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Wang C-H, Chueh L-H et al. J Endod 2011; 37: 1–5.

This study was carried out in Taiwan. In this country, there is compulsory universal health insurance that includes the funding for root canal therapy. The investigators followed for 2 years, 49,334 randomly selected teeth that had received non-surgical endodontic treatment. If the tooth was subsequently extracted, associations were sought with diabetes mellitus, hypertension and coronary artery disease. The hazard ratio was used to estimate the effect of the systemic disease on the risk of extraction. At the end of 2 years, 3.2% of the teeth had been extracted. After adjustment for age, gender and tooth type, diabetes mellitus and hypertension were independent risk factors for tooth extraction (hazard ratio = 1.29 and 1.18 respectively, both p values <0.05). The authors did not speculate as to the direction of the causal relationships.