Influence of different test parameters on the microshear bond strength of two simplified etch-and-rinse adhesives.

PURPOSE: To evaluate the effect of different test parameters on the resin-dentin microshear bond strength (µSBS). MATERIALS AND METHODS: A 1.5-mm-thick dentin disk was prepared in each of 140 human molars. The disks were divided into five groups to test the following variables: time of adhesive light polymerization (n = 20), storage time (n = 40), bonding area (n = 40), Tygon tube removal (n = 20), and time of composite placement (n = 20). The adhesives were applied and each specimen was subjected to µSBS testing. All fractured specimens were observed with SEM. The data from each experiment were subjected to two-way ANOVA and Tukey's test (α = 0.05). RESULTS: The storage time, bonding area, and Tygon tube removal did not influence the µSBS. Higher µSBS values were found when empty Tygon tubes were filled after positioning and when the adhesive was light polymerized before Tygon tube placement (p < 0.05). CONCLUSIONS: Differences in test parameters affected the µSBS of adhesives, especially the time of adhesive light polymerization and composite placement.

Push-out bond strength of fiber posts to root canal dentin using a one-step self-etching adhesive: the effect of solvent removal and light-curing methods.

PURPOSE: To evaluate the effect of solvent removal and light-curing methods on the push-out bond strength of fiber posts to root canal dentin using a one-step self-etching adhesive. MATERIALS AND METHODS: Eighty single-rooted, single-canal human mandibular premolars were used in this study. After removal of the crown, the pulp was extirpated and the post space was prepared. The teeth were divided into two main groups according to the solvent removal method, either using the paper point or the air-drying method. Each of the above main groups was further subdivided into 4 subgroups according to the light-curing method: group 1: both adhesive and resin cement were cured from the top of the post in the same step (cocuring) for 40 s; group 2: the adhesive was light cured for 20 s and the resin cement for 40 s; group 3: the adhesive was light cured for 40 s as was the resin cement; group 4: an intracanal tip was used to cure the adhesive inside the post space for 20 s. In groups 1 to 4, the solvent was evaporated using oil-free compressed air for 5 s from the root surface and excess adhesive was removed from inside the canal using a paper point. In groups 5 to 8, the adhesive and cement were applied and light cured as in groups 1 to 4, except the solvent was evaporated (air dried) from inside the post space using an intra-canal disposable plastic tip attached to the tip of a 3-way syringe. After 24 hours, three 2-mm-thick root slices were obtained from each root. Each slice was subjected to the push-out bond strength test at a crosshead speed of 0.5 mm/min. Factorial analysis (two-way ANOVA) was run to test the effect of solvent evaporation method, light-curing method, and their interactions on bond strength. One-way ANOVA followed by Duncan's Multiple Range Test were used to test the effect of lightcuring method on bond strength within each solvent evaporation method. Student's t-test was performed to compare the effect of solvent evaporation method on bond strength within each light-curing method. RESULTS: Two-way ANOVA revealed that the solvent removal method had a significant effect on the bond strength of fiber post to root canal dentin. Neither the light-curing method nor the interaction between the two independent variables had a significant effect on the push-out bond strength. CONCLUSIONS: Only air drying the one-step self-etching adhesive could influence the bond strength of the fiber post to root canal dentin.

Influence of shade and light-curing distance on the degree of conversion and flexural strength of a dual-cure core build-up resin composite.

PURPOSE: To investigate the influence of shade and light-curing distance on the degree of conversion (DC) and flexural strength (FS) of a dual-cure core build-up resin composite. METHODS: 135 specimens were prepared and divided into three main groups according to the shade of the composite core material; dentin, blue and white shades. Each group was further subdivided into three subgroups according to the light-curing distance; 0 mm, 3 mm and 5 mm. The DC was measured using FTIR spectrometer. For testing the FS, the mini flexural test specimens were prepared and subjected to three point bending test in a universal testing machine. The results were analyzed using two-way and one-way ANOVA followed by Duncan's Multiple Range Test. The significance level was set at P = 0.05. RESULTS: Both the DC and FS of the dual-cure core build-up material used in this study were influenced by the shade of the material and the light-curing distance. The blue shade exhibited the highest percentage DC values while the white shade revealed the lowest percentage DC. The dentin shade at 0 mm light-curing distance exhibited the highest mean FS value; however the 3 mm and 5 mm light-curing distance of the white shade showed the lowest mean FS values.

Immediate vs delayed repair bond strength of a nanohybrid resin composite.

PURPOSE: To evaluate both the immediate and water-stored repair tensile bond strength (TBS) of a nanohybrid resin composite using different bonding protocols. MATERIALS AND METHODS: One hundred sixty half hourglass-shaped slabs were prepared. Eighty half-slabs were wet ground immediately after light curing using high-speed abrasive burs, while the other half-slabs were stored in water for one month (delayed) and then wet ground for repair. Each set of the 80 repaired slabs was split into two groups to be tested for TBS after 24 h or 1 month of water storage. For all repaired slabs, either immediate or delayed, four bonding procedures were used involving wet and dry bonding with a 3-step etch-and-rinse adhesive with or without silane pretreatment. TBS tests were performed at a crosshead speed of 0.5 mm/min. To determine the cohesive strength of the resin composite itself, which served as the reference, additional whole slabs were prepared and tested in tension after a 24-h (n = 10) and a 1-month storage period (n = 10). Failure modes were evaluated using a stereomicroscope at 40X magnification. Three-way ANOVA was run to test the effect of water storage, testing time, bonding protocols, and their interactions on the repair TBS, which was given as a percentage of the reference values. RESULTS: For the immediate repair groups, the repair TBS ranged from 40% to 61.9% after 24-h storage and from 26% to 53.1% after 1-month water storage compared to the TBS of the whole slabs. For the delayed repair group, the repaired TBS ranged from 47.2% to 63.6% for the 24-h repairs and from 32.2% to 44.2% for the test groups stored in water for 1 month. Three-way ANOVA revealed that water storage had no significant effect on the repair TBS (p = 0.619). Both testing time and bonding protocols had a significant effect on the repair TBS (p = 0.001). The interactions between the independent variables (water storage, testing time, and bonding protocols) had no significant effect (p = 0.067). CONCLUSION: The repair bond strength was consistently and highly significantly less than the cohesive strength of the composite. A delay of 1 month before carrying out the repair had no effect on the bond strength, irrespective of the bonding procedure used. Silane treatment did not improve the repair bond strength. In all instances, except for the immediate wet bonding plus silane procedure and delayed dry bonding, the bond strength of the repairs significantly dropped after 1 month of storage in water.

Effect of air-drying pressure and distance on microtensile bond strength of a self-etching adhesive.

PURPOSE: To investigate the effect of pressure and distance during air drying on the microtensile bond strength (µTBS) of a single-step self-etching adhesive to bovine dentin. MATERIALS AND METHODS: A total of 36 bovine molars was used in this study. Twenty-seven teeth were used for µTBS testing and 9 teeth for the evaluation of the resin/dentin interface. The teeth were divided into 9 groups according to the variation in solvent evaporation pressure and the distance from the dentin surface. The adhesive was applied according to the manufacturer's instructions. The pressure was adjusted using a pressure regulator and the distance was fixed by measuring the distance from the tip of the syringe to the flat dentin surface. Each tooth was restored with a composite crown 6 mm in height and was cut to produce composite/dentin rectangular sticks with a cross-sectional area approximately 1 mm2 and 12 mm in length. The sticks were tested in tension until failure at a crosshead speed of 0.5 mm/min. The fracture pattern was evaluated using a stereomicroscope under 40X magnification. For the resin/dentin interface, the samples were gold sputtered and examined using SEM operated at 20 kV. RESULTS: Two-way ANOVA showed that both pressure and distance from the dentin surface significantly affect the µTBS of the single-step self-etching adhesive (p = 0.001). The interaction of the two independent variables (pressure and distance from dentin surface) showed a significant difference (p = 0.001). CONCLUSION: On the basis of the µTBS data generated in this study, the single-step self-etching adhesive used proved to be technique sensitive.

The effect of the pre-conditioning step on the shear bond strength of nano-filled resin-modified glass-ionomer to dentin.

OBJECTIVES: The purpose of this study was to evaluate the effect of the pre-conditioning step using different dentin conditioners on the shear bond strength (SBS) of the nano-filled resin-modified glass ionomer (RMGI) to dentin. METHODS: Twenty-four human molars were used in this study. Subsequent to teeth sectioning in the mesio-distal direction and creation of the smear layer, the teeth were divided into six groups with and without the pre-conditioning step. Dentin surfaces were restored with RMGI cylinders and the specimens were stored in distilled water at 37ºC for 24 hours. SBS test were performed using a Universal Testing Machine at a crosshead speed of 0.5 mm/minute. Statistical analysis was performed using One-Way ANOVA followed by Duncan's Multiple Range Test. RMGI/dentin interface was evaluated using SEM operated at 12 Kv at 2000X magnification. RESULTS: 35% phosphoric acid and EDTA yielded significantly higher SBS (12.0±1.8 and 11.9±4.4 MPa, respectively), compared to all tested groups. In addition, 25% polyacrylic acid (8.6±3.1 MPa) reported significantly higher SBS than the nano-filled RMGI when applied according to manufacturer instructions (5.5±2.2 MPa). When nano-filled RMGI was applied without its nano-primer, or directly over 25% polyacrylic acid conditioned dentin exhibited 100% pre-test failure, and their SBS were expressed as 0.0±0.0 MPa. SEM revealed that the nano-primer was unable to decalcify and hybridize the dentin surface. CONCLUSIONS: Based on the results of the current study, the pre-conditioning step effectively improves the SBS of nano-filled RMGI to dentin. The self-adhesiveness of nano-filled RMGI was not proved in this study.

Tensile bond strength of immediately repaired anterior microfine hybrid restorative composite using nontrimmed hourglass specimens.

PURPOSE: To investigate the effect of different surface treatments on the tensile bond strength (TBS) of immediately repaired anterior microfine hybrid restorative composite using nontrimmed hourglass-shaped specimens. MATERIALS AND METHODS: Fifty-six nontrimmed hourglass composite specimens were prepared in this study. Eight specimens were used for the evaluation of the cohesive tensile strength as the control group. The remaining 48 were divided into 6 equal groups according to the method of proposed treatment. Groups IM1 and IM2: The specimens were repaired without intermediate treatment. Group IM3: A thin layer of Excite self-priming adhesive was applied to the proposed repaired area of each half-specimen. Group IM4: The repaired area was ground using an abrasive stone, each half-specimen was rinsed and dried, and the adhesive applied. Group IM5: Treatment consisted of 37% phosphoric acid etching of the proposed repair area. The adhesive was then applied. Group IM6: The repaired area was ground and acid etched before applying the adhesive. In all repaired groups except for IM2, repaired specimens were prepared and cured against a single layer of transparent polyester strip (matrix) to prevent the formation of an oxygen inhibition layer. In group IM2, specimens were cured in air without the polyester strip. Specimens were then tested for the repair tensile bond strength (TBS) in a universal testing machine at a crosshead speed of 0.5 mm/min until failure. Twelve more samples were used for SEM characterization of nontreated, ground, acid-etched, and ground/acid-etched samples. The failure mode was evaluated using a stereomicroscope at 30X magnification. All TBS data were expressed as mean and standard deviation, and were analyzed using StatsDirect 2.5.7. One-way ANOVA followed by Tukey-Kramer multiple-comparison post-hoc tests were used to compare the TBS between all tested groups. Differences were considered significant at p < 0.05. RESULTS: Groups that were cured against a matrix and received no treatment or were repaired with adhesive only had significantly lower TBS than the control group. Groups which were cured without the matrix and received no treatment or grinding/adhesive, acid etching/adhesive, and grinding/acid etching/adhesive showed no significant difference in TBS compared to the control group. SEM evaluation showed that acid etching did not change the morphology of the composite surface. The ground specimens showed a grooved pattern with smeared grinding products. Ground/acid-etched specimens showed removal of the smeared products with a less distinct grinding-groove pattern. Stereomicroscopic evaluation of the debonded surfaces for all repaired groups showed that the failure mode was predominantly adhesive for all evaluated debonded surfaces in each repair group. CONCLUSION: In the absence of an oxygen inhibition layer, the immediate repair bond strength was decreased. In contrast, in the presence of an oxygen inhibition layer, the immediate repair bond strength of composite was improved. The application of a thin adhesive layer did not improve the immediate repair bond strength as the other surface treatments did. When the composite was cured against a matrix, chemical and/or mechanical treatments of composite surface prior to application of the adhesive proved to be an effective method to improve the immediate repair bond strength.

Effect acidic and alkaline/heat treatments on the bond strength of different luting cements to commercially pure titanium.

OBJECTIVE: The purpose of this study was to characterize the effects of either acidic or combined alkaline/heat treatments on the surface of grit-blasted commercially pure (cp) titanium. The effects of the previous treatments on the shear bond strength (SBS) of cp titanium to conventional glass ionomer, resin-reinforced glass ionomer and self-adhesive resin luting cements were evaluated. METHODS: Titanium discs were machined and received one of the following treatments; grit-blasting (GB), grit-blasting followed either by etching in HNO(3)/HF solution (GB/Ac) or by combined 5M NaOH treatment/heat treatment at 600 degrees C for 1h, then immersed for 24h in SBF solution before cementation (GB/Ak). The treated surfaces were characterized by atomic force microscope (AFM), scanning electron microscope (SEM) and laser-induced brake-down spectroscopy (LIBS). Discs were cemented either by Fuji I, Fuji Plus or Rely X Unicem luting cements. The SBS was evaluated and the debonded discs were investigated by SEM. RESULTS: Two prominent results were revealed; first, GB/Ak treatment showed the highest SBS than the other treatments (P<0.0001). Second, Rely X Unicem showed the highest SBS than the other cements (P<0.0001). Fuji I and Fuji Plus showed predominant cohesive type of failure, whereas Rely X showed predominant adhesive type of failure. SIGNIFICANCE: Combined alkaline/heat treatments of commercially pure titanium surface shows to be of beneficial effect in enhancing SBS to glass ionomer, resin-modified glass ionomer and adhesive resin luting cements.

Effect of surface treatments on the tensile bond strength of repaired water-aged anterior restorative micro-fine hybrid resin composite.

OBJECTIVES: The purpose of this study was to characterize changes in surface topography associated with different surface treatments and their effect on tensile bond strength (TBS) of repaired water-aged anterior restorative micro-fine hybrid resin composite. METHODS: The TBS of repaired resin-based composite slabs either non-treated or exposed to different mechanical and/or chemical surface treatment procedures were measured. The cohesive tensile strength of non-repaired intact slabs was used as a control group. The topographical effects of acid etching, grinding, and grinding followed by acid etching were characterized by AFM and SEM. RESULTS: All repaired groups showed significantly lower TBS than the control group. The TBS of repaired groups was ranged from 15% to 59% of the cohesive tensile strength of the control group (18.8+/-4.5MPa). The surface roughness of the non-treated aged specimens was significantly higher than other treated specimens. Specimens treated by acid etching showed significant increase in surface area compared to the non-treated and treated specimens. CONCLUSIONS: Aging process resulted in the formation of degradable surface layer which adversely affects the repair bond strength. The use of silane primer prior to the application of the adhesive after mechanical grinding, with or without the use of 37% phosphoric acid etching; improves the repair bond strength.

Sodium hypochlorite as dentin pretreatment for etch-and-rinse single-bottle and two-step self-etching adhesives: atomic force microscope and tensile bond strength evaluation.

PURPOSE: The aim of this study was to evaluate the effect of using 5.25% commercial sodium hypochlorite treatment prior to the application of etch-and-rinse and self-etching adhesives on dentin surface microtopography and tensile bond strength. MATERIALS AND METHODS: Thirty-two noncarious, nonrestored human third molars were collected. The occlusal enamel of all teeth was removed using diamond disks to expose flat dentin surfaces. The exposed dentin surfaces were abraded using 600-grit SiC disks, to create a uniform dentin smear layer. For AFM characterization, 12 teeth were equally divided into 4 groups according to the proposed dentin surface treatment. Three dentin disks, 2 mm thick, were evaluated per group using tapping mode assessment. Twenty teeth were used for TBS and SEM evaluation and were equally divided into 4 groups, according to the proposed dentin surface treatment. For TBS, 8 dentin/composite slabs, 2 mm thick, were used in each group, while for SEM evaluation 2 slabs were used. Each slab was tested in tension at a crosshead speed of 0.5 mm/min until failure occurred. The samples were examined using SEM operated at 30 kv to evaluate the hybrid layer photographically at 1500X. Statistical analysis was carried out using StatsDirect 2.5.7. One-way ANOVA followed by Tukey-Kramer multiple-comparison post-hoc tests were performed to test the difference between roughness parameters and TBS between groups. RESULTS: Sodium hypochlorite followed by the application of 37% phosphoric acid significantly increased the arithmetic average of the absolute values of surface height deviations (Sa), the surface area ratio which expresses the ratio between the surface area (taking the z height into account) and the area of the flat x,y plane (Sdr), and the surface bearing index (Sbi) parameters, while the application of sodium hypochlorite prior to the application of the self-etching primer significantly increased the valley fluid retention index (Svi) parameter. Self-etching primer without sodium hypochlorite pretreatment significantly increased the core fluid retention index (Sci) parameter. Sodium hypochlorite/AdheSE (7.42 +/- 2.16 MPa) significantly increased TBS value compared to other groups. However, no statistically significant difference was found between sodium hypochlorite/Excite (4.68 +/- 1.26 MPa), AdheSE (4.42 +/- 1.36), and Excite (4.06 +/- 1.35). Remnants of smear layer were detected with areas devoid of resin tags in SEM images of samples bonded with AdheSE self-etching adhesive, in contrast to samples bonded with sodium hypochlorite followed by AdheSE self-etching adhesive. CONCLUSION: The application of 5.25% commercial sodium hypochlorite with rubbing action for 60 s (total application time 120 s) seems to positively influence the TBS of the self-etching adhesive; however, it has no significant effect on TBS of etch-and-rinse single-bottle adhesive to dentin. The addition of functional roughness parameters to study the dentin surface was shown to be of importance in evaluating the relationship between bond strength and surface topography of conditioned dentin.

Shear bond strength of glass-ionomer adhesive to dentin: effect of smear layer thickness and different dentin conditioners.

PURPOSE: To investigate the effect of two different smear layer thicknesses treated with different dentin conditioners on the bond strength of glass-ionomer adhesive to dentin. MATERIALS AND METHODS: Fifty human molars were used. Each tooth was sectioned in a mesiodistal direction into halves, using a low-speed diamond disk. The 100 halves were randomly divided into 10 equal groups. Groups I to V for the thick smear layer and groups VI to X for the thin smear layer. Eighty halves were used for shear bond strength testing, while the remaining 20 halves were used for SEM evaluation of the adhesive/dentin interface. After each dentin pretreatment, the glass-ionomer adhesive was applied over the conditioned dentin surfaces for all tested groups and restored with resin composite cylinders. Each half with its attached composite cylinder was subjected to shear load at crosshead speed of 0.5 mm/min until failure occurred. The dentin surfaces for SEM evaluation were treated as described for shear bond strength testing. The samples were examined using SEM operated at 30 kv, and the resin/dentin interface was examined at 1500X. RESULTS: Two-way ANOVA showed that there was no significant effect of the smear layer thickness on shear bond strength. There was a significant effect of the different conditioners used (p = 0.001). The interaction of the two independent variables (smear layer thickness and the dentin conditioners) showed no significant difference in the shear bond strength to dentin. The common feature in all evaluated specimen interfaces was the presence of a hybrid layer of different thicknesses with no visible resin tags. CONCLUSIONS: The shear bond strength of the glass-ionomer adhesive to dentin proved to be independent of the smear layer thickness. The use of dentin conditioner prior to the application of the glass-ionomer adhesive appeared to be an important step to improve its bond strength to dentin. Glass-ionomer adhesive failed to produce resin tags regardless of the type of dentin conditioner used.

Reattachment of a severely traumatized maxillary central incisor, one-year clinical evaluation: a case report.

Traumatic fracture of anterior teeth is one of the common dilemmas facing the dentist during daily practice. Classical treatment of a fractured tooth involving the pulp includes the use of post and core with or without a crown, or extraction of the remaining part of the fractured tooth and replacement with a three-unit fixed partial denture or an implant. With the improvement of adhesive systems, reattachment of the fractured tooth fragment became possible as a mode of treatment that immediately improves the esthetic quality of the restored tooth. This article presents a clinical technique for the restoration of a fractured maxillary central incisor, by reattaching the labial enamel fragment using a metallic post and resin composite restoration. One-year clinical evaluation revealed successful results for this technique.