الفهرس 
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Abstract
SUMMARY
This In vitro study was designed to evaluate the effect of different endocrown materials used for restoring pulpotomized primary molars, on their Fracture Resistance and Marginal Adaptation.
Twenty four extracted human maxillary left second molars, with at least one third of their roots remaining, and at least three of their axial walls intact, without visible fracture lines or cracks were selected based on the teeth having similar (BL) and (MD) Dimensions. The teeth specimens were cleaned and disinfected then stored in distilled water until required to undergo experimentation.
Pulpotomy procedure was done for the specimens followed by obturation with compatible medicament, a layer of reinforced Glass ionomer was placed to seal the orifice and block undercuts.
The selected teeth were divided into three groups randomly, according to the type of material used to fabricate endocrowns.
group (A):
n= 8 was restored by CAD/CAM Milled Hybrid Ceramics (VitaEnamic)
group (B):
n= 8 was restored by CAD/CAM Milled Poly-methyl methacrylate (Telio CAD).
group (C):
n=8 was restored by Nano hybrid Composite resin (Filtek Z250) using an Indirect Technique.
A mounting surveyor was used to ensure upright position of teeth in moulds which were filled with non-shrink epoxy resin. Then all teeth were kept in separate closed vials containing distilled water according to grouping.
For all specimens, the milling surveyor was modified such that a straight hand piece and stones could be mounted to ensure standard occlusal clearance of 2mm, and standard 8 degree divergence for all the axial walls.
For Groups (A) & (B) Endocrown restorations were fabricated using The CEREC AC system and milled from VITA ENAMIC blocks, Telio CAD blocks respectively. The restorations were then polished and verified by measuring the occlusal thickness of each restoration.
Marginal Adaptation test was done before cementation, were a light microscope was used to measure the gap between Restoration and tooth surface; software was used to calibrate the measurements and to obtain the data in millimeters instead of pixels.
The tooth fitting surfaces were surface treated by 39% phosphoric acid etched and a bonding agent was applied.
Surface treatment of the restorations was performed following the manufacturers guidelines, for VitaEnamic: hydrofluoric acid and silane but for Telio CAD and Filtek Z 250 Composite groups sandblasting was done before cementation with resin cement.
Marginal Adaptation test was repeated after cementation of the specimens.
All samples were loaded in a universal testing machine until fracture occurred.
Independent student-t test was used to assess effect of cementation on marginal gap mean values of the endocrown materials on each group before and after cementation.
One-Way ANOVA followed by Tukey’s post-hoc test was used to assess the marginal gap mean values between the different endocrown materials either before or after cementation
Kruskal-Wallis test followed by Mann-Whitney U test were used to assess the fracture resistance between the different endocrown materials.
The results showed that:
1. Regarding the effect of cementation on marginal adaptation of each endocrown material: that within Vita Enamic and Indirect Composite groups, there was a statistically significant difference in marginal gap mean values before cementation (0.15±0.06 mm and 0.29±0.07, respectively) than those measured after cementation (0.23±0.08 mm and 0.47±0.13 mm, respectively) (P=0.007 and P=0.006, respectively). While within Telio CAD group, there was no statistically significant difference in marginal gap mean value before cementation (0.21±0.05 mm) than that recorded after cementation (0.31±0.06 mm) (P=0.068).
2. Regarding the effect of endocrown material on marginal adaptation before and after cementation there was statistically significant difference in marginal gap mean values between the different endocrown materials either before or after cementation (P=0.001 and P<0.0001, respectively). Before cementation, Vita Enamic group (0.15±0.06 mm) yielded the significantly lowest marginal gap readings; while Indirect Composite group (0.29±0.07 mm) yielded the significantly highest marginal gap values. The marginal gap values of Telio CAD group (0.21±0.05 mm) had no statistically significant difference from Vita Enamic and Indirect Composite groups. Whereas after cementation, Vita Enamic group (0.23±0.08 mm) displayed the significantly lowest marginal gap readings, but was statistically similar to Telio CAD group (0.31±0.06 mm); while Indirect Composite group (0.47±0.13 mm) showed the significantly highest marginal gap values.
3. Regarding fracture resistance test the results showed that there was no statistically significant difference in fracture resistance mean values (Vita Enamic: 1407.53±432.24 N, Telio CAD: 1399.98±264.18 N and Indirect Composite: 1215.17±207.63 N) between the different endocrown materials (P=0.375).