In this in-vitro study, 60 maxillary anterior teeth extracted 3 months before the study were selected. The teeth had no cracks, carious lesions or coronal restorations. After removing the tissue remnants, the teeth were rinsed under running water and im- mersed in 0.5% chloramine T solution. Then the teeth were immersed in distilled water (Shahid Ghazi Co., Tabriz, Iran) at room temperature for 24 hours before the experiment. The roots were cut at 2 mm apical to the CEJ using M016-878 di- amond bur (SS White Inc, Lack Wood, USA) and high-speed handpiece with air and water spray. The pulp of the coronal segment was removed. The samples were placed in molds measuring 35×25×10 mm, containing translucent acrylic resin (Marlic Med Co., Tehran, Iran), with the labial surfaces facing outward. The samples were placed in cold water in order to control the heat generated during the polymerization of the acrylic resin. The enamel labial surfaces with 4×4 mm dimensions were polished with wet 400- and 600-grit silicone papers to achieve a flat homogeneous labial sur- face in all specimens.
dried. Finally, compositeresin build-up procedure was done. All the bleached surfaces were etched by using 37% phosphoric acid gel for 15 seconds (Total Etching Gel; Ivoclar Vivadent, Schaan, Liechtenstein). Then they were rinsed with water spray for 15 seconds, Adper Single Bond (3M ESPE; Dental Products, St Paul, MN, USA) was applied, and light-cured by an LED unit (Demi Plus; Kerr, Switzerland) for 20 seconds at a light intensity of 1200 W/cm 2 . Finally, the restoration proce- dure was done with compositeresin (Filtek Z350; 3M Dental Products) by using a Teflon mold (5×2 mm). They were light-cured for 20 seconds by the same LED light-curing unit. All the samples were immersed in distilled water at room temperature for 24 hours. For measuring the shearbondstrength, the samples were placed in a universal testing machine (ZwickRoell Test- ing Machine Z020; Germany) with a blade-shaped tip, and the force was applied to the compositeresin‒enamel interface at a crosshead speed of 0.5 mm/min (Figure 1).
oxygen free radicals. The findings of our study showed equal antioxidant efficacy of grape seed and sodium ascorbate, which is in accord with the results of Vidhya et al,  and Sharafeddin et al, . Two in-vitro studies demonstrated that grape seed extract inhibited the demineralization and enhanced the remineralization of carious root lesions [4,33]. The results of microscopic analysis confirmed the findings of shearbondstrength testing in our study, since group 2 with the lowest bondstrength value had the highest frequency of adhesive failure. In the current study, antioxidants were applied in the form of solution. Use of antioxidants in the form of hydrogel is recommended in future studies. In the current study, antioxidants were used for 10 minutes. Other studies are required to assess the effect of higher concentrations of antioxidants with shorter application times. Since antioxidants have a short shelf life, future studies are recommended to focus on the storage methods of antioxidants. The current study had an in-vitro design and clinical studies are needed to further elucidate this issue.
Aims: Residual peroxide on the enamel surface and in the interprismatic spaces decreases the shearbondstrength (SBS) of composite to bleachedenamel. Evidence shows that 10% sodium ascorbate can efficiently neutralize the singlet oxygen generated by the bleaching agents. This study aimed to assess the effect of duration of application of sodium ascorbate on SBS of composite to bleachedenamel. Materials and Methods: This in vitro experimental study was conducted on 30 sound human third molars, which were randomly divided into three groups (n=10). In group 1, the teeth were bleached for 45 minutes and were then subjected to immediate bonding and restoration with compositeresin. In groups 2 and 3, the teeth were bleached, immersed in 10% sodium ascorbate solution for 5 (group 2) and 10 (group 3) minutes and were then bonded and restored with composite, and the SBS was then measured. Results: The highest SBS (14.02±8.6MPa) was noted in group 3 (immersion in 10% sodium ascorbate for 10 minutes before bonding). The lowest SBS was noted in group 1 (immediate bonding after bleaching) (p<0.05). The difference in SBS of groups 1 and 2 was not significant (p=0.4). Conclusion: Application of 10% sodium ascorbate for 10 minutes increases the SBS of composite to bleachedenamel.
Since, there is a limited information available on the use of the newer natural antioxidant agents like Oligomeric Proanthocyanidin Complexes (OPCs) that they increases the bondstrength of compositeresin to bleachedenamel. OPCs present in natural antioxidants like grape seed extract and pine bark extract have free radical scavenging activity 4 ,36 . Hence, the aim of this in-vitro study was to evaluate and compare the effect of 10% Sodium Ascorbate , 10 % pine bark extract, and Aloe vera leaf solution on the SBS of compositeresin to bleachedenamel.
Perhydroxyl radicals are not only associated with high permeability and diffusibility but also split the long chained, dark colored macromolecules of pigments into smaller, less colored and more diffusible molecules which are removed from the structure producing the bleaching effect. Following bleaching, these free radicals react with the organic enamel and can result in morphological alterations, surface irregularities and reduced bondstrength of compositeresin to enamel.
Various researchers have demonstrated that 2 minutes of etching with 10% HF gel is the best method for increasing the bondstrength of resin to feldspathic ceramic [3, 23]. Yadav et al, in 2010 reported the highest micro-shearbondstrength values in feldspathic porcelain surface etched with hydrofluoric acid and coated with silane agent. Samples treated with airborne-particle abrasion with alumina and application of silane agent ranked second in this respect. The mode of failure was cohesive in porcelain similar to the present study result . Thus, this method was selected for the control group in our study. In the present study, two-part silane was used since the atmospheric humidity is not optimal for the pre-hydrolyzed (one part) silane . In a study by Khoroushi and Motamedi the bondstrength achieved after Ceramco3 porcelain surface treatment with HF and silane was almost similar to that in the present study although samples were subjected to 5000 thermal cycles in the present study whereas only 1000 cycles were used in theirs .
significantly influence enamelbondstrength, but had an important effect on bonding to the dentin, and ethanol-based bonding produced better bondstrength compared to acetone-based systems . Miyazaki M et al. also found that shearbondstrength clearly reduced, when bonding was ap- plied to samples immediately after bleaching . Results of the present study also showed a signifi- cant reduction in shearbondstrength of composite to bleached tooth (immediately restored) compared to unbleached tooth. Bonding systems used in the present study were Clearfil SE bond and Single Bond, but in samples that were washed in water and bonding applied 24 hours after bleaching, only a small reduction was observed, which was statisti- cally insignificant. Researchers have proposed that if samples are kept in water for 24 hours after bleaching, shearbondstrength to enamel in self- etch systems will be less affected by bleaching ma- terials. In the present study also, in case of Single Bond, shearbondstrength was significantly re- duced after bleaching, but the level of resin poly- merization did not reach zero. This can be attribut- able to its ethanol-based solvent which was able to reduce the effects of the superficial oxide layer. Therefore, complete polymerization of the resin was not impeded. In Clearfil SE Bond, reduction in bondstrength was also evident, though not statisti- cally significant. In this case also, the alcohol present in HEMA was able to lower the effects of oxide layer to some extent. However, the higher bondstrength of Clearfil SE Bond after bleaching is thought to be associated with the presence of two alcohol layers in HEMA, both in the first layer and in the bond, which can react with more free oxygen radicals and neutralize them. Perhaps, it could also be explained in the following manner; in Clearfil SE bond, when applying the first layer, nearly 20 seconds time elapses, which allows bet- ter infusion of solvent, and since it is not washed off, the 10 MDP and HEMA present in the first layer cover the superficial oxide layer and conse- quently prevents its negative effects reaching the second layer of bond. While in the case of Single Bond, the phosphoric acid that is used at the be-
This study investigated the influence of the waiting time for placing resincomposite (RC) restorations after dental bleaching on the shearbondstrength (SBS) to enamel. Seventy bovine incisors were obtained, of which 60 were stained in coffee solution for 1 week and then bleached with the whitening agent Lase Peroxide Sensy (DMC Equipments, Brazil), following the manufacturer directions of use. Next, all teeth were allocated into seven groups (n = 10) according to the waiting time after bleaching for placing the RC: immediately (0 h), 24 h, 3, 7, 14 and 28 days (d). Ten teeth were not bleached to serve as control. The specimens were prepared for SBS test and also for failure mode analysis. Scanning electron microscopy images were taken in non- bleached and bleached specimens. Data was analyzed by one-way ANOVA and Tukey’s test (α = 0.05). The SBS means (standard deviations), in MPa, were: control = 8.5 b (5.8);
Studies have examined the physical alteration after bleaching to find a possible explanation for decrease in enamelbondstrength caused by bleaching agents. Titley KC et al also suggested that the reduction in bondstrength might be related to the presence of residual hydrogen peroxide at or near the enamel surface which interfered with resin attachment and inhibited resin polymerization. (28) There are more studies that have described this effect. (29,85) The loss of calcium and alterations in the organic substance might be important factors to cause a decrease in enamelbond strengths. (37) Rotstein I et al suggested that bleaching agents changed the original ratio between the organic and inorganic components of the tissues and increased their solubility. (41) Also, Bistey T et al reported that at-home and in-office peroxide- containing bleaching agents are capable of causing structural alteration in enamel at low and high concentrations as well. (62) These studies probably explains the reduction in shearbondstrength after office bleaching.
Several studies investigated the effect of adding different amounts and sizes of apatite powder to GIC for improving the physical property of this cement. [19-22] These studies demonstrated that GICs containing hy- droxyapatite exhibit better mechanical properties and higher bondstrength to dentin than the conventional GICs. A study reported that hydroxyapatite-reinforced glass-ionomer, 75wt% of glass-ionomer and 25wt% of hydroxyapatite, exhibited the highest bondstrength to dentin.  It has been demonstrated that adding nano- hydroxyapatite (nano-HA) to glass-ionomer shows higher bondstrength to tooth structure compared to mi- cro-hydroxyapatite (micro-HA). The decreased size of nano-HA particles, similar to that of the minerals in tooth, leads to increased surface area and higher solubil- ity, filling the enamel defects with higher performance ;this phenomenon occurs through releasing calcium and phosphate ions and by increasing the bondstrength be- tween the tooth and the restorative material. 
20 Prevention (CDC) has adopted guidelines for infection control of extracted teeth used for research and teaching. These guidelines require that teeth not containing amalgam be heat-sterilized by an autoclave cycle for 40 minutes before use. Teeth that contain amalgam should be stored in 10 percent formalin for two weeks before use. Although autoclaving does not seem to alter the tooth's physical properties sufficiently for research purposes, it is unknown whether autoclaving affects the chemical and micromechanical relationship between dentin and dental. In this study, we investigated the effect of storage conditions and sterilization methods on the composite-to-dentin bondstrength. Within the rotations of this study, we can draw the following conclusions. When storage solutions alone are compared, 0.9 percent NaCl and 5.25 percent NaClO resulted in significantly lower SBS values an those obtained with H 2 O 2 . Therefore,
This in-vitro study was conducted on 18 premolar and 18 incisor teeth extracted for orthodontic, periodontal or prosthetic treatments. The teeth had to be free from caries, restorations, enamel defects (hypoplasia or use of forceps) and fractures since the aim of this study was to assess the compositeresinbond to sound enamel. After washing and removal of tissue appendages, the teeth were immersed in 0.5% chloramine T solution and then stored in saline until the experiment (maximum of 6 months). For preparation of specimens, the premolar and incisor teeth were each randomly divided into three groups of 6 and then the 3 incisor and the 3 premolar groups were randomly combined in such way that eventually 3 groups of 12 teeth including 6 premolars and 6 incisors were created. Next, enamel of the buccal surface of the teeth was ground using a disc in such way that a plastic cylinder containing composite measuring 3mm in diameter and 3mm in height could be placed on the enamel surface. Next, the specimens were mounted in Acropars auto polymerizing acrylic resin (Marlic, Tehran, Iran) in molds (specific for Instron machine) up to the level of the cementoenamel junction in such way that the composite-buccal surface interface was parallel to the lateral surfaces of the mold in order for the blade to apply load perpendicular and directly to the resin-tooth interface.
Resin based composite cements are the cements of choice for the adhesive luting of ceramic restorations. 6 Resin cements are capable of producing micromechanical attachment to the tooth structure. 20 Two types of resin cements available are dual-cured and light-cured resin cement. 27 Light- cured cements have some proven advantages in that working time is increased, the ability to remove excess cement is facilitated and this reduces the finishing time. 27 Dual-cured cements traditionally are used when ceramic thickness does not allow light penetration for maximal conversion of the luting cement. 30,43 Disadvantages of dual-cured cements include porosity from mixing, reduced working time, decreased degree of conversion and color instability due to amine degradation. 27 In accordance with the literature, the present in vitro study used a dual-cured resin cement for the bonding of ceramic blocks (5 x 5 mm) onto the surface treated tooth samples.
In the present study, green tea solution was used as an antioxidant at 5% concentrations for 10 minutes. Significant increase was observed in SBS of resincomposite to 38% hydrogen peroxide bleachedenamel in group B2 (hydrogen peroxide + green tea), but there were no significant increase in SBS of resincomposite to 15% carbamide peroxide bleachedenamel in group A2 (carbamide peroxide + green tea). In the study mentioned above, the different types, concentrations and application times of antioxidant used might explain the differences noticed in the results. In the present study, 15% carbamide peroxide and 38% hydrogen peroxide were used as a bleaching agents but in the above mentioned study, 17% carbamide peroxide was used. This difference, i.e., 17% carbamide peroxide with 38% hydrogen peroxide, might be the underlying reason for producing more peroxide molecules and hence this could be the reason for greater effectiveness of antioxidants on the SBS of resincomposite to the bleachedenamel.
Vital tooth bleaching which is a routine treatment in modern dental practice is accomplished by either an at-home technique or in-office procedures with high-concentration bleaching agents [1,2]. Although the clinical effectiveness of tooth bleaching has been demonstrated extensively , there are some concerns about potential complications. Whitening agents have adverse effects on the dental pulp [4,5] may decrease micro-hardness of the bleached substrate , and have deleterious effect on bondstrength of the resin materials [7,8]. One of the theories regarding the deleterious effect of bleaching on the bondstrength of resin materials is related to the decrease in bondstrength with the free radicals from oxygen that remain in the dental tissues released by the bleaching agents. After an adhesive system application, the oxygen responds to the closures of the forming polymeric chains, finishing the polymeric extension, lessening the level of transformation of the adhesive system and resin composites and declining the bond quality . The use of bleaching techniques modified by a remineralizing agent called CPP-ACP (casein phosphopeptide amorphous calcium phosphate) has been suggested in an attempt to recover minerals that are lost during bleaching . A recent study revealed that the associative utilization of CPP- ACP and high concentration hydrogen peroxide may be a fruitful strategy for diminishing tooth sensitivity and restricting changes in the enamel morphology during in-office bleaching . Another modification is using fluoride with bleaching agents to prevent either hypersensitivity or demineralization accompanying tooth-whitening therapy. The addition of sodium fluoride to the bleaching agent was found to generate fluoridated hydroxyapatite and calcium fluoride crystals on the enamel surfaces, which potentially accelerated the remineralization of the bleachedenamel . But there is inadequate evidence on the influence of hydrogen peroxide and CPP-ACP on composite-enamel bonding. Additionally, despite profound scientific suggestions which support the remineralization capability of fluoride , the impact of fluoride on resin–enamel holding is dubious. Decreased resinbondstrength has been reported for fluoride-treated enamel, particularly
still not clear, the reduced bondstrength of bleachedenamel has been related to the presence of residual free radicals due to the breakdown of hydrogen peroxide [14, 18] and alter- ations in the enamel composition and structure [6, 19] fol- lowing the bleaching treatment. The residual oxygen in the interprismatic spaces can hamper resin infiltration and in- hibit resin polymerization . Moreover, morphological and compositional changes (e.g., porosity, loss of enamel prismatic form, loss of calcium, and changes in organic sub- stances) in the enamel may weaken the adhesive interface and compromise bondstrength [21, 22]. Therefore, bonding procedures should not be performed immediately after bleaching treatment . A waiting period of 1–3 weeks has been advocated by various researchers [21, 24, 25]. In addition to the delayed bonding procedure, the application of antioxidant agents (e.g., sodium ascorbate, sodium bi- carbonate, and grape seed extract) [18, 26, 27] and laser ir- radiation [28, 29] have been proposed to restore the compromised bondstrength of bleachedenamel. By neu- tralizing residual free radicals  and promoting micro-retentions in the enamel surface , antioxidant agents and laser irradiation have been shown to reverse the reduced bondstrength between the compositeresin and bleachedenamel. However, it is important to point out that most of the above-mentioned studies measured the bondstrength without thermocycling [24–29]. Ther- mocycling is the in vitro process of subjecting a restor- ation and tooth to temperature limits similar to those experienced in the oral cavity . It would be of interest to investigate the effects of thermocycling on the bondstrength between the composite resins and the bleachedenamel.
Use of nanotechnology for the fabrication of composite resins with unique properties is among the most important achievements in dental material science . It has been documented that nanoparticles have superior physical, chemical, mechanical and optical properties compared to microparticles and they have been used to manufacture dental materials with high mechanical properties and antimicrobial effects . Curcumin is a yellow, active ingredient of turmeric, which is derived from the underground stems of Curcuma longa. It is used not only as a spice, but also as a medicinal herb for treatment of many conditions . Curcumin inhibits the growth and proliferation of many bacterial strains such as staphylococci, lactobacilli and streptococci .
Abstract- Objective: to evaluation the effect of different surface treatment on shearbondstrength between composite increments to determine the most effective procedure that increase bondstrength between composite increments Methods: four groups used in this study and each group consist of 20 blocks of composite, The block made at the same dimension: (3mm, 3mm, 2 mm) made from 3M Nano Hybrid Z 250XT.1 st group: include Oxygen polymerization inhibited samples. 2 nd group: include sample that inhibit the formation of Oxygen polymerization inhibited layer by utilize strip.3 rd group: include the samples that uses3M one bottle self etch bond that contain silane . 4 th group: include surface grinding of first composite increment by turbine diamond bur, each of these four groups composite from 20 block of composite . Using VALO Cordless curing light for composite increment curing. Results: the mean of bondstrength for first group is 32.14 ± 1.148 Mpa , second group 30.75 ± 1.854 Mpa, third group 13.73 ± 1.301 Mpa and last group 19.67 ± 1.919 Mpa. The one way ANOVA (F-test) utilized to identify the significant differences between the four groups , L.S.D was apply to compare the differences of two groups as multiple comparison. The higher shearbondstrength in group cotain oxygen inhibiter layer and group use one bottle bond (saline) group,and lowest mean result of group that Inhibit oxygen inhibiter layer formation and surface grinding groups. Conclusions: the shearbondstrength between composite increment increase when there is oxygen inhibiter layer on the composite surface and also increase when used one bottle bond agent contain silane while the absence of oxygen inhibiter layer lower the bondstrength between the increment when add another composite layer. also the rough surface gave better bondstrength result compared to smooth surface.
Administration of topical agents containing fluoride or casein phosphopeptide-amorphous calcium phosphate (CPP- ACP), oral hygiene maintenance, and dietary control have been suggested as mechanisms to control the formation of enamel lesions during fixed-appliance treatment 14 . However, these strategies have considerable limitations in noncompliant patients 15 . It was found that new white spot lesions developing on the maxillary front teeth during orthodontic treatment were seen in 60.9% of the patients with only standardized general measures of prophylaxis 16 . Introducing non-patient dependent preventive measures have gained popularity by limiting the problem of demineralization.