This randomized controlled clinical study aims to evaluate the clinical performance of five different bulk-fill composite materials representing distinct technological approaches according to the World Dental Federation (FDI) criteria. The materials include a thermoviscous bulk-fill composite applied with preheating, a sonic-activated bulk-fill composite, a flowable bulk-fill composite, an ORMOCER-based bulk-fill composite, and a conventional bulk-fill composite. Restorations will be clinically assessed at baseline, 1 month, 6 months, and 12 months for esthetic, functional, and biological outcomes.

This randomized controlled clinical follow-up study is planned to evaluate the clinical performance of posterior restorations performed with five different bulk-fill composite materials representing distinct technological approaches. The materials to be investigated include a thermoviscous bulk-fill composite applied with preheating, a sonic-activated bulk-fill composite, a flowable bulk-fill composite, an ORMOCER based bulk-fill composite, and a conventional bulk-fill composite.

The study will be conducted in patients requiring direct posterior restorations. After cavity preparation and restorative procedures performed according to the manufacturers' instructions, restorations will be placed using the assigned bulk-fill composite material. Clinical evaluations will be performed according to the World Dental Federation (FDI) criteria. The restorations will be assessed in terms of esthetic, functional, and biological properties.

Follow-up examinations will be carried out at baseline, 1 month, 6 months, and 12 months. The primary aim of the study is to compare the short-term clinical performance of bulk-fill composite materials with different technological characteristics. The findings are expected to provide clinically relevant information regarding the effectiveness and reliability of these restorative materials in posterior teeth.

Inclusion Criteria:

• Patients aged 18 years and older
• Patients in good general health (systemically healthy)
• Patients with good oral hygiene
• Patients with good periodontal health
• Presence of at least one posterior tooth requiring restoration
• Teeth must be vital and asymptomatic
• Teeth must have proximal contact with adjacent teeth on both mesial and distal surfaces
• Teeth must be in functional occlusion with an antagonist tooth
• Presence of at least one carious lesion not extending deeper than two-thirds of dentin, with a clinical ICDAS code ≤ 3
• Absence of periapical pathology confirmed by radiographic evaluation
• Patients who voluntarily agree to participate and provide written informed consent

Exclusion Criteria:

• Presence of any systemic disease
• Poor oral hygiene
• Presence of active or severe periodontal disease
• Teeth with previous restorations or endodontic treatment
• Non-vital (devitalized) or symptomatic teeth
• Patients who are pregnant or breastfeeding
• Patients undergoing active orthodontic treatment
• Presence of parafunctional habits (e.g., bruxism) or xerostomia
• Current tobacco use or history of heavy smoking
• Patients unwilling or unable to attend follow-up visits

Participants and outcome assessors will be blinded to the group allocation. The operator performing the restorations will not be blinded due to the different handling characteristics and application procedures of the tested bulk-fill composite materials.