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1.The description suggest the possible cause could be the cyst arising from the bone -
dentigerous cyst. And other possible cause for pain less lump are
salivary gland dilatation due to distal obstruction.
2.This if you are my patient i would have examined and ask for an
ultrasound to assess the nature of the lump, its source and extensions.
3.In case of dentigerous cyst an x-ray panoramic view will be helpful, it will detect the nature and extensions of the cyst.
4.Further CT might be needed for better demarcation of the lesion and cyst description.
5.Sugget forst to see your GP after that the GP with initial examination or investigation decide where to direct you. Good luck.
Hope i have answered your query,
any thing to ask do not hesitate to ask.
http://doctor.healthcaremagic.com/doctors/dr-ganesh/62888