Effect of overglazed and polished surface finishes on the compressive fracture strength of machinable ceramic materials

Abstract

Controversy prevails over the effect of overglazing on the fracture strength of ceramic materials. Therefore, the effects of different surface finishes on the compressive fracture strength of machinable ceramic materials were investigated in this study. Plates prepared from four commercial brands of ceramic materials were either surface-polished or overglazed (n=10 per ceramic material for each surface finish), and bonded to flat surfaces of human dentin using a resin cement. Loads at failure were determined and statistically analyzed using two-way ANOVA and Bonferroni test. Although no statistical differences in load value were detected between polished and overglazed groups (p>0.05), the fracture load of Vita Mark II was significantly lower than those of ProCAD and IPS Empress CAD, whereas that of IPS e.max CAD was significantly higher than the latter two ceramic materials (p<0.05). It was concluded that overglazed and polished surfaces produced similar compressive fracture strengths irrespective of the machinable ceramic material tested, and that fracture strength was material-dependent.

Impact of surface treatment of different reinforced glass-ceramic anterior crowns on load bearing capacity

“…A study published in 2010 found that 4 different glass-ceramic CAD/CAM materials presented different FLs 20) . For these polished or overglazed geometric specimens of these materials were fixated to a plane dentin layer and FLs were compared.…”

“…These two techniques however, have not yet been directly compared. It is therefore not yet evident whether polishing or glazing is the more effective way of strengthening the surface of the ceramic restorations 2,20,[22][23][24] . It is therefore essential to find a surface treatment that will protect ceramic restorations from the strong physiological and paraphysiological forces of the masticatory system 12,16,25) .…”

“…It is therefore essential to find a surface treatment that will protect ceramic restorations from the strong physiological and paraphysiological forces of the masticatory system 12,16,25) . Glaze firing provides the most homogeneous, and thereby smoothest, most hygienic, and resistant surface 19,20,26) . However, sometimes a restoration requires grinding immediately after a newly applied glaze, and sometimes definitely cemented crowns show bite rising, and then require grinding.…”

“…The crystalline structure and the surface treatment have a direct effect on the flexural strength and cracking tendency of the glass-ceramic restoration 2,11,16,18) . So as to create smoother surfaces and avoid surface roughness and porosities, either glaze firing or a special polishing regimen can be applied 10,19,20) . A smoother surface also augments the stability of the glass-ceramic restoration 4,16,20) and reduces the occurrence and growth of flaws 2) .…”

“…So as to create smoother surfaces and avoid surface roughness and porosities, either glaze firing or a special polishing regimen can be applied 10,19,20) . A smoother surface also augments the stability of the glass-ceramic restoration 4,16,20) and reduces the occurrence and growth of flaws 2) . Existing flaws are minimized in depth and sharpness.…”