Thermo Cycling Research Articles

Effect of Acid Surface Treatments on the Shear Bond Strength of Metal Bracket to Zirconia Ceramics

The surface treatment of zirconia prior to bonding remains controversial and unclear. This study aimed to compare the shear bond strength (SBS) of metal brackets to zirconia under surface treatments with either 4% HF or 37% PA in both immediate loading (IML) and artificial aging by thermocycling (TMC). Methods: Eighty-four zirconia were randomly assigned to six groups based on the surface treatment and artificial aging by TMC: (1) No surface treatment (NT); (2) NT + TMC; (3) HF (4% HF for 2 min); (4) HF + TMC; (5) PA (37% PA for 2 min); and (6) PA + TMC. After bracket bonding, only the TMC groups were thermocycled for 5000 cycles. The SBS and adhesive remnant index (ARI) of all groups were analyzed (p < 0.01). Results: TMC significantly lowered the SBS more than the IML in all acid surface treatment groups (p < 0.01). The ARI score after TMC was significantly higher than the IML in all acid surface treatment groups (p < 0.001). No significant differences in the SBS values or ARI scores were observed among the surface treatments (p > 0.01). Conclusions: Two-minute simple etching methods, using either 4% HF or 37% PA, showed an insufficient SBS of metal orthodontic brackets to zirconia after TMC.

Evaluation of surface microhardness and gingival marginal adaptation of three different bulk-fill flowable resin composites: A comparative study.

To evaluate surface microhardness and gingival marginal adaptation of three different bulk-fill flowable resin composites (FB-RBCs) in Class V cavities with enamel or dentin margins before and after thermocycling (TMC). Three available FB-RBCs were used; Palfique Bulk Flow (PaBF) (Tokuyama Dental), SDR Flow+ Bulk Fill Flowable (Dentsply Sirona), and I-Flow Bulk Fill (I-Dental). Thirty discs were prepared from each type of FB-RBCs. The discs were subjected to Vickers microhardness tester machine. Class V cavities were prepared on 180 molars. Gingival margins of half the specimens were prepared above CEJ and the other half below CEJ. Cavities were restored with FB-RBCs for gingival marginal adaptation test. Two-way ANOVA was used in microhardness, while three-way ANOVA was used for marginal adaptation. The used materials showed statistically significant differences in microhardness and marginal adaptation. Regarding microhardness, PaBF showed the highest value before TMC and SDR was the highest after TMC. Regarding marginal adaptation, SDR revealed the best marginal adaptation than PaBF and I-flow, either subjected to TMC or not. The longevity of cervical restorations depend on both the location of the cavity margin and the material used. The microfractures in resin composite surface due to low surface microhardness as well as marginal gaps seen in laboratory studies could be considered as an indicative parameter for clinical problem associated with marginal differences.

Effect of silver diamine fluoride on the microleakage of flowable resin composite and glass ionomer cement restorations to carious primary dentin: an-in vitro study

BackgroundThis study aimed to evaluate the effect of Silver Diamine Fluoride (SDF) on the microleakage of flowable resin composite (FRC) and resin-modified glass ionomer cement (GIC) restorations bound to carious primary dentin.MethodsForty-four extracted carious primary molars were allocated into four groups as follows (n = 11 teeth/group): Group I, Flowable resin composite (FRCa): SDF38% treatment + FRC, Group II, Flowable resin composite (FRCb): FRC without SDF treatment, Group III, Resin-modified glass ionomer cement (GICa): SDF38% treatment + GIC, Group IV, Resin-modified glass ionomer cement (GICb): GIC without SDF treatment. Specimens were subjected to thermo cycling at 500 cycles between 5 to 55 °C (dwell time of 60 seconds) in baths before being immersed for 24 h in a 1% toluidine blue solution. Microleakage testing was conducted for each specimen in two areas; occlusal and gingival. Specimens were evaluated under stereomicroscope at 4x magnification. Results were analyzed using Kruskal-Wallis test followed by pairwise comparisons utilizing Dunn’s post hoc test at p ≤ 0.05.ResultsInsignificant differences between different groups (p = 0.49) were observed at the gingival walls area readings. The highest value was found in GICb (2.33 ± 0.52), while the lowest value was found in FRCa (1.71 ± 0.76). Insignificant differences between different groups (p = 0.982) were observed at the occlusal walls area readings. The highest value was found in FRCa (1.43 ± 0.98), while the lowest value was found in GICb (1.17 ± 1.33).ConclusionSDF does not adversely affect the microleakage of FRC and GIC restorations bound to carious primary dentin.

Dimensional stability of acrylic denture base material after poly vinyl pyrrolidone addition

Problem Denture base dimensional changes were found with commercial theremocured acrylic resins. The dimensional stability of acrylic resin denture base is the main necessity effects the retention and stability of the denture. This study was conducted to measure the dimensional accuracy of experimental prepared material in comparison with control material before and after thermo cycling cured by water bath and microwave. In this stady the total (40) specimens of heat cure acrylic resin lower denture base were cured by water bath and microwave after addition poly vinyl pyrrolidone (PVP). (Experimental). Preparation of modified heat cured denture base acrylic resin was carried out by preparing of (PMMA) (80%) and poly vinyl pyrrolidone (PVP) (20%) and the liquid part composed of methyl methacrylate (MMA) monomer. Evaluation was made by measuring dimensional stability and accuracy. Distances were measured between (3) points marked on denture bases "AB, AC and BC" before and after thermo cycling for both control and experimental groups. The result of this study showed that there was no significant differences (p>0.05) between control and experimental groups at three point "AB, AC and BC" before and after thremocycling. Dimensional stability and accuracy was not influenced by addition of PVP to acrylic denture base resin before and after thermo cycling in both heat and microwave treatment.

The Effect of Thermo Cycling on Fracture Resistance Of Temporary Prosthesis Fabricated By CAD/CAM With Composite- Based Material

Aim: The objective of this study was to evaluate the effect of thermo cycling on fracture resistance of temporary prosthesis constriction by computer-aided design/ computer-aided manufacturing (CAD/CAM) with those of composite materials. Material and Methods: A dentoform maxillary molar tooth was prepared for full coverage crown, temporary prosthesis was constriction and divided into the following groups: CAD/CAM poly (methyl methacrylate) (PMMA) blocks, and auto- polymerizing temporary material. All specimens were subjected to thermo cycling and then fracture strength was measured by a universal testing machine. Results: The mean ± Stander deviation values for CAD CAM group before thermo cycling (560.50 ±83.581 Newton) and after thermo cycling (901.00± 311.598 Newton) were recorded statistically significant higher fracture resistance mean compared with composite fabricated interim restorations. Conclusion: Interim prosthesis constructed using CAD CAM technique showed higher fracture

Recycling CAD/CAM lithium disilicate ceramic: effect of surface treatment and aging on the bond strength to resin cement.

To investigate the effect of recycling of lithium disilicate (LD), surface treatment and thermocycling (TC) on the bond strength (SBS) to resin cement. Blocks of LD were made according to the recycling cycle, with 24 blocks for each strategy: Control-conventional sintering; 1R (1 recycling cycle) and 3R (3 recycling cycles). For the recycling groups, blocks were waxed (10x10x3mm), mounted in a silicone ring, poured with investment material, and then residues of sintered LD blocks were pressed by the lost wax technique. The residual LD was reused as described until reach 3R. Afterwards, the blocks were embedded in acrylic resin, sanded and divided (n=15) according to the factors "surface treatment" (HF20s+Silane and HF120s+Silane and Monobond Etch&Prime- MEP) and TC (with/10.000 cycles and without). After surface treatment, cylinders (Ø:2mm) of resin cement were made and submitted to SBS test (100KgF,1mm/min). Data (MPa) were analyzed by 3-way ANOVA, Tukey's test (5%) and Weibull analysis. Failure analysis was performed with stereomicroscope. ANOVA revealed that all factors were significant (P=.000*). The group 3RMEP(105.09±19.49) presented the highest SBS among the experimental groups. 1RHF20sTc(7.50±1.97) group had the lowest SBS, similar to the CHF20sTc(15.69±3.77), 1RHF20s(15.12±3.03), 1RHF120sTc(14.60±3.43) and 3RHF20sTc(15.65±0.97). The Weibull modulus and characteristic strength varied among the experimental groups (P=0.0). Failure analysis revealed adhesive and mixed types. The recycling of DL ceramics increases the SBS to resin cement when the ceramic is treated with HF120s+S or MEP.

The effect of thermal aging on flexural strength of CAD/CAM hybrid and polymeric materials

The field of dentistry is consistently innovating with the introduction of novel hybrid and polymer materials for computer-aided design and manufacturing (CAD/CAM). It is noteworthy that the temperature within the oral cavity has a significant impact on the strength of new biomaterials utilized for CAD/CAM fabrication of fixed partial dentures (FPDs). Studies have demonstrated that alterations in intraoral temperature may significantly affect the longevity and durability of dental restorative materials. This study aimed to evaluate the flexural strength, flexural modulus, and effect of thermal aging on CAD/CAM restorative materials. Five CAD/CAM materials were investigated: nano-ceramic-hybrid (GR), polymer-infiltrated-ceramic-network (VE), polyether-ether-ketone (PK), fiberglass-reinforced epoxy-resin (CT), and Feldspar Ceramic (VB). A total of 100 bar-shaped specimens were prepared (N = 20). Each group was subdivided into thermocycling (TC) and no-thermocycling (NTC) subgroups (n = 10). All the specimens underwent a 3-point bending test. The mean flexural strengths and moduli were statistically analyzed using paired t-test, analysis of variance (ANOVA), and Bonferroni pair-wise comparison (p < 0.05). Significant differences were observed in the flexural strength (FS) and modulus (E) between the materials (p < 0.001). GR had the highest FS among tested hybrid materials. NTC CT had the highest FS (924.88 ± 120.1 MPa), followed by GR (385.13 ± 90.73 MPa), then PK (309.56 ± 46.84 MPa). The FS of brittle ceramic VB was the lowest (p < 0.001), but similar to that of PICN VE. Only resin-containing VE and CT significantly decreased in E after thermocycling (p < 0.01, p = 0.013), showing the softening effect of thermocycling on their resin matrix. It can be concluded that new hybrid materials (GR) had higher flexural strength than feldspar ceramic and other resin/polymeric CAD/CAM materials. Polymeric PEEK and GR hybrid materials were resistant to significant deleterious effects of TC. Therefore, they would be appropriate for situations with a higher stress load.

Comparison of Resin Composite and Biodentine Cervical Marginal Elevation on the Marginal Gap of Two Computer-Aided Design/Computer-Aided Manufacture Endocrown Materials: In Vitro Study

Objective: This study is the impact of resin composite and bio dentine cervical marginal elevation on vertical marginal gap using two CAD/CAM endo-crowns. Materials and Methods: 32 molars were employed, separated into two main groups: Group R, which included 16 molar teeth elevated distally with resin composite each; and Group B, which included 16 molar teeth elevated distally with dentine. The prepared teeth were then restored using endo-crown restorations. There were 2 equal subgroups for each main group (Vita MarkII and Lava Ultimate endo-crowns; n = 8). The samples underwent thermocycling (TC) after the restorations were bonded using dual-cure resin cement. A digital microscope was used to measure the vertical marginal gap. Results: A significant difference in the vertical marginal gap following thermocycling in all groups, except for the Resin composite. The polymer-based group demonstrated better marginal adaptation than other groups. The marginal accuracy produced by the marginal elevation approach, which involves placing a composite filling and dentine in the proximal box before the insertion of ceramic indirect restorations, is comparable to those of ceramics implanted in dentine without margin elevation. Conclusion: The margin elevation technique ensures that the margins created with these materials are as precise as those placed directly in dentin.

Zirconia Nanoparticles as Reinforcing Agents for Contemporary Dental Luting Cements: Physicochemical Properties and Shear Bond Strength to Monolithic Zirconia.

Nanofillers in resin materials can improve their mechanical and physicochemical properties. The present work investigated the effects of zirconia nanoparticles (NPs) as fillers in commercial dental luting cements. Two dual-cured self-adhesive composites and one resin modified glass ionomer (RMGI) luting cement were employed. Film thickness (FT), flexural strength (FS), water sorption (Wsp), and shear bond strength (SBS) to monolithic zirconia were evaluated according to ISO 16506:2017 and ISO 9917-2:2017, whereas polymerization progress was evaluated with FTIR. Photopolymerization resulted in double the values of DC%. The addition of 1% wt NPs does not significantly influence polymerization, however, greater amounts do not promote crosslinking. The sorption behavior and the mechanical performance of the composites were not affected, while the film thickness increased in all luting agents, within the acceptable limits. Thermocycling (TC) resulted in a deteriorating effect on all composites. The addition of NPs significantly improved the mechanical properties of the RMGI cement only, without negatively affecting the other cements. Adhesive primer increased the initial SBS significantly, however after TC, its application was only beneficial for RMGI. The MDP containing luting cement showed higher SBS compared to the RMGI and 4-META luting agents. Future commercial adhesives containing zirconia nanoparticles could provide cements with improved mechanical properties.

Influence of adhesive application method and thermocycling on the bonding performance of different adhesive systems to dentin

Aim: To assess the effect of multiple layers application of different adhesive systems on the microshear bond strength (μSBS) of dentin with and without thermocycling. Materials and Methods: Two hundred forty sound human premolars had their enamel surfaces removed to expose even surfaces of dentin. The teeth were mounted in acrylic resin blocks and then assigned arbitrarily into four main groups (n = 60) representing the investigated adhesives (a self-etch [SE] adhesive, a total-etch [TE] adhesive, and a multimode [MM] adhesive used in TE and SE modes). Individually, the main groups were equally alienated into three subgroups (n = 20), each representing the number of the applied adhesive layers (one layer [1L], two layers [2L], and three layers [3L]). Then, each respective subgroup was divided subsequently into two equal divisions with n = 10 each according to thermocycling (with and without thermocycling). Each occlusal surface received three composite microrods. Prepared specimens were reserved in distilled water at temperature of 37°C until the μSBS test was performed after 24 h or after thermocycling for 3000 cycles at 5°C–55°C water bath. Results: A three-way analysis of variance (ANOVA) disclosed that multilayer application, adhesive type, and thermocycling showed a significant statistical impact on μSBS. The 1L, 2L, and 3L groups showed a statistically significant difference between the groups. The 3L groups showed the highest μSBS, whereas 1L groups recorded the least μSBS. Within the adhesive groups, a statistically significant difference was evident. The highest μSBS was recorded for TE, whereas SE recorded the least μSBS. Thermocycling (TC) has a statistically significant effect on μSBS and “no-thermocycling” (T0) groups recorded higher μSBS than thermocycled groups. Conclusion: Multilayer application of the tested adhesives had the potential to increase dentin μSBS.

Methylene Blue Penetration of Resin Infiltration and Resin Sealant in Artificial White-Spot Lesions.

This study determined the potency of resin infiltrations and resin sealant in impeding microleakage on artificial white-spot lesions (AWL) by methylene blue penetration. Eighty AWL specimens were randomly separated into two groups for water storage for 24 hours (groups 1-4) and 20,000 cycles of thermocycling (TC) (groups 5-8). Each group was then separated into four subgroups (n = 10) based on the AWL surface treatments: (1) no Tx, (2) treated with resin infiltration (ICON, DMG, Hamburg, Germany), (3) treated with resin infiltration (Surface pre-reacted glass-ionomer (S-PRG) barrier coat, SHOFU, Kyoto, Japan), (4) treated with resin sealant (Clinpro sealant, 3M ESPE, Minnesota, United States). Nail varnish was covered to all samples, with the exception of a 4 × 4 mm2 patch on the buccal measurement region, which was subsequently submerged in a 2% methylene blue solution and cut into buccolingual sections. Stereomicroscope measurements were used to calculate methylene blue penetration scores. The Kruskal-Wallis test and the Bonferroni post-hoc correction were performed to evaluate the data. Application of resin infiltrants and resin sealant reduced microleakage in AWL by methylene penetration both before and after thermal cycling. In addition, group 6 (ICON + TC) and group 7 (S-PRG + TC) had a significantly different value from group 8 (sealant + TC). Both the resin infiltration approach and the resin sealant seem to help seal AWL and might perhaps offer long-term defense against microleakage in AWL caused by methylene blue penetration. The greatest sealing and defense for microleakage in AWL were demonstrated by the resin infiltrations.

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

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

A remineralizing orthodontic etchant that utilizes calcium phosphate ion clusters.

This study aimed to investigate whether a phosphoric acid (H3PO4) solution containing calcium phosphate ion clusters (CPICs) could minimize enamel damage during long-term bracket bonding by dissolving the enamel surface and promoting enamel remineralization. The experimental design is as follows: first, three experimental etchants (H3PO4, CPICs-incorporated H3PO4 solution-I, and CPICs-incorporated H3PO4 solution-II) and two bonding resins (conventional orthodontic resin and self-adhesive orthodontic resin) were used in combination to create six groups, respectively. Each of these six groups was then divided into two sub-groups based on the presence or absence of thermocycling (TC). Twenty samples were assigned to each of the 12 groups (independent variables), and thus a total of 240 metal bracket-attached human premolars were used in this experiment. Bracket debonding was performed on each of 20 premolars in 12 groups, and shear bond strength (SBS) and adhesive remnant index (ARI) values were measured as dependent variables. Next, the three experimental etchants were applied (independent variables) to each of the three enamel samples, and the remineralization of the enamel surface was investigated as a dependent variable. The enamel surface was observed using electron scanning and atomic force microscopy. Furthermore, X-ray diffraction, energy dispersive spectroscopy (EDX) spectrum X-ray spectroscopy, and elemental mapping were performed, and the Knoop microhardness scale was measured. Therefore, the experiment was performed in two steps: SBS and ARI measurements for 12 groups, followed by observation of the enamel surface and microhardness measurements, according to the three types of etchants. As a result of the experiment, first, when the bracket was debonded, SBS did not decrease, and residual adhesive was hardly observed in the C2A group (before TC), C2A, and C1C groups (after TC) (p < 0.001). Second, the experimental etchant containing CPICs achieved remineralization while demineralizing the enamel. This was verified through SEM/EDX, element mapping, XRD, and AFM. Also, the roughness and microhardness of the enamel surface were better in the remineralized surface by the experimental etchant containing CPICs (p < 0.017). The CPICs-incorporated H3PO4 solution reduced ARI while maintaining SBS during bracket debonding, regardless of whether TC was performed or the type of resin. The etchant containing CPICs was also shown to remineralize the enamel and increase its microhardness.

Effect of Thermocycling on Color, Surface Characteristics, Compressive Fracture, and Fracture Modes of Prosthetic CAD/CAM Ceramics After Smokeless Tobacco Immersion.

BackgroundThe study aimed to assess effect of smokeless tobacco (ST) immersion with thermocycling (TC) on color of Vita Classical shade-guide, surface roughness (Ra) and roughness depth (Rz), and compressive fracture force (CFF) of hybrid polymer-infiltrated-feldspathic ceramic (Vita Enamic), leucite-Feldspathic glass (Vitablocs® Mark II), and zirconia-reinforced lithium silicate (Vita Suprinity) CAD/CAM prosthetic ceramic materials.Material/MethodsA 48 samples were milled from Vita Enamic, Vita mark II, and Vita Suprinity. VitaPan shade-guide, Ra, and Rz were registered before ST immersion. Then, the same parameters were recorded again after 15 days of ST staining with and without TC. CFFs and fracture modes of samples after 3 months of aging were documented.ResultsA slight change was observed in VitaPan shade-guide. Ra and Rz of Vita Suprinity (VS) recorded the highest values among ceramic groups at 3 time intervals. Increases in Ra and Rz were observed after immersion and staining with TC. ANOVA and Bonferroni post hoc tests were used. Significant differences among and between groups were noticed only before immersion in ST and TC, with P value ≥0.00. The highest mean value and SD of CFFs (MPa and Newton) were recorded in Vita Suprinity, followed by Vita Enamic (VE) and Vita mark II (VMII). Reparable fracture was higher in VMII and VS.ConclusionsST staining and TC caused color changes in VitaPan shade-guide and increases in Ra and Rz of tested materials, with highest and lowest values recorded in VS and VE. CFFs were marginally equal to clinically accepted values for VS and equal or slightly higher than the half values for VE and VMII groups.

Push-out Bond Strength of Two Fiber Posts in Composite Resin Using Different Types of Silanization.

The aim of this study was to evaluate the effect of different surface treatments and thermocycling (TC) on the push-out bond strength of two brands of glass fiber posts (GFPs) to composite resin. White Post DC (WP) (FGM Dental Group International, Joinville, Santa Catarina, BR) and Exacto (EC) (Angelus, Clinical Research Dental, Londrina, PR, Brazil). GFPs were cleaned with 70% alcohol and divided into five groups, according to the surface treatment (n=15): control (C), without treatment; prehydrolyzed silane (S-pre) (Prosil, FGM Dental Group International); 37% phosphoric acid + prehydrolyzed silane (AcS-pre); Scotchbond Universal Adhesive System (AdU), 3M Oral Care; two-bottle silane (S2B) (Dentsply Sirona Inc). The composite resin was inserted around the posts by using a split matrix. The samples were cut into 1-mm slices. Half of the samples were subjected to the push-out test immediately, and the other half underwent TC before the test. After failure analysis, the data were submitted to three-way analysis of variance (ANOVA) (α=0.05). EC achieved higher bond strength than WP, regardless of TC (p<0.05). Regarding WP, surface treatments (p<0.001) and TC (p<0.001) influenced bonding strength. As for EC without TC, the highest bond strength (p<0.05) was found for C, then AcSpre, S-pre, AdU, and S2B. Application of TC resulted in a statistically higher bond strength values for the EC AcS-pre group (p<0.05), followed by S2B, S-pre, C, and AdU. The WP failures were predominantly cohesive, similar to the EC AdU and EC S2B groups. The other EC groups showed mostly mixed failures. Surface treatment and TC affected the bond strength to composite resin, depending on which post was used. It is important for dentists to understand the effects of different types of silanization on their chosen post.

Comparative Evaluation of Load-Bearing Capacity and Fracture Analysis of PEEK and Zirconia Three-Unit Fixed Dental Prostheses: An In Vitro Study.

The purpose of this exploratory in vitro study was to compare and evaluate the load-bearing capacity (LBC) of ceramic-veneered zirconia and composite-veneered polyetheretherketone (PEEK) three-unit fixed dental prostheses (FDPs) with and without thermocycling (TC). The study included 40 samples of three-unit FDPs replacing mandibular first molars. The four groups included were: ceZIR (feldspathic ceramic-layered zirconia), ceZIR TC (feldspathic ceramic-layered thermocycled zirconia), cPEEK (composite-layered PEEK), and cPEEK TC (composite-layered thermocycled PEEK) (n = 10 per group). All frameworks were CAD/CAM milled. Ten PEEK and 10 zirconia samples were subjected to TC (6,000 cycles). All 40 FDP specimens were loaded by applying static load, using a universal testing machine. The maximum load required to fracture the specimens denoted the LBC. The comparison of LBC between the four groups was done by using two-way ANOVA with Tukey's post-hoc analysis (α = .05). There was no statistically significant difference between LBC of cPEEK and ceZIR (P > .001) without thermal aging. LBC values decreased considerably for thermally aged specimens. Statistically significant differences were observed between LBC of cPEEK TC and ceZIR TC (P < .001), cPEEK TC and cPEEK (P < .001), and ceZIR TC and ceZIR (P = .001). On fracture analysis, cPEEK showed delamination failures whereas ceZIR displayed catastrophic connector fractures. This comparative evaluation offers preliminary data highlighting substantial depreciation in the LBC of layered PEEK under simulated intraoral conditions, thus raising a question regarding the clinical longevity of layered PEEK multi-unit restorations. In contrast, feldspathic-layered zirconia can be suitable for use in posterior FDPs.

O4 - Silane Containing Universal Adhesive/Cement for Bonding to Silica-Coated High-Translucent Zirconia

The aim of this study was to evaluate the bonding performance of high-translucent zirconia when pretreated with glass beads and the efficiency of silane contained in self-adhesive resin cement and universal adhesive as chemical treatment for silica-coated high-translucent zirconia. 240 fully sintered disk-shaped zirconia specimens (Y-PSZ, Zpex smile, Tosoh, Japan) were assigned to 4 groups according to mechanical surface pretreatment: alumina particles abrasion with 0.2 MPa pressure (AB2), tribochemical silica-coating with 0.2 MPa (TSC), and glass beads air-abrasion with 0.2 MPa (GB2) and 0.4 MPa (GB4). Each group was cemented with Panavia SA Universal (SAU), Rely X Ceramic Primer (3 M ESPE) + Panavia SA plus (Kuraray Noritake Dental) (S-SAP), and Clearfil Universal Bond Quick + SAP (U-SAP). Tensile bond strength (TBS) was measured at crosshead speed of 2 mm/min after 24 h or 10000 thermocycling (TC) followed by the failure modes analysis (n=10). Surface morphology and surface elemental composition of the abraded zirconia surface analyses were examined under SEM/EDS. Survival analysis was done for TBS data (p = 0.05). After TC, there was a significant decrease in bond strength all groups except TSC and GB4 treated with S-SAP. S-SAP showed highest TBS with TSC, GB2, and GB4. AB2 indicated the highest TBS with U-SAP. SAU showed higher TBS with GB4 compared to GB2. GB4 represented the highest Si content compared to TSC and GB2. Sailanization of glass beads air-abraded zirconia ceramic is mandatory step for successful adhesion to resin cement. Silane containing self-etch adhesive cement was more effective than universal adhesive for glass beads treated zirconia especially with higher air-pressure, but both are less efficient than pure silane treatment. While universal adhesive is efficient pretreatment on tribochemical silica-coating surface and the most effective on alumina-blasted zirconia ceramic.

Chemo-mechanical properties of the new bioceramic cement PBS CIMMO® compared to MTA REPAIR HP Angelus® cement

Objective: To evaluate the bond strength (BS), pH and solubility (Sol) of a new PBS HP® bioceramic cement compared to MTA REPAIR HP® cement. Material and methods: Twenty human premolars were selected for BS analysis. Roots were cut into thirds (cervical, medium and apical) and filled with one of the cements (n=10): PC (PBS HP) or MC (MTA REPAIR HP). Half of these samples were subjected to 2,000 thermal cycles. After 48 hours, the BS test was performed in a universal testing machine (0.5mm/min). Cylindrical specimens (1.0mm in diameter and 10mm in height) were made with PC or MC and immersed in distilled water for pH analysis. After 0.3 and 24 hours, the pH was measured. Solubility was evaluated through the mass loss of the samples after 24 hours. Teflon rings of 20mm in diameter and 1.5mm in height were filled with PC or MC and kept at 37ºC in 100% humidity. Descriptive and exploratory analyzes of BS, pH and Sol data were performed (p&lt;0.05). Results: There was no significant difference in BS between the two types of cement. Thermo cycling did not affect the BS (p&gt;0.05). MC cement showed significantly higher pH values than the PC at the initial and 3 hours (p&lt;0.05). There was no difference between them (p&gt;0.05) after 24 hours. There was no significant difference regarding solubility (p&gt;0.05). Conclusion: Bioceramic cements have similar properties, as they did not differ in relation to dentin bond strength, pH after 24 hours and solubility.

The effects of different silicatization and silanization protocols on the bond durability of resin cements to new high-translucent zirconia.

The aim of this study was to assess the influence of different silicatization protocols with various silane treatment methods on the bond performance to high-translucent zirconia. High-translucent zirconia specimens were assigned to five groups according to mechanical surface pretreatment: as-sintered (Con), 0.2MPa alumina sandblasting (AB2), tribochemical silica coating (TSC), 0.2 and 0.4MPa glass bead air abrasion (GB2) and (GB4). Each group was subjected to 4 different cementation protocols: Panavia SA Universal (SAU), Panavia SA plus (SAP), silane + SAP (S-SAP), and Universal adhesive + SAP (U-SAP). Tensile bond strength (TBS) was measured after 24h and 10,000 thermocycling (TC). Surface topography, surface energy, and elemental composition of the abraded zirconia surface analyses were completed. TBS data was analyzed using the Weibull analysis method. Surface roughness and surface energy were compared by one-way ANOVA analysis of variance (α = 0.05). After 24h, higher TBS was achieved with all cementation protocols in AB2 and TSC, also, in GB2 with all protocols except U-SAP, and in GB4 with SAU and S-SAP. After aging, GB4/S-SAP, GB2/S-SAP, AB2/U-SAP, and TSC/S-SAP showed the highest bond strength. GB groups showed the lowest surface roughness and highest surface energy. Glass bead abrasion achieved the durable bond strength to high-translucent zirconia using a separate silane coupling agent while altered surface chemistry, surface energy, and roughness without effect on morphology. Glass bead air abrasion is an alternative to alumina sandblasting and tribochemical silica coating and improves bond strength to high translucent zirconia.

Limited Etching Time Increases Self-adhesive Resin Cement Adhesion to Enamel.

To evaluate the influence of different enamel etching times on the bond strength of two self-adhesive resin cements (RCs) with and without thermocycling (TMC). One hundred twenty bovine teeth were used. Blocks of enamel (8×4×2mm) were obtained, polished, and randomly divided into two groups, according to the RC used: MaxCem Elite or RelyX U200. Groups were subdivided into four groups (n=16), according to the etching time: Control (0 seconds), 5 seconds, 10 seconds, and 20 seconds. Three RC cylinders (1-mm diameter) were built on each enamel block. The specimens were submitted to two storage conditions: 24 hours in distilled water or TMC (5000 cycles/5°C-55°C). Afterward, the specimens were submitted to the shear bond strength (SBS) test. The failure modes and adhesive interfaces were analyzed by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Data were analyzed with three-way analysis of variance (ANOVA) and Tukey test (α=0.05). Etching increased the SBS for both the RCs,especially forthe groups etched for 5 and 10 seconds. TMC affected negatively the SBS of the control groups (p<0.05). No resin tags were observed in control groups, and the formation of tags was time dependent. The 10 seconds etching time was more effective in increasing the enamel-resin bond strength. TMC negatively affected bond strength in specimens without acid etching.