If piggy eating normally, and incisors look fine, then unlikely to be an issue with back teeth. If piggy eating awkwardly, struggling to eat or not eating and incisors look good/slanted/uneven/broken/misaligned, then a proper examination of the back teeth needs to be done by a vet. We have had some with perfect looking incisors, but dreadful back teeth. Also they can have incisors that are dreadful, but back teeth fine. Basically a quick check of the incisors weekly, together with weekly weighing of your piggy is the best way to pick up on any problem, dental or otherwise!