The aim of this study is to evaluate chipping and the degree of natural enamel loss opposing to monolithic zirconia compared to veneered zirconia restoration.

While increase using of zirconia in extra coronal restoration as a substitute for metal ceramic restoration still high rate of technical complications specifically chipping of veneering ceramic and wear of antagonist are usually associated with veneered zirconia restoration which led to development of new monolithic zirconia to overcome these technical complications.

Therefore this study will be conducted to evaluate chipping and wear of antagonist of veneered zirconia versus monolithic zirconia all ceramic crowns in posterior area.

Benefits of the research to the patient:

Patient will receive a restoration with superior function, esthetics, and quality.

It will save teeth such as mutilated teeth, endodontically treated and teeth with massive loss of tooth structure that cannot be restored with direct restoration.

As a result of properly functioning restoration, teeth will be restored with predictable prognosis and the patient will be psychologically improved.

Benefits of the research to the clinician:

Practitioner will have the advantage to clinically assess a new material that can be used in different situations for better function and esthetic outcomes.

It will improve patient confidence with the dentist.

Explanation for choice of comparators:

The use of veneered zirconia is well documented in the literatures as successful restoration modality. A two Clinical performance of two different CAD/CAM-fabricated ceramic crowns revealed no chipping for veneered zirconia.

A 3 years Randomized Controlled Clinical Trial of Zirconia-Ceramic and Metal-Ceramic Posterior Fixed Dental Prostheses reported Alpha Scores A=66.6%, B =25% , C=5.6% and Only D= 2.8 A 5 years prospective clinical study of posterior zirconia fixed dental prosthesis reported Alpha scores greater than 95% indicating no predictable changes during the 5 years Another 3 years Randomized controlled clinical Trial of Posterior veneered zirconia for fixed dental prostheses revealed 20% chipping and also 30% reported alpha for antagonist wear and 70% reported bravo after 3 years of clinical use.

Inclusion Criteria:

1. Age range of the patients from 20-60 years old; able to read and sign the informed consent document, illiterate patient will be avoided.
2. Patients able physically and psychologically to tolerate conventional restorative procedures.
3. Patients with no active periodontal or pulpal diseases, having teeth with good restorations.
4. Patients with teeth problems indicated for full coverage restoration (e.g. Moderate to severe discoloration, coronal fracture where partial coverage would lack retention, malposed or malformed teeth).
5. Patients with root canal treated teeth requiring full coverage restorations.
6. Patients willing to return for follow-up examinations and evaluation.

Exclusion Criteria:

1. Patients in the growth stage with partially erupted teeth.
2. Patients with poor oral hygiene and motivation.
3. A pregnant woman's to avoid any complication that may occur in dental office due to pregnancy or due to injected anesthetic solution.
4. Patients with psychiatric problems or unrealistic expectation (patient that has phobia from dental treatments or needle bunch).
5. Patients have no opposite occluding dentition in the area intended for restoration.
6. Patients suffer from Para functional habits.