根管牙发炎

我一年前有一颗牙（二号牙）做了根管治疗。现在牙不疼但颈部靠那个牙的下面总是觉得不太对劲。 按上去有些疼。 如何知道根管下面有无发炎。 x-ray cannot detect detect anything wrong due to its crown. Since the tooth is dead, so I will not feel any pain, but I don't want to have any infection there. Without opennign the crown, is there a way to find if there is infection or not?