Introduction: Dental restorations are widely used in dentistry as the most common way to replace the lost parts of the tooth that occur due to decay. Secondary caries is the primary cause of replacing an existing restoration. Nowadays, modified restorations were introduced to the market to solve the drawbacks of the conventional ones in respect to the early loss of strength, and moisture sensitivity. New dental restorations are possibly associated with lesser degree of secondary caries formation. Aim: Evaluate secondary caries formation around three different restorative materials by measuring the surface area of the lesions using stereo-microscope. Materials and Methods: Thirty six human premolar teeth were collected from the Outpatient clinic of the Maxillofacial Department, Faculty of Dentistry, Suez Canal University, and were divided into three groups according to the type of restoration used. Group I restored with Fuji II LC material,  group II restored with Equia Forte material, and Group III restored with Z100 material according to manufacture instructions. All teeth were preserved in an artificial caries solution for 5 weeks, and then divided into thin sections to be evaluated under Stereomicroscope to assess secondary caries lesions formed around restorations.
Results: There was statistically significant difference between secondary caries values on both the buccal and lingual surfaces of the three groups. Equia Forte (Group II) showed the least secondary caries lesions followed by Fuji II LC (Group I), while the highest values were recorded at Z100 (group III).
Conclusion: Glass ionomer have an inhibitory effect on formation of secondary caries, which is higher in glass hybrid
ionomer compared to resin-reinforced glass. Composite resin restoration is not an effective material on preventing secondary caries lesions.