Bone mineral density in mandibles of ovariectomized rabbits

Effects of the Application Local Zoledronic Acid On Different Dental Implants in Rats On Osseointegration

Objective

Recently, a lot of research has been done around the world to popularize the osseointegration of dental implants. In this study, it was investigated the effect of local zoledronic acid application on implants with machined (MAC), resorbable blast materials (RBM), sandblasted and acid-etched (SLA) surface implants integrated in rat tibias.

Methodology

A total of 60 female Wistar rats weighing between 270 and 300 g were used in the study. The rats were passing divided into six classes: controls; MAC (n = 10), RBM (n = 10), SLA (n = 10), and local zoledronic acid (LZA) applied groups; LZA-MAC (n = 10), LZA-RBM (n=10) and LZA-SLA (n = 10) and implants were surgically placement into rat tibias in general anesthesia. After a four-week experimental period, the biomechanical bone implant connection level was determined with reverse torque analysis.

Results

Osseointegration levels were detected highly in SLA and RBM surface compared with the machined surfaced implants in both control and treatment groups (p < 0.05). Additionally, local application of zoledronic acid in both three groups; implants increased the biomechanic osseointegration level compared with the controls (p < 0.05).

Conclusion

In this research, we observe that the local application of the zoledronic acid could increase the osseointegration, and RBM and SLA surface could be better than machined surfaced implants in terms of bone implant connection. In addition, local application of zoledronic acid may be a safer method than systemic application.

Effects of a single intravaneous dose of zoledronic acid on bone healing following tooth extraction in ovariectomized rabbits

Objective

The present study is aimed to investigate the effects of administering a single intravenous dose of zoledronic acid (ZA) on bone healing following tooth extraction in ovariectomized rabbits.

Materials and methods

Female, New Zealand rabbits were randomly divided into three groups including Control, ovariectomy + saline (OVX) and ovariectomy + zoledronic acid group (ZOL). Bilateral ovariectomy was performed to the rabbits in OVX and ZOL groups under general anesthesia. Control group underwent sham surgery. Eight weeks later, mandibular right incisors of all animals were extracted under general anesthesia. Before the procedure, Control and OVX groups were given saline and 0.1 mg/kg ZA was administered to ZOL group intravenously. All animals were sacrificed after 12 weeks.

Results

The findings of histopathological and biochemical evaluations reflected insignificant differences among study groups in vascular endothelial growth factor (VEGF), increases in osteoclasts, ossification, vascularization and mononuclear cell infiltration measures (p > 0.05). In contrast, bone morphogenic protein 2 (BMP-2), tumor necrosis factor alpha (TNF-α) and organization of the extraction wound differed significantly between groups (p < 0.05)

Conclusion

The potential beneficial effects of ZA administration on the wound healing process following tooth extraction were demonstrated via serum TNF-α, BMP-2 and VEGF levels in an osteoporotic model in ovariectomized rabbits.

Age-related changes in size, bone microarchitecture and volumetric bone mineral density of the mandible in the harbor seal (Phoca vitulina)

Detailed knowledge of age-related changes in the structure and mineralization of bones is important for interpreting osseous changes in wild mammals caused by exposure to environmental contaminants. This study analyzed mandibular size, microarchitecture and volumetric bone mineral density (vBMD) in harbor seals (n = 93, age range 0.5 months to 25 years) from the German North Sea. Bone microarchitecture and vBMD were assessed using high-resolution peripheral quantitative computed tomography (HR-pQCT). Significant differences were observed between the analyzed age classes (i) young juveniles (0.5–10 months), (ii) yearlings (12–23 months), and (iii) adults (12–25 years) for several of the variables, indicating an overall increase in cortical and trabecular area, cortical thickness and total and cortical vBMD with age. Furthermore, for juvenile animals (≤ 23 months), significant positive correlations with age were observed for mandible length and perimeter, cortical area, cortical thickness, trabecular separation, and total and cortical vBMD. The findings demonstrate a rapid increase in overall size, cortical dimensions and the degree of mineralization of the harbor seal mandible during the first two years after birth. Negative correlations with age existed for trabecular number and thickness as well as for trabecular bone volume fraction in the juveniles. The findings suggest a reduction in trabecular bone volume fraction with age, due to the bone trabeculae becoming thinner, less numerous and more widely spaced. Given the strong age dependence of most analyzed parameters, it is recommended to standardize samples with respect to age in future studies comparing microarchitecture and mineralization of harbor seal mandibles from different populations or different collection periods.

Rabbit as model for osteoporosis research

Osteoporosis is a major public health problem affecting more than 200 million people worldwide. The use of different animal models, for the study of its pathophysiology and treatments, is important being actually the ovariectomized rat the most widely used; although this model has several problems due its small size, lack of true closure of epiphyseal plate and bone differences with humans. This review is aimed at summarizing the most common methods published for osteoporosis induction in rabbits as model for human disease with their advantages and disadvantages. The paper shows the advantages of the use of this specie compared with the rat. All the techniques seemed to achieve the osteoporotic condition, but the one which obtained the most consistent bone mineral reduction in less time was the combination of surgery and corticoid treatment. The conclusion of the review was that rabbits are promising as a model of osteoporosis research because of their size, haversian remodelling and closure of epiphyseal plate, which solve some of the problems of the rat model. There are different techniques in the literature used to achieve the osteoporotic condition with diverse results, but there is a lack of consensus as to the best one.

Impaired osseointegration of dental implants associated with orthognathic surgery: Possible regional acceleratory phenomenon

BACKGROUND

Regional acceleratory phenomenon (RAP) is demonstrated to decrease regional bone mineral density and accelerate bone turnover. Hypothesizing that RAP can negatively affect the osseointegration of biomaterials, this study aimed to investigate the possible influence of the RAP on dental implant osseointegration.

MATERIALS AND METHODS

Orthognathic surgery, one of the major surgeries on oral and maxillofacial region was set as intervention for RAP. Considering that RAP exerts its physiologic effects until 4 months after noxious stimuli, patients were classified according to the time interval between orthognathic surgery and dental implant installation; group I was designated to patients who had implant installation within 4 months from orthognathic surgery. Group II were those with installation after 4-12 months and group III was longer than 12 months. Radiographic and clinical evaluations of dental implants including peri-implant marginal bone changes (MBR), implant stability, cumulative survival rates were analyzed.

RESULTS

A total of 54 patients with 106 implants (mean follow-up of 72.6 months) were included in the study. MBR was significantly higher in group I (2.62 ± 0.91 mm) and II (2.25 ± 0.95 mm) compared to that of group III (0.94 ± 0.90 mm) at last follow up (P < 0.05) and this group difference over time was also significant (P < 0.001). Compared to group III, groups I and II exhibited lower ISQ values and higher biological complications including peri-implantitis and peri-implant gingivitis (P < 0.05). Group I showed significantly low-cumulative survival rate (89.2%; implant-level) compared to groups II and III.

CONCLUSIONS

In this study, impaired osseointegration of dental implants was demonstrated associated with orthognathic surgery. Micro-environmental changes of hard tissue induced by major surgery on the jaw showed deteriorating effects on integrity of biomaterial osseointegration. Special considerations should be addressed for ideal treatment results and prognosis.

Orthognathic surgery Deteriorates the osseointegration of dental implants: A propensity-matched multicentre cohort study

This study aimed to investigate the possible influence of the regional acceleratory phenomenon (RAP) on dental implant osseointegration. Orthognathic surgery was set as an intervention for RAP, and a multicentre cohort study of two groups was undertaken. Group O included patients with single implant placement at least 4 months after orthognathic surgery and functional loading for more than 1 year, while controls (Group C) were without any major surgery. Clinical and radiographic assessments of implants, including changes in marginal bone levels, were analysed at baseline, 6- and 12-month follow-up. Bivariate analysis of two groups with propensity score matching was performed. After propensity score matching, all 10 confounding variables had acceptable standardised difference scores (<20%), indicating that the matching procedure had efficiently balanced the two groups. Following the propensity score adjustment, the marginal bone loss was significantly higher in Group O than the control at 6 months (1.66 ± 1.05 mm vs 0.59 ± 0.64 mm, P < 0.001) and 12 months (2.30 ± 1.27 mm vs 0.82 ± 0.78 mm, P < 0.001). Compared to Group C, subjects in Group O had a higher incidence of peri-implant mucositis and implantitis (11.8% vs 1.5%, P = 0.033). Impaired osseointegration of dental implants was associated with orthognathic surgery. Special considerations for peri-implant soft and hard tissue stability should be addressed to obtain ideal treatment results and prognosis for patients who have had prior orthognathic surgery.

Effect of Bone Mineral Density on Rotator Cuff Tear: An Osteoporotic Rabbit Model

Introduction

An increased bone mineral density (BMD) in the proximity to tendon insertion can improve rotator cuff repair and healing. However, how a decrease of BMD in the humeral head affects the biomechanical properties of the rotator cuff tendon is still unclear. Previous studies have demonstrated ovariectomy in animals to lead to osteoporosis and decreased BMD, and Teriparatide (PTH) administration to improve BMD and strength of bone. This study aimed to explore the correlation between humeral head BMD and infraspinatus (ISP) tendon insertion strength, and if an increase in bone quantity of the humeral head can improve the strength of the rotator cuff.

Materials and Methods

Eighteen New England white rabbits were divided into the 3 groups: Control, Ovariectomy-Saline (OVX-Saline), and Ovariectomy-PTH (OVX-PTH). The OVX-Saline group and the OVX-PTH were administered daily saline and Teriparatide injections for 8 weeks starting at 17 weeks of OVX. BMD of the humeral head was measured, the ISP tendon failure load was tested and the failure stress was calculated. One specimen from each group was used for histological analysis. Linear regression analysis was used to derive equations for the BMD and failure stress.

Results

Significant differences were observed in the measured humeral head BMD of the Control and OVX-PTH groups compared to the OVX-Saline group (P = 0.0004 and P = 0.0024, respectively). No significant difference was found in failure stress among the three groups, but an expected trend with the control group and OVX-PTH group presenting higher failure strength compared to the OVX-Saline group. BMD at the humeral head showed a positive linear correlation with stress (r² = 0.54). Histology results showed the superiority in OVX-PTH group ISP enthesis compared to the OVX-Saline group.

Conclusion

Bone loss of the humeral head leads to decreased tendon/bone insertion strength of the infraspinatus tendon enthesis. Teriparatide administration can increase bone density of the humeral head and may improve the mechanical properties of the infraspinatus tendon enthesis.

Effects of OsteoKing on osteoporotic rabbits

Heng-Gu-Gu-Shang-Yu-He-Ji, also known as OsteoKing, is used as a herbal Traditional Chinese Medicine for the treatment of bone disease, including femoral head necrosis and osteoarthritis. However, whether OsteoKing has anti-osteoporotic properties has remained to be elucidated. The purpose of the present study was therefore to investigate the effects of OsteoKing on ovariectomy-induced osteoporosis in rabbits. Female New Zealand white rabbits were randomly divided into an ovariectomized (OVX) group and a sham-surgery group. The rabbits in the OVX group were subjected to an ovariectomy, while the rabbits in the sham group were subjected to the removal of an area of fat near the two ovaries. Bone mineral density, mechanical properties, serum biochemical parameters and micro-architecture were examined at 150 days post-OVX to characterize the experimental animal model. Once the osteoporotic rabbit model had been established, the rabbits in the OVX group were divided into the following groups: Model group, nilestriol group and 300 and 600 mg/kg OsteoKing groups, containing 16 rabbits in each group. OsteoKing and nilestriol were administered orally. The bone mineral density, mechanical properties, serum biochemical parameters, histology and micro-architecture were examined using dual-energy X-ray absorptiometric analysis, mechanical assessments, enzyme-linked immunosorbent assays, histopathological evaluation and micro-computerized tomography examination following 60 days and 120 days of treatment, respectively. Treatment with OsteoKing led to an elevation in the bone mineral density of the vertebra and serum phosphorus levels, reduced serum concentrations of osteocalcin, procollagen type I N-terminal peptide, tartrate-resistant acid phosphatase 5b and cross-linked N-telopeptide of type I collagen, improved mechanical properties (maximum load, stiffness and energy absorption capacity), and micro-architecture of the lumbar vertebra in the OVX osteoporotic rabbit model following treatment for 120 days. In conclusion, it was demonstrated that OsteoKing is effective in the prevention of estrogen deficiency-associated bone loss and may be a promising drug for the treatment of post-menopausal osteoporosis.

Zinc enhances bone metabolism in ovariectomized rats and exerts anabolic osteoblastic/adipocytic marrow effects ex vivo

Investigations of bone mass and marrow adiposity are critical for defining the role of zinc (Zn) in bone metabolism. Rats used for study were grouped as follows: control (sham), ovariectomy (OVX), ovariectomy + estradiol (OVX-E), ovariectomy + Zn treatment (OVX-Zn). Bone mineral density (BMD) was quantified (microCT); serum osteocalcin, adiponectin, RANKL, and TRAP levels were assayed (ELISA); and biochemical determinations of serum alkaline phosphatase (ALP), calcium (Ca), and phosphorus (P) were done. Cells derived from bone mesenchymal stem cell (BMSC) isolates of respective test groups were compared, identifying primary osteoblasts by MTT assay and adipocytes by Oil Red O stain. Osteocalcin and adiponectin levels in culture supernatants were determined by ELISA. Zn supplementation resulted in a modest increase in BMD, but serum osteocalcin and ALP activity increased significantly (P < 0.01, both). Serum levels of RANKL and TRAP were lower in OVX-Zn (vs OVX) rats (P < 0.01), whereas serum concentrations of adiponectin, Ca, and P did not differ by group. Osteocalcin level was significantly upregulated ex vivo (P < 0.01) in the supernatant of cultured OVX-Zn (vs OVX) cells, accompanied by a slight upturn in osteoblastic differentiation. However, Oil Red O uptake and adiponectin level in supernatant were sharply diminished in cultured OVX-Zn (vs OVX) cells (P < 0.01). Overall, we concluded that Zn contributes to bone mass by marginally stimulating differentiation and proliferation of osteoblasts and by effectively inhibiting osteoclastic and adipocytic differentiation of BMSCs.

Bone Healing in Ovariectomized-rabbit Calvarial Defect with Tricalcium Phosphate Coated with Recombinant Human Bone Morphogenetic Protein-2 Genetically Engineered in Escherichia coli

Purpose:

This study compares the bone formation ability of tricalcium phosphate (TCP) with and without recombinant human bone morphogenetic protein-2 (rhBMP-2) and assesses TCP as a carrier of rhBMP-2.

Methods:

Bilateral round defects (diameter: 8.0 mm) were formed in the cranium of eight New Zealand white rabbits. The defects were grafted with TCP only (control group) or with rhBMP-2-coated TCP (experimental group). The animals were sacrificed at 1st week, 2nd week, 4th week, and 8th week postoperatively; two rabbits sacrificed each time. The skulls were harvested and subjected to radiographic and histological examination.

Results:

Radiologic evaluation showed faster bone remodeling in the experimental group than in the control group. Histologic evaluation (H&E, Masson’s trichrome stain) showed rapid bone formation, remodeling and calcification in the 1st and 2nd week in the experimental group. Immunohistochemical evaluation showed higher expression rate of osteoprotegerin, receptor activator of nuclear factor κB ligand, and receptor activator of nuclear factor κB in the experimental group at the 1st and 2nd week than in the control group.

Conclusion:

rhBMP-2 coated TCP resulted in rapid bone formation, remodeling, and calcification due to rhBMP-2’s osteogenic effect. TCP performed properly as a carrier for rhBMP-2. Thus, the use of an rhBMP-2 coating on TCP had a synergic effect on bone healing and, especially, bone remodeling and maturation.

Osteogenic effects of dedifferentiated fat cell transplantation in rabbit models of bone defect and ovariectomy-induced osteoporosis

We have previously reported that mature adipocyte-derived dedifferentiated fat (DFAT) cells have a high proliferative activity and the potential to differentiate into lineages of mesenchymal tissue similar to bone marrow mesenchymal stem cells (MSCs). In the present study, we examined the effects of autologous DFAT cell transplantation on bone regeneration in a rabbit bone defect model and an ovariectomy (OVX)-induced osteoporosis model. The formation of tissue-engineered bone (TEB) was observed when rabbit DFAT cells were loaded onto a β-tricalcium phosphate (TCP)/collagen sponge and cultured in an osteogenic differentiation medium for 3 weeks. Autologous implantation of DFAT cell-mediated TEB constructs promoted bone regeneration in a rabbit tibial defect model. Regenerated bone tissue induced by transplantation of DFAT cell-mediated TEB constructs was histologically well differentiated and exhibited higher bone strength in a three-point bending test compared to that induced by the β-TCP/collagen sponge alone. In OVX-induced osteoporosis model rabbits, DFAT cells were obtained with the osteogenic activity similar to cells from healthy rabbits. Intrabone marrow injection of autologous DFAT cells significantly increased the bone mineral density (BMD) at the injected site in the OVX rabbits. Transplanted DFAT cells remained mainly on the injection side of the bone marrow by at least 28 days after intrabone marrow injection and a part of them expressed osteocalcin. In conclusion, these results demonstrate that autologous implantation of DFAT cells contributed to bone regeneration in a rabbit bone defect model and an OVX-induced osteoporosis model. DFAT cells may be an attractive cell source for cell-based bone tissue engineering to treat nonunion fractures in all patients, including those with osteoporosis.

The improved biological performance of a novel low elastic modulus implant

BACKGROUND

The mismatch of the elastic modulus between implants and bone tissue can lead to stress shielding, bone resorption and poor osseointegration. Compared with normal bone tissue, this problem is much more serious in osteoporosis. The purpose of this study was designed to find out whether the novel Ti-24Nb-4Zr-7.9Sn (TNZS) implant with low elastic modulus and high strength was suitable for biomedical material, especially in osteoporosis.

METHODOLOGY

In vitro study, the viability and Alkaline phosphatase (ALP) activity of osteoblasts on the TNZS and Ti-6V-4V (TAV) were observed. In vivo study, 30 adult female New Zealand rabbits were selected and divided randomly into two groups: sham-operation (SHAM, n=6) and ovariectomised in combination with methylprednisolone treatment (OVX+MP, n=24). Two implants were then placed in the tibia of each OVX + MP group rabbit, one in each side (left: TAV; right: TNZS). The OVX + MP group rabbits were sacrificed at 4 and 12 weeks after the implantation. The osteoporotic bone responses to the TNZS and TAV implants were evaluated by pull-out test, Micro-CT analyses and histological observation.

PRINCIPAL FINDINGS

Compared with the TAV group, the TNZS group showed a significant increase (P<0.05) in cell viability and ALP activity, new bone formation and pull-out force.

CONCLUSIONS

The novel TNZS implants show good biological performance both in vitro and in vivo, which suggests that the alloys are suitable for biomedical applications, especially in osteoporosis.

Effects of glucocorticoid on BMD, micro-architecture and biomechanics of cancellous and cortical bone mass in OVX rabbits

The incidence of osteoporosis continues to increase with progressively aging populations. The purpose of this study was to detect the effects of glucocorticoid (GC) treatment on bone mineral density (BMD), biomechanical strength and micro-architecture in cancellous and cortical bone in ovariectomized (OVX) rabbits. Twenty adult female New Zealand white rabbits were randomly divided into three groups. The OVX-GC group (n=8) received a bilateral ovariectomy first and then daily GC treatment (methylprednisolone sodium succinate, 1mg/kg/day) for 4 weeks beginning 2 weeks after ovariectomy treatment. The OVX group (n=4) received a bilateral ovariectomy without GC treatment. The sham group (n=8) only received the sham operation. BMD was determined prior to and 6 weeks after the operation in the spine. Six weeks after the operation, the animals were sacrificed, and cancellous bone specimens were harvested from the femoral condyle and lumbar vertebrae. Cortical bone specimens were obtained from the femoral midshaft. The femoral specimens were scanned for apparent BMD. All specimens were tested mechanically and analyzed by microcompute tomography (micro-CT). In cancellous bone, GC treatment resulted in significant decreases in BMD, bone biomechanical strength and micro-architecture parameters in lumbar vertebrae. Similar trends in BMD and micro-architectural changes were also observed in the femoral condyle in the OVX-GC group compared with the sham group. However, there was no significant decline in any parameter in either lumbar vertebrae or femoral condyle in the OVX group. Similarly, no significant difference was found in any parameter in cortical bone among the three groups. Thus, the 4-week GC treatment in OVX rabbits could result in a significant bone loss in cancellous bone but not in cortical bone. This model is comparable to the osteoporosis-related changes in humans. OVX alone was not sufficient to induce osteoporosis.

Effect of zoledronic acid on osseointegration of titanium implants: an experimental study in an ovariectomized rabbit model

PURPOSE

Zoledronic acid (ZA), a new-generation intravenous bisphosphonate, exhibits the greatest affinity for bone mineral with the longest retention, thereby leading to its ability to be dosed at annual intervals in the treatment of osteoporosis. The purpose of this preliminary study was to evaluate the effects of systemic administration of a single dose of ZA on osseointegration and bone healing around titanium dental implants.

MATERIALS AND METHODS

Thirty-six female New Zealand rabbits (aged 6-12 months) were used in this study. Rabbits were randomly assigned to 1 of 3 groups: sham control group (SH), ovariectomy group (OVX), and OVX and ZA group (OVX + ZA). Animals in the OVX and OVX + ZA groups were subjected to bilateral ovariectomy, whereas animals in the SH group were sham operated. Eight weeks later, 1 implant was placed in each tibia of the animals. ZA was administered in the OVX + ZA group during the implantation, whereas the OVX and SH groups received saline solution infusions. All of the subjects were sacrificed 8 weeks after the implantation, and tibial specimens were harvested. Histomorphometric bone-to-implant contact analysis, resonance frequency analysis, removal torque testing, and digital radiographic absorptiometry were administered, and the data were statistically analyzed.

RESULTS

Histomorphometric, resonance frequency, and radiodensitometric analyses showed significant improvement in osseointegration of implants in the OVX + ZA group compared with the OVX group. However, the differences in removal torque results between the groups were not statistically significant.

CONCLUSIONS

The results of this study suggest that systemic ZA administration may improve osseointegration of titanium implants placed in estrogen-deficient states of bone.

Osteoprotegerin and ligand of receptor activator of nuclear factor kappaB expression in ovariectomized rats during tooth movement

OBJECTIVE

To test the null hypothesis that increased tooth displacement in ovariectomized rats is not related to differential expressions of OPG and RANKL in the periodontium.

MATERIALS AND METHODS

Eighty-four 12-week female rats were used; half were ovariectomized and half were not. Three months later, the maxillary first molar was moved mesially. Groups of rats were sacrificed at days 0, 1, 3, 5, 7, 10, and 14 after activation. Tooth movement was measured at each time point. OPG and RANKL expressions were examined through immunohistochemistry.

RESULTS

Ovariectomized and nonovariectomized rats showed three-phase tooth movement. In both groups, OPG expression increased at the tension area and RANKL increased at the pressure area. The OPG/RANKL ratio coincided with tooth movement, especially in the linear phase from 7 to 14 days.

CONCLUSIONS

The null hypothesis is rejected. The increased rate of tooth movement in ovariectomized rats was related to differential expressions of OPG and RANKL.

Characterization of a new experimental model of osteoporosis in rabbits

To characterize an experimental model of osteoporosis in rabbits induced either by ovariectomy (OVX), glucocorticoids, or by a combination of both. Thirty-five rabbits were randomly allocated into five groups: bilateral OVX, daily methylprednisolone hemisuccinate (MPH) injections at a 1.5 mg/kg/day dose for 4 consecutive weeks (MPH group), or variable dose of MPH between 0.5 and 2 mg/kg/day in combination with OVX (OVX + MPH at low, medium, and high dose). Twenty-two animals were killed 6 weeks after OVX, and 13 were killed 16 weeks later. Dual-energy X-ray absorptiometry was obtained at baseline and 6 and 16 weeks after OVX. High-resolution magnetic resonance imaging (MRI) was carried out at 0 and 6 weeks after OVX. Glucose, total cholesterol, triglyceride, and oestradiol blood levels before and 16 weeks after OVX were determined. Bone mineral density (BMD) decreased significantly at lumbar spine in MPH and OVX + MPH medium-dose groups, and at global knee and subchondral bone of the knee in MPH, OVX + MPH low- and medium-dosage groups (P < 0.05). BMD variations in OVX rabbits were not significant in any of the three anatomical locations analyzed. BMD variation 16 weeks after OVX was significant at lumbar spine and global knee in the OVX + MPH medium-dose group and only at global knee in the OVX + MPH low-dose group (P < 0.05). MRI did not show bone or cartilage changes. Osteoporosis can be induced experimentally in rabbits through isolated MPH or by a combination of OVX and medium dose corticosteroid for 4 weeks. OVX alone was not sufficient to induce osteoporosis.

A review of the association between osteoporosis and alveolar ridge augmentation

OBJECTIVE

Because of increasing life expectancy and popularity of dental implants, surgeons face a larger number of osteoporotic patients who require bone augmentation. Relationship between low bone density/osteoporosis and bone graft success is still not clear. The purpose of this article is to review and summarize the literature regarding the success of alveolar bone augmentation in osteoporosis.

STUDY DESIGN

The study design includes a literature review of relevant preclinical and clinical articles that address the association between osteoporosis and alveolar bone augmentation.

RESULTS

Increased rate of complications such as resorption of bone graft, non-integration of bone graft, delayed healing time, and implant failure in augmented bone especially in the maxilla may be associated with compromised bone health.

CONCLUSIONS

Despite the decreased success rate, osteoporosis is not an absolute contraindication for bone augmentation and dental implant placement. The modifiable risk factors for osteoporosis should be eliminated before surgery.

Oral implications of osteoporosis

OBJECTIVES

The association between osteoporosis and oral health remains a matter of controversy. It is important to confirm whether there is a role of osteoporosis in bone loss in the jaws, periodontal diseases, tooth loss, and other oral tissue changes. The objective of this article is to review and summarize the published literature on the associations between osteoporosis and various oral conditions such as bone loss in the jaws, periodontal diseases, and tooth loss.

METHODS

A search of the computerized database MEDLINE was conducted. Clinical information concerning systemic osteoporosis and animal studies reporting possible associations between osteoporosis and changes in the dental and oral tissues were included. The review focus was on studies involving (1) methods for assessing bone mineral density (BMD); (2) methods for assessing osteoporosis-related changes in intraoral sites; (3) associations between mandibular BMD and skeletal BMD; (4) changes in the jaws, periodontal tissues, and temporomandibular joint concurrent with osteoporosis; (5) changes in the oral tissues following estrogen deficiency; and (6) effects of estrogen-hormone replacement therapy and/or calcium and vitamin D on oral health.

RESULTS

Ninety-seven studies conducted in various parts of the world were identified. Evidence from prospective studies supports the contention that individuals with osteoporosis may be at increased risk for the manifestations of oral osteoporosis; however, such risk is not definitively proven. Studies suggest that findings on dental panoramic radiographs may be used to detect individuals with low BMD.

CONCLUSIONS

Further well-controlled studies are needed to better elucidate the inter-relationship between systemic and oral bone loss and to clarify whether dentists could usefully provide early warning for osteoporosis risk.

Bone mineral measurements of subchondral and trabecular bone in healthy and osteoporotic rabbits

INTRODUCTION

Experimental models of osteoporosis in rabbits are useful to investigate anabolic agents because this animal has a fast bone turnover with predominant remodelling over the modelling processes. For that purpose, it is necessary to characterize the densitometric values of each type of bony tissue.

OBJECTIVE

To determine areal bone mass measurement in the spine and in trabecular, cortical and subchondral bone of the knee in healthy and osteoporotic rabbits.

DESIGN

Bone mineral content and bone mineral density were measured in lumbar spine, global knee, and subchondral and cortical bone of the knee with dual energy X-ray absorptiometry using a Hologic QDR-1000/W densitometer in 29 skeletally mature female healthy New Zealand rabbits. Ten rabbits underwent triplicate scans for evaluation of the effect of repositioning. Osteoporosis was experimentally induced in 15 rabbits by bilateral ovariectomy and postoperative corticosteroid treatment for 4 weeks. Identical dual energy X-ray absorptiometry (DXA) studies were performed thereafter.

RESULTS

Mean values of bone mineral content at the lumbar spine, global knee, subchondral bone and cortical tibial metaphysis were: 1934+/-217 mg, 878+/-83 mg, 149+/-14 mg and 29+/-7.0 mg, respectively. The mean values of bone mineral density at the same regions were: 298+/-24 mg/cm(2), 455+/-32 mg/cm(2), 617+/-60 mg/cm(2) and 678+/-163 mg/cm(2), respectively. Bone mineral content and bone density of healthy rabbits followed a normal distribution at the four skeletal regions studied. Precision after triplicate repositioning yielded a coefficient of variation ranging from 2.6% to 3.8%. The least significant change ranged between 7.3% and 10.7%. Bone mineral density measured at the four different skeletal regions correlated significantly. Bone mineral density in osteoporotic rabbits was significantly lower in the four regions studied than that in controls, rendering a T-score of, respectively, -2.0+/-1.1 in the lumbar spine, -2.2+/-2.1 in the global knee, -1.9+/-0.6 in the subchondral bone, and -5.7+/-3.1 in the cortical tibia (P<0.05).

CONCLUSIONS

DXA is a reliable and precise method to evaluate the bone mass in rabbits. Our results also suggest that subchondral bone is a bone of mixed densitometric characteristics with marked cortical bone predominance.

The effect of ovariectomy on mandibular cortical thickness in the rat

OBJECTIVES

The purpose of this study was to investigate the effects of long-term oestrogen deficiency on mandibular cortical thickness in ovariectomized rats.

METHODS

Twelve female rats either underwent ovariectomy or received a sham-operation. One year later images of the left side of the mandible were made using a standardized radiographic protocol. Manual measurements were made of the lower mandibular cortical thickness at three locations. The mean cortical thickness was also assessed using a specially developed image analysis program by placing points at three positions, identical to those used for the manual measurements, and additionally at 20 points evenly distributed along the mandibular cortex.

RESULTS

The mean mandibular cortical thickness of the ovariectomized mandibles was significantly less than that of the sham-operated rats, measured using the computer image analysis (p=0.016, 95% CI=0.125, 0.016) and measured manually (p=0.011, 95% CI=0.0218, 0.1309). When 20 computational points were used, the mean mandibular cortical width of the ovariectomized rats was significantly less than that for the control rats (p=0.016, 95% CI=0.127, 0.018).

CONCLUSIONS AND CLINICAL IMPLICATIONS

Long-term oestrogen deficiency in ovariectomized rats decreased the mandibular cortical thickness. If our result is applicable to human studies, a considerable duration of oestrogen deficiency may be necessary before a reduction of mandibular cortical bone loss can be observed. Because mandibular cortical bone is resistant to resorption, the value of clinically determined mandibular cortical thickness measurements as a method of detecting patients at risk of osteoporosis may have a reduced importance in younger postmenopausal patients.

Effects on bone formation in ovariectomized rats after implantation of tooth ash and plaster of Paris mixture

PURPOSE

Our goal was to report on tooth ash and plaster of Paris mixture in bone defects in an ovariectomized rat osteoporosis model.

MATERIALS AND METHODS

Sixty rats were randomly assigned to 4 groups and each group was further divided into 3 subgroups: 4, 8, and 16 weeks after implantation. The defect was filled with different grafting conditions as follows: group 1, ovariectomy and nongraft group; group 2, ovariectomy and tooth ash-plaster graft group; group 3, nonovariectomy and nongraft group; and group 4, nonovariectomy and tooth ash-plaster graft group. Histologic sections and histomorphometric analysis of defects were obtained 4, 8, and 16 weeks after surgery.

RESULTS

For the 4-week ovariectomy group, there was significantly greater bone formation in tooth ash-plaster group compared with the nongraft group. In the nonovariectomy group, the tooth ash-plaster group also showed better bone formation than the nongraft group. However, there was no statistical significance. In both the ovariectomy and nonovariectomy groups, a significant increase in bone formation was observed according to the elapse of time. The nonovariectomy group showed increased new bone formation compared with the ovariectomy group, with the tooth ash-plaster group showing statistical significance in each subgroup (P =.048).

CONCLUSIONS

Ovariectomy acts as a negative factor in new bone formation. For a critical size bony defect, the tooth ash-plaster treatment of the osseous defect produces more stable, effective, and rapid new bone formation.

Bone formation after implantation of autolysed antigen extracted allogeneic bone in ovariectomized rabbits

This study was undertaken to evaluate the bone formation response to AAA bone in healthy and oestrogen deficient animals. Seventeen young healthy New Zealand female rabbits were used. Nine rabbits were subjected to ovariectomy and the remaining eight were sham-operated. Four weeks after ovariectomy standardized round cavities, 5mm in diameter, were made medially in the cortical part of each proximal tibia. To half of the cavities autolysed antigen-extracted allogeneic AAA bone granules were added. After another 8 weeks the animals were sacrificed and sections of the tibial experimental areas were obtained. These were studied in light microscopy and the bone and non-bone areas were measured with computer support. The study showed that the addition of a bone inductive substance such as AAA bone enhances bone formation also in oestrogen deficient animals.