Composite resin materials are the first treatment choice in direct restorations due to their good mechanical properties, excellent esthetic properties, conservative preparation, and successful clinical performance. However, resin-based composite materials in deep cavities are more likely to irritate the pulp tissue due to insufficient polymerization and residual monomer release. Therefore, glass ionomer-based restorative materials can be used more successfully in deep cavities. In addition, the hardening mechanisms of high-viscosity glass ionomer cement are the same as those of conventional glass ionomer cement, and their wear resistance, surface hardness, compression, and bending strength are increased. No clinical studies evaluate the performance of different restorative materials in deep cavities. This clinical study aims to evaluate the clinical performance of high-viscosity glass ionomer, bulk-fill composite, and conventional composite in deep cavities.

This study was a double-blind (evaluator and patient) randomized controlled clinical study with three study groups with an equal allocation. Three different restorative materials were compared in deep cavities.

The treated patients were called back for controls after one week, six months, and twelve months. Restorations were evaluated clinically according to modified FDI criteria (marginal discoloration, color match, anatomical form, fracture and retention, marginal adaptation, contact point, post-operative sensitivity, secondary caries and periodontal response).

Clinical evaluation was performed by one qualified clinicians using a mirror and probe under reflector light. Bite-wing radiographs were taken from the patients who were called for controls at 6-moth and 12-month to evaluate the formation of secondary caries.

Differences between adhesives at each time period were evaluated using Fisher's Exact test. The effect of time on restorations was evaluated using Wilcoxon Signed rank test (p < 0.05).

Inclusion Criteria:

• Systemically healthy patients aged 18 and over
• Patients with good oral hygiene.
• Vital teeth are to be included in the study.
• The presence of an antagonist and a contact tooth for the tooth to be restored.
• Teeth with deep caries lesions or radiographically reaching ¾ of the dentin but with a hard dentin region between the caries and the pulp according to ESE (European Society of Endodontology) criteria.

Exclusion Criteria:

• Patients with a history of bruxism and periodontal disease
• Patients under 18 years of age
• Spontaneous pain in the tooth to be restored
• Intense carious lesion reaching the entire thickness of the dentin according to ESE (European Society of Endodontology) criteria
• Observation of mechanical perforation during caries cleaning
• Patients suspected of pregnancy or pregnant

The characteristics of the teeth were recorded before the restorative procedures. Periapical radiographs were used to determine the status and extent of caries and any potential periodontal or periapical pathology that might require endodontic treatment. The treated teeth were vital, asymptomatic, and in occlusal contact. As a result of the clinical and radiographic evaluations, teeth with deep caries lesions according to the ESE (European Society of Endodontology) criteria or those with radiographically reaching ¾ of the dentin but with a hard dentin zone between the caries and the pulp were included in the study.