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,Wegold&De), low leucite (Finesse, Ceramco), glass-infiltrated (Inceram Alumina,Vita) and lithium disilicate materials (E.max press, Ivoclar) were fabricated according to each manufacturers’ instructions (thickness: 3 mm, diameter: 5 mm). Their individual veneering ceramics were vibrated, condensed in a stainless steel mold (diameter: 5 mm, height: 5 mm) and fired on the core materials. The specimens were stored in distilled water at 37°C for 24 hours prior to indentation tests and embedded in polyesther moulds. Vickers hardness values (DUH±SD) were measured (cross-head speed:7,2 gf/s, load:200 gf) and statistically analysed (ANOVA). A load of 400 N was applied on the surfaces of specimens with a diamond indentor (diameter:1 mm) at the macro hardness test machine for crack formation. The crack modes for each group were observed under the scanning electrone microscope. Results: The Vickers hardness values for low leucite veneering ceramic were significantly (P<0.05) higher (236±17), followed by the leucite (129±51), glass-infiltrated (117±38), and lithium disilicate (85±34) veneering ceramic materials in decreasing order. Mainly radial or cone cracks were observed after the application of load. Conclusion: The increase in the hardness of the material led to more crack formation and resulted in longer cracks. No crack formation extending to the core materials were observed in neither of the ceramic groups under these experimental conditions. ÖZET Amaç: Bu çalışmanın amacı güçlendirilmiş dental seramiklerin Vickers sertlik değerlerinin ve yük altındaki kırılma şekillerinin belirlenmesidir. Gereç ve Yöntem: Lösit (Evopress,Wegold&De), düşük lösit (Finesse, Ceramco), cam infiltrasyonlu aluminöz seramik (Inceram Alumina,Vita) ve lityum disilikat (E.max press, Ivoclar) bazlı dört farklı seramik alt yap_ materyali (n=7/grup) her bir üretici firmanın önerileri doğrultusunda hazırlandı (3 mm kalınlıkta; 5 mm çapta). Her bir alt yapı seramiğine özgü kaplama seramikleri; paslanmaz çelik bir metal kalıpta (5mm çap 5mm yükseklikte) vibrasyonla kondanse edildi ve alt yapı seramiklerinin üzerine pişirildi. Örnekler batırma testlerinden önce 37°C’ de 24 saat distile suda bekletildikten sonra polyester kalıplara gömüldü. Vickers sertlik değerleri (DUH±SD) ölçüldü (çene hızı:7,2 gf/s, yük:200 gf) ve veriler istatistiksel olarak analiz edildi (ANOVA). Çatlak oluşumu için örneklerin üst yüzeylerine makro sertlik test cihazında batıcı elmas uç ile (1 mm çaplı) 400 N yük uygulandı. Alınan taramalı elektron mikroskop görüntüleri ile her bir gruba ilişkin çatlak şekilleri gözlemlendi. Bulgular: Gruplar arasında ortalama Vickers sertlik değerleri düşük lösit grubu için anlamlı olarak (P<0.05) en yüksek bulunur iken (236±17), bunu lösit (129±51), cam infiltrasyonlu aluminöz seramik (117±38), ve lityum disilikat (85±34) kaplama seramik materyalleri azalan sırayla izledi. Yük uygulaması sonrasında genellikle ışınsal ya da koni şekilli çatlakların oluştuğu gözlendi. Sonuç: Seramik materyalin sertliğinin artması daha fazla ve daha uzun çatlak oluşumuna yol açtı. Bu çalışmadaki deneysel koşullar altında kaplama seramik gruplarının hiçbirinde alt yapı seramiklerine ulaşan çatlak oluşumu gözlenmedi

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

WOS: 000357624000025PubMed ID: 25858221Statement 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 (alpha=.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 (a=.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 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).Ege University Scientific Project DepartmentEge University [2012-DIS-020]Supported by Ege University Scientific Project Department (project number: 2012-DIS-020)

Seven-year clinical follow-up study of probond ceramic crowns

WOS: 000248726700003PubMed ID: 17823668Objective: The Probond metal-ceramic system was proposed as an alternative to conventional metal-ceramic restorations. This study examined the 7-year survival and clinical performance of Probond metal-ceramic crowns. Method and Materials: A total of 200 patients were included in the study. All subjects required single-unit fixed prosthodontics in various areas of the mouth. The patients without any active periodontal or pulpal diseases, having adequate tooth structure and good oral hygiene, were included in the study, while patients with parafunctional habits were excluded, Overall clinical performance over 7 years was determined by using modified USPHS criteria and evaluated with Kaplan-Meier survival analysis. Results: Seven failures were recorded among the 260 crowns placed. In the 4th year, 2 Probond crowns had minimal incisal fractures, and 1 restoration had a cervical fracture in the 2nd year, After 7 years, 2 Probond crowns were replaced with new Probond crowns as a result of fracture or trauma. Two restorations lost their occlusal contact integrity due to marginal ridge fractures. The formation of cracks and fractures as well as caries were significant (P < .05) at the 4- and 7-year recalls. Overall survival rates for marginal integrity, color stability, caries and crack formations, and occlusal integrity were 90.7%, 98.1 %, 98.1%, 95.4%, and 99%, respectively, at 7 years. Conclusion: The durability of Probond ceramic crown restorations proved to be successful after 7 years

Stress Analysis of Fiber-reinforced Maxillary Dentures Under Different Loadings

WOS: 000282429100006The 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 degrees, 15 degrees, 30 degrees, 45 degrees, 60 degrees, 75 degrees, and 90 degrees, 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 degrees and 45 degrees angles, under loadings of 150N to molar and 75N 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 sigma(x) 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

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

WOS: 000271624900001The 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 degrees C, cooled from 37 to 5 degrees 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 sigma(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