Orthodontics is a specialized branch of dentistry that diagnoses, prevents, and treats dental and facial irregularities called malocclusions. Orthodontics includes dentofacial orthopedics, which is used to correct problems involving the growth of the jaw.

Humans have attempted to straighten teeth for thousands of years before orthodontics became a dental specialty in 1900. Although orthodontic treatment often improves facial appearance and occasionally is performed for solely cosmetic reasons, it is used primarily to correct health problems and to ensure the proper functioning of the mouth. Properly aligned teeth, which close together correctly, simplify oral hygiene and enable children to chew their food efficiently.

Few children have perfectly symmetrical teeth and a perfect bite. In an ideal bite, the following are characteristics:

• All of the teeth fit easily without crowding or spacing.
• The teeth are not rotated, twisted, or leaning forward or backward.
• The teeth of the upper jaw slightly overlap those of the lower jaw.
• The points of the molars fit into the grooves of the opposite molars.

• crowded, crooked, or misaligned teeth
• extra or missing teeth
• bite problems
• jaws that are out of alignment

Most malocclusions are caused by hereditary factors that affect the contours of the face and the size of the teeth and jaw. The most common cause of malocclusion is a disproportion in size between the jaw and teeth or between the upper and lower jaws. A child who inherits a mother's small jaw and a father's large teeth may have teeth that are too big for the jaw, causing overcrowding. Specific inherited malocclusions include:

• overcrowded teeth
• too much space between teeth
• extra or missing teeth
• various irregularities in the teeth, jaw, or face

• accidents such as a jaw fracture that causes misalignment
• prolonged sucking on thumbs, fingers, or pacifiers, particularly after the age of four
• fingernail or lip biting
• a lost tooth that causes nearby teeth to move into the empty space, throwing them out of alignment
• airways that are obstructed by tonsils or adenoids
• dental disease
• tumors in the mouth or jaw
• improperly fitted fillings, crowns, or braces
• premature loss of baby teeth or permanent teeth
• late loss of baby teeth

Occasionally children have mild, temporary symptoms of malocclusion resulting from a growth spurt. However, symptoms of malocclusion usually develop gradually beginning at the age of six. Symptoms may include the following:

• crowded or misaligned teeth
• abnormal spacing between teeth, most often occurring because teeth are small or missing or the dental archthe arch-shaped jawbone that supports the teethis very wide
• incisors (front teeth) that do not meet
• an open bite, occurring when the upper and lower incisors do not touch each other during biting, thereby putting all of the chewing pressure on the back teeth and resulting in inefficient chewing and excessive tooth wear
• an overbite or overjet, in which the upper incisors protrude, often caused by a lower jaw that is significantly shorter than the upper jaw
• a deep or closed bite, an excessive overbite in which the lower incisors bite too closely to or into the gum tissue or palate behind the upper teeth
• a crossbite, in which a protruding lower jaw that is longer than the upper jaw causes the upper front or back teeth to bite inside the lower teeth

Minor misalignment or crowding may not require treatment. However untreated malocclusions can cause the following:

• teeth that are partially impacted or fail to erupt
• lips, tongue, or cheeks that contact biting surfaces due to poor tooth alignment
• inefficient or uncomfortable biting, chewing, and digestion
• speech impairments
• teeth that are hard to clean, leading to cavities and gum disease
• abnormal wear of tooth surfaces
• chipped teeth
• loosening or fracturing of a misaligned tooth that is overstrained
• injury to a protruding upper incisor
• thinning and receding of bone and gums covering the roots of very crowded teeth
• accelerated gum disease and bone loss
• temporomandibular joint (TMJ) misalignments at the point where the lower jaw attaches to the skull
• stress and trauma to the teeth, gum tissue, ligaments, muscles, jawbone, and jaw joints
• premature loss of teeth
• adverse effects on facial development and appearance
• the need for surgery

Untreated malocclusions often worsen with time. TMJ problems can cause chronic headaches or pain in the face and neck. A deep overbite can cause significant pain and bone damage and may contribute to excessive wear on the incisors.

Although orthodontic treatment can be performed at any age, children are easier, faster, and less expensive to treat than adults. Most often orthodontic treatment is used on older children and adolescents whose teeth are still developing. However some types of problems are corrected more readily before all of the permanent teeth have erupted and facial growth is complete. If a child's permanent lower incisors erupt behind each other, braces may be required at a young age. Crossbites are usually treated early because they can interfere with biting and chewing. Early treatment also is used when thumb- or finger-sucking has affected teeth positioning.

Early orthodontic intervention can provide the following:

• straighten crooked teeth
• preserve or create space for incoming permanent teeth
• guide erupting permanent teeth into the correct positions
• prevent impacted permanent teeth, those that remain partially covered by gum tissue or partially or completely buried in the jawbone
• correct harmful habits such as thumb- or finger-sucking
• lower the risk of accidents to protruding upper incisors

Other advantages of early orthodontic treatment include the following:

• correction of bite problems by guiding jaw growth and controlling the width of the upper and lower dental arches
• reduction or elimination of abnormal swallowing or speech problems
• shortening and simplification of later orthodontic treatment
• prevention of later tooth extractions
• improvements in appearance and self-esteem

Alignment problems usually become apparent as the permanent teeth begin erupting at about age six. Dentists monitor the development of a child's permanent teeth and refer the child to an orthodontist if a problem is suspected. The American Association of Orthodontists recommends that all children be screened by an orthodontist by the age of seven.

Once a child's lower baby incisors have erupted, an orthodontist can measure the child's jaw and tooth size, project their growth rate, and possibly predict whether the child will have orthodontic problems with their permanent teeth. The orthodontist may be able to perform preventative or interceptive orthodontics that can reduce or eliminate the need for braces later.

In a procedure called selective serial extraction, the orthodontist removes one or more baby or permanent teeth. Doing so creates space for the permanent teeth, especially unerupted canine teeth that might become impacted or erupt in the wrong position. After the removal or loss of a tooth, braces or another orthodontic appliance may be used to prevent the remaining teeth from moving into the empty space. If a baby molarthat acts as a space-holder for later permanent teethis lost, a fixed orthodontic wire is inserted between the teeth to keep the space available.

The orthodontist compiles pretreatment records that are used for diagnosis, determining the course of treatment, and measuring the progress of treatment. These records may include:

• a complete medical and dental history
• a clinical examination
• x rays revealing the positions of erupted and unerupted teeth, development of unerupted teeth, any missing or impacted teeth, shortened or damaged tooth roots, and the amount of bone supporting the teeth
• a facial-profile x ray or cephalometric film revealing the sizes, positions, and relationships of the teeth and jaw, as well as facial form, growth pattern, and the inclinations of tipped or tilted incisors
• plastic impressions of the bite and plaster models made from the impressions
• photographs and other measurements of the teeth and face

Based on the diagnosis the orthodontist develops a custom treatment plan and designs the appropriate corrective appliances that will gradually straighten or move the teeth. Severe overcrowding may necessitate the extraction of permanent teeth, usually the premolars, to create space prior to using braces to move teeth.

By applying constant gentle pressure in a specific direction, braces can slowly move teeth through the supporting bone to a new position. Springs and wires put pressure on teeth in order to straighten them. The pressure causes bone in the jaw to dissolve in front of the moving tooth as new bone grows behind the tooth. Braces and other appliances may be removable or fixed and are made of clear or colored metal, ceramic, or plastic. Removable appliances are often plastic plates that fit into the roof of the mouth and clip onto a tooth.

Fixed braces exert more pressure than removable braces and can achieve more complex movements. They consist of wires and springs that are held in place by small brackets glued to the outside surfaces of the incisors and sometimes the premolars. Lingual braces have brackets bonded to the back of the teeth. Bands encircling the molars also can be used for attachments. The wires, springs, and other devices attached to the brackets or bands put pressure on the teeth, gradually shifting them into new positions. The nickel-titanium wires are very light, and some are heat-activated. These are very flexible at room temperature and actively begin to move the teeth as they warm to body temperature. Elastic bands sometimes connect the upper and lower teeth to create tension.

There are several appliances that can be used to direct jaw growth and development in growing children and adolescents. These include:

• Headgear attached to braces and usually worn for 10 to 12 hours at night puts pressure on the upper teeth and jaw and influences the direction and speed of upper jaw growth and upper teeth eruption.
• Herbst appliances attached to the upper and lower molars correct a severe overbite by holding the lower jaw forward, influencing jaw growth and tooth position; they force the jaw muscles to work in ways that promote forward development of the lower jaw; treatment with Herbst appliances must begin several years before the jaw stops growing and they must remain in place throughout the treatment.
• Palatal or upper jaw expansion devices can widen a narrow upper jaw and correct a crossbite within months.
• Removable bionators hold the lower jaw forward and guide tooth eruption while helping the upper and lower jaws to grow proportionately.

Headgear and Herbst appliances can significantly reduce protrusion of the four top incisors and enable the growing lower jaw to catch up with the upper jaw, eliminating swallowing problems.

Orthodontic treatment usually continues until the desired outcome is reached. Active orthodontic treatment lasts an average of two years, with a range of one to three years. Some children respond to treatment faster than others and interceptive or early treatments may continue for only a few months.

Appliances are adjusted periodically during treatment. Factors affecting the duration of treatment include:

• the growth of the mouth and face
• the severity of the problem
• the health of the teeth, gums, and supporting bones
• the child's level of cooperation

Orthodontic appliances trap food, bacteria, and plaque, leading to tooth decay. Extra brushing with specially shaped and/or electric toothbrush and fluoride toothpaste is required around the areas where the braces or appliances attach to the teeth. Both the tops and bottoms of braces must be brushed and irrigated with a water jet directed from the top down and the bottom up. If possible, teeth should be flossed. A fluoride mouthwash may be recommended. Removable appliances should be brushed every time the teeth are brushed. Regular dental check-ups and cleanings must be continued.

Children with braces should eat raw fruits and vegetables and avoid soft, processed, and refined foods that attract bacteria, as well as hard or sticky foods, including gum, caramels, peanuts, ice chips, and popcorn. Chewing on hard items, such as fingernails or pencils, can damage braces. Children with braces should wear a protective mouth guard while playing contact sports.

After braces are removed the teeth must be stabilized in their new positions. This phase of treatment commonly takes two to three years. Occasionally it continues indefinitely. Types of retainers used for stabilization include:

• positioners, rubber-like mouthpieces that are worn at night and bitten into for a few hours during the day
• removable retainers with a plastic plate that snaps onto the roof of the mouth and wires on the outside of the teeth
• removable, clear, plastic retainers that completely cover the sides and biting surfaces of the teeth
• semi-rigid wires that are bonded onto the inside of the incisors.

Braces may cause discomfort when they are first installed or adjusted during treatment. For the first three to five days teeth may hurt during biting. Lips, cheeks, and tongue may be irritated for one to two weeks before they toughen and adapt to the braces. Some appliances may interfere with speech for the first day or two. Damaged appliances can extend the length of treatment and negatively affect the outcome.

Food particles and plaque deposits around orthodontic appliances can cause demineralization of the tooth enamel, leading to cavities and permanent whitish scars on the teeth.

Orthodontic treatment is usually very successful at correcting malocclusions. Even a significant size discrepancy between the upper and lower jaws often can be corrected. Sometimes, particularly in adults, corrective orthognathic surgery is required to shorten or lengthen a jawbone. The height of the lower face also can be shortened or lengthened. Sometimes surgery reduces the duration of the orthodontic treatment.

Maturational change can cause teeth to gradually shift with ageat least until one's early 20scausing crowding. Nighttime retainers can prevent maturational movement.

In general the earlier an orthodontic problem is detected, the easier and less expensive it is to correct. Parents can compare their child's dental development with standard charts and pictures.

Children with problems involving the width or length of the jaws should be evaluated no later than age 10 for girls and age 12 for boys. For children receiving orthodontic care, the orthodontist should be notified immediately if an appliance breaks. Indications that children may need an early orthodontic examination include:

• early or late loss of baby teeth
• crowded, misplaced, or blocked-out teeth
• upper and lower teeth that do not meet normally
• thumb- or finger-sucking
• biting of the cheek or roof of the mouth
• difficulty biting or chewing
• breathing through the mouth
• jaws that shift or make noise
• jaws and teeth that are out of proportion to the rest of the face