Aim/objective/purpose: To present a novel guided bone regeneration (GBR) concept that consists of combining Boneject ^® (a biomaterial containing atelocollagen and bovine hydroxyapatite particles) with thermoplastic, bioresorbable plates (DeltaSystem ^® ) known to resist mechanical loading.

Materials and methods: In rat calvariae, standardized bone defects were filled with Boneject ^® and covered with a convex DeltaSystem ^® plate. Histology assessments were conducted at 1, 2, 4, 8, and 12 weeks post-operatively.

Results: At 1 week, alkaline phosphatase (ALP)-negative cells deriving from the bottom region of the defect could be found up to half the height of the cavity. Boneject ^® particles at the bottom region revealed intense osteopontin immunopositivity on their surfaces whereas those at the upper region did not. Tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts accumulated on the surfaces of osteopontin-coated particles. A newly formed, woven-like bone featuring ALP-positive osteoblasts extended from the native bone. At the second week, newly formed woven bone had surrounded the Boneject particles. Four weeks after surgery, the new bone had reached the height of the DeltaSystem ^® plate, and just beneath it a periostin-positive fibrous layer covered the mix of new bone and Boneject ^® particles. By then, despite having acceptable histological features, electron probe microanalyzer (EPMA) and transmission electron microscope (TEM) analyses revealed that the new bone could not be regarded as compact bone. At 8 and 12 weeks, the new bone showed compact bone-like features according to TEM and EPMA assessments.

Conclusions: The combination of hydroxyapatite and a thermoplastic bioresorbable plate appears to promote desirable osteoconduction and bone remodeling, resulting in compact bone formation.

Conflict of interest: None declared.