As mentioned above, alerting callers that they won’t be getting an immediate call back is of upmost importance for an entity’s reputation and a caller’s satisfaction.
A dentist is similar to a doctor. Unlike a doctor, a dentist is going to get far more non-urgent calls as patients will want to know when they can pick up various orders, as well as to book follow-up appointments. The key here is prioritizing so the dentist can respond promptly to the patients who need emergency dental work and other urgent consultations.

Your voicemail needs to have relevant information such as your name, who the prospects are connecting to, the department you work in, why your not available to assist your prospects, when you will call them and related information, this is what the prospects would prefer hearing instead of dragging the voicemail messages speaking about your brand and more.
From the Skype for Business desktop app (if you are running Click-2-Run build C2R 8201.1002 or later), select Set Up Voice Mail. Change your Call Answering Rules You can change what options your callers have when they reach the voicemail service; get disconnected, hear your greeting, record a message, choose to be transferred to the number or user you select. Change your prompt language This is the prompt language that is played to callers. For list of supported languages, see Languages for voicemail greetings and messages from Skype for Business. Configure your Out of Office greeting This is the customized greeting message that is played to callers when your status is Out of Office. This option can be activated "Always," when you have an active "Auto Reply" in Outlook, or whenever you have an out-of-office calendar appointment.  Where you can get your voicemail messages from