Chipping fracture resistance of dental CAD/CAM restorative materials: Part I – Procedures and results

Abstract

Objective The edge chipping test was used to measure the fracture resistance of CAD/CAM dental restoration ceramics and resin composites. Methods An edge chipping machine was used to evaluate six materials including one feldspathic porcelain, two glass ceramics, a filled resin-composite, a yttria-stabilized zirconia, and a new ceramic-resin composite material. Force versus edge distance data were collected over a broad range of forces and distances. Data were analyzed by several approaches and several chipping resistance parameters were evaluated. The effects of using different indenter types were explored. Results The force versus distance trends were usually nonlinear with good fits to a power law equation with exponents usually ranging from 1.2 to 1.9. The order of chipping resistance (from least to greatest) was: feldspathic porcelain and a leucite glass ceramic (which were similar), followed by the lithium disilicate glass ceramic and the two resin composites (which were similar), and finally the zirconia which had the greatest resistance to chipping. Chipping with a Vickers indenter required 28% to 45% more force than with the sharp conical 120° indenter. The two indenters rank materials approximately the same way. The power law exponents were very similar for the two indenters for a particular material, but the exponents varied with material. The Rockwell C indenter gives different power law trends and rankings. Significance Despite the variations in the trends and indenters, simple comparisons between materials can be made by chipping with sharp conical 120° or Vickers indenters at 0.50 mm. Broad distance ranges are recommended for trend evaluation.

A multi technique study of a new lithium disilicate glass-ceramic spray-coated on ZrO2 substrate for dental restoration

“…Yttrium-stabilized tetragonal zirconium dioxide has a Vickers hardness of more than 1250 MPa [13,17,18,26,27]. The hardness of natural tooth enamel is lower, closer to 275-550 MPa [10,26,27], and thus, comparable to the hardness of glasses and glass-ceramics [28]. Abrasion depends foremost on the smoothness and only secondarily on the difference in hardness, therefore, the observed difference in hardness between TZ3Y and natural teeth is only a minor factor.…”

“…Leucite, for example, displays an unsatisfactory failure which is revealed in a high incidence of fracture or chipping [3,8,12,14,15,25,28,[30][31][32][33]. The strong increase of chipping with time, as discussed in reference [33] for glass-ceramic veneers on ZrO 2 substrate indicates that many parameter and fatigue mechanisms contribute to eventual failure.…”

Trueness of four different milling procedures used in dental CAD/CAM systems

“…Glass ceramics are often used in single tooth treatment and milling should result in sufficient marginal quality when using this material. As glass ceramic is more prone to chipping than other materials [43]; it should illustrate machining problems very clearly. The restriction to one milling material (VITABLOCS Mark II) in this study was considered reasonable, as different materials could be milled with different results even when using the same milling device.…”

In Vitro Analysis of the Fracture Resistance of Cad-Cam Cerasmart Molar Crowns with Different Occlusal Thickness

“…Digital chairside techniques as well as production procedures allow for standardized processing of restorative materials, reduce fabrication times and improve costeffectiveness [6,12]. Ceramic blocks may suffer from their intrinsic brittle nature and could abrade opposite dentition whereas composite blocks may be negatively affected by material wear and could show reduced fracture resistance [12,13].…”