Temperature Change in Dentin using an Electric Slowspeed Handpiece

Objective: This study assessed temperature change utilizing a thermographic camera while preparing dentin samples with an electric slowspeed handpiece and tungsten carbide burs.

Methods: Following IRB approval, 2mm thick dentin samples (n=28) were obtained from freshly, extracted human non-carious third molars. Three pilot studies determined operator preference for handpiece speed and handpiece pressure, and the average time to run the bur the length of the sample. The samples were demineralised to simulate caries. A previous cutting regimen with an electric slowspeed handpiece (KaVo Electrotorque, KaVo America, Inc., Lakeside, IL) was used to simulate 99.0 gm of hand pressure at 7,143 rpm with 40 PSI without irrigant. Preparations were made in an occluso-gingival direction for 19 seconds using tungsten carbide (H31.010) fissure burs (Brasseler USA, Savannah, Georgia). A thermocamera (Thermovision A20M,FLIR Systems) provided simultaneous thermal recording of temperature changes on the dentin wall. Temperature changes were analyzed using ThermaCAM Software (Flir Systems). Temperature changes per sample were plotted graphically against time using this software. Generalized Estimating Equations were used to examine the relationship between temperature change and time.

Results: An increase and decrease in temperature was recorded. The maximal temperature increase was recorded as +1.94 degrees Celsius and the maximal temperature decrease -2.62 degrees Celsius. No statistical relationship was observed between temperature change and time.

Conclusion: There was no consistent significant temperature change with the slowspeed electric handpiece under the study conditions. The use of irrigant, mandated in European dental practice for slow and highspeed handpieces, may not be necessary using an electric slowspeed handpiece. Under clinical conditions, where handpiece pressure and proximity to the pulp vary, significant temperature changes may occur. The heat decrease in this investigation is likely due to the coolant effect of the airspray and poor dentin conductivity.