A bicuspid aortic valve may cause the heart's aortic valve to narrow (aortic stenosis). This includes bicuspid aortic valve and coarctation (narrowing) of the aorta. Blood is prevented from flowing backwards (regurgitation) by the tricuspid, bicuspid, aortic, and pulmonary valves. A deficiency can be associated with bicuspid aortic valve. In many cases, a bicuspid aortic valve will cause no problems. A bicuspid aortic valve affects about one to two percent of the population. Bicuspid aortic valve abnormality is seen in 1 to 2 percent of all live births. The crown, which has two cusps (bicuspid), is attached to a pedicel by collagenous fibers. Premolars are bicuspid while molars are multi-cuspid. First, incisions are made from the first bicuspid to the first bicuspid, exposing the mandible. Additionally, amphibians that undergo a metamorphosis develop bicuspid shaped teeth. The central tooth is small and bicuspid. The creation of a bicuspid valve is currently the most reproducible. However, bicuspid valves are more likely to deteriorate and later fail.