DISTORTED IMPRESSION - This is usually easy to identify through the observation of unusual contours or pulled areas and bur marks that fade away on certain areas of the die.
SOLUTION - Control moisture, There’s some great products on the market to dry the mouth. Moisture is the number one cause of distorted impressions in our lab
CHIPPED DIE – If a tooth is prepped in a manner that leaves many jagged edges and peaks, they often don’t pull well from the impression, break off and are not always noticed by the technician and inevitably in the end will result in an internal interference in the crown that can be very difficult for the dentist to locate.
SOLUTION – Always smooth the preps, the patient won’t think a little extra prep time is unusual, but if you grind on a crown for a half an hour they will definitely be thinking they are paying a lot of money for a crown that doesn’t fit.
CROWN DOESN'T SEAT - During crown fabrication abrasion of adjacent contacts is normal and the result is a crown that is too large to seat.
SOLUTION - Fit crown to uncut model to fine tune contacts.
TEMPORARY PLACED WITH LITE CONTACTS - The temporary is a space maintainer and is very important to the fit of the final crown. Too light a contact means final crown will always have heavy contacts. Too heavy contacts and the crown will have light contacts or not at all.
SOLUTION - close attention to the fit of the temporary will improve the fit of the final restoration.
SOLUTION - Better attention to occlusal contacts during crown fabrication. Better attention to articulation particularly subtle occlusal anomalies that prevent maximum occlusal contact.
TEMPORARY OCCLUSION INACCURATE - No occlusal contact on the temporary will cause crown to drift ensuring the final restoration will have heavy occlusal contacts.
SOLUTION - ensure occlusal contacts when fabricating temporary
INACCURATE MODEL ARTICULATION:
SOLUTION - Better educate model technician to identify occlusal landmarks for better accuracy during articulation.
Take impression that captures more teeth to help technician articulate more accurately and be able to identify occlusal interferences during Protrusive and lateral movements.