Effect Of Thermocycling Research Articles

Surface Microhardness, Flexural Strength, and Clasp Retention and Deformation of Acetal vs Poly-ether-ether Ketone after Combined Thermal Cycling and pH Aging

To evaluate the effect of combined thermocycling and artificial saliva pH on flexural strength, surface microhardness, as well as clasp retention and deformation of two different thermoplastic polymers. Three groups were created, heat-cured polymethyl methacrylate, acetal, and poly-ether-ether ketone (PEEK) resins. Specimens were wrapped in plastic bags containing artificial saliva with three pH values (acidic 5.8, neutral 7.2, and alkaline 8.3). Two Aker clasps materials (acetal and PEEK), for premolar and molar, were stored in neutral salivary pH. Specimens were subjected to 2,000 thermocycles (5-55°C). Surface microhardness, flexural strength, and clasp retention and deformation were evaluated before and after aging. Data were analyzed by ANOVA, Tukey's test, Student's t-test, and paired t-tests (p < 0.05). Thermal cycling at acidic and alkaline pH significantly decreased flexural strength and surface microhardness of acetal. It had no significant effect on PEEK properties. Poly-ether-ether ketone showed statistically significant higher mechanical properties in all groups. Acetal clasps exhibited a statistically significant deformation and a corresponding decrease in retention after thermocycling at neutral pH. Mechanical properties of acetal, as well as its clasp retention and deformation, significantly decreased after combining thermal and pH aging and thermal cycling in neutral pH, respectively. Meanwhile, PEEK clasps were not significantly affected. Different intraoral variables may significantly affect mechanical performance, retention, and deformation of TMs used for denture base and clasp construction. Some of these TMs may behave better than the other types with recommended improvement of the design like increasing clasp cross-section area.

Effect of Thermocycling on Surface Roughness and Shear Bond Strength of Acrylic Soft Liner to the Surface of Thermoplastic Acrylic Treated with Ethyl Acetate

Objective: To enhance bonding strength between thermoplastic denture base and acrylic soft liner through ethyl acetate surface treatment.Materials and Methods: Modifications of thermoplastic acrylic denture base surface were investigated with SEM. FTIR was used to detect whether there was a chemical bond between thermoplastic acrylic and the organic solvent. A total of 80 samples were prepared and divided into 20 samples for the surface roughness test and 60 samples for the shear bond strength test. Failure type was assessed visually.Results: Shear bond strength and surface roughness values of un treated samples were lower in comparison to surface treated groups; the greatest post thermocycling bond strength value was recorded for the samples treated with ethyl acetate following 1500 cycles.Conclusions: Bonding strength was improved following ethyl acetate surface treatment.

Polymethylmethacrylate Incorporating Nanodiamonds for Denture Repair: In Vitro Study on the Mechanical Properties.

Objective This study aimed to evaluate the effect of nanodiamond (ND) addition to repair resin with repair gap modifications on the flexural and impact strength of repaired polymethylmethacrylate denture base. Materials and Methods Heat-polymerized acrylic resin specimens ( N = 100/test) were prepared and sectioned to half creating two repair gaps: 2.5- and 0 mm with 45 degrees beveling. They were further divided into subgroups ( n = 20) according to ND concentration (control, 0.25%ND, and 0.50%ND), thermocycling (500 cycles) was done to half the specimens in each subgroup. Flexural strength was tested using 3-point bending test and impact strength was tested by Charpy's impact test. Analysis of variance and post-hoc Tukey's tests were performed for data analysis ( α = 0.05). Scanning electron microscope was employed for fracture surface analysis and ND distribution. Results Before and after thermocycling, the addition of ND significantly increased the flexural strength and elastic modulus in comparison to control group ( p ˂ 0.001), while 0 mm repair gap showed insignificant difference between ND-reinforced groups ( p ˃ 0.05). Regarding impact strength, ND addition increased the impact strength with 0 mm gap in comparison to control and 2.5 mm with ND ( p ˂0.001), while later groups showed no significant in between ( p ˃ 0.05). Comparing thermocycling effect per respective concentration and repair gap, thermocycling adversely affected all tested properties except elastic modulus with 0 mm–0.25 and 0 mm–0.5% and impact strength with 2.5 mm, 2.5 mm–0.25%, 2.5 mm– 0.5% ( p ˃ 0.05). Conclusion ND addition combined with decreased repair gap improved the flexural strength, elastic modulus, and impact strength of repaired denture resin, while thermocycling has a negative effect on denture repair strength.

The Effect of Ceramic Material and Thermocycling on the Marginal Adaptation of Onlay Restorations

The Effect of Ceramic Material and Thermocycling on the Marginal Adaptation of Onlay Restorations

The Effect of Polishing and Thermocycling on the Surface Roughness of Two Nanohybrid Composites

The Effect of Polishing and Thermocycling on the Surface Roughness of Two Nanohybrid Composites

Effect of thickness, cement shade, and coffee thermocycling on the optical properties of zirconia reinforced lithium silicate ceramic.

ObjectiveTo investigate the effect of thickness, cement shade, and coffee thermocycling (CTC) on the optical properties of zirconia reinforced lithium silicate (ZLS) paired with different shades of a resin cement.Materials and MethodsThirty ZLS specimens were prepared in two different thicknesses (0.8 and 1.5 mm) and three different resin cement shades (Tr, A2, and A3) were applied (n = 5). Color determinations were done before and after 5000 CTC by using a noncontact spectroradiometer. Color change due to CTC and relative translucency parameter (RTP) before and after CTC were calculated by using CIEDE2000. Data were analyzed using ANOVA and Bonferroni‐corrected t‐tests(α = 0.05).ResultsMaterial thickness and resin cement shade (P < 0.001) affected baseline color. Material thickness affected color difference (P = 0.025). Thickness, resin cement shade, and CTC (P ≤ 0.0001) affected RTP. The difference between the color changes of the 0.8‐ and 1.5‐mm specimens combined with A2 shade cement after CTC was significant (P = 0.01). RTPs of all pairs decreased after CTC (P < 0.001).ConclusionsCement shade and material thickness affected the baseline color. The thickness of ZLS affected the color change after CTC only with A2 resin cement and the color change was less when the ZLS was thicker. CTC reduced the translucency of all pairs.Clinical SignificanceClinicians and patients should be aware of a potential color change after long‐term coffee consumption when zirconia reinforced lithium silicate is used particularly for laminate veneers with A2 shade of the tested resin cement.

The Effect of Thermocycling on Interfacial Bonding Stability of Self-Etch Adhesives: OCT Study.

Objective The aim of this study was to monitor the behavior of interfacial gaps formed under different bonded polymeric restorations before and after thermocycling (TC), using swept-source optical coherence tomography (SS-OCT) and confirming the obtained findings with confocal laser scanning microscopy (CLSM). Materials and Methods Cylindrical class I cavities were prepared in twenty noncarious human premolar teeth (1.5 mm depth × 3.5 mm diameter) and divided randomly into two groups: TS and SN, according to the adhesive system (n = 10). In the TS group, one-step self-etch adhesive Clearfil Tri-S Bond Plus (Kuraray Noritake Dental, Japan) was used, followed by composite restoration using Estelite Sigma Quick (Tokuyama Dental, Japan). In the SN group, the cavities were restored with the two-step self-etch/composite silorane-based resin restoration system (3M ESPE, USA). All specimens were restored in bulk filling technique and cured in accordance with the manufacturers' instructions. Both groups were imaged under SS-OCT after 24 h and recorded as controls. Then, each group was subjected to thermal challenge using the TC machine (5–55°C) and B-scans were recorded at different TC intervals (2600, 5200, and 10000). In order to confirm the SS-OCT findings, additional specimens were prepared, scanned, and sectioned for CLSM observation. Results B-scans demonstrated white clusters at the tooth-resin interface that corresponded to the gap location on CLSM images. The TS group showed significantly less gap formation than the SN group before and after TC (p < 0.001). Conclusions An optimal composite adaptation can be achieved when the bonded restoration comprises a combination of an adhesive containing 10-MDP monomer and a considerable highly filled composite.

Ceramic Printing - Comparative Study of the Flexural Strength of 3D Printed and Milled Zirconia.

To determine and compare the mechanical properties of 3D-printed yttriastabilized zirconia to milled isostatic pressed yttria-stabilized zirconia, with the following hypotheses: (1) The flexural strength of 3D-printed yttria-stabilized zirconia is comparable to milled yttria-stabilized isostatic pressed zirconia; and (2) thermocycling and chewing simulation do not affect the flexural strength of 3D-printed yttria-stabilized zirconia. A total of 30 bars of an experimental 3D-printed 3 mol% yttriastabilized zirconia (LithaCon 3Y 230, Lithoz) and 10 bars of milled isostatic pressed zirconia (Prettau Zirconia, Zirkonzahn) were utilized. The printed zirconia bars were divided into three groups (n = 10 bars per group): (1) untreated (control); (2) thermocycled; and (3) tested after chewing simulation. A flexural strength test was performed on all samples using a three-point bend test in an Instron Universal testing machine. One-way analysis of variance on ranks was used to compare milled to printed zirconia. The effects of thermocycling and load cycling on 3D-printed zirconia were also determined. The flexural strength values for milled and printed zirconia were 936.3 ± 255.0 MPa and 855.4 ± 112.6 MPa, respectively. There was no statistically significant difference in flexural strength between the milled and printed zirconia (P = .178). No statistically significant differences were observed between the control 3D-printed zirconia group and the thermocycled (888.4 ± 59.3 MPa) or load-cycled printed zirconia (789.6 ± 133.8 MPa; P = .119). Printed 3 mol% yttria-stabilized zirconia has comparable flexural strength to milled yttria-stabilized isostatic pressed zirconia. The thermocycling and chewing simulation used in this study did not significantly alter the flexural strength of the printed 3 mol% yttria-stabilized zirconia. These results indicate a promising role for 3D printing in the fabrication of zirconia restorations. Additional studies are needed to explore the full potential of this technology.

Effect of Thermocycling and Mechanical Loads on Corrosion Resistance of High-Strength Nitrogen Austenitic Steels

The effect of long-term thermocycling and mechanical loads on the corrosion resistance of novel nitrogen austenitic Cr – Ni – Mn steels melted under laboratory conditions is studied in various aggressive environments. The steels are subjected to 400 thermal cycles in the temperature range from –100 to 100°C and to cyclic mechanical loading during 1 × 106 cycles. The structure and the mechanical properties of the steels after the cyclic loading are studied. Tests for resistance to general and pitting corrosion in sea water (3% NaCl) and in an acid environment (0.5M H2SO4 including blasting with hydrogen sulfide), to pitting corrosion in an aqueous solution of iron chloride, to intercrystalline corrosion in a test solution, to corrosion cracking under load, and for cavitation damage in a 3% solution of NaCl are conducted. It is shown that the developed high-strength nitrogen austenitic steels 10Kh19G10N6AM2 and 09Kh19G10N6AM2D2 both in the initial condition and after the thermocycling and cyclic mechanical loading have high resistance to the types of corrosion studied, which exceeds the resistance of steels 04Kh18N9 and 04Kh18AN9. Requirements on the composition and the structure of the steels are developed.

The effect of thermocycling on microhardness and surface roughness of two zirconia reinforced lithium silicate glass-ceramics

Nowadays, dental glass-ceramics are experiencing remarkable development in terms of aesthetics and hardness. New materials with high fracture resistance were developed and can be obtained by milling ceramic blocks or by heat-pressing prefabricated ceramic ingots.This paper aims to evaluate the effect of thermocycling (10,000 cycles) on the microhardness and roughness of two zirconia reinforced lithium silicate glass-ceramics (ZLS) obtained using two different processes, milling, and heat-pressing ceramic.The tested ZLS ceramics behaved differently to the aging and surface treatments. The milled ZLS ceramic was more affected by the aging process. Glazed samples presented higher surface roughness and higher microhardness compared to the polished samples before and after thermocycling.

Effect of Artificially Accelerated Ageing and Different Mouth Rinses on Color Stability of Veneered PEEK Crowns

Statement of problem:Veneered polyetheretherketone(PEEK) is a recent alternative choice for fixed dental prostheses.There is a lack of data about the color stability of different veneering composite techniques of CAD/CAM PEEK cores. Purpose:To verify the effect of thermocycling and different mouth rinses on color stability of CAD/CAM composite versus conventional nanohybrid composite veneered PEEK crowns. Methods:Forty-two duplicated epoxy resin dies of prepared mandibular first molar to receive ceramic crown were fabricated.42 CAD/CAM PEEK cores were fabricated and divided into two groups(n=21)based on the veneering technique;group(C):nanohybrid crea.lign composite veneered PEEK cores and group(H):HIPC veneered PEEK cores. Each group was subdivided based on mouth rinse into 3 groups(n=7):Listerine-alcohol free, Hexitol and Distilled water.The color at baseline, after thermocycling equivalent to clinical 6 months service and 1-week immersion in mouth rinses were measured utilizing a spectrophotometer.The data were statistically analyzed using ANOVA,pair-wise Tukey’s post-hoc and student t-tests to reveal the significance between groups(P ≤ 0.05). Results:All specimens showed visually unperceptible color differences after thermocycling and immersing in mouth rinses(∆E* 0.05). Conclusions:Although visually nonperceptible,HIPC or nanohybrid composite veneered PEEK crowns showed a color difference after thermocycling and immersion in different mouth rinses.

Effect of Thermocycling on the Compressive Strength of Selected Luting Cements

Introduction: The purpose of this in vitro study was to evaluate the effect of thermocycling on the compressive strength of selected luting cements. Material and methods: 5 types of luting cements were tested. A total of thirty cylindrical specimens measuring 6mm in height and 4mm in diameter were prepared for each type of cement which were then divided into two groups ie Group 1: Exposure, and Group 2: Control. Both groups were stored in distilled water at 37°C for 24 hours. Group 1 was subjected to 500 cycles in a thermocycling baths of 5ºC and 55ºC with 20 seconds in each bath. Group 2 was not exposed to thermocycling procedure. The compressive strength for each cement type was determined by using a universal testing machine. Results: Resin adhesive cement had the highest compressive strength; followed by conventional glass ionomer cement (GIC) whilst resin modified GIC was the least. Thermocycling had no significant effect on the compressive strength of RelyXTM ARC and Fuji I (p&gt;0.05), but a significant effect on Fuji I CAPSULE, Fuji CEM, Fuji Plus CAPSLUE (p&lt;0.05) was observed. Conclusion: The effect of thermocycling on the compressive strength of luting cements differed considerably with respect to their chemical compositions.

Effect of decontamination methods on shear bond strength of resin cement to translucent monolithic zirconia

Objective. The aim of this study was to evaluate the effect of decontamination methods on shear bond strength of resin cement to translucent monolithic zirconia. Material and Methods. Eighty 4-mol yttria-stabilized tetragonal zirconia polycrystal specimens were fabricated. All specimens were subjected to saliva contamination and divided into four groups (n=20) according to the decontamination methods: 70% isopropanol (AL); zirclean (ZC); 5.25% sodium ypochlorite (NaOCL); and no cleaning (NC). All specimens were bonded by using self-adhesive resin cement. Half of the specimens in each group (n=10) were subjected to thermocycling. All specimens were subjected to shear bond strength test in a universal testing machine. Failure modes were evaluated by using a scanning electron microscope (SEM). The data obtained were statistically analyzed by using one-way ANOVA followed by the HSD Tukey test (P &lt; 0.05). Results. ANOVA test revealed a significant difference among the different decontamination methods (P &lt; 0.05). No significant differences were found among NaOCL, ZC, and AL groups as revealed by the HSD Tukey test (P &gt; 0.05). The effect of thermocycling was significantly different in all groups (P &lt; 0.05); whereas, no significant difference was found in group ZC (P &gt; 0.05). (SEM) analysis showed mixed failures in all groups except in group NC where only adhesive failure was observed. Conclusion. Saliva contamination during clinical evaluation significantly decreases the shear bond strength between self-adhesive resin cement and translucent monolithic zirconia. The cleaning gel has an impact on improving the bond strength between resin cement and translucent monolithic zirconia. KEYWORDS Monolithic zirconia; Resin cement; Shear bond strength test; Translucent zirconia; Zirclean.

Effects of Endodontic Access Cavity Design and Thermocycling on Fracture Strength of Endodontically Treated Teeth.

IntroductionThis study aimed to assess the fracture strength of endodontically treated mandibular molars with traditional endodontic access cavity (TEC) and truss endodontic access cavity (TREC) designs that were restored with composite resin and underwent thermocycling.MethodsSixty mandibular first and second molars were randomly divided into 6 groups (n=10) of intact controls without thermocycling (group 1), intact controls with thermocycling (group 2), TEC without thermocycling (group 3), TEC with thermocycling (TEC-TC, group 4), TREC without thermocycling (group 5) and TREC with thermocycling (TREC-TC, group 6). The root canals were then instrumented to #25,7% using nickel-titanium files and were filled with gutta-percha and AH26 sealer with lateral compaction technique. Access cavity was restored with Gradia composite. All teeth were then thermocycled for 480 cycles between 5°C and 55°C for 30 seconds and their fracture strength was measured in a universal testing machine with a round-end piston with 6 mm diameter at a speed of 1 mm/min. Data were analyzed using two-way and one-way ANOVA.ResultsWithout thermocycling, the fracture strength of endodontically treated teeth with TREC designs had no significant difference with the control group (P>0.05). However, both TEC and TREC designs significantly decreased the fracture strength of endodontically treated teeth after thermocycling (P<0.05), such that minimum fracture strength was noted in TEC-TC group.ConclusionUnder the conditions of this ex vivo study, TREC enhances the fracture strength of endodontically treated teeth under thermal stresses.

The Effect of Thermocycling and Surface Treatments on the Surface Roughness and Microhardness of Three Heat-Pressed Ceramics Systems

Dental ceramic restorations are widely used in restorative dentistry. However, these restorations can be affected once cemented in the oral cavity by several factors. How can conventional surface treatments, such as glazing and mechanical polishing, diminish the effects of aging? The purpose of this in vitro study was to evaluate the effect of thermocycling and conventional surface treatments on the surface roughness and microhardness of three types of glass-ceramics by using a profilometer, scanning electron microscopy (SEM), atomic force microscopy (AFM), and a microhardness tester. Three types of ceramic systems (zirconia reinforced lithium silicate glass-ceramic, lithium disilicate glass-ceramic, and feldspathic glass-ceramic) (n = 48) were prepared. The samples were subjected to thermocycling for 10,000 cycles. Surface roughness was evaluated numerically using a profilometer and visually by using SEM and AFM. Microhardness was performed using a microhardness tester. The data were interpreted using the ANOVA test, and the results were correlated using Pearson’s correlation formula (r). Significant differences were found before and after thermocycling for the Ra (p &lt; 0.01) and Rz (p &lt; 0.05) parameters. As well, differences between glazed and polished surfaces were significant before and after thermocycling for surface roughness and microhardness (p &lt; 0.05). A correlation was made between average surface roughness and microhardness (r = −460) and for the maximum surface roughness and microhardness (r = −606). Aging increases the roughness and decreases in time the microhardness. The tested ceramic systems behaved differently to the aging and surface treatments. Surface treatments had a significant impact on the microhardness and surface characteristics. The glazed groups were reported with higher surface roughness and lower microhardness when compared to the polished groups before and after thermocycling. The measuring roughness techniques determine the scale-dependent values for the Ra (Sa) and Rz (Sq) parameters. Thermocycling almost doubled the surface roughness for all the tested samples. Microhardness decreased only for the Celtra glazed samples. Nano-roughness increased the values for Vita and slightly for Emax. Thermocycling had little effect on Emax ceramic and a more significant impact on Celtra Press ceramic.

The Effect of Thermocycling on the Translucency and Color Stability of Modified Glass Ceramic and Multilayer Zirconia Materials.

AimThe aim of this in vitro study was to evaluate the new, multilayered, translucent zirconia and enhanced glass-ceramics to determine if their translucency (TP) and color stability (ΔE) are affected by thermocycling at 10,000, 30,000, and 50,000 cycles.Materials & methodsTwo pre-shaded, multilayer zirconia products: Prettau® 2 Dispersive® (PRT) and Prettau® 4 Anterior® Multi® (PRTA), and two glass-ceramic: IPS e.max CAD® HT (E.max) and Vita Suprinity® HT (VS) were used. All were prepared and sectioned to get plate specimens with dimensions 12.5x14.5x1 mm (n=12) for each material. The L*a*b* values were recorded using a spectrophotometer before and after thermocycling for 10,000, 30,000, and 50000 cycles. The translucencies of the specimens were calculated using the TP formula and the color changes were giving by the color differences ΔE formula at each interval.ResultsOne-way analysis of variance (ANOVA) was used to analyze the data followed by Scheffe’s post-hoc test and multiple paired t-tests (P < 0.05). There was a statistically significant higher TP for E.max before (16.2) and after aging (16.9) (p<0.001**). All the tested groups showed a statistically significant increase in their TP at different intervals. PRT showed significantly higher ΔE (p<0.001**) after 50,000 cycles.ConclusionThere was a mild but significant increase in translucency in both Zirconia and glass-ceramic after thermocycling. In addition, all materials showed a significant color change with time, however, this is not clinically perceptible.

Effect of Thermocycling, Surface Treatments and Microstructure on the Optical Properties and Roughness of CAD-CAM and Heat-Pressed Glass Ceramics.

Dental ceramic restorations are widely spread nowadays due to their aesthetics and biocompatibility. In time, the colour and structure of these ceramic materials can be altered by aging processes. How does artificial aging affect the optical and surface roughness of ceramics? This study aims to assess the effect of thermocycling, surface treatments and microstructure upon translucency, opalescence and surface roughness on CAD-CAM and heat-pressed glass-ceramic. Forty-eight samples (1.5 mm thickness) were fabricated from six types of A2 MT ceramic: heat-pressed and milled glass-ceramic (feldspathic, lithium disilicate and zirconia reinforced lithium silicate). The samples were obtained respecting the manufacturer’s instructions. The resulted surfaces (n = 96) were half glazed and half polished. The samples were subjected to thermocycling (10,000 cycles) and roughness values (Ra and Rz), colour coordinates (L*, a*, b*) and microstructural analyses were assessed before and after thermocycling. Translucency (TP) and opalescence (OP) were calculated. Values were statistically analysed using ANOVA test (one way). TP and OP values were significantly different between heat-pressed and milled ceramics before and also after thermocycling (p < 0.001). Surface treatments (glazing and polishing) had a significant effect on TP and OP and surface roughness (p < 0.05). The heat-pressed and milled zirconia reinforced lithium silicate glass-ceramic experienced a loss in TP and OP. Ra and Rz increased for the glazed samples, TP and OP decreased for all the samples after thermocycling. Microstructural analyse revealed that glazed surfaces were more affected by the thermocycling and especially for the zirconia reinforced lithium silicate ceramic. Optical properties and surface roughness of the chosen ceramic materials were affected by thermocycling, surface treatments and microstructural differences. The least affected of the ceramics was the lithium disilicate ceramic heat-pressed polished and glazed.

Effect of Thermocycling on the Colour Stability of Aesthetic Restorative Materials: An in-vitro Spectrophotometric Analysis

Objective: To compare the color stability of Cention N, Fuji IX GP Extra, and Fuji IX GP after thermocycling. Material and Methods: Ten discs of each material of dimension 10 x 1 mm were prepared using a split mold. The preparations of the specimens were done according to the powder/liquid ratio as recommended by the manufacturers [4.6:1, 3.4:1 and 3.6:1 for the groups I, II, and III, respectively]. After setting, the samples were retrieved, and the thickness of each specimen was measured using a micrometer at five different locations. The specimens with variations in thickness, porosity or cracks were discarded and thus not included in the study. The selected specimens were stored in distilled water for 24 hours prior to testing. The prepared specimens were thermocycled at 5°C and 55°C, with a dwell time of 15 seconds for 250 or 500 cycles. Subsequently, the color parameters of the discs were measured using a spectrophotometer. The data were analyzed using two way ANOVA test, and a p-value <0.001 was considered. Results: Thermocycling resulted in changes in the color of both Glass Ionomer cement and Cention N (p<0.001). Among the materials tested, Cention N showed superior color stability. Conclusion: Cention N exhibited better color stability compared to Glass ionomer cements.

Microleakage of a Self-adhesive Composite of Class V Cavities: Effect of Surface Treatment and Thermocycling

This study aimed to assess the microleakage of a self-adhesive composite compared to conventional composites in class V cavities. In this in vitro experimental study, standard class V cavities were prepared in the buccal surface of 204 extracted teeth and randomly divided into six groups for restoration with (A) Vertiseflow (Kerr) self-adhesive composite, (B) acid etching (Kerr) + Vertiseflow, (C) acid etching + Optibond FL (Kerr) + Vertiseflow, (D) Er,Cr:YSGG laser + Vertiseflow, (E) acid etching + Optibond FL + Premise Flowable (Kerr), and (F) acid etching + Optibond FL + Z250 (3M). The teeth in each group were then randomly divided into two subgroups of with and without thermocycling (10,000 cycles between 5°C and 55°C). The microleakage was then determined at the enamel and dentin margins under a stereomicroscope using the dye penetration method. Data were analyzed using the Kruskal-Wallis test (α = 0.05). No significant difference was noted in occlusal margin microleakage of no thermocycling groups, but acid etching + Vertiseflow showed the highest microleakage. At the gingival margin, the difference between acid etching + bonding agent + Z250 and laser + Vertiseflow was significant (p = 0.004). In thermocycling groups, the difference in the microleakage at the occlusal margin of Vertiseflow with that of acid etching + bonding agent + Premise (p = 0.002), acid etching + bonding agent + Vertiseflow (p = 0.009), and acid etching + bonding agent + Z250 (p = 0.037) groups was significant. The difference in the microleakage at the dentin margin was also significant among the groups (p < 0.05). The highest and the lowest microleakages were noted in laser + Vertiseflow and acid etching + bonding agent + Vertiseflow groups, respectively. Surface preparation with etching and adhesive application results in lower microleakage in class V cavities. But laser irradiation and the use of self-adhesive composite increase the microleakage. It seems that self-adhesive composites cannot provide acceptable marginal integrity without any surface treatment.

Shear bond strength evaluation of metallic brackets bonded to a CAD/CAM PMMA material compared to traditional prosthetic temporary materials: an in vitro study.

ABSTRACTIntroduction: Orthodontic treatment for adults is currently increasing, and therefore the need to bond brackets to restorations and temporary crowns. The use of CAD/CAM PMMA provisional restorations for orthodontic purposes have not yet been described, and there is currently insufficient information regarding the strength of bracket adhesion. Objective: This study aimed at evaluating the effects of thermocycling (TC) and surface treatment on shear bond strength (SBS) of brackets to different provisional materials. Methods: Forty specimens were made from each material [PMMA (Telio Lab), bis-acryl (Telio CS C&B), and PMMA CAD/CAM (Telio CAD)], sandpapered, and divided according to surface treatment (pumiced or sandblasted) and TC (half of the samples = 1,000 cycles, 5°C/55°C water baths) (n = 10/group). Stainless-steel brackets were bonded to the specimens (using Transbond XT), and SBS testing was performed. Data were analyzed by three-way ANOVA and LSD post-hoc tests (α = 0.05). Failure types were classified with adhesive remnant index (ARI) scores. Results: SBS values ranged from 1.5 to 14.9 MPa. Sandblasted bis-acryl and sandblasted auto-curing PMMA groups presented similar values (p> 0.05), higher than the CAD/CAM material (p< 0.05), with or without TC. When thermocycled, pumiced bis-acryl showed higher SBS than pumiced acrylic (p= 0.005) and CAD/CAM materials (p= 0.000), with statistical difference (p= 0.009). TC showed negative effect (p< 0.05) for sandblasted bis-acryl and pumiced acrylic groups. ARI predominant score was mostly zero (0) for CAD/CAM, 1 and 2 for bis-acryl, and 1 for acrylic groups. Conclusion: In general, bis-acryl material showed the highest SBS values, followed by acrylic and CAD/CAM materials, which showed SBS values lower than an optimum strength for bonding brackets.