Healing masseter entheses of mandibular reconstruction with autograft--Raman spectroscopic and histological study

Autogenous bone graft represents the gold standard for mandibular reconstruction. The authors used a beagle mandibular defect model and reconstructed with iliac crest and ulna graft. Healing masseter entheses were harvested 24 weeks after surgery and analyzed by histology and Raman microspectroscopy. The intensity ratio of 960/2940 was to document mineral-to-collagen ratio as degree of mineralization. Pearson correlation was used to evaluate the association between the intensity ratios of 960/2940 and the tendon-to-bone insertion site. In the normal control group (n=4) and the experimental control group with detached masseter muscle (n=4), the degree of mineralization at the insertion site increased linearly from tendon to bone. In the iliac graft (n=4) and ulna graft groups (n=4), healing entheses were far less mature than controls and a linear trend was not observed. There was no significant correlation between degree of mineralization and insertion site in the ulna group (r(spearman)=0.519, P>0.001). These results indicate that transplanted bone plays a critical role in healing of entheses and healing enthesis to reconstructed mandible is inferior to normal. Raman spectroscopy provides quantitative information about different healing entheses and gives valuable insight into mechanical properties of entheses in functional mandibular reconstruction.