tooth Any of the hard structures in the mouth used for biting and chew¬ ing and in speech. Each consists of a crown above the gum and one or more roots below it, embedded in the jaw. Its inner pulp contains the blood and nerve supply for the bonelike dentin, covered in the crown by enamel, the hardest tissue in the body. Twenty primary (baby) teeth come in by age 2 1/2 and fall out between ages 5 and 13 to be replaced by 32 per¬ manent teeth. The incisors, in front, are shaped mostly for biting, the pointed canines for tearing, and the premolars and molars for grinding food. The teeth are subject to caries (decay), caused by acid from bacte¬ ria in plaque, a yellowish film that builds up on teeth. Misalignment of teeth between the upper and lower jaws can grind down the teeth and cause problems in chewing. Elsewhere, it is a cosmetic problem. Both can be treated with braces. See also dentistry. See illustration on opposite page.
tooth decay See caries
toothed whale Common term for members of the cetacean suborder Odontoceti. Toothed whales have slicing teeth and a throat large enough to swallow chunks of giant squid, cuttlefish, and fish of all kinds. Included in this group are the beluga, killer whale, pilot whales, sperm whale, and mammalian dolphins, porpoises, and narwhals.
Topa See Northern Wei dynasty
topaz Aluminum silicate mineral, Al 2 Si0 4 (F,OH) 2 , that is valued as a
gemstone. It is formed by fluorine¬ bearing vapours given off during the last stages of the crystallization of igneous rocks. Pure topaz may be colourless and, when brilliant-cut, has been mistaken for diamond. It may also be various shades of yel¬ low, blue, or brown. Imperial topaz, with vivid reddish orange colour, from Minas Gerais, Braz., is very highly valued.
Topeka Uo-'pe-koX City (pop., 2000: 122,377), capital of Kansas, U.S. Situated on the Kansas River,
Topaz from Minas Gerais state, Brazil
LEE BOLTIN
© 2006 Encyclopaedia Britannica, Inc.
Topeka Constitution ► torii I 1923
Cross section of an adult molar. The crown (the part of the tooth above the gum) is protected by a hard outer layer of enamel. The roots sit in a socket in the jawbone and are covered with cementum, a bonelike material. The periodontal ligament anchors the cementum in the jaw and cushions the tooth from the pressures of chewing. The tooth's main portion, the dentin, surrounds the soft pulp, which carries the blood vessels and nerves. Specialized cells of the pulp project threadlike exten¬ sions into the dentin through narrow channels and serve to form new dentin from minerals in the blood.
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Topeka was founded in 1854 by a group of antislavery colonists and was prominent in the political conflict between proslavery groups and the antislavery Free Soil Party. In 1859 it was the headquarters for the build¬ ing of the Atchison, Topeka, and Santa Fe Railway system. It has been the state capital since Kansas was admitted to the Union in 1861. The economy is based on agriculture, manufacturing, and governmental ser¬ vices. The Menninger family established its clinics there, making Topeka a national centre for the treatment of mental illness.
Topeka Constitution (1855) Resolution to establish an antislavery territorial government in Kansas. To counter the proslavery government established after passage of the Kansas-Nebraska Act, antislavery settlers met in Topeka to draft a constitution that banned slavery. In January 1856 they elected a free-state governor and legislature, which created two gov¬ ernments. Pres. Franklin Pierce condemned the Topeka document and sup¬ ported the proslavery government. The U.S. House of Representatives voted to admit Kansas under the Topeka Constitution, but the Senate blocked the move. The unresolved situation led to the conflict known as Bleeding Kansas.
topiary Art of training living trees and shrubs into artificial, decorative shapes. Topiary is known to have been practiced in the 1st century ad. The earliest topiary was probably the simple development of edgings, cones, columns, and spires to accent a garden scene. This architectural use gave way to elaborate shapes such as ships, hunters, and hounds. The fashion reached its height in Britain in the late 17th and early 18th cen¬ tury but was displaced by the so-called natural garden.
topology \t3-'pa-lo-je\ In mathematics, the study of the properties of a geometric object that remains unchanged by deformations such as bend¬ ing, stretching, or squeezing but not breaking. A sphere is topologically
equivalent to a cube because, without breaking them, each can be deformed into the other as if they were made of modeling clay. A sphere is not equivalent to a doughnut, because the former would have to be bro¬ ken to put a hole in it. Topological concepts and methods underlie much of modem mathematics, and the topological approach has clarified very basic structural concepts in many of its branches. See also algebraic topol¬ ogy.
Torah \to-'ra, 'to-ro, 'tor-3\ or Pentateuch Vpen-te- 1 tuk\ In Judaism, the divine revelations to Israel; specifically, the first five books of the Bible: Genesis, Exodus, Leviticus, Numbers, and Deuteronomy. By tradition their authorship has been ascribed to Moses, but biblical scholarship has shown that they were written and compiled at a much later date, probably in the 9th-5th century bc, though drawing on much older traditions. The Scroll of the Torah (Sefer Torah) is kept in the Synagogue Ark. The term Torah (but not Pentateuch) is often applied to the whole Hebrew Scripture (i.e., the later books of the Old Testament), or, even more generally, to that and other Jewish sacred literature and oral tradition.
torana Vtor-o-noX Indian gateway, usually of stone, marking the entrance to a Buddhist shrine or stupa or to a Hindu temple. Toranas typi¬ cally consist of two pillars carrying two or three transverse beams that extend beyond the pillars on either side. Strongly reminiscent of wooden construction, toranas are often covered from top to bottom with exquisite sculpture. The four toranas of the Great Stupa at Sanchi (see Sanchi sculp¬ ture) are superb examples. See also torn.
Tordesillas X.tor-da-'sel-yasV, Treaty of (June 7, 1494) Agreement between Spain and Portugal aimed at settling conflicts over lands explored by voyagers of the late 15th century. In 1493 Pope Alexander VI had granted Spain all the lands west of a line 100 leagues (about 320 miles) west of the Cape Verde Islands, in return for an agreement to Christian¬ ize the peoples of the New World;
Portuguese expeditions were to keep to the east. At Tordesillas (a village in Spain), ambassadors from Spain and Portugal moved that line west, thereby allowing Portugal to claim Brazil when it was discovered in
Tori style In Japanese art, a style of sculpture that emerged during the Asuka period (552-645) and lasted into the Nara period (710-784).
Derived from the style of the Chi¬ nese Northern Wei dynasty (ad 386- 534), Tori was named after a sculptor of Chinese descent whose only known piece is a Buddhist triad (623). Works in the Tori style are characterized by slender, elegant bodies, a strong linear interest in drapery, and a tendency toward squatness in the proportion of the faces and also in the relation of the body to the feet.
torii Vt6r-e-,e\ Symbolic gateway marking the entrance to Shinto shrines or other sacred spots in Japan. It has many variations, but it characteristi¬ cally consists of two cylindrical posts topped by a crosswise rectan¬ gular beam extending beyond the posts on either side and a second crosswise beam a short distance below. The top beam often curves upward. Some authorities relate the torii to the Indian torana, others to Manchurian and Chinese gates.