patients with non carious cervical lesions suffer from dentin sensitivity and presence of cavitations and gingival recession. Restoring these lesions with different composites and evaluation of restorations every 6 months will be done to know the effect of different composite types and consistencies in retention of restorations of such lesions.

A split-mouth randomized clinical trial (RCT), based on the adhesion strategy, will be held on 52 patients attending to the outpatient clinics of the department of operative dentistry, Faculty of Dentistry, Ain Shams University with 2 non-carious cervical lesions in each side. Patients included in this study are those who seek restorative treatment of non-carious cervical lesions (NCCLs) in premolars and canines, which are due to chemical and/or mechanical predisposing factors. An informed consent will be signed by all participants who will be allocated in this study before being involved in the study. Male and female patients will be selected according to the inclusion and exclusion criteria. The patients will be randomly assigned into 4 main groups (n=13 patients/group) according to the type of restorative material will be inserted. In each group, two adhesive approaches will be employed, either etch-and-rinse (E&R) or self-etching (SE)approach. For each patient's mouth, one side will receive restorations with the etch-and-rinse approach (n=26 restorations/E&R approach), while the other side will receive restorations using the self-etching approach (n=26 restorations/SE approach). This will result in a total of 208 restorations will be inserted in this study. A treatment follow-up will be performed every six months for two years to investigate the clinical performance of the different resin composite restorations/the two different adhesive approaches.

Restorations will be evaluated at baseline and every 6 months by two blinded examiners, who will not be involved in the study. During evaluation, the examiners will not be informed about the type of restoration used or the adhesive approach and will have a code for each patient and the restored tooth. Restorations will be evaluated according to the modified United State Public Health Service criteria (USPHS).(6,9,13,30) Primary outcome will be the retention of the restoration, but the following secondary outcomes as marginal discoloration and adaptation, anatomic form, secondary caries, texture, and postoperative sensitivity will be also evaluated.

Inclusion Criteria:

- Patients' age will range from 18 to 65 years.

• Presence of at least 2 NCCLs in one side.
• Patients with no medical condition could interfere with the routine dental care.
• Patients who will be able to attend for each recall visit.
• Patients with healthy periodontal tissues.
• Cavities presenting no more than 50% of margins in enamel.

Exclusion Criteria:

• Medically compromised patients.

  • Pregnant or breast-feeding patients.
  • Patients undergoing orthodontic treatment or bleaching treatment in the time of the study.
  • Patients with periodontal disease in the target area.
  • Patients presented with less than 20 teeth in the oral cavity.
  • Patients without antagonists.
  • Lesions superimposed with caries

expecting to have all data by october 2026