New digital dynamometer for measurement of cementation pressure

Objectives: This study was to develop a standardization technique of cementation pressure. 

Methods: Firstly, a digital dynamometer containing strain gauges for clinical application was developed for standardization of the cementation pressure. Next, the accuracy of the dynanometer was verified through a comparative evaluation of the internal adaptation of all-ceramic crowns cemented under digital pressure or using the device. Ten human extracted molars were prepared for full crowns, and received all-ceramic crowns fabricated using an injection-molded system (IPS Empress 2) veneered by IPS e.max Ceram. Before the cementation simulation tests, a manikin containing the adapted teeth was mounted to an artificial head with a mask to simulate lips and cheeks. At the moment of the test of simulated cementation, each crown was filled by a freshly mixed, PVS material especifically designed for this purpose, and immediately seated at the final position on the respective tooth. In the Mechanical Group, the fork of the dynamometer was inserted into the oral cavity, and the tip protected by the silicone was placed over the ceramic crown. The patient was asked to stabilize the bite pressure for 3 minutes when the dynamometer’s digital display indicated ~20.0 N. Three graduate students performed the procedures for the Manual Cementation Group. After the polymerization of the silicone film, cross-sections of replicas were obtained, after serial cuts in the labial-lingual and mesiodistal directions. Four segments were obtained and three local measurements were taken (cervical, axial, and occlusal). 

Results: Mean final film thicknesses were 86.48 µm for the Mechanical group, and 103.58µm, 103.05µm, and 104.49µm for the Manual Cementation group.

Conclusions: its use reduces the need of the aid by a dental assistant, and take the hands free to remove excess material, for checking accuracy fit, and stabilization of the indirect restoration, including at the lightcuring step.