Accuracy of Two Methods of Making Impressions for Complete-arch Implant Supported Fixed Prosthesis

Inclusion Criteria: * Age 18-70 years old (including 18 and 70 years old); * The patient's maxilla or mandible cannot be preserved due to missing teeth or remaining teeth proposed for implant-retained restoration; * The patient's missing teeth area is available for placement of 4-6 implants; * Completion of osseointegration of the patient's implants after implant surgery; * The patient has at least 2 mm width of keratinized mucosa in the remaining alveolar ridge; * The patient voluntarily participates in the trial and signs an informed consent form Exclusion Criteria: * The patient has a severe gag reflex; * The patient has an intermaxillary distance of less than 20 mm in the posterior region; * The distance between the two implants is less than 10 mm; * Implants fitted with composite abutments with the abutment screw holes penetrating at an angle greater than 60 degrees to the alveolar ridge; * Other patients judged by the investigator to be unsuitable for inclusion