My boyfriend was wrestling and half of his front tooth is gone and he didn't get to the dentist in time. How can he fix it?

Depending on the scenario, a few options could work, including dental bonding or a porcelain crown. A consultation can help him explore the choices available.

It is important to have your boyfriend see a dentist ASAP. The tooth needs to be evaluated to make sure that the nerve hasn't been exposed. If it has been exposed a root canal needs to be done prior to putting on a final restoration. How the tooth will be restored is based on how much has broken off. A photo would be helpful to give you a precise answer but anything from bonding to a crown may be needed. The most important point is not to wait.

There are many ways to repair that tooth.  Your boyfriend should go to his dentist as soon as he can and have the tooth assessed.  Some options are Bonded resin filling repair ..., porcelain veneer, porcelain crown.  It's not too late, but don't wait for decay, or nerve pain, or infection, or for the tooth to break even more.Take care of it now ... the sooner the better.