Shear Bond Strength Of Composite Research Articles

Shear bond strength of a composite resin restoration in primary teeth following cavity preparation using laser- an in-vitro study.

To evaluate and compare the shear bond strength of composite resin restorations in primary teeth, following cavity preparation with both traditional dental burs and laser irradiation. One hundred primary molars extracted from the children visiting our department were collected and randomly divided into five groups (A-E) with 20 teeth in each group. In groups A, B, C, D, and E the teeth samples were etched with phosphoric acid, Er; YAG laser followed by acid etching, Er, Cr: YSGG laser followed by acid etching, Er; YAG laser etching only and Er, Cr: YSGG laser etching only, respectively. Following, all the samples were restored with composite resin and subjected to 500 cycles of thermocycling. The shear bond strength of the resin composite was analyzed. The type of fractures was also noted. Data obtained were subjected to statistical analysis. The mean value of shear bond strength of Group A, B, C, D, and E was 17.562 ± 0.810, 15.928 ± 0.415, 14.964 ± 0.566, 11.833 ± 0.533 and 11.187 ± 0.517, respectively. Adhesive failure was most commonly seen in all the groups. The phosphoric acid etching remains a highly effective technique for pre-treating dentin in composite resin restorations. The shear strength of composite resin to the dentin of laser-prepared cavity in primary teeth can be improved by the addition of acid etching.

Comparison of the Shear Bond Strength of Orthodontic Composites Containing Silver and Amorphous Tricalcium Phosphate Nanoparticles: an ex vivo Study.

It is important to use orthodontic composites with favorable properties, which are easily removed after the end of the treatment but not easily debonded during treatment. Nanoparticles have drawn attention for their antibacterial properties when added to composite resins. However, the effect of addition of nanoparticle on shear bond strength is not broadly discussed. The present study was designed to compare the shear bond strength of orthodontic brackets bonded by orthodontic composite containing silver nanoparticles with orthodontic composite containing amorphous tricalcium phosphate nanoparticles. In this ex vivo study, 36 sound extracted human premolars were used and randomly divided into three groups. The brackets were bonded in the first group by composite without nanoparticles, in the second group by composite containing 3% amorphous tricalcium phosphate nanoparticles and in the third group by composite containing 0.3% silver nanoparticles at the buccal surface of the teeth. The shear bond strengths of the samples were measured 24 hours after preparation by a universal testing machine. Data were analyzed using SPSS 21 software through one-way ANOVA and Tamhane's T2 multiple comparison tests. pValues under 0.05 were considered significant. There was no significant difference between the mean shear bond strength of composite containing amorphous tricalcium phosphate nanoparticles with composite without nanoparticles (p= 0.142). However, the mean shear bond strength in the composite containing silver nanoparticles was significantly lower than the other two groups (p< 0.001). According to the results of this study, the addition of amorphous tricalcium phosphate nanoparticles to orthodontic composite does not significantly decrease the shear bond strength while silver nanoparticles reduce the shear bond strength of orthodontic composite.

Comparative Evaluation of Effect of Different Antioxidants on Shear Bond Strength of Composites on Bleached Enamel: An In Vitro Study.

To evaluate the effect of antioxidants on the shear bond strength of composite resin to bleached enamel. A total of 120 extracted permanent anterior teeth were split into four major groups, one among them being a control group. Group I (bleaching + without antioxidant), group II (bleaching + 10% sodium ascorbate), group III (bleaching + 5% grape seed extract), and group IV (bleaching + 5% pine bark extract). All of the groups were bleached using a gel containing 35% carbamide peroxide, and then they were divided into two subgroups depending on when the bonding operation was to be completed-subgroup A was done in 24 hours, while subgroup B took 3 weeks. The universal testing machine was used to measure the shear bond strength. Subgroup IA showed poor shear bond strength than other groups, there was no statistically significant difference between subgroup IB, IIA, and IVA. Subgroup IIIA showed the highest shear bond strength than the remaining groups. Between subgroups IIA and IIB, IIIA and IIIB, and IVA and IVB there was no statistically significant difference. This shows that delaying the bonding procedure for 3 weeks shows similar shear bond strength when compared to groups that were immediately bonded after antioxidant applying groups. All the antioxidants' immediate application could reverse compromised bond strength. Among them, 5% grape seed extract shows the highest increase in shear bond strength. Maddula DC, Vasepalli M, Martha S, et al. Comparative Evaluation of Effect of Different Antioxidants on Shear Bond Strength of Composites on Bleached Enamel: An In Vitro Study. Int J Clin Pediatr Dent 2023;16(1):87-92.

Effect of shape of titanium dioxide nanofillers on the properties of dental composites

The main objective of the present study was to evaluate the effect of the morphology of titanium dioxide nanofillers on the flexural strength and shear bond strength of the dental composite. Spherical and rhombic-shaped nano titanium dioxide fillers were synthesized via solvothermal method and were characterized. Subsequently, these fillers were incorporated into a flowable composite (Filtek™ Z350 XT Flowable Restorative) at 0.5 wt.% and 1.5 wt.% and the prepared specimens were stored in water for 24 h. The specimens were then evaluated for flexural strength using a universal testing machine. Similarly, the shear bond strength of modified composites to the tooth was evaluated and bond failures were analyzed using stereomicroscope magnification. Incorporation of nanofillers significantly enhanced the flexural strength of flowable composite (p = 0.009) with a significant increase at 0.5wt.% of spherical (p = 0.015) and rhomboidal-shaped fillers (p = 0.010). However, no statistically significant difference in flexural strength was observed among the different shapes of nanofillers. The results of our study did not show a significant effect on the shear bond strength of the composites. Thus the reinforcing ability of titanium dioxide nanofillers on dental composite was confirmed in this study, although the effect of using nanofillers with different morphology was not significant.Graphical abstract

Comparing the Efficacy of Shear Bond Strength with Composite Attachments and Different Ceramic Surfaces-Zirconia, Lithium Disilicate, and Feldspathic Porcelain

Introduction: Dental practitioners utilize many different dental materials to fabricate durable and aesthetic fixed prostheses. The practitioners may not be considering the future treatment options of their patients. In the field of orthodontics, there have traditionally been concerns about the bond strength between brackets and ceramic crown materials. However, as the popularity of esthetic treatment options continues to grow, there will be increased importance in extending this bonding knowledge to the application of the composite buttons utilized in clear aligner therapies. Since this bonding performance with the crown materials has been shown to be an issue in dentistry today, we investigated the most retentive ceramicbased crown materials to deliver optimal composite shear bond strength for attachment buttons.

Comparative Analysis of Shear Bond Strength of Composites to the Sodium Ascorbate Hydrogel-treated Bleached Enamel Surfaces: An In Vitro Analysis.

AimTo compare the shear bond strength of composites to the sodium ascorbate hydrogel-treated bleached enamel surfaces.Materials and methodsSixty-six extracted human maxillary first premolars were sectioned mesiodistally to obtain two nonocclusal surfaces (n = 132). The specimen in the experimental group (n = 80) were divided into four treatment groups depending upon bleaching protocols used: group I (10% FGM home bleach), group II (22% Pola Night home bleach), group III (37% light-activated in-office bleach Pola Office+), and group IV (35% Pola office in-office bleach without light activation). Specimens were subjected to the 1-minute application twice with sodium ascorbate hydrogel and were further divided into two subgroups “a” (acetone-based) and “b”(ethanol-based) depending upon the bonding agents used. The specimens of the control group (n = 52) were further divided into two treatment groups, that is, positive control and negative control. The specimens were tested using universal testing machine.ResultsThe result of the present study revealed that the specimens bleached with 10% FGM home bleach showed the greatest shear bond strength and specimens bleached with 35% in-office bleach Pola Office showed the lowest shear bond strength.ConclusionA twice 1-minute application of sodium ascorbate hydrogel was effective to reverse the deleterious results of bleaching on enamel shear bond strength. Bonding agent containing acetone as a solvent (Prime and Bond NT) in this present study showed greater shear bond strength values than the bonding agent containing ethanol as a solvent (Adper Single Bond).Statement of clinical relevanceThe shear bond strength of composite restorative materials could be improved by applying sodium ascorbate gel to the bleached enamel surfaces.How to cite this articlePathak K, Kumar P, Choudhary A, et al. Comparative Analysis of Shear Bond Strength of Composites to the Sodium Ascorbate Hydrogel-treated Bleached Enamel Surfaces: An In vitro Analysis. Int J Clin Pediatr Dent 2021;14(6):741–747.

Chemical Composition, Knoop Hardness, Surface Roughness, and Adhesion Aspects of Additively Manufactured Dental Interim Materials.

To measure the chemical composition, Knoop hardness, surface roughness, and composite bond strength of additive manufactured (AM) and conventional interim materials. Disks were prepared using conventionally (CNV group) and additively manufactured (AM group) materials: CNV-1 (Protemp 4; 3M ESPE), CNV-2 (Anaxdent new outline dentin; Anaxdent), AM-1 (FreePrint temp; Detax), AM-2 (E-Dent 400 C&B MFH; Envisiontec), AM-3 (NextDent C&B MFH; 3D Systems), and AM-4 (Med620 VEROGlaze; Stratasys). Each group was subdivided into 3 subgroups (n = 20) for analyzing Knoop hardness (KHN), chemical composition, superficial roughness (Ra), and composite shear bond strength. The first subgroup was exposed to a microhardness test. Subsequently, EDAX analysis was selected to analyze the chemical composition. The second subgroup was selected to measure the superficial roughness (Ra) using a contact profilometer. The third subgroup was used to measured composite shear bond strength using a universal testing apparatus. A digital microscope was used to analyze the fracture mode. The Shapiro-Wilk test showed normally distributed data. One-way ANOVA and post hoc Sidak tests were selected (α = 0.05). Major variances in chemical composition were observed among the specimens. Significant differences in Knoop hardness (p < 0.001) and surface roughness (p < 0.001) were detected. The AM-4 (13.45± 2.93KHN), the CNV-2 (13.35± 5.84 KHN), the AM-2 (13.03± 3.29 KHN), and the AM-1 (12.55± 2.93KHN) groups obtained the highest Knoop hardness values, followed by the AM-3 and the CNV-1 groups (p < 0.05). The AM-1 group (1.88± 1.11 Ra) obtained the highest surface roughness values among the groups, followed by the AM-3 group (0.90± 0.14 Ra) (p < 0.05). However, no significant differences in shear bond strength values were found between the groups ranging from 23.18± 8.88MPa to 33.29± 9.17MPa (p = 0.061). All the groups showed a cohesive mode of failure. The AM interim materials tested had significant chemical composition variations compared to conventional materials. For the mechanical properties evaluated, the AM materials obtained appropriate mechanical properties for use as an interim dental restoration. However, further studies are required to evaluate more extensively its mechanical properties and verify their applicability in the oral cavity, clinical behavior, and biocompatibility.

Effect of alcoholic beverages on shear bond strength of composites to enamel.

Background:Longevity of composite restoration in the oral cavity is dependent on various factors. One such factor is exposure to various foods and beverages which could alter the properties of the material.Aim:The aim of this in vitro study was to evaluate the effect of most widely consumed alcoholic beverages on shear bond strength of composites to enamel.Material and Methods:A total of seventy human premolars were embedded in acrylic resin blocks. Labial enamel surfaces was flattened, etched, bonded, and restored with composite resin (Tetric N Ceram – Ivoclar Vivadent AG, Schaan, Liechtenstein). The specimens were randomly divided into four groups: Group I: beer; Group II: wine; Group III: whiskey, and Group IV: artificial saliva. Group I to Group III were again divided into moderate (Group IA, IIA, and IIIA) and heavy (Group IB, IIB, and IIIB) consumption subgroups. The specimens were soaked in their respective groups for 90 min daily in Group IA, IIA, and IIIA and for 30 min every alternate day in Group IB, IIB, and IIIB until 30 days. Universal testing machine was used to determine the shear bond strength of composite with enamel.Statistical Analysis Used:The values obtained were statistically analyzed using two-way analysis of variance followed by post hoc test with the significant level set at P < 0.05, using GraphPad prism software version 6.01.Results:Group IIB showed the highest reduction in shear bond strength, with a mean value of 6.6 ± 1.2 Mpa in comparison to control with a mean value of 21.8 ± 1.6 Mpa.Conclusion:As the content of alcohol and time of exposure increased along with a decrease in the pH of alcoholic beverages, shear bond strength between composite and enamel decreased.

Effect of Desensitization Using Bioactive Glass, Hydroxyapatite, and Diode Laser on the Shear Bond Strength of Resin Composites Measured at Different Time Intervals: An In vitro Study.

Background:Dentin desensitizers may change the properties of smear layer and have adverse effects on the bonding performance of adhesive systems.Aim:The aim of this study was to compare the effect of bioactive glass (BG), hydroxyapatite, and diode laser desensitization on shear bond strength of resin composites to dentin at different time intervals.Materials and Methods:Seventy-two caries-free maxillary premolars were selected. Buccal surfaces were flattened to expose dentin. Teeth were divided into four groups (Groups 1, 2, 3, and 4) according to treatment modality (control with no pretreatment, Sensodyne Repair and Protect, Teethmate Desensitizer, diode laser). Bonding was performed using self-etch adhesive followed by composite buildup. Universal testing machine was used to determine shear bond strengths immediately after bonding, after 3 months, and 5 months storage in artificial saliva.Results:Pretreatment with BG and hydroxyapatite desensitizers increased, whereas diode laser decreased mean shear bond strength of composite to dentin as compared to control group. No statistical significant difference in shear bond strength values was seen in groups after storage.Conclusion:Desensitizing toothpastes incorporating remineralizing agents not only occluded open dentinal tubules but also increased shear bond strength of composite to dentin.

Effect of whitening toothpastes on bonding of restorative materials to enamel of primary teeth.

The aim of this in vitro investigation was to measure shear bond strength (SBS) of a resin composite and a resin-modified glass ionomer to enamel of primary teeth after application of different whitening toothpastes (WTs). Eighty labial enamel surfaces of primary incisors were randomly distributed into 8 groups of 10 each according to the surface treatment and bonding material. G1 and G2, control (brushed with water without WT); G3 and G4, (brushed with Colgate Optic White WT [Colgate-Palmolive Company, New York, NY, USA]), G5 and G6, (brushed with Crest Pro-Health Whitening WT [Procter and Gamble, Cincinnati, OH, USA]) and G7 and G8, (brushed with Arm and Hammer Advance White Extreme Whitening with Stain Defense WT [Church and Dwight Co., Princeton, NJ, USA]). SBS was measured at a crosshead speed of 0.5 mm/min and the type of bond failure was assessed using a stereomicroscope. There was significant difference between SBS of composite resin in groups 1, 3, 5, and 7 (P < 0.001), but no difference between resin-modified glass ionomer in groups 2, 4, 6, and 8 (P < 0.056). SBS of group 1 (control) was greater than groups 3, 5, and 7. There was a significant difference between group 1 and group 2 as well as group 7 and group 8 (P < 0.001). WTs affect SBS of resin composite, but not resin-modified glass ionomer to enamel of primary teeth. No difference of failure modes between different groups of tested materials.

Application of 10% Ascorbic Acid Improves Resin Shear Bond Stregth in Bleached Dentin

Restoration of the teeth immediately after bleaching with H2O2 35% is contraindicated due to the remnants of free radical that will stay inside dentin for 2-3 weeks which will compromise the adhesiveness of composite resin. Objective: The aim of this study was to evaluate the influence of 10% ascorbic acid on shear bond strength of composite placed on bleached dentin. Methods: Twenty seven samples were divided equally into three groups. Group 1: dentin was etched with 35% phosphoric acid; Group 2: dentin was bleached with 35% H2O2 followed by etching with 35% phosphoric acid; Group 3: dentin was bleached with 35% H2O2, followed by application of 10% ascorbic acid and etched with 35% phosphoric acid. All samples were then stored at 370C for 24 hours. The Universal Testing Machine was used to measure shear bond strength and the results were analyzed with Kruskal Wallis and Mann Whitney test. Results: After nine independent experiments, 10% ascorbic acid application on bleached dentin resulted in highest increased in bond stregth (56.04±11.06MPa) compared to Group 2 (29.09±7.63MPa) and Group 1 (25.55±2.22MPa) and the difference was statistically significant (p<0.05). Conclusion: Application of 10% ascorbic acid to the bleached dentin improved the shear bond strength of resin composite.

Evaluation of the Effect of Tooth Surface Wetting and Bond Strength of Composite-an In vitro Study

Adhesive restorations have become integral part of routine dental treatment. To achieve clinical success with such restorations, it is of clinical importance to ensure good bonding between this restoration and tooth surface. Bonding to dentin is far more challenging. Bond between dentin and dentin bonding adhesives is greatly influenced by: (1) Surface condition of dentin (moist/dry); (2) Chemical nature of dentin bonding agents. The present study has been designed: (i) to study the effect of various conditions (moist/dry) of dentin on bonding with dentin bonding agents; (ii) to compare the strength achieved by dentin, bonding agent of different systems (water/acetone based). This study was conducted to evaluate the effect of tooth surface wetting on shear bond strength of composite. Freshly extracted central incisors were taken. Cavities were prepared in middle 1/3 of teeth. Teeth were divided in groups A,B,C depending on their surface treatment (wet, semi dry, dry surface) and again in to sub groups depending on whether they are treated water based or acetone based dentin bonding agents(scotch bond, prime bond NT, clear fil SE) . All the cavities in samples were filled with composite and light cured. Composite was debonded from teeth by Instron machine. Debonded samples were scanned and micro graphed under SEM. From the observations made, statistically analyzed and duly discussed, following conclusions are drawn: 1. Optimal water content is necessary for achieving good bonding between dentin and composite. 2. Water based dentin bonding agents, show maximum shear bond strength with dentin in dry conditions. 3. Acetone based dentin bonding agents show maximum shear bond strength with dentin in wet conditions. Overview of the results shows that moisture plays a vital role in bonding of composite with dentin. Optimal water should be present for better bonding of dentin with composite. If dentin is in dry stage, then water based dentin-bonding agents should be used as they produce best results in dry conditions and if dentin is in wet state then acetone based dentin-bonding agents should be used as they produce best results in wet conditions.

Light Cure Tip Distance and Shear Bond Strength: Does It have any Clinical Significance?

Aim: The purpose of this study was to assess whether minor change in distance of the light cure tip to the bonding surface produce any significant effect on shear bond strength of composites and resin-modified glass ionomer cement used for bonding brackets. Materials and methods: Ninety therapeutically extracted human premolar teeth were randomly allocated to six groups of 15 specimens each. Resin-modified glass ionomer (GC Fuji Ortho LC) was used to bond brackets to the teeth in three groups with curing light held at three distances from the bracket: 2, 4 and 6 mm. For the other three groups light cured composite resin (Transbond TM XT) was used to bond brackets with curing light held at three distances from the bracket: 2, 4 and 6 mm. After bonding, all samples were stored in distilled water at room temperature for 24 hours and subsequently tested for shear bond strength. Results and conclusion: (1) Light tip distance of 2 or 4 mm does not affect the shear bond strength of composites significantly; however increase in the distance to 6 mm significantly reduces the shear bond strength, (2) There was a significant decrease in the shear bond strength, with the progressive increase in distance of the light source from 2 to 4 and 6 mm in case of resin-modified glass ionomer cement, (3) The mean shear bond strength of light cure composites is higher than resin-modified glass ionomer cement at all the three light source distances compared, i.e. 2 or 4 or 6 mm.

Effect of Er,Cr:YSGG Laser, Air Abrasion, and Silane Application on Repaired Shear Bond Strength of Composites

Aged resin composites have a limited number of carbon-carbon double bonds to adhere to a new layer of resin. Study objectives were to 1) evaluate various surface treatments on repaired shear bond strength between aged and new resin composites and 2) to assess the influence of a silane coupling agent after surface treatments. Eighty disk-shape resin composite specimens were fabricated and thermocycled 5000 times prior to surface treatment. Specimens were randomly assigned to one of the three surface treatment groups (n=20): 1) air abrasion with 50-μm aluminum oxide, 2) tribochemical silica coating (CoJet), or 3) Er,Cr:YSGG (erbium, chromium: yttrium-scandium-gallium-garnet) laser or to a no-treatment control group (n=20). Specimens were etched with 35% phosphoric acid, rinsed, and dried. Each group was divided into two subgroups (n=10): A) no silanization and B) with silanization. The adhesive agent was applied and new resin composite was bonded to each conditioned surface. Shear bond strength was evaluated and data analyzed using two-way analysis of variance (ANOVA). Air abrasion with 50-μm aluminum oxide showed significantly higher repair bond strength than the Er,Cr:YSGG laser and control groups. Air abrasion with 50-μm aluminum oxide was not significantly different from tribochemical silica coating. Tribochemical silica coating had significantly higher repair bond strength than Er,Cr:YSGG laser and the control. Er,Cr:YSGG laser and the control did not have significantly different repair bond strengths. Silanization had no influence on repair bond strength for any of the surface treatment methods. Air abrasion with 50-μm aluminum oxide and tribochemical silica followed by the application of bonding agent provided the highest repair shear bond strength values, suggesting that they might be adequate methods to improve the quality of repairs of resin composites.

The influence of different fiber-reinforced composites on shear bond strengths when bonded to enamel and dentin structures

Background/purpose The aim of this study was to evaluate the effect of different fiber-reinforced composites (FRCs) on the shear bond strength of composites bonded to tooth structures. Materials and methods One hundred human non-carious upper central incisors were used. The FRC test specimens consisted of 4 commercially available polyethylene fiber products (Ribbond, Construct (CT), glass-fiber everStick (ES), and Stick, and one nanohybrid composite (Grandio), bonded to the vestibular surface of adhesive-treated enamel and dentin. Control groups were prepared using the nanohybrid composite along without fiber reinforcement. Specimens were stored wet for 24 hours at 37°C and thermocycled 5000 times between 5 and 55°C. Then, the shear bond strength (SBS) was determined using a universal test machine (Instron) at a crosshead speed of 0.5 mm/min. The failure patterns of the debonded specimens were evaluated using a stereoelectron microscope. Scanning electron microscopy (SEM) was used to assess the fiber resin interface of representative samples. SBS data were analyzed using analysis of variance (ANOVA) and Duncan’s test (α = 0.05). Results SBS data ranged 21.54–40.18 MPa for the enamel substrates and 20.83–36.87 MPa for the dentin substrates. The one-way ANOVA results revealed statistically significant differences between the shear bond strengths of the experimental and control groups (P < 0.001). Two-way ANOVA of the experimental groups demonstrated statistically significant differences in SBSs between different fiber types and substrates (P < 0.05). A typical SEM micrograph of the surface of the fractured specimens following the shear bond test exhibited no evidence of debonding between the fiber and matrix when using the CT and ES fibers. The SEM analysis revealed that Stick fiber reinforcement contained some air voids in the final FRC structure. Combined cohesive and mixed fracture modes at the tooth/composite interface for CT/enamel, CT/dentin, ES/enamel, and ES/dentin were 50%, 60%, 40%, and 30%, respectively. The adhesive fracture mode was predominant in the control groups. Conclusions The addition of an FRC at the interface showed positive effects on the SBSs of the composite bonded to the tooth structure and resulted in changes in the fracture pattern.

Role of oxygen inhibited layer on shear bond strength of composites.

Background and Aim:Rising demand for aesthetic adhesive restorations has led to wide use of composites. A multilayer technique is recommended for success of these restorations. The surface layer of composite coming in contact with air forms a superficial sticky layer called oxygen inhibited layer, upon polymerization, allowing resins from both sides to cross the interface and form an interdiffusion zone. The present study was sought to test whether oxygen inhibited layer increases or decreases the shear bond strength at the interface of composites.Materials and Methods:A microhybrid composite Esthetic –X (Dentsply, Caulk) was used in this study. A cylindrical mold of composite, five mm thick and eight mm long, was prepared and embedded in acrylic resin molds after curing. This was placed in distilled water for two hours and sheared in universal testing machine at a cross head speed of one mm/sec.Statistical Analysis:Data analyzed statistically to determine the significant difference between the groups. Mean and standard deviation values were estimated for the study groups and compared by one way ANOVA.Results:No significant difference in shear bond strength of composites cured with and with out oxygen inhibited layer.Conclusions:The presence or absence of oxygen inhibited layer made no significant difference in shear bond strength of composite resins.

Comparison of the Effect of Hydrogel and a Solution of Sodium Ascorbate on Dentincomposite Bond Strength After Bleaching

The aim of this study was to compare the effects of solution and different sodium ascorbate hydrogels on dentin-resin composite shear bond strength subsequent to a bleaching procedure with 10% carbamide peroxide. Sixty buccal dentin surfaces obtained from intact human third molars were randomly divided into five groups (n=12). Dentin surfaces received different treatments: (1) no treatment; (2) bleaching (10% carbamide peroxide gel); (3) bleaching + 10% sodium ascorbate solution; (4) bleaching + 10% sodium ascorbate hydrogel, and (5) bleaching + 20% sodium ascorbate hydrogel. Dentin surfaces were bonded with Single Bond and restored with a composite (Z100). The samples were tested for shear bond strengths. Data was analyzed using analysis of variance (ANOVA) and Tukey tests. Significantly higher bond strengths were observed subsequent to treatment with hydrogel and solution forms of sodium ascorbate (p<0.05). No significant differences were demonstrated between different forms of sodium ascorbate preparations. In addition, no significant differences were observed among groups with antioxidant treatment (Groups 3, 4, and 5) and Group 1 (no treatment). Reduced bond strength to bleached dentin can be amended by the use of sodium ascorbate as an antioxidant. Both hydrogel and solution forms of sodium ascorbate can significantly improve the reduced bond strength of resin composite to dentin subsequent to a bleaching procedure with 10% carbamide peroxide.

The role of oxygen inhibited layer on the shear bond strength of composites - An in-vitro evaluation

Light or chemically cured dental composite resins leave a soft, sticky superficial layer upon polymerization. The layer is commonly referred to as Oxygen Inhibited Layer and it is always present when a composite or bonding resin is polymerized in air. For years. it <http://years.it> wa s believed that Oxygen Inhibited Layer is required before adding more layers of bonded composite.<br>But reports on how Oxygen Inhibited Layer affects the bond strength have been inconsistent and contradictory.<br>The aim of the present study was to compare the shear bond strengths of composite composite bonded specimens prepared with or without Oxygen Inhibited Layer. The shear bond strengths were tested using Universal Testing Machine.<br>The results of the present study show that the presence of Oxygen inhibited layer increases the shear bond strength values at the interphase of incrementally built 2 layer composite specimens. Within the limitations of the present study, it can be conclusively stated a higher shear bond strength results from Oxygen Inhibition on the surface layer of composite.

The effect of hydrogel and solution of sodium ascorbate on the bond strength of bleached enamel

The purpose of the study was to compare the effect of hydrogel and solution of sodium ascorbate on enamel-resin composite shear bond strength after bleaching. 40 buccal enamel surfaces of maxillary molar were taken, divided into 4 groups (n=10). Group I (bleaching with 10% carbamide peroxide), group 2 (bleaching and 10% sodium ascorbate solution), group 3 (bleaching + 10% sodium ascorbate hydrogel) and group 4 (bleaching + 20%) sodium ascorbate hydrogel). All the teeth were restored with composite and subjected to shear bond testing. The results were evaluated. The data was analyzed by ANOVA test and multiple comparisons by Post Hoc tests. It was concluded that there was increase in the bond strength when antioxidants were used after bleaching but there was no significant difference among the different forms of sodium ascorbate.

Evaluation of shear bond strength of composite to newly condensed and set amalgam by using two adhesive systems.

The introduction of adhesives has created a new opportunity to bond compositeresin to existing amalgam restoration on aesthetically disturbing surfaces. Further more ,the composite laminate would probably improve the restoration .This in vitro study was conducted to evaluate the shear bond strength ofcomposite resin to fresh and set amalgam by the use of two adhesive systems and to studythe effect of water storage time on the shear bond strength of composite resin to fresh andset amalgamOne hundred and eighty cylindrical specimens, 5mm high x 5 mm in diameter ,composed of 3 mm of amalgam and 2 mm of composite with a layer of bonding materialin between were prepared. Syntac Sc, Excite, control (non bonding) used to bondcomposite resin (Tetric) to the amalgam bases in three groups I, Il and lll (each onecomposed of 60 amalgam bases). Each group divided into two minor groups each of 30amalgam bases one for fresh amalgam bases referred (F) and the other one for setamalgam bases referred (S), each minor group, F and S subdivided into 3 subgroupsaccording to water immersion period into 48hrs, lmonth, 3months,stored at 37 C forscheduled period of time .