Operative Dentistry and the Abuse of Dental Hard Tissues: Confocal Microscopical Imaging of Cutting

Abstract

SUMMARYWe reviewed studies wherein the cutting of dental tissues, simulating interactions that would occur under clinical circumstances in the mouth, have been observed directly-first by real time, video rate, stereoscopic, three-dimensional scanning electron microscopy; and second and more conveniently, by video rate confocal optical microscopy. We have observed, directly, both the interactions of slow-moving cutting instruments emulating "chisels" and high-speed 216Operative Dentistry events, including the effects of rotary burs and air-propelled abrasive particles and soft powder slurries. The observational data contribute to our basic understanding of the functional behavior of dental tissues and formed a useful background for the practitioner of operative dentistry.

Evaluation of machinability and flexural strength of a novel dental machinable glass-ceramic

“…27 Cracks are significantly longer in the direction parallel to the enamel rods than perpendicular to the rods, 26 and travel easily along straight prism boundaries but are slowed by decussation of the enamel prisms. 27 In this study, there was no statistical difference in machinability among Group 1, Group 4 and human enamel, while Group 2 was significantly better than human enamel. The results suggest that, under a definite heat treatment procedure, the PMC ceramic could be machined better than enamel, which enables the PMC material to be cut by conventional tools as enamel.…”

“…26 The mechanisms for cutting enamel have been attributed to fracture along the weak boundaries between the enamel rods, with some degree of plastic deformation below the blade edge. 15,27 Moreover, since enamel is an anisotropic biomaterial, the fracture mode is expected to depend on the enamel rod orientation. 27 Cracks are significantly longer in the direction parallel to the enamel rods than perpendicular to the rods, 26 and travel easily along straight prism boundaries but are slowed by decussation of the enamel prisms.…”

“…15,27 Moreover, since enamel is an anisotropic biomaterial, the fracture mode is expected to depend on the enamel rod orientation. 27 Cracks are significantly longer in the direction parallel to the enamel rods than perpendicular to the rods, 26 and travel easily along straight prism boundaries but are slowed by decussation of the enamel prisms. 27 In this study, there was no statistical difference in machinability among Group 1, Group 4 and human enamel, while Group 2 was significantly better than human enamel.…”

Root dentine and endodontic instrumentation: cutting edge microscopic imaging

“…Previous work by Boyde [57] has shown the effects of cutting dental tissues using scanning electron microscopy evaluation. The unique aspect of our studies has been the application of video-rate reflection confocal microscopy for imaging the cutting interactions [58]. However, this technology has not been applied to the imaging of dentine while being cut.…”

Slice–push, formation of grooves and the scale effect in cutting

“…Tooth enamel is inherently brittle in bulk and the stresses and strains at fracture are controlled by elastic fracture mechanics (e.g. [27,28]) (but note the production of very thin ductile shavings off the surface of brittle enamel-exactly as in PMMA in figure 9 at sufficiently small depths of cut when t , (ER/k 2 )-illustrated by Watson et al [29]). The microstructural features that act as starter cracks in teeth are the lamellae, variable in depth, but well spaced between the 7 mm diameter prism-like microstructure of enamel.…”