Healing of maxillary alveolus in transport distraction osteogenesis for partial maxillectomy.
OBJECTIVE
This study aims to evaluate histologic healing of the new bone and soft tissue in the distraction gap of maxillary alveolus after transport distraction at different consolidation intervals.


METHODS
In a monkey model, dentoalveolar segment was distracted backward to a surgical defect in the posterior maxilla with an internal distractor at a rate of 1 mm/day for 2 weeks. The distracted dentoalveolar processes were harvested at 1, 2, and 3 months of consolidation after the completion of distraction. Histologic examination included the new bone, gingiva of the distraction gap, and teeth carrying the transport segments. Tartrate-resistant acid phosphatase was used to assess the presence of osteoclasts in the new bone. The collagen type and expression of bone morphogenetic proteins (BMPs) in the new bone were assessed by immunohistochemistry.


RESULTS
The histology confirmed new bone bridging the distraction gap at 1 month of consolidation. Woven bone was progressively replaced by mature lamellar bone at the second and third months. The gingiva covering the distraction gap was of normal appearance. There were no pathologic pulpal changes noted in the transport segment. Tartrate-resistant acid phosphatase-positive osteoclasts were minimal in the new bone. The mode of ossification was confirmed as intramembranous, and the fibrous stroma consisted mainly of collagen type I. At 1 month of consolidation, the BMPs were expressed profusely in the fibrous matrix and also inside the fibroblasts and osteoblasts. At 2 and 3 months of consolidation, the BMP expression intensity was reduced significantly in the fibrous stroma.


CONCLUSIONS
The study confirmed that the bone regenerate in maxillary transport distraction was formed by intramembranous ossification and teeth in the transport segment remain viable after maxillary transport distraction osteogenesis.
Cheung
Lim K
LK
Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, The University of Hong Kong, Hong Kong SAR, People's Republic of China. lkcheung@hkucc.hku.hk
Zhang
Qian
Q
D000539:Alveolar Process / Q000502:physiology / Q000601:surgery*; D000818:Animals; D019485:Bone Morphogenetic Proteins / Q000032:analysis / Q000096:biosynthesis*; D001861:Bone Regeneration / Q000502:physiology*; D024042:Collagen Type I / Q000096:biosynthesis; D024043:Collagen Type II / Q000096:biosynthesis; D005881:Gingiva / Q000502:physiology; D007124:Immunoenzyme Techniques; D008253:Macaca mulatta; D008297:Male; D008437:Maxilla / Q000601:surgery*; D010006:Osteoblasts / Q000378:metabolism; D010010:Osteoclasts; D019857:Osteogenesis, Distraction
D019485:Bone Morphogenetic Proteins; D024042:Collagen Type I; D024043:Collagen Type II