Excite DSC Research Articles

Influence of the depth of intraradicular dentin on the pushout bond strength of resin materials.

The aim of the present study was to evaluate the pushout bond strength between glass-fiber posts to different regions of intraradicular dentin with different materials for adhesive cementation. After endodontic filling, 40 teeth were divided into five groups according to adhesive cementation: Adper Single Bond 2+RelyX ARC, Excite DSC+RelyX ARC (EXC), Adper SE Plus+RelyX ARC (SEP), RelyX Unicem, and Set. After the bonding process, roots were sectioned obtaining slices to be analyzed from each third. The bond strength was measured using the pushout test in a universal testing machine (Emic DL 3000) at a cross-head speed of .5mm/minutes in different areas of the post space (cervical, middle, and apical). Data were subjected to analysis of variance and Fisher's test (α=.05). The highest values for the pushout bond strength were found for the SEP group in all experimental conditions, without a significant difference for the EXC group in the middle and apical regions. There was a decrease in pushout bond strength in the cervical-apical direction for all groups, except the EXC group, which did not show a difference among the different regions. The different interactions of the resin materials and the intraradicular depth influenced the bond strength of adhesives materials to dentin substrate.

Ultimate tensile strength of total and self-etch adhesives: Effect of light irradiation distance

Objective: To evaluate the ultimate tensile strength (UTS) of total and self- etch adhesives irradiated at different distances. Materials and Methods: Sixty cylindrical specimens of 0.78mm diameter and 10 mm length were prepared of two types of adhesive systems total etch Excite DSC (EX – Ivoclar Vivadent, Schaan, Liechtenstein) and one-step self-etch Clearfil S3 Bond (S3, Kuraray Medical Inc., Tokyo, Japan). Specimens of each adhesive were divided into three groups according to the light irradiation distance (0, 2, 4mm) (n=10). Each specimen was attached to universal testing machine (Digital Force Gauge, IMADA CO., LTD, Japan) and loaded at cross head speed of 1mm/min until failure. Data were analyzed using two-way ANOVA and Independent Student t-test at p< 0.05. Results: Mean UTS for total etch (24.63, 18.19, 17.26 Mpa) and for self-etch (12.68, 8.53, 7.58Mpa) at (0, 2, 4mm) distances. Specimens irradiated directly show significantly the highest UTS while those irradiated at 4mm show the lowest values (p<0.05). Excite DSC total etch adhesive have higher UTS than Clearfil S3 self-etch adhesive regardless of irradiation distance (p<0.05).Conclusions: The UTS of the evaluated adhesives was light irradiation distance and adhesive system dependant.

Effect of timing of dentin sealing and provisional restoration method on bond strength of composite resin to dentin

The purpose of this study was to evaluate the effect of timing of dentin sealing and provisional restoration methods on the bond strength of composite resin to dentin. Flat dentin surfaces were prepared and the teeth were divided into three groups: control, resinrestoration with immediate dentin sealing (IDS), and resin restoration with delayed dentin sealing (DDS). For the control group, a dentin surface was bonded by using dual-curing dentin adhesive (Excite DSC) and restored with resin immediately. For the IDS groups, a dentin was sealed with OptiBond FL (OB) or Hybrid Coat (HC), and it was restored with following 3 provisional restoration methods: SQ/PQ/CQ {SQ, water-soluble separator (SEP) + provisional resin; PQ, petroleum jelly + provisional resin; CQ, temporary cement (Cavitec) + provisional resin}. For the DDS groups, a dentin was temporized with 2 provisional restoration methods: Q/CQ (Q, provisional resin only) without dentin sealing. After a week, the provisional restoration was removed and cleaned. The treated dentin surface was bonded using Excite DSC and restored with resin, followed by microtensile bond strength (μTBS) tests. The μTBS of control and the IDS-OB groups were not significantly different (P>0.05). The DDS groups presented lower μTBS than control and the IDS-OB groups (P 0.05). However, using CQ significantly lower the μTBS than using Q in the DDS groups (P<0.05). IDS with a etch-and-rinse type dentin bonding agent improved the bond strength. The use of ZOE-containing cement on the unsealed dentin surface decreased the μTBS.

EVALUATION OF MICRO LEAKAGE IN COMPOSITES WITH NEWER DENTIN BONDING SYSTEMS BY DIRECT TECHNIQUE IN CLASS V CAVITIES: AN IN-VITRO FLUORESCENT DYE PENETRATION STUDY

The objective of this study is to evaluate the micro leakage of class V lesions restored with composite material ( Tetric Ceram) using one total etch bonding system and two self etch bonding systems using fluorescent dye penetration technique. Class V cavity were prepared on forty five extracted intact human molars. The teeth were divided randomly and equally into one control grou p and two experimental groups. In Control group Conventional etching was carried out with 37 % phosphoric acid (Total Etch) and bonded with Excite DSC . In Experimental groups Group 1 - Self etching primer ( AdheSE ) was applied and cured : Group 2 – Self etchin g primer (Uni fi l Bond) was applied and cured. Al l the 45 teeth were restored with Tetric Ceram . The specimens were immersed in Rhodamine 6G for 24 hours. Longitudinal sections were prepared and were subjected for microscopic evaluation. Results were stati stically analyzed using ANOVA and Multiple comparison tests. The study showed that both the self etching primers showed significantly lesser micro le a kage when compared to the total etch bonding system. Self - etching dentin bonding systems (Uni fil Bond and AdheSE ) gave the better results in terms of less micro leakage when compared to the total – etch dentin bonding system when used with composites.

Fracture Resistance of Roots Restored with Four Different Fiber-Reinforced Composite Posts

Objective: The aim of this study was to compare the resistance to vertical root fracture of root-filled teeth restored with four different fiber-reinforced composite (FRC) post systems and two types of dual-cured resin luting agents. Materials and Methods: Ninety extracted human maxillary central incisors were selected and decoronated to obtain a standardized root length of 14 mm. After root canal obturation, post spaces were prepared to a depth of 10 mm with a No. 3 post drill. The specimens (n = 80) were divided into two groups (n = 40) according to the resin luting agents used: group 1, Variolink II + ExciTE DSC; group 2, RelyX Unicem. These groups were subdivided into four subgroups (n = 10) and restored with one of the following post systems: (a) DT Light, (b) DT Light SL, (c) FRC Postec and (d) Everstick, while the remaining 10 teeth served as controls. The roots were subjected to axial compressive loading using a 2.2-mm-diameter metal sphere in a universal testing machine (0.5 mm/min). A factorial experiment with a single control group (analysis of variance) was used to test the resistance of the specimens. Results: Groups 2a (DT Light + RelyX Unicem; 398.5 N) and 1b (DT Light SL + Variolink II + ExciTE DSC; 431.1 N) had significantly higher resistance to fracture than the control group (334.1 N; p < 0.05). DT Light SL and FRC Postec Plus were more resistant to fracture when Variolink II was used as the luting cement. DT Light and Everstick had higher fracture resistance when they were luted with RelyX Unicem (p < 0.05). Conclusion: The results of this study indicate that the use of quartz fiber posts (DT Light and DT Light SL) with an adhesive luting cement in root-filled teeth may reinforce the root to some extent.

Mechanical properties of components of the bonding interface in different regions of radicular dentin surfaces

Statement of problemThe mechanical properties of the adhesive materials used in intraradicular treatments could vary according to the interaction between the restorative material and dentin substrate. An evaluation of these properties is essential to determine the success of the luting procedures performed on glass-fiber posts. PurposeThe purpose of this study was to evaluate the mechanical properties of dentin adhesives, resin cements, and the dentin that underlies the bonding interface in different thirds of intraradicular dentin. Material and methodsForty extracted, single-rooted human teeth were used in this study. After the endodontic treatment of the post spaces, the teeth were divided into 5 groups (n=8): Adper Single Bond 2 + RelyX ARC, Excite DSC + RelyX ARC, Adper SE Plus + RelyX ARC, RelyX Unicem, and Set. The hardness and elastic modulus values were measured at the adhesive interface in different thirds of the radicular dentin by using an ultramicrohardness tester. The data were subjected to 2-way ANOVA and the Fisher protected least significant difference test (α=.05). ResultsIn the underlying dentin, the highest Martens hardness values were found in the apical region for all groups; the exceptions were the groups with the self-etching adhesive. In the adhesive layer, the highest Martens hardness values were obtained for the Adper SE Plus + RelyX ARC group; further, no statistical differences were found among the different regions for this group. RelyX ARC had the lowest Martens hardness and elastic modulus values in the apical regions when used with Adper Single Bond 2 and Adper SE Plus. No differences were found in the Martens hardness and elastic modulus values for the self-adhesive resin cement in the regions investigated. ConclusionThe mechanical properties of adhesive materials and the underlying dentin are influenced by the interaction between the two as well as by the depth of the analyzed intraradicular area.

Influence of the resin cement thickness on bond strength and gap formation of fiber posts bonded to root dentin.

To evaluate the effect of the resin cement thickness (RCT) on bond strength (BS) and gap formation (GF) of fiber posts bonded to root dentin. The roots of 24 extracted human mandibular premolars were treated endodontically and the post spaces were prepared using drills with different diameters according to the following groups (n = 8): well adapted (WA), moderately well adapted (MA) and poorly adapted (PA). The fiber glass posts were cemented (Excite DSC and Variolink II) in accordance with the manufacturer's instructions. After 1 week, the roots were transversely sectioned into six 1-mm-thick disks and photographed using an optical microscope to determine the RCT. After this, epoxy resin replicas of each sample were observed using SEM, and the mean length and width of the gaps formed in the cement/dentin/post interface were measured. Finally, each sample was subjected to the push-out test (0.5 mm/min), and the data were statistically analyzed using one-way ANOVA and Tukey's tests at the 5% level of significance. The lowest RCT (μm) was observed for WA and the highest for PA. The group MA showed an intermediate value. Significantly higher push-out BS values were observed for WA compared to the other groups. The MA and PA groups were statistically similar. The highest mean gap length (%) and width (μm) were observed for PA. The groups MA and WA were statistically similar. Lower resin cement thickness resulted in better fiber post adhesion, that is, in higher bond strength and less gap formation.

Evaluation of Apical Micro-leakage of Different Endodontic Sealers in the Presence and Absence of Moisture.

Background and aims. With availability of hydrophilic sealers, drying of the canals before endodontic obturation is still a matter of debate. The aim of this study was to compare the apical micro-leakage of AH26, Excite DSC, MTA Fillapex, and ZOE sealers in dry and moist root canals.Materials and methods. This experimental study was performed on 90 extracted maxillary central incisors. Rotary files were used for preparation of the canals. Root canals were filled with a single gutta percha cone, using one of the four sealers, under dry and moist root canal conditions (10 teeth in each group). Orifices were sealed with glue wax and all root surfaces were covered with nail polish except the positive control group. After ten days in 100% humidity, teeth were placed in methylene blue, and then were cut in longitudinal axis. Blue color permeability was measured by stereomicroscope in micrometers. Data were analyzed by t-test, ANOVA and Scheffe post hoc test using SPSS V.18 software at P < 0.05.Results. Mean apical micro-leakage was significantly lower in the dry groups (P < 0.001). Minimum and maximum micro-leakage was seen in AH26 and ZOE, respectively. MTA Fillapex did not exhibit a significant difference in apical micro-leakage between dry and moist conditions (P > 0.05). Apical micro-leakage was significantly higher in the Excite DSC groups (P < 0.001).Conclusion. AH26 provided the least apical micro-leakage under dry conditions while ZOE had the highest micro-leakage under moist conditions. MTA Fillapex provided acceptable apical seal regardless of moisture.

The effect of photoactivation time and light tip distance on the degree of conversion of light and dual-cured dentin adhesives

The degree of conversion of dental adhesive is an important parameter since poor mechanical properties are related to low percentage of monomer-to-polymer conversion within resin-based materials. To evaluate the influence of polymerization time and light guide distance on the degree of conversion (DC) of three contemporary dental adhesives. The spectral data of ExciTE DSC, Single Bond ® , and Adper ® Prompt L-Pop were analyzed using FTIR spectroscopy after 20 s, 40 s, and 60 s of photoactivation times. Light tip distances were kept at 1, 3, and 6 mm during the exposures. Data were analyzed using ANOVA and Tukey's test (α = 0.05). Within groups, greater DC values were found using a tip distance of 1 mm or a 60-s curing time for Single Bond ® (59%) and Adper ® Prompt L-Pop (65%). No statistically significant difference (P > 0.05) was found using either 1 mm or 3 mm tip distances after 20 s, 40 s, and 60 s of light curing time for Single Bond ® . ExciTE ® DSC showed the greatest DC values with light tip distances of 1 mm (90%) and 3 mm (89%), using 60 s of light curing. The self-etch adhesive Adper ® Prompt L-Pop could be applied in shallow cavity preparations and must be light cured for at least 40 s. The light-cured total-etch adhesive ExciTE ® DSC could be applied in every restorative scenario if the curing time is extended up to 60 s or if the tip distance is extended up to 3 mm.

Interfacial nanoleakage and internal cement thickness of three esthetic crown systems

ObjectivesTo evaluate interfacial nanoleakage expression of the combination of different cementation procedures and different crown systems. MethodsForty-five human premolars prepared to receive single crowns were randomly divided into three groups (n=15) based on the materials to be used for crown fabrication and cementation: group 1: Zirc (Ivoclar-Vivadent) cemented with Multilink Automix; group 2: Ivoclar disilicate IPS Empress 2 luted with Excite DSC in combination with Variolink II; group 3: AAdva Zirconia (GC) cemented with G-Cem Automix. The specimens were then assessed for interfacial nanoleakage expression and the amount of silver deposits along the interface was quantified. The thickness of the cement was assessed at 5 different levels: cervical margins, midway between the cervical margin and the occlusal wall along the axial walls and at the occlusal wall. The nanoleakage scores and the cement thickness were analyzed with Kruskall–Wallis non-parametric Analysis of Variance and Dunn's Multiple-range post hoc test. ResultsGroup 2 showed significantly less nanoleakage expression than group 1 (p<0.05). The groups can be ranked in the following order 3<1<2 with regard to the cement thickness. ConclusionsThere was no correlation among combination of different cementation procedures and different crown systems and interfacial nanoleakage. Also the cement thickness and the degree of nanoleakage cannot be related. The amount of cement found at the cervical margins of all groups showed discrepancies within a clinical acceptable range.

Extent of cement polymerization along dowel space as a function of the interaction between adhesive and cement in fiber post cementation.

To assess whether the polymerization extent of cement is influenced by curing mode of the adhesive and/or by photoactivation of the cement. One hundred five root segments were prepared from endodontically treated teeth. After post space preparation, the root segments were randomly divided into 7 groups, based on the cementation procedure to lute RelyX Fiber Posts (3M ESPE): 1. Variolink II (V, Ivoclar Vivadent); 2. V light-cured (LC); 3. Excite LC (ELC, Ivoclar Vivadent)/V; 4. ELC/V LC; 5. ELC-V LC (One Shot); 6. Excite DSC (EDSC)/V; 7. EDSC-V LC (One Shot). Each root segment was submitted to the acetone shake test to remove the unpolymerized resin and then cut longitudinally. On each half, the extent of cure of the cement was measured with image analysis software. The deepest and basically complete polymerization was obtained with EDSC (groups 6 and 7), regardless of whether light curing was performed. The extent of polymerization was most limited when adhesive was not applied (groups 1 and 2), or when ELC was only light cured, while V was allowed to auto-cure (group 3). With the one-shot polymerization of ELC and V (group 5), the extent of polymerization was similar to the procedure involving separate irradiation of adhesive and cement (group 4). The one-shot technique was significantly more effective if EDSC was used (group 6). The use of a self-activating dual-curing adhesive system in combination with a dual-curing cement enables effective luting of FRC posts regardless of the amount of light transmitted through the post.

Effects of self-curing activator and curing protocol on the bond strength of composite core buildups.

To determine the effect of the polymerization mode of simplified bonding systems and the corresponding core buildup resin composite on the bond strength to dentin. Composite core buildups were bonded to flat prepared dentin surfaces of 320 human molars using a two-step etch-and-rinse (Excite, ER) and a two-step self-etching (AdheSE, SE) bonding system. Bonding systems were used both with and without their respective self-curing activators (Excite DSC, ER+SC; AdheSE DC, SE+SC). Six curing protocols for the dual-curing composite (MultiCore Flow) were examined: self-curing for 5 min (a); irradiation with light from each aspect for 10 s (b), 20 s (c), and 40 s (d); and irradiation with light from the occlusal aspect only for 60 s (e) and 120 s (f). Shear bond strengths were measured immediately after curing. Additional measurements were performed after water storage of the specimens for 24 h at 37°C. These specimens had been cured according the curing protocols given in the manufacturer's instructions (groups a and d). Failure modes were analyzed using scanning electron microscopy. Immediate bond strengths were significantly different among the bonding systems (p < 0.001): SE > ER > ER+SC > SE+SC. Immediate bond strengths of ER and SE were significantly lower when the composite was self-cured (p < 0.05). The use of SC activators reduced the bond strength and promoted adhesive failures to dentin. A severe incompatibility problem was observed between the composite and SE+SC. Dentin bonding of dual-curing composite core buildups in combination with simplified bonding systems is still unsatisfactory, even when SC activators are employed. For adequate bonding to dentin, polymerization of the dual-curing composite should always be light initiated.

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 24h 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.

Shear bond strength of three self-adhesive resin cements to dentin

The result of the studies concerning the bonding of self-adhesive resin cements to dentin is controversial. To assess in vitro shear bond strength (SBS) of three self-adhesive dual-cured resin cements to dentin compared to a currently used dual-cured resin cement, using SBS test. The extant study is an experimental in vitro one on extracted human third molars dentin. 40 intact human third molars were selected and randomly divided into 4 groups of 10. Buccal dentin surfaces were exposed perpendicular to the long axis and prepared with SiC papers. A translucent plastic ring, was placed over the dentin surfaces. Group I (Control group): After 15 s of etching and application of Excite DSC Bond (Ex), Variolink II (Var II) resin cement was injected into the plastic ring and was light cured for 40 s. Group II: RelyX Unicem (RX) was injected into the plastic ring and after 30 s, was light cured for 40 s. Group III: Maxcem (Mc) was injected into the plastic ring and after 30 s, was light cured for 40 s. Group IV: Multilink Sprint (MS) was injected into the plastic ring and after 30 s, was light cured for 40 s. After thermal cycling, SBS were measured with a universal testing machine. Statistical computations were conducted according to Student's t-test. The mean SBS and standard deviations (in parentheses) for groups I, II, III, and IV were 12.95 (2.64), 6.73 (0.79), 3.01 (0.90), 4.60 (0.75) MPa, respectively. Statistical analysis, revealed that: (1) the mean SBS of Var II were significantly higher than the other groups (P<0.05). (2) The mean SBS of Mc and MS were significantly lower than RX (P<0.05). (3) The mean SBS of Mc and MS did not show significant difference (P>0.05). Bond strength of three self-adhesive resin cements was significantly lower than the conventional total-etch resin cement. RX significantly performed better SBS than Mc and MS to dentin.

In vitro enterococcus faecalis biofilm formation on five adhesive systems

Objective: To determine the E. faecalis biofilm formation on the surface of five adhesive systems (AS) and its relationship with roughness. Study Design: The formation of E. faecalis biofilms was tested on the surface of four dual-cure AS: AdheSE DC, Clearfil DC Bond, Futurabond DC and Excite DSC and one light-cure antimicrobial AS, Clearfil Protect Bond, after 24 hours of incubation, using the MBEC high-throughput device. Results: E. faecalis biofilms grew on all the adhesives. The least growth of biofilm was on Excite DSC, Clearfil Protect Bond, and the control. Futurabond DC resulted in the greatest roughness and biofilm amount. There was a close relationship between the quantity of biofilm and roughness, except for Clearfil Protect Bond, which showed little biofilm but high roughness. Conclusion: None of the tested AS prevented E. faecalis biofilm formation, although the least quantity was found on the surface of Clearfil Protect Bond. Key words:Adhesive systems, biofilm, Enterococcus faecalis, roughness.

Push‐out strength of translucent fibre posts cemented using a dual‐curing technique or a light‐curing self‐adhering material

To compare by means of a push-out test the interfacial strength of a dual-curing resin cement and a light-curing self-adhering resin composite when used in translucent fibre post cementation. Thirty-four extracted human premolars with single canals were selected and root filled. Translucent fibre posts (RelyX Fiber Post) were luted into the root canal using two resinous luting systems (n = 17). Dual-Curing Technique (DC): the specimens were treated with Excite DSC and RelyX ARC, which were light-cured simultaneously through the post for 60 s. Light-Curing Self-Adhering Technique (LCSA): the specimens were treated with Vertise Flow, which was light-cured through the post for 60 s. The specimens were sectioned transversally into six slices to perform the push-out test at the coronal, middle and apical regions of the root canals. Data were analysed by two-way anova. All specimens were analysed by stereomicroscopy and SEM to determine fracture patterns. There were no significant differences between the DC and LCSA techniques (P = 0.703) in any of the canal regions. Root region was not a significant factor for push-out values (P = 0.255) and group-region interactions were not significant (P = 0.740). For the DC technique, the majority of the fracture patterns (73.3%) were adhesive at the interface between dual-curing resin cement and adhesive. For the LCSA technique, the majority of the fracture patterns (71.7%) were adhesive at the interface between light-curing self-adhering resin composite and dentine. The interfacial strength between light-curing self-adhering resin composite and root canal walls is equivalent to the interfacial strength between dual-curing cement and root canal walls.

Bond Strength of Two-Step Etch-and-Rinse Adhesive Systems to the Dentin of Primary and Permanent Teeth

The purpose of this study was to compare the immediate microtensile bond strength (microTBS) of two-step etch-and-rinse adhesive systems to the dentin of primary and permanent teeth. Non-carious human teeth (12 primary molars and 12 premolars) were assigned to 3 groups according to the adhesive system. The adhesive systems were applied to flat superficial coronal dentin surfaces etched with phosphoric acid and composite resin blocks were built up. The teeth were sectioned to produce beam-shaped specimens with 0.81 mm2 cross-sectional area subjected to microTBS testing. MicroTBS data were analyzed statistically by ANOVA and Tukey's test (a = 0.05). The adhesive systems produced statistically similar mean microTBS to each other (p > 0.05) and no significant differences (p > 0.05) were found when the same material was applied to primary or permanent tooth dentin. The mean microTBS values (MPa) obtained were: Prime & Bond NT: 41.7 +/- 14.4 (permanent) and 40.8 +/- 13.4 (primary); Single Bond: 42.9 +/- 8.6 (permanent) and 41.4 +/- 11.9 (primary); Excite DSC: 46.3 +/- 11.3 (permanent teeth) and 43.4 +/- 12.0 (primary). There was no difference in the immediate microTBS of two-step etch-and-rinse adhesive systems when applied to the dentin of primary and permanent teeth.

Bond strength and fracture analysis between resin cements and root canal dentin

The aim of this research is to evaluate bond strength between translucent fibre posts (White Post DC, FGM or FRC Postec Plus, Ivoclar/Vivadent) and intraradicular dentin at three different levels (cervical, middle and apical) using a dual-cure (AllCem, FGM) or self-curing (Multilink, Ivoclar/Vivadent) resin cement. Also, the fracture type after push-out test was analysed under SEM. Thirty-two extracted single-root teeth were selected. After undergoing endodontic therapy, they were randomly divided into four groups according to their post type and resin cement. Root canals were etched using 37% phosphoric acid, and Excite DSC adhesive (Ivoclar/Vivadent) was applied in all groups. The root was sectioned to obtain nine 1-mm-thick slices (three per third: coronal, middle, apical). All slices were subjected to push-out tests. Data were analysed using two-way anova. The mean bond strengths vary from 6.6 (4.6) MPa [apical] to 11.9 (5.9) MPa [cervical]. There were no significant differences between groups. Pearson χ(2)-test revealed significant differences in fracture types for all groups (P < 0.0001). The apical third had the lowest bond strengths and it was also shown to be the most critical region for luting fibre posts.

Luting glass ceramic restorations using a self-adhesive resin cement under different dentin conditions

ObjectivesThe aim of this study was to investigate the bond strength of ceramic restorations luted using a self-adhesive resin cement (RelyX Unicem, 3M ESPE) under different dentin conditions.Material and MethodsIn the experimental groups, ceramic restorations were luted to bovine incisors with RelyX Unicem under the following conditions: [Dry dentin]: surface was dried using air stream for 15 s; [Moist dentin]: excess dentin moisture was removed with absorbent paper; [Bonding agent]: Clearfil SE Bond (Kuraray) self-etching adhesive system was previously applied to dentin. In the Control group, cementation was done using an etch-and-rinse adhesive (Excite DSC) and Variolink II resin cement (Ivoclar Vivadent). Photoactivation of the resin cements was performed with UltraLume LED 5 unit (Ultradent). The restorations (n=5 per group) were sectioned into beams and microtensile testing was carried out. Data were subjected to ANOVA and Tukey's test (p<0.05). Failure modes were classified under Scanning Electron Microscopic (SEM) (×120 magnification).ResultsThe bond strength was dependent on the moisture status of the dentin. Bond strength in the "dry dentin group" was significantly lower than that of all other groups, which showed similar results. A predominance of mixed failures was detected for the control group, while a predominance of adhesive failures was observed for the "bonding agent" and "dry dentin" groups. The "moist dentin" group presented predominantly cohesive failures within the luting material. The previous application of a self-etching adhesive showed no significant effect.ConclusionsOnly excess dentin moisture should be removed for the cementation of ceramic restorations with self-adhesive resin cements.

Push-out strength of fiber posts depending on the type of root canal filling and resin cement

The purpose of this study was to analyze the push-out strength of two fiber post systems/resin cements (RelyX Unicem/RelyX Fiber Post (RLX) and Variolink II/DT Light SL (VL)) depending on the root canal filling (RF). One hundred sixty extracted human teeth were divided into four groups: gutta-percha/AH Plus (GP), gutta-percha/Guttaflow (GF), pre-existing root canal filling (PRF), and without root canal filling (WRF). After root canal treatment, fiber posts were inserted using either RelyX® or Variolink II®/Excite DSC®. Half of the specimens were thermocycled (TC, 5,000 cycles, 5-55°C). All specimens were subjected to the push-out test (crosshead speed 1 mm/min). Three-way ANOVA showed a significant influence of either the RF or the resin cement/post system (p < 0.001). The highest bond strength was measured for VL-WRF without TC (16.5 ± 6.4 MPa). TC had no significant influence within the RLX groups. For groups PRF and WRF, significant differences were documented between VL and RLX (PRF 16.3 ± 6.0 vs 7.0 ± 2.4 MPa, p = 0.001; WRF 16.5 ± 6.4 vs 8.0 ± 5.0, p = 0.004) before TC. No differences were found after TC. The fracture mode analysis for VL showed mainly adhesive fractures between post and cement. For RLX, mixed fractures between post and tooth and between tooth and cement were predominantly determined. The adhesion of resin cements/post systems could be dependent on the type of RF. Higher bond strength values were found for the conventional ("etch and rinse") adhesive than for the "self-adhesive resin cement."