Inhibitory effects of a bisphosphonate (risedronate) on experimental periodontitis in rats

Mitigating osteonecrosis of the jaw (ONJ) through preventive dental care and understanding of risk factors

It is well established that alterations in phosphate metabolism have a profound effect on hard and soft tissues of the oral cavity. The present-day clinical form of osteonecrosis of the jaw (ONJ) was preceded by phosphorus necrosis of the jaw, ca. 1860. The subsequent removal of yellow phosphorus from matches in the early 20th century saw a parallel decline in "phossy jaw" until the early 2000s, when similar reports of unusual jaw bone necrosis began to appear in the literature describing jaw necrosis in patients undergoing chemotherapy and concomitant steroid and bisphosphonate treatment. Today, the potential side effect of ONJ associated with medications that block osteoclast activity (antiresorptive) is well known, though the mechanism remains unclear and the management and outcomes are often unsatisfactory. Much of the existing literature has focused on the continuing concerns of appropriate use of bisphosphonates and other antiresorptive medications, the incomplete or underdeveloped research on ONJ, and the use of drugs with anabolic potential for treatment of osteoporosis. While recognizing that ONJ is a rare occurrence and ONJ-associated medications play an important role in fracture risk reduction in osteoporotic patients, evidence to date suggests that health care providers can lower the risk further by dental evaluations and care prior to initiating antiresorptive therapies and by monitoring dental health during and after treatment. This review describes the current clinical management guidelines for ONJ, the critical role of dental-medical management in mitigating risks, and the current understanding of the effects of predominantly osteoclast-modulating drugs on bone homeostasis.

Role of periodontal disease in bisphosphonate-related osteonecrosis of the jaws in ovariectomized rats

OBJECTIVE

This study aimed to investigate the role of progressive periodontal disease in inducing bisphosphonate-related osteonecrosis of the jaws (BRONJ) using an ovariectomized (OVX) rat model mimicking human intracortical remodeling process.

MATERIALS AND METHODS

Thirty 12-week-old Spraque-Dawly (SD) female rats were randomly assigned into two groups. All rats underwent bilateral ovariectomy. Six weeks after surgery, zoledronic acid (ZA) or vehicle control was administered intraperitoneally for 12 weeks. On the same day of injection, a cotton ligature was placed subgingivally around the first left lower molar to induce periodontitis. All animals were sacrificed 12 weeks after injection. The entire mandibles were harvested for micro-computed tomography (micro-CT) and histological examinations.

RESULTS

Micro-CT examination showed that ligature placement caused significant alveolar bone loss both in ZA (0.63 ± 0.13 vs. 0.38 ± 0.06 mm, P < 0.001) and in control (0.88 ± 0.19 vs. 0.40 ± 0.06 mm, P < 0.001) groups. Whereas in the ZA group, bone loss was attenuated compared with the control group (P < 0.01); the bone mineral density in the ZA group (1.00 ± 0.02 g/cm(3)) was significantly higher than that in vehicle control group (0.96 ± 0.03 g/cm(3), P < 0.001). Histological examination found necrotic bone tissue with extensive, empty lacunae in two of 15 rats in ZA group, but in none of the control group.

CONCLUSION

Bisphosphonates inhibit alveolar bone resorption in progressive periodontal disease, which might benefit the management of periodontitis, but increase the risk of developing BRONJ.

Host modulation therapy: An indispensable part of perioceutics

Traditionally, only antimicrobials have been used as the chemotherapeutic modality for the treatment of periodontitis. Though bacteria are the primary etiologic factors of periodontal diseases, yet the extent and severity of tissue destruction seen in periodontitis is determined by the host immuno-inflammatory response to these bacteria. This increasing awareness and knowledge of the host-microbial interaction in periodontal pathogenesis has presented the opportunity for exploring new therapeutic strategies for periodontitis by means of targeting host response via host-modulating agents. This has lead to the emergence of the field of "Perioceutics" i.e. the use of parmacotherapeutic agents including antimicrobial therapy as well as host modulatory therapy for the management of periodontitis. These host-modulating agents used as an adjunct tip the balance between periodontal health and disease progression in the direction of a healing response. In this article the host-modulating role of various systemically and locally delivered perioceutic agents will be reviewed.

Zoledronate effects on systemic and jaw osteopenias in ovariectomized periostin-deficient mice

Osteoporosis and periodontal disease (PD) are frequently associated in the elderly, both concurring to the loss of jaw alveolar bone and finally of teeth. Bisphosphonates improve alveolar bone loss but have also been associated with osteonecrosis of the jaw (ONJ), particularly using oncological doses of zoledronate. The effects and therapeutic margin of zoledronate on jaw bone therefore remain uncertain. We reappraised the efficacy and safety of Zoledronate (Zol) in ovariectomized (OVX) periostin (Postn)-deficient mice, a unique genetic model of systemic and jaw osteopenia. Compared to vehicle, Zol 1M (100 µg/kg/month) and Zol 1W (100 µg/kg/week) for 3 months both significantly improved femur BMD, trabecular bone volume on tissue volume (BV/TV) and cortical bone volume in both OVX Postn^+/+ and Postn^−/− (all p<0.01). Zol 1M and Zol 1W also improved jaw alveolar and basal BV/TV, although the highest dose (Zol 1W) was less efficient, particularly in Postn^−/−. Zol decreased osteoclast number and bone formation indices, i.e. MAR, MPm/BPm and BFR, independently in Postn^−/− and Postn^+/+, both in the long bones and in deep jaw alveolar bone, without differences between Zol doses. Zol 1M and Zol 1W did not reactivate inflammation nor increase fibrous tissue in the bone marrow of the jaw, whereas the distance between the root and the enamel of the incisor (DRI) remained high in Postn^−/− vs Postn^+/+ confirming latent inflammation and lack of crestal alveolar bone. Zol 1W and Zol 1M decreased osteocyte numbers in Postn^−/− and Postn^+/+ mandible, and Zol 1W increased the number of empty lacunae in Postn^−/−, however no areas of necrotic bone were observed. These results demonstrate that zoledronate improves jaw osteopenia and suggest that in Postn^−/− mice, zoledronate is not sufficient to induce bone necrosis.

Relationship between periodontal disease and osteoporosis

BACKGROUND

For many years an association between the low bone density of osteoporosis and increased risk of periodontal bone loss has been suspected. In this review the relationship between osteoporosis and periodontal disease is considered.

METHODS

For this narrative review a very broad search strategy of the literature was developed using both PubMed and Scopus databases using the search words "perio" and "osteoporosis". The reference lists from the selected papers were also scanned and this provided an additional source of papers for inclusion. The inclusion/exclusion criteria, were also quite liberal with only those papers dealing with bisphosphonates and osteonecrosis of the jaws, osteoporosis in edentulous individuals, as well as those not written in English being excluded.

RESULTS

The data available suggest that reduced bone mineral density is a shared risk factor for periodontitis rather than a causal factor. However, more prospective studies are required to fully determine what, if any, relationship truly exists between periodontitis and reduced bone mineral density.

CONCLUSIONS

More prospective studies are required to determine what, if any, relationships exist between periodontal disease and reduced bone mineral density.

Effects of alendronate on bone healing after tooth extraction in rats

OBJECTIVES

Tooth extraction has been identified as an important risk factor for bisphosphonate-induced osteonecrosis of the jaw. Therefore, the main goal of this study was to determine the effects of alendronate on healing of the extraction socket and on interdental alveolar bone after tooth extraction in rats.

MATERIALS AND METHODS

Animals were injected subcutaneously with vehicle or alendronate for 3-4 weeks before the first mandibular molar was extracted and these treatments were continued during post-extraction periods of 10, 21, 35 and 70 days. Mandibles were processed to evaluate healing of the extraction socket and adjacent alveolar bone by assessing bone formation, bone resorption and vascularity by histomorphometric techniques.

RESULTS

Alendronate decreased new woven bone formation, blood vessel area, perimeter and number in the extraction socket at 10 days postextraction, but not at later time points. Furthermore, alendronate-treated rats had increased interdental alveolar bone volume and height only at 10 days postextraction. In addition, a 2.5-fold increase in the percentage of empty osteocyte lacunae was found in alveolar bone of alendronate-treated rats only at 10 days postextraction.

CONCLUSIONS

Alendronate transiently decreases bone formation and vascularity in the extraction socket and delays the removal of interdental alveolar bone after tooth extraction in rats.

Effects of mevastatin on grafted bone in MRL/MpJ mice

Statins, lipid-lowering drugs, have been reported to influence bone metabolism. However, the available information about their effects on bone formation and resorption in vivo is still limited. The present study was undertaken to determine whether the topical administration of mevastatin could increase the bone mass of isografted bone. The tibiae were bilaterally dissected from a donor MRL/MpJ mouse and transplanted subcutaneously in the dorsal region of a recipient mouse. One grafted tibia was topically infused for either 1, 2, 3, or 4 weeks with mevastatin, using an osmotic minipump at a dose of 2.5 pmol/hr. The other tibia was infused with 0.9% NaCl (control). Our three results were: (1) Topical mevastatin stimulated bone formation and numerous cuboidal osteoblasts appeared on the surface of newly formed bone. Bone mineral density and bone area in mevastatin-treated bone were significantly increased. (2) Topical mevastatin increased the number of osteoclasts. (3) The expression of bone morphogenetic protein-2 (BMP-2) mRNA and receptor activator of NF-kB ligand (RANKL) mRNA were upregulated in mevastatin-treated bone. These results suggest that the topical infusion of mevastatin increases bone mass of isografted bone by increasing bone turnover and, at least in part, by promoting the expression of BMP-2 and RANKL mRNA.

Osteonecrosis of the jaw and bisphosphonate treatment for osteoporosis

A potential side effect associated with bisphosphonates, a class of drugs used in the treatment of osteoporosis, Paget's disease and metastatic bone disease, is osteonecrosis of the jaw (ONJ). The incidence of ONJ in the general population is unknown; this rare condition also may occur in patients not receiving bisphosphonates. Case reports have discussed ONJ development in patients with multiple myeloma or metastatic breast cancer receiving bisphosphonates as palliation for bone metastases. These patients are also receiving chemotherapeutic agents that might impair the immune system and affect angiogenesis. The incidence or prevalence of ONJ in patients taking bisphosphonates for osteoporosis seems to be very rare. No causative relationship has been unequivocally demonstrated between ONJ and bisphosphonate therapy. A majority of ONJ occurs after tooth extraction. Furthermore, the underlying risk of developing ONJ may be increased in osteoporotic patients by comorbid diseases. Treatment for ONJ is generally conservative.

Incidence of osteonecrosis of the jaw in women with postmenopausal osteoporosis in the health outcomes and reduced incidence with zoledronic acid once yearly pivotal fracture trial

BACKGROUND

The authors determined incidence of osteonecrosis of the jaw (ONJ) in a large, prospective three-year clinical trial of zoledronic acid in women with postmenopausal osteoporosis (PMO).

METHODS

A total of 7,714 women with PMO received intravenous zoledronic acid 5 mg or a placebo. No spontaneous reports of ONJ were received. An independent, blinded adjudication committee searched the trial's adverse event database by using 60 terms. On an ongoing basis, the committee reviewed the identified events, and it defined ONJ as exposed bone in the maxillofacial area with delayed healing for more than six weeks despite appropriate care.

RESULTS

One participant who received a placebo and one participant who received zoledronic acid experienced delayed healing associated with infection. Both conditions resolved after antibiotic therapy, débridement or both.

CONCLUSION

The occurrence of ONJ is rare in a PMO population, and delayed healing of lesions can occur with and without bisphosphonate use over three years.

CLINICAL IMPLICATIONS

The low incidence of ONJ must be assessed in the context of the clinical benefit of zoledronic acid therapy in reducing hip, vertebral and nonvertebral fractures in this at-risk population. There is no evidence to suggest that healthy patients with osteoporosis who are receiving bisphosphonates require any special treatment beyond routine dental care or to support altering standard treatment practices.

Effects of lactation on alveolar bone loss in experimental periodontitis

BACKGROUND

The development and progression of periodontitis are accelerated by various systemic conditions. The present study was designed to determine whether lactation affects alveolar bone loss in rat models of experimental periodontitis.

METHODS

Sixty-two female Wistar rats were bred with male rats and divided into three groups that were fed diets containing 0.9%, 0.3%, and 0.02% calcium. They were divided further into two subgroups of lactating and non-lactating animals. An elastic ring was placed around the neck of the right mandibular first molar to induce periodontitis (experimental side) on day 32 after mating. The left first molar was not fitted with an elastic ring (control side). After the lactation period, bone mineral density (BMD) was determined, and a histologic examination of the interdental alveolar bone was performed.

RESULTS

On the experimental and control sides, BMD decreased significantly according to the amount of calcium in the diet; however, the magnitude of this decrease was much greater in the lactating group. Histologic examination revealed that in lactating and non-lactating rats, the decrease in BMD was accompanied by a decrease in alveolar bone height on the experimental side, whereas similar results were not seen on the control side.

CONCLUSIONS

Lactation could be a risk factor for alveolar bone loss, especially under conditions of calcium insufficiency. Increased systemic demand for calcium and an insufficient supply of calcium might enhance the development of alveolar bone loss in periodontitis.

Inhibitory Effect of Alendronate on Bone Resorption of Autogenous Free Bone Grafts in Rats

PURPOSE

This study was designed to investigate the effect of alendronate on the resorption of autogenous free bone grafts by biochemical and histopathologic methods. Alendronate is a potent inhibitor of osteoclast-mediated bone resorption with no adverse effect on the mineralization of bone.

MATERIALS AND METHODS

In this experimental study, 56 male Wistar rats were used. Autogenous free bone grafts were prepared with standard trephine bur in the right femur of each rat. The animals were then divided into 2 groups. In the first group, rats were treated with a daily subcutaneous injection of alendronate (0.25 mg/kg/day) for 2, 4, and 12 weeks, respectively. In the second group, rats were treated with saline solution injection for the same time periods. At the end of these periods, serum and overnight fasting urine samples were collected from all animals. In serum, the level of calcium, phosphate, parathyroid hormone, and 25 dihydroxyvitamin D were measured. In urine, pyridinoline, deoxypyridinoline, calcium, and creatinine were analyzed. The rats were sacrificed at 2, 4, and 12 weeks postsurgery. The number of osteoclasts and the number and size of resorptive lacunae were evaluated histopathologically.

RESULTS

Alendronate caused significant reduction in urinary pyridinoline, deoxypyridinoline levels biochemically, and the number of osteoclasts and resorptive lacunae histopathologically.

CONCLUSION

Suppression of the graft resorption occurred in the alendronate-treated group.

Matrix metalloproteinases, tissue inhibitor of matrix metalloproteinase-1, and laminin-5 gamma2 chain immunolocalization in gingival tissue of endotoxin-induced periodontitis in rats: effects of low-dose doxycycline and alendronate

BACKGROUND

Matrix metalloproteinases (MMPs) play important roles in tissue destruction mechanisms of periodontitis. MMP-8 and -13 are the major collagenases that act in extracellular matrix degradation in periodontal tissues. MMP-14 is a membrane-type MMP, and laminin (Ln)-5 is a basal membrane component. The aim of the present study was to evaluate the effects of doxycycline and alendronate on gingival tissue expression of MMP-8, -13, and -14; tissue inhibitors of MMP (TIMP)-1; and Ln-5 gamma2 chain in experimental periodontitis induced by Escherichia coli endotoxin (LPS) in rats.

METHODS

Experimental periodontitis was induced by repeated injection of LPS. Forty-four adult male Sprague-Dawley rats were divided into five study groups: saline control, LPS, LPS + doxycycline, LPS + alendronate, and LPS + doxycycline + alendronate. Doxycycline and alendronate were given as a single agent or as combination therapy during the 7 days of the experimental study period. On day 7, the rats were sacrificed, and the gingival tissues were analyzed immunohistochemically for expression of MMP-8, -13, and -14, Ln-5 gamma2 chain, and TIMP-1. Alveolar bone loss was evaluated morphometrically under a stereomicroscope. Data were tested statistically by Kruskal-Wallis and Mann-Whitney tests and Spearman correlation analysis.

RESULTS

Alveolar bone loss was significantly higher in the LPS, doxycycline, alendronate, and combination groups than in the saline control group (all P <0.01). MMP-8 expression was significantly higher in the LPS group than in the saline control group (P = 0.001). Individual administration of doxycycline or alendronate significantly decreased the expression of MMP-8 compared to LPS (P = 0.01). Combined drug administration reduced MMP-14 significantly compared to doxycycline (P = 0.004). No significant differences in Ln-5 gamma2 chain expression were found between the study groups (P >0.05). MMP-14 significantly correlated with the Ln-5 gamma2 chain in the LPS + alendronate group (P = 0.04) and with the amount of alveolar bone loss in the LPS + doxycycline + alendronate group (P = 0.03).

CONCLUSIONS

Our findings suggest that alendronate and/or doxycycline may inhibit MMP-8 expression significantly; particularly, their combined administration may provide beneficial effects in periodontal treatment. Moreover, individual administration of alendronate and doxycycline results in significant increases in TIMP-1 expression in gingiva. However, these effects of combined low-dose doxycycline and alendronate on MMPs and TIMP should be verified by clinical human trials before these agents are used in dental practice.

A novel inhibitor of vacuolar ATPase, FR202126, prevents alveolar bone destruction in experimental periodontitis in rats

An acidic microenvironment formed by vacuolar ATPase (V-ATPase) expressed in plasma membranes of osteoclasts is thought to be indispensable for bone resorption. This study examined the efficacy of a novel V-ATPase inhibitor, FR202126, in reducing alveolar bone loss caused by experimental periodontitis in rats. FR202126 inhibited H+ transport in plasma membrane vesicles of murine osteoclasts, whereas FR202126 exerted no effect on H+ transport of mitochondrial ATPase or gastric H+,K+-ATPase, indicating that FR202126 is a specific inhibitor of V-ATPase. As expected from the mechanism, FR202126 remarkably inhibited in vitro bone resorption whatever bone resorptive factors were added. Moreover, FR202126 was also able to exert an inhibitory effect on in vivo bone resorption. Experimental periodontitis was induced by ligature wire tied around the contact between the first and second maxillary molars. Insertion of ligature wire for 7 days induced alveolar bone destruction by activating osteoclasts. Oral administration of FR202126 (u.i.d.) significantly prevented alveolar bone loss in experimental periodontitis which may offer a new approach to treatment of periodontal disease.

Bone response to different strength orthodontic forces in animals with periodontitis

BACKGROUND

Occlusal alterations resulting from tooth movements caused by periodontitis-related bone loss are often corrected with orthodontic treatments. Although the outcome is usually satisfactory, a quantitative histomorphometric study of bone response would contribute to improving treatment planning and optimizing results.

METHODS AND RESULTS

This study is a histomorphometric analysis of alveolar bone response to 51 and 75-g orthodontic forces applied to rat molars subjected to experimental periodontitis by placing a ligature around the neck of the molar during 48 h. The orthodontic device consisted of two bands with a tube welded to their palatine aspect, through which the arms of a helicoidal spring were threaded so as to exert force toward palatine. The device was placed immediately and 48 h after removing the ligatures. When applied 48 h post-removal of the ligature, both orthodontic forces caused an increase in bone volume in the periodontitis group.

CONCLUSIONS

Our study shows that application of orthodontic forces once periodontal infection has been controlled contributes to increasing alveolar bone volume, consequently improving bone quality.

Effect of Topical Administration of Monosodium Olpadronate on Experimental Periodontitis in Rats

BACKGROUND

Periodontitis is characterized by gingival inflammation, periodontal pocket formation, and bacterial plaque that lead to alveolar bone destruction. Research studies have recently begun to evaluate the effect of antiresorptive agents using experimental models of periodontitis. Bisphosphonates are the most frequently tested antiresorptive agents; their main effect is inhibition of bone resorption. The aim of this study was to perform a histomorphometric evaluation of the preventive effect of monosodium olpadronate (OPD), an aminobisphosphonate, on experimental periodontitis (EP).

METHODS

Twenty male Wistar rats were used in this experiment. The animals were assigned to one of two groups: group I: EP; and group II: EP plus topical administration of OPD (EP + OPD). The contralateral side in both groups served as untreated controls (CI and CII), respectively. Mesio-distally oriented sections of each lower first molar were obtained for histomorphometric evaluation.

RESULTS

The treated group (EP + OPD) exhibited marked inhibition of bone loss; interradicular bone volume was significantly greater than that observed in the EP group. The height of the periodontal ligament in the interradicular alveolar bone, which served as an indirect measure of bone loss, was found to be significantly increased in the EP group as compared to the EP + OPD group. Osteoclasts in the OPD treated group were detached from the bone surface, were round in shape, and exhibited a loss of polarity and lack of ruffled borders.

CONCLUSIONS

The dose used herein was found to inhibit bone loss and to cause marked morphologic changes in osteoclasts. The drug effectively prevented bone loss caused by periodontitis.

Systemic Low-Dose Doxycycline and Alendronate Administration and Serum Interleukin-1Beta, Osteocalcin, and C-Reactive Protein Levels in Rats

BACKGROUND

The aim of the present study was to evaluate the effects of systemic administration of low-dose doxycycline and a bisphosphonate, alendronate, on serum levels of interleukin-1beta (IL-1beta), osteocalcin (OC), and C-reactive protein (CRP) in experimental periodontitis in rats.

METHODS

Experimental periodontitis was induced by repeated injection of purified lipopolysaccharide (LPS) derived from Escherichia coli endotoxin. Forty-seven adult male Sprague-Dawley rats were divided into five study groups and given LPS, LPS + doxycycline, LPS + alendronate, LPS + doxycycline + alendronate, and saline control. At the end of the 1-week protocol, blood samples were obtained, and the rats were sacrificed. Serum samples were analyzed for IL-1beta, OC, and CRP concentrations by enzyme-linked immunosorbent assay (ELISA). The jaws were defleshed, and alveolar bone loss was assessed morphometrically. Data were evaluated statistically by non-parametric tests.

RESULTS

Morphometric measurements revealed significantly more bone loss in the LPS group compared to the saline control group (P <0.05). Alendronate revealed slight inhibition on alveolar bone loss either alone or in combination with doxycycline (alveolar bone loss: 0.41 mm in alendronate and combined drug treatment groups versus 0.45 mm in LPS and doxycycline groups). Significantly higher IL-1beta levels were observed with alendronate either alone or in combination with doxycycline than in the LPS group (P <0.05). Combined administration of doxycycline and alendronate showed significantly higher levels of OC than all of the other groups (P <0.01). Serum CRP levels did not exhibit significant differences between the study groups.

CONCLUSIONS

Alendronate either alone or in combination with doxycycline provided slight inhibition on LPS-induced alveolar bone resorption. The significantly increased serum OC level observed in the combined drug treatment group suggests that combined administration of alendronate and doxycycline might increase bone remodeling and thereby inhibit the progression of alveolar bone resorption in rats.

Host response modulation in the management of periodontal diseases

OBJECTIVE

To review the biological mechanisms and clinical utility of therapeutic modulation of the host response in the management of periodontal diseases.

MATERIAL AND METHODS

A search of MEDLINE-PubMed was performed up to and including December 2004. The search was limited to in vitro, experimental animal and clinical studies published in English. The selection criteria included all levels of available evidence: systematic reviews, randomised-controlled clinical trials, controlled clinical trials, prospective and retrospective cohort studies and case reports of human and experimental animal studies.

RESULTS

Six targets for non-microbial chemotherapeutic intervention were identified. Clinical trials have demonstrated the ability of non-steroidal anti-inflammatory drugs to slow periodontal disease progression. However, recently reported serious adverse effects preclude the use of cyclooxygenase-2 inhibitors as an adjunct to periodontal therapy. Adjunctive use of subantimicrobial dose doxycycline to non-surgical periodontal therapy is beneficial in the management of chronic periodontitis over 12 months. Controversial data exist on the effects of bisphosphonate administration as an adjunct to periodontal therapy. Evidence on modulation of other host mediators including lipoxins, cytokines and nitric oxide synthase is limited to animal research.

CONCLUSION

After validation in long-term clinical trials, adjunctive host modulation therapy may prove advantageous in the management of periodontal diseases.

Effects of combined systemic administration of low-dose doxycycline and alendronate on endotoxin-induced periodontitis in rats

BACKGROUND

Doxycycline has been widely used in periodontal treatment for its antimicrobial and anti-enzymatic effects. Recently, bisphosphonates have been shown to inhibit alveolar bone resorption. The aim of the present study was to evaluate the effects of doxycycline and the bisphosphonate alendronate on the gingival tissue levels of prostaglandin E2 (PGE2), prostaglandin F2alpha (PGF2alpha), leukotriene B4 (LTB4), and platelet-activating factor (PAF) in endotoxin-induced periodontal breakdown in rats.

METHODS

Experimental periodontitis was induced by repeated injection of Escherichia coli endotoxin (LPS) and 44 adult male Sprague-Dawley rats were divided into five study groups as follows: LPS, doxycycline + LPS, alendronate + LPS, doxycycline + alendronate + LPS, and saline control. Doxycycline and alendronate were given either as a single agent or as a combination therapy during the 7-day study period. At the end of the 1-week protocol, the rats were sacrificed, the gingival tissues were dissected and extracted, and the extracts were analyzed for PGE2, PGF2alpha, LTB4, and PAF levels. The defleshed jaws were analyzed morphometrically for alveolar bone loss. Data were evaluated statistically by using parametric tests.

RESULTS

Alveolar bone loss measurements revealed significantly higher values in LPS, doxycycline + LPS, alendronate + LPS, and doxycycline + alendronate + LPS groups in comparison to the saline control group (P <0.05). Combined administration of doxycycline and alendronate exhibited the most prominent inhibition on gingival tissue levels of PGE2 and PGF2alpha (P<0.05). Doxycycline + alendronate + LPS group also significantly reduced LTB4 and PAF levels, although doxycycline provided the most reduction in the levels of these mediators (P <0.05).

CONCLUSIONS

Alendronate and/or doxycycline may provide significant inhibition of the major inflammatory mediators of periodontal tissue destruction, and combined administration of these agents may provide beneficial effects in periodontal treatment. However, this hypothesis must be further verified by clinical human trials before introducing its use in dental practice.

The influence of alendronate on bone formation after autogenous free bone grafting in rats

OBJECTIVE

This study was undertaken to investigate the influence of alendronate on bone formation after autogenous free bone grafting in rats.

STUDY DESIGN

Fifty-six male Wistar-Albino rats were divided into 3 groups: baseline, saline-treated, and alendronate-treated groups, and followed up at 2, 4, and 12 weeks. In the femur of the rats, autogenous free bone grafts 3 mm in diameter and 2 mm in length were harvested with a standard trephine bur. The bone defects 3 mm in diameter and 2 mm in length were created 5 mm from the donor sites. Each graft was placed in the bone defect and stabilized by perifemoral wiring. The alendronate-treated rats were administered 0.25 mg/kg alendronate subcutaneously daily. The saline-treated rats were given daily saline solution. Serum calcium, phosphate, parathyroid hormone, 1,25-dihydroxyvitamin D, bone alkaline phosphatase (BAP), osteocalcin, and urine calcium were measured. The changes in the number of osteoblasts bordering active bone formation surface and osteoid and lamellar bone formation were evaluated to measure anabolic bone activity.

RESULTS

Alendronate caused significant increase in serum osteocalcin and BAP levels biochemically and the number of osteoblasts histopathologically.

CONCLUSION

Alendronate may be considered among therapeutic options to improve bone formation process in different bone remodeling cases. Further detailed studies should be focused on dosage- and time-dependent effects of alendronate on bone formation.

Can we successfully maintain risk patients?

The most fundamental premise in the current view of periodontal disease is that not all individuals are at equal risk for disease and disease progression. Studies reveal that about 5-20% of the population is at risk for severe disease progression. The purpose of this paper is to define at-risk patients, review risk factors and indicators of disease progression, and outline an evidence-based strategy that includes both self-care and professional care for maintaining periodontal health. Risk factors/risk indicators considered include history of previous disease, increased pocket depth and loss of clinical attachment, frequency of dental care, specific bacterial pathogens, and systemic/environmental host factors such as smoking, diabetes mellitus, genetics, and stress. Because host factors may have more influence on disease progression than periodontal pathogens, personal and professional maintenance care must include the role of the host in periodontal disease progression. By examining the evidence surrounding these complex issues, dentists and dental hygienists are able to determine the extent to which evidence supports available approaches to maintain periodontal health and control disease progression.

A Histopathological Investigation on the Effect of Systemic Administration of the Bisphosphonate Alendronate on Resorptive Phase Following Mucoperiosteal Flap Surgery in the Rat Mandible

BACKGROUND

The present study was designed to assess histopathologically whether the systemic administration of aminobisphosphonate (alendronate), 0.5 mg/kg body weight, is effective in preventing alveolar bone resorption following mucoperiosteal flap surgery, and whether alendronate modulates tissue factors.

METHODS

The effect of alendronate on bone resorption was evaluated in mucoperiosteal flaps used as a resorptive model. The animals were given subcutaneous injections of either saline (control group) or 0.5 mg/kg of alendronate (experimental group). The alendronate or saline was administered subcutaneously 1 week prior to surgery, immediately prior to surgery, and 1 week after surgery. The parameters determined with a semiquantitative subjective method for histopathological evaluation were as follows: inflammatory cell infiltration (ICI) of adjacent periodontal tissue, degree of fibrosis and collagen bundle formation, number and morphology of osteoclasts of the alveolar bone and interdental septum, resorption lacunae (osteoclast surfaces), and osteoblastic activity (forming surfaces).

RESULTS

There were no statistically significant differences between the saline and alendronate groups with regard to inflammatory cell infiltration, number of osteoclasts, and osteoblastic activity. Fibrosis and collagen bundle formation, osteoclast morphologies, and resorption lacunae formation were significantly different between the two groups, in favor of the alendronate group.

CONCLUSIONS

The systemic administration of 0.5 mg/kg alendronate was effective in preventing alveolar bone loss and in modulating tissue factors. These findings indicate that alendronate would be a valuable addition to the therapeutic armamentarium available for the treatment of periodontal diseases, either alone or in combination with regenerative components such as anti-inflammatory drugs, bone graft materials, and guided tissue regeneration techniques, and even with dental implants.

Inhibitory effects of incadronate on the progression of rat experimental periodontitis by porphyromonas gingivalis infection

BACKGROUND

Incadronate (YM175, disodium cycloheptylaminomethylenediphosphonate monohydrate), a bisphosphonate, has been suggested to prevent the bone resorption associated with periodontitis by inhibiting osteoclast activity. The purpose of this study was to investigate the effect of incadronate in preventing periodontal destruction in rats with Porphyromonas gingivalis-induced periodontitis.

METHODS

Periodontitis was induced in 35 Wister rats by inoculating P. gingivalis into the oral cavity and feeding the rats a soft diet for 4 weeks. Incadronate or placebo was administered to the oral cavity of the rats 2 days per week for 2, 4, or 8 weeks.

RESULTS

P. gingivalis infection resulted in destruction of the periodontal ligament, reduced bone density, and caused inflammatory cell migration. Radiographic, morphometric, and histological results showed that incadronate had the ability to increase the bone mineral density (quantum level score; cortex 518.9 [placebo 612.8]; sponge 579.8 [placebo 672.0]) and to prevent periodontal ligament destruction (width 0.16 mm [placebo 0.20 mm]; area 0.36 mm2 [placebo 0.54 mm2]) after 8 weeks' administration. Furthermore, the polymorphonuclear leukocyte (PMN) infiltration in gingival tissue was significantly decreased.

CONCLUSION

These results showed that incadronate inhibits bone resorption and PMN migration in P. gingivalis-induced periodontitis.

Mandible and maxilla bone mineral density and threshold analysis studies by pQCT in two edentulous women receiving pamidronate

The mandible and maxilla of two edentulous women, treated during 25 weeks with oral pamidronate, were monitored by peripheral quantitative tomography (pQCT). Whole bone volumetric mineral density failed to show meaningful variations after treatment. However, an analysis of separated cortical and medullar areas disclosed focal bone loss at the right mandible cortex of patient #1 and at the left maxilla cortex of patient #2. These and other bone sub-regions were further studied by clustering the internal sites with a different degree of bone mineral density, resorting to the mineral threshold analysis provided by the system. Where bone loss was detected, it corresponded to increased loss of the most osteopenic sites, while medium and high-density portions tended to remain unchanged within the region. There were no significant variations in all other regions, or alternatively, minor losses at osteopenic sites were compensated by an increase at high-density portions. Hence, the pQCT system allowed monitoring volumetric bone mineral density at particular sites of interest, discriminating variations at portions with a dissimilar degree of bone volume. Further studies should confirm whether pamidronate exerts a protective effect on sub-regions with previous medium and high degrees of bone mineralization, as suggested by our present findings.

Circadian rhythms in serum bone markers and their relation to the effect of etidronate in rats

Circadian rhythmicity is an essential feature of bone metabolism. The present study was undertaken to (Aoshima et al., 1998) determine the changes in bone resorption and formation in rats over 24h, (Black et al., 1999) evaluate the effect of the consecutive administration of etidronate on circadian rhythms of serum bone markers, and (Blumsohn et al., 1994) determine whether the effect of etidronate on bone metabolism is circadian time-dependent. One hundred twenty male Wistar rats, which had been adapted to a 12/12h light/dark cycle, were injected subcutaneously once daily with either 0.5 mgP/kg etidronate or 0.9% NaCl (control group) at 0090, 1300, 1700, 2100, 0100, or 0500h for 10d. Serum was collected and tibiae were dissected 24h after the last injection. Serum pyridinoline (Pyd), tartrate-resistant acid phosphatase (TRAP), osteocalcin (OC), alkaline phosphatase (ALP), calcium (Ca), phosphorus (Pi), calcitonin (CT), and parathyroid hormone (PTH) were determined. Bone mineral density (BMD) in the proximal tibia, and the rate of formation of longitudinal trabecular bone over the past 48h were also determined using a chronological labeling method with NTA-Pb. The results showed characteristic circadian rhythms in serum bone markers in rats, with peaks in both bone resorption and bone formation during the animals' rest span. The administration of etidronate at the different times of the day decreased the level of bone-resorption markers (Pyd and TRAP) without affecting the circadian patterns of markers of bone formation (OC and ALP). However, the magnitude of the decrease due to etidronate was not uniform throughout the day, and was greatest during the daytime. Etidronate increased the BMD in the tibial metaphysis in all of the time-treatment groups, but the magnitude of the increase did not vary with the time of etidronate administration. The present data provide a physiological basis for future studies on bone metabolism and may be important in the design of future experiments and in the interpretation of experimental data.

Effects of topical administration of clodronate on alveolar bone resorption in rats with experimental periodontitis

BACKGROUND

We examined whether topical administration of a bisphosphonate clodronate could prevent alveolar bone loss in rats with experimental periodontitis.

METHODS

On day 0, elastic rings were placed around the cervix of the right and left maxillary first molars (M1) to induce inflammatory periodontitis. Fifty microl of clodronate solution at a concentration of either 0 (0.9% NaCl), 20, 40, or 60 mM was injected into the subperiosteal palatal area adjacent to the interdental area between M1 and M2 on either the left or right (experimental) side on days 0, 2, 4, and 6. The contralateral side served as a control and received 0.9% NaCl solution without clodronate. The animals were sacrificed on day 7.

RESULTS

Histological examination and determination of bone mineral density in the interdental alveolar bone area between M1 and M2 revealed that placement of an elastic ring caused severe vertical and horizontal bone resorption on the control side, while the topical administration of clodronate significantly prevented such alveolar bone loss. The number of osteoclasts on the experimental side was decreased compared with the control side. Furthermore, many of the osteoclasts on the experimental side were detached from the surface of the alveolar bone and had degenerated appearances, such as rounded shapes and a loss of polarity.

CONCLUSIONS

These results suggest that topical administration of clodronate may be effective in preventing osteoclastic bone resorption in periodontitis.

Review of risedronate in the treatment of osteoporosis

Risedronate (Actonel, Procter & Gamble and Aventis) is a novel, orally administered pyridinyl bisphosphonate. Preclinical studies have shown that risedronate is a potent inhibitor of osteoclasts. Risedronate inhibited bone resorption and increased bone density in the spine and hip. Prospective, randomised, placebo-controlled trials (RCTs) in patients with postmenopausal osteoporosis (PMO) have demonstrated that risedronate decreased the risk of vertebral fractures by up to 49% and of non-vertebral fractures by up to 39% over 3 years in postmenopausal women with one or more prevalent vertebral fractures. This reduction of the risk for vertebral fractures was significant from the first year of treatment (risk reduction up to 65%). Risedronate was the first bisphosphonate to be studied in a large RCT with prevention of hip fracture as the primary end point. In this study, risedronate reduced the risk of hip fracture by 40% in elderly women with low hip bone density and one clinical risk factor for hip fracture and by 60% in women with low bone density and a prevalent vertebral fracture at baseline. Risedronate was also effective in the prevention and treatment of bone loss in glucocorticoid-induced osteoporosis (GIO), with a positive effect on vertebral fractures within the first year. Risedronate was well-tolerated with a safety profile comparable to placebo in all clinical studies. Patients with a previous or current history of upper GI illness or who were taking NSAIDs or aspirin were not excluded from these studies. Importantly, the upper GI safety profile of risedronate was shown to be similar to that of placebo in endoscopic studies. There was no evidence of acute-phase reactions or primary mineralisation defects. The most appropriate dose of risedronate was 5 mg/day.

Clinical effect of etidronate on alveolar pyorrhoea associated with chronic marginal periodontitis: report of four cases

Etidronate 200 mg daily was administered to four female patients with periodontitis and resultant alveolar pyorrhoea for periods of 2 weeks, followed by off-periods of 10 weeks or more, for 2-3 years. The macroscopic appearance of gingival mobility of the teeth, depth of periodontal pockets, and X-ray findings of alveolar bones improved markedly during this time. The effects were first observed after 6-12 months of treatment. These findings indicate that bisphosphonates may be effective in the treatment of periodontitis and resultant alveolar pyorrhoea. The effect may be mediated by the inhibitory action on bone resorption and the anti-inflammatory action of etidronate. Concomitant conventional dental management is also required.

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.

Effectiveness of local delivery of alendronate in reducing alveolar bone loss following periodontal surgery in rats

BACKGROUND

Mucoperiosteal flaps are used to access bone and root surfaces for debridement, pocket elimination, management of periodontal defects, and in regenerative procedures, as well as in implant surgery. Many reports show that periodontal surgery stimulates osteoclast activity with varying amounts of alveolar bone loss. Alendronate given intravenously significantly reduced alveolar bone loss in mucoperiosteal flap procedures. In the present study, we explored the effectiveness of different concentrations of alendronate, delivered at the surgical site at the time of surgery, in distant delivery in reducing alveolar bone loss.

METHODS

Following elevation of a mucoperiosteal flap next to molars of the rat mandible, a gelatin sponge soaked with different concentrations of alendronate (0, 1, 5, 20, or 40 mg/ml; experiment A) was applied to exposed bone on the experimental side. In the second group (experiment B), alendronate (0, 50, 200, or 400 microg) was topically delivered in the cheek submucosa on the left side (distant to the surgical site) in a small cut into which the gelatin sponge soaked with the drug was placed.

RESULTS

Topical application of 200 microg and 400 microg doses of alendronate at the time of surgery was significantly effective (P <0.001) in reducing bone loss. Generally, the percentage of sections with mild bone loss (V1, V2) increased with an increase in the dose of alendronate, while the percentage of sections with severe bone loss (H1, H2) decreased with an increase in alendronate dose. Topical application of 400 microg of alendronate had a systemic effect.

CONCLUSIONS

This study implies that topical delivery of alendronate at the time of surgery reduces bone loss in periodontal procedures involving mucoperiosteal flap surgery. The most effective dose is 200 microg for topical delivery at the surgical site and 400 microg for distant sites.

Bone mineral density of alveolar bone in rats during pregnancy and lactation

BACKGROUND

The present study was designed to investigate the effect of pregnancy and lactation on the bone mineral density (BMD) of alveolar bone in rats fed diets containing different amounts of calcium (Ca). The effects of different levels of Ca intake by the mothers on the BMD of alveolar bone in their pups were also examined.

METHODS

Ten-week-old female Wistar rats were housed with male rats for breeding and were divided into 3 groups fed diets containing 0.9, 0.3, and 0.02% Ca, respectively. They were further divided into 2 groups according to pregnancy or non-pregnancy. Animals in the pregnant group were raised with their own pups for lactation. After the experiment, all animals were sacrificed, their mandibles were dissected, and soft x-ray microradiographs were taken to determine BMD in the interdental area with an image analyzer.

RESULTS

In both groups, BMD in alveolar bone decreased based on the amount of Ca in the diet, but the magnitude of this decrease was much greater in the pregnant group than in the non-pregnant group. There was no significant difference in BMD between 2 groups fed a 0.9% Ca diet. The BMD of alveolar bone in the pups also decreased depending on the amount of Ca in the diet.

CONCLUSIONS

The above results suggest that pregnancy and subsequent lactation could be risk factors for alveolar bone loss, especially under conditions of Ca insufficiency or deficiency and that Ca insufficiency or deficiency in the mother caused decreases in the BMD of alveolar bone in the pups.

Mandibular bone formation rates in aged ovariectomized rats treated with anti-resorptive agents alone and in combination with intermittent parathyroid hormone

Anti-resorptive agents--including estrogen (E), calcitonin (CT), and bisphosphonates--are established in the treatment of osteoporosis. Intermittent administration of parathyroid hormone (PTH) stimulates bone formation and is a possible therapeutic agent for the restoration of bone mass. The purpose was to determine the effects of the anti-resorptive agents alone and in combination with intermittent PTH on bone formation in the mandible and a long bone in the aged ovariectomized (Ovx) rat. Female rats were ovariectomized or sham-operated. One year later, groups of Ovx rats were treated with E, CT, or the bisphosphonate, Risedronate (NE). Additional groups of Ovx rats were treated with each of these agents in combination with human PTH for 10 weeks. Estrogen treatment suppressed most indices of bone formation in the humerus and mandible, while NE decreased some indices of formation at the endocortical and endosteal surfaces of the mandible and humerus. Increased double-labeled surface and mineral apposition rates were observed only on the mandibular endosteal surfaces following CT treatment. When the anti-resorptive agents were combined with intermittent PTH, most indices of bone formation at all skeletal sites were substantially greater than those of the untreated Ovx controls as well as the E-, CT-, and NE-treated groups, respectively. These results provide additional evidence that established and emerging therapies for osteoporosis affect osseous tissues in the oral cavity, and this may influence the progression of diseases and/or aging changes at this site.

A histopathological investigation on the effects of the bisphosphonate alendronate on resorptive phase following mucoperiosteal flap surgery in the mandible of rats

BACKGROUND

The present study was designed to examine histopathologically whether local delivery of aminobisphosphonate (alendronate) could be effective in preventing the alveolar bone resorption associated with mucoperiosteal flaps.

METHODS

Following mucoperiosteal flap elevation in the molar region of the rat mandible, a surgical pellet soaked with aminobisphosphonate was locally applied on the exposed bone surface and covered by flap. The determined parameters with a semi-quantitative subjective method for the histopathological evaluation were as follows: existing inflammatory cell infiltration of the related periodontal tissue; fibrotic component content and bundles of collagen fibers; the number and morphology of osteoclasts of the alveolar bone and interdental septum; existing resorption lacunae (osteoclast surfaces); and existing osteoblastic activity (forming surfaces).

RESULTS

The results showed that while there were no detectable statistically significant differences between the saline and alendronate-treated groups on the existing inflammatory cell infiltration (ICI), number of osteoclasts, and osteoblastic activity, the results for the fibrotic and collagen component, osteoclast morphologies, and existing resorption lacunae were statistically significant.

CONCLUSIONS

These results suggest that local application of the aminobisphosphonate alendronate can be used as an adjunct in therapy for reducing bone resorption following surgery. It can also be suggested for consideration that, even for the surgical approaches in dentistry where bone graft materials and/or dental implants are needed, using bisphosphonate may achieve a new dimension in periodontal therapy in the near future.

Alveolar bone response to submerged bisphosphonate-complexed hydroxyapatite implants

BACKGROUND

In most studies using submerged hydroxyapatite implants, maintenance of alveolar bone after tooth extraction was attempted with plain hydroxyapatite materials. However, clinical results have shown that hydroxyapatite may require biological modification with a bone resorption-inhibiting agent which may be beneficial for maintenance of alveolar bone. We conducted experimental and clinical studies to evaluate the effect of highly bisphosphonate-complexed hydroxyapatite implants on osteoconduction and repair in alveolar bone.

METHODS

Porous hydroxyapatite implants were pre-incubated in 10(-2)M bisphosphonate solutions at pH 3.49. The implants had a diameter of 2.1 mm and a height of 2 mm and adsorbed 115 microg bisphosphonate. Five goats were implanted with 4 plain hydroxyapatite implants on each side of the mandible in root extraction sockets for the precision analysis of dual x-ray absorptiometry (DEXA) measurements. Ten goats were implanted with 4 bisphosphonate/hydroxyapatite implants on one side of the mandible and 4 plain hydroxyapatite implants on the opposite mandible. In a clinical study, 23 bisphosphonate/hydroxyapatite implants were placed in periodontally destroyed tooth root sockets and followed up during one year.

RESULTS

The range for the bone mineral density (BMD) measurement errors for goat histologic sections was 0.48% to 1.03%. There were large differences in peri-implant BMDs in the left and right mandible of the same goat, irrespective as to whether hydroxyapatite or bisphosphonate/hydroxyapatite implants were present. This was due to local anatomical differences typical of alveolar bone. These differences were not significant. Histologically, all bisphosphonate/hydroxyapatite as well as hydroxyapatite controls appeared to be fully integrated and effective as bone replacement material in goat alveolar bone. They exhibited vascularization and osteoconduction of alveolar bone growth along and inside their porous structure. In patients peri-implant healing was clinically and radiographically comparable to plain hydroxyapatite implants. All implants were retained and no dehiscences developed. Radiographically, peri-implant radiolucencies disappeared and alveolar bone was deposited in close proximity to the implants.

CONCLUSIONS

This study contributes to the understanding of the biological properties of hydroxyapatite implants as carriers for the bone-modulating agent bisphosphonate. Our study suggests that normal osteoconduction and repair occurred in alveolar bone around the highly bisphosphonate-complexed hydroxyapatite implants.

Normal osteoconduction and repair in and around submerged highly bisphosphonate-complexed hydroxyapatite implants in rat tibiae

BACKGROUND

Ceramic hydroxyapatite implants have been used in dentistry for their unique compatibility with alveolar bone. Recently it was reported that bisphosphonates may be beneficial in preventing alveolar bone destruction associated with natural and experimental periodontal disease. Furthermore, bisphosphonate does prevent resorption of alveolar bone following mucoperiosteal flap surgery. We undertook a preliminary study evaluating the effects of highly bisphosphonate-complexed hydroxyapatite implants on osteoconduction and repair in rat tibiae.

METHODS

Porous hydroxyapatite implants were pre-incubated in 10(-2)M bisphosphonate solutions at pH 3.49 and pH 7.32. The implants had a diameter of 2.1 mm and a height of 2 mm and adsorbed 115 microg bisphosphonate in vitro. Bisphosphonate/hydroxyapatite implants and plain hydroxyapatite implants were inserted in opposite tibial metaphyses of 35 rats. The measurement errors for the mineral density (MD) of the implants and the proximal trabecular mineral bone density (TD) were estimated by peripheral computed tomography and the bone mineral density (BMD) measurement error by dual x-ray absorptiometry.

RESULTS

The measurement errors for the MD of the implants and the TD by peripheral computed tomography were 0.81% and 1.96%, respectively ex vivo. The BMD measurement error estimated by dual x-ray absorptiometry was 0.51% ex vivo. TD and BMD for bisphosphonate/hydroxyapatite implants were insignificantly higher compared to plain hydroxyapatite implants. Bisphosphonate/hydroxyapatite pre-incubated at pH 7.32 were found to be nondegradable implants, while bisphosphonate/hydroxyapatite (pH 3.49) implants were slowly degradable and lost a significant 5% of their density. Histologically, all bisphosphonate/hydroxyapatite implants appeared to be fully integrated and effective as bone replacement material in rat tibial bone. They exhibited vascularization and osteoconduction of tibial bone growth along and inside their porous structure.

CONCLUSIONS

Our study suggests that normal osteoconduction and repair occurred in and around the highly bisphosphonate-complexed hydroxyapatite implants in rat tibiae.

An ultrastructural study of the effects of bisphosphonate administration on osteoclastic bone resorption during relapse of experimentally moved rat molars

This study was designed to clarify the effects of systemic administration of bisphosphonate, pamidronate, on the bone resorbing activity of osteoclasts during relapse of rat molars, after experimental movement. An elastic band was inserted between the upper first and second molars of 7-week-old rats and removed 21 days later. At 1 day before elastic band removal, bisphosphonate was administered via a tail vein. After elastic band removal, the rats were further maintained for 0, 5, or 10 days. The relapse of the first molars was studied by means of light and scanning-electron and transmission-electron microscopy. When an elastic band was removed, the mean interdental distance between the first and second molars in all rats was approximately 435 micrometer. In the control rats, it had decreased to 108 micrometer by day 5 and 57 micrometer by day 10. In these control rats, numerous osteoclasts appeared along the alveolar bone surface in the compressed side of the periodontal ligament of first molars. Administration of bisphosphonate significantly inhibited the prominent decrease in interdental distance. In these rats, it averaged 313 micrometer at day 5 and 115 micrometer at day 10. In bisphosphonate-treated rats, osteoclasts aggregated mainly in vascular canals of alveolar bone but were occasionally observed along the alveolar bone surfaces facing the periodontal ligament. Administration of bisphosphonate also induced structural changes, such as disappearance of ruffled borders and cytoplasmic polarity, in osteoclasts. A degenerated osteoclast was also observed in a bisphosphonate-treated rat. However, bisphosphonate induced no structural changes in osteoblasts, osteocytes, or periodontal ligament fibroblasts. These results suggest that a single systemic administration of bisphosphonate decreases the extent of initial relapse in experimentally moved rat molars via a mechanism involving impairment of the structure and resorptive functions of osteoclasts.

Inhibitory effects of YM175, a bisphosphonate, on the progression of experimental periodontitis in beagle dogs

This study examined the efficacy of YM175 [disodium dihydrogen (cycloheptylamino) methylene-1, 1-bisphosphonate] in reducing alveolar bone loss caused by experimental periodontitis in beagle dogs. Thirty-six dogs were used and divided into 6 groups. Periodontitis was induced in 30 dogs (groups 2-6) by ligating the bilateral mandibular third and fourth premolar teeth with silk ligatures and by feeding a soft diet. Six dogs were sham-operated (group 1). Saline (placebo), flurbiprofen (0.02 mg/kg) and YM175 (0.01, 0.1 and 1.0 mg/kg) were administered to the dogs (groups 2-6) 5 d/wk for 25 wk. Radiographic and morphometric analyses were performed. In placebo-treated animals (group 2), the ligation caused a significant decrease in the alveolar bone height by 0.57 and 1.91 mm at 2 and 25 wk, respectively. YM175 (1.0 mg/kg) prevented the decrease in bone height by 47 and 31% at 2 and 25 wk. YM175 (0.1 mg/kg) and flurbiprofen tended to prevent bone loss after 15 wk. Although the ligation elicited no significant change in bone mineral density, it significantly decreased bone volume. YM175 (1.0 mg/kg) and flurbiprofen tended to increase the bone volume. The number of formative or resorptive Haversian canals and the bone turnover through the periosteal bone surface were increased by the ligation, indicating the increased turnover of the cortical bone. YM175 (1.0 mg/kg) reduced the increased bone turnover. The gingival index was maximally increased at 2 wk and was suppressed by YM175. These results suggest that YM175 prevents alveolar bone loss by reducing the increased alveolar bone turnover in dogs with periodontitis.