Comparison of nonrandomized trials with slow-release sodium fluoride with a randomized placebo-controlled trial in postmenopausal osteoporosis

Pathophysiology of Demineralization, Part I: Attrition, Erosion, Abfraction, and Noncarious Cervical Lesions

PURPOSE OF THE REVIEW

Compare pathophysiology for infectious and noninfectious demineralization disease relative to mineral maintenance, physiologic fluoride levels, and mechanical degradation.

RECENT FINDINGS

Environmental acidity, biomechanics, and intercrystalline percolation of endemic fluoride regulate resistance to demineralization relative to osteopenia, noncarious cervical lesions, and dental caries. Demineralization is the most prevalent chronic disease in the world: osteoporosis (OP) >10%, dental caries ~100%. OP is severely debilitating while caries is potentially fatal. Mineralized tissues have a common physiology: cell-mediated apposition, protein matrix, fluid logistics (blood, saliva), intercrystalline ion percolation, cyclic demineralization/remineralization, and acid-based degradation (microbes, clastic cells). Etiology of demineralization involves fluid percolation, metabolism, homeostasis, biomechanics, mechanical wear (attrition or abrasion), and biofilm-related infections. Bone mineral density measurement assesses skeletal mass. Attrition, abrasion, erosion, and abfraction are diagnosed visually, but invisible subsurface caries <400μm cannot be detected. Controlling demineralization at all levels is an important horizon for cost-effective wellness worldwide.

Synthesis Bone Mineral (SBM) for Osteoporosis Therapy: Part 1 - Prevention of Bone Loss from Mineral Deficiency

Osteoporosis is a ‘silent’ disease characterized by thinning cortical bone and disorganized trabecular architecture causing bone fragility leading to fracture. Osteoporosis results when the rate of bone resorption far exceeds the rate of bone formation. Current pharmaceutical interventions (estrogen therapy, bisphosphonate-based drugs) focus on inhibiting bone resorption. However, some of these therapies have serious side effects (e.g., cancer risk from estrogen therapy; osteonecrosis of the jaw and delayed fracture healing from bisphosphonate-based drugs). The long term objective of the study was to develop a novel material for potential osteoporosis therapy, prevention and fracture repair. This novel material MZF-CaP or synthetic bone mineral, SBM) incorporates Mg, Zn and F ions in a calcium phosphate matrix. Separately, magnesium (Mg), zinc (Zn) and fluoride (F) ions have been associated with biomineralization and osteoporosis therapy in human and in animals. MZF-CaP or SBM was prepared by a modified hydrolysis method previously described and characterized using x-ray diffraction, FT-IR spectroscopy, inductive coupled plasma and dissolution in acidic buffer. Separately, male and female Sprague-Dawley rats were randomly assigned to the following groups depending on the diet: GA: normal on basic diets; GB: on mineral deficient diets (md); GC: on md + Mg-CaP; GD: on md + Zn-CaP; GE: md+F-CaP; and GF: md+MZF-CaP. The rats were sacrificed after 3 months and the femur bones separated, cleaned of extraneous soft tissues and stored until needed for analyses. Femur bones were analyzed using microradiography (Faxitron), scanning electron microscopy (SEM) and microCT. Results: SEM, Faxitron and microCT analyses showed thinning of cortical bone and disorganized trabecular bone architecture for osteoporotic rats on mineral deficient diet (GB) and prevention of bone loss in rats receiving the supplemented diets (GC,GD,GE,GF). Conclusion: These results indicate that the novel material, MZF-CaP or SBM had a potential for osteoporosis therapy and prevention. Studies to demonstrate the use of SBM in reversing (recovering) bone loss are in progress.

Water fluoridation, osteoporosis, fractures--recent developments

BACKGROUND

Optimal (1ppm) water fluoridation is seen as the most socially equitable way to prevent dental caries, however concerns about the safety of fluoridation are periodically raised.

METHODS

Research on effects on bone published since the 1991 National Health and Medical Research Council report on water fluoridation was reviewed.

RESULTS

Thirty-three studies were identified. Adverse effects in animal feeding studies were only seen at doses much greater than those currently used in artificial water fluoridation. The majority of animal studies showed no effect or a beneficial effect of low fluoride doses. The results of ecological studies were conflicting. One of the two cohort studies showed an increase in fracture incidence at fluoride levels four times greater than optimal water fluoridation and the other showed no effect after 20 years' optimal fluoridation. The cross-sectional studies showed a favourable effect on bone mineral density. The clinical trials predominantly showed increased bone density in several sites associated with fluoride treatment of 9-22.6mg fluoride per day for one-four years.

CONCLUSION

These studies provide a substantial body of evidence that fluoride at up to 1ppm does not have an adverse effect on bone strength, bone mineral density or fracture incidence.

Comparative safety of bone remodeling agents with a focus on osteoporosis therapies

This article reviews the different treatments currently available for osteoporosis and examines the benefits and adverse events that are associated with each. While emphasizing safety considerations, this review summarizes the following treatments for osteoporosis: calcium supplements, fluoride, hormone replacement therapy, raloxifene, bisphosphonates, salmon calcitonin, and calcitriol. Before prescribing any of these agents, the clinician should review the risk/benefit profile of each drug in the context of the individual patient's history, concomitant diseases, concurrent medications, and general physical condition.

Cyclical etidronate versus sodium fluoride in established postmenopausal osteoporosis: a randomized 3 year trial

To compare the effects of sodium fluoride and etidronate in severe postmenopausal osteoporosis, we conducted a 3 year, prospective, trial in 118 postmenopausal osteoporotic women with at least one vertebral fracture, who were randomly assigned to receive sodium fluoride (25 mg twice daily, as enteric-coated tablets) plus calcium (1000 mg/day) or intermittent etidronate (400 mg/day for 14 days) followed by calcium (1000 mg/day for 76 days). Lateral spine X-ray films and dual-energy X-ray absorptiometry (DXA) measurements of the lumbar spine and proximal femur were performed at enrollment and yearly. Nonvertebral fractures were recorded every 6 months. Thirty-one women in the fluoride group and 47 in the etidronate group completed the trial. At 36 months, the mean change from baseline of the lumbar bone density in the fluoride group was 8.5 +/- 2.04% (p = 0.001) and in the etidronate group was of 3.6 +/- 0. 84% (p < 0.001). The changes in the fluoride group were significantly higher than in the etidronate group (p = 0.01). Both groups showed nonsignificant changes in femoral neck bone density. There was no significant difference between groups in the cumulative proportion of women with new vertebral fractures, with an incidence in the fluoride group of 16% vs. 17% in the etidronate group. However, the number of new vertebral fractures was significantly lower in the fluoride group (6 fractures) than in the etidronate group (19 fractures) (p = 0.05). The number of patients with nonvertebral fractures was similar in both groups. A high incidence of side effects, mainly gastrointestinal symptoms and lower extremity pain syndrome, was observed in the fluoride group. Etidronate was well tolerated. We conclude that, in women with severe osteoporosis, although sodium fluoride is more favorable than cyclical etidronate for increasing lumbar bone mass, no differences were observed in the incidence of fractures.

The role of fluoride in the prevention of osteoporosis

Osteoporosis defined as low bone mass and increased susceptibility to fracture is a reflection of the sum of peak bone mass and any bone that has been lost once peak mass has been attained. Several strategies have been applied to optimize peak bone mass and to prevent bone loss. Fluoride has greatest potential as a therapy for osteoporosis once bone has been lost. It has been demonstrated both experimentally and clinically to stimulate bone formation directly and to increase bone mass in patients who already have osteoporosis. Several bone formation/stimulation therapies are under development, and some of these have reached the stage of clinical trial. None of these therapies has been as extensively studied as fluoride, and none is sufficiently advanced in development to be clinically available in the next 3 to 5 years. Fluoride therapy for osteoporosis is already performed in many countries, and approval for use in osteoporosis in the United States is pending. The first clinical trials of NaF therapy for osteoporosis were reported by Rich and Ensinck in 1961. Since then, hundreds of reports on the successes and failures of fluoride therapy have appeared in the literature. At first glance, it seems disappointing and inexplicable that, after 40 years of research, fluoride is still considered an experimental drug in the United States. One plausible explanation is that much of the early research on this drug was suboptimal, including the author's contributions. Fluoride as a naturally occurring element is difficult to patent, and this has kept major pharmaceutical companies from investing heavily in fluoride therapy despite its obvious potential. As a result, pharmacologic and pharmacokinetics studies of fluoride are limited in scope, as are phase I and phase II human toxicology and dose-finding studies. Most early studies of large doses of plain NaF were unable to demonstrate a consistent effect on fracture rate despite a consistent and dramatic effect on bone density. Once this became obvious and as new technologies for measuring bone density became available, it became equally clear that future clinical trials would have to be performed using different formulations of fluoride and lower doses. This approach has not resulted in uniformly positive clinical trials, and one must look elsewhere for answers. The most compelling explanation is that the trials have included patients with different severity of disease, suggesting that there is point in the bone loss spectrum at which even a potent bone-stimulating agent such as fluoride is ineffective. This possibility should provoke a reappraisal of the earlier negative studies: was the failure a result of the drug or of patient selection? The answer to this question is crucial, because these failures have cast a long shadow over the safety of fluoride and are contributing more to the absence of this drug from the pharmacopoeia than any other factor.