A case is described of a 13-year-old boy who presented with infra-occluded primary molars in three quadrants. Creation of space allowed the second premolars in two quadrants to erupt spontaneously. The first premolar in the remaining quadrant did not erupt spontaneously, failing to reach occlusal contact despite orthodontic traction.
CPD/Clinical Relevance: This case demonstrates apparent intermittent ankylosis of a maxillary first premolar.
The majority of unerupted teeth that fail to erupt have a physical obstruction; either osteogenic, odontogenic, soft tissue, or there may be a history of trauma. Removal of the obstruction often leads to spontaneous eruption of the affected tooth.1 Other causes for failure of eruption include abnormal tooth germ position, bony deficiency, such as in cleft palate cases, ankylosis and genetic conditions. Genetic conditions that can impede tooth eruption are often associated with syndromes such as Cleido-Cranial Dysplasia (CCD) and Gorlin-Goltz syndrome. The physical mechanism of tooth eruption is unknown but the most popular theories are:
Vascular pressure theory;
Periodontal traction theory;
Root elongation theory;
Bony remodelling theory.
Ankylosis is defined as the fusion of bone and cementum due to a discontinuation of the periodontal ligament. It is more common in the deciduous than the permanent dentition and is most often seen in the buccal segments. The aetiology of tooth ankylosis is essentially unknown but appears to develop due to a disturbance of the periodontal ligament. These disruptions are thought to include endocrine and metabolic disorders, genetic tendency, periapical infections, trauma or previous dental procedures. Treatment of ankylosed teeth often involves extraction, restorative build-up or localized osteotomy.
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