A few thoughts about having a spouse work in a dental practice:
a. It can be the worse of times for obvious reasons.
b. It can be the best of times as the spouse has a vested interest in the practice.
c. The spouse can never use the "spouse card" in interacting with the other staff.
d. Just as you would not interact at home with your spouse as if he or she is an "employee" you shouldn't interact with your spouse at work as you would at home.
In my opinion, the ideal situation is for the spouse to learn each position backwards and forwards so that he or she can be used as a trainer of the staff as well as fill in when an employee is absent or while there is an open position that you are getting filled. The spouse can then help hire and train them. In this situation you could also use a spouse to oversee finances, marketing, etc.