recently i had a patient.with root stumps since 5 yrs. the patient complained of redddis swelling in the gum area near that decayed tooth. on biopsy we found that it was pyogenic grauloma. we did a surgery and removed the granuloma and removed the decayed tooth as well as the granuloma originated frm that .
if a carious tooth left in the oral cavity for long unattended, it may even lead to problems like tumour,abcess or cancer. so you should never leave a tooth unattended. either get a filling done or RCT or at least get it extracted although extraction dentistry is outdated.