If the crown were broken due to a lack of care or ability on the part of the enthodonist, she may well be liable for your costs incurred as a result--such as the cost to replace. If the enthodonist will not pay your costs voluntarily, however, you'd have to sue her to recover the money. One option is to sue in small claims court, where your costs are significantly lower (e.g. you can be your own attorney and avoid legal fees).