Purpose: To evaluate the effect of adding nano ZrO2 and nano TiO2 nanoparticles on trueness and dimensional deviation of maxillary 3D printed denture base resin on completely edentulous patients.

Materials and Methods: This study was carried out on 24 completely edentulous patients. The patients were divided randomly into three equal groups; Group I: Patients received 3D printed maxillary complete denture without additives, Group II: Patients received 3D printed maxillary complete denture reinforced by Nano ZrO2 (0.4%) by Wt and Group III: Patients received 3D printed maxillary complete denture reinforced by Nano TiO2 (0.4%) by Wt. Trueness was evaluated by scanning the denture using an extraoral scanner after the printing process, before insertion. Dimensional deviation was evaluated by scanning the denture using an extraoral scanner at the time of insertion and after 6 months, 12 months, and 18 months. The trueness and dimensional deviation values were analyzed using repeated measure ANOVA, followed by multiple comparison Turkey test.

• Primary and final impressions of the maxillary and mandibular arches were taken for each patient following basic prosthetic principles.
• Maxillary and mandibular record blocks were made on the master casts and adjusted in the oral cavity of the patients in a normal manner to ensure an acceptable vertical dimension at occlusion and a freeway space of 2-4 mm. The centric relationship was recorded via the static method.
• An extra-oral scanner was used for scanning master casts (upper and lower), then occlusion blocks on the master cast were scanned after spraying with the scanner spray.
• Master casts and jaw relation records. Standard tessellation language (STL) files were sent to the software platform (Exocad). The software enabled virtually simultaneous mounting and alignment.
• Virtual design of the upper and lower bases and virtual setting of the upper and lower teeth were performed.
• The virtual denture STL file was exported to the LCD printer, which prints the denture base and teeth (trial base) as one unit.
• The try-in step was performed via the trial denture base to check for occlusion, esthetics, and denture border extension.

If any modification was performed on teeth using articulating paper or in the denture base using pressure-indicating paste, the trial denture bases were scanned by an extraoral scanner. The STL file was then sent again to the software for correction of the design, and then sent to the 3D printer software.

• Before printing, each file was checked for support adequacy, the printing orientation was 45 degrees, the thickness of the printed layer was 50 microns, and the printing time was 4 hours and 7 seconds for each denture15
• The denture base and the teeth were printed separately via a 3D printer.16
• For Group Ι, Pink denture base resin was used without nanoparticles for printing the denture bases. However, for Group II, Pink denture base resin reinforced by nanoparticles (ZrO2) (0.4%) by weight was used for printing the denture bases.
• Additionally, for Group III, pink denture base resin reinforced with nanoparticles (TiO2) (0.4%) by weight was used for printing the denture bases.
• For printing the teeth, white tooth resin was used for all groups.
• To remove any residual monomers after printing, the denture bases and teeth were placed in isopropyl alcohol for five minutes.
• Finally, resin was used to attach teeth to recessed pockets in the denture bases, after which the dentures were placed in the postcuring unit.
• Eventually, the dentures were finished, and the teeth were coated with resin glaze to protect and polish areas of posterior pits and fissures and interproximal surfaces from staining or discoloration.
• The dentures were inserted into the patient's mouth and checked for any necessary adjustments, and every patient was given the same post-insertion instructions for home care and follow-up evaluation, and a regular oral and denture hygiene protocol.

Inclusion Criteria:

All patients participating in this study were selected according to the following criteria:

• Completely edentulous patients with good local and systemic health.
• With an age range of 50 to 70 years old.
• Have adequate interarch space and class Ⅰ angle classification.
• Have good neuromuscular control. Patient exclusion criteria
• Any disease that may affect denture construction
• Oral parafunctional habits.
• Temporomandibular disorders

Following the research ethics committee of the faculty of dentistry Tanta university