Is to glue/cement a crown back on a slightly decaying tooth a really bad move?

I had a Crown come loose (Front lower molar which had root canal treatment) I went to the dentist gave me various options. I just went for having the crown glued/cemented back on, however a bit of the tooth underneath had a bit of decay. Is this a particularly bad idea or will sealing it with glue and the crown stop the decay spreading?

Doctor Answers 1

Sealing decay won't stop process

Yes, it's a bad idea. The decay will continue and then WHEN the crown breaks off again, the tooth will not be restorable and will need to be removed. 

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