Celal Artunç

Effects of soldering and laser welding on bond strength of ceramic to metal.

STATEMENT OF PROBLEM Welding or soldering of metal frameworks negatively affects the overall bond strength between the veneering ceramic and metal. PURPOSE The purpose of this study was to evaluate the effect of soldering and laser-welding procedures on the bond strength between ceramic and metal. MATERIAL AND METHODS Thirty Ni-based metal specimens (Wiron 99) (8 × 4 × 4 mm) were fabricated and divided into 3 groups; soldered (S), laser welded (L), and control (untreated cast alloy) (n=10). In S and L specimens, a notch (1 × 1.5 mm) was prepared longitudinally on the surface of each specimen and filled with compatible alloy (Wiron soldering rods and Wiroweld NC, respectively). Vickers hardness measurements were made after polishing the surfaces with a metallographic polishing kit. A veneering ceramic (VITA VMK 95) was vibrated, condensed in a mold, and fired on the metal frameworks. The specimens were sectioned in 2 axes to obtain nontrimmed bar specimens with a bonding area of approximately 1 mm². Forty bars per block were obtained. Each bar was subjected to microtensile bond strength (μTBS) testing with a crosshead speed of 1 mm/min. The μTBS data (MPa) were recorded, and SEM was used for failure analysis of the tested bars. The measurements were statistically analyzed using a 1-way ANOVA and Tamhane tests (α=.05). RESULTS The mean differences in μTBS of veneering ceramic to soldered (10.4 ±2.4 MPa) and laser-welded (11.7 ±1.3 MPa) metal surfaces were not significantly different and were significantly lower than that of the cast alloy (25.4 ±3.6 MPa) (P<.05). The mean Vickers hardness of cast alloy was significantly higher (236 ±17 HV) than soldered (114 ±9 HV) and laser-welded groups (129 ±11 HV) (P<.05). CONCLUSIONS Soldering and laser welding significantly decreased the μTBS of a veneering ceramic to a base metal alloy.

Preliminary evaluation of titanium tetrafluoride as an alternative ceramic etchant to hydrofluoric acid.

PURPOSE The etching of dental ceramics with a glassy matrix by means of hydrofluoric acid (HF) is highly effective and after the application of a silane coupling agent, a strong link between the adhesive and the ceramic is achieved. The purpose of this study was to investigate whether aqueous titanium tetrafluoride (TiF4) solution could be used as an alternative ceramic etchant or not. MATERIALS AND METHODS Seventy lithia-based all-ceramic specimens (IPS Empress 2, Ivoclar Vivadent) (diameter: 4 mm, height: 4 mm) were prepared and ultrasonically cleaned for 15 min in ethanol and deionized water, then divided into 1 control and 4 experimental groups (n = 14/group). The control group was acid etched with 4.9% HF for 20 s as described by the manufacturer. The experimental groups were treated with 2.5% TiF4 solution for 60 s, 2.5% TiF4 solution for 120 s and 5% TiF4 solution for 60 s, as well as 5% TiF4 solution for 120 s. Seven of the ceramic specimens in each group were luted to the other seven by a dual-curing cement (Variolink II, Ivoclar Vivadent,) with silane application (Monobond-S). After storage of luted specimens in deionized water at 37 degrees C for 24 h, the specimens were embedded in plastic holders with cyanoacrylate, and the shear-bond strength (SBS) tests were performed with a Shimadzu universal testing machine at a crosshead speed of 0.5 mm/min. A one-way ANOVA and Bonferroni correction, followed by the Tukey test, were applied for statistical analysis. Scanning electron microscopic examination was performed to evaluate the pattern of debonding. RESULTS Significantly higher SBS values (p <or= 0.05) were obtained for the control group (28.71 +/- 9.74). The SBS for 2.5%-60 s (25.25 +/- 5.13) and 2.5%-120 s TiF4 (22.65 +/- 5.68) were significantly higher than 5%-60 s (16.77 +/- 3.92) and 5%-120 s TiF4 (18.54 +/- 3.52) groups (p <or= 0.05). Differences between 60- and 120-s groups irrespective of TiF4 concentrations were insignificant (p > 0.05). CONCLUSION Aqueous TiF4 solution exhibited similar shear bond strength values in comparison to commonly used HF and can be considered as an alternative ceramic etchant within the limitations of this preliminary report.

Comparison of the mechanical properties of nitrogen ion implantation and micro-pulsed plasma nitriding techniques of Cr-Ni alloy

Abstract Cr–Ni alloys are frequently used in dentistry for economical reasons. While they gain popularity, an increase in systemic and local concerns of these dental metals is observed. With the progressions in surface technology, the surface characteristics of the metals can be changed. In this study, nitrogen ion (N ion) implantation and plasma nitriding techniques were used to change the properties of Cr–Ni alloy (Wirollay). Nitrogen implantation at dose 1×10 17 ion/cm 2 and micro-pulsed plasma nitriding techniques were applied to Cr–Ni alloy samples. After the process, the friction coefficient was decreased in ion implantation, but this ratio was increased in the plasma nitriding technique with respect to the substrate. The roughness did not change after N ion implantation but it increased after the plasma nitriding procedure. Wear volume of the implanted and plasma nitriding samples were lower than the substrate. Hardness values were increased four times for N ion implantation and eight times for the plasma nitriding technique.

Laser use vs. handpiece for tooth preparation: A preliminary in vitro study

The key fields of research of dental lasers have focused on the use of different wavelengths on hard and soft tissues; however it is not clear whether they can be used for tooth preparation for full coverage restorations or not. The objective of this study was to investigate the possibility of tooth preparation for full coverage restorations using a scanner assembly added-on Er:YAG laser system and compare the tooth preparation durations performed with dental drills and the laser. The 20 freshly extracted human molar teeth were allocated to two groups (A and B) of 10. Group A was prepared with dental drills, whereas group B was prepared with a scanner assembly added-on Er:YAG laser system. The preparation duration means of the groups were calculated and analyzed by one-way analysis of variance. The difference between group A (20, 2±1, 9 min) and B (45, 2±|3, 1 min) (P<0.01) was significant. Laser preparation took more time than the conventional rotary instrumentation. The recommended amount of tooth reduc...

Adhesive retention of experimental fiber-reinforced composite, orthodontic acrylic resin, and aliphatic urethane acrylate to silicone elastomer for maxillofacial prostheses

STATEMENT OF PROBLEM A key factor of an implant-retained facial prosthesis is the success of the bonding between the substructure and the silicone elastomer. Little has been reported on the bonding of fiber reinforced composite (FRC) to silicone elastomers. Experimental FRC could be a solution for facial prostheses supported by light-activated aliphatic urethane acrylate, orthodontic acrylic resin, or commercially available FRCs. PURPOSE The purpose of this study was to evaluate the bonding of the experimental FRC, orthodontic acrylic resin, and light-activated aliphatic urethane acrylate to a commercially available high-temperature vulcanizing silicone elastomer. MATERIAL AND METHODS Shear and 180-degree peel bond strengths of 3 different substructures (experimental FRC, orthodontic acrylic resin, light-activated aliphatic urethane acrylate) (n=15) to a high-temperature vulcanizing maxillofacial silicone elastomer (M511) with a primer (G611) were assessed after 200 hours of accelerated artificial light-aging. The specimens were tested in a universal testing machine at a cross-head speed of 10 mm/min. Data were collected and statistically analyzed by 1-way ANOVA, followed by the Bonferroni correction and the Dunnett post hoc test (α=.05). Modes of failure were visually determined and categorized as adhesive, cohesive, or mixed and were statistically analyzed with the chi-squared goodness-of-fit test (α=.05). RESULTS As the mean shear bond strength values were evaluated statistically, no difference was found among the experimental FRC, aliphatic urethane acrylate, and orthodontic acrylic resin subgroups (P>.05). The mean peel bond strengths of experimental fiber reinforced composite and aliphatic urethane acrylate were not found to be statistically different (P>.05). The mean value of the orthodontic acrylic resin subgroup peel bond strength was found to be statistically lower (P<.05). Shear test failure types were found to be statistically different (P<.05), whereas 180-degree peel test failure types were not found to be statistically significant (P>.05). Shear forces predominantly exhibited cohesive failure (64.4%), whereas peel forces predominantly exhibited adhesive failure (93.3%). CONCLUSION The mean shear bond strengths of the experimental FRC and aliphatic urethane acrylate groups were not found to be statistically different (P>.05). The mean value of the 180-degree peel strength of the orthodontic acrylic resin group was found to be lower (P<.05).

Stress Analysis of Fiber-reinforced Maxillary Dentures Under Different Loadings

The aim of this study was to compare maxillary dentures having different reinforcing materials in terms of stress distribution under concentrated forces applied to anterior and posterior regions. For this purpose, stress analyses of finite element models of 3 mm thick maxillary denture-bone systems were performed by using ANSYS software. First, concentrated forces making various angles, such as 0°, 15°, 30°, 45°, 60°, 75°, and 90°, with horizontal axis were applied to the anterior incisor and the posterior molar tooth regions of a maxillary denture without reinforcement material. The results show that the highest stress in critical zones occur at 75° and 45° angles, under loadings of 150 N to molar and 75 N to incisor region, respectively. Secondly, four different reinforcing materials including unidirectional and woven glass fibers, unidirectional carbon fibers, and alloyed chrome—cobalt fibers were placed in the denture in two different positions. Under vertical loadings, the σx stress distributions occurring in critical zones were investigated. It is concluded from the stress analyses that use of Cr—Co as a reinforcing material at the center of the maxillary denture gives the best results in terms of stress distribution and strength.

A Comparison Of The Performance Of Different Resin Luting Cements After Thermomechanical Aging

Objectives: To investigate the effects of the thermomechanical aging on microtensile bond strength and nanoleakage of different adhesive resin luting cements. Methods: Thirty human third molar teeth were cut under water cooling to obtain flat dentine surface. Then composite specimens were adhered onto prepared teeth with different adhesive resin cements. Samples were divided into five groups according to the luting cements used; 1-Variolink II-convantional etch-and-rinse resin cement, 2-Multilink-selfetch resin cement, 3-Panavia F2.0-self-etch resin cement, 4-RelyX U200-self-adhesive resin cement, 5-SuperBond C&B-conventional etc-and-rinse resin cement. Each resin cement group was separated into two subgroups as control and thermomechanical aging group. No thermomechanical aging was applied to the samples in the control group. Samples in thermomechanical aging group were subjected to 10.000 thermocycles at 5-55oC and 50.000 loadingcycles using a loading force of 50 N. After samples were immersed in a solution consisting of 50% ammoniac silver nitrate for 24h, bond strength test was performed and samples were observed under FEI-SEM/EDX. Results: It was seen that microtensile bond strength and nanoleakage were not significantly affected by aging (p≥0,05), but a significant difference was found among the luting resin cements (p˂0,05). Conclusion: It was determined that the performance of resin luting cements used in this study was not affected by thermomechanical aging and concluded that the type of adhesive resin cement is effective on longevity of the restoration.

Comparison of Stress Distributions of Dental Woven and Unidirectional Fiber-Reinforced Composite Crowns Under Different Loadings

The aim of this numerical study was to investigate and compare the stresses occurring in dental woven and unidirectional experimental fiber-reinforced composite (FRC) crowns under different thermal and singular force loading conditions. For this reason, finite element models of FRC crown and tooth systems were performed by using the ANSYS program. Stress analyses of the models were carried out under thermal loading conditions heated from 37 to 55°C, cooled from 37 to 5°C, and 450 N singular force loading conditions at different angles. The results indicated that high stresses occurred in both woven and unidirectional FRC crowns under horizontal loadings because of bending moment. Thermal stresses exhibited small values that did not cause any damage. It can also be concluded that since the stress component of σ z in the woven type FRC was smaller than that of unidirectional type FRC, use of the woven FRC might be beneficial in comparison with the unidirectional composite.

Güçlendirilmiş dental seramiklerin vickers sertlikleri ve yük altında kırılma davranışları

Objective: The objectives of this study were to determine the Vicker`s hardness of reinforced dental ceramics and determine the modes of fractures under load. Methods: Four ceramic core groups (n=7/group) from leucite (Evopress,WegoldD 5 mm capta). Her bir alt yapi seramigine ozgu kaplama seramikleri; paslanmaz celik bir metal kalipta (5mm cap 5mm yukseklikte) vibrasyonla kondanse edildi ve alt yapi seramiklerinin uzerine pisirildi. Ornekler batirma testlerinden once 37°C’ de 24 saat distile suda bekletildikten sonra polyester kaliplara gomuldu. Vickers sertlik degerleri (DUH±SD) olculdu (cene hizi:7,2 gf/s, yuk:200 gf) ve veriler istatistiksel olarak analiz edildi (ANOVA). Catlak olusumu icin orneklerin ust yuzeylerine makro sertlik test cihazinda batici elmas uc ile (1 mm capli) 400 N yuk uygulandi. Alinan taramali elektron mikroskop goruntuleri ile her bir gruba iliskin catlak sekilleri gozlemlendi. Bulgular: Gruplar arasinda ortalama Vickers sertlik degerleri dusuk losit grubu icin anlamli olarak (P<0.05) en yuksek bulunur iken (236±17), bunu losit (129±51), cam infiltrasyonlu aluminoz seramik (117±38), ve lityum disilikat (85±34) kaplama seramik materyalleri azalan sirayla izledi. Yuk uygulamasi sonrasinda genellikle isinsal ya da koni sekilli catlaklarin olustugu gozlendi. Sonuc: Seramik materyalin sertliginin artmasi daha fazla ve daha uzun catlak olusumuna yol acti. Bu calismadaki deneysel kosullar altinda kaplama seramik gruplarinin hicbirinde alt yapi seramiklerine ulasan catlak olusumu gozlenmedi.

Three Dimensional Stress Analysis in the Crowned Human Teeth

The stress distribution on a mandibular right second premolar tooth was investigated by using a three dimensional finite element model. Three crowns cast in different materials were subjected to 11 simulated biting force of 100 N with six different postures. The distribution of compressive and tensile stresses on cole and apex was evaluated by using a computer program. The stress component in transverse direction on the cole with porcelain crown was found to be most compatible with enamel when compared with other materials.