Will these impacted teeth respond?
Published: December 2015
Bulletin #50 December 2015
Will these impacted teeth respond to extrusive mechanics?
It is probably true to say that, when an experienced orthodontist looks at the teeth of a child with a malocclusion, for the most part he/she more or less immediately forms a mental and tentative treatment plan that will bring the teeth into alignment and into occlusion. The orthodontist is rarely concerned with the possibility that the teeth may not respond to orthodontic forces. The reason for this is that, if the teeth have erupted autonomously into the oral environment, it may be safely assumed that they have a normal attachment to the supporting tissues and therefore can be successfully moved using suitable orthodontic appliances.
In a malocclusion that features an impacted tooth, many of us will study the 2-dimensional view of the ectopic tooth, assess how the tooth may be brought into place in the arch and may even set about arranging for the surgeon to expose it before any other form of treatment is initiated. Unless spontaneous eruption of the tooth is expected, this line of action ignores the possibility that the tooth will not respond to traction forces and the fact that there is the need for a solid anchorage base from which to apply these forces.1
The first and most important prerequisite that needs to be addressed in these cases is to find the reason that the tooth has failed to erupt. This is not a theoretical or academic question. Accurate diagnosis of the cause is usually the key to deciding if the tooth can be moved and, from there, to success in its treatment.
The most common reason is an obstruction that lies directly in the path of the tooth’s progress – a condition which may be termed mechanical failure of eruption (MFE). Often, an adjacent tooth is to blame, which may take the form of non-resorption or eccentric partial resorption of a deciduous predecessor, or an overall condition of crowding or a supernumerary tooth. It is something of a relief to know when this is the etiology, since its elimination in general provides a good prognosis for potential resolution of the impaction. On the other hand, if the diagnosis is primary failure of eruption (PFE), then there is no chance of the tooth ever erupting or being mechanically erupted, whether or not there is space.
There are also occasional instances where the diagnosis is not possible to determine, for lack of any of the clinical and radiographic signs that one can usually expect to find. This month’s bulletin is devoted to the description of such a case, with non-eruption of the teeth in the mandibular right premolar/molar area, whose etiology and diagnosis were unknown.
In the absence of a diagnosis, the sole approach available to the orthodontist is to treat the case empirically. Essentially, this means applying a force and attempting to move each tooth individually. Why individually, you ask? If one of the teeth refuses to respond, it will prevent the others from moving if they are in any way linked together. It should be remembered that the unwanted side effect of using a continuous archwire to erupt a single resistant impacted tooth, will be to intrude the adjacent teeth. In these circumstances, we cannot offer the patient an assessment of the chances of success until we have completed several months of treatment to align and level, to open space, to insert a full thickness base arch wire and begin applying traction to the tooth. Only after the extrusive force has been active for several weeks or months will we learn whether the tooth shows signs of movement or not …… and the outcome may be total disappointment, particularly if there was little or no real malocclusion to treat, aside from the impacted tooth.
Case report
Fig. 1a, b. The initial condition in August 2008 at age 13 years shows the largely edentulous mandibular right side. Cusp tips of #43 and #47 are barely discernible.
Fig. 1c. The panoramic view taken in July 2005. Note the presence of bone covering the lower molars and premolars. The mandibular right first permanent molar has strongly distally-curved roots, with the apices close to the lower border of the mandible.
The patient was a 13 year old male who was referred to me by an orthodontist in his small home town in the south of Israel. At the first examination (Fig. 1a, b), his father pointed out that the two deciduous molars of the maxillary left and the two deciduous molars of the mandibular right quadrants had been extracted several years earlier, at age 5 years, due to caries. As the result, the maxillary first permanent molar had drifted mesially. However, in the mandibular right quadrant, no premolar nor permanent molar teeth had erupted in the eight years since the extractions were done. Only the two buccal cusps of the second
mandibular permanent molar were partially visible on that side. In contrast, all the permanent teeth on the left side in the mandible, from canine to second molar, were erupted. Furthermore, all the unopposed teeth of the affected right side of the maxillary dental arch had markedly over-erupted, with the first maxillary permanent molar in occlusal contact with the mucosa of the opposite jaw. This resulted in a distinct cant in the occlusal plane in which the right side was approximately 7-8mms lower than the left.
A panoramic radiograph was commissioned at that time, from which it was noted that all the permanent teeth in both jaws, were seen to be developing, including third molars. It is pertinent to point out that the film was executed with conventional screen film radiography, in 2008. As the result, there was only a single printed original film and this was lost in the patient’s several round trips between orthodontist and oral surgeon. This was an unfortunately relatively common occurrence when a patient was treated by different specialists, until digitally imaged panoramic films permitted computerized and internet duplication to provide copies for all concerned. For this reason, that critically important film is presently missing from this account of the case, although it was available at the time!
However, an earlier film was available, taken by another practitioner at age 10 years, elsewhere. This can be seen in Fig. 1c. Studying the relative development of the roots of the erupted and unerupted permanent teeth, the overall dental age of the patient was clearly younger than his years and estimated to be 8.5 years. The maxillary incisor root apices were still open and the premolar and second permanent molars roots were less than one third developed. The canine and premolars of the lower right side were covered by alveolar bone. Extrapolating the expected root growth from this 10 year old depiction to the 13 year old boy seen at the first examination, would lead us to expect eruption of these teeth, given that they would have ½ to ¾ of their expected final root length.
N.B. For
an explanation of how to assess dental age, please refer to Chapter 1 of my text
“Orthodontic Treatment of Impacted Teeth” as advertised on the right hand
column of this page.
The unerupted mandibular right first molar roots were turned distally to an exaggerated degree, with the apices in close proximity to the mandibular lower border. Its crown was covered with a fairly thick layer of bone.
This film and the intra-oral photographs confirmed the non-eruption of the first permanent molar, but the crucial question is: why should this be? That very early extraction of the deciduous molars had resulted in delayed eruption of the premolars is easily understood and accepted. However, a first permanent molar has no deciduous predecessor and it seems most unlikely that trauma could have played a part in its impaction, given its very posterior location in the mouth and no supporting history. Why, too, did the roots develop with this strong distal curvature and, more importantly, why were the root apices located in close proximity to the lower border of the mandible?
These are features that are usually associated with pathologic processes which prevent the vertical development and eruption of the tooth while perhaps permitting adjacent area growth, such as ankylosis or invasive cervical root resorption, or perhaps primary failure of eruption which also influences adjacent and more distal areas.
Dr. Sylvia Frazier-Bowers, Associate Professor in Orthodontics at the University of North Carolina, Chapel Hill has pointed out in recent personal correspondence that “ …….. an evidence-based approach to evaluate eruption disorders 2 is available, by applying a straightforward rubric to determine if PFE can be ruled out. While an analysis of the PTH1R gene is not 100% diagnostic, due to a likely heterogeneity of PFE, it is still a good first step to take if available. However, there are some cases that can be ruled out due to pathology and/or a mechanical failure of eruption (MFE). Based on the diagnostic rubric described recently, 2 the first feature that should be addressed is whether the bony pathway is completely cleared. If it is not completely cleared then it is not PFE. In these cases exposure of the tooth and orthodontic traction should result in successful tooth movement”. As can be seen (Fig. 1c) the bony pathway in the present case was not clear at the outset.
The presence of these factors, recognized at the outset, should serve to make the cautious and prudent orthodontist wary of offering more than a very guarded prognosis for the chances of successfully raising this tooth. On the other hand, the maxillary posterior teeth had all over-erupted to a marked degree and were contacting the mucosa covering the mandibular teeth, rendering rehabilitation of the entire right side and the establishment of a functional working unit, highly problematic.
It was clear that, with successful treatment, the patient had very much to gain and very little to lose in the event of failure. There was no way to use conventional orthodontics to establish dental anchorage from the already over-erupted maxillary teeth , which meant that skeletal anchorage remained the only option both for raising the mandibular teeth and for intruding the maxillary teeth.
Treatment Plan
1. Upper fixed appliance with a soldered palatal arch, to level, align and create space for unerupted #25
2. General anesthetic surgical session to
a. Extract the remaining deciduous teeth
b. Expose the mandibular teeth #43, 44, 45, 46, 47 and bond small hooks
c. Place a zygomatic plate temporary anchorage device on each side
3. Apply extrusive force to the mandibular premolars and first molar using vertical (up-and-down) elastics from the bonded attachment hooks to the zygomatic plate TAD and placed by the patient
4. Apply intrusive force to the maxillary molars and premolars using elastic chains from the brackets of the maxillary teeth/archwire to the TAD
5. Following the hoped-for eruption, a full lower fixed appliance to level and align mandibular teeth.
The maxillary fixed appliance was
placed in October 2008. The surgical episode was successfully performed by
Prof. Nardy Caspi, in all its parts (Fig. 2), at the beginning of December 2008
and under general anesthesia.
Fig. 2a. December 2008. A broad occluso-buccal flap was reflected to immediately reveal the canine, first premolar and second molar.
Fig. 2b. The second premolar and first molar were exposed
following removal of their bony cover.
Fig. 2c. Simple attachments were bonded with twisted steel ligatures drawn occlusally.
Fig. 2d. The flap was re-sutured back to its former place, with only the two twisted ligatures visible. These were shortened and fashioned into two traction hooks. Note the open exposure of the canine, first premolar and second molar.
The canine, first premolar and second molar were merely exposed in an open surgical procedure (Fig. 2a), while attachments were placed on the deeper second premolar and first molar (Fig. 2b-d).
Fig. 3. The zygomatic plate screwed into place on the inferior aspect of the zygomatic process of the maxilla.
Fig. 4. Elastic traction is applied direct from the traction hooks to the zygomatic plate.
The zygomatic
plate was screwed into place at the same surgical session (Fig. 3). Vertical
elastic traction individually to these teeth was initiated I week later and
placed by the patient (Fig. 4). At this time, the maxillary dentition was well
aligned and leveled and a heavy 0.020” round archwire was in place. At each
visit in the maxilla, an elastic chain was placed either direct on the molar
tube and premolar brackets or on the archwire itself and intrusive force
applied by stretching it to the TAD. 
Fig. 5a. January 2011. Intra-oral views to show the final
alignment, with corrective leveling of the occlusal plane.
Fig. 5b, c. Panoramic and periapical radiographic views at the completion of active treatment.
The impacted teeth responded very favorably to the extrusive traction and, by late September 2009, they were sufficiently erupted for a full multibracketed orthodontic appliance to be placed and the remainder of the, then, routine orthodontic treatment was undertaken and completed in January 2011, when the appliances were removed (Fig 5). Removable retainers were placed at the end of treatment, with instructions that they be worn at night – advice that was totally ignored by the patient!
During the treatment and following a traumatic incident to the patient’s maxillary anterior teeth, a root canal treatment became necessary and the tooth subsequently acquired a blue-grey hue.
Fig. 6. Panoramic of the dentition in July 2015, 4.6 years post-treatment.
The patient was seen again only in May 2013, when a minor degree of incisor crowding relapse was noted, for which the patient refused treatment. In July 2015 , he was seen by the original oral surgeon (Prof. Nardy Caspi) who extracted his wisdom teeth (Fig. 6).
Acknowledgement
I am grateful to Dr. Sylvia Frazier-Bowers for her scholarly input for this bulletin.
References
1. Becker A, Chaushu G, Chaushu A. An analysis of failure in the treatment of impacted maxillary canines. American Journal of Orthodontics & Dentofacial Orthopedics 2010;137:743-54.
2. Rhoads SG, Hebdricks HM Frazier-Bowers SA. Establishing the diagnostic criteria for eruption disorders based on genetic and clinical data. American Journal of Orthodontics & Dentofacial Orthopedics 2013;144:194-202.
