Möller P, Berg K, Ruud A F, Kvien T K
Scand J Dent Res. 1981 Feb;89(1):16-8. doi: 10.1111/j.1600-0722.1981.tb01272.x.
Hypodontia was demonstrated in a mother and her monozygotic triplets. The triplets and their mother exhibited considerable variation in the expression of the trait. The variation within the triplets must be due to non-genetic factors.