Comparisons of ISO depth of cure for a resin composite in stainless-steel and natural-tooth molds.

The purpose of this study was to compare the depth of cure (DOC) of a resin-based composite (RBC) using the ISO DOC protocol with stainless-steel and molar-tooth molds (4 mm cylindrical cavity). The tooth mold included testing with and without the occlusal surface being covered with black tape around the cavity opening. The RBC was cured with either halogen (HAL) or light-emitting diode (LED) light. The results showed that specimens made in the non-taped tooth mold had DOCs that were significantly greater (28%-35%) than those in the stainless-steel mold. The taped tooth mold also produced significantly greater DOCs, but only by 6%-8%. Knoop hardness (KNH) measurements along the central axis of the RBC specimens showed that depths for 80% of maximum hardness were substantially greater than those determined by the ISO DOC protocol but were limited to the center and quickly dropped below 80% in a lateral direction. The KHN mapping for each of the three molds found that the ISO DOCs could validate a KHN of ≥80% across the RBC to the periphery, only for the non-taped tooth mold. This was due to light incident on the tooth surrounding the RBC being scattered into the RBC.

Shear fatigue strength of resin composite bonded to dentin at physiological frequency.

The purpose of this study was to examine the shear fatigue strengths of a resin composite bonded to dentin. Three adhesive systems - a two-step self-etch adhesive (OptiBond XTR; Kerr) and two universal adhesives [Scotchbond Universal (3M ESPE) and G-Premio Bond (GC)] - were used in self-etch mode to bond a resin composite to dentin at a physiologic frequency of 2 Hz over 50,000, 100,000, and 1,000,000 cycles. A staircase method of fatigue testing was used. Twenty specimens were used for each test condition. There was no significant difference in shear fatigue strength across the cycling periods for the three individual adhesives. Differences in shear fatigue strength were found among the three adhesives within each cycling period. Regardless of the adhesive used in self-etch mode for bonding a resin composite to dentin, shear fatigue strength was not influenced by the number of cycles used for testing.

Effect of mold diameter on the depth of cure of a resin-based composite material.

The purpose of this study was to examine the effect of mold diameter on depth of cure of a resin-based composite material for varying amounts of irradiation. A resin-based composite was light-cured for 10-80 s in stainless-steel molds of either 6 mm or 4 mm in diameter and then dark-stored for 24 h. Specimens were then scraped back and the length of the cured specimens was measured to provide depth of cure (DSB ). Radiant exposure to each of the mold diameters was determined by measuring the power. The DSB values using the 4-mm molds were lower than those of the 6-mm molds. The average difference between the two groups for each irradiation time was 0.45 ± 0.02 mm. A fixed depth of cure required about 39% more irradiation time for the 4-mm mold than for the 6-mm mold but 75% more radiant exposure. The difference in cure depth for a fixed radiant exposure was 0.79 mm. A better comparison of depth of cure is obtained by using identical radiant exposures for different mold diameters. It is believed that greater loss of light by absorption at the stainless-steel cylinder walls for the 4-mm-diameter cylinders accounts for the lower depth of cure when compared with the 6-mm molds.

Effect of a functional monomer (MDP) on the enamel bond durability of single-step self-etch adhesives.

The present study aimed to determine the effect of the functional monomer, 10-methacryloxydecyl dihydrogen phosphate (MDP), on the enamel bond durability of single-step self-etch adhesives through integrating fatigue testing and long-term water storage. An MDP-containing self-etch adhesive, Clearfil Bond SE ONE (SE), and an experimental adhesive, MDP-free (MF), which comprised the same ingredients as SE apart from MDP, were used. Shear bond strength (SBS) and shear fatigue strength (SFS) were measured with or without phosphoric acid pre-etching. The specimens were stored in distilled water for 24 h, 6 months, or 1 yr. Although similar SBS and SFS values were obtained for SE with pre-etching and for MF after 24 h of storage in distilled water, SE with pre-etching showed higher SBS and SFS values than MF after storage in water for 6 months or 1 yr. Regardless of the pre-etching procedure, SE showed higher SBS and SFS values after 6 months of storage in distilled water than after 24 h or 1 yr. To conclude, MDP might play an important role in enhancing not only bond strength but also bond durability with respect to repeated subcritical loading after long-term water storage.

Influence of different pre-etching times on fatigue strength of self-etch adhesives to dentin.

The purpose of this study was to use shear bond strength (SBS) and shear fatigue strength (SFS) testing to determine the influence on dentin bonding of phosphoric acid pre-etching times before the application of self-etch adhesives. Two single-step self-etch universal adhesives [Prime & Bond Elect (EL) and Scotchbond Universal (SU)], a conventional single-step self-etch adhesive [G-aenial Bond (GB)], and a two-step self-etch adhesive [OptiBond XTR (OX)] were used. The SBS and SFS values were obtained with phosphoric acid pre-etching times of 3, 10, or 15 s before application of the adhesives, and for a control without pre-etching. For groups with 3 s of pre-etching, SU and EL showed higher SBS values than control groups. No significant difference was observed for GB among the 3 s, 10 s, and control groups, but the 15 s pre-etching group showed significantly lower SBS and SFS values than the control group. No significant difference was found for OX among the pre-etching groups. Reducing phosphoric acid pre-etching time can minimize the adverse effect on dentin bonding durability for the conventional self-etch adhesives. Furthermore, a short phosphoric acid pre-etching time enhances the dentin bonding performance of universal adhesives.

Influence of Pre-etching Times on Fatigue Strength of Self-etch Adhesives to Enamel.

PURPOSE: To use shear bond strength (SBS) and shear fatigue strength (SFS) testing to determine the influence of phosphoric acid pre-etching times prior to application of self-etch adhesives on enamel bonding. MATERIALS AND METHODS: Two single-step self-etch universal adhesives (Prime&Bond Elect and Scotchbond Universal), a conventional single-step self-etch adhesive (G-ӕnial Bond), and a conventional two-step self-etch adhesive (OptiBond XTR) were used. The SBS and SFS were obtained with phosphoric acid pre-etching for 3, 10, or 15 s prior to application of the adhesives, and without pre-etching (0 s) as a control. A staircase method was used to determine the SFS with 10 Hz frequency for 50,000 cycles or until failure occurred. The mean demineralization depth for each treated enamel surface was also measured using a profilometer. RESULTS: For all the adhesives, the groups with pre-etching showed significantly higher SBS and SFS than groups without pre-etching. However, there was no significant difference in SBS and SFS among groups with > 3 s of preetching. In addition, although the groups with pre-etching showed significantly deeper demineralization depths than groups without pre-etching, there was no significant difference in depth among groups with > 3 s of pre-etching. CONCLUSION: Three seconds of phosphoric acid pre-etching prior to application of self-etch adhesive can enhance enamel bonding effectiveness.

Depth and distribution of the cure in a resin-based composite cured in a simulated Class II cavity.

PURPOSE: To examine the effect that a stainless steel (SS) matrix band has on the depth and distribution of cure of a resin-based composite (RBC) in a simulated Class II cavity. METHODS: RBC was cured for 20 seconds in a simulated Class II cavity with and without a SS matrix band, and after 24 hours the specimens were scraped back and ground to expose a vertical central plane where Knoop micro-hardness (KHN) mapping was conducted from 0.05-1.5 mm from the band and in 0.5 mm intervals from the top of the specimens. The effect of different angles of the light guide on the distribution of hardness was also examined. RESULTS: KHN values near the SS matrix band were significantly lower (P < 0.05) than within the bulk of the specimen and were lower than those found without the matrix band. Angles of incidence for the curing light-guide produced changes in the distribution of KHN within the specimens, but particularly near the matrix band, and with a 35° angle of incidence, the depth of cure was significantly different from that of normal incidence of the light.

Adhesive bond strengths to enamel and dentin using recommended and extended treatment times.

This study examined the effect of different enamel and dentin conditioning times on the shear bond strength of a resin composite using etch-and-rinse and self-etch adhesive systems. Shear bond strengths were determined following treatment of flat ground human enamel and dentin surfaces (4000 grit) with 11 adhesive systems: 1) AdheSE One Viva Pen-(ASE), 2) Adper Prompt L-Pop-(PLP), 3) Adper Single Bond Plus-(SBP), 4) Clearfil SE Bond-(CSE), 5) Clearfil S3 Bond-(CS3), 6) OptiBond All-In-One-(OBA), 7) OptiBond Solo Plus-(OBS), 8) Peak SE-(PSE), 9) Xeno IV-(X4), 10) Xeno V-(X5) and 11) XP Bond-(XPB) using recommended treatment times and an extended treatment time of 60 seconds (n = 10/group). Composite (Z100) to enamel and dentin bond strengths (24 hours) were determined using Ultradent fixtures and debonded with a crosshead speed of 1 mm/minute. The data were analyzed with a three-way Analysis of Variance (ANOVA) and Fisher's LSD post hoc test. The highest shear bond strengths (MPa) to enamel were achieved by the three etch-and-rinse systems at both the recommended treatment time (SBP-40.5 +/- 6.1; XPB-38.7 +/- 3.7; OBS- 35.2 +/- 6.2) and the extended treatment time (SBP-44.5 +/- 8.1; XPB-40.9 +/- 5.7; OBS-35.0 +/- 4.5). Extending the enamel treatment time did not produce a significant change (p > 0.05) in bond strength for the 11 adhesive systems tested. OBS generated the highest (46.2 +/- 7.9) bond strengths to dentin at the recommended treatment time. At the extended treatment time X4 (42.2 +/- 11.7), PSE (42.1 +/- 9.7) and OBS (41.4 +/- 8.0) produced the highest bond strengths to dentin. The bond strength change between recommend and extended treatment times was significant (p < 0.05) for PSE, but the other 10 systems did not exhibit any significant change.

Effect of enamel etching time on roughness and bond strength.

The current study examined the effect of different enamel conditioning times on surface roughness and bond strength using an etch-and-rinse system and four self-etch adhesives. Surface roughness (Ra) and composite to enamel shear bond strengths (SBS) were determined following the treatment of flat ground human enamel (4000 grit) with five adhesive systems: (1) Adper Single Bond Plus (SBP), (2) Adper Prompt L-Pop (PLP), (3) Clearfil SE Bond (CSE), (4) Clearfil S3 Bond (CS3) and (5) Xeno IV (X4), using recommended treatment times and an extended treatment time of 60 seconds (n = 10/group). Control groups were also included for Ra (4000 grit surface) and SBS (no enamel treatment and Adper Scotchbond Multi-Purpose Adhesive). For surface roughness measurements, the phosphoric acid conditioner of the SBP etch-and-rinse system was rinsed from the surface with an air-water spray, and the other four self-etch adhesive agents were removed with alternating rinses of water and acetone. A Proscan 2000 non-contact profilometer was used to determine Ra values. Composite (Z100) to enamel bond strengths (24 hours) were determined using Ultradent fixtures and they were debonded with a crosshead speed of 1 mm/minute. The data were analyzed with ANOVA and Fisher's LSD post-hoc test. The etch-and- rinse system (SBP) produced the highest Ra (microm) and SBS (MPa) using both the recommended treatment time (0.352 +/- 0.028 microm and 40.5 +/- 6.1 MPa) and the extended treatment time (0.733 +/- 0.122 microm and 44.2 +/- 8.2 MPa). The Ra and SBS of the etch-and-rinse system were significantly greater (p < 0.05) than all the self-etch systems and controls. Increasing the treatment time with phosphoric acid (SBP) and PLP produced greater surface roughness (p < 0.05) but did not result in significantly higher bond strengths (p > 0.05).

SEM observation of novel characteristic of the dentin bond interfaces of universal adhesives.

OBJECTIVE: The aim of this study was to observe the resin/dentin interfaces of universal adhesives by using scanning electron microscopy (SEM), and to compare their morphologies with conventional etch & rinse (ER) and self-etch (SE) adhesive systems. METHODS: Two three-step and one two-step ER adhesives and two two-step and two single-step SE adhesives were used for comparison with seven universal adhesives in ER mode and SE mode, respectively. Bonded surfaces with bovine teeth were longitudinally sectioned and mirror-polished. Half of the samples were treated with HCl and NaOCl solutions. The interfaces were subjected to argon ion beam etching and then observed by scanning electron microscopy. RESULTS: The thickness of the adhesive layer (AL) of most of the seven universal adhesives and single-step SE adhesives was similar. Universal adhesives in SE mode formed a hybrid smear layer as a high-density zone between the AL and dentin. The thickness of the hybrid layer (HL) of the universal adhesives in ER mode was ∼1-2µm, with a high-density zone (reaction layer [RL]) below the HL. CONCLUSION: The morphological features of most universal adhesives in SE mode and single-step SE adhesives are similar. Although resin-dentin interfaces of universal adhesives in ER mode resemble those of ER adhesives, universal adhesives have a distinctive feature, an RL. SIGNIFICANCE: The RL might be a sign of chemical bonding even when using universal adhesives in ER mode.

Effect of pre-etching enamel on fatigue of self-etch adhesive bonds.

OBJECTIVE: A previous study found that the shear bond strength (SBS) to bovine enamel for the self-etching adhesive Adper Prompt-L-Pop (PLP) was 75% of that found with the etch-and-rinse material SingleBond, while the comparative value for the shear fatigue limit (SFL) was only 58% at 10(5) load cycles. Resin penetration into the enamel surface was substantially less for PLP but it was not conclusive that this was the reason for the lower results cited above. The objective of this study was to determine if pre-etching enamel would substantially improve the SBS and SFL of the PLP adhesive over those found in the previous study. MATERIALS AND METHODS: All test methods were the same as for the previous study. SBS measurements were conducted for composite bonds to bovine enamel using a phosphoric acid pre-etch with the PLP adhesive (PLP-10) and for a conventional enamel-bonding adhesive (EB). Fatigue testing was done with the same test fixtures, load cycling at 2Hz up to a maximum of 10(5) cycles at four selected peak load values between 35 and 60% of the respective bond strengths. Fatigue limits were determined from the data obtained. SEM analysis of resin penetration of the enamel surface was carried out for each adhesive. RESULTS: A significantly greater SBS and SFL were found for EB (SBS: 30.4MPa; SFL: 15.6MPa) than for PLP-10 (SBS: 20.2MPa; SFL: 9.9MPa). Compared with previously found results, the pre-etching of enamel had no significant improvement in SBS and only slight improvement in SFL. Resin tag penetration of the enamel surface for PLP-10 was similar to that previously found for PLP alone, suggesting that the porosity created by phosphoric acid was effectively removed by the acidic PLP adhesive. SIGNIFICANCE: Unlike some self-etching adhesives reported in the literature, pre-etching enamel did not improve the performance of the Prompt-L-Pop adhesive.

Wear simulation of resin composites and the relationship to clinical wear.

This study used a new generalized wear model to examine the relationship between wear simulation and the clinical wear of two resin composites. Ten specimens each of P50 and Z100, were subjected to 100,000, 400,000 and 800,000 cycles in a spring-loaded piston-type wear simulator. Wear was generated using flat, cylindrically-shaped stainless steel antagonists on the resin composites, which were placed in custom stainless steel fixtures. A slurry of polymethyl methacrylate beads was used as the abrasive media. Wear was determined using profilometry, and the parameters examined included volume loss (mm3), maximum depth (microm), mean maximum depth (microm) and mean depth (microm). Statistical analysis of the laboratory wear data using ANOVA and Tukey's post hoc test showed a significant difference (p<0.05) for wear between the two materials and the number of cycles. Mean maximum wear (microm) values (100K--P50--11.5 +/- 1.8; Z100--4.9 +/- 1.0; 400K--P50--17.2 +/- 2.7; Z100--6.0 +/- 1.7; 800K--P50--20.5 +/- 4.6; Z100--9.6 +/- 2.5) were used for comparisons with clinical data. Previous clinical studies of P50 and Z100 were used to examine the relationship between laboratory and clinical wear. Linear regression analysis was used to predict laboratory and clinical wear rates. The laboratory wear rate for P50 was 1.3 microm/100K cycles and the rate for Z100 was 0.7 microm/100K cycles. The clinical wear rates for P50 and Z100 were 8.3 microm/year and 4.0 microm/year, respectively. The ratio of wear rates of P50 to Z100 for wear simulation was 1.9 and the ratio of P50 to Z100 for clinical rates was 2.1. These ratios showed good agreement between the relative wear rates of laboratory and clinical wear. For the two composite materials examined, this new simulation model appears to be effective for evaluating the relative wear of resin composites.

Influence of the number of cycles on shear fatigue strength of resin composite bonded to enamel and dentin using dental adhesives in self-etching mode.

The influence of the number of cycles on shear fatigue strength to enamel and dentin using dental adhesives in self-etch mode was investigated. A two-step self-etch adhesive and two universal adhesives were used to bond to enamel and dentin in self-etch mode. Initial shear bond strength and shear fatigue strength to enamel and dentin using the adhesive in self-etch mode were determined. Fatigue testing was used with 20 Hz frequency and cycling periods of 50,000, 100,000 and 1,000,000 cycles, or until failure occurred. For each of the cycling periods, there was no significant difference in shear fatigue strength across the cycling periods for the individual adhesives. Differences in shear fatigue strength were found between the adhesives within the cycling periods. Regardless of the adhesive used in self-etch mode for bonding to enamel or dentin, shear fatigue strength was not influenced by the number of cycles used for shear fatigue strength testing.

Influence of different smear layers on bond durability of self-etch adhesives.

OBJECTIVE: The purpose of this study was to determine the influence of different smear layers on enamel and dentin bond durability of various types of self-etch adhesives. METHODS: Two universal adhesives, Scotchbond Universal (SU) and Prime & Bond elect (PE); a conventional single-step self-etch adhesive, G-ænial Bond (GB); and two two-step self-etch adhesives, Optibond XTR (OX) and Clearfil SE Bond (SE) were used in this study. Shear bond strengths (SBS) and shear fatigue strengths (SFS) to human enamel and dentin were determined with different smear layer conditions. The prepared specimens were divided into three groups. The bonding surfaces were prepared by grinding with either (1) #180, (2) #600, or (3) #4000-SiC papers before making the bonded assemblies. For each group, 15 specimens were prepared for the SBS and 30 specimens for the SFS. RESULTS: The two-step self-etch adhesives showed significantly higher SFS values than the single-step self-etch adhesives, regardless of the smear layer condition or substrate. Although most of the tested adhesives showed no significant differences in enamel SFS values among the smear layer groups, SU, GB, and SE showed significantly lower SFS values in the #180 in dentin groups than the #600 and #4000 groups. CONCLUSION: The influence of different smear layer conditions on bond durability was adhesive dependent. Furthermore, the smear layers generated on different substrates also influenced the bond quality of the self-etch adhesives. SIGNIFICANCE: Smear layer conditions of enamel and dentin influence the bond durability of universal adhesives and conventional single and two-step self-etch adhesives.

Effect of double-layer application on bond quality of adhesive systems.

OBJECTIVES: The aim of this study was to determine the effect of double-layer application of universal adhesives on the bond quality and compare to other adhesive systems. METHODS: Two universal adhesives used were in this study: Scotchbond Universal (SU), [3M ESPE] and Prime & Bond elect (PE), [Dentsply Caulk]. The conventional single-step self-etch adhesives G-ӕnial Bond (GB), [GC Corporation.] and BeautiBond (BB), [Shofu Inc.], and a two-step self-etch adhesive, Optibond XTR (OX), [Kerr Corporation], were used as comparison adhesives. Shear bond strengths (SBS) and shear fatigue strengths (SFS) to human enamel and dentin were measured in single application mode and double application mode. For each test condition, 15 specimens were prepared for SBS testing and 30 specimens for SFS testing. RESULTS: Enamel and dentin SBS of the universal adhesives in the double application mode were significantly higher than those of the single application mode. In addition, the universal adhesives in the double application mode had significantly higher dentin SFS values than those of the single application mode. The two-step self-etch adhesive OX tended to have lower bond strengths in the double application mode, regardless of the test method or adherent substrate. CONCLUSION: The double application mode is effective in enhancing SBS and SFS of universal adhesives, but not conventional two-step self-etch adhesives. SIGNIFICANCE: These results suggest that, although the double application mode may enhance the bonding quality of a universal adhesive, it may be counter-productive for two-step self-etch adhesives in clinical use.

Fatigue testing of enamel bonds with self-etch and total-etch adhesive systems.

OBJECTIVE: Etching of enamel by self-etching adhesive systems is not as pronounced as with phosphoric acid employed with most total-etch adhesive systems. This may result in differences in the effectiveness of the bonds for the two types of systems. The aim of this study was to compare two such systems by bond strength and fatigue testing. MATERIALS AND METHODS: Shear bond strengths for Single Bond (SB) and Adper Prompt-L-Pop (PLP) were obtained on bovine enamel surfaces. Fatigue measurements were made with the same test fixtures using cyclical loading at 2 Hz for a maximum of 10(5) cycles or until the bond failed. Four selected loads between 40 and 70% of the shear bond strength were tested for each adhesive and the number of cycles to failure was recorded. S-N curves were constructed from the data and fatigue stress limits were determined. The Mann-Whitney U-test and t-tests were used for statistical comparisons of the results. SEM analysis of resin tag formation into enamel surfaces was carried out. RESULTS: A significantly greater bond strength was found for SB (25.3 MPa) than for PLP (19.2). Sustainable stresses after 10(5) load cycles were substantially lower than the corresponding shear bond strengths and fatigue limits were found to be 8.4 MPa for PLP and 14.6 MPa for SB. The ratio of fatigue limit to bond strength was less for PLP (44%) than for SB (57%). Resin tag penetration into enamel was substantially less for PLP than for SB. SIGNIFICANCE: Fatigue testing in conjunction with bond strength testing can provide a better means for assessing the performance of adhesive systems used for bonding to enamel.

Effect of frequency on the fatigue strength of dentin bonds.

This study aimed to investigate the effect of frequency on shear fatigue strength (SFS). The SFS of a resin composite bonded to dentin was determined using three self-etch adhesive systems: G-ænial Bond, Scotchbond Universal, and Optibond XTR. The staircase method of fatigue testing was used to determine the SFS at frequencies of 5, 10, and 20 Hz for 50,000 cycles. The failed bonding sites observed were classified based on the type of bond failure as follows: adhesive failure, cohesive failure in composite, cohesive failure in dentin, or mixed failure (partially adhesive, partially cohesive). A modified t-test with Bonferroni correction was used to analyze the SFS data, and a complex chi-square test was used to analyze the fracture modes. The SFS of OX was significantly greater than that of GB at both 5 and 10 Hz. However, no significant differences in SFS were found among the three frequencies (5, 10, and 20 Hz) in the three self-etch adhesive systems. Furthermore, no significant differences in bond failure mode were observed among the three frequency rates in all the three adhesives used.(J Oral Sci 58, 539-546, 2016).

Influence of frequency on shear fatigue strength of resin composite to enamel bonds using self-etch adhesives.

OBJECTIVES: The purpose of this study was to determine the influence of different frequency rates on of bond durability of self-etch adhesives to enamel using shear fatigue strength (SFS) testing. METHODS: A two-step self-etch adhesive (OX, OptiBond XTR), and two single step self-etch adhesives (GB, G-ӕnial Bond and SU, Scotchbond Universal) were used in this study. The shear fatigue strength (SFS) to enamel was obtained. A staircase method was used to determine the SFS values with 50,000 cycles or until failure occurred. Fatigue testing was performed at frequencies of 5Hz, 10Hz, and 20Hz. For each test condition, 30 specimens were prepared for the SFS testing. RESULTS: Regardless of the bond strength test method, OX showed significantly higher SFS values than the two single-step self-etch adhesives. For each of the three individual self-etch adhesives, there was no significant difference in SFS depending on the frequency rate, although 20Hz results tended to be higher. CONCLUSIONS: Regardless of the self-etch adhesive system, frequencies of 5Hz, 10Hz, and 20Hz produced similar results in fatigue strength of resin composite bonded to enamel using 50,000 cycles or until bond failure. SIGNIFICANCE: Accelerated fatigue testing provides valuable information regarding the long term durability of resin composite to enamel bonding using self-etch adhesive system.

Influence of different etching modes on bond strength and fatigue strength to dentin using universal adhesive systems.

OBJECTIVES: The purpose of this study was to determine the dentin bonding ability of three new universal adhesive systems under different etching modes using fatigue testing. METHOD: Prime & Bond elect [PE] (DENTSPLY Caulk), Scotchbond Universal [SU] (3M ESPE), and All Bond Universal [AU] (Bisco) were used in this study. A conventional single-step self-etch adhesive, Clearfil Bond SE ONE [CS] (Kuraray Noritake Dental) was also included as a control. Shear bond strengths (SBS) and shear fatigue strength (SFS) to human dentin were obtained in the total-etch mode and self-etch modes. For each test condition, 15 specimens were prepared for the SBS and 30 specimens for SFS. SEM was used to examine representative de-bonded specimens, treated dentin surfaces and the resin/dentin interface for each test condition. RESULTS: Among the universal adhesives, PE in total-etch mode showed significantly higher SBS and SFS values than in self-etch mode. SU and AU did not show any significant difference in SBS and SFS between the total-etch mode and self-etch mode. However, the single-step self-etch adhesive CS showed significantly lower SBS and SFS values in the etch-and-rinse mode when compared to the self-etch mode. Examining the ratio of SFS/SBS, for PE and AU, the etch-and-rinse mode groups showed higher ratios than the self-etch mode groups. SIGNIFICANCE: The influence of different etching modes on dentin bond quality of universal adhesives was dependent on the adhesive material. However, for the universal adhesives, using the total-etch mode did not have a negative impact on dentin bond quality.

Influence of water storage on fatigue strength of self-etch adhesives.

OBJECTIVES: The purpose of this study was to determine enamel and dentin bond durability after long-term water storage using self-etch adhesives. METHODS: Two single step self-etch adhesives (SU, Scotchbond Universal and GB, G-ӕnial Bond) and a two-step self-etch adhesive (OX, OptiBond XTR) were used. The shear bond strength (SBS) and shear fatigue strength (FS) of the enamel and dentin were obtained with and without phosphoric acid pre-etching prior to application of the adhesives. The specimens were stored in distilled water at 37 °C for 24 h, 6 months, and one year. A staircase method was used to determine the FS using a frequency of 10 Hz for 50,000 cycles or until failure occurred. RESULTS: The SBS and FS of enamel bonds were significantly higher with pre-etching, when compared to no pre-etching for the same water storage period. The FS of dentin bonds with pre-etching tended to decrease relative to no pre-etching at the same storage period. For the one year storage period, SU and GB with pre-etching showed significantly lower FS values than the groups without pre-etching. CONCLUSIONS: The influence of water storage on FS of the self-etch adhesives was dependent on the adhesive material, storage period and phosphoric acid pre-etching of the bonding site. CLINICAL SIGNIFICANCE: Phosphoric acid pre-etching of enamel improves the effectiveness of self-etch adhesive systems. Inadvertent contact of phosphoric acid on dentin appears to reduce the ability of self-etch adhesives to effectively bond resin composite materials.