"Ace in the hole" is an old expression meaning that you have something in reserve just in case you need to get out of a challenging situation.
I saw a patient today who I treated 11 years ago when I virtually rebuilt her entire front tooth with resin bonding. Today she presented with the resin veneer in a plastic bag as it had come off of her tooth. These restorations are not meant for long term use and are generally used when a patient can't afford a crown.
I meticulously cleaned the resin veneer and the remaining natural tooth and carefully rebonded the restoration back onto the tooth and who knows, the patient may keep the restoration for a quarter of a century.
At the end of the appointment, my patient tells me that she has her routine dentistry done by her "REGULAR DENTIST." I always chuckle to myself when patients tell me that they only come to me when there they have a challenging dental problem. Some people keep me as their "Ace in the hole" instead of their regular dentist.
I AM a 'regular' dentist. lol