evaluation and comparison of the accuracy of conventional and digital impression for full arch screw retained prosthesis for edentulous maxilla.

Each patient received 6 implants in the maxillary ridge (widely distributed across the arch) in the following positions: central incisors, canines/first premolar teeth and first molar teeth aided by surgical stent. then each patient received 2 types of impression techniques Technique 1 :conventional impression conventional open tray impression technique with splinted transfers using vinylpolysiloxane and Technique2 : Digital impression taken using original scan bodies torqued to the implants .three dimensional accuracy of impression techniques was evaluated using linear measurements and 3D deviation between the two techniques was measured.

Inclusion Criteria:

• The patients were selected according to the following inclusion criteria:

  1. Completely edentulous maxillary and mandibular ridges

  2. Healthy ridge covered by normal oral mucosa and free from any ridge flabbiness.

  3. All of the patients were dissatisfied with the retention and stability of their maxillary conventional dentures and expressed a strong desire for a more stable prosthesis.

  4. Sufficient bone quantity and quality in the front and posterior maxillary regions, as determined by preoperative CBCT, to accommodate six implants with a diameter of at least 3.5 mm and a length of at least 10 mm.

  5. Enough restorative space (from the mucosa covering the crest of the maxillary residual ridge to the occlusal plane) to allow the fixed prosthesis to be constructed ,preliminary jaw relationship revealed this.

  6. It's been at least a year since the last extraction.

     Exclusion Criteria:

  1. Systemic diseases that may alter tissue response to implantation and affects osseointegration (radiation, diabetes, osteoporosis, bleeding disorders or hepatic patients)
  2. Long term immunosuppressive and corticosteroid drug therapy.
  3. Patient with abnormal habits as clenching and bruxism.
  4. Smoking patients.
  5. Patients with problems in TMJ.
  6. Neuromuscular diseases.