Some people are fortunate enough to have access to employer-paid traditional dental insurance,  Usually the employee must pay into the plan but the employer pays something as well.  Dental insurance is available only through group plans and cannot be purchased by an individual.  Most insurance does not cover everything.  If anything is covered completely it will be basic services like exams, root canals, cleanings and some fillings.  Advanced treatments, like orthodontics, periodontics and crown and bridge treatment, may be payable at a lower rate (50 - 80%) if at all.
     With a traditional dental insurance plan, the patient goes to the dentist of his or her choice and services are covered according to the plan chosen by the employer to the extent charges are "reasonable" and "Customary."  Since the insurance  company decides the amount that is reasonable and customary,  the dentists fee may not be covered and the patient will owe the remainder.  Usually, a yearly deductible is not payable and there is a yearly limit.
     Some traditional plans are PPOs, or preferred provider organizations.  This means that dentists who "participate" in the plan can only charge the amount allowed by the plan and cannot charge you more.  If you go to a dentist outside the plan, that dentist will charge whatever insurance does not pay.  Why would anyone go to a non-participating dentist?  The answer is that you may not find a dentist on the list in your area that you want to see.  Dentists join and quit all the time. 
     In my opinion, many plans pay so little that dentists cannot spend adequate time to do their best work.  It may be better to go to a non-participating dentist with whom you are happy and pay the difference.  In my own case,  I once joined a plan that paid less for a cleaning that I paid my hygienist to do it.  The only way I could stay a participant would be to ask her to do a faster and less thorough job.  Maybe some dentists can keep up the quality and take a lower fee but I could not.

These are also provided to groups of employees.  A list of dentists is provided and if the patient goes outside the plan, the HMO pays nothing.  Dentists are paid a certain amount per patient each month as long as the patient is enrolled at that dentist's patient.  The dentist,  for this fee, is supposed to provide all basic services, exams, x-rays, cleanings, fillings.  The patient may be charged for more complicated work but only to the extent allowed.  My own opinion of these plans is that the dentist has very little incentive to do a through job and find all the problems that need to be addressed since the dentist is paid the same amount regardless of the work done. 

These are the plans that can be joined by individuals and families.  They are not provided by employers.  They are not really insurance plans and they work a different way:  The patient pays a yearly fee.  In return, the patient can visit participating dentists who bill according to a discounted fee schedule.  The dentist joins and takes a lower fee and, in return, the plan sends patients to him or her.
     Discount Dental Plans can be found on the Internet and they are sponsored by traditional insurance companies.  They work very well as long as you can find dentists in your area that you want to see who are participating.  Also,  the dentist should be supplying you with the same care that non-plan patients are getting.

A dentist owes all patients treatment that is up recognized standards.  Legally, the same standard of care is owed to a patient who pays full fee and one for which the dentist is reimbursed less that his/her regular fee.  Unfortunately, dentists do not always understand this concept.  If they have to cut corners, do work faster, take less x-rays, do a less thorough cleaning on plan patients in order to make ends meet, they should not stay members.   Also,  the plan patients should be treated with the same courtesy, recalled as frequently as regular patients and should not be giving only unpopular appointment times. 

Dental Insurance companies take a big percentage of funds off the top for administration.  What if the employer just paid each employee a certain tax free amount per year and let the employee choose his or her dentist.  This is the concept endorsed by the American Dental Association and it is called direct reimbursement. Employers need to consider this option more often when choosing dental plans.  Frequently, employers choose from medical plans and the same insurance providers also sell the dental plan.  The employer never even considers the easiest and most efficient plan.