Compression Induces Sutural Osteogenesis Instead of Net Bone Resorption

Clinical medicine and dentistry subscribe to the notion that macroscopic tension leads to bone formation, and compression leads to bone resorption. Objectives: Here we examined this notion by coupling known exogenous forces and intrinsic mechanical strain from our previous work with the present model of chronic delivery of the same compressive loads. Methods: An in vivo rabbit model consisting of seventeen, 6-week-old, male NZW rabbits was established for daily delivery of compressive forces under general anesthesia for 10 minutes per day over 12 days. Two types of compressive forces with the same peak magnitudes of 5 Newtons were delivered to the maxilla: static forces at 0 Hz with 1 cycle per day (cpd) and dynamic forces at 1 Hz with 600 cpd. Results: Histomorphometric analysis revealed that the average linear length of the premaxillomaxillary sutures treated with dynamic forces at 1 Hz (89.5±13.8 microns) was significantly greater (p < 0.01) than sham controls (69.8±16.3 microns) and static forces of matching peak magnitude and duration (58.9±7.4 microns). Cell counting averaged from 110×110 micron grids laid over sutures disclosed significantly more osteoblast-like and fibroblast-like cells of dynamically treated samples (50.5±8.8) (p < 0.01) than sham controls (38.4±5.2) and statically treated samples (38.5±5.5). Although a small number of osteoclast-like cells were present between sutural connective tissue and bone, there were many islands of newly formed woven bone along with marked angiogenesis in association with treated samples. Conclusions: Taken together, these findings suggest that albeit the same peak magnitude, dynamic forces induce more sutural osteogenesis than static forces, and thus form the basis for an alternative hypothesis that compressive forces lead to osteogenesis in cranial sutures instead of net bone resorption. Supported by Whitaker Biomedical Engineering Research Grant and NIH grants, DE 13964 and DE13088.