Clinical Performance of Injectable and Conventional Resin Composites in Posterior Class I Restorations

This was a prospective, randomized, assessor-blinded, split-mouth clinical trial conducted at the Department of Restorative Dentistry, Faculty of Dentistry, Van Yüzüncü Yıl University. Systemically healthy individuals with good oral hygiene and at least two carious lesions classified as International Caries Detection and Assessment System scores 4 or 5 in permanent premolars and/or molars were eligible. Individuals with bruxism, malocclusion, xerostomia, or periodontal disease were excluded. Teeth with previous restorations, endodontic treatment, periodontal or periapical pathology, or no antagonist or adjacent tooth were also excluded.

Thirty-eight participants aged 20 to 26 years were enrolled. A total of 120 posterior Class I restorations were placed. Each participant received both study materials in different eligible teeth according to a split-mouth design. The first eligible tooth and the material assigned to that tooth were determined by coin toss, and allocation of the remaining eligible teeth continued clockwise within the dental arches. G-ænial Posterior, a conventional resin composite, was used for 60 restorations, and G-ænial Universal Injectable, a highly filled injectable resin composite, was used for 60 restorations.

All restorations were placed by the same clinician using standardized cavity preparation, adhesive, light-polymerization, finishing, and polishing procedures. Participants were unaware of the material used in each tooth. Clinical assessments were performed by another investigator who was not involved in placing the restorations.

The restorations were evaluated one week, six months, and 12 months after placement using the FDI evaluation system. Esthetic, functional, and biological properties were scored from 1 to 5. Scores of 1 to 3 were considered clinically acceptable, whereas scores of 4 or 5 were considered clinically unacceptable.

Twenty participants with 64 restorations were randomly selected for micromorphological assessment. Digital impressions were obtained at one week, six months, and 12 months. Three-dimensional resin replicas were manufactured and examined by scanning electron microscopy. The visible restoration margins were assessed for marginal integrity, excess material, marginal fractures, negative marginal steps, marginal leakage, and other surface or marginal defects. The examiner performing the micromorphological assessment was blinded to the clinical evaluation results.

Inclusion criteria

• Systemically healthy individuals with good oral hygiene.
• Presence of at least two carious lesions classified as International Caries
• Detection and Assessment System (ICDAS) scores 4 or 5 in permanent premolars and/or molars.
• Teeth suitable for direct Class I resin composite restoration.
• Presence of an antagonist and adjacent tooth for each eligible tooth.
• Provision of written informed consent.

Exclusion criteria

• Bruxism.
• Malocclusion.
• Xerostomia.
• Periodontal disease.
• Previous restoration or endodontic treatment in an eligible tooth.
• Periodontal or periapical pathology involving an eligible tooth.
• Absence of an antagonist or adjacent tooth.