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Figure 2. Hazards ratios (
) and 95% confidence interval (error bars) for risk of root canal treatment among current cigarette smokers, by total yrs smoked. Numbers in each interval are 48 participants/1347 teeth with 
4 yrs, 78 participants/1782 teeth with 5 to 12 yrs, and 99 participants/2099 teeth with > 12 yrs. Never-smokers (n = 230 participants/5765 teeth) are the reference group. Hazard ratios are adjusted for age, presence of crown (yes, no), any caries (yes, no), periradicular radiolucency (yes, no), and alveolar bone loss score.
