The Journal of Adhesive Dentistry, 02/2013

Purpose: To evaluate the composite-to-enamel bond following double etching of the enamel using phosphoric acid and different self-etching (SE) bonding systems with and without the application of their respective acidic primers. Materials and Methods: The enamel surfaces of 90 human molars were ground (600 grit) flat and randomly divided into nine groups (n = 10). Three two-step SE systems (AdheSE, ASE; Clearfil SE Bond, CSE; OptiBond Solo Plus SE, OSE) were tested, both with and without primer application on enamel pre-etched with phosphoric acid under dry bonding conditions. As the controls, the SE systems were applied according to their original directions without pre-etching. All the specimens were built up with a microhybrid composite resin (Arabesk Top). After water storage for 24 h at 37°C, the bonded specimens were sheared to failure in the Zwicki 1120. Etching and failure patterns were evaluated using a scanning electron microscope (SEM). Shear bond strength was analyzed with two-way ANOVA and Tukey's test. Failure modes were analyzed with Fisher's exact test. Results: Without pre-etching, CSE showed significantly higher bond strengths than ASE and OSE (p 0.05). Enamel etching prior to the application of the SE systems tended to result in higher bond strengths, but significantly increased the values only for ASE (p 0.05). Contamination of the pre-etched enamel with the SE primer decreased the bond strength by values of 19% for ASE (p > 0.05), 36% for CSE (p 0.05), and 75% for OSE (p 0.05). SEM analysis showed that omission of the priming step significantly increased the number of cohesive failures within the resin for OSE (p 0.0001). Conclusion: Additional etching with phosphoric acid before the application of SE systems does not necessarily result in better enamel bonding, since unavoidable primer contamination of the pre-etched enamel was shown to significantly reduce the bond strength for two of the three systems tested. Keywords: bond strength, enamel, adhesive resin, phosphoric acid-etching, self-etching, primer contamination

Purpose: To evaluate the effect of layer thickness of flowable composites on the marginal adaptation of Class II fillings after thermomechanical loading (TML). Materials and Methods: Sixty standardized Class II box cavities were prepared under simulation of intrapulpal pressure with gingival margins located 1 mm below the cementoenamel junction (CEJ) in dentin. The samples were evenly distributed into six groups (A to F). After adhesive (XPBond) application, box preparations were filled with a first increment of either a nanohybrid composite (A, D) Ceram•X mono, or with one of two flowable materials SDR (B, E) or x-Flow (C, F). The first increments were 1 (A,B,C) or 4 mm (D,E,F) thick. All cavities were finally filled incrementally with Ceram•X mono. Replicas were prepared before and after TML (1.2 x 106 cycles; 5/50°C; maximum load 49 N). Replicas were evaluated for marginal adaptation (tooth/composite) using scanning electron microscopy (200X). The percentage of continuous margins was compared between and within groups before and after TML using ANOVA and Scheffé's post-hoc tests. Results: For group F before TML, adaptation of cervical margins located in dentin was compromised compared to the other groups (p 0.05). After TML, at the same location, group F showed significantly worse adaptation compared with groups A to C and E (p 0.05), but no difference to group D was found. The marginal integrity of all interfaces before and after TML was significantly worse in group F compared with all other groups (p 0.05). Conclusion: Different flow application techniques for Class II cavities have an influence on the marginal adaptation (before/after TML). Applying a 4-mm first increment, both Ceram•X mono and SDR showed no differences vs groups in which the first increment was 1 mm thick. Keywords: Class II cavities, flowable composite, incremental technique, SDR, UEDMA

Purpose: To assess the shear bond strength to unground human enamel (ESBS) and flexural strength (FS) of different reinforcing fibers used in combination with a flowable composite resin. Materials and Methods: For ESBS testing, 90 human molars were selected and randomly divided into 9 groups (n = 10) according to the reinforcing fiber to be tested: 1. RTD Quartz Splint additionally impregnated at chairside with Quartz Splint Resin (RTD); 2. RTD Quartz Splint without additional impregnation; 3. Ribbond-THM (Ribbond) impregnated with OptiBond FL Adhesive; 4: Ribbond Triaxial (Ribbond) impregnated with OptiBond FL Adhesive; 5. Connect (Kerr) impregnated with OptiBond FL Adhesive; 6. Construct (Kerr) impregnated with Opti- Bond FL Adhesive; 7. everStick PERIO (Stick Tech); 8. everStick C&B (Stick Tech); 9. nonreinforced composite Premise flowable (Kerr). Cylinders of flowable composite reinforced with the fibers were bonded to the intact buccal surface of the teeth. After 24 h of storage, shear loading was performed until failure occurred. FS was assessed performing three-point bending test according to ISO Standard 4049/2000. ESBS and FS data were analyzed using one-way ANOVA, followed by Tukey's HSD test for post-hoc comparisons (p 0.05). Results: For each group, the ESBS and FS, respectively, in MPa were: 1. 17.07 ± 4.52 and 472.69 ± 30.49; 2. 14.98 ± 3.92 and 441.77 ± 61.43; 3. 18.59 ± 5.67 and 186.89 ± 43.89; 4. 16.74 ± 6.27 and 314.41 ± 148.52; 5. 14.38 ± 4.14 and 223.80 ± 77.35; 6. 16.00 ± 5.55 and 287.62 ± 85.91; 7. 16.42 ± 3.67 and 285.35 ± 39.68; 8. 23.24 ± 5.81 and 370.46 ± 29.26; 9. 12.58 ± 4.76 and 87.75 ± 22.87. For most fibers, no significant difference in ESBS was found compared to the control group, except for everStick C&B, which yielded higher ESBS. Nonreinforced composite exhibited the lowest FS, while all fibers positively affected the FS. Conclusions: Fiber reinforcement of flowable composite does not affect its ESBS. The flexural strength of FRCs is significantly influenced by fiber composition and pattern. Keywords: fiber-reinforced composite, bond strength, enamel, flexural strength

Purpose: To evaluate the fracture strength of inlay-retained, surface-retained, and cantilevered fiber-reinforced adhesively fixed dental prostheses (FRA-FDPs) in the anterior region. Materials and Methods: Thirty-two sound human right central incisors and canines were divided into four groups. Test groups were as follows: group 1, both teeth had deep cavity preparation; group 2, both teeth had shallow cavity preparation; group 3, only the canine teeth had deep cavity preparation; group 4, no preparation was made on the abutment teeth. Lateral pontics were restored with FRA-FDPs. All restorations were subjected to fracture loading from the lateral pontic. The restorations were tested in a universal testing machine (LRX Material Testing Machine) with a crosshead speed of 1 mm/min. One-way ANOVA was used for statistical analyses. Fracture modes were examined visually. Results: The highest (667.3 ± 90.4 N) and the lowest (409.3 ± 158.1 N) debonding values were found for groups 4 and 3, respectively. Conclusions: Different preparation designs (inlay-retained, surface-retained) had no significant effect on fracture strength of FRA-FDPs in the anterior region. However, a cantilever design exhibited significantly lower fracture strength. Delamination of the veneering composite was observed as the primary failure type after fracture tests. Keywords: fracture strength, adhesive FDPs, fiber-reinforced composites

Purpose: To evaluate the effect of two adhesive systems and different aging protocols on the bond strength of a -repaired microhybrid composite. Materials and Methods: Eighty test specimens (n = 20) and 10 control specimens measuring 8 x 4 mm were fabricated of a microhybrid composite (4 Seasons, shade A2) and grouped according to time/aging protocol: G1: 24 h in artificial saliva; G2: 7 days in artificial saliva; G3: 30 days in artificial saliva; G4: artificial accelerated aging (AAA) for 384 h; G5: control. After aging, samples were submitted to three types of surface treatment: SB2: Adper Single Bond 2, a two-step adhesive (3M ESPE); SB3: Adper Scotchbond Multi-Purpose, a three-step adhesive (3M ESPE); C: without application of adhesive (control). After this, test specimens were repaired with the same composite of a different shade (C3), and submitted to the microtensile test at a crosshead speed of 0.5 mm/min. Failure modes were analyzed by scanning electron microscopy (Jeol JSM 7500). Statistical analysis was performed using ANOVA and Tukey's test (p 0.05). Results: G2/SB2 presented significantly lower bond strength values in comparison with the other groups (p 0.05). The control group presented the highest bond strength values, which differed statistically significantly from SB3, G3/SB2, and G4/SB2 (p 0.05). Fractographic analysis demonstrated that most samples presented predominantly cohesive failures, excepting GI/SB2, which presented mixed and cohesive failures, and G4/SB2 and G1/SB3, which showed adhesive failures. Conclusion: The repair was more effective when performed after a short period of time and when the 3-step adhesive system (SB3) was used. Keywords: dental materials, composites, bond strength, artificial aging

Purpose: To evaluate the microshear bond strength of resin cements to yttrium-stabilized tetragonal zirconium oxide surfaces after water storage for 24 h or 1 year. Materials and Methods: Four self-adhesive (BisCem, G-Cem, RelyX Unicem, SeT) and one conventional resin cement (RelyX ARC) were tested. The materials were mixed and inserted in tubes (0.75 mm diameter × 1 mm height) that were placed over the zirconium oxide surface. Specimens were tested after 24-h or 1-year water storage. Microshear testing was performed using a universal testing machine. Shear bond strength results were analyzed using two-way ANOVA and Tukey's test (5%). Results: After 24-h water storage, no difference was found between G-Cem and RelyX Unicem resin cements; however, their bond strength means to zirconium oxide were statistically higher than RelyX ARC. The bond strength values of all resin cements dropped significantly after 1 year of water storage. G-Cem presented the highest values among cements after long-term water exposure. Conclusions: One-year water storage decreased the microshear bond strengths to zirconium oxide for all resin cements tested. Keywords: resin cement, zirconium oxide, bond strength

Purpose: To compare the effect of silica (Si)-based nano-coating deposited by reactive magnetron sputtering (RMP) with that of conventional surface conditioning using metal/zirconia primer alone or after air-particle abrasion on the adhesion of resin cements to zirconia ceramic. Materials and Methods: Two hundred forty zirconia ceramic blocks (Cercon) were sintered, finished with 1200- grit SiC paper under water cooling, and cleaned ultrasonically in distilled water for 10 min. The blocks (4.5 mm x 3.5 mm x 4.5 mm) were randomly divided into 24 groups (n = 10) according to 3 testing parameters: a) resin cements (Multilink, Panavia F, RelyX U100), b) surface conditioning (no conditioning as control group; Metal/Zirconia Primer; air abrasion + Metal/Zirconia Primer; Si-based nanofilm + Monobond s); c) aging (no aging vs thermocycling at 5°C to 55°C, 6000 cycles). The nanofilm was deposited by direct current using argon/oxygen plasma (8:1 in flux) on the zirconia surface. Resin cements were bonded to zirconia surfaces using polyethylene molds. The shear bond strength (SBS) test was performed using a universal testing machine (1 mm/min), and after debonding, the substrate and adherent surfaces were analyzed using optical and scanning electron microscopes to categorize the failure types. The data were statistically evaluated using 3-way ANOVA and Tukey's test (5%). Results: Resin cement type (p 0.05), surface conditioning method (p 0.05), and aging condition (p 0.05) had a significant effect on the bond strength results. Interactions were also significant (p 0.05). In the nonaged condition, while control groups presented the lowest results with all cements (0 to 5.2 MPa), the airabraded group in combination with RelyX U100 resulted in the highest SBS (21.8 ± 6.7 MPa). After aging, the SBS results decreased in the air-abraded groups for all cements (4.54 to 9.44 MPa) and showed no statistical significance compared to the Si-based nanocoated groups (4.24 to 6.44 MPa). After air-abrasion and primer application, only Panavia F and RelyX U100 cements showed exclusively mixed failures, but after nanofilm coating and silanization, all cements showed exclusively mixed failures with and without aging. Conclusion: Chemical adhesion of the resin cements tested to zirconia was similar after silica-based nanofilm deposition and air abrasion followed by primer application. Keywords: adhesion, bond strength, nanocoating, nanofilm, plasma coating, reactive magnetron sputtering, silica, Y-TZP, zirconia, zirconia primer

Purpose: To compare the push-out bond strength of a new glass fiber root canal filling material to that of Resilon/ Epiphany, EndoREZ, and gutta-percha/AH Plus root canal filling materials. Materials and Methods: Sixty roots were randomly divided into four groups (n = 15) according to the obturation material: group 1, Resilon/Epiphany (RE) (Pentron Clinical Technologies); group 2, gutta-percha/AH Plus (GP) (Dentsply DeTrey); group 3, EndoREZ obturation system (ER) (Ultradent); and group 4, glass fiber root canal filling (GF) (Stick Tech) and dual-curing resin sealer (MetaSeal, Parkell). Two-mm-thick horizontal sections from the coronal, middle, and apical thirds of each root were sliced for the push-out bond strength measurement. Results: GF showed the significantly highest mean bond strength values at the coronal and middle thirds. At the apical third, GF showed significantly higher bond strength values than did RE and ER. However, there was no significant difference at the apical third between the GF and GP groups. The lowest bond strength values were recorded for ER. Conclusion: Glass fiber root canal filling material seems to provide promising bond strength to root canal dentin. Keywords: glass fiber, push-out bond strength, adhesion in root canal

Purpose: To compare the in vitro fracture resistance of endodontically treated molars with mesio-occluso-distal (MOD) cavities restored with two different types of fibers. Materials and Methods: Sixty extracted human mandibular first molars were selected for the study and randomly assigned to six groups (n = 10). Group 1 served as the control. In groups 2 through 6, endodontic access and standard MOD cavities were prepared. Following root canal treatment, group 2 was left unrestored. In group 3, the teeth were restored with composite resin (Venus, Heraeus Kulzer). In group 4, flowable composite resin (Venus, Heraeus Kulzer) was used before restoring the teeth with composite resin. In group 5, leno-woven ultrahigh molecular weight polyethylene ribbon fiber (Ribbond) was inserted in the flowable resin in a buccal to lingual direction, and the teeth were then restored with composite resin. In group 6, translucent glass fiber (Vectris, Ivoclar) was adapted over the flowable resin in the bucco-lingual direction and restored with composite resin. The specimens were stored in 100% humidity at 37°C for 1 day. Compressive loading of the teeth was performed using a universal testing machine at a crosshead speed of 0.5 mm/min. The mean load necessary to fracture the samples was recorded in Newtons (N). Data were subjected to analysis of variance (ANOVA) and Duncan's post-hoc test, where significance was set at p 0.001. Results: The highest and the lowest mean fracture strengths were found in sound teeth (1598.8 N) and unrestored teeth (393.7 N), respectively. The mean load necessary to fracture the samples was 958.6 N in the polyethylene ribbon group (group 5), 913.2 N in the glass-fiber group (group 6), 699.7 N in teeth restored with flowable resin and composite (group 4), and 729.3 N in group 3 with composite resin alone. Statistical analysis showed significantly higher fracture resistance of both the fiber groups compared to composite resin alone (p 0.001). Conclusion: Both polyethylene ribbon and glass fiber under MOD composite restorations significantly increased fracture strength with no statistical difference between the two groups. Therefore, both polyethylene- and glassfiber- reinforced composites can be used for access cavity restorations in teeth with weakened cusps. Keywords: composite resin, endodontic therapy, fracture resistance, polyethylene fiber, glass fiber, molars

Purpose: To examine the bond strength and interfacial nanoleakage expression of fiber posts luted to intraradicular dentin with self-adhesive cements. Six-month and 1-year aging effects were examined. Materials and Methods: Post space was created in endodontically treated human incisors. Each tooth was assigned to a self-adhesive cement/post combination: (1) Bifix SE Cement (Voco) with proprietary posts (Rebilda Post, Voco), (2) RelyX Unicem (3M ESPE) with proprietary posts (Rely X Fiber Post, 3M ESPE), (3) MaxCem (Kerr) with Rebilda Posts. Each specimen was cut into 1-mm-thick sections and either immediately stressed to failure with the push-out bond strength test or aged in artificial saliva for 6 months or 1 year before testing. Additional specimens were processed for quantitative interfacial nanoleakage analysis using ammoniacal silver nitrate. Results: Immediate bond strength ranked in the following order: Bifix SE (7.8 ± 2.9 MPa) = RelyX Unicem (8.4 ± 2.7 MPa) > MaxCem (4.6 ± 2.4 MPa) (p 0.05). Aging significantly reduced the bond strength of all cements after 1 year: Bifix SE (3.8 ± 1.4 MPa) = RelyX Unicem (5.8 ± 1.7 MPa) > MaxCem (1.3 ± 0.9 MPa; p0.05). No immediate difference in interfacial nanoleakage expression was found. Nanoleakage increased after aging, and MaxCem showed the highest values. Conclusion: The push-out strength and interfacial nanoleakage expression of fiber posts luted with self-adhesive cements were dependent on luting material and type of post, and were significantly affected by storage time. Keywords: dentin, dentin bonding agents, fiber posts, self-adhesive cement, aging, nanoleakage analysis, push-out

Purpose: This randomized controlled split-mouth clinical trial evaluated the short-term survival rate of indirect resin composite and ceramic laminate veneers. Materials and Methods: A total of 10 patients (mean age: 48.6 years) received 46 indirect resin composite (Estenia; n = 23) and ceramic laminate veneers (IPS Empress Esthetic; n = 23) on the maxillary anterior teeth. Veneer preparations with incisal overlap were performed and existing resin composite restorations of good quality were not removed but conditioned using silica coating (CoJet) and silanization (ESPE-Sil). Enamel and dentin were etched and rinsed; adhesive resin (ExciTE) was then applied. After cementation (Variolink Veneer), restorations were evaluated at baseline and thereafter every 6 months for up to 3 years using modified USPHS criteria. Results: Seventeen laminate veneers were bonded onto intact teeth and 29 on teeth having existing resin composite restorations. In total, 3 failures were observed in the form of debonding (n = 1) and fracture (n = 2) in the group of resin composite laminate veneers. No significant difference was observed between the survival rates of composite and ceramic laminate veneers (Estenia: 87%, IPS Empress Esthetic: 100%; p > 0.05). The overall survival rate was 93.5% (Kaplan-Meier). Of the 43 laminate veneers, minor voids and defects were observed in 6 of the composite and 3 of the ceramic veneers. Slight staining at the margins (n = 3) and slightly rough surfaces were more frequently observed for the resin composite laminate veneers (n = 18) up to the final recall. Conclusion: Early findings of this clinical trial on two veneer materials showed statistically similar survival rates. Surface quality changes were more frequent in the composite veneer material. Keywords: adhesion, ceramic, ceramic aging, composite aging, dental materials, indirect composite, laminate veneers, randomized controlled clinical trial, silica coating, split mouth, surface conditioning