Thesis (M.Sc.) - Cairo University - Faculty of Oral and Dental Medicine - Department of Prosthodontics

The aim of this in-vitro study was to evaluate the marginal adaptation and internal fit of Zirconia reinforced Lithium silicate crowns fabricated with heat pressed 2Celtra Press3 ingots compared to crowns fabricated with milled 2Celtra Duo3 blocks. Methodology: Ten (n=10) zirconia reinforced lithium silicate crowns were studied and divided into two groups (n=5) according to fabrication method; Heat pressed group (Celtra Press ingot) and Milled group (Celtra DUO blocks). A stainless steel die was prepared according to the customary all-ceramic tooth preparation criteria. The metal die was scanned by intraoral scanner (CEREC Omnicam). Group I (n=5) was constructed by means of heat pressing of milled wax patterns (Bilkim CAD wax) into Celtra Press ingots. Group II (n=5) was milled by milling machine (CEREC MC XL) from Celtra DUO blocks. Each crown was placed on the metal die and the vertical marginal adaptation was measured by direct viewing method by means of a stereomicroscope with a fixed magnification of 45x. The internal fit of crowns was measured using silicone replica technique.Data were statistically analysed by 1-way ANOVA, followed by the Tukey honestly significant difference test (P < 0.05). vii Results: The mean values of vertical marginal misfit were 24.69 ± 1.28 om for the heat-pressed group and (24.23 ± 1.26 om) 39.2 8.7 mm for the milled group, with statistically non-significant difference between both groups as indicated by t-test (p=0.7755> 0.05). Regarding the internal fit, regardless to measurement surface it was found that the milled group recorded higher internal gap mean value of 93.94 ± 1 om than heat pressed group mean value of 60.77 ± 6.3 om. There was statistically significant difference between both groups in terms of internal fit as indicated by t-test (p= <0.0001< 0.05)

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