ginning may expose more oxygen layer to the sur- face by removing smear layer, and as a result mo- nomer comes into direct contact with oxygen. Al- so, in Clearfil SE Bond, despite its weak acidity and mild etching, the amount of mineral ions in- volved in hybrid bonding layer is expected to in- crease, which will lead to an increase in bondstrength . Since Clearfil SE bond contains 10 weight percent filler it has some desirable mechan- ical properties, which elevates bondstrength to enamel. The low viscosity filler in Clearfil SE Bond with its high tensile strength can neutralize polymerization shrinkage forces . It should be noted that the 10 MDP monomer (Methacryloy- loxydecyl Dehydrogenphosphate), developed by Kuraray Company, due to its polar property, in- creases the bondstrength through chemical bond- ing with mineral ions like calcium that exist in re- sidual hydroxyapatite [32, 33]. In the present study, as well as in a study by Jaberi-Ansari et al., despite claims of increased bondstrength by manu- facturer (Kuraray Medical Inc), Clearfil S3 Bond showed the lowest bondstrength of all threebond- ing materials tested . A study by Senavongse et al. also confirmed this result, and found that the lowest bondstrength to intact enamel was asso- ciated with one-bottle self-etch systems . The Kuraray company attempted to increase per- meation of bond into enamel, thereby increase bondingstrength of Clearfill S3 bond by increasing acidity of monomers, but this acidity caused de- struction of the primer before increasing permea- tion. Also, addition of filler and 10-MDP polymer to Clearfill S3 Bond did not help increase bondstrength. A major drawback in Clearfil S3 Bond is being one stage, and due to the presence of both hydrophilic and hydrophobic monomers in one bottle, it may impair their performance and lower the efficacy of each component, and consequently reduce bondstrength achieved by Clearfil S3 Bond. In this regard, Jaberi-Ansari argued that be- ing one-stage means water and solvents of the bond such as alcohol or acetone exists in bonding solution. After application of the bond and before hardening by light, the water and solvents are ex-
Use of nanotechnology for the fabrication of compositeresins 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 .
Many authors have investigated and published the effects of bleaching on bond strengths of composite to enamel and dentin. For brightening discolored teeth, the use of peroxide releasing agents such as hydrogen peroxide, carbamide peroxide or sodium perborate has become a popular treatment modality, which is comparatively safe. 18 This is possible because hydrogen peroxide is of low molecular weight and can denature proteins, which increases tissue permeability and allows ions to move through the tooth. Studies show that bleaching causes changes in the organic enamel matrix, a loss of calcium and a decrease in micro-hardness that are potential causes for the reduction of bondstrength. 18, 19
distilled water for 20 s, and dried thoroughly. Two consecu- tive coats of adhesive agents (Adper Single Bond 2, 3 M ESPE, St Paul, MN, USA) were applied and light polymer- ized for 10 s with an LED light-curing unit (Elipar S10, 3 M ESPE, St Paul, MN, USA). A polyethylene tube with an in- ternal diameter of 1 mm and a height of 1.5 mm was mounted on the enamel surface and filled with the compos- ite resin (RelyX Veneer, 3 M ESPE, St Paul, MN, USA). The composite resin was then light cured using the abovemen- tioned light-curing unit for 40 s. The excess material sur- rounding the tube was removed with a sharp scalpel. The specimens were stored at room temperature for 1 h prior to removal of the polyethylene tubes. All the specimens were then examined with a stereomicroscope to exclude any spec- imens with air bubbles, evident interfacial gaps, or any other bonding defects.
Reynolds 65 suggested that at the minimum, a bondstrength of 6-8 MPa would be clinically acceptable. This value is often used as a benchmark in orthodontic bonding studies to enamel and non-tooth surfaces. The use of this minimum value as a reference for in vitro bond strengths has been criticized. 43,66 It has never been tested whether 6-8 MPa in vitro is clinically acceptable. It is known that bond strengths achieved in vitro are approximately 40% higher than that found in vivo. 67 Finnemore 43 recommends that extrapolation of bondstrength data and comparison to a minimum reference value should be avoided. Furthermore, comparison of bondstrength data between different studies is inappropriate, due to wide variation in methodology. Rather, bondstrength data should only be used to assess the relative effectiveness of the adhesives within the study.
Materials and Methods: Sixty bovine teeth were randomly divided into five groups (n=12). PrpNPs were prepared at concentrations of 0% (control), 1%, 2%, 5%, and 10% in Transbond XT composite to bond stainless steel brackets to the teeth. SBS between brackets and teeth was measured using a universal testing machine. After debonding, the adhesive remnant index (ARI) on bracket bases was measured. In the microbial test, composites with the aforementioned concentrations of prpNPs were cured in metal discs. The bacteria included Streptococcus mutans (S. mutans), Streptococcus sanguinis (S. sanguinis), and Lactobacillus acidophilus (L. acidophilus), and antimicrobial effects of prpNPs were investigated by anti-biofilm, disc agar diffusion and eluted component tests. Results: The 10% prpNPs group showed the lowest SBS. Colony growths of S. mutans and S. sanguinis at all concentrations (except for 1%) was significantly lower than the control group. L. acidophilus colony growth was significantly reduced at 5% and 10% concentrations. Growth inhibition zone developed at 2%, 5%, and 10% concentrations for S. mutans and S. sanguinis. The lowest numbers of S. mutans and S. sanguinis colonies at all concentrations were observed on day 15. L. acidophilus colonies decreased significantly at all concentrations (except for 1%) until day 30. Conclusion: Nano propolis has a significant antimicrobial effect at 2% and 5% concentrations, and the SBS is maintained within the acceptable clinical range. Keywords: Propolis Nanoparticles; Orthodontic Composite; Dental Bonding; Microbial Sensitivity Tests; Transbond XT
Based on the results of the present study, the low- est bondstrength values were observed in group 1, compared to the other groups. Some studies have shown that enamel structure undergoes some phys- ical changes due to the effect of bleachingagents and the decrease in bondstrength is attributed to an increase in enamel surface porosity due to over- etching and loss of the crystalline structure of the enamel . One study showed that the decrease in bondstrength after application of bleachingagents on enamel is due to a decrease in the calcium con- tent of enamel, a decrease in enamel surface hard- ness and destruction of enamel structure . Rotestein et al. reported a decrease in the strength and solubility of enamel, dentin and cementum after bleaching procedures . Changes in the mineral and organic content of teeth are attributed to an increase in solubility. Some other studies have attributed an increase in enamel porosity to the retention of oxygen in the form of free radicals. In general, the results of the present study are con- sistent with those of Kaya et al, Bulut et al, and Khoroshi et al [3,4,6]. It has been suggested that storage of bleached specimens in the saliva or a humid environment can gradually release the resi- dual oxygen in the form of liquid or gas until it is completely eliminated.
and insufficient bondstrength of porcelain is one reason for porcelain fracture [7,8]. Bond to porcelain has been an interesting topic of research  and depends on the type of porcelain surface treatment . Since removal of a fractured or chipped porcelain restoration is difficult in the oral cavity, intraoral repair of these restorations is desirable and eliminates the need for replacement of the entire crown and saves time and cost. Therefore, it is desirable for both patient and clinician. For this purpose, the safest and most efficient technique of repair must be chosen. The primary repair systems were based on mechanical retention and use of organosilane cou- pling agents. Several surface preparation methods such as surface roughening, abrasion by aluminum oxide particles and etching with HF or phosphoric acid have been assessed in vitro to enhance the bond of composite resin to porcelain [10-12]. Acid etching is one method to eliminate the smear layer and debris from the porcelain surface and enable micromechanical retention of resin. Silane coupling agent is also used to increase the bond of composite resin to ceramics [13,14]. Sandblasting is another modality to increase the bonding surface area and surface roughness and create undercuts on the ceramic surface [15,16]. Silane was introduced to create adhesion in dentistry. It creates an interface between a mineral substrate such as glass, metal or a mineral compound and an organic substrate such as an organic polymer in order to bond dissimilar materials to each other. Liu et al.  evaluated porcelain repair with hydrophilic resin following sandblasting, surface roughening, etching with phosphoric acid and a combination of all. They concluded that the most effective method of surface preparation was surface roughening and acid etching; however, the differences were not statistically significant. The new generation of porcelain systems include a wide range of chemical materials and chemical methods for porcelain surface preparation. Surface preparation plays an important role in enhancing the bond of composite to porcelain and success of repair . Several surface preparation methods have been evaluated to enhance the bond of resin to porcelain . Sorensen et al.  measured the shearbondstrength of composite to porcelain using different
This study investigated the influence of the waiting time for placing resin composite (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 bleachingagents. 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 bleachingagents 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 bleachingagents 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.
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 composite resin bond 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.
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 resin composite to 38% hydrogen peroxide bleached enamel in group B2 (hydrogen peroxide + green tea), but there were no significant increase in SBS of resin composite to 15% carbamide peroxide bleached enamel 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 bleachingagents 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 resin composite to the bleached enamel.
eliminated while preventing over-drying of collagen fibrils. Despite adequate care, the collagen structure may remain over-hydrated or over-dried. Another important parameter affecting the bond is the polymerization shrinkage of composite resin resulting in separation of resin from the hybrid layer . A gap-free interface is often seen when a particle filled, thick adhesive resin is applied beneath the composite restoration and this suggests the elastic bonding theory [24, 25]. In this situation, an unfilled or semi-filled thick elastic adhesive resin layer can prevent microleakage due to polymerization shrinkage and prevent resin separation due to elastic elongation of this layer . Powell et al. showed that use of resin modified GI liner in bilayer technique minimized stiffness and prolonged the clinical service of adhesive layer and restoration . GC Fuji Bond LC as a GI-based adhesive was recently introduced as an alternative to conventional adhesive resins .
Conventional compositeresins need completely dry surfaces to achieve clinically acceptablebond strength values; however, complete isolation of the bonding site against moisture is not possible during bracket bonding  and salivacontamination is always probable during the process of etching the enamel surface or after using primers.  In the case of contaminated enamel surfaces prior to pri- mer application, the developed porosities following acid etching areclosed off and the enamel surface energy will be decreased.Due to impaired resin penetration anddecreased micromechanical reten- tion, substantial reductions occur in the bondstrength of resin to etched enamel . To solve this problem, some moisture-resistant primers have been developed.
One probable explanation for the reported differ- ences is that the PLP bonding does not have equal compatibility with all resin materials. Peutzfeldt in 2004  mentioned that the shearbondstrength of 6 compositeresins to dentin by use of PLP bond- ing agent changed between 1 to 13 MPa. Signifi- cant changes in bondstrength may be attributed to the fact that unlike etching with phosphoric acid, PLP bonding agent cannot yield an optimal bond to enamel with all types of fissure sealants and the bondstrength is influenced by the mechanical properties of the resin material . Another expla- nation for the variable efficacy of self-etch bond- ing system is that numerous parameters namely tooth structure, enamel preparation, test method, bonding surface area, speed of load application (cross-head speed) and the operator-related factors may affect the results . Moreover, duration of water storage and thermocycling also play a role in this respect . Small number of studies have evaluated the bondstrength of self-etch bonding systems to unprepared enamel of primary teeth reporting different bonding quality in primary and permanent teeth. Marquezan et al, in 2008 com- pared the microtensile bondstrength of self-etch and Total Etch systems to primary enamel and den- tin and reported equal bondstrength of self-etch to primary enamel and dentin . Furthermore, Ra-
Materials and Methods: Forty flat enamel surfaces were prepared from freshly extracted human premolars using a low speed diamond saw. Then the specimens were divided into four random groups (n = 10). All the groups were treated with 30% H2O2. The specimens in Group I were bonded immediately after bleaching, whereas Group II, III and IV were treated with antioxidants Sodium ascorbate, Pomegranate peel extract and Grape seed extract respectively. After preparation, a standard shaped resin composite was applied to all specimens. The teeth were stored in deionized water for 24hrs at 37°C and a universal testing machine determined their shearbondstrength. The data were evaluated using ANOVA and Tukey Post Hoc tests.
Various methods have been suggested to improve the compromised bond to the bleached enamel and dentin, including using antioxidant materials [26-27], postponing the procedure for 24 hours to three weeks [20,28-30], and applying whitening agents with fluoride . CPP-ACP has been demonstrated in animal and human studies to significantly reduce caries activity and promote the enamel subsurface remineralization. CPP-ACP advances remineralization by giving a supply of Ca 2+ and PO4 2- ions near the tooth surface and permits mobilization of these ions in regions of acid challenge [11,32]. The result of our study revealed that the concomitant use of CPP-ACP and hydrogen peroxide couldn’t improve the compromised bond to the bleached enamel. Enamel treated with CPP- ACP has been found to be more resistant to a subsequent acid challenge. It seems that the reduced bondstrength to the CPP-ACP treated enamel may be due to the inability of Clearfil SE Bond as a mild self-etch adhesive to effectively etch and penetrate to the hyper-mineralized enamel surface. Moreover, the remaining CPP-ACP complexes may stay on the enamel surface and be consolidated into the bonding layer or restrain the bond between the Clearfil SE Bond and enamel. Chuang et al.  revealed that treatment with 0.37% fluoridated carbamide peroxide maintained the microtensile bondstrength as effectively as the unbleached enamel. The result of our study revealed that the concomitant use of fluoride and hydrogen peroxide couldn’t improve the compromised bond to the bleached enamel. A study also revealed that fluoride treatment post-bleaching did not prevent the reduction in the enamel/resin shearbondstrength in the time-period from immediately after treatment to 14 days after treatment . The results of this study revealed that using modified bleachingagents acts as unmodified bleachingagents in decreasing the bondstrength of the composite resin to the enamel if it was used immediately before composite restoration. However, if the enamel was bleached one week before restoration, the bondstrength of
is harder to be reflected in clinical applications . The distribution of the ARI scores was found different between the three major groups. In the ICON group, for both self- etching and conventional etching subgroups, higher ARI scores tended to be more frequent, while in Clinpro and control groups, both self-etching and conventional etching subgroups, less adhesive remnant tended to be seen left on the enamel surface after debonding. This could be at- tributed to the chemical bond between the resin infiltrant and the adhesive resin. However, the adhesive remaining on the enamel surface after debonding was not different in the three major groups between the self-etching sub- group and the conventional etching subgroup indicating a similar effect of the enamel protective material with the two types of adhesive systems. These results differed from the results of Naidu et al.  study that found using ICON as preconditioning before bonding orthodontic brackets to sound enamel did not affect ARI scores distri- bution compared to the control groups using Transbond XT primer and Transbond PSEP. The importance of the site of bond failure was found not to be a reflection of bondstrength; therefore, the site of failure did not reflect different bond strengths at different interfaces [44,45]. On the other hand, a variety of factors could affect bondstrength including the type of enamel conditioner, acid concentration, length of etching time, composition of the adhesive, bracket base design, bracket material, oral envir- onment, skill of the clinician, and time of light exposure in case of light-cure approach .
covered with 2% CHX gel (Ultradent, South Jordan, USA,). The samples wee then covered in cellophane to prevent moisture loss and each sample was placed in a separate container. Dentin was exposed to the understudy materials for 10 days. During this time period, the samples were stored at 37°C. The samples were removed from the incubator every three days and CHX gel was refreshed and the samples were placed again in the incubator. After 10 days, exposed dentin surface was rinsed with saline for five seconds. In groups one and four (exposed to saline and CHX), primer of P90 composite (3M ESPE, St. Paul, MN, USA) was gently applied on the dentin surface by an applicator and was then spread on the surface by gentle dry air spray and light cured for 10 seconds using a light curing unit (LED Turbo South Jordan, USA). Next, the bonding agent of P90 composite was gently applied on the dentin surface by an applicator. The bonding agent was then gently spread on the surface by air spray and light cured for 20 seconds. Next, transparent plastic molds with an internal diameter of 2mm and height of 3mm were placed on the surface and filled with A2 shade of P90 composite. Excess material was removed by a scalpel and the composite was light cured for 20 seconds from four directions (at the sides and from the top for a total of 80 seconds). Plastic mold was gently cut by a scalpel and separated from the composite.
for unnecessary removal of tooth structure. The GC Tooth Mousse is among these agents available in dental markets . It is a smooth, sugar-free, water-based mixture available for use as a topical crème with a nano-complex base of casein protein referred to as CPP-ACP. It is composed of CPP and ACP parts . CPP localizes the ACP molecules on the tooth surface and bonds to biofilm macromolecules on the tooth surface and serves as a reservoir of calcium phosphate ions . ACP is biologically active and capable of releasing calcium and phosphate ions to maintain a supersaturated level of these ions. Calcium phosphate ions in a liquid phase easily diffuse into the porous lesions and are deposited in the partially demineralized enamel crystals, reforming apatite crystals . By doing so, the process of demineralization is slowed down and replaced by remineralization [5,6]. Positive efficacy of CPP- ACP for increasing the pH of the saliva has been shown in clinical studies . The potentials of CPP-ACP [inhibition of demineralization, increasing remineralization, decreasing adhesion  and its bacteriostatic and bactericidal effects] are similar to those of fluoride, the gold standard cariostatic material [9-11]. Higher efficacy  and greater remineralizing potential of CPP-ACP compared to fluoride have been documented in several studies. CPP-ACP does not show any of the adverse effects of fluoride overdose such as fluorosis (moderate overdose) or toxicity (high overdose). The favorable efficacy of CPP-ACP in conjunction with fluoride has also been documented . In an in-vitro study, CPP-ACP paste used following a fluoridated toothpaste in an erosive cycle resulted in less enamel loss compared to the single use of fluoride (50-250 ppm) or CPP- ACP. It was also shown that the acid resistance of enamel exposed to CPP-ACP was higher when fluoride was used in combination with CPP-ACP .