Evaluation of a new protocol for removing metal retainers from multirooted teeth.

Introduction: The aim of this study was to evaluate in vitro a new protocol for removing intraradicular retainers from multirooted teeth applying ultrasonic vibration.

Methods: Forty mandibular molars were endodontically treated to receive cast intraradicular retainers, which were distributed into the following 4 groups: group 1: control without a slot and without ultrasound, group 2: control with a slot and without ultrasound, group 3: ultrasonic vibration in the core without a slot, and group 4: ultrasonic vibration in the core with a slot. After the intraradicular retainers were cemented with zinc phosphate, ultrasonic vibration was applied for 1 minute. The test specimens were then submitted to the traction test in the universal testing machine at a speed of 1 mm/min. The maximum traction force required to remove the intraradicular retainer was recorded in newtons, and the data were statistically analyzed using analysis of variance and the Tukey-Kramer test (P < .05).

Results: The results showed statistically significant differences among the groups tested (group 1 = 234.34 N, group 2 = 201.67 N, group 3 = 139.57 N, and group 4 = 83.23 N). The lowest mean value of traction force recorded was when ultrasonic vibration was applied on the core with a slot.

Conclusions: Creating a slot in the core and the ultrasound application on all surfaces and inside the slot reduced the force required for removing intraradicular metal retainers from multirooted teeth cemented with zinc phosphate.