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Purpose: To evaluate the microshear bond strength (µSBS) of different bonding protocols to commercially pure titanium (CP Ti) using two universal adhesives and Alloy Primer. Materials and Methods: A total of 120 cubes of CP Ti were airborne-particle abraded and then divided into 6 groups (n = 20 each) according to bonding protocol: (1) Scotchbond Universal (SU; 3M Espe), (2) Alloy Primer (AP; Kuraray) + SU; (3) G-Premio Bond (GP; GC); and (4) AP + GP. The specimens from groups 1 to 4 were cemented with RelyX Unicem (3M Espe), while those from groups 5 and 6 were cemented using Panavia F2.0 cement (PAN; Kuraray) without and with prior AP application, respectively. After 24 hours, half of the specimens were subjected to µSBS measurement and the other half to thermocycling (5,000 cycles) before testing. Data were analyzed using Shapiro-Wilk, two-way analysis of variance, Games-Howell, and independent samples t test (a = .05). Results: The µSBS values obtained from the AP + SU group were significantly higher than from the GP (P = .003) and the AP + GP (P = .022) groups. After thermocycling, the µSBS of both groups treated with SU were significantly higher than those of other groups (P < .001). The application of AP did not improve adhesion of resin cements to CP Ti. Thermocycling significantly reduced the µSBS values of the PAN group, whereas it noticeably enhanced the adhesion of SU and AP + SU. The predominant failure mode in all groups was adhesive. Conclusion: The application of AP, followed by SU, produced the most effective bonding to CP Ti, which was able to endure limited thermal aging. [ABSTRACT FROM AUTHOR]

Background: The purpose of this study was to evaluate the effect of different surface treatments on the microshear bond strength (^SBS) of resin cement to zirconia-reinforced lithium silicate ceramic and to compare it with lithium disilicate ceramic. Materials and Methods: In this in vitro study, 80 specimens containing two glass ceramics of IPS e.max press and VITA SUPRINITY were prepared and categorized into four groups according to the surface treatments (n = 10) as Group 1 (C): no treatment (control); Group 2 (HF): etching with 9% hydrofluoric acid (HF) for 90 s followed by silane application; Group 3 (SPH): sandblasting with Al2O3 particles (50 µm), etching with 35% phosphoric acid for 40 s followed by application of silane and adhesive (Clearfil liner bond F); and Group 4 (SB): sandblasting with Al2O3 followed by silanization. Then, a resin cement (Panavia F2) was applied to the prepared ceramic surfaces. All samples were subjected to thermal aging (5000 cycles, 5-55). The μSBS test was evaluated and failure modes were recorded. Data were analyzed using the Shapiro-Wilk, two-way analysis of variance and Tukey's Honest Significant Difference post hoc tests (P < 0.05). Results: IPS e.max press samples revealed significantly higher μSBS values compared to VITA SUPRINITY (P < 0.001), in whole surface treatments. The HF group showed the highest μSBS value, followed by the SPH and SB groups, respectively (P < 0.001). Adhesive failure was recorded as a predominant failure mode. Conclusion: The adhesion performance of IPS e.max press was significantly higher than VITA SUPRINITY. The common surface treatment protocol including HF application followed by silanization was the most effective surface treatment for both glass ceramics. [ABSTRACT FROM AUTHOR]

Background: The type of housing retaining material may affect the bond strength of the housing to denture base resin. The aim of this in vitro study was to evaluate the bond strength of locator housing attached to polymethyl methacrylate (PMMA) denture base resin secured with different retaining materials. Materials and Methods: In this in vitro study Forty-four PMMA blocks (10 mm × 15 mm × 15 mm) were prepared with a central cylindrical canal inside to allow the insertion of locator housings. The prepared specimens were then randomly divided into four groups (n = 11). Each group received one of the following retaining materials for housing insertion: Auto-polymerized acrylic resin (APAR), auto-polymerized composite resin (Quick up), application of alloy primer on titanium housing plus Quick up (AL-Quick), and heat-polymerized acrylic resin (HPAR). The specimens were thermocycled 5000 times between 5°C and 55°C, followed by 1000 cycles of vertical insertion separation on the locator abutment. A push-out force was applied on the flat back surface of the housing after which the failure and shear bond strength values were calculated. The data were analyzed using one way-ANOVA and Games-Howell test (α = 0.05). Results: HPAR group had significantly higher shear bond strength values compared to the other groups (P < 0.05). No significant differences were found among the other remaining material groups (P > 0.05). Conclusion: Inserting of locator housing using HPAR resulted in higher bond strength between housing and denture base resin. The application of alloy primer did not improve the bond strength of locator housing which was retained with "Quick up". [ABSTRACT FROM AUTHOR]

Introduction: Detachment of denture teeth from denture base is one of the most common reasons for costly denture repairs .This study aimed at evaluating the bond strength of an acrylic denture tooth to polyamide injection-molded thermoplastic denture base material compared with three conventional polymethylmethacrylate (PMMA) denture base resins. Materials and Method: A total of 40 acrylic denture molar teeth were randomly allocated into four groups (n=10) of heat-polymerized (HP), Auto-polymerized (AP), Injection molded (IM) and Polyamide thermoplastic (PT). All denture base/acrylic teeth combinations underwent 5000 thermal cycles (5- 55◦C).Samples were subjected to shear bond strength test by a universal testing machine with a 1 mm/min crosshead speed .Data were analyzed using ANOVA and Tukey's tests(α=0.05). Results: Mean ±SD of shear bond strength values were (MPa) 4.82±1.21, 4.52±1.67, 3.7±0.84 and 4.13±2.21 for groups HP, AP, IM and PT respectively. No significant difference was found among the experimental groups (P=0.429). Conclusion: Polyamide thermoplastic denture base resin was similar to conventional PMMA denture base materials in terms of bond strength to artificial denture teeth. [ABSTRACT FROM AUTHOR]

Introduction: A dental impression is a negative imprint of an oral structure that can be used to produce a positive cast of a patient's teeth as a permanent record. The accuracy of the impression affects the accuracy of the cast, and a precise impression is needed in order to create prosthesis with optimal fitting. Minimization of misfit is an important aim in prosthesis science and dental implants. The aim of this study was to evaluate the effects of the materials and techniques used to take an impression on the vertical misfit of implant-supported, screw-retained, three-unit bridges. Materials and Methods: The principal model used was an acrylic block with two ITI implants. A 1.5-mm abutment was attached to fixtures with torque of 25 N.cm. A base-metal framework was built on the abutment in the acrylic block. The abutments of the acrylic model were unscrewed and fixture-level impressions were made. The impression techniques included open/closed-tray techniques and the impression materials were polyether and polyvinyl siloxane. Forty acrylic custom trays were built for each impression. The marginal gap in the framework at three points (buccal, lingual, and distal) was measured using an optical microscope with ×250. Results: It is demonstrated that in all 360 evaluated samples, the mean vertical misfit in polyether samples of molar and premolar teeth was significantly lower than in polyvinyl siloxane (P < 0.001 and P = 0.017, respectively) in all three locations of the molar and lingual premolar examined (buccal, lingual, and distal), the mean vertical misfit of the polyether samples was significantly lower than those of polyvinyl siloxane (P < 0.01). On the other hand, although the mean vertical misfit using the open-tray technique in the molar teeth was significantly lower than with the closed-tray method (P = 0.002), no statistical difference was seen between the open-tray and closed-tray technique in general (P = 0.87). Conclusion: Within the limitations of this study, the following conclusions can be drawn: The impression method had no effect on marginal discrepancy of 3-unit screw retained fixed partial dentures. A higher marginal accuracy was obtained using polyether impression material compared to polyvinyl siloxane. [ABSTRACT FROM AUTHOR]

Background: Accurate impression making is an essential prerequisite for achieving a passive fit between the implant and the superstructure. The aim of this in vitro study was to compare the three-dimensional accuracy of open-tray and three closed-tray impression techniques. Materials and Methods: Three acrylic resin mandibular master models with four parallel implants were used: Biohorizons (BIO), Straumann tissue-level (STL), and Straumann bone-level (SBL). Forty-two putty/wash polyvinyl siloxane impressions of the models were made using open-tray and closed-tray techniques. Closed-tray impressions were made using snap-on (STL model), transfer coping (TC) (BIO model) and TC plus plastic cap (TC-Cap) (SBL model). The impressions were poured with type IV stone, and the positional accuracy of the implant analog heads in each dimension (x, y and z axes), and the linear displacement (ΔR) were evaluated using a coordinate measuring machine. Data were analyzed using ANOVA and post-hoc Tukey tests (α = 0.05). Results: The ΔR values of the snap-on technique were significantly lower than those of TC and TC-Cap techniques (P < 0.001). No significant differences were found between closed and open impression techniques for STL in Δx, Δy, Δz and ΔR values (P = 0.444, P = 0.181, P = 0.835 and P = 0.911, respectively). Conclusion: Considering the limitations of this study, the snap-on implant-level impression technique resulted in more three-dimensional accuracy than TC and TC-Cap, but it was similar to the open-tray technique. [ABSTRACT FROM AUTHOR]

Background: The final position of the abutment changes with the amount of tightening torque. This could eventually lead to loss of passivity and marginal misfit of prostheses. The aim of this study was to evaluate the effect of three different tightening torques on the marginal adaptation of 3-unit cement-retained implant-supported fixed dental prostheses (FDPs). Materials and Methods: Two implants (Straumann) were inserted in an acrylic block so that one of the implants was placed vertically and the other at a 15° vertical angle. A straight abutment and a 15° angulated abutment were connected to the vertically and obliquely installed implants, respectively, so that the two abutments were parallel. Then, 10 cement-retained FDPs were waxed and cast. Abutments were tightened with 10,20,and 35 Ncmtorques, respectively. Following each tightening torque, FDPs were luted on respective abutments with temporary cement. The marginal adaptation of the retainers was evaluated using stereomicroscope. FDPs were then removed from the abutments and were sectioned at the connector sites. The retainers were luted again on their respective abutments. Luting procedures and marginal adaptation measurement were repeated. Data were analyzed by ANOVA and least significant difference tests (α = 0.05). After cutting the FDP connectors, the independent samples t-test was used to compare misfit values (α = 0.05). Results: Following 10,20, and 35 Ncm tightening torques, the marginal discrepancy of the retainers of FDPs significantly increased (P < 0.05).There was no significant difference between the marginal discrepancies of these two retainers (P > 0.05).The marginal gap values of angulated abutment retainers (ANRs) were significantly higher than those of the straight abutment after cutting the connectors (P = 0.026). Conclusion: Within the limitations of this study, the marginal misfit of cement-retained FDPs increased continuously when the tightening torque increased. After cutting the connectors, the marginal misfit of the ANRs was higher than those of the straight abutment retainers. [ABSTRACT FROM AUTHOR]

Introduction: Some clinicians use a handheld screw driver instead of a torque wrench to definitively tighten abutment screws. The aim of this study was to compare the removal torque of one-piece and two-piece abutments tightened with a handheld driver and a torque control ratchet. Methods: 40 ITI implants were placed in acrylic blocks and divided into 4 groups. In groups one and two, 10 ITI one-piece abutments (Solid®) and in groups three and four, 10 ITI two-piece abutments (Synocta®) were placed on the implants. In groups one and three abutments were tightened by 5 experienced males and 5 experienced females using a handheld driver. In groups two and four abutments were tightened using a torque wrench with torque values of 10, 20 and 35 N.cm. Insertion torque and removal torque values of the abutments were measured with a digital torque meter. Results: The insertion torque values (ITVs) of males in both abutments were significantly higher than those of females. ITVs in both Solid® and Synocta® abutments tightened with a handheld screwdriver were similar to the torque of 20 N.cm in the torque wrench. Removal torque values (RTVs) of solid® abutments were higher than those of synocta® abutments. Conclusion: The one- piece abutments (solid®) showed higher RTVs than the two-piece abutments (synocta®). Hand driver does not produce sufficient preload force for the final tightening of the abutment. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the micro-shear bond strength (μSBS) of different bonding protocols to commercially pure titanium (CP Ti) using two universal adhesives and Alloy Primer., Materials and Methods: A total of 120 cubes of CP Ti were airborne-particle abraded and then divided into 6 groups (n = 20 each) according to bonding protocol: (1) Scotchbond Universal (SU; 3M ESPE), (2) Alloy Primer (AP; Kuraray) + SU; (3) G-Premio Bond (GP; GC); or (4) AP + GP. The specimens from groups 1 to 4 were cemented with RelyX Unicem (3M ESPE), while those from groups 5 and 6 were cemented using Panavia F2.0 cement (PAN; Kuraray) without and with prior AP application, respectively. After 24 hours, half the specimens were subjected to μSBS measurement and the other half to thermocycling (5,000 cycles) before testing. Data were analyzed using Shapiro-Wilk, two-way analysis of variance, Games-Howell, and independent sample t test (α = .05)., Results: The μSBS values obtained from the AP + SU group were significantly higher than from the GP (P = .003) and the AP + GP (P = .022) groups. After thermocycling, the μSBS of both groups treated with SU were significantly higher than those other groups (P < .001). The application of AP could not improve adhesion of resin cements to CP Ti. Thermocycling significantly reduced the μSBS values of the PAN group, whereas it noticeably enhanced the adhesion of SU and AP + SU. The predominant failure mode in all groups was adhesive., Conclusion: The application of AP, followed by SU, produced the most effective bonding to CP Ti, which was able to endure limited thermal aging.

Background: The most appropriate luting agent for attaching the prefabricated Ti-based insert of hybrid abutments to its ceramic component has not yet been determined. This study was done aimed at examining the micro-shear bond strength (μSBS) of different cements to commercially pure titanium (Cp Ti)., Material and Methods: A total of 100 milled cubes of Cp Ti was airborne-particle abraded using 250 μm aluminum oxide particles. Specimens were then divided into 5 groups (n=20) according to the type of resin cement used: (1) Panavia F.2, (2) Rely X U200, (3) Panavia SA LUTING Plus, (4) GC Fuji I, and (5) GC FujiCEM 2. After 24h storage, half of the samples were subjected to 5000 cycles of thermal aging. Next, the bonded samples were tested in the micro-shear mode. Data (MPa) were analyzed using a two-way ANOVA and the post hoc Tukey test (α=0.05). After debonding, each sample was examined for the failure mode classification., Results: The highest μSBS value in the study cements was obtained for Panavia F.2 cement ( P <0.001) with no significant difference with Rely X U200 ( P =0.07). The μSBS values of both GI-based cements were significantly lower than those of resin cements. Thermal aging decreased the μSBS values of all groups ( P =0.003) significantly. The mainly occurred failure mode in all groups was the adhesive feature., Conclusions: Resin cements demonstrated acceptable bonding to Cp Ti, yet Gl-based cements did not. From among the cements examined, Panavia F.2 can be considered as the best option for bonding to Ti. Key words: Bond strength, Glass ionomer, Hybride abutment, Resin cement, Titanium., Competing Interests: Conflict of interest statement:The authors declare no potential conflicts of interest with respect to the authorship and/or publication of this article., (Copyright: © 2019 Medicina Oral S.L.)

Objectives: To evaluate the effect of ozone and two common denture cleansers on the surface hardness and bond strength of a silicone-based soft liner to acrylic denture base material., Materials and Methods: Sixty cylindrical specimens were fabricated using heat-cured poly-methyl methacrylate denture base resin. Three millimeters of the material was ground from the midsection and filled with the soft liner. The resilient liner specimens (n=40) used for the hardness test were 10 mm in diameter and 5 mm in height. Cylindrical and disc-shaped samples were randomly divided into four groups (37°C distilled water, Corega ® tablets, 0.5% sodium hypochlorite (NaOCl), and a home ozone generator). To simulate six months of denture cleansing clinically, samples were placed in their cleanser once a day for six months according to the manufacturer's instructions. All cylindrical specimens were placed under tension until failure in a universal testing machine at a crosshead speed of 5 mm/minute. For disc-shaped samples, hardness was measured using a Shore-A durometer. The results were analyzed using Kruskal-Wallis test, analysis of variance (ANOVA), and Tukey's post hoc test., Results: The mean tensile bond strength was not significantly different among the studied groups (P>0.05). The mean hardness in the ozone and Corega tablet groups was significantly lower than that of the control and NaOCl groups (P<0.05)., Conclusion: The type of denture cleanser does not affect the tensile bond strength of silicone soft liners. Home ozone generators and cleansing tablets have less effect on the hardness of soft denture liners compared to 0.5% NaOCl., Competing Interests: CONFLICT OF INTEREST STATEMENT None declared, (Copyright© Dental Research Center, Tehran University of Medical Sciences.)

Introduction: A dental impression is a negative imprint of an oral structure that can be used to produce a positive cast of a patient's teeth as a permanent record. The accuracy of the impression affects the accuracy of the cast, and a precise impression is needed in order to create prosthesis with optimal fitting. Minimization of misfit is an important aim in prosthesis science and dental implants. The aim of this study was to evaluate the effects of the materials and techniques used to take an impression on the vertical misfit of implant-supported, screw-retained, three-unit bridges., Materials and Methods: The principal model used was an acrylic block with two ITI implants. A 1.5-mm abutment was attached to fixtures with torque of 25 N.cm. A base-metal framework was built on the abutment in the acrylic block. The abutments of the acrylic model were unscrewed and fixture-level impressions were made. The impression techniques included open/closed-tray techniques and the impression materials were polyether and polyvinyl siloxane. Forty acrylic custom trays were built for each impression. The marginal gap in the framework at three points (buccal, lingual, and distal) was measured using an optical microscope with ×250., Results: It is demonstrated that in all 360 evaluated samples, the mean vertical misfit in polyether samples of molar and premolar teeth was significantly lower than in polyvinyl siloxane ( P < 0.001 and P = 0.017, respectively) in all three locations of the molar and lingual premolar examined (buccal, lingual, and distal), the mean vertical misfit of the polyether samples was significantly lower than those of polyvinyl siloxane ( P < 0.01). On the other hand, although the mean vertical misfit using the open-tray technique in the molar teeth was significantly lower than with the closed-tray method ( P = 0.002), no statistical difference was seen between the open-tray and closed-tray technique in general ( P = 0.87)., Conclusion: Within the limitations of this study, the following conclusions can be drawn: The impression method had no effect on marginal discrepancy of 3-unit screw retained fixed partial dentures. A higher marginal accuracy was obtained using polyether impression material compared to polyvinyl siloxane.

Aim: The aim of this study is to evaluate the effects of three different surface treatments and thermocycling on the tensile strength of a silicone lining material to denture resin., Materials and Methods: A total of 96 cube-shaped specimens were fabricated using heat-cured polymethyl methacrylate (PMMA) denture base resin. Three millimeters of the material was cut from the midsection. The specimens were divided into four groups. The bonding surfaces of the specimens in each group received one of the following surface treatments: no surface treatment (control group), airborne particle abrasion with 110 pirn alumina particles (air abrasion group), Er:yttrium aluminum garnet laser irradiation (laser group), and air abrasion + laser. After the lining materials were processed between the two PMMA blocks, each group was divided into two subgroups (n = 12), either stored in distilled water at 37°C for 24 hours or thermocycled between 5 and 55°C for 5,000 cycles. The specimens were tested in tensile and shear strength in a universal testing machine. Data were analyzed with two-way analysis of variance and Tamhane's post hoc tests (α = 0.05). The mode of failure was determined, and one specimen in each group was examined by scanning electron microscopy., Results: Surface-treated groups demonstrated significantly higher tensile strengths compared to the control group (p < 0.001). Nonetheless, no significant differences were found between surface-treated groups (p > 0.05). The tensile strength was significantly different between thermocycled and water-stored specimens (p = 0.021)., Conclusion: Altering the surface of the acrylic denture base resin with air abrasion, laser, and air abrasion + laser increased the tensile strength. Thermocycling resulted in decrease in bond strength of silicone-based liner to surface-treated acrylic resin., Clinical Significance: Pretreatment of denture base resins before applying the soft liner materials improves the bond strength. However, thermocycling results in decrease in bond strength of soft denture liner to surface-treated acrylic resin.

Aim: To evaluate the ability of dental students to match shades under three various light conditions., Materials and Methods: Sixty senior dental students participated in this study. All students were tested for color deficiency using Ishahara's tests. Nine classical vita shade tabs were randomly selected and their identification codes were concealed. The students were asked to match these 9 selected items by using a complete vita shade guide under three various light conditions (natural light, clinical light, and correcting light source). The chosen shade tabs were recorded and the correct matches were counted. Scores were calculated by adding the number of correct matches., Results: The mean values of correct match scores with natural light, clinical light and correcting light source were 4.82, 4.75 and 6.82, respectively. There was no significant difference in correct matches scores between men and women, nor among various vita A, B, C and D shades., Conclusion: The students showed a better performance in shade matching under the correcting light source than natural light and clinical light. Gender had no effect on shade matching selection and there was no difference in shade matching ability among vita A, B, C, D shades., Clinical Significance: Shade matching performance is significantly improved with correcting light source.