Assertion: electric toothbrush's head | /r/HasProperty | replaced
Facets:
Source sentences:
text: The head on mechanical toothbrushes should be replaced every three months or so, before the bristles become worn and frayed.
text: Along with the initial cost of the unit and its charging base, the heads should be replaced just as frequently as a manual toothbrush should be, and these can be pricey depending on the toothbrush model type.