Michael J Aldred, Angus C Cameron, Nigel M King and Richard P Widmer
The diagnosis and management of dental anomalies constitute important areas of paediatric dentistry. Although most dental anomalies present in childhood, many are misdiagnosed or left untreated, perhaps because of lack of experience or because the case is perceived to be ‘too difficult’. In some instances, genetic consultation is desirable, not merely to diagnose the condition but also to provide appropriate advice on the prognosis and the risk of recurrence in future generations. In many cases, the presence of an inherited dental disorder in one child would not stop a family from having additional children, but it is important to give parents and the affected children themselves appropriate information on which to base their decisions. Genetic services are usually available at most paediatric hospitals.
In this chapter, reference to particular inherited conditions is made to entries in OMIM (Online Mendelian Inheritance in Man). This online database is a catalogue of genetic disorders developed by Dr Victor McKusick of the Johns Hopkins University and the National Center for Biotechnology Information (see References and further reading, below).
Considerations in the management of dental anomalies
Treatment planning for children with dental anomalies
Treatment planning should be multidisciplinary. Decision-making must involve the child and the parents and should consider the present and future needs and development of the child. Although children will cope with a range of appliances and treatments during childhood, early adolescence represents a period of social adjustment, as well as the transitional changes in the dentition. It is perhaps the most difficult time in which to formulate a long-term plan. Teenagers are most concerned about aesthetics, yet it may be too early to provide definitive restorations; extensive orthodontic treatment may be required or later orthognathic surgery. In institutions, various teams exist to treatment plan and/or manage these cases and a list is suggested below. Note the involvement of the child’s local general dental practitioner.
The team approach
It is essential to seek advice from colleagues in the management of children with uncommon dental conditions. Local and international collaboration provides the best opportunities to increase our knowledge and improve the outcomes for these children.
Dental anomalies at different stages of dental development
It is convenient to consider dental anomalies by the development stage at which they arise.
Migration of neural crest cells (ectomesenchyme) into branchial arches
Dental lamina formation stage
Induction and proliferation
Developmental defects of multiple dental tissues
Organic matrix deposition and mineralization
Eruption and root development
Formation of dental lamina
Alternative terminology: Hypodontia, oligodontia, anodontia.
Hypodontia, oligodontia and anodontia are terms that can be interpreted to refer to progressive degrees of missing teeth, though the term hypodontia is preferred because it is inclusive of any number of missing teeth (Figure 11.1A). ‘Oligodontia’ refers to six or more missing teeth, and ‘anodontia’ to the complete absence of teeth. It is implicit in all cases that the teeth are missing because of failure of development. The term ‘congenitally missing teeth’ is a misnomer when applied to the permanent dentition because these teeth do not commence development until after birth (and with regard to the primary dentition one cannot usually determine this clinically at birth); ‘partial anodontia’ is a nonsense term. Some degree of hypodontia is not uncommon, occurring sporadically or with a hereditary component. The teeth most commonly absent are the last teeth in each series (i.e. the lateral incisor, the second premolar and the third molar). Clinically, it is less important to know how many, but rather which types of tooth are absent. It is particularly unusual for a patient to be missing central incisors, canines or first permanent molars. Multiple missing teeth in a child should lead to investigations to determine if there are other affected family members. The presence of a rudimentary or conical tooth may be associated with the absence of the same tooth on the opposite side of the arch. A common example of this is the peg lateral incisor. Furthermore, that lateral incisor itself may be absent in subsequent generations. Missing teeth are also a manifestation of many syndromes of the head and neck.
Figure 11.1 (A) The teeth most commonly missing are the last teeth in each series, namely the upper lateral incisors, the second premolars and the third molars. (B) Panoramic radiograph of a boy with autosomal dominant ectodermal dysplasia with absence of both primary and permanent teeth.
Third molars > maxillary lateral incisors > second premolars > mandibular central incisors.
Major conditions manifesting hypodontia
Hypodontia is a major clinical feature of over 50 syndromes. These include:
Ectodermal dysplasia describes a group of developmental, often inherited, disorders involving the ectodermally derived structures, i.e. the hair, teeth, nails, skin and sweat glands. The most common is the X-linked hypohidrotic form (OMIM 305100, EDA1, Xq12-q13.1; short arm of X chromosome). In this condition the usual presentation is a male child with:
Figure 11.2 (A) Typical appearance of a boy with X-linked hypohidrotic ectodermal dysplasia (wearing a denture). The skin around the eyes is dry and wrinkled and may be pigmented (not shown here). (B) The hair is fine and sparse and often displays longitudinal grooves on the surface under the scanning electron microscopy.
Teeth are small and conical, often with a large anterior diastema (Figure 11.4). Heterozygous females are often identified by dental examination and their manifestations may be limited to a single missing tooth or to a peg lateral incisor (see the Lyon hypothesis, below).
In the group of ectodermal dysplasias, autosomal dominant and recessive modes of inheritance are also seen. In such families, there will not be such a striking difference in the degree of the disorder between males and females compared with X-linked hypohidrotic ectodermal dysplasia (Figures 11.2A, 11.3). Mutations in the MSX1 gene (4p16.1) have been identified in families with missing third molars and second premolars with or without clefting, as well as in families with tooth-nail (Witkop) syndrome. PAX9 (14q12–q13) gene mutations have been found in other families with autosomal dominant missing teeth. More genes implicated in missing teeth and other anomalies continue to be identified.
Figure 11.4 (A,B) Typical intra-oral and radiographic presentations in a boy with ectodermal dysplasia with multiple missing teeth; the teeth that are present are small and conical in shape. In the regions where teeth are absent, alveolar bone does not develop. (C) Composite resin build-ups of the conical teeth have provided improvement in the aesthetics; however, the problem of the diastema remains, given that there are only a few teeth for orthodontic anchorage.
In some countries, dental care (including prevention, orthodontics and prosthetics) for affected children may be provided under government-funded schemes.
The aim of treatment is to provide adequate function, maintain the vertical dimension and restore aesthetic appearance. Ideally, for social reasons, treatment should begin at around 2–3 years of age. A first step is often the placement of composite restorations to mask the ‘fang-like’ appearance of the caniniform anterior teeth (Figure 11.4A). There is often considerable parental pressure to ‘normalize’ the appearance and later, steps may involve the provision of dentures to reduce the likelihood of teasing, often at about the time that the child starts school. This can begin as soon as the child allows adequate impressions to be taken. Often, however, the first denture is initially worn in the pocket(!), but as the child grows, there is often a desire to have a more ordinary appearance. With encouragement and positive reinforcement, most children will soon try their new appliances.
Treatment planning for children with hypodontia
Treatment planning should be multidisciplinary and should consider the present and future needs and development of the child, while being cognizant of the concerns of the individual and parents.
Figure 11.5 (A,B) Closure of an anterior diastema and reshaping of the canines with composite resin in a child with absence of the upper lateral incisors. The successful masking of upper canines to appear like lateral incisors is dependent very much on their size.
Figure 11.6 (A,B) Conical primary teeth are often associated with missing permanent teeth. This child had an autosomal recessive form of ectodermal dysplasia and was missing almost all of the permanent teeth. (C) These teeth have been built up with composite resin strip crowns. (D) Radiographic appearance of the same child at 15 years of age. Most of the primary teeth have exfoliated even in the absence of a permanent successor. There has also been loss of bone in the region of the tuberosity due to pneumatization of the sinus that will complicate implant placement.
Figure 11.7 (A–C) Dentures for young children with ectodermal dysplasia. (A) Young children tolerate dentures extremely well and Adams’ cribs and ball retainers provide retention around primary molars. In this case, an overdenture covers two conical, widely spaced incisors. (B) A full upper denture for a child of 30 months will require periodic relining and re-making as the child grows. (C) Stock prosthetic teeth are sometimes difficult to obtain but paediatric denture teeth may be made freehand from acrylic and the palate can be customised.
The Lyon hypothesis (X chromosome inactivation)
During cellular differentiation, one of the two X chromosomes in each female somatic cell is inactivated. This means that in families with X-linked disorders, approximately 50% of the cells of heterozygous females will express the mutant gene disorder, whereas the remainder will express the normal gene. In the tissues affected by the condition, such females have a mosaic of affected and normal cells. This is of particular importance in X-linked forms of conditions such as haemophilia, hypohidrotic ectodermal dysplasia, vitamin D-resistant rickets and amelogenesis imperfecta. Thus, heterozygous females with X-linked hypohidrotic ectodermal dysplasia may have missing teeth, although they are invariably less severely affected than males. Similarly, in haemophilia A, heterozygous females do not usually have a clinical bleeding abnormality but this can occur if lyonization is severely skewed so that there is a preponderance of cells producing factor VIII under control of the mutant gene.
In patients affected by dentoalveolar clefting, disruption of the dental lamina at that site, there may be abnormal cellular induction or proliferation. This may give rise to either missing teeth, usually the maxillary lateral incisor, and/or supernumerary teeth adjacent to the cleft. However, it is extremely rare for the canine tooth to be affected in the same way.
Solitary median maxillary central incisor syndrome (OMIM 147250)
Solitary median maxillary central incisor syndrome (SMMCI) (Figure 11.8) is very rare. It presents with a midline symmetrical maxillary central incisor. The condition may also be associated with other midline disturbances such as cleft palate, choanal stenosis or atresia, imperforate anus or umbilical hernia and is probably part of the spectrum of the holoprosencephaly malformation complex. Of importance in some cases is the association with hypoplasia of the sella turcica, pituitary dysfunction, growth hormone deficiency and subsequent short stature. The syndrome is usually diagnosed on the basis of the dental manifestations. A mutation in the SHH gene (7q36) has been identified in one family but it is probable that there is genetic heterogeneity in the condition.
Figure 11.8 (A) Solitary median maxillary central incisor syndrome presenting with a symmetrical incisor in the midline. This child had a mild growth hormone deficiency, with his height on the 10th centile. (B) Periapical radiograph of the same patient in the primary dentition showing the single primary and permanent central incisors.
Ultimately, management of the dental anomaly is by orthodontic and prosthodontic therapy, determined by space considerations. In most cases, the single central incisor is moved to one side of the midline with either creation of space for a prosthodontic replacement, or the adjacent lateral incisors are recontoured.
Osseointegrated implants in children
There has been much controversy about the timing of placement of osseointegrated implants in young children. To date, there has been only limited published material about early placement and any long-term consequences. It is generally understood that implants act similarly to ankylosed teeth and do not move occlusally with the growing bone around adjacent natural teeth. Recent animal research has confirmed that most fixtures do become osseointegrated in growing jaws; however, there was no evidence from this research that the fixtures behaved like normal teeth during development. In the mandible, the fixtures came to lie lingual to the natural teeth; in the maxilla, they came to lie palatal and superior to the adjacent teeth and did not follow the normal downwards and forwards growth of this bone. This latter point is important when considering the placement of implants in the anterior maxilla. Furthermore, placement of fixtures retarded alveolar growth locally and changed the eruptive path of distally positioned tooth buds. Implants should, in most cases, not be considered before the cessation of growth. It should be noted, however, that in children with conditions such as ectodermal dysplasia, alveolar bone does not develop where teeth are not present. Consequently, it may be considered appropriate, particularly where there are multiple missing teeth, to place implants much earlier in these children than in those with a normal alveolus. Recent research suggests that in cases of anodontia, implants are best placed in the mandibular canine region at around 8–10 years of age (which is after the period of maximal mandibular transverse growth) to facilitate lower denture construction.
Disorders of proliferation
Supernumerary teeth (Figure 11.9)
• Supernumerary teeth have been considered to be manifestations of a separate dentition (occurring between the primary and permanent dentitions), and consequently it may be possible to predict when and where supernumeraries may form (Jensen & Kreiborg 1990).
Figure 11.9 Common presentation of supernumerary teeth. (A) Conical teeth often erupt, except when inverted. (B) The late eruption of a permanent central incisor is most commonly caused by a supernumerary tooth. (C) Supplemental upper primary lateral incisor. (D) A panoramic radiograph is useful in determining the vertical orientation of the extra tooth (arrowed) and the degree of displacement of the permanent central incisor. In this case, after removal of the supernumerary, an upper denture was used as a space maintainer and the impacted tooth subsequently erupted into a normal position. (E,F) Dependent on the degree of displacement, given adequate space, most impacted incisors will normally erupt once an obstruction such as a supernumerary is removed. The rotation can be corrected later.
Mesiodens (a term restricted to supernumerary teeth in the midline of the maxilla), paramolar, distomolar, hyperdontia, polydontism, supplemental teeth.
• Tuberculate and/or inverted conical teeth require surgical removal ((Figure 11.9D)) as early as possible to allow uninhibited eruption of the permanent teeth.
• It is essential to localize the position of the tooth to be removed prior to surgery. Periapical films using a tube-shift technique can be used to locate the tooth, however this is always open to errors and misinterpretation. Panoramic and standard maxillary occlusal films may be used in the same way.
• Digital imaging techniques using cone-beam tomography (CBCT) provide high definition, 3-dimensional imaging of the head and neck with much reduced radiation exposure than traditional computed tomography (CT) (see Figure 11.19, below).
• Before 10 years of age: if the unerupted central incisor is correctly aligned the treatment of choice is to remove the supernumerary surgically and allow normal eruption of the permanent tooth. Gingival exposure may be required later because of surgical scar formation that can inhibit final soft-tissue emergence. Some authorities recommend the simultaneous removal of primary canines to counteract this tendency. Inverted supernumeraries can be removed less traumatically if surgery is performed early, however, this needs to be done with caution to avoid damage to the adjacent tooth germs.
Figure 11.11 Surgical exposure and bonding of a gold chain to a central incisor which was impacted by a supernumerary tooth. (A) Elevation of the labial and palatal flaps and removal of the supernumerary. (B) Acid-etch applied to the labial surface of the upper left central incisor (C) Rinsing the acid etch gel from the tooth. (D) The appearance of the etch pattern on the prepared tooth. (E) Bonding of a gold chain attachment to the labial surface of the incisor. (F) The flap is closed and the chain is sutured to the gingiva with surgical nylon. The chain will be attached to an archwire and orthodontic traction will be applied to orthodontically align the tooth.
Cleidocranial dysplasia (Figure 11.10) (OMIM 119600)
This condition has an autosomal dominant mode of inheritance, with a high frequency of spontaneous mutations. The condition has been mapped to 6p21 with mutations found in the CBFA1 gene.
Note that the simple extraction of a primary tooth will frequently guarantee the eruption of the impacted permanent tooth. A two-stage surgical procedure is usually required with an attachment placed on the permanent tooth followed by orthodontic traction. The first procedure involves exposure of the anterior segments with removal of the anterior primary teeth and any supernumeraries that may be present. The permanent teeth are surgically exposed, either with primary apically repositioned flaps or with bonded gold chains attached for orthodontic traction. The anterior teeth are then aligned orthodontically. The second stage involves extraction of the primary molars, surgical removal of remaining supernumerary teeth and exposure of the premolars and molars in the buccal segments. Definitive orthodontic therapy follows; orthognathic surgery may be required in cases with severe skeletal Class III malocclusion. Treatment obviously extends over many years and clinicians should be aware of the potential problems relating to the child’s compliance and the need for multiple surgical procedures.
Cherubism (OMIM 118400)
Cherubism is an autosomal dominant condition caused by mutations in the SH3BP2 gene at 4p16.3.
Patients may present in childhood with facial swelling and/or failure of eruption of teeth, typically the mandibular molars. Radiographs will reveal multilocular radiolucencies, typically involving the angles of the mandible (Figure 11.12). A biopsy will reveal multinucleate giant cells in a fibrous tissue stroma. Developing teeth in the affected area tend to be displaced and fail to erupt at the normal time. The maxillae can also be affected, as can the ribs. The facial swelling reflects the involvement of the underlying bone. In some patients the sclera in the lower part of the eyes may be exposed to give the cherubic or heavenward gaze that gives the condition its name. In some cases, there is no discernible facial swelling and the condition is identified as a result of routine radiographic studies such as for orthodontic treatment planning, or because of delayed eruption of teeth.
Figure 11.12 Dental panoramic radiograph showing almost symmetrical multilocular radiolucencies in the angles of the mandible of an 8-year-old boy. The displacement of developing molars and delayed eruption of teeth is usually seen in cherubism.
The condition progresses into adolescence and then tends to resolve, so that by the 3rd or 4th decade radiographic changes may no longer be found. In some families more affected males than females may be identified – this is a result of reduced penetrance in females and needs to be taken into account in genetic counselling. A subset of patients with cherubism is more severely affected with the multilocular radiolucencies affecting the whole of the mandible and maxillae. In mildly affected cases regular review may be all that is necessary, in more severely affected cases surgical reduction may be considered if the patient is distressed by their appearance.
Inflammatory follicular cysts
Some children may present with failure of eruption of a mandibular premolar associated with a radiolucency involving the roots of the primary molar and crown of the unerupted premolar (see Figure 7.2B and Figure 10.27). There is controversy as to whether such cases are due to radicular cyst formation associated with the roots of the primary tooth (which is considered by some to be a rare occurrence) or dentigerous cyst formation around the crown of the premolar. The common characteristics of such cases tend to be:
Histopathological examination tends to show intense acute and chronic inflammation of the curetted tissue which is lined by hyperplastic stratified squamous epithelium. Such cases have been designated ‘inflammatory follicular cysts’, with persistent inflammation from the endodontically treated primary molar leading to an inflammatory enlargement of the follicle of the underlying permanent tooth.
Odontomes (Figure 11.13)
Odontomes occur because of disordered differentiation and often present because of failure of eruption of a permanent tooth. In compound odontomes, multiplex of irregular denticles are found in a circumscribed soft-tissue stroma. Complex odontomes are disordered lesions with a discrete, haphazard mass of calcified tissue containing all dental elements. There is either a normal complement of teeth or the odontome replaces a tooth of the normal series.
Figure 11.13 Odontomes. (A) Compound odontome with multiple denticles causing displacement of the maxillary right central incisor. (B) Macroscopic specimen of a compound odontome from the anterior maxilla showing the numerous denticles surrounded by a well-defined capsule. (C) Complex odontome following elevation of a labial flap.
Odontogenic tumours (see Chapter 10)
The ameloblastic fibroma, fibrodentinoma and fibro-odontome are uncommon benign odontogenic mixed tumours. All are seen as altered differentiation of the tooth bud: in an ameloblastic fibroma no hard tissue is formed, in an ameloblastic fibrodentinoma only dentine-like tissue is recognizable and in an ameloblastic fibro-odontome enamel is also formed. The lesions tend to be well demarcated.
Odontogenic keratocysts (see Chapter 10)
Odontogenic keratocysts may arise in place of a tooth of the normal series or from the dental lamina in addition to a normal complement of teeth. They constitute 5–15% of odontogenic cysts.
Regional odontodysplasia (Figure 11.14)
Regional odontodysplasia is a sporadic defect in tooth formation with segmental involvement, usually localized to one, or part of one quadrant, but it may cross the midline to affect the contralateral central incisor. All dental tissues are involved in a bizarre dysplasia with hypoplastic teeth which are slow to erupt and which typically radiographically show a ghost-like appearance. The aetiology of the condition is unclear.
Figure 11.14 (A) Regional odontodysplasia presenting with abscessed primary molars in the maxillary left quadrant, soon after eruption. (B) The panoramic radiograph shows involvement of all the teeth in this quadrant including the permanent teeth. (C) Grossly abnormal enamel in an affected tooth and (D) the hard-tissue section demonstrates the disruption of odontogenesis. (Courtesy Dr N Pai, Sydney, Australia.)
Figure 11.15 Morphological anomalies. (A) Mamelons, which are variations of normal anatomy. (B) Double tooth involving the right mandibular incisor, probably caused by fusion of the lateral and central incisor tooth germs.
• In spite of attempts to restore teeth with stainless-steel crowns or composite resin, most affected teeth require extraction. Permanent successors of affected primary teeth are invariably affected, though sometimes to a lesser degree. There is no justification for bony excision at the time of tooth removal. There are reports of successful autologous tooth transplantation into the sites of removal of affected teeth.
Abnormalities of morphology
Macrodontia (Figure 11.16)
Figure 11.16 Macrodontia. (A) Isolated macrodontia in a mandibular second premolar tooth. (B) Generalized macrodontia associated with KBG syndrome. These children present with intellectual disabilities, broad facies, short stature and skeletal abnormalities.
• Unknown for a single tooth, but generalized macrodontia may be caused by a hormonal imbalance, as this has been described in pituitary gigantism. It should be remembered that an illusion of generalized macrodontia will occur if the jaws are small relative to the size of the teeth.
• Generalized macrodontia is also associated with KBG syndrome (the initials are taken from the surnames of the families first reported with the condition). These children present with short stature, intellectual disability, skeletal abnormalities, syndactyly, a broad face with microcephaly and other facial anomalies (Figure 11.16B).
Megadontia, megalodontia and gigantism.