NEWSLETTERS

Can we stop the distally migrating mandibular second premolar?

Published: July 2016

Bulletin #57, July 2016

Can we stop the distally migrating mandibular second premolar?

A definite distal angulation of the developing tooth bud of the mandibular second premolar has received relatively little attention in the orthodontic literature. Nevertheless it seems to be a trait that occurs with some regularity and, in its most extreme expression, has serious implications for its own future. It additionally may become a factor that challenges the future of adjacent teeth and occlusal function.

In an earlier bulletin on this website,1 I noted that the tooth may be found with its occlusal surface jammed against the mesial root, usually close to the CEJ, of the first molar. Sometimes it may more horizontally orientated and well down at the level of the mucosa of the floor of the mouth and located lingual to the molar roots. In either of these two cases, molar root resorption may occur in the premolar contact area with the molar root. It was also pointed out there that the second premolar is often late in its development and, aside from the third molars, is the most likely tooth to be congenitally missing. An association has been found between the distally tipped premolar, late-developing second premolars, late-developing dentitions, infraoccluded deciduous predecessors and the incidence of palatal canines.2-6

The aim of that bulletin was to describe a method of treatment in which the tooth is first brought occlusally simultaneously with a lingual directional component, in order to draw it clear of the roots and broad lingual bulge of the crown of the molar. Once the impaction of the tooth is resolved in this manner, it is drawn mesially and buccally into its place in the arch.

My purpose in this month’s bulletin is to illustrate the natural history of the development of this uncommon anomaly in a specific case and to discuss whether anything could have been done to avoid these damaging consequences.

The Patient

aab_2009_pan

Fig. 1. Panoramic view of a 9 year old male patient, taken in 2009, showing an unusually early mixed dentition with only first permanent molars and 4 mandibular incisors erupted. With the exception of the mandibular first primary molars and left primary deciduous canine, all deciduous teeth were in place. The clinical examination revealed severe caries experience, with untreated cavities present. All the permanent teeth could be identified on the radiograph, although the dental age of the patient was assessed as 6-7 years. Space loss was noted following the extraction of the deciduous first molars. The second premolar tooth germs could be seen to be rotated distally at almost 90 degrees and their state of calcification was assessed as corresponding to a dental age 4-5 years.


Figure 1 is the panoramic film of a 7.5 year old male in the early mixed dentition stage, taken in 2009. He already has considerable caries experience, having already lost the two mandibular first deciduous molars and displaying active caries in the other deciduous molars. The apices of the erupted mandibular permanent incisors and first permanent molars are open and there is still some development of these roots to be expected over the next year or two.

While the overall dental age of this patient is a year or so late, in relation to his chronologic age, the mandibular second premolars are markedly retarded by as much as 2-3 years behind their expected development, at this dental age. Calcification of the crowns of these teeth still has more than a year to go before their completion and before root development begins. Secondly, both these teeth are 900 rotated distally within their respective crypts and displaying a horizontal orientation. aab_2011_pan

Fig. 2. The patient in 2011. The maxillary incisors have erupted, the mandibular canine and first premolars appear to be vying for the already reduced space which is being stabilized by a fixed lingual arch. The maxillary canines a very high in close proximity to the apices of the lateral incisors. Both second premolars appear to have uprighted to a degree.


In figure 2, taken 2 years later, a lingual arch space maintainer is evident, the maxillary incisors have erupted and some restorative treatment has been performed. The orientation of the second premolars has noticeably improved by 25-300 with the calcification of the crowns nearing completion. Shortly after this film was taken, the practitioner extracted the mandibular second deciduous molars, in the hope that this would further influence the premolars to favorably and spontaneously change their eruptive path.

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Fig. 3. In 2013, with the patient now 13 years of age, only the maxillary primary second molars remain. The second mandibular primary molars had been extracted some time earlier and the erupted first premolars have tipped distally to a considerable. The second premolars are clearly visible in line with the mesial aspect of the first permanent molars, which are themselves noticeably tipped mesially.


Figure 3 was taken 2 years later and shows erupted premolars and canines with appropriate root development, although the first premolars have also drifted distally into close relation to the first permanent molars. At the same time, the second premolars still show less than a quarter of their final expected root length. Concurrently, these teeth have slightly worsened the angle of their orientation and some space has been lost in the erupted dental arch, despite the presence of the space maintainer.

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Fig. 4. In the space of a further 3 years, this 16 year old male has a fully erupted dentition, aside from the second premolars, which have now completely by-passed the roots of the first molars and on the right side is in line with the mesial aspect of the root of the second molar.

The final panoramic view (Fig. 4), taken 2.7 years later, shows a slightly worsened orientation of the premolars, but a strong distal migrational movement on both sides, to bring the occlusal surfaces of these teeth to beyond the distal aspect of the first molars and almost in a line with the mesial aspect of the erupted second permanent molars. To date, no orthodontic intervention has been undertaken.

Discussion

Following are a series of questions and answers relating to various forms of early interceptive therapy that were performed and others that might have been considered. As one may imagine the answers to these questions are highly subjective and, when attempting to set down guidelines, it is emphasized that each individual case must be judged on its merits in relation to the myriad of aspects that are involved, from objective dental development issues through susceptibility to caries, to patient management problems. As such, none of these answers will be supported by solid evidence-based data, but will be buttressed by a healthy clinical bias based on my own 55 years of clinical experience, highly influenced by that of the collected wisdom of several of my closest colleagues.

Question: Was the decision to extract the second deciduous molars at that time a logical step?

Answer: There is no evidence that extraction of the deciduous second molar could de-rotate the second premolar tooth buds in their follicles. Furthermore, by extracting these teeth, any minor restraint to distal drifting that could be expected from the short-term continued presence of the distal root of the deciduous tooth, was removed.

Question: If the rapid distal tipping of the first premolar that occurred following the extraction of the second deciduous molar had been prevented by modifying the space maintainer or had been subsequently corrected by the addition of a few orthodontic brackets and a coil spring, to create space, would that have influenced the second premolar to improve its eruption path?

Answer: This, too, is most unlikely, although it cannot be ruled out altogether.

Question: Could early orthodontic treatment to tip the first molars distally, with correction of the first premolar, have positively influenced the outcome?

Answer: This option does offer hope of some limited self-correction but, again, the chances are still not high.

Question: At what stage would it have been advantageous to have exposed, attachment bonded and applied traction?

Answer: In general, the best time to expose an impacted tooth is when 2/3 of its potential root length has developed, since this is the time when a permanent tooth normally erupts autonomously. If the tooth were to be exposed when a third or less of the root is calcified, there is a significant chance that the surgical procedure will result in damage to the tooth germ and may lead to premature root closure and shorter-than-normal root length. On the other hand, this may turn out to be the lesser of the two evils, since the tooth will be much more accessible and provide an improved chance of orthodontic treatment success. Unfortunately, the rapid distal drift appears to gather momentum well before the root development has proceeded to the desired root length.

Question: Clearly, the orientation of the crown of the tooth dictates its eruption path. That being so, would surgical exposure and manipulative rotation of the follicle incorporating the tooth bud be an appropriate procedure?

Answer: We have done this on one or two occasions, but our follow-up has not been adequate and our experience is lacking. Can we conclude that all was well? Obviously not. However, in much the same way that the autogenous transference of an immature tooth can be successfully implanted from its original developmental site to the prepared socket in an edentulous area, there may be a good argument for using this procedure in the present context. These rotated second premolar teeth frequently display very late development and root development may not have commenced. However, the more the root has developed, the less the practicability of turning the tooth through 70-90 degrees.

Question: Is the present location of the errant premolars treatable in the manner described in the February 2012 bulletin or is the situation now beyond what is amenable to orthodontic treatment?

Answer: When a second premolar has migrated further distally than the distal root of the molar, technically it can still be drawn to its place. However, it is difficult in these circumstances to draw it mesially and superiorly while ensuring that it remains within the confines of the alveolar bone and to avoid fenestrating the tooth through the lingual plate of the mandible. In this eventuality, the tooth could undoubtedly be brought into its place in the dental arch, but its lingual side would be devoid of its bony socket wall on the lingual side and its attendant prognosis would be compromised.

Question: If we extract these errant premolars, is orthodontic space closure a good alternative treatment plan or perhaps we should simply hold the space for later implant placement? 

Answer: This must depend on the dental and skeletal relations of the patient and the plan for the orthodontic treatment of the malocclusion as a whole. In an extraction case, space closure would obviously be a factor to be considered. In the case illustrated here, the second deciduous molar had been extracted fairly early on and, in the absence of the premolar, the form of the ridge will be adversely affected by resorption over the long period of time that must elapse before this child will be ready for implants. Orthodontic space closure in a non-extraction case would best be approached with the use of temporary anchorage devices in preference to dental anchorage, while monitoring eruption of the third molars (Fig. 4).

References

1.See http://dr-adrianbecker.com/page.php?pageId=281&nlid=26 February 2012 bulletin #8 on this website

2.Shalish M, Peck S, Wasserstein A, Peck L. Increased occurrence of dental anomalies associated with infraocclusion of deciduous molars. Angle Orthod. 2010;80:440-5

3.Shalish M, Chaushu S, Wasserstein A. Malposition of unerupted mandibular second premolar in children with palatally displaced canines. Angle Orthod. 2009;79:796-9

4.Shalish M, Will LA, Shustermann S. Malposition of unerupted mandibular second premolar in children with cleft lip and palate. Angle Orthod. 2007;77:1062-6.

5.Wasserstein A, Brezniak N, Shalish M, Heller M, Rakocz M. Angular changes and their rates in concurrence to developmental stages of the mandibularsecond premolar. Angle Orthod. 2004;74:332-6

6.Shalish M, Peck S, Wasserstein A, Peck L. Malposition of unerupted mandibular second premolar associated with agenesis of its antimere. Am J Orthod Dentofacial Orthop. 2002;121:53-6.