Reverse torque evaluation in indexed and nonindexed abutments of Morse Taper implants in a mechanical fatigue test

Abstract

Background: This experimental study assessed reverse torque of indexed and nonindexed (NI)
abutments in Morse Taper (MT) implants in a mechanical fatigue test.
Materials and Methods: In this experimental study It was used 37 implants MT and over them
installed Pilar Flex abutments (4.8 mm × 6 mm × 1.5 mm). The groups were as follows: Group A
used 19 MT implants with a NI Pilar Flex abutment loaded with 32 N/cm and Group B used 18
MT implants with an indexed (IN) Pilar Flex abutment loaded with 20 N/cm. The abutments
were tested according to ISO standard 14801/2007. The specimens were installed at 30° from the
axial axis and underwent a 133 N load, 4 Hz frequency, and 1,000,000 cycles. Once the test was
completed, the reverse torque was provided by an electronic torque meter. Data were submitted
to statistical analysis using the t‑test for independent samples and paired t‑test. The significance
level was considered P < 0.05.
Results: Results obtained showed that the indexed Pilar Flex abutment had a percentage of torque
loss from the initial torque of 49% and the NI Pilar Flex abutment lost 14%. Paired Student’s t‑tests
revealed that for both NI (P < 0.001) and indexed (P < 0.001) abutments, the counter torque values
were significantly lower than those applied at the initial torque.
Conclusion: According on the methodology used, the NI Pilar Flex abutment was more effective
regarding the reverse torque in single‑unit implant prostheses versus the indexed Pilar Flex
abutment. A greater loosening in the indexed Pilar Flex abutment retaining screw was noted in
the reverse torque test, and the Pilar Flex abutment failed to show good outcomes related to the
cold welding effect.
Key Words: Dental implant–abutment design, dental implants, torque