Bond Strength Of Universal Adhesives Research Articles

Effect of double-layer application on the early enamel bond strength of universal adhesives.

The present study aimed to investigate the changes in the enamel bond strengths of universal adhesives in the early phase of specimen creation and evaluate the effect of double-layer application on enamel bond effectiveness using different etching modes. Four universal adhesives, namely Clearfil Universal Bond Quick, G-Premio Bond, Scotchbond Universal, and Tokuyama Universal Bond, were used. Clearfil SE Bond two-step self-etch adhesive system was used as a comparison. Fifteen specimens per group were used for determining the shear bond strength (SBS) to bovine enamel in the etch-and-rinse or self-etch mode. The adhesive was applied to specimens in accordance with the manufacturers' instructions (single-layer application), or the adhesive was applied twice (double-layer application). The bonded specimens were stored in distilled water at 37°C for 5min or 1, 6, 12, or 24h before SBS testing. The flexural properties of the resin composite Clearfil AP-X were measured for the same storage periods. All universal adhesives exhibited increased SBS values with prolonged storage periods regardless of the application technique or etching mode used. Double-layer application was associated with higher SBS values than single-layer application for most universal adhesives over the same storage period. Phosphoric acid pre-etching and double-layer application of universal adhesives resulted in increased enamel bond strength in the early phase of specimen bonding. Care should be taken when using universal adhesives in the self-etch mode for enamel bonding because the enamel adhesion is sensitive to the duration after filling.

Bonding Strength of Universal Adhesives to Indirect Substrates: A Meta-Analysis of in Vitro Studies.

To evaluate the in vitro bond strength of universal adhesive systems to indirect substrates. Two reviewers performed a literature search up to March 2018 in seven databases: PubMed, Web of Science, SciELO, Scopus, LILACS, IBECS, and BBO. The review included studies that compared the bond strength of universal adhesives and well-established material-specific primers to indirect substrates: lithium disilicate ceramic, yttrium-stabilized zirconium dioxide ceramic, leucite-reinforced ceramic, feldspathic porcelain, polymer infiltrated ceramic material, resin composite or metal alloys. Analyses were carried out using RevMan 5.3.5. A global comparison was performed with the standardized mean difference using a random-effects models at a significance level of p < 0.05. A total of 45 studies were included in the qualitative analysis, and the meta-analysis was performed with 42 studies. Bond strength to glass-based ceramics and alloys was improved with the use of a specific-primer as separate step before the bonding procedures (lithium disilicate, p < 0.001; alloys, p < 0.001). The bond strength to zirconium substrates was improved with the use of universal adhesives (p < 0.001). For bond strength to composite resin as indirect substrate, universal adhesives performed in a manner similar to that of the material-specific primer (p = 0.11). The clinical procedure of luting zirconia and resin composite restorations could be simplified by using single-bottle universal adhesives. However, the ability of universal adhesives to achieve an adequate and durable bond to glass-based ceramics and alloys appears to be limited.

Effect of the double application of universal adhesives on the dentine bond strength after radiotherapy.

This study aimed to evaluate the effect of double application of universal adhesives on bond strength to dentine after ionizing radiation. One hundred and forty caries-free human third molars were used. Half of the teeth were irradiated (IR) (70.2Gy). The IR and non-IR teeth were assigned into seven groups (n=10). Universal adhesives Single Bond Universal (3M Oral Care), Gluma Bond Universal (Heraeus Kulzer) and Prime&Bond Elect (Dentsply) were employed (following manufacturer's instructions and double application). Two-step self-etch adhesive Clearfil SE Bond (Kuraray Noritake) was used as control. After composite build-ups were bonded to mid-coronal occlusal dentine surfaces, the specimens were stored in water (37°C/24h) and sectioned into microspecimens. The specimens were subjected to μTBS testing (1.0mm/min). Failure analysis was performed using stereomicroscope and scanning electron microscopy. Data were analysed with two-way ANOVA and Tukey's test (P=0.05). The radiotherapy caused reduction in the bond strength of universal adhesives when the adhesives were used with single application after radiotherapy (P<0.05). The double application resulted in increased bond strength of the universal adhesives to IR dentine (P<0.05). The double application was beneficial in improving the dentine bond strength of universal adhesives affected by radiotherapy after ionizing radiation.

Bond Stability of Universal Adhesives Applied To Dentin Using Etch-And-Rinse or Self-Etch Strategies.

This study evaluated the immediate and 6-month dentin bond strength of universal adhesives used in etch-and-rinse or self-etch bonding strategies. The adhesives tested were Ambar Universal, G-Bond, Single Bond Universal, Tetric N-Bond Universal, and Ybond Universal. Gold standard adhesives (Scotchbond Multipurpose Plus and Clearfil SE Bond) were controls. Microtensile dentin bond strength (n=5 teeth), pH, and C=C conversion (n=3) were evaluated. Data were analyzed at α=0.05. All adhesives showed differences in pH. Ybond had intermediately strong aggressiveness, whereas the others were ultra-mild. The C=C conversion was different in most adhesives. In the etch-and-rinse strategy, all adhesives showed similar results generally except for G-Bond, which had lower bond strength than most adhesives. G-Bond and Tetric-N-Bond showed lower bond strengths after 6 months compared with 24 h, whereas the other adhesives had stable dentin bonds. In the self-etch strategy, G-Bond had lower bond strength than most adhesives. After 6 months, Ambar was the only adhesive showing lower dentin bond strength compared with 24 h. Most adhesives had discreet drops in bond strength during aging when used in the self-etch strategy. The failure modes were also material dependent, with a general pattern of increased adhesive and/or pre-testing failures after storage. In conclusion, the bonding performance of universal adhesives to dentin is material dependent. Most adhesives had stable dentin bonds with results comparable to the gold standard materials, particularly when applied in the self-etch mode. In general, it seems the use of universal adhesives in dentin should not be preceded by phosphoric acid etching.

Immediate enamel bond strength of universal adhesives to unground and ground surfaces in different etching modes.

The purpose of this study was to determine the immediate bond effectiveness of universal adhesives to unground and ground enamel surfaces in different etching modes, through shear bond strength (SBS) tests and scanning electron microscopy observations. Three universal adhesives, a conventional two-step self-etch adhesive, and a conventional single-step self-etch adhesive were compared. Human enamel specimens from lower anterior teeth were divided into four groups and subjected to the following treatments: (i) unground enamel in self-etch mode; (ii) ground enamel in self-etch mode; (iii) unground enamel in etch-&-rinse mode; and (iv) ground enamel in etch-&-rinse mode. Bonded assemblies were subjected to SBS testing. All the adhesives showed significantly higher SBS values in etch-&-rinse mode than in self-etch mode, regardless of whether enamel was unground or ground. The influence of the enamel surface condition on SBS was different in different etching modes. Without pre-etching, all tested materials showed lower SBS values in unground enamel than in ground enamel. In etch-&-rinse mode, no significant differences in SBS values were observed between unground enamel and ground enamel for any of the adhesives tested. Phosphoric acid pre-etching before application of self-etch adhesives to an unground enamel surface is essential to enhance initial enamel bond effectiveness.

Bonding Performance of Universal Adhesives: An Updated Systematic Review and Meta-Analysis.

To evaluate through a systematic review and meta-analysis whether the immediate and long-term bonding performance of universal adhesives would be improved by prior acid etching. Two reviewers performed a literature search up to April 2018 in eight databases: PubMed, Web of Science, Cochrane Library, SciELO, Scopus, LILACS, IBECS, and BBO. Only studies that evaluated the dentin or enamel bond strength of universal adhesives using a self-etch or etch-and-rinse strategy were included. Analyses were carried out using RevMan 5.3.5 (The Nordic Cochrane Centre, The Cochrane Collaboration, Copenhagen, Denmark). A global analysis comparing self-etch or etch-and-rinse strategies and the influence of aging on bonding performance was performed with random-effects models at a significance level of p < 0.05. A total of 59 in vitro studies were included in the meta-analysis. The enamel bond strength of universal adhesives was improved by the etch-and-rinse approach (p < 0.05). In dentin, this effect was observed for ultra-mild and intermediately strong universal adhesives (p < 0.05). Irrespective of the strategy employed, intermediately strong adhesives showed a decrease in bond strength after all types of aging. This effect was also observed for ultra--mild universal adhesives used in the etch-and-rinse approach (p < 0.05). Mild universal adhesives showed bond strength stability in both strategies (p > 0.05). The in vitro evidence suggests that bonding performance of mild universal adhesives can be improved by using the selective enamel-etch strategy. Mild universal adhesives seem to be the more stable materials, in both etch-and-rinse or self-etch strategies.

Reconsideration of Enamel Etching Protocols for Universal Adhesives: Effect of Etching Method and Etching Time.

To evaluate whether different etching methods with reduced etching times would improve the enamel bonding efficacy of universal adhesives. Three enamel etching methods were evaluated - 1. phosphoric acid ester monomer etching (PPM); 2. phosphoric acid etching (PPA); and 3. polyalkenoic acid etching (PLA) - as were three universal adhesives: 1. BeautiBond Universal (BU); 2. Prime&Bond elect (PE); and 3. Scotchbond Universal Adhesive (SU). The shear bond strengths of the universal adhesives to ground enamel and ground enamel etched for 1, 5, 10, and 15 s with different etching methods were determined after 24 h and 10,000 thermal cycles. Surface roughness average (Ra) and surface area ratio (surface area:planar area) were measured using a confocal laser scanning microscope. Field-emission scanning electron microscope (FE-SEM) observations of enamel with different etching protocols were also conducted. The bond strengths of universal adhesives to enamel subjected to PPA etching with maximum times of 1-15 s and PLA etching for 15 s were significantly higher than those to ground enamel. The bond strength to enamel subjected to PPM etching did not increase and was similar to that for ground enamel. PPA and PLA etching were effective at increasing the Ra and surface area ratio of enamel. Although both values were significantly higher than those of ground enamel, those subjected to PPA etching were significantly higher than those which underwent PLA etching. In addition, the Ra and surface area of enamel subjected to PPM etching were similar to those of ground enamel, regardless of the etching time. Phosphoric acid etching for <1-15 s and polyalkenoic-acid etching for 15 s both improve the bonding of universal adhesives, the Ra, and the surface area ratio of enamel. However, phosphoric acid ester monomer etching was not effective, regardless of the etching time.

Effects of etching mode on bond strength of universal adhesives

Effects of etching mode on bond strength of universal adhesives

Microshear bond strength of universal adhesives for use with artificially demineralized enamel, with and without pre-etching

The aim of this study was to investigate the microshear bond strength of five universal adhesives for use with demineralized enamel, with and without pre-etching. Using five universal adhesives (Single Bond Universal (SBU), Clearfil Universal (CU), Prime&Bond Elect Universal (PBU), Bisco All Bond Universal (ABU), Gluma Bond Universal (GU)), composite cylinders were bonded to the labial surfaces of extracted upper incisor teeth, with or without pre-etching. A micro-shear bond strength test was performed. The debonding surfaces were evaluated with the use of SEM. The data was analyzed using one-way ANOVA and Tukey’s Post-hoc tests. SBU, ABU, and PBU increased the bond strength statistically when used in etch&rinse mode (p < 0.05). GU and CU did not change the bond strength statistically with the use of pre-etching (p > 0.05). The bond strength of universal adhesives on demineralized enamel, with and without initial acid etching, depends on the type of adhesive system used.

Effect of air-blowing time and long-term storage on bond strength of universal adhesives to dentin.

To evaluate the effects of air-blowing time and storage time on microtensile bond strength (μTBS) of universal adhesives to dentin. Ninety flat dentin surfaces from extracted human third molars were bonded with three universal adhesives (Clearfil Universal Bond-CU; G-Premio Bond-GP; Scotchbond Universal Adhesives-SB). Bonded dentin surfaces were air-dried for 5s, 15s, or 30s followed by resin composite built-up. Resin-dentin beams were tested with μTBS test after different storage time in distilled water (24h and 1year). Data were analyzed by three-way ANOVA and Duncan test at (α = 0.05). Failure mode and resin-dentin interfaces were observed using a scanning electron microscope (SEM). Specific features of fractured beams after μTBS were further observed using SEM at high magnification. Extension of air-blowing time from 5s to 30s increased the 24h μTBS of CU only. Bond strength of all adhesives significantly decreased after 1-year storage except for CU at 5s and 30s of air-blowing time. One-year μTBS were significantly higher when air-blowing times were extended to 15s for SB and 30s for CU. Air-blowing time had no influence on GP. The effect of air-blowing time and storage time on resin-dentin bond was material-dependent. Extended air-blowing time increased the bond strength and bond durability of CU. Extension of air-blowing time to 15s and 30s improve the long-term bond strength of SB and CU, respectively.

Does Shortened Application Time Affect Long-Term Bond Strength of Universal Adhesives to Dentin?

This study evaluated the effect of shortened application time on long-term bond strength with universal adhesives. Three universal adhesives were used: Clearfil Universal Bond (CU, Kuraray Noritake Dental Inc, Tokyo, Japan), Scotchbond Universal Adhesive (SB, 3M ESPE, St Paul, MN, USA) or G-Premio Bond (GP, GC Corp, Tokyo, Japan). Sixty molars were cut to expose midcoronal dentin and prepared with a regular diamond bur. Each adhesive was applied either according to the manufacturer's instruction or with shortened time. Specimens were stored in distilled water at 37°C for 24 hours and then cut into resin-dentin sticks. Microtensile bond strength (μTBS) was tested after either 24 hours or 1 year of water storage. Data were analyzed by the three-way ANOVA and Duncan tests ( α=0.05). Fracture modes were analyzed under a scanning electron microscope (SEM). One dentin stick per group was selected after fracture mode analysis and further observed using transmission electron microscopy (TEM). Six additional dentin discs were prepared and conditioned with each adhesive under the different application time to observe the adhesive-smear layer interaction by SEM. Shortened application time affected the μTBS ( p<0.001) while storage time did not affect bond strength ( p=0.187). A significant effect of shortened application time on μTBS was observed in the CU at 1 year and in the GP at both storage times. One-year storage time had no effect on the μTBS of universal adhesives to bur-cut dentin. The performance of universal adhesives can be compromised when applied using a shortened application time.

Microtensile bond strength of universal adhesives to flat versus Class I cavity dentin with pulpal pressure simulation.

The aim of this study was to test long-term microtensile bond strength (µTBS) of 2 universal adhesives applied to dentin following "total-etch" (TE) or "self-etch" (SE) protocols and aged by direct or indirect water exposure using simulated pulpal pressure. Single Bond Universal (SBU, 3M ESPE) or Ipera Bond (IP, Itena) were applied to mid-coronal dentin ("flat dentin") or Class I cavity ("cavity dentin") following TE or SE protocols in 112 extracted human third molars. Sixteen groups (n = 7 per group) were prepared, 8 groups for µTBS measurements after 24 hours, and further 8 groups for measurements after 6 months storage. "Cavity dentin" groups were subjected to simulated hydrostatic pulpal pressure of 15 cm H2 O using a custom-made device before cutting 1 × 1 mm sticks while "flat dentin" groups were cut into sticks and directly exposed to deionized water. Generally, the TE protocol resulted in highest µTBS values on flat dentin initially for both adhesives (general linear model, P < .05). Long-term storage resulted in significantly lower µTBS values for the TE protocol (P < .05) while the SE protocol showed comparable values after 6 months (P > .05). "Cavity dentin" with simulated pulpal pressure resulted in lower µTBS than "flat dentin" (P < .05). For both adhesives, µTBS was in the range of 19-42 MPa initially and 16-36 MPa after 6 months storage. µTBS to dentin of universal adhesives is more stable in the long term following the SE than TE protocol. Simulated pulpal pressure and cavity-type sample preparation may be recommended for µTBS testing as a more clinically relevant strategy. Microtensile bond strength to dentin of universal adhesives appears more stable following the "self-etch" than "total-etch" protocol after long-term degradation. More clinically relevant data may be obtained using simulated pulpal pressure and cavity-type sample preparation in the study design.

Bonding strength of universal adhesives to Er,Cr:YSGG Laser-Irradiated Dentin.

Universal adhesives have been recently introduced for use as self-etch or etch-and-rinse adhesives depending on the dental substrate and clinical condition. However, their bonding effectiveness to laser-irradiated dentin is still not well known. Therefore, the aim of this study was to compare the shear bond strength (SBS) of two universal adhesives (Single Bond Universal, Nova Compo-B Plus) applied following laser-etching with SBS of the same adhesives applied in self-etch and acid-etch modes, respectively. Sixty bovine incisors were used to obtain the flattened dentin surfaces. Specimens were divided into two groups according to universal adhesives. Each universal adhesive was applied with one of the following modes, self-etch, acid-etch, or laser-etch (n = 10). Er,Cr:YSGG laser was used for laser-etching with 1.5 W-20 Hz parameters. After adhesive applications and composite buildups, SBS was determined after storage in water for 24 h using a universal testing machine with a crosshead speed of 0.5 mm/min. Failure modes were evaluated using a stereomicroscope. Data were analyzed using two-way of analyses of variances (ANOVA) (P = 0.05). Two-way ANOVA revealed that adhesive had no effect on SBS (P > 0.05), but application mode significantly influenced SBS (P < 0.001). Laser-etch significantly increased SBS for NCP when compared to self-etch mode, whereas laser-etch provided similar SBS with self-etch mode for SBU. The influence of different application modes on dentin bond strength of universal adhesives was dependent on the adhesive material. For universal adhesives, laser etching may provide some benefits on bonds strength but this would depend on product.

Micro-shear bond strength of universal adhesives used for amalgam repair with or without Alloy Primer.

Aim:The aim of this study was to investigate the adhesive performance of three different universal adhesives to repair aged amalgam by composite resins with or without Alloy Primer.Materials and Methods:Sixty amalgam samples were prepared, aged, and randomly divided into 12 main groups according to adhesive procedures used. Composite buildups were placed on amalgam surfaces. After micro-shear bonding test, the fracture surfaces were examined under the scanning electron microscopy statistical analysis was performed using two-way analysis of variance and Tukey's post hoc tests.Results:Without use of Alloy Primer, all of the universal adhesives provided similar bond strength values with conventional adhesives (P > 0.05); however, an Alloy Primer significantly increased the bond strength values of universal adhesives (P < 0.05). No significant difference in bond strength values was noted for conventional adhesives with or without Alloy Primer (P > 0.05) except for Clearfil SE Bond (P < 0.05).Conclusions:Within the limitations of this study, it can be concluded; using Alloy Primer before universal adhesives increased the bond strength significantly.

Effect of rubbing force magnitude on bond strength of universal adhesives applied in self-etch mode.

This study investigated the effect of rubbing force magnitude on dentin bond strengths of multi-mode adhesives applied in self-etch mode. Seventy-two extracted human molar teeth were used. Two different universal adhesives Single Bond Universal (SB) and Clearfil Universal (CL) were applied onto dentin surfaces in three different modes: without rubbing (NR), rubbing with 40 gf (gram-force) (40) or 80 gf (80) load. Teeth were restored with a resin composite. Half of the specimens were subject to thermal aging (10,000 cycles). Microtensile bond strength was measured and data were statistically analyzed with two-way analysis of variance and Tukey's test (α=0.05). Baseline bond strength values for CL adhesive were improved by rubbing (40 and 80 gf) as compared to no rubbing (p<0.05). Rubbing did not significantly improve bond strength values for SB, regardless of aging (p>0.05). Rubbing improves bonding performance of some universal adhesives to dentin when applied in self-etch mode.

Effect of Dentin Wetness on the Bond Strength of Universal Adhesives.

The effects of dentin wetness on the bond strength and adhesive interface morphology of universal adhesives have been investigated using micro-tensile bond strength (μTBS) testing and confocal laser scanning microscopy (CLSM). Seventy-two human third molars were wet ground to expose flat dentin surfaces. They were divided into three groups according to the air-drying time of the dentin surfaces: 0 (without air drying), 5, and 10 s. The dentin surfaces were then treated with three universal adhesives: G-Premio Bond, Single Bond Universal, and All-Bond Universal in self-etch or etch-and-rinse mode. After composite build up, a μTBS test was performed. One additional tooth was prepared for each group by staining the adhesives with 0.01 wt % of Rhodamine B fluorescent dye for CLSM analysis. The data were analyzed statistically using ANOVA and Tukey’s post hoc tests (α = 0.05). Two-way ANOVA showed significant differences among the adhesive systems and dentin moisture conditions. An interaction effect was also observed (p < 0.05). One-way ANOVA showed that All-Bond Universal was the only material influenced by the wetness of the dentin surfaces. Wetness of the dentin surface is a factor influencing the micro-tensile bond strength of universal adhesives.

Comparative microtensile bond strength of universal adhesives in primary teeth

IntroductionAlmost 50 % of carious lesions in primary teeth remain untreated either due to limited compliance, or due to technique sensitivity of multi-step bonding systems or due to doubts about durability of resin composite restorations in primary teeth. Universal self-etch adhesives have been introduced in order to overcome the material- and technique-related problems because of their easy handling and their functional monomers, which have been reported to enhance bonding performance. Objective of the study was to compare 3 universal adhesives to a self-etch adhesive used as control.Material and methodsMid-coronal dentin was exposed in 20 primary molars, adhesives were applied followed by composite resin build-up: 1. Prime & Bond NT [PBNT] (control); 2. One Coat 7 Universal [OC7U]; 3. Futurabond U [FU]; 4. Prime & Bond active [PBA]. Beams were cut from specimen slabs and subjected to µ-tensile bond strength and mode of failure evaluation.ResultsFollowing bond strength values were re — corded (in MPa [SD]): PBNT (48.2 [14.3]), OC7U (69.7 [17]), FU (71.3 [17.7]), PBA (77.9 [23.5]). Sta — tistically significant differences were computed for all test groups compared to PBNT (p < 0.001, Bonferroni). PBA exhibited significantly higher values than OC7U (p < 0.05, Bonferroni). OC7U showed the lowest percentage of adhesive failures.ConclusionAll tested universal adhesives exhibited higher bond strength values in primary tooth dentin, in comparison to the traditional self-etch approach and can therefore be suggested as an alternative option in adhesive restorations in paediatric dentistry.

Effect of Different Protocols in Preconditioning With EDTA in Sclerotic Dentin and Enamel Before Universal Adhesives Applied in Self-etch Mode.

The aim of this study was to investigate the effect of different protocols of 17% ethylene diamine tetra-acetic acid (EDTA) conditioning on the etching pattern and immediate bond strength of universal adhesives to enamel and sclerotic dentin. Forty bovine teeth with sclerotic dentin and 20 human third molars were randomly divided into eight groups resulting from the combination of the main factors surface treatment (none, two-minute EDTA conditioning manual application, 30-second EDTA manual application, 30-second EDTA sonic application) and adhesives systems (Scotchbond Universal Adhesive [SBU] and Prime & Bond Elect [PBE]). Resin-dentin and enamel-dentin bond specimens were prepared and tested under the microtensile bond strength (μTBS) and microshear bond strength (μSBS) tests, respectively. The etching pattern produced on the unground enamel and the sclerotic dentin surfaces under the different protocols and adhesive systems was evaluated under scanning electron microscopy. For enamel, only the main factor adhesive was significant (p<0.0001), with SBU showing the highest μSBS. In sclerotic dentin, the lowest mean was observed for the group without EDTA application and the highest mean in the group with EDTA application with the sonic device for 30 seconds. Regardless of the EDTA protocol, the highest means of μTBS were observed for SBU (p<0.05). EDTA conditioning improves the bonding performance of universal adhesives in the self-etch mode on sclerotic dentin, mainly when applied for 30 seconds with the aid of a sonic device. EDTA pretreatment also improves the retentive etching pattern of enamel, but it does not result in higher enamel bond strength.

Influence of dentin pretreatment on bond strength of universal adhesives

Objective: The purpose of the present study was to compare bond strength of different universal adhesives under three different testing conditions: when no pretreatment was applied, after 37% phosphoric acid etching and after glycine application.Materials and methods: One hundred and fifty bovine permanent mandibular incisors were used as a substitute for human teeth. Five different universal adhesives were tested: Futurabond M+, Scotchbond Universal, Clearfil Universal Bond, G-Premio BOND, Peak Universal Bond. The adhesive systems were applied following each manufacturer’s instructions. The teeth were randomly assigned to three different dentin surface pretreatments: no pretreatment agent (control), 37% phosphoric acid etching, glycine pretreatment. The specimens were placed in a universal testing machine in order to measure and compare bond strength values.Results: The Kruskal–Wallis analysis of variance and the Mann–Whitney test were applied to assess significant differences among the groups. Dentin pretreatments provided different bond strength values for the adhesives tested, while similar values were registered in groups without dentin pretreatment.Conclusions: In the present report, dentin surface pretreatment did not provide significant differences in shear bond strength values of almost all groups. Acid pretreatment lowered bond strength values of Futurabond and Peak Universal Adhesives, whereas glycine pretreatment increased bond strength values of G Praemio Bond adhesive system.

Effect of Reduced Phosphoric Acid Pre-etching Times on Enamel Surface Characteristics and Shear Fatigue Strength Using Universal Adhesives.

To examine the effect of reduced phosphoric acid pre-etching times on enamel fatigue bond strength of universal adhesives and surface characteristics by using atomic force microscopy (AFM). Three universal adhesives were used in this study (Clearfil Universal Bond [C], G-Premio Bond [GP], Scotchbond Universal Adhesive [SU]). Four pre-etching groups were employed: enamel pre-etched with phosphoric acid and immediately rinsed with an air-water spray, and enamel pre-etched with phosphoric acid for 5, 10, or 15 s. Ground enamel was used as the control group. For the initial bond strength test, 15 specimens per etching group for each adhesive were used. For the shear fatigue test, 20 specimens per etching group for each adhesive were loaded using a sine wave at a frequency of 20 Hz for 50,000 cycles or until failure occurred. Initial shear bond strengths and fatigue shear strengths of composite adhesively bonded to ground and pre-etched enamel were determined. AFM observations of ground and pre-etched enamel were also conducted, and surface roughness as well as surface area were evaluated. The initial shear bond strengths and fatigue shear strengths of the universal adhesives in the pre-etched groups were significantly higher than those of the control group, and were not influenced by the pre-etching time. Significantly higher surface roughness and surface area of enamel surfaces in pre-etched groups were observed compared with those in the control group. While the surface area was not significantly influenced by etching time, surface roughness of the enamel surfaces in the pre-etched groups significantly increased with pre-etching time. The results of this in vitro study suggest that reduced phosphoric acid pre-etching times do not impair the fatigue bond strength of universal adhesives. Although fatigue bond strength and surface area were not influenced by phosphoric-acid etching times, surface roughness increased with increasing etching time.