Factors that influence the period required for the restoration of anticoagulant effect after tooth extraction in patients receiving oral warfarin therapy

We statistically analyzed factors that influence anticoagulant effect after tooth extraction in patients receiving oral warfarin therapy. The study group comprised 60 of 109 patients who were receiving warfarin and presented at our hospitalfor tooth extraction from August 1991 through December 2001. The Prothrombin International Normalized Ratio (PT INR) of these 60 patients was measured and followed up until 4 weeks after tooth extraction. Multiple linear regression based on AMOS was used for statistical analysis. The dependent variable was the period oftime required after tooth extraction for the PT INR (cardiologist-determined PT INR), a cardiologist-determined coagulation index for the purpose of cardiovascular therapy, to recover to its pre-extraction level. Our study revealed that anticoagulant effect after tooth extraction was influenced by a history of prosthetic heart valve placement (prosthetic valve), the dosage of warfarin administered (the dosage), the numbers of days of treatment cessation and of administering a reduced dose of warfarin, and the cardiologist-determined PT INR. The effects of prosthetic valve and the number of days of cessation of warfarin treatment were statistically significant (partial regression coefficient, 0.31). The influence of the number of days of treatment cessation was indirectly, affected by the prosthetic valve, the dosage, and the cardiologist-determined PT INR.