Annual failure rate

Annual failure rate is a simple, standardized way researchers describe how long a restoration or treatment tends to last: the average percentage of a group of restorations that fail per year of use, which lets studies with different follow-up lengths be compared on a common scale. A material with a 1% annual failure rate implies roughly 90% survival at ten years if failures accumulated evenly, though real failure patterns are rarely perfectly linear.

The number is most useful for comparing materials or techniques head to head rather than as a precise prediction for any single restoration in any single mouth, since a restoration's actual longevity depends heavily on factors the annual rate averages away: the tooth's position in the arch, whether the patient grinds, and whether the abutment is vital, all of which move survival more than the material choice alone.

Reading annual failure rate alongside the specific study population and follow-up length matters, because a rate calculated from three years of data on a small sample carries far less certainty than one built from a large cohort followed for a decade or more.