Disposition of alendronate following local delivery in a rat jaw

Histopathological Examination of the Effects of Local and Systemic Bisphosphonate Usage in Bone Graft Applications on Bone Healing

Background

The effect of bisphosphonates on the resorption process of normal bone tissue has been clearly mentioned in the literature, while their effect on the grafting material is a new research area. Limited former study is not sufficient to determine the strength, reliability and dosage of bisphosphonates. In this study, our aim is to examine the effects of local and systemic use of bisphosphonates in bone graft applications on bone healing, histopathologically.

Methods

Therefore, 32 Sprague-Dawley rats are separated into four groups. In the first group, only an empty bone defect is made on tibia and the tissue is sutured primarily without any other application. In the second group, bone defect is filled with allograft material and closed without any other application. In the third group (LA), alendronate solution is locally added to the graft material before its application to the site of bone defect. In the fourth group, alendronate is applied systemically after the site of bone defect is grafted and primarily closed. After 6 weeks, all rats are killed and the obtained samples are examined histopathologically.

Results

Local and systemic application of alendronate increases new bone formation in a statistically significant degree. In LA group, newly formed bone was observed more mature and well developed. Alendronate application does not cause an increase in inflammation, fibrosis and necrosis. There is no increased necrosis with alendronate application.

Conclusion

Local and systemic application of alendronate in bone grafting increases bone formation without any other complication. But we believe that further research should be made on dosage, usage and possible side effects.

Anabolic and antiresorptive actions of locally delivered bisphosphonates for bone repair: A review

During the last decades, several research groups have used bisphosphonates for local application to counteract secondary bone resorption after bone grafting, to improve implant fixation or to control bone resorption caused by bone morphogenetic proteins (BMPs). We focused on zoledronate (a bisphosphonate) due to its greater antiresorptive potential over other bisphosphonates. Recently, it has become obvious that the carrier is of importance to modulate the concentration and elution profile of the zoledronic acid locally. Incorporating one fifth of the recommended systemic dose of zoledronate with different apatite matrices and types of bone defects has been shown to enhance bone regeneration significantly in vivo. We expect the local delivery of zoledronate to overcome the limitations and side effects associated with systemic usage; however, we need to know more about the bioavailability and the biological effects. The local use of BMP-2 and zoledronate as a combination has a proven additional effect on bone regeneration. This review focuses primarily on the local use of zoledronate alone, or in combination with bone anabolic factors, in various preclinical models mimicking different orthopaedic conditions.

Cite this article: I. Qayoom, D. B. Raina, A. Širka, Š. Tarasevičius, M. Tägil, A. Kumar, L. Lidgren. Anabolic and antiresorptive actions of locally delivered bisphosphonates for bone repair: A review. Bone Joint Res 2018;7:548–560. DOI: 10.1302/2046-3758.710.BJR-2018-0015.R2.

Autologous liquid platelet rich fibrin: A novel drug delivery system

There is currently widespread interest within the biomaterial field to locally deliver biomolecules for bone and cartilage regeneration. Substantial work to date has focused on the potential role of these biomolecules during the healing process, and the carrier system utilized is a key factor in their effectiveness. Platelet rich fibrin (PRF) is a naturally derived fibrin scaffold that is easily obtained from peripheral blood following centrifugation. Slower centrifugation speeds have led to the commercialization of a liquid formulation (liquid-PRF) resulting in an upper plasma layer composed of liquid fibrinogen/thrombin prior to clot formation that remains in its liquid phase for approximately 15 min until injected into bodily tissues. Herein, we introduce the use of liquid PRF as an advanced local delivery system for small and large biomolecules. Potential target molecules including large (growth factors/cytokines and morphogenetic/angiogenic factors), as well as small (antibiotics, peptides, gene therapy and anti-osteoporotic) molecules are considered potential candidates for enhanced bone/cartilage tissue regeneration. Furthermore, liquid-PRF is introduced as a potential carrier system for various cell types and nano-sized particles that are capable of limiting/by-passing the immune system and minimizing potential foreign body reactions within host tissues following injection.

STATEMENT OF SIGNIFICANCE

There is currently widespread interest within the biomaterial field to locally deliver biomolecules for bone and cartilage regeneration. This review article focuses on the use of a liquid version of platelet rich fibrin (PRF) composed of liquid fibrinogen/thrombin as a drug delivery system. Herein, we introduce the use of liquid PRF as an advanced local delivery system for small and large biomolecules including growth factors, cytokines and morphogenetic/angiogenic factors, as well as antibiotics, peptides, gene therapy and anti-osteoporotic molecules as potential candidates for enhanced bone/cartilage tissue regeneration.

Effect of 1% sodium alendronate in the non-surgical treatment of periodontal intraosseous defects: a 6-month clinical trial

Background and objectives

Few studies have evaluated the effect of the topical application of sodium alendronate (ALN) on the treatment of intrabuccal bone defects, especially those caused by periodontitis. This 6-month randomized placebo controlled clinical trial aimed at evaluating the effect of non-surgical periodontal treatment associated with the use of 1% ALN, through clinical evaluations and cone-beam computed tomography (CBCT).

Material and Methods

Twenty individuals with chronic periodontitis underwent periodontal examination at the baseline as well as 3 and 6 months after periodontal treatment, registering clinical attachment level (CAL), periodontal probing depth (PPD), and bleeding on probing (BOP) as the clinical outcomes. After manual scaling and root planing, 40 bilateral sites with interproximal vertical bone defects were randomly treated with either 1% ALN gel or a placebo. Bone defects were evaluated through CBCT at the baseline and 6 months post-treatment. The clinical and CBCT parameters were compared using the Wilcoxon and Friedman tests (p<0.05).

Results

Although ALN produced a greater CAL gain when compared to the placebo at 6 months post-treatment (p=0.021), both treatments produced similar effects on the PPD, BOP, and bone height. Significant differences in bone fill were observed only in patients of the ALN group (4.5 to 3.8 mm; p=0.003) at 6 months post-treatment.

Conclusions

Topical application of 1% ALN might be a beneficial adjuvant to non-surgical periodontal therapy.

Effect of a local, one time, low-dose injection of zoledronic acid on titanium implant osseointegration in ovariectomized rats

INTRODUCTION

Local application of bisphosphonates has been proven to be safer than systemic administration to promote implant fixation. The objective of this study was to introduce such a simple, convenient and efficient method to enhance titanium (Ti) implant osseointegration in ovariectomized (OVX) rats.

MATERIAL AND METHODS

Twenty female Sprague-Dawley rats sequentially underwent bilateral ovariectomy and tibia implantation, and injection of 30 µg/implant zoledronic acid (ZOL) at the site of implantation was performed. At the end of the study, the tibiae, mandibles, femurs and vertebrae were harvested for dual energy X-ray absorptiometry, histology and micro-computed tomography examination.

RESULTS

Ovariectomized rats showed poor bone density, bone mass and trabecular microstructure. OVX + ZOL rats were characterized by significantly improved peri-implant bone area (1.72-fold), bone contact (2.30-fold), bone mineral density (1.57-fold) and bone mineral content (1.67-fold), as well as moderately increased bone volume to total volume ratio (1.34-fold), percentage osteointegration (1.54-fold), connectivity density (1.45-fold), and trabecular number (1.43-fold), but decreased trabecular separation (57.69%) when compared with the control levels (p < 0.05). No histological signs of jaw osteonecrosis were observed in the rats treated with ZOL, and there was no significant difference between the OVX group and OVX + ZOL group in the bone mass of the mandible, femur and 5^th lumbar vertebra (p > 0.05). In addition, the overproduction of osteoporosis-induced advanced glycation end-products (AGEs) was completely prevented by local treatment with 30 µg/implant ZOL.

CONCLUSIONS

A local, one time, low-dose injection of ZOL at the site of implantation is able to promote the osseointegration of Ti implants following postmenopausal osteoporosis, and this action may be partly mediated by inhibition of the osteoporosis-induced AGE overproduction in the bone marrow.

Effect of Alendronate with β - TCP Bone Substitute in Surgical Therapy of Periodontal Intra-Osseous Defects: A Randomized Controlled Clinical Trial

INTRODUCTION

Alendronate (ALN), an aminobisphosphonate, inhibits osteoclastic bone resorption and also stimulates osteogenesis. Beta-Tricalcium Phosphate (β-TCP) is an osteoconductive graft material which provides a scaffold for bone formation and also a widely used drug delivery vehicle for growth factors and antibiotics. Drug delivery vehicles, like β-TCP, improve the potency of the drugs by specific local site delivery of the drug, optimal release characteristics and easy handling.

AIM

The aim of the this study was to evaluate the bone formation potential of 400μg ALN delivered in β-TCP in the treatment of periodontal intra-osseous defects.

MATERIALS AND METHODS

Thirty patients with periodontal defects were randomly assigned to 400μg ALN + β-TCP + Saline (test) group and β-TCP + Saline (active-control) group. Clinical parameters like Clinical Attachment Level (CAL) gain, Probing Depth (PD) reduction, post-operative Gingival Recession (GR) were assessed from the baseline, 3 months and 6 months recordings. Radiographic parameters like Linear Bone Growth (LBG), Percentage Bone Fill (%BF), and change in alveolar crest height (ACH) were assessed from baseline and 6 months radiographs.

RESULTS

Mean measurements in the ALN test group for CAL gain (3.4 ± 0.74 mm), PD reduction (4.33 ± 0.82 mm), LBG (2.88 ± 0.88 mm), and %BF (51.98 ± 15.84%) were significantly greater with a p-value <0.05 compared to the mean measurements of CAL gain (2.20 ± 0.86 mm), PD reduction (3.20 ± 1.15 mm), LBG (1.70 ± 0.39 mm), and %BF (30.35 ± 6.88%) of the control group. There was mild alveolar crestal apposition (0.32 ± 0.68 mm) in the ALN test group and mild alveolar crestal resorption (-0.24 ± 0.40 mm) in the control group.

CONCLUSION

400μg ALN combined with β-TCP bone graft material was effective in improving soft tissue parameters, inhibiting alveolar crestal resorption and enhancing bone formation, compared to β-TCP alone.

Potential Applications of Biphosphonates in Dental Surgical Implants

Biphosphonates are largely used for their unquestionable properties of inhibiting bone resorption by osteoclast in the treatment of various osteometabolic illnesses such as osteoporosis, multiple myeloma, tumors which metastasize to the bone and malignant hypercalcemia. In this literature review the physico-chemical properties, biologic activities and the mechanisms of action of biphosphonates are described. The use of these drugs is discussed, analyzing the quantity of results which have emerged through in vitro and in vivo experiments on animal models. In this study the efficiency of these drugs is demonstrated in contrasting the osteolitic processes of the alveolar bone, in promoting the neoformation and in bettering the quality of bone implants. However, it is important to draw attention to a worrying correlation which has emerged during the last 3–4 years, between osteonecrosis of the jaw (ONJ) and the systemic administration of aminobiphosphonates. This collateral effect did not emerge following the use of non-aminobiphosphonates. The aim of this revie w is to identify the guidelines for the use of biphosphonates in oral implant surgery.

The Local Effect of Alendronate with Intra-alveolar Collagen Sponges on Post Extraction Alveolar ridge Resorption: A Clinical Trial

INTRODUCTION

Extraction of teeth is followed by resorption of the residual alveolar ridge that continues throughout life resulting in loss of alveolar height and width. Of the numerous techniques that have been used to arrest post extraction alveoloar ridge resorption, the placement of a graft material inside the socket immediately after extraction has been mostly followed. Type 1 collagen is one of the commonly used graft material that prevent resorption by providing dimensional stability to the socket. Bisphosphonates are an anti-osteoclastic drug that prevent resorption by disrupting the membrane ruffling of the osteoclasts. Alendronate a bisphosphonate, is primarily used in diseases with bone loss. It has been used to reduce active bone resorption significantly without interfering with bone mineralization and quality. The need for the study is to examine the inhibitory effect of alendronate on residual ridge resorption when applied locally in combination with type I collagen on alveolar bone immediately following tooth extraction.

MATERIALS AND METHODS

Twenty patients with age between 30 and 65 years were selected from the out patient department of The Oxford Dental College and Hospital. The patients were divided into two groups. In the first group after extraction of teeth from premolar to midline the sockets were irrigated with saline and sutured. On the left side type I collagen sponge was placed and sutured. In the other group the right side was treated the same way after extraction as in first group where as in the left side sockets type I collagen soaked in 20 mg/ml of alendronate was placed and sutured. Patients were evaluated clinically for any local irritation as well as radiologically with orthopantomograph X-rays were taken immediately after the extraction, 1 month after extraction and 4 months after extraction to determine the amount of bone loss prevented.

RESULTS

The statistically significant bone loss prevented by the collagen alone was 22.8 % and in collagen with alendronate group was 44.38 % at the end of 4 months.

CONCLUSION

Type I collagen soaked with alendronate when placed in the socket immediately after extraction of teeth prevents post-extraction alveolar ridge resorption.

Local delivery of small and large biomolecules in craniomaxillofacial bone

Current state of the art reconstruction of bony defects in the craniomaxillofacial (CMF) area involves transplantation of autogenous or allogenous bone grafts. However, the inherent drawbacks of this approach strongly urge clinicians and researchers to explore alternative treatment options. Currently, a wide interest exists in local delivery of biomolecules from synthetic biomaterials for CMF bone regeneration, in which small biomolecules are rapidly emerging in recent years as an interesting adjunct for upgrading the clinical treatment of CMF bone regeneration under compromised healing conditions. This review highlights recent advances in the local delivery small and large biomolecules for the clinical treatment of CMF bone defects. Further, it provides a perspective on the efficacy of biomolecule delivery in CMF bone regeneration by reviewing presently available reports of pre-clinical studies using various animal models.

Impact of local and systemic alendronate on simvastatin-induced new bone around periodontal defects

BACKGROUND

Simvastatin has been shown to stimulate new bone growth on rat mandibles, but much of the bone is lost over time. The purpose of this study is to evaluate the impact of a locally or systemically applied antiresorptive agent (alendronate) on simvastatin-induced bone formation in and adjacent to a rat periodontal defect.

METHODS

Fenestration defects were created over mandibular molar roots in 65 mature female Sprague-Dawley rats. Two weeks later, animals were divided into eight groups of eight to nine rats, and three weekly injections around the defect were applied: 1) 0.5 mg simvastatin in ethanol (SIM-EtOH); 2) 0.5 mg simvastatin in alendronate-cyclodextrin conjugate (SIM-ALN-CD); 3) EtOH alone; 4) ALN-CD alone; or 5) no injections. Twenty-four animals were evaluated for new bone width around the defect 21 days after the last injections (short-term) and 41 rats were followed for 48 days (long-term). Three SIM-EtOH groups of long-term rats also were subjected to 2 weeks of daily systemic ALN or saline either during or 3 to 4 weeks after SIM-EtOH injections. Decalcified, hematoxylin-and-eosin-stained cross-sections of the defect area were analyzed for new bone width and groups were compared using mixed-model analyses of variance.

RESULTS

All groups showed nearly 100% bone fill, with no differences among the short-term groups. However, in the long-term animals, two-fold to three-fold more new bone width (≤ 0.004) was seen around the periphery of the defect with the use of systemic ALN after SIM-EtOH injections (0.93 ± 0.12 and 0.78 ± 0.11 mm with early and late systemic ALN, respectively) compared to local SIM/ALN-CD preparations (0.32 ± 0.10 mm) or short-term SIM-EtOH injections (0.35 ± 0.10 mm). No significant new cementum formation or ankylosis was noted.

CONCLUSION

The use of a short course of systemic ALN during the healing period after bone anabolic SIM injections has the potential to enhance local bone augmentation.

Transplantable delivery systems for in situ controlled release of bisphosphonate in orthopedic therapy

IMPORTANCE OF THE FIELD

Bisphosphonates (BPs), structurally similar to pyrophosphates and functionally superior in restraining osteoclast-induced bone resorption, have been widely used as clinical drugs in the treatment of osteoporosis, bone voids and associated inflammation. However, owing to their high aqueous solubility and the consequently high rate of loss during oral administration, the loading and targeting of BPs pose major challenges in practice. Alternative delivery routes such as nasal, subcutaneous/intramuscular injection have contributed little to improving the bioavailiability and efficacy of BPs. To improve and optimize the delivery efficiency and efficacy of BPs, numerous strategies have been developed and adopted. Studies on controlled release of BPs provide important information on the fabrication of BP delivery systems for in situ treatment. As BPs play an important therapeutic role in osteoporosis and similar diseases, it has become essential and vital to survey various reported fabrication methodologies of these systems and the consequential orthopedic treatments so as to keep abreast with advances in their clinical use.

AREAS COVERED IN THIS REVIEW

Transplantable delivery systems for controlled release of BP are reviewed from literature published since 2000. The fabrication pathways and the release of BPs from various material systems are discussed in case studies. Recent progress in CaP models based on the strong and specific chelation between BPs and calcium phosphate crystals is highlighted.

WHAT THE READER WILL GAIN

This review offers an outline of the advances in BP controlled release and delivery systems for orthopedic therapy.

TAKE HOME MESSAGE

Understanding the cutting-edge BP controlled release and delivery systems for in situ treatment is key to the successful design of a more promising and perfect delivery system for orthopedic therapy. Moreover, developing such delivery systems incorporating the numerous advantages of BPs and controlled release environment requires substantially more flexible models to control better the fate of BP drugs.

Bisphosphonate remains highly localized after elution from porous implants

BACKGROUND

Local elution of zoledronic acid from a porous implant reportedly enhances periimplant bone formation and implant fixation. However, there is no information in the literature on the extent to which eluted bisphosphonate remains localized around the implant or becomes systemically distributed.

QUESTIONS/PURPOSES

We ascertained to what extent eluted zoledronic acid remains local and whether there is systemic exposure after local elution from porous implants.

METHODS

A hydroxyapatite-coated porous tantalum implant dosed with 100 μg (14)C-labeled zoledronic acid was implanted into the left femoral intramedullary canal of six dogs. Bone samples near to and distant from the implant were harvested from three dogs at 6 weeks and three dogs at 52 weeks. The concentration of radiolabeled bisphosphonate in each sample was quantified using liquid scintillation spectrophotometry and its distribution in periimplant bone was revealed by exposing histologic sections to autoradiography film.

RESULTS

In all six dogs, the concentration of zoledronic acid in immediate periimplant bone was two orders of magnitude higher than in any other sampled tissue, averaging 732.6 ng/g at 6 weeks and 377.2 ng/g at 52 weeks. Minute amounts of zoledronic acid (≤ 7.2 ng/g) were detected throughout the skeleton, indicating some escape into the circulation after local elution. Autoradiographs revealed the greatest concentration of zoledronic acid on and within the implant, with rapid decrease short distances away and no uptake within the femoral cortex.

CONCLUSIONS

Zoledronic acid eluted from an implant remains mainly localized with minimal systemic distribution.

CLINICAL RELEVANCE

Local bisphosphonate elution reduces the risk of systemic side effects and skeletal bisphosphonate exposure.

Effect of risedronate on bone resorption during consolidation phase of distraction osteogenesis: a rabbit model

PURPOSE

To evaluate the effects of continuous local injection of risedronate in the prevention of bone resorption in a lengthened segment.

METHODS

11 male rabbits underwent subperiosteal osteotomy of the left tibia and an external fixator was applied anteromedially. After a lag phase of one week, a 2-week distraction phase and a 5-week consolidation phase followed. Risedronate was continuously injected into the centre of the distracted segment at a rate of 10 micro g/kg/day during the first 14 days of consolidation by a subcutaneously implanted osmotic pump. A control group received purified buffer solution (PBS) using the same protocol. The lengthened bone segments were evaluated using radiography, quantitative computed tomography, and 3-point bending mechanical test.

RESULTS

Risedronate injection prevented osteopenia as compared to PBS injection. The mean bone mineral content, volumetric density and cross-sectional area of the lengthened segments were significantly higher in the risedronate group than in controls (as much as 65%, 30%, and 25%, respectively). There was no significant difference between the 2 groups regarding the ultimate load to failure.

CONCLUSION

Continuous local injection of risedronate into the lengthened segment can prevent osteopenia during distraction osteogenesis but fails to enhance mechanical strength of newly distracted segments.

Implante de biomateriais e a consolidação óssea em cadelas submetidas à ovariossalpingo-histerectomia

Avaliou-se a hidroxiapatita com alandronato e hidroxiapatita com colágeno na aceleração da consolidação óssea do rádio de cadelas adultas submetidas à ovariossalpingo-histerectomia (OSH). Utilizaram-se 14 cadelas adultas, distribuídas aleatoriamente em dois grupos: grupo-controle e grupo OSH (submetidas à OSH). Quatro meses após a OSH, as cadelas dos dois grupos foram submetidas à cirurgia para produção de uma falha óssea de 4mm de diâmetro nos terços distal e proximal do rádio. No terço distal do membro direito, foi utilizada a hidroxiapatita com alandronato e, no membro esquerdo, a hidroxiapatita com colágeno; no terço proximal, não se utilizou nenhum biomaterial. Houve retardo na consolidação das falhas ósseas nas cadelas submetidas à OSH comparadas com as não submetidas. A hidroxiapatita com alandronato acelerou o processo de reparação e, em todos os animais dos dois grupos, a densidade óssea foi significativamente maior no terço distal onde foi implantada. Os dois biomateriais apresentaram biocompatibilidade, constatada pela ausência de reação inflamatória ou outra reação indesejável.

Alendronate PLGA microspheres with high loading efficiency for dental applications

PURPOSE

Alendronate sodium, used systemically as a bone protective agent, proved to also be effective locally in various dental bone applications. Development of alendronate-loaded microspheres with high loading efficiency for such applications would be greatly challenged by the hydrophilicity and low MW of the drug. The aim of this study was to incorporate alendronate sodium, into poly (lactide-co-glycolide) (PLGA) microspheres (MS) with high loading efficiency.

METHODS

Three multiple emulsion methods: water-in-oil-in-water (W/O/W), water-in-oil-in-oil (W/O(1)/O(2)) and solid-in-oil-in-oil (S/O(1)/O(2)) were tested. In addition to entrapment efficiency, MS were characterized for surface morphology, particle size, in vitro drug release and in vitro degradation of the polymer matrix. Alendronate microspheres with maximum drug loading and good overall in vitro performance were obtained using the W/O(1)/O(2) emulsion technique.

RESULTS

Drug release from the microspheres exhibited a triphasic release pattern over a period of 13 days, the last fast release phase being associated with more rapid degradation of the PLGA matrix.

CONCLUSIONS

Biocompatible, biodegradable PLGA microspheres incorporating alendronate sodium with high loading efficiency obtained in this study may offer promise as a delivery system for bisphosphonates in dental and probably other clinical applications.

Effect of local delivery of alendronate on bone formation in bioactive glass grafting in rats

OBJECTIVE

The aim of this study was to investigate whether local delivery of alendronate could improve bone formation after bioactive glass grafting in rat mandible.

STUDY DESIGN

Twenty-six male Sprague-Dawley rats were divided into control and experimental groups (13 rats/group). A surgical defect was created on the angle of mandible of each animal. In the experimental group, a bioactive glass soaked with the alendronate solution was placed in the bone defect, and in the control group the bioactive glass soaked with saline was used. All animals were killed after 4 weeks. The number of osteoclasts and the amount of new bone formation were evaluated and compared.

RESULTS

Four weeks after surgery, the experimental group had significantly more bone formation than the control groups (P < .05). However, no statistically significant difference was found between the groups when the numbers of osteoclasts were compared.

CONCLUSION

Histologic results showed that a single dose of local delivery of alendronate improves bone formation. However, further studies are required to elucidate the effect of local delivery of alendronate on bone formation in humans.

Locally administered low-dose alendronate increases bone mineral density during distraction osteogenesis in a rabbit model

We investigated the effect of locally administered bisphosphonate on distraction osteogenesis in a rabbit model and evaluated its systemic effect. An osteotomy on the right tibia followed by distraction for four weeks was performed on 47 immature rabbits. They were divided into seven equal groups, with each group receiving a different treatment regime. Saline and three types of dosage of alendronate (low, 0.75 μg/kg; mid, 7.5 μg/kg and high 75 μg/kg) were given by systemic injection in four groups, and saline and two dosages (low and mild) were delivered by local injection to the distraction gap in the remaining three groups. The injections were performed five times weekly during the period of distraction.

After nine weeks the animals were killed and image analysis and mechanical testing were performed on the distracted right tibiae and the left tibiae which served as a control group. The local low-dose alendronate group showed a mean increase in bone mineral density of 124.3 mg/cm3 over the local saline group (analysis of variance, p < 0.05) without any adverse effect on the left control tibiae.

The findings indicate that the administration of local low-dose alendronate could be an effective pharmacological means of improving bone formation in distraction osteogenesis.

Alveolar bone loss and aging: a model for the study in mice

BACKGROUND

Several animal studies have shown a positive correlation between aging and alveolar bone loss (ABL). The purpose of this study was to develop a model for the study of ABL in mice and aging.

METHODS

Mucoperiosteal flap surgery (MFS) was performed on the buccal aspect of the left side of the mandible (BL) in 72 CF(1) Mus domesticus mice and divided into three groups as follows: males, breeding (non-virgin) females, and virgin females. The MFS was performed in 3-, 6-, 9-, and 12-month-old animals under anesthesia. The buccal aspects of right hemimandibles were used as controls (BR). Animals were sacrificed under anesthesia 21 days after surgery. Mandibles were removed, defleshed, stained with toluidine blue, and photographed in a microscope. The photographs were digitized, and ABL was measured as the exposed root surface area (mm(2)). Blinded measurements were performed using a computer-assisted image analysis system.

RESULTS

In terms of alveolar bone loss, the BL (operated) area showed a significant difference (paired Student t test; P <0.001) when compared to the BR area in all three groups. Sex and breeding differences were not observed in this experiment. ABL in the left hemimandibles was significantly larger in 3- (mean: 0.70; 95% confidence interval [CI]: 0.59 to 0.80) and 12-month-old animals (mean: 0.58; 95% CI: 0.46 to 0.71) than in 6- (mean: 0.39; 95% CI: 0.33 to 0.46) and 9-month-old animals (mean: 0.42; 95% CI: 0.35 to 0.48); P <0.001.

CONCLUSION

The results suggest that 3-month-old CF(1) mice, in a sex and breeding independent process, could be a useful model for provoked alveolar bone loss studies in aging.

Topical, single dose bisphosphonate treatment reduced bone resorption in a rat model for prosthetic loosening

Fluid pressure, instability or particles have been suggested to cause peri-prosthetic bone resorption. High intracapsular pressures have been reported in hip joints with loose prosthetic components, and oscillating fluid pressure has been shown to cause dramatic bone resorption in animal models. Resorption can be reduced by systemic bisphosphonate treatment in rat models with oscillating fluid pressure, but this has required higher doses than needed to inhibit normal remodelling. Bisphosphonates have high affinity to bone mineral. Topical application of the drug is therefore feasible. We used a previously described rat model where oscillating fluid pressure causes bone resorption. Before pressurization, a 1 mg/ml solution of alendronate was applied onto the bone surface for 1 min, after which excess bisphosphonate was rinsed away. Bone resorption was measured on histological slides as soft tissue area at the interface. Rats treated with topical alendronate had soft tissue areas reduced by half. Topical bisphosphonate treatment before cementing a joint implant could possibly reduce the risk of later loosening.

Strain relaxation of fibroblasts in the marginal periodontium is the common trigger for alveolar bone resorption: a novel hypothesis

In summary, the present commentary proposes a hypothesis that alveolar bone remodeling and bone loss in periodontitis, periodontal surgery, and in orthodontic tooth movement is triggered by a common "strain relaxation" signaling pathway of gingival and periodontal fibroblasts. The abrupt splitting, degradation, or relaxation of collagen fibers in the marginal periodontium produces a "strain relaxation" signal in the local fibroblasts which reside on these fibers, activating an ECM-integrin-cytoskeleton pathway. A cascade of cellular reactions which lead to osteoclastic bone resorption starting on the inner aspect (periodontal) of the alveolar bone then persists. A novel therapeutic approach is suggested here by using locally delivered drugs intervening in the cell contractile apparatus.

Pharmacokinetic and pharmacodynamic evaluation of intermittent versus continuous alendronate administration in rats

We studied the differences in pharmacokinetics and pharmacodynamics of the same dose of alendronate administered subcutaneously as intermittent bolus injection or continuous infusion in rats. Two rat models of bone disease were applied. Bone cancer was produced by intratibial inoculation of Walker carcinosarcoma cells, and a model of augmented bone resorption was produced by vitamin D(3) treatment of rats that had undergone thyroidparathyroidectomy. Higher amounts of alendronate were found in bones and in internal organs after bolus drug administration as compared with continuous infusion. Drug effects on plasma calcium levels and on urine calcium excretion were similar in both modes of alendronate administration. Results of the study indicate that the pharmacokinetics (disposition) of alendronate is administration-dependent. The total amount found in bone does not directly represent the amount of alendronate that is pharmacologically active at the site of action in the bone and that affects bone remodeling. The findings suggest that there is no pharmacodynamic advantage for continuous infusion of alendronate. It is concluded that the preferred mode of administration should be selected according to secondary clinical criteria (like incidence of adverse effects and convenience of administration).

The effect of topical delivery of novel bisacylphosphonates in reducing alveolar bone loss in the rat model

BACKGROUND

Periodontal surgery stimulates osteoclast activity, leading to varying amounts of alveolar crest loss. We have established that topical application of 20 mg/ml of alendronate placed at the surgical mucoperiosteal site produced a striking reduction of alveolar bone loss in the rat model. The aim of this investigation was to examine the antiresorptive efficacy of 3 novel bisacylphosphonates topically delivered at the surgical site, in comparison to alendronate and etidronate which are in clinical use.

METHODS

Mucoperiosteal flap (MF) surgery was performed on the buccal and lingual aspects next to molars on both sides of the rat mandible. A gelatin sponge soaked in the bisphosphonate solution prepared by dissolving 20 mg of the bisphosphonate (alendronate, etidronate, VS-5, VS-6, ISA-13, SuBP) in 1 ml of saline was applied to exposed bone on the right side of the mandible (experimental, MF + BPs ) and the left side was treated with saline only (control, MF + S). Sections were evaluated for bone loss using microradiography pattern and amount.

RESULTS

The 3 novel bisacylphosphonates, VS-5 VS-6, and ISA-13 were more effective than etidronate, and less effective than alendronate. The most effective among this group was ISA-13 followed by VS-5 and VS-6.

CONCLUSION

We conclude that ISA-13-like alendronate is effective in reducing alveolar bone loss when delivered at surgical sites. Since ISA-13 is well absorbed through mucose tissues, we suggest that ISA-13 efficacy on reducing bone loss should be tested by its application on the mucosal tissue.

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.