Implant impression accuracy of parallel and non-parallel implants: a comparative in-vitro analysis of open and closed tray techniques

Abstract

Background The outcome of the evaluation of impression techniques accuracy may improve the selection criteria for an ideal technique. The aim was to evaluate the accuracy of the open and closed tray techniques for implant impressions, in a partially edentulous maxilla, replaced with a three-unit fixed partial denture, as well as to assess the effect of implants parallelism on accuracy. Material and methods This is an experimental in vitro study to evaluate impressions accuracy of a simulated area restored with an implant retained FPD, using the open and closed tray implant impression techniques. The effect of implant position angulation, parallelism, and implant systems (Straumann, SIC Invent, Osstem) was also evaluated. Three custom-made acrylic resin test models were prepared with two parallel and two non-parallel implants, on either side of a maxillary arch. One hundred and ninety-two impressions were made using monophase VPS impression material. Their master casts were obtained and evaluated for the horizontal and vertical discrepancy. The casts were scanned using a model scanner. The distances between the two reference points were measured. Results The Straumann and SIC Invent implants showed no statistically significant differences (Mann-Whitney U test), regarding accuracy for both the open and closed tray impression techniques ( P = 0.667 and P = 0.472). There were no significant differences for the parallel and non-parallel implants ( P = 0.323 and P = 0.814), respectively, while the Osstem system showed statistically significant differences for both the open and closed tray impression techniques ( P = 0.035) and between the parallel and non-parallel implants ( P = 0.045). For the vertical discrepancies, significant differences were detected (chi-square test) between the open and closed tray impression techniques ( P = 0.037). Conclusions Within the limitations of this study, there were generally no significant differences between open and closed, although better results were obtained for the open tray techniques. On the use of the non-parallel implants, the open tray technique provided a better result than the closed tray technique.

A prospective clinical study on implant impression accuracy

“…This recorded intraoral horizontal distances would later be compared against similar horizontal measurements on the master casts, to evaluate discrepancies or horizontal displacements between the positions intraorally and on the master casts. The same impression evaluation criteria used in our previous study were also used here [8], which was described by Lee and Gallucci as follows [14]: 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.

Fig. 1Horizontal measurements between the two impression copings in the patient’s mouth

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“…The research on implant impression accuracy is mostly from in vitro studies, and the limited number of clinical studies might be contributing to the controversy as to which technique should be considered to be more superior [5, 8]. We hypothesize that clinically, there is no impact or differences in impression accuracy.…”

The impact of impression coping geometrical design on accuracy of implant impressions: an experimental study

“…The horizontal discrepancy between the coping for the test and the master casts was evaluated and recorded for analysis. The measurements were recorded and used to compare the horizontal distance measurements between the test models and the cast digital measurements for every technique and each implant system [21].…”

“…The horizontal distances between the two implants in parallel and non-parallel sides were measured from the center to the center of the implant fixture, using software (exocad-Dental CAD). The distance on the right side between implants 14 (with long axis) and 16 (angulated distally 15 degrees) was assigned as D1, and the distance on the left side between implants 24 and 26 (parallel implants) was assigned as D2 [21].…”

“…This evaluation was made using verification jigs fabricated from a CAD/CAM acrylic resin block (BILKIM® PMMA blank for CAD-CAM applications 14 mm-A2 color-Turkey). Accordingly, the stone casts were sectioned to a base of 20 mm, to facilitate placement under the stereomicroscope [21].…”