According to Stopbullying.gov, an initiative by the United States Department of Health and Human Services, between one in three and one in four American children have experienced some sort of bullying, and over 70 percent have witnessed it among their peers. Bullying can often cause children to become quiet and withdrawn, isolating themselves from their parents and peers. So, how do you know as parents if your child is being bullied – especially if they won’t tell you? According to a new study in the Journal of Oral Rehabilitation, you might want to ask their dentist.  The study, conducted by the Department of Pediatric Dentistry and Orthodontics at Universidade Federal de Minas Gerias in Belo Horizonte, Brazil, revealed that teenagers who experienced verbally abusive bullying at school were four times more likely to experience bruxism, or teeth grinding, than those who were not bullied. According to the study, bullied students were found to grind their teeth at a rate of about 65 percent, compared to about 17 percent for students who are not bullied.