If you know true exhaustion, you know how burdensome brushing your teeth can be.It’s not that it’s the most difficult part of the nighttime routine. (For me, that’s applying all the unctuous goos my eczema-prone flesh demands.) But brushing your teeth is tedious.It requires focus, plus repetitive wrist and arm movement. It requires self-awareness to track how long you’ve been at it, whether you’ve reached every tooth, whether you’ve reached every tooth sufficiently. It requires spitting into a sink.And you must do it at least twice a day, every day, until the day that you die.The Philips Sonicare 4100 will not free you from the shackles of corporeal conservation. But it will make this one element of that duty just a bit easier.