OBJECTIVEThe purpose of this study was to observe the roentgenographic characters of distraction osteogenesis (DO) correction of cleft palate (CP), to study the expression of BMP proportional to fixation period time intervals, and to explore the new bone formation mechanism in Cleft Palate bone shelf.

METHODS12 cats were used to establish the CP animal model surgically, and then were assigned randomly to (1) Experimental group (12 cats): CP defects were DO repaired at the rate and rhythm of 0.4 mm x 2/day. Specimen retrieval at 2, 4, 6, 8, 12 weeks after completion of distraction, roentgenography and Anti-BMP immunohistochemistry studies were performed; (2) Experimental control group (2 cats): CP defects without any treatment procedures, and (3) Empty control group of 2 cats.

RESULTSAnti-BMP immunohistochemistry study showed positive DAB dye in early 2 weeks and most extensively positive expression of BMP in 4 to 6 weeks. The expression of BMP wore off gradually through 8 to 12 weeks. The roentgenography showed that the newly mineralized bone was developed from the cut bone edges bilaterally to the central transparent zone, and the newly formed bone bridged the defect area completely at the end of the study. The CP bone defect was reconstructed and the distraction gap was filled with de nove osteogenesis. No new bone formation was observed in experimental control group.

CONCLUSIONThe process of new bone formation in the distraction area is dynamic. Being stimulated primarily, the process was kept highly active till quiescence phase finally. The X-ray examination shows that there is distinctively low roentgenopeque. Nevertheless, roentgenography is so far a very effective and convenient method to evaluate and monitor the DO correction efficiency.