Orthodontic technology

Orthodontic technology is a specialty of dental technology that is concerned with the design and fabrication of dental appliances for the treatment of malocclusions, which may be a result of tooth irregularity, disproportionate jaw relationships, or both.

There are three main types of orthodontic appliances: active, passive and functional. All these types can be fixed or removable.

Active appliances

An active appliance is a device used to apply forces to the teeth to change the relationship of the teeth.

Removable active appliances

Removable appliances are useful for the following tooth movements: [1]

  • Tipping movements of teeth
  • Movement of blocks of teeth
  • Influencing the eruption of opposing teeth

Indications for the use of removable appliances[1]

  • Treatment of malocclusions where simple tipping movements are required. However, its limitations are apparent when treatment of the malocclusion necessitates more complex tooth movements.
  • Movement of blocks of teeth, for example applying extra-oral traction of segments of teeth, or an entire arch to achieve intrusion and distal movements of the teeth.
  • To achieve maxillary arch expansion

Advantages and disadvantages

There are several advantages and disadvantages of removable appliances. The advantages of removable appliances include the fact that it may be easier to maintain oral hygiene as it can be removed when tooth-brushing. Furthermore, for upper removable appliances the palatal coverage provides increase anchorage during tooth movement. It is also easier to adjust, and there is a lower risk of causing iatrogenic damage to teeth compared to fixed appliances.[1] The acrylic base plate of the appliance can be thickened to provide a flat-anterior bite plane or buccal capping which may be useful in certain cases to alter the development of the posterior teeth and/or to free the occlusion with the lower arch. Moreover, removable appliances are useful for transmitting forces to blocks of teeth.

Meanwhile, the disadvantages of removable appliances include the inability to produce complex three-dimensional tooth movements as only tilting movements are possible. The appliance is unable to cause individual tooth movements. Poor compliance may also be an issue as the appliance can be removed by the patient, which may affect the duration of treatment required. Due to the baseplate on the palate, speech may be affected during initial wearing of the appliance. Furthermore, lower removable appliances are difficult to tolerate.

Components of a removable appliance

There are four components in every removable appliance, these are

  1. Active component(s) - e.g. springs, screws and elastics[1]
  2. Retentive component(s) - e.g. Adams clasp, Southend clasp, Ball-ended clasp, Plint clasp, and labial bows[1]
  3. Baseplate - the baseplate can be a passive or active component of the appliance. The baseplate can be constructed using self-cure or heat-cure acrylic, and additional modifications such as an anterior bite-plane and buccal capping can be added if the treatment necessitates these.[1]
  4. Anchorage[1]

Fixed active appliances

Edward Angle, regarded as the father of American orthodontics,[2] developed many universal fixed active appliances, unifying orthodontic practice.[3]

  • Begg lightwire appliances
  • Pre-adjusted edgewise appliances
  • Self-ligating edgewise appliances
  • Bi helix
  • Tri helix
  • Quad helix
  • Palatal expander/rapid maxillary expansion appliance (RME)
  • Tip-edge appliance

Functional appliances

Upper and Lower Jaw Functional Expanders

There is a totally different orthodontics approach without extraction and pain, is called functional orthodontics, the functional orthodontic technology is different and called functional appliance, that is an appliance that produces all or part of its effect by altering the position of the mandible/maxilla. Also known as dentofacial orthopaedic appliances, these appliances utilize the muscle action of the patient and responses of nervous system to produce orthodontic or orthopaedic forces. Various functional appliances have been described. There is a List of Orthodontic Functional Appliances.

Functional appliances are orthodontic appliances that are used to correct a malocclusion by avoiding mouth breathing and utilising, eliminating or guiding muscle function forces, tooth eruption and growth. Although there are many different types (fixed and removable), the majority work by via forward mandibular posturing to promote mandibular growth in growing patients. They are mostly used to reduce the projection of the front teeth (increased overjet) in patients with class II malocclusion. These appliances are not very effective at correcting dental irregularities or improving alignment and so are usually followed by treatment with fixed appliances.[4] Whilst functional appliances have been suggested for treatment of Class III malocclusion, their limited success has been superseded by substantially improved treatment results with protraction headgear.

Orthodontic headgear

Headgear.

Orthodontic headgear is a type of appliance attached to dental braces that aids in correcting more severe bite problems.

Headgear is an orthodontic appliance for the correction of Class II correction, typically used in growing patients to correct overbites by holding back the growth of the upper jaw, allowing the lower jaw to catch up.

The headgear can also be used to make more space for teeth to come in. The headgear is then attached to the molars (via molar headgear bands & tubes), and helps to push or draw them backwards in the mouth, opening up space for the front teeth to be moved back using braces and bands.

Full orthodontic headgear with headcap, fitting straps, facebow and elastics

Headgear needs to be worn approximately 12 to 22 hours a day to be truly effective in correcting the overbite, and treatment is usually anywhere from 6 to 18 months in duration, depending on the severity of the overbite and how much a patient is growing.[5]

Orthodontic facemask and reverse-pull headgear

Facemask

Facemask or reverse-pull headgear is used to control the growth of the maxillary and mandibular bones during orthodontic treatment.

The appliance is used in growing patients to correct under bites (known as a Class III orthodontic problem) by pulling forward and assisting the growth of the upper jaw, allowing the upper jaw to catch up.

Facemasks or reverse-pull headgear needs to be worn approximately 12 to 22 hrs to be truly effective in correcting the under bite, usually anywhere from 6 to 18 months depending on the severity of the bite and how much a patient is growing.[5]

The appliance normally consists of a frame or a centre bars that are strapped to the patients head during a fitting appointment. The frame has a section which is positioned in front of the patients mouth, which allows for the attachment of elastic or rubber bands directly into the mouth area. These elastics are then hooked onto the child's braces (brackets and bands) or appliance fitted in his or her mouth.

This creates a forward 'pulling' force to pull the upper jaw forward.

Fixed functional appliances

  • Herbst appliance: A Herbst appliance corrects overbites by realigning the jaw. Typically used in children, this device attaches rings glued to the top and bottom teeth. This metal appliance is often worn at the same time as braces.[6]
  • Twin block appliance: The twin block appliance is a removable appliance, and its high comfort level allows you to wear it 24 hours a day. This appliance actually is made up of two separate appliances that work together as one. The upper plate includes an optional expansion screw to widen your upper arch, if needed, as well as pads to cover your molars. The lower plate includes pads to cover your lower bicuspids. These two appliances interlock at an angle, and they move your lower jaw forward and lock it into the ideal position when you bite together. This new position, while temporary, will eventually become the permanent corrected position.
  • Fixed Lingual Mandibular Growth Modificator (FLMGM): The FLMGM consists of two separate and fixed parts. The upper one is palatally positioned but bucally clipped to traditional upper molars bands, while the lower is lingually welded to traditional lower molars bands.

Maxillary part: It has the following components: Acrylic button, two retention wires: one in each side, two retention hooks and advancement loops. Mandibular part: It is made in a similar manner to a standard lingual arch with 1.0 mm stainless steel hard wire welded to the lingual aspect of fi rst molars bands. From a clinical perspective, the FLMGM offers the following advantages: 1) Permanent effect, independent of patient compliance, as it is fixed. 2) Esthetics, as it is small and lingually located. 3) Eliminates the need for two separate treatment phases, as it is suitable for use in parallel with complete multibracket appliance in both arches. 4) Flexibility in treatment timing, as it can be used anytime during the mixed and permanent dentition. 5) No interference with occlusal development. 6) Wide and comfortable range of mastication movements, as the appliance consists of two separate parts with no permanent and physical intermaxillary connection.

Treatment Timing

Timing of treatment with functional appliances is crucial as they must be used whilst the patient is still growing in order to achieve maximum benefit. It has been suggested that the best time to prescribe one of these appliances is in alignment with the pubertal grown spurt.[7]

Types

There are many different types of fixed and removable functional applications. Only a few of the most common are discussed below.

The most popular functional appliance is the Twin-block appliance as it has been found to be the most “patient-friendly”.[8] This consists of upper and lower removable appliances that each have bite blocks posturing the mandible into a forward position.[4] However, patient compliance can sometimes be an issue with this appliance as the bulky acrylic blocks can cause issues with eating and speaking and patients can easily remove them.[8] Removable Twin-blocks have been found to be as effective as the fixed Herbst appliance.[9]

The Herbst appliance is a fixed-functional appliance. It consists of sections attached to the upper and lower posterior teeth that are attached by a rigid arm pushing the mandible forwards. The fact that it is a fixed appliance eliminates the patient compliance issues that accompany the Twin-block appliance.[8] O’Brien et al. (2003) found that treatment the Herbst appliance displayed a lower failure-to-complete treatment rate (12.9%) than Twin-block appliances (33.6%).[10] However, the Herbst application still remains the less popular choice than the Twin-blocks due to a higher breakage rate and increased cost of appliance manufacture and clinical time.[4]

A myriad of other functional appliance have been invented including the standard activator, the medium opening activator (MOA), Bionator and Frankel. The MOA is a single piece functional appliance that allows for greater patient comfort with minimal acrylic than any of the other single-piece removable functional appliances but complaince with all of these can be limited due to these paradoxically limiting normal mandibular function during wear. All of these appliances allows selective eruption of the lower posterior teeth which is useful for reducing a deep overbite whilst correcting the Class II malocclusion.[4]

Additional benefits

Tulloch et al. (1998) found that functional appliances reduce the need for orthognathic surgery.[11] The use of functional appliances to correct Class II malocclusion can also have psychological benefits. O’Brien at el. (2003) found that early treatment using Twin-block appliances increased the patient’s self-esteem and resulted in reduced negative social encounters.[9]

See also

References

  1. 1 2 3 4 5 6 7 Mitchell, Laura (2013). An introduction to orthodontics. Simon J. Littlewood, Zararna Nelson-Moon, Fiona Dyer (4th ed.). Oxford: Oxford University Press. ISBN 978-0-19-100303-5. OCLC 854583725.
  2. ↑ Peck, Sheldon (Nov 2009). "A biographical portrait of Edward Hartley Angle, the first specialist in orthodontics, part 1". Angle Orthod. United States. 79 (6): 1021–7. doi:10.2319/021009-93.1. ISSN 0003-3219. PMID 19852589.
  3. ↑ King, Sam (18 January 2015). "The History of Orthodontic Technology". King Orthodontics. Retrieved 4 April 2015.
  4. 1 2 3 4 MITCHELL L. (2007). An introduction to orthodontics. 3rd ed. Chapter 19: Functional appliances. Pg 203-215.
  5. 1 2 Children and Orthodontics: Types of Braces, Retainers, Headgear and Facemasks www.webmd.com/oral-health/guide/children-and-orthodontics WebMD describes common types of orthodontics for children, including braces headgear, and retainers.
  6. ↑ "Can I Straighten Teeth Without Braces? All About the Options". Healthline. 2020-03-31. Retrieved 2020-10-29.
  7. ↑ FRANCHI L., PAVONI C., FALTIN K., MCNAMARA J.A. and COZZA P. (2013). Long-term skeletal and dental effects and treatment timing for function appliances in Class II malocclusion. The Angle Orthodontist. 83(2): 334-340.
  8. 1 2 3 CLARK W. (2010). Design and management of Twin Blocks: reflections after 30 years of clinical use. Journal of Orthodontics. 37: 209-216.
  9. 1 2 O’BRIEN K. et al. (2003). Effectiveness of early orthodontic treatment with the Twin-block appliance: a multicentre, randomized, controlled trial. Part 2: Psychosocial effects. American Journal of Orthodontics and Dentofacial Orthopedics. 124(5): 488-494.
  10. ↑ O’BRIEN K. et al. (2003). Effectiveness of treatment for Class II malocclusion with the Herbst or twin-block appliances : a randomized, controlled trial. American Journal of Orthodontics and Dentofacial Orthopedics. 124(2): 128-137.
  11. ↑ TULLOCH J.F., PHILLIPS C. and PROFFIT W.R (1998). Benefit of early Class II treatment: progress report of a two-phase randomized clinical trial. American Journal of Orthodontics and Dentofacial Orthopedics. 113: 62-72.
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