Application of a crown would require cutting into the gum

Three weeks ago, the inside part of my second bicuspid tooth broke off leaving just a bit of the tooth enamel proud of the gum on the inside. The outer side of the tooth is completely intact so the appearance has not been damaged. There was a rather large filling in the interior of the tooth which came out a week or so later. I have had no pain and it doesn't affect my chewing and doesn't catch food.

I had a cleaning this past week and the dentist has recommended a crown, but I am wondering if this is necessary if the application of a crown would require cutting into the gum in order for it to attach properly. I am 57 and have some recession of the gums (mostly 3-4 measurements) though borderline for periodontic care on the molars (6).
By leaving the tooth as is, would it hasten decay? My concern is additional irritation of the gum and unnecessary dental work.