Influence of duration of phosphoric acid pre-etching on bond durability of universal adhesives and surface free-energy characteristics of enamel

One-Step Surface-Treatment Reagent (35% 3-O-Ethyl-l-ascorbic Acid Plus 50% Citric Acid Solution) Restores the Shear Bond Strength of Metal Brackets Bonded to Bleached Human Enamel: An In Vitro Study

This study investigates how a new substance, composed of ethyl ascorbic acid and citric acid, affects the shear bond strength (SBS) of metal brackets when bonded to bleached teeth. Forty maxillary premolar teeth were used and randomly placed into four groups (n = 10): the control group did not undergo bleaching; the remaining groups underwent bleached using 35% hydrogen peroxide. In group A, 37% phosphoric acid was applied after bleaching. In group B, 10% sodium ascorbate was used for ten minutes before 37% phosphoric acid. In group C, 35%3-O-ethyl-l-ascorbic acid plus 50% citric acid solution (35EA/50CA) was applied for 5 min. The subgroups were bonded immediately after bleaching. The SBS was determined with a universal testing machine and analyzed using one-way ANOVA and then Tukey's HSD tests. Adhesive remnant index (ARI) scores were determined with a stereomicroscope and analyzed with a chi-squared test. The significance level was 0.05. Group C demonstrated significantly higher SBS values than group A (p < 0.001), but was not significantly different than the control group or group C (p > 0.05). The ARI scores were significantly different among the groups (p < 0.001). In conclusion, enamel surface treatment using 35EA/50CA improved the reduced SBS to an acceptable clinical level and reduced the clinical chair time.

Effect of Er,Cr: YSGG Laser on Bonding of Laminate Veneers using CAD/CAM (In Vitro Study)

AIM: This in vitro study was designed to evaluate the shear bond strength after bonding between porcelain laminate veneers and the tooth surface using different etching methods METHODS: Thirty freshly extracted maxillary premolars were used and prepared for receiving Enamic laminate veneers. Specimens were divided into two groups (n = 15), according to the surface treatment protocol. The specimens were sandblasted with 50 μm Al2O3 for 20 s; 2 bar pressure was maintained for air abrasion. Distribution of groups was as follow G1: Prepared enamel surface treatment of each tooth was according to the manufacturer’s instructions. G2: The prepared enamel surface of each tooth was subjected to Erbium,Chromium-Doped: Yttrium, Scandium, Gallium, and Garnet laser application. Light cured adhesive resin cement was applied to fitting surface of each ceramic specimen. To simulate thermal aging, the samples were subjected to 5000 thermal cycling in a thermocycler. By dividing the failure load (N) by the bonding area (mm2), debonding loads were calculated as shear stress (MPa). Numerical data were presented as mean and standard deviation values. They were explored for normality by checking the data distribution using Shapiro–Wilk test. Data showed parametric distribution and were analyzed using independent t-test. The significance level was set at p ≤ 0.05 within all tests. Statistical analysis was performed with R statistical analysis software version 4.1.2 for Windows. RESULTS: Group (II) (15.84 ± 3.09) had significantly higher mean value than group (I) (13.69 ± 2.36) (t = 2.15, p = 0.041). CONCLUSION: Within the limitation of this study, it was revealed that the laser surface treatment for tooth substrate plays a significant role in increasing the shear bond strength of laminate veneers.

Universal Adhesives and Adhesion Modes in Non-Carious Cervical Restorations: 2-Year Randomised Clinical Trial

This prospective, double-blind, six-arm parallel randomised controlled trial aimed to compare the performance of two universal adhesives (UAs) in non-carious cervical lesions (NCCLs), using the FDI criteria, and analysed if participants/NCCLs’ characteristics influenced the outcome. Thirty-eight 18- to 65-year-old participants were seeking routine dental care at a university clinic. At baseline, 210 NCCLs were randomly allocated to six groups (35 restorations’ each). The UAs tested were FuturabondU (FBU) and AdheseUniversal (ADU) applied in either etch-and-rinse (ER) and self-etch (SE) modes. FuturabondDC (FBDC) in SE and in SE with selective enamel etching (SE-EE) modes were controls. NCCLs were restored with AdmiraFusion. The analysis included nonparametric tests, Kaplan-Meier and log-rank tests (α = 0.05). At 2-years, of 191 restorations, ten were missed due to retention loss (all groups, p > 0.05). FBDC (p = 0.037) and FBU (p = 0.041) performed worse than ADU in SE mode. FBDC and FBU also showed worse functional success rate (p = 0.012, p = 0.007, respectively) and cumulative retention rates (p = 0.022, p = 0.012, respectively) than ADU. Some participants/NCCLs’ characteristics influenced (p < 0.05) the outcomes. FBU did not perform as well as ADU, especially in SE mode and due to functional properties. Participants’ age and NCCLs’ degree of dentin sclerosis and internal shape angle influenced FBU performance.

An 18-month clinical evaluation of prolonged polymerization of a universal adhesive in non-carious cervical lesions: A double-blind randomized clinical trial

OBJECTIVE

This study aimed to evaluate the effect of prolonging polymerization time on the 18 months clinical performance of a universal adhesive system used as etch-and-rinse (ER) and self-etch (SE).

METHODS

140 restorations were randomly placed in 35 subjects according to the following groups: ER10 (light-curing for 10 s); ER40 (light-curing for 40 s); SE10 (light-curing for 10 s) and; SE40 (light-curing for 40 s/1200 mW/cm²). A resin composite was placed incrementally. The restorations were evaluated at baseline and after 18 months by using the FDI criteria. The following outcomes were evaluated: marginal staining, marginal adaptation, spontaneous post-operative sensitivity and recurrence of caries. The differences among the groups were calculated using Friedman repeated measures analysis of variance rank (α = 0.05).

RESULTS

After 18 months the retention/fracture rates were 88.9% (95%CI 74.1-95.6%) for ER10, 94.3% (95%CI 91.4-98.5%) for ER40, 77.2% (95%CI 60.1-87.9) for SE10 and 97.2% (95%CI 85.5-99.9%) for SE40. A significant difference was detected in the retention rate when SE10 was compared to the SE40 (p = 0.01). Also, ER40 showed a significant improvement of the marginal adaptation when compared to ER10 (p = 0.01).

SIGNIFICANCE

This is the first study that demonstrates an improvement in the clinical performance of universal adhesive systems in non-carious cervical lesions when prolonged light-cured was applied.

Influence of different acid etching times on the shear bond strength of brackets bonded to bovine enamel

Introduction

The most used product for surface acid conditioning for enamel is 37-40% phosphoric acid, which promotes greater mechanical retention.

Aim

The objective of this study was to compare the shear bond strength (SBS) of brackets bonded to bovine enamel with different acid conditioning protocols and to analyze the surface morphology.

Materials and methods

169 teeth (n = 13) were divided into 4 groups: control group without conditioning (G1), Dental Gel 37% phosphoric acid (Dentsply) (G2), Ultra Etch 35% (Ultradent) (G3) and Attaque gel 37% (Biodinâmica) (G4). Groups G2, G3 and G4 were subdivided according to the conditioning time into: 10 s (a), 15 s (b), 30 s (c) and 60 s (d). The superficial enamel morphology (n = 3) was analyzed using a scanning electron microscopy (SEM) to analyze the depth of the microporosities. The samples were submitted to the shear test (SBS) with the aid of a universal testing machine (INSTRON) with a speed of 1 mm/min. The enamel after debonding was analyzed to determine the adhesive remnant index (ARI) in a stereoscopic magnifying glass.

Statistical analysis used

The SBS data were analyzed using two-way ANOVA. ARI data were analyzed using generalized linear models and SEM measurements were analyzed using Kruskal Wallis and Dunn tests. The 95% significance level was used.

Results

The SBS within G2, G3 and G4 ranged from 11.11 to 12.66 MPa. ARI score 3 was observed in 35% of the samples. The samples analyzed in the SEM showed microporosity depth rangingfrom 1.28 to 2.48 μm.

Conclusions

There was no difference between the acids and times evaluated for SBS. The ARI analysis showed that the studied acids provide protection to the enamel surface, keeping the adhesive attached to the buccal surface after debonding. The increase in conditioning time is directly proportional to the deterioration of the prismatic and interprismatic content.

Marginal quality of a full-body bulk-fill composite placed with an universal adhesive system in etch-and-rinse and self-etch mode: An in vitrostudy

Background

Marginal seal of a nanohybrid bulk-fill composite compared to a nanohybrid conventional composite, using a universal adhesive (UA) applied in etch-and-rinse (ER) and self-etch (SE) mode was investigated.

Material and Methods

Thirty-six intact molars were selected and two standardized cavities in each tooth were prepared and allocated into four groups according to restorative material and etching strategy. All samples were placed in a 1% methylene blue solution for 24 h, then cut in the middle of the restorations obtaining two parts (n=144) and used for microscopic evaluation (50x) for dye penetration measurements.

Results

The data were analysed by ANOVA and Tukey post-hoc test (p<0.05). Marginal seal was influenced by adhesive strategy (p<0.05) but not from the composite used (p>0.05).

Conclusions

Simplified restorations with nanohybrid bulk-fill composite showed comparable marginal leakage to incrementally placed nanohybrid composite. The UA used with a ER technique resulted in better marginal seal irrespective of the restorative material used.

Key words:Bulk-fill composite, universal adhesive, self-etching, etch-and-rinse, marginal seal.

Limited Etching Time Increases Self-adhesive Resin Cement Adhesion to Enamel

AIM

To evaluate the influence of different enamel etching times on the bond strength of two self-adhesive resin cements (RCs) with and without thermocycling (TMC).

METHODS

One hundred twenty bovine teeth were used. Blocks of enamel (8×4×2mm) were obtained, polished, and randomly divided into two groups, according to the RC used: MaxCem Elite or RelyX U200. Groups were subdivided into four groups (n=16), according to the etching time: Control (0 seconds), 5 seconds, 10 seconds, and 20 seconds. Three RC cylinders (1-mm diameter) were built on each enamel block. The specimens were submitted to two storage conditions: 24 hours in distilled water or TMC (5000 cycles/5°C-55°C). Afterward, the specimens were submitted to the shear bond strength (SBS) test. The failure modes and adhesive interfaces were analyzed by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Data were analyzed with three-way analysis of variance (ANOVA) and Tukey test (α=0.05).

RESULTS

Etching increased the SBS for both the RCs,especially forthe groups etched for 5 and 10 seconds. TMC affected negatively the SBS of the control groups (p<0.05). No resin tags were observed in control groups, and the formation of tags was time dependent.

CONCLUSION

The 10 seconds etching time was more effective in increasing the enamel-resin bond strength. TMC negatively affected bond strength in specimens without acid etching.

Influence of reduced application time on bonding durability of universal adhesives to demineralized enamel

OBJECTIVES

This study aimed to assess the effect of application time on the microshear bond strength (μSBS) of three universal adhesives in demineralized and sound enamel before and after aging.

MATERIALS AND METHODS

Bovine teeth (192) were prepared where buccal surfaces were ground and divided into two groups (sound enamel and demineralized enamel). The specimens in each group were divided into 12 subgroups by combining 3 adhesive agents (All-Bond Universal, Scotchbond Universal, and Tokuyama Universal Bond) × 4 adhesion strategy. Each adhesive was applied with either prolonged (PA) or reduced (RA) application time in etch-and-rinse or self-etch mode. Bonded composites were subjected to μSBS testing after 24-h or 2-year water storage. The results were evaluated using four-way ANOVA and Tukey's post-hoc test (α = 0.05).

RESULTS

The μSBS of adhesives to sound enamel in both etching modes was mostly similar to demineralized enamel, regardless of application time and aging time. At 24-h, all adhesives with PA in self-etch mode showed higher μSBS when compared with RA, except Tokuyama Universal Bond, but after 2-year aging, no significant difference was found in μSBS between RA and PA. The μSBS of adhesives with PA in etch-and-rinse mode depended on used adhesive and enamel condition compared to RA, regardless of μSBS testing time.

CONCLUSIONS

PA of adhesives did not reveal a significant difference in μSBS to enamel, regardless of substrate type and etching mode.

CLINICAL RELEVANCE

After 2-year aging, the bond strength of universal adhesives presented no significant difference between PA and RA treatments.

Current perspectives on dental adhesion: (1) Dentin adhesion - not there yet

The essential goal of any adhesive restoration is to achieve a tight and long-lasting adaptation of the restorative material to enamel and dentin. The key challenge for new dental adhesives is to be simultaneously effective on two dental substrates of conflicting nature. Some barriers must be overcome to accomplish this objective. While bonding to enamel by micromechanical interlocking of resin tags within the array of microporosities in acid-etched enamel can be reliably achieved and can effectively seal the restoration margins against leakage, bonding effectively and durably to organic and humid dentin is the most puzzling task in adhesive dentistry.

Much of the research and development of dental adhesives has focused on making the clinical procedure more user-friendly by reducing the number of bottles and/or steps. Although clinicians certainly prefer less complicated and more versatile adhesive materials, there is a trade-off between simplification of dental adhesives and clinical outcomes. Likewise, new materials are launched with claims of being novel and having special properties without much supporting evidence.

This review article discusses dental adhesion acknowledging pioneer work in the field, highlights the substrate as a major challenge to obtain durable adhesive restorations, as well as analyzes the three adhesion strategies and their shortcomings. It also reviews the potential of chemical/ionic dental adhesion, discusses the issue of extensively published laboratory research that does not translate to clinical relevance, and leaves a few thoughts in regard to recent research that may have implications for future adhesive materials.

Influence of different phosphoric acids before application of universal adhesive on the dental enamel

BACKGROUND

There are different etching gels available, which have different composition, different pH, and different viscosity, and there is little information in the literature comparing all these products.

OBJECTIVE

To evaluate the mean microshear bond strength and morphological characteristics of tooth enamel by evaluating different phosphoric acids combined with a universal adhesive system.

MATERIALS AND METHODS

Eighty-four enamel samples were used, which were divided according to the acid conditioning: G1: Scotchbond Etchant (3M Oral Care), G2: Ultra-Etch (Ultradent), G3: Eco-Etch (IvoclarVivadent), G4: ETCH-37 with BAC (Bisco), G5: Etching gel (Densell), G6: Condac 37 (FGM), and G7: Scotchbond Universal Adhesive (3M Oral Care) in self-etch mode. For the adhesive procedure, Scotchbond Universal Adhesive was the one used as indicated the manufacturer's instructions, 0.9-mm-diameter resin cylinders were placed. The microshear bond strength test was performed after being stored for 24 hours in water. The morphological characteristics of tooth enamel were analyzed using the Raman confocal microscope alpha300RA. The analysis of variance (ANOVA) test and Tukey post-test were used to analyze the differences between the groups.

RESULTS

The mean microshear bond strength values obtained for groups 1, 4, 5 were significantly greater than groups 2, 3, 6 and 7 (p < .05). All groups presented demineralization after the application of the etching acid, and few signs of demineralization were evident in group 7.

CONCLUSIONS

Acid-etching with ETCH-37 with BAC, Etching gel, and Scotchbond Etchant improved the adhesive strength in the enamel using an universal adhesive, and acid-etching with Condac 37, Ultra-Etch, and Eco-Etch provides similar adhesive strength values to self-etch mode of universal adhesive.

CLINICAL SIGNIFICANCE

All acid etchants should be considered as different. The test confirms that enamel etching prior to the application of a universal adhesive system depends on the selected acid etchand product.

The impact of etching time and material on bond strength of self-adhesive resin cement to eroded enamel

The purpose of this study was to assess the effect of pre-etching time and material on shear bond strength (SBS) of self-adhesive resin cements to eroded and sound enamel. Eroded enamel specimens were assigned into 5 groups (n=20 each) based on enamel surface treatment as follow: Group N, eroded enamel (without surface pre-treatment); Group PH15, 35% H₃PO₄ etching for 15 s; Group PH30, 35% H₃PO₄ etching for 30 s; Group L30, 20% lactic acid etching for 30 s and Group L60, 20% lactic acid etching for 60 s.Composite blocks were fabricated and cemented to enamel surfaces with one of two self-adhesive cements. Notched-edge SBS was assessed. Bond strength of self-adhesive cement to eroded enamel surface significantly enhanced following application of 20% lactic acid for 30 s.

Bond strength and adhesive interfacial micromorphology of self-adhesive resin cements: Effect of reduced times of pre-etching

Background

Although acid-etching could increase enamel bond strength of self-adhesive (SA) cements, it may lead to negative effect on dentin. The aim of this study was to assess the effect of shortening of phosphoric acid pre-etching duration on enamel/ dentin shear bond strength (SBS) and interfacial microstructure of Panavia SA Luting Plus (PASA) and Bifix SE (BXSE).

Material and Methods

For both enamel and dentin, effect of pre-etching time was significant (p<0.001); however, effect of cement brand and the interaction of two factors was significant only for dentin (p≤0.008). Three pre-etching times increased SBS of both cements to enamel and BXSE to dentin. In case of dentin SBS of PASA, this improvement was significant only for 5 and 10 seconds (p<0.001). Adding acid-etching in the three times to both cements similarly improved interfacial adaptation, particularly for enamel.

Results

The evaluations of the biofilm elimination showed results that indicate that the 4% sodium hypochlorite group with positive pressure irrigation presented significant differences with the group that had irrigation with sodium hypochlorite activated with XP-endo Finisher and the chlorhexidine groups to 2% (P<0.05).

Conclusions

Interfacial bond strength and adaptation of SA cements used in this study were improved following addition of enamel/dentin etching step for a short time. This was not exceeded for longer times than 5-second.

Key words:Dentin bond strength, enamel bond strength, pre-etching time, self-adhesive cement.

Comparison of shear bond strength of orthodontic brackets bonded with a universal adhesive using different etching methods

Objective:

The aim of this study was to compare the effects of three enamel etching modes - laser-etch, self-etch and acid-etch (5, 10 and 15 s) - on bracket bonding, using a universal adhesive.

Methods:

Eighty-four maxillary premolars were randomly divided into seven groups (n=12) based on the etching method and the adhesive used for bracket bonding. After water storage and thermocycling, shear bond strength was measured, and adhesive remnant index scores on debonded enamel were determined.

Results:

There were significant differences between the seven groups regarding bond strength values (p< 0.001). The highest values were observed in universal adhesive with laser etching group, while Transbond XT with acid or laser etching, and universal adhesive used in self-etch mode demonstrated the lowest bond strength. The universal adhesive with the three different etching times presented with statistically similar results, all showing an improvement in bond strength, compared with Scotchbond universal (SBU)/SE.

Conclusions:

The universal adhesive evaluated in the present study demonstrated statistically similar bond strengths to conventional orthodontic adhesive in self-etch mode. The bond strength can be improved by adding an initial acid etching or laser conditioning step, although enamel damage was observed in some cases.

Enamel Etching for Universal Adhesives: Examination of Enamel Etching Protocols for Optimization of Bonding Effectiveness

OBJECTIVE

The purpose of this study was to evaluate whether different enamel etching methods with reduced etching times would improve the bonding effectiveness of universal adhesives.

METHODS AND MATERIALS

Three enamel etching methods, phosphoric acid ester monomer (PPM) etching, phosphoric acid (PPA) etching, and polyalkenoic acid (PLA) etching, and three universal adhesives, G-Premio Bond (GP), Prime&Bond elect (PE), and Scotchbond Universal Adhesive (SU), were evaluated. Initial bond strengths and fatigue strengths of universal adhesives to ground enamel and ground enamel etched for less than one, five, 10, and 15 seconds using different etching methods were determined. The bonded fatigue specimens were loaded using a sine wave at a frequency of 20 Hz for 50,000 cycles or until failure occurred with a staircase method. Atomic force micrograph (AFM) observations along with measurements of surface Ra roughness and modified surface area of enamel with different etching protocols were also conducted.

RESULTS

The bond fatigue durability of universal adhesives to enamel with PPA etching from less than one to 15 seconds and PLA etching for 15 seconds was significantly higher than that to ground enamel. The bond fatigue durability to enamel with PPM etching was not increased compared with ground enamel. The surface Ra roughness and surface area obtained with AFM of enamel increased after PPA and PLA etching, and those values were significantly higher than those of ground enamel. Furthermore, surface Ra roughness and surface area with PPA etching were significantly higher than those with PLA etching. However, surface Ra roughness and surface area of enamel with PPM etching were similar to those of ground enamel regardless of etching time.

CONCLUSION

PPA etching for less than one to 15 seconds and PLA etching for 15 seconds improve universal adhesive bonding, surface Ra roughness, and surface area of enamel. However, PPM etching is not effective, regardless of etching time, in improving bonds strengths, increasing surface roughness, and increasing surface area.

Effect of a hydrophobic bonding resin on the 36-month performance of a universal adhesive-a randomized clinical trial

OBJECTIVES

To evaluate if the addition of a layer of a hydrophobic bonding resin to the recommended application sequence of a universal adhesive improves the respective clinical behavior in non-carious cervical lesions (NCCLs) after 36 months.

MATERIALS AND METHODS

Scotchbond Universal Adhesive (SBU, 3M Oral Care) was applied in NCCLs of 39 subjects using four adhesion strategies: (1) three-step ER (etch-and-rinse), (2) two-step ER, (3) two-step SE (self-etch), and (4) one-step SE. An extra layer of a hydrophobic bonding resin was applied for strategies three-step ER and two-step SE. The same composite resin (Filtek Supreme XTE, 3M Oral Care) was used for all strategies. Restorations were evaluated at baseline and 18 and 36 months using the modified United States Public Health Service (USPHS) criteria. Kruskal-Wallis, Mann-Whitney U, Friedman, and Wilcoxon non-parametric tests were computed.

RESULTS

The cumulative failure rate was 8.6%. The 36-month retention rates were 100% for both 3-ER and 2-ER, 76.0% for 2-SE, and 86.2% for 1-SE. A lower retention rate was observed for two-step SE at 36 months compared with both three-ER (p < 0.01) and two-ER (p < 0.01). Identical retention rates were measured for the two SE groups. When retention rate was compared at baseline versus 36 months for each adhesion strategy, a significant decrease was observed for 2-SE. The restorations performed with 3-ER, 2-SE, and 1-SE had a significant deterioration in marginal discoloration at the 18-month recall.

CONCLUSIONS

The 36-month clinical performance of Scotchbond Universal Adhesive improved for both etch-and-rinse strategies.

CLINICAL RELEVANCE

Phosphoric acid etching is still recommended to provide retention to composite restorations in NCCLs.

Universal dental adhesives: Current status, laboratory testing, and clinical performance

Increasing demand for simplified and user-friendly adhesive systems has led to the development of a new class of adhesives termed as Universal Adhesives (UAs). The term "Universal" reflects manufacturers' claims that these adhesives can be applied with any adhesion strategy and offer the versatility of use with a variety of direct and indirect restorative materials. The aim of this review was to synthesize the literature regarding the current status of UAs, their adhesion potential to various substrates and their performance in different restorative situations. In vitro studies, clinical trials and systematic reviews were identified utilizing controlled vocabulary and keyword searches in Medline and EMBASE databases. About 282 studies (272 in vitro studies; 11 clinical studies) were included. Available laboratory and clinical evidence does not support the claim that UAs can be used with any adhesive strategy. Although, they can chemically bond to various tooth and direct/indirect restorative substrates, the stability of this bond is material-dependent and subject to hydrolytic degradation. Hence, additional measures are still needed to ensure long-term durability. which undermines the versatility of UAs. The lack of long-term data regarding the clinical performance of UAs further complicates clinical decision-making. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2121-2131, 2019.

Effect of Reduced Universal Adhesive Application Time on Enamel Bond Fatigue and Surface Morphology

Objective:

The purpose of this study was to evaluate the effect of reduced application times of universal adhesives on enamel bond fatigue and surface morphology of the treated enamel with constant force atomic force microscopy (AFM).

Methods:

Four universal adhesives—Adhese Universal (AU), Clearfil Universal Bond Quick (CU), G-Premio Bond (GP), and Scotchbond Universal Adhesive (SU)—were evaluated in a laboratory for their ability to adhesively bond resin composite to enamel. Shear bond strengths were initially determined using 15 specimens per test group for each adhesive. Shear fatigue strengths were then determined using 20 specimens per test group for each the adhesives. The fatigue specimens were loaded using a sine wave at a frequency of 20 Hz for 50,000 cycles or until failure occurred. AFM observations, surface Ra roughness measurements, and geometric surface area evaluations of enamel surface treated with the adhesive agents were also conducted.

Results:

A strong relationship was found between the initial shear bond strength and shear fatigue strength for enamel surface Ra roughness but not for geometric surface area. The initial shear bond strength and shear fatigue strength of CU and GP were not influenced by different application times, unlike those of AU and SU. While the surface area of enamel treated with the adhesive agents was not significantly influenced by different application times and type of adhesive, surface Ra roughness of the enamel in the AU and SU groups significantly increased with increasing application time, unlike CU and GP.

Conclusions:

The results of this study suggest that universal adhesives, used with reduced application times, have adequate Ra surface roughness to provide sufficient resistance to enamel bond fatigue at application times from &lt;1 second to 20 seconds, while the geometric surface area of adhesive-treated enamel did not show any significant changes at these different application times.

Influence of enamel prism orientations on color shifting at the border of resin composite restorations

This study aimed to investigate the influence of enamel prism orientations on color adjustment of resin composite restoration. The color measurements (L*, C*, or h* values) at the restored bovine enamel disk (1.0 mm-thick) with resin composite (Estelite Asteria, Estelite Pro, Kalore, Clearfil Majesty) were performed using a CIE XYZ camera (RC500). The color shifting rate and range at the coronal and cervical border were calculated. The coronal border was significantly lower L* and C* color shifting rate than the cervical border (p<0.05). The L* color shifting range was significantly affected by regions in the 3-mm cavity group (p<0.05), but not in the 1-mm cavity group (p>0.05), while the C* color shifting range was not significantly affected by regions (p>0.05). The coronal enamel border with diagonal-cut of enamel prisms would have an advantage for color adjustment of resin composite restorations compared to the cervical border with longitudinal-cut of enamel prisms.

Effect of Oxygen Inhibition Layer of Universal Adhesives on Enamel Bond Fatigue Durability and Interfacial Characteristics With Different Etching Modes

OBJECTIVE

The purpose of this study was to evaluate the effect of the oxygen inhibition layer of universal adhesive on enamel bond fatigue durability and interfacial characteristics with different etching modes.

METHODS

The three universal adhesives used were Scotchbond Universal Adhesive (3M ESPE, St Paul, MN, USA), Adhese Universal (Ivoclar Vivadent, Schaan, Lichtenstein), and G-Premio Bond (GC, Tokyo, Japan). The initial shear bond strength and shear fatigue strength to enamel was determined in the presence and absence of the oxygen inhibition layer, with and without phosphoric acid pre-etching. The water contact angle was also measured in all groups using the sessile drop method.

RESULTS

The enamel bonding specimens with an oxygen inhibition layer showed significantly higher (p<0.05) initial shear bond strengths and shear fatigue strengths than those without, regardless of the adhesive type and etching mode. Moreover, the water contact angles on the specimens with an oxygen inhibition layer were significantly lower (p<0.05) than on those without, regardless of etching mode.

CONCLUSION

The results of this study suggest that the oxygen inhibition layer of universal adhesives significantly increases the enamel bond fatigue durability and greatly changes interfacial characteristics, suggesting that the bond fatigue durability and interfacial characteristics of these adhesives strongly rely on its presence.