ABSTRACT
BACKGROUND:To measure the occlusal force index of patients with missing teeth before and after restoration is an effective way to evaluate the restoration effect and oral function recovery after dental restoration.OBJECTIVE:To observe the changes of occlusal force and periodontal tissue in patients undergoing CO-Cr alloy-based porcelain-fused-to-metal crown and bridge restoration.METHODS:100 male patients were randomly divided into five groups (n=20 per group), and respectively received CO-Cr alloy porcelain crown restoration of the anterior teeth (group A), CO-Cr aloy porcelain crown repair of the premolar (group B), CO-Cr aloy porcelain crown restoration of the molar (group C), CO-Cr alloy porcelain bridge restoration of the anterior teeth (group D), or CO-Cr alloy porcelain bridge restoration of the posterior teeth (group E). Changes of occlusal force and periodontal related indexes were detected before, immediately and 6 months after dental restoration.RESULTS AND CONCLUSION:(1) Occlusal force: The occlusal force in all the five groups was increased immediately and 6 months after restoration (P 0.05) before and after restoration. To conclude, the CO-Cr alloy-based porcelain-fused-to-metal crown and bridge restoration can significantly enhance the patient's occlusal force of the abutment teeth, exert little effect on the periodontal tissue and have good biocompatibility.
ABSTRACT
BACKGROUND:Domestic scholars use the potentiodynamic polarization technique to determine the corrosion potential of the dental aloys, which is used to evaluate the corrosion performance of the lownoble metal. They have discovered that the main reason affecting corrosion resistance is the content of noble metal. OBJECTIVE:To evaluate the corrosion resistance of Ti, Au aloy, Co-Cr aloy, Ti aloy, and Ni-Cr aloy. METHODS: Five aloys were immersed in synthetic saliva solution. The corrosion potential and corrosion current density of the aloys were determined with potentiadynamic polarization technique. RESULTS AND CONCLUSION:The galvanic series of five kinds of aloys were ranged as folows: Au aloy > pure Ti > Ti aloy > Co-Cr aloy > Ni-Cr aloy. Au aloy and pure Ti had more positive potential that were not easy to produce corrosion; Ti aloy and Co-Cr aloy could form stable oxidation film with a strong ability of anti-pitting and crevice corrosion; Ni-Cr aloy potential was more negative and easy to be dissolved. The corrosion current density of five kinds of aloys was ranged as folows: Au aloy < pure Ti < Ti aloy < Co-Cr aloy < Ni-Cr aloy. Au aloy and pure Ti had lowest current density which was 10-8, indicating that the corrosion rate of Au aloy and pure Ti was lower; in contrast, Ni-Cr aloy possessed the maximum corrosion rate. These findings indicate that Au aloy and pure Ti exhibit a very high corrosion resistance. The corrosion rate of Ni-Cr aloy is the highest; therefore, Ni-Cr aloy is the least acceptable material for implant suprastucture.
ABSTRACT
BACKGROUND:Porcelain jacket crowns have achieved good results in the repair of porcelain ceramic crown and bridge colapse. OBJECTIVE:To test the bond strength of single porcelain jacket crown, thus determining the feasibility of clinical application of repairing colapsed crown and fixed bridge by porcelain jacket crown, and meanwhile to discuss the influence between blastsanding and silane coupling agent treatment on the metal bonding strength in the repair of porcelain fracture. METHODS: The porcelain jacket crown was cast in the same shape from disk-shaped waxpatterns. Twenty specimens were chosen without blowholes and casting defects and they were al routinely burnished and cleaned in an ultrasonic bath and dried using an oil-free air stream stand-by. Then we randomly divided the specimens into four groups: specimens were treated with nothing (control), sandblast, silane coupling agent and sandblast+silane coupling agent, respectively. Each of the specimen was bonded with Poly-F Plus. AG-10TA universal testing machine was used to test the tensile strength. RESULTS AND CONCLUSION:The tensile bond strength of control, sandblast, silane coupling agent and sandblast+silane coupling agent groups respectively were (0.68 0.04), (1.00 0.02), (1.31 0.08), and (1.09 0.04) kN. There were significant differences between groups (P < 0.01). In the control group, the metal surface was smooth, showing some irregular smal superficial veins. In the sandblast group, the metal surface showed irregular scaly protrusions conducive penetrate adhesives. In the silane coupling group, the metal surface manifested a honeycomb structure in favor of chimeric adhesives. The sandblast+silane coupling agent group showed some metal projections ranging in size, on the rough metal surface, which was conducive to bond. Porcelain jacket crown applied to repair colapsed crown and fixed bridge is feasible. Sandblasting and silane coupling agent can improve bond strength of porcelain jacket crown. The bond strength of metal specimens treated with silane coupling agent is the best folowed by the sandblasting+silane coupling agent.