Welcome to The BRIDGE, the social and information hub of the dental lab industry. Connect with industry peers and vendors, ask questions, sign up for events, review products, read LMT articles and industry news and more!
The most common cause of that for me would be weak or improperly positioned connectors. The zirconia likes to be uniform and shrink as a whole. Thin areas tend to shrink faster (for obvious reasons). Connectors that are too far lingual or facial also seem to "bend" the frame slightly due to the thicker, less evenly distributed portions on either side.