Application of Grinding Fundamentals to Develop Material-Specific Relationships in the Dental-Grinding Procedure
Adam H. Carreon, Advised by Paul Funkenbusch
Friday, May 17, 2019
In restorative dentistry, the use of machinable ceramics for patient tooth restoration has become common practice. In fact, more than 15 million dental procedures are performed each year that require the grinding of tooth enamel and dentin. This results in the need for machinable ceramics to properly restore the structure of a patient's tooth. As with any invasive procedure, there exist health risks that could negatively impact the patient, for example, pulpal death and oral health. Additionally, there exist aesthetic risks that can occur such as chipping and cracking of teeth. Negative risks such as these arise due to the interaction between abrasive grinding tool and workpiece material (human teeth, dental prosthetic, etc.) during the dental grinding process being damage-inducing and not fully understood. One approach to alleviate the dental grinding process of these damage risks is to reduce the force applied during procedures. Therefore, in this research quasi-static nanoindentation and nanoscratching were used to establish a semi-analytical material-specific high-speed abrasive grinding-force model for dental applications. A model that determines ploughing friction coefficient, grain penetration, and grain-material contact area was first developed. The friction coefficient model uses a previously published analytical friction coefficient model as its foundation, and extends it to include material-specific characteristics that affect friction coefficient behavior. The grinding-force model created uses output from the friction model to demonstrate how material properties and characteristics affect abrasive grinding. The tool-workpiece interactions and grinding process kinematics developed in this research allow for the approximation of procedural grinding forces on macrostructurally homogeneous materials and give an explanation of magnitude based on process parameters, material properties, and material characteristics. Human enamel and dentin are anisotropic materials, therefore, nanoindentation and nanoscratching were used to quantify deformation as a function of enamel rod and dentin tubule orientation at the nanoscale. Material properties such as elastic modulus, hardness, and fracture patterns were found. Additionally, nanoscratch parameters such as material recovery, scratch hardness, and scratch roughness were found. The orientation-specific deformation of human teeth in addition to the material-specific grinding force model of brittle materials provides knowledge that can be used to reduce procedural forces and minimize tooth damage.