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Root development in impacted teeth

Published: March 2015

Bulletin #42 – March 2015

Root development in impacted teeth

This month, I turned my attention to the roots of teeth growing in a limiting/crowded environment. When a tooth erupts into the oral environment, it vacates a virtual space behind it into which the root has room to grow. But what about an impacted tooth? Eruption is prevented for one reason or another, but a potent capacity for root development remains. In some cases, root development that would otherwise have the potential for excellent growth in length, may be impaired by the restricted space available to it. If you rummage through the biological waste disposal receptacle in the operatory of any self-respecting oral and maxillofacial surgeon you will reveal a very large number of extracted third molars. In most cases, wisdom teeth are extracted because they are impacted to some extent and a majority of these will feature bizarre root configurations. It is often assumed that abnormal root development of these commonly impacted teeth occurs due to the confined circumstances in which they are obliged to grow.

I well remember my first teacher of orthodontics, who was perhaps the most important influence on my choice of profession . He was a proponent of the extraction of second permanent molars, rather than premolars, in extraction cases. Among the many arguments that he put forward for its efficacy, he maintained that the third molar would eventually erupt into the place of the extracted tooth and would develop a much improved root form and root length than would otherwise be the case.1-3

If you initiate a PubMed search using the key words “impacted teeth” and “root development”, you will find a very long reference list of clinical articles and individual case reports on the management of difficult cases, the outcomes of some of which are so remarkable that they may be classed as sensational. However, there do not appear to be published studies of the inter-relation between tooth impaction and restricted/stunted/diverted development of the roots of these teeth and whether the roots would recover to realize their root-forming potential, if the impactions were to be resolved.

What then is the evidence available to support this notion? Clearly, in the absence of properly designed clinical studies, we can only derive information on an individual anecdotal manner, with all the many drawbacks and tendencies towards bias that this entails.

Infraoccluded deciduous molar obstructing a mandibular premolar: In an early case report that I published in the American Journal of Orthodontics, in 1982,4 I described a patient whose left mandibular second deciduous molar was severely infraoccluded (submerged), with its crown completely buried in gingival tissue. Whether or not this tooth had ever erupted into the oral cavity was not known, but considered unlikely. The adjacent first molar and first premolar were strongly tipped towards one another, almost completely closing off what gave the appearance of being an extraction space. What was interesting was that the second premolar was located apical to the infraoccluded deciduous molar and its stunted but incompletely developed root could be seen on the lateral oblique radiograph (panoramic films were not in general use at the time the patient was treated) to have altered the profile of the lower border of the mandible.

Treatment consisted of extraction of the infraoccluded deciduous molar and the second permanent molar, with no active orthodontic therapy. Space between first molar and first premolar re-created spontaneously under the influence of the erupting premolar which went on to grow a very long root, when compared with its unaffected antimere.

EEE_Fig_1a__b EEE_Fig_1c

Fig. 1a. Panoramic view of a 6 year old boy with an unerupted right mandibular first permanent molar (arrow). The large dentigerous cyst can be seen as a wide radiolucent area surrounding the crown of the tooth, which is now situated in soft tissue only. Note the relative lack of development of the roots of the tooth and also resorption of the distal root of the second deciduous molar.

Fig. 1b. Two years after resolution of the cyst, the tooth has erupted fully.

Fig. 1c. Three years later, at 11 years of age, the 12 year molar has erupted on that side and the patient was due to commence orthodontic treatment at that time. Note the similarity between the completed root length and pattern of the two mandibular first molars.

Dentigerous cyst obstructing a mandibular molar: A dentigerous cyst arrested the eruption of the mandibular right first permanent molar and, at the same time had resorbed the distal root of the second deciduous molar (Fig. 1). The root development of the tooth was also arrested in relation to that of the left side first permanent molar. In the follow-up radiographs taken 2 and 5 years after resolution of the cystic lesion, the roots developed fully, with the same bizarre morphology of its unaffected antimere.

EEE_Fig_2a__b EEE_Fig_2c__d

Fig. 2a. A panoramic radiograph of the 4 year old child with unerupted deciduous molars, absence of the second premolar tooth bud and early calcification of the first permanent molar. Note the diffuse radiolucent area above and encircling the second deciduous molar and the first permanent molar. The biopsy report revealed a benign ameloblastic fibro-odontoma.

Fig. 2b. Three years later, at 7 years of age, the left mandibular first molar has erupted with most of its roots develop as, too, has the right primary first molar. The roots of the affected molar and the adjacent deciduous molar have developed only as far as the bifurcation and the neither tooth has made eruptive progress.

Fig. 2c. 18 months later, there is no apparent change in either root development or eruptive progress and there remains bone covering the occlusal aspect of the two teeth.

Fig. 2d. A clinical occlusal view of the dentition 6 months later.

Benign osteogenic tumor obstructing a mandibular molar: At age 4 years, the child was referred to the Department of Oral and Maxillofacial Surgery at the Hebrew University-Hadassah School of Dental Medicine in Jerusalem, because of an absence of erupted teeth in the right mandibular area distal to the deciduous canine, while all other deciduous teeth in the mouth were present. The radiograph revealed the presence of unerupted deciduous molars, absence of the second premolar tooth bud and early calcification of the first permanent molar (Fig. 2a). There was a diffuse radiolucent area above and encircling the second deciduous molar and the first permanent molar. The lesion was excised and the subsequent pathologic report described it as an ameloblastic fibro-odontoma, which is a rare benign odontogenic tumor.

The child was followed up with repeat panoramic radiographs taken at ages 7 and 9 (Fig. 2b, c). Remarkably little change occurred over this period, with the first permanent molar and second deciduous molar remaining very low in the mandible, close to the lower border and recovered with bone. There was a minimal degree of root development at this time, even though the erupted left first permanent molar showed advance root formation. The first primary molar on that side had erupted (Fig. 2b, d).

At 10 years of age, surgery was performed to extract the second deciduous molar and to re-expose and bond eyelet attachments to the permanent tooth. At the same time, a temporary anchorage plate was screwed into place on the inferior aspect of the zygomatic process of the maxilla.


Fig. 2e. Post-surgical panoramic view at age 10 years, following extraction of the right second deciduous molar and attachment bonding of the exposed first permanent molar. Note the incomplete and stunted root development of the molar, which appears to have penetrated the compact bone of the lower mandibular border, whereas its opposite number has developed and apexified its long roots. The zygomatic plate (arrow) was placed at the same time.

Extrusive intermaxillary (up-and-down) elastic traction was applied between one of two hooks formed from the steel ligature threaded into the eyelets and a similar hook drawn from the zygomatic plate. The post-surgical radiograph (Fig. 2e) shows the enormous difference between the root lengths of the right to the left first permanent molars, but it also shows that, while the left molar had completed apexification of its roots, the right molar apices were still open and low in the compact bone of the mandible and beginning to alter the smooth profile of its lower border. Clearly, there was a factor that appears to have resisted eruptive movements of this tooth.EEE_Fig_2fEEE_Fig_2g

Fig. 2f, g. A periapical and panoramic view to show the development of excellent roots on the molar and the relocation of the first premolar into the second premolar position to overcome the ridge defect caused by the missing second premolar, while leaving a good implant site in the first premolar location.


Fig. 2h. Clinical views of the completed orthodontic treatment result.

The molar extruded without incident and the phase 1 treatment was halted, with the tooth in occlusion. Following comprehensive orthodontic treatment, commenced at age 14 years, the post-treatment panoramic and periapical views (Fig. 2f, g) clearly show the development of very long and healthy-looking roots on the affected molar, of the same length as the roots of its antimere and this despite a serious time-lag having interfered with its earlier development. The first premolar was finally drawn distally into the second premolar place, in order to provide good alveolar bone in its initial location for the future implant, rather than the narrow, defective ridge that that resulted from the absence of the second premolar (Fig. 2f-h).

Three cases of pre-eruptive trauma affecting maxillary permanent incisors: When a very young child receives a blow to the anterior maxilla, damage will often occur to the deciduous incisors, which may result in their shedding or in the need for their extraction. In many cases of this type there is also indirect conductive damage to the unerupted developing permanent incisors. In the more minor instances, the only result may be a disturbance of enamel mineralization, which may feature in the erupted tooth as a white or brown patch. More serious damage may cause altered development or dilaceration of the crown or root of the tooth or an arrest of root formation and a loss of eruptive potential.

Case #1.

EEE_Fig_3a__b EEE_Fig_3c__d

Fig. 3a. Clinical view of the anterior dentition of a 10.1 year old boy with absence of anterior teeth since age 5 years, due to trauma to the deciduous dentition.

Fig. 3b. A panoramic view at age 10.1 years shows the presence of all teeth and a dental age of 8.5 years, with late developing second premolars. Note the extreme height and lack of root development of the maxillary central incisors.

Fig. 3c. The height of the central incisors is seen in this anterior section of the lateral cephalogram.

Fig. 3d. Anterior occlusal view of the incisor region shows little or no root growth of the central incisors.

In the present case, the trauma occurred at age 5 years and the patient attended first at age 10 years for routine dental treatment (Fig. 3a). At that time her mandibular and maxillary posterior teeth were evaluated for a dental age assessment in terms of root development. An overall delayed dental age of 8.5 years was determined (Fig. 3b). The second premolars, which are variable teeth, were considered to be late in their development and thus not included in the assessment. In other words, the dental development lagged behind the patient’s chronologic age by a factor of about 18 months. The unerupted maxillary incisors were located high in the alveolus, close to the floor of the nasal cavity, with no signs of having progressed from their initial embryonic position (Fig. 3c).


Fig. 3e. Three consecutive coronal cuts from the CBCT shows the close relation between the dental papillae of the incisors and the floor of the nasal cavity.

Their crown calcification was completed, but their roots were wide open and only a millimeter or two in length (Fig. 3d, e). They were adjudged as being compatible with a dental age of about 4 years which, given the delay in her dental age, corresponds to the 5 year chronologic age at the time of the trauma. It was concluded that the traumatic incident had arrested the development of the roots of these teeth and had disrupted their eruption potential.


Fig. 3f. Three adjacent periapical views of the anterior teeth to show the development of excellent root length of all the incisors, notwithstanding the root canal treatment in the left central incisor.EEE_Fig_3g__h

Fig. 3g, h. 45 degrees facial view and anterior clinical view of the dentition 4 years post-treatment. Note mild trauma-related dilacerations of the cervical root areas and long clinical crowns of the six anterior teeth.

Extrusive orthodontic mechanics, begun at age 10.6 years, had generated the eruption of these teeth and all orthodontic treatment was completed by age 13 years. In the radiographic follow-up of the case at age 17.5 years, all 4 incisors had developed long roots with closed apices (Fig. 3f-h). The left central incisor had subsequently lost its vitality a year earlier, but only after its root apex had already closed. Root canal treatment had been performed.

Case #2:


Fig. 4a. Anterior section of the lateral cephalogram of a 9 year old boy who suffered severe trauma at age 2 years. Note the extreme height of the central incisors, at the level of the anterior nasal spine.

Fig. 4b. Panoramic view taken on the same date shows a dental age of 8 years, but with late-developing lateral incisors whose eruptive progress is in line with their development.

At age 2 years, this child was involved in a traumatic accident in which his deciduous maxillary anterior teeth were avulsed. At age 9 years, the permanent successors were still unerupted. An assessment of tooth development as seen on the panoramic radiograph indicated a dental age of about 8 years and, thus the position and degree of root development of the two lateral incisors could arguably be considered normal (Fig. 4a, b). However, their crown form indicated anomaly associated with trauma. The central incisors were seen on radiographs to be very high in the anterior maxilla, at the level of the anterior nasal spine. Their root development was very rudimentary in relation to the dental age.

All four incisors were surgically exposed with a closed surgical exposure and drawn down with extrusive orthodontic treatment. They erupted into their place, with white and brown hypoplastic patches on the enamel, but all remained vital.


Fig. 4c. At completion of the phase 1 treatment, 3 incisors have developed very long and spindly roots, which still have open apices, indicative of further growth potential. The left central incisor has a prematurely closed, stunted and rounded root end, yet it has erupted with a broad rim of alveolar bone that will serve as an implant site, if and when the tooth is lost. 

It appears that 3 of the teeth involved had open apices, while the left central incisor root had apexified very early on and had remained vital. This tooth responded to the orthodontic traction as well and as rapidly as the others. It did not increase its root length, but it was accompanied in its eruption by new supporting alveolar bone. The other 3 incisors developed long roots. The root of the right central incisor was long and spindly and its open apex showed signs of a bone-like tissue growth in the root canal, which has been associated with trauma (Fig. 4c).5

Case #3:


Fig. 5a. A panoramic radiograph of the 7.4 year old girl, showing the extreme height (arrow) of the left central incisor which was traumatized in infancy.

Fig. 5b. A periapical view of the left central and lateral incisors showing only the earliest root formation of both. The lateral incisor (#22) is very small and late developing but was not damage and has the potential for producing a normal root. The damaged but vital central incisor (#21) has experienced early apexification, leaving it with a stunted and contorted root.

This 7.4 year old child presented with a history of early trauma, which had severely damaged the area of the newly forming CEJ of the maxillary left central incisor. The tooth had remained very high in the anterior maxilla in close relation to the floor of the nose, the root end had closed between the time of the accident and the commencement of treatment, there was no additional root development and there was loss of its innate eruptive potential (Fig. 5a, b). Fourteen months later, the tooth had been drawn down into alignment by orthodontic extrusive mechanics, in a phase 1 procedure. Comprehensive orthodontic treatment was initiated at age 11.1 years. EEE_Fig_5c_e

Fig. 5c. At the end of phase 2 treatment, at age 14 years, the central incisor is aligned and the lateral incisor enlarged by composite enhancement. The central incisor with its extremely short root appears to have a very tenuous connection to the alveolar bone. Note the asymptomatic resorptive lesion at the CEJ area of the tooth. The tooth is surprisingly stable and is not splinted.

Fig. 5d. The same view taken at age 17.6 years shows healthy, if extremely short, alveolar bone support, with a good trabeculation pattern. While the tooth is firm, the resorptive lesion has advanced considerably. This extremely compromised tooth has served as an excellent temporary “restoration” for the duration of the growth period. Given the excellent ridge enhancement achieved, the patient has now been referred for an implant-borne crown.

Fig. 5e. A panoramic view of the dentition.

Post-treatment follow-up was maintained till age 18 years (Fig. 5c-e). During this time, an invasive cervical root resorptive lesion developed in the tooth and it was recommended for extraction and replacement with an implant-borne restoration.


If success in the treatment of these cases could be a guarantee of success in the treatment of all other similar cases, then we would be in a position to conclude as follows:-

1. When a tooth is prevented from erupting or if it loses its eruptive potential due to traumatic injury, its root development may be slowed or arrested by the crowded environment within which it is attempting to grow. It may also be slowed or arrested by its close proximity to the floor of the nose, the lower border of the mandible, a dentigerous cyst and, probably, the floor of the maxillary sinus.

2. We would also be in a position to speculate that perhaps other eruption-restricting agents, such as invasive cervical root resorption (ICRR) or pre-eruptive intracoronal resorption (PEIR) of the tooth itself will act similarly.

3. We would further be in a position to declare that, when the cause of the problem is eliminated and the tooth completes its eruption, either autonomously or by orthodontic extrusive traction, the spark of root development will re-kindle and will compensate for lost time. It is also likely to achieve a normal or close-to-normal root length in the final instance, on the condition that the root apices are still open.

4. Whether recovering from the results of lesser levels of trauma or affected by restricted space conditions, many of these teeth that remain vital, lose their eruptive potential. They appear to undergo a dormant stage in which root development is arrested, but the potential for a re-awakening of root production remains for a long time, even after the completion of the apexification of the antimere.

5. When the root apex is prematurely closed, which is more likely to occur in the trauma cases, the tooth will not generally erupt autonomously. In these cases, orthodontic extrusive traction is capable of erupting the tooth without difficulty, but further root development will not occur. Nevertheless, a newly erupted tooth of this type will be accompanied by a generous collar of new alveolar bone, which will serve the patient well when the time comes to substitute the unfortunate tooth for an implant. It also seems that many of these successfully aligned teeth, against all odds, will often remain functional and with good appearance for many years with their short root, before they need to be replaced.6

However, in the cases described here, I have made no claim that the successful outcomes achieved are representative of the diagnoses/conditions concerned, even though there may be many similar cases with similar treatment results. In order for the practitioner to accept the purported lessons that may be learned from them without reservation, evidence is needed. This can only be supplied in disciplined clinical studies that show these features to be valid in a large cohort of patients.

Equally, however, it does not mean that nothing may be learned from anecdotal isolated case reports, in general and from those described above, in particular. There are many advantages to be had in undertaking resolution of the impaction and bringing the imperfect tooth into the line of the arch and into function, not the least in relation to appearance and potential implant site enhancement for future implantation. Even with a limited prognosis they have considerable value in the young growing patient as temporary “restorations” rather than replacing them with acrylic flippers, resin-bonded bridges, fixed lingual arches with artificial teeth etc. The patient’s own natural (if third rate) teeth are the only option that guarantees preservation and even enhancement of alveolar bone for future implant substitution, in adulthood. Nevertheless, in a good number of parallel situations, these unfortunate teeth are needlessly extracted.

It is hoped that the presentation of the results seen here will encourage us all to take a second look at some of these severely compromised teeth, to see their potential and the promise of what they may become, rather than extracting them on the basis of what they are and how they are evaluated at the present.

The figures in the above bulletin are copyright from Becker A. Orthodontic Treatment of Impacted Teeth. 3rd edition. Oxford: Wiley-Blackwell Publishers, 2012.


1. Wilson HE, Extraction of second permanent molars in orthodontic treatment. Orthodontist, 1971;3:18-24

2. Wilson HE, The extraction of second permanent molars as a therapeutic measure. Transactions of the 42nd Congress European Orthodontic Society, 1966;42:141-145

3. Wilson, H. E.: Long term observation on the extraction of second permanent molars. Transactions of the 50th Congress European Orthodontic Society, 50:215-221, 1974.

4. Becker A, Shochat S, Submergence of a deciduous tooth, its ramifications on the dentition and treatment of the resulting malocclusion. American Journal of Orthodontics 81:240-244, 1982.

5. Heling I, Slutzky-Goldberg I, Lustmann J, Ehrlich Y, Becker A. Bone-like tissue growth in the root canal of immature permanent teeth after traumatic injuries. Endodontics and Dental Traumatology 2000;16:298-303.

6. Becker A, Chaushu S S. Long-term follow-up of severely resorbed maxillary incisors after resolution of an etiologically associated impacted canine. American Journal of Orthodontics and Dentofacial Orthopedics, 2005;127:650-654