***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: The aim of this in vitro study was to evaluate the fracture load and marginal accuracy of  crowns made from a shrinkage-free ZrSiO4 ceramic cemented with glass-ionomer or composite cement  after chewing simulation . Thirty-two human m and ibular molars were r and omly divided into two groups . All teeth were prepared for and restored with shrinkage-free ZrSiO4 ceramic crowns ( Everest HPC , KaVo ) . The crowns of group A ( N = 16 ) were luted to the teeth using KetacCem and group B ( N = 16 ) were adhesively cemented using Panavia21EX . Measurements of the marginal accuracy before and after cementation were made using replicas and an image analysis system . All specimens were exposed to 1.2 million cycles of thermo-mechanical fatigue in a chewing simulator . Surviving specimens were subsequently loaded until fracture in a static testing device . Fracture loads ( N ) were recorded . All specimens survived chewing simulation . The mean fracture loads ( + /-s.d . ) were Group A , 1622 N ( + /-433 ) ; group B , 1957 N ( + /-806 ) . There was no significant difference between the two groups ( P > 0.05 ) . The marginal gap values before cementation were ( mean + /- s.d . ) : Group A , 32.7 microm ( + /-6.8 ) ; group B , 33.0 microm ( + /-6.7 ) . The mean marginal gap values after cementation were ( + /-s.d . ) : Group A , 44.6 microm ( + /-6.7 ) ; group B , 46.6 microm ( + /-7.7 ) . The marginal openings were significantly higher after cementation for both groups ( P < 0.05 ) . All test groups demonstrated fracture load and marginal accuracy values within the range of clinical acceptability PURPOSE This in vitro study investigated the marginal adaptation and fracture resistance of heat-pressed glass-ceramic and fiber-reinforced composite molar crowns luted with resin , resin-modified glass-ionomer , or zinc-oxide-eugenol-free cements .  MATERIAL S AND METHODS A total of 24 heat-pressed all-ceramic and 24 glass fiber-reinforced composite crowns were constructed and cemented using the above-mentioned luting agents ( eight crowns per cement ) . The restorations were thermocycled and mechanically stressed , and fracture resistance was determined . Marginal adaptation was evaluated before and after stress application using semiquantitative analysis in a scanning electron microscope . RESULTS All-ceramic and fiber-reinforced composite crowns reached the highest fracture resistance after stress application in combination with the resin cement . When luted with resin-modified glass-ionomer or zinc-oxide-eugenol-free cements , the fracture resistance of all-ceramics decreased significantly , while the fiber-reinforced composite crowns maintained their fracture resistance level ; the lowest values were found for zinc-oxide-eugenol-free cements . The marginal adaptation remained unchanged after stress for all-ceramics and fiber-reinforced composite restorations if they were luted with resin cements . Luting with resin-modified glass-ionomers significantly deteriorated the marginal adaptation after stress application , with the exception of the crown-cement interface of all-ceramics . CONCLUSION The highest fracture resistance and marginal adaptation were found for all-ceramic and glass fiber-reinforced composite molar crowns if they were luted with resin cement BACKGROUND The authors analyzed the in vitro and in vivo performance of  lithium disilicate glass-ceramic ( LDGC ) restorations and yttria-stabilized tetragonal zirconia polycrystalline ( Y-TZP ) ( that is , zirconium oxide ) restorations  with regard to reliability , clinical performance and abrasion resistance . METHODS In the in vitro study , four authors subjected sample s of LDGC , Y-TZP and metal-ceramic crowns to step-stress fatigue testing . Four investigators assessed the in vivo clinical performance of LDGC and zirconium oxide-based restorations at four and seven years , respectively . In addition , one author conducted a r and omized , controlled clinical trial to analyze the volumetric loss of enamel and ceramic antagonist surfaces . RESULTS The LDGC crowns exhibited the highest fatigue load-to-failure values in the in vitro analysis . The results of the in vivo assessment showed that the clinical performance of the LDGC restorations at four years was comparable to that of the zirconium oxide-based crowns at seven years . The results of the in vivo , r and omized , controlled clinical trial showed that LDGC crowns were not only resistant to wear , but also were wear friendly to enamel antagonist surfaces . CONCLUSIONS The LDGC crowns in the in vitro and in vivo studies exhibited high durability , and they were wear friendly to opposing natural dentition . CLINICAL IMPLICATION S LDGC and zirconium oxide-based crowns are a clinical ly acceptable means of treating teeth that require full-coverage restorations . In addition , LDGC material s exhibit excellent clinical performance , as well as demonstrate acceptable abrasion compatibility with the opposing natural dentition STATEMENT OF PROBLEM The influence of different types of adhesive resin cements on the long-term prognosis of aluminum oxide ceramic posterior crowns is unclear . PURPOSE The purpose of this study was to evaluate the fracture resistance of  aluminum oxide ceramic on maxillary posterior crowns cemented with different resin luting agents before and after cyclic thermomechanical loading . Material and methods Forty-eight maxillary first molars were prepared and restored with st and ardized aluminum oxide ceramic ( In-Ceram Alumina ) crowns .  The test specimens were r and omly divided into 3 groups ( n=16 ) . The crowns were luted with an acrylic resin cement ( Super-Bond C&B , control , Group SB ) and 2 composite luting agents ( Panavia F , Group PV ; and Rely X Unicem , Group RX ) . Half of the specimens were exposed to thermomechanical fatigue in a masticatory simulator . All specimens were tested for fracture strength ( N ) using quasistatic loading . The Wilcoxon rank sum test was used to compare the fracture strength ( alpha=.05 ) . RESULTS All specimens survived the exposure to the simulator . The following median fracture strength values were obtained without/with thermomechanical fatigue loading : Group SB , 2726 N/2673 N ; Group PV , 2520 N/2083 N ; and Group RX , 2036 N/2369 N. The fracture strength in Group PV after thermomechanical fatigue loading was significantly lower compared to the fracture strength in Group PV without artificial aging ( P = .016 ) , as well as significantly lower compared to Group SB with artificial aging ( P = .003 ) . CONCLUSION Within the limitations of this study , all tested cements are capable of successfully luting aluminum oxide ceramic crowns . The fracture strength of Group PV after artificial aging was comparatively low The aim of the present study was to investigate the fracture resistance of zirconia crowns  and to compare the results with  crowns  made of a material with known clinical performance ( alumina ) in away that reflects clinical aspects . Sixty crowns were made , 30 identical crowns of alumina and 30 of zirconia .  Each group of 30 was r and omly divided into three groups of 10 crowns that were to undergo different treatments : ( i ) water storage only , ( ii ) pre-loading ( 10 000 cycles , 30 - 300 N , 1 Hz ) , ( iii ) thermocycling ( 5 - 55 degrees , 5000 cycles ) + pre-loading ( 10 000 cycles , 30 - 300 N , 1 Hz ) . Subsequently , all 60 crowns were subjected to load until fracture occurred . There were two types of fracture : total fracture and partial fracture . Fracture strengths ( N ) were : group 1 , alumina 905/zirconia 975 ( P = 0.38 ) ; group 2 , alumina 904/zirconia 1108 ( P < 0.007 ) and group 3 , alumina 917/zirconia 910 ( P > 0.05 ) . Total fractures were more frequent in the alumina group ( P < 0.01 ) . Within the limitations of this in vitro study , it can be concluded that there is no difference in fracture strength between crowns made with zirconia cores compared with those made of alumina if they are subjected to load without any cyclic pre-load or thermocycling . There is , however , a significant difference ( P = 0.01 ) in the fracture mode , suggesting that the zirconia core is stronger than the alumina core . Crowns made with zirconia cores have significantly higher fracture strengths after pre-loading PURPOSE Existing composite restorations on teeth are often remade prior to the cementation of fixed dental prostheses . The aim of this study was to evaluate the effect of static and cyclic loading on ceramic laminate veneers adhered to aged resin composite restorations . MATERIAL S AND METHODS Eighty sound maxillary incisors were collected and r and omly divided into four groups : group 1 : control group , no restorations ; group 2 : two Class III restorations ; group 3 : two Class IV restorations ; group 4 : complete composite substrate . St and ard composite restorations were made using a microhybrid resin composite ( Anterior Shine ) . Restored teeth were subjected to thermocycling ( 6000 cycles ) . Window preparations were made on the labial surface of the teeth for ceramic laminate fabrication ( Empress II ) . Teeth were conditioned using an etch- and -rinse system . Existing composite restorations representing the aged composites were silica coated ( CoJet ) and silanized ( ESPE-Sil ) . Ceramic laminates were cemented using a bis-GMA-based cement ( Variolink Veneer ) . The specimens were r and omly divided into two groups and were subjected to either static ( groups 1a , 2a , 3a , 4a ) or cyclic loading ( groups 1b , 2b , 3b , 4b ) . Failure type and location after loading were classified . Data were analyzed using one-way ANOVA and Tukey 's test . RESULTS Significantly higher fracture strength was obtained in group 4 ( 330 ± 81 N ) compared to the controls in group 1 ( 179 ± 120 N ) ( one-way ANOVA , p < 0.05 ) . Group 1b survived a lower mean number of cyclic loads ( 672,820 cycles ) than teeth of groups 2b to 4b ( 846x103 to 873x103 cycles ) . Failure type evaluation after the fracture test showed predominantly adhesive failures between dentin and cement , but after cyclic loading , more cohesive fractures in the ceramic were seen . CONCLUSION Ceramic laminate veneers bonded to conditioned aged composite restorations provided favorable results . Surface conditioning of existing restorations may eliminate the necessity of removing aged composite restorations 
    Output:
    
An inclination for decreased static fracture strength could be observed after cyclic loading of all-ceramic single crowns and FDPs , but this was material specific .