The aim of this study is to evaluate the interdental separation of various separation systems and their impact on the proximal contact tightness and contour in compound class II nanohybrid resin composite restorations.

The target population consists of adult patients aged 25-40, with posterior compound proximal carious cavities (ICDS score 4 or 5) in molars. The interventions under investigation include three different separation systems: the Resin ring (DR-Resin ring, Egypt), Elliot separator (Pfingst & Co, USA), and Stainless Steel Metal ring (TOR VM ring, Russia). These systems will be compared to a Nickel titanium 3D-fusion ring (Garrison, USA). The primary outcomes assessed are proximal contact tightness and form/contour, measured visually according to FDI criteria, with scoring systems adapted from Hickel et al. (2023). Secondary outcomes, such as patient comfort (measured by a pain rating scale), and the emergence profile (assessed via bitewing radiographs), will also be considered. Data will be collected immediately postoperatively (T0), at 30 days (T1), and after 6 months (T2). The study will be conducted as a randomized clinical trial. The null hypothesis suggests that there will be no significant differences in proximal contact tightness or contour across the different separation systems used.

Inclusion Criteria:

1. Individuals with posterior compound proximal carious cavities in molars.
2. Age of (25-40) years.
3. Molars with compound proximal carious cavities score 4 or 5 ICDS.
4. Vital upper or lower posterior teeth with no signs of irreversible pulpitis.
5. Presence of adjacent and opposing teeth with normal occlusion

Exclusion Criteria:

1. Patients with major systemic disorders or xerostomia.
2. Patients with periodontal disease.
3. Patients with para-functional habits.
4. Presence of malocclusion or signs of pathological teeth wear
5. Non vital teeth or teeth with signs of pulpal pathology.
6. Teeth mobility or clinical attachment loss.