What is an undercut in tooth?

Undercut: Is a term used in dentistry in removeable and fixed prosthodontics - crowns bridges and dentures. Undercuts prevent proper fabrication of these devices and hence need to be eliminated in the design. Hope this helps.

Concavity: Outer surface of enamel has areas that stick out and others that are recessed, undercut. Dentists often utilize undercuts to provide retention for clasps on partial dentures.