Even though these amalgams are conservative, multiple enamel cracks are evident. Signs of stress are everywhere. This tooth needs cuspal coverage before it becomes necrotic, fractures a cusp, or develops a fractured root.
When you find a tooth that has cracks on the mesial and distal marginal ridge, the tooth is under extreme forces. If left untreated, the buccal and lingual sides of this tooth will continue to flex and the cracks will eventually meet in the middle and the tooth will become non-restorable.
I'm no practice management guru, but I know if you identify the cracked teeth already in your practice, do proper endodontic evaluation, and protect your patient's teeth with cuspal coverage, you will be doing them a great service and building your practice at the same time. If your patients question the need for cuspal coverage of cracked teeth, send them over for a consultation with your endodontist. We see teeth everyday that could have been saved if they had only been crowned earlier.
This last image is what I call the "Past, Present & Future Cracked Tooth". Past (#3-extracted), Present (#4-buccal cusp fracture), Future (#5-MMR crack waiting for buccal cusp to fracture). Proper diagnosis & treatment will save your patients time and money.