the current study was conducted to evaluate and compare the flowable short fiber-reinforced (SFRC) and flowable bulk-fill resin composites (BFCs) regarding their 4-year clinical performance as dentin replacement materials in class II cavities.

the current study was conducted to evaluate and compare the flowable short fiber-reinforced (SFRC) and flowable bulk-fill resin composites (BFCs) regarding their 4-year clinical performance as dentin replacement materials in class II cavities. Forty patients were enrolled in the study. Each patient received three class II cavities; one of them was restored with flowable SFRC for dentin replacement, while in the other two cavities, dentin was replaced with two different flowable BFCs. The three dentin replacements were veneered with one particulate filler resin composite (PFC) (Essentia, GC). World Dental Federation (FDI) criteria were used for clinical assessment of the restorations at 1-week (baseline), 6, 12, 18-months, 2, 3, and 4-year intervals.

Inclusion Criteria:

• having good oral hygiene.
• having at least 3 posterior teeth with moderate to large primary proximal carious lesions (score 4 or 5 ICDAS).
• ranging in age from 20 to 40 years.
• with normal occlusion.
• accepting to participate in the study by signing an Arabic-written consent according to the regulations of the Mansoura University Ethical Committee.

Exclusion Criteria:

• bad oral hygiene.
• severe chronic periodontitis.
• having installed orthodontic appliances.
• abnormal occlusion.
• parafunctional habits or allergic reaction to any of the materials used in the study.
• teeth with irreversible pulpitis or non-vital teeth.
• fractured or cracked teeth. previously restored teeth.
• teeth with deep sub-gingival cavity margins.

no specific reason