Effect of Two Self-Adhesive Cements on Marginal Adaptation and Strength of Esthetic Ceramic CAD/CAM Molar Crowns

Purpose: This study evaluated the effects of adhesive cements on marginal adaptation and fracture resistance of ceramic molar crowns. Materials and Methods: Seventy‐five extracted maxillary molars were selected. The occlusal morphology of 15 molars (control) was scanned and transferred to the crowns in the test groups by CAD/CAM. Sixty molars received full‐coverage crown preparations with 6‐degree axial taper, 1.0‐mm shoulder, and 2.0‐mm occlusal reduction. They were assigned to four groups, and pulpal pressure was simulated. The 15 crowns in each test group were seated with resin‐based self‐adhesive cements, Rely‐X (RX) and Multilink (MS), one multistep bonded adhesive luting composite resin, Variolink (VL), and glass‐ionomer cement, Ketac Cem (KC). Test and control molars were subjected to thermal and mechanical fatigue stress (TMS: 12,000 × 5°C to 50°C; 2.4 million × 49 N) for 18 days in a masticator. Marginal adaptation [“continuous margin%” (CM%)] of the crowns was determined by scanning electron microscopy (200×). Finally, molars were occlusally loaded until fracture in a testing machine, and fracture load (N) was recorded. Marginal adaptation and strength data were statistically analyzed. Results: TMS significantly (p < 0.001) reduced CM% in all groups. After TMS, CM% at the cement‐dentin interface was significantly (p < 0.001) higher for RX than for all other cements. At the crown‐cement interface both self‐adhesive cements MS and RX had significantly better CM% than VL (p < 0.05) and KC (p < 0.001). Fracture resistance of natural untreated molars was significantly (p < 0.001) higher than that of experimental crowns. Fracture resistance of RX cemented crowns was significantly (p < 0.05) higher than that of other crowns. Occlusal morphology significantly influenced fracture resistance (p < 0.05). Conclusions: Self‐adhesive cement RX offers a valid alternative to multistep resin‐based luting composite with respect to marginal adaptation to dentin and fracture resistance. The latter is also influenced by occlusal morphology, necessitating careful monitoring of occlusal contacts.     

Shear Bond Strength of Four Resin Cements Used to Lute Ceramic Core Material to Human Dentin

Purpose: This study evaluated the effect of four resin cements on the shear bond strength of a ceramic core material to dentin. Materials and Methods: One hundred twenty molar teeth were embedded in a self‐curing acrylic resin. The occlusal third of the crowns were sectioned under water cooling. All specimens were randomly divided into four groups of 30 teeth each according to the resin cement used. One hundred twenty cylindrical‐shaped, 2.7‐mm wide, 3‐mm high ceramic core materials were heat‐pressed. The core cylinders were then luted with one of the four resin systems to dentin (Super‐Bond C&B, Chemiace II, Variolink II, and Panavia F). Half of the specimens (n = 15) were tested after 24 hours; the other half (n = 15) were stored in distilled water at 37°C for 1 day and then thermocycled 1000 times between 5°C and 55°C prior to testing. Shear bond strength of each specimen was measured using a universal testing machine at a crosshead speed of 1 mm/min. The bond strength values were calculated in MPa, and the results were statistically analyzed using a two‐way analysis of variance (ANOVA) and Tukey HSD tests. Results: The shear bond strength varied significantly depending on the resin cement used (p < 0.05). The differences in the bond strengths after thermocycling were not remarkable as compared with the corresponding prethermal cycling groups (p > 0.05). Significant interactions were present between resin cement and thermocycling (p < 0.05). After 24 hours, the specimens luted with Variolink II (5.3 ± 2.2 MPa) showed the highest shear bond strength, whereas the specimens luted with Chemiace II (1.6 ± 0.4 MPa) showed the lowest. After thermocycling, the bond strength values of specimens luted with Chemiace II (1.1 ± 0.1 MPa) and Super‐Bond C&B (1.7 ± 0.4 MPa) decreased; however, this was not statistically significant (p > 0.05). The increase in the shear bond strength values in the Panavia F (4.5 ± 0.7 MPa) and Variolink II (5.5 ± 2.1 MPa) groups after thermocycling was also not statistically significant (p > 0.05). Conclusion: Variolink II and Panavia F systems showed higher shear bond strength values than Chemiace II and Super‐Bond C&B. They can be recommended for luting ceramic cores to dentin surfaces.     

Durability of Adhesion between Feldspathic Ceramic and Resin Cements: Effect of Adhesive Resin,Polymerization Mode of Resin Cement,and Aging

Purpose : Adhesive cementation is an important step for restorations made of feldspathic ceramic as it increases the strength of such materials. Incorrect selection of the adhesive resin and the resin cement to adhere to the ceramic surface and their durability against aging can affect the adhesion between these materials and the clinical performance. This study evaluated the effect of adhesive resins with different pHs, resin cements with different polymerization modes, and aging on the bond strength to feldspathic ceramic. Materials and Methods : One surface of feldspathic ceramic blocks (VM7) (N = 90) (6.4 × 6.4 × 4.8 mm³) was conditioned with 10% hydrofluoric acid for 20 seconds, washed/dried, and silanized. Three adhesive resins (Scotchbond Multi‐Purpose Plus [SBMP], pH: 5.6; Single Bond [SB], pH: 3.4; and Prime&Bond NT [NT], pH: 1.7) were applied on the ceramic surfaces (n = 30 per adhesive). For each adhesive group, three resin cements with different polymerization modes were applied (n = 10 per cement): photo‐polymerized (Variolink II base), dual polymerized (Variolink II base + catalyst), and chemically polymerized (C&B). The bonded ceramic blocks were stored in water (37°C) for 24 hours and sectioned to produce beam specimens (cross‐sectional bonded area: 1 ± 0.1 mm²). The beams of each block were randomly divided into two conditions: Dry, microtensile test immediately after cutting; TC, test was performed after thermocycling (12,000×, 5°C to 55°C) and water storage at 37°C for 150 days. Considering the three factors of the study (adhesive [3 levels], resin cement [3 levels], aging [2 levels]), 18 groups were studied. The microtensile bond strength data were analyzed using 3‐way ANOVA and Tukey's post hoc test (α= 0.05). Results : Adhesive resin type (p < 0.001) and the resin cement affected the mean bond strength (p= 0.0003) (3‐way ANOVA). The NT adhesive associated with the chemically polymerized resin cement in both dry (8.8 ± 6.8 MPa) and aged conditions (6.9 ± 5.9 MPa) presented statistically lower bond strength results, while the SBMP adhesive resin, regardless of the resin cement type, presented the highest results (15.4 to 18.5 and 14.3 to 18.9 MPa) in both dry and aged conditions, respectively (Tukey's test). Conclusion : Application of a low‐pH adhesive resin onto a hydrofluoric acid etched and silanized feldspathic ceramic surface in combination with chemically polymerized resin cement did not deliver favorable results. The use of adhesive resin with high pH could be clinically advised for the photo‐, dual‐, and chemically polymerized resin cements tested.     

Alternative Pretreatment Modalities with a Self‐Adhesive System to Promote Dentin/Alloy Shear Bond Strength

Purpose: The aim of this study was to evaluate alternative pretreatment modalities to enhance the dentin/alloy shear bond strength using a self‐etch adhesive system. Material and Methods: Ninety discs were fabricated and divided into three groups (n = 30). The discs of the first group were cast in gold palladium (Au‐Pd); those of the second group were cast in palladium silver alloy (Pd‐Ag); the discs of third group were cast in nickel chromium alloy (Ni‐Cr). Each group was further divided into three subgroups (n = 10) according to the dentin pretreatment used to lute the discs. Subgroup U (no pre‐treatment): Rely X Unicem resin cement. Subgroup GU: G‐Bond then Rely X Unicem. Subgroup ZU: Zinc‐Zeolite pretreatment then Rely X Unicem. Shear bond strength was determined using a compressive mode of force applied at the dentin/alloy interface using a monobevelled chisel‐shaped metallic rod. Data were collected and statistically analyzed to assess the effect of alloy type, pretreatment modality, and their interactions on the shear bond strength. Scanning electron microscopic examination (1000×) at the dentin/resin interface was performed. Two‐way ANOVA was used in testing significance for the effect of pretreatment, alloy, and their interaction. Duncan's post hoc test was used for pairwise comparison between the means when the ANOVA test was significant. The significance level was set at p≤ 0.05. Statistical analysis was performed with SPSS 15.0^®. Results: Regarding the pretreatment modality, the mean shear bond strength and 95% CI of subgroups ZU (18.00 MPa; 16.8 to 19.2) and GU (16.91 MPa; 15.4 to 18.4) were significantly higher than subgroup U (12.81 MPa; 11.4 to 14.2). Regarding the alloy type, the mean shear bond strength and 95% CI of Ni‐Cr groups (18.39 MPa; 16.9 to 19.9) were significantly higher than Au‐Pd (15.33 MPa; 13.8 to 16.8) and Pd‐Ag (13.99 MPa; 12.3 to 15.7). Conclusions: Pretreatment of dentin with G‐Bond and Zinc Zeolite improved the dentin/alloy shear bond strength. Base metal alloys provided superior bond strength values with any adhesive modality compared to noble alloys. Treatment of the dentin surface prior to the application of a self‐adhesive system is of great importance to enhancement of the dentin/alloy bond strength.     

不同全瓷材料在CAD/CAM系统中的边缘适合性研究

目的 研究不同全瓷材料由同一种CAD/CAM系统制作后其边缘适合性的差异,观察不同材料在烧结、结晶、上釉前后的边缘适合性变化,为临床选择全瓷材料提供一定的参考依据。方法 制作前磨牙牙备后树脂试件,分别使用长石类全瓷材料,二硅酸锂全瓷材料和氧化锆全瓷材料在SironainLab CAD/CAM系统中制作全瓷修复体各8个,在体视显微镜下观察各冠边缘与试件间隙。结果 在基底冠和全冠两个阶段的边缘间隙,长石类分别为（59.18±8.15）μm和（59.78±8.47）μm,二矽酸锂类分别为（56.16±6.64）μm和（57.22±7.45）μm,氧化锆类分别为（18.12±4.69）μm和（22.36±4.48）μm。其中,长石类与二矽酸锂类的边缘间隙差异无统计学意义（P>0.05）,但他们与氧化锆类比较,差异有统计学意义（P<0.05）。而同组的修复体在两阶段的数据差异均无统计学意义（P>0.05）。结论 三种材料制作的全冠适合性均在临床可接受的范围内,但氧化锆组更接近美国牙科协会的标准,值得推广应用。     

Effect of prolonged application of single-step self-etching primer and hydrofluoric acid on the surface roughness and shear bond strength of CAD/CAM materials

This in vitro study aimed to assess the influence of different concentrations and durations of hydrofluoric acid (HF) and Monobond Etch & Prime (MEP) etching on the surface roughness (R_a) of different CAD/CAM materials and on the shear bond strength (SBS) of a self-adhesive resin bonded to the materials. Seventy specimens of hybrid ceramic, leucite-based glass-ceramic, lithium disilicate glass-ceramic, and zirconia-reinforced lithium silicate glass-ceramic were prepared and divided into seven groups according to the surface treatments: Control (C); MEP etching for 60 (MEP₆₀) and 120 (MEP₁₂₀) s; 5% HF etching for 60 (HF-5%₆₀) and 120 (HF-5%₁₂₀) s; 9.5% HF etching for 60 (HF-9.5%₆₀) and 120 (HF-9.5%₁₂₀) s. The R_a was measured using a 3D profilometer. All groups were treated with a universal primer except for the C, MEP₆₀, and MEP₁₂₀ groups. A self-adhesive resin cement was bonded to all specimens, and the bond strengths were measured using a universal testing machine. All surface treatments increased both R_a and SBS values compared to the control in each material. Neither the duration of surface treatments nor the HF acid concentrations had a statistically significant effect on SBS. Within the limitations of this experimental study, it can be concluded that Monobond Etch & Prime may be a preferable method to achieve high bond strength values.     

CAD/CAM瓷嵌体的适合性研究

应用体视显微镜观测新型的ＣＥＲＥＣⅡ型机制作的瓷嵌体与离体人牙粘接前后的适合性。结果表明：粘接前，洞型与嵌体轴壁间隙，龈壁间隙，Ｈｅ面平均间隙５８．５μｍ；粘接后，平均边缘浮升量，粘接剂厚度在轴壁，龈壁，Ｈｅ面平均厚度８０μｍ。提示：ＣＥＲＥＣⅡ型机制作的瓷嵌体具有良好的适合性，可以满足临床的应用。     

Shear bond strength of a new self-adhering flowable composite resin for lithium disilicate-reinforced CAD/CAM ceramic material

PURPOSE

The purpose of this study was to evaluate and compare the effects of different surface pretreatment techniques on the surface roughness and shear bond strength of a new self-adhering flowable composite resin for use with lithium disilicate-reinforced CAD/CAM ceramic material.

MATERIALS AND METHODS

A total of one hundred thirty lithium disilicate CAD/CAM ceramic plates with dimensions of 6 mm × 4 mm and 3 mm thick were prepared. Specimens were then assigned into five groups (n=26) as follows: untreated control, coating with 30 µm silica oxide particles (Cojet™ Sand), 9.6% hydrofluoric acid etching, Er:YAG laser irradiation, and grinding with a high-speed fine diamond bur. A self-adhering flowable composite resin (Vertise Flow) was applied onto the pre-treated ceramic plates using the Ultradent shear bond Teflon mold system. Surface roughness was measured by atomic force microscopy. Shear bond strength test were performed using a universal testing machine at a crosshead speed of 1 mm/min. Surface roughness data were analyzed by one-way ANOVA and the Tukey HSD tests. Shear bond strength test values were analyzed by Kruskal-Wallis and Mann-Whitney U tests at α=.05.

RESULTS

Hydrofluoric acid etching and grinding with high-speed fine diamond bur produced significantly higher surface roughness than the other pretreatment groups (P<.05). Hydrofluoric acid etching and silica coating yielded the highest shear bond strength values (P<.001).

CONCLUSION

Self-adhering flowable composite resin used as repair composite resin exhibited very low bond strength irrespective of the surface pretreatments used.     

Two new clinical/laboratory protocols for CAD/CAM implant restorations

BACKGROUND: Conventional casting technology has some disadvantages for dental laboratory technicians and restorative dentists, including porosity of restorations, miscasting and inaccuracy. It also is labor-intensive. Computer-aided design/computer-aided manufacturing (CAD/CAM) technology was developed in the late 1980s for dentistry, and it significantly reduced and/or eliminated problems associated with dental castings. The purpose of this article is to give readers an overview of the use of CAD/CAM technology for dental implants and illustrate two clinical protocols for that use. CLINICAL IMPLICATIONS: The CAD/CAM technology described in this article can reduce restorative dentists' chairside time associated with implant treatment in both edentulous and partially edentulous patients, can decrease costs without sacrificing accuracy or biocompatibility for both clinicians and dental laboratory technicians, and is available to dental laboratories without the capital expenses associated with purchasing new technology.     

Cerec CAD/CAM全瓷嵌体和高嵌体3年临床研究

目的：本研究描述和探索Cerec2计算机辅助设计和制作系统的临床应用各个环节,并对Cerec2嵌体／高嵌体的临床修复效果进行评价及分析。方法：本研究运用Vita MK Ⅱ系列瓷块共制作Cerec2嵌体／高嵌体59个,修复体用树脂粘结剂粘结完成。修复后每半年由两位医师按照改良USPHS标准对嵌体进行检查和评价。结果：通过Kalplan—meier生存率计算法计算嵌体／高嵌体使用3～4年的生存率为93％,修复体失败的原因为瓷破裂（4例）和脱落（1例）。结论：Cerec2系统可以制作全瓷嵌体,高嵌体,贴面和全冠多种修复体。它为牙医提供了一个独特的治疗方法,在一次就诊时间内完成了一种天然牙色的、高质量的全瓷修复体。     

An in-vitro comparison of fracture resistance of three CAD/CAM Ceramic materials for fabricating Veneer

AimsThis research aims to measure and compare the fracture resistance and modes of failure of the following three chemically varied computer-aided design/computer-aided manufacturing (CAD/CAM) ceramic veneering materials: IPS e.max CAD, Vita Enamic, and Shofu HC.Materials and methodsTwenty-seven sound human upper premolars were collected and stored in saline at room temperature until the experiment started and were assigned to three groups at random (n = 9). Putty indices were prepared to ensure a standardized butt joint preparation. An InEos X5 scanner was used to scan all the samples, and the resulting data were transferred to a CAD/CAM milling machine for veneer fabrication based on the materials used. Twenty-seven machined ceramic veneers were milled from three different ceramic materials. The cementation process was conducted for each material according to the manufacturer's instructions. To quantify the fracture resistance, all the samples underwent 2000 water cycles in a thermocycler and were then mounted in a universal testing machine at a 90° angle at the occlusal part of the veneer. The modes of failure were determined under a stereomicroscope and grouped into type I, ceramic fracture; type II, combined ceramic and tooth fracture; and type III, root fracture.ResultsShofu HC had the highest mean (±standard deviation) fracture resistance (480.8 ± 92.8 N), followed by IPS e.max CAD (415.9 ± 147.2 N) and Vita Enamic (372.3 ± 123.9 N). However, the results of a one-way analysis of variance did not reveal statistically significant differences among the experimental groups (p = 0.194). The different groups exhibited different modes of failure, with ceramic fracture being the most common type of failure.ConclusionAll the materials tested in this study exhibited strong fracture resistance values, thereby indicating their use as veneering materials for the upper premolars.