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Methods

Typically treatment for malocclusion can take around 2 years to complete, with braces being altered slightly every 6 to 8 weeks by the orthodontist. There are multiple methods for adjusting malocclusion, depending on the needs of the individual patient. In growing patients there are more options for treating skeletal discrepancies, either promoting or restricting growth using functional appliances, orthodontic headgear or a reverse pull facemask. Most orthodontic work is started during the early permanent dentition stage before skeletal growth is completed. If skeletal growth has completed, orthognathic surgery can be an option. Extraction of teeth can be required in some cases to aid the orthodontic treatment. Starting the treatment process of overjets and prominent upper teeth in children rather than waiting until the child has reached adolescence has been shown to reduce damage to the lateral and central incisors. However the treatment outcome does not differ .

This Image shows a reverse pull functional appliance.

Functional appliances

When there is a maxillary overjet, or Class II occlusion, functional appliances can be used to correct the occlusion. These may be fixed or removable Fixed dental braces are wires that are inserted into brackets secured to the teeth on the labial or lingual surface (lingual braces) of teeth. Other classes of functional appliances include removable appliances and over the head appliances, and these functional appliances are used to redirect jaw growth. Post treatment retainers are frequently used to maintain the new position of the dentition.

Dental braces, with brackets removed after completion of treatment.

During fixed orthodontic treatment, metal wires are held in place by elastic bands on orthodontic brackets (braces) on each tooth and inserted into bands around the molars. The wires can be made from stainless steel, nickel-titanium (Ni-Ti) or a more aesthetic ceramic material. Ni-Ti is used as the initial arch wire as it has good flexibility, allowing it to exert the same forces regardless of how much it has been deflected. There is also heat activated Ni-Ti wire which tightens when it is heated to body temperature.. The arch wires interact with the brackets to move teeth into the desired positions.

Fixed orthodontic appliances aid tooth movement, and are used when a 3-D movement of the tooth is required in the mouth and multiple tooth movement is necessary. Ceramic fixed appliances can be used which more closely mimic the tooth colour than the metal brackets. Some manufacturers offer self-litigating fixed appliances where the metal wires are held by an integral clip on the bracket themselves. These can be supplied as either metal or ceramic .

The surfaces of the teeth are etched, and brackets are attached to the teeth with an adhesive that is durable enough to withstand the orthodontic forces, but is able to be removed at the end of treatment without damaging the tooth. Currently there is not enough evidence to determine whether self-etch preparations or conventional etchants cause less decalcification around the bonding site and if there is a difference between them in bond failure rate . The bonding material must also adhere to the surface of the tooth, be easy to use and preferably protect the tooth surface against caries (decay) as the orthodontic appliance becomes a trap for plaque. Currently a resin/matrix adhesive which is command light cured is most commonly used. This is similar to composite filling material .

Anchorage for the appliance prevents unwanted movement of teeth and it can come from the headgear worn, the palate, or surgical implants .

For young patients with mild to moderate Angle Class III malocclusions (prognathism), a functional appliance is sufficient for correction. Examples of functional appliances are: facemask, chin-cup, tandem traction bow or headgear . As the malocclusion increases, orthognathic surgery might be required. This treatment comes in three stages. Prior to surgery there is orthodontic treatment to align teeth into their post-surgery occlusion positions. The second stage is surgery such as a mandibular step osteotomy or sagittal/bilateral sagittal split osteotomy depending on whether one or both sides of the mandible are affected. The bone is broken during surgery and is stabilised with titanium plates and screws, or bioresorbable plates to allow for healing to take place . The third stage of treatment is post-surgical orthodontic treatment to move the teeth into their final positions to ensure the best possible occlusion . Treatment involves the expansion of the maxillary arch to restore functional occlusion, which can either be 'fast' at 0.5mm per day or 'slow' at 0.5mm per week. Palatal expansion can be achieved using either fixed or removable appliances . Banded maxillary expansion involves metal bands bonded to individual teeth which are attached to braces, and bonded maxillary expansion is an acrylic splint with a wire framework attached to a screw in the palatal mid-line, which can be turned and opened to expand the maxilla.

Removable functional appliances are useful for simple movements and can aid in altering the angulation of a tooth: retroclining maxillary teeth and proclining mandibular teeth; help with expansion; and overbite reduction.

Headgear works by applying forces externally to the back of the head, moving the molar teeth posteriorly (distalising) to allow space for the anterior teeth and relieving the overcrowding .

Some removable appliances have a flat acrylic bite plane to allow full disocclusion between the maxillary and mandibular teeth to aid in movement during treatment. An example of this is the Clark Twin Block. This design has two blocks of acrylic which disocclude the teeth and protrude the mandible. It is used to treat Class II malocclusion.

Invisalign aligner

Vacuum-formed aligners such as Invisalign consist of clear, flexible, plastic trays that move teeth incrementally to reduce mild overcrowding and can improve mild irregularities and spacing. They are not suitable for use in complex orthodontic cases and cannot produce body movement. They are worn full time by the patient apart from when eating and drinking . A large benefit of these types of orthodontic appliance are that they suitable for use when the patient has porcelain veneers: as metal brackets cannot be bonded to the veneer surface .

Adjunctive therapy

Adjunctive surgical and non surgical therapy have been researched as options to help reduce the duration of orthodontic treatment. Surgical intervention such as alveolar decortication, and corticision have been used in conjunction with orthodontic treatment to reduce the time spent in functional appliances, but more research is required into the possible effects of the surgery . Non-surgical therapy involves the use of vibrational forces during treatment, but it has not been shown whether this significantly reduces the treatment time, orincreases the comfort for the patient .

Extensive research has been done proving the effectiveness of functional appliances, but maintaining the results is important once the active treatment phase has completed.

Post treatment

After orthodontic treatment has completed, there is a tendency for teeth to return, or relapse, back to their pre-treatment positions. Over 50% of patients have some reversion to pre-treatment positions within 10 years following treatment . To prevent relapse, the majority of patients will be offered a retainer (orthodontics) once treatment has completed, and will benefit from wearing their retainers. Retainers can be either fixed or removable. Removable retainers will be worn for different periods of time depending on patient need to stabilise the dentition . Fixed retainers are a simple wire fixed to the labial surface of the incisors using dental adhesive and can be specifically useful to prevent rotation in incisors. Other types fixed retainers can include labial or lingual braces, with brackets fixed to the teeth.

Hawley retainers This picture shows retainers for the top and bottom of the mouth.

Removable retainers can include one known as a Hawley retainer, made with an acrylic base plate and metal wire covering the canine to canine region. Another form of removable retainer is the Essix retainer which is made from vacuum formed polypropylene or polyvinylchloride and can cover all the dentition .

See also

• Accelerated orthodontic treatment
• American Association of Orthodontists
• Canadian Association of Orthodontists
• Indian Orthodontic Society
• Orthodontic technology
• Orthognathic surgery
• List of Orthodontic Functional Appliances
• Molar distalization