Electric current induced in teeth by electromagnetic fields from electric toothbrushes and curing lights

Abstract

Purpose

The purpose of this study was to examine the electric current induced in teeth and tooth-bonded brackets by electromagnetic fields from electric toothbrushes and the curing lights used for photo-activating light-cured resins.

Materials and methods

Curing lights-generated low-frequency magnetic fields (1–2000 Hz) were measured with a spectrum analyzer. Temperature changes induced in the enamel and pulpal dentin surface of extracted upper premolar teeth (with or without a stainless steel or zirconia bracket) by electric toothbrushes and curing lights were estimated using an infrared thermometer. Electric current induced in these extracted teeth by electric appliances was estimated using a digital multimeter.

Results

Curing lights generated low-frequency magnetic fields. Irradiation of the tooth surface by curing lights elevated the temperature of the enamel and pulpal dentin surfaces, but there were no differences between curing lights. About electric current induced in extracted teeth (with or without a bracket) by electric toothbrushes and curing lights, the highest current was induced in teeth to which a zirconia bracket was bonded, whereas the lowest current was in unmodified teeth. Intermediate currents were generated in teeth bonded to stainless steel brackets.

Conclusion

The low-frequency magnetic fields induced by electric toothbrushes and light curing units induce electric current in tooth tissue, irrespective of whether these teeth are bonded to stainless steel or zirconia brackets.

Keywords:

• Electromagnetic
• Voltage
• Current
• Surface temperature
• Tooth–bracket couple

Acknowledgment

The authors are grateful to Associate Prof. Nozomu Ishii, Department of Biocybernetics, Faculty of Engineering, Niigata University, for providing valuable advice.