Magnesium-enriched hydroxyapatite versus autologous bone in maxillary sinus grafting: combining histomorphometry with osteoblast gene expression profiles ex vivo

Abstract

Background: Many biomaterials are proposed for sinus floor lifting and grafting in the posterior maxilla for insufficient bone volume (BV). The aim of this study was to compare the use of magnesium-enriched hydroxyapatite (mHA) versus autogenous bone graft (AB) for maxillary sinus lift procedures by histomorphometric and ex vivo gene expression profiling.

Methods: Fifteen patients requiring bilateral maxillary sinus augmentation received autologous bone particles (group A) and mHA (group B) (split-mouth design). Five months later, implants were placed, and biopsies were obtained. Bone specimens were analyzed by histomorphometry, BV and vital bone (VB) percentages were calculated, and ex vivo osteoblast expansion followed by highly sensitive osteoblast specific gene expression profiling for cbfa1, osteocalcin, osteopontin, collagen type I, receptor activator of nuclear factor-kappa B ligand (RANKL), and osteoprotegerin (OPG) by quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR) were performed. Comparisons were made using the Student t test.

Results: After healing with no complications, BV was comparable in the two groups (80.79% +/- 14.27% for autologous versus 76.72% +/- 11.47% for mHA; P = not statistically significant), but VB was lower in the mHA group (29.65% +/- 9.81% versus 78.40% +/- 16.72%; P <0.05). Real-time RT-PCR analyses showed significantly higher expression of the osteoblast differentiation factor Cbfa1 and the matrix formation marker osteocalcin in the mHA group compared to the AB group, whereas type I collagen was comparable, and osteopontin was decreased. Attesting to a lower osteoclastogenic potential, the RANKL/OPG ratio was diminished.

Conclusions: Autogenous bone samples provided higher vital over comparable total bone levels than mHA-grafted sites. Osteoblast gene expression profiles from mHA grafts revealed higher expression of certain specific markers of osteoblast differentiation and bone formation, associated with a lower osteoclastogenic potential.