J Periodontal Implant Sci.  2010 Aug;40(4):180-187.

Spontaneous healing capacity of rabbit cranial defects of various sizes

• Sohn JY
• Park JC
• Um YJ
• Jung UW
• Kim CS
• Cho KS
• Choi SH

Abstract

PURPOSE
This study evaluated the spontaneous healing capacity of surgically produced cranial defects in rabbits with different healing periods in order to determine the critical size defect (CSD) of the rabbit cranium.
METHODS
Thirty-two New Zealand white rabbits were used in this study. Defects of three sizes (6, 8, and 11 mm) were created in each of 16 randomly selected rabbits, and 15-mm defects were created individually in another 16 rabbits. The defects were analyzed using radiography, histologic analysis, and histometric analysis after the animal was sacrificed at 2, 4, 8, or 12 weeks postoperatively. Four samples were analyzed for each size of defect and each healing period.
RESULTS
The radiographic findings indicated that defect filling gradually increased over time and that smaller defects were covered with a greater amount of radiopaque substance. Bony islands were observed at 8 weeks at the center of the defect in both histologic sections and radiographs. Histometrical values show that it was impossible to determine the precise CSD of the rabbit cranium. However, the innate healing capacity that originates from the defect margin was found to be constant regardless of the defect size.
CONCLUSIONS
The results obtained for the spontaneous healing capacity of rabbit cranial defects over time and the underlying factors may provide useful guidelines for the development of a rabbit cranial model for in vivo investigations of new bone materials.

Keyword

Experimental design; Osseous defect; Wound healing

MeSH Terms

Animals
Islands
Rabbits
Research Design
Skull
Wound Healing

Figure

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  Figure 1 Trephine burs and different sizes of defects (A) The trephines with outer diameters of 6, 8, and 11 mm. (B) The trephine with an outer diameter of 15 mm. (C) Photograph of three standardized circular defects created with diameters of 6, 8, and 11 mm. (D) Photograph of a 15-mm defect, which includes a portion of the sagittal suturing.

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  Figure 2 Schematic diagram of a calvarial osteotomy defect showing the measurement parameters from which the following histometric parameters were determined (with linear and area measurements in millimeters and millimeters squared, respectively): defect closure (%): (b1 + b2)/a × 100, new bone area ratio (%): (B1 + B2)/A × 100, new bone ingrowth (mm): (b1 + b2)/2, new bone area (mm2): B1 + B2 where A represents the area within the dotted lines, corresponding to the total defect area; B1+B2 is the new bone area; and a, b1, and b2 represent the total defect width and the new bone ingrowth from the left and right margins, respectively.

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  Figure 3 Radiographic views of the surgical defects at different healing periods.

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  Figure 4 Histologic views of the surgical defects at different healing periods (H&E stain, × 10). Arrowheads point to the original defect margins, and the arrows show bony islets. The scale bar indicates 10 mm. Defect sizes: (A) 6 mm, (B) 8 mm, (C) 11 mm, and (D) 15 mm.

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