This clinical trial aims to compare three different impression techniques used to fabricate full-arch implant-supported dental prostheses. Accurate impressions are essential to ensure a passive and precise fit of the final prosthetic framework, which contributes to long-term implant success and patient comfort.
In this crossover study, participants with four osseointegrated dental implants in the lower jaw will undergo three types of impressions:
Conventional splinted impression using polyvinyl siloxane (PVS) material.
Standard digital impression using an intraoral scanner.
Geometric pattern-assisted digital impression, which incorporates a visual reference pattern to improve scan alignment and accuracy.
Each participant will receive all three impression techniques in a randomized sequence, at different time points. The accuracy of each method will be assessed by evaluating the passivity of the resulting prosthetic frameworks using two methods: (1) digital superimposition analysis to measure three-dimensional (3D) spatial deviation, and (2) the clinical "one-screw test" to detect misfit.
The study seeks to determine whether digital scanning, particularly with geometric pattern assistance, can provide accuracy comparable to or better than conventional methods. Findings may guide improvements in digital prosthodontic workflows and support more efficient, predictable treatment outcomes.
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Crossover
Intraoral Scanner - Standard Protocol
DeviceA full-arch digital impression is obtained using a high-precision intraoral scanner. Scan bodies are placed on multi-unit abutments and scanned without the use of external reference markers or geometric aids. The scan follows the manufacturer-recommended scanning path to capture the complete arch. This serves as a baseline digital technique for comparison with geometric pattern-assisted scanning.
Intraoral Scanner with Geometric Reference Pattern
DeviceThe same intraoral scanner is used, but with an additional geometric reference pattern introduced in the scanning field to improve stitching accuracy and alignment of the digital scan.
Conventional Splinted Impression Technique
Procedure/SurgeryA physical impression is taken using open-tray impression copings splinted with DuraLay resin and polyvinyl siloxane (PVS) material in a custom tray, according to conventional protocols for full-arch implant prostheses.
Mean 3D deviation (in microns) between test and reference scans using digital superimposition.
Accuracy will be assessed by digitally superimposing the scan obtained from each method (conventional splinted impression, standard digital scan, geometric pattern-assisted digital scan) onto a reference scan (conventional method). Specialized software will calculate the mean 3D deviation in microns to quantify spatial accuracy. Lower deviation indicates higher accuracy.
Number of frameworks exhibiting passive fit as determined by the one-screw test.
Clinical assessment of framework passivity will be performed using the one-screw test. A passive fit will be recorded if no lifting or rocking is observed upon tightening a single screw at one end of the framework while the others remain untightened. Count and percentage of frameworks with passive fit will be reported.
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Mirna ashraf anis heneen
Lead sponsor
Mansoura University
Sponsor institution
