If your son grinds his teeth to the level of destruction, this activity is related to an excessive, spastic and potentially harmful activity of chewing muscles and braces are not going to stop / prevent this process. But from the information you provided, if only canines are showing a signs of wear, most likely it is not related to muscle’s parafunction - grinding - but rather traumatic teeth position. Your dentist suggested braces to move your son’s teeth into more favorable position and away from heavy contacts.