There is strong evidence to show that not only do they prevent dental injuries, but also reduce the incidence of jaw fractures and concussion. They can be made small enough to be quite unobtrusive and snug fitting. I'm not sure to what extent the club recommends that players wear them, but many schools will not allow kids to play football or hockey without them. I'm assuming the club covers players for the costs associated with injuries, either directly or via insurance. It would be in everyone's best interests to enforce a mouth guard policy, and as an incentive have the players responsible for the costs of dental injuries if they choose not to.