Clinical Assessment of Maxillary Screw-retained Implant Prosthesis Fabricated From Digital Versus Conventional Full-arch Implant Impression: A Randomized Controlled Clinical Trial

Treatment sequence Pretreatment examination For all participants, diagnosis and treatment planning were performed. They were assessed clinically through oral examination by inspection and palpation, and radiographically using preoperative panoramic radiograph and cone beam computed tomography CBCT to evaluate bone morphology, bone height, bone density, and vertical as well as horizontal bone resorption.

New maxillary complete dentures were fabricated for all participants to serve as temporization and to perform prosthetically driven computer guided implant placement. Preoperative CBCT scan (i-CAT Visions; Imaging Sciences International, Hatfield, PA, USA) was performed for all participants using the newly fabricated dentures with extra oral ready-made radiopaque markers. The markers were placed in relation to the maxillary dentures laterals/canines position, first premolars position, and first molars position. The superimposition of these markers on the maxilla determines the potential implants sites. Implant planning was performed and a stereolithographic surgical guide was fabricated with 6 sleeves on these preplanned implants sites.

Surgical procedures Computer-guided surgery was performed; each participant of both groups received six axially placed implants (Neobiotech, South korea) in the preplanned implant positions in maxilla. The final insertion torque for implants was 40 N cm. Post-operative instructions were given for patients. Chlorhexidine mouth wash 0.2% was prescribed for two weeks.

Prosthetic procedures Patients of both groups were recalled after a healing period of soft and hard tissues of four months for second stage surgery. Transmucosal titanium abutments were screwed in after uncovering of the six implants. For the fabrication of the definitive prosthesis, two different approaches were implemented: conventional pick up versus digital impressions.

For group I patients (CIG), a conventional open tray full- arch implant impression was implemented to fabricate the definitive maxillary screw retained prosthesis. Six long impression transfers were screwed over the fixtures. Using a periapical radiographs the seating of the open-tray long impression copings was confirmed. Splinting of impression copings was performed using special resin (Duralay; Reliance Dental, Alsip, IL, USA) (Fig----). Conventional border molding of the custom open trays (Fig----) was performed, then light body vinyl polysiloxane (Imprint 3, 3M ESPE, St. Paul, MN, USA) was injected around the impression transfer (Fig---). The tray was then filled with a heavy body vinyl polysiloxane ((Imprint 3, 3M ESPE, St. Paul, MN, USA) and a conventional pick up impression was made. Implant analogues were then attached to the impression copings and stone models were pored to replicate the exact implant positions in the cast.