Forty patients ( 24female and16 male )with completely edentulous maxilla and mandible . All patients received implant supported mandibular and maxillary overdentures. The patients were randomly divided into two groups according to attachments retaining Max IOD that supported by four axial implants in maxilla . The TA was used to retain group I (GrI) MaxIOD , while that of group II (Gr II) was retained by LA. MaxIOD retention and MBL(vertical and horizontal) around implants of both groups was recorded at time of insertion (R0) ,then twelve(R12)and (R24) months following insertion of the prosthesis.

Parallel groups, two arms, randomized controlled trial (RCT) with 1:1 allocation ratio was designed, retention of telescopic attachment and locator attachment among patients with completely edentulous maxillary arch and intended to use maxillary overdenture was compared. The minimum proper sample size was 20 participants in each group to be able to detect a real difference in retention equal to 2 N with 80% power at α = 0.05 level using Student's t test for independent samples.

The stone casts were poured and mounted guided by the the occlusion of upper and lower dentures in centric relation to evaluate inter-arch distance. Pre-operative panorama was initially made to assess bone quality and quantity of edentulous maxillary ridge New Complete maxillary and mandibular dentures were made using semi-anatomic teeth arranged following balanced occlusion . The stent is scanned in the patient's mouth using CBCT. DICOM (digital imaging and communications in medicine) was applied for the virtual planning of the implants using exocad software .

Two virtual implant models were used and their criteria are mentioned (in table 2). Implants were planned at lateral-canine areas equidistant from midline and another two implants at first molar bilaterally . A safety zone of a minimum of 2 mm between the implants and vital structures like the maxillary sinus was planned Surgical procedure Two stage surgical protocol was followed for insertion of implants for both groups in their planned position via the same oral and maxillofacial surgeon. Presurgical prophylactic medications were prescribed, including: 1gm Augmentin®, prednisone, and 0.2% chlorhexidine digluconate started 8 hours before surgery and continued for 7 days following surgery. Analgesic drug was prescribed once daily or when needed. Flapless surgical technique was followed guided by mucosa-supported surgical stents that were checked intraorally for stability and fitness. The stents were fixed to the bone using three fixation screws. Implants were inserted at a minimum of 35 Ncm torque. After complete insertion of fixtures and screwing of covering abutments , tissue conditioner was used for relining and fitting of the existing maxillary denture to the mucosa. Participants were instructed to eat a soft diet and perform oral hygiene procedures.

Inclusion Criteria:

• have sufficient bone volume(classes IV to VI, Cawood and Howell) and quality (classes I to III, Lekholm and Zarb)
• be fully edentulous for at least 1 year and did not have an American Society of Anesthesiologists score (ASA) of IV or higher.
• be with Angle Class I maxillo- mandibular relationship
• have Adequate zone of keratinized attached mucosa >5mm over the crest of the upper and lower ridge
• have adequate inter-arch space (22 mm) as determined by the mounted casts carrying the patient upper and lower complete dentures .

Exclusion Criteria:

• Any medical disorders that could complicate the surgical phase or affect osseointegration as osteoporosis, uncontrolled diabetes and hypertension
• Smoking; - Former radiotherapy in the head and neck region
• Former pre-prosthetic surgery or loss of implants in the maxilla
• Patients with para-functional habits (as clenching or bruxism)
• Hard tissue augmentation / grafting.