Fracture resistance of CAD/CAM blocks cemented on dentin using different cementation strategies.

PURPOSE: To determine whether the fracture resistance of computer-aided design/computer-aided manufacturing (CAD/CAM) resin-based composites and polymer-infiltrated ceramic network materials cemented on dentin is influenced by the restoration thickness and composite cement application strategy. METHODS: Disc-shaped specimens (Ø = 7 mm) of 0.8 mm and 1.5 mm thicknesses were milled from two CAD/CAM materials: resin-based composite (RBC, Cerasmart 270) and polymer-infiltrated ceramic network (PICN, Vita Enamic). The discs (n = 8 per group) were cemented on flattened dentin using three different cementation strategies: 1) self-adhesive composite cement (RelyX U200) in light-curing mode (LC-SAC), 2) universal adhesive (Single Bond Universal) with composite cement (RelyX Ultimate) in auto-curing mode (AC cement), and 3) adhesive and composite cement as in 2) but in light-curing mode (LC cement). The restorative surface was indented perpendicularly with a compressive load using a universal testing machine until fracture. The fracture resistance (N) of RBC and PICN was separately analyzed using two-way ANOVA and Tukey's post-hoc test (α = 0.05). RESULTS: The fracture resistance of each material was significantly influenced by the material thickness and cementation strategy (P < 0.05). Irrespective of the material type and cementation strategy, thicker materials exhibit higher fracture resistance. For RBC, the fracture resistance of the LC cement group was significantly higher than that of AC cement only at 0.8 mm thickness. For PICN, the LC-cement cementation strategy produced superior fracture resistance, regardless of the restoration thickness. CONCLUSIONS: The fracture resistance of Cerasmart 270 was higher for the thicker material; the fracture resistance of LC cement was higher than that of AC cement at 0.8 mm thickness cemented to dentin. In comparison, LC cement showed the highest fracture resistance for Vita Enamic for both material thicknesses.

Contamination of Dentin with Hemostatic Agents - Is EDTA a Valuable Decontaminant before Using a Self-etch Universal Adhesive?

PURPOSE: To investigate the effects of dentin decontamination procedures with ethylenediaminetetraacetic acid (EDTA) after contamination with two hemostatic agents, ViscoStat (VS) and ViscoStat Clear (VSC), on the microtensile bond strength (µTBS) of two different universal adhesives, before and after thermocycling (TC). MATERIALS AND METHODS: Dentin surfaces of 100 human caries-free molars were either contaminated with one of the hemostatic agents or contaminated and then decontaminated with EDTA before the universal adhesives Scotchbond Universal Adhesive (SBU) or Prime & Bond Active (PBA) were applied in self-etch mode. Composite buildups were made and the teeth were sectioned into sticks (n = 90). Half of them immediately underwent the µTBS test, the other half after aging via TC. The data were statistically analyzed using Welch's ANOVA and the Games-Howell post-hoc test (p < 0.05). RESULTS: Significant differences were observed between the groups (p < 0.001). When the dentin surface was contaminated with VSC, TC significantly reduced the mean bond strength, regardless of the universal adhesive. Decontamination with EDTA showed a significant decrease in bond strength after VS contamination and SBU application. The fracture analysis showed mainly adhesive fractures (78.8%) in all test groups. CONCLUSION: As EDTA application did not significantly increase the µTBS of either universal adhesive in self-etch mode in-vitro, it cannot be recommended as a decontaminant.

Do Different Pretreatment Methods Influence the Microtensile Bond Strength of Composite Cements to Silicate Ceramic?

PURPOSE: The pretreatment of glass-ceramic before adhesive cementation can be performed with hydrofluoric acid (HF)/silanization (S) or with an ammonium polyfluoride-containing primer (APF). It can be modified by application of a silane-containing universal adhesive (UA) and/or additional silanization. The aim of this study was to evaluate the bond strength of composite cements to two different glass ceramics after different pretreatments and aging. MATERIALS AND METHODS: Disks of leucite-reinforced glass-ceramic or lithium-disilicate glass-ceramic were pretreated with HF+S, HF+UA, HF+S+UA, APF, or APF+S, bonded in pairs with composite cement and sectioned into microsticks (n = 96/group). The microtensile bond strength was determined either after 24 h (n = 48) or after aging for 6 months in water (n = 48). Fracture patterns were analyzed at 50X magnification. Statistical evaluation was performed using the Kruskal-Wallis test, pairwise comparisons with Bonferroni's correction, and the chi-squared test (p < 0.05). RESULTS: Pretreatment with HF+UA or APF led to significantly lower bond strength compared to HF+S. Additional silanization after application of UA or APF resulted in a significant increase in bond strength. After aging, HF+UA groups showed significantly lower bond strengths, independent of additive silanization. Aging did not affect APF-pretreated leucite-reinforced glass-ceramic; for lithium-disilicate glass-ceramic, the bond strength dropped significantly. Additional silanization improved aging resistance for the respective groups. CONCLUSION: Bond strength and its long-term stability depend on the ceramic used and on the pretreatment. An ammonium polyfluoride-containing primer seems to be a promising option compared to conventional pretreatment with hydrofluoric acid. Additive silanization improves the long-term stability of the microtensile bond strength.

Composite restorations placed in non-carious cervical lesions-Which cavity preparation is clinically reliable?

The purpose of this in-vivo study was to evaluate the clinical performance of restorations placed in non-carious cervical lesions (NCCLs), using different cavity preparation designs, after 7.7 years. A total of 85 NCCLs with coronal margins in enamel and cervical margins in dentin were randomly assigned to the following treatment protocols: dentin surface cleaning, dentin surface roughening with round bur plus flowable composite, dentin surface roughening/cervical groove preparation with round bur, dentin surface roughening/cervical groove preparation with round bur plus flowable composite. After enamel beveling and selective enamel etching, the defects were restored with composite. The restorations were assessed by two independent, calibrated and blinded investigators, using modified USPHS criteria. At 7 years (7.7 (± 0.35)), a total of 64 restorations (75.3%) were available for follow-up examination. The total retention rate, irrespective of the test groups, was 82.8%. Restorations placed without any preparation showed the highest loss rate (27.8%). Esthetic appearance, marginal adaptation, anatomic form and marginal discoloration did not differ significantly between the groups. Composites are long-term stable materials for restoring NCCLs. Restorations placed without any dentin preparation (cavity cleaning only) showed the highest loss rate.

Comparison of the shear bond strength of 3D printed temporary bridges materials, on different types of resin cements and surface treatment.

BACKGROUND: Thus, purpose of this study was to compare the shear bond strength of the resin cement and the resin modified glass ionomer cement on 3D printed temporary material for crowns and bridges in combination with different surface treatment modalities. MATERIAL AND METHODS: Test specimens VarseoSmile Temp material (Bego, Bremen, Germany) (n=64) in the form of rectangular blocks (n=32) and cylindrical test specimens (n=32) were printed using the Varseo S 3D printer (Bego, Bremen, Germany). The specimens were divided into 4 groups, with 8 specimens of each kind. Two groups (n=16 pairs) were blasted with Perlablast® Micro [PM] 50µm (Bego, Bremen, Germany) and two groups (n=16 pairs) were blasted with alumina [AL] 50µm. The cylindric specimen were cemented on the rectangular block with a load of 20N using a Zwick/Roell machine (Ulm, Germany), to ensure a comparable cementing process. One group (n=8) of each pre-treatment was cemented with Fuji Cem 2 [Fuji+AL & Fuji+PM] and one of each with Variolink® Esthetic [Vario+AL & Vario+PM]. The Fuji Cem 2 was chemically cured while dual curing Variolink® Esthetic was additionally light cured using LED (Bluephase II, Ivoclar Vivadent, Ellwagen, Germany; light intensity, >1,000 mW/cm2, high power modus). The shear strength was performed with Zwick/Roell universal test machine (speed, 0.8 mm/min), fracture and statistical analysis was performed (T-test, p<0.05). RESULTS: T-test showed a significant difference Fuji Cem 2 (Fuji+AL & Fuji&PM) and Variolink® Esthetic (Vario+AL &Vario+PM) (p=0.000). Fuji+AL & Fuji+PM showed a significant difference for surface pre-treatment (p=0.002). Vario+AL & Vario+PM no significance (p=0.872) for pre-treatment method was detectable. CONCLUSIONS: Variolink® Esthetic showed a higher bond strength compared to Fuji Cem 2 and an increasing bond strength for Fuji Cem 2 with alumina pre-treatment. There was no significant difference for Vario+AL and Vario+PM. Key words:Shear bond strength, adhesion, adhesive resin cement, resin modified glass ionomer cement, 3D printable materials, mechanical testing, provisional restoration.

Luting of CAD/CAM ceramic inlays: direct composite versus dual-cure luting cement.

The aim of this study was to investigate bonding effectiveness in direct restorations. A two-step self-etch adhesive and a light-cure resin composite was compared with luting with a conventional dual-cure resin cement and a two-step etch and rinse adhesive. Class-I box-type cavities were prepared. Identical ceramic inlays were designed and fabricated with a computer-aided design/computer-aided manufacturing (CAD/CAM) device. The inlays were seated with Clearfil SE Bond/Clearfil AP-X (Kuraray Medical) or ExciTE F DSC/Variolink II (Ivoclar Vivadent), each by two operators (five teeth per group). The inlays were stored in water for one week at 37°C, whereafter micro-tensile bond strength testing was conducted. The micro-tensile bond strength of the direct composite was significantly higher than that from conventional luting, and was independent of the operator (P<0.0001). Pre-testing failures were only observed with the conventional method. High-power light-curing of a direct composite may be a viable alternative to luting lithium disilicate glass-ceramic CAD/CAM restorations.

Interfacial fracture toughness of aged adhesive-dentin interfaces.

OBJECTIVE: To assess interfacial fracture toughness of different adhesive approaches and compare to a standard micro-tensile bond-strength (µTBS) test after 6 months water storage. METHODS: Chevron-notched beam fracture toughness (CNB) was determined using a modified ISO 24370:2005 standard. Adhesive-dentin micro-specimens (1.0 mm × 1.0 mm × 8-10 mm) were stressed in tensile until failure to determine the micro-tensile bond strength (µTBS). RESULTS: The highest mean µTBS and interfacial fracture toughness were measured for the multi-step adhesives Clearfil SE Bond (Kuraray Noritake) and OptiBond FL (Kerr). While large differences were observed in the bond strength values (from 7.4 to 27.2 MPa) of the one-step self-etch adhesives tested, interfacial fracture toughness was less different (from 0.7 to 1.0 MPam(1/2)). The adhesive with the lowest mean toughness (All-bond Universal, Bisco) had however the highest Weibull reliability, which might be a better parameter in regard to more consistent clinical performance. The self-adhesive composite Vertise Flow (Kerr) scored significantly lower at all levels. SIGNIFICANCE: Although the ranking of the adhesives tested using CNB and µTBS corresponded well, the outcome of CNB appeared more reliable and less variable.

3D-microleakage assessment of adhesive interfaces: exploratory findings by µCT.

OBJECTIVES: To explore the feasibility of a 3D-microleakage protocol for the evaluation of various configurations of adhesive-tooth interfaces. METHODS: Three different kinds of specimens were prepared: (1) a Class-I composite restoration placed without any bonding to maximize gap formation at the interface; (2) a glass-fiber post cemented with a self-adhesive composite cement into a prepared root canal; and (3) inlay MOD composite restorations placed with either a 1-step self-adhesive or a 2-step etch-and-rinse composite cement. After silver-nitrate (AgNO3) infiltration, the specimens were scanned using a Skyscan 1172 X-ray microtomograph (µCT; Skyscan Bruker) at 100kV, 100µA and 7.8-9.5µm resolution. Projection images were reconstructed, after which maximum-intensity projections (MIPs) and 3D-volumetric renderings were produced. For the inlays, an additional conventional stereomicroscopic (SM) microleakage evaluation was accomplished after specimen sectioning. RESULTS: MIPs and 3D-renderings from specimens (1) and (2) revealed strongly varying microleakage patterns along the marginal gap/interface. For the specimens of setup (3), the high radiopacity of the 2-step composite cement hindered evaluation of the MIPs. MIP-microleakage patterns along the enamel margin of the restoration cemented with the 1-step composite cement corresponded well to the stereomicroscopic images. SIGNIFICANCE: The reported µCT-protocol revealed good sensitivity to detect AgNO3 infiltration at the adhesive-tooth interface when considerable microleakage was present. When microleakage was less apparent and spread in a more diffuse pattern, evaluation with µCT was less sensitive compared to stereomicroscopic evaluation.

Curing mode affects bond strength of adhesively luted composite CAD/CAM restorations to dentin.

OBJECTIVES: To determine the effect of curing mode and restoration-surface pre-treatment on the micro-tensile bond strength (µTBS) to dentin. METHODS: Sandblasted CAD/CAM composite blocks (LAVA Ultimate, 3M ESPE) were cemented to bur-cut dentin using either the etch & rinse composite cement Nexus 3 ('NX3', Kerr) with Optibond XTR ('XTR', Kerr), or the self-etch composite cement RelyX Ultimate ('RXU', 3M ESPE) with Scotchbond Universal ('SBU', 3M ESPE). All experimental groups included different 'curing modes' (light-curing of adhesive and cement ('LL'), light-curing of adhesive and auto-cure of cement ('LA'), co-cure of adhesive through light-curing of cement ('AL'), or complete auto-cure ('AA')) and different 'restoration-surface pre-treatments' of the composite block (NX3: either a silane primer (Kerr), or the XTR adhesive; RXU: either silane primer (RelyX Ceramic Primer, 3M ESPE) and SBU, or solely SBU). After water-storage (7 days, 37°C), the µTBS was measured. Additionally, the degree of conversion (DC) of both cements was measured after 10min and after 1 week, either auto-cured (21°C/37°C) or light-cured (directly/through 3-mm CAD/CAM composite). RESULTS: The linear mixed-effects model (α=0.05) revealed a significant influence of the factors 'curing mode' and 'composite cement', and a less significant effect of the factor 'restoration-surface pre-treatment'. Light-curing 'LL' revealed the highest µTBS, which decreased significantly for all other curing modes. For curing modes 'AA' and 'AL', the lowest µTBS and a high percentage of pre-testing failures were reported. Overall, DC increased with light-curing and incubation time. SIGNIFICANCE: The curing mode is decisive for the bonding effectiveness of adhesively luted composite CAD/CAM restorations to dentin.

Composite cements benefit from light-curing.

OBJECTIVE: To investigate the effect of curing of composite cements and a new ceramic silanization pre-treatment on the micro-tensile bond strength (µTBS). METHODS: Feldspathic ceramic blocks were luted onto dentin using either Optibond XTR/Nexus 3 (XTR/NX3; Kerr), the silane-incorporated 'universal' adhesive Scotchbond Universal/RelyX Ultimate (SBU/RXU; 3M ESPE), or ED Primer II/Panavia F2.0 (ED/PAF; Kuraray Noritake). Besides 'composite cement', experimental variables were 'curing mode' ('AA': complete auto-cure at 21°C; 'AA*': complete auto-cure at 37°C; 'LA': light-curing of adhesive and auto-cure of cement; 'LL': complete light-curing) and 'ceramic surface pre-treatment' ('HF/S/HB': hydrofluoric acid ('HF': IPS Ceramic Etching Gel, Ivoclar-Vivadent), silanization ('S': Monobond Plus, Ivoclar-Vivadent) and application of an adhesive resin ('HB': Heliobond, Ivoclar-Vivadent); 'HF/SBU': 'HF' and application of the 'universal' adhesive Scotchbond Universal ('SBU'; 3M ESPE, only for SBU/RXU)). After water storage (7 days at 37°C), ceramic-dentin sticks were subjected to µTBS testing. RESULTS: Regarding the 'composite cement', the significantly lowest µTBSs were measured for ED/PAF. Regarding 'curing mode', the significantly highest µTBS was recorded when at least the adhesive was light-cured ('LA' and 'LL'). Complete auto-cure ('AA') revealed the significantly lowest µTBS. The higher auto-curing temperature ('AA*') increased the µTBS only for ED/PAF. Regarding 'ceramic surface pre-treatment', only for 'LA' the µTBS was significantly higher for 'HF/S/HB' than for 'HF/SBU'. SIGNIFICANCE: Complete auto-cure led to inferior µTBS than when either the adhesive (on dentin) or both adhesive and composite cement were light-cured. The use of a silane-incorporated adhesive did not decrease luting effectiveness when also the composite cement was light-cured.

Use of elaborate feedback and an audience-response-system in dental education.

INTRODUCTION: The aim of the study was to examine the effect of an elaborate feedback and an audience response system (ARS) on learning success. METHODS: Students of the 1st clinical semester were randomly assigned to a study and a control group. The randomization was carried out considering the factors of age, gender and power spectrum during preliminary dental examination. Within 10 lectures 5 multiple-choice questions were asked about the learning objectives and answered by the students using an ARS. Only the study group received an immediate comprehensive feedback on the results. A final exam at the end was carried out in order to evaluate whether the elaborate feedback leads to a successful learning. Furthermore the effect of the ARS on the lecture atmosphere was investigated. RESULT: The results of the final exams showed no significant difference between the study and the control group regarding the learning success. CONCLUSION: Although no significant effect on learning success was found, the ARS creates a more interactive, positive learning environment.

Potential smear layer interference with bonding of self-etching adhesives to dentin.

PURPOSE: To evaluate the effect of smear-layer interposition on the bonding effectiveness of self-etching adhesives with different etching potential. MATERIALS AND METHODS: Bur-cut dentin specimens were obtained from 25 human molars after preparation of the dentin surface with a medium-grit diamond bur (bur-cut). An additional 25 molars were fractured at the midcoronal dentin to create a smear-layer-free surface (smear-free dentin). The prepared teeth were assigned to 5 groups, according to the adhesive to be applied: a strong one-step self-etching adhesive (PLP, Adper Prompt L-Pop, 3M ESPE, pH = 0.8); two ultra-mild one-step self-etching adhesives (C3S, Clearfil Tri-S Bond, Kuraray, pH = 2.7; AEB, Adper Easy Bond, 3M ESPE; pH = 2.7 ); as the self-etching control, a mild two-step self-etching adhesive (CSE, Clearfil SE Bond, Kuraray, pH of primer = 1.9); and as the etch-and-rinse control, a three-step etch-and-rinse adhesive (OFL, Optibond FL, Kerr). After composite buildups were made, all specimens were stored in distilled water (24 h/37°C) prior to microtensile bond strength testing (µTBS). The failure mode was determined with a stereomicroscope at 50X magnification. Representative µTBS specimens were processed for analysis in a Feg-SEM. The Kruskal-Wallis test was performed to determine statistical differences (p < 0.05). RESULTS: Except for the strong one-step self-etching adhesive, all other self-etching adhesives (mild and ultramild) revealed a significantly lower bond strength to bur-cut dentin than to smear-free dentin. The etch-and-rinse adhesive presented the highest µTBS, which was not significantly different when bonded to bur-cut or smear-free dentin. Fracture analysis demonstrated a prevalence of adhesive failures for the self-etching adhesives, while OFL revealed more mixed failures. SEM revealed that smear debris remained part of the adhesive interfacial complex produced by the ultra-mild one-step self-etching adhesive C3S when applied on bur-cut dentin. CONCLUSION: Smear debris interferes with the interaction of mild and ultra-mild self-etching adhesives with dentin.

Does inhibition of proteolytic activity improve adhesive luting?

Endogenous enzymes may be involved in the biodegradation of adhesive restoration-tooth interfaces. Inhibitors of matrix metalloproteinases (MMPs) have been suggested to retard the bond-degradation process. Limited data are available on whether composite cements may also benefit from MMP inhibitors. Therefore, the aim of this study was to determine the effect of two MMP inhibitors--chlorhexidine digluconate (CHX) and galardin--on the microtensile bond strength (µTBS) of two self-adhesive composite cements to dentin. Ceramic specimens were cemented to bur-cut dentin surfaces using the self-adhesive composite cements RelyX Unicem 2 (3M ESPE) or Clearfil SA (Kuraray), or the etch-and-rinse composite cement Nexus 3 (Kerr) that served as the control. The surfaces were left untreated or were pretreated with MMP inhibitors (2% CHX or 0.2 mM galardin). The µTBS was determined 'immediately' and upon ageing (water storage for 6 months). Statistical analysis revealed a significant effect of the factors 'composite cement' and 'storage', as well as all interactions, but no effect of the MMP inhibitors. After 6 months of ageing, the µTBS decreased for all cements, except for the multistep etch-and-rinse luting composite when it was applied without MMP inhibitors. The MMP inhibitors could not prevent the decrease in µTBS upon ageing and therefore do not improve the luting durability of the composite cements tested.

Hydrolytic stability of three-step etch-and-rinse adhesives in occlusal class-I cavities.

OBJECTIVES: A dental adhesive without small and hydrophilic monomers such as 2-hydroxyethyl methacrylate (HEMA) and triethylene glycol dimethacrylate (TEGDMA) would be beneficial in order to avoid contact allergies. However, these monomers are important to increase infiltration and polymerization of the adhesive. Therefore, the purpose of this study was to evaluate the bonding effectiveness and bond durability of a more hydrophobic and biocompatible adhesive as compared to a conventional three-step etch-and-rinse adhesive. METHODS: Sixteen non-carious human third molars were used to determine the micro-tensile bond strength testing (µTBS) and interfacial ultrastructure by transmission electron microscopy (TEM) of the more hydrophobic cmf adhesive system (Saremco) adhesive as compared to the control OptiBond FL (Kerr). RESULTS: The more hydrophobic and biocompatible three-step etch-and-rinse adhesive was able to produce a reasonable short-time bonding effectiveness. In the long term, the collagen fibrils in the hybrid layer were not effectively protected and were prone to hydrolytic degradation. As a result, long-term bonding effectiveness of this novel adhesive was very low. CONCLUSIONS: Application of a more hydrophobic adhesive without altering the application procedure considerably results in a reduced durability of the created bond CLINICAL RELEVANCE: Omitting small and hydrophilic components from the adhesive formulation may impair the durability of your composite restoration.

Comparison of the push-out strength of two fiber post systems dependent on different types of resin cements.

The purpose of this study was to compare the push-out strength of glass fiber posts dependent on the resin cement. One hundred human teeth were divided into five groups (n = 20). Two glass fiber post systems (DT Light SL (DTSL) and RelyX Fiber Post (RF)) were used. DTSL posts were cemented with one "etch & rinse" system (ER) or one of three self-adhesive resin cements (SA). The RF posts were cemented with RelyX Unicem. Afterwards, half of the specimens were thermocycled (TC; 5°C/55°C, 5,000 cycles). All specimens were cut into disks (thickness, 2 mm). The push-out test was performed (crosshead speed, 1 mm/min), fracture types were determined (×25 and ×40 magnification), and statistical analysis was performed (one-way analysis of variance (ANOVA), Scheffe test, p < 0.05). One-way ANOVA showed a significant influence of the resin cement on the push-out strength of the glass fiber posts before thermocycling (p < 0.001). After TC, no significant differences were detected. Microscopic evaluation showed mainly adhesive failures between post and cement for ER or mixed fractures for SA. The bond strength of adhesively cemented glass fiber posts is not dependent on the type of resin cement after TC. The use of SA can lead to bond strength values comparable to ER. Self-adhesive resin cements could be used just as well as resin cements with "etch & rinse" adhesive systems for the cementation of glass fiber posts.

Conservative treatment of periodontal recessions with class V-defects using gingiva-shaded composite--A systematic treatment concept.

UNLABELLED: Periodontal recessions can cause aesthetic and functional problems, especially in the anterior region or when combined with exposed crown margins. A combination of periodontal disease, recession with exposed root surface, hard-tissue defects and age emphasizes the need for treating these defects. If crown margins are exposed and surgical treatment is not possible, aesthetics and function can only be improved by replacement of the restoration. The restorative treatment option with a gingiva-shaded composite is especially valuable for dental fear patients or older patients with general or local risk factors, surgical contra-indications or Class III and IV recessions with questionable prognosis of surgery. The step-by-step-approach described in this article is an alternative, minimal-invasive treatment concept for cervical lesions in combination with all kinds of periodontal recessions, that is especially suitable for wedge-shaped defects next to exposed crown margins. CLINICAL RELEVANCE: With this treatment concept, the reader should be able to use gingiva-shaded composite for different indications, such as exposed root surfaces or crown margins in combination with recessions.

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."

Repairability of dental siloranes in vitro.

OBJECTIVES: Aim of the study was the investigation of the repairability of a silorane (Filtek Silorane, 3M Espe, Seefeld, Germany) after different surface pretreatments in vitro. METHODS: 54 silorane specimens (5 mm × 5 mm × 5 mm) were fabricated and stored in saline solution (24 h/37°C). Their surface was polished with abrasive paper (600 grit), etched with phosphoric acid (10 s) and rinsed with water (30 s). Repair was performed with a silorane based on one of the 9 treatment protocols (each n=6): no additional treatment (NAT), silorane primer (P) and silorane bond (B), B only, sandblasting (SB), SB plus P/B, SB plus B, CoJet and silane (CJ), CJ plus P/B, CJ plus B. Whole silorane specimens (5 mm × 5 mm × 10 mm) with no repair served as control. Specimens were sectioned and microtensile bond strength (µTBS) was measured (30 beams per group, surface area approx. 1.2 mm², crosshead-speed 1 mm/min) statistical analysis (ANOVA, Tukey HSD, p<0.05) was performed. RESULTS: µTBS of the specimens was significantly influenced by the surface pretreatment (p<0.001). The highest µTBS was determined for CJ/B and SB/B, which were not significantly different from the control. NAT, SB and CJ benefited from an additional treatment with B (p<0.01). The additional use of P did not improve µTBS, but was detrimental for the SB and CJ groups (p<0.05). SIGNIFICANCE: Siloranes can be repaired with either SB or CJ in combination with a silorane bond, the additional use of silorane primer is disadvantageous.

Shear bond strength of self-etch adhesives to enamel with additional phosphoric acid etching.

This study evaluated the shear bond strength of self-etch adhesives to enamel and the effect of additional phosphoric acid etching. Seventy sound human molars were randomly divided into three test groups and one control group. The enamel surfaces of the control group (n=10) were treated with Syntac Classic (SC). Each test group was subdivided into two groups (each n=10). In half of each test group, ground enamel surfaces were coated with the self-etch adhesives AdheSe (ADH), Xeno III (XE) or Futurabond NR (FNR). In the remaining half of each test group, an additional phosphoric acid etching of the enamel surface was performed prior to applying the adhesives. The shear bond strength was measured with a universal testing machine at a crosshead speed of 1 mm/minute after storing the samples in distilled water at 37 degrees C for 24 hours. Fracture modes were determined by SEM examination. For statistical analysis, one-way ANOVA and the two-sided Dunnett Test were used (p>0.05). Additional phosphoric etching significantly increased the shear bond strength of all the examined self-etch adhesives (p<0.001). The highest shear bond strength was found for FNR after phosphoric acid etching. Without phosphoric acid etching, only FNR showed no significant differences compared to the control (SC). SEM evaluations showed mostly adhesive fractures. For all the self-etch adhesives, a slight increase in mixed fractures occurred after conditioning with phosphoric acid. An additional phosphoric acid etching of enamel should be considered when using self-etch adhesives. More clinical studies are needed to evaluate the long-term success of the examined adhesives.