Chatter stability investigation of micro-milling dental bur at enamel and dentin layers

Tooth restoration is the most frequent operation in dentistry. During this process, chip can be removed from carious or damaged restoration part of tooth by a high-speed rotating dental bur. The dental bur used in this process is very close to a micro-milling tool. An undesired phenomenon that can occur during micro-milling operations is called regenerative chatter. This is a kind of unstable self-generative vibration. Incidence of this event may leads to limit the efficiency of dentistry through a diminution in the dental bur life-time and physical harm to the tooth or dental bur. The main object of current research is chatter stability investigation of dental bur in enamel and dentin layers. The dental bur is modeled as a nonlinear rotating clamped-free Timoshenko beam that is excited by cutting forces. In addition, the length scale parameters and real geometry of dental bur are considered here. The specific cutting force coefficients for the two main dental layers are obtained by using finite element software. The delay partial differential equations of dental bur are solved in analytical form. Finally, the effects of the tool diameter, the number of the cutter flutes, the tool length, and length scale parameter on the chatter stability in the two main layers have been investigated. To the best author's knowledge, the chatter stability for the dental bur in the two main layers is obtained for the first time in current study by using analytical procedure.