The protection of the dentin-pulp complex consists of the application of one or more layers of specific material between the restorative material and dental tissue to avoid additional challenge to the pulp tissue caused by operative procedures, toxicity of restorative materials and bacteria penetration due to microleakage. Protection of the dentinpulp complex has also the function to recover pulp vitality.The materials that can be used for this purpose are varnishes,calcium hydroxide (CH)-based products, glass ionomer cements (GICs) and adhesive systems.The biological compatibility together with the sealing capabilities of dental materials is of paramount importance to avoid or limit pulp tissue irritation and dentinal hypersensitivity.

Pulp plays an important role in the formation and nutrition of dentin as well as in the innervation and defense of the teeth. The primary pulp function is dentin formation, which begins in the moment that the peripheric mesenchimal cells differentiate into odontoblasts and starts the deposition of collagen matrix, in a sequence of deposition/mineralization that ends with the complete tooth formation. Even after the initial formation, pulp continues to physiologically produce dentin due to the tooth aging. Reparative dentin may also be produced in response to physical and/or chemical injuries. Odontoblasts maintain their processes inside the newly formed tissue, thus creating real channels that are responsible for dentin nutrition. changes in the flow of the fluid in the dentinal tubules can trigger pain receptors present on nerve endings in the pulpal aspect to fire nerve impulses, thereby causing pain . This hydrodynamic flow can be increased by changes in temperature, humidity, air pressure and osmotic pressure, or forces acting on the tooth. Hot or cold foods and drinks, and physical pressure are typical triggers in people with dentin hypersensitivity.

Inclusion Criteria:

1. Patient's age ranges from 20-50 years old with vital first permanent molar tooth on testing by vitality test, such as thermal or electrical pulp tester.
2. Class I or II cavities.
3. Deep carious lesions.
4. Absence of clinical signs or symptoms suggesting non-vital tooth such as spontaneous pain, tenderness to percussion, abscess, fistula, periodontal tissue swelling, or abnormal tooth mobility.
5. Sufficient tooth structure for restoration.
6. Healthy patients with good general health.
7. Patients are cooperative and motivated.

Exclusion Criteria:

1. Patient with systemic diseases such as uncontrolled diabetic, cardiovascular diseases, or patient received chemotherapy or radiotherapy.
2. History of spontaneous, unprovoked toothache or mobility, (grade I, II and III).
3. Sensitivity to percussion, external or internal root resorption, periapical lesions or presence of a fistulae.
4. Pregnant females.
5. Drug abuser patients.
6. Previously restored teeth.