<prompt> Endodontic therapy is contraindicated for a single-rooted tooth that has:DiscolorationAn acute apical abscessA vertical fracture of the root and an associated deep periodontal defectA horizontal fracture of the root and an associated deep periodontal defect  <response>: The vertical fracture of teeth has poorer prognosis, in addition to this presence of periodontal problem contraindicates root canal therapy. 