Mean Shear Bond Strength Values Research Articles

Development and testing of multi-phase glazes for adhesive bonding to zirconia substrates

Objectives The aims of the study were to develop and test multi-phase glaze coatings for zirconia restorations, so that the surface could be etched and adhesively bonded. Methods Zirconia disc specimens ( n = 125, 16 mm × 1 mm) were cut from cylinders of Y-TZP (yttria-stabilized tetragonal zirconia polycrystals) ZS-Blanks (Kavo, Everest) and sintered overnight. Specimens were subjected to the recommended firing cycles, and next sandblasted. The specimens were divided into 5 groups of 25, with Group 1 as the sandblasted control. Groups 2–5 were coated with overglaze materials (P25 and IPS e.max Ceram glazes) containing secondary phases. Group 2 was (wt%): 10% hydroxyapatite (HA)/P25 glaze, Group 3: 20% IPS Empress 2 glass–ceramic/glaze, Group 4: 20% IPS Empress 2 glass/glaze and Group 5: 30% IPS Empress 2 glass/glaze. After sintering and etching, Monobond-S and composite resin cylinders (Variolink II, Ivoclar-Vivadent) were applied and light cured on the test surfaces. Specimens were water stored for 7 days. Groups were tested using the shear bond strength (SBS) test at a crosshead speed of 0.5 mm/min. Overglazed and the fractured specimen surfaces were viewed using secondary electron microscopy. Room and high temperature XRD and DSC were carried out to characterize the materials. Results The mean (SD) SBS (MPa) of the test groups were: Group 1: 7.7 (3.2); Group 2: 5.6 (1.7); Group 3: 11.0 (3.0); Group 4: 8.8 (2.6) and Group 5: 9.1 (2.6). Group 3 was significantly different to the control Group 1 ( p < 0.05). There was no significant difference in the mean SBS values between Group 1 and Groups 2, 4 and 5 ( p > 0.05). Group 2 showed statistically lower SBS than Groups 3–5 ( p < 0.05). Lithium disilicate fibres were present in Groups 3–5 and fine scale fibres were grown in the glaze following a porcelain firing cycle (Groups 4 and 5). XRD indicated a lithium disilicate/minor lithium orthophosphate phase (Group 3), and a tetragonal zirconia phase for the sintered Y-TZP ZS-Blanks. DSC and high temperature XRD confirmed the crystallization temperatures and phases for the IPS Empress 2 glass. Conclusions The application of a novel glass–ceramic/glaze material containing a major lithium disilicate phase might be a step in improving the bond strength of a zirconia substrate to a resin cement.

Bond strength of a composite resin to an adhesive luting cement

This study evaluated the influence of surface treatment on the shear bond strength of a composite resin (CR), previously submitted to the application of a temporary cement (TC), to an adhesive luting cement. Eight-four CR cylinders (5 mm diameter and 3 mm high) were fabricated and embedded in acrylic resin. The sets were divided into 6 groups (G1 to G6) (n=12). Groups 2 to 6 received a coat of TC. After 24 h, TC was removed and the CR surfaces received the following treatments: G2: ethanol; G3: rotary brush and pumice; G4: air-abrasion; G5: air-abrasion and adhesive system; G6: air-abrasion, acid etching and adhesive system. G1 (control) did not receive TC or any surface treatment. The sets were adapted to a matrix and received an increment of an adhesive luting cement. The specimens were subjected to the shear bond strength test. ANOVA and Tukey's tests showed that G3 (8.53 MPa) and G4 (8.63 MPa) differed significantly (p=0.001) from G1 (13.34 MPa). The highest mean shear bond strength values were found in G5 (14.78 MPa) and G6 (15.86 MPa). Air-abrasion of CR surface associated with an adhesive system provided an effective bond of the CR to the adhesive luting cement, regardless the pre-treatment with the phosphoric acid.

Evaluation of the Bond Strength of Denture Base Resins to Acrylic Resin Teeth: Effect of Thermocycling

The purpose of this study was to evaluate the thermocycling effects and shear bond strength of acrylic resin teeth to denture base resins. Three acrylic teeth (Biotone, Trilux, Ivoclar) were chosen for bonding to four denture base resins: microwave-polymerized (Acron MC), heat-polymerized (Lucitone 550 and QC-20), and light-polymerized (Versyo.bond). Twenty specimens were produced for each denture base/acrylic tooth combination and were divided into two groups (n = 10): without thermocycling (control groups) and thermocycled groups submitted to 5000 cycles between 4 and 60 degrees C. Shear strength tests (MPa) were performed with a universal testing machine at a crosshead speed of 1 mm/min. Statistical analysis of the results was carried out with three-way ANOVA and Bonferroni's multiple comparisons post hoc analysis for test groups (alpha = 0.05). The shear bond strengths of Lucitone/Biotone, Lucitone/Trilux, and Versyo/Ivoclar specimens were significantly decreased by thermocycling, compared with the corresponding control groups (p < 0.05). The means of Acron/Ivoclar and Lucitone/Ivoclar specimens increased after thermocycling (p < 0.05). The highest mean shear bond strength value was observed with Lucitone/Biotone in the control group (14.54 MPa) and the lowest with QC-20/Trilux in the thermocycled group (3.69 MPa). Some acrylic tooth/denture base resin combinations can be more affected by thermocycling; effects vary based upon the materials used.

Shear Bond Strength of Orthodontic Brackets Bonded to Provisional Crown Materials Utilizing Two Different Adhesives

To test the hypothesis that there is no difference in the shear bond strength of brackets bonded to provisional crown materials (PCMs) using two adhesive agents. Four PCMs were tested: Integrity, Jet, Protemp, and Snap. Forty cylindrical specimens of 10 mm diameter x 5 mm were prepared for each PCM. Ten specimens from each group were bonded to one of the two brackets, Clarity or Victory, using one of the two adhesives, Fuji Ortho LC or Ortho Bracket Adhesive. The brackets were debonded in shear at a cross-head speed of 5 mm/min, and the shear bond strength (SBS) was calculated. The type of failure was visually determined. The numeric data were analyzed using three-way analysis of variance and Tukey multiple range test at alpha = .05. The mean SBSs ranged from 2.81 MPa to 9.65 MPa. There was a significant difference between Snap and the other three materials (P < .0001). There was no significant difference between the two brackets or the two adhesives (P > .05). The bond failure for all the specimens was of the adhesive type between the PCM and the adhesive resin. The PCM Snap yielded a significantly lower mean SBS value compared to the other three materials. No significant differences were found between the brackets or the adhesives. The bond failure was of the adhesive type.

Effects of erbium:yttrium–aluminum–garnet and neodymium:yttrium–aluminum–garnet laser hypersensitivity treatment parameters on the bond strength of self-etch adhesives

This in vitro study evaluated the shear bond strength (SBS) of two self-etch adhesives to coronal and root dentin treated with erbium:yttrium-aluminum-garnet (Er:YAG) or neodymium:yttrium-aluminum-garnet (Nd:YAG) lasers for dentin hypersensitivity. The coronal and root dentin surfaces of 60 extracted human cuspids were divided into three groups (n = 20): (1) control (without treatment); (2) treated with Er:YAG; (3) treated with Nd:YAG laser and a one-step (S3) or two-step self-etch adhesive (SE). A nano-composite was applied and SBS tests were performed. The mean SBS values were calculated, failure modes were determined, and data were subjected to statistical analysis (P = 0.05). Control/SE exhibited higher values than did control/S3 and Nd:YAG/S3 on coronal dentin (P < 0.05). No significant differences were observed between the SE and S3 groups in root dentin (P > 0.05). Comparisons of two dentin substrates did not show any difference except control/SE (P < 0.05). The failure modes were mainly adhesive. The SBSs of self-etch adhesives to Er:YAG or Nd:YAG laser-treated surfaces were comparable with control for both coronal and root dentin.

Shear bond strengths between different zirconia cores and veneering ceramics and their susceptibility to thermocycling

Objectives The purpose of this study was to evaluate the shear bond strength between various commercial zirconia core and veneering ceramics, and to investigate the effect of thermocycling. Methods The Schmitz–Schulmeyer test method was used to evaluate the core–veneer shear bond strength (SBS) of three zirconia core ceramics (Cercon Base, Vita In-Ceram YZ Cubes, DC-Zirkon) and their manufacturer recommended veneering ceramics (Cercon Ceram S, Vita VM9, IPS e.max Ceram). A metal ceramic system (Degudent U94, Vita VM13) was used as a control group for the three all-ceramic test groups ( n = 30 specimens/group). Half of each group ( n = 15) was thermocycled (5–55 °C, 20,000 cycles). Subsequently, all specimens were subjected to shear force in a universal testing machine. Fractured specimens were evaluated microscopically to determine the failure mode. Results The initial mean SBS values in MPa ± S.D. were 12.5 ± 3.2 for Vita In-Ceram YZ Cubes/Vita VM9, 11.5 ± 3.4 for DC-Zirkon/IPS e.max Ceram, and 9.4 ± 3.2 for Cercon Base/Cercon Ceram S. After thermocycling mean SBS values of 11.5 ± 1.7 MPa for DC-Zirkon/IPS e.max Ceram, 9.7 ± 4.2 MPa for Vita In-Ceram YZ Cubes/Vita VM9, and 9.6 ± 4.2 MPa for Cercon Base/Cercon Ceram S were observed. Neither the differences between the SBS values of the all-ceramic test groups nor the influence of thermocycling on all groups were statistically significant. Irrespective of thermocycling the metal ceramic control group (27.6 ± 12.1 MPa, 26.4 ± 13.4 MPa) exhibited significantly higher mean SBS than all three all-ceramic groups tested. The all-ceramic groups showed combined failure modes as cohesive in the veneering ceramic and adhesive at the interface, whereas the metal ceramic group showed predominately cohesive fractures. Significance The results indicated that the SBS between zirconia core and veneering ceramics was not affected by thermocycling. None of the zirconia core and veneering ceramics could attain the high bond strength values of the metal ceramic combination.

Comparison of hydroxyapatite and dental enamel for testing shear bond strengths

Abstract Aims To investigate the feasibility of using artificial hydroxyapatite as a future biomimetic laboratory substitute for human enamel in orthodontic bond strength testing by comparing the shear bond strengths and nature of failure of brackets bonded to samples of hydroxyapatite and enamel. Method One hundred and fifty hydroxyapatite discs were prepared by compression at 20 tons and fired in a furnace at 1300°C. One hundred and five enamel samples were prepared from the buccal and palatal/lingual surfaces of healthy premolars extracted for orthodontic purposes. Orthodontic brackets were bonded to each sample and these were subjected to shear bond strength testing using a custom-made jig mounted in an Instron Universal Testing Machine. The force value at bond failure was obtained, together with the nature of failure which was assessed using the Adhesive Remnant Index. Results The mean shear bond strength for the enamel samples was 16.62 MPa (95 per cent CI: 15.26, 17.98) and for the hydroxyapatite samples 20.83 MPa (95 per cent CI: 19.68, 21.98). The difference between the two samples was statistically significant (p &lt; 0.001). When the nature of failure was assessed with the ARI Index, 83 per cent of the enamel samples scored 2 or 3, while 49 per cent of the hydroxyapatite samples scored 0 or 1. Conclusions Hydroxyapatite was an effective biomimetic substrate for bond strength testing with a mean shear bond strength value (20.83 MPa) at the upper end of the normal range attributed to enamel (15–20 MPa). Although the difference between the shear bond strengths for hydroxyapatite and enamel was statistically significant, hydroxyapatite could be used as an alternative to enamel for comparative laboratory studies until a closer alternative is found. This would eliminate the need for extracted teeth to be collected. However, it should be used with caution for quantitative studies where true bond strengths are to be investigated.

Bonding of brackets using a caries-protective adhesive patch

Objectives The purpose of this study was to assess the shear bond strength (SBS) of metal brackets when placed with a caries protective adhesive patch. Methods Forty stainless steel brackets (Ormco) were bonded to 40 bovine enamel samples according to the following conditioning/bonding procedures using a resin-based orthodontic luting material (Heliosit Orthodontic, N = 10 per group): (A) 35% phosphoric acid (30 s), rinse and dry; (B) as in A but additional placement of a prototype adhesive patch (Ivoclar Vivadent) using a bonding agent (Heliobond); (C) application of a two-step self-etch adhesive (AdheSE); (D) as in C but additional patch placement. Samples were stored at 37 °C for 24 h. SBS was measured with a universal testing machine with a crosshead speed of 0.5 mm/min and the adhesive remnant index (ARI) was determined under a stereomicroscope (16×). Results Mean SBS (standard deviation) values were as follows: (A) 16.6 (6.4) MPa; (B) 12.2 (5.8); (C) 12.9 (5.0); and (D) 10.5 (4.7). Analysis of variance followed by Bonferroni correction revealed no statistically significant differences. In 2 (B) and 4 (D) specimens, complete retention of the adhesive patch was observed. Conclusions All treatment groups showed adequate bond strength values. The adhesive patch could therefore be applied in combination with orthodontic brackets and seal the enamel adjacent to the bracket.

Shear Bond Strength of Different Adhesive Systems to Primary Dentin and Enamel

The aims of this study were to evaluate the shear bond strength (SBS) off our adhesive systenms applied to primary dentin and enamel and verify, after SBS testing, the failure mode of the adhesive interface. Sixty extracted sound primary molars were selected and crowns were sectioned in a mesial-distal direction. Specimens were randomly assigned into two groups (adhesion to enamel and adhesion to dentin) and then subdivided into four subgroups according to the adhesive system (n=15). Scotchbond Multi-Purpose (SMP)--Single Bond (SB)--Clearfil SE Bond (and Adper Prompt L-Pop (APL)--SBS tests were performed and the obtained values were statistically analyzed using ANOVA and Tukey tests (p < 0.05). The failure mode analysis was performed with a Scanning Electron Microscope (XL-30, Philips). SBS mean values on enamel were [MPa (SD)]: SMP--2789 (749); SB--23.92 (8.8); CSB--24.36 (6.69), APL--25.96 (4.08); and on dentin: SMP--17.29 (4.25) SB--18.2 (8.74); CSB--16.13 (714); APL--6. 04 (3.35). The predominant failure mode was cohesive (primarily of the bonding agent). On enamel SBS was statistically similar for all four adhesives. On dentin SBS ofAPL was lower than the other tested adhesives.

Experimental dental bio-adhesives for direct restorations: The influence of PMnEDM homologs structure on bond strength

Objectives The purpose of this study was to evaluate the effect of PMnEDM dental monomer homologs chemical structure on shear bond strength between polymer-based composite and alloy. Methods Four light-cured experimental universal dental bio-adhesives (group codes: A (PMDM), B (PM2EDM), C (PM3EDM), D (PM4EDM)) were preliminarily evaluated with respect to sensitivity to ambient light, curing time, depth of cure, and uncured film thickness according to standardized procedures. Appropriate tests were performed to measure shear bond strength (SBS) of polymer-based composite to cobalt-based alloy with the use of the adhesives investigated. Variability of results was evaluated by use of the coefficient of variation (CV). Results were estimated with the aid of one-way analysis of variance (ANOVA), performed on the logarithmic values, with α = 0.05 significance level. Results All materials passed the requirements according to physicochemical properties. Except for formulation D, all results estimating SBS were positive with respect to standardized requirements. The uppermost mean SBS was achieved for the A adhesive (11.45 MPa) and appeared to be significantly different compared to D one (5.07 MPa) ( p = 0.0495). Also the B adhesive, having slightly lower mean SBS value (10.50 MPa) exhibited a significant difference in respect to D one ( p = 0.0455). The means for other trial pairs did not differ statistically. Significance The materials here studied might be considered to have a practical use in dental clinics, especially the formulations B and C.

Shear bond strength of metallic brackets bonded with four different composite resins

The objective of this study was to assess the shear bond strength of metallic brackets with different types of Concise composites and the Adhesive Remnant Index (ARI). Sixty bovine permanent lower incisors were inserted into PVC tubes and divided into four groups (n = 15): Group 1 – Transbond XT (control) composite; Group 2– Concise restorative composite; Group 3 – Concise diluted restorative composite (Artun and Zachrisson's technique); and Group 4– Concise Orthodontic composite. After bonding the brackets, the samples were stored in distilled water at 37° C for 24 hours and then submitted to shear strength tests (Instron) at a crosshead speed of 0.5 mm/min. Analysis of variance and Tukey's test (5%) were used for statistically analysing the data regarding the shear bond strength results, whereas Kruskal-Wallis test was used for analysing the ARI scores. The shear bond strength mean values (MPa) for Group 1 (12.13) and Group 2 (12.20) were found to be statistically higher (p < .05) than that for Group 3 (8.20). No statistically significant differences were observed (p > .05) between Groups 1, 2, and 4 (9.86) as well as between Groups 3 and 4. Regarding the ARI evaluation, the majority of the fractures involved the bracket/ composite interface.

Shear Bond Strength Evaluation of Different Veneering Systems on Ni‐Cr Alloys

The aim of this study was to evaluate the shear bond strength of four esthetic veneering materials on nickel-chromium (Ni-Cr) alloy. Forty square patterns (10 x 10 x 1.5 mm) were cast with Ni-Cr, divided equally into four groups, and received four treatments for veneering: conventional porcelain-fused-to-metal (PFM), Artglass, Targis/Vectris, and Biodent light-cured prosthodontic composite resins. After sandblasting of the cast metal surfaces with 50 micro m alumina, the composites were applied to the surfaces according to manufacturers' recommendations. Shear bond strength was determined at a crosshead speed of 0.5 mm/min. Results were analyzed statistically with Kruskal-Wallis analysis of variance and multiple comparison tests. Mean shear bond strength values were 34.96 MPa for PFM, 14.17 MPa for Targis/Vectris, 13.64 MPa for Artglass, and 10.56 MPa for Biodent. The PFM group exhibited significantly higher bond strength values compared with the other three groups (p < 0.001). PFM showed considerably higher shear bond strength values than the three metal-resin bonding techniques.

Comparative evaluation of shear bond strength of conventional composite resin and nanocomposite resin to sandblasted primary anterior stainless steel crown

To evaluate and compare the shear bond strength of conventional composite resin and nanocomposite resin to sandblasted primary anterior stainless steel crown. The study samples consisted of 30 primary anterior stainless steel crowns (Unitek TM, size R4), embedded in resin blocks with crown, in test groups of 15 samples each. Mounting of the crown was done using resin block with one crown each. Sandblasting was done and the bonding agent Prime and Bond NT (Dentsply) was applied on the labial surface of the primary anterior sandblasted crown. The composite resin and nanocomposite resin were placed into the well of Teflon jig and bonded to Stainless Steel Crowns. The cured samples were placed in distilled water and stored in incubator at 37 degrees C for 48 hours. Shear bond strength was measured using universal testing machine (Hounsefield U.K. Model, with a capacity of 50 KN). Independent sample 't' test revealed a nonsignificant (P < 0.385) difference between mean shear bond strength values of conventional and nanocomposite group. The bond strength values revealed that nanocomposite had slightly higher mean shear bond strength (21.04 +/- 0.56) compared to conventional composite (20.78 +/- 0.60). It was found that conventional composite resin and nanocomposite resin had statistically similar mean shear bond strength, with nanocomposite having little more strength compared to conventional composite.

A Comparison of Two Different Methods and Materials Used to Repair Polycarbonate Crowns

The aim of this study was to evaluate the bond strength and crown-repair material interface of polycarbonate crown repaired using flowable resin composite and hybrid resin composite following two different surface preparations. The facial surfaces of fifty-two polycarbonate crowns were flattened and roughened. Specimens were then divided into four test groups. A bonding agent alone (Groups 1 and 2) or a combination of methylmethacrylate (MMA) + bonding agent (Groups 3 and 4) was applied to the prepared surfaces. Then either a flowable (Groups 1 and 3) or a microfilled hybrid (Groups 2 and 4) resin composite was placed on the surfaces. Forty-eight of the original fifty-two specimens were used for shear bond strength testing. Failure types (adhesive, cohesive, and mixed) were evaluated. The remaining four specimens, one from each group, were used for crown-resin composite interface analysis using a scanning electron microscope (SEM). There were significant differences in both mean shear bond strength values and failure types (P<0.05). The SEM evaluation revealed a close interface relationship in Groups 3 and 4. MMA monomer application on a polycarbonate crown prior to application of an adhesive agent improved the shear bond strength of the repair material.

Dentin Bond Strength of Composites with Self-etching Adhesives Using LED Curing Lights

The purpose of this study was to investigate the effect of light-emitting diode (LED) light curing units (LCUs) compared with halogen LCUs on the shear bond strength (SBS) of one nanofill composite (Filtek Supreme) and one microhibrid composite (Artemis) with self-etch adhesives. The buccal surfaces of 60 non-carious extracted human molars were flattened to expose dentin and, subsequently, polished for 60 seconds with 600-grit wet silicon carbide abrasive paper. Specimens were assigned into six groups (n=10) according to composite material, self-etch adhesive, and curing light used as follows: Group 1: Adper Prompt L-Pop (AP) and Filtek Supreme (FS) using an Elipar Free Light (EFL); Group 2: AP and FS using an Elipar Free Light 2 (EFL2); Group 3: AP and FS using a Hilux Expert (HE) light, Group 4: AdheSE (AS)+Artemis (AR) using an EFL; Group 5: AS+AR using an EFL2; and Group 6: AS+AR using a HE light. The specimens were thermocycled for 500 cycles (5 masculineC-55 masculineC) and then loaded to failure in a Zwick universal testing machine at a crosshead speed of 5 mm/minute. SBS values were calculated as megapascals (MPa) and statistically analyzed using the one-way analysis of variance (ANOVA) test at a significance level of 0.05. Mean SBS (+/- standard deviations) values were as follows: Group1: 15.99+/-5.18; Group 2: 18.76+/-6.71; Group 3: 17.70+/-5.04; Group 4: 16.93+/-3.99; Group 5: 18.01+/-5.19, and Group 6: 17.46+/-5.40. There were no statistically significant differences for SBS to dentin among the groups tested. The LED curing lights used in the study seem to be comparable with the halogen curing light for nanofill and microhybrid composites used in conjunction with self-etching systems in dentin. The EFL2 reduces curing time, which can be considered as an advantage.

Shear bond strength of metal-ceramic repair systems

When clinical fractures of the ceramic veneer on metal-ceramic prostheses can be repaired, the need for remake may be eliminated or postponed. Many different ceramic repair materials are available, and bond strength data are necessary for predicting the success of a given repair system. This study evaluated the shear bond strength of different repair systems for metal-ceramic restorations applied on metal and porcelain. Fifty cylindrical specimens (9 x 3 mm) were fabricated in a nickel-chromium alloy (Vera Bond II) and 50 in feldspathic porcelain (Noritake). Metal (M) and porcelain (P) specimens were embedded in a polyvinyl chloride (PVC) ring and received 1 of the following bonding and resin composite repair systems (n=10): Clearfil SE Bond/Clearfil AP-X (CL), Bistite II DC/Palfique (BT), CoJet Sand/Z100 (CJ), Scotchbond Multipurpose Plus/Z100 (SB) (control group), or CoJet Sand plus Scotchbond Multipurpose Plus/Z100 (CJSB). The specimens were stored in distilled water for 24 hours at 37 degrees C, thermal cycled (1000 cycles at 5 degrees C to 55 degrees C), and stored at 37 degrees C for 8 days. Shear bond tests between the metal or ceramic specimens and repair systems were performed in a mechanical testing machine with a crosshead speed of 0.5 mm/min. Mean shear bond strength values (MPa) were submitted to 1-way ANOVA and Tukey honestly significant difference tests (alpha=.05). Each specimen was examined under a stereoscopic lens with x30 magnification, and mode of failure was classified as adhesive, cohesive, or a combination. On metal, the mean shear bond strength values for the groups were as follows: MCL, 18.40 +/- 2.88(b); MBT, 8.57 +/- 1.00(d); MCJ, 25.24 +/- 3.46(a); MSB, 16.26 +/- 3.09(bc); and MCJSB, 13.11 +/- 1.24(c). On porcelain, the mean shear bond strength values of each group were as follows: PCL, 16.91 +/- 2.22(b); PBT, 18.04 +/- 3.23(ab); PCJ, 19.54 +/- 3.77(ab); PSB, 21.05 +/- 3.22(a); and PCJSB, 16.18 +/- 1.71(b). Within each substrate, identical superscript letters denote no significant differences among groups. The bond strength for the metal substrate was significantly higher using the CJ system. For porcelain, SB, CJ, and BT systems showed the highest shear bond strength values, and only SB was significantly different compared to CL and CJSB (P<.05). This study suggests that when fracture involves only feldspathic porcelain, any of the evaluated systems may be used, since the fracture occurred on the porcelain substrate and not on the bond interface of porcelain-restorative material. However, for the nickel-chromium alloy tested, the CoJet Sand system showed the best results for repair.

Comparison of two bond strength testing methodologies for bilayered all-ceramics

Objectives This study compared the shear bond strength (SBS) and microtensile (MTBS) testing methodologies for core and veneering ceramics in four types of all-ceramic systems. Methods Four different ceramic veneer/core combinations, three of which were feldspathic and the other a fluor–apatite to their respectively corresponding cores, namely leucite-reinforced ceramic ( IPSEmpress, Ivoclar), low leucite-reinforced ceramic (Finesse, Ceramco), glass-infiltrated alumina (In-Ceram Alumina, Vita) and lithium disilicate ( IPSEmpress 2, Ivoclar) were used for SBS and MTBS tests. Ceramic cores ( N = 40, n = 10/group for SBS test method, N = 5 blocks/group for MTBS test method) were fabricated according to the manufacturers’ instructions (for SBS: thickness, 3 mm; diameter, 5 mm and for MTBS: 10 mm × 10 mm × 2 mm) and ultrasonically cleaned. The veneering ceramics (thickness: 2 mm) were vibrated and condensed in stainless steel moulds and fired onto the core ceramic materials. After trying the specimens in the mould for minor adjustments, they were again ultrasonically cleaned and embedded in PMMA. The specimens were stored in distilled water at 37 °C for 1 week and bond strength tests were performed in universal testing machines (cross-head speed: 1mm/min). The bond strengths (MPa ± S.D.) and modes of failures were recorded. Results Significant difference between the two test methods and all-ceramic types were observed ( P < 0.05) (2-way ANOVA, Tukey's test and Bonferroni). The mean SBS values for veneering ceramic to lithium disilicate was significantly higher (41 ± 8 MPa) than those to low leucite (28 ± 4 MPa), glass-infiltrated (26 ± 4 MPa) and leucite-reinforced (23 ± 3 MPa) ceramics, while the mean MTBS for low leucite ceramic was significantly higher (15 ± 2 MPa) than those of leucite (12 ± 2 MPa), glass-infiltrated (9 ± 1 MPa) and lithium disilicate ceramic (9 ± 1 MPa) (ANOVA, P < 0.05). Significance Both the testing methodology and the differences in chemical compositions of the core and veneering ceramics influenced the bond strength between the core and veneering ceramic in bilayered all-ceramic systems.

Dentin adhesion and microleakage of a resin-based calcium phosphate pulp capping and basing cement.

An experimental resin-based bioactive calcium phosphate cement, intended as a pulp capping and basing material, was evaluated for dentin shear bond strength and microleakage. The interfacial morphology was examined by scanning electron microscopy (SEM). For microleakage, dentin cavities without (Group A) or after (Group B) acid etching were restored with the calcium phosphate cement. A resin-based calcium hydroxide (VLC Dycal; Group C) was used as control material according to the manufacturer's instructions. After water storage and thermocycling, the microleakage was scored using a AgNO(3) staining procedure. For the shear bond strength, flat exposed dentin surfaces were treated as for the microleakage test. Metal irises pressed against the dentin surface were filled with the cements, which were photocured. Both tests were carried out after 1 wk. While acid etching did not result in significantly greater microleakage, it led to higher shear bond strength, and allowed, as shown by SEM, the formation of a hybrid layer and resin tags. Both groups treated with the calcium phosphate cement had significantly lower microleakage scores and higher mean shear bond strength values than the groups treated with the control material.

Effect of different bonding agents on shear bond strengths of composite-bonded porcelain to enamel

Statement of Problem. The use of bonding agents in the luting procedure for porcelain laminate restorations to enamel is not clear. Purpose. This study evaluated the shear bond strength differences between an enamel-luting composite and a heat-pressed ceramic with 6 different bonding systems. Material and Methods. Seventy standardized heat-pressed IPS Empress ceramic discs (4-mm diameter, 3-mm height) were prepared. A vertical planar enamel-bonding surface was prepared on the buccal or lingual enamel of 70 freshly extracted sound human molars and premolars. The teeth were oriented to maintain a parallel relationship between the bonding plane and the shear loading axis of a universal testing machine. Tooth specimens were divided into 7 groups (n=10) comprising equal numbers of molars and premolars. The enamel surfaces of specimens in groups 1 through 6 were prepared with 1 of 6 bonding agents (Scotchbond Multi Purpose Plus, Heliobond, PQ1, SE Bond, Prime&Bond NT, and Prompt L-Pop). Finally, the specimens were luted to the ceramic discs with the composite cement (Opal Luting Composite). Ceramic discs in the seventh group (Control) were luted to the etched enamel with the composite cement without using bonding material. Enamel-ceramic specimens were kept in distilled water at room temperature for 30 days after cementation. All specimens were shear loaded axially in a universal testing machine with a crosshead speed of 0.05 mm/min until fracture. Shear bond strength was measured and recorded for each group in MPa. To determine the statistical significance of the differences between the mean shear bond strength values, a 1-way analysis of variance was used (α=.05). Post-hoc multiple comparisons were made with Duncan's multiple range analysis. Fractured surfaces of each specimen were also inspected with a stereomicroscope to evaluate failure modes. Results. A 1-way analysis of variance revealed significant differences between the test groups (P=.00). Bond strength values (MPa) from the highest to the lowest were as follows: Prompt L-Pop, 25.46 ± 5.6; Prime&Bond NT, 18.99 ± 4.93; Heliobond, 17.28 ± 4.0; SE Bond, 16.21 ± 2.6; PQ1, 15.60 ± 2.8; Scotchbond MPP, 14.82 ± 2.4; and Control, 10.55 ± 1.6. Duncan's multiple range post hoc analysis exhibited significant differences between the control group and the adhesive bonding agent groups (P<.05). There were also significant differences between the bonding agent groups (P<.05). Prompt L-Pop showed the highest bond strength values. Conclusion. Within the limitations of this study, bonding agents appear to have a strengthening effect on the shear bond strengths of the enamel/composite/porcelain interface of the materials tested. Bonding agents used in this study showed similar bond strength values except for Prompt L-Pop, which demonstrated the highest bond strength values. (J Prosthet Dent 2003;89:394-9.)

The semi-interpenetrating polymer network matrix of fiber-reinforced composite and its effect on the surface adhesive properties.

This aim of this study was to examine the effect of further-impregnation time of polymer pre-impregnated fiber-reinforcement on polymer matrix structure of the fiber-reinforced composite (FRC) used in dental applications. In addition, shear bond strength between the FRC and veneering composite after various length of further-impregnation was studied. Polymethyl methacrylate (PMMA) pre-impregnated glass fiber-reinforcement was further-impregnated with a diacrylate monomer resin by using five lengths of further-impregnation from 10 min to 24 h. The test specimens (n=5) from each five groups were treated with the solvent tetrahydrofuran and examined with a scanning electron microscope (SEM) to determinate the existence of linear PMMA in the polymer matrix of the FRC. The same lengths of further-impregnation were used to form an adhesive substrate for veneering composite and to measure the shear bond strength (n=8). The SEM examination showed that linear PMMA-polymer and cross-linked diacrylate polymer formed two independent networks for the polymer matrix of FRC. The highest mean shear bond strength value (18.7+/-2.9 MPa) was achieved when the fiber reinforcement was further-impregnated for 24 h. The shortest further-impregnation, 10 min, resulted in the lowest mean shear bond strength (12.7+/-2.9 MPa). A correlation between increased shear bond strength and longer further-impregnation was found (0.689, p<0.001). The results revealed that linear PMMA network of the polymer matrix of the FRC remained in the structure regardless of the various lengths of the further-impregnation with diacrylate resin.