Effect of composite resin contamination with powdered and unpowdered latex gloves on its shear bond strength to bovine dentin

SUMMARY The aim of the present study was to evaluate the effect of composite resin contamination with powdered and unpowdered latex gloves on the shear bond strength of etch-and-rinse and two-step self-etch adhesive systems. Standard flat dentin surfaces were prepared on the facial aspect of 120 bovine incisors and randomly assigned into two (n=60) groups: group 1: Single Bond (SB), group 2: Clearfil SE Bond (CSE). Furthermore, each group was randomly subdivided into three (n=20) based on the type of composite contamination (without contamination, contamination with powdered latex gloves, and contamination with unpowdered latex gloves). The adhesives were applied and resin composite bonded to the dentin. After thermocycling, the specimens were subjected to a shear bond strength test. Two-way analysis of variance (ANOVA) and a post hoc Bonferroni test were used for statistical analysis. One-way ANOVA was used to compare shear bond strength values in each group. Statistical significance was set at p < 0.02. Two-way ANOVA showed that the shear bond strength was significantly influenced by the type of composite surface contamination (p=0.001). In the SB group there were no significant differences between different surface treatments (p=0.08). In the CSE group a significant difference was observed between the subgroup without contamination and the subgroup with powdered latex glove contamination (p=0.01); however, no significant differences were observed between the other subgroups.     

One-day bonding effectiveness of new self-etch adhesives to bur-cut enamel and dentin

Self-etch adhesives try to solve difficulties commonly associated with the clinical application of etch-and-rinse adhesives. Their application procedure is considered less time-consuming and, more importantly, less technique-sensitive. The main objective of this study was to determine the bonding effectiveness to and the interaction with enamel/dentin of three contemporary one- and two-step self-etch adhesives by microtensile bond strength testing (microTBS), Fe-SEM and TEM when compared to a control two-step self-etch and a three-step etch-and-rinse adhesive. The one-step self-etch adhesive, Adper Prompt (3M ESPE), scored the lowest microTBS of all experimental and control adhesives tested. Conversely, the two-step self-etch adhesives Clearfil SE (Kuraray) and OptiBond Solo Plus Self-Etch (Kerr) approached the values obtained by the three-step etch-and-rinse control (OptiBond FL, Kerr) when bonded to enamel and dentin. Ultramorphological characterization showed that interfacial morphology and the pH of the self-etch primer/adhesive are strongly associated. The interaction with dentin varied from the formation of a submicron, hydroxyapatite-containing hybrid layer for the "mild" self-etch adhesive Clearfil SE to a 3-5 microm thick, hydroxyapatite-depleted hybrid layer for the "strong" self-etch adhesive Adper Prompt. The two-step self-etch adhesives AdheSE and OptiBond Solo Plus Self-Etch presented with a hybrid layer with a hydroxyapatite-depleted top part and a hydroxyapatite-containing base part and were therefore classified into a new group of self-etch adhesives, namely "intermediary strong" self-etch adhesives.     

Resin tags do not contribute to dentin adhesion in self-etching adhesives

PURPOSE: Self-etching adhesives partly remove or dissolve the dentin smear layer, causing incomplete resin tag formation or low resin tag density. The quantitative contribution of properly formed resin tags to dentin adhesion was evaluated. MATERIALS AND METHODS: We assessed how the presence or absence of resin tags affects tubules of human deep-coronal dentin. G-Bond was used to bond Gradia resin composite. To ensure deep tubule penetration, we used a vacuum exsiccator. For eliminating tag formation, dentin tubules were presealed with adhesive and reverse bonded after finishing. Microtensile bond strength (muTBS) was measured on flat specimens and on Class I cavity floors. Thermocyclic loading was used to estimate the influence of resin tags on long-term behavior. Confocal laser scanning microscopy was used to evaluate adhesive interface dimensions. RESULTS: Hybrid layer thickness, tag length, and tag diameter increased under vacuum treatment. Presealing dentin tubules led to a residual tag area of 3.1% with a tag length of 10.8 microm. Under vacuum, 24.7% of the total dentin surface was covered with tags of 87.8 microm. Low C-factor preparations produced superior muTBS (71.8 to 92.7 MPa) compared with high C-factor Class I cavities (47.0 to 67.6 MPa). Thermocyclic fatigue differed from low to high C-factor situations. In Class I cavities, muTBS significantly decreased after thermocycling. On flat specimens, vacuum infiltration led to reduced muTBS after thermocyclic loading. CONCLUSION: Initially, resin tag formation did not influence the muTBS in either type of C-factor preparation. After thermocyclic loading, muTBS decreased with or without resin tags. Adhesive fracture patterns occurred at the hybrid layer/dentin interface.     

脱矿牙本质与四种粘接剂的粘接强度测试及粘接界面观察

目的比较脱矿牙本质与4种全酸蚀或自酸蚀粘接剂的粘接强度及粘接界面超微结构的差异,以期对临床治疗有所指导。方法选择20颗面龋坏的离体磨牙,在龋显示剂的指示下去除牙本质龋的感染层,保留脱矿牙本质。平齐龋洞洞底平面,去除冠向牙体组织,作为粘接面。选择临床常用的2种全酸蚀粘接剂:材料A(All Bond2)、材料B(Prime&BondNT)和2种自酸蚀粘接剂:材料C(ClearfilSEBond)、材料D(XenoⅢ),分别按说明书要求粘接。用慢速锯将样本牙切为粘接面积约0.9mm×0.9mm的长方体试件。体视显微镜下将试件分为正常牙本质组和脱矿牙本质组,用微拉伸测试仪检测粘接强度。扫描电镜观察各组试件粘接界面的超微形态。结果方差分析提示牙本质类型和粘接剂对微拉伸粘接强度的影响均有统计学意义(P<0.05)。对正常牙本质,不同粘接剂的微拉伸粘接强度差异无统计学意义(P>0.05);对于脱矿牙本质,材料D的微拉伸粘接强度较其他粘接剂明显降低(P<0.05)。扫描电镜下观察脱矿牙本质的混合层多孔稀疏,树脂突短少,无侧枝形成。结论对脱矿牙本质,本项实验中全酸蚀粘接剂的粘接强度优于自酸蚀粘接剂。     

Microtensile bond strength of one- and two-step self-etching adhesives on sclerotic dentin: the effects of thermocycling

This study evaluated the effects of thermocycling on the microtensile bond strength (microTBS) of one- and two-step self-etch adhesives (SEAs) to sclerotic dentin. Two adhesives, Clearfil S3 Bond (S3), a one-step self-etch adhesive (1-SEA), and Clearfil SE Bond (SE), a two-step self-etch adhesive (2-SEA), were applied on cervical lesions in human premolars with sclerotic or normal dentin. After adhesive application, the lesions were restored and built up using a resin composite (Clearfil AP-X). After 24 hours in water storage, the restored teeth were sectioned into 0.7 x 0.7 mm composite-dentin beams. The beams were then aged with 0, 5,000 or 10,000 thermocycles. The use of two adhesives, two substrate types and three thermocycling regimens yielded 12 experimental groups of 14-19 beams each. The beams were subsequently subjected to microTBS testing at a crosshead speed of 1 mm/minute and statistical analyses were computed with three-way ANOVA and Tukey's post hoc test at p < 0.05. Three-way ANOVA showed statistically significant effects on bonding effectiveness by lesion type, adhesive system, thermocycling or combinations of the adhesive system and thermocycling (p < 0.05). With sclerotic dentin, although S3 and SE provided comparable microTBS after 24 hours of water storage, S3 showed significantly lower microTBS than SE after thermocycling (p < 0.05). Regardless of lesion type, the microTBS for S3 decreased significantly after 5,000 or 10,000 thermocycles, while the microTBS for SE showed a significant decrease only after 10,000 thermocycles. Regardless of the extent of thermocycling, the microTBS values for either SE or S3 bonded to sclerotic dentin were significantly lower than to normal dentin (p < 0.05). The results suggested that thermocycling had a significant negative effect on the bond strength of the two SEAs tested. In contrast to 2-SEA, 1-SEA might not be a good choice for sclerotic dentin when seeking durability of the resin-dentin bond.     

Comparison of different etch-and-rinse adhesive systems based on shear fatigue dentin bond strength and morphological features the interface

ObjectivesThe aim of this study was to investigate dentin bonding durability of different etch-and-rinse (ER) adhesive systems under fatigue stress and to compare morphological features of resin/dentin interfaces using SEM.MethodsTwo three-step ER adhesives, a two-step ER adhesive, and a universal adhesive in ER mode were evaluated. Before application of either primer or adhesive, phosphoric acid etching of human dentin was completed. Fifteen bonded specimens for each adhesive system were stored in distilled water at 37 °C for 24 h, then subjected to a shear bond strength (SBS) test. Bonding durability was assessed from the perspective of biomechanical stress. 25 bonded specimens for each adhesive system were subjected to shear fatigue strength (SFS) testing with a repeated subcritical load at a frequency of 20 Hz for 50,000 cycles or until failure.ResultsMean SBS and SFS values ranged from 33.3 to 41.2 MPa, and from 18.3 to 20.3 MPa, respectively. Three-step adhesives showed higher SBS and SFS values than the other adhesive systems. Under SEM, resin tags in different adhesive systems showed similar features, but morphology below the hybrid layer was material dependent. The universal adhesive in ER mode showed an obvious thin, high-density reaction layer below the hybrid layer.SignificanceThree-step adhesives showed higher dentin bond durability than the other ER adhesives; no significant differences in SFS were found between the universal adhesive in ER mode and the three-step ER adhesives. The results of this in vitro study indicate that some ER adhesives might establish chemical bonding with intact dentin below the hybrid layer in addition to micromechanical retention.     

The effect of thermocycling on the adhesion of self-etching adhesives on dental enamel and dentin

AIM: The aim of the present study was to investigate the effectiveness of one total-etch self-priming adhesive and two one-step self-etching adhesive systems on the adhesion of a resin composite to both dentin and enamel. The effect of thermocycling on the adhesion was also investigated. The null hypothesis tested was thermocycling would not affect bond strengths to enamel and dentin treated with self-etching adhesives or a total-etch adhesive. METHODS AND MATERIALS: Two single-step self-etching adhesives [Xeno III (XE3) and Prompt L-Pop (PP)] and one two-step total-etch adhesive system (Prime & Bond NT) (P&B NT) were used in this study. Thirty caries-free unrestored human third molars were used to make specimens of enamel and dentin. Different adhesives were applied on enamel and dentin surfaces according to the manufacturer's instructions then hybrid composite restorative material was condensed on the surface using a mold. The bonded specimens were stored in distilled water at 37 masculineC for 24 hours before being tested. Half of the bonded specimens were tested for shear bond strength without thermocycling. The other half of the test specimens were thermocycled using a thermocycling apparatus in water baths held at 5 masculineC and 55 masculineC with a dwell time of one minute each for 10,000 cycles prior to shear testing. The mean shear bond strength before and after thermocycling was calculated, and the results were subjected to two-way analysis of variance (ANOVA) and repeated measure design to show the interaction between different materials and different times. RESULTS: The results showed shear bond strength on both enamel and dentin of the total-etch adhesive and the self-etching adhesives decreased after the specimens were subjected to thermocycling. CONCLUSIONS: The null hypothesis tested "thermocycling would not affect bond strengths treated with self-etching adhesives" was rejected. Furthermore, the study revealed the following: 1. The shear bond strength to both enamel and dentin of the total-etch adhesive and the self-etching adhesives decreased after the specimens were subjected to thermocycling. 2. XE3 achieved the highest bond strength to both enamel and dentin (26.994+/-1.17 and 25.22+/-1.26, respectively). 3. XE3 showed even better bonding after thermocycling to enamel and dentin than the total-etching system or PP. 4. Although PP bonded to enamel showed lower shear bond strength value than XE3, it has durable bond strength even after thermocycling.     

Effect of dentin adhesives used as sealers and provisional cementation on bond strength of a resin cement to dentin

PURPOSE: To evaluate the effects of dentin adhesives employed as resin sealers and provisional cementation on the bond strengths of a resin cement to dentin. METHODS: A two-step etch-and-rinse adhesive (Excite DSC--Group 1) and two-step self-etch adhesive (AdheSE--Group 2) were applied to exposed dentin surfaces prepared from human molars (N=4). Water was used instead of a resin sealer in control Groups 3 and 4. A eugenol-free provisional cement (except for Group 4) was applied to the treated surfaces. After storing in distilled water for 1 week, the provisional cement was removed and cylindrical composite blocks were luted with a resin cement (Variolink II). 0.9 x 0.9 mm sticks were produced from these luted specimens for microtensile bond testing and SEM examination. RESULTS: One-way ANOVA revealed that neither the resin sealer nor the temporary eugenol-free cement had a negative effect on the final bond strength (P> 0.05). Mixed failures were predominantly identified from SEM.     

Fatigue of enamel bonds with self-etch adhesives

ObjectiveFatigue testing of adhesive bonds to tooth structures in conjunction with bond strength testing can provide more useful information for examining the effectiveness of dental adhesives. The purpose of this study was to determine the shear bond strength (SBS) and shear fatigue limit (SFL) of composite to enamel bonds using modern adhesive systems.MethodsTwelve specimens each were used to determine 24-h resin composite (Z100-3M ESPE) to enamel shear bond strengths with an etch-and-rinse system (ERA), Adper Single Bond Plus (SB), and four self-etch adhesives (SEA)—Adper Prompt-L-Pop (PLP), Clearfil SE (CSE), Clearfil S³ (CS3) and Xeno IV (X4). A staircase method of fatigue testing was used in a four-station fatigue cycler to determine the SFL of composite to enamel bonds with the adhesives (16–20 specimens for each adhesive) at 0.25 Hz for 40,000 cycles. ANOVA and Tukey's post hoc test were used for the SBS data and a modified t-test with Bonferroni correction was used for comparisons of the SFL.ResultsThe SBS and SFL of the etch-and-rinse system were significantly greater (p < 0.05) than those of the four self-etch adhesives. The SBS and SFL of CSE were also significantly greater than for the other three self-etch systems. The ratio of SFL to SBS was highest with the etch-and-rinse system and the ratio became increasing smaller in the same order that the values for SBS decreased with the self-etch systems.SignificanceThe lower fatigue limits for composite to enamel bonds obtained with the self-etch adhesive systems may indicate that greater enamel margin breakdown will occur with restorations where these systems are used for bonding.     

Effect of oxalate desensitizer on the bonding durability of adhesive resin cements to dentin

PurposeThis study investigated whether the tubular occluding effect of oxalate desensitizer (OX) during adhesive cementation improved bonding of a self-etch and two etch-and-rinse resin cements to dentin after 6 months.MethodsA flat dentin surface was prepared on 120 extracted premolars, which were randomly divided into six groups of 20 teeth each according to the adhesive resin cement system used: ED primer II/Panavia F2.0, Excite DSC (Ex DSC)/Variolink II, and One-Step Plus (OS Plus)/Duolink, with or without OX (BisBlock) application. After cementation of an indirect composite rod, two subgroups (n = 10) were tested after 24 h and 6 months of water storage plus thermocycling, and shear bond strengths were recorded in MPa.ResultsStatistical tests showed that although oxalate had a borderline significant negative effect on initial bonding of ED primer II/Panavia F2.0, it significantly improved bonding durability (p < 0.05). OX severely compromised the initial bond strength of Ex DSC/Variolink II (p < 0.001) but had no effect on the reduction in bonding after aging. OX was compatible with OS Plus/Duolink and did not affect the loss of bonding strength after 6 months (p > 0.05).ConclusionCombining an oxalate desensitizer with three types of resin cements had different effects on bond strength to dentin after aging, depending on the interaction of oxalate with the adhesive system associated to the resin cement.     

Influence of caries infiltrant contamination on shear bond strength of different adhesives to dentin

Objectives

To analyze whether the contamination with a caries infiltrant system impairs the adhesive performance of etch-and-rinse and self-etching adhesives on dentin.

Materials and methods

Dentin contamination with the caries infiltrant system (Icon, DMG) was simulated by applying either hydrochloric acid (15 % HCl, Icon Etch, 15 s), the resin infiltrant (Icon infiltrant, 4 min), or both prior to the application of the respective adhesives (each group n?=?10). In the control groups, the etch-and-rinse adhesive (Optibond FL, Kerr) and the self-etching adhesive (iBOND Self Etch, Hereaus) were applied without former contamination with the infiltrant system. Additionally, the adhesive performance of the resin infiltrant alone was tested. Shear bond strength of a nano-hybrid composite was analyzed after thermocycling (5,000×, 5–55°C) of the specimens and analyzed by ANOVA/Scheffé post hoc tests (p?<?0.05) and Weibull statistics. Failure mode was inspected under a stereomicroscope at?×?25 magnification.

Results

Contamination with the resin infiltrant alone did not impair shear bond strength, while contamination with hydrochloric acid or with hydrochloric acid and the resin infiltrant reduced shear bond strength (MPa) of the adhesives (Optibond FL: 20.5?±?3.6, iBOND Self Etch: 17.9?±?2.6) significantly. Hydrochloric acid contamination increased the number of adhesive failures. The adhesive performance of the caries infiltrant system alone was insufficient.

Conclusion

The contamination with the caries infiltrant system impaired the shear bond strength of conventional dental adhesives.

Clinical relevance

Contamination of the caries infiltrant system on dentin should be avoided due to the detrimental effect of hydrochloric acid etching.     

Analysis of resin tags formation in root canal dentine: a cross sectional study

Aim  To evaluate the length, density and quality of resin tags formed by penetration of various types of adhesive systems into dentinal tubules at various cross section levels of the root canal in correlation to the density of dentinal tubules.
Methodology  Thirty mandibular premolars were instrumented and fibre posts were inserted with three different adhesive systems with and without activator: etch & rinse XP Bond and XP Bond/Self Cure Activator; self-etch (two-step) AdheSE and AdheSE/AdheSE DC Activator and self-etch (one-step) Hybrid Bond and Hybrid Bond/Hybrid Brushes. The resin tags were evaluated from slices obtained from sections perpendicular to the long axis of the teeth at 3, 6, and 9 mm from the root apex under a Confocal Laser Scanning microscope.
Results  In all groups, lack of continuity of resin tag length, density and quality was observed not only from the cervical to the apical region of each root canal, but also in a mesio-distal direction to the long axis of the root. Application of etch & rinse adhesive in contrast to the self-etch adhesives provided the formation of the shorter, but considerably denser, more homogeneous and not interrupted resin tags with similar length. Use of the activator for all types of adhesives significantly increased the completeness ( P  = 0.014) and continuity ( P  = 0.024) of resin tags.
Conclusions  None of the investigated adhesives were able to completely infiltrate the dentinal tubules in the entire root canal. Use of the etch & rinse adhesive system and the activators significantly increased the density and the quality of resin tags.     

Dental adhesion review: aging and stability of the bonded interface.

OBJECTIVE: Most of current dental adhesive systems show favorable immediate results in terms of retention and sealing of bonded interface, thereby counteracting polymerization shrinkage that affects resin-based restorative materials. Despite immediate efficacy, there are major concerns when dentin bonded interfaces are tested after aging even for short time period, i.e. 6 months. METHODS: This study critically discusses the latest peer-reviewed reports related to formation, aging and stability of resin bonding, focusing on the micro and nano-phenomena related to adhesive interface degradation. RESULTS: Most simplified one-step adhesives were shown to be the least durable, while three-step etch-and-rinse and two-step self-etch adhesives continue to show the highest performances, as reported in the overwhelming majority of studies. In other words, a simplification of clinical application procedures is done to the detriment of bonding efficacy. Among the different aging phenomena occurring at the dentin bonded interfaces, some are considered pivotal in degrading the hybrid layer, particularly if simplified adhesives are used. Insufficient resin impregnation of dentin, high permeability of the bonded interface, sub-optimal polymerization, phase separation and activation of endogenous collagenolytic enzymes are some of the recently reported factors that reduce the longevity of the bonded interface. SIGNIFICANCE: In order to overcome these problems, recent studies indicated that (1) resin impregnation techniques should be improved, particularly for two-step etch-and-rinse adhesives; (2) the use of conventional multi-step adhesives is recommended, since they involve the use of a hydrophobic coating of nonsolvated resin; (3) extended curing time should be considered to reduce permeability and allow a better polymerization of the adhesive film; (4) proteases inhibitors as additional primer should be used to increase the stability of the collagens fibrils within the hybrid layer inhibiting the intrinsic collagenolytic activity of human dentin.     

Shear bond strength of one etch-and-rinse and five self-etching dental adhesives when used by six operators

Objective. To test the hypothesis that some single-bottle self-etching adhesives bond as well to enamel and dentin as a typical two-bottle etch-and-rinse adhesive. Material and methods. Six operators used one two-bottle etch-and-rinse dentin adhesive (Scotchbond MP) and five all-in-one self-etching adhesives (iBond Gluma Inside, Clearfil S³ Bond, iBond Experimental, Xeno IV, and G-BOND). Each operator carried out six bondings to enamel and six bondings to dentin with each adhesive. After 24 h of storage in water at 37°C, bond strength was determined in shear. Results. The pooled results of all the adhesives revealed no significant difference (p>0.05) in bond strength between dentin and enamel. However, there were significant differences (p<0.0001) between the different adhesives. The etch-and-rinse adhesive did better than the self-etching adhesives when substrate was not an issue (pooled enamel and dentin results). On comparing the performance of the different adhesives, it became clear that there were significant interactions (p<0.0001) between substrates and products. There were also significant differences (p<0.0001) between operators, and the interaction between operators and products was significant (p<0.0002). Conclusions. The tested etch-and-rinse adhesive did better than the tested self-etching adhesives. The shear bond strength results were also strongly affected by the operator as well as by the interaction between operator and used product. The pooled bond strength values of the different adhesives revealed no difference in bond strength to dentin versus enamel.     

Interactions of self-etch adhesives with resin composites

OBJECTIVE: Aim of this in vitro study was to investigate the correlation of shear bond strength and marginal cavity adaptation, together with polymerization shrinkage and contraction stress, using the combination of four self-etch adhesives and three resin composites. MATERIALS AND METHODS: Interactions were studied between one two-step and three one-step adhesives, and the hybrid-type resin composites, Beautifil (BEU, Shofu) and Venus (VEN, Heraeus), and an experimental nano-hybrid resin composite NEUN (NEU, Heraeus). For all 12 combinations shear bond strengths (SBS) were determined on human dentin. Marginal adaptation (MGW) was assessed in cylindrical butt-joint dentin cavities. Further, polymerization contraction and contraction stress of the resin restoratives were measured. RESULTS: Significant determinants of SBSs on dentin were time of testing (10min or 24h) and adhesives (p<0.001). Marginal adaptation was best for NEU, followed by VEN and BEU. Only the resin composite used was a highly significant determinant of cavity adaptation. Polymerization shrinkage after 5min was 2.58, 2.74, and 1.53% for BEU, VEN, and NEU, respectively. Polymerization contraction stresses were largest for BEU, less for VEN, and smallest for NEU (p<0.05). CONCLUSIONS: No correlation was found between bond strength and marginal cavity adaptation. In contrast, reduced shrinkage and low polymerization contraction stress of resin composites were identified as important determinants of marginal cavity adaptation.     

Dentin and enamel bond strengths of dual-cure composite luting agents used with dual-cure dental adhesives

OBJECTIVE: The purpose of this in vitro study was to evaluate and compare dentin and enamel bond strengths obtained with dual-cure composite luting agents when used with dual-cure dental adhesives. METHODS: Human molars were ground flat to expose enamel (n=80) or dentin (n=80). Specimens in each substrate group were randomly assigned to eight treatment sub-groups, according to four adhesive-luting agent combinations and two test conditions (with or without thermocycling). Pre-polymerized composite resin posts (TPH Spectrum) were luted to either the enamel or dentin surfaces with one of the following adhesive-luting agent combinations: (1) Xeno IV Dual Cure (dual-cure self-etch adhesive) and Calibra (dual-cure luting agent); (2) Prime & Bond NT Dual Cure (dual-cure total-etch adhesive) and Calibra; (3) OptiBond All-in-One Dual Cure (dual-cure self-etch adhesive) and Nexus 2 Dual Syringe (dual-cure luting agent); (4) OptiBond Solo Plus Dual Cure (dual-cure total-etch adhesive) and Nexus 2 Dual Syringe. For each treatment sub-group, half the specimens (n=10) were tested after 24h storage in water at 37 degrees C, and the other half (n=10) were tested after thermocycling for 1800 cycles between water baths held at 5 and 55 degrees C, with a dwell time in each bath of 30s, and a transfer time of 10s. Bond strengths were measured in shear mode, and expressed in MPa. The fracture mode (adhesive, cohesive, mixed) was examined. Data were analyzed for statistical significance with a factorial ANOVA and post hoc tests. RESULTS: Mean enamel bond strengths ranged from 8.4MPa for non-thermocycled OptiBond All-in-One|Nexus 2 to 35.5MPa for non-thermocycled Prime & Bond NT|Calibra. Mean dentin bond strengths ranged from 14.5MPa for non-thermocycled OptiBond Solo Plus|Nexus 2 to 30.9MPa for thermocycled Xeno IV|Calibra. The fracture mode was predominantly adhesive for all groups. CONCLUSIONS: On enamel, the total-etch adhesives performed better than their self-etch counterparts, while in dentin, the opposite was found, i.e., the self-etch adhesives performed better than their total-etch counterparts. Thermocycling for 1800 cycles did not affect the SBS of the materials tested to dentin and enamel.     

Laboratory evaluation and clinical application of a new one-bottle adhesive.

PURPOSE: The purposes of this project were to compare the enamel and dentin bond strengths of a new nanofilled one-coat adhesive system with its predecessor, an unfilled two-coat adhesive system; to analyze the dentin interfacial ultramorphology, using scanning and transmission electron microscopy (SEM and TEM); and to illustrate the clinical technique associated with the use of the new nanofilled one-coat adhesive system. MATERIAL AND METHODS: Twenty flat dentin surfaces and 20 flat enamel surfaces were polished on the labial surface of bovine incisors mounted in acrylic resin. The specimens were equally and randomly assigned to four bonding groups: (1) dentin with Prime & Bond 2.1; (2) dentin with Prime & Bond NT; (3) enamel with Prime & Bond 2.1; and (4) enamel with Prime & Bond NT. A composite post was then adapted to the treated area and light-cured. After thermocycling, shear bond strengths were determined by testing the shear strength of the specimens. The data were analyzed using one-way analysis of variance (ANOVA) and Student's t-test. For SEM and TEM, six dentin disks were obtained from middle dentin of human third molars and assigned equally to each adhesive. The adhesives were applied to dentin according to manufacturer's directions. The hybrid layer and resin penetration into dentin tubules were analyzed at an ultramorphologic level, and the observations were compared. RESULTS: Shear bond strengths were as follows: group 1: 17.8 +/- 4.1 MPa; group 2: 20.5 +/- 3.5 MPa; group 3: 24.7 +/- 6.7 MPa; and group 4; 27.0 +/- 5.4 MPa. Electron microscopy showed that both adhesives penetrated the dentin tubules and formed a fully infiltrated hybrid layer. The nanofiller included in the new one-application adhesive penetrated the dentin tubules and infiltrated the microspaces between the collagen fibers within the hybrid layer. CLINICAL SIGNIFICANCE: The new one-application nanofilled adhesive tested in this study resulted in bond strengths and dentin hybridization comparable to those obtained with the corresponding two-application system. The clinical sequences presented illustrate the ease of use of the newest simplified adhesives.     

Adhesion of 10-MDP containing resin cements to dentin with and without the etch-and-rinse technique

PURPOSE

This study evaluated the adhesion of 10-MDP containing self-etch and self-adhesive resin cements to dentin with and without the use of etch-and-rinse technique.

MATERIALS AND METHODS

Human third molars (N=180) were randomly divided into 6 groups (n=30 per group). Conventional (Panavia F2.0, Kuraray-PAN) and self-adhesive resin cements (Clearfil SA, Kuraray-CSA) were bonded to dentin surfaces either after application of 3-step etch-and-rinse (35% H₃PO₄ + ED Primer) or two-step self-etch adhesive resin (Clearfil SE Bond). Specimens were subjected to shear bond strength test using the universal testing machine (0.5 mm/min). The failure types were analyzed using a stereomicroscope and quality of hybrid layer was observed under a scanning electron microscope. The data (MPa) were analyzed using two-way ANOVA and Tukey''s tests (α=.05).

RESULTS

Overall, PAN adhesive cement showed significantly higher mean bond strength (12.5 ± 2.3 - 14.1 ± 2.4 MPa) than CSA cement (9.3 ± 1.4 - 13.9 ± 1.9 MPa) (P<.001). Adhesive failures were more frequent in CSA cement groups when used in conjunction with two-step self-adhesive (68%) or no adhesive at all (66%). Hybrid layer quality was inferior in CSA compared to PAN cement in all conditions.

CONCLUSION

In clinical situations where bonding to dentin substrate is crucial, both conventional and self-adhesive resin cements based on 10-MDP can benefit from etch-and-rinse technique to achieve better quality of adhesion in the early clinical period.     

Conditioning effect on dentin, resin tags and hybrid layer of different acidity self-etch adhesives applied to thick and thin smear layer

OBJECTIVES: to assess the conditioning effect (CE) of self-etch adhesives of different acidity applied to thick and thin smear layer (SL), the corresponding resin tags (RT) and hybrid layer (HL). METHODS: Twenty-seven molars had their occlusal dentin exposed and were sectioned into two halves. Each of them was ground with a 60 or 600-grit SiC paper, respectively for thick and thin SL production. Three self-etch adhesives: a mild (Clearfil SE Bond), an intermediary (Optibond Solo SE and Solo Plus) and a strong (Tyrian Self Priming Etchant+One Step Plus) and an etch-&-rinse system (Scotchbond Multi Purpose Plus) were used. For CE evaluation, the self-etch primers were applied and rinsed off with acetone and alcohol prior to SEM preparation. For RT and HL specimens self-etch adhesives were applied and restored with Z-250. For RT specimens, dentin was removed with HCl (6N) and NaClO (1%) baths. The HL specimens were fixed, dehydrated, dried with HMDS, embedded, polished and slightly demineralized (6N HCl) and deproteinized (1% NaClO). After gold sputtering they were observed by SEM. RESULTS: The thick smear layer was clearly not totally removed by the mild self-etch primer. RT varied in density and shape among the self-etch adhesives. Thicker HL was observed for the strong self-etch and etch-&-rinse adhesives. CONCLUSIONS: The etch-&-rinse adhesive presented the thickest HL and was the only adhesive to produce RT in high density and uniform distribution along the whole dentin surface, independently of the SL thickness.     

Electric-current-assisted application of self-etch adhesives to dentin

The use of electric current during the application of etch-and-rinse adhesive systems has been recently claimed to increase bonding of etch-and-rinse adhesives by enhancing substrate impregnation. The null hypothesis tested in this study was that electrically assisted application has no effect on bond strength of self-etching bonding systems. Three self-etch adhesives (Protect-Bond, Xeno III, and Prompt L-Pop) were applied with the aid of an electric signal-generating device (ElectroBond) and tested vs. controls prepared with the same disposable sponges but without electric current. Specimens bonded under the influence of electric current exhibited increased microtensile bond strength compared with the controls (p<0.05). High-resolution SEM analysis showed that bonding under the influence of electricity reduced interfacial nanoleakage. It is speculated that resin infiltration may be improved by the attraction of polar monomers by an electric current or by modification of the dentin surface charges, resulting in better water substitution or evaporation.