Incidence of symptoms in previously symptom-free impacted lower third molars assessed in general dental practice

To determine the potential of a pathology-free impacted lower third molar to cause symptoms within a year and whether these symptoms can be linked to clinical characteristics, lifestyle or socio-demographic status.

One-year prospective cohort study of patients registered in general dental practice in Scotland with at least one asymptomatic impacted lower third molar.

All general dental practices with panoramic radiography facilities in Tayside, Fife and Greater Glasgow (Scotland, UK) were invited to participate in the study. Orthopantomographs taken between 1995 and 2002 were reviewed and eligible patients were contacted and invited to participate. Patients were assessed in their own dental surgery by the same research dentist. In this baseline assessment, the presence of impaction was confirmed and all patients with a previous history of symptoms and/or pathology were excluded from further analysis. Clinical characteristics such as the angulation and the degree of impaction were recorded. Patients also completed a socioeconomic questionnaire. Eligible patients were re-assessed by the same research dentist one year later when they were asked about their experience of symptoms within the past year. Information was cross-referenced with patients' dental records.

A total of 613 patients attended the baseline appointment. Of those, 30 (4.89%) had a history of symptoms and were excluded from the study, leaving 583 (95.10%) eligible patients. From those, 421 (69%) patients with a total of 676 lower third molars were examined one year later. 22.67% of all vertically impacted teeth examined had developed symptoms, along with 13.15% of all mesially impacted, 30.69% of all distally impacted and 6.45% of all horizontal third molars. This association was statistically significant (p < or =0.001). 23.05% of all partially erupted teeth and a surprising 10.49% of all unerupted teeth were associated with symptoms during the study period. This association was also significant (p < or =0.001). There was also a statistically significant inverse association between the development of symptoms and age (p = 0.0028).

The predictability that an impacted lower third molar will develop symptoms in future remains unclear. However, some clinical characteristics such as the angulation, the degree of impaction and the patient's age could be useful in predicting the likelihood of future symptomatology.