From Volume 14, Issue 3, July 2021 | Pages 125-133
Supernumerary teeth occur in approximately 1–2% of the population. Multiple supernumerary teeth are less common and usually associated with certain medical conditions. Most supernumeraries develop at a similar time to the normal series; however, this article describes the presentation and management of three patients who developed multiple supernumerary teeth during active orthodontic treatment in the permanent dentition.
Supernumeraries are tooth-like structures that form in addition to the normal series of teeth. Their incidence has been reported at 0.8% in the primary dentition rising to 1–2% in the permanent dentition.1,2 In a Swedish population, research has shown that supernumeraries in the permanent dentition are twice as common in males compared to females; however, no sexual dimorphism has been found in the primary dentition.3
Supernumerary teeth can be classified by location4 or morphology.5 A supernumerary occurring in the midline is known as a mesiodens, one in the premolar region a para-premolar, while those occurring in the molar region and distal to the third molar, a paramolar and distomolar, respectively. However, classification according to morphology (Table 1) is more useful because it helps in understanding the likely behaviour.
| Type | Origins | Morphology | Behaviour |
|---|---|---|---|
| Conical or ‘early forming’ | Off-shoot of dental lamina | Crown: small, peg-shaped. Root: usually well-developed | Often develop before permanent incisors. They often erupt; however, can be inverted |
| Tuberculate or ‘late forming’ | Representative of a tertiary dentition | Crown: barrel-shaped Root: Little or no root formation | Often appear in pairs and fail to erupt, resulting in impaction of permanent incisors |
| Supplemental | Gemination of tooth bud | Apparent duplication to the normal series | Often located at end of a tooth series and erupt like normal series |
| Composite odontome | Odontogenic hamartoma | Complex: disorganized collection of tooth tissues Compound: multiple small tooth-like structures | One-third compound and a half complex odontomes that prevent tooth eruption |
Supernumeraries can occur individually or as multiples and may be located in the maxilla or mandible. Single supernumeraries are most likely to occur in the anterior maxilla, whereas multiple supernumeraries are most commonly located in the posterior mandible.6,7 Multiple supernumerary teeth are often associated with other medical conditions, such as cleidocranial dysplasia, cleft lip and palate and Gardner's syndrome.
The association with particular medical conditions, along with the trend for their occurrence in families, with sexual and ethnic variations, indicate that there is a genetic component to their aetiology.8 The precise nature of their development remains unclear; however, research suggests that it is likely to be due to overactivity of the dental lamina at specific sites in the jaws.9 It is proposed that the different types of supernumerary arise from different stages of tooth formation, with supplemental forms arising from gemination of the tooth bud, while less differentiated supernumeraries, for example tuberculate and odontomes arise earlier in the tooth development.10
The impact of supernumeraries on the dentition is variable. They may have no effect and may only be picked up as an incidental finding on a radiograph. Conversely, supernumeraries may affect the eruption path and final position of the normal series resulting in prevention of eruption, spacing, displacement, crowding and rotations. They can also be associated with pathological changes, most commonly cyst formation (dentigerous cyst) and root resorption of adjacent teeth.
Described below are three cases referred to the orthodontic department at Bristol Dental Hospital in which non-syndromic multiple supernumerary teeth show an apparent ‘late’ development and their implications on orthodontic treatment are discussed.
A 12-year-old male was referred from a specialist orthodontic practitioner regarding unerupted supernumerary teeth bilaterally in the lower premolar regions. The presenting complaint was of ‘extra teeth’. The patient had an unremarkable medical history and was a regular dental attender.
Two years previously, the patient had been referred to the same orthodontic department regarding the presence of two anterior unerupted supernumerary teeth, which were obstructing the eruption of the upper central incisors. Clinically, he had a Class II malocclusion complicated by retained primary upper central incisors. Orthopantomogram and upper standard occlusal (USO) radiographs revealed the presence of two midline supernumeraries lying palatal to the upper permanent central incisors. At this stage, there was no evidence of additional supernumeraries in either arch and the rest of the dentition was developing normally. No other pathology was detected at this stage.
The patient was referred to oral surgery for extraction of the supernumeraries and remaining primary teeth, along with bonding of a gold chain to the unerupted permanent central incisors. Between referral and the general anaesthetic, the UL1 spontaneously erupted and the URC naturally exfoliated. As the UR1 was nearing eruption and labially positioned, this tooth was exposed using an apically repositioned flap. The patient was subsequently discharged back to his specialist orthodontist for follow up.
On examination, he presented with a Class II division 1 incisor relationship on a moderate Class 2 skeletal base with average vertical proportions in the permanent dentition. The malocclusion was complicated by a 10 mm overjet with a reduced and incomplete overbite, lower lip trap, severe upper arch and mild lower arch crowding and an upper centreline shift of 2 mm to the left. His molar relationship was a full unit Class II bilaterally with buccal crossbites (Figure 1).
An orthopantomogram revealed the presence of all permanent teeth including the third molars (Figure 2). In addition, there were supernumerary teeth positioned between the roots of the lower premolars on both sides of the mandible. There was a well demarcated radiolucent area with areas of radiopacity lying halfway down the roots of the UR3 and UR4, which had the appearance of an early developing supernumerary tooth. The upper central incisor roots were dilacerated, potentially as a result of the mesiodens that had previously been extracted.
The patient elected to undergo orthodontic treatment to correct his malocclusion. The initial treatment plan involved growth modification with a modified Clark twin block appliance to be followed by reassessment of the supernumerary teeth and the need for fixed appliances.
With good compliance, the functional appliance phase lasted 10 months and corrected the molar and incisor relationships to Class I. The patient was keen to improve the alignment of the incisors with a phase of fixed appliances. A cone beam CT (CBCT) (Figure 3) was undertaken to delineate the relationship of the supernumerary teeth to the permanent dentition, and potentially aid surgical planning in relation to the proximity of the inferior dental nerve. The CBCT showed the supernumeraries to be developing lingual to the normal series, with no evidence of root resorption of the adjacent teeth. In the maxilla, however, it showed two supernumeraries that had fused together and were enclosed in an enlarged follicle lying palatal to the UR4 roots.
The findings of the CBCT were discussed with the patient and his mother. Due to the risk of nerve injury, the patient did not wish to have the lower supernumerary teeth removed. Therefore, a second phase of orthodontic treatment was planned involving upper arch expansion with a quadhelix appliance, followed by upper and lower fixed appliances.
It was decided to bypass all mandibular premolars with fixed appliances to avoid potentially increasing the risk of root damage to the established dentition. In the maxilla, the quad helix appliance would result in predominately buccal movement of the majority of the roots away from the supernumerary; however, some palatal movement of the root apices towards the supernumerary would occur because the premolars were tipped about their centre of resistance, although this palatal movement should be relatively small. The upper premolars were later bonded with MBT prescription brackets because the higher buccal root torque (7°) would aid buccal root movement away from the palatal supernumerary tooth, and counteract the tipping movement of the quadhelix appliance.
A further orthopantomogram was requested 18 months into treatment to reassess development of the supernumeraries and associated root resorption of the adjacent teeth (Figure 4). This demonstrated continued root development of the lower supplemental teeth, and further crown formation of the fused maxillary supernumeraries. There was no evidence of root resorption.
Following 12 months of fixed appliances, the patient was happy with the outcome and appliances debonded (Figure 5). Retention comprised bimaxillary vacuum-formed retainers.
Eighteen months post-debond, the patient presented with the supplemental LL5 partially erupted and lingually positioned (Figure 6). The supplemental LR5 was palpable lingually, but in the upper right quadrant, the supplemental teeth were not palpable. At this point an orthopantomogram showed continued development of all the supplemental teeth (Figure 7). There appeared to be no resorption to the adjacent teeth and the patient remained firm in his wish not to have them removed.
Twenty-four months post debond the supplemental LR5 had also erupted lingually and the upper supplemental tooth was palpable palatally, but not erupted (Figure 8). The patient had not changed his mind about extractions despite the significantly more favourable position of the mandibular supernumerary teeth. Annual review was planned to monitor the eruption of the upper supplemental teeth supervised by his GDP. The patient was warned that if the position of the supernumerary teeth compromises oral hygiene in the future with a plaque trap potentially leading to decalcification or cavitation, then their removal would be required. There is also potential for the maxillary supernumerary to erupt through the palate, which would then require removal. These possibilities were discussed with the patient.
An 8-year-old female patient was referred by a general dental practitioner regarding late eruption of the maxillary incisors. The patient was otherwise medically fit and well.
On examination, she presented in the mixed dentition with retained maxillary primary incisors. On initial radiographic review, there were multiple supernumerary teeth present in the anterior maxilla preventing eruption of the permanent dentition (Figure 9). To aid orthodontic and surgical treatment planning, a CT was taken, which showed that the incisors were rotated and palatally inclined, impacted against four late forming ‘tuberculate’ supernumeraries, two of which were fused/geminated (Figure 10).
In line with guidelines from the Royal College of Surgeons, the supernumerary teeth were removed, and gold chains bonded to the unerupted central incisors.11 The primary lateral incisors were not removed as the patient was extremely worried about the size of the gaps that would be left in the anterior maxilla and requested that they be maintained for the time being, in the knowledge that a further intervention to remove them and uncover the other incisors would be needed in the future. Over the following 12 months the incisors erupted, and the gold chains were removed (Figure 12). However, on eruption the incisors were ‘diminutive’ and in cross-bite. Further investigation confirmed that it was in fact the lateral incisors that had erupted, and the central incisors were unerupted and completely transposed with the lateral incisors (Mx.I1.I2) (Figures 13 and 14). Despite the CBCT being reported by a consultant dental radiologist, the transposition was unfortunately not originally picked up; however, with the benefit of hindsight the difference in size and morphology of the incisors can be seen.
At this stage the patient was referred for extraction of both primary lateral incisors and an upper removable appliance fitted to correct the anterior cross-bite as well maintain space for the unerupted incisors (Figure 15).
On radiographic review 12 months following removal of the lateral primary incisors (Figure 16), there was no improvement in the position of the central incisors. Of note, the lower right first premolar had failed to progress further in its eruption path. On closer inspection, there was evidence of a radiopacity between the LR4 crown and LR3 root, potentially indicative of supernumerary formation. With the benefit of hindsight, a subtle opacity was also present at this site in Figure 11, obscured by the superimposition of the LR4 crown, follicle and the LRD roots.
Based on the Class I molar relationship, with mild lower arch crowding and bimaxillary incisal retroclination, the patient was referred for extraction of the supernumerary in the LR4 region, as well as exposure and bonding of gold chains to the central incisors (Figure 17). In preparation for this, a fixed appliance was used to close the median diastema and open space for the central incisors through proclination of the incisors. Parallax intra-oral radiographic views were used to aid surgical planning, highlighting the lingual position of development (Figure 18). An USO taken during fixed appliance treatment (Figure 19) highlighted the improving position of the central incisors. This view also showed evidence of apical root resorption of both lateral incisors. The UL1 erupted spontaneously following creation of space and, therefore, no longer required exposure (Figure 21); however, the UR1 was still unerupted and required an exposure and bonding of gold chain (Figure 20).
Following removal of the supernumerary and exposure of the UR1, the LR4 and UR1 erupted and were aligned with the fixed appliances. The challenge that remained was camouflaging the maxillary anterior segment and the patient was aware of the further challenges ahead, that would involve joint management between orthodontic and restorative colleagues to achieve the best aesthetic and functional outcome for the patient.
A 13-year-old male, referred by his general dental practitioner, presented with a Class II division 1 incisor relationship on a high angle skeletal 2 pattern. The malocclusion was complicated by bimaxillary proclination and crowding with a 6 mm overjet. The lower right first premolar was unerupted (Figure 22).
An orthopantomogram showed the presence of four supernumeraries. One in the lower left premolar region, as well as two in the lower right premolar region, with the more superficial supernumerary preventing eruption of the first premolar (Figure 23). Furthermore, a fourth molar (disto-molar) showed early signs of development in the upper right quadrant.
The treatment plan involved removal of all first premolars to facilitate relief of crowding and overjet reduction. In order to allow retraction of the canines for incisor alignment, the supernumeraries in the premolar regions were required to be removed otherwise they risked root resorption and preventing canine retraction and full space closure.
Following review with oral surgery colleagues, a CBCT was requested to aid surgical planning based on the proximity of the supernumeraries to the mental nerve and adjacent teeth (Figure 24). The CBCT showed the supernumeraries to be positioned lingual to the normal series, one of which was also lying over the occlusal surface of LR4, preventing its eruption. There was no evidence of any associated root resorption.
The first premolars and supernumerary teeth were removed with no adverse consequences and the patient underwent fixed appliance treatment for correction of the malocclusion. The upper right disto-molar was left in situ due its position and lack of pathology. It is likely this tooth will continue to develop in time; however, it will be short of space and unlikely to erupt. Periodic monitoring for any associated cystic change will be required.
The above cases highlight the varied presentation of supernumerary teeth and the effect they can have on the developing permanent dentition. While the Royal College of Surgeons' guidelines on the management of unerupted central incisors focus on the need for interceptive extraction of a supernumerary,11 the reported cases highlight that in a small proportion of patients, further development and eruption of supernumeraries may occur. These ‘later’ developing supernumeraries tend to develop in the premolar region.12 This is not surprising because premolars develop later and therefore, supernumerary teeth originating from a premolar tooth germ are also likely to develop later. Combined with a possibly ectopic position and probable crowding, their eruption can be delayed or prevented from the surrounding dentition. While these are rare, consideration may be given to follow up of the subsequent dental development of these patients.
Nevertheless, the development of these supernumerary teeth may be considered a contraindication to orthodontic alignment. As evident in these cases, mandibular supernumeraries normally develop lingually with no serious adverse effects. However, they can be associated with failure of eruption and malformation of permanent teeth, reported in around 20–30% of cases in the literature, or cystic change in 4–11% of cases,10,13,14,15 as well as root resorption.16 Normally these teeth can be removed without complications, and this is ideal for optimal dental alignment and facilitation of oral hygiene.
The main reason for not extracting the mandibular supplemental teeth in the illustrated cases was due to patient choice. In these circumstances, informed consent is important, and patients and parents should be made aware of the increased risk of cystic change and root resorption if they are left. However, this is by no means guaranteed, and they can be left in situ, often without interference to the rest of the dentition. The need for review of these retained unerupted teeth is necessary, usually radiographically. There is, however, no clear advice on how often or for how long they should be monitored. Where orthodontic treatment is undertaken, it can be modified to avoid any active tooth movement of the adjacent teeth towards the supernumerary, which risks root resorption. Modifications could be with simple removable appliances to limit tooth movement to tipping. Fixed appliances can bypass the adjacent teeth to prevent their movement; however, this does prevent their alignment from being improved. If the teeth were to be bonded, then care should be taken to ensure that all root movements are away from the supernumerary tooth. This could be done with the early use of open coil, variation in bracket prescription or positioning and rounding out of rectangular archwires to prevent torque expression.
Surgical removal of mandibular supernumerary teeth risks injury to the inferior alveolar dental and lingual nerves, as well as other surrounding dental structures. There is no reported quantification for the incidence of nerve injury following surgical dental extractions from this region; however, based on the local anatomy, the risk of nerve injury cannot be underestimated and there must be informed consented. It may well then be favourable to delay any intervention until there has been further development with possible migration towards a more superficial location to facilitate surgical access and reduce potential surgical complications.
These cases highlight the unusual ‘late’ presentation of multiple supernumeraries in both the maxilla and mandible, often in the premolar regions, as well as the effect these can have on the dentition. It also highlights that unerupted supernumerary teeth do not always require surgical removal and are not always a contraindication to fixed appliances. However, if supernumeraries are left in situ during treatment, it is important that the clinician has an awareness of the effects of any potential treatment mechanics upon the adjacent roots. It is necessary to monitor for cystic change and associated potential root resorption, as well as ensure patients are fully informed of the risks and potentially limitations of treatment.
