Back Tooth, An XRay Has Shown A Capped Tooth Has Been Leaking.Would It Be Prudent To Leave It?

Back toothAn XRay has shown a capped tooth has been leaking and that it is decayed underneathGiving no trouble Male 76 no health problems. Regularly attend dentists under a twice yearly program. Now using a 1st year new dentist. (Our surgery takes newly qualified dentists for their first year supervision experience , after they have qualified at university.) She is very professional -already discovered three fillings all successflly treated - which have appeared over the last six months , since the last new dentist completed her final 12 months and moved on. XRayed my mouth, and discovered an old capped tooth had been leaking. No outward problems or pain. The pictures of the stump underneath the tooth were showing signs of decay. It is proposed that the tooth be drilled into and the suspect decay treated. Or cap removed ? I do hope the suspect decay is actually that, rather than something else giving that kind of image . e.g cement/filling etc. As the treatment is NHS funded, cost is not a problem to me. Just deep concerns!! Is the proposed treatment best? Or, would it be prudent to leave it? One assumes, if the treatment goes wrong, then the stump will have to be removed, possibly also a big, difficult extraction also. Your thoughts doctors would be appreciated -Fast !! The work starts at 11.00 AM GMT Today. Worried patient. Stan