I buy those cheap battery powered toothbrushes, and they are great, make my teeth nice and clean, but they have a serious design flaw. Namely, once the batteries die, it’s really tough to get them back together after changing the batteries.
It’s a simple problem really. The o-ring which acts as a gasket, keeping water away from the batteries, gets caught on the lip of the handle when you go to put it back together. What I do is clean it real good, spray a little PAM cooking spray on my finger and coat the gasket. Makes it go right back together.
Happy brushing!
Lubricating o-rings is always a good idea. Two examples that come to mind are paintball guns and the inline water filter at home.