I looked at the evidence regarding electric/powered toothbrushes vs. manual. Generally, for medical topics, the highest quality meta-analyses come from the Cochrane Collaboration. They have a fairly recent review from June 2014 (open access). http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD002281.pub3/full
Powered versus manual toothbrushing
Powered versus manual toothbrushing
Powered versus manual toothbrushing
I looked at the evidence regarding electric/powered toothbrushes vs. manual. Generally, for medical topics, the highest quality meta-analyses come from the Cochrane Collaboration. They have a fairly recent review from June 2014 (open access). http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD002281.pub3/full