The effect of bone loss on rod-like and plate-like trabeculae in the cancellous bone of the mandibular condyle.

Bone loss may affect the structure of cancellous bone. But its effect on trabeculae with different characteristics, like rods and plates, is not accurately known. This study analyzes the effect of bone loss on individual rod-like and plate-like trabeculae. 94 specimens were obtained from mandibular condyles from both dentate and edentate humans and scanned with a micro-CT scanner. The bone volume fraction (BV/TV) of these specimens ranged from 7% to 30%. Next, the rod-like and plate-like trabeculae were identified with an especially developed algorithm. Plate volume fraction (PV/TV), rod volume fraction (RV/TV), plate thickness, rod thickness, number of plates, and number of rods were determined. In individual specimens, the thickness of the rods ranged from 40 mum to 180 mum, while the thickness of the plates ranged from 40 mum to 300 mum. In every specimen, the thickness of the plates was larger than the thickness of the rods. Statistical analysis revealed that PV/TV was proportional (r = 0.98, P < 0.001) and RV/TV inversely proportional (r = -0.45, P < 0.001) to BV/TV. Also the thickness of the plates correlated with BV/TV (r = 0.62, P < 0.001), while the thickness of the rods (mean = 90 mum, SD = 7 mum) remained constant (r = -0.09, P = 0.378). A four-fold reduction of the bone volume fraction was accompanied by a three-fold reduction of the number of plates and a 40% reduction of their thickness, but also by a three-fold increase in the number of rods and RV/TV. It was concluded that the effect of bone loss on plate-like trabeculae was opposite to its effect on rod-like trabeculae. Remarkably, the thickness of the rods (90 mum) was independent of the bone volume fraction. This suggests that there is a minimal thickness for trabeculae.