5.2 Delayed Eruption

Eruption of each primary and permanent tooth is based on an exact and predetermined genetic plan. Delayed or disrupted occlusion can lead to future malocclusion. Long delays in eruption can lead to failure of eruption into the mouth, the so‐called impaction (Figure 5.2).

5.3 Early Eruption

Teeth appear in the oral cavity much earlier than normally expected. In the primary dentition, natal or neonatal teeth are not uncommon. In the permanent dentition, local causes such as premature loss of the primary predecessor tooth or localized hemangiomata may lead to early eruption. Systemic causes include hormonal disturbances with excess growth hormone or thyroid hormones. In early eruption, the root structure may be immature, thus endangering tooth survival (Figure 5.3).

5.4 Failed Exfoliation (Primary Dentition)

There are several reasons why the normal exfoliation of a primary tooth is disrupted. Ankylosis (replacement resorption) is one of the most common causes. Normal root resorption does not occur, and there is fusion of surrounding bone to the tooth root, with no discernible periodontal ligament. Ankylosed teeth are progressively infraoccluded and interfere with the normal eruption of the permanent successor (Figure 5.4).

5.5 Early Exfoliation/Loss of Primary Teeth

5.5.2 Systemic Factors

1. Familial fibrous dysplasia (Cherubism): This is a rare disturbance in which teeth are lost sooner than expected, with no known and clear etiology. There have been reports of unilateral/bilateral enlargements of commonly posterior segments of the jaws, with multilocular cysts visible on radiographs.
2. Acrodynia: Long‐term exposure to mercury leading to pink disease in children, presenting with fever, anorexia, and exfoliating skin of palms and feet. Oral inflammation and mucosal lesions are the two main intraoral findings, along with increased salivary rate, abnormal cementum thickness, alveolar bone resorption, and inevitable consequent tooth loss.
3. Hypophosphatasia: Early loss of primary anterior teeth and alveolar bone are reported in such cases, owing to defective cementum, without any changes in gingival appearance. This condition is associated with lowered alkaline phosphatase, a condition widely known as hypophosphatasia (Figure 5.5).
4. Pseudohypophosphatasia: This is a hereditary disease with signs of hypophosphatasia and cementum defects without any change in the serum alkaline phosphatase level.
5. Anomalous dental structures: There are cases in which the crown or root structure are defective, causing delayed eruption to early loss of teeth. These include Dilaceration, Amelogenesis Imperfecta, dentine dysplasia, odontodysplasia and Ehlers Danlos Syndrome (Figures 5.6–5.9).
6. Systemic diseases: There are certain systemic conditions where the teeth are easily exfoliated early: cyclic neutropenia associated with bone loss; acatalasia; increased growth hormone; juvenile diabetes; progeria; histiocytosis X; and leukemia (Figure 5.10).

5.6 Failed Eruption and Impaction

Wrong positioning of the tooth bud may result in failure of eruption into the oral cavity. This failure of eruption is called impaction, which could be due to several factors, including: the presence of a supernumerary tooth (Figure 5.11b); an ankylosed primary tooth (Figure 5.4a); sequel of trauma to primary teeth (Figure 5.4a and b); amelogenesis imperfecta (Figure 5.12b); fibrous tissue formation (Figure 5.12a); odontomas (Figure 5.13b); or cysts (Figure 5.14