Eighteenth century parish registers are replete with the names of infants who had died as a result of teething. Nevertheless the idea that teething, the normal eruption of infants’ teeth, can cause systemic symptoms or serious illness is of course a myth. The time of teething coincides with a period of naturally low resistance to infection and declining maternal passive immunity so that infection during the period of teething is merely coincidental.
As might be expected, several studies have shown that teething does not cause systemic disorders. Nevertheless, so resistant is this traditional belief to rational explanation, that yet another study was carried out in 2000, confirming yet again that teething was harmless.
However, an ingenious neuropathologist has suggested that the minute wounds left by the shedding of deciduous teeth could provide a means of entry for the BSE (‘mad cow disease’) prion to cause variant CJD. In view of an incubation period of many years, this suggestion is consistent with the onset of the disease in adolescence. However, this theory is as yet unproven. Eruption of deciduous teeth starts at about 6 months, usually with the appearance of the lower incisors, and is complete by about 2 years. Mass failure of eruption is very rare. More often eruption of a single tooth is prevented by local obstruction. In the permanent dentition, delay in eruption of a tooth or, more frequently, too early loss of a deciduous predecessor tends to cause irregularities because movement of adjacent teeth closes the available space.
Delayed eruption associated with skeletal disorders
Metabolic diseases particularly cretinism and rickets are now uncommon causes of delayed eruption of teeth. Cleidocranial dysplasia, in which there are typically many additional teeth but failure of most of them to erupt, has been mentioned earlier.
In severe hereditary gingivalfibromatosis, eruption may apparently fail merely because the teeth are buried in the excessive fibrous gingival tissue and only their tips show in the mouth (pseudoanodontia). In cherubism several teeth may be displaced by the proliferating connective tissue masses containing giant cells and are prevented from erupting.
Local factors affecting eruption of deciduous teeth
Having no predecessors, deciduous teeth usually erupt unobstructed. Occasionally an eruption cyst may overlie a tooth but is unlikely to block eruption.
Local factors affecting eruption of permanent teeth
A permanent tooth may be prevented from erupting or misplaced by various causes.
Local causes of failure of eruption of permanent teeth
• Loss of space
• Abnormal position of the crypt
• Overcrowding
• Supernumerary and supplemental teeth
• Displacement in a dentigerous cyst
• Rentention of a deciduous predecessor
Treatment depends on the circumstances, but room may be made for the unerupted tooth by orthodontic means or extractions. A retained deciduous tooth should be extracted if radiographs show a normal permanent successor. If a buried tooth partially erupts and becomes infected, it may have to be removed- mandibular third molars are the main source of this complication.
Changes affecting buried teeth
Teeth may occasionally remain buried in the jaws for many years without complications. The roots of these teeth may undergo varying degrees of hypercementosis or resorption. Alternatively the teeth may become enveloped in dentigerous cysts, as in cleidocranial dysplasia for example.
