A new patient who came to my office had lost an implant-supported crown on tooth #2 because the abutment screw had broken. The patient's history showed that crown #2 was seated in 2008, and 5 years later crown #3 was seated in 2013.
Upon X-ray review, the distal margin of crown #3 had opened slightly as a result of incomplete marginal seating. This indicates that there was heavy stress between crowns #2 and #3 when crown #3 was seated. Since implant-supported crowns do not migrate, the existing and continued stress between crowns #2 and #3 eventually caused the abutment screw to break and the crown to fall off.
Fig. 1 - Crown #2 has fallen off because the abutment screw was broken.
Incomplete marginal seating is an indication of excessive stress between crowns #2 and #3. The stress has continued because implants cannot migrate, which caused the abutment screw of #2 to break.
Fig. 2 - Alternate angle more clearly shows evidence of severe incomplete marginal seating.
Fig. 3 - A new crown #2 is seated with complete marginal seating.
Prior to cementation the proximal contact was adjusted using the Black Diamond Strip and then Interproximal Relief (IR) was confirmed using the Gray Final Polishing Strip after cementation.