(google search on "rose hips" + "tooth enamel"
Hmmm, okay, I knew the synthetic vitamin C would/could erode tooth enamel, and my immediate thought was that the 'whole herb' wouldn't/shouldn't be harmful.
It "looks" to me like all these warnings are for rose hips when mixed with other types of 'vitamin c', but I can't tell for sure without taking hours to search "in depth".
Of course, when an unnatural substance like "ascorbic acid Vitamin C" is known to be bad for something, then the whole world thinks & publishes that the whole herb/plant form is just as bad...which almost always is 100% cow patties.
Certainly (to me) chewing a handful once or twice shouldn't be of harm (especially with a good brushing afterward). That might give you and your doctor within a 'sense' of whether or not is was harmful.
'Wish I had more conclusive info to share. It's always best to err ont he side of caution :)