The GI, or digestive, tract extends from mouth to anus (see the image below). The division of the GI tract into upper and lower is a matter of some confusion and debate.
Dental PPO insurance plans, also known as dental preferred provider organizations or DPPOs, are a popular dental insurance option due to their flexibility in allowing insured members to choose dentists and dental specialists.
DHMO plans: Dental HMO's are the third type of plan, and these plans are the most popular among insurance companies offering individual coverage, as the insurance company is not assuming any risk. There is really no concept of insurance at work here.