Mouthguards are very important for your child. They protect teeth from injuries that may require implants, bridges or crowns in the future. Mouthguards also prevent concussions. Trauma to the chin can cause the jaw to be driven up into the skull and cause a concussion. The mouthguard can absorb part of this trauma and protect the brain.
As to the type of mouthguard, a store bought or a custom one can work effectively. Custom mouthguards are usually more comfortable and allow easier breathing and speaking, so a child may be more apt to wear it.
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.