No – you cannot trim the NeoMorph Mouthguard. NeoMorph is designed to cover to the first molar (and possibly the middle of the second molar) of an adult or person wearing orthodontic appliances. It is a trilaminate mouth guard which means that it has 3 layers. The NCore® layer (middle layer) needs to be completely encapsulated by the outer layer. If the guard is trimmed it may expose this layer which could effect performance. We offer an Authentic Dental Warranty which will become void if the guard is trimmed. Review our fitting instructions for more information on ways to improve the fit. Our Prodigy range is not recommended for children under 11 years old.