PICN Versus Bioactive Composite for Cervical Restorations in Ballet Dancers

This prospective, split-mouth, randomized controlled trial was conducted at the Centre for Sports and Ballet Trauma and Rehabilitation of the Priorov National Medical Research Centre of Traumatology and Orthopaedics (Moscow, Russian Federation) in collaboration with the Borovskiy Institute of Dentistry, Sechenov University. The protocol was approved by the Local Ethics Committee of Sechenov University (Protocol No. 22-21, 9 December 2021) and followed CONSORT 2010 and OHStat guidelines.

Participant recruitment and screening:

Professional ballet dancers (current or retired, ≥10 years of professional experience, aged 18-50 years) were screened for the presence of at least two non-adjacent cervical defects (Class V carious or abfraction) located in different quadrants. Each defect had a depth ≥1.5 mm and width ≤4 mm. Teeth had to be vital, with probing depth ≤3 mm and no pulpal pathology. Exclusion criteria included severe bruxism requiring occlusal splint, uncontrolled systemic disease, pregnancy/lactation, known allergy to study materials, and inability to attend follow-up.

Randomization and blinding:

A computer-generated randomization sequence (1:1 allocation, block size 4) assigned the two materials to the two defects within each participant. Allocation was concealed using sequentially numbered, opaque, sealed envelopes opened immediately before the procedure. Participants and the outcome assessor (calibrated dentist) were blinded to material assignment; the operating dentist could not be blinded due to handling differences.

Restorative procedures (detailed):

All restorations were placed by a single operator under local anesthesia (4% articaine with epinephrine 1:100,000).

PICN group (VITA Enamic): After minimally invasive cavity preparation (caries removal and etching for carious defects; no preparation for abfraction), a polyvinyl siloxane impression was taken. PICN inlays were fabricated in a dental laboratory. At a second visit, the inlay was bonded with dual-cure resin cement (G-CEM ONE) following the manufacturer's instructions.

Self-curing composite group (Stela, SDI): The two-step protocol was applied: Stela Primer for 15 seconds, followed by bulk placement of Stela (single increment). No light curing was used. After setting, finishing was performed with fine diamond burs and polishing discs.

Outcome assessment schedule:

Patients were recalled at 6, 12, and 24 months post-restoration. Two calibrated, blinded examiners (intra-examiner kappa=0.86, inter-examiner kappa=0.82) independently assessed:

Marginal integrity using modified USPHS criteria (Alpha, Bravo, Charlie, Delta; failure = Charlie or Delta).

Dye penetration (Borovsky-Aksamit test): 2% methylene blue applied for 2 minutes, rinsed, and scored as present/absent.

Secondary caries (clinical + radiographic).

Postoperative hypersensitivity (Visual Analogue Scale, 0-100 mm).

Oral Health Impact Profile-14 (OHIP-14) at baseline, 6, 12, and 24 months.

Statistical analysis summary (detailed):

Paired binary outcomes were analyzed using McNemar's test with Holm-Bonferroni correction across three time points (α=0.017) and two co-primary outcomes (α=0.025). Fisher's exact or chi-square tests were used for group comparisons. Kaplan-Meier survival curves with log-rank test compared restoration survival. Subgroup analyses by defect type were exploratory; uncorrected p-values are reported. Sample size (40 defects, 20 per material) was calculated a priori (G*Power) to detect a 30% difference in marginal defects with 80% power, assuming 20% dropout (actual dropout 0%). Analyses followed intention-to-treat.

Data management:

Anonymized data are stored at Sechenov University. No missing data occurred. The dataset is available from the corresponding author upon reasonable request and ethics approval.