You have no recourse against the patients, who are innocent third party purchasers of the property. Also, there would be no criminal liability against the dentist--i.e. the property is not stolen to begin with--unless you can show that the dentist had no intention from the beginning of paying for the property; in that case, there might be criminal intent, but otherwise, if after the fact a dispute about the quality of the work, the amount owed, etc. caused the nonpayment, that is a civil, not a criminal matter.Your recourse is straightforward: when not paid for work you did or goods you delievered, sue; you have a right to be paid as per the agreement between you and the dentist (i.e. as per what he agreed to pay, even if only implicitly by commissioning the work), and you may sue to enforce it. For several hundred dollars, consider suing in small claims court, acting as your own attorney (unless your business is a corporation or LLC; laypersons cannot represent corporatons or LLCs); for larger amounts, let an attorney sue for you.