Advanced Orthodontic Treatment and Retention

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ORTHODONTIC EXTRACTIONS

Crowding due to a lack of arch space may warrant the extraction of teeth (usually premolars) before orthodontic treatment is started. It is possible to camouflage a Class II or Class III by extracting the premolars in one arch to achieve a canine Class I relationship with normal overjet and overbite. Extractions may be considered when there is large amount of crowding (more than 4mm), flared incisors, minimal overbite or open bite, full/protrusive lips, acute nasolabial angle, to camouflage a Class II or Class III, already missing or compromised teeth, or to balance occlusal asymmetry. In severe crowding (>10mm) extractions are almost always required. Extractions should be avoided where there is minimal crowding (may create too much space), upright incisors, deep overbite, flat/recessive lip profile, or obtuse nasolabial angle.

SPACE MAINTENANCE

One of the challenges in pediatric dentistry is the management of space loss following the loss of primary teeth. Potential problems can be prevented or minimized if the practitioner employs adequate planning and space maintenance during initial treatment in the mixed dentition. Various appliances can be used for space maintenance based on the patient’s age, the growth and development of dental arches and the patient’s level of cooperation. Removable space maintainers are more appropriate for short-term space maintenance due to several disadvantages, including:

Poor retention.
Less tolerance.
High chances of appliance dislodgement.

A patient’s own tooth is often the best space maintainer. Keeping deciduous teeth until they are due to naturally exfoliate is most likely to result in a good orthodontic outcome, so if restoring the deciduous tooth is an option it’s often the best option. If a deciduous incisor is lost early, it is very unlikely to cause space issues, unless overcrowding is predicted. The parents may be concerned about aesthetics and you can consider something like a kiddie partial (fixed or removable).

The loss of a primary canine can cause space loss, lingual collapse of the incisors, midline deviation and loss of arch length. If only one canine has been lost, consider removing the contralateral canine and placing a space maintainer (to maintain symmetry). The loss of a baby molar or adult tooth will very likely cause space loss, unless the deciduous tooth is close to exfoliation and the adult tooth is close to erupting (know your eruption times). A radiograph may be needed to see where the unerupted teeth are positioned.

Space maintainers help to hold open the space originally held by a baby tooth and maintain proper arch architecture. Resin bonded space maintainers have become popular due to:

The ease of bondability.
The ease of fabrication.
Patient comfort and aesthetics.

Studies show that resin fiber space maintainers can be a successful option but are better used over a short period of time.

Single missing tooth

Band and loop – this device is most often used when the primary first molar is prematurely lost unilaterally. The second molar is banded, with the loop sitting against the distal surface of the canine. The band and loop is removed once the first premolar starts erupting. It can be used on other teeth. The most common reason stated for the failure of the appliance is cement failure and solder breakage. Crown and loop space maintainer – similar to a band and loop design but it has a higher survival rate.

Distal shoe – a modification of the band and loop, where one tooth (usually the adult first molar) is unerupted or partially erupted.

Orthodontic wire or fiber reinforced resin bonded directly to teeth can act as an inexpensive and immediate solution.

Multiple missing teeth

Nance (or transpalatal) appliance – used when there is bilateral premature loss of deciduous teeth. This appliance uses the soft tissue in rugae area as a brace to prevent the first molars from rotating and drifting mesially. This is a maxillary appliance (only) and can be utilized for anchorage.

Partial denture – can be used as a space maintainer, while also improving aesthetics and function.

Lower lingual arch – wire adapted to the lingual aspect of lower teeth. U loops allow for adjustments. Can be used for anchorage.

Early loss of first molars

Premature loss of the adult first molars will cause the mesial migration and tipping of the second molars. In order to re-establish the correct vertical orientation of occlusal forces and overall health, teeth may need to be moved into an upright position. Orthodontic correction may be accomplished through a combination of tipping and translation. In general, the larger surface area of the tooth and the increased complexity of movement means a larger force is required, increasing the likelihood of complications. For these heavy orthodontic movements a band (instead of a bracket) and thicker gauge wire would likely be used. Longer treatment time (6-12 months) and longer retention time (6 months) is expected. Occlusal interferences may slow treatment significantly.

SERIAL EXTRACTION

Serial extractions refer to the structured removal of teeth in a predetermined order. It’s usually used in Class I malocclusion cases where there is insufficient arch length (space issue, not skeletal). Teeth are extracted and space maintained with either a Hawley appliance (maxilla) or lingual arch (mandible). Orthodontic treatment is usually required afterwards. Extractions are spaced by 6-15 months, and the teeth are removed in the following order:

primary canine.
first primary molar.
permanent first premolar before adult canines erupt.

ORTHOGNATHIC SURGERY

Some orthodontic problems are too severe for orthodontic treatment alone. A selection of maxillary and mandibular surgeries are available, depending on the cause of the malocclusion. There are options for anteroposterior, vertical and transverse corrections that can be made. Surgery is usually performed after the jaws have finished growing, and after a course of orthodontic treatment to align the teeth with the appliances in place. Orthodontic treatment follows the surgery.

Maxillary surgery – A LeFort I downfracture is used to mobilize the maxilla. This can be moved anteriorly to treat a Class III, posteriorly to treat a Class II (though this is difficult, and usually is done as segmental osteotomy), or vertically up to fix an open bite and long face, or down to reduce an overbite and lengthen the face. Moving the maxilla inferiorly is the least stable surgical procedure.

Mandibular surgery – bilateral sagittal split osteotomy (BSSO) of the ramus is the preferred procedure. The mandible can be moved forward (advancement) to correct a Class II, or moved backwards (setback) to fix a Class III. Vertically the jaw can be rotated open to correct for a deep bite, but rotating the mandible closed is not recommended. Inferior alveolar nerve/mental nerve paraesthesia is a common side effect, usually resolving in 2 to 6 months, but in a quarter of patients damage may be permanent.

Transverse corrections can be accomplished in the maxilla by surgically opening up the sutures and expanding or constricting, or surgically freeing the sutures followed by treatment with a rapid maxillary expander. Genioplasty can be performed to change the appearance of the chin.

RETENTION

A tooth that has been orthodontically moved will exhibit a tendency to move back towards its pretreatment position due to the elastic supracrestal gingival fibers (free gingival and transseptal collagen fibers). Lower anterior teeth appear to be the most prone to relapse. Occlusal and soft tissue forces may also contribute. Long term retention (e.g. lingual bar) is often used to hold anterior teeth in place to avoid relapse.

After orthodontic treatment, stabilization should last until the lamina dura and PDL reorganize. This could take 2 months for simple movement, or 6 months for more complicated treatment like uprighting, osseous surgery, grafts etc. Full time retention is usually applied for 3-4 months, part time retention for up to 12 months. Permanent retention may be necessary if the teeth are left in an unstable position (e.g. lower incisors, late mandibular growth). Retention is generally not necessary after anterior crossbite treatment (the bite is the retainer). There are a few types of retainers used:

Fixed retainers – are the most commonly used, often bonded canine to canine. Fixed retainers can be placed lingually or palatally, though care must be taken not to interfere with the patient’s bite. They do not rely on patient compliance, but can break.

Removable retainer – wire and acrylic base (Wrap around or Standard Hawley) or vacuum formed/3D printed (Essix, Invisalign retainer).

Post-orthodontic Circumferential Supracrestal Fiberotomy is indicated for rotated maxillary lateral incisors because the supra-alveolar PDL tissue is often responsible for the relapse of rotated teeth. An incision is made in the sulcus to the crest of the bone to sever all collagen fibers. The fibers will reorganize into a stable configuration.

POSSIBLE NEGATIVE OUTCOMES

Orthodontic treatment is associated with a number of possible adverse effects, such as:

Pain – especially after adjustments. Heavy forces are more likely to lead to tissue necrosis.

Pulpal changes – mild pulpitis most common, but orthodontic treatment could result in the loss of vitality, especially if there was a history of trauma or extensive treatment to the tooth. Certain treatments may pose a risk to the periapical blood supply. Generally there is no discernible difference in outcome when treating RCT teeth vs normal teeth.

Trauma to soft tissue – especially when fixed appliances are first bonded.

Increased caries risk – fixed appliances make the teeth more difficult to clean. Decalcification around brackets is commonly seen.

Tooth mobility – can be worsened by periodontal disease or occlusal interferences.

Root resorption – there is an increased risk of root resorption when treating teeth with short roots. Clinicians should be wary of the use of heavy forces, difficult movements, a history of dental trauma, bruxism, or cases of previous root resorption. Maxillary lateral incisors are most at risk.