الفهرس 
Dental Ceramics
Lithium Disilicate CeramicsOnly 14 pages are availabe for public view
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Abstract
Bonding of indirect esthetic restorations to the tooth structure
remains a challenging matter, as the bonding interfaces are increased with
the indirect restorative procedure. It is essential to improve the bond strength
between the indirect restorative materials and cements, since they are the
principal factors in the success of resin-bonded fixed dental prosthesis.
The present study was designed to assess and evaluate the effect of
aging on the μTBS of resin cement to two recent CAD/CAM hybrid esthetic
materials which are zirconia-reinforced lithium silicate ceramic (Celtra TM
Duo) and hybrid resin nano-ceramic (Cerasmart TM) using 2 surface
treatment protocols; hydrofluoric acid etching and sandblasting, both were
followed by silanization.
Plates were cut from each ceramic material block. Then, the Celtra
TM Duo plates were placed inside the ceramic furnace for further maturation.
Then, one surface of each ceramic plate was polished using (400, 600) grit
SiC paper followed by ultrasonic cleaning in distilled water for 5 minutes. A
plate from each material was treated with HF-acid etching and the other
plate was sandblasted according to the manufacturer’s recommendations.
Then, SEM examination was carried out. Finally, all the plates received a
silane coupling agent application.
A Teflon mold of dimensions similar to the cut ceramic plates was
fabricated to prepare the composite plates. Another Teflon mold of 6.1 mm
thickness was fabricated where the treated ceramic plate was placed inside it,
followed by generous application of adhesive resin cement on the ceramic
plate then the composite plate was placed above the resin cement, and finally
a fixed load (500 gm) was positioned and was light cured using Blue-phase LED unit from each side to ensure optimal polymerization. The resinceramic
blocks were stored in distilled water for 24 hours. Then, the blocks
were fixed on epoxy resin cylinders.
Each resin-ceramic block was vertically sectioned into serial slabs.
Then, it was rotated 90◦ to make additional vertical cuts so that the resinceramic
block has perpendicular cuts in order to obtain a thin long microbeam
using Isomet 4000. Twenty micro-beams were obtained from each
block excluding the use of the peripheral slices to avoid slices with an excess
or a deficient amount of resin cement at the interface. Half of the microbeams
from each subgroup (n=10) was tested after 24 hours storage in
distilled water, and the other half (n=10) was tested after being subjected to
5000 cycles of thermocycling between 5 and 55 °C with dwell time of 20
seconds in each bath. After that, all the specimens were subjected to a tensile
load in the universal testing machine to gather data about the μTBS before
and after aging. Finally, data were statistically analyzed.
The results showed that aging (thermocycling) dramatically affected
the mean μTBS of both ceramic materials. There was a statistically
significant decrease in mean μTBS after aging. Using either Celtra Duo TM or
Cerasmart TM, whether with hydrofluoric acid or sandblasting, there was a
statistically significant decrease in mean micro-tensile bond strength after aging.
But hydrofluoric acid showed higher mean μTBS than sandblasting after aging.
Regarding the effect of surface treatment, Hydrofluoric acid showed
statistically significant higher mean μTBS than sandblasting. Using Celtra
Duo TM before aging, there was no statistically significant difference between
mean μTBS values of the two surface treatments. After aging, Hydrofluoric
acid showed statistically significant higher mean μTBS than sandblasting. Using Cerasmart TM whether before or after aging, Hydrofluoric acid showed
statistically significant higher mean μTBS than sandblasting.
Regarding the effect of the type of the ceramic material, Celtra TM
Duo showed statistically significant lower mean micro-tensile bond strength
than Cerasmart TM before aging. After aging, there was no statistically
significant difference between the two ceramic types.