Resin Luting Agents Research Articles

The Effect of Surface Treatments on the Micro-shear Bond Strength of a Resin Luting Agent and Four All-ceramic Systems

The current study evaluated the micro-shear bond strength between a resin luting agent and four strengthened all-ceramic systems under different surface treatments. Rectangular specimens of IPS Empress 2 (Ivoclar-Vivadent), Cergogold (DeguDent), In Ceram Alumina (Vita) and Cercon (DeguDent) ceramics were fabricated and randomly divided into three groups: 1-no treatment; 2-etched with 9.5% hydrofluoric acid and 3-airborne-particle abraded with 50 microm aluminum oxide particles. The ceramic surfaces of the specimens were coated with a silane agent (Clearfil Porcelain Bond, Kuraray), then bonded with a resin-luting agent (Panavia F, Kuraray). A micro-shear bond test was carried out to measure the bond strength. Moreover, each ceramic surface was observed morphologically by scanning electron microscopy. The results were submitted to analysis of variance and Tukey's post-hoc analysis (p<0.05). The bond strength of all ceramic systems evaluated was affected by the surface treatments (p<0.05). The highest values for bond strength of IPS Empress 2 were found when the surface treatment used was hydrofluoric acid etching, followed by airborne particle abrasion treatment. On the other hand, airborne particle abrasion treatment and acid etching were not different for Cergogold and In Ceram Alumina ceramics, but they were higher when compared to the control (p<0.05). The highest bond strength to Cercon was found when it was treated with airborne particle abrasion with aluminum oxide. The SEM photographs showed that the hydrofluoric acid etching treatment affected the surface of IPS Empress 2 and Cergogold; however, Cercon and In Ceram surface morphology were not changed by the hydrofluoric acid etching. The airborne particle abrasion treatment altered the Cercon ceramic morphology but it did not change the other ceramic's surface.

Comparison of fracture resistance of pressable metal ceramic custom implant abutments with CAD/CAM commercially fabricated zirconia implant abutments

The adequacy of the strength of dental zirconia abutments under heavy occlusal load conditions is questionable, with degradation of the mechanical properties of zirconia having been reported. Therefore, some alternatives must be considered. The purpose of this study was to determine the efficacy of fabricating pressable metal ceramic custom implant (Pr) abutments, and to evaluate the fracture resistance of these abutments. Two groups of implant abutment specimens were fabricated (n=10). The experimental group consisted of Pr abutments, and the control group consisted of CAD/CAM-designed zirconia-based ceramic (Zr) abutments. For the experimental group, custom metal abutments were cast using a compatible metal alloy (Lodestar); this was followed by injection molding with lithium disilicate pressable ceramic (IPS e.max Press) around the metal column of the custom implant abutment. For the control group, 10 specimens were fabricated from CAD/CAM-designed zirconia abutments (Procera Zirconia). Following scanning, all-ceramic crowns with the average dimensions of a human central incisor were fabricated for the experimental and control abutments (n=20) using lithium disilicate pressable ceramic (IPS e.max Press). Each crown was cemented to the implant abutments with a resin luting agent (Variolink II). The crown-abutment test specimens were fixed to titanium implant analogs and placed in a test stand at 30 degrees from the vertical axis of the specimens in a computer-controlled universal testing device. The independent t test was used to detect if the mean values of the fracture load differed significantly (alpha=.05) between the 2 groups. The mean (SD) fracture load was significantly higher in the Pr group (901.67 (102.05) N) than in the Zr group (480.01 (174.46) N, P<.005). This study found that Pr abutments are stronger than Zr abutments.

Impact of immediate and delayed light activation on self-polymerization of dual-cured dental resin luting agents

This study investigated the impact of immediate and delayed light activation on self-polymerization of a model dual-cured luting agent. The material presented the following components: base paste – 2,2-bis[4-(2-hydroxy-3-methacryloxyprop-1-oxy)phenyl]propane/triethylene glycol dimethacrylate (TEGDMA), camphorquinone, dimethyl- p-toluidine, butylated hydroxytoluene (BHT), glass fillers; catalyst paste – bisphenol-A ethoxylated dimethacrylate/TEGDMA, benzoyl peroxide, BHT, fillers. The pastes were mixed and seven polymerization scenarios tested: immediate light activation using low (5 J cm −2) or high (20 J cm −2) energy dose; delayed light activation (after 2 min – short delay) using low or high dose; delayed light activation (after 10 min – long delay) using low or high dose; and self-polymerization only. The degree of conversion (DC) and rate of polymerization ( R p) were evaluated for 30 min by real-time infrared spectroscopy. The lowest DC was detected for the self-polymerized and immediate–low dose groups, whereas the immediate–high dose and short delay–high dose groups showed the highest values. For the self-polymerized and immediate–high dose samples, R p max was detected after approximately 7 s, whereas this took approximately 14 s for the immediate–low dose group. R p max for the immediate–high dose group was higher than for the self-polymerized sample, which in turn was higher than for the immediate–low dose group. R p max for the short delay groups was higher than for the long delay groups. In conclusion, the extent of self-polymerization was influenced by the light dose reaching the material, which was dependent on high radiant exposure for optimal polymerization and the moment at which the light was applied; the short delay increased the DC for lower doses, while also generally decreasing the R p for all scenarios.

Kinetic analysis of monomer conversion in auto- and dual-polymerizing modes of commercial resin luting cements

Lack of knowledge regarding the kinetics of the setting reaction of dual- and autopolymerizing resin luting agents (RLA) leads the clinician to underestimate the care required during occlusal adjustments of indirect restorations. The purpose of this study was to evaluate the degree of conversion (DC), maximum rate of polymerization (R(p)(max)), and potential of cure (ratio of conversions in autopolymerized relative to dual-polymerized modes; PC(A/D)) of 5 dual-polymerizable RLAs at 5 and 10 minutes, after mixing RLA components using infrared (IR) spectroscopy. The RLAs evaluated included Calibra, Duo-Link, Lute-It, Nexus 2, and RelyX ARC. The RLAs were manipulated and applied to the horizontal diamond element in the optical bench of an IR spectrometer. The materials were either light activated for 40 seconds (dual-polymerizing mode) or were allowed to autopolymerize (autopolymerizing mode). The DC, R(p)(max), and PC(A/D) were calculated using standard techniques of observing changes in aliphatic-to-aromatic peak ratios before and after polymerization. Data (n=5) were analyzed by 2-way repeated measures ANOVA and Tukey's post hoc test (alpha=.05). All autopolymerizing groups exhibited lower DC and R(p)(max) values than the dual-polymerizing groups (P<.001), and higher DC values at 10 minutes than at 5 minutes, only in the autopolymerizing mode. Duo-Link exhibited the highest R(p)(max) values among dual-polymerizing groups, while Lute-It and Calibra showed the lowest R(p)(max) values and the highest PC(A/D) values. Within autopolymerizing groups, Nexus 2 and Lute-It exhibited the highest R(p)(max) values, while RelyX ARC demonstrated the lowest R(p)(max) as well as the lowest PC(A/D) values. The DC values of all autopolymerized groups of RLAs were lower than those of the dual-polymerized RLAs, but the differences in R(p)(max) and PC(A/D) were product dependent. The DC of all products was higher at the 10-minute interval than at the 5-minute interval, only in the autopolymerizing mode.

The Effect of Different Adhesive Types and Curing Methods on Microleakage and the Marginal Adaptation of Composite Veneers

The aim of this in vitro study was to evaluate the influence of application techniques (with pre-curing vs without pre-curing) for dentin adhesive on microleakage and marginal adaptation of indirect composite veneer restorations. A total-etch bonding system, Excite/Variolink II (EXV), and a self-etching primer system, Panavia F2.0 (PF2), were used in the study. Forty-eight human central incisors were prepared for composite veneer restorations. The teeth were divided into two groups (n=24). For each resin cement, one half of each experimental group included an adhesive pre-cure (PC) with a halogen light source while the other half received no pre-cure (NPC) prior to resin cement insertion. Thus, four experimental groups were created: A (PC+EXV), B (NPC+EXV), C (PC+PF2), and D (NPC+PF2). Veneers made of Tetric Ceram resin composite were cemented using dual-cured resin luting agents. After storage in distilled water at 37 degrees C for 24 hours, the teeth were prepared for marginal leakage. Two samples of each group were selected at random for scanning electron microscopic (SEM) observation and evaluation of marginal adaptation at 1050x magnification. Data were analyzed using the Kruskal-Wallis and Mann-Whitney tests (a <0.05). The highest and lowest microleakage values were observed in dentinal margins of groups B and A, respectively. Dentin margins opposite to enamel margins had a significant difference in microleakage values of PC and NPC groups (P<0.05). The influence of the adhesive pre-cure was more pronounced than the type of resin cement used. No adhesive layer was visualized for the adhesives used without employing the pre-curing step. The effect of pre-cured adhesives was not material specific. The pre-cured adhesives showed the best resistance to dye penetration although the film thickness of these luting agents was only slightly increased. Different curing methods (with pre-curing/without pre-curing) regardless of total-etch or self-etch adhesive systems influenced microleakage and the marginal adaptation, especially dentin margins of indirect composite veneers.

Preparation and Evaluation of Dental Resin Luting Agents with Increasing Content of Bisphenol-A Ethoxylated Dimethacrylate

Resin luting agents in which bisphenol-A glycidyl dimethacrylate (Bis-GMA) and/or triethylene glycol dimethacrylate (TEGDMA) are replaced with increasing amounts of bisphenol-A ethoxylated dimethacrylate are prepared. Degree of conversion (DC), diametral tensile strength (DTS), Young's modulus (YM), Knoop hardness (KHN), film thickness (FT), water sorption (W(sp) ), and solubility are evaluated. Regression analyses investigate the substitution of each monomer. The most appreciable differences are detected when TEGDMA is replaced: decreased DC, DTS, and W(sp), and increased YM, KHN, and FT. For substitution of Bis-GMA, the only significant differences are reduced W(sp) and increased YM. An ideal formulation of resin cement would make use of the three monomers.

Marginal Adaptation of All‐Ceramic Crowns on Implant Abutments

Studies focusing on the marginal accuracy of all-ceramic crowns on implant abutments are in short supply. This study evaluated the marginal accuracy of all-ceramic crowns on different implant abutments. Ninety-six standardized maxillary central incisor crowns (48 alumina and 48 zirconia) were fabricated for each of the six test groups (n = 16) (Ti1, titanium abutments-alumina crowns; Ti2, titanium abutments-zirconia crowns; Al1, alumina abutments-alumina crowns; Al2, alumina abutments-zirconia crowns; Zr1, zirconia abutments-alumina crowns; Zr2, zirconia abutments-zirconia crowns). The crowns were adhesively luted using a resin luting agent. The marginal gaps were examined on epoxy replicas before and after luting as well as after masticatory simulation at 200x magnification. The geometrical mean (95% confidence limits) marginal gap values before cementation, after cementation, and after masticatory simulation were group Ti1: 39(37-42), 57(53-62), and 49(46-53); group Ti2: 43(40-47), 71(67-76), and 64(59-69); group Al1: 57(54-61), 87(85-90), and 67(65-69); group Al2: 66(63-69), 96(90-101), and 75(72-78); group Zr1: 54(51-57), 79(76-82), and 65(63-67); and group Zr2: 64(60-68), 85(80-91), and 75(70-81). The comparison between non-cemented and cemented stages in each group demonstrated a significant increase in the marginal gap values after cementation in all groups (p < .001), while the comparison between cemented and aged stages in each group showed a significant decrease in the marginal gap values in groups Al1, Al2, and Zr1 (p < .0001). This reduction was not significant for groups Ti1, Ti2, and Zr2 (p > .05). The marginal accuracy of all tested restorations meets the requirements for clinical acceptance.

Development of dental resin luting agents based on Bis-EMA4: bond strength evaluation

The aim of this study was to investigate the influence of incorporating Bis-EMA4 monomer into experimental Bis-GMA/TEGDMA-based resin luting agents on the bond strength to dentin. Seven mixtures were prepared with the fol- lowing ratios (wt%) of Bis-GMA/TEGDMA/Bis-EMA4: 50/50/0, 50/30/20, 50/10/40, 50/0/50, 30/10/60, 10/10/80 and 0/0/100. Camphorquinone (0.4 wt%), N,N-dimethyl-p-toluidine (0.8 wt%) and hydroquinone (0.2 wt%) were dissolved in each mixture, which was loaded with silanated strontium glass fillers to a constant content of 60 wt%. Bond strength was evaluated by microshear testing (n = 10) on bovine dentin. Data were submitted to Analysis of Variance (p < 0.05). Modes of failure were classified under magnification (200×). Bond strength means (MPa), respective to each agent, were: 19.4, 19.8, 20.0, 19.1, 16.8, 18.7 and 17.8. No significant differences were detected among groups. Mixed failures were generally predominant for all materials. In conclusion, the addition of Bis-EMA4 presented no significant influence on the bond strength of the experimental resin luting agents to dentin.

Microleakage of All-ceramic Crowns Using Self-etching Resin Luting Agents

Self-etching adhesive systems are a new generation of materials that possess acidic methacrylates that can generate self-adhesion. There is limited data reported on the marginal leakage of ceramic restorations bonded with self-etching adhesive materials. This study assessed and compared the amount of microleakage of bonded ceramic crowns using three different types of self-etching adhesive systems with and without a die spacer. Eighteen human molars were prepared for all-ceramic IPS Empress crowns and the teeth were randomly assigned to each experimental group. The buccal side had the preparation finish line 1.5 mm below the CEJ, and the lingual finish line was 1.5 mm above the CEJ, creating margins in enamel and dentin. Two die-spacing techniques were used (three layers or no layer of die spacer). Each crown restoration was cemented with one of three self-etching resin luting agents (Panavia F 2.0, Multilink and RelyX Unicem). The specimens were thermally cycled for 1000 cycles, then immersed in a 5% methylene blue dye solution for 24 hours. The teeth were then rinsed, embedded in clear epoxy resin and sectioned. A total of 60 sections were evaluated for each type of resin luting agent using digital image analysis at 70x magnification. A novel formula, using mean percentage of microleakage, was developed by dividing the extent of dye penetration along the tooth/resin luting cement interphase and the total perimeter of the tooth crown surface. The data were analyzed using three-way analysis of variance at the 0.05 level of significance. Fisher's PLSD intervals were calculated for comparing significant means. Panavia F 2.0 showed a lower degree of microleakage than RelyX Unicem and Multilink at both the enamel and dentin margins. Interactions of the main effects (cement, margin and die spacer technique) were all highly significant (p< or =0.004). The degree of microleakage was higher on the dentin margins than on the enamel margins (p<0.0001). The degree of microleakage for the die spacer group was not significantly different from the group with no die spacer technique (p>0.1). Overall, Panavia F 2.0 showed the least microleakage, followed by RelyX Unicem and Multilink, respectively.

Selective infiltration-etching technique for a strong and durable bond of resin cements to zirconia-based materials

Establishing a strong and a stable adhesive bond between yttrium, partially stabilized, tetragonal zirconia, polycrystal materials (Y-TZP) and resin luting agents has proven to be difficult using conventional surface roughening and coating methods. The purpose of this study was to evaluate the zirconia-resin bond strength and durability using a selective infiltration-etching technique. Seventy-two Y-TZP discs (19.5 x 3 mm) were airborne-particle abraded with 110-mum aluminum oxide particles and divided into 4 groups (n=18). One test group received the selective infiltration-etching surface treatment. Three commercial adhesive systems (Panavia F 2.0, RelyX ARC, and Bistite II DC) were used to bond the airborne-particle-abraded zirconia specimens to preaged restorative composite resin discs (Filtek Z250). Panavia was used to bond the selective infiltration-etched specimens. The bonded specimens were cut into microbars (6 x 1 x 1 mm), and a microtensile bond strength test (MTBS measured in MPa) was conducted immediately, after 1 week, 2 weeks, 3 weeks, and after 1 month of water storage (5 microbars/disc/time interval/group, n = 450 microbars/group). Scanning electron microscopy was used to examine the fractured microbars. The density (g/cm(3)) and the 4-point flexure strength (MPa) of the selective infiltration-etched and airborne-particle-abraded specimens were measured to evaluate the effect of selective infiltration etching on the structural integrity of the Y-TZP specimens. A repeated measures ANOVA with 1 within-subjects factor (time, 5 levels) and 1 between-subjects factor (technique, 4 levels) was used to analyze the data (alpha=.05). Pairwise comparisons were made using the Bonferroni post hoc test. There were significant differences in the initial MTBS values (MPa) between the 4 bonding techniques (P<.001). Airborne-particle-abraded specimens bonded with either Panavia F 2.0, RelyX ARC, or Bistite II DC resulted in a mean (SD) bond strength of 23.3 (2.4), 33.4 (2.1), 31.3 (2.8) MPa, respectively, while the highest bond strength of 49.8 (2.7) MPa was achieved for the selective infiltration-etched specimens bonded with Panavia F 2.0. There was a significant interaction between water storage time and the bonding technique (P<.001) as reduction in MTBS values was observed with time, except for the specimens bonded with Panavia (selective infiltration-etched and airborne-particle-abraded specimens). Additionally, the observed failure mode was primarily cohesive for the selective infiltration-etched specimens, in contrast to the other groups, which showed primarily an interfacial failure. For the materials used in this study and under the same testing conditions, selective infiltration etching is a reliable method for establishing a strong and durable bond with zirconia-based materials.

Micro push-out bond strengths of four fiber-reinforced composite post systems and 2 luting materials

The aim of this study was to compare the bond strengths of 2 types of dual-cured luting agents used for cementation of 4 different fiber-reinforced composite (FRC) posts by using a push-out test and to evaluate the failure modes of these systems. Eighty human maxillary central incisors were divided into 8 groups (n = 10), decoronated, and roots filled and restored with one of the following post systems: groups 1 to 4: translucent quartz FRC posts; groups 5 and 6: opaque glass FRC post; and groups 7 and 8: individually formed electrical glass fiber post. Cementation was performed with 2 types of dual-polymerizing resin luting agents: Variolink II (groups 1, 3, 5, and 7) and a new self-adhesive resin cement, RelyX Unicem (groups 2, 4, 6, and 8). Slices with a thickness of 1.00 +/- 0.05 mm were prepared from the coronal third of each root by using a low-speed saw. Push-out tests were performed at a crosshead speed of 1 mm/min by using a universal testing machine, and the data was statistically analyzed (analysis of variance [ANOVA] and Duncan tests; P < .05). Fracture modes were evaluated at original magnification x40. Micro push-out bond strengths were significantly affected by the type of luting agent and the type of post (P < .05, 2-way ANOVA). A significant difference was found among the groups (1-way ANOVA, P < .05). Fiber-reinforced composite posts luted with Variolink II showed higher bond strengths, and the groups ordered as 5, 1, 3, 7, 6, 2, 4, and 8, with the values (MPa, mean +/- SD): 13.80 +/- 5.00, 13.77 +/- 3.78, 12.20 +/- 4.79, 9.39 +/- 2.48, 9.21 +/- 7.76, 7.25 +/- 1.56, 3.89 +/- 4.41, and 3.77 +/- 1.20, respectively. Adhesive failures between dentin and cement were observed more than cohesive failures in cement or post. Push-out bond strengths can be affected by luting agent and post type. Variolink II and fiber post combinations resulted in high bond strength values.

Mechanical Properties of Dual‐Cured Resin Luting Agents for Ceramic Restoration

The aim of the present study was to evaluate mechanical properties, including surface hardness, flexural strength, and flexural modulus, of two dual-cured resin luting agents [Clearfil Esthetic Cement (CEC) and Variolink II (VLII)] irradiated through four thicknesses of leucite ceramics (0, 1, 2, and 3 mm) and to evaluate their shear bond strength to zirconia ceramic (Cercon) using each ceramic primer. Knoop hardness was measured on a thin layer of resin luting agent on the ceramic surface. Three-point bending tests were performed after 24 hours of storage at 37 degrees C. Two differently shaped zirconia ceramic specimens with or without sandblasting with alumina were treated with each primer. The specimens were then cemented together with each resin luting agent. Half of the specimens were stored in water at 37 degrees C for 24 hours and the other half were thermocycled 5000 times. VLII revealed statistically higher Knoop hardness and flexural modulus than CEC for each thickness of ceramic. No significant differences in flexural strength were observed between VLII and CEC for each ceramic spacer. Reduction of the mechanical properties with increase of ceramic thickness varied for each property; however, these properties were similar in the two materials. Blasting with alumina was significantly effective for increasing shear bond strength of both resin luting agents before and after thermal cycling. The use of Clearfil Ceramic Primer showed the highest shear bond strength and maintained bond durability after 5000 thermocycles. Mechanical properties of CEC dual-cured resin luting agent appear adequate for ceramic restorations.

Influence of ceramic thickness on mechanical properties and polymer structure of dual-cured resin luting agents

Objective To investigate the influence of ceramic thickness on the mechanical properties and polymer structure (degree conversion and cross-linking density) of three dual-cured resin luting agents. Methods Three dual-cured resin luting agents [Linkmax HV (GC), Nexus 2 (Kerr), and Variolink IIHV (Ivoclar-Vivadent)] were polymerized with or without 800 mW/cm 2 irradiation through 0–3-mm-thick GN-I (GC) machinable ceramic. Bar-shape specimens were subjected to three-point bending to determine flexural strength (FS) and elastic modulus (EM) after dry storage at 37 °C for 24 h. Knoop hardness was measured on the irradiated surface of disk-shaped specimens before (KHN1) and after (KHN2) storage of 100% ethanol solution at 37 °C for 24 h. KHN1 and KHN2 were estimated as indirect indicators of degree of conversion (DC) and cross-linking density, respectively. Data were analyzed by one-way ANOVA and Student–Newman–Keuls test for each luting agent, and four mechanical properties were subjected to regression analysis. Results For three resin luting agents with dual-cured mode, FS, EM, KHN1, and KHN2 decreased with the increase of ceramic thickness. FS except for Nexus 2 and EM for three resin luting agents had a positive linear relationship with both KHN1 and KHN2. Significance The variables tested behaved differently. When the ceramic thickness increased, the chemical cured components of dual-cured resin luting agents did not produce significant compensation for all variables. Mechanical properties and polymer structure of dual-cured resin luting agents was dependent on the intensity of light irradiation.

Influence of ceramic thickness and polymerization mode of a resin luting agent on early bond strength and durability with a lithium disilicate-based ceramic system

Influence of ceramic thickness and polymerization mode of a resin luting agent on early bond strength and durability with a lithium disilicate-based ceramic system

Retentive Force of Three Fiber-reinforced Resin Composite Posts and a Zirconia Post Cemented with Two Adhesive Luting Agents: In Vitro Study

By means of a pull-out test, this study compared the retentive force of three fiber-reinforced resin composite posts and a zirconia post. These posts were cemented using two different dual-polymerizing adhesive resin luting agents. Forty freshly extracted canines were selected for the study. All tooth root were endodontically treated and the post spaces prepared. The posts were luted using luting agents according to the manufacturers' guidelines. A tensile force was applied, and all data were collected and analyzed statistically. Glass fiber posts that were luted with Panavia F (Group 3) had the highest median load (3.610 N), while zirconia posts that were luted with RelyX ARC (Group 8) had the lowest median load (0.926 N). Among the different post systems that were luted with Rely X ARC, significant differences were observed in their median tensile loads (p < 0.047). When comparing between Panavia F and RelyX ARC of each post system, a significantly higher tensile load was seen with zirconia posts luted with Panavia F (Group 7) (p < 0.032).

Influence of Light Irradiation Condition on Microshear Bond Strength of Dual-cured Resin Luting Agents

The purpose of this study was to evaluate the microshear bond strength and bond durability between ceramic and two dual-cured resin luting agents irradiated by different light intensities. Ceramic specimens were bonded with two resin bonding systems: Ceramic Primer and Linkmax HV (CP/LMHV) and Monobond S and Variolink IIHV (MBS/VLIIHV), and were either irradiated by 800, 310, 160, 80, and 40 mW/cm2 light or not irradiated. Bond strength was measured after 24-hour water storage at 37 degrees C and after subsequent 10,000 times of thermal cycling. Failure modes were determined by stereomicroscopy. After 24-hour water storage, there were no significant differences among the various irradiation conditions for both MBS/VLIIHV and CP/LMHV. However, regardless of light intensity, MBS/VLIIHV showed higher bond strength than CP/VLIIHV at each thermal cycling, except for no irradiation condition at 10,000 thermal cycles. In conclusion, thermal cycling significantly reduced the bond strength for all groups.

Fracture resistance of weakened roots restored with a transilluminating post and adhesive restorative materials

The increase in wall thickness of weakened roots using composite resins may increase the root resistance to fracture. However, little is known about the recently developed methods for intraradicular reinforcement of weakened roots. The purpose of this study was to determine the fracture resistance of experimentally weakened roots reinforced with composite resins, compared with conventional systems that use cast and prefabricated posts. Forty-eight maxillary incisors were divided into 6 groups (n = 8). The control group (C) used a conventionally prepared root canal filled with cast CuAl posts. Experimental groups had the root canals overprepared to weaken them and were restored as follows: CP, cast CuAl posts; LT, light-transmitting polymerization post (Luminex) + Tetric Ceram resin + prefabricated titanium post (PTP); LF, Luminex posts + Filtek Supreme resin + PTP; LZ, Luminex posts + Z100 resin + PTP; and LR, Luminex posts + Renew resin + PTP. All posts were cemented with a resin luting agent (C & B Cement). Specimens were subjected to compressive load (N) until fracture. Data were submitted to 1-way analysis of variance and the Dunnett test (alpha = .05). There was significant difference (P < .01) between the conventionally prepared specimens and those filled with a cast post (C, 447.8 +/- 167.9) and the overprepared specimens and those filled with a cast post (CP, 212.8 +/- 62.4). No significant differences were found among the control specimens (447.8 +/- 167.9) and the weakened-roots filled with Luminex and composite resins LT (520.9 +/- 173.1), LF (479.9 +/- 214.9), LZ (391.6 +/- 173.6), and LR (333.0 +/- 112.2). The use of composite resins in root canals reinforced the weakened roots during fracture resistance testing.

Interfacial characteristics of adhesive luting resins and composites with dentine

Purpose To evaluate the interfacial characteristics of five adhesive resin luting agents with dentine including tensile bond strength, failure mode, extent of demineralisation, morphological changes and hybrid layer formation. Materials and methods The products tested were Bistite II DC (BDC), C&B Super-Bond (CBM), M-Bond (MBD), Panavia-F (PAF) and Rely-X Unicem (RXU). For tensile bond strength measurements (TBS), metallic rods were bonded to standardised dentine surface areas ( n = 10), thermal-cycled (3000× 5–55 °C, 4 cycles/min) and debonded at 1 mm/min crosshead speed. The failure mode was examined on dentine surfaces by LV-SEM ( n = 10), whereas the thickness of the hybrid layer by HV-SEM ( n = 4). FT-IR microscopy ( n = 4) and ESEM ( n = 4) were used to assess the extent of demineralisation and the morphological changes induced on dentine by the conditioning and priming treatments. Results TBS (MPa) values were BDC (13.01), MBD (9.19) and PAF (7.07) significantly different from CBM (4.79) and RXU (4.47). The percentage of debonded dentine area covered with resin showed the highest values in BDC (47.80) and MBD (38.12) significantly different from CBM (17.20), PAF (16.47), and RXU (16.50). The extent of demineralisation for CBM was 100%. No statistical differences were found among BDC (60.86%), MBD (60.22%) and PAF (51.99%). RUX (45.03%) showed the lowest value. CBM induced the most pronounced tubule funneling and intertubular dissolution, followed by PAF, BDC and MDB. RXU partially removed the smear layer without opening tubule orifices. The thickest hybrid layer was found in CBM (4.17 μm) followed by MBD (2.39 μm). No statistically significant differences were found between PAF (0.95 μm) and BDC (1.12 μm), whereas RXU showed no detectable hybrid layer. Significance Significant differences were found in the interfacial properties among the materials tested, that may lead to differences in their clinical performance.

Effect of zirconium-oxide ceramic surface treatments on the bond strength to adhesive resin

Surface treatment methods used for resin bonding to conventional silica-based dental ceramics are not reliable for zirconium-oxide ceramics. The aim of this study was to compare the effects of airborne-particle abrasion, silanization, tribochemical silica coating, and a combination of bonding/silane coupling agent surface treatment methods on the bond strength of zirconium-oxide ceramic to a resin luting agent. Sixty square-shaped (5 x 5 x 1.5 mm) zirconium-oxide ceramic (Cercon) specimens and composite resin (Z-250) cylinders (3 x 3 mm) were prepared. The ceramic surfaces were airborne-particle abraded with 125-microm aluminum-oxide (Al(2)O(3)) particles and then divided into 6 groups (n = 10) that were subsequently treated as follows: Group C, no treatment (control); Group SIL, silanized with a silane coupling agent (Clearfil Porcelain Bond Activator); Group BSIL, application of the adhesive 10-methacryloyloxydecyl dihydrogen phosphate monomer (MDP)-containing bonding/silane coupling agent mixture (Clearfil Liner Bond 2V/ Porcelain Bond Activator); Group SC, silica coating using 30-microm Al(2)O(3) particles modified by silica (CoJet System); Group SCSIL, silica coating and silanization (CoJet System); and Group SCBSIL, silica coating and application of an MDP-containing bonding/silane coupling agent mixture (Clearfil Liner Bond 2V/Porcelain Bond Activator). The composite resin cylinders were bonded to the treated ceramic surfaces using an adhesive phosphate monomer-containing resin luting agent (Panavia F). After the specimens were stored in distilled water at 37 degrees C for 24 hours, their shear bonding strength was tested using a universal testing machine at a crosshead speed of 0.5 mm/min. Debonded specimen surfaces were examined with a stereomicroscope to assess the mode of failure, and the treated surfaces were observed by scanning electron microscopy. Bond strength data were analyzed using 1-way analysis of variance and the Duncan test (alpha = .05). The bond strengths (mean +/- SD; MPa) in the groups were as follows: Group C, 15.7 +/- 2.9; Group SIL, 16.5 +/- 3.4; Group BSIL, 18.8 +/- 2.8; Group SC, 21.6 +/- 3.6; Group SCSIL, 21.9 +/- 3.9; and Group SCBSIL, 22.9 +/- 3.1. The bond strength was significantly higher in Group SCBSIL than in Groups C, SIL, and BSIL (P<.001), but did not differ significantly from those in Groups SC and SCSIL. Failure modes were primarily adhesive at the interface between zirconium and the resin luting agent in Groups C and SIL, and primarily mixed and cohesive in Groups SC, SCSIL, and SCBSIL. Tribochemical silica coating (CoJet System) and the application of an MDP-containing bonding/silane coupling agent mixture increased the shear bond strength between zirconium-oxide ceramic and resin luting agent (Panavia F).

Fracture resistance of single‐tooth implant‐supported all‐ceramic restorations after exposure to the artificial mouth

The purpose of this in vitro study was to evaluate the fracture resistance of single-tooth implant-supported all-ceramic restorations, composed of zirconium dioxide all ceramic restorations on different implant abutments, and to identify the weakest component of the restorative system. Forty-eight standardized maxillary central incisor zirconia crowns (Procera) were fabricated for two test groups and one control group (group Al: alumina abutments; group Zr: zirconia abutments; control group Ti: titanium abutments). All abutments were placed on the implants (Replace) using titanium screws. The crowns were adhesively luted using a resin luting agent (Panavia 21) and artificially aged through dynamic loading and thermal cycling. Afterwards, all specimens were tested for fracture resistance using compressive load on the palatal surfaces of the crowns. Pair-wise Wilcoxon rank tests were performed to test for differences in fracture resistance values with a global significance level of 0.05. All test specimens survived aging in the artificial mouth. No screw loosening was recorded. The median fracture resistance was 1251, 241 and 457 N for groups Ti, Al and Zr respectively. Statistically significant differences were found for the comparisons of group Ti with groups Al and Zr (P < 0.00001), and for the comparison of group Al with Zr (P < 0.00001). Results of this study showed that all tested implant-supported restorations have the potential to withstand physiological occlusal forces applied in the anterior region. Because of the low fracture resistance values of group Al, the combination of zirconia crowns and alumina abutments should carefully be considered before clinical application.