There should be accurate imprints of the implant areas.

There should be no voids in the occlusal, buccal, lingual, and interproximal surfaces of the neighboring teeth.

There should be a proper reproduction of the implant area.

There should be no impression material in the analog-impression coping interfaces.

The impression material should not be separated from the custom tray.

The transfer copings should not be displaced from the impression.

Any impression not meeting these criteria was repeated until the criteria were met. Two impressions were made for every patient by the same clinician, one using the open and a second with the closed tray technique.

For the analysis of accuracy in the vertical direction or marginal discrepancy, verification jigs were constructed to connect the two impression copings [15]. These verification jigs were used to transfer the relationships between the two impression copings and their implants from the patients’ mouths to the master casts. To construct the verification jig, the two impression copings would be attached to their implant, inside the patient mouth, and a string of dental floss is wrapped around to connect the two impression copings (Fig. 2). A light cure acrylic resin (Al dente dental products GmbH, Germany) adapted over the dental floss in increments and cured according to the manufacturer’s instructions. The impression coping’s screws would then be loosened, and the jig removed [16].

The impression copings for both the open and closed tray techniques were re-assembled and fixed into their corresponding implant analogs. Dental Stone Type IV (Elite Rock, Zhermack) was mixed using a vacuum machine for 30 s, then poured using the boxing technique over a vibrator, and the casts separated after 45 min according to the manufacturer’s instruction [17, 18]. The master casts were then sectioned to a base of 20 mm, to allow their allocation under the stereomicroscope (AmScop14370, Myford Road, #150, Irvine, CA 92606 USA), to be examined at a × 50 magnification, and to evaluate the presence or absence of marginal discrepancy [8, 19].