DNT-Theses-MSc

Permanent URI for this collectionhttps://iorep.miuegypt.edu.eg/handle/20.500.13071/12

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Assessment of fracture resistance of endodontically treated molars restored with endocrowns fabricated by two different materials : in-vitro study /
Bassyouni, Hanan Salah El Din,; Supervisor : Hussein Gomaa, Inas Mohsen El Zayat, Ahmed Mohamed Hoseny Fayed. Includes Arabic Summary.
This in vitro study was conducted to assess the fracture resistance of endodontically treated molars restored with endocrowns fabricated by pressed lithium disilicate and nanohybrid resin composite cemented by conventional etch and rinse resin cement. Forty mandibular second molars were collected according to the inclusion and exclusion criteria. Teeth were divided into four equal groups; Group (1): sound molars as a negative control (sound), Group (2): unrestored endodontically treated molars with occluso-mesial cavities as a positive control (unrestored), Group (3): endodontically treated molars with occluso-mesial cavities and lithium disilicate endocrowns (LDS) and Group (4): endodontically treated molars with occluso-mesial cavities and nanohybrid resin composite endocrowns (NRC). Teeth of unrestored, LDS and NRC were endodontically treated. All groups were embedded in self-cure acrylic resin blocks. Teeth of LDS, and NRC groups received a standardized occluso-mesial cavities. Each tooth of LDS and NRC groups were prepared for endocrown restorations and scanned using digital intraoral scanner. Casts were designed on a software and printed using 3D printer. For LDS group, restorations were designed using CAD/CAM software with same anatomy, 2 mm occlusal heights and 80 μm cement space. Wax patterns were milled, then sprued and invested to produce lithium disilicate endocrowns using heat pressed technique. For NRC group, four coats of 20 μm die spacer were coated on the 3D printed casts. Increments (2 mm) of nanohybrid composite were applied until building the entire shape and thickness using the silicon index. Nanohybrid resin composite endocrowns were removed after initial curing and subjected to additional dry heat curing. Lithium disilicate endocrowns were surface treated using 9.5% hydrofluoric acid followed by application of silane coupling agent. Nanohybrid resin composite endocrowns were sandblasted using 50 μm aluminum oxide particles followed by silanization. While teeth surfaces were etched using 37% phosphpric acid and total-etch adhesive. All endocrowns were cemented using conventional dual cure resin cement. Teeth of all groups were mounted to universal testing machine with a 6 mm diameter ball applying load perpendicularly to the long axis of the tooth to test the fracture resistance. Maximum force required for fracture were recorded in Newton. Fracture modes were also identified under stereomicroscope and divided into repairable fracture which extends above the CEJ and irreparable fractures which extends below the CEJ. Results of this study showed a statistically significant difference between groups (p< 0.001). Sound teeth presented the highest mean fracture resistance followed by NRC then LDS with statistically insignificant difference between the three groups. Unrestored teeth showed the least mean fracture resistance with a statistically significant difference to the other three groups. Mean percent recovery in fracture resistance of both test groups and fracture modes of all groups were also evaluated. Results showed that NRC has higher mean percent recovery than that of LDS, which emphasize the ability of NRC to restore 91.08% of the fracture strength lost after endodontic treatment and occluso-mesial cavity preparation. While LDS restored only 75.66%. On the other hand, Sound teeth showed the highest percentage of samples with repairable fractures (80%) followed by NRC (70%). While LDS showed unfavorable fractures of (80%).
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Clinical evaluation of self-adhesive bulk-fill composite versus conventional Nano-hybrid composite in cervical cavities : A randomized controlled clinical trial /
El-Shazly, Riham Kamal El-Desouky,; Supervisor : Mohamed Mahmoud AbdelMohsen, Inas Mohsen Gamil El-Zayat. Includes Arabic Summary.
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Color Change and Postoperative Hypersensitivity of Discolored Teeth Pretreated with Microabrasion before Bleaching using light versus chemically activated agents : Randomized Controlled Trial /
Shawky, Aya Khaled Mohamed,; Supervisor : Olfat ElSayed Hassanein, Asmaa Ali Mohamed Yassen, Inas Mohsen El-Zayat.
Dental aesthetics is considered an important concern that many patients seek for, aiming to reach an attractive smile. Tooth discoloration can be classified as the main etiological factor for esthetic problems in dental patients. It can be correctly evaluated and managed by detecting its type, location and intensity. There are two types of discoloration. Superficial extrinsic which is resulted from tea, coffee, smoking, wine and poor oral hygiene and it is considered the common type of dental staining. The second type is the intrinsic discoloration which is described as deep stains involving the inner dentin layer of the teeth and resulted from internal trauma , diseases , medications like tetracycline , over exposure to fluoride and aging .(1) Many techniques aid in improving tooth color such as whitening tooth pastes, professional cleaning and polishing by abrasive pastes, whitening strips and gels, enamel microabrasion by using abrasives and acids and bleaching techniques either internal or external. (2) Nowadays dental bleaching is one of the most dental procedures that can greatly overcome the problem of teeth discoloration. Generally, there are three different bleaching approaches including in office bleaching, at home bleaching and over the counter bleaching whitening products. Both in office and at home bleaching techniques are done under the dentist’s supervision in contrast to over the counter bleaching products. Each approach varies in concentrations of the bleaching agent and contact time of exposure. (3) Bleaching agents used in these bleaching approaches are hydrogen peroxide and carbamide peroxide which act as active ingredients. In office bleaching technique requires high concentration of hydrogen peroxide (25-35%) and short treatment time. On the other hand at home bleaching technique requires a low concentration of 10% carbamide peroxide which contains only 3% hydrogen peroxide and long treatment time. Despite, the great advancement in the field of dental bleaching, a lot of patients still suffer from heavy stained teeth that cannot be treated by applying the traditional high concentration bleaching agent even if it is combined with home bleaching. Hence, trials are being done to overcome this problem by enamel pretreatment using different acids or combined acids and abrasive particles as in the microabrasion technique. This technique aids to remove the porous surface enamel layer and any entrapped stains and increases the enamel surface energy that aids for more penetration of bleaching agents through these created micro pores. Enamel microabrasion can be done either by using acidic and abrasive agents such as (6% hydrocloric acid and silica or 37% phosphoric acid with pumice). It was claimed that this treatment is safe when combined with bleaching to achieve perfect smile appearance. Attaining and maintaining a lighter tooth color is the main goal of tooth bleaching, yet color regression usually happens after using hydrogen peroxide bleaching agent by time .(5) Thus, color change should be assessed immediately after bleaching and over an extended time period. Tooth color is a complex phenomenon that can’t be detected correctly by visual shade selection. Different color measuring devices are used for more accuracy such as spectrophotometer and colorimeter. Tooth is a biological unit in which other considerations rather than esthetics should be taken into consideration. Dental bleaching cannot be considered a successful technique when it leads to painful teeth. Sensitivity is one of the most common patients complain after vital tooth bleaching procedure. Hence, different desensitizing agents were added to some bleaching gels such as (fluoride and potassium nitrate) to overcome this problem. So that it was of value to evaluate the use of surface pretreatments as micro abrasion before bleaching on color change and teeth sensitivity.
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Comparative Study between Different Bleaching Techniques, in terms of color Stability and Postoperative Hypersensitivity : "A Randomized Controlled Clinical Trial" /
Abouelfotouh, Ingy Farag Ismail,; Supervisor : Adel Ezzat Khairy, Ola Mohamed Ibrahim Fahmy, Dina Mohamed Salah El Dine
Cosmetic dentistry is becoming one of the main concerns for most of the patients. Whiter teeth are believed to be associated with health or beauty.(1) Patients are demanding a ‘perfect smile’. Tooth discoloration has different etiologies; can be internal or external or combined. Intrinsic tooth discoloration can be due to remnants of pulp tissue trapped inside the pulp chamber, or due to internal bleeding of the pulp vessels due to trauma or systemic drug intake, while extrinsic stains results mainly from dietary factors and smoking. (2) Food containing stains as red wine, coffee and tea may cause development of stains, also carotene containing food as oranges and carrots and tobacco use either chewing or smoking will cause extrinsic stains.(3) Tooth discoloration could be treated by different treatment approaches starting from the least invasive method as whitening tooth paste, professional cleaning (scaling and polishing) to remove surface stains, internal bleaching of non vital teeth, external bleaching of vital teeth, micro abrasion of enamel with abrasives and acids, macro abrasives, crowns and veneers, which are the most aggressive method. (4, 5) Bleaching is one of the least aggressive modality that gained popularity. Mechanism of bleaching with hydrogen peroxide works by the breakdown of hydrogen peroxide (H2O2) molecules into hydroxyl free radicals. These free radicals attack the organic molecules in teeth and break the carbon double bonds into single bonds which ends up with teeth more lighter in color.(6) Although tooth whitening has been accepted as one of the least aggressive methods for treatment of tooth discoloration, tooth bleaching can be done either in office or at home or a combined method between inoffice and at-home bleaching. Some authors suggested that, (7,8,9) at-home bleaching is more cost effective, commonly used and provides better color stability. In-office technique was said to give better results and Introduction 2 owing to its short application time made it more requested by the patients.(10) In an attempt to overcome the drawbacks of in-office bleaching technique and the long exposure time of at-home technique, the combined bleaching technique which immerged. This technique is supposed to give better and more durable results in whitening teeth.(11,12) Also, it gives less exposure time to bleaching materials decreasing the susceptibility to hypersensitivity as side effect with the in-office bleaching technique.(13,14) However going “too far” with the bleaching process can result in some adverse effects as tooth sensitivity and gingival inflammation. Thus, the efficiency in terms of color change, color stability and safety in terms of tooth sensitivity had to be studied. Therefore, a randomized controlled clinical trial was done to assess which technique gives better results with minimal side effects.
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Comparison Between Color Stability of Different Bleaching Protocols Randomized single-blinded Controlled Clinical Trial /
AL-Ghonaimy, Hadeel Essam Ahmed Aboufotouh,; Supervisor : Adel Ezzat Khairy, Inas Mohsen ElZayat, Ahmed Mohamed Hoseny Fayed.
In the last two decades, the demand for esthetic treatment has increased tremendously. Factors such as the increase of patient awareness about minimally invasive and noninvasive aesthetic procedures and the paradigm shift in technological energybased devices caused the growth of the global medical aest hetics market. Bleaching is a chemical process characterized by oxidative decomposition of bleaching agents to remove external stains from the tooth surface to reach lighter tooth color. The teeth bleaching market has been divided into two main groups: inoffice bleaching and athome bleaching. Inoffice bleaching offers the patient less exposure time to the bleaching agent, more acceptable results, and professional control over the treatment process to ensure its effectiveness. High concentration hydrogen peroxide (25% to 40%) or carbamide peroxide (35% to 38%) are usually the agents used in the inoffice bleaching. They are activated either by chemical means or by using external energy sources such as blue colored halogen curing lamps, advanced LED light, or by light amplification by stimulated emission of radiation "LASER". The need for external activation of the bleaching gel is one reason for the high treatment cost. Chemical activated bleaching is one of the most common methods used to increase the efficiency of the bleaching process. Bleaching agents are unstable molecules that undergo dissociation once applied on the tooth surface. The idea behind chemical bl eaching is incorporating a catalyst such as some enzymes and salts of transition metals to bleaching agents before use in order to increase the rate of its dissociation and the formation of free radicals. It was proposed that the use of high-intensity light in bleaching acts as an accelerator for bleaching agents by increasing its temperature, thus improving the effectiveness of the treatment. This theory was first reported in 1918 by Abbot. There are various types of external light sources used in the bleaching process. Still, unfortunately, there are no sufficient studies that can show the difference in results between them, indicating the source with the most acceptable outcome. A LASER is defined as an intense beam of coherent monochromatic light generated by stimulated photons' emission from excited atoms or electromagnetic radiation. LASERs were introduced recently in bleaching to accelerate bleaching efficiency by enhancing hydrogen peroxide's oxidization effect, thus reducing patient chair time and increasing acceptance. LASER types used in teeth whitening are argon LASERs, diode LASERs of a wavelength of (810 nm – 980 nm), or Nd: YAG LASERs with a wavelength of 1064 nm. One of the greatest concerns after bleaching is bleached color regression. Authors addressed some potential adverse effects on enamel when they evaluated the effect of various bleaching systems on extracted bovine and human extracted teeth such as porosities, change in microhardness, and surface roughness of enamel. The presence of microscopic enamel porosities was found to be one reason that can cause color change. The change in surface topography of an alteration in calcium phosphate ratio of tooth structure will cause surface roughness and irregularities that will affect the color stability of bleached teeth. The rough surface will be more susceptible to retain stains, and color rebound will occur. Another concern is the post bleaching most prevalent drawback of inhypersensitivity which is the office bleaching technique. Although being the most prevalent drawback, the etiology of post ble hypersensitivity is not yet fully understood. There is a great controversy when it comes to state aching which mode of activation has the best clinical results in terms of color stability after aging. Therefore, this research was designed to assess the effect of three different in office bleaching on color stability and post bleaching hypersensitivity.
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Comparison of fracture resistance of endodontically treated molars restored by two different restorative techniques : An in vitro study /
Amer, Esraa Mohamed Mahmoud Sayed,; Supervisor : Mohamed Adel Ezzat Khairy, Ola Ibrahim Fahmy, Ahmed Mohamed Hosney Fayed. Includes Arabic Summary.
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Comparison of microleakage around resin composites restorations bonded to Er, Cr : YSGG laser treated enamel and dentin surfaces versus conventional acid etching : An in-vitro study /
Saad, Lobna Hamed Taha,; Supervisor : Olfat Elsayed Hassanein, Inas Mohsen El-Zayat. Includes Arabic Summary.
The aim of the current study was to determine the effect of Er,Cr:YSGG laser surface treatment on enamel and dentin compared to conventional acid etching on the marginal integrity of resin composite. Sixty-foursound human permanent molars were used in this study. Teeth were randomly divided into 4 groups, 16 each, according to the type of surface treatment used. Group (A) Universal Adhesive on enamel and dentin (etch and rinse strategy), group (B) Laser surface treatment on enamel and dentin, group (C) Laser surface treatment and etching on enamel and dentin and group (D) selective etch on enamel and laser on dentin. In all groups the cavities were then restored with resin composite. All groups were further divided into two subgroups; the specimens of the first subgroup for immediate evaluation after (24 hours) and second subgroup were subjected to 10000 thermal cycles between 5- 55°C proposed to represent approximately 1 year in vivo. The teeth were sectioned longitudinally in a buccolingual direction and observed under a stereomicroscope to determine microleakage. The results showed that there was no statistical significance obtained in both immediate groups (p-value =0.52) and thermocycle groups (p-value =0.20). Multiple comparisons cannot be performed because the overall test does not show significant difference across samples.
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Effect of Diode Laser Treatment and Nano-Desensitizing Agent on Degree of Tubular Occlusion : "In Vitro Study''
Gouda, Salma Raafat,; Supervisor : Ola Fahmy, Hussein Abdelfattah Gomaa.
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Effect of LED, Plasma Arc and CaCl2 on the solubility and water sorption of conventional GIC : (An in-Vitro Study) /
Amer, Nahla Ali Sayed,; Supervisor : Mohamed Mahmoud Abdelmohsen, Dina Wafik Elkassas, Kosmas Tolidis. Includes Arabic Summary.
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Effect of two different deproteinizing agents on microtensile bond strength between resin composite and deep dentin using two restorative protocols : An in-vitro study /
Ahmed, Mohamed Ayman Hamdy,; Supervisor : Makeen Amin Moussa, Hussein Gomaa, Ahmed Mohamed Hoseny Fayed. Includes Arabic Summary.
Bonding to deep dentin is considered a challenging procedure due to few intertubular dentin, increased number of dental tubules and difficult moisture control. One of the difficulties in achieving optimal hybridization in etch and rinse adhesive systems is the incomplete penetration of adhesive system into demineralized dentin leaving the collagen fibrils susceptible to enzymatic degradation. Deproteinization is a suggested method introduced to dissolve the organic smear layer and increase the mineral/organic ratio aiming to improve resin monomer infiltration and increase bond strength with dentin. Two deproteinizing agents, sodium hypochlorite (NaOCl) and bromelain enzyme showed the ability to remove collagen fibers from acid etched dentin. However, sodium hypochlorite showed several side effects such as the formation of a fragile zone, intolerable taste, unfavourable odour and cytotoxicity. While bromelain enzyme showed a deproteinizing effect without the side effects associated with sodium hypochlorite. The study used two different bulk-fill resin composite materials, a packable nanohybrid bulk-fill resin composite and a bulk fill flowable resin composite as a liner, to investigate their microtensile bond strength to deproteinized deep dentin. A total of 45 sound extracted human molars were selected for this study. The selected teeth were equally divided into one control group and four experimental groups (n=9). Group 1 (control): Acid etching + Bonding agent + Packable nanohybrid bulk-fill RC, Group 2: Acid etching + 10% NaOCl + Bonding agent + Packable nanohybrid bulk-fill RC, Group 3: Acid etching + 10% NaOCl + Bonding agent + bulk-fill flowable RC + Packable nanohybrid bulk-fill RC, Group 4: Acid etching + 10% bromelain enzyme + Bonding agent + Packable nanohybrid bulk-fill RC and Group 5: Acid etching + 10% bromelain enzyme + Bonding agent + bulk-fill flowable RC + Packable nanohybrid bulk-fill RC. The selected molars were embedded in self-cured acrylic resin blocks, occlusal surface was flattened to expose deep dentin, and resin composite was applied according to their corresponding groups. Teeth were sectioned to obtain marked central beams with a surface area (0.9 mmx 0.9 mm±0.1 mm for both dimensions and a height of 5.5±1. Marked beams were stored for 24 hours at 37oC in distilled water then subjected to microtensile bond strength testing using a universal testing machine. Their failure modes were also examined. The results showed that there was a statistically significant difference between the microtensile bond strength values of different groups (P-value <0.001, Effect size = 0.704). Pair-wise comparisons between groups revealed that Group 1 recorded the highest microtensile bond strength with a non-statistically significant difference from Group 4, but statistically significantly higher than other groups. Group 5 showed the least microtensile bond strength value of all tested groups. Failure mode examination showed different types of failure between the tested groups. The main failure mode in Group 1 and 4 was cohesive failure while Group 2, 3 and 5 adhesive failure mode predominated.
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Evaluation of fracture resistance of maxillary premolars with MOD cavities restored with different dentin replacement techniques : An in-vitro study /
Assar, Sara Magdi Ali Moustafa,; Supervisor : Khalid Mohamed Noaman, Inas Mohsen Gameel El Zayat, Mohamed Essam Mohamed Labib. Includes Arabic Summary.
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Fracture resistance of injectable composite versus packable composite in class II cavities : An in vitro study /
Gerges, Peter Medhat Youssef,; Supervisor : Makeen Amin Moussa Khalaf, Sameh Mahmoud Nabih Ibrahim, Mohamed Essam Mohamed Labib. Includes Arabic Summary.
Restoration of posterior teeth has been always a demanding procedure for both the dentist and the patient. Class II cavities pose great risks on the tooth and the restorative material as well. Detrimental occlusal stresses constitute one of the main causes of composite failure which is bulk fracture. The complexity of the procedure is not only limited to restoring proper tooth contact, contours and anatomy but also to restore the physiologic fracture resistance while respecting biomechanical concepts. Manufacturers have claimed that the recently developed injectable composites will provide a time-efficient solution while providing sufficient mechanical properties to withstand stresses in such cavities. However, there is lack of evidence regarding the fracture resistance of injectable composites as compared to conventional packable composites. Therefore, the aim of this study was to investigate and compare between the fracture resistance of teeth with small and large class II cavities restored with injectable composite versus packable composite. Therefore, the study tested the effect of restorative material and cavity size on fracture resistance. In addition, the study evaluated the failure modes of both restorative materials. Accordingly, extracted maxillary premolar teeth were divided into five groups. The first group was control with intact teeth. Second group was small class II cavities restored with injectable composite and the third group was large class II cavities restored with injectable composite. Fourth group was small class II cavities restored with packable composite and the fifth group was large class II cavities restored with packable composite. Small cavities were box-only while large cavities were occluso-mesial. Teeth were molded in cylindrical acrylic blocks. Fracture resistance was assessed by a universal testing machine that loaded the teeth axially at the marginal ridges of the restorations and the cuspal inclines as well. The loading tip was a four millimeters diameter stainless steel ball and the loading rate was 1 mm/min. Teeth were loaded until the first sign of fracture and the load was recorded in Newtons. Finally, the mode of failure of the fractured specimens were analyzed under stereomicroscope whether restorable or non-restorable fracture. Fractures were considered restorable if they were coronal or 1 mm or less apical to the CEJ. Fractures were considered non-restorable if they were more than 1 mm apical to the CEJ. Regarding the results, there were no statistically significant differences between the fracture resistance of all five groups. Moreover, there were no statistically significant differences between the failure mode of all five groups where most of the fractures were restorable. Further laboratory and clinical studies are required to reach a consensus regarding the use of injectable composites in stress-bearing cavities.
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Micro shear bond strength of resin based composite restorations to Er, Cr:YSGG Laser treated tooth surfaces versus conventional acid etching : an in vitro study
Shalaby, Ahmed Nabil Hassan,; Supervisor : Dina Wafik ElKassas, Sameh Mahmoud Nabih.
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Micro tensile bond Strength of resin composite to artificially demineralized dentin after remineralization by different remineralizing agents : In vitro study /
Fahmy, Sara Ibrahim Mohamed,; Supervisor : Ola Mohamed Ibrahim Fahmy, Sabry Abd El-Hamid El- Korashy, Mohamed Essam Mohamed Labib. Includes Arabic Summary.
The purpose of this In vitro study was to investigate the micro-tensile bond strength of resin composite restoration to proximal artificially demineralized dentin, and sound dentin compared to demineralized dentin after being remineralized with two remineralizing agents (NaF solution and eggshell nHAp) separately and combined using the universal bonding system. As well as evaluating the effect of the two modes of application (Etch-and-Rinse / Self-Etch) on the applied remineralizing agent and the micro-tensile bond strength of resin composite restoration. A total of 30 sound molars’ proximal surfaces were used in this study. The teeth’s occlusal enamel was removed till the DEJ to allow exposing the proximal DEJ, then the proximal surfaces were cut 3mm from the outer proximal enamel surface to allow working on the deep proximal dentin. The teeth were split into two halves parallel to the long axis (mesial half and distal half) to allow each tooth to be its own comparator regarding the bonding mode, all done using a water-cooled Sectioning IsoCut Wafering Blade mounted on IsoMet 4000 linear sawing (Buehler). Finally, the teeth were decoronated perpendicular to the long axis, the roots were discarded and the coronal samples were used in the study. Each deep dentin sample (mesial and distal halves) was fixed in pink self-cured acrylic resin cylinders; their proximal deep dentin surface facing upward and their pulpal surface in the acrylic, the samples were placed slightly above the acrylic resin surface by approximately 1 mm. Then each half was coded to make sure that each tooth was its own comparator regarding the bonding mode. The samples were stored in distilled water till the day of the study (2 days after samples preparation). The samples were randomly divided into five groups according to the remineralization protocols (G), positive control group (G1): the dentin was left sound without demineralization process or any surface treatment, negative control group (G2): the dentin surfaces were demineralized and left without any surface treatment, (G3) the dentin surfaces were demineralized then treated by 2% NaF solution as a remineralizing protocol, (G4) the dentin surfaces were demineralized then treated by eggshell nHAp as a remineralizing protocol, and (G5) the dentin surfaces were demineralized then treated by a combination of eggshell nHAp with 2% NaF solution as a remineralizing protocol. Each group was then further divided into two subgroups using the previous coding to make sure that each tooth was its own comparator regarding the mode of application of the bonding agent (B), where (B1) represents the Etch-and-Rinse mode, while (B2) represents the Self-Etch mode. Dentin artificial demineralization was done to all the groups except G1, using demineralizing gel {5 mL of 6% carboxymethylcellulose acid gel (0.1 M lactic acid titrated to pH 5.0 in a KOH solution) at pH 5.0 and 37 ◦C}. The deep proximal dentin surfaces were covered in gel for 48 hours without renewal. Where this model has been reported to supposedly provide a demineralized dentin similar to that of caries-affected dentin. After 48 hours the samples were rinsed with distilled water and air dried. Surface treatments were done to only G3, G4 and G5 as follow: G3: The surfaces were treated by a chemically prepared 2% NaF solution which was applied by a 1mm polyethylene plastic pipette and left on the surfaces for 1 min then blot dried. G4: The surfaces were treated by chemically prepared eggshell nHAp dissolved in distilled water (1.8 g of nHAp was mixed with 0.3 mL of distilled water), applied by a spatula, and left on the surfaces for 1 min then rinsed with distilled water and blot dried. G5: The surfaces were treated by a combination of eggshell nHAp dissolved in a 2% NaF solution (1.8 g of nHAp was mixed with 0.3 mL of 2% NaF solution), applied by a spatula, and left on the surfaces for 1 min then rinsed with distilled water and blot dried. In Etch-and-Rinse groups the pretreated dentin surfaces were etched with Meta Etchant 37% phosphoric acid semi-gel for 15 seconds, rinsed for 10 seconds, and blot dried. Then for both groups (Etch-and-Rinse and Self-Etch) 3M™ Single Bond Universal Adhesive was applied following the manufacturer instructions. Then 3M™ Filtek™ Z350 XT Universal Restorative (A3 Body Shade nanocomposite) was used to build a 3-4 mm composite block on the deep dentin surfaces and it was measured using a periodontal probe. The samples were then kept in artificial saliva for 24 hours before sectioning. The samples were transferred to the IsoMet 4000 Linear Precision Saw (BUEHLER, Ltd., Lake Bluff, IL, USA) to allow sectioning of each surface longitudinally in horizontal cuts, then vertical cuts using a Sectioning IsoCut Wafering Blade to create rods, of similar cross sectional area (1mm x 1mm). The rods with dentin thickness 2-3 mm were chosen for each group, specimens that showed pretest failures were not included (n = 9). A total of 72 rods for 8 subgroups were collected and stored in distilled water. Each beam was then mounted to the Gerald Eli’s jig to allow micro tensile testing. The results of the current study revealed that the bond strength of resin composite restoration to negative control group (G2) proximal artificially demineralized dentin without any surface treatment showed the worst results with pretest failure, and that all surface treatments done regardless of the type of the remineralizing agent (G3, G4, G5) showed an improvement in the bond strength to be similar to positive control (G1) sound dentin. The NaF solution group (G3) and the eggshell nHAP group (G4) when used separately showed the highest results and weren’t affected by the different bonding modes. While the combined group nHAP and NaF (G5) showed less results, yet it showed improvement in comparison to the untreated dentin surfaces. As well as it was affected by the etching step in the Etch-and-Rinse mode, therefore it showed better results when used with universal adhesive in Self-Etch mode.

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