The Genetic Influence of Facial Structure and Tooth Development

I just returned from the College of Diplomates of the American Board of Orthodontics annual summer meeting. I attended four days of speakers presenting research related to how genetics influences the treatment of our orthodontic patients.  Topics included the genetic influence on temporomandibular disorder (TMD), obstructive sleep apnea (OSA), missing and malformed teeth, external apical root resorption (roots of teeth becoming shorter during braces), and the latest research on a possible connection between missing upper lateral incisor teeth and an increased risk of ovarian and colorectal cancer. I will write a separate blog about several of these topics individually, but below are some interesting points about genetics.

• The human genome contains 3.2 billion (!!) base pairs, or chemical nucleotides.
• There are approximately 25,000-30,000 human genes, which are the smallest units of “instructions”.
• 99.9% of the human genome sequence is the same!
• Genetic variation can often arises from what is called a SNP (“snip”), a single nucleotide polymorphism. One nucleotide change within a gene can result in no discernible change, or can result in a change in phenotype (an observable trait, characteristic, shape, etc…)
• Tooth development, or odontogenesis, involves over 300 genes.
• Sporadic changes, or snips, in the genome can cause dental agenisis (failure to develop, or missing teeth), or a change in the size or number of teeth.
• About 2-9% of the U.S. population has hypodontia, or teeth that are developmentally missing.
• Genes such as AXIN2 and PAX9 have been identified as genes that can contribute to a family history of teeth that are missing.

I will follow up with an article on the genetic influence on obstructive sleep apnea, and its ramifications on orthodontic treatment.

Dr, Dan Rejman is a Board Certified Orthodontic Specialist. He practices in Castle Rock, Colorado, and treats children and adults with braces, clear braces, and Invislaign.