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Can early treatment change root shape of a dilacerate incisor? Part 2

Published: December 2017

Bulletin #72 December 2017

Can early treatment change root shape of a dilacerate incisor? Part 2

Last month, I described the phase 1 treatment of a 7 year old child who was seen and diagnosed very early in the mixed dentition period for the presence of an impacted, dilacerate central incisor, of the “classic” type (Bulletin #71, November 2017). In that bulletin, questions were raised regarding the timing of treatment of the affected incisor in relation to the overall malocclusion and whether a phase 1 treatment was justified. Perhaps the situation would worsen due to further growth of the root, if left untreated. Alternatively, perhaps the situation would actually improve with a phase 1 treatment. The rhetorical question regarding the ethics of leaving a child without a front tooth until the time a phase 2 plan could be put into operation, was also posed.

As documented, treatment began in December 2013, surgical exposure was performed in early March 2014 and vertical extrusive mechanics applied immediately before full closure and suturing of the labial flap was completed, in the surgeon’s operatory – by the orthodontist, of course!! In August 2014, an apically-repositioned attached gingival flap was performed when the tooth appeared about to break through the oral mucosa on the labial side and labial root torque was initiated in December 2014. This required a period of 4 months to correct the long axis of the crown of the incisor by approximately 1050 of labio-lingual rotation, i.e. clockwise rotation when viewed from the right side. The appliance was removed in April 2015 and a removable Hawley retainer placed, following completion of the root torque. At the time, the root apex was wide open and clearly had much growth potential remaining. Figures 1-7 in the November bulletin illustrate the initial condition, the diagnosis and the stages of the treatment performed.

71 Fig 8_1

Fig. 8. The case at the completion of phase I, in April 2015.

71 Fig 9_2

Fig. 9a, b. Post-treatment panoramic and periapical views of the dentition. The apices of the incisors are still open, indicating considerable potential for further post-phase I treatment root growth.

The immediate post-treatment intra-oral photographs (Fig. 8) and radiographs are presented here (Fig. 9a, b). The present bulletin continues on and describes the growth changes that have occurred in the root of the tooth during the post-treatment follow-up period.

Had it been decided not to undertake this phase I treatment, the growth potential would have been expressed in the form of the tight semi-circular, labially-facing, root apex as I have described in earlier bulletins on this site. This tight curve is typical of the “classic” dilacerate incisor and was already evident on the CBCT (Fig. 3 in the November bulletin) in 2013.

For this reason, my retention protocol in the post-treatment follow-up of a dilacerate incisor case where the root is still growing is to hold the situation with a Hawley retainer until root growth of the incisor ceases and the patient reaches the age where a phase II intervention can be initiated, i.e. in the full permanent dentition.

As noted in last month’s bulletin, the patient did not attend for follow-up examinations thereafter and, it was learned, had stopped wearing the retainer after a few months. He returned only in October 2017, 2.6 years after completion of the phase 1 treatment and a full 2 years without wearing his retainer.

It seemed logical that the consequence of the altered root growth would generate a progressive relapse in the position of the crown of the tooth in a labial and superior tipping movement and that this would continue for as long as the growth of the apical portion of the root persists, because there is resistance to its elongation from the labial periosteum of the alveolar ridge.

However, on examination of the patient a month ago, I was surprised to see an early permanent dentition, with maxillary canines now erupting and only a very slight labial relapse of the affected incisor, which could easily be explained away by the mild degree of crowding that was present in the inter-canine arrangement (Fig. 8).

My curiosity was aroused to understand why the much feared relapse had not occurred.

71_Fig_10

Fig. 10a. The incisor area as seen in this extracted portion of the panoramic view (horizontal projection) shows a long root with a circle indicating a horizonal extension of the apex (arrow).

Fig. 10b. A periapical view (oblique projection) of the same area and on the same day, showing the additional root growth during and subsequent to the orthodontic treatment (arrows).

Radiography (Fig. 10a, b) did not reveal what I had expected to see. A periapical view of the tooth revealed an extended length of root apex (arrows) which had grown at an odd angle to the curved root seen on the pre-treatment CBCT. On the panoramic view of the dentition, the same central incisor apex appeared as a small circle (arrow), indicating that the new root extension was in the same plane as the x-ray and was imaged “end on”.

It should be remembered that periapical views of an incisor tooth are taken with the x-ray cone angled 60 degrees above the horizontal plane, while a panoramic film is shot at an angle slightly below the horizontal plane. From this positional discrepancy between the films and using the same logic exploited in Clark’s tube shift method, it may be deduced that the new apical portion of root is at an angle of about 90 degrees to the general orientation of the root and that it is pointing posteriorly.

71 Fig 11_1

Fig. 11. A comparison of serial cross-sectional cuts from the pre-treatment CBCT (upper row) and the parallel situation in the 2.6 years post-treatment follow-up CBCT (lower row). Note the additional root length that has been acquired and its direction of growth, counter to the direction of the labial root torque. The tooth is vital, as expected.

However, in order to evaluate the apical extension more accurately, a new CBCT of this limited area was commissioned. It revealed an irregular but long and thin apical portion at right angles to the main and mildly curved original corpus of the root (Fig. 11). Despite its odd configuration, the entire length of root is invested in alveolar bone, with no danger of any part fenestrating through the labial or palatal bony plates. 71_Fig_12

Fig. 12. The maxillary occlusal view and the anterior view of the teeth in occlusion are seen here, in October 2017 and unretained for 2 years. The dentition shows a mild degree of generalized crowding and very slight labial relapse of the position of the affected incisor. The color of the teeth is completely natural. This could not have been expected had the tooth undergone root canal treatment and apicoectomy, which is frequently needed when treatment is begun after most of the root of the tooth has been completed. The proposal for a routine phase 2 treatment is presently under consideration by the patient and parents.

The crown of the tooth is of excellent colour and form, exactly matching its unblemished antimere (Fig. 12). It is the perfect alternative to a healthy natural tooth. Despite the extreme degree of orthodontic movement that it had undergone, its vitality was maintained as witnessed by the growth of this long and bizarre apical portion. It is reasonable to conclude that the same extreme degree of labial root torque was directly responsible for the uncalcified root turning posteriorly rather than continuing on the facially curved path that would normally be expected in “classic” dilacerate incisors.

It is generally accepted that success in the orthodontic/surgical modality of treatment of a dilacerate central incisor usually requires the surgical amputation of the curved apex of the root, which bulges the labial oral mucosa covering the alveolar ridge on its facial side. This, in turn, dictates the need for root canal therapy, which further reduces the length of the root of the tooth. Over time, the crown of the root-filled tooth loses its color and may later require a laminate or crown restoration. Each of these elements reduces its longterm prognosis.

If this obvious growth-altering effect of orthodontic torqueing forces can be shown to be universally applicable, the following advantages may be gained by performing a phase 1 treatment performed as early as possible.

a. It reduces the likelihood that apicoectomy and root canal treatment will be necessary, thereby significantly improving the prognosis and the esthetic quality of the result

b. It reduces the likelihood of post-treatment orthodontic relapse.


a.

72_Fig_13

Fig. 13. A frame from the MPR video clip from the CBCT to show the posteriorly-directed apical outcrop of the root at 2.6 years post-treatment, in October 2017.

But are there disadvantages of treatment performed in this way? Without question the odd shape and orientation of the elongated root apex must raise the eyebrows of a traditionally conservative dentist and a dental morphologist (Fig. 13), but does it really matter if the tooth has a beautiful crown and as long as the tooth is vital and pathology-free?

It certainly provides a significantly longer root and makes for a better prognosis than the apicoectomized and root-treated incisor that would have otherwise been its fate. There is no reason why the longterm survival value of this tooth should not be excellent. Should root canal therapy ever become necessary for any one of a variety of reasons not necessarily related to the orthodontic treatment, only then will an apicoectomy be indicated since access to the canal extension in the apical portion of the root will not be possible.

P.S. One may be permitted to speculate what would be the likelihood of a similar phenomenon occurring (welcome or not!) as the result of the application of lingual root torque on normal but developmentally immature maxillary incisor teeth or, perhaps, mesio-distal uprighting forces on recently erupted canine and premolar teeth. Food for thought when considering phase I treatment in general!