Experimentally induced periodontitis in beagle dogs causes rapid increases in osteoclastic resorption of alveolar bone

Do periodontal defects affect periodontal inflammation and destruction? Histological/microbiological changes and gene expression profiles of a pilot study in beagle dogs

BACKGROUND

The present study focused on the inflammatory disease progress after periodontal defect induction and aimed to specifically determine periodontal tissue responses following dental plaque accumulation by ligatures on a site with/without standardized periodontal defect induction.

METHODS

After 1 month from extraction of the adjacent teeth, semi-circumferential defects were surgically created in the unilateral second and fourth premolars (test group), whereas no defects were being induced at the contralateral sites (control group). One week later, silk was used to ligate the tooth cervix at both sites to encourage the accumulation of dental plaque. Four weeks later, the tissue samples were collected for histological/histomorphometric and microarray analysis. Microbiological analysis was performed before defect induction and at ligatures, and after 4 weeks of dental plaque accumulation.

RESULTS

Remarkable inflammation was clinically and histologically observed in both groups after plaque accumulation, and the intrabony type of periodontal defect exaggerated inflammatory cell infiltration into the connective tissue layer. Expression of genes related to inflammation such as IL-1 was highly up-regulated in test sites. However, these inflammatory infiltrations did not invade to a boundary of periodontal ligament and connective tissue attachment in both groups, and histomorphometric results corresponds to these observational results. Bacterial findings also showed no significant differences in detected microbiome compositions between control and test groups at three-time points.

CONCLUSION

Intrabony defect might exaggerate the plaque-induced inflammation in the aspect of inflammatory cell infiltration and the related gene expression, but both dental plaque and the pre-existing periodontal defect negligibly disrupt periodontal attachment and the underlying alveolar bone.

Adjunctive Effects of a Sub-Antimicrobial Dose of Doxycycline on Clinical Parameters and Potential Biomarkers of Periodontal Tissue Catabolism

Objectives: The aim of the present randomized, double-blind, placebo-controlled, parallel-arm study was to examine the effectiveness of a sub-antimicrobial dose of doxycycline (SDD) in combination with nonsurgical periodontal therapy, compared to nonsurgical periodontal therapy alone, on potential gingival crevicular fluid (GCF) biomarkers of periodontal tissue catabolism related to the clinical outcomes over a 12-month period. Materials and Methods: GCF was collected and clinical parameters were recorded from 30 periodontitis patients randomized either to an SDD or placebo group. The SDD group received SDD (20 mg) b.i.d for 3 months plus scaling and root planing (SRP), while the placebo group was given placebo capsules b.i.d for 3 months plus SRP. The patients were evaluated every 3 months during the 12-month study period. At each visit, clinical parameters and GCF sampling were repeated. Matrix metalloproteinase (MMP)-8, MMP-9, MMP-13, myeloperoxidase (MPO), osteoprotegerin (OPG), and tartrate-resistant acid phosphatase-5 (TRAP-5) were determined by IFMA and ELISA. Results: Significant improvements were observed in all clinical parameters in both groups over 12 months (p < 0.0125) while the SDD group showed significantly better reduction in gingival index (GI) and pocket depth and a gain in clinical attachment compared to the placebo group (p < 0.05). GCF MMP-8 and OPG levels significantly reduced in the SDD group compared to baseline (p < 0.05). GCF MMP-9 significantly decreased in both groups compared to baseline (p < 0.05). GCF MPO significantly decreased at 3 and 9 months in the SDD group, while it significantly decreased at 6 months in the placebo group (p < 0.05). TRAP and MMP-13 could be detected in none of the samples. Conclusions: The present results indicate that three months of adjunctive usage of SDD to nonsurgical periodontal therapy compared to nonsurgical periodontal therapy alone in periodontitis patients results in further improvement of clinical periodontal parameters and GCF markers of periodontal tissue breakdown over a 12-month period. Beneficial effects of adjunctive SDD therapy is likely to be related to the reduced levels of two major periodontitis-associated MMPs, MMP-8 and -9, and their potential oxidative activator MPO.

Oral health in geroscience: animal models and the aging oral cavity

Age is the single greatest risk factor for many diseases, including oral diseases. Despite this, a majority of preclinical oral health research has not adequately considered the importance of aging in research aimed at the mechanistic understanding of oral disease. Here, we have attempted to provide insights from animal studies in the geroscience field and apply them in the context of oral health research. In particular, we discuss the relationship between the biology of aging and mechanisms of oral disease. We also present a framework for defining and utilizing age-appropriate rodents and present experimental design considerations, such as the number of age-points used and the importance of genetic background. While focused primarily on rodent models, alternative animal models that may be particularly useful for studies of oral health during aging, such as companion dogs and marmoset monkeys, are also discussed. We hope that such information will aid in the design of future preclinical studies of geriatric dental health, thus allowing more reliability for translation of such studies to age-associated oral disease in people.

Inflammation-induced Bone Remodeling in Periodontal Disease and the Influence of Post-menopausal Osteoporosis

During physiological conditions, the skeleton is remodeled in so-called bone multi-cellular units. Such units have been estimated to exist at 1–2 x 106 sites in the adult skeleton. The number and activities of these units are regulated by a variety of hormones and cytokines. In post-menopausal osteoporosis, lack of estrogen leads to increased numbers of bone multi-cellular units and to uncoupling of bone formation and bone resorption, resulting in too little bone laid down by osteoblasts compared with the amount of bone resorbed by osteoclasts. Inflammatory processes in the vicinity of the skeleton, e.g., marginal and apical periodontitis, will affect the remodeling of the nearby bone tissue in such a way that, in most patients, the amount of bone resorbed exceeds that being formed, resulting in net bone loss (inflammation-induced osteolysis). In some patients, however, inflammation-induced bone formation exceeds resorption, and a sclerotic lesion will develop. The cellular and molecular pathogenetic mechanisms in inflammation-induced osteolysis and sclerosis are discussed in the present review. The cytokines believed to be involved in inflammation-induced remodeling are very similar to those suggested to play crucial roles in post-menopausal osteoporosis. In patients with periodontal disease and concomitant post-menopausal osteoporosis, the possibility exists that the lack of estrogen influences the activities of bone cells and immune cells in such a way that the progression of alveolar bone loss will be enhanced. In the present paper, the evidence for and against this hypothesis is presented.

Sinusitis and oroantral fistula in patients with bisphosphonate-associated necrosis of the maxilla

Background

The management of bisphosphonate related necrosis of the jaw has become clinical routine. While approximately two thirds of the lesions are in the mandible, one third is located in the maxilla. In 40–50 % of maxillary necrosis the maxillary sinus is involved, leading to maxillary sinusitis and oro-antral communications.

Methods

This retrospective single center study includes all patients with diagnosis of BP-ONJ of the maxilla and concomitant maxillary sinusitis. The information collected includes age, gender, primary disease, bisphosphonate intake, involving type of bisphosphonate, route of administration and duration of BP treatment previous to surgical treatment and treatment outcome.

Results

A total of 12 patients fulfill the criteria of the diagnosis of maxillary sinusitis associated to maxillary necrosis, of which 6 Patients showed purulent sinusitis. All patients underwent surgical treatment with complete resection of the affected bone and a multilayer wound closure. A recurrence appeared in one patient with open bone and no sign of sinusitis and was treated conservatively.

Conclusions

Purulent maxillary Sinusitis is a common complication of bisphosphonate-related necrosis of the maxilla. The surgical technique described can be suggested for the treatment of these patients.

Zoledronate induces bisphosphonate-related osteonecrosis of the jaw in osteopenic sheep

OBJECTIVES

Bisphosphonate-related osteonecrosis of the jaw (BP-ONJ) occurs in 1 % of patients with medication-induced osteoporosis treated with bisphosphonates. Sheep are an established large animal model for investigating osteoporotic skeletal changes. Zoledronate significantly reduces tissue mineral variability in ovariectomized sheep. The aim of this study was to analyze bone healing after tooth extraction in sheep with induced osteopenia and zoledronate administration.

MATERIALS AND METHODS

Eight adult ewes were randomly divided into two groups of four animals. All sheep underwent ovariectomy and a low-calcium diet. Dexamethasone was administered weekly for 16 weeks. Zoledronate was then given every third week for a further 16 weeks in four sheep; these infusions were repeated after extraction of two lower premolars. Four sheep without zoledronate administrations served as controls.

RESULTS

Due to general health conditions, two sheep of the zoledronate group had to be excluded before surgery. The remaining two sheep of this group developed BP-ONJ lesions at the extraction site and various other sites in both jaws. Control group animals showed uneventful wound healing. Histology of the alveolar processes as well as lumbar spine revealed larger portions of old bone and smaller portions of new bone in the zoledronate group.

CONCLUSIONS

This animal study showed uneventful wound healing after tooth extraction in osteopenic sheep whereas zoledronate treatment leads to development of BP-ONJ-like lesions.

CLINICAL RELEVANCE

As bisphosphonate administration is a standard treatment for glucocorticoid-induced osteoporosis, this model can be used for further research in pathogenesis and management of bisphosphonate-related adverse events.

The adaptive nature of the bone-periodontal ligament-cementum complex in a ligature-induced periodontitis rat model

The novel aspect of this study involves illustrating significant adaptation of a functionally loaded bone-PDL-cementum complex in a ligature-induced periodontitis rat model. Following 4, 8, and 15 days of ligation, proinflammatory cytokines (TNF-α and RANKL), a mineral resorption indicator (TRAP), and a cell migration and adhesion molecule for tissue regeneration (fibronectin) within the complex were localized and correlated with changes in PDL-space (functional space). At 4 days of ligation, the functional space of the distal complex was widened compared to controls and was positively correlated with an increased expression of TNF-α. At 8 and 15 days, the number of RANKL(+) cells decreased near the mesial alveolar bone crest (ABC) but increased at the distal ABC. TRAP(+) cells on both sides of the complex significantly increased at 8 days. A gradual change in fibronectin expression from the distal PDL-secondary cementum interfaces through precementum layers was observed when compared to increased and abrupt changes at the mesial PDL-cementum and PDL-bone interfaces in ligated and control groups. Based on our results, we hypothesize that compromised strain fields can be created in a diseased periodontium, which in response to prolonged function can significantly alter the original bone and apical cementum formations.

Proteomic analysis of saliva identifies potential biomarkers for orthodontic tooth movement

Orthodontic treatment has been shown to induce inflammation, followed by bone remodelling in the periodontium. These processes trigger the secretion of various proteins and enzymes into the saliva. This study aims to identify salivary proteins that change in expression during orthodontic tooth movement. These differentially expressed proteins can potentially serve as protein biomarkers for the monitoring of orthodontic treatment and tooth movement. Whole saliva from three healthy female subjects were collected before force application using fixed appliance and at 14 days after 0.014'' Niti wire was applied. Salivary proteins were resolved using two-dimensional gel electrophoresis (2DE) over a pH range of 3-10, and the resulting proteome profiles were compared. Differentially expressed protein spots were then identified by MALDI-TOF/TOF tandem mass spectrometry. Nine proteins were found to be differentially expressed; however, only eight were identified by MALDI-TOF/TOF. Four of these proteins-Protein S100-A9, immunoglobulin J chain, Ig alpha-1 chain C region, and CRISP-3-have known roles in inflammation and bone resorption.

Morphometric, histomorphometric, and microcomputed tomographic analysis of periodontal inflammatory lesions in a murine model

BACKGROUND

Porphyromonas gingivalis is recognized as one of the major periodontal pathogens in chronic periodontitis, a common infectious disease characterized by inflammation and destruction of periodontal tissues. Several animal models with P. gingivalis have been used in periodontitis studies. Additionally, multiple approaches have also been applied to measuring alveolar bone loss in periodontitis models, including histomorphometry, morphometry, and radiography. The aims of this study were to assess periodontal inflammatory lesions after P. gingivalis-induced periodontitis and use this model to compare three approaches for assessing alveolar bone loss.

METHODS

Twelve-week-old male C57BL/6 mice were divided into two groups: 48 P. gingivalis-infected and 52 untreated control mice. Periodontitis was induced by wrapping P. gingivalis-soaked ligatures around the left maxillary second molar and changing the ligatures every other day. Mice were euthanized on days 0, 3, 7, and 10 after ligature placement, for a total of 12 experimental and 13 control mice per time point. Epithelial downgrowth, inflammation, and osteoclast activity were evaluated; alveolar bone loss was determined by histomorphometry, morphometry, and microcomputed tomography.

RESULTS

The P. gingivalis-infected group showed significantly increased epithelial downgrowth (P <0.05), inflammation (P <0.05), alveolar bone loss (P <0.05), and osteoclast activity (P <0.05) throughout the experimental period compared to the controls. All three methods yielded efficient evaluation of alveolar bone loss.

CONCLUSIONS

Our results show evidence that the P. gingivalis-soaked ligature-induced murine model mounts an adequate inflammatory response and exhibits periodontal tissue breakdown compatible with other models of periodontal disease. In addition, alveolar bone loss can accurately be quantified using any of the three alveolar bone analyses presented in this article.

Oral fluid-based biomarkers of alveolar bone loss in periodontitis

Periodontal disease is a bacteria-induced chronic inflammatory disease affecting the soft and hard supporting structures encompassing the teeth. When left untreated, the ultimate outcome is alveolar bone loss and exfoliation of the involved teeth. Traditional periodontal diagnostic methods include assessment of clinical parameters and radiographs. Though efficient, these conventional techniques are inherently limited in that only a historical perspective, not current appraisal, of disease status can be determined. Advances in the use of oral fluids as possible biological samples for objective measures of current disease state, treatment monitoring, and prognostic indicators have boosted saliva and other oral-based fluids to the forefront of technology. Oral fluids contain locally and systemically derived mediators of periodontal disease, including microbial, host-response, and bone-specific resorptive markers. Although most biomarkers in oral fluids represent inflammatory mediators, several specific collagen degradation and bone turnover-related molecules have emerged as possible measures of periodontal disease activity. Pyridinoline cross-linked carboxyterminal telopeptide (ICTP), for example, has been highly correlated with clinical features of the disease and decreases in response to intervention therapies, and has been shown to possess predictive properties for possible future disease activity. One foreseeable benefit of an oral fluid-based periodontal diagnostic would be identification of highly susceptible individuals prior to overt disease. Timely detection and diagnosis of disease may significantly affect the clinical management of periodontal patients by offering earlier, less invasive, and more cost-effective treatment therapies.

Effect of rhPDGF-BB on bone turnover during periodontal repair

PURPOSE

Growth factors such as platelet-derived growth factor (PDGF) exert potent effects on wound healing including the regeneration of periodontia. Pyridinoline cross-linked carboxyterminal telopeptide of type I collagen (ICTP) is a well-known biomarker of bone turnover, and as such is a potential indicator of osseous metabolic activity. The objective of this study was to evaluate the release of the ICTP into the periodontal wound fluid (WF) following periodontal reconstructive surgery using local delivery of highly purified recombinant human PDGF (rhPDGF)-BB.

METHODS

Forty-seven human subjects at five treatment centres possessing chronic severe periodontal disease were monitored longitudinally for 24 weeks following PDGF regenerative surgical treatment. Severe periodontal osseous defects were divided into one of three groups and treated at the time of surgery with either: beta-tricalcium phosphate (TCP) osteoconductive scaffold alone (active control), beta-TCP+0.3 mg/ml of rhPDGF-BB, or beta-TCP+1.0 mg/ml of rhPDGF-BB. WF was harvested and analysed for local ICTP levels by radioimmunoassay. Statistical analysis was performed using analysis of variance and an area under the curve analysis (AUC).

RESULTS

The 0.3 and 1.0 mg/ml PDGF-BB treatment groups demonstrated increases in the amount of ICTP released locally for up to 6 weeks. There were statistically significant differences at the week 6 time point between beta-TCP carrier alone group versus 0.3 mg/ml PDGF-BB group (p<0.05) and between beta-TCP alone versus the 1.0 mg/ml PDGF-BB-treated lesions (p<0.03). The AUC analysis revealed no statistical differences amongst groups.

CONCLUSION

This study corroborates the release of ICTP as a measure of active bone turnover following local delivery of PDGF-BB to periodontal osseous defects. The amount of ICTP released from the WF revealed an early increase for all treatment groups. Data from this study suggests that when PDGF-BB is delivered to promote periodontal tissue engineering of tooth-supporting osseous defects, there is a direct effect on ICTP released from the wound.

Diagnostic biomarkers for oral and periodontal diseases

This article provides an overview of periodontal disease diagnosis that uses clinical parameters and biomarkers of the disease process.This article discusses the use of biomarkers of disease that can be identified at the tissue, cellular, and molecular levels and that are measurable in oral fluids such as saliva and gingival crevicular fluid. Biomarkers identified from these biologic fluids include microbial, host response, and connective tissue-related molecules that can target specific pathways of local alveolar bone resorption. Future prospects for oral fluid-based diagnostics that use micro-array and microfluidic technologies are presented.

The a3 isoform of the 100-kDa V-ATPase subunit is highly but differentially expressed in large (>or=10 nuclei) and small (<or= nuclei) osteoclasts

Osteoclasts dissolve bone through acidification of an extracellular compartment by means of a multimeric vacuolar type H+-ATPase (V-ATPase). In mammals, there are four isoforms of the 100-kDa V-ATPase "a" subunit. Mutations in the a3 isoform result in deficient bone resorption and osteopetrosis, suggesting that a3 has a unique function in osteoclasts. It is thus surprising that several studies show a basal level of a3 expression in most tissues. To address this issue, we have compared a3 expression in bone with expression in other tissues. RNA blots revealed that the a3 isoform was expressed highest in bone and confirmed its expression (in decreasing order) in liver, kidney, brain, lung, spleen, and muscle. In situ hybridization on bone tissue sections revealed that the a3 isoform was highly expressed in multinucleated osteoclasts but not in mononuclear stromal cells, whereas the a1 isoform was expressed in both cell types at about the same level. We also found that a3 expression was greater in osteoclasts with 10 or more nuclei as compared with osteoclasts with five or fewer nuclei. We hypothesize that these differences in a3 expression may be associated with previously demonstrated differences between large and small osteoclasts with reference to their resorptive activity.

Bone turnover markers in serum and periodontal microenvironments

BACKGROUND

Periodontitis is characterized by altered bone turnover, but local measurements are difficult.

OBJECTIVES

The objective of this study was to develop a method to measure multiple markers of bone turnover from single samples collected at various bone surfaces of the periodontium, and to test the ratios of these markers against more traditional serum and gingival crevicular fluid (GCF) samples.

MATERIALS AND METHODS

Fourteen subjects with untreated periodontitis were recruited for sampling serum, GCF (from sites > or = 5 mm probing depth that bled on probing) and washes of periodontal bone surfaces (adjacent interproximal, vestibular cortical and trabecular bone) with a novel irrigating device. All samples were analyzed for osteocalcin (OC, bone turnover marker; RIA), cross-linked N-telopeptide of type I collagen (NTx, bone resorption marker; ELISA) and albumin (Alb, serum protein; ELISA). Results were reported as ratios: OC/NTx to determine relative bone turnover, and OC/Alb or NTx/Alb to determine local OC or NTx production.

RESULTS

The OC/NTx ratio was significantly higher (p < or = 0.05) in serum vs. GCF (OC undetectable), interproximal bone and cortical vestibular bone, but significantly lower than in trabecular vestibular bone. The OC/Alb ratio for serum was also statistically lower than for vestibular trabecular bone. The NTx/Alb ratio for serum was statistically lower than for GCF and all the bone wash test sites. The results indicated considerable local production of both OC and NTx.

CONCLUSIONS

This system demonstrated that multiple markers of bone turnover can be harvested by irrigation from periodontal bone microenvironments. Bone turnover profiles from periodontal bone surfaces and GCF differed from systemic bone turnover profiles (serum) and may be valuable in tracking site-specific responses to disease or treatment.

Elevated levels of collagen cross-link residues in gingival tissues and crevicular fluid of teeth with periodontal disease

Lysylpyridinoline (LP) and hydroxylysylpyridinoline (HP) are collagen cross-link residues. Lysylpyridinoline is present in most tissues, whereas LP is present mainly in mineralized tissue. Both are elevated in tissue with increased collagen resorption. The purpose of this investigation was to assess if the concentrations of LP and HP are elevated in gingiva and gingival crevicular fluid (GCF) of teeth with advanced periodontitis (AP). We investigated human gingival biopsies of healthy teeth (n = 19) and teeth with AP (n = 43) in 49 individuals. Samples of GCF from 54 teeth with AP were collected in seven patients and compared with samples from 11 patients with experimentally induced gingivitis. Levels of LP and HP were measured by HPLC and fluorescence detection. Gingival concentrations of HP but not LP around teeth with advanced periodontitis were significantly elevated compared with teeth with healthy periodontium. While significant amounts of HP and LP were measurable in the GCF of teeth with AP, no HP and LP was identified 3 months following non-surgical periodontal therapy of the teeth or in fluid from teeth subjected to experimentally induced gingivitis. Elevated concentrations of HP and LP in GCF may serve as indicators of ongoing destruction of periodontal tissues and alveolar bone in advanced periodontitis.

Mediators of periodontal osseous destruction and remodeling: principles and implications for diagnosis and therapy

Osteoclastic bone resorption is a prominent feature of periodontal disease. Bone resorption via osteoclasts and bone formation via osteoblasts are coupled, and their dysregulation is associated with numerous diseases of the skeletal system. Recent developments in the area of mediators of osteoclastic differentiation have expanded our knowledge of the process of resorption and set the stage for new diagnostic and therapeutic modalities to treat situations of localized bone loss as in periodontal disease. This review describes the current state of knowledge of osteoclast differentiation and activity, mediators, and biochemical markers of bone resorption and their use and potential use in clinical periodontics. Finally, therapeutic strategies based on knowledge gained in the treatment of metabolic bone diseases and in periodontal clinical trials are discussed, and the potential for future strategies is proposed relative to their biologic basis. The intent is to update the field of periodontics on the current state of pathophysiology of the osteoclastic lesion and outline diagnostic and therapeutic strategies with a rational basis in the underlying biology.

Clinical, radiographic and biochemical assessment of IL-1/TNF-alpha antagonist inhibition of bone loss in experimental periodontitis

OBJECTIVES

To assess clinical, radiographic, and biochemical markers as diagnostic indicators of disease activity by comparing ligature-induced bone loss in the presence or absence of IL-1/TNF-alpha antagonist inhibition of bone loss in a primate model.

MATERIAL AND METHODS

6 animals with a naturally-occurring gingivitis were evaluated over a 6-week time period following the placement of silk ligatures and initiation of a soft diet. Three animals received intrapapillary injections of soluble receptors (blockers), capable of blocking the biologic activity for both IL-1 and TNF-alpha, and 3 animals received vehicle (control) injections. Injections were given 3X per week over the course of the study. Clinical assessments included a gingival index and quantification of gingival crevicular fluid (GCF) levels. Collected GCF samples were then used in the biochemical assessment of pyridinoline (PYD) and bone alkaline phosphatase (BAP). Radiographic assessment was made using computer-assisted subtraction radiography to measure both bone density (CADIA) values and linear changes in crestal bone height.

RESULTS

Significant (p<0.01) changes using both radiographic measures occurred between 2 and 4 weeks following initiation of disease in this model. The use of the blockers significantly (p<0.01) reduced the levels of radiographic bone loss by approximately 50% over that found in the control sites. Both biochemical markers showed the greatest increase during the first two weeks of the study with PYD levels increased 35-fold over baseline levels after 1 week. This difference in response was significantly (p<0.05) greater than the levels found in the non-ligated teeth or in the ligated teeth receiving blockers injections. BAP levels showed significant increases in ligated teeth compared to non-ligated teeth, but failed to show any significant differences between animals treated with vehicle and those treated with IL-1/TNF antagonists. In contrast to these radiographic and biochemical effects, there were no significant differences detected between animals treated with antagonists and the control group for any of the clinical measures.

CONCLUSIONS

The results of this study demonstrate that both subtraction radiography and PYD crevicular fluid levels can detect relative differences in periodontal disease progression, while BAP crevicular fluid levels cannot.

Alveolar bone resorption following coronal versus apical approach in a mucoperiosteal flap surgery procedure in the rat mandible

BACKGROUND

In several publications, we have reported that a distinct resorptive phase of alveolar bone developed during 3 weeks following elevation of a mucoperiosteal flap in rats by a coronal surgical approach. In the present study, we compared the alveolar bone loss after mucoperiosteal flap surgery by a coronal approach (COR) to a surgical approach incising the mucosa close to the tooth apices and separating the mucoperiosteum toward the tooth crown (apical approach, AP).

METHODS

Eighteen Wistar rats were divided into 2 experimental groups; each group consisted of 9 rats. In the first group, COR was performed on both buccal and lingual aspects on the right side of the rat mandible, while the left side served as a sham-operated control. In the second experimental group, AP was performed.

RESULTS

In the AP group, the outer aspect (buccal or lingual) of the alveolar bone was slightly resorbed usually at the level where the mucosa was incised. In many sections, extensive modeling of new trabecular bone was seen, coronal to the surgical incision. On the contrary, the coronal surgical approach revealed an extensive resorptive phase, mainly of the periodontal aspect of the alveolar bone.

CONCLUSIONS

The results of this study show that periodontal surgery by a coronal surgical approach stimulates a burst of remodeling of the alveolar bone in a very specific pattern.

Bisphosphonate inhibits alveolar bone resorption in experimentally-induced peri-implantitis in dogs

The purpose of this study was to determine the effect of bisphosphonate on alveolar bone resorption in experimentally-induced peri-implantitis in beagle dogs. Experimental peri-implantitis was induced by ligation around the abutments, 6 months after placement of a fixture. Pamidronate (0.6 mg/kg) was injected intramuscularly every 3 days into each of 5 dogs. Another 5 dogs served as the control group and were injected with saline only. Peripheral blood and urine samples were collected every week up to 12 weeks after placement of the ligature. Standard X-rays were taken every week. Urinary deoxypyridinoline (DPD) and serum osteocalcin (OC) were evaluated by ELISA as markers of alveolar bone remodeling. X-ray films were analyzed with a computer image analyzer. After 12 weeks, the bone level was measured after removal of the gingival flap. The distance between the top surface of the fixture and the fundus of the defect was significantly lower in the Pamidronate group (1.59+/-0.55 mm, mean+/-SD) than in the control group (2.41+/-0.48 mm). Bone density analyzed from the X-ray films was significantly higher in the bisphosphonate group (69.2+/-8.7%, mean+/-SD) than in the control group (50.3+/-12.8%) after 2 to 8 weeks compared with the baseline value (100%). OC and DPD levels fluctuated during the experimental period. These findings suggest that bisphosphonate inhibits the progression of alveolar bone resorption during ligature-induced peri-implantitis in dogs.

Resorptive state and cell size influence intracellular pH regulation in rabbit osteoclasts cultured on collagen-hydroxyapatite films

Diseases exhibiting excessive bone loss are often characterized by an increase in the size and number of osteoclasts in affected areas, suggesting that osteoclast size is associated with increased resorptive activity or efficiency. Because osteoclastic bone resorption depends on proton extrusion via a bafilomycin A1-sensitive vacuolar type H+ ATPase (V-ATPase), we investigated the relationship between osteoclast size and state of activity on the one hand, and proton-extruding mechanisms (bafilomycin A1-sensitive V-ATPase and amiloride-sensitive Na+/H+ exchange) on the other. In determining resorptive activities of individual osteoclasts, osteoclast-containing cell suspensions obtained from newborn rabbit long bones were cultured on apatite-collagen complex (ACC)-coated coverslips. Large osteoclasts resorbed 2.5 times more per cell than small osteoclasts, but the amount resorbed per nucleus was the same for the two categories. However, a much larger percentage of large osteoclasts was resorbing compared with small osteoclasts. To study pH regulatory mechanisms in individual large and small osteoclasts, the cells were loaded with the pH-sensitive indicator BCECF and analyzed by single-cell fluorescence. Small and large resorbing osteoclasts had significantly higher basal pH(i) than their nonresorbing counterparts. Also, small nonresorbing osteoclasts were insensitive to bafilomycin A1 addition or Na+ removal from the medium, large nonresorbing osteoclasts responded slightly, and all resorbing osteoclasts (small and large) responded strongly. Differences were also seen in the recovery from an acid load: both small and large nonresorbing osteoclasts were more sensitive to amiloride inhibition, while large resorbing cells were more sensitive to bafilomycin A1 inhibition. Small resorbing cells were inhibited equally by bafilomycin A1 and amiloride. These results clearly show that a greater proportion of large osteoclasts are active in resorption and that pH(i) regulation is associated with enhanced proton pump activity in actively resorbing osteoclasts. Thus, large and small osteoclasts differ in the proportion of cells that are resorbing, while pH regulatory mechanisms differ mainly between resorbing and nonresorbing cells.

Urinary markers of type I collagen degradation in the dog

Urinary assays for type I collagen metabolites provide a non invasive index of bone resorption in humans, and are widely used in the management of patients with metabolic bone diseases. The specific aims of this study were to investigate the feasibility of using commercial human assay kits for quantifying the urinary excretion of type I collagen metabolites in dogs of different ages. Urine and serum samples were collected from 35 beagle dogs in five age groups (0 to 1 years; 1 to 2 years; 2 to 3 years; 3 to 7 years; > 8 years old). Urinary concentrations of pyridinoline (Pyd), deoxypyridinoline (Dpd), and the carboxy- and amino-terminal cross-linked telopeptides of type I collagen (CTx and NTx, respectively) were measured with commercial enzyme-linked immunoassay kits. Serum concentrations of another type I collagen metabolite, the carboxy-terminal cross-linked teloptide of type I collagen (ICTP), were measured with a commercial radioimmunoassay. Dilutional studies indicated that the four urinary assays show specific cross-reactivity with canine urine. Age-related differences in urinary marker excretion were identified, with young dogs excreting the highest concentrations of Pyd, Dpd, NTx and CTx. The correlation between the individual urinary markers was excellent (r = 0.87 to 0.98), while the correlation between serum ICTP and individual urinary markers was weaker (r = 0.52 to 0.64). These results validate the usefulness of the commercial assay kits in monitoring type I collagen metabolism in dogs. Histomorphometric studies have confirmed the relationship between collagen degradation and bone resorption in humans, and similar studies are now needed in dogs.

C-telopeptide pyridinoline cross-links. Sensitive indicators of periodontal tissue destruction

C-telopeptides and related pyridinoline cross-links of bone Type I collagen are sensitive markers of bone resorption in osteolytic diseases such as osteoporosis and osteoarthritis. We have studied the release of C-telopeptide pyridinoline crosslinks of Type I collagen as measures of bone destruction in periodontal disease. Studies in preclinical animal models and humans have demonstrated the relationship between radiographic bone loss and crevicular fluid C-telopeptide levels. We have recently found that C-telopeptide levels correlate strongly with microbial pathogens associated with periodontitis and around endosseous dental implants. Host-modulation of bone-related collagen breakdown has been shown by studies in humans demonstrating that MMP inhibition blocks tissue destruction and release of C-telopeptides in patients with active periodontal disease.

Macrophage colony stimulating factor increases bone resorption in dispersed osteoclast cultures by increasing osteoclast size

Several reports indicate that macrophage colony stimulating factor (MCSF) is one of the major factors required for osteoclast proliferation and differentiation. Paradoxically, it has also been reported that MCSF inhibits osteoclastic activity. We therefore decided to investigate in detail the effects of MCSF on resorption and osteoclast formation to try and clarify this issue. Osteoclast-containing cultures were obtained from rabbit long bones and cultured on plastic culture dishes or devitalized bovine bone slices. MCSF (4-400 ng/ml) stimulated osteoclastic bone resorption in a time-dependent manner and at all doses examined. After 48 h of culture in the presence of MCSF, we observed a 2-fold increase in the total area of bone resorbed, as well as a significant increase in the area of bone resorbed per osteoclast and the number of resorption pits per osteoclast. This effect was paralleled by an increase in the number of larger osteoclasts (as determined by the number of nuclei per cell) and an increase in the size and depth of the resorption pits. Since the total number of osteoclasts remained the same, the MCSF-induced increase in resorptive activity appeared to be related to an increase in the average size of the osteoclasts. When resorption was expressed as the amount of bone resorbed per osteoclast nucleus, larger osteoclasts resorbed more per nucleus, suggesting that large osteoclasts, as a population, are more effective resorbers than small osteoclasts. Interestingly, when osteoclasts were plated at one-fifth the standard density, the amount of bone resorbed per osteoclast decreased considerably, indicating that resorptive activity is also affected by cell density of osteoclasts and/or of other cells present. However, at this lower density MCSF still increased osteoclast size and resorption by the same fold increase over control, suggesting that the effect of MCSF was independent of factors related to cell density.

Relationship between C-telopeptide pyridinoline cross-links (ICTP) and putative periodontal pathogens in periodontitis

Crevicular fluid pyridinoline cross-linked carboxyterminal telopeptide of type I collagen (ICTP) is predictive for future alveolar bone loss in experimental periodontitis in dogs. The present study sought to relate ICTP to a panel of subgingival species in subjects exhibiting various clinical presentations such as health (n=7), gingivitis (n=8) and periodontitis (n=21). 28 subgingival plaque and GCF samples were taken from mesiobuccal sites in each of 36 subjects. The presence and levels of 40 subgingival taxa were determined in plaque samples using whole genomic DNA probes and checkerboard DNA-DNA hybridization. GCF ICTP levels were quantified using radioimmunoassay (RIA). Clinical assessments made at the same sites included: BOP, gingival redness, plaque, pocket depth, and attachment level. Differences among ICTP levels in the 3 subject groups were sought using the Kruskal-Wallis test. Relationships between ICTP levels and clinical parameters as well as subgingival species were determined by regression analysis. The results demonstrated significant differences among disease categories for GCF ICTP levels for healthy (1.1+0.6 pg/site (mean+/-SEM)) gingivitis (14.8+/-6.6 pg/site) and periodontitis subjects (30.3+5.7 pg/site) (p= 0.0017). ICTP levels related modestly to several clinical parameters. Regression analysis indicated that ICTP levels correlated strongly with mean subject levels of several periodontal pathogens including B. forsythus, P. gingivalis, P. intermedia, P. nigrescens and T. denticola (p<0.01). The data indicate that there is a positive relationship between the putative bone resorptive marker ICTP and periodontal pathogens.

Use of hyaluronic acid binding protein for detection of hyaluronan in ligature-induced periodontitis tissue

This study was designed to demonstrate, by use of biotin-labeled hyaluronic acid binding protein (HABP) and an avidin-enzyme system, the localization of hyaluronan (HA) in periodontal tissue of beagle dogs during experimentally induced periodontitis. Experimental periodontitis was induced in the dogs by ligation of the gingival sulcus. Experimental tissue was collected at 0, 3, 7 and 21 days after ligation. HA was revealed by strong staining in the intercellular space around epithelial cells and periodontal ligament, and by light staining in the gingival connective tissue. According to the progression of periodontal tissue breakdown, HA was detected in a small number of leukocytes and monocytes, on the surface of osteoclasts, the surface of alveolar bone, thickened endothelium and in epithelial cells related to rete peg formation. Streptomyces hyaluronidase-treated specimens gave negative staining. This study suggests that HA may be associated with the inflammatory reaction in experimental periodontitis tissue.