disease. Bone density was decreased in alveolar bone from patients with periodontal disease. Bone density of normal alveolar bone increased with age. A similar finding was obtained in rat diaphyseal bone, suggesting that this is a general phenomenon in aging bone. This could be significant inasmuch as high density bone would be expected to be more brittle. In contrast to these findings in normal alveolar bone, bone density decreased rather than increased in the 50- to 59-year-old age group in patients with periodontal disease. The cause of decreased bone density remains to be established.

Prostaglandins: bone resorption stimulating factors released from monkey gingiva

Gingival fragments from monkeys have been found to release a factor in vitro into incubation medium which stimulates bone resorption in organ culture. Indomethacin effectively blocks the occurrence of this stimulatory factor in the gingival incubation medium. All of this bone resorptive activity can be accounted for by prostaglandin-like material. The prostaglandins contributing to the bone resorptive activity have been found to be prostaglandins E1 and E2.

Formation of extracellular lipoteichoic acid by oral streptococci and lactobacilli

Examination of the culture fluids from a number of strains of oral streptococci and latobacilli has shown the presence of an erythrocyte-sensitizing antigen with the properties of lipoteichoic acid. The antigen was isolated from the culture fluids of Lactobacillus casei and Lactobacillus fermentum and characterized chemically and serologically, For other strains, serological evidence for the presence of lipoteichoic acid depends on the reactivity with antiserum specific for the glycerol phosphate backbone. The relative concentrations of the antigen in culture fluids from different organisms, in culture fluids from different stages of growth, and in extracts of organisms was estimated by determining the maximum dilution that fully sensitized erythrocytes; the culture fluid titer, which is the reciprocal of the dilution, varied from 4 to 320. Strains of Streptococcus mutans were generally characterized by a high level of extracellular lipoteichoic acid, the amount being greater than that detectable in cell extracts; this conclusion was confirmed by using the quantitative precipitin method. A high-molecular-weight fraction obtained from S. mutans BHT culture fluid was effective in sensitizing erythrocytes at a concentration of 1 mug/ml, compared with 2 mug/ml required for cellular lipoteichoic acid from L. casei. The detecting procedure depends on the teichoic acid sensitizing erythrocytes but, as shown with L. fermentum, low-molecular-weight nonsensitizing teichoic acid may also be present in culture fluid.