The aim of study is evaluation of accuracy of completely versus partially limiting computer generated surgical three-dimensional guides during placement of zygoma implants in patients with atrophic maxillae.

According to World Oral Health Organization (WHO), losing teeth and arch edentulism is the result of a life long history of oral diseases like advanced dental caries and severe periodontal disease. Complete tooth loss estimated global average prevalence is 7% among people aged 20 years and 23% among people aged 60 years or older. Tooth loss lead to bone resorption in all direction.

Non-grafting solutions have been developed to reduce risks, morbidity, and treatment time. These types of treatment are often preferred by patients, considering that they may minimize total treatment time and have less morbidity than staged procedures of grafting solutions.One of non-grafting solutions is the zygomatic implants.

Zygomatic implants have shown improved clinical results compared with bone grafting in compromised maxillary bone.But the same as any surgical procedure, placing zygomatic implants has potential complication, such as: oro-antral communication, paresthesia or altered sensation of the infra orbital nerve also penetration of the orbital cavity may occur. In order to achieve the optimal position of zygomatic implant, computer-based planning has been introduced with the use of surgical guides.

Surgical guides are classified according to design concepts for fabrication of surgical guide to non-limiting, partially limiting design and complete limiting. In partially limiting design,the first drill is used then the surgical guide is removed and the osteotomy and implant placement are completed in freehand while in complete limiting design all the instruments used in surgical procedure during implant placement are restricted.

In literature, there is low evidence of using partially guided surgery for zygomatic implant and also of comparing the two designs with each other. the aim of study is evaluation of accuracy of completely versus partially limiting computer generated surgical three-dimensional guides during placement of zygoma implants in patients with atrophic maxillae.

Inclusion Criteria:

1. Patients older than 18 years.
2. Patients with severe alveolar bone atrophy in posterior maxilla (residual alveolar crest less than 4 mm in height, in the area immediately distal to the canine pillar).

Exclusion Criteria:

1. Patients with systemic conditions contra-indicating general anesthesia.
2. Patients with conditions contraindicating implant placement (e.g.: radiation to the head and neck, intra-venous bisphosphonates, uncontrolled Diabetes mellitus).
3. Patients with acute maxillary sinus infection or maxillary sinus cyst.
4. Restricted mouth opening (less than 3 cm inter-arch distance anteriorly).