Effect of different surface treatments on Bond Strength to Tetragonal and Cubic Zirconia / Submittrd by Mohamed Mahmoud Abdelnaby, B.D.S. (Pharos University Faculty of Dentistry 2011); Supervisors A.Prof. Amr El Etreby Associate Professor of Fixed Prosthodontics,Faculty of Oral and Dental Medicine , Prof. Ossama Saleh Abdelghany, Professor of Fixed Prosthodontics, Faculty of Dental Medicine , Prof. Moustafa Nabil Aboushlib, Professor and Head of Biomaterials Department, Faculty of Dentistry

Faculty of Oral and Dental Medicine

Thesis (M.Sc.) - Future University in Egypt - Faculty of Oral and Dental Medicine Department of Fixed Prosthodontics, 2019.

Includes bibliographical references

Z
irconia, has the greatest mechanical properties of all dental ceramics. It has been used for over a decade and has become an increasingly popular restorative material. A major drawback with the first and second generation of conventional zirconia is its esthetic properties. In particular, the opacity of the material has rendered it inferior to glass-ceramics, especially for use in anterior restorations. This limit the conventional zirconia to be used as a framework material in porcelain-veneered crowns.
The problems related to porcelain chipping led to the development of the third-generation monolithic zirconia which have better optical properties and have translucency close to the lithium disilicate ceramics.
Establishing a durable adhesive bond between zirconia and adhesive cement systems has been proven to be a difficult task and highly dependent on the surface treatment and the structure of zirconia, because the material is chemically inert, non-polar and does not react to common chemical primers used with other glass ceramic materials.
Therefore, in the present study, the effect of low pressure airborne particle abrasion, selective infiltration etching and fusion sputtering on shear bond strength of tetragonal and cubic zirconia will be evaluated and evaluation the pattern of failure after debonding.
Ninety two specimens of zirconia will be used in this study. Two specimens will be investigated for surface analysis and ninety specimens was divided into 2 groups according to type of zirconia used cubic zirconia (bruxzir anterior) and tetragonal zirconia (cercon), specimens of each group will be divided into 3 subgroups according to type of surface treatments low pressure airborne-particle abrasion, selective infiltration etching and fusion sputtering, then will be divided into 3 divisions according to time interval as immediate, thermocycling and water storage.
All the zirconia specimens were cleaned ultrasonically, then six composite discs were bonded to each zirconia specimen using panavia V5 resin cement. The zirconia specimens were divided into immediate, 12 months water storage and thermocycling for 15,000 cycle. After that bond strength test and pattern of failure were evaluated.
SEM examination of the internal structure of tested zirconia showed, cubic zirconia revealed a much larger grain with more refined grain boundary regions, while tetragonal zirconia was composed of submicroscopic round grains demonstrating homogenous and thick grain boundary regions. Larger cubic grains in bruxzir anterior were frequently interrupted by smaller round grains, these differences were associated with higher surface hardness and lower surface roughness parameters for high translucency zirconia.
Statistical analysis of data revealed significant differences in surface treatments on shear bond strength between the three types of surface treatments, with SIE associated with the highest bond strengths and particle abrasion with the lowest.
Analysis of data revealed significant differences between the materials used between the two types of material (tetragonal cercon / cubic bruxzir anterior), tetragonal zirconia associated with high bond strength and cubic zirconia with lower bond strength.
There were significant differences between the three tested time intervals, immediate group showed the highest bond strength and the other two groups (15000 cycle and 12 month) reduction in bond strength.
Tetragonal zirconia specimens showed for immediate group the highest bond strength 26 MPa while the lowest 22.80 MPa, thermocycling group the highest bond strength 21.10 MPa while the lowest 16.30 MPa and water storage group the highest bond strength 21.40 MPa while the lowest 13.90 MPa.
Cubic zirconia specimens showed for immediate group the highest bond strength 20.70 MPa while the lowest 16.20 MPa, thermocycling group the highest bond strength 15 MPa while the lowest 5.20 MPa and water storage group the highest bond strength 14.80 MPa while the lowest 3.30 MPa,
After debonding pattern of failure were analyzed, showed that selective infiltration etching, fusion sputtering and low pressure particle abrasion was predominantly cohesive failure within composite discs.