Effect of β-tricalcium phosphate grafting on implant stability and peri-implant radiodensity following immediate implant placement in sites with jumping gaps exceeding 2 mm: a randomized controlled trial

Abstract Background Whether grafting peri-implant jumping gaps exceeding 2 mm during immediate implant placement improves outcomes remains uncertain. This trial evaluated the effect of β-tricalcium phosphate (β-TCP) grafting on implant stability and peri-implant radiodensity in such sites. Methods In this prospective, parallel-group randomized controlled trial, 16 patients (8 per group) receiving 39 immediate maxillary anterior/premolar implants at sites with a jumping gap exceeding 2 mm were randomized 1:1 to no grafting (control) or injectable β-TCP (test); the patient was the unit of analysis. The pre-specified primary comparison was implant stability quotient (ISQ) at 6 months. Peri-implant radiodensity was monitored on standardized periapical radiographs (grayscale value) at baseline, 3, and 6 months, and quantified by cone-beam CT (CBCT) at 6 months only (ALARA principle); CBCT values are relative, arbitrary gray-value radiodensity, not true Hounsfield units. Between-group differences were analyzed with independent-samples t tests, within-group changes with repeated-measures ANOVA, and group×time interactions with mixed-design ANOVA (α = 0.05). Results No statistically significant between-group differences were detected in baseline age or jumping-gap width. No significant between-group difference in ISQ was detected at any time point, and the ISQ group×time interaction was not significant ( p = 0.49); ISQ increased significantly over time in both groups. Periapical grayscale value increased significantly faster in the test group on unadjusted analysis (group×time interaction, p = 0.009), but this was no longer significant after adjusting for a small baseline difference (ANCOVA, p = 0.39). On 6-month CBCT, radiodensity was significantly higher in the test group (1224.0 ± 237.0) than control (931.9 ± 100.4 arbitrary units; mean difference 292.1; 95% CI 87.7 to 496.5; p = 0.010), a secondary outcome not included in the a priori sample-size calculation. Conclusions β-TCP grafting of jumping gaps exceeding 2 mm did not significantly affect ISQ or baseline-adjusted periapical grayscale value. The test group showed significantly higher 6-month CBCT-derived radiodensity, but this was not prospectively powered and may partly reflect residual graft material, so it should be interpreted cautiously. Larger, adequately powered equivalence trials are needed before conclusions about grafting necessity can be drawn. Trial registration ClinicalTrials.gov, NCT07709676. Registered 2026-07-12. Retrospectively registered.