"Abnormalities of Teeth"
– 1 –
Charles Dunlap, DDS
There are many acquired and inherited developmental abnormalities that alter the size, shape and number of teeth. Individ-
ually, they are rare but collectively they form a body of knowledge with which all dentists should be familiar. The discus-
sion of each condition is short and to the point. Comprehensive reviews of each may be found in any reasonably new text-
book of oral pathology. For those conditions that are inherited (eg: ectodermal dysplasia, dentinogenesis imperfecta and
others) go to: www3.ncbi.nlm.nih.gov/ ,it will bookmark as OMIM (Online Mendelian Inheritance in Man).
Slide #1 is an example of an extra incisor. When located in the midline between the two permanent central incisors, they
are referred to as mesiodens. Slide #2 depicts an extra molar tooth (a paramolar) and Slide #3 is an example of a super-
numerary bicuspid tooth. These are the most common supernumerary teeth in the order shown.
Slide 1: mesiodens
Slide 2: fourth molar
Slide 3: supernumerary bicuspid
Hyperdontia and Cleidocranial dysplasia
Count the teeth in Slide #4 — there are more than 50. This patient has cleidocranial dysplasia (CCD). This is inherited
as an autosomal dominant trait, the gene maps to chromosome #6. The gene encodes a protein called Core Binding Fac-
tor Alpha 1 (CBFA1). This protein is essential for the formation of a normal skeleton but its role in tooth formation is
not yet known. The heterozygous state produces the CCD phenotype, the homozygous state is lethal. Main features of
the phenotype include hyperdontia, small or missing clavicles, delayed closure of the cranial fontanelles (soft spots) and
short stature. Slide #5 shows multiple supernumerary teeth removed from a patient with CCD. Gardner syndrome (intes-
tinal polyposis and skeletal osteomas) also features supernumerary teeth but not to the extent seen in CCD. ( J. Med.
Genetics 1999;36 p177-182 and Cell 89; 773-779 May 1997)
Slide #6 is a little tric