NEWSLETTERS

Should we always create space in the dental arch for an impacted canine, before it is exposed?

Published: September 2011

Should we always create space in the dental arch for an impacted canine, before it is exposed?

In general, the answer to this question is a resounding yes! There are many good reasons for this…..

  1. ….. by creating space, the canine will often re-awaken its natural eruptive potential and begin to move in the right direction. In the most favorable scenario, this could result in the avoidance of surgery, although it may take a very long time before the canine erupts (fig. 1). It should be remembered that canines take a long time to erupt fully, even in the normal situation. Thus, when the circumstances are hindered by displacement of the canine from its normal line of eruption, spontaneous eruption will take considerably longer, sometimes stretching into a year or more. This would mean leaving the orthodontic appliances in place to maintain space and to later complete the finishing procedures, which may include rotation, uprighting and root torque of the canine, before the braces may be removed. This could be a high price to pay for too conservative an attitude. In this situation, it is often wiser to expose and actively erupt the canine, in order to complete the treatment in short order and to remove the appliances – thereby avoiding unnecessary collateral damage due to the long term side effects (decalcification, frank caries and periodontal disease) of leaving appliances on the teeth, particularly in a young patient1.
  2. …… even without spontaneous eruption, the intra-bony position and orientation are usually improved, which will simplify the surgical exposure of the canine and thus reduce treatment time and improve the periodontal prognosis of the outcome.
  3. …… by creating space, we also create an area of attached gingiva through which a displaced tooth may erupt or be erupted. Without the creation of space, a labially displaced canine will likely erupt through the very mobile and non-keratinized oral mucosa, high in the sulcus and thus start intra-oral life at a periodontal disadvantage.
  4. ……. the lateral incisor root and the palatal root of the first premolar are usually lingually oriented and, as such, will often stand in the way of a palatal canine (fig. 2c). When creating space, therefore, it is important to mesially upright the root of the lateral incisor. Additionally, it is important to distally upright the root of the premolar and to de-rotate its palatal root distally, to clear a path high in the alveolar ridge, for the canine.

Fig._1_september_2011

Fig. 1. The right maxillary canine has been diagnosed to be impacting palatally. Additionally, the mandibular second premolars have insufficient space to erupt due to early loss of the deciduous molars. Appliances were used simply to create space in both arches and the teeth erupted spontaneously, without surgical intervention.

But there are other situations in which space opening should be avoided until after the surgical exposure has been made and sometimes until certain other functions have been carried out. Thus, space opening is contraindicated as a first step …….

  1. ….. when the root of the lateral incisor/central incisor is undergoing resorption in association with the close proximity of the advancing canine crown.
    Creating space in the simplest cases requires several months of orthodontic treatment, but this may stretch into a year or more, when leveling and alignment need to be achieved first and when adjacent roots need to be moved away from the prepared canine eruption path. During this time, the canine continues its devastating resorptive advance on the incisor roots, which may leave nothing worth saving, when the stage is set for canine exposure. In these circumstances, the canine must be exposed as a first and urgent prerequisite to any other form of treatment and active traction force applied to it in a direction away from the threatened incisor root. This force may be labially- or palatally-directed using a custom-made spring or elastic tie to a soldered palatal arch or self-supporting buccal arm, until the tooth is distanced from the incisor roots and erupted into a “neutral corner”. The root resorption may then confidently be expected to arrest2 and space preparation initiated, along with the other needed orthodontic movements for the overall treatment of the case and including alignment of the errant canine.
  2. …… when the canine is in the line of the arch and is in close relationship with the distal aspect of the root apex of the lateral incisor, with no apparent overlap seen with Clark’s tube-shift (parallax) method of radiographic positional diagnosis. In these circumstances, the orientation of the canine is mesio-angular, with a distal inclination of the lateral incisor (fig. 2a). Mesial uprighting the incisor would appear to be the logical way of increasing the space in the arch for the canine, but it causes distal displacement of the apex of the lateral incisor, which is resisted by the canine. In this scenario, there is a distinct danger of iatrogenic root resorption of the incisor (fig. 2b). It would therefore be advisable to leave the lateral incisor without a bracket, until the canine has been drawn clear of its proximity to the incisor apex.

Fig._2aFig. 2b_1Fig. 2c_2

Fig. 2. (a) the impacted right maxillary canine is in the line of the arch and has displaced the lateral incisor root mesially.

(b) bonded appliances were placed to re-open space for the canine prior to surgical exposure. Root uprighting has caused severe resorption of the lateral incisor root due to resistance from the canine crown.

(c) the CBCT 3D view shows the severe resorption. It also shows how space opening at the occlusal level has caused some tipping and rotation of the premolar bringing its palatal root into contact with the canine in the area of the CEJ, further blocking its eruption path.

3…… in the adult patient, when there is reason to believe that the canine will not move due to ankylosis, crown or cervical root resorption3. When deciding on the orthodontic treatment of a particular case, we plan the part each tooth will play in the overall dental scheme. If the canine will respond to orthodontic traction forces, then plan A will be employed, to include it in the final alignment. If the tooth will not respond, then plan B will be substituted. However, in order to test the responsiveness of the canine, we would normally use an orthodontic appliance and get ourselves deeply into much treatment, which may turn out to be entirely superfluous, before we are in a position to make the crucial decision. Is there a way to avoid this? In these cases, it is worthwhile to place a temporary anchorage device in a convenient location in the palate or elsewhere, at the same time as the impacted canine is being exposed. An attachment is bonded to the tooth and an elastic tie is drawn under tension between the two will quickly permit the diagnosis to be made, without involving unnecessary appliance construction, discomfort, time and money (fig. 3).

Fig. 3a_1Fig. 3b_1

Fig. 3 (a) the palatal canine in an adult patient has been exposed and an eyelet bonded.

(b) The twisted steel ligature has been drawn through the fully sutured flap and turned into a hook, which is linked to the TAD by an elastic chain under tension.

4. …… in any patient where there is loss of integrity/continuity of the outline of the follicle or where there is invasive cervical root resorption (ICRR) of the canine itself. A collapsed or undefinable follicle around the unerupted tooth or ICRR should always make the orthodontist suspicious that the tooth may not respond to orthodontic forces. By contrast, follicular enlargement is not a contraindication.

It is clear, therefore, that comprehensive radiography of the impacted canine is crucial and it has two important aspects. A good quality periapical view of the tooth is essential and is the best plane film method of diagnosing local pathology, in the forms of invasive cervical root resorption of the affected tooth or root resorption of the neighbouring teeth, lack of dental follicle integrity, follicle enlargement and other strictly local conditions. The second aspect is in relation to its 3D orientation within the maxilla and its proximity to the adjacent teeth and to other structures. There are some situations in which well chosen plane radiographic films alone will provide this information, but there are many others in which cone beam computerized tomography (CBCT) is crucial.1,4,5

References

  1. Becker A. The orthodontic treatment of impacted teeth. 2nd edition. Abingdon: Informa Healthcare Publishers. 2007. ISBN-13: 978 1 84184 475 6.
  2. Becker A, Chaushu S. Long-term follow-up of severely resorbed maxillary incisors following resolution of etiologically-associated canine impaction. American Journal of Orthodontics and Dentofacial Orthopedics 2005,127:650-654.
  3. Becker A, Chaushu S. Success rate and duration of orthodontic treatment for adult patients with palatally impacted maxillary canines. American Journal of Orthodontics and Dentofacial Orthopedics 2003,124:509-514.
  4. Chaushu S, Chaushu G, Becker A. The role of digital volume tomography in the imaging of impacted teeth. World Journal of Orthodontics 2004,5:120-132.
  5. Becker A, Chaushu S, Casap-Caspi N. CBCT and the Orthosurgical Management of Impacted Teeth. Journal of the American Dental Association 2010;141(10 suppl):14S-18S