Tooth brushing

Tooth brushing is the act of scrubbing teeth with a toothbrush equipped with toothpaste. Since only two thirds of the outer tooth can be reached by a toothbrush, interdental cleaning (with floss or an interdental brush) can usefully accompany tooth brushing. Together, these two activities are the primary means of cleaning teeth, one of the main aspects of oral hygiene.

Brushing teeth properly helps prevent cavities, and periodontal, or gum disease, which causes at least one-third of adult tooth loss. If teeth are not brushed correctly and frequently, it could lead to the calcification of saliva minerals, forming tartar. Tartar hardens (then referred to as 'calculus') if not removed every 24 hours. Poor dental health has been associated with heart disease and shortened life expectancy.

History

As long ago as 3000 BC, the ancient Egyptians constructed crude toothbrushes from twigs and leaves to clean their teeth. Similarly, other cultures such as the Greeks, Romans, Arabs and Indians cleaned their teeth with twigs. Some would fray one end of the twig so that it could penetrate between the teeth more effectively.

Compact disc

Compact disc (CD) is a digital optical disc data storage format. The format was originally developed to store and play only sound recordings but was later adapted for storage of data (CD-ROM). Several other formats were further derived from these, including write-once audio and data storage (CD-R), rewritable media (CD-RW), Video Compact Disc (VCD), Super Video Compact Disc (SVCD), Photo CD, PictureCD, CD-i, and Enhanced Music CD. Audio CDs and audio CD players have been commercially available since October 1982.

Standard CDs have a diameter of 120 millimetres (4.7 in) and can hold up to about 80 minutes of uncompressed audio or about 700 MiB of data. The Mini CD has various diameters ranging from 60 to 80 millimetres (2.4 to 3.1 in); they are sometimes used for CD singles, storing up to 24 minutes of audio, or delivering device drivers.

At the time of the technology's introduction in 1982, a CD had greater storage capacity than a personal computer hard drive. By 2010 hard drives commonly had capacities exceeding those of CDs by a factor of several thousand.

Nursery rhyme

A nursery rhyme is a traditional poem or song for young children in Britain and many other countries, but usage only dates from the late 18th /early 19th century. In North America the term Mother Goose Rhymes, introduced in the mid-18th century, is still often used.

History

Lullabies

The oldest children's songs of which we have records are lullabies, intended to help a child sleep. Lullabies can be found in every human culture. The English term lullaby is thought to come from "lu, lu" or "la la" sound made by mothers or nurses to calm children, and "by by" or "bye bye", either another lulling sound, or a term for good night. Until the modern era lullabies were usually only recorded incidentally in written sources. The Roman nurses' lullaby, "Lalla, Lalla, Lalla, aut dormi, aut lacta", is recorded in a scholium on Persius and may be the oldest to survive.

Many medieval English verses associated with the birth of Jesus take the form of a lullaby, including "Lullay, my liking, my dere son, my sweting" and may be versions of contemporary lullabies. However, most of those used today date from the 17th century. For example, a well known lullaby such as "Rock-a-bye, baby on a tree top", cannot be found in records until the late-18th century when it was printed by John Newbery (c. 1765).

Tooth

A tooth (plural teeth) is a small, calcified, whitish structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores, also use teeth for hunting or for defensive purposes. The roots of teeth are covered by gums. Teeth are not made of bone, but rather of multiple tissues of varying density and hardness. The cellular tissues that ultimately become teeth originate from the embryonic germ layer, the ectoderm.

The general structure of teeth is similar across the vertebrates, although there is considerable variation in their form and position. The teeth of mammals have deep roots, and this pattern is also found in some fish, and in crocodilians. In most teleost fish, however, the teeth are attached to the outer surface of the bone, while in lizards they are attached to the inner surface of the jaw by one side. In cartilaginous fish, such as sharks, the teeth are attached by tough ligaments to the hoops of cartilage that form the jaw.

Sesame Street

Sesame Street is a long-running American children's television series created by Joan Ganz Cooney and Lloyd Morrisett. The program is known for its educational content, and images communicated through the use of Jim Henson's Muppets, animation, short films, humor, and cultural references. The series premiered on November 10, 1969, to positive reviews, some controversy, and high viewership; it has aired on the U.S.'s national public television provider (PBS) since its debut, with its first run moving to premium channel HBO on January 16, 2016.

The show has undergone significant changes throughout its history. The format of Sesame Street consists of a combination of commercial television production elements and techniques which have evolved to reflect the changes in American culture and the audience's viewing habits. With the creation of Sesame Street, producers and writers of a children's television show used, for the first time, educational goals and a curriculum to shape its content. It was also the first time a show's educational effects were studied.