I am often asked when we design a website for our clients about the describe the services they provide. The best way for search engine optimization (SEO) is to have the doctor, or a copy writer right down some information about the procedure. About a paragraph or 2 for each procedure would be the minimum recommendation, but if the doctor has more information to give the better. Basically the search engines like Google are looking to see how much quality information is provided on your site. So if someone is looking for information on dental implants and you have written an in depth description of the procedure, you are more likely to be on the first few pages in Google or other search engines.
That being said, I know most of our clients have a hard time finding the time to come up with this content, so here at DentalPC I normally help the doctor by writing a short description and the doctor can later make any additions or deletions if necessary to save them time. It is nice to link to other dental sites that provide the patient with good information, but this generally doesn't do as much for your rankings as actually having the text on your site. So my suggestion is to write as much as you can and then link to outside website for more info if needed.