Remove the cause and the problem goes away – or does it?

Published: August 2011

Bulletin #2 - August 2011

Remove the cause and the problem goes away – or does it?

The young patient is 8 years old and mother has brought him in because the left central incisor erupted a year ago, but not the right one. She did not bring him in at the time, because she thought that it would erupt eventually and she was not overly concerned. However, she is now worried because both lateral incisors have erupted and the space for the unerupted right central incisor has been partially closed off by the three erupted incisors, which have tipped mesially. The left central incisor has in fact moved 2 mms to the right and across the midline.

At your clinical examination, the alveolus in the right central incisor region appears fairly wide or perhaps a little bulky and it certainly feels as though there is a tooth underneath the mucosa. You prescribe a periapical radiograph which clearly shows a supernumerary conical tooth, with little or no root development, superimposed on the image of what appears to be a normal, but displaced, central incisor. The root of this incisor is well over 2/3 of its final root length, although its apex is still open and the tooth itself is quite high in the alveolus.

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Fig. 1. the clinical and panoramic radiographic views of an 8 year old child with an impacted right maxillary central incisor, due to a small mesiodens.

If you are a GP or a pediatric dentist, what would you do?

Many GP’s will refer the patient to an oral and maxillofacial surgeon and have the supernumerary tooth removed, on the assumption that this abnormal tooth is the cause of the problem and that, following its removal, the unerupted right central incisor can be expected to erupt spontaneously. The OMFS is delighted to oblige and the child comes back to you 3 months later, then 6 months later and then a year later, but still with no right central incisor in sight.

If you are an OMFS, what would you do?

It is reasonable to assume that you would do the same and, most likely, you will have allayed mother’s worry by radiating confidence that the tooth would erupt very quickly in the months that followed. However, as an OMFS, you most probably do not have an efficient recall system to follow up the patient and may never know if the incisor erupted.

If you are an orthodontist, what would you do?

A large proportion of orthodontists would also do exactly the same. Of all dental practitioners, the orthodontist probably has the most reliable recall system, but failure of the tooth to erupt means that something must be done. By the time failure has been determined and accepted, the child is 9 or 10 years of age, he has a seriously compromised dental alignment, he refuses to smile, the kids at school are making fun of him and mother is mighty concerned.

Is this scenario a common occurrence or do teeth that are impacted due to obstruction usually erupt spontaneously?

The literature goes back a long way on this particular point, but some basic principles have evolved over the years, the concensus largely being that (a) space should be prepared by orthodontic movement of the adjacent teeth, then (b) the supernumerary tooth should be removed.1-11

In practice, however, the expected rosy future has not been as assured as had been predicted. These studies have shown that one third to one half of the cases showed failure to erupt. When eruption occurred, it took over 1½ years. About a quarter of the patients required a second surgical procedure to expose the unerupted incisor, followed by a further 2½ to 3 years period of observation before the tooth erupted. When the teeth did erupt, nearly half the cases required orthodontic treatment to achieve some semblance of acceptable alignment, without aiming for a more perfect alignment. A very recent study12 has shown that, where supernumerary teeth had been removed without other forms of treatment, the impacted incisors failed to erupt in 64% of the cases and in 9% there was only partial eruption. In 17% eruption was successful but into an ectopic location. Only 10% ended up with adequate eruption and alignment, while 90% required orthodontic extrusive traction and/or alignment treatment!

Should the impacted incisor be exposed at the same time as the supernumerary tooth is removed?

If we look at the number of problems that remain unsolved by simply removing the obstruction, perhaps it would be best if the unerupted permanent incisor were exposed and left to erupt spontaneously, in the hope that the exposure will encourage eruption. The problem with merely exposing the tooth is that we are then depriving the tooth of its follicle and it is the follicle that is crucial for eruption through the bone and soft tissues. Consequently, the absence of the follicle is a hindrance. If the tooth is fairly superficially located, this may still be a good idea but, given the often seen severe displacement of the tooth, the likelihood of the tooth becoming re-covered with healing soft tissue and new bone is very high, even if a surgical or periodontal pack is placed for a few weeks.

So, if we are to expose the impacted tooth, perhaps we should place an attachment, with a ligature or chain exiting the healing wound. In this way we may ensure later access for the application of extrusive traction, even though the ability of the tooth to spontaneously erupt may be reduced.

In this present scenario, the central incisor is often displaced very considerably from it final place in the dental arch. If the surgeon aims for an open surgical procedure, then he must remove considerable quantities of bone and soft tissue around the tooth and place a surgical pack for several weeks to maintain access to the tooth after healing has occurred. The effect of this procedure on the periodontal condition of the adjacent incisors will likely be very deleterious and the outcome on the gingival and periodontal health markedly compromised. The gingival architecture and appearance will also be very poor ….. and this at the front of the mouth, for all to see.

Performing a split pedicle graft, which is the modified form of open exposure recommended by Vanarsdall,13,14 will reduce the amount of bone and soft tissue removal needed, but the post-treatment appearance of the gingiva in a successfully resolved impaction will leave much to be desired. Reparative periodontal surgery will be needed in later years to improve this. A successful open exposure operation aims to leave the tooth accessible in the post-surgical period, for future bracket bonding if and when necessary. In practice, this may be difficult to achieve in the long term and soft tissue re-closure will often occur, necessitating renewed surgery, should the tooth not erupt. The inability of the patient to effectively clean this tender and haemorrhagic area in the post-exposure weeks and months, make attachment bonding highly unreliable. As a precaution, therefore, an attachment is often placed either at surgery or shortly afterwards, to maintain access for later biomechanics, in the likely event that this becomes necessary.

A closed exposure procedure must have an attachment bonded at the time of surgery and the ligature or chain is usually drawn from the eyelet attachment (see Newsletter Archive July 2011 bulletin on this website), to exit the tissues through the sutured edge of the completely closed surgical flap. The chances of spontaneous eruption are still relatively low, for the reasons noted above. A bonded appliance should be used to create space along the full length of the roots of the adjacent teeth and to then to act as an anchorage base from which to apply extrusive forces to the impacted tooth, through the ligature or chain. The tooth will usually respond very quickly and, depending on the range of the light forces applied, will erupt into the mouth within 3 or 4 months. Once the tooth has erupted, the appliance will still be needed to align and upright the anterior teeth and, often, to lingually root torque the formerly impacted incisor. Root torque is frequently needed, since the earlier presence of the extracted supernumerary tooth may well have displaced the incisor root in a labial (usually) orientation. Closed exposure does not require the removal of more than a small area of bone and dental follicle overlying the labial aspect of the crown of the tooth and no bone or soft tissue removal more occlusally. It does not therefore compromise the periodontal condition of the adjacent teeth and, following eruption of the tooth, produces superior gingival health, architecture and appearance.

So, what is the recommended protocol?

Remember that we are dealing specifically with an 8 year old child, with an impacted incisor displaced very high in the maxilla, associated with the presence of a supernumerary tooth and it is emphasized that the following recommendations do not necessarily apply to other forms of central incisor impaction nor to other age groups.

1. accurate diagnosis of the location of the impacted tooth and its relative proximity to the adjacent teeth through an appropriate clinical and radiographic examination.15

2. orthodontic treatment limited to re-creating space in the intended location within the dental arch, at the level of the crowns at root apices.

3. surgery to extract the supernumerary tooth and to expose the central incisor, with eyelet attachment placed at the time of surgery.

4. orthodontic traction to erupt the impacted tooth

5. orthodontic alignment including root movement of the affected tooth

6. appliance removal and retention pending final orthodontic re-evaluation at dental age 12-13 years.


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