This randomized split-mouth clinical trial aims to evaluate the clinical performance of bioactive restorative materials used in Class II restorations in permanent posterior teeth. The study compares a giomer-based bulk-fill restorative material, a giomer restorative material, and a resin-modified glass ionomer cement in terms of clinical success and overall clinical performance. Patients requiring at least three Class II restorations in posterior teeth are treated under standardized clinical conditions. Clinical evaluations are performed at baseline and follow-up visits to assess short- and long-term outcomes.

This is a single-center, randomized, controlled split-mouth clinical trial conducted at Hacettepe University Faculty of Dentistry. The aim of the study is to compare the clinical performance of bioactive restorative materials used in Class II posterior restorations.

Eligible patients requiring at least three Class II restorations in permanent posterior teeth are included in the study. Each patient receives restorations with different bioactive restorative materials in separate treatment sites according to a split-mouth design. The tested materials include a giomer-based bulk-fill restorative material, a giomer restorative material, and a resin-modified glass ionomer cement. Randomization is used to assign the restorative materials to the treatment sites.

All restorative procedures are performed under standardized clinical protocols. Clinical performance is evaluated using modified FDI criteria.

Follow-up evaluations are planned at 6, 12, and 24 months after treatment. The 6-month results are used for interim analysis, while long-term follow-up will assess the durability and clinical success of the restorative materials.

Inclusion Criteria:

1. Healthy individuals without any systemic disease that could contraindicate restorative treatment
2. Individuals aged between 18 and 50 years
3. Individuals who agreed to participate in the study and signed the informed consent form
4. Individuals with at least three proximal carious lesions in premolar or molar teeth, classified as D2 (lesions extending to the middle third of dentin) or D3 (lesions extending to the inner third of dentin) according to the ICDAS classification
5. Teeth with intact enamel and dentin structure that had not been previously restored
6. Individuals who brushed their teeth at least twice a day
7. Individuals without physical disabilities that could prevent attendance at follow-up visits
8. Individuals with at least 20 teeth in occlusion and with antagonist teeth in the opposing arch
9. Vital teeth without signs of periapical pathology
10. Periodontally healthy teeth that were not used as abutments for any prosthetic restoration
11. Teeth without displacement or mobility
12. Individuals who had undergone initial periodontal therapy

Exclusion Criteria:

1. Pregnant or breastfeeding individuals
2. Individuals with advanced periodontal disease
3. Individuals using removable partial dentures
4. Individuals with bruxism
5. Individuals with severe malocclusion
6. Individuals with known allergies to resin-based restorative materials or adhesive agents
7. Individuals with a history of allergy to local anesthetics or their administration
8. Individuals with latex allergy
9. Individuals with poor oral hygiene
10. Teeth that had been previously restored or were undergoing orthodontic treatment

Individual participant data sharing plans have not yet been determined.

Participants and outcome assessors were blinded to the restorative material assigned to each treatment site. The operator was aware of the material allocation during the restorative procedures.