The purpose of this study was to evaluate the effects of primers on the bond strength and durability of an acrylic resin luting agent bonded to zirconia. Disk specimens were fabricated from zirconia partially stabilized with yttrium oxide. The disks were primed with one of the following materials: Alloy Primer (AP), Ceramic Primer (CP), Liquid A of the Porcelain Liner M (PLM-A), Liquid B of Porcelain Liner M (PLM-B), Porcelain Liner M (PLM-A+PLM-B), Monobond Plus (MP), and mixture of AP and PLM-B. The specimens were bonded with a tri-n-butylborane (TBB)-initiated luting agent. The shear bond strengths were determined both before and after thermocycling. The results were statistically analyzed with a non-parametric procedure. The highest post-thermocycling bond strength was generated from the groups primed with MP, CP, and AP. It can be concluded that the application of three phosphate primers is recommended for bonding the zirconia with the TBB-initiated luting agent.

This study aimed to evaluate the effect of surface preparation on bond strength of a tri-n-butylborane initiated resin (MMA-TBB) bonded to zirconia. Zirconia disks were either airborne-particle abraded with alumina or silica-coated. The disks were thereafter primed with one of the following materials: phosphate-silane (Clearfil Ceramic Primer), phosphate (Alloy Primer), or silane (ESPE Sil). The specimens were bonded with the MMA-TBB. Shear bond strength was determined both before and after thermocycling. Bond strength of unprimed zirconia (control) was not affected by the surface roughness of each adherend. Priming with phosphate was effective for bonding alumina-blasted zirconia. Priming with silane was effective for bonding silica-coated zirconia. Priming effect of the phosphate-silane was superior to that of silane alone for bonding silica-coated zirconia. Bond strength to zirconia of the MMATBB is significantly influenced by a combination of the specific functional monomer and the surface modification performed rather than the material surface roughness.

This study compared the wear characteristics of a heat-pressed lithium disilicate ceramic material opposed to feldspathic porcelain, a lithium disilicate glass ceramic, and zirconia materials. Ceramic plate specimens were prepared from feldspathic porcelain (EX-3 nA1B), lithium disilicate glass ceramics (e.max CAD MO1/C14), and zirconia (Katana KT 10) and then ground or polished. Rounded rod specimens were fabricated from heatpressed lithium disilicate glass ceramic (e.max press LT A3) and then glazed or polished. A sliding wear testing apparatus was used for wear testing. Wear of glazed rods was greater than that of polished rods when they were abraded with ground zirconia, ground porcelain, polished porcelain, or polished lithium disilicate ceramics. For both glazed and polished rods, wear was greater when the rods were abraded with ground plates. The findings indicate that application of a polished surface rather than a glazed surface is recommended for single restorations made of heat-pressed lithium disilicate material. In addition, care must be taken when polishing opposing materials, especially those used in occlusal contact areas. (J Oral Sci 58, 117-123, 2016)

The purpose of this study was to evaluate the influence of ceramic surface texture on the wear of rounded rod specimens. Plate specimens were fabricated from zirconia (ZrO2), feldspathic porcelain, and lithium disilicate glass ceramics (LDG ceramics). Plate surfaces were either ground or polished. Rounded rod specimens with a 2.0-mm-diameter were fabricated from type 4 gold alloy and heat-pressed ceramics (HP ceramics). Wear testing was performed by means of a wear testing apparatus under 5,000 reciprocal strokes of the rod specimen with 5.9 N vertical loading. The results were statistically analyzed with a non-parametric procedure. The gold alloy showed the maximal height loss (90.0 µm) when the rod specimen was abraded with ground porcelain, whereas the HP ceramics exhibited maximal height loss (49.8 µm) when the rod specimen was abraded with ground zirconia. There was a strong correlation between height loss of the rod and surface roughness of the underlying plates, for both the gold alloy and HP ceramics.

Zirconium dioxide (zirconia) has become more widely used for ceramic restorations and in clinical practice. Given its outstanding mechanical properties, chemical stability, biocompatibility, and aesthetics, zirconia is now widely used in restorations, fixed dental prostheses, and superstructures of implant-supported prostheses 1,2). Regarding zirconia bonding, 10-methacryloyloxydecyl dihydrogen phosphate (MDP) monomer is known to chemically bond with the zirconia surface 3-5). Moreover, mechanical adhesion still remains the main prerequisite to achieve durable retention of zirconia restorations 5-12). Given the acid resistant properties of zirconia, etching with hydrofluoric acid, which is used for silica-based ceramic materials, is ineffective 12,13). In many laboratory 5,7,9-12) and clinical 14,15) studies, alumina blasting is used to increase the roughness of the zirconia surface instead of etching with hydrofluoric acid. Recently, Ruyter et al. reported that etching with potassium hydrogen difluoride (KHF 2) and ammonium hydrogen difluoride (NH4HF2) was effective for zirconia 16). However, that study did not strictly evaluate whether etching with KHF 2 and NH4HF2 yielded micromechanical interlocking because the primer and the luting agent used on zirconia surface contained a functional monomer that could influence the bond strength. Therefore, the consensus on etching with KHF 2 and NH4HF2 on zirconia remains unclear. The purpose of the present study was to investigate the effect of etching with KHF2 and NH4HF2 on the bond strength of a self-polymerizing MMA resin bonded to zirconia. The MMA resin did not contain any functional monomers. The null hypothesis was that the shear bond strength would not be affected by each of the surface treatments. MATERIALS AND METHODS Materials The materials used in this laboratory investigation are listed in Table 1. A total of 44 disk specimens (11.4 mm in diameter and 2.8 mm thickness) were fabricated with yttrium-oxide-partially-stabilized zirconia ceramics (Katana, Kuraray Noritake Dental, Tokyo, Japan) and used as the bonding substrate. The following abrasive particles were used for alumina blasting: 50-70 μm alumina (Hi-Aluminas, Shofu, Kyoto, Japan). Two chemical powders were used as the experimental etching agents: potassium hydrogen difluoride (KHF 2; Tokyo Chemical Ind., Tokyo, Japan) and ammonium hydrogen difluoride (NH 4HF2; Sigma-Aldrich Japan, Tokyo, Japan). The melting point of KHF2 is 239ºC and that of NH4HF2 is 125ºC. A self-polymerizing resin was selected as the luting material. This resin consisted of a partially oxidized trin-butylborane (TBB) initiator (Super-Bond Catalyst V, Sun Medical, Moriyama, Japan), methyl methacrylate (MMA; Tokyo Chemical Ind.