Elastics are

rubber band A rubber band (also known as an elastic band, gum band or lacky band) is a loop of rubber, usually ring or oval shaped, and commonly used to hold multiple objects together. The rubber band was patented in England on March 17, 1845 by Stephen P ...

s frequently used in the field of orthodontics to correct different types of

malocclusion In orthodontics, a malocclusion is a misalignment or incorrect relation between the teeth of the upper and lower dental arches when they approach each other as the jaws close. The English-language term dates from 1864; Edward Angle (1855-19 ...

s. The elastic wear is prescribed by an orthodontist or a dentist in an orthodontic treatment. The longevity of the elastic wear may vary from two weeks to several months. The elastic wear can be worn from 12 to 23 hours a day, either during the night or throughout the day depending on the requirements for each malocclusion. The many different types of elastics may produce different forces on teeth. Therefore, using elastics with specific forces is critical in achieving a good orthodontic occlusion. The term ''intermaxillary elastics'' is used when elastics can go from the

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. T ...

ry to the

mandibular arch The pharyngeal arches, also known as visceral arches'','' are structures seen in the embryonic development of vertebrates that are recognisable precursors for many structures. In fish, the arches are known as the branchial arches, or gill arche ...

. ''Intra-maxillary elastics'' are elastics used in one arch only, either mandibular or maxillary. People using elastics for orthodontic correction change their elastics three to four times during the day. Elastic wear is recommend to be used in a rectangular wire to minimize side effects. Elastic wear depends on the compliance of the patient. A non-compliant patient should never be instructed to continue wearing elastics, for whom other options may be considered.

History

Natural rubber, used by the

Incan The Inca Empire (also known as the Incan Empire and the Inka Empire), called ''Tawantinsuyu'' by its subjects, (Quechua for the "Realm of the Four Parts", "four parts together" ) was the largest empire in pre-Columbian America. The admin ...

and

Mayan Mayan most commonly refers to: * Maya peoples, various indigenous peoples of Mesoamerica and northern Central America * Maya civilization, pre-Columbian culture of Mesoamerica and northern Central America * Mayan languages, language family spoken ...

cultures, was the first known elastomer.

Charles Goodyear Charles Goodyear (December 29, 1800 – July 1, 1860) was an American self-taught chemist and manufacturing engineer who developed vulcanized rubber, for which he received patent number 3633 from the United States Patent Office on June 15, 1844. ...

developed the process of

vulcanization Vulcanization (British: Vulcanisation) is a range of processes for hardening rubbers. The term originally referred exclusively to the treatment of natural rubber with sulfur, which remains the most common practice. It has also grown to includ ...

, after which the use of natural rubber increased.

Henry Albert Baker Henry Albert Baker (November 27, 1848 – April 24, 1934) was an American orthodontist who is known to introduce orthodontics to the use of intermaxilary elastics. He is also known for the Baker anchorage. Life Henry Albert Baker was born in Ne ...

is the first person known to have used elastics to correct the position of teeth. In the late 1800s he named his elastic wear the Baker Anchorage. Others, including

Edward Angle Edward Hartley Angle (June 1, 1855 – August 11, 1930) was an American dentist, widely regarded as "the father of American orthodontics". He was trained as a dentist, but made orthodontics his speciality and dedicated his life to standardizing ...

, the father of orthodontics, suggest that

Calvin Case Calvin Suveril Case (April 24, 1847 – April 16, 1923) was an American orthodontist who is known to be one of the earliest prominent figures in orthodontics. Case did extensive work with cleft lip and palate and is known for developing the Vel ...

was the first to use intermaxillary elastics. Natural rubber is known to absorb water, and its elasticity deteriorates fairly quickly. Therefore, latex elastics became prominent in orthodontic usage in the early 1900s. Later synthetic elastics developed in the 1960s superseded other types of elastics for use in orthodontic correction.

Elastic forces

Elastics are available in many different type of forces. Following is the list of forces that can be found in different elastics. The forces and the labelling of the forces may depend on different manufacturers and types of elastics used. These forces pertain to intermaxillary elastics.

Class II elastics

Class 2 elastics are used from the lower first molar to the upper canine tooth. They can be used for many different reasons, such as Class 2 malocclusions, to reinforce anchorage in a case where an extraction has been done, to allow the

maxillary incisor Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wher ...

s to move backwards, and to correct midline deviation and allow buccal movement of backward-tipped lower incisors. Orthodontists generally use 12-16 oz elastics (3/16") in extraction cases or 2× 6 oz elastics on either side of the mouth (3/16"), but in non extraction cases 16-20 oz elastics (3/16") or 2× 8 oz elastics are used. It is very important to know the side effects of Class II elastics before using them in an orthodontic treatment. The following are the effects of Class 2 elastics: * Extrusion of upper incisors * Extrusion of lower first molar * Flaring of the lower incisors * Distal movement of the upper teeth and mesial movement of the lower teeth * Steepening of the occlusal plane

Effect on Class II Malocclusion

A systematic review done by Janson et al. looking at the effect of Class 2 elastics in correcting class II malocclusions concluded that Class II elastics are effective in correcting Class II malocclusions and that their effects are primarily dento-alveolar.

Class III elastics

Class 3 elastics are used when the molar relationship is close to Class 1 malocclusion. Class 3 malocclusions due to skeletal discrepancy (mandibular prognathism) cannot be corrected with Class 3 elastics. It is important to evaluate

soft tissue Soft tissue is all the tissue in the body that is not hardened by the processes of ossification or calcification such as bones and teeth. Soft tissue connects, surrounds or supports internal organs and bones, and includes muscle, tendons, ...

and hard tissue esthetics of a patient before attempting to use Class 3 elastics. Elastic wear will only produce changes in dentition, with no documented changes produced in soft and hard tissue. The following are the side-effects of Class 3 elastics: * Distal movement of the lower teeth and mesial movement of the upper teeth * Flaring of the upper incisors * Extrusion of the lower incisors * Extrusion of the upper first molar * Flattening of the occlusal plane

Elastic ligatures

The small elastic band used to affix the

archwire An archwire in orthodontics is a wire conforming to the alveolar or dental arch that can be used with dental braces as a source of force in correcting irregularities in the position of the teeth. An archwire can also be used to maintain existing ...

to the bracket is called a ligature. Usually changed at each adjustment, these come in many varied colours, including transparent. A series of ligatures connected to each other and used to pull teeth together with more strength is called a power chain. Ligatures can also be made of wire. Self-ligation makes use of a bracket with a sliding or rotating mechanism to ligate an archwire. This type of bracket replaces traditional elastic ligatures and typically cuts orthodontic appointment times drastically . Currently, self-ligating brackets make up about 10 percent of total bracket sales worldwide.

References

{{Orthodontology Orthodontic appliances