The objective of this trial is to compare patient satisfaction and retention of complete denture manufactured by three different techniques: CAD/CAM milling, CAD/CAM 3D printing and conventional technique.

Patient examination and diagnosis will be made at the outpatient clinic, department of prosthodontics, faculty of Dentistry-Cairo University. Eligible Patients following the inclusion criteria will be consented to enrol in the trial. Randomization and allocation concealment will be done through sealed envelopes having groups for interventions and comparator. Each patient enrolled in the trial will pick an envelope having either the intervention or control group.

Preliminary impressions will be made and poured to study casts. Customizing trays from autopolymerising acrylic resins for final impressions with Zinc Oxide Eugenol , then impressions will be poured into dental stone producing master casts. Record bite blocks will then be constructed and bite registration will be made.

All bite records with their corresponding master casts will be digitalized by an extraoral desktop 3D scanner having the station sequence of scanning upper cast, lower cast then bite registration to be stored as standard triangulation language (STL) files.

STL files are then imported to EXOCAD design software designing full dentures with their permanent bases, teeth sizes and shapes following the recorded inter-arch space. Full upper and lower designed denture bases will be stored as STL files ready for manufacturing.

In first Intervention: STL files will be imported to SHERA CNC CAM software ready for nesting each file for the suitable PMMA block size and height, ready for milling them in denture bases with SHERA 5-axis Eco-mill milling machine . After milling denture bases, acrylic teeth will be chosen for each patient with the suitable shade and size following the inter-arch space, then glued by auto-polymerizing resin in their corresponding sockets in the milled denture bases.

In second intervention: STL files will be imported to Mogassam 3D-printer CAM software followed by adjusting the object to be virtually placed on X,Y and Z axes on the printer plate to be ready for layering it in three dimension. Photopolymerizable PMMA liquid resin will be added in the printer and the files processed into 3D printed upper and lower denture bases. Acrylic teeth are then glued in their sockets in the printed denture bases using auto-polymerizable resin.

In control group:Conventional complete denture construction by normal processing steps will be made for patients enrolled in the control group.

For the three groups, full dentures will be delivered and checked for occlusion, speech and mastication. Patient satisfaction will be assessed by a questionnaire template for each patient to be recorded at the day of delivery (baseline), 3months then 6 months. Retention for dentures will be assessed by engaging the snap hook on denture bases and pulling action will be made with the digital force gauge device to obtain the records on the day of delivery (baseline), 3months then 6 months' follow-up interval.

Inclusion Criteria:

• Completely edentulous patients ranging from age 55 to 75 years.
• Angle's Class I skeletal relationship.
• Well-developed ridge with U-shaped palatal vault and adequate firm mucosa.
• Last extraction took place six months ago.
• Normal facial symmetry.
• Cooperative patients.

Exclusion Criteria:

• -Temporomandibular disorders
• Uncontrolled diabetes
• Bleeding disorders or anticoagulant therapy
• Flabby tissues or sharp mandibular residual ridge.
• Heavy smokers.
• Patient's with neuromuscular disorders
• Patients on chemotherapy or radiotherapy
• Severe psychiatric disorders
• Angle's class II and III skeletal relationship

The Principal investigator, main supervisors and co-supervisor cannot be blinded as the trial will include digital designing of complete dentures on the CAD software and in the steps of the manufacturing techniques.