Rhenium (Re, also known as NSC-600662) is a chemical element that was discovered in 1925. It is one of the scarcest elements on earth. This metal has a silvery-white color, high density, and high melting point. It is part of an alloy used to make X-ray tubes and rotating X-ray anodes, because the addition of rhenium prevents crazing of the anode surface. Apart from this medical application, rhenium is also used in plating, jewelry, igniters for flash bulbs, electrodes, thermocouples, electrical contacts, components for missiles, and other products and equipment. Its toxicity has been insufficiently studied, but exposure may cause health problems such as respiratory problems, skin and eye irritation, and burns. Also, more research is needed on environmental effects of rhenium.

Tetrapotassium Etidronate is the diphosphonic acid derivative. It is used in cosmetics as chelating agent.

Etidronate is a salt of etidronic acid (brand name Didronel, also known as EHDP) a diphosphonate, which is indicated for the treatment of symptomatic Paget’s disease of bone and in the prevention and treatment of heterotopic ossification following total hip replacement or due to spinal cord injury. Didronel is not approved for the treatment of osteoporosis. This drugs acts primarily on bone. It can inhibit the formation, growth, and dissolution of hydroxyapatite crystals and their amorphous precursors by chemisorption to calcium phosphate surfaces. Inhibition of crystal resorption occurs at lower doses than are required to inhibit crystal growth. Both effects increase as the dose increases. Preclinical studies indicate etidronate disodium does not cross the blood-brain barrier. Didronel is not metabolized. The amount of drug absorbed after an oral dose is approximately 3 percent. Bisphosphonates, when attached to bone tissue, are absorbed by osteoclasts, the bone cells that breaks down bone tissue. Although the mechanism of action of non-nitrogenous bisphosphonates has not been fully elucidated, available data suggest that they bind strongly to hydroxyapatite crystals in the bone matrix, preferentially at the sites of increased bone turnover and inhibit the formation and dissolution of the crystals. Other actions may include direct inhibition of mature osteoclast function, promotion of osteoclast apoptosis, and interference with osteoblast-mediated osteoclast activation. Etidronic acid may promote osteoclast apoptosis by competing with adenosine triphosphate (ATP) in the cellular energy metabolism. The osteoclast initiates apoptosis and dies, leading to an overall decrease in the breakdown of bone.

Readily soluble in water, SnF2 is hydrolysed. At low concentration, it forms species such as SnOH+, Sn(OH)2 and Sn(OH)3−. At higher concentrations, predominantly polynuclear species are formed, including Sn2(OH)22+ and Sn3(OH)42+. Aqueous solutions readily oxidise to form insoluble precipitates of SnIV, which are ineffective as a dental prophylactic. Tin(II) fluoride, commonly referred to commercially (with tin(II) in Latin) as stannous fluoride, is a chemical compound with the formula SnF2. It is a colorless solid used as an ingredient in toothpastes that are typically more expensive than those that use sodium fluoride. Stannous fluoride has both bactericidal and bacteriostatic properties, which fight plaque and treat/prevent gingivitis. The stannous fluoride also deposits a protective mineral barrier over exposed dentinal tubules to help prevent sensitivity pain from triggers such as hot or cold liquids and foods. Stannous fluoride is used under the trade name "Fluoristan" in the original formulation of the toothpaste Crest, though it was later replaced with sodium monofluorophosphate, or "Fluoristat". It is the active ingredient in Crest Pro Health brand toothpaste. Crest Pro Health issues a warning on the tube that stannous fluoride may cause staining, which can be avoided by proper brushing, and that its particular formulation is resistant to staining. Any stannous fluoride staining that occurs due to improper brushing is not permanent. Stannous fluoride is also used in Oral-B Pro-Expert. Stannous fluoride is also readily available in over-the-counter rinses.

Rhenium Re-186 is radioisotope of rhenium. It is produced in many nuclear reactors throughout the world, and the 90-hour half-life can often permit distribution to sites distant from the production facilities. Re-186 decays with emission of beta-particles which have a range of up to 4.5 mm in tissues. Rhenium-186 complex with 1-hydroxy-ethylidene-1,1 diphosphonic acid (HEDP) is used for palliative treatment of bone metastases originating from breast or prostate cancer. Re-186-labeled sulfur colloid particles are used for the therapy of rheumatoid arthritis of the synovial joints.