Case• 5. A missing incisor
A 9-year-old boy is referred to you in the orthodontic department with an unerupted upper left central incisor. What is the cause and how may it be treated?
The patient’s upper left central incisor has not erupted although he is 9 years old. The mother is very concerned about her son’s appearance and is anxious for him to be treated.
History of complaint
The upper left deciduous predecessor had been present until about 4 months ago. It was extracted by the patient’s general dental practitioner in an attempt to speed up the eruption of the permanent successor. Despite this, there has been no change in appearance. The upper permanent central incisor on the opposite side erupted normally at 7 years of age.
The patient has suffered from asthma since he was 4 years old. This is controlled using salbutamol (Ventolin).
There are no extraoral signs or symptoms and the patient is an active, happy boy.
▪ The appearance of the mouth is shown inFigure 5.1. What do you see?
The patient is in the early mixed dentition stage and the teeth present are:
No upper left central incisor is present, but there is a pale swelling high in the upper labial sulcus above the edentulous space and the upper left B. There has been some loss of space in the region of the absent upper central incisor.
There is a tendency to an anterior open bite which is slightly more pronounced on the right.
There is mild upper and lower arch crowding and a unilateral crossbite on the left. If you were able to examine the patient you would discover that this is associated with a lateral displacement of the mandibular position. The lower centre line is shifted to the left.
There are no restorations but the mouth is not very clean.
▪ What are the possible causes of an apparently absent upper central incisor?
The incisor may be missing or have failed to erupt. Possible causes include the following:
|Failure to erupt||
Dilaceration and/or displacement as a result of trauma
Scar tissue preventing eruption
Supernumerary tooth preventing eruption
Insufficient space as a result of crowding
Pathological lesion (e.g. cyst or odontogenic tumour)
▪ What specific questions would you ask the parents?
The most important questions are related to trauma. Avulsion or dilaceration would follow significant trauma which is likely to be recalled by the parent. The parent should be asked whether the deciduous predecessor was discoloured. If it was this would provide evidence of loss of vitality, perhaps related to trauma.
Extraction would be unusual and a cause should be readily obtained in the history.
In response to your questioning the parent reports that the patient fell on his face when he was much younger. At the time of the accident there was considerable injury to his lips and teeth, but no tooth loss was noticed and no dental opinion was sought.
▪ What are the likely causes of the anterior open bite and shift in the lower centre line?
The anterior open bite is probably associated with a thumb- sucking or similar habit. The shift in the centre line is probably caused by the combination of crowding and early exfoliation of the lower left C.
▪ Give a differential diagnosis for the cause of the missing incisor. Explain each possibility.
Dilaceration of the central incisor as a result of the injury appears the most likely cause. However, it is unclear whether the injury was severe enough to cause dilaceration. Dilaceration usually follows intrusion and the intruded tooth might well have re-erupted into its normal position. The swelling in the sulcus does not lie on the normal eruption path of the central incisor, and dilaceration could explain the abnormal position.