Just googled and found this on Baby Centre
"Is it a good idea to use an electric toothbrush on my toddler's teeth?
Jane Shaw answers:
Yes - electric toothbrushes are more effective at removing plaque and most toddlers find them fun to use. My three-year-old son has been using one to clean his teeth for the last six months and I find that he does a much better job with it. I still check his teeth afterwards with a manual toothbrush but there is less for me to do. This boosts his morale and makes him feel he has done a good job.
Your toddler will be more likely to take to an electric toothbrush if he sees you using one and he will probably ask you if he can have a go. Look for a quality brand with a timer and a small oscillating head. A rechargeable brush is much better than a battery operated one (battery ones slow down as the battery runs down and won't clean so well). It really is worth investing in these features if you decide to get an electric brush. As the heads are easy to change, it is possible to have one handle, with a separate head for each family member, to make the outlay more cost-effective.
If your toddler is reluctant to use an electric brush then just carry on with his favourite toothbrush until he feels ready to try again. Brushing his teeth well is more important than the type of toothbrush he uses."
Jane Shaw, BDS. Area of expertise: Dentist. Dr Jane Shaw qualified as a dentist in 1995 from Guy's Dental School (University of London). She currently works part-time in a family practice in Tenterden, Kent, with her husband and one other dentist. She has two children, George and Eleanor.
Dental expert on this site suggests yes too