Panoramic radiographs of 1834 patients older than 21 years were evalua
ted for the prevalence of impacted teeth at different ages. The freque
ncy of impacted teeth by age was constant, that is, the presence of co
mpletely impacted teeth could not be related to age. The interrelation
ship between the angulation of impacted teeth and the existence of adj
acent teeth was studied in individuals older than 61 years. The angula
tion of most of the completely impacted teeth in the upper-third molar
region was horizontal when adjacent teeth were not present, whereas i
mpacted teeth in the upper-third molar region showed vertical angulati
on when adjacent teeth were present, suggesting that vertically impact
ed teeth may become exposed by bone resorption or infection and should
be removed. The angulation of impacted lower third molars was horizon
tal irrespective of the presence of adjacent teeth. It appears that th
e interrelationship between the angulation of completely impacted teet
h and the presence of adjacent teeth is different between the upper an
d lower third molar regions. The angulation of completely impacted tee
th and the presence of adjacent teeth should be included in those crit
eria which determine whether or not completely impacted teeth should b
e removed.