New sonic cleaner may beat standard tools for stubborn tooth infections

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Molars showing radiographic evidence of post-treatment apical periodontitis: a lesion that exceeds 3 mm in diameter on one or more roots. * Evidence from periapical and CBCT examination suggests that retreatment is a viable option, i.e., there are low risks of vertical root fracture, no major root canal obstruction, evidence of coronal leakage, and potential improvement on the previous treatment. * The initial root canal therapy was performed at least 2 years previously, or more than 1 year if the patient has signs and symptoms or symptomatic disease (pain, swelling, or sinus tracts). * Patients show no chronic systemic disease that may influence the outcome of care, such as uncontrolled diabetes, autoimmune disease, malignancy treated with chemotherapy or patients who are on immunosuppressive medications or require antibiotic prophylaxis before dental treatment. * Patients who are able to read and consent in English. Exclusion Criteria: * Patients with a tooth requiring RCT retreatment that also presents with periodontal pocket(s) deeper than 5mm * Patients with a tooth requiring RCT retreatment that also presents with severe crown destruction that would prevent proper rubber dam isolation or an adequate restoration * Patients with a tooth requiring RCT retreatment that also presents with evidence of vertical root fracture, or cracks with probing defects \> 5 mm * Patients with a tooth requiring RCT retreatment that is deemed unrestorable * Patients who received antibiotic therapy within the previous 3 months. * Patients under the age of 16 or those incapable of providing informed consent * Patients with a tooth requiring RCT retreatment that also presents with immature or open apices * Patients with a tooth requiring RCT retreatment that also presents with apices in the maxillary sinus or those teeth where the apical lesion has eroded the bone of the maxillary sinus floor * Patients with a tooth requiring RCT retreatment that also presents with apices that are less than 1 mm from the mandibular canal * Patients with a tooth requiring RCT retreatment that also presents with internal or external root resorption