Should you cover the hole on the brush head of an electric toothbrush? (read description)?

I've had HEAPS of electric toothbrushes, i just bought a new one today, an oral b one, it was more expensive than the previous ones i've owned so i really don't want it to break. On the head, under the bristle bit, theres like a hole.. kinda .. is that suposed to be covered? my mum puts like.. medicalishh tape .. around it so water won't get in because she thinks it'll leak into the battery or something and break it. Should it be covered?? Why is the hole there?? Is that the reason my other ones stopped working?