Digitally Guided Transcrestal Sinus Floor Elevation Using Collagenated Synthetic Hydroxyapatite or Collagenated Xenograft: Histologic and Volumetric Comparison.

Objectives This study evaluated clinical, radiographic, and histological outcomes after digitally guided transcrestal maxillary sinus floor elevation using two bone substitutes: a composite of cross-linked collagen with synthetic hydroxyapatite (test) and a collagen-enriched bovine-derived bone substitute (control). Methods In a prospective controlled trial, 26 patients with <5 mm residual bone height underwent digitally guided transcrestal sinus augmentation using test or control biomaterial, followed by staged implant placement after six months (T1). Bone cores were harvested during implant site preparation for histological analysis using a dedicated surgical guide. Radiographic volumetric and linear changes were evaluated on pre- and post-operative CBCT scans. Data were analyzed using Mann-Whitney U-test, Kruskal-Wallis, and Fisher's exact tests. Results At T1 both groups achieved significant graft volume gain with no intergroup difference. The test group showed a higher percentage of newly-formed bone (31.6 ± 21.6% vs. 18.2 ± 16.0%; p = 0.004) and lower residual graft (2.2 ± 6.3% vs. 6.2 ± 6.8%; p = 0.003). Inflammatory infiltration was lower in the test group (p < 0.001). Significant differences in residual graft distribution among biopsy regions were found only in the test group (p = 0.03). Conclusions The cross-linked collagen/synthetic hydroxyapatite scaffold promoted greater bone regeneration with lower graft remnants than the collagen-enriched xenograft. The digital workflow was used to standardize surgical planning, guided crestal access, biopsy harvesting, and implant placement, supporting procedural consistency in the histological assessment. Clinical Significance Both biomaterials supported bone regeneration after staged transcrestal sinus floor elevation. The synthetic hydroxyapatite scaffold showed more newly-formed bone and a lower percentage of area occupied by residual graft material at 6 months, but the clinical significance of these preliminary findings requires confirmation in larger randomized studies with long-term follow-up.