Laju, S (2011) Comparative evaluation of shear bond strength of veneering porcelain to base metal alloy and zirconia substructures before and after aging: An In Vitro study. Masters thesis, Ragas Dental College & Hospital, Chennai.
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Abstract
The present in vitro study was conducted to evaluate and compare the shear bond strength of veneering porcelain to base metal alloy and zirconia substructures before and after aging. Twenty base metal alloy cores and twenty zirconia cores of dimension 9mm length x 4mm width x 4mm height were prepared and veneered with corresponding veneering porcelain to the dimension of 3mm length x 4mm width x 4mm height. Ten porcelain veneered base metal alloy samples were used to determine the shear bond strength before aging (Group I). Ten porcelain veneered base metal alloy samples were used to determine the shear bond strength after aging (Group II). Ten porcelain veneered zirconia samples were used to determine the shear bond strength before aging (Group III). Ten porcelain veneered zirconia samples were used to determine the shear bond strength after aging (Group IV). All samples were tested for shear bond strength in Universal testing machine. The basic values of shear bond strength of all test samples in four groups were tabulated. The mean shear bond strength for each group was calculated and tabulated. The results were subjected for statistical analysis. The data obtained in the present study revealed the highest shear bond strength value of porcelain veneered base metal alloy samples before aging (Group I- Mean value 39.51MPa) followed by porcelain veneered base metal alloy samples after aging (Group II- Mean value 37.2MPa), porcelain veneered zirconia samples before aging (Group III- Mean value 28.12MPa) and porcelain veneered zirconia samples after aging (Group IV- Mean value 26.2 MPa). Group I > Group II > Group III > Group IV. On comparison between mean shear bond strength of Group I and Group II, the mean shear bond strength was found to be decreasing after aging and the difference was found to be statistically insignificant. On comparison between mean shear bond strength of Group III and Group IV, the mean shear bond strength was found to be decreasing after aging and the difference was found to be statistically significant. On comparison between the mean shear bond strength of Group II and Group IV, the mean shear bond strength of Group II was found to be higher than the mean shear bond strength of Group IV. It was evidenced that aging had an influence on the shear bond strength of porcelain veneered base metal alloy as well as porcelain veneered zirconia samples. Aging facilitate stress corrosion of ceramic materials, resulting in slow crack growth and finally leading to failure of ceramic materials. On comparison between the mean shear bond strength of Group I and Group III, the mean shear bond strength of Group I was found to be higher than the mean shear bond strength of Group III. The results showed higher shear bond strength of base metal alloy group which were in agreement with the ISO requirements and previous studies. Tested samples were qualitatively analyzed using scanning electron microscopy and interface chemistry was analyzed using energy dispersive x-ray microanalysis. Group I samples revealed cohesive failure of metal ceramic bonding, predominantly failure within the veneering ceramic. Group II samples revealed cohesive failure of veneering ceramic. Group III samples revealed mixed cohesive and adhesive failure of veneering ceramic, predominantly cohesive failure of veneering ceramic. Group IV samples revealed mixed cohesive and adhesive failure of veneering ceramic, predominantly cohesive failure of veneering ceramic. The quantitative results of this study were in correlation with the qualitative results of the study. In this study, the shear bond strength of porcelain veneered base metal alloy was found to be statistically significantly higher than the shear bond strength of porcelain veneered zirconia before and after aging. SEM analysis revealed predominantly cohesive failure of veneering ceramic. Since the bond strength of the interface was higher than the cohesive strength of ceramic, it was concluded that the veneering ceramic was the weakest link. Based on the shear bond strength results of the present study the interceramic bond between zirconia core and veneering ceramic requires considerable refinements to match the values set by the porcelain veneered base metal alloy gold standard. Improving the zirconia core-veneer bond strength and the strength of the veneering porcelain may reduce the failure and is paramount to the longevity of the restoration. The metal ceramic restorations have been extensively used in dentistry for the past five decades. The problem of metal discoloration at the margins and allergic reactions to metals have led to the development of metal free ceramic restorations for superior esthetics and biocompatibility in fixed prosthodontics. Considering all ceramic materials available in dental health care, zirconia offers the best mechanical properties and has the potential to be applied as an alternative support material to alloys for the fabrication of fixed dental prosthesis. The problem involving early fracture of the veneer porcelain of zirconia supported restorations and the unclear effect of the low temperature degradation have led clinicians to question the total substitutution of alloys through zirconia based dental restorations. As zirconia has demonstrated good mechanical and biological performance, future technology is attempting to improve esthetics and minimize veneer fracture, aiming to create confidence in dental community towards this all ceramic system. Zirconia is being widely applied in dentistry starting from oral implant fabrication to the manufacturing of dental crown and bridge work. Zirconia and zirconia - supported ceramics are worthy of being further evaluated particularly with improved production methods.
| Item Type: | Thesis (Masters) |
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| Uncontrolled Keywords: | Comparative evaluation, shear bond strength, veneering porcelain, base metal alloy, zirconia substructures, before and after aging. |
| Subjects: | DENTAL > Prosthodontics and Crown and Bridge |
| Depositing User: | Kambaraman B |
| Date Deposited: | 19 Jan 2018 01:26 |
| Last Modified: | 19 Jan 2018 01:26 |
| URI: | http://repository-tnmgrmu.ac.in/id/eprint/5500 |
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