Differences In Shear Bond Strength Research Articles

The difference between porcelain and composite resin shear bond strength in the administration of 4% and 19.81% silane

Background: Damage to porcelain restorations such as fractures requires a repair that can be performed either directly or indirectly. Direct repair involves directly performing restoration of fractured porcelain with a composite resin application. This technique has more advantages than indirect repair because it requires no laboratory work and can be completed during a single visit. Silane, on the other hand, has been widely used and is reported to increase porcelain and composite resin attachments during the direct repair process. Purpose: This study aimed to determine the differences in shear bond strength between porcelain and composite resin during the administering of 4% and 19.81% silane. Methods: 27 porcelain samples were divided into three groups, namely: Group A - 4% silane, Group B - 19.81% silane and Group C - no silane, prior to the application of composite resin. Each sample was tested for shear bond strength by means of Autograph and fracture analysis performed through stereomicroscope and scanning electron microscope tests. Data analysis was subsequently performed using an ANOVA test. Results: There was a significant difference between the three groups with p=0.000 (p<0.005). The lowest bond strength was found in the group without silane, while the highest was in the group with 4% silane (p<0.005). Conclusion: The use of 4% silane can produce the highest shear bond strength of porcelain and resin composite.

Zirconia Primers Improve the Shear Bond Strength of Dental Zirconia.

Various resin cements and priming agents are available for adhesive luting of zirconia restorations. The purpose of this study was to investigate how cement type and priming protocol affect the shear bond strength on zirconia ceramics. Yttria-stabilized tetragonal zirconia polycrystalline ceramic cylinders were bonded to flat zirconia ceramic surfaces using 7 commercially available resin cements. Ten specimens of each cement group were pretreated with a universal primer, and 10 specimens per group were bonded without pretreatment. In addition, 10 specimens per group were pretreated with system-specific zirconia primers, which were available for 3 cements. Altogether, 170 bonded specimens were water-stored, thermal-cycled, and then submitted to shear bond strength tests. The shear bond strength and the fracture types were documented. Differences in shear bond strengths were assessed using 2-way ANOVA with post-hoc test (α = 0.05). A point-biserial correlation was run between the fracture patterns and the shear bond strengths. The mean shear bond strengths of cements in the unprimed group showed large variations between 2.52 ± 3.01 (mean ± SD) MPa and 33.15 ± 7.35 MPa. Pretreating the specimens with a universal primer improved the shear bond strengths significantly in all groups (p < 0.05) with a range of 21.80 ± 12.51 to 57.20 ± 11.40 MPa. The system-specific primers also improved the shear bond strength significantly, compared to the unprimed group (p < 0.01); however, only one system-specific primer achieved a shear bond strength superior to the universal primer (p < 0.01). There was also a statistical correlation between the fracture type and the shear bond strength (p < 0.0005), with cohesively fractured specimens showing higher shear bond strengths (37.24 ± 19.87 MPa) than adhesively fractured specimens (23.10 ± 17.65 MPa) (p < 0.001). Using universal primer can enhance the maximal shear bond strength of zirconia.

EFFECT OF NANOPARTICLES MODIFIED GLASS IONOMER CEMENT ON THE COLOUR AND SHEAR BOND STRENGTH OF LITHIUM DISILICATE CERAMIC

The effect of glass ionomer cement modified by nanoparticles on the bond strength and colour of lithium disilicate ceramic was studied. Glass ionomer cement modified by nanosilver or nanogold, glass ionomer cement and IPS e.max CAD A2 were used. Thirty e.max CAD discs were constructed. The samples were divided into 3 groups, the first group, 10 samples (control group) used non modified glass ionomer cement (GIC), the second and third groups, 10 samples each used modified glass ionomer cement : nano silver (NSGIC), nanogold (NGGIC). The samples were then subdivided according to the test to which they will be subjected: colour test - shear bond strength test (5 samples each).The samples subjected to colour test were cemented to a composite discs with a shade A2 while those subjected to shear bond strength test were cemented to dentine, using the 3 tested types of glass ionomer. Results showed that ΔE of all the tested samples recorded values in the range of clinical acceptability. NGGIC group showed less ΔE than NSGIC group compared to the control group. Also, the results showed no statistical significant difference in shear bond strength between the control group (GIC) and the two experimental groups (NSGIC) and (NGGIC). Conclusion: The addition of nanoparticles to glass ionomer cement resulted in ΔE within the clinical acceptance. Also, they showed no significant difference as regards to shear bond strength.

Evaluation of the effect of collagen stabilizing agents like chitosan and proanthocyanidin on the shear bond strength to dentin and microleakage of resin composite at enamel and cemental walls: An in vitro study.

Objectives:The objective is to evaluate the effect of collagen stabilizing agents-chitosan and proanthocyanidin (PA) on the shear bond strength to dentin and microleakage of resin composite at enamel and cemental walls.Materials and Methods:Thirty premolars were decoronated 2 mm above cemento-enamel junction and restored with composite resin. Teeth were then randomly divided into three groups: Group I - Control, Group II - Pre-treatment with chitosan, and Group III - Pre-treatment with PA. Samples were then subjected to thermocycling for 500 cycles at 5°C and 55°C with the dwell time of 30 s and transfer time of 5–10 s. Then, the samples were subjected to shear bond strength evaluation on Universal testing machine. Shear load was applied until failure occurred. The load to failure was recorded individually and statistical analysis was done. Microleakage was determined by methylene blue dye penetration method and subjected to stereomicroscopic evaluation. Statistical analysis was carried out using Mann–Whitney test and Chi-square test.Results:Group II specimens produced the highest median shear bond strength and group I showed the least. In addition, Group I, Group II, and Group III showed no statistically significant difference in microleakage.Conclusions:Application of Chitosan and PA improved the shear bond strength to dentin as compared to the control. However, no significant difference in shear bond strength and microleakage was found between them.

Searching the effect of anodization process as a surface treatment

Objective: The aim of this study was to compare the effect of anodization and air-particle abrasion surface treatments on shear bond strength between Ni-Cr and ceramics.Material and Methods: 30 cylindrical Ni-Cr specimens (7x10 mm) were divided into three groups according to the surface treatments [control group (no-treatment), air-particle abrasion group (110 µm Al2O3at 75 psi from 20 cm for 30 seconds), and anodization group]. One sample from each group was evaluated by using SEM. Ceramics with a dimension (5x3 mm) built-up on specimens and shear bond strength tests were performed by using universal testing machine with a 1 mm/min crosshead speed. Stereomicroscope was used to evaluate the failure mode of specimens. One-way ANOVA with post-hoc Tukey’s test was used to analyze the differences in shear bond strength values.Results: The shear bond strength of air-particle abrasion (21,35∓4,64) was higher than anodization group (20,92∓4,85) however, no statistically significant difference was detected. Both groups showed higher bond strength than control group (8,02∓1,47).Conclusion: Anodization process can be used in order to increase the metal-ceramic bond strength. However, according to the failure mode, air-particle abrasion forms stronger bond strength than anodization.

In-vitro assessment of physico-mechanical properti es of nanopartic le glass carbomer

Aim: This study was conducted to evaluate and compare the shear bond strength, water sorption,solubility, microhardness, and compressive strength of a recent product of glass ionomer(Glass Carbomer) compared to conventional glass ionomer.Materials and Methods: Twenty primary molars were utilized for assessment of shear bondstrength (SBS) test. Crown surfaces of the selected teeth were fixed in acrylic blocks then, groundwith water-cooled silicon carbide papers to obtain a flattened dentin surfaces. The specimens(n=20) were distributed into two equal groups according to the type of glass ionomer cement (GIC)bonded to the dentin surface (10/ each group): group I (Fuji IX GP) and group II (Glass Carbomer).To measure shear bond strength (SBS) a universal testing machine was used. For measurementof water sorption (WS) and solubility (SL) 10 specimens of each material were prepared and immersedin artificial saliva of pH 7 for seven days. The difference between initial and final weightwas estimated. Microhardness was estimated using a Vickers microhardness tester. Compressivestrength was evaluated using a universal testing machine.Results: No significant difference in shear bond strength and microhardness between bothmaterials. The water sorption, solubility and compressive strength of CAR (Glass Carbomer Fill)were significantly greater than that of Fuji IX.Conclusions: Glass Carbomer demonstrated some favourable results. Among these includethe higher compressive strength and comparable shear bond strength and microhardness of glasscarbomer, compared to conventional GIC. On the other hand glass carbomer showed higher watersorption and solublity than conventional GIC. Thus, glass carbomer holds a promise to be used asa potential restorative material particularly in pediatric dentistry.

Shear bond strength of the metal bracket on the porcelain surface using three silane coupling agents: a laboratory-based experimental study

This study aims to assess differences in shear bond strength using three materials of silane coupling agents with various organosilane compositions. The samples were 21 porcelain plates categorized into three groups as follows: (a) Monobond Plus (agent A); (b) Ultradent Silane (agent B); and (c) Porcelain Repair Primer (agent B). 37% phosphoric acid etching, silane coupling agents and Transbond XT adhesive were applied to the porcelain surface, followed by 24-h immersion in distilled water before measuring shear bond strength. The results revealed statistically significant differences in shear bond strength among the three silane coupling agents. Agent A had the highest shear bond strength (12.827 ± 1.228 MPa) and B had the lowest shear bond strength (6.295 ± 0.642 MPa) and 6–8 MPa fulfilled the minimum criteria of shear bond strength. Per the Adhesive Remnant Index scores, agent B revealed a clean porcelain surface, whereas agent A and C displayed the presence of bonding adhesive on the entire surface of the porcelain. While agent A and C could be used if the porcelain is replaced, agent B could be used if porcelain is not replaced.

Effect of Adhesion Booster on Fluoride-releasing Composite: An in vitro Study

Objective: To evaluate the shear bond strength of stainless steel brackets bonded with fluoride-releasing composite resins, comparing effect of adhesion booster and conventional primer.Materials &amp; Method: Sixty extracted premolars were subjected to bracket bonding with fluoride-releasing composite resin; which were bonded by randomly divided into two groups of bonding agents: Group 1- conventional primer as control group, Group 2- adhesion booster. After bonding, the samples were thermocycled (500 cycles) at 5ºC and 55ºC temperatures. After 48 hours they were subjected to shear bond strength testing in occluso-gingival direction, using an MTS 810 Universal Testing Machine with load speed of 0.5 mm/min.Result: Mean shear bond strength was significantly more in samples bonded with adhesion booster (14.792±3.805 Mpa) as compared to conventional primers (11.327±4.047 Mpa). There was statistically significant difference in shear bond strength between the groups (p=0.001).Conclusion: The use of the adhesion booster significantly increased the bond strength of bracket bonded with fluoride-releasing composite.

The Effect of Various Composite Resin Types, Surface Treatments, and Repaired Materials on the Shear Bond Strength of Composite Resin Repair

Background and Objectives: Composite resin are widely used in the field of restorative dentistry, as the time passes, composite resin restoration are subjected to failure. This in vitro study conducted to evaluate the effect of two types of composite resin, surface treatment, and three types of repaired materials on shear bond strength. Methods: Total of 120 undercut cylindrical cavities 8 mm in diameter in 2.5 mm in depth were cut at the center of self-cured acrylic resin blocks, the samples divided randomly according to the types of composite resin into 2 groups; microfilled and hybrid, the samples in each groups subdivided according to surface treatment; diamond bur and phosphoric acid. Then all the samples received bonding agent, these groups were subdivided into subgroups according to three composite repair materials. After that the samples were thermocycled manually 500 times, and then each bonded sample subjected to shear bond testing with a universal testing machine. Results: The results showed that groups filled with hybrid composite had higher mean shear bond strength than groups filled with microfilled. Groups received surface roughness with diamond bur had higher mean shear bond strength than groups roughened by phosphoric acid. Conclusion: The highest repair bond strength was obtained by roughening the hybrid composite surface with diamond bur. There was no any significant difference in shear bond strength among groups repaired with different repaired materials, while combination of surface roughness with diamond bur and repaired with microfilled composite had higher mean shear bond strength.

Effect of two erosive protocols using acidic beverages on the shear bond strength of orthodontic brackets to bovine enamel.

Objective: To assess the short-term effect of two in vitro erosive challenge protocols on the bond strength of metal orthodontic brackets on bovine enamel. Methods: Sixty bovine incisors were selected and randomly divided into six groups: AS7 (artificial saliva - 7 days, Control Group); CC7 (Coca-Cola™ - 7 days); LJ7 (lime juice - 7 days); AS30 (artificial saliva - 30 days, Control Group); CC30 (Coca-Cola™ - 30 days); LJ30 (lime juice - 30 days). Microhardness testing was performed prior to the erosive challenge to verify the standardization of samples. Immersion was performed 4x/day for five minutes, for either 7 or 30 days. After immersions were concluded, the brackets were bonded and shear bond strength was assessed after 48 hours. The Adhesive Remnant Index (ARI) was also assessed. Data were analyzed by two-way ANOVA, followed by Tukey’s post-hoc and Student’s t test for paired samples, and the Kruskal-Wallis non-parametric test (α = 5%). Results: The mean and standard deviation of microhardness testing of total samples were 281.89 ± 44.51 KHN. There was no statistically significant difference in shear bond strength for the time factor (7 or 30 days; F5.54= 0.105; p = 0.901). However, there was a statistically significant difference for the solution factor (F5.54= 6.671; p = 0.003). These differences occurred among solutions of Saliva x Coca-Cola™ (p = 0.003) and Coca-Cola™ x Lime Juice (p = 0.029). The assessment of the Adhesive Remnant Index showed no significant difference between groups. Conclusions: The immersion time used in the erosion protocols did not affect the bond strength of brackets to teeth. Coca-Cola™ induced significantly higher shear bond strength values than lime juice and artificial saliva. However, the short term effects of 7/30 days in this in vitro study may not be extrapolated for in vivo ones. Clinical studies should be conducted, substantiating the laboratory results.

Evaluation of the effect of diode laser for debonding ceramic brackets on nanomechanical properties of enamel

The heat from laser can lead to the destruction of organic components of enamel and consequently changes in the mechanical properties of enamel. The purpose of this study was to evaluate the effect of diode laser on the nanomechanical properties of enamel in the process of debonding the ceramic brackets. In This in vitro study Eighteen ceramic brackets were bonded on the intact premolars in 3 groups of 6 (one control and two study groups). To debond the brackets in the study groups, laser diode was used for 3 s with 1W and 3W power. Shear bond strength and adhesive remnant index were recorded for all groups. Hardness and elastic modulus were measured in 1-31 μ depth from enamel surface in each debonded area. Analysis of variance was used for determining the difference in shear bond strength (SBS), hardness, and elastic modulus and was followed by post hoc Tukey's honest significant difference test. One-sample t-test was used to compare the changes in the pulp temperature with the standard threshold (5.5°C). The significance level was set at %5 in this study. SBS was significantly greater in the control group compared to the study groups. There was no significant difference in the average of hardness and elastic modulus of enamel between the groups. Pulp temperature elevation in the study groups was significantly < 5.5°C (P = 0.000). The diode laser with either 1W or 3W power for 3 s is effective in debonding the ceramic brackets without any detrimental effect on the pulp or mechanical properties of enamel. In regard to the pulp health, the 1W power laser is rather recommended for debonding the ceramic brackets than the 3W laser power.

A comparative evaluation of shear bond strength of composite resin to pulp chamber dentin treated with sodium thiosulfate and proanthocyanidin: An in vitro study.

Aim:Based on the importance of coronal sealing right after endodontic treatment, this in vitro study aimed to evaluate the difference of shear bond strength to pulp chamber dentin treated with sodium thiosulfate and proanthocyanidin (PA).Materials and Methods:Fifteen extracted mandibular molar teeth were decoronated at the level of cementoenamel junction horizontally. The individual teeth were then sectioned mesiodistally to expose the pulp chamber dentin using a diamond disc. The specimens were randomly divided into three groups (n = 10). Group A: control group, treated with 5.25% sodium hypochlorite (NaOCl) for 30 min followed by a final rinse with 17% ethylenediaminetetraacetic acid (EDTA) solution for 3 min; Group B: after pretreatment with NaOCl and EDTA, it is further treated with 5% sodium thiosulfate (Na2S2O3) for 10 min; and Group C: after pretreatment with NaOCl and EDTA, it is further treated with 6.5% PA for 10 min. After drying the specimens, a bonding agent namely One Coat Bond SL (SwissTEC, Coltene) was applied to the pulp chamber dentin followed by a composite restoration (SwissTEC, Coltene). Each specimen was then tested under a universal testing machine at the dentin/resin interface to determine the shear bond strength.Results:Both the groups in which 5% Na2S2O3 and 6.5% PA were used for 10 min showed bond strength that was found to be statistically higher than the positive control (P < 0.05).Conclusion:The use of Na2S2O3 and PA can significantly increase the bond strength of composite resin to NaOCl/EDTA-treated dentin, allowing adhesive restorations to be immediately applied after endodontic treatment.

SHEAR BOND STRENGTH OF RESTORATIVE PARTICULATE RESIN COMPOSITE WITH A SHORT FIBER-REINFORCED RESIN COMPOSITE SUBSTRUCTURE

Objective: This study aimed to identify the shear bond strength of two different restorative particulate resin composites with a short fiber-reinforced resin composite (SFRC) substructure.Methods: Two restorative particulate resin composites, G-aenial PosteriorTM (Group A, 10 specimens) and Tetric N-Ceramtm (Group B, 10 specimens), were used as an upper layer of everX posteriorTM, an SFRC. A shear bond strength test was performed using a universal testing machine with a load of 100 kgf and a crosshead speed of 0.5 mm/min. The data were analyzed statistically using the independent samples t-test.Results: The mean shear bond strength values were found to be18.64±1.5 MPa (Group A) and 22.05±1.8 MPa (Group B). A significant difference in shear bond strength between the two groups was found.Conclusion: The shear bond strength value is higher in the Tetric N-CeramTM restorative particulate resin composite with SFRC as a substructure than the G-aenial PosteriorTM restorative particulate resin composite.

Composite resin shear bond strength on bleached dentin increased by 35% sodium ascorbate application

Background: Restoration of the teeth immediately after bleaching with 35% hydrogen peroxide (H2O2) is contraindicated due to the remnant of free radicals that will stay inside enamel and dentin for 1-3 weeks and reduce the adhesion of composite resin. Sodium ascorbate is an antioxidant substance known to bind free radical residues, thereby shortening the delay in restoration. Purpose: The purpose of this study was to examine the resin bond strength of bleached dentin influenced by the application of 35% sodium ascorbate. Methods: Nine premolars were divided into their crown and root sections, with the crown subsequently being cut into four equal parts to obtain 36 samples. These were then divided into four groups, each containing nine samples. Group A (control): samples were bleached using35% hydrogen peroxide, immersed in an artificial saliva, stored in an incubator at 37°C for seven days and then filled with a composite resin. Group B:samples were also bleached by means of 35% H2O2 followed by one application of 0.025 ml 35% sodium ascorbate for 5 minutes and restored with composite resin. Group C: samples were bleached with 35% H2O2, followed by two applications of 0.025 ml 35% sodium ascorbate for 5 minutes, and restored with a composite resin. Group D: dentin was bleached with 35% H2O2 followed by three applications of 0.025 ml sodium ascorbate 35% for 5 minutes and restored with a composite resin. The shear bond strength of the composite resin was measured by a universal testing instrument (Zwick, USA). Data was analyzed by means of one-way Anova and LSD. Results: The highest mean shear bond strength of composite resin was in group C, while the lowest was in group B. The result of one-way Anova indicated a difference in the shear bond strength of composite resin in the four treatment groups (p &lt; 0.05). An LSD test showed there to be a difference in shear bond strength of composite resin between group A and groups C and D or between group B and groups C and D. There was no difference in shear bond strength of composite resin between group A and group B or between group C and group D. Conclusion: Application frequency of 35% sodium ascorbate affect on shear bond strength of composite resin restoration in bleached dentin by 35% H2O2.

Effects of Ozone and Prophylactic Antimicrobial Applications on Shear Bond Strength of Orthodontic Brackets.

The present study aimed to evaluate the effects of ozone and prophylactic antimicrobial applications on the shear bond strengths and bond failure interfaces of orthodontic brackets. Sixty human canine teeth were randomly divided into three groups (n=20), receiving the following treatments: Group I-pumice prophylaxis (Isler Dental, Ankara, Turkey)+37% orthophosphoric acid (Dentsply, Rio de Janeiro, Brazil)+Transbond XT primer and adhesive (3M Unitek, Monrovia, USA); Group II-prophylaxis paste (Topex, NJ, USA)+37% orthophosphoric acid (Dentsply, Rio de Janeiro, Brazil)+ Transbond XT primer and adhesive paste (3M Unitek, Monrovia, USA); and Group III-ozone application (Biozonix GmbH, Munich, Germany)+37% orthophosphoric acid (Dentsply, Rio de Janeiro, Brazil)+Transbond XT primer and adhesive (3M Unitek, Monrovia, USA). All specimens were stored at 37°C water for 24 h. Shear bond strength was assessed using a universal testing device (Autograph AGS-X; Shimadzu, Japan). Adhesive remnant index (ARI) scores were obtained through examination of teeth under stereomicroscope at 10× magnification after debonding. Shear bond strengths of orthodontic brackets were 16.10, 18.01, and 19.23 MPa for Groups I, II, and III, respectively. No statistically significant difference in shear bond strength of orthodontic brackets was found among the groups (p=0.273), based on Kruskal-Wallis analysis. Additionally, no significant difference was found in the ARI scores of each group using chi-square analysis (p=0.992). Shear bond strength of orthodontic brackets and ARI scores was not found to be negatively impacted by ozone application.

Double-Layer Surface Modification of Polyamide Denture Base Material by Functionalized Sol-Gel Based Silica for Adhesion Improvement.

Limited surface treatments have been proposed to improve the bond strength between autopolymerizing resin and polyamide denture base materials. Still, the bond strength of autopolymerizing resins to nylon polymer is not strong enough to repair the fractured denture effectively. This study aimed to introduce a novel method to improve the adhesion of autopolymerizing resin to polyamide polymer by a double layer deposition of sol-gel silica and N-2-(aminoethyl)-3-aminopropyltrimethoxysilane (AE-APTMS). The silica sol was synthesized by acid-catalyzed hydrolysis of tetraethylorthosilicate (TEOS) as silica precursors. Polyamide specimens were dipped in TEOS-derived sol (TS group, n = 28), and exposed to ultraviolet (UV) light under O2 flow for 30 minutes. UV-treated specimens were immersed in AE-APTMS solution and left for 24 hours at room temperature. The other specimens were either immersed in AE-APTMS solution (AP group, n = 28) or left untreated (NT group, n = 28). Surface characterization was investigated by fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM). Two autopolymerizing resins (subgroups G and T, n = 14) were bonded to the specimens, thermocycled, and then tested for shear bond strength with a universal testing machine. Data were analyzed with one-way ANOVA followed by Tukey's HSD (α = 0.05). FTIR spectra of treated surfaces confirmed the chemical modification and appearance of functional groups on the polymer. One-way ANOVA revealed significant differences in shear bond strength among the study groups. Tukey's HSD showed that TST and TSG groups had significantly higher shear bond strength than control groups (p = 0.001 and p < 0.001, respectively). Moreover, bond strength values of APT were statistically significant compared to controls (p = 0.017). Amino functionalized TEOS-derived silica coating is a simple and cost-effective method for improving the bond strength between the autopolymerizing resin and polyamide denture base. Amino-functionalized silica coating could represent a more applicable and convenient option for improving the repair strength of autopolymerizing resin to polyamide polymer.

Shear bond strength evaluation of chemically-cured and light-cured orthodontic adhesives after enamel deproteinization with 5.25% sodium hypochlorite

This study aimed to assess the effect of enamel deproteinization with 5.25% sodium hypochlorite (NaOCl) before etching on the shear bond strength (SBS) of Unite (UN; 3M Unitek) and Xihu-BIOM adhesive (XB). Fifty-two maxillary first premolars were divided into four groups: (1) UN and (2) XB according to manufacturer’s recommendation and (3) UN and (4) XB deproteinized with 5.25% NaOCl. Brackets were bonded, and a mechanical test was performed using a universal testing machine. The mean SBS value for groups A1, A2, B1, and B2 was 13.51 ± 2.552, 14.36 ± 2.902, 16.43 ± 2.615, and 13.05 ± 2.348 MPa, respectively. A statistically significant difference in SBSs was observed between chemically cured groups and between group B (p < 0.05). No statistically significant difference in SBSs was observed between light-cured adhesive groups and between group A (p > 0.05). NaOCl enamel deproteinization before acid etching has a significant effect on the SBS of Unite adhesive, but not on that of the Xihu-BIOM adhesive. Furthermore, a significant difference in the SBS of Unite and Xihu-BIOM adhesives within the enamel deproteinization group was observed in this study.

The Effect of Er:YAG Laser Irradiation and Different Concentrations of Sodium Hypochlorite on Shear Bond Strength of Composite to Primary Teeth's Dentin.

Introduction: The aim of this study was to evaluate the effect of various concentrations of NaOCl on shear bond strength of composite resin to dentin of primary teeth, prepared with laser and bur. Methods: In this in vitro study, 48 primary molars were sectioned at mesiodistal direction and were randomly divided into 6 groups; G1: bur, G2: bur + NaOCl 2.5%, G3: bur + NaOCl 5.25%, G4: laser, G5: laser + NaOCl 2.5%, G6: laser + NaOCl 5.25%. One-Step Plus adhesive was applied after phosphoric acid gel and NaOCl over the dentin surfaces for all groups, and composite resin cylinders were bonded to the samples. After thermocycling, shear bond strengths of composite resin to dentin were measured and statistical analyses were done by means of t test and analysis of variance (ANOVA). Results: The mean shear bond strength showed no significant difference between the groups prepared with bur (13.82 ± 3.49) and laser (14.18 ± 3.65) (P > 0.05). The mean difference of shear bond strength between three groups G1, G2 and G3 and between G4, G5 and G6 were not statistically significant (P > 0.05). Scanning electron microscopy (SEM) figures showed an irregular surface in laser groups and fairly complete removal of smear layer from the orifices of the dentinal tubules, in the group in which NaOCl was used. Conclusion: The application of different concentrations of NaOCl does not significantly improve the bond strength in dentin surfaces prepared with laser or bur.

An In vitro Study to Evaluate the Effect of Eugenol-free and Eugenol-containing Temporary Cements on the Bond Strength of Resin Cement and Considering Time as a Factor.

Aims and Objectives:The aim of this study was to assess the outcome of eugenol-free and eugenol-containing cements on the bond strength of resin cement.Materials and Methods:Dentin was exposed in five groups of extracted teeth (20 specimens each). In Group 1, specimens were not given temporary cementation. In Groups 2 and 3, specimens were given temporary restoration fixed with eugenol-free temporary cement for 7 and 14 days, respectively. In Groups 4 and 5, specimens were given temporary restoration fixed with eugenol-containing temporary cement for 7 and 14 days, respectively. Permanent cementation was done for all groups after specified period of time. Shear bond strength testing of specimens was carried under universal testing machine. The data were analyzed by SPSS for Windows (version 14) statistical package (SPSS Inc., Chicago, IL, USA).Results:One-way analysis of variance test revealed that Group 1 specimens produced higher shear bond strength than Groups 2, 3, 4, 5 and the difference was statistically significant (P < 0.001). In Groups 2, 3, 4, and 5, no significant difference in shear bond strength was observed between provisional restoration with eugenol-containing zinc oxide cement and provisional restoration with eugenol-free zinc oxide cement (P = 0.095).Conclusion:The findings of this in vitro experiment lend no support to the common opinion that eugenol-containing cements should be avoided as temporary cement.

The effect of oxalate-based desensitizers on the microleakage and shear bond strength of resin modified glass ionomer.

BackgroundThe first line of intervention to alleviate tooth sensitivity is to use dentin desensitizers such as oxalate-based desensitizers. When the dentin sensitivity continues even after application of desensitizers the next intervention would be restoration of the lesion. The aim of this in vitro study was to investigate the effect of prior application of oxalate-based desensitizer on the marginal microleakage and shear bond strength of resin modified glass ionomer (RMGI) restorations.Material and MethodsIn order to prepare the specimens for microleakage test standard class v cavities were prepared on buccal surfaces of 45 teeth. The specimens were randomly divided into three equal groups. In control group, the cavities were restored with RMGI. In group 2, oxalate-based desensitizer was applied and the specimens were kept in distilled water for 14 days before restoration. In group 3 the specimens were prepared similar to group 2 and the surface of the cavities were slightly cut with bur before restoration. Methyleneblue penetration was evaluated using stereomicroscope. The data were analyzed using non-parametric tests. For shear bond strength test cervical dentin specimens were prepared and were divided into 3 groups. Surface treatments were similar to microleakage test. RMGI was packed into cylindrical plastic molds which were placed on the cut surface of the tooth and light cured. The data were analyzed by one-way ANOVA.ResultsThere was not any significant difference in dye penetration in dentin margins among the groups, but microleakage in enamel margins of group 2 and 3 was higher than group 1. There was no significant difference in shear bond strength among the groups (p =0.285).ConclusionsNon carious cervical lesions which were treated for hypersensitivity with oxalate-based desensitizers could be restored with resin modified glass ionomer if the hypersensitivity persists. Key words:Dentin hypersensitivity, oxalate-based desensitizers, microleakage, shear bond strength.