FA are generally used for children (in the period of permanent dentition) and teenagers/ adults in the following cases:
· Correction of mild to moderate skeletal discrepancies
· Intrusion/extrusion of teeth
· Correction of rotations
· Overbite reductions by intrusion of incisors
· Multiple tooth movement required in one arch
· Active closure of extraction spaces
· FA can be used in conjunction with other appliances and /or headgear
· Inter-maxillary traction is often used to aid anteroposterior correction and increase anchorage
Fixed appliances can’t be an alternative to removable appliances and can be used in patients who are willing to:
· maintain a high level of oral hygiene;
· avoid hard and sticky foods and the consumption of sugar-containing foodstuffs between meal;
· cooperate fully with wearing headgear or elastic traction, if required;
· attend regularly to have the appliance adjusted.
2. Components of fixed appliances.
Tooth movement with fixed appliances is achieved by the interaction between the attachment or bracket on the tooth surface and the archwire which is tied into the bracket.
The components of fixed appliances and their usage are summarized in Table 2.
Components of fixed appliances
Usually used on molar teeth to retain the end of the archwire. Prior to placement of a band it may be necessary to separate the adjacent tooth contacts using elastic doughnuts stretched around the contact point for 1-7 days. Use GI cements for band cementation to decrease risk of decalcification.
Bonded attachments are fixed to enamel with modern composites.
There are three types: 1 –metal (poor aesthetic), 2 – plastic; 3- ceramic brackets or buttons (can cause enamel wear).
The amount and type of force applied to individual tooth can be controlled by varying the cross-sectional diameter and form of the archwire, and/or material of its construction. In the initial stages of treatment flexible wires (NiTi, twisted stainless steel) with good resistance to permanent deformation displace teeth without application of excessive forces. In the later stages of treatment rigid archwires are required to engage the archwire slot fully and to provide fine control over tooth position.
Metal and elastic ligatures (to fix archwire into the slot of bracket), intra-oral elastic bands (intra-maxillary and inter-maxillary traction), palatal or lingual bars (reinforced anchorage, correction of positions of molars), quadhelix appliance (to achieve expansion), springs, elastic chains.
3. Types of fixed appliances.
Begg uses round wires which fit loosely into a vertical slot I the bracket, thus allowing the teeth to tip freely. Auxiliaries are required to achieve apical and rotational movements.
Edgewise uses rectangular brackets that are wide mesio-distally for rotational control. Round wires are used initially for alignment, but rectangular wires are necessary for apical control.
Pre-adjusted systems. These “pre-programmed” brackets allow increase use of pre-formed archwires. They are also known as straight wire appliance. As each tooth has its own individual bracket these systems are more expensive, but that is offset by savings on orthodontist time. Andrew’s Straight Wire appliance is the best known and popular system.
Lingual appliances. They are popular with patients, but not with orthodontists as they difficult to adjust.