Orthodontic Update - The multidisciplinary management of unerupted maxillary incisors. A report of three cases

Abstract

An unerupted maxillary incisor can have a major impact on aesthetics and function. To achieve optimum results, early detection, referral and treatment is essential. This article will review the aetiology of delayed eruption and discuss the clinical and radiographic assessment of unerupted maxillary incisors. Three treated cases will be presented that demonstrate the management according to guidelines produced by the Royal College of Surgeons, England. These cases illustrate the importance of early referral as the treatment strategy varies according to the patient's age and stage of root development and late treatment has been shown to have a longer treatment time and increased risk of damage to the incisor.

CPD/Clinical Relevance: This article reviews the aetiology, diagnosis and management of unerupted incisors.

Article

An unerupted maxillary incisor can have a major impact on aesthetics and function. To achieve optimum results, early detection, referral and treatment is essential. Early detection and referral by general dental practitioners (GDPs) to secondary care will increase the treatment options available for the multidisciplinary team and reduce the risk of complications.

The incidence of unerupted maxillary central incisors has been reported as 0.13% in the 5–12 year-old age group.¹ In a referred population to regional hospitals the prevalence has been estimated at 2.6%.²

The Royal College of Surgeons, England (RCS) has developed guidelines for the management of unerupted incisors.³ The treatment protocol differs, depending on the age of the patient and stage of root development. This highlights the importance of early referral to achieve the best possible outcome for the patient.

Aetiology of delayed eruption

The aetiology of delayed eruption of maxillary incisors can be broadly subdivided into two causative groups, local and systemic. Examples are shown in Table 1.

Table 1. Aetiology of delayed eruption.

Local	A supernumerary toothMucosal barrierTrauma to primary tooth (particularly intrusion that may result in dilaceration of the permanent successor)Retained primary toothEarly extraction or loss of primary tooth resulting in space lossCrowdingLocal pathology such as a cystEctopic position of tooth germRadiation damage
Systemic	Cleidocranial dysplasiaCleft lip and palateGardner's syndromeOsteopetrosisHypothyroidismHypoparathyroidismHypopituitarism

Owing to the range of local and systemic factors contributing to unerupted maxillary incisors, a detailed medical and dental history can help to identify patients that are at an increased risk of delayed eruption.

Dental trauma to the deciduous incisors is particularly important due to the damage that can occur to the developing permanent incisor tooth germ. Intrusion of a deciduous incisor may result in dilaceration of the developing permanent incisor, affecting its eruption. If the deciduous incisor is avulsed or subject to severe trauma, the tooth may require extraction. This premature loss may result in space loss for the permanent incisors and therefore affect their eruption.

Patient examination

When examining patients in the mixed dentition it is important to assess the following aspects:

Identification of the presence of deciduous teeth that have been retained beyond their normal exfoliation date;

Loss of chronological symmetry of more than 6 months;

Buccal swelling, indicative of an ectopic tooth;

Availability of suitable space for the eruption of incisors; 9 mm for a central incisor and 7 mm for a lateral incisor, on average, although the contralateral tooth should be measured.

Figure 1 demonstrates the circumstances where further investigation is required.

Figure 1. Pathway indicating further investigation is required.

Radiographic examination

Any abnormalities detected should be further investigated with radiographic imaging to assess the reason for non-eruption and morphology of the crown and root. An upper standard occlusal, dental panoramic or periapical radiographs should be taken for assessment purposes. Two radiographs allow for localization of the tooth position. Figures 2 and 3 demonstrate the importance of two types of radiograph combined. In Figure 2, an upper standard occlusal has been taken, however, it is difficult to determine the orientation of the upper left central incisor. Figure 3, a dental panoramic radiograph, reveals that the upper left central incisor is inverted and has a poor prognosis for alignment.

Figure 2. Upper standard occlusal radiograph showing an unerupted upper left central, however, it is difficult to assess its position.

Figure 3. Dental panoramic radiograph confirming the inverted position of the upper left central incisor.

Although not routinely used in the detection of impacted maxillary incisors, a lateral cephalogram can be a useful adjunct when a dilacerated incisor is suspected (Figure 4).

Figure 4. Lateral cephalogram showing a dilacerated upper incisor.

More recently, cone beam computed tomography (CBCT) has been used for localization of impacted teeth. However, a CBCT is only justified if the information will influence treatment and when information cannot be obtained adequately by lower dose conventional radiography. Guidelines on the use of CBCT have been released by the SEDENTEXCT project in 2012.⁴

Management

The failure of a permanent incisor to erupt should be identified early and referred to secondary care. The average age of central incisor eruption is 7–8 years of age, so patients should be referred by their GDP if the incisor has not erupted before their ninth birthday. A regional audit published in the British Orthodontic Society Clinical Effectiveness Bulletin found that 31% of patients referred to secondary care were over ten years of age.⁵ This is unacceptable and may limit the treatment options available, increase the treatment time and increase the risk of complications to the incisor.

The treatment stages for an unerupted incisor, according to the Royal College of Surgeons, England guideline³ are as follows.

Extraction of retained deciduous incisors

Extraction of the retained deciduous teeth is indicated if there are no other obvious causative factors for the unerupted permanent incisor.

Create space

Space can be created with removable or fixed orthodontic appliances. Extraction of the deciduous canines may also be required to increase the space available for eruption. Following creation of sufficient space, a study has shown 75% of incisors will spontaneously erupt if there is no obstruction.⁶^,7 A study found that an absence of pre-operative orthodontics to open space for the incisor also dramatically increased treatment time.⁸ A prospective study has found that rapid maxillary expansion after the extraction of a supernumerary increased the number of incisors that erupted after one year from 39–82%.⁹

Remove obstruction

In most cases, it is necessary to remove anything impeding the path of eruption of the maxillary incisors. It has been shown that the early removal of the causative factor preventing eruption improves the tooth's prognosis, provided there is sufficient space.¹⁰^,11

The pathology most commonly obstructing teeth are supernumeraries. The presence of a supernumerary tooth may have no effect on the developing dentition or may deflect the path of an erupting tooth or prevent eruption entirely.

The Royal College of Surgeons England guidelines have suggested different treatment methods, depending on the patient's age and stage of root development³ and this is summarized in Table 2.

Table 2. Treatment protocol guidelines depending on the patients' age and stage of root development. Adapted from the Royal College of Surgeons, England guidelines.3

Age	Stage of Root Development	Treatment Protocol
Under 9 years	Incomplete	Removal of supernumerary and any retained deciduous incisorCreate and maintain spaceMonitor eruption for 18 monthsExpose/bond bracket if tooth has not erupted within 18 months
9–10 years	Nearly complete apex	Removal of supernumerary and any retained deciduous incisorCreate and maintain spaceMonitor eruption for 12 monthsExpose/bond bracket if tooth has not erupted within 12 months
Over 10 years	Complete	Removal of supernumerary and expose +/- bond bracket at first operation

There is evidence that, if a tooth is not exposed and bonded at the first operation when indicated by the patient's age and stage of root development, the treatment time is extended. Lygidakis et al found that the mean treatment time increased from 10 to 23 months.⁸ However, when it was appropriate to wait for spontaneous eruption due to the patient's age and stage of root development, the treatment time was not statistically different.⁸

Omer et al looked at the consequences of late removal of unerupted supernumeraries to the central incisors. They found that, if the supernumerary teeth were extracted after root completion, there was an increased risk of root resorption and arrested root development.¹² The risks of increased treatment time and damage to the central incisor therefore increase with age, highlighting the importance of early referral and treatment.

Exposure

Surgical exposure of the unerupted tooth can be done using either an open or closed technique. When using an open technique, it is important to preserve as much gingival tissue as possible to ensure eruption through attached mucosa and thereby optimal gingival aesthetics. Buccal superficially positioned incisors may be exposed with an apically repositioned flap. Deeply positioned incisors require a closed exposure with a gold chain. Following a closed exposure, the gold chain is then attached to a fixed or removable appliance to apply traction. Initially, orthodontic traction may be achieved with an upper removable appliance as the palate provides good vertical anchorage support. A two by four appliance (bands on upper first molars and bonds on the upper incisors) may also be used.

Cases

In the following three example cases, different management protocols were followed due to the age of the patient and stage of root development.

Case 1

An eight-year-old patient was referred to the orthodontic department in the mixed dentition with a retained upper right deciduous central incisor and unerupted permanent incisor. The upper left central incisor had been erupted for more than 6 months and the patient was therefore referred to secondary care. Radiographic examination revealed an unerupted upper right central incisor associated with a tuberculate supernumerary (Figure 5).

Figure 5. Dental panoramic radiograph showing an unerupted upper right central incisor and associated supernumerary.

The patient had a general anaesthetic for the extraction of the retained deciduous incisor and supernumerary. As the patient was eight years of age and the root formation of the central incisor was not complete, the tooth was not exposed at the first operation. Figure 6 shows the patient after removal of the supernumerary and deciduous incisor and before space creation.

Figure 6. Post extraction of URA and supernumerary but prior to space creation.

Space was created with an upper removable appliance and the eruption of the teeth monitored for 18 months. The incisor did not spontaneously erupt and the patient had a second surgical procedure with an apically repositioned flap. As space had been created, the incisor was able to erupt spontaneously after exposure (Figure 7). This tooth will soon be aligned with fixed orthodontic appliances subject to improvement in oral hygiene.

Figure 7. Post space creation and apically repositioned flap for UR1.

Case 2

A nine-year-old patient was referred to the Orthodontic Department with retained upper deciduous incisors beyond exfoliation age and unerupted permanent central incisors. As there was a deviation from the normal eruption sequence and the lower incisors had been erupted for greater than a year, the patient was referred to secondary care. Radiographic examination (Figure 8) revealed two tuberculate supernumeraries preventing the eruption of both upper central incisors.

Figure 8. Dental panoramic radiograph demonstrating two unerupted central incisors due to the presence of supernumeraries.

The patient had a general anaesthetic for extraction of the retained deciduous incisors and supernumeraries. As the patient was nine years of age and the root formation of the central incisors was not complete, they were not exposed and bonded at the first operation. Space was created with an upper removable appliance and the eruption of the teeth monitored for 12 months. Figure 9 demonstrates that, after 9 months, the upper right incisor is beginning to erupt.

Figure 9. UR1 is erupting 9 months after the initial surgical procedure.

At 12 months both central incisors are erupting (Figure 10).

Figure 10. UL1 is erupting 12 months after the initial surgical procedure.

The patient is now undergoing orthodontic alignment of the dentition (Figure 11).

Case 3

A 10-year-old patient was referred to the Orthodontic Department regarding an unerupted upper left central incisor (Figure 12). This patient should have been referred earlier by his GDP as there is a deviation from the normal sequence of eruption. Radiographic examination demonstrated a superficially positioned unerupted upper left central incisor and two associated supernumeraries (Figure 13).

Figure 13. (a, b) Upper standard occlusal and dental panoramic tomograph showing an unerupted UL1 and 2 supernumeraries.

The patient had a general anaesthetic for the exposure of the upper left central incisor and extraction of associated supernumeraries. As the patient was 10 years of age and the root formation of the incisor complete, the tooth was exposed at the first operation with an apically repositioned flap. Space was created with an upper removable appliance via a midline screw (Figure 14).

Figure 14. Upper removable appliance with a midline screw to create space for the UL1.

Three weeks post exposure a bracket was bonded to the UL1 and an upper removable appliance fitted to apply traction to this tooth. Traction was applied via a split labial bow and the patient replaced the elastic every day between the upper left incisor and labial bow. Figure 15 demonstrates the labial bow in the passive and active position, providing a vertical eruptive force to the incisor.

Figure 15. (a, b) Labial bow in a passive and active position applying an extrusive force to the UL1.

The dentition was then aligned with upper and lower fixed appliances (Figure 16). Note the high gingival margin even though care was taken to ensure that the tooth erupted through attached mucosa.

Figure 16. Alignment of UL1 with fixed appliances.

Conclusion

Early detection, referral and treatment of unerupted incisors is essential to increase the treatment options available to the patient, reduce the treatment time and reduce the risk of complications, such as root resorption.

A hill to die on?

The dilemma: concerns about an overjet

References

The multidisciplinary management of unerupted maxillary incisors. A report of three cases

Authors

Rozana Valiji Bharmal

Claire Furness

David Slattery

Catherine Campbell