Chewing bars

Hoover is my old male, he's about six maybe older and he lives alone (rescued alone and too old to neuter) anyway every morning at about 6.30am he begins chewing on the bars - and I wake up! lol I think the girls next door tease him abit or he is waiting for his food (7.30) but I'm worried about his teeth - can they hurt themselves doing it? He does it through out the day when the girls get abit close too so I've moved the big pile of hay he sits on to the otherside. He has plenty of toys/cozies, so I'm not sure how to stop it really...just wondered if it's really dangerious like with his teeth etc? I put a fleece between them last night and he didnt wake me up which is good but I obviously take it down during the day for the light and to he can socialise atleast abit.

Thanks