Management of the developing dentition

10 Management of the developing dentition

A number of developmental anomalies can affect both the deciduous and permanent dentitions. These include variations in the number of teeth or their individual morphology, the position they attain within the dental arches and the composition of their constituent hard tissues. The aetiological basis of these abnormalities can be genetic, environmental or multifactorial, but they can all impact upon the developing occlusion, either directly or indirectly. In this chapter the aetiology and management of malocclusion in the developing dentition is discussed.

Early loss of deciduous teeth

The early loss of deciduous teeth is usually the result of extraction due to caries or trauma and can have implications for the developing occlusion: in particular, future space distribution and symmetry within the affected dental arch. The degree of space loss and potential occlusal disruption will be influenced primarily by:

The timing of deciduous tooth extraction can also influence the eruption rate of permanent successors. Very early loss of deciduous teeth can delay successional tooth eruption, whilst later extraction can have the opposite effect.

Balancing and compensating extractions

Balancing and compensating extractions aim to preserve arch symmetry and occlusal relationships by extracting teeth opposing those requiring enforced extraction.

The decision to carry out a balancing or compensating extraction will depend upon a number of factors (Box 10.1). However, before the elective extraction of any deciduous tooth is instituted, a radiographic screen should be carried out to check for the presence, position and normal formation of the developing permanent dentition. Any other deciduous teeth of questionable prognosis should also be considered as candidates for balancing or compensating extraction, particularly if general anaesthesia is required. It can be more difficult to justify these extractions if local anaesthesia is used for the elective extraction of a single symptomatic tooth and cooperation for further extractions may be poor.

Space maintenance

A space maintainer is a removable or fixed orthodontic appliance that preserves space within the dental arches (Fig. 10.3). These appliances are most commonly used in the mixed dentition to prevent forward drift of the first permanent molars following early loss of deciduous second molar teeth, or to maintain space and serve as a prosthesis in the labial segment after traumatic loss of permanent incisors.

A space maintainer in the posterior dentition can be useful in the following situations:

It should always be remembered that a tooth is the ideal space maintainer and every effort should be made to preserve deciduous teeth until the time of their natural exfoliation (Fig. 10.3). If a space maintainer is to be used it should be in a mouth with good oral hygiene and ideally, a low risk of further caries. Unfortunately, cases requiring elective tooth extraction due to dental caries are often the least suitable for long-term space maintenance.

Prolonged retention of deciduous teeth

Considerable variation can exist in the timing of deciduous tooth exfoliation and the subsequent eruption of permanent successors. The presence of marked asymmetry in the retention of deciduous teeth should be investigated radiographically.

Occasionally a permanent successor will erupt having failed to resorb the roots of the overlying deciduous tooth (Fig. 10.4). The patient should be encouraged to exfoliate these retained deciduous teeth themselves and if this is not possible, they should be extracted under local anaesthetic.

Crowding, or an ectopic position affecting the permanent successor, can also lead to prolonged retention of the overlying deciduous tooth.

Another cause of deciduous tooth retention is congenital absence of the permanent successor. For most of these deciduous teeth, the long-term prognosis is poor and they will either be lost naturally or ultimately require extraction. However, they can often act as useful maintainers of arch space or alveolar bone in the shorter term.

Ankylosis and infraocclusion

A tooth becomes ankylosed when the periodontal ligament is lost and direct fusion occurs between root dentine and the surrounding alveolar bone. Ankylosis most commonly affects deciduous molars, occurring in up to 9% of children (Kurol, 1981). A number of factors are thought to contribute:

A consequence of ankylosis can be the apparent ‘submergence’ or infraocclusion of the affected tooth relative to the occlusal plane (Fig. 10.6). This occurs in the growing child because alveolar bone and occlusal height increase with development, whilst the position of the ankylosed tooth remains fixed.


The congenital absence of one or more teeth is a relatively common anomaly in human populations.

The term hypodontia is generally used to describe congenital tooth absence, but the definitions are actually quite specific (Fig. 10.7):

Nonsyndromic hypodontia

Nonsyndromic hypodontia can either appear sporadically within a member of a family or be inherited. This form can follow autosomal dominant, autosomal recessive or autosomal sex-linked patterns of inheritance, with considerable variation in both penetrance and expressivity. This is by far the most common type of congenital tooth absence and can be further categorized based upon clinical presentation:

Within these clinical entities, certain teeth fail to develop more often than others:

Nonsyndromic hypodontia can be associated with other developmental anomalies affecting the dentition, which provides evidence of a genetic influence (Table 10.1). However, a multifactorial model has also been suggested (Brook, 1984), with the phenotypic effect being related to certain thresholds, themselves influenced by both genetic and environmental factors. Clearly, within this model, the mutation of a major gene may be a significant enough event to result in inherited tooth loss (Box 10.2).

Table 10.1 Dental anomalies associated with hypodontia

Box 10.2 Candidate genes for nonsyndromic human hypodontia

Targeted deletion of many genes in mutant mice can disrupt tooth formation and these have provided a reference point in the search for candidate genes in human populations. However, given the large number of potential genes available, it is somewhat surprising that only three have been positively identified in human familial hypodontia (Cobourne, 2007):

Mutations in the human MSX1 gene have been predominantly associated with familial oligodontia (Vastardis et al, 1996). Associations between MSX1 and the more common form of incisor–premolar hypodontia are rarer.

Syndromic hypodontia

Congenital tooth absence is also seen in association with other recognizable structural defects or abnormalities (Table 10.2).

Table 10.2 Syndromic conditions associated with hypodontia

Syndrome Gene
Anhidrotic ectodermal dysplasia (OMIM 305100) EDA
Adult (OMIM 103285) TP73L
Ehlers Danlos (OMIM 225410) ADAMTS2
Incontinentia pigmenti (OMIM 308300) NEMO
Limb mammary (OMIM 603543) TP63
Reiger (OMIM 180500) PITX2
Witkop (OMIM 189500) MSX1
Ellis–van Creveld (OMIM 225500) EVC or EVC2

Mutations in the homeobox gene MSX1 have been associated with a syndromic condition demonstrating various combinations of CLP, CP and hypodontia (van den Boogaard et al, 2000) and with Witkop syndrome (OMIM 189500), a form of ectodermal dysplasia (Jumlongras et al, 2001). Thus, MSX1 represents a candidate gene for both syndromic and nonsydromic hypodontia (see Box 10.2).

Supernumerary teeth

Supernumerary teeth are teeth present in addition to the normal complement and can occur within either dentition.

In common with hypodontia, supernumerary teeth also occur either as an isolated trait or as a manifestation of a clinical syndrome (Table 10.3), but they are usually classified according to morphology and location:

Conical supernumeraries are small peg-shaped teeth with normal root formation. When located in the midline of the anterior maxilla these teeth are known as mesiodens (Box 10.3); whilst in the maxillary molar region they are known as paramolars (buccal, lingual or interproximal to the second and third molars) or distomolars (distal to the third molar) (Fig. 10.8).
Tuberculate supernumeraries are characterized by a multicusped coronal morphology and a lack of root development (Fig. 10.9). These teeth are usually found palatal to the maxillary permanent incisors, often occur in pairs and frequently prevent eruption of the permanent incisors (Fig. 10.10).
Supplemental supernumeraries represent the duplication of a tooth within a series and can be difficult to differentiate from the normal tooth (Fig. 10.11). These teeth are usually found at the end of a series and can be seen in the incisor, premolar and molar fields. They represent the most common type of supernumerary found in the primary dentition (Fig. 10.12).
Odontomes are developmental malformations that contain both enamel and dentine (Fig. 10.13), and can be compound (containing many small separate tooth-like structures usually situated in the anterior jaw) or complex (a large mass of disorganized enamel and dentine usually situated in the posterior jaw).

Table 10.3 Syndromic conditions associated with supernumerary teeth

Syndrome Gene
Cleft lip and palate
Cleidocranial dysostosis (OMIM 119600) RUNX2
Gardner (OMIM 175100) APC
Ellis–van Creveld (OMIM 225500) EVC; EVC2
Incontinentia pigmenti (OMIM 308300) NEMO

Box 10.3 Managing the mesiodens

The mesiodens is one of the commonest forms of supernumerary tooth and is often detected in the anterior maxilla as a chance radiographic finding. Whilst removal is indicated if they interfere with the eruption, position or proposed orthodontic movement of adjacent teeth, quite often they are asymptomatic and in these circumstances, they should be left alone (Kurol, 2006). The potential risks associated with leaving these teeth in situ, such as follicular enlargement, cystic formation and resorption of maxillary incisor roots, would appear to be small (Tyrologou et al, 2005). In addition, if the mesiodens subsequently erupts, it can be removed with a relatively simple extraction under local anaesthesia.


Figure 10.12 Supplemental URB.

Courtesy of Thantrira Porntaveetus.

Supernumerary teeth occur individually or in groups and can be unilateral or bilateral. These teeth are found most frequently in the anterior maxilla, but are also seen in the premolar and molar regions. In the permanent dentition, the majority fail to erupt and are asymptomatic, only being discovered during routine radiographic screening. However, they can also cause dental problems, which include:

Failure of tooth eruption—the presence of a supernumerary can prevent the eruption of a permanent tooth (Fig. 10.14). In these circumstances, the supernumerary should be removed and provided space is available and the tooth is in a good position, there is a high chance the impacted tooth may well erupt unaided. However, exposure of the tooth is often undertaken at the same time, particularly in older children so orthodontic traction can be applied to the tooth to mechanically erupt it into the dental arch if it does not erupt spontaneously (see Fig. 10.22).
Crowding—supernumerary teeth can contribute to dental crowding, either directly as a result of eruption (particularly for supplemental teeth) or indirectly by causing displacements or rotations of adjacent erupted teeth (Fig. 10.15). These supernumerary teeth will usually require extraction as part of a definitive orthodontic treatment plan. When extracting these teeth, care must be taken to ensure the most poorly formed is removed.

Asymptomatic supernumerary teeth not affecting the occlusal relationships of the erupted dentition can be left in situ. These teeth should be kept under periodic radiographic review to ensure they are not damaging any adjacent structures or undergoing cystic change.

Abnormalities of tooth size

Teeth either larger or smaller than the normal population range for dimensions are usually referred to as megadont or microdont, respectively. These variations in tooth size can affect either the crown or root in isolation, or the whole tooth. Little is known about the aetiology of tooth size variation but it is almost certainly genetic.

Megadontia most frequently affects the maxillary permanent incisors (Fig. 10.16) or mandibular second premolars and is often symmetrical. These teeth can be differentiated from double teeth by the absence of coronal notching and presence of normal pulpal morphology. Extraction of megadont teeth is often indicated, particularly with maxillary central incisors, because the aesthetics can be poor. Depending upon the space requirements, either the lateral incisors can be approximated and adjusted restoratively to look like central incisors or space maintained for prosthetic replacement.
Microdontia is commonly associated with hypodontia and can affect the whole dentition or individual teeth. The maxillary permanent lateral incisor is one of the commonest teeth to be affected, often having a characteristic peg-shaped crown morphology (Fig. 10.17) and this has a causal association with palatal impaction of the maxillary canines. Whether a microdont maxillary lateral incisor is retained or extracted depends not only on the underlying malocclusion and the need for extractions, but also on the shape and form of the lateral incisor and whether it can ultimately be an aesthetic and functionally viable tooth. If this tooth is to be retained, the crown will require restorative buildup to improve the aesthetics and symmetry if it is unilateral. Space will often need to be created to allow this, which usually necessitates fixed appliances. If the lateral incisor is extracted, space will also need to be created if prosthetic replacement is planned, as these teeth are usually smaller than the space required for suitable pontics.

Abnormalities of tooth form

A number of anomalies associated with tooth form have been described. These conditions are generally rare, occurring with prevalence well below 5% of Caucasians, and with the exception of double teeth, they generally affect the permanent dentition more commonly than the deciduous.

Double teeth can range from a slightly enlarged tooth with minor coronal notching to almost complete separation of two normally formed teeth. They are most commonly seen in the labial region of the mandibular deciduous dentition (Fig. 10.18), but can also affect permanent teeth. In the deciduous dentition, it is important to establish whether a double tooth is associated with hypodontia because this can indicate possible tooth absence affecting the permanent teeth. Conversely, if the double tooth is part of a normal complement, supernumerary teeth may be seen in the permanent dentition. Localized crowding or spacing can be seen in association with double teeth in both dentitions but in the deciduous, extraction is rarely indicated. Permanent double teeth can be managed restoratively if the coronal portion is not too large; however, those with more deviant anatomy may require extraction followed by space closure or prosthetic replacement.
Taurodont (OMIM 272700) or bull-like teeth have a pulp chamber enlarged at the expense of the roots (Fig. 10.21). This condition is seen in around 2.5–5% of adult Caucasians and can occur in isolation, or in association with amelogenesis imperfecta.

Figure 10.19 Talon cusp.

Courtesy of Evelyn Sheehy.

Primary management relies upon ensuring adequate space exists in the dental arch to accommodate the unerupted tooth and removing any potential obstruction. In these circumstances, the majority of teeth will erupt. If this fails to happen, or the unerupted tooth is ectopic from its normal path of eruption, surgical exposure, with or without orthodontic traction, may be required to accommodate the affected tooth into the dental arch (Box 10.4).

Box 10.4 Surgical exposure of impacted teeth

In the labial regions of the maxilla, and both labially and lingually in the mandible, the alveolar crest is covered by a keratinized, firmly attached gingiva, which is replaced by a more mobile, non-keratinized alveolar mucosa at the mucogingival junction. In contrast, on the palatal side of the maxilla there is no alveolar mucosa, the attached gingiva and palatal mucosa are both keratinized and firmly attached to the underlying bone, with no recognizable boundary between them. It is important for an impacted tooth to erupt through attached gingiva because this tissue provides a firm attachment at the dentogingival junction, is robust enough to maintain integrity of the periodontium during masticatory function and provides the best potential for long-term periodontal health. This will influence the method of exposure for teeth impacted in different areas of the jaws.

Impacted teeth are surgically exposed using one of two basic techniques:

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Jan 1, 2015 | Posted by in Orthodontics | Comments Off on Management of the developing dentition

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