ill fitting crowns

What are the top reasons of poor fitting dental restorations (fixed restorations).  What causes warpage, rocking, short margins, etc.  Looking to troubleshoot laboratory technique.   Thank you

[scottma]

I rarely receive ill fitting fixed restorations from my technician. However, occasional restorations need to be redone are caused by minutue distortion of impression, which can not be detected clinically. I authorize my technician to reject my impression if the impression is not perfect.However, this is not a common practice in taiwan. I am fully aware of your frustration when dealing with imperfect impression. Technician's responsibility is to fabricate restorations well fitted in the cast. If problems arise in the patient's mouth, most time it's dentist's responsibility. Impression material does play important role in the final outcome of restoration. I have used polyether for fixed restoration for decades. My technician told me that polyether does yield a better fitness than polyvinyl siloxane. Certainly, lab procedures performed by technician are vitaaly important. I wonder if you can request your custmer to retake impression if working cast is not workable. Good luck