CHARLES DARWIN FIRST DOCUMENTED the incidence of missing teeth:
“..in a Hindu family in Scinde...ten men, in the course of four generations, were furnished, in both jaws with only four small and weak incisor teeth and eight posterior molars.”
Tooth Agenesis May Be More Common Than You Think
The incidence of tooth agenesis “lack of development” of teeth ranges from 1.6% to 9.6% in the general population excluding third molars. The term “congenitally” missing teeth, commonly used in dentistry, is a misnomer since permanent teeth are not normally present in the mouth at birth.
Maxillary laterals incisors have been noted to be the most frequently missing teeth when only one or two teeth are absent. The Dariusleut Hutterites of western Canada have the highest incidence of maxillary lateral tooth agenesis found in 47% of this population.
Tooth Agenesis Can Increase Through Generations
Tooth agenesis is a familial trait. Hypodontia, small number and size of teeth, is determined by a dominant autosomal gene pattern with incomplete penetrance and variable expressivity. Children inherit tooth agenesis from less severely affected parents. Tooth agenesis increases in number and magnitude after the mating of affected subjects.
Hypodontia May Be Linked To Ectodermal Dysplasia
Several authors have suggested that hypodontia is “micro” form of ectodermal dysplasia. Besides aberrations in the permanent dentition, these patients also exhibit delayed tooth eruption, hair and nail dysgenesis, dry skin, bilateral congenital hip dislocation and an asthmatic condition.
Several genes have been found to be required for the development or teeth. In the most specific human molecular study Vastaridis, H. (1996) found that a point mutation of a G to C transversion in the MSX1 gene at nucleotide residue 2125 produces tooth agenesis.
The G to C transversion results in the substitution of a positively-charged arginine to a neutral proline at residue 31 of the MSX1 homeodomain. Arg31 is within helix II of the homeodomain located close to the backbone of the alpha strand of DNA, and is thought to specifically interact with DNA via a salt bridge to the G-5 phosphate group. Perhaps the ARG31Pro mutation similarly attenuates MSX1 interaction with target DNA.
Orthodontists Can Recognize And Treat This Condition
Orthodontist Ann Marie Gorczyca, DMD, MPH, MS spent four years in the UCSF Oral Biology PhD program. She is a member of the Angle Society of Orthodontists where she presented the paper: “Tooth Agenesis: A Molecular Genetic Model.”
Orthodontists should be encouraged to extensively inquire about the family history of individuals with dental anomalies. Orthodontists could play a crucial role in the diagnosis of underreported entities of ectodermal dysplasia by bringing attention to its oral manifestations. Patients with numerous missing teeth should be referred to an orthodontist and a dermatologist.