For new employees their first day on the job can seem like trying to board a moving train. If you just grab onto the train while trying to board you just might get your arm ripped off.
I don't recommend trying this but to board a moving train you run along side of it until you are moving at the same speed and then hopefully you can jump on.
Using this analogy for your new dental employee this means (other than the obvious such as showing them around and introducing them to the other staff) you need to bring them along on a gradient. See to it that your new hire is shown the ropes of their job either by another employee or an OM if you have one.
Take at least a week apprenticing them. Don't just thrown them into the water to see if they can swim or not. Apprentice them!
Ideally you have written materials such as a general policy manual of what is expected of them both as an employee as well as for their specific job. The new employee should be given some time each day to study these.
The key is to not overwhelm the employee with too much information. If you haven't already done so I recommend creating a checklist that covers all the above.