Coming in as the No. 1 bestselling electric toothbrush on Amazon is the Philips Sonicare ProtectiveClean 4100 ($65). Not only does this brush have a pressure sensor that gently pulses to alert you when you're brushing too hard, but it's also fitted with a two-minute timer for consistent cleaning and a brush-head replacement reminder. Even better, it's supposed to last 14 days before its next charge.