Lowest Bond Strength Values Research Articles

Assessment of the Ability of Different Cleaning Protocols to Remove Eugenol-based Endodontic Sealer from the Root Dentin

The aim of this study is to assess three protocols for removing a eugenol-based filling endodontic sealer from root dentin and the bond strength of fiberglass posts luted with resin cement. Sixty single-rooted bovine teeth were prepared and filled with the Endofill endodontic sealer and gutta-percha cones. After 7 days, 9 mm of the filling was removed and divided into five groups (n = 12) according to the cleaning protocol: G1 (negative control), unfilled; G2 (positive control), saline solution; G3, 95% alcohol; G4, amyl acetate; and G5, Largo bur. The canals were hybridized and fiberglass posts were luted with resin cement. They were cross-sectioned in slices of 1 mm and subjected to the push-out test. The other samples were sectioned longitudinally and visualized in a scanning electron microscope (SEM), and the existing chemical elements were quantified by energy dispersive spectroscopy (EDS). The statistical analysis used variance analysis (ANOVA)-one way and Fisher's test, at a 5% significance level. The 95% alcohol was more effective for cleaning the canal, resulting in a clean dentinal surface and bond strength statistically similar to the negative control. The Largo bur was also statistically similar to the negative control, with only a few debris impregnated on the wall. Amyl acetate showed more sealer residues on the canal walls, with a consequent lower bond strength value than the other groups, only higher than the positive control. The 95% alcohol and Largo burs may be used after removing the canal filling, so that the bond strength is improved when using the eugenol-based sealer.

The Use of Different Photoinitiator Systems in Photopolymerizing Resin Cements Through Ceramic Veneers.

To evaluate the effect of different photoinitiator systems on photopolymerizing resin cements through ceramic veneers with different thickness on microshear bond strength (μSBS), flexural strength (FS), and ultimate tensile strength (UTS) and verify the light attenuation through these ceramic veneers. Four photopolymerizing experimental resin cements were produced with the same resin matrix and associated with four different photoinitiator systems: camphorquinone (CQ), diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), Ivocerin, and TPO + Ivocerin. Eighty disc-shaped ceramic veneers (IPS Empress Esthetic, Ivoclar Vivadent) were fabricated (10-mm diameter) in two different thicknesses: 0.7 and 1.5 mm. A previously characterized multiwave LED (Bluephase G2, Ivoclar Vivadent) was standardized for 40 seconds of photoactivation. Light transmittance through each ceramic veneer thickness (n=5) was measured using a spectrometer (USB 2000, Ocean Optics). The μSBS of each resin cement (n=15) to the ceramic veneer was evaluated using 0.5-mm cylinders with 0.7-mm diameters photoactivated through the different ceramic veneer thicknesses. Samples for FS and UTS tests were made either with or without ceramics veneers (0.7 and 1.5 mm) fixed to the light-curing tip. Data were submitted to two-way analysis of variance and the Tukey test (α=0.05). The multiwave LED emitted higher irradiance into the blue wavelength spectra than into the violet wavelength spectra (p=0.0001). Light transmittance through the ceramic veneers was reduced in a systematic manner based on thickness regardless of the wavelength spectra emitted from the multiwave LED (p=0.00037). The μSBS was reduced in a systematic manner based on thickness regardless of the photoinitiator system (p<0.05). However, resin cements with CQ and Ivocerin showed higher bond strength values in comparison to the resin cement with TPO regardless of the ceramic veneer thickness (p<0.05). The FS and UTS means decreased (p<0.05) with the interposition of 0.7- and 1.5-mm ceramic veneers for all resin cements. The resin cement containing only TPO showed the lowest FS and UTS means (p<0.05) for all ceramic veneers. The thickness of the ceramic veneers reduced the irradiance of the multiwave LED in all wavelength spectra. Ivocerin alone or associated with TPO showed to be an effective alternative photoinitiator to substitute for CQ. The resin cement containing only TPO had lower bond strength values in comparison to resin cements with CQ, Ivocerin, and Ivocerin + TPO.

Push-Out Bond Strength and SEM Evaluation in Roots Filled with Two Different Techniques Using New and Conventional Sealers.

The aim of this study was to evaluate the influence of calcium-silicate-based sealer (Endosequence-BC-Sealer) in roots, filled with thermo-plasticized injectable technique aided by Calamus-Flow-Delivery-System, on bond strength to radicular dentin, in comparison with conventional epoxy-resin-based sealer (AH-Plus) along with cold-lateral-compaction technique. Root canals of mandibular-premolar teeth (n = 80) were instrumented using Protaper Universal rotary files and were randomly divided into four experimental groups (n = 20) as follows: (1) AH-Plus + cold-lateral-compaction technique; (2) Endosequence-BC-Sealer + cold-lateral-compaction technique; (3) AH-Plus + thermo-plasticized injectable technique; and (4) Endosequence-BC-Sealer + thermo-plasticized injectable technique. Horizontal disc shaped samples from each group (n = 60/group) were obtained and push-out bond strength testing was performed at a cross-head speed of 0.5 mm/min. Data were analyzed statistically using nonparametric Kruskal-Wallis analysis and Mann-Whitney test (p < 0.001). The statistical analysis revealed a significant difference amongst the groups (p < 0.001). The highest bond strength values were found in group 1 compared with all the other experimental groups (p < 0.001), whereas the lowest bond strength values were found in group 4 (p < 0.001). It was concluded that thermo-plasticized injectable technique with Calamus-Flow-Delivery-System lowered the bond strengths of the sealers, especially Endosequence-BC-Sealer. Therefore, this technique is not recommended to calcium-silicate-based sealers. Further studies are needed to confirm the findings of this study.

Effect of collagen cross-linkers on micro tensile bond strength of total-etch adhesive to dentin

Purpose: To evaluate the efficiency of collagen cross-linkers on micro-tensile bond strength of total-etch adhesive with and without thermal cycling. Materials and methods: The occlusal surfaces of twenty-four caries-free permanent human molars were ground flat to obtain a uniform surface free of enamel exposing the mid thickness of dentine. The prepared speciemens were randomly divided into four equal test groups according to the type of dentin pretreatment (n=6). Group I; control group: the exposed dentin did not receive additional treatment after acid etching. Group II; the etched dentin was treated with Gluma Desensitizer(GA). Group III; the specimens surface was painted with 5% glutaraldhyde solution (GD). Group IV; the specimen surface was painted with 15% proanthocyanidin (PA). Single Bond Universal adhesive was applied to the dentin surface of all the test groups and the dentin specimens were restored with resin composite. The specimens were sectioned to obtain beams of 0.9±0.1 mm in thickness and 5.5±1 mm in length and half of the resultant beams of each group were subjected to thermo cycling. Tensile load was applied until bonding failure of the specimen occurred and micro tensile bond strength was calculated in Mega Pascal. Comparison between all test groups was done using One Way ANOVA followed with Tukey’s post hoc test when the ANOVA test was significant. p value was ≤0.5. Comparison between the thermocycled and none thermocycled groups was done using unpaired student t test. Results: The highest statistically significant microtensile bond strength values were found in the Gluma and GD surface pretreated groups, with no statistical significant difference between them. The lower micro tensile bond strength values were found in the control and PA groups with no significant difference between them, while thermocycling did not decrease the microtensile strength values of the PA group.Conclusions:1-Gluma and glutaraldehyde used as cross-linkers increased the microtensile bond strength of dental adhesive to dentin and maintain collagen stability with thermocycling. 2-The PA cross-linkers did not improve microtensile bond strength but maintain bond stability with thermocycling increasing the longevity of the adhesive bond.

Effect of Thermocycling, Teeth, and Polymerization Methods on Bond Strength Teeth-Denture Base.

Objective To evaluate the shear bond strength between different artificial teeth and denture base polymerized by two polymerization methods submitted to thermocycling. Materials and Methods Two acrylic resins were selected according to the polymerization method (water-bath and microwave), and four different artificial teeth (Biotone, Dentsply; Trilux, Vipi Dent; Premium 8, Heraeus Kulzer; Soluut PX, Yamahachi) were also tested. The polymerization of the acrylic resin was performed by using conventional cycle (8 h at 74°C) in water-bath and using two cycles (20 min at 270 W + 5 min at 360 W) by the microwave method. The shear bond strength was evaluated after 24 h of water storage at 37°C (immediately) and after the thermocycling test (5,000 cycles, 5–55°C). The shear bond strength (n=10) was performed using a universal testing machine (Instron 4411) at a crosshead speed of 1.0 mm/min. Modes of failures were classified as cohesive and adhesive. The data (MPa) were statistically analyzed by three-way ANOVA, and the mean values were compared by the Tukey test (α = 0.05). Results In general, the polymerization by microwave showed the highest shear bond strength values, and Trilux artificial teeth had the lowest bond strength values (p < 0.05). Thermocycling did not affect the shear bond strength (p < 0.05). There was a predominance of cohesive failures for all groups. Conclusions The chemical composition of the artificial teeth affects the bond strength, and the microwave method is preferable to perform the acrylic resin polymerization.

Assessment the Bond Strength of Ceramic Brackets to CAD/CAM Nanoceramic Composite and Interpenetrating Network Composite after Different Surface Treatments.

Adult orthodontics may confront problems related to the bonding performance of orthodontic brackets to new generation restorative materials used for crown or laminate restorations. The aim of the present study was to investigate the shear bond strength of ceramic brackets to two new generation CAD/CAM interpenetrating network composite and nanoceramic composite after different surface treatments. Er,Cr:YSGG Laser, hydrofluoric acid (9%), sandblasting (50 μm Al2O3), and silane were applied to the surfaces of 120 CAD/CAM specimens with 2 mm thickness and then ceramic brackets were bonded to the treated surfaces of the specimens. Bond strength was evaluated using the shear bond strength test. According to the results, CAD/CAM block types and surface treatment methods have significant effects on shear bond strength. The lowest bond strength values were found in the specimens treated with silane (3.35 ± 2.09 MPa) and highest values were found in the specimens treated with sandblast (8.92 ± 2.77 MPa). Sandblasting and hydrofluoric acid surface treatment led to the most durable bonds for the two types of CAD/CAM blocks in the present study. In conclusion, different surface treatments affect the shear bond strength of ceramic brackets to CAD/CAM interpenetrating network composite and nanoceramic composite. Among the evaluated treatments, sandblasting and hydrofluoric acid application resulted in sufficient bonding strength to ceramic brackets for both of the CAD/CAM materials.

Longevity of bond strength of resin cements to root dentine after radiation therapy.

To evaluate the bond strength and adhesive interface between several resin cements and root dentine immediately and 6months after radiotherapy. Sixty maxillary canines were selected and randomly assigned to two groups (n=30): one group was not irradiated and the other one was subjected to a cumulative radiation dose of 60Gy. The teeth were sectioned to obtain roots 16mm long and the canals were prepared with the Reciproc system (R50) and filled using a lateral condensation technique with an epoxy resin sealer. Each group was divided into three subgroups (n=10) according to the resin cement used for fibreglass fibre post cementation: RelyX-U200, Panavia-F2.0 and RelyX ARC. The posts were cemented in accordance with the manufacturer's recommendations. Three 1-mm-thick dentine slices were then obtained from each root third. The first two slices in the crown-apex direction of each third were selected for the push-out test. The failure mode after debonding was determined with a stereo microscope. The third slice from each root third was selected for scanning electron microscopy (SEM) analyses to examine the resin cement-dentine interface with 100, 1000, 2000 and 4000× magnification. Bond strength data were analysed by anova and Tukey's test (α=0.05). Significantly lower bond strength (P<0.0001) was obtained after irradiation compared to nonirradiated teeth. RelyX-U200 cemented fibre posts had the higher bond strength (15.17±5.89) compared with RelyX ARC (P<0.001) and Panavia-F2.0 (P<0.001). The evaluation after 6months revealed lower bond strength values compared to the immediate values (P<0.001) for irradiated and nonirradiated teeth. Cohesive failures occurred in the irradiated dentine. SEM revealed fractures, microfractures and fewer collagen fibres in irradiated root dentine. RelyX-U200 and Panavia-F2.0 were associated with a juxtaposed interface of the cement with the radicular dentine in irradiated and nonirradiated teeth, and for RelyX ARC, hybrid layer formation and tags were observed in both irradiated and nonirradiated teeth. Radiation was associated with a decrease in the push-out bond strength and with lower resin cement/root dentine interface adaptation. Self-adhesive resin cement was a better alternative for fibre post cementation in teeth subjected to radiation therapy. The bond strength decreased after 6months.

INFLUENCE OF DIFFERENT BLEACHING SYSTEMS ON THE BOND STRENGTH OF LAMINATE VENEER TO ENAMEL

Purpose: The objective of this in-vitro study was to examine the microtensile bond strength of a porcelain laminate veneer (PLV) to tooth surface bleached with photoactivation by blue light-emitting diode (LED) or diode laser. Methods: Eigthteen extracted human central incisors were randomly divided into three groups. Two sticks were obtained from each tooth (n=12). Before surface treatments; teeth were prepared to provide space for PLVs. The first group teeth were bleached with Whiteness HP which is contain 35% hydrogen peroxide (HP) and then photoactivated with a LED for 20 seconds. The second group were bleached with Laserwhite 20 which is contain 46% HP and photoactivated with a diode laser for 30 seconds. The third group received no surface treatment and served as the control group. IPS Esthetic ceramic veneers were luted with Variolink II veneer cement . The teeth were sectioned to obtain porcelain-resin-enamel/dentin sticks and submitted to a MTB testing device. The maximum load at fracture was recorded. Data were analyzed using one-way ANOVA followed by the Tukey HSD post-hoc test at a preset α of 0.05. Results: One-way ANOVA revealed that there was significant difference between LED unit group and control group (p&lt;.05) but no statistical differences were observed with diode laser group (p&gt;.05) The LED unit group presented significantly lower bond strength value (6.49±2.3 MPa) than diode laser (8.49 ±3.1 MPa) and control groups (9.53±2.7 MPa). Conclusion: The results suggested that bleaching therapy with activation by LED or diode laser reduced the bond strength of IPS Esthetic ceramic veneers to tooth surfaces.&#x0D; Keywords: Teeth Bleaching; Photoactivation; Semiconductor lasers; Diode laser; Microtensile.

Effects of Postsurface Treatments Including Femtosecond Laser and Aluminum-oxide Airborne-particle Abrasion on the Bond Strength of the Fiber Posts.

Bond strength of fiber posts. The purpose of this study was to evaluate the effect of different Post Surface treatment techniques on the push-out bond strength of the quartz fiber posts. A total of 30 maxillary central incisors were decoronated at cementoenamel junction. Root canals were filled and postspaces were prepared. The specimens were classified into three groups according to the surface treatment performed to the postsurface (n = 10) as no surface treatment (control group) (Group 1), A 50-μm aluminum-oxide airborne-particle abrasion group (Group 2), femtosecond laser (FS) group (Group 3). A self-curing adhesive cement was used for cementation of posts. Six sections (two coronal, two middle, and two apical) of 1-mm thickness specimens were prepared with a slow speed diamond saw. Specimens were stored in distilled water at 37°C for 24 h. Then, push-out test was performed on a universal testing machine. The data were analyzed by one-way ANOVA (α = 0.05). The test results indicated that push-out test values significantly different according to surface treatments among groups (P < 0.05). There were no significant differences between root sections of each group for bond strength (P > 0.05). All dislodged Group 3 posts were free of cement, indicating adhesive failure, Group 1 and 2 were partially coated with cement, indicating a mixed failure at the cement/postsurface. Based on the results, aluminum-oxide airborne-particle abrasion group showed higher and FS irradiation group showed lower bond strength values. Push-out bond strength values of the root segments were the same in all groups.

The Etching Effect of Co2 Laser on The Shear Bond Strength of Bleached Teeth

Background: Tooth discoloration is one of the great esthetic problems in dentistry, Despite vital bleaching, is often considered a first step to improve the appearance of teeth, reports are controversial about the effect of bleaching on the shear bond strengths (SBS) of brackets. Etching of enamel surface can be carried out by acid or laser, there was controversial about the efficiency of CO2 laser as enamel surface etchant Objective: The aim of the present study is to detect if there is a significant reduction in SBS of bleached teeth, and to detect the effect of CO2 laser as etchant on both bleached and normal teeth. Methods and materials: Forty non-carious first premolars are divided into 2 main groups: None- bleached (A) and Bleached (B) groups, of 20 specimens for each group, then the groups were subdivided into 2 subgroups (10 specimens for each subgroup). Group (B) teeth were bleached with chemically activated 40% hydrogen peroxide, while group (A) teeth were left without bleach- ing. The subgroups teeth (A1 and B1) were etched with CO2 laser and the subgroups (A2 and B2) were etched with 37% phosphoric acid. After bracket bonding, samples were then thermally cycled for 500 cycles between( 5°C and 55°C). Debonding was performed with a shearing force using the universal testing machine, then ANOVA and LSD test were used to specify if there was a significant difference between groups. Results: there was the nonsignificant difference in mean SBS of both phosphoric acid etching and CO2 laser etching in both bleached and normal surface enamel specimens A and B groups. Whereas there was a significant difference in mean shear bond strength between the CO2 laser etched and the phosphoric acid etched groups with highest mean values in the phosphoric acid etched subgroups, Conclusion: The results of this in vitro study suggest that hydrogen peroxide bleaching does not affect the shear bond strength of metal orthodontic brackets when bonding occurred 1 week after bleaching and CO2 laser etching has low shear bond strength values making it not suitable for clinical use.

Bond strengths of bulk-fill resin composite repairs: effect of different surface treatment protocols in vitro

To evaluate the effect of different surface treatment protocols on the microtensile bond strength (μTBS) of bulk-fill resin composite repairs. Thirty-five bulk-fill resin composite samples (Filtek Bulk Fill) were prepared (5 × 5 × 5 mm) and aged by thermocycling (X5000). Samples were randomly divided into five groups (n = 7): a control (no treatment) and four surface treatment groups (Single Bond Universal [SBU]; phosphoric acid (37%) + SBU; Er,Cr:YSGG laser + SBU; aluminum oxide sandblasting + SBU). Filtek Ultimate Universal composite was used as a repair material. After storage for 24 h in distilled water (37 °C), sticks were obtained and subjected to a μTBS test. The data (MPa) were analyzed by one-way ANOVA with a post hoc test (α = 0.05). Failure mode was evaluated using a light microscope (10×). There were significant differences between the groups (p < 0.05). The lowest bond strength values were obtained in the control group (p < 0.05). No significant difference was observed between Group II (universal adhesive) and Group III (acid etch + universal adhesive) (p > 0.05). The bond strength of Group II was significantly lower than that of the other surface treatment groups (p < 0.05). While Group III showed significantly lower values than those of the laser treatment group (Group IV), similar values were obtained with Al2O3 sandblasting group (Group V). The highest repair bond strength was obtained in Group IV (p < 0.05) which was not significantly different from the Al2O3 sandblasting group (p > 0.05). The predominant failure mode was adhesive. Treatment of aged bulk-fill resin composite surfaces with laser and Al2O3 sandblasting provided higher repair bond strength values.

BONDING ABILITY OF DIFFERENT LINERS TO BULK-FILL RESIN COMPOSITE USING SILANE-CONTAINING ADHESIVE

Aims: To compare and evaluate the bonding ability of bulk-fill resin composite (RC) to four different liners: Biodentine (BD), TheraCal (TLC) - a novel resin-modified calcium silicate cement, resin-modified glass ionomer cement (RMGIC) and conventional glass ionomer cement (GIC) using a universal silane-containing adhesive and characterizing their failure modes.Materials and Methods: Forty extracted intact human premolars with occlusal cavity (4-mm diameter and 2-mm height) were mounted in acrylic blocks and divided into four groups of (n=10 samples) each based on the liner used as group I; (BD), group II; (TLC), group III; (RMGIC) and Group IV; (GIC). Bulk-fill composite buildup of 3 mm diameter and 5 mm height was then bonded to each sample using universal adhesive. Shear bond strength (SBS) analysis was performed using materials testing machine at a cross-head speed of 0.5 mm/min. Statistical Analysis: Statistical analysis was performed with one-way analysis of variance (ANOVA) and Tukey’s post hoc test for numerical data while chi square test for categorical one. Results: One-way analysis with ANOVA revealed significant difference in bond strength values between the different groups (p<0.001). The observed modes of failure were predominantly cohesive in Biodentine, TheraCal and GIC groups while RMGIC showed majority of mixed and minority adhesive failures.Conclusions: Biodentine demonstrated lower bond strength values when immediately bonded to bulk-fill resin composite compared with RMGIC, TheraCal and GIC groups

Influence of early mineral deposits of silicate- and aluminate-based cements on push-out bond strength to root dentine.

To evaluate mineral trioxide aggregate (MTA), Biodentine and several formulations of calcium aluminate cements (CACb) in terms of their ability to release calcium ions (Ca2+ ) and form apatite-like precipitates after short-term immersion in phosphate-buffered saline (PBS) and its influence on the bond strength to the root-end cavity. Ten samples of MTA, Biodentine, CACb and calcium-enriched aluminate cement (CACb+) were placed in contact with PBS or deionized water for 14days. The cement surfaces were analysed using SEM, EDS-X and FTIR. Eighty standardized root-end cavities filled with the cements (ten samples of each cement) were immersed in PBS or deionized water for 14days, and the bond strengths were measured. Data from the push-out test were analysed using two-way ANOVA and Tukey's tests (α=0.05). A gradual decrease was observed in Ca2+ concentrations and pH of all solutions. FTIR bands of different phases of hydroxyapatite were identified. Crystalline formation was observed on the surface of all cements after immersion in PBS. No significant difference was observed in the bond strength of the test materials (P>0.05); however, all cements without contact with the solution revealed significantly lower bond strength values than those in contact with the solution (P<0.05). MTA, Biodentine, CACb e CACb+ were associated with precipitation of crystals after being in contact with PBS for 14days, indicated by different phases of hydroxyapatite crystalline formation, which also increased dislodgment resistance of the material from root-end cavities. The CACb+ had similar bond strengths and precipitation of crystals to existing materials.

Adhesive system affects repair bond strength of resin composite.

This study evaluated the effects of different adhesive systems on repair bond strength of aged resin composites. Ninety composite discs were built and half of them were subjected to thermal aging. Aged and non-aged specimens were repaired with resin composite using three different adhesive systems; a two-step self-etch adhesive, a two-step total-etch adhesive and a one-step self-etch adhesive; then they were subjected to shear forces. Data were analyzed statistically. Adhesive type and aging significantly affected the repair bond strengths (p<0.0001). No statistical difference was found in aged composite groups repaired with two-step self- etch or two-step total-etch adhesive. One-step self-etch adhesive showed lower bond strength values in aged composite repair (p<0.0001). In the repair of aged resin composite, two-step self-etch and two-step total-etch adhesives exhibited higher shear bond strength values than that of one-step self-etch adhesive.

Composite resin repairs: What is the most effective protocol?

Objective: The objective of this study was to evaluate the combination effect of surface treatments and bonding agents on bond strength of repairs on aged composite resin. Materials and Methods: One hundred twenty microhybrid composite units (Filtek Z250) aged in distilled at 37ºC water for six months were submitted to different surface treatment prior to resin repairs. Ten specimens were randomly divided into 12 groups: non-treated/no bonding agent (negative control), sandblasting /no bonding agent, silane/no bonding agent, non-treated/ etch-and-rinse; non-treated/one-step self-etch; non-treated/ two-step self-etch; sandblasting/etch-and-rinse; sandblasting/one-step self-etch; sandblasting/two-step self-etch; silane coupling agent/etch-and-rinse; silane coupling agent/ one-step self-etch; silane coupling agent/two-step self-etch. Microshear testing was performed to bond strength assessment. Results: Two-way ANOVA and Tukey’s test (?=0.05) demonstrated significant difference between the surface treatments and adhesive systems. Only no treated surface/etch-and-rinse group showed lower bond strength values when compared to other groups. Conclusion: The considered surface treatments were capable to increase the effectiveness of the repair in composite resin when using the adhesive etch-and-rinse.

Prototype to measure bracket debonding force in vivo.

ABSTRACTIntroduction: Material biodegradation that occurs in the mouth may interfere in the bonding strength between the bracket and the enamel, causing lower bond strength values in vivo, in comparison with in vitro studies. Objective: To develop a prototype to measure bracket debonding force in vivo and to evaluate, in vitro, the bond strength obtained with the prototype.Methods: A original plier (3M Unitek) was modified by adding one strain gauge directly connected to its claw. An electronic circuit performed the reading of the strain gauge, and the software installed in a computer recorded the values of the bracket debonding force, in kgf. Orthodontic brackets were bonded to the facial surface of 30 bovine incisors with adhesive materials. In Group 1 (n = 15), debonding was carried out with the prototype, while tensile bond strength testing was performed in Group 2 (n = 15). A universal testing machine was used for the second group. The adhesive remnant index (ARI) was recorded.Results: According to Student’s t test (α = 0.05), Group 1 (2.96 MPa) and Group 2 (3.08 MPa) were not significantly different. ARI score of 3 was predominant in the two groups.Conclusion: The prototype proved to be reliable for obtaining in vivo bond strength values for orthodontic brackets.

Evaluation of Effect of Zirconia Surface Treatment, Using Plasma of Argon and Silane, on the Shear Bond Strength of Two Composite Resin Cements.

Yttria stabilised tetragonal zirconia opens new vistas for all ceramic restoration by the mechanism of transformation toughening, making it much stronger compared to all other ceramic materials. Currently, it is the most recent core material for all ceramic fixed partial dentures due to its ability to withstand high simulated masticatory loads. Problems which have been reported with zirconia restorations involve the core cement interface leading to loss of retention of the prosthesis. Different reasons which have been reported for the same include the lack of adhesion between zirconia and commonly used cements due to absence of silica phase which makes zirconia not etchable. In addition, the hydrophobic nature of zirconia causes low wettability of zirconia surface by the adhesive cements which are commonly used. The purpose of this in vitro study was to compare and evaluate the effect of two pre-treatments of zirconia, using plasma of argon and silane, on the shear bond strength values of two composite resin cements to zirconia and to evaluate the failure pattern of the debonded areas using stereomicroscopic analysis. Sixty zirconia discs (10 mm×2 mm) were randomly divided into three groups (n=20), following surface treatment, with airborne particle abrasion, using 110 µm Al2O3: Group I (control), Group II (plasma of argon cleaning), and Group III (application of silane primer). Each group had two subgroups based on the type of resin cement used for bonding: subgroup A; Rely X Ultimate (3M ESPE) and subgroup B; Panavia F (Kuraray). In subgroup A, Rely X universal silane primer and in subgroup B Clearfil ceramic primer was used. Shear bond strengths were determined after water storage for one day and thermocycling for 5000 cycles. Data (megapascal) were analyzed using ANOVA and Bonferroni test. Specimens were subjected to stereomicroscopic analysis, for evaluation of failure pattern. Group III produced the highest shear bond strength followed by Group II and Group I. Subgroup A showed higher shear bond strength than Subgroup B. Stereomicroscopic analysis showed cohesive failure in Group III, while in Group I adhesive failure was seen. Silane primer application caused maximum increase in shear bond strength due to increased wettability. Argon plasma treatment was less effective in comparison to silane treatment. Air abrasion when used alone resulted in lower bond strength values, thereby making it necessary to use a combination of surface treatments. Rely X Ultimate cement was superior to Panavia F in terms of adhesive bonding to zirconia.

Comparison between three glass fiber post cementation techniques.

The aim of this experimental study was to compare the traditional cement systems with those of the latest generation, to assess if indeed these could represent of viable substitutes in the cementation of indirect restorations, and in the specific case of endodontic posts. The assessment of the validity of the cementing methods was performed according to the test of the push-out, conducted on sections obtained from the roots of treated teeth. The samples were divided into three groups. Group A (10 samples): etching for 30 seconds with 37% orthophosphoric acid (Superlux-Thixo-etch-DMG) combined with a dual-curing adhesive system (LuxaBond-Total Etch-DMG), dual-cured resin-composite cement (LuxaCore-DMG) and glass fiber posts (LuxaPost-DMG). Group B (10 samples): self-adhesive resin cement (Breeze-Pentron Clinical) and glass fiber posts (LuxaPost-DMG). Group C (10 samples): 3 steps light-curing, self-etching, self-conditioning bonding agent (Contax-Total-etch-DMG), dual-cured resin-composite cement (LuxaCore-DMG) and glass fiber posts (LuxaPost-DMG). The survey was conducted by examining the breaking resistance of the post-cement-tooth complex, subjected to a mechanical force. Statistical analysis was performed using SPSS Inc. ver. 13.0, Chicago, IL, USA. Group A values of bond strenth ranged from a minimum of 10.14 Mpa to a maximum value of 14.73 Mpa with a mean value of 12.58 Mpa. In Group B the highest value of bond strength was 6.54 Mpa and the minimum 5.55 Mpa. The mean value of the bond strength for the entire group was 6.58 Mpa. In Group C the highest bond strength was 6.59 Mpa whereas the lowest bond strength was 4.84 Mpa. Mean value of the bond strength of Group C was calculated at 5.7 Mpa. Etching with orthophosphoric acid combined with a dual-curing adhesive system and a dual-cured resin-composite cement was the technique that guaranteed the highest bond strength. Lowest bond strength values were obtained when dual self-adhesive cement was used.

Influence of pH cycling and mechanical loading on the resin-dentin microtensile bond strength

The durability of adhesive interfaces is still a problem in adhesive restorations in dentistry. Laboratorial ageing methods have been proposed to predict the performance of materials, but they still require standardization. The objective of this study was to evaluate the resin-dentin microtensile bond strength of composite restorations subjected to pH cycling and different levels of mechanical loading. Resin blocks were built over a flat superficial dentin of bovine incisors (n = 40), using a three-step adhesive system. Half of the specimens were submitted to 10 cycles of pH cycling, followed by mechanical loading (0, 500,000; 1,000,000; 2,000,000 cycles – 98 N, 4 Hz). The other half was directly subjected to mechanical loading. After ageing, all groups were subjected to a microtensile bond test. Data were analyzed using two-way ANOVA and Tukey’s test (α = 0.05). The frequency of the early de-bonding was compared using the Chi-square test (α = 0.05). The statistical analysis revealed that the cross-product interaction ‘pH cycling’ vs. ‘number of mechanical loading cycles’ (p = 0.72) as well as the main factor ‘pH cycling’ (p = 0.49) was not statistically significant, and they were not able to reduce the resin–dentin bond strength values. Regarding the number of mechanical loading cycles, the groups subjected to 2,000,000 cycles showed lower bond strength values than the others (p = 0.003). The frequency of debonded specimens increased with mechanical loading. Therefore, it can be concluded that in this restorative model, at least 2,000,000 mechanical cycles are need to decrease the microtensile strength and simulate the ageing of the interface.

The effect of denture cleansers on surface roughness and bond strength of a denture base resin‏

Purpose: The purpose of this study was to evaluate the effect of different denture cleaning regimens on surface roughness of denture base material and bond strength to hard reline material.Materials and methods: 100 disk-shaped specimens were prepared from a denture base resin and immersed into the following five groups (n = 20): Group C: Corega Tabs, Group P: Protefix Tabs, Group CU: ultrasonic device with Corega Tabs and Group PU: ultrasonic device with Corega Tabs, and Control: distilled water. All cleaning protocols were applied for 90 times to each specimen according to the instructions of the manufacturers. Surface roughness values were measured using a profilometer and surface evaluations were performed with scanning electron microscope (SEM). Reline materials were applied on the specimens and shear tests were performed using a Universal Testing Machine. Data were analyzed using One-way ANOVA and Tukey’s post hoc tests were used for comparison among groups with a significance level of 0.05.Results: Group PU and group CU showed significant increase in surface roughness values compared to group P, C, and Control (p < 0.05). Control group showed significantly lower shear bond strength values compared to the other groups (p < 0.01). Group P exhibited higher shear bond strength values compared to group C (p = 0.003). No significant differences were found between group P and PU (p = 0.945), same results were found between group C and CU (p = 0.283).Conclusion: Using denture cleansers with ultrasonic devices significantly affected the surface topography of denture bases. All tested cleaning regimens increased the bond strength of hard reline material to the denture base.