1001 D3000 new imprint Word template Vol 13, No 1 (2025) ISSN 2167-8677 (online) DOI 10.5195/d3000.2025.1001 http://dentistry3000.pitt.edu Shear Bond Strength and SEM/EDX of Two Bioactive Bulk Fill Resin Base Composite Restorations Rana Fahad Ahmed Al Azawee, Nadia Modhafer Ahmed Al Shakir College of Den*stry, University of Mosul, Iraq Abstract Objec;ve: To compare the shear bond strength of two bioacKve bulk-fill dental restoraKve materials to sound denKn aPer aging in arKficial saliva and to evaluate the mode of failure and elemental analysis by SEM/EDX. Material and Methods: Forty maxillary premolars ex- tracted due to orthodonKc reasons from subjects with ages between 14 and 30 years were used in this study. The teeth were divided into two groups according to the type of compo- site, Predicta BioacKve or CenKon Forte. Each group had samples stored or not stored in ar- Kficial saliva. Occlusal denKn of all teeth was exposed by cu\ng 2mm below the deepest point on the occlusal surface of each tooth's crown. Each restoraKve material was applied according to the corresponding manufacture instrucKons. The shear bond strength was measured between the composite and denKn and by using SEM-EDX to evaluate the mode of failure and element analysis. Results: The study revealed that CenKon Forte, aPer storage, exhibited the highest shear bond strength (10.13 MPa), followed by its non-stored samples (8.38 MPa), while Predicta BioacKve showed the lowest values, especially in the non-stored samples (6.38 MPa). Con- clusion: CenKon Forte had stronger bonding than Predicta BioacKve. Open Access Cita%on: Al Azawee RFA, et al. (2025) Shear Bond Strength and SEM/EDX of Two Bioac%ve Bulk Fill Resin Base Composite Restora%ons. Den%stry 3000. 1:a001 doi:10.5195/d3000.2025.1001 Received: July 27, 2025 Accepted: August 4, 2025 Published: September 9, 2025 Copyright: ©2025 Al Azawee RFA, et al. This is an open access ar%cle licensed under a Crea%ve Commons AVrib- u%on Work 4.0 United States License. Email: Nadia.Mudhafar@uomosul.edu.iq Introduc)on Composite restorations are widely used in direct esthetic dentistry due to their ability to mimic various shades and translucencies, providing high-quality aesthetic outcomes. Additionally, the incremental placement of conventional composite materials can intro- duce voids and interfacial bonding failures, leading the remaining tooth structure and restoration interface to greater stress [1,2]. A main affecting factor for maintaining a res- toration chemically bonded to the tooth structure is its ability to withstand shear stresses (that can be deBined as the stresses created at the interface between restoration and tooth surface) which are caused by per- pendicular or parallel forces acting on the tooth surface [3]. The oral environment is dynamic and com- plex, exposing restorative materials to varia- tions in pH, temperature, microbial activity, and mechanical stress, dental tissues are in constant ionic exchange with Bluoride, cal- cium, and phosphate, regulated by saliva, which plays a crucial role in maintaining a balanced mineral environment [4]. With this understanding, the focus of restorative den- tistry has gradually shifted from biocompat- ibility to bioactivity, emphasizing materials that can interact with the oral environment to promote remineralization and inhibit bac- terial growth [5]. Bioactive resin composites are designed to discharging remineralizing ions, elevating pH levels, and generating hy- droxyapatite, thereby enhancing the longev- ity and effectiveness of restorations [6]. Several bioactive composites have been de- veloped with properties aimed to combating caries while maintaining their stability un- der occlusal forces, temperature changes, and enzymatic degradation [7,8]. Among these materials and for direct restorations, Predicta Bioactive which is a bulk-Bill resin composite was designed. According to the manufacturer, it demonstrates high com- pressive, tensile, and Blexural strengths while also releasing Bluoride, calcium, and phosphate ions to facilitate the formation and mineral apatite remineralization at the tooth-restoration interface [9]. Similarly, Cention Forte (Ivoclar Vivadent) belongs to the Alkasite material family and is characterized by its high Blexural strength and esthetic properties. It contains an alka- line Biller that releases hydroxide ions to Shear Bond Strength and SEM/EDX of Two BioacKve Bulk Fill Resin Base Composite RestoraKons Vol 13, No 1 (2025) DOI 10.5195/d3000.2025.1001 http://dentistry3000.pitt.edu 2 regulate pH during acid attacks, preventing demineralization and promoting reminerali- zation through the release of calcium and Blu- oride ions. Additionally, it exhibits moderate viscosity and strong mechanical properties [10]. The aim of this study was to evaluate and compare shear bond strength of two bioac- tive bulk-Bill dental restorative materials to sound dentin after aging in artiBicial saliva, and to evaluate their mode of failure and el- ement analysis by SEM/EDX. Material and Methods An ethical approval was received from the “Research Ethics Committee” of the College of Dentistry, University of Mosul (no. UoM. Dent.25/1013) Because the research study used extracted human teeth. Forty maxillary premolar teeth extracted for orthodontic purposes from patients aged 14 to 30 years were collected for this study from different health center in Mosul, each tooth was examined using a stereomicroscope at10X magniBication. Only teeth that were free of caries, cracks, attrition, abrasion, or restorations were included. The teeth cleaned to remove debris using an ultrasonic scaler, then were immersed in a 0.1% thymol solution (DBH, England) for 48 hours to en- sure disinfection and subsequently stored in deionized water (Almansur factory, Iraq) un- til the time of the study, for the next mount- ing step the teeth samples were prepared [11-13]. For mounting the teeth a retentive tube pol- yvinyl chloride (PVC), 2cm in diameter and 2cm in length, was used as a mold, each tooth was positioned with the aid of a dental sur- veyor and a sticky wax (Hoppegarten, Ger- many) was used to attach the tooth to the rod of the surveyor, the selected teeth with their roots were embedded at the tube center and parallel to its long axis to a level of 2 mm be- low the cement-enamel junction simulate the position of the tooth in the alveolar bone [14,15]. Forty teeth were divided randomly into two groups according to the type of composite restorative materials (20 teeth for each group). Then, each group was subdivided into two subgroups. The Birst 10 teeth were not stored in artiBicial saliva, while the sec- ond 10 teeth were stored for 30 days in arti- Bicial saliva. All teeth were tested for shear bond strength using a universal testing ma- chine (Hongjin HAS-UT-5PC, China) and for mode of failure and element analysis using SEM/EDX (Axia ChemiSEM, Holland). The occlusal dentin of each tooth was ex- posed by cutting 2 mm below the deepest point on the occlusal surface of each tooth's crown. this cut was made using a diamond coated separating disc attached to a slow- speed hand piece with water coolant. per- pendicular to the long axis of the tooth the cutting was made. Occlusal dentin surface of all specimens was polished using 600-grit Wet Silicon Carbide abrasive papers for ten time in a circular motion under running tap water to obtain Blat dentin bonding surface [12,16]. For Predicta Bioactive (Parkell, USA) bulk Bill resin composite, an etch and rinse protocol was used following the manufacturer’s rec- ommendations, where the dentin surface was exposed, 37% phosphoric acid gel (Spi- dent, Korea) was used for 15 seconds and then rinsed with water for 15 seconds. The teeth were dried with oil-free air for 5 sec- onds [17]. According to the manufacturer’s instructions, one layer of G-Premio Bond (Universal Bond Quick, GC, Japan) was rubbed onto the dentin surface for 20 sec- onds with a microbrush, the bond remained on the dentin surface for 10 seconds and was dried at the maximum airBlow rate for 5 sec- onds. Finally, the adhesive layer was light cured at a light intensity of 1000 mW/cm2 for 10 seconds using light emitting diode light curing unit (Rogin Dental, China) at a 1mm distance [18]. For a standardized dis- tance we used celluloid crown which cut 1mm from cervical margin so the distance between occlusal surface of celluloid crown and occlusal surface of coronal dentin is 1mm. A custom-made TeBlon mold was designed to standardize bulk Bill composite application on bonded dentin to produce a 4mm diame- ter and 2mm height [16]. Each restorative material was applied according to the corre- sponding manufacture instructions utilizing the bulk placement technique. For the Cen- tion Forte (Ivoclar Vivadent, Schaan, Liech- tenstein), the primer was dispensed as one drop in a dish and mixed with the applicator for 5 seconds, applying on dentin for 10 s, blowing by air pressure for 5 seconds (self- cure) [19]. Cention Forte capsules were acti- vated by pressing the plunger on a Blat sur- face to allow mixing of the powder and liq- uid. Immediately after activation, the capsule was inserted in the amalgamator (capsule mixer) (Softly8, Italy) and mixed for 17 sec- onds at room temperature (21°C) (low tem- perature led to delay setting of material). Af- ter mixing, immediately the capsule was placed into the applicator, clicked 3 clicks and dispensed to Bill the mold, keeping the tip immersed in the material to prevent the formation of air bubbles [20]. The Predicta Bulk Bioactive (Parkell, USA) composite was delivered on bonded dentin by a spiral nozzle to Bill the mold and slowly express the composite as we withdraw the tip, keeping the tip immersed in the material to eliminate air entrapment. A celluloid strip was placed over the resto- ration to achieve a smooth, Blat surface to prevent oxygen inhibition surface layer, then the material was light-cured using a light- emitting diode (LED) curing unit with an in- tensity of 1000 mW/cm² (Rogin Dental, China) in a one step for 20 seconds. The tip of light-curing was positioned perpendicu- larly to the occlusal surface of the restorative material, maintaining a standardized dis- tance of 1 mm (equal to the thickness of a metal plate from a custom-made TeBlon mold). Additional curing was performed for 20 seconds on each side of the restorative material to optimize polymerization [21,22]. Each group were subdivided into two sub- groups. The Birst subgroup was not stored in artiBicial saliva. All samples were stored in plastic container containing 30 ml of deion- ized water in an incubator (Binder, Ger- many) at 37± 2°C in 95% humidity for 48 hours until subjected to shear bond strength test [13,23]. The second subgroup was stored in artiBicial saliva. Samples were placed upright inside a plastic container. Each container was then Billed with 30 ml of artiBicial saliva (pH 7) and securely covered. The containers were incubated at 37 ± 2 °C and 95 % humidity for 30 days, and they were replenished every week until the end- point time (30 days) [24,25]. An universal testing machine (Hongjin HAS- UT-5PC, China) was used to measure the shear bond strength between the composite and dentin. All samples were loaded at a speed of 0.5 mm per minute until de-bonding occurred with a maximum failure load that was recorded automatically in Newton (N) by a computer connected to the testing ma- chine [16]. To calculate shear bond strength in MPa, the maximum force was divided by the surface area of the sample. Shear bond strength = (𝐅) Fracture Load (N)/ (𝐀) Surface area (mm2) The surface area (A) was calculated from the following equation: A= π r 2 Where π = 3.14 r = Radius of each specimen (2mm), A=3.14*2 2 =12.56mm2. To identify the mode of failure, all samples (de-bonded dentin surfaces) following shear bond strength test were examined using a stereromicroscope at 40X magniBication [27]. Also, Scanning Electron Microscopy (SEM) of three de-bonded surface samples were done to determine the micromorpho- logical topography at 5000X and the mode of failure at 1300X [26]. The mode of failure was categorized as adhe- sive (failure at the adhesive-substrate inter- face), cohesive (within the material mass), or Shear Bond Strength and SEM/EDX of Two BioacKve Bulk Fill Resin Base Composite RestoraKons Vol 13, No 1 (2025) DOI 10.5195/d3000.2025.1001 http://dentistry3000.pitt.edu 3 mixed (a combination of adhesive and cohe- sive) [23]. All corresponding samples (de-bonded sur- faces and fractured composite stubs) were collected after shear bond strength testing to prepared for SEM/EDX (Axia ChemiSEM, Holland), the teeth samples from each sub- group (non-storage and storage in artiBicial saliva for 30 days) were subjected to longitu- dinal sectioning (sectioning at the middle of mesio-distal direction) to the surface of acrylic base and then by using slow speed hand piece with cutting diamond disc each half sectioned horizontally below cement- enamel junction near the acrylic base, then one of the obtained sections from each tooth sample was randomly selected and cleaned in an ultrasonic water bath (Granbo, China) for 3 min, in order to remove the debris and left to dry for 24 hours [28]. The correspond- ing samples were secured to the aluminum stubs using carbon double-sided tape. After that, a thin gold coating (15nm) was spat- tered on the surface for 20 seconds to deter- mine the mode of failure and micromorpho- logical topography. The SEM system was ad- justed to a 30 kV accelerating voltage for this purpose [29]. The weight percentages of chemical elements in the de-bonded dentin and restorative material core for each tooth have been identiBied by analyzing the chemi- cal composition using EDX data. In addition, the calcium-to-phosphorus (Ca/P) ratio was determined for both the storage and non- storage groups [30]. The statistical analysis included the follow- ing tests: “two-way analysis of variance” (ANOVA) was analyzed the results for shear bond strength and “Duncan's multiple range” to identify the signiBicance among groups at P≤0.05; independent sample t-test was used to compare different groups to as- sess the effect of storage in artiBicial saliva on the shear bond strength. Statistical signiBi- cance was set at p<0.05; and chi-square test to compare different groups to assess the ef- fect of storage in artiBicial saliva on the mode of failure. Results Shapiro Wilks test showed that the data were normally distributed (p<0.05). in most of the groups, The results of the descriptive statistics that included the minimum, maximum, mean, and standard deviation value of shear bond strength of all groups of the study as shown in Table 1. The highest shear bond strength was ob- served for Cention Forte, whereas the lowest shear bond strength was observed for Pre- dicta Bioactive. Mode of failure De-bonded tooth samples were inspected using a steromicroscope at 40X magniBica- tion as shown in Figure 1. The most common failure pattern was mixed except for Cention Forte stored in artiBicial saliva, which had a cohesive failure. SEM\EDX analysis SEM imaging was performed at 5000X mag- niBication to examine the de-bonded areas of all restorative material core and the coronal dentin samples stored or not in artiBicial sa- liva. The de-bonded samples were analyzed to assess morphological changes at these critical regions (Figures 2 and 3). SEM for Predicta bioactive showed a slightly precipitation of hydroxyapatite (HA) at the de-bonded area of composite for both groups (Figure 4). SEM for Cention Forte showed precipitation of hydroxyapatite (HA) at the de-bonded area of composite for both the samples not stored in artiBicial saliva (B1) and stored (B2) (Figure 5). SEM images showed the presence of "crystal- like" deposits at de-bonded coronal dentin areas in the Predicta Bioactive samples in both stored and not stored in artiBicial saliva (Figure 6). SEM images of Cention Forte samples, both not stored and stored in artiBicial saliva showed that de-bonded coronal dentin areas had “crystal-like” depositions (Figure 7). EDX analysis EDX analysis was conducted to evaluate the elemental composition of the de-bonded ar- eas of all restorative materials core and the coronal dentin samples. This analysis aimed to detect compositional changes associated with aging in artiBicial saliva. The weight per- centage of calcium and phosphorus elements were used to calculate the calcium/phospho- rus ratios as illustrated in the following equation: The EDX spectra showed low concentration of phosphorous (P) for samples not stored in artiBicial saliva (Figure 8). The EDX spectra showed low concentration of phosphorous (P) Centrion Forte samples (Figure 9). The EDX spectra of Predicta Bioactive for both not stored and stored in artiBicial saliva showed a change in the spectra for both phosphorous (P) and calcium (Ca). Predicta Bioactive samples showed increase in the spectra of calcium (Ca) with slightly de- crease in the spectra of phosphorous (P) (Figure 10). The EDX spectra for Cention Forte both sam- ples showed a change in the spectra for both phosphorous (P) and calcium (Ca). Cention Forte samples stored in artiBicial saliva showed an increase in the spectra of calcium (Ca) that was higher than Predicta Bioactive with slightly decrease in the spectra of phos- phorous (P) (Figure 11). The mean Ca/P ratios was (1.84±0.71) in Predicta Bioactive samples stored in artiBi- cial saliva, which is higher than the ratio of natural HA (1.67). This indicated apatite deposition, which conBirms the SEM analysis that showed apatite deposition at the resto- ration surface. The mean Ca/P ratio for Cention Forte sam- ples stored in artiBicial saliva was (2.63±0.62), which was higher than the ratio for natural HA (1.67). This indicated apatite deposition, which would support the SEM analysis that showed apatite deposition at the restoration surface. For Predicta Bioactive samples not stored in artiBicial saliva exhibited a mean Ca/P ratio of (1.81±0.45), signiBicantly above the natu- ral hydroxyapatite (HA) ratio of dentin (1.67), suggesting a composition like native minerals. In samples stored in artiBicial sa- liva, the Ca/P ratio at the de-bonded area of the coronal dentin samples increased to (2.71 ± 0.38). The rising ratio, signiBicantly above that of natural dentin hydroxyapatite, indicates the development and deposition of a hydroxyapatite-like crystals. The EDX elements for samples not stored in artiBicial saliva of Cention Forte detected the mean Ca/P ratio (1.97±0.38) slightly higher than natural HA ratio (1.67) for dentin. While after storage in artiBicial saliva, the coronal dentin area of Cention Forte showed Ca/P ratio about (4.01±1.98), which is higher than that for natural HA ratio for dentin. This in- dicates HA precipitation. Discussion Alkasite-based tooth-colored restorative material is a hybrid that releases calcium, Bluoride, and hydroxyl ions, which exhibit ef- fective anti-cariogenic properties. This novel material combines the advantages of glass ionomer cements (GICs) and resin-based composites. Dual-cure capability allows bulk placement with or without adhesive [31]. Shear bond strength test was selected to evaluate bonding strength of the two differ- ent restorative materials when applied to Blat (mid-coronal) dentin. The clinical im- portance of this test because of it closely sim- ulates the shearing forces found at the tooth– restoration interface [32]. The aging procedure is essential in deter- mining the bond durability, one of the factors which affect the properties of restorative material is Saliva which is a slightly acidic body Bluid having a pH scale of 6–7 and whose main ingredient is water (99%). Shear Bond Strength and SEM/EDX of Two BioacKve Bulk Fill Resin Base Composite RestoraKons Vol 13, No 1 (2025) DOI 10.5195/d3000.2025.1001 http://dentistry3000.pitt.edu 4 ArtiBicial saliva was used to simulate the wet oral environment. The teeth were stored in artiBicial for a period as the restoration re- mains in continuous contact with saliva in the oral cavity [33]. In the current study, teeth were stored in ar- tiBicial saliva in an incubator at (37 ℃ ± 1) for 30days at pH 7. This was performed to mimic the oral cavity’s environment for assessing the behavior of restorative materials [34]. In this vitro study, bonding effectiveness and bond durability after artiBicial aging (30 days in artiBicial saliva) were investigated through evaluate 1) shear bond strength of these tested material according to storage condi- tion 2) micromorphological analysis of these materials at debonded dentin area by SEM identify the main failure modes 3)elemen- tary analysis of both core of materials and debonded dentin area by SEM/EDX analysis. The null hypothesis was rejected since there were signiBicant differences of two bioactive bulk-Bill dental restorative materials in val- ues of bonding to sound dentin and failure patterns after aging in artiBicial saliva In the current study, Cention Forte showed the greatest value of shear bond strength. The highest mean in the Cention Forte with storage group (10.13 MPa), followed by Cen- tion Forte without storage (8.38 MPa). These values were signiBicantly higher compared to Predicta Bioactive, indicating that Cention Forte exhibited superior bonding perfor- mance, particularly after being stored in ar- tiBicial saliva. This could be due to the strong mechanical properties of Cention Forte which is due to its chemical composition as its monomer ma- trix consists of a mixture of urethane di- methacrylates (UDMA), tricyclodecan-di- methanol dimethacrylate (DCP), tetrame- thyl-xylylendiurethane dimethacrylate (aro- matic aliphatic-UDMA) and polyethylene glycol 400 dimethacrylate (PEG-400 DMA), which interconnects (cross-links) during the process of polymerization leading to stronger mechanical properties. This agrees with Bassiouny et.al. (2024) [23], who valu- ate the shear bond strength (SBS) of Cention Forte and Tetric N-Ceram Bulk Fill compo- site Methacrylate-ModiBied Polyacrylic Acid pre- sent in the primer offering dual adhesion mechanisms (mechanical and chemical) by forming micro-mechanical interlocking pro- vided by the surface roughness, most likely combined with chemical interaction through its acrylic / itaconic acid copolymers. Poly- acrylic acid can remove the smear layer and leave the smear plug, producing a partial de- mineralization of the dentin, leaving hydrox- yapatite around the collagen Bibers, allowing the chemical interaction of the carboxylic groups with dentin hydroxyapatite [35]. These results agree with previous work [36], who determine and compare Blexural strength and microhardness of Cention N with other materials at a distinctive period in artiBicial saliva. The current study also agrees with previous work [37,38] that compared the bonding ef- Bicacy of three bioactive self-adhesive re- storative systems to dentin after storage in artiBicial saliva revealed that using of pri- mers prior to application of alkasite-based restorative material is highly recommended and show high microshear bond strength values for both immediate and storage groups of Cention Forte with primer among other tested groups. The contrary, Predict Bioactive showed a lower SBS (with p value less, than or equal 0.05) which could be attributed to its unique monomer composition , a novel monomer (Poly-2-HEMA), which has been advocated to reduce the risk of potentially toxic effects of BisGMA-based compounds that cause in- creased solubility[39] by promotes the for- mation of an unstable aqueous gel that is sus- ceptible to hydrolytic degradation ,HEMA has a negative interaction with 10-MDP in the adhesive agent (G-Premio BOND) used in this study, which signiBicantly reduces the demineralization of hydroxyapatite. This de- creases the formation of MDP Ca salts and partially inhibits the deposition of the nanolayers, which are necessary to obtain an adequate chemical interaction with the den- tin substrate [40]. This may be explained the low viscosity of Predicta bulk bioactive composite (as the Predicta Bioactive type used in the current study is low viscosity type as claimed by manufacture). the morphology of the Biller particles and the amount of Biller loading that improved the mechanical and physical prop- erties of the resin-based composites. Re- duced Biller content of bulk-Bill composites results in an increase in the polymerization shrinkage and shrinkage stresses to poten- tially debond the material from dentin dur- ing polymerization [41,43].This come in agreement with the study conducted by Hegde et al., 2023) [44] , who compare mi- crotensile bond strength of high-viscosity bulk-Bill composites and low-viscosity bulk- Bill composites revealed that the high-viscos- ity bulk-Bill composites exhibited the highest microtensile bond strength in comparison to other resin-based composites, nanocompo- sites, and bulk-Bill Blowable composites. Although aging in artiBicial saliva did not yield a statistically signiBicant overall effect. Cention Forte demonstrated the highest SBS after storage, Predicta Bioactive also exhib- ited improved SBS following storage. The use of ion-releasing materials in restorative den- tistry may contribute to the reduced activity of proteases such as metalloproteinases (MMPs) and cathepsins involved in collagen degradation. Such enzymes are considered one of the main causes for reduction of bond- ing longevity when simpliBied bonding sys- tems are applied in dentine with self-etching or etch-and-rinse protocols [45], thus reduc- ing the enzymatic degradation at the bond- ing interface. It may be also possible that in the case of diffusion of calcium and phos- phate ions through permeable hybrid layers, these may precipitate and crystallize in com- plex calcium-phosphates and inhibit MMPs through the formation of a Ca-PO/MMP com- plex [46]. Cention Forte storage group had the mean value (10.13±2.11) in which the increase was statistically signiBicant in comparison to the non-storage group of the same material (8.38 ± 1.12) After storage, Predicta Bioactive showed some improvement, but not nearly as much as Cention Forte, according to the results. For Predicta Bioactive, its capacity to release ions that promote bond stability implies it can aid in remineralisation and improve the connection. This material demonstrates great potential as a bioactive bulk-Bill compo- site, which can release F, Ca, and P ions, for long-term restoration treatments. This bulk- Bill resin-based composite is simple to apply, cures in two stages, and has optical proper- ties [47]. presence of "HEMA" in Predicta bioactive, a hydrophilic monomer with enhanced solu- bility which may explain its ability to release more ions and enhance its bioactiv- ity[48] also downsizing bioactive glass par- ticles to nano-size improves the alkalizing and hydroxyapatite-forming Based on the in- formation provided by the manufacturer and validated by the EDX study, one of the unique compositions of Predicta Bioactive as manu- facture claimed is titanium dioxide (TiO2 ) TiO2 nanoBller incorporation has no effect on the shear bond strength of the Blowable com- posites[49] however ,may enhance the bio- activity and hydroxyapatite (HA) formation of this material. This in agreement with (Witkowska et al., 2024) [50], Who indicates the good bioactivity of titanium oxide layers. Under simulated biological conditions at pH 7.4 found that TiO2 surface shows predomi- nantly negative properties, creating an elec- trostatic environment that attracts oppo- sitely charged ions, such as calcium. Subse- quently, the positively charged Ca2+ under- goes a reaction with negatively charged PO43− and CO32−, leading to the formation of a surface layer containing Ca–P. Over time, this layer may crystallize into hydroxyapatite [51,52]. The current study found that the storage group of Cention Forte exhibited the highest Shear Bond Strength and SEM/EDX of Two BioacKve Bulk Fill Resin Base Composite RestoraKons Vol 13, No 1 (2025) DOI 10.5195/d3000.2025.1001 http://dentistry3000.pitt.edu 5 shear bond strength, having a low incidence of mixed failure and a higher incidence of co- hesive failure. On the other hand, the non- storage group of Predicta Bioactive revealed the lowest shear bond strength, associated with a greater rate of adhesive failure. These Bindings align with Sabatini’s work, [53] which demonstrated a link between the highest bond strength and mixed failure, while the lowest strength corresponded to adhesive failure. Evidence from several stud- ies supports the hypothesis that cohesive failure in dentin is related to high bond strength [54] perhaps because of the strong bonding to dentin developed by universal adhesives [55]. Scanning electron microscopy (SEM) is often used for the morphological analysis of adhe- sive-dentin interfaces. Many studies have in- vestigated the relationship between bonding performance and interfacial properties [56], (SEM) analysis for Cention Forte showed the interface was completely sealed as an acid-resistant, resin-dentin interdiffu- sion zone with resin tags extending into the dentinal tubules. close the dentinal tubules in storage group while partially cover den- tinal tubules in non-storage group, indicat- ing that the primer effectively demineralized the dentin surface and facilitated the diffu- sion of resin into exposed collagen Bibrils. Both Cention Forte and Predicta Bioactive demonstrated the ion releasing property, which supported the formation of a hybrid layer and improved bond strength after stor- age in artiBicial saliva. this Binding supported by (SEM) analysis that show mixed failure in storage group of Predicta Bioactive. The combined Scanning Electron Micros- copy (SEM) and Energy-Dispersive X-ray (EDX) analytical technique was utilized to assess both the morphology and mineral content of dentin surfaces. This technique al- lowed for qualitative evaluation of surface morphology and quantitative assessment of mineral changes resulting from experi- mental interventions. The preservation of the crystalline structure and the measured Ca/P ratio were used to determine the extent of remineralization, reBlecting the effective- ness of the applied treatments. SEM, with magniBication ranging from 50X to over 10,000X, is a valuable tool in dental research, especially when paired with EDX, which de- tects elemental composition and can indicate the presence of hydroxyapatite through cal- cium phosphate analysis [57,58]. The deBinition of "bioactive" will vary based on the application. In restorative dentistry, the capacity of materials to release ions like as calcium, phosphorus, and Bluoride, hence facilitating remineralisation and the for- mation of hydroxyapatite crystals upon con- tact with physiological Bluids, is referred to as bioactivity [59,60]. An increase in the Ca/P ratio is a critical indicator of remineral- isation, which allows for the assessment of a material's suitability for use on demineral- ised dental tissue. The typical Ca/P ratio in natural dentition is 1.67, when the Ca/P ratio is less than 1.67, it can be classiBied as a non- stoichiometric crystal that is deBicient in cal- cium [61,62]. The study found that under controlled stor- age conditions, SEM/EDX revealed differ- ences in both the restorative materials sur- face and the area of the coronal dentin-resto- ration interface on tooth structure in Cention Forte and Predicta Bioactive indicated their bioactivity by increase the Ca/P ratio of re- storative materials surface for Predicta Bio- active and Cention Forte (1.21±0.20 to 1.84±0.71, 1.31±0.12to2.63±0.63, respec- tively) and also for coronal dentin-restora- tion interface area (1.75±0.35 to 2.71±0.34, 1.97±0.38 to 4.01±1.98, respectively) after storage in artiBicial saliva at pH =7 in 37 C temperature for 30 days. this Binding agree- ment with (Di Lauro et al., 2023) [63], in which this study evaluated the effect of pH and temperature on the ion release of a resin-based material containing alkaline Bill- ers and a self-setting high-viscous glass ion- omer cement the highest amount detected at pH = 6.8 was at 37 °C after 28 days which is comparable to the condition of our study. In neutral and alkaline solutions, Ca and PO4 ions can be precipitated as apatite [64,65]. In this study SEM images supported these Bindings which showed apatite-like crystal in both the restorative materials surface and the area of the coronal dentin-restoration in- terface on tooth structure in Cention Forte and Predicta Bioactive. The Results of the present study showed no signiBicant different in Ca/P ratio in both the restorative materials surface and the area of the coronal dentin-restoration interface on tooth structure in Cention Forte and Predicta Bioactive in non-storage and storage groups. In non-storage groups of this study Cention Forte and Predicta Bioactive showed no sig- niBicant different in Ca/P ratio and less than storage groups .For Cention Forte this can be due to the Billers in which three inorganic glasses: barium alumino-silicate glass, cal- cium barium alumino-Bluoro-silicate and a basic calcium Bluoro-silicate glass referred to as an “Alkasite”Bille [66] that lead to the for- mation of a superBicial layer of calcium Bluo- ride and calcium phosphate with 0.5 mm thickness on the surface of Cention Forte at the initiation of setting reactions, which re- sists dissolution with deionized water for some time[67] . Previous work [68] showed that the phosphate ion release from Cention N bioactive materials signiBicantly increased as the storage time increased 24 h to 4 h, and 6 months in distilled water. Cention Forte primer and Predicta Bioactive contain HEMA, which is hydrophilic mono- mer, high hydrophilicity promotes increased water acceptance that results in the hydro- lytic degradation [69], with increased their solubility, that explain their ability to release more ions and enhance their bioactivity. In this study, the storage media was artiBicial saliva with pH=7 at 37°C temperature for 30 days that is preferable environment for Cen- tion®Forte to release Ca, F, and P ions, which results in the formation of apatite on its surface, like previous results [7,70]. In the current study, even there is no signiBi- cant different in Ca/P ratio in both Cention Forte and Predicta Bioactive in non-storage and storage groups. However, in storage groups, the Ca/P ratio of Cention Forte is higher in both the restorative materials sur- face and the area of the coronal dentin-resto- ration interface on tooth structure (2.63±0.63), (4.01±1.98) respectively than Predicta Bioactive (1.84±0.71, 2.71±0.34, re- spectively). This can be attributed to the fact that it contains alkaline Billers with a strong afBinity for water [71] .When alkaline Billers come in contact with the saliva three salts are connected (Na2O, CaO, CaF2) in SiO2 are dissolved and released Ca, F and OH ions de- pend on the pH, forming apatite in vitro on dentine at pH 7 if phosphate available Com- bine with a speciBic primer [72]. Clinical trials are essential to assess the du- rability of these bioactive restorative materi- als, their performance in patients, and the mechanisms by which these hybrid materi- als release ions and interact with de- cayed dentin. Cention Forte appears suitable for durable restorations, however Predicta Bioactive may still be advantageous in cases where bioactivity and remineralisation properties are required. Conclusion This study showed that employing ion-re- leasing restorative material, speciBically al- kasite-based primers before applying it, is highly suggested because this method seems to be the best way to get a stronger binding with dentin. As a result, this study's Binding that applying primer can improve bonding to dentin goes against the manufacturer's ini- tial advice and classiBication of this type of restoration as self-adhesive. Compared to Predicta Bioactive, Cention Forte had a stronger connection and was better at gener- ating apatite. Higher Ca/P ratios and SEM im- ages suggest that storing in artiBicial saliva made mineral deposition at the contact bet- ter. These results support the idea that Cen- tion Forte can interact with living things, es- pecially when it is moist and old. 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Commercially Available Ion- Releasing Dental Materials and Cavitated Carious Lesions: Clinical Treatment Options. Materials (Basel, Switzerland), 14(21), 6272. Table 1. Shear bond strength values in all groups of the study in Mpa. Restorative materials Saliva ArtiBicial N Minimum Maximum Mean Std. Deviation Predicta Bioactive Non-stored 10 5.10 8.52 6.38 1.15 Stored 10 4.57 8.99 7.18 1.31 Cention Forte Non-stored 10 7.05 10.31 8.38 1.12 Stored 10 7.22 13.42 10.13 2.11 Shear Bond Strength and SEM/EDX of Two BioacKve Bulk Fill Resin Base Composite RestoraKons Vol 13, No 1 (2025) DOI 10.5195/d3000.2025.1001 http://dentistry3000.pitt.edu 8 Figure 1. The mode of failure: (a) adhesive failure, (b) mixed failure, and (c) cohesive failure. Then, Scanning Electron Microscopy (SEM) at 1300X was used in three samples from each subgroup to determine the mode of failure of each de–bonded coronal dentin samples (Figures 2 and 3). Figure 2. SEM images at 1300x magniBication for Predicta Bioactive representing the mode of failure of de-bonded coronal dentin samples; adhesive failure of a sample not stored in artiBicial saliva (a); mixed failure of a sample stored in artiBicial saliva (b). Notes: OD = open dentinal tubules, C = composite material, D = dentin, DA = de-bonded area. Figure 3. SEM images at 1300x magniBication for Cention Forte representing the mode of failure of de-bonded coronal dentin sample; mixed failure of a sample not stored in artiBicial saliva (a); cohesive failure of a sample stored in artiBicial saliva (b). Notes: CD = closed dentinal tubules, OD = open dentinal tubule, D = dentin, DA = de-bonded area. DO C DA DA C a b HA HA HA HA HA HA C Shear Bond Strength and SEM/EDX of Two BioacKve Bulk Fill Resin Base Composite RestoraKons Vol 13, No 1 (2025) DOI 10.5195/d3000.2025.1001 http://dentistry3000.pitt.edu 9 Figure 4. The SEM image at 5000X magniBication for:(a); Predicta Bioactive composite not stored in artiBicial saliva (A1) showed slightly pre- cipitation of hydroxyapatite (b); after storage in artiBicial saliva (A2) showed hydroxyapatite deposition (HA) at the de bonded area of compo- site (C). Figure 5. The SEM image at 5000X magniBication for (a) Cention Forte composite not stored in artiBicial saliva and (b) after storing in artiBicial saliva showed hydroxyapatite (HA) deposition at the de-bonded area of the composite (C). Figure 6. SEM image at 5000X magniBication for de-bonded areas of coronal dentin samples: (a) Predicta Bioactive not stored in artiBicial saliva and (b) after storage in artiBicial saliva. Both images showed crystal-like deposition of hydroxyapatite (HA) at the de-bonded coronal dentin area. D = dentin, DA = de-bonded area. HA HA HA HA HA HA HA HA HA HA HA HA a b a b HA HA HA HA HA HA HA HA DA D DA D Shear Bond Strength and SEM/EDX of Two BioacKve Bulk Fill Resin Base Composite RestoraKons Vol 13, No 1 (2025) DOI 10.5195/d3000.2025.1001 http://dentistry3000.pitt.edu 10 Figure 7. SEM images at 5000X magniBication for de-bonded areas of coronal dentin samples: (a) Cention Forte not stored in artiBicial saliva and (b) after storage in artiBicial saliva. Both images showed crystal-like hydroxyapatite (HA) depositions at the de-bonded coronal dentin areas. D = dentin, DA = de-bonded area. Figure 8. The EDX spectra for one core sample of Predicta Bioactive not stored in artiBicial saliva (A1) and after storage for 30 days in artiBicial saliva (A2) at pH=7 showing the identiBication of the phosphorus peak after storage. Figure 9. The EDX spectra for one core sample of Cention Forte not stored in artiBicial saliva (B1) and after storage for 30 days in artiBicial saliva at pH=7 (B2) showing the phosphorus peak identiBication after storage. a b HA HA D HA HA HA HA HA HA DA DA D Shear Bond Strength and SEM/EDX of Two BioacKve Bulk Fill Resin Base Composite RestoraKons Vol 13, No 1 (2025) DOI 10.5195/d3000.2025.1001 http://dentistry3000.pitt.edu 11 Figure 10. The EDX spectra of one tooth sample (de-bonded coronal dentin) for Predicta Bioactive not stored in artiBicial saliva (A1) and after storage for 30 days in artiBicial saliva (A2) showing a change in the spectra for both phosphorous (P) and calcium (Ca). Figure 11. The EDX spectra of one tooth sample (de-bonded coronal dentin area) for Cention Forte not stored in artiBicial saliva (B1) and after storage for 30 days in artiBicial saliva (B2) showing a change in the spectra for both phosphorous (P) and calcium (Ca).