Given these circumstances, we evaluated the difference in postextraction bleeding incidences in otherwise healthy controls

without WF administration (non-WF group) and in patients under reasonable coagulation control inhibitor order us with WF (WF group). We selected the participants for the latter group whose PT-INR was 3.0 or lower at the time of the procedure, as the PT-INR of 3.0 was indicated as the maximum safety threshold for tooth extraction in the Guidelines for Patients on Antithrombotic Therapy Requiring Dental Extraction in Japanese.16 We also investigated the risk factors for the incidence of postextraction bleeding in patients receiving WF therapy. Materials and methods This was a prospective multicentre observational study of postextraction bleeding events in patients receiving and not receiving WF therapy. Study period and eligibility criteria Twenty-six hospitals located across

Japan participated. This study included patients who underwent simple tooth extraction from 1 November 2008 to 31 March 2010 at the department of oral surgery of these hospitals and who met the eligibility criteria listed below. Simple tooth extraction referred to a tooth removed without traumatising the surrounding alveolar bone or elevating a mucoperiosteal flap. Eligibility criteria included the following: 20 or more years of age at the time of tooth extraction; no contraindications for tooth extraction; surgery was performed by oral surgeon with a minimum of 3 years of experience in dental practice; the oral extraction procedure lasted for no longer than 15 min; and platelet count

within 7 days prior Drug_discovery to the procedure was normal. In addition, in patients receiving WF therapy, PT-INR measured within 7 days prior to the procedure should be less than 3.0. Patients receiving antiplatelet medication were not excluded but recorded as such. According to “The Guidelines for Patients on Antithrombotic Therapy Requiring Dental Extraction”,14 we instructed the participating hospitals that dental extraction should be performed without discontinuing or reducing the dose of WF in patients whose PT-INR was not exceeding 3.0 when measured within 7 days prior to the procedure.