Osteonecrosis of the jaws refers to the death of bone marrow in the maxilla or the mandible due to inadequate blood supply. It is not necessarily a painful condition, typically there will be no pain at all unless bone necrotic bone becomes exposed to the mouth or through the facial skin, and even then this continues to be painless in some cases. When pain does occur, it is variable in severity, and may be neuralgiform or neuropathic in nature. The term NICO is used to describe pain caused by ischemic osteonecrosis of the jaws, where degenerative extracellular cystic spaces (cavitations inside the bone) are said to develop as a result of ischemia and infarctions in the bone marrow, possibly in relation to other factors such as a hereditary predisposition for thrombus formation within blood vessels, chronic low-grade dental infections and the use of vasoconstrictors in local anesthetics during dental procedures. This proposed phenomenon has been postulated to be the cause of pain in some patients with AFP or trigeminal neuralgia, but this is controversial. NICO is said to be significantly more common in females, and the lesions may or may not be visible on radiographs. When they are visible, the appearance is very variable. About 60% of the lesions appear as a "hot spot" on an technetium 99 bone scan.
While permethrin may be marketed as an insect repellent, it does not prevent insects from landing. Instead it works by incapacitating or killing insects before they can bite. In pet flea preventive collars or treatment (safe for use on dogs but not cats)
In timber treatment

Medical use
Permethrin is available for topical use as a cream or lotion. It is indicated for the treatment and prevention in exposed individuals of head lice and treatment of scabies.For treatment of scabies: Adults and children older than 2 months are instructed to apply the cream to the entire body from head to the soles of the feet. Wash off the cream after 8–14 hours. In general, one treatment is curative.For treatment of head lice: Apply to hair, scalp, and neck after shampooing. Leave in for 10 minutes and rinse. Avoid contact with eyes. Pest control / effectiveness and persistence
In agriculture, permethrin is mainly used on cotton, wheat, maize, and alfalfa crops. Its use is controversial because, as a broad-spectrum chemical, it kills indiscriminately; as well as the intended pests, it can harm beneficial insects, including honey bees, as well as cats and aquatic life.Permethrin kills ticks and mosquitoes on contact with treated clothing. A method of reducing deer tick populations by treating rodent vectors involves stuffing biodegradable cardboard tubes with permethrin-treated cotton. Mice collect the cotton for lining their nests. Permethrin on the cotton kills any immature ticks feeding on the mice. Permethrin is used in tropical areas to prevent mosquito-borne disease such as dengue fever and malaria.