Abstract: High-speed cutting of tooth enamel surface is a key procedure for dental restoration surgeries, with problems such as large cutting force, low surface quality and surface damage in the cutting process. Therefore, related scientific research is required. For the occlusal and buccal/lingual surfaces of the human teeth, an experimental plan for the high-speed enamel surface milling with carbide cutters is designed for key processing characteristics, and the material fracture and surface formation mechanisms are further discussed. The results show that the up-milling process produces high friction and extrusion, further resulting in unsteady material fracture. In addition, the cutting force, surface roughness and surface damage are all significantly increased accordingly. And down-milling mode is preferred for the enamel surface cutting in dental restoration surgeries. There are three main types of material fracture and surface formation in cutting: the relatively steady material fracture which produces lamellar chips, the non-steady material fracture which produces fractured chips, and the smooth plastic surface formation by embrittlement effect and ironing mechanism. For occlusal and the buccal/lingual surfaces cutting under down-milling mode, some sub-micron thick layers of stable chips with folds and cracks can be cut to obtain, reflecting the material embrittlement and dislocation at high strain rate. Different from the perpendicular intersection cutting of the occlusal surface, the cutting edge crosses the enamel rod obliquely during buccal/lingual cutting. In this way, the material is more difficult to fracture, resulting in more unstable blocks or tearing chips, more cutting force and surface damage. Good plastic surfaces can be obtained with the down milling mode, which is directly related to the tail section of the cut-in-cut-out arc. The tail section arc satisfies the conditions for producing plastic surface, and the processing results are dominated by embrittlement and ironing mechanisms.

Key words: enamel, high speed milling, carbide milling cutter, material fracture, surface formation