The aim of this study is to assess the effect of the newly introduced (hybrid dental ceramic) superstructure materials, Vita Enamic versus IPS Emax on implant stability, patient satisfaction and crestal bone loss.

This study will be conducted on patients requiring single implant replacement in the maxillary premolar area, admitted to the Outpatient Clinic of Fixed Prosthodontics Department, Faculty of Oral and Dental medicine, Cairo University.

After a period of healing of 6 months, an implant abutment of accurate diameter and angulation will be placed to fit precisely into the internal hex of the fixture after removal of the cover screw. The platform matched abutment will be then secured into its final position using the abutment screw. Alginate impression will be taken and poured into dental stone. Using the impression transfers, impressions with polyvinylsiloxane are taken. After taking the impressions, the Impression transfers are removed and fixed to the implant replica.

Surgeons' assistants will be asked to open the sealed envelope containing the information regarding the crown placement. The impressions will be sent to dental laboratory with the result of the sealed envelope, for preparation of the future crowns, either vita enamic crowns or Ips e max crowns.

Inclusion Criteria:

Patients > 18 yrs. Patients with missing teeth in the maxillary premolar region. Absence of any pathological condition in the recipient site.

Stabilization phase will be performed including:

• Scaling
• Debridement.
• Elimination of all carious cavities and root canal treatment if needed.
• Elimination of over-hanging restoration. Systemic condition of the subjects was evaluated according to dental modification of the Cornell medical index (Kerr and Millard 1966).

Patients who are cooperative, motivated, and hygiene conscious. Patients should have adequate ridge width (>5mm).

Exclusion Criteria:

Patients unable to undergo minor surgical procedure. Patients with history of drug abuse or metabolic drugs. Patients with history of psychiatric disorder. Patients with insufficient bone. Patients with insufficient vertical inter-arch space, upon centric occlusion, to accommodate the available restorative components.

Patients with any systemic condition that may contraindicate implant therapy. Patients that may have any habits that may jeopardize the osseo-integration process, such as heavy smoking and alcoholism.

Patients with para-functional habits that produce overload on the implant such as bruxism and clenching.