This can be done fairly easily if you have the skill sets. This is not for those who are untrained and not for those who are IT novices.
Having said the above, this is what I have done for other dental offices that are my customers:
1. Make sure the dental office Internet connection has a static LAN IP address.
2. Make sure the dental office's network has a router that will host an IPSec Virtual Private Network (VPN). This requires a business class router, not a home grade router. Cisco, Adtran, 3Com business class routers can do this. Netgear, Linksys, D Link, Belkin, etc cannot.
3. You will need the same type of router at your home but you need not have a static public IP address - however it would be nice if you did.
4. You should have a network printer at home and at the office. The network printer has its own LAN IP address. This enables you to print from the office LAN to your home printer and from the home to the office printer. The server should be set up with your home printer as one of its printers. Your home pc should be set up with your office printer as one of its pcs. If there is no need to print as indicated, these printers are not needed. Usually they are.
5. Your home pc must have Remote Desktop on it (XP Pro or Vista Business). Your server must have Remote Desktop enabled on it.
6. You configure the two routers to enable a Virtual Private Network (VPN) link between the two locations. This enables you to access the office from home.
7. After VPN link is made, use Remote Desktop to access server, log in with your user name and you can run the server based programs and print off either at office printer or home printer, whichever is prudent for your needs.
8. Check with the phone companies serving your area in regards to call forwards. Some offer the forwarding that requires someone at the office to activate and deactivate call forwarding which may be cumbersome for you. Others offer a service that enables you to call forward enable or disable via a phone company web site which would be pretty helpful to you. You will likely need more than one phone line. If all calls come to you, you need to be able to route some calls back to the office (e.g. another doctor needs to talk to your doctor). This can be done but this is not a home grade phone.
This pretty much sums it up.
I recommend you hire someone to do this for you.
Note - I see some have recommended a web based remote access program. Be careful! These are not secure and can be compromised. This would be a breach of confidentiality and can get you into legal hot water. A VPN is secure and safe and acceptable. Cutting corners with a compromisible system is likely to come back to haunt you.