Evaluation the clinical performance of premolars restored with ceramic vonlays versus onlays using modified USPHS criteria after follow-up period of 0,3,6,9,12 months

two groups of patients with vital premolars indicated for fixed restorations will be selected according to special inclusion criteria (n=13) in each group (total of 26). one group will receive minimally invasive cavity preparations for posterior indirect restorations either vonlay or onlay according to each group the patient will be assessed using Modified USPHS Criteria at 0,3,6,9,12 months regarding fracture, marginal integrity and marginal discoloration

Inclusion Criteria:

1. Age range of the patients from 25-44 years old, who could read understand and write to sign the consent by himself /herself

2. Have no active periodontal or pulpal diseases, have teeth with good restorations.(19)

3. Psychologically and physically able to withstand conventional dental procedures

4. Patients with teeth problems indicated for onlay and vonlay (premolars).

   1. Decayed teeth.
   2. Teeth restored with large filling restorations.

5. Able to return for follow-up examinations and evaluation.

Exclusion Criteria:

1. Patient less than 25 or more than 44 years.
2. Patient with active resistant periodontal diseases.
3. Patients with poor oral hygiene, high caries risk and uncooperative patients.
4. Pregnant women.
5. Patients in the growth stage with partially erupted teeth.
6. Psychiatric problems or unrealistic expectations.
7. Lack of opposing dentition in the area of interest. 8- The presence of a removable or fixed orthodontic appliance, signs of bruxism or clenching, the absence of more than one unit in the posterior region

Double blinding