Implant Retained Rehabilitation With Surgical and Prosthetic Digital Workflow

The study protocol was reviewed and approved by an Ethics Committee (EC) in Brazil.

Sample size was calculated based on an alpha level of 5% and beta of 20% to detect a mean intergroup difference of 0.2mm, with a standard deviation of 0.2mm, in peri-implant bone level change 24 months after implant loading. Sample size calculation showed that a sample of 17 implants is needed for each group. With rate of 2 implants per patient and a "worst-case" drop-out rate of 20%, a sample size of 24 patients resulting in an estimated number of 24 implants, in each group, is thought to be sufficient to allow statistical analysis of clinical outcome data.

A total of 48 healed implant sites (at least 4 months post-extraction) shall be prospectively and consecutively selected during the sample enrollment (24 patients).

Data concerning the studied variables will be collected in the following stages: Screening (First visit); TP - Implant placement; TT - Impressions for temporary prosthesis confection (2 ± 1 days prior to T0); T0 - Implant Loading (temporary prosthesis placement - 21 ± 1 days after implant placement); TF - Impressions for final prosthesis confection (10 ± 1 business days prior to T6); T2 - Final prosthesis placement (2 months ± 1 week after loading); T12 and T24 - 12 and 24 months ± 1 month, respectively, after loading.

In both study groups, 4.0x10 mm Neodent GM Helix Implants will be placed 2mm subcrestally (in relation to the buccal bone plate) in the posterior region of the maxilla, under local anesthesia and with adequate bone bed preparation, as recommended by the manufacturer, using the guided surgery technique. Two implants (one of each group) will be placed in the same individual, to be restored by single prostheses.

In Group 1, customizable healing abutments will be placed at the time of implant placement. Twenty-one days later, the implants will be loaded by means of placement of temporary single prostheses (early loading), fabricated with centric and eccentric occlusal contacts [1], over temporary abutments (Pro PEEK Abutment). The final prosthesis will be delivered after a 2-months period of implant loading. Thus, digital models will be obtained (intraoral scanning or conventional impression and model scanning) 10 ± 1 business days prior to T2 (TF) for the confection of the final prostheses, to be placed over Titanium Bases and Zirconia Copings, following the digital workflow.

The transgingival height of the Titanium Base shall be selected by the clinician so as to leave, preferably, a distance greater than or equal to 2mm between the cementation line of the Zirconia Coping over the Titanium Base and the cementation line of the prosthesis over the Zirconia Coping due to assure better esthetics of the final prosthesis.

In Group 2, the final abutment will be placed at the time of surgery and will not be replaced during the rehabilitation process. A Titanium Base and a Zirconia Coping will be placed over the implant at TP, without loading (placement of an acrylic cap, without occlusal contact, to cover the coping), planned using the initial intraoral scans. Implants will be restored following the same time interval of Group 1, with temporary prosthesis placement in 21 days after surgery, and with final prosthesis placement 2 months thereafter. The clinician shall evaluate the need to re-prepare the Zirconia Coping edge line before obtaining the digital models (intraoral scanning or conventional impression and model scanning) for prostheses confection, in order to obtain the proper distance between the previously mentioned cementation lines.

In both groups, prostheses' passivity, occlusal and interproximal adjustments shall be checked, to avoid compromising the implant/prosthesis set.

Standardized digital periapical radiographs and close-up view photographs will be taken in an usual daily practice frequency, as determined by the investigator to verify prostheses setting and the osseointegration process. Computed tomography Scans will be obtained, in addition to pre-surgery, at T2 for evaluation of clinical parameters and comparison with the implant position planned by guided surgery.