Thursday, 13 May 2010

Postorthodontic root approximation after opening space for maxillary lateral incisor implants

This is one of the most common implications - problem after successfully treating a lateral incisor(s) agenesia patient. Treatments are usually quite lengthy but also carried out sometimes a bit earlier in the patients life.

Optimal age for the patient to have his/her implant reconstruction on the missing laterals would be 19-21 years, after the growth has ceased completely.

Most of those patients however are finished with orthodontic treatment, especially if carried out by the community, around 15-16 years. and the main implication during retention is that even if on the crown level there is enough space for the implant, the roots approximate.

The solution would then be a resin bonded Maryland bridge like the one showed above, which of course if constructed by an experienced technician and prosthodontist the result as shown above is very aesthetic as well.

The above pictures are from an article published on the AmJO in February this year by V.Kokich that has years of clinical experience and follow ups on those cases. 

Volume 137, Issue 2, February 2010, Pages 158.e1-158.e8

  • The experienced clinician advocates of at least 6.3mm of space on the crown level, and 5.7mm on the root level, for a facilitation of an implant insertion on the aplasia sites.
In this study 94 patients were collected retrospectively, and the measurements were done on peri-apical and panorama x-rays, at treatment finish and prior the insertion of the implant after some years in retention. All patients were in their adolescence when the opening of the space was obtained and were in retention until adulthood.
  • 11% of those cases, resulted to approximation of the roots, and an implant could not be placed without re-treatment orthodontically
That is 1 out of 10 patients, that leads to the need of a contemporary retention scheme for those cases. Retaining only the crown level with a plate or an essix with a temporary resin crown on the missing space, is not enough

Adding to the above, is a weakness of this study, as the measurements were done in peri-apical and panorama x-rays, that do not take into consideration, the bucco-lingual aspect of the bone thickness.Maybe the 11% failure-relapse would have been even higher, if the measurements were done with a 3D software on CBCT reconstructions.

Take home message:
  • 6.3mm on the crown level and 5.7mm of root proximity always depending on the skill of the surgeon inserting the implant, should be the minimum space obtained for lateral incisor aplasia patients.
  • An increase of the above to 7mm and 6mm could be an option to asses minor relapse during retention period.
  • Bonded wire (19x25 SS) in a "Π" shape could be added to the canine and central to increase retention on the root level.
  • Also resin bonded temporary Maryland is an expensive but aesthetic retention option as well.
  • Lastly a less expensive approach would be, with an acrylic crown using mesio-distally a mesh bracket with a vertical slot (for example Begg bracket) and bonding it to the neighboring teeth of the aplasia site.
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