This randomized crossover clinical trial aims to compare three different impression techniques for the construction of 3d-printed mandibular implant overdentures in completely edentulous patients. Sixteen patients will receive two mandibular implants and three overdentures fabricated using:(1) conventional open-tray implant level impression (2) functionally generated reline impression, and (3)mucostatic base with functional borders impression. Each overdenture will be worn for three months with a washout period between interventions.

The primary outcome is masticatory efficiency, assessed using a color -mixing ability test at 3,6, and9 months.

Secondary outcome is patient satisfaction, assessed using a Visual Analog Scale (VAS) at the same intervals. the study hypothesis is that the impression technique influences both chewing efficiency and patient satisfaction

Edentulism has a significant impact on oral function and quality of life. The use of mandibular implant overdentures supported by two implants is widely considered the minimum standard of care, providing improved stability, function, and patient satisfaction compared with conventional complete dentures. Recently, digital workflows and additive manufacturing (3D printing) have created new opportunities for fabricating complete dentures with improved efficiency and reduced costs.

Several impression techniques are currently available for implant-retained overdentures, but there is limited evidence on how these techniques influence functional outcomes and patient-reported satisfaction, particularly when using 3D-printed prostheses.

This randomized crossover clinical trial will be conducted at the Faculty of Dentistry, Mansoura University. Sixteen completely edentulous patients aged 45-70 years will receive two implants placed in the mandibular canine region. After the osseointegration period, each participant will be provided with three different mandibular implant overdentures fabricated using different impression techniques:

1. Conventional open-tray implant-level impression
2. Functionally generated reline impression
3. Mucostatic base with functional borders impression Each overdenture will be worn for a period of three months, with a two-week washout period using a provisional denture before switching to the next overdenture. Randomization will determine the sequence of interventions for each patient.

The primary outcome is masticatory efficiency, measured with a color-mixing ability test at 3, 6, and 9 months. The secondary outcome is patient satisfaction, measured using a Visual Analog Scale (VAS) at the same intervals.

The study is designed to provide evidence on whether the choice of impression technique affects clinical and patient-centered outcomes in 3D-printed mandibular implant overdentures.

Inclusion Criteria:

• Healthy patients, free from systemic diseases that affect bone resorption (e.g., uncontrolled diabetes, osteoporosis)
• Residual alveolar ridges covered with healthy, firm mucosa
• Adequate mandibular bone length and width to accommodate standard implant sizes.
• Angle's Class I maxillo-mandibular relationship.

Exclusion Criteria:

• Absolute contraindications to implant placement (e.g., active cancer, immune system diseases)
• History of head and neck irradiation or chemotherapy within the past 3 years
• Metabolic bone diseases such as uncontrolled diabetes, osteoporosis, or hyperparathyroidism
• Parafunctional habits such as bruxism or clenching
• Smoking or alcoholism
• Any physical or medical condition that may interfere with study follow-up or implant success