The internal fit and the marginal integrity of digital impression for FPDs
Ashtewi, Faisel Abdulhamid A
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PURPOSE: To evaluate the internal and the marginal gap of CAD/CAM milled three-unit Zirconia YZ framework and lPS e.max CAD using a digital impression. Compare the internal fit and the marginal gap of zirconia YZ and e.max CAD, which were milled using a digital impression using the same dies. MATERIALS AND METHODS: A typodont model with a missing mandibular right first molar was used. Occlusion was checked and adjusted using an articulating paper. Plastic Ivorine typodont teeth # 29, 31 were the abutment teeth. A 1.2mm chamfer margin preparation 360 degree was made on the abutment teeth using fine diamond burs. To insure the uniform reduction thickness in the occlusaI and the axial surfaces a silicone impression was made prior to the teeth preparation. An impression was taken for the lower ach with a light and medium body polyvinyl sioxanes (PVS). The impession was poured with resin-modified stone (epoxy stone). An impression was taken for the upper arch using medium body polyvinyl-siloxane (PVS) and poured with yellow stone. Casts were mounted in semi adjustable articulator. The prepared teeth, the opposing arch and the bite were scanned with a chairside Biuecam CEREC machine, software version 3.82. After the final dies image of the digital model was obtained, the process of designing the three-unit FPDs in CEREC Biuecam were the same, 5 samples of IPS e.maX and 5 samples of VITA YZ FPDs were milled using CEREC MC XL inLab. After complete the sintering, both VITA lnCeram YZ framework and IPS e.maX 5 samples were weighted using the digital weight scale. A test-fit silicon paste (Black Fit-Checke) was mixed according to the manufacturer's instructions and used to check the internal fit of the IPS e.max FPD frameworks and VITA inCeram YZ sample on the master cast, IPS e.maX FPDs and VITA InCeram YZ framework samples were weighed with the fit-checker. After checking the fit with black fit-checker, the thin film in the abutment was stabilized by injecting a white fit-Checker in and around the retainers for both VITA lnCeram YZ and lPS e.max samples. All the replicas were sectioned using a blade # 25 mesio-distally and bucco-lingually through the center of the molar and premolar. The marginal gap and the internal fit between the die and the restoration were measured using the optical microscope (Digitai Micro Hardness Tester CM700). For marginal gap measurement, four landmarks at the premolars and four landmarks for the molars were defined. The gap widths were measured as the perpendicular distance from the internal surface of the restoration to the reparation. Four landmarks at the middle of the axial walls, and four at the middle of the occlusal half were defined at the molar and premolar replicas. Measurements were performed using the optical microscope at magnification of 100. RESULTS: The weight of fit-checker for each material was measured from the different in the weight with and without the fit-checker. Knowing the weight of the fit-checker for each sample for the both materials (IPS e.max FPDs, VITA InCeram YZ) and the density of the fit-check, the volume was measured for each sample for the two materials. The mean was measured for VITA In Ceram YZ and it was 0.050 cm3. For IPS e.max, the mean was 0,03684 cm3. Data statistics for t-test method performed in Microsoft Excel for the internal gap of the two materials. Because the P-value was 0.005 (less than 0,05), there is a statistically significant difference between the mean internaI gap of the IPS e.maX and VITA InCeram YZ. After sectioning the die replicas, the mean marginal gap for lPS e.max was 58.72 (mu)m while the mean marginal gap for VITA InCeram YZ was 63.9 (mu)m. Data statistics for t-test method performed in Microsoft Excel for the marginal gap of the two materials. Because the P-value was 0.263 (more than 0.05), there is no statistical significant difference between the mean marginal gap of the IPS e.max and VITA inCeram YZ. The mean intimal gap for the IPS e.max was 200.025 (mu)m. The mean internal gap for the VITA InCeram YZ was 277.587 (mu)m. Statistical analysis using the t-test method was performed in Microsoft Excel for the internal gap of the two materials. Because the P-value was 8.93X 10_14 internal (less than 0,05), there is a statistical significant between the mean internal gap of the lPS e.max and VITA InCeram YZ. CONCLUSIONS: Within the limitation of this vitro-study, there is no significant difference in the mean marginal gap between the IPS e.max and VITA InCeram FPDs that were milled from a digital impression of the same dies (P=0.263).There was a signicant difference in the mean internal fit between IPS e.max and VITA InCeram YZ that were milled from a digital impression of the same dies (P=8.93X 1O_14). There was a significant difference in the mean internal volume between IPS e.max and VITA InCeram YZ that were milled from a digital impression of the same dies (P=0.263). The internal fit for IPS e.max and VITA InCeram YZ was clinically accepted.
PLEASE NOTE: This work is protected by copyright. Downloading is restricted to the BU community: please click Download and log in with a valid BU account to access. If you are the author of this work and would like to make it publicly available, please contact firstname.lastname@example.org.Dissertation (MSD) --Boston University, Henry M. Goldman School of Dental Medicine, 2014 (Department of Restorative Sciences and Biomaterials).Includes bibliographic references: leaves 60-67.
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