Fatigue resistance of monolithic and multilayer zirconia crowns using veneer layering or CAD-on technique

Abstract This study aims to evaluate the fatigue resistance of monolithic zirconia (Yz) and multilayer ceramic structures using the CAD-on technique in different thicknesses. Fifty (N=50) standardized single crowns preparations were made in fiberglass-reinforced epoxy resin (NEMA grade G10), digitalized, and restorations were machined in CAD-CAM, composing 5 groups (n= 10): Control: 1.5 mm (milled zirconia framework + manual layered porcelain); Yz monolithic 1.5 mm; Yz monolithic 1.0 mm; CAD-on 1.5 mm; and CAD-on 1.0 mm (milled zirconia framework 0.5 mm thickness bonded by a low fuse ceramic to a milled lithium disilicate layer of 1.0 mm or 0.5 mm, respectively). The G10 bases were conditioned with 10% hydrofluoric acid; the crowns were air abraded with 110 μm alumina particles; and then luted onto each other with self-adhesive resin cement. A cyclic fatigue test was performed (initial load: 400N for 10,000 cycles, frequency of 20 Hz, step size of 200N) until failure, and the data was submitted to a survival statistical analysis. No failures were observed at Yz monolithic 1.5 mm. High and similar performance was observed for Cad-On groups and Yz monolithic 1.0 mm. The control group depicted the worst behavior. The Weibull modulus of CAD-on 1.5 mm was higher than the control while being similar to the other conditions. Both the monolithic systems and the CAD-on technique showed high and similar fatigue fracture behavior and survival rates, which were also higher than the control bilayer system. Both systems reduced the occurrence of delamination failures, making them suitable for clinical use.

Resumo Este estudo teve como objetivo avaliar o comportamento à fadiga de estruturas cerâmicas monolíticas de zircônia (Yz) e multicamadas utilizando a técnica CAD-on em diferentes espessuras. Cinquenta (N=50) preparos unitários padronizados foram confeccionados em resina epóxi reforçada com fibra de vidro (NEMA grau G10), digitalizados e as restaurações usinadas em CAD-CAM, compondo 5 grupos (n= 10): Controle: 1,5 mm (estrutura de zircônia fresada + porcelana estratificada manualmente); Yz monolítica 1,5 mm; Yz monolítica 1,0 mm; CAD-on em 1,5 mm; e CAD-on 1,0 mm (estrutura de zircônia fresada com 0,5 mm de espessura ligada por uma cerâmica de baixa fusão a uma camada de dissilicato de lítio fresado de 1,0 mm ou 0,5 mm, respectivamente). As bases do G10 foram condicionadas com ácido fluorídrico a 10%; as coroas foram jateadas com partículas de alumina de 110 μm; e então cimentadas uma sobre a outra com cimento resinoso autoadesivo. Foi realizado um teste de fadiga cíclica (carga inicial: 400N para 10.000 ciclos, frequência de 20 Hz, step de 200N) até a falha, e os dados foram submetidos a uma análise estatística de sobrevivência. Nenhuma falha foi observada para Yz monolítica de 1,5 mm. Desempenho alto e semelhante foi observado para os grupos Cad-On e Yz monolítica 1,0 mm. O grupo controle apresentou o pior comportamento. O módulo de Weibull do CAD-on 1,5 mm foi maior que o grupo controle, sendo semelhante às outras condições. Tanto os sistemas monolíticos quanto a técnica CAD-on apresentaram alto e semelhante desempenho mecânico e taxas de sobrevivência, que também foram superiores ao sistema bicamada de controle. Ambos os sistemas reduziram a ocorrência de falhas de delaminação, tornando-os adequados para uso clínico.

Effect of internal stress on cyclic fatigue failure in .06 taper ProFile

OBJECTIVES: The purpose of this study was to evaluate the relation between intentionally induced internal stress and cyclic fatigue failure of .06 taper ProFile. MATERIALS AND METHODS: Length 25 mm, .06 taper ProFile (Dentsply Maillefer), and size 20, 25, 30, 35 and 40 were used in this study. To give the internal stress, the rotary NiTi files were put into the .02 taper, Endo-Training-Bloc (Dentsply Maillefer) until auto-stop by torque controlled motor. Rotary NiTi files were grouped by the number of induced internal stress and randomly distributed among one control group and three experimental groups (n = 10, Stress 0 [control], Stress 1, Stress 2 and Stress 3). For cyclic fatigue measurement, time for separation of the rotary NiTi files was recorded. The fractured surfaces were observed by field emission scanning electron microscope (FE-SEM, SU-70, Hitachi). The time for separation was statistically analyzed using two-way ANOVA and post-hoc Scheffe test at 95% level. RESULTS: In .06 taper ProFile size 20, 25, 30, 35 and 40, there were statistically significant difference on time for separation between control group and the other groups (p < 0.05). CONCLUSION: In the limitation of this study, cyclic fatigue failure of .06 taper ProFile is influenced by internal stress accumulated in the files.

Effect of internal stress on cyclic fatigue failure in K3

OBJECTIVES: This study aimed to evaluate the relationship between the cyclic fatigue of a K3 file and internal stress intentionally induced until the activation of the auto-stop function of the torque-controlled motor. MATERIALS AND METHODS: K3 (Sybron Endo) .04 and .06 taper, size 25, 30, 35, 40 and 45 were used in this study. To give the internal stress, the K3 files were put into the .02 taper Endo-Training-Bloc (Dentsply Maillefer) until the activation of the auto-stop function of the torque-controlled motor. The rotation speed was 300 rpm and torque value was 1.0 N.cm. K3 were grouped by the number of induced internal stress and randomly distributed to 4 experimental groups (n = 10, Stress 0 [control], Stress 1, Stress 2 and Stress 3). For measuring the cyclic fatigue failure, the K3 files were worked against a sloped glass block and time for file separation was recorded. Data was statistically analyzed Statistical analyses were performed using two-way ANOVA and Duncan post-hoc test at p < 0.05 level. RESULTS: Except .04 taper size 30 in Stress 1 group, there were statistically significant differences in time for file separation between control and all experimental groups. K3 with .04 taper showed higher cyclic fatigue resistance than those of .06 taper. CONCLUSION: In the limitation of this study, the cyclic fatigue of the K3 file was influenced by the accumulated internal stress from use until the auto-stop function was activated by the torque-controlled motor. Therefore, clinicians should avoid the reuse of the K3 file that has undergone auto-stops.

Evaluation of Porosity in Cylindrical Bone Cement Specimen Using Image Analysis System / 대한정형외과연구학회지

PURPOSE: The porosity of the bone cement is the most important cause of fatigue failure, the most common mode of failure of bone cement using widely in arthroplasty. It is important to evaluate the porosity of bone cement for improvement or development of bone cement, but the conventional 'stain, 'cut, and 'polish, manual method takes long time and efforts. So it is necessary to develop a new technique for evaluation of porosity of bone cement. We tried a technique using computer image analysis system to evaluate the porosity of bone cement specimen and assess efficacy of the method. Simultaneously we evaluated the relationship between the porosity of bone cement and fatigue failure. MATERIAL AND METHODS: We made 59, 2.5inch-length bone cement specimens(30 Simplex P, 29 Palacos R) using Simplex P and Palaces R which are widely using in clinical situation and checked radiogram using mammography film. After scanning the mammography film, we measured the porosity of the bone cement specimens using NIH(National Institute for Health) Image 1.6 version image analysis program. We also, measured the porosity of the bone cement specimens with conventional 'stain','cut' and 'polish' method, after then compared the results of two methods. Simultaneously, we evaluated the relationship between porosity & fatigue failure by loading 9.0, 10.0, 12.5 and 15.0 MPa load with frequency of 10Hz to the bone cement specimens under the physiologic condition. RESULTS: The coefficient of relation of simplex P and palaces R was 0.729 and 0.713 respectively, so there was high relationship between the image analysis system method and conventional one. It was easy and took shorter time to measure the porosity of bone cement specimens with image analysis system. There was high correlation between cement porosity and fatigue failure, regardless of level of load. CONCLUSION: It was very easy and fast to measure the porosity of the bone cement specimens with image analysis system and there was high correlation between cement porosity and fatigue failure.

A study of the cause of metal failure in treatment of femur shaft fracture: Fractographical and clinical analysis of metal failure / 영남의대학술지

The author fractographically analyzed the cause of metal failure (the first time this procedure has been used for this metal failure) and also analyzed in clinically. In this study, I selected eight cases which have been analyzed fractographically. In all these cases, the analysis was done after treatment of metal failure of implants internally fixed to femur shaft fractures at the Department of Orthopedic Surgery, Yeung-Nam University Hospital during the six year period from May 1983 to September 1989. 1. Metal failure occurred in five dynamic-compression plates, one Jewett nail, one screw in Rowe plate, and one interlocking nail. 2. The clinical cause of metal failure was deficiency of medial buttes in five cases, incorrect position of implant in one case, and incorrect selection of implant in two cases. 3. The time interval between internal fixation and metal failure was four months in one case, between five months to twelve months in six cases, three years in one case. 4. The fractographically analytical cause of metal failure was ; first, impact failure, one case, second, fatigue failure, six cases, machining mark (stress riser), four case type: low consistent cyclic fatigue failure irregular cyclic fatigue failure third, stress corrosion crack, one case. 5. 316 L Stainless Steel has good resistance to corrosion. However, when its peculiar surface film is destroyed by fretting, it shows pitting corrosion. This is, perhaps, the main cause of metal failure. 6. It is possible that mechanical injury occurred in implants during the manufacturing of implants or that making a screw hole in the main cause of metal failure.

Fatigue Failure of Wire in Orthopaedic Use / 대한정형외과학회잡지

Orthopaedic wire has been used widely as a good internal fixator in cases of fracture, the ligament reconstruction, and for the stabilization of cervical spine. But if it is used inappropriately, a wire can be easy to fail by elongation, untwisting, or breakage. Among them, the most common failure of wire is breakage. To clarify the mechanism and the causes of wire failure, the authors analysed serial roentgenograms and scanning electronmicroscopic findings of broken wire in total 13 cases, which were experienced at the department of orthopaedic surgery, St. Mary's Hospital, Catholic University Medical College From January 1981 to December 1987. The results obtained were as follows :1. The mechanism of wire failure were classified into the 4 types ; minor continual flexing motion in 6 cases, repeated minor back and forth torsion in 1 case, tension failure in 2 cases and combined type in 4 cass. 2. The causes of wire failure were in appropriate use and inadequte application, a lack of s ufficient mechanical strength, micromotion due to inadequate postoperative imm obilization, early mobilization before tissue healing as well as certain injuries to the wire during handling in operation.