Being sued by a customer for his broken tooth. Help!?

Few days ago, a man came into our restaurant claimed that after he ate our food yesterday one of his teeth broke. Now he had this lawyer send me a letter and wanted me to pay for his dental work and some money for the pain that he had suffered. He ordered his food to to and he didn't find anything in the food. We've been cooking the same way ever since we've opened 10 years ago, and nobody has ever complained that our food being too hard to chew and all the meats we serve are boneless. We actually have many senior customers. Does he have a case against us? If his has bad teeth already, and that tooth just happened to break when he was eating our food, are we still responsible for it?