Influence of Core and Veneer Thickness Ratio and Veneer Thickness on Flexural Strength of Lithium Disilicate.
Hemali, Wagdi.
2012
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Abstract: Abstract Statement of the problem: There is no clear guideline to the amount of reduction of the lithium disilicate core and its strength value as core/veneer thickness ratios changes. Purpose: The purpose of this study is to investigate the effects of different core/veneer thickness ratios and veneer thickness on the flexural strength of lithium disilicate. Material and Methods: Eighty-four ... read moredisc-shaped IPS e.max Press (11.5mm diameter) were produced by investing and hot pressing according to manufacturer's recommendations, and divided to two main groups of 12 samples each. Set (A) comprised four groups made into four different core thicknesses (1.5mm, 1.25mm, 1.0mm and 0.8mm). Set (B) included three groups made into the same core thickness (0.8mm). Group 1 did not have a veneer layer, groups 2, 3, 4, 5, 6 and 7 were veneered with IPS e.max Ceram Dentin in layers of different thicknesses (0.25mm, 0.5mm, 0.7mm, 1.0mm, 1.5mm and 2.0mm respectively). The specimen's final thicknesses were adjusted and glazing procedures were performed onto the top surface of all specimens. All specimens were then immersed in artificial saliva for two weeks prior to testing. Biaxial flexural strength was measured using a piston-on-three-ball test carried out in a universal testing machine (Model 4204, Instron Corb.Canton, MA) with a crosshead speed of 0.5 mm/minute. Results: The mean strength and standard deviation for the studied groups were as follows (MPa ± SD). Group 1 exhibited the highest mean biaxial flexural strength value among all groups (266.96 ± 35.13), followed by group 2 (254.24 ± 37.89) than group 6 (253.81 ± 63.97). Group 3 and 5 exhibited similar mean flexural strength (231.53 ± 36.90) and (231.77 ± 40.55) respectively, followed by group 4 (228.25 ± 18.37). Group 7 exhibited the lowest mean value among all groups (199.68 ± 42.65). The result of One-way analysis of variances test was statistically significant P= .004. The result of post- hoc test (Bonferroni) indicated that there was statistically significant between group (6) and group (7). Conclusion: Within the limitations of this study, it can be concluded that different core/veneer ratios seem to affect on the flexural strength of lithium disilicate specimens but is not statistically significant. Furthermore, there is no statistical evidence that veneer layer thickness has an effect on a fixed core thickness of 0.8mm. However, when a 2.0mm veneer thickness was applied to a core, the mean biaxial flexural strength was significantly lower.
Thesis (M.S.)--Tufts University, 2012.
Submitted to the Dept. of Posthodontics.
Advisor: Yong Jeong Kim.
Committee: Kiho Kang, Sujey Rodriguez, and Matthew Finkelman.
Keyword: Dentistry.read less - ID:
- 05742440r
- Component ID:
- tufts:20366
- To Cite:
- TARC Citation Guide EndNote
