PPO insurance is a newer breed of insurance.  In order to cut costs, insurance companies lowered treatment fees.  PPO plans also have an added restriction on which doctor you can visit.  To be able to use your insurance, your doctor or dentist has to be signed up as a member of the PPO plan.  You're not free to simply visit any dentist or doctor you'd like.  However, most dentists DO accept PPO plans.

PPO insurance is similar to indemnity insurance in that they pay a portion of the balance, but at a reduced fee.  They also mandate that the doctor or dentist charge the patient a lower fee as well, the PPO contracted fee.  This saves the insurance company and patient money.

Of course this cost-saving plan comes with compromises.  Based on our observations, under a PPO plan, a patient may not receive the full benefits they would if under an indemnity plan.  In other words, not all treatment that might otherwise be covered with an indemnity plan would be covered by a PPO plan.  Furthermore, the patient-dentist relationship is not as free with a PPO plan as it is with an indemnity plan to develop an optimal treatment plan.  Thus, PPO plans are a cost-saving compromise to traditional, indemnity insurance plans.