The aim was to evaluate the clinical performance of HEMA-containing and HEMA-free all-in-one self-etch adhesives with and without a surface sealing process with a nanohybrid composite in occlusal caries restorations. The hypothesis is that the HEMA-containing and HEMA-free all-in-one self-etch adhesive and the surface sealing process would significantly effect clinical performance of occlusal restorations.

Inclusion Criteria:

• patients who received four direct Class I composite restorations, those with good oral hygiene with no active periodontal or pulpal diseases, whose permanent first or second molar required restorations for occlusal carious lesions with neighboring teeth and were in occlusion with antagonist teeth, and were willing to return for follow-up examinations as outlined by the investigators.

Exclusion Criteria:

• patients with uncontrolled parafunction, those presenting with poor oral hygiene and disinterested in or refused oral hygiene instructions, molars and premolars with carious lesions on a surface other than the occlusal surface and in continuity with the occlusal cavity, pulp exposure during caries removal procedure or cavities with the risk of pulp exposure, having spontaneous pain or sensitivity to percussion, and patients with periodontal or gingival disease.