Development and testing of multi-phase glazes for adhesive bonding to zirconia substrates

Ntala, Polyxeni; Chen, Xiaohui; Niggli, Jason; Cattell, Michael

doi:10.1016/j.jdent.2010.06.008

« Previous Next »Journal of Dentistry
Volume 38, Issue 10 , Pages 773-781, October 2010

Development and testing of multi-phase glazes for adhesive bonding to zirconia substrates

Polyxeni Ntala
- Centre of Adult Oral Health, Queen Mary University of London, Barts and The London School of Medicine and Dentistry, Institute of Dentistry, Turner Street, London, E1 2AD, UK
Xiaohui Chen
- Dental Physical Sciences, Queen Mary University of London, Barts and The London School of Medicine and Dentistry, Institute of Dentistry, Mile End Road, E1 4NS, UK
Jason Niggli
- Centre of Adult Oral Health, Queen Mary University of London, Barts and The London School of Medicine and Dentistry, Institute of Dentistry, Turner Street, London, E1 2AD, UK
Michael Cattell
- Centre of Adult Oral Health, Queen Mary University of London, Barts and The London School of Medicine and Dentistry, Institute of Dentistry, Turner Street, London, E1 2AD, UK
- Corresponding author. Tel.: +44 (0)207 377 0000x2160; fax: +44 (0)207 377 7064.

Received 5 May 2010; received in revised form 16 June 2010; accepted 17 June 2010. published online 28 June 2010.

Abstract

Objectives

The aims of the study were to develop and test multi-phase glaze coatings for zirconia restorations, so that the surface could be etched and adhesively bonded.

Methods

Zirconia disc specimens (n=125, 16mm×1mm) were cut from cylinders of Y-TZP (yttria-stabilized tetragonal zirconia polycrystals) ZS-Blanks (Kavo, Everest) and sintered overnight. Specimens were subjected to the recommended firing cycles, and next sandblasted. The specimens were divided into 5 groups of 25, with Group 1 as the sandblasted control. Groups 2–5 were coated with overglaze materials (P25 and IPS e.max Ceram glazes) containing secondary phases. Group 2 was (wt%): 10% hydroxyapatite (HA)/P25 glaze, Group 3: 20% IPS Empress 2 glass–ceramic/glaze, Group 4: 20% IPS Empress 2 glass/glaze and Group 5: 30% IPS Empress 2 glass/glaze. After sintering and etching, Monobond-S and composite resin cylinders (Variolink II, Ivoclar-Vivadent) were applied and light cured on the test surfaces. Specimens were water stored for 7 days. Groups were tested using the shear bond strength (SBS) test at a crosshead speed of 0.5mm/min. Overglazed and the fractured specimen surfaces were viewed using secondary electron microscopy. Room and high temperature XRD and DSC were carried out to characterize the materials.

Results

The mean (SD) SBS (MPa) of the test groups were: Group 1: 7.7 (3.2); Group 2: 5.6 (1.7); Group 3: 11.0 (3.0); Group 4: 8.8 (2.6) and Group 5: 9.1 (2.6). Group 3 was significantly different to the control Group 1 (p<0.05). There was no significant difference in the mean SBS values between Group 1 and Groups 2, 4 and 5 (p>0.05). Group 2 showed statistically lower SBS than Groups 3–5 (p<0.05). Lithium disilicate fibres were present in Groups 3–5 and fine scale fibres were grown in the glaze following a porcelain firing cycle (Groups 4 and 5). XRD indicated a lithium disilicate/minor lithium orthophosphate phase (Group 3), and a tetragonal zirconia phase for the sintered Y-TZP ZS-Blanks. DSC and high temperature XRD confirmed the crystallization temperatures and phases for the IPS Empress 2 glass.

Conclusions

The application of a novel glass–ceramic/glaze material containing a major lithium disilicate phase might be a step in improving the bond strength of a zirconia substrate to a resin cement.

Keywords: Glaze, Adhesive bonding, Zirconia, Microscopy, X-ray diffraction