Stretch force guides finger-like pattern of bone formation in suture

Abstract

Mechanical tension is widely applied on the suture to modulate the growth of craniofacial bones. Deeply understanding the features of bone formation in expanding sutures could help us to improve the outcomes of clinical treatment and avoid some side effects. Although there are reports that have uncovered some biological characteristics, the regular pattern of sutural bone formation in response to expansion forces is still unknown. Our study was to investigate the shape, arrangement and orientation of new bone formation in expanding sutures and explore related clinical implications. The premaxillary sutures of rat, which histologically resembles the sutures of human beings, became wider progressively under stretch force. Micro-CT detected new bones at day 3. Morphologically, these bones were forming in a finger-like pattern, projecting from the maxillae into the expanded sutures. There were about 4 finger-like bones appearing on the selected micro-CT sections at day 3 and this number increased to about 18 at day 7. The average length of these projections increased from 0.14 mm at day 3 to 0.81 mm at day 7. The volume of these bony protuberances increased to the highest level of 0.12 mm3 at day 7. HE staining demonstrated that these finger-like bones had thick bases connecting with the maxillae and thin fronts stretching into the expanded suture. Nasal sections had a higher frequency of finger-like bones occuring than the oral sections at day 3 and day 5. Masson-stained sections showed stretched fibers embedding into maxillary margins. Osteocalcin-positive osteoblasts changed their shapes from cuboidal to spindle and covered the surfaces of finger-like bones continuously. Alizarin red S and calcein deposited in the inner and outer layers of finger-like bones respectively, which showed that longer and larger bones formed on the nasal side of expanded sutures compared with the oral side. Interestingly, these finger-like bones were almost paralleling with the direction of stretch force. Inclined force led to inclined finger-like bones formation and deflection of bilateral maxillae. Additionally, heavily compressive force caused fracture of finger-like bones in the sutures. These data together proposed the special finger-like pattern of bone formation in sutures guided by stretch force, providing important implications for maxillary expansion.

The effect of cetirizine, a histamine 1 receptor antagonist, on bone remodeling after calvarial suture expansion

“…19,20 Several animal studies have shown that tensional forces progressively widen the sutures and that cartilaginous tissue is replaced by new bone formation in irregular patterns that parallel the stretching force. 21,22 In this study, the histological evaluations showed finger-like projections of new non-lamellar bone starting from the ends of the parietal bones and extending irregularly towards the center of the expanded sutures; this was similar to the findings of previous studies using expansion devices on rat sutures. 21,23 Bone remodeling occurs via sequential steps that are mediated by osteoclasts resorbing old bone and osteoblasts depositing new bone.…”

“…21,22 In this study, the histological evaluations showed finger-like projections of new non-lamellar bone starting from the ends of the parietal bones and extending irregularly towards the center of the expanded sutures; this was similar to the findings of previous studies using expansion devices on rat sutures. 21,23 Bone remodeling occurs via sequential steps that are mediated by osteoclasts resorbing old bone and osteoblasts depositing new bone. Histamine has been reported to promote osteoclastogenesis by acting on the differential expression of histamine receptors on osteoblasts and osteoclasts.…”

Bone remodeling induced by mechanical forces is regulated by miRNAs

“…Both compressive force and hypoxia may initiate osteoclastogenesis during OTM [ 28 ]. Heavy compression causes bone fracture of finger-like patterns [ 29 ]. TNF-α levels are higher on the compression side of periodontal ligament fibroblasts than on the tension side, which may influence RANKL expression during OTM [ 30 ].…”

T cells participate in bone remodeling during the rapid palatal expansion

“…Palatal expansion has been widely used for the transverse discrepancy or maxillae hypoplasia, which is the main approach to stimulate bone regeneration around the suture area during orthodontics treatment 1‐3 . Palatal expansion is based on mechanical force‐induced bone remodeling, 4,5 but its underlying biological mechanisms remains largely unknown. It has been reported that osteoclasts played a crucial role during orthodontic tooth movement (OTM) and palatal expansion process 6,7 .…”