From Volume 42, Issue 10, December 2015 | Pages 945-950
Intracoronal resorption of the permanent dentition in cases of amelogenesis imperfecta (AI) is a rare finding which poses an added complication to the already complex management of this condition. This paper presents three cases of AI associated with delayed eruption of permanent teeth in which asymptomatic intracoronal resorption occurred.
Amelogenesis Imperfecta (AI) is a group of relatively rare inherited defects that affect the quantity and/or quality of enamel formation. The disorder is generalized, predominantly affecting all teeth in both primary and permanent dentitions. The prevalence of AI is known to vary by population, ranging from 1:700 to 1:14000.1 Its mode of inheritance can be autosomal dominant, autosomal recessive or X-linked. Sporadic cases, representing spontaneous mutation, may also present.2
AI arises as a result of genetic alteration associated with the process of formation and maturation of enamel.3 Alterations occurring at different levels of enamel formation and maturation result in clinically different presentations. To date, 14 different types of AI have been identified on the basis of genetic pattern, clinical and radiological features, and histological changes.4 In the classifications most commonly used by clinicians, the main types of AI are initially described phenotypically as hypoplastic or hypomineralized; hypomineralized AI can be further sub-classified into hypocalcified and hypomaturation types, with hypocalcified being a more severe type. A combination of hypoplasia and hypomineralization can also be observed in some patients with AI.
Despite the observation that AI results from disorders in the genes involved in enamel formation and maturation, a variety of non-enamel manifestations also occur in association with the disorder. Those reported in the literature include:
Resorption of the crowns of permanent teeth is an uncommon finding not widely reported in the dental literature. Here we report three cases of AI (summarized in Table 1) presenting to the Unit of Paediatric Dentistry at the Eastman Dental Hospital (UCLH Foundation Trust, London) in which intracoronal resorption associated with delayed eruption and gingival overgrowth presented as a feature of AI.
| Case 1 | Case 2 | Case 3 | |
|---|---|---|---|
| Phenotype | Hypoplastic | Hypoplastic | Hypocalcified |
| Mode of transmission | Autosomal dominant | Recessive trait? | Autosomal dominant |
| Medical history | Precocious puberty |
Nil relevant | ADHD |
| Number of teeth with intracoronal resorption | Two | One | One |
| Affected teeth | Maxillary |
Maxillary left |
Mandibular right |
| Stage of eruption | Unerupted |
Unerupted |
Unerupted |
| Associated symptoms | Asymptomatic | Asymptomatic | Asymptomatic |
| Extent of lesion | Pulpal involvement | Pulpal involvement | Pulpal involvement |
| Outcome | Extracted | Extracted | Endodontic treatment |
A 6-year-old female (CB) was referred for the management of AI. It was reported that her father had suffered from a similar dental condition and that all his teeth had been extracted at an early age. CB had two sisters, one of whom was affected by AI. This family history is illustrated in Figure 1. A comprehensive medical history revealed that CB suffered from myopia and thymic enlargement; she subsequently developed precocious puberty. No syndrome had been identified.
The crowns of CB's teeth were pitted but of normal colour. The enamel appeared thin, the cusps being pointed. The entire primary dentition was affected and, as they erupted, it became evident that the permanent teeth were similarly affected by AI. There was a notable delay in the eruption of the permanent teeth. At 10 years of age the occlusal surfaces of the maxillary first molars were mostly obscured by gingival tissue. A panoramic radiograph taken at this time shows delayed eruption of teeth, with no evidence of resorption of molars at this age (Figure 2).
CB was reviewed a year later. The maxillary first permanent molars were still not fully erupted (Figure 3) and a panoramic radiographic examination (Figure 4) suggested that the partially erupted maxillary first permanent molars were undergoing coronal resorption. Impaction of the unerupted maxillary right canine was also noted. In order to investigate the condition of the maxillary right first permanent molar further, the gingival tissue overlying this tooth was excised. The occlusal defect was found to be deep and the overlying fibrous gingival tissue continuous with the pulp. In view of this unusual finding, it was deemed that the maxillary first permanent molars were of poor prognosis. After a specialist orthodontic opinion, extraction of the maxillary first permanent molars, maxillary first premolars and mandibular left first permanent molar was advised, their loss being incorporated into a long-term orthodontic treatment plan. These teeth were extracted under general anaesthesia.
The impacted maxillary right canine was subsequently exposed surgically under local anaesthetic and a bracket bonded to facilitate its guidance into occlusion. The second permanent molars which, at 14 years of age showed delayed eruption, were also surgically exposed under local anaesthesia. At operation, these teeth exhibited severe occlusal hypoplasia and were initially dressed with glass-ionomer. Following healing of the surgical site, these surfaces were restored with nickel chrome onlays. CB has since been kept under regular review.
An 8-year-old male (AA) was referred by his general dental practitioner regarding excessive wear of his primary incisors. There was no previous family history of any similar condition and AA had two siblings whose teeth appeared normal. This family history is illustrated in Figure 1.
Clinical examination revealed AA to be in the mixed dentition with generalized marked wear of the primary teeth. The teeth were smooth and yellow in colour. In addition, the lower permanent central incisors appeared diminutive. The partially erupted maxillary left first permanent molar exhibited rough pitted enamel and a deep occlusal defect. The mandibular first permanent molars and maxillary right first permanent molar were unerupted and covered by fibrous gingival tissue. Radiographically, while all permanent teeth were present, there was evidence of delayed eruption. Intracoronal resorption of the partially erupted maxillary left first permanent molar was noted on a panoramic radiograph (Figure 5). Following consultation with a specialist in orthodontics, a decision was made to extract both maxillary first permanent molars. At operation, the mandibular first permanent molars and upper central incisors were surgically exposed. Stainless steel crowns were placed on the second primary molars to provide space anteriorly, thus enabling the provision of aesthetic composite restorations. AA will be kept under regular review to monitor the eruption of the second permanent molars.
A 14-year-old male (SS) was referred by his general dental practitioner regarding management of AI, his chief complaints being in relation to aesthetics and sensitivity. A comprehensive medical history revealed that SS suffered from mild attention deficit hyperactivity disorder (ADHD). There was a clear family history of AI, SS's brother, mother, uncle and maternal grandparent all being affected. This family history is illustrated in Figure 1.
Clinical examination revealed delayed eruption of the second permanent molars and the presence of an anterior open bite. SS's oral hygiene was noted to be poor. The gingival tissues overlying the partially erupted second permanent molars appeared hyperplastic. Panoramic radiographic examination showed no evidence of intracoronal resorption at this stage (Figure 6).
SS's initial treatment included the provision of oral hygiene and scaling and polishing. Aesthetics and function were improved by the placement of composite veneers on the maxillary anteriors and nickel-chrome onlays on the erupted first permanent molars. A decision was made to monitor the second permanent molars until full eruption, restoring them with occlusal onlays when feasible. On review one year later, the mandibular right second permanent molar had not fully erupted (Figure 7). A decision was made to expose its coronal surface by excising the overlying gingival tissue. As in case 1, an extensive area of intracoronal resorption was seen, the gingival tissue appearing continuous with the dental pulp. Following consultation with a specialist in endodontics, a decision was made to attempt to treat the tooth endodontically. This treatment is currently ongoing.
As stated previously, AI is a group of inherited defects of dental enamel formation that show both clinical and genetic heterogeneity. Genetic alteration at different levels of enamel formation and maturation result in clinically different presentations. In the reported cases, cases 1 and 2 exhibited a hypoplastic form of AI, while case 3 exhibited a hypocalcification variant.
Most of the reports of pre-eruptive resorption in the dental literature affect the permanent dentition. Usually a single tooth is affected;12 mandibular premolars and molars being the most frequently reported teeth.13 In all 3 cases reported here, intracoronal resorption was noted in permanent molar teeth before they had emerged into the oral cavity. Two cases exhibited resorption of a single tooth, but one had resorption of two teeth. Although aggressive in nature, intracoronal resorption tends to be asymptomatic, usually being identified only on radiographic examination. The presentation of all three cases conformed to this observation.
It has been recommended that surgical exposure of unerupted teeth be carried out as soon as resorption is detected radiographically in order to prevent progress of the lesion into the pulp.14,15 Although this recommendation was followed in the reported cases, the resorption was extensive and the pulp was already involved in two of them.
The pathogenesis of the lesions present in these three cases is unclear. The dental hard tissues of permanent teeth do not normally undergo resorption, though this may occur as a result of inflammatory conditions, mechanical stimulation or neoplastic processes. In the intracoronal resorption of unerupted teeth, the lesions are often located within the dentine-enamel junction, in the occlusal aspect of the crown. Indeed, they are often referred to as pre-eruptive caries.16 It has been suggested that the retentive nature of the cavitated lesion favours caries development, and the lesion becomes distinguishable as a carious lesion once it is exposed to the oral cavity.17 While nearly half of the lesions extend to more than two-thirds of the dentine width,14 it is not certain whether they remain stable or enlarge.
Local factors may play a role in the aetiology of this condition, the following having been implicated:
In a SEM study carried out on unerupted third molars by Owens and co-workers, ameloblasts rather than multinucleated cells were implicated in the idiopathic external resorptive process. It was suggested that resorptive activity of, and by, enamel epithelium may explain the coronal origin of the resorption and its progression into pulp.20
The intracoronal resorption in the reported cases could be due to defective mineralization of the teeth affected with AI, leading to exposed dentinal tubules. This may have led to inflammation of the pulp and, in turn, external resorption of the crown. Alternatively, these features could be attributed to premature degeneration of the reduced enamel epithelium which covers the crown of unerupted teeth.
Intracoronal resorption of permanent teeth is a rare but a significant finding in AI. Prompt intervention is necessary to limit the damage and restore the tooth. Elective endodontics should be started in suitable cases; alternatively, extraction may be considered, the affected teeth being incorporated into an orthodontic treatment plan. Both specialist orthodontic and endodontic input is of benefit in treatment planning. Further research is needed in relation to the aetiopathogenesis of this unusual condition.
