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.

This is a prospective, crossover clinical trial designed to evaluate and compare the accuracy of three different impression techniques used in the fabrication of full-arch implant-supported prosthesis frameworks. The study includes four participants, each with four osseointegrated dental implants in the mandibular arch.

The three impression techniques being compared are:

Conventional Splinted Impressions: A traditional method utilizing rigidly splinted impression copings and polyvinyl siloxane (PVS) impression material to capture implant positions.

Standard Digital Scanning: A fully digital technique using an intraoral scanner and scan bodies placed on the implants to generate a digital impression.

Geometric Pattern-Assisted Digital Scanning: An enhanced digital method incorporating a geometric reference pattern during the scanning process to improve stitching accuracy and reduce scan distortion across the arch.

Each participant will receive all three impression techniques in a randomized sequence to minimize order bias. Digital models will be generated from each impression method, and test frameworks will be designed using computer-aided design/computer-aided manufacturing (CAD/CAM) technology. These frameworks will be fabricated using 3D laser sintering.

The primary outcome of the study is the assessment of accuracy, defined as the mean three-dimensional (3D) deviation between the test scan and a reference scan, measured via digital superimposition software. A secondary outcome is clinical passivity, evaluated using the one-screw test to detect any misfit between the framework and implant interfaces.

The results of this study aim to provide clinical evidence regarding the accuracy and feasibility of advanced digital impression techniques, particularly the use of geometric pattern references, in full-arch implant prosthodontics. This may support improvements in digital workflow reliability, patient outcomes, and prosthetic longevity.

Inclusion Criteria:

Adults aged 30 to 70 years

Completely edentulous mandible

Presence of four osseointegrated implants in the lower jaw

Good oral and general health

Willingness to participate and provide written informed consent

Availability for all study appointments

Exclusion Criteria:

Systemic diseases or conditions that affect bone healing or implant integration

Presence of oral inflammation, infection, or soft tissue abnormalities at implant sites

History of bruxism or parafunctional habits

Inability to understand or comply with study procedures

De-identified individual participant data (IPD), including digital scan accuracy values and framework fit results, will be made available upon reasonable request after publication of the study results. Data will be shared with qualified researchers for academic and non-commercial purposes only, subject to ethical approval and data-sharing agreements.

Beginning 6 months after publication of the study results and for up to 5 years.

De-identified individual participant data (IPD) and supporting materials (study protocol, statistical analysis plan, and informed consent form) will be available to qualified researchers affiliated with academic institutions or non-profit organizations. Access will be granted for non-commercial, ethically approved research purposes. Interested researchers must submit a formal request to the Principal Investigator via email, including a research proposal and institutional ethical approval. Access will be provided through secure, password-protected file sharing platforms.