With how rapid technology is changing the field of dentistry these days, if your not taking CE courses within motnhs of finishing any d-school or residency, your behind the learning curve, and frankly if your just taking bare bones minimum CE credit hours to satisfy your state's license requirement, that's not nearly enough given the wide range of topics this profession deals with.
Myself personally, I try and take between 75 and 100 hours of CE a year, which basically works out to 1 full day course a month plus attending a couple of dental meetings (i.e. my state annual meeting, the ADA national meeting, or a large regional meeting such as The Yankee Dental Conference, or The Greater New York Dental Meeting)