Lithium Disilicate Glass-ceramic Versus Hybrid Ceramic Superstructure Materials on Implant Stability

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.