... out and are replaced by the erupting permanent teeth. This begins a transitional phase of tooth development that takes place over the next 15 years. As baby teeth are pushed out by permanent teeth, the entire mouth and ja transform from their childhood shape to a more pronounced, adultlike structure. From age six to age nine, a childs permanent incisors, canines, and first molars erupt. The bicuspids erupt from age 10 to age 12, and the second molars come in by age 13. The third molars, or isdom teeth, usually erupt by the age of 21.hen human teeth gro to a certain size, the root essentially closes and the teeth stop groing. Closed-rooted teeth have narro root openings that are only big enough for the periodontal ligament, blood vessels, and a nerve. CDisorders of Human Teeth The three main diseases of human teeth are tooth decay, also called dental caries gum disease, or periodontal disease and problems ith tooth alignment, called malocclusions. Human teeth problems are treated or prevented by dentists, professionals ho are specially trained to practice dentistry.Tooth decay affects approximately 90 percent of all children by the time they are 14 years old. Tooth decay begins hen bacteria are passed from mothers or caregivers to children beteen their first and second birthdays. hen these bacteria are exposed to sugars commonly found in foods, the bacteria produce harmful acids that attack tooth enamel. Left unchecked, the acid eats holes in the enamel and forms cavities of tooth decay. Most tooth decay forms in the deep grooves on the cheing surfaces of the molars, called pits and fissures. Daily tooth brushing and proper dental care help prevent and reduce tooth decay. Dentists use preventive treatments to reduce the risk of tooth decay clear plastic coatings painted on the teeth, called dental sealants, and applications of the mineral fluoride, hich fortifies tooth enamel, are to such treatments. Fluoride is also added to public ater supplies in a process called fluoridation, hich benefits more than 150 million Americans.Gum disease, or periodontal disease, is a progressive condition that orsens ith age. Gum disease occurs hen bacteria eat aay at gum tissue, causing it to pull aay from the teeth. This space beteen the tooth and gum, called a periodontal pocket, traps even more bacteria. Gum disease develops in to stages. Gingivitis, the early stage, causes red, sollen gums that bleed easily. Gingivitis can be eliminated through good oral hygiene and dental care. If not treated, gingivitis can progress to periodontitis, hen bacteria attack the bone supporting the teeth. To treat periodontitis, dentists may have to surgically cut out the infected portion of the gum so the bacteria can be removed.Malocclusionsteeth that are croded, crooked, or out of alignmentmake it more difficult to clean teeth, hich can lead to other oral health problems such as tooth decay and gum disease. Many of these disorders start to appear beteen the ages of 6 and 12, hen permanent teeth begin to erupt. Generally, malocclusions result hen the ja is too small to hold all of the teeth. Malocclusions are often genetic, tending to run in families. In other cases, dental injury or chronic thumb sucking may lead to poorly aligned teeth. Malocclusions are treated by dentists specially trained to correct them, called orthodontists.IIITEETH IN OTHER ANIMALS Animal teeth have the same four tissues that make up human teeth enamel, dentin, cementum, and pulp. The composition and structure of each substance may differ in each animal. In horses, for example, enamel is found inside the tooth as ell as on the outer surface, rather than simply encasing the dentin and the pulp as it does in human teeth.Some animals are monophydont, developing only one set of teeth that gro continuously throughout an animals lifetime. These animals have open-rooted teeth, hich have ide openings at the root that permit dentin- ... Download