الفهرس 
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Abstract
The dentin is a complicated, mineralized, three-dimensional tissue, composed of several tubules, that extends from the pulp to the dentino-enamel junction, as well as intertubular and peritubular dentin. Its weight is distributed as 70% of its bulk in minerals, while the organic component and the fluids occupy 20% and 10% respectively.
The effective bonding of the bonding agent and the tooth structure determines the success of the composite resin restoration. When comparing enamel and dentin in regards to bonding, it is more difficult to bond to dentin due to its histological structure, water content, and organic tissue, where it is predominated by one type of collagen, occupying 90%, while the remainder consists of non-collagenase proteins like phosphoproteins and proteoglycans.
Dentin Etching prior to or during the application of adhesive systems exposes the collagen, thus allowing the adhesive monomer to infiltrate and encapsulate the exposed collagen fibrils, creating collagen – resin interface. This interface is the most vulnerable section of the bonded interface, in which most failures take place due to stress concentrations.
Attempts have been made, through research, to improve the mechanical properties of the adhesive interface. It was found that enhancement of this interface can be achieved by either the improvement of the intrinsic properties of dentin through biomimetic (tissue engineering) or through the induction of further formation of inter and intramolecular cross-linkers, by the use of extrinsic collagen crosslinking agents. The two most widely used materials are Chlorhexidine and glutaraldehyde, although their limitations and their drawbacks, such as cytotoxicity, tooth discoloration, and short affect potency.
Proanthocyanidin, on the other hand, is a natural cross-linker, that could be found in fruits, vegetables, nuts as well as seeds and flowers. For example, grape seeds, which is a Proanthocyanidin rich solution, were found to improve the mechanical properties of demineralized dentin, hence, the dentine resin interface.
Aim of the study:
This study aimed to evaluate the effect of collagen cross-linker Proanthocyanidin (PA) on:
- Nanoleakage of composite bonded to primary dentin surface
- Shear bond strength,
- THe length of the resin tags
Study design
In this experimental study, 28 teeth were intact, carries free human molar teeth, and teeth with any sign of crack or developmental defect were excluded
Sample groups
Thermocycling procedure:
All specimens were subjected to thermocycling, in an attempt to simulate the temperature changes that take place in the oral cavity, according to the International Organization for Standardization (ISO) TR11405 standard of 500 cycles, at 5° to 55 °C, with a 15-second dwell time.
c. Sample preparation Nanoleakage evaluation:
The occlusal cavity was prepared and bonded, samples from each group were used for nanoleakage analysis. The selected teeth were sectioned in an occluso-gingival direction into 1 mm slabs. Each slab was blot-dried and subsequently coated with two layers of transparent nail varnish leaving 1 mm exposed at the resin-dentin bonded interfaces. The slabs were then thoroughly rinsed in distilled water for 10 min. The rehydrated tooth slabs were immersed in 50 weight% ammoniacal silver nitrates (AgNO3) solution for 24 h in a dark environment, then the slabs were submerged in a photo-developing solution under a fluorescent light for 8 h to expedite the reduction of silver nitrate ions into metallic silver grains. The silver-stained bonded slabs were then polished with increasingly fine diamond pastes (2 μm and 1 μm). Subsequently.
The specimens were cleaned ultrasonically, air dried, affixed on aluminum stubs, left in a desiccator for 24 h, and carbon-coated. The interfacial nanoleakage of the mounted resin-dentin slabs was analyzed with a field-emission scanning electron microscope using the backscattered electron mode. Multiple images of the bonded interfaces were acquired per group.
The degree of interfacial nanoleakage was examined based on the amount of silver deposition along the bonded interface, scored using the method of Saboia et al 2008.
D. Measurement of Penetration of the Resin:
A sample from each group was prepared for SEM analysis. Then the samples were sectioned vertically through the resin build-up and dentine into two halves (mesial and distal) to expose the resin–dentine interface.
Specimens were placed in 4% NAOCL for 20 min followed by 20% HCL acid for 30 seconds rinsed with distilled water then all samples were sequentially dehydrated in ascending grades of ethanol i.e. 60%, 70%, 80% 90% alcohol for 20 min and in 100% alcohol for 1 hour.
Tested samples were dried, mounted on aluminum stubs, and then placed in a vacuum chamber, and sputter was coated with an aluminum layer and observed under a scanning microscope.
The specimens were observed with the scanning electron microscope to illustrate the resin-dentin bonding interface series of photos were taken field by field for view the dentine/resin interface. The length of resin tags was measured on the photographs by a caliper according to the scale given on the photograph.
Sample preparation for shear bond strength:
The extracted teeth were cleaned from any debris by scrubbing and stored in distilled water until the sample size is achieved then were split into two halves (buccal and lingual &palatal) and were embedded into the acrylic resin mold with the buccal, lingual or palatal surface facing upwards. The surfaces were ground flat under a copious amount of coolant water to remove enamel and expose dentin. The flat dentin surfaces were acid-etched for 15 sec with 37% phosphoric acid, and then teeth were randomly divided according to the treatment and bonding system used.
Each group received a different treatment after being embedded in acrylic. The first group, after etching with total-etch, received a primer-bonding, the second group, after being etched with total-etch, rinsed and s GSE applied for 10 minutes, and then bond was applied. The third group was etched with self-etch, And the fourth group was etched with self-etch, rinsed and the GSE was applied for 10 minutes, and then the bond was applied
then all groups received cylindrical composite resin with a 3-mm diameter and a 2- mm length. The specimens were stored in distilled water until subjected to a testing procedure.
All the completed specimens were subjected to a shear bond strength test using a universal testing machine. Loads were applied until restoration failure occur. A load of failure was measured by Newtons.
B. Fracture Mode Analysis:
Failure mode was observed under a light microscope and classified as cohesive, adhesive, or mixed.
• Statistical Analysis:
The mean of nanoleakage percentage in Total Etch Groups increased from (19.81±3.88) in the control group (Tc) to (25.16±4.90) in the grape seeds group (T-GSE), and this increase was not statistically significant (P < 0.05) whereas Self- Etch Groups According to the results, the mean of nanoleakage percentage increased from (13.10±2.49) in the control group (Sc) to (18.93±3.65) in the grape seeds group (S-GSE), and this increase was statistically significant Depending on the means we can arrange the groups (Descending order) as the following T-GSE > Tc > S-GSE > Sc.
The mean of shear bond strength in Total etch groups increased from (8.96±2.23) in the control group (Tc) to (12.20±3.61) in the grape seeds group (T-GSE), and this increase was not statistically significant (P < 0.05). whereas the mean of shear bond in Self-etch groups increased from (6.65±2.82) in the control group (Sc) to (11.81±4.68) in the grape seeds group (S-GSE), and this increase was statistically significant Depending on the means we can arrange the groups (Descending order) as the following T-GSE > S-GSE > Tc > Sc
The length of resin tags in total-etch groups is greater than the self-etch groups. Thus, from SEM observation of resin tag length, we can arrange the groups (Descending order) as the following T-GSE > Tc > S-GSE > Sc.