During the 1980s, dentist Hal Huggins, sparking severe controversy, spawned biological dentistry, which claims that conventional tooth extraction routinely leaves within the tooth socket the periodontal ligament that often becomes gangrenous, then, forming a jawbone "cavitation" seeping infectious and toxic material. Sometimes forming elsewhere in bones after injury or ischemia, jawbone cavitations are recognized as foci also in osteopathy and in alternative medicine, but conventional dentists generally conclude them to be nonexistent. Although the International Academy of Oral Medicine & Toxicology claims that the scientific evidence establishing the existence of jawbone cavitations is overwhelming, and even published in textbooks, the diagnosis and related treatment remain controversial, and allegations of quackery persist.