Lingual braces

Below are listed generations of the Ormco brackets that were created between 1976 and late 1980s.

1. Generation #1 - This was the original appliance that Craven made with Ormco in 1976. The initial appliance included low profile brackets, maxillary occlusal plane on the upper brackets. These brackets did not have hooks on the brackets.
2. Generation #2 - In this generation, hooks on canines were added in the year 1980.
3. Generation #3 - All premolar and anterior brackets received hooks in 1982.
4. Generation # 4 - The anterior inclined plane was made to be more of low profile in this generation, and at this point due to concerns of gingival impingement from the hooks of brackets, they were made to be optional by the company.
5. Generation # 5 - In 1985, this generation received more torque values for the maxillary incisors, and the company increased the size of the anterior inclined plane.
6. Generation #6 - In 1988, his generation saw a Transpalatal bar hook being added to the molar brackets and the inclined plane on the anterior brackets became more of square shape.
7. Generation #7 - This last generation the inclined plane was made to be heart shaped. Hooks were made longer to allow easier ligation of the elastic o rings. The premolar brackets were also widened mesio-distally.

An advantage of the lingual brackets over the buccal brackets is the less decalcification marks on the buccal side of the teeth which is more visible to the naked eye. Patients with poor oral hygiene can have increased white spot lesions which present themselves buccally and can stay there post-orthodontically if proper oral hygiene is not maintained.[11]

Initial appliances formed in 1980s irritated patient's tongues and had higher breakage rate. However, different companies made the bracket profile smaller and smoother which allowed less irritation to soft tissues around the bracket. However, the same problems still persisted over the years and treatment approach presently is to inform the patient that irritation and speech impairment will improve in 2–3 weeks after the bracket placement.[12][13]

A systematic review and a meta-analysis published in 2016 stated that lingual braces cause greater amount of pain in tongue, problem maintaining oral hygiene and problems with speech and eating difficulties.[14]

Lingual brackets are located more closely to the center of resistance of a tooth than brackets placed on a buccal surface of a tooth. Thus when a patient bites down, the biting forces are directed through the center of resistance of those anterior teeth. Thus the light continuous forces directed towards the upper lingual brackets may induce slight intrusion of the upper anterior teeth. However, forces that are felt on the anterior teeth seem to be minimal, in milligrams. An optimum force needed to intrude teeth is 30-40g.[15]

As the mandibular teeth are biting on the upper brackets, it results in an anterior bite plane effect. This eventually leads to the light, continuous intruding force that is being felt on the front incisors. This bite plane effect may also induce slight opening in the posterior molar teeth and these teeth may extrude, leading to correction of deep bite or worsening of an already open bite. This can worsen a Class 2 malocclusion as mandible rotates down and back, leading to more of a Class 2 molar relationship.

Due to the small interbracket distance in the lingual braces, compare to the buccal braces, compensatory bends which can be made in finishing phase are tough to create. The distance between brackets anteriorly in lingual braces is about 40% smaller than the buccal braces. Despite the bends, making loops to close spaces also becomes mechanically tough.[16][17]

Lingual orthodontics is known to have both vertical and horizontal bowing effects during space closure. These effects are related to in terms of closing spaces on an archwire which may not fill the slot completely. Therefore, increased play in the wire to bracket relationship can cause effects which may lead to more of a tipping tooth movement than pure translation, as desired in most cases. These effects can be counteracted by either placing anti-bowing effect curves both vertically and horizontally, by using lighter retraction forces or by steel-ligation of posterior teeth as a unit to prevent the side-effects.

Incognito lingual brackets and wires are made by 3M in Germany. These appliances were initially designed by Dirk Wiechmann. He published his results in 2003 in American Journal of Orthodontics and Dentofacial Orthopedics, where he reported testing these appliances for 18 months on 600 bonded arches on patients in his private practice.[18] The company uses a CAD/CAM technology to combine bracket fabrication and bracket positioning which is done on computer models. The wires and brackets are customized to each patient's anatomy of the lingual tooth surface. The bases of these brackets are bigger than other brackets produced by different companies, however these appliances have thinner bracket base and use less bonding material than other brackets. This may be seen as an advantage by some due to low profile of brackets which may cause less irritation to the tongue of patients, but this does lead to creating 1st order bends in the wires to compensate for the low profile of these brackets. A study done in Germany in 2005 compared the pre-adjusted lingual brackets (Ormco) to customized lingual brackets (Incognito) on a group of 40 German-speaking women. The results stated that customized brackets in the study induced significantly fewer cases of tongue space restriction, pressure sores, reddening or lesions to the tongue in the long term than the pre-fabricated brackets.[19] Even though the results favor the Incognito appliance, it should be kept in mind that this is a subjective opinion of people which may confound the results.