1- Fatigue-Resistance and Microleakage of CAD/CAM Ceramic and Composite Molar crowns

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1 1- Fatigue-Resistance and Microleakage of CAD/CAM Ceramic and Composite Molar crowns A. KASSEM1, O. ATTA1, and O. EL-MOWAFY2, 1Suez Canal University, Ismailia, Egypt, 2University of Toronto, Toronto, ON, Canada Purpose: Aim of this study was to determine effect of compressive cyclic-loading on fatigueresistance and microleakage of monolithic molar ceramic and composite crowns fabricated using CEREC-3D and cemented with two adhesive resin cements. Methods: Thirty two extracted molars were prepared to receive CEREC crowns according to manufacturer's guidelines using special paralleling device (Parallel-A-Prep, Dentatus) for standardized angle of convergence. Sixteen feldspathic all-ceramic crowns (Vita Mark-II, VITA Zahnfabrik) and sixteen resin composite crowns (Paradigm-MZ100 blocks, 3M/ESPE) were made using CEREC-3D machine (Sirona Dental Systems). Eight crowns of each group were cemented to their respective teeth using self-etching resin cement (Panavia F-2.0, Kuraray) and eight crowns were cemented using self-adhesive resin cement (Rely-X Unicem Clicker, 3M/ESPE). Following storage for 1 week in water crowns were subjected to uniaxial compressive cyclic-loading in a universal testing machine (Instron) at 12 Htz for 1,000,000 cycles. Load applied at cental fossa and cycle range was N. Specimens were then subjected to microleakage testing. Data were statisticallyanalyzed using factorial ANOVA and Post Hoc (Tukey HSD) tests at a significance level of P<.05. Results: All composite crowns survived the compressive cyclic-loading while three ceramic crowns (37.5%) from the group cemented with Rely-X Unicem Clicker developed surface cracks at center of occlusal surfaces and extended laterally. Microleakage scores of the ceramic crowns cemented with Panavia F-2.0 were significantly lower than those of the other three groups (p<.05). Conclusions: After 1 million cycles of compressive cyclic loading Paradigm MZ100 composite molar crowns were more fatigue-resistant than Vita MarkII ceramic ones with none of 16 crowns undergoing any signs of breakdown. Microleakage scores of ceramic crowns cemented with Panavia F-2.0 were significantly lower than those of ceramic crowns cemented with Rely-X Unicem Clicker and those of all composite crowns. Acknowledgements: Egyptian Ministry of Higher Education, 3M/ESPE, Vita Zahnfabrik, Kuraray, Sirona. Journal of dental research-89(b):1297,2010

2 2-Influence of Storage Times on Bond Strength of Resin Cements to Root Canal MatheusCoêlhoBandécaa,b*, AmrSheblKassemb,c, Omar El-Mowafyb, Michele Regina Nadalind,Renato Souza Queiroza, Victor Rene Grover Clavijoa, José Roberto CurySaada adepartment of Restorative Dentistry, Araraquara School of Dentistry, University of São Paulo State UNESP 1680 Humaitá St., Araraquara - SP, Brazil bdepartment of Restorative Dentistry, Faculty of Dentistry, University of Toronto Toronto, ON M5G 1G6 CCrown and Bridge Department, Faculty of Dentistry, Suez Canal University, Ismailia, Egypt duniversity of RibeirãoPreto, Costábile Romano Ave, RibeirãoPreto - SP, Brazil Abstract: The resin cements are responsible to retention of the indirect materials decreasing marginal leakage, increasing failure resistance compared with conventional cementation. The cementation within root canal is very hard due unfavorable conditions regarding the application of adhesive techniques caused by inadequate access. Therefore, considering the possibility to decrease steps of cementation, this study was performed to evaluate the bond strength of self-adhesive resin cement (RelyXTM U100, 3M ESPE) and resin cement combined with self-ecthing adhesive system (Panavia F 2.0, Kuraray) light-cured with Quartz Tungsten Halogen (QTH) following storage at 37 C immediately after light-curing, 24 and 48 hours and 7 days. The root canals were prepared to receive the glass fiber post in the depth of 10 mm, irrigated with 17% EDTA and NaOCl, rinsed with distilled water and dried using paper points. The roots were perpendicularly sectioned into approximately 1 mm thick sections, obtaining ninety-six slices (n = 12). The slices were trimmed using a cylindrical diamond bur in the proximal surfaces until it touched the post and attached into a device, which were mounted on a strength tester (Bisco) and loaded in tension at a speed of 0.5 mm/min until failure occurred at specimens. The analysis of variance (ANOVA) and Tukey s post-hoc tests showed significant statistical differences (P <.05) to all resin cements immediately after

3 light-curing and 24 hours, 48 hours and 7 days. The Panavia F 2.0 showed higher mean values than RelyXTM U100 for all storage times, however no different statistically significant was reported (P >.05). The resin cements 24 and 48 hours after light-curing were statistically similar among themselves (P >.05). The both resin cement showed similar bond strength into root canal on different storage times. The highest bond strength values of the resin cements were showed 7 days after curing. Materials Research. 2010; 13(1): Fatigue Resistance and Microleakage of CAD/CAM Ceramic and Composite Molar Crowns Amr S. Kassem, BDS, MSc,1 Osama Atta, BDS, MSc, PhD,2 & Omar El-Mowafy, BDS, PhD, FADM3 1Assistant Lecturer and PhD candidate, Crown and Bridge Department, Faculty of Dentistry, Suez Canal University, Ismailia, Egypt 2Professor and Head, Crown and Bridge Department, Faculty of Dentistry, Suez Canal University, Ismailia, Egypt 3Professor in Restorative Dentistry, Department of Clinical Sciences, Faculty of Dentistry, University of Toronto, Canada Abstract Purpose: The aim of this study was to determine effect of compressive cyclic loading on fatigue resistance and microleakage of monolithic CAD/CAM molar ceramic and composite crowns. Materials and Methods: Thirty-two extracted molars were prepared to receive CEREC crowns according to manufacturer s guidelines using a special paralleling device (Parallel-A-Prep). Sixteen feldspathic ceramic crowns (VITABLOCS Mark II) (VMII) and 16 resin-composite crowns (Paradigm-MZ100 blocks) (PMZ) were milled

4 using a CEREC-3D machine. Eight crowns of each group were cemented to their respective teeth using self-etching resin cement (Panavia-F-2.0) (PAN), and eight were cemented using self-adhesive resin cement (RelyX-Unicem-Clicker) (RXU). Following storage for 1 week in water, specimens were subjected to uniaxial compressive cyclic loading in an Instron testing machine at 12 Hz for 1,000,000 cycles. Load was applied at the central fossa, and the cycle range was N. Specimens were then subjected to microleakage testing. Data were statistically analyzed using factorial ANOVA and Post Hoc (Tukey HSD) tests. Results: All composite crowns survived compressive cyclic loading without fracture, while three ceramic crowns from the subgroup cemented with RXU developed surface cracks at the center of occlusal surfaces, extending laterally. Microleakage scores of ceramic crowns cemented with PAN were significantly lower than those of the other three subgroups (p < 0.05). Conclusions: After 1,000,000 cycles of compressive cyclic loading, PMZ composite molarcrownsweremore fatigue-resistant thanvmii ceramic crowns. Cement type had a significant effect on fatigue resistance of the ceramic crowns but not the composite ones. Microleakage scores of ceramic crowns cemented with PAN were significantly lower than those of the other subgroups (p < 0.05). Journal of Prosthodontics 21 (2012) 28 32

5 4-Survival rates of porcelain molar crowns-an update. Kassem AS, Atta O, El-Mowafy O. Department of Fixed Prosthodontics, Faculty of Dentistry, Suez Canal University, Ismailia, Egypt. Abstract The aim of this study was to identify recent studies that dealt with the clinical performance of porcelain molar crowns and to explore the possibility of grouping the findings from similar studies together to draw overall conclusions. A MEDLINE literature search was conducted in early 2009 covering the preceding 12 years. Seventeen studies were indentified. However, only seven met the specific inclusion criteria and were analyzed. Among seven studies, five European countries were covered. Five studies reported on ProceraAllCeram molar crowns while one reported on In-Ceram Alumina and Spinell crowns and another on CEREC crowns. For comparison, one additional study that reported on premolar crowns was included. In the five ProceraAllCeram studies, 235 molar crowns were evaluated for 5 or more years, of which 24 failed. When the results of the five studies on the performance of ProceraAllCeram molar crowns were considered collectively, an overall failure rate of 10.2% was found at 5 or more years. Int J Prosthodont 2010;23: Combined effects of thermocycling and load-cycling on microleakage of computer-aided design/computer-assisted manufacture molar crowns. A. KASSEM 1, O. ATTA1, and O. EL-MOWAFY2, 1 Suez Canal University, Ismailia, Egypt, 2University of Toronto, Toronto, ON, Canada Abstract This study evaluated the combined effects of thermocycling and compressive loadcycling on microleakage of computer-aided design/computer-assisted manufacture molar crowns. Sixteen ceramic (Vita Mark-II) and 16 composite resin (Paradigm MZ-100) crowns were milled using the CEREC 3D system. Eight crowns of each group were

6 cemented to prepared molars using Panavia F 2.0, and 8 were cemented using RelyXUnicem Clicker. Specimens were thermocycled for 500 cycles and subjected to load-cycling for 1,000,000 cycles (60 to 600 N). Specimens were then tested for microleakage. Data were analyzed statistically using the Tukey post hoc test. All composite resin crowns survived load and thermal fatigue, while 6 ceramic crowns developed cracks. There were no statistically significant differences among groups regarding microleakage scores. Paradigm MZ-100 crowns were more crack-resistant to combined load and thermal fatigue than those composed to Vita Mark-II. However, microleakage scores of both types of crowns were similar. Int J Prosthodont 2011;24: