Dental plans generally fall into a couple of key categories if purchased on your own or through your company-sponsored program, so how does choosing a PPO, HMO, or Indemnity differ? PPO plans usually have larger numbers of providers available in the network. They work in and out of the plan network of doctors. They tend to be the most expensive and have annual limits on how much they cover in a given year. UCR and MAC define how the plan works when you use an out of network