Reduction In Shear Bond Strength Research Articles

In vitro bleaching effect of hydrogen peroxide with different time of exposition and concentration on shear bond strength of orthodontic brackets to human enamel: A meta-analysis of in vitro studies

Controversy exists regarding the effect of bleaching on shear bond strength (SBS) of orthodontic brackets to enamel. This study aims to do a review and meta-analysis on the effect of bleaching with hydrogen peroxide on SBS according to the interval between bleaching and bonding to human enamel and the concentration of Hydrogen Peroxide. An electronic search of the literature was performed in Scopus, PubMed and Cochrane databases including CENTRAL and Cochrane library for relevant in vitro studies on the effect of bleaching with hydrogen peroxide on shear bond strength of human enamel, published until June 2018. Modified Cochrane Risk of Bias tool was used to assess the quality of the individual studies. AMSTAR tool was used for assessing the quality of the study. Nineteen studies were included in the qualitative analysis. Regardless of the interval between bleaching and bonding, reduction in SBS was not statistically significant when the hydrogen peroxide of less than 35% is used. Bleaching with 35% hydrogen reduces SBS when the bonding is conducted immediately (P<0.0001) or the time interval was shorter than one day (P<0.0005). On the other hand, use of high dose hydrogen peroxide resulted in a statistically significant reduction in SBS irrespective of the time interval between the procedures (P<0.05 for all categories of time interval). Bleaching with hydrogen peroxide decreases the SBS of brackets in patients undergoing orthodontic treatment especially if the time interval between bleaching and bonding procedures is short and a high concentration of hydrogen peroxide is used.

The effect of surface treatment and thermocycling on the shear bond strength of porcelain laminate veneering material cemented with different luting cements

Aim: The study aimed to evaluate and compare the effect of different surface treatment and thermocycling on the shear bond strength (SBS) of different dual-/light-cure cements bonding porcelain laminate veneers (PLV). Methods: One hundred and twenty A2 shade lithium disilicate discs were divided into three groups based on the resin cement used and on the pretreatment received and then divided into two subgroups: thermocycling and control. The surface treatment were either micro-etched with aluminium trioxide and 10% hydrofluoric acid or etched with 10% hydrofluoric acid only before cementation. Three dual-cure (Variolink Esthetic (I), RelyX Ultimate (II), and RelyX Unicem (III)) and three light-cure (Variolink Veneer (IV), Variolink Esthetic (V), RelyX Veneer (VI)) resin cements were used for cementation. The SBS of the samples was evaluated and analysed using three -way ANOVA with statistical significant set at α=0.05. Results: For all resin cements tested with different surface treatments, there was a statistically significant difference within resin cements per surface treatment (p&lt;0.05). The shear bond strength in the micro-etch group was significant higher than the acid-etch group (p&lt;0.05) There was statistically significant interaction observed between the surface treatment and thermocycling (p&lt;0.05) as well as the cement and thermocycling(p&lt;0.05). It was observed that the reduction in shear bond strength after thermocycling was more pronounced in the acid etch subgroup as compared to the microetch subgroup. However, the interaction between the three factors: surface treatments, thermocycling and resin cements did not demonstrate statistically significant differences between and within groups (p=0.087). Conclusions: Within the limitations of the present study, it acan be concluded that Dual cure resin cements showed a higher Shear bond strength as compared to light cure resin cements. Thermal cycling significantly decreased the shear bond strength for both ceramic surface treatments. After thermocycling, the specimens with 10% HF surface treatment showed lower shear bond strength values when compared to those treated by sandblasting with Al2O3 particles.

Laser Aided Ceramic Restoration Removal: A Comprehensive Review.

Introduction: All-ceramic restorations are being widely used due to its various advantages. However, they have restricted durability and may have to be removed. The conventional procedure for removal is grinding the restoration with rotary instruments which are considered time-consuming and inconvenient. A newer advantageous method is the application of lasers for debonding ceramics from the tooth surface. The objective of this study is to provide a comprehensive literature review on laser-aided ceramic restorations debonding. Methods: We searched PubMed and Google Scholar databases. Seven articles from 2011 to 2018 were identified. Studies were assessed for the efficacy of laser application and the amount of pulpal temperature rise. Results: Studies selected were categorized according to variables including shear bond strength, debonding time and intrapulpal temperature. Oztoprak and Iseri investigated that erbium-doped yttrium, aluminum, and garnet (Er:YAG) laser application reduced shear bond strength of ceramic laminate veneers. The time of debonding took an average of 190 seconds in Rechmann's study and 106 seconds in Morford's study. One of the main issues while using the laser is thermal irritation of the pulp. A 5.5°C temperature increase may cause pulpal damage according to Zach and Cohen. Philips et al and Rechmann et al reported no intrapulpal harm due to temperature increase. Additionally, Phillips et al demonstrated that the laser setting affects both the debonding time and the temperature alterations and that a laser adjustment of 2.5 W/25 Hz would be the best safest group. Conclusion: Removal of ceramic crowns and veneers from tooth surfaces can be successfully done by Er:YAG laser application in a less time-consuming procedure and without any harm to the underlying dentin. However, a temperature rise in the pulp may occur which could be overcome by adequate air water cooling.

Evaluation of the effect of silicone residue after different surface treatments on shear bond strength of glass ionomer cement to the dentin surface.

Aim:Use of silicone fit-checking material during cementation of fixed restoration has shown to leave residual silicone film after peeling off of fit checker (FC). This residual film reduced bond strength of cement to the inner surface of restoration. Silicone residue effect on tooth surface needs to be studied. The aim of this study was to evaluate the effect of residual silicone film on shear bond strength (SBS) of glass ionomer cement (GIC) to dentin surface and the efficacy of different surface treatments (STs) on dentin in the removal of silicone residue.Materials and Methods:Fifty freshly extracted human molars were individually mounted on acrylic blocks and occlusal surfaces were ground flat until dentine surface was exposed. Specimens were divided into five groups as follows: Group I: without application of FC (n = 10) as control group; Group II: without any ST after peeling off FC (n = 10); Group III: ST using wet pumice after peeling off FC (n = 10); Group IV: ST with 37% phosphoric acid after peeling off FC (n = 10); and Group V: ST with 10% polyacrylic acid after peeling off FC (n = 10). GIC was placed on the dentinal surface using polyvinyl mold and subjected to SBS test using universal testing machine. The debonded specimens were observed under stereomicroscope for the mode of failure. Selected debonded dentinal surfaces from each group were examined under scanning electron microscope. One-way analysis of variance and Tukey's test.Results:Group II (1.083 MPa) showed significantly lower SBS. Among the STs, Group III (2.047 MPa) was comparable to the control group whereas Group IV (1.376 MPa) and Group V (1.63 MPa) were significantly lower. There was no significant association between failures and groups at P = 0.257.Conclusion:The residue of silicone was demonstrable on dentin surface after peeling off FC and caused a significant reduction in SBS between GIC and dentin. ST with wet pumice is found to be beneficial in removing silicone residue and improving SBS, followed by phosphoric acid and polyacrylic acid.

Effect of antioxidants on the shear bond strength of composite resin to enamel following extra-coronal bleaching.

BackgroundRecently patients need faster treatments, and delaying restoration is not possible following bleaching treatment. The purpose of this study was to determine the effect of antioxidants, namely 10% sodium ascorbate, 10% alpha-tocopherol, 10% green tea and 10% Aloe vera extract on the shear bond strength of composite resin to enamel following extra-coronal bleaching using 40% hydrogen peroxide.Material and MethodsSeventy premolars were randomly assigned into 7 groups of 10 each. Group 1: bleaching treatment and no antioxidants application. Group 2: composite was built-up immediately after bleaching. Group 3: bleached specimens received composite build-up delayed by 2 weeks. Group 4, 5, 6 and 7: bleached specimens received an application of 10% sodium ascorbate, 10% alpha-tocopherol, 10% green tea, and 10% Aloe vera before composite build-up. Specimens were immersed in artificial saliva, stored in an incubator 37°C (24 hours), thermocycling, and tested using a universal testing machine. Data were analyzed by one-way ANOVA and Tukey’s test with 95% level of significance.ResultsBleaching caused significantly reduced shear bond strength (p<0.05), and application of 10% sodium ascorbate, 10% alpha-tocopherol, 10% green tea and 10% Aloe vera produced significantly greater shear bond strength compared to bleached group (P <0.05). However, no significant differences occurred between antioxidant groups (P >0.05).ConclusionsApplication of antioxidants increased the shear bond strength of composite resin to enamel following extra-coronal bleaching using 40% hydrogen peroxide. 10% sodium ascorbate, 10% alpha-tocopherol, 10% green tea and 10% Aloe vera extracts produced the same effect on the shear bond strength of composite resin to enamel following extra-coronal bleaching using 40% hydrogen peroxide. Key words:Antioxidants, shear bond strength, composite resin, extra-coronal bleaching.

Altered adhesion of dental sealant to tooth enamel microscopically modified by Er:YAG laser irradiation: An in vitro study.

Er:YAG laser has become optional for enamel and dentin preparation for a decade. However, it is unclear if Er:YAG laser is acceptable for enamel conditioning prior to an application of a pit-and-fissure sealant. This in vitro study thus aimed to investigate shear bond strength of a sealant to enamel etched with Er:YAG laser, as well as to demonstrate an alteration of enamel surface after the laser was applied. One hundred and twenty extracted human premolars were divided into 4 groups (N = 30 per group) in which the enamel surfaces were treated with 1) 37% phosphoric acid, 2) Er:YAG laser 80 mJ/pulse, 2 Hz, 3) Er:YAG laser 120 mJ/pulse, 10 Hz, and 4) Er:YAG laser 140 mJ/pulse, 2 Hz. Prior to sealant application. Shear bond strength was determined by using a universal testing machine. Statistical analysis was performed using One-way ANOVA. Modification of enamel surface after laser ablation was also investigated using scanning electron microscope. Phosphoric acid-etched enamel yielded the highest shear bond strength when bonded with a sealant. Ablation of enamel with Er:YAG laser did not significantly improve sealant bonding since it demonstrated lower shear bond strength, compared to acid-etched enamel. Despite the presence of cracks after Er:YAG laser application, dissolution of enamel substances was limited. Our study has shown a reduced shear bond strength of dental sealant to an Er:YAG laser-irradiated enamel, compared with phosphoric acid-etched enamel.

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.

The Micro-Shear Bond Strength of Various Resinous Restorative Materials to Aged Biodentine.

Introduction:The type of materials and application time of veneering restorations on calcium silicate cements are important factors which influence the interfacial properties. The aim of this study was to measure the micro-shear bond strength of a resin composite (RC) using several adhesive systems and a resin-modified glass ionomer cement (RM-GIC) to different aged Biodentine specimens. Methods and Materials:A total of 15 Biodentine blocks were prepared and assigned to three aging periods: 12 min, one week and one month. Then they were subdivided into five sub-groups to receive cylinders of resinous materials. RC was applied using different adhesive systems: A) no adhesive B) etch and rinse C) two-step self-etch and D) universal adhesive in self-etch mode and E) RM-GIC applied directly over Biodentine. Micro-shear bond strength was measured and the data were analyzed using one-way and two-way ANOVA. The level of significance was set at 0.05. Result:There was significant interaction between Biodentine aging periods and resinous materials (P<0.05). The highest value was obtained in group D bonded to the recently set Biodentine. Increasing the aging period to one week resulted in increased micro-shear bond strength in all groups expect for group D. One-month incubation time led to reduced shear bond strength in group A, C and D. Micro-shear bond strength values of group E increased to the longer aged Biodentine. Conclusion:Group D showed the highest bond strength to freshly mixed Biodentine.

Effect of mangosteen peel extract as an antioxidant agent on the shear bond strength of orthodontic brackets bonded to bleached teeth.

Introduction: The number of patients who seek orthodontic treatment that may have a history of tooth bleaching is increasing over the time. Bleaching may influence the decrease of the bond strength of orthodontic brackets. Objective: To determine and prove the effect of mangosteen peel (MP) extract to reverse the reduced shear bond strength (SBS) of orthodontic brackets after bleaching. Methods: A total of 150 maxillary first premolar teeth were randomly divided into 6 experimental groups as follow (n=25): negative-control (N: no bleaching), positive-control (P: bleaching + no treatment), and the treatment groups (bleaching + 10% sodium ascorbate (SA), 10% (MP-10), 20% (MP-20) and 40% (MP-40) MP extract gel). After treatment, the brackets were bonded with the resin-modified glass ionomer cement, SBS testing was performed using universal testing machine, and the adhesive remnant index (ARI) was examined using stereoscopic microscope after debonding. The SBS data were analyzed by analysis of variance (Anova) and the Tukey test. For the ARI, the Kruskal-Wallis test was performed. Result:There was significant SBS difference (p< 0.001) between various groups. The group without bleaching showed significantly higher SBS (8.19 ± 2.26 MPa) compared to others, while SBS in the group treated with 40% MP gel was significantly higher (7.93 ± 1.92 MPa) than other groups treated with antioxidants. The failure of orthodontic brackets bonded after bleaching and treatment using MP extract occurred at the enamel-adhesive interface. Conclusion: The application of MP extract as an antioxidant after bleaching was effective in reversing the reduced shear bond strength of orthodontic brackets after bleaching.

INFLUENCE OF PROLONGED CONTINUOUS ORTHODONTIC FORCE ON THE SHEAR BOND STRENGTH OF METALLIC BRACKETS BONDED WITH VARIOUS ADHESIVE SYSTEMS

Purpose: To estimate the effect of prolonged continuous force on the shear bond strength (SBS) of orthodontic brackets bonded with different adhesive systems. Materials and Methods: Eighty premolars were randomly divided into four groups (I, II, III and IV) according to the bonding adhesive used. Orthodontic metal brackets were bonded with one of the succeeding adhesives; Rely-a-bond, Transbond XT primer and adhesive, Transbond Plus self-etch primer (SEP) and Transbond XT adhesive and Smart Bond. Half of the brackets were subjected to 150 g of force for 12 months. All the specimens were thermocycled 1000 times between 5° C and 55° C. A Universal Testing Machine was used to measure SBS. Results: Transbond XT primer and adhesive exhibited the highest significant SBS value (12.8Mpa). Smart bond showed the lowest value (7.7Mpa). Rely-a-bond and Transbond Plus SEP adhesive systems had middle values (8.8 and 7.8Mpa). There was a significant decrease in the SBS of all studied adhesives (P<0.05) accompanied force application (P <0.05). Smart Bond showed the higher reduction in SBS while Transbond XT primer + Transbond XT adhesive revealed the lesser reduction. Conclusion: Application of 150 gram of force for 12 months produced a pronounced negative effect on SBS especially with either SEP or Smart Bond.

Effect of various dentin disinfection protocols on the bond strength of resin modified glass ionomer restorative material.

BackgroundDisinfection of dentin surface prior to any restorative therapy is important for the longevity of the treatment rendered. However, these dentin disinfection methods should itself not interfere with the adhesion of the restorative material. Therefore the aim of this study was to determine the effect of various dentin disinfection protocols on the shear bond strength (SBS) of resin modified glass ionomer cement (RMGIC).Material and MethodsThe occlusal surface of 40 extracted premolars were trimmed to obtain a flat dentinal surface and was randomly divided into four groups. CTRL was the control group; NaOCl was 1% sodium hypochlorite disinfection group; CHX was 2% chlorhexidine disinfection group; and PAD was the photo-activated disinfection group. Then a predetermined dimension of RMGIC was bonded to the pre-treated dentin surfaces. Following this, each sample was tested for SBS using universal testing machine at a crosshead speed of 0.5mm/min.ResultsAmong the test groups, CHX showed the least reduction in SBS and NaOCl the highest reduction in SBS as compared to the control group. PAD on the other hand showed significantly lower SBS than CTRL and CHX groups, but the values were higher than the NaOCl group.ConclusionsThus, it could be concluded from the present study that use of chlorhexidine based dentin disinfection does interfere with the adhesion of RMGIC. However, photo-activated disinfection should be done with caution. Moreover, sodium hypochlorite based disinfectants should be avoided prior to the use of RMGIC. Key words:Chlorhexidine, Dentin disinfection, Photo-activated disinfection, Resin modified glass ionomer cement, Shear bond strength, Sodium hypochlorite.

Effect of Dentin Disinfection with 2% Chlorhexidine Gluconate and 0.3% Iodine on Dentin Bond Strength: An in vitro Study.

Objective Cavity preparation is a surgical procedure that attempts to remove all infected dentin.1 Bacteria left beneath the filling material is greatest threat to the pulp. To reduce the potential for residual caries development and sensitivity, an antibacterial solution with the ability to disinfect the prepared tooth surface would be of help.2 So this study was conducted to evaluate and compare the effect of dentin disinfection with 2% chlorhexidine gluconate (Consepsis) and 0.3% iodine (Ora5) on shear bond strength (SBS) of self-etch adhesives to dentin.Materials and methods Buccal surfaces of 36 caries-free permanent third molars were ground to expose dentin. All specimens were mounted on acrylic block, divided randomly into three groups, namely group I (control), group II (Con-sepsis), and group III (Ora5). After the application of cavity disinfectant and bonding procedures as per manufacturer’s instructions, composite cylinders were built. Then SBS was measured using universal testing machine.Results Statistical analysis of the measurements were made using one-way analysis of variance (ANOVA), which showed that when cavity disinfectants (Consepsis and Ora5) were used there was significant reduction in SBS of composite to dentin when compared with that of control group.Interpretation and conclusion The results indicate that the use of commercially available cavity disinfectants, Consepsis containing 2% chlorhexidine gluconate and Ora5 containing 0.3% iodine and 0.15% potassium iodide with self-etch adhesive (Adper Prompt), would significantly lower SBS of composite to dentin.How to cite this article Suma NK, Shashibhushan KK, Reddy VVS. Effect of Dentin Disinfection with 2% Chlorhexidine Gluconate and 0.3% Iodine on Dentin Bond Strength: An in vitro Study. Int J Clin Pediatr Dent 2017;10(3):223-228.

Comparative evaluation of orthodontic bracket base shapes on shear bond strength and adhesive remnant index: An in vitro study.

BackgroundThe objective of this study was to evaluate the effect of orthodontic bracket base shape on shear bond strength and adhesive remnant index.Material and MethodsIn this in vitro study using 140 bovine incisors, shear bond strength (SBS) of brackets with different base shapes (rectangle, flower, round, heart, diamond, star, and football) were measured with an Instron testing machine and tested until bond failure. Adhesive Remnant Index (ARI) scoring was evaluated after debonding to evaluate the location of bond failure. Descriptive and one-way ANOVA post-hoc Tukey statistical analyses were performed with a statistical significance set at p≤0.05.ResultsStatistically significant difference in mean SBS in Newtons was observed for multiple base shapes (p<0.05). The highest mean SBS (N ± SD) was observed in football and flower base shapes (73.83 N ± 53.46; 65.82 N ± 37.89 respectively); the lowest mean was observed with diamond and heart shapes (30.51 N ± 11.73; 33.28 N ± 16.89 respectively). When reported in Megaspascals, statistically significant difference was observed for rectangle base shape (3.54 MPa ± 2.69) when compared to all other base shapes.ConclusionsBracket base shape has an effect on SBS. Higher SBS (N) for rectangle, flower, and football base shape indicates even stress distributions throughout the bracket base. Base shape with a pronounced converging tip over the axial plane may contribute to the reduction in SBS due to increased peak stress concentration resulting in bond failure. Key words:Shaped brackets, Shear bond strength, Adhesive remnant index, WildSmiles®.

Orthodontic shear bond strength to porcelain surface in wet conditions

Objective: To evaluate the shear bond strength of orthodontic accessories bonded to a porcelain surface after storage in water.Methods: One-hundredand-twenty feldspathic porcelain discs were divided into 4 groups, according to the surface treatment: Group 1 – 37% phosphoric acid etching; Group 2 – 10% fluorhydric acid; Group 3 – 37% phosphoric acid and silane application; Group 4 – 10% fluorhydric acid and silane application. After the accessories were bonded, the sample was divided into two subgroups, according to the time interval of storage in distilled water: Control – 24 hours; and Test – 150 days. Shear bond strength was determined using a universal test machine, and failure type was verified by scanning electron microscopy.Results: In the test groups there was reduction in shear bond strength, particularly when silane was used. Test Groups 2 and 4 presented shear bond strength values within those proposed as adequate for orthodontic bonding. Groups 1 and 3 presented adhesive failures between porcelain and resin, whereas in Groups 2 and 4 cohesive failures in porcelain were recorded.Conclusion: Storage in water for 150 days decreased the bond strength at silanized interfaces. Fluorhydric acid etching generates adequate bond strength in wet conditions, however, increases the fracture rate in porcelain.

Evaluation of the bonding ability of a nano-structured adhesive system

The most significant advantage of self-etching primers is to simplify bonding procedures and reduce technique sensitivity. AimsThe aim of this study is to evaluate the shear bond strength (SBS) of self-etch primers, such as polyhedral oligomeric silsesquioxanes (POSS) and silica filled adhesive systems and to assess the nano-leakage (NL) at the resin–dentin interface with field-emission scanning electron microscope (FE-SEM) before and after aging. MethodsOne light cured nano-hybrid composite resin and two self-etch primer adhesive systems (Nano-bond and AdheSE) have been used. Sixty extracted sound human molars were prepared for SBS: two self-etch primer adhesive systems (Nano-bond and AdheSE) have been used for bonding a light cured nano-hybrid composite resin. The test was performed at a universal testing machine and twelve were prepared for evaluation of NL at the interface with FE-SEM before and after aging. Data were statistically analyzed using multiple ANOVA and post hoc Scheffe test (p<0.05). ResultsNano-bond showed higher significant SBS values compared to AdheSE groups in the testing groups. Mean while a significant reduction in SBS was observed in each of the tested adhesive systems, after aging, where the highest was recorded by the control, followed by the thermal cycling and finally by the thermal cycling and water storage. The representative micrographs revealed more pronounced NL pattern in the specimens of AdheSE groups when compared to those of Nano-bond. ConclusionsWithin the limitation of this laboratory study, the following conclusions could be drawn:1.The incorporation of the POSS molecules in the dentin adhesive improves its bonding strength.2.Chemical formulation of the dental adhesive influences its bonding efficiency.3.Nano-structured adhesive system shows better resistance to nano-leakage.

Effect of Desensitizing Agents on the Bond Strength of Mild and Strong Self-etching Adhesives.

Desensitizing agents are used, almost as routine practice, in many adhesive restorative procedures. There is still debate as to their effect in dentin bonding, particularly with self-etching adhesives. The present study aimed to evaluate the effect of different desensitizing agents on the bond strength of mild and strong self-etching adhesive systems to dentin. One hundred twenty recently extracted, noncarious human molars were used to obtain superficial dentin substrate for bonding. No desensitizer was used in the control groups. The experimental groups were pretreated with Gluma Desensitizer, MicroPrime B, and Dentin Desensitizer immediately prior to bonding with self-etching adhesives Optibond XTR, Xeno IV, and iBond. A bonding jig was used to fabricate composite cylinders, which were stored for either 24 hours or three months, after which the shear bond strength (SBS) was evaluated using a notched-edge testing device at a crosshead speed of 1 mm/min. Failure mode distribution was also evaluated at 24 hours and three months. A two-way analysis of variance, Tukey test, and Student t-test, with a significance level of p<0.05, were used for data analysis. At 24 hours, there was no significant difference in SBS when the same adhesive was used with any of the experimental desensitizing agents compared with the control group without desensitizer. However, at three months, Dentin Desensitizer bonded with Optibond XTR demonstrated significantly lower SBS (p<0.001), while Gluma bonded with iBond showed significantly higher SBS values (p=0.034) relative to their corresponding control group. Only MicroPrime B bonded with Xeno IV and iBond with no desensitizer demonstrated a significant reduction in SBS after three months (p=0.034 and p=0.002, respectively). The most prevalent type of failure was adhesive. Desensitizing agents can be used in combination with self-etching adhesives to control hypersensitivity without adversely affecting their bond strength to dentin.

Early and delayed effect of 2% chlorhexidine on the shear bond strength of composite restorative material to dentin using a total etch adhesive

Background: Lack of durability of the bond of the dental adhesive systems to tooth structure is one of the most important problems in tooth colored restorative work. This in vitro study was performed to evaluate the effect of 2% chlorhexidine gluconate(CHX) on dentin bond strength by using total etch adhesive system at twenty-four hours and three months of water storage. Material and methods:A flat dentin surface was prepared for forty sound human maxillary premolar teeth which were acid etched with 36% phosphoric acid gel after being divided randomly into four groups of ten teeth each according to storage time and CHX application, theCHX was applied for 60 seconds before adhesive application for groups I and III which were tested after twenty-four hours and three months respectively, while the distal water was applied for 60 seconds before the application of adhesive for group II and IV which were tested after twenty-four hours and three months respectively.The Prime and Bond® NT™ adhesive (Dentsply) was applied and cured, Composite (Ceram X mono, Dentisply) was applied through special mold with 2 mm thickness and light cured, Then all specimens were stored in distilled water 37oC until the time of testing of each group.Shear bond strength test was performed at the end of the storage period (24 hours or 3 months). Results:T-test results showed high statistically significant reduction in shear bond strength (SBS) in non CHX group IV (tested after 3 months) compared to non CHX group II (tested after 24 hours)(P 0.05).On the other hand result showed statistically no significant differences between groups I and II in 24 hours shear bond strength (P> 0.05). After 3 months water storage, there was statistically high significant differences between the groups III and IV (P< 0.01). Conclusion: the use of 2 % CHX glocounate solution after acid etching and before bonding of dentin have no adverse effect on immediate bond strength (24 hours storage), and was effective in reducing degradation of resin-dentin bond interface after three months of water storage.

Evaluation of shear bond strength between thermosens as relining material and different denture base materials

Denture relining is the process of resurfacing of the tissue side of the ill fitting denture, the bond strength at the relining-denture base interface is most important for denture durability.The aim of present study was to evaluate the shear bond strength between the thermosens as relining material and different denture base materials that bonded by thermo fusing liquid. As this corrective procedureis the common chair side procedure in the dental clinic. Material and method: Sixty samples were prepared and divided into three main groups according to the type of denture base materials.Group (A) referred to the heat cure acrylic samples which consisted of 20 samples. Group (B) referred to the high impact acrylic samples which consisted of 20 samples. Group (C) referred to the thermosens samples which consisted of 20 samples. All groups then subdivided into two groups; each one consists of 10 samples, according to the surface roughness: (A1, B1and C1 for groups with surface roughness and A2, B2 and C2for groups without surface roughness). Each sample consisted of two similar parts represent the denture base material each part of the sample was designed with dimensions of (70mm X 12mm X 5mmlength, width and depth respectively) having a stopper of depth 3mm. One part of the sample was placed on the other in a manner thatleaving a space between them of dimensions (12mm X 12mm X 3mm length, width and depth respectively) to sandwich the relining material. Results: The results showed that the thermosens samples had the highest value of shear bond strength followed by the high impact acrylic samples, then heat cure acrylic samples which had the lowest value of shear bond strength. The results of present study showed that rough samples had reducedshear bondstrength in comparison with the smooth samples of the same denture base material.

Comparative Study of the Shear Bond Strength of Flowable Composite in Permanent Teeth Treated with Conventional Bur and Contact or Non-Contact Er:YAG Laser.

The aim of this study was to evaluate and compare the in vitro effect of the Erbium-Doped Yttrium Aluminum Garnet (Er:YAG) laser with different radiation distances and high-speed rotary treatment on the shear bond strength of flowable composite to enamel of human permanent posterior teeth. freshly extracted human molar teeth with no caries or other surface defects were used in this study (n=45). The teeth were randomly divided into 3 groups. Group 1: treated with non-contact Er:YAG Laser and etched with Er:YAG laser, Group 2: treated with contact Er:YAG Laser and etched with Er:YAG laser, Group 3 (control): treated with diamond fissure bur and etched with acid phosphoric 37%. Then the adhesive was applied on the surafces of the teeth and polymerized using a curing light appliance. Resin cylinders were fabricated from flowable composite. Shear bond strength was tested at a crosshead speed of 0.5 mm/min. The amount of Shear Bond Strength (SBS) in the 3 treatment groups was not the same (P<0.05).The group in which enamel surfaces were treated with diamond fissure bur and etched with acid (conrtol group) had the highest mean shear bond strength (19.92±4.76) and the group in which the enamel surfaces were treated with contact Er:YAG laser and etched with Er:YAG laser had the lowest mean shear bond strength (10.89±2.89). Mann-whitney test with adjusted P-value detected significant difference in shear bond strength between the control group and the other 2 groups (P < 0.05). It was concluded that both contact and non-contact Er:YAG laser treatment reduced shear bond strength of flowable resin composite to enamel in comparison with conventional treatment with high speed rotary. Different Er:YAG laser distance irradiations did not influence the shear bond strength of flowable composite to enamel.

Effect of surface treatments of zirconia ceramics on the bond strength to resin cement.

The purpose of this in vitro study was to evaluate the bond strength of a resin luting cement to zirconia surfaces that had received two novel surface pretreatment methods: etching of a pre-fired overglaze or paste liner on the zirconia substrate. Fully sintered zirconia disks were assigned to 6 groups according to the surface pretreatment: firing of 2 layers of paste liner which was then etched with hydrofluoric acid and treated with silane (Liner group); firing of 2 layers of overglaze which were then etched with hydrofluoric acid and treated with silane (glaze group); Rocatec treatment and silane application (Rocatec group); Rocatec treatment followed by ultrasonic cleaning and silanization (ultrasonic-Rocatec group); sandblasted with alumina (alumina group); as-sintered with no pretreatment (control group). Twenty composite resin cylinders were bonded to each group with Panavia F 2.0. Each group was further divided into 2 subgroups (n = 10) for 2 different storage conditions: 24 h water storage or 3 weeks water storage plus 6000 thermocycles between 5°C and 55°C. The shear bond strength was then determined. Statistical analyses with two-way ANOVA were conducted; the level of significance was set at p < 0.05. At 24 h, the shear bond strength values of all groups except the control showed no statistically significant difference. After artificial aging, the mean bond strength of all groups dropped, but the decrease in the glaze group was not statistically significant. The glaze group showed the highest shear bond strength. However, that was not statistically different from the liner or the Rocatec group without ultrasonic cleaning (p < 0.05). All the control specimens debonded spontaneously after aging. Ultrasonic cleaning after Rocatec treatment caused a reduction in shear bond strength, but the difference was not statistically significant. Both the fired paste liner and overglazed ceramic treated zirconia surfaces provided a strong and durable bond to resin cement under the conditions tested.