NEWSLETTERS

Interceptive uprighting of incisor roots to eliminate maxillary canine impaction

Published: September 2014

Bulletin #36 - September 2014

Interceptive uprighting of incisor roots to eliminate maxillary canine impaction

A girl aged 8 years was referred by her pediatric dentist, who had examined the clinical and radiographic presentation of the maxillary permanent incisors, which had made her concerned about the possibility of bilateral canine eruption problems. The young girl exhibited class 1 occlusal relationships in the early mixed dentition stage with widely spaced maxillary incisors. Deciduous canines and molars were present, in addition to all four permanent first molars. As the result of trauma a year or so earlier, the left central incisor had fractured off its mesial incisal corner, but the tooth was vital with a normal response to the pulp tester.

The child arrived for her first visit with a panoramic radiograph that had been taken in February 2012 and the relationship between the unerupted permanent canine crowns and the lateral incisor apices could be clearly seen. gUIDANCE

Fig. 1a, b. The first of these two figures shows the initial relationship between the long axes of the incisor teeth and the unerupted canines in the maxilla in the “Ugly Duckling” stage of dental development. At this age, the canines are high up on the roots of the incisors, restricting the roots, which become tipped towards the midline, thereby causing spacing and distal flaring of their crowns. The second diagram describes how eruptive movement of the canines is guided by the distal surface of the roots and, eventually, the crowns of the lateral incisors. This releases the incisor roots from the restrictive influence, while pushing the crowns of the incisors together and changing the orientation of the long axes of each of these teeth.

This figure is taken from the second edition of my textbook entitled: Treatment of Impacted Teeth, published by Informa Healthcare, for whose permission to publish on this website, I am grateful.

The pediatric dentist’s worries were focused on the fact that the long axes of the maxillary incisors were oriented such that their apices were distally displaced, which is highly unusual. In the “ugly duckling” stage of development of the anterior dentition, the crowns of the four incisors are typically flared distally and labially, with their long axes convergent apically and held tightly together by the presence of the crowns of the unerupted canine, high up on the distal side of the lateral incisor roots (Fig. 1).

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Fig. 2a, b. Pre-treatment panoramic and periapical views of the initial condition, showing the divergent roots.

The roots of the lateral incisor teeth in this case were divergent as they proceeded apically (Fig. 2). The concern was that these root apices would be distally located to the crowns of the developing canines and would prevent normal eruption by, thus, blocking their eruption paths.

The treatment plan was to close the incisor spacing by mesially uprighting the roots of the four incisors towards the midline, with the expectation that the canine crown relationship with the lateral incisor roots would improve and permit a more favorable eruption path for the canines. This would then improve the chances for the normal and spontaneous eruption of the maxillary canines.

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Fig. 3a. The colored locating jigs on the brackets at the time of bonding show the degree of divergence of the long axes of the incisor teeth.

Fig. 3b. The initial 0.014” round NiTi archwire is ligated on 6 January 2014. N.B. Tip Edge brackets permit a broad degree of tip in the horizontal slot, enabling full ligation before uprighting is achieved.

Accordingly, molar bands and Tip Edge Plus brackets (TP Orthodontics Inc.) brackets were placed on all the permanent and deciduous teeth in the maxilla, on 6 January, 2014 (Fig. 3). Leveling and alignment were quickly achieved using a 0.014” NiTi archwire and anterior spaces closed.

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Fig. 4a. The 0.020” round steel base arch is still in place after the uprighting spring auxiliaries have bee removed, immediately prior to de-bonding.

Fig. 4b. Following de-bonding on 7 July 2014, the lateral incisors crowns, in particular, may be seen to be distally flared, as seen in a naturally occurring and normally developing incisor alignment, in the mixed dentition stage.

Mesial uprighting of the strongly divergent roots of the teeth was then performed until the long axes of the incisor teeth were made to converge as they proceeded apically, which is what one would expect to see in normal development at this age (Fig. 4). This was accomplished using a base arch of 0.020” stainless steel round and employing individual uprighting springs in the vertical slots of the 4 incisor brackets. The panoramic film taken immediately prior to debonding shows the re-orientation of the long axes of the incisors and it also shows considerable improvement in their relation to the unerupted canines, which can be seen to be moving down the distal aspect of the lateral incisors in a new eruption path towards spontaneous eruption into their places in the dental scheme (Fig. 5).

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Fig. 5a, b. The panoramic and periapical views seen post-treatment, show the converging long axes of the roots. The canines now appear to be more vertically directed, on the distal of the lateral incisor roots and heading downwards in an excellent eruption path.

At the completion of treatment, debonding was performed on 7 July 2014, a simple Hawley retainer was placed and the patient was referred for the extraction of the maxillary deciduous canines and first deciduous molars. This precaution was taken to further encourage the canines to erupt into their correct place. The rationale for the extraction of the deciduous canines is well known and has become an established interceptive measure in the mixed dentition, when canine impaction is suspected. However, the concurrent extraction of the deciduous first molar is a less known remedy.1 Its extraction will serve to encourage the rapid eruption of the first premolar. When the premolar erupts, its bulky crown will have become distanced from its close proximity to the canine, in favor of the mesio-distally narrower cervical and bifurcation areas. This provides space for the canine to drift distally enough, it is hoped, for it to improve its eruption path and its chances of normal eruption.

So, in summary for this case, 3 distinct elements were used to persuade the permanent canines to correct their aberrant eruption paths, namely:

1. Moving the roots of the incisor apices mesially towards the midline, to bring them mesial to the crowns of the unerupted permanent canines

2. Extract the deciduous canines to influence the permanent canines to redirect

3. Extract the deciduous first molars to generate a rapid eruption of the premolars and to provide a modicum of space distal to the canine to further encourage them to adopt a normal eruption path.

Reference

1. G A Bonetti, M Zanarini, S I Parenti, I Marini, M R Gatto. Preventive treatment of ectopically erupting maxillary permanent canines by extraction of deciduous canines and first molars: A randomized clinical trial. Am J Orthod Dentofacial Orthop 2011;139:316-23