Part II: Hypothetical case control

Instead of investigating the chance of going 18 months without a root canal your practice is only interested in the chance of having a root canal given various exposures, so you decide to a case-control study is done.

Suppose that for every root canal case from the previous 18 months, 3 controls were selected and both cases (43) and controls (129) were asked the about various exposures.

**Please note the comparison is with the previous case study where individuals that already had a filling were selected.

a.Fill in the ORs for all the exposures in the table below (counts in the table are for those patients who had the exposure). For each OR use the odds of having the particular exposure in cases compared to controls.

exposure Cases Controls 0R Have gum disease 15 10 6.4 Chew sugarless gum 6 20 Floss regularly 10 65 Taken antibiotics in 5 36 previous 6 months Overweight/obese 20 38 Recent viral infection 17 51