At first, separate application of enamelbond to enamel and dentinbond to dentin was recommend- ed; which was extremely difficult in the clinical setting. However, over time, by the advances in bondingagents, the manufacturers claimed that dentinbondingagents could also be applied to enamel without any reduction in their efficacy. The enamelbondstrength varies from 18-22 MPa; affected by the thickness of the bonding agent, and shear resistance and type of enamel crystals. Usually, 20 MPa resistance is sufficient to tolerate loads applied to the teeth [1, 2, 5, 6]. Following the clinical success of enamelbondingagents, differ- ent bonding systems were introduced for optimal bond to dentin. Although dentinbonding is still not as favorable as the bond to enamel, dentinbondingagents currently show acceptable results [5, 7]. Enamelbonding systems often include a saturated acrylic monomer that is applied to the acid etched enamel. The monomer penetrates into the porosi- ties in between and within the enamel crystals. Re- sins that penetrate into the etched enamel often include Bis-GMA (bisphenol glycidyl methacry- late) or UDMA (urethane dimethacrylate). Both monomers are viscous and hydrophobic and are often diluted with lower viscosity monomers like TEG-DMA (Triethylene glycol dimethacrylate) or HEMA (Hydroxyethyl methacrylate) [2, 5, 8, 9, 10, 11].
The aim of this study was to compare the bonding ability of a universal dental adhesive (Scotchbond Universal/SBU, 3 M ESPE) and other contemporary dental bondingagents applied to different substrates: enamel, dentin, resin composite, and porcelain. SBU was tested using both the etch-and-rinse/ER and self-etch/SE bonding approaches. The other adhesives tested were Scotchbond Multipurpose/SBMP (3 M ESPE), Single Bond 2/SB (3 M ESPE), and Clearfil SE Bond/CLSE (Kuraray). Specimens of each substrate were prepared for microtensile bondstrength test/ μ TBS (dentin and composite) or shear/SBS test (enamel and porcelain). In composite and porcelain, negative (no treatment) and positive (silane + SB) control groups were tested. Data were analyzed using One-Way ANOVA and Tukey ’ s test ( α = 0.05). In enamel, SBU resulted in similar SBS (p ≥ 0.458) compared to all other adhesives (SBMP = 19.0 ± 10.2 B ; SB = 26.6 ± 9.3 A ; CLSE = 26.0 ± 8.5 A ; SBU-SE = 23.5 ± 8.4 AB ; SBU-ER = 22.6 ± 9.9 AB ). In dentin, SBU showed similar results to all other materials (p ≥ 0.123), except SB (p ≤ 0.045), which showed the highest μ TBS (SBMP = 35.4 ± 10.5 AB ; SB = 39.4 ± 11.2 A ; CLSE = 36.6 ± 10.9 AB ; SB-SE = 28.1 ± 13.7 B ; SBU-ER = 26.9 ± 7.4 B ). In resin composite, SBU and the positive control presented similar μ TBS (p = 0.963), and were higher than the negative control (p ≤ 0.001) (SBU = 28.4 ± 9.9 A ; positive control = 29.5 ± 11.7 A ; negative control = 12.1 ± 8.7 B ). In porcelain, SBU had higher SBS than the positive control (p = 0.001), which showed higher SBS (p < 0.001) than the negative control (SBU = 29.0 ± 6.9 A ; positive control = 21.0 ± 7.0 B ; negative control = 5.3 ± 2.7 C ). Equilibrium of adhesive and mixed failures occurred in dentin and resin composite, whereas a predominance of adhesive failures was observed in enamel and porcelain. In conclusion, the bonding ability of the universal adhesive was comparable to the other contemporary bondingagents tested, although it was dependent on the substrate evaluated. Universal adhesives seem to have potential applicability in adhesive dentistry.
generation resin bondingagents) and a GI adhesive (GC Fuji Bond LC) and showed that the SBS of composite to dentin among the understudy groups was significantly different. In this study, shear load was used to assess the bondstrength because the shear forces are the most common type responsible for bond failure in the clinical setting. Also, shearbondstrength test can be performed easily and rapidly. Although the control of force application to the interface of the two materials is difficult . Also, in the current study, all specimens were immersed in distilled water at room temperature for 2 weeks to allow completion of polymerization and prevent dehydration.
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.
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 composite resins 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 primaryenamel and den- tin and reported equal bondstrength of self-etch to primaryenamel and dentin . Furthermore, Ra-
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 .
site to the tooth reduced 24 hours after bleaching, which is in agreement with results found in this study . Perdigo et al. point out in their studies that loss of calcium, reduction in microhardness, and changes in organic component can be impor- tant factors in reducing the bondstrength to enamel after bleaching . Van der Vyver P.J, Titley K.C, Dishman M.V, and Ghavam in separate stu- dies have shown that the reduction in bondstrength could be due to permeation of hydrogen peroxide into enamel and formation of free-radicals, which inhibit the initiation of polymerization and forma- tion of resin tags, which concurs with the results of this study [9, 15, 12, 16]. Zho et al. in 2000 showed that peroxide ions can replace free radicals in the apatite hydroxide network, and thus, produce apatite peroxide, causing destruction of the enamel prisms structure . Several methods have been proposed for prevention from the clinical problems associated with reduced bondstrength after bleach- ing: the most common is delaying application of bonding agent (any type) after bleaching . Shimahara M.S et al. and Van Der Vyver et al. in 2004 reported that the best time for restoration of enamel and dentin is two weeks after bleaching, since the resin bondstrength to enamel be im- proved [12-18]. Bulucu et al. also found that in the samples restored two weeks after bleaching, the difference in bondstrength, compared to control group was insignificant. They also stated that the type of light cure system did not affect bondstrength . Other studies have shown that stor- ing the samples in distilled water or in artificial saliva after bleaching and before bonding can im- prove resin bondstrength by removing layer of Bonding Bleach Number Mean Standard deviation Standard error
for 3 min with GC Labolight LV-III (GC Co., Tokyo, Japan). Half of the specimens were performed thermal cycling (TC) between 5°C and 55°C (±2) for 5000 cycles with a dwell time of 30 seconds in each bath, according to ISO 10477. All specimens were then submitted to shearbondstrength test (Autograph AG-IS 5K-N SHIMADZU, Kyoto, Japon) at a crosshead speed of 1 mm/min until failure. The shearbondstrength (SBS) values were obtained in Newton (N) and converted into MPa. The shearbond strengths were calculated according to the formula: B = F / S, (B: shearbondstrength (MPa), F: load at fracture (N), and S: bonded surfaces area (mm2). Fracture surfaces were evaluated with a scanning electron microscope (SEM) (Quanta 450FEG, USA). During evaluation of the study data, NCSS (Number Cruncher Statistical System) 2007 Statistical Software (Utah, USA) was used. As the parameters showed compatibility to normal distribution, the One-Way ANOVA was used in intergroup comparisons of parameters, while the Post Hoc Tukey HSD test was used in comparisons of sub-groups. The results were evaluated at the significance level of P˂0,01.
Water rinsing is an easy choice to combat saliva contamination of a prepared tooth surface. In a study by Sattabanasuk V et al., showed that simply rinsing saliva-contaminated enamel surfaces with water restores the bondstrength . On the other hand, studies have demonstrated that conventional washing protocols do not completely remove the coating of salivary proteins on the enamel surface and a subsequent reapplication of the adhesive after water rinsing and air-drying restores bondstrength value . This could be attributed to increased resin-dentin interaction due to multiple coatings of adhesive [40-42]. Erickson SO et al., and Cobanoglu N et al., after evaluating several saliva decontamination procedures, proposed application of adhesive after rinsing and drying to be more reliable than just drying, rinsing [31,38]. They suggested that washing and drying should remove the adhesive layer providing a demineralised surface non infiltrated by monomers. Hence, water decontamination followed by reapplication of adhesive was the method of choice used for decontamination in this study.
The bondstrength of lactic acid alone was found to be lowest as compared to maleic acid. This was in accordance to the studies done by Hughes et al. (2000), Ballal (2009), Ayad (1996) and Luque et al. (2012). The reason for the above finding was due to the formation of weak bonds of lactic acid to enamel, gentle rinsing with distilled water almost completely removing the acid as seen by X-Ray photoelectron spectroscopy in the study done by Yoshioka et al. (2002). They also found that amount of Ca & P extracted from hydroxyapatite powder was more for maleic acid than lactic acid. The fact that acids adhere to or decalcify hydroxyapatite crystals appears to depend largely upon the dissolution rate of the respective calcium salts in their respective acidic solutions. The less soluble their respective salts, the more stable their bond to hydroxyapatite (HAp) and less they decalcify Hap. The lactic acid salts were less soluble in their respective acid solution compared to maleic acid and therefore, their ability to decalcify hydroxyapatite crystals of enamel was less than maleic acid. 33
Both Alloy Primer and Scotchbond Universal adhesive used in the current study have MDP monomer in their composition. Presence of MDP monomer along with silane in the composition of bonding agent increases the bondstrength of resin to metal, alumina, zirconia and ceramic. This characteristic enables intraoral repair of damaged indirect restorations. MDP monomer chemically bonds to non-precious metals from its phosphoric acid group end; while, the double bond in the other end of the molecule is copolymerized with resin monomers [19,20]. Based on our results, the highest SBS belonged to S+U group while the lowest was observed in N+S group. In groups where Universal Scotch Bond was used as the bonding agent, significant differences were noted in SBS among different MSTs and the SBS in S+ U and R+U groups was significantly higher than that in N+U group. The difference in SBS between S+U and R+U groups was not statistically significant. It appears that both MSTs can adequately enhance the SBS probably by increasing the surface area and creating a macro-retentive surface. In groups where Alloy Primer was used for bonding, significant differences were noted in SBS among groups with different MSTs and S+A group had significantly higher SBS than R+A and N+A groups. Moreover, no significant difference was found in groups N+A and R+A. The difference between sandblasting and surface roughening by diamond bur may be due to the different surface area receiving the MST. In the sandblasting method, the entire surface area of the interface between the SSC and composite is sandblasted by aluminum oxide particles. But, in surface
The teeth of the control and experimental groups were further subdivided into 2 groups, to give a total of 6 groups of 10 specimens each, whose brushed dentine surfaces would be treated with either a filled dentine- bonding agent (Perma Quick 1, PQ-1 Ultradent Products Inc, South Jordan, UT, USA) or an unfilled dentine bonding agent (Single Bond, 3M ESPE, St Paul, MN, USA). The dentine surfaces were etched with 37% phos- phoric acid etchant for 15 seconds and then thoroughly rinsed with distilled water and gently dried using oil free compressed air to reveal frosty surfaces. The respective dentine-bondingagents were applied using microtips and gently thinned with compressed air and light cured (Elipar Freelight 2, 3M ESPE, St Paul, MN, USA) for 10 seconds. A transparent plastic mold of internal diameter 6mm was stabilized in the middle of the dentine surface. A 2 mm increment of composite (Z250 Composite Shade A3, 3M ESPE, St Paul, MN, USA) was placed in the mold and light cured for 40 seconds by using a sweeping action around the transparent mold. The specimens were returned to fresh distilled water at room temperature for storage for a period of two weeks prior to me- chanical testing.
peroxide for 6h/day for 7 consecutive days. They found that the SBS decreased when the samples were restored with composite resin immediately after bleaching; in addition, RMGI did not bond to the bleached enamel immediately after bleaching. Therefore, application of sodium ascorbate increased the SBS of composite resin restorations to the enamel bleached with 9.5% hydrogen peroxide.  In the current study, 15% carbamide per- oxide was used 6h/day for 5 consecutive days as the bleaching agent; while, in the above-mentioned study, hydrogen peroxide was used which is more potent than carbamide peroxide. It can produce more residual oxy- gen molecules that would significantly decrease the SBS. This might explain the significant effect of antiox- idant treatment in that study.
According to the results of this study and previous studies on adhesive resins, it seems that increased rate of polymerization is effective in reducing lea- kage in dentin margin. In fact, by increasing curing time, the changes in elastic and mechanical proper- ties of bonded layers cannot increase microlea- kage, and the cohesive strength of adhesive layer is more than shrinkage stress induced in composite resins. In addition, it can resist the difference of coefficient of thermal expansion.
Page 51 and zirconia ceramic specimens ,without using orthodontic brackets and measured shearbondstrength values of 15.6±1.2MPa, as did other recent studies which stated that phosphate monomers in the bonding agent play a key role in providing good bond with zirconia. The scotch bond universal self-etch adhesive also contains 10- methacryloxydecyl dihydrogen phosphate(MDP) which is said to account for the enhanced bonding on the zirconia surfaces .Such phosphate monomers form chemical bonds with the zirconia surfaces and have polymerizable resin terminal end groups(eg.methaacrylate)thereby enabling cohesive bonding to appropriate resins .(33,44). Such high shearbond strengths greater than 13 MPa ,could probably be attributed to the intimate micromechanical bond to zirconia surface However shearbond strengths more than optimal are undesirable in clinical situations for fear of producing cracks on the bonding surface during debonding. (56,62)
Subramonian et al,  reported that herbal products such as pine bark and grape seed extract can compensate for the reduced bondstrength of composite to bleached enamel, and pine bark had a greater efficacy than grape seed; the results of our study demonstrated similar antioxidative efficacy of green tea and grape seed, which was in agreement with the results of Sharafeddin et al . However, sage was not evaluated in their study. The current study showed that sage had antioxidant activity and increased the microshear bondstrength of composite to bleached enamel. The mechanism of action of sage has yet to be fully understood; however, the antioxidant property of this material is due to its polyphenolic nature and chemical formulation. Polyphenols like caffeic acid, hispidulin, apigenin, rosmanol, carnosic acid, carnosol and ursolic acid are among the active ingredients of sage. Similar to other antioxidants, these polyphenols inhibit the formation of reactive oxygen species [22,34]. This finding was in accord with the results of Khamverdi and Safari . Abraham et al,  compared the antioxidant property of sodium ascorbate and grape seed and concluded that application of grape seed had greater efficacy for reversal of compromised bondstrength of composite to bleached enamel; whereas, Arumugam et al,  reported opposite results. It is stated that high molecular weight of proanthocyanidin is an important factor responsible for its less penetration into tooth structure and reducing
The current study also assessed the antimicrobial activity of Transbond XT composite containing 1%, 5% and 10% concentrations of curcNPs against S. mutans, S. sanguinis and L. acidophilus. The three selected bacterial strains are the main constituents of dental plaque. Initiation of caries mainly depends on the activity of S. mutans while lactobacilli (mainly L. acidophilus) are responsible for progression of caries. Presence of S. sanguinis in the oral cavity decreases the population of S. mutans and these two are in equilibrium . Biofilm inhibition test was carried out to assess the antimicrobial activity of composites since it has been shown that bacteria in the form of biofilm are four times more resistant to antibacterial agents compared to planktonic form . The current results showed that addition of curcNPs to composite significantly decreased the bacterial count of all three strains compared to the control group in all three concentrations. The results for S. mutans were highly favorable since S. mutans colony count in presence of all concentrations of curcNPs decreased to zero. This indicates low minimum inhibitory concentration and minimum bactericidal concentration of curcNPs against S. mutans . This finding is clinically significant since S. mutans is the main cariogenic microorganism in the oral cavity. On the other hand, L. acidophilus showed higher resistance, which may be due to its role in progression of caries and formation of a very strong biofilm. In
This study compared the microtensile bondstrength (BS) and the micromorphology of resin‑dentin interface (MI) of a conventional adhesive to two‑steps etch‑and‑rinse bondingagents after 1 year of water storage. Twenty‑eight human third molars were used (n = 7). Teeth were divided into four groups (GCB: Gluma Comfort Bond; OPB: OptiBond FL; OCB: One Coat Bond SL; PUB: Peak Universal Bond). Specimens were tested in tension after 24 h or 1 year of water storage. Dentin BS strength data were analyzed by split‑plot two‑way ANOVA followed by Tukey–Kramer tests (α = 0.05). Water‑storage for 1 year significantly decreased BS for OCB; however, no significant difference was noted between OCB and GCB and PUB adhesives after 1 year of water‑storage. OPB showed the highest BS values at both storage times. All adhesives formed a hybrid layer with resin tags, and both interfacial structures were maintained after 1 year. However, degradation signals within interfacial structures were observed only for the adhesive with a bondstrength reduction. BS test showed that only one adhesive declined after 1 year of water storage. The degradation of some structures of the interface collaborated this finding. The classic three‑step etch‑and‑rinse (OPB) presented higher values of bondstrength than GCB and OCB after 1 year, but it was not statistically different from PUB.
Thiyagarajah (2.9% for direct technique, 2.2% for indirect one). The reasons of this difference can be found in the numerous differences in the study drawing: type of bracket and adhesive system, procedure used for the transfer tray confection, number of patients included in the sample and study design. It is important to consider that in our investigation, the first molar tubes were included in all statistical analysis and these attachments presented a great number of bond failure: on 28 total detachments in the direct technique, 13 were molar tubes, while 8 were the molar tube detachments on 26 of the total bond failure observed for the indirect technique.
seconds and transfer time of 10 seconds . The teeth were then mounted in molds measuring 2.5x2.5 cm. The internal surface of the mold was coated with petroleum jelly and the teeth were fixed using 16x22 inch rectangular stainless steel ligature wire. Each tooth was positioned at the center of the mold and the rectangular wire was fixed to the mold using sticky wax so that the teeth remained fixed when applying acrylic resin. Auto- polymerizing acrylic resin was applied to the mold and the teeth were embedded in acrylic to the level of their cementoenamel junction. After polymerization of acrylic resin, the teeth in acrylic blocks were separated from the mold (Fig. 1). The shearbondstrength test was performed in Tehran University Dental Research Center. Universal testing machine (Zwick Roell, Ulm, Germany) was used for shearbondstrength testing. The teeth were placed in the machine such that the bracket base was parallel to the load application vector. Load was applied in occlusogingival direction at a crosshead speed of 0.5 mm/minute to the bracket- tooth interface (Fig. 2). Load at debonding was recorded in Newtons (N) and converted to Megapascals (MPa) by dividing the load in Newtons by the bracket base surface area in square-millimeters (mm 2 ).