ABSTRACT
Objective:To analyze the biomechanics trait of one-piece computer aided design and com-puter aided manufacture ( CAD/CAM ) zirconia post and core by the three-dimensional finite element . Methods:The three-dimensional finite element models of three upper central incisors restored with one -piece CAD/CAM zirconia post and core ( group 1 ) , refabricated zirconia post and hot-pressed porcelain core ( group 2 ) , and cast gold alloy post and core ( group 3 ) were built by geometry method respectively . 100 N vertical loading through the central incisor models long axis and 100 N loading along directing at an angle of 45°with the models long axis were used to imitate the central incisor stress state in biting and mandible physiological protraction movement .Results:Under vertical loading , the restored teeth without dentin ferrule, the maximum Von-Mises stress value of the tooth root in group 1 was the least(11.02 N), which was the largest (13.17 N)in group 2.The stress became weaker from the upper to the lower of the tooth root.The maximum Von-Mises stress value of the tooth root , post and core became smaller while the restored teeth with the 2.0 mm high dentin ferrule.Under directing at an angle of 45°loading, without the design of dentin ferrule in the restored teeth , the maximum Von-Mises stress value of the post and core in group 1 was the greatest(20.45 N), while that stress of post and core in group 3 was the smallest (13.61 N).With 2.0 mm high dentin ferrule design in the restored teeth , the tooth root stress became weaker.The maximum Von-Mises stress value of the tooth root was the greatest (14.10 N) in group 3, but which was the lowest (13.38 N) in group 1.Conclusion:The results of the three-dimensional finite element analysis infers that one-piece zirconia post and core restoration is more beneficial to disperse the bite force than the prefabricated zirconia post and the cast gold alloy post and core .The one-piece of zirconia post and core is good to protect the teeth and keep the restoration intact .
ABSTRACT
Objective: To measure the fracture strength of the posterior galvano-ceramic bridges made by Ni-Cr pontic fired bonding galvano caps with highly temperature-resistant adhesive and to provide re-ference data for clinical application. Methods: A standard low dental cast was achieved with 46 missing. Five posterior galvano-ceramic bridges made by Ni-Cr pontic fired bonding galvano caps, with abutments being 47 and 45 . The low dental cast was fixed on the panel of the universal testing machine, vertical load given on the central of the pontic as the velocity of 2 mm/min. Results: The fracture strength of the posterior galvano-ceramic bridges made by Ni-Cr pontic fired bonding galvano caps was (877.00?126.53) N, the fracture strength of the metal frame was (1 448.94?51.02) N. Conclusion: Posterior galvano-ceramic bridges made by Ni-Cr pontic fired bonding galvano caps could endure the normal human occlusal force.
ABSTRACT
Objective:To evaluate the clinical effect of galvano-ceramic bridges made by Ni-Cr pontic fired bonding galvano caps with highly temperature-resistant adhesive based on three-year clinical trials. Methods : A total of 29 galvano-ceramic bridges made by Ni-Cr pontic fired bonding on the galvano caps were used for 26 patients. Abutment teeth plaque indices (PI) were compared according to Silness and Loe standards and their papillary bleeding indices ( FBI) according to Mazza standards before restoration and after 36 months' restoration. At the same time, the integrity and marginal fitness of galvano-ceramic bridges were observed. Results:The FBI at abutment teeth were higher than those before restoration, Wilcoxon test revealed significant difference. Their PI were lower than those before restoration, Wilcoxon test revealed significant difference. All the galvano-ceramic bridges were perfect in marginal fitness and color. The rate of integrity was 89. 7% in the period of observation. Conclusion:Galvano-ceramic bridges made by Ni-Cr pontic fired bonding galvano caps with highly temperature-resistant adhesive hold out good prospects for clinical use in fixed restoration.