Natural frequency assessment of stability of root keeper magnetic devices

Abstract

The aim of the study was to evaluate the potential for using natural frequency (NF) as an indicator for assessing the stability of a magnetic keeper device used in prosthodontic treatment. A three-dimensional finite element (FE) model of a root keeper-cement-dentine system was established for NF analysis. The model was first validated against a series of in vitro experiments. Then, NF values of the first vibrational mode of the FE model with various boundary conditions were calculated. The in vitro results showed that the measured NF values of the root keeper-incisor units decreased significantly (p<0.01) from 9.07 +/- 0.37 to 5.73 +/- 0.10 kHz when the units were embedded in simulated bony tissue. Results obtained from FE simulations demonstrated that the root keeper would fully loosen when the constant values of the spring elements were lower than 10(4) N-m(-1). Furthermore, a linear increase in the NF values of the model was observed from 6.16 to 15.52 kHz, when the constant was increased from 10(4) to 10(7) N-m(-1), and the values then reached a plateau. The results indicate that the NF value of a root keeper has the potential to be used for monitoring the stability of such a device.

Radiofrequency heating and magnetically induced displacement of dental magnetic attachments during 3.0 T MRI

“…However, these keepers were cemented onto or cast to a dental prosthesis; therefore, the strength of the dental cement used for luting could be considered sufficiently strong. [32][33][34] In conclusion, we have demonstrated the feasibility of evaluating RF heating of keepers with copings or dental implants during MRI examinations and the interaction between MRI system-generated magnetic fields and keepers. The relatively minor RF heating (temperature increase 5 0.8 u C) of keepers with coping in the Achieva 3.0 T Nova Dual and Signa HDxt 3.0 T systems in the normal operating mode does not pose a risk to patients.…”

Non-destructive natural frequency tests of cyclic fatigue-loaded nickel–titanium rotary instruments

“…NF testing is a non-destructive and noninvasive testing technique. It has been used for measuring the NF value of small threaded structures, such as orthopaedic fixation pins [11] and dental implants [5,10]. Therefore, aim of this study was to investigate whether NF is a useful parameter for monitoring the structural status of fatigueloaded NiTi rotary instruments.…”

Application of non-destructive impedance-based monitoring technique for cyclic fatigue evaluation of endodontic nickel–titanium rotary instruments

“…However, the major problem with this technique is that the cracks on the fractured surface might be too small to trigger a sufficient response in the strain gauge-based sensing instrument. The natural frequency (NF) of a mechanical structure is a function of the stiffness and the mass and has been developed as a practical, non-destructive testing technique for detecting the stiffness of metal structures in orthopedic fixation pins and dental implants [8,[12][13][14][15]. In 2010, Hsieh et al used NF for monitoring the structural changes in a Ni-Ti instrument during and after the instrumentation process [8].…”