Magnesium Resorbable Membrane for Guided Bone Regeneration in Critical Size Defect Model in Rabbits-Histomorphometric Analysis

Abstract

Objectives: To evaluate the effectiveness of a Mg-based membrane as a barrier for guided bone regeneration in rabbits calvaria.

Materials and methods: Nine rabbits had four critical size defects created in each calvarium, randomly filled with a blood clot or bovine xenograft. One side was covered with the Mg-based membrane, and the control was left without membrane. After 8 weeks, histomorphometric analysis was performed to compare new bone formation with the pristine bone.

Results: Mg-supported membrane for guided bone regeneration (GBR) is safe and promotes bone formation in critical size defects (CSD) in a rabbit calvaria. Gas accumulation was observed in a third of the specimens due to membrane degradation. Histomorphometric analysis revealed greater bone formation in the defects grafted with the Mg membrane (4.85 ± 1.73 mm²) compared to the blood clot (2.14 ± 2.22 mm²). Treating lesions with filler or the magnesium membrane resulted in significantly higher bone formation in all three examined regions (25%-62%). New bone formation was observed beyond the original bone envelope.

Conclusion: Mg-based membrane supports guided bone regeneration (GBR), and when used in combination with a bone graft, enhances the performance despite the gas accumulation associated with membrane degradation.

Clinical relevance: Limited data exist on the use of Mg-based membranes in GBR and its effect on bone formation.

Keywords: critical size defects; guided bone regeneration; histomorphometry; magnesium; rabbits calvaria model; resorbable membrane.

FIGURE 1

The surgical procedure: (A) The calvaria model: the four groups within each calvaria. One defect on each side was filled with either blood or graft material. (B) The full thickness flap was elevated. (C) Four CSDs (8 mm diameter), two defects on each side. (D) One side was covered with fixed Mg‐membrane. (E,F) Sutures.

FIGURE 2

(A) Schematic representation of the histologic section shows that the section passes through the center of the defect (indicated by the red dashed line). Each defect was divided into outer, middle, and inner regions, as well as the surrounding pristine bone (the periphery). All parts had equal thickness R, where R was calculated as the defect diameter divided by 6. (B) The histologic slides were calibrated (with the light blue line representing 5 mm), and the area of the bone tissue stained with toluidine blue was calculated.

FIGURE 3

Histological section of an FM‐defect: (A) red asterisks indicate the gas voids, and the yellow arrows indicated the membrane residuals. (B) A cavity formed where the membrane was biodegraded (marked by the red dashed lines) and the filler material compressed. New bone forms in that cavity; the yellow arrows indicate the membrane residual. (C) There is less bone formation observed in this specimen.

FIGURE 4

Histological slices from the same specimen: (A) The F&M‐defect and (B) the M‐defect. Notice the red arrow on the new formed bone from the pristine bone. (C) The F‐defect and (D) the B‐defect. A bone bridge can be seen in both grafted defects.

FIGURE 5

(A) A diagram that illustrates the area around the fixation screw (indicated by the red dashed line), which is a non‐grafted area where the fixation screw was inserted to fix the membrane, and the membrane underwent biodegradation. (B) The histologic slide stained with toluidine blue; the red dashed line marks the boundary of the pristine bone. The bone formation outside the bone envelope, around the fixation screw.

FIGURE 6

(A) Histomorphometric results: mean and standard deviation of the ratio of bone formation within each area. The red lines mark significant differences. (B) Total and standard deviation of bone area by histomorphometry.