For anyone who really cares about dental hygeine or even just the way they look to other people, you can't not use an electric toothbrush anymore. I laughed at the idea at first, but once I began using one I will never be able to use a regular toothbrush again without feeling like my mouth isn't clean. When you go to the dentist--what type of toothbrush does he/she use on you? Electric--for a reason, because it cleans better.
The marginally higher cost of replacing the heads rather than buying an entirely new disposable toothbrush is insignificant when you actually feel as clean as you can when you use an electric brush. Personal dental care has evolved to the next step, and you don't want to be caught be the last person using a slide ruler because you were too frugal to purchase the more expensive but more effective calculator.
Your teeth (and anyone who comes in contact with them) will thank you.