Purpose: To determine whether chemical and thermal stress as well as sharpening are aspects that must be considered
to determine when a curette has become too weak to be used safely without the threat of breakage.
Materials and Methods: A total sample of 35 curette blades was divided into 2 principal groups, control (groups 1
to 3) and experimental (groups 4 to 6). The control group was divided into 3 colour-coded groups of 19 similar curette
blades and was only subjected to progressive sharpening wear (not sterilised). The test group included 16 Gracey
curette blades that were subjected to various degrees of progressive wear and different numbers of sterilisation cycles
in 3 subgroups (subgroup 4 had 5 sterilisation cycles; subgroup 5 had 30 cycles and experimental subgroup 6 had
55 cycles). Using a universal testing machine, all blades were tested for strength until they fractured.
Results: No evidence was found that the simple presence or absence of sterilisation cycles produced a statistically
significant difference between the two studied groups (sterilised and not sterilised). However, when comparing the
six subgroups that underwent different numbers of sterilisation cycles, the analysis showed that the more sterilisation
cycles a curette underwent, the more likely the curette was to fracture (p = 0.047).
Conclusion: Sterilisation by itself does not produce a significant change in the fracture strength, whereas the number
of sterilisation cycles clearly weakens the instrument. Sterilisation is a factor to control when evaluating the life of a
periodontal curette for the patients’ and professionals’ safety.