Objective To scan and accurately reconstruct mandible models printed via fused deposition modeling(FDM)that contain screw path information,using cone-beam CT(CBCT),to achieve the digital transfer of preoperative model screw paths.Methods CBCT scans were conducted on 12 FDM-printed mandibular models(Model1 group)intended for prebending reconstruction plates.Mim-ics software was employed to reconstruct scanned data into mandibular models(Model2 group)and extract digital screw path informa-tion.Model2 was then compared with original models(Model0 group)in three dimensions,evaluating reconstruction accuracy through root mean square(RMS).Reconstruction parameters were optimized to enable automatic matching of Model2 with Model0,facilitating precise digital transfer of screw paths.In clinical application,this method was utilized to produce digital short-segment drilling guides,assisting in the reduction surgery of three mandibular fracture patients.Results Model2 demonstrated automatic matching with Model0,exhibiting detailed surface characteristics and clear screw path position and orientation information.The RMS was measured at(0.32±0.09)mm.Utilization of digital segmented screw path transfer guides assisted in the satisfactory reduction surgery of three pa-tients with comminuted mandibular fractures.Conclusion CBCT scanning of FDM-printed preoperative models accurately captures screw path position and orientation information,enabling digital transfer of screw paths and providing a novel method for precise design of digital surgical guides.

Objective To scan and accurately reconstruct mandible models printed via fused deposition modeling(FDM)that contain screw path information,using cone-beam CT(CBCT),to achieve the digital transfer of preoperative model screw paths.Methods CBCT scans were conducted on 12 FDM-printed mandibular models(Model1 group)intended for prebending reconstruction plates.Mim-ics software was employed to reconstruct scanned data into mandibular models(Model2 group)and extract digital screw path informa-tion.Model2 was then compared with original models(Model0 group)in three dimensions,evaluating reconstruction accuracy through root mean square(RMS).Reconstruction parameters were optimized to enable automatic matching of Model2 with Model0,facilitating precise digital transfer of screw paths.In clinical application,this method was utilized to produce digital short-segment drilling guides,assisting in the reduction surgery of three mandibular fracture patients.Results Model2 demonstrated automatic matching with Model0,exhibiting detailed surface characteristics and clear screw path position and orientation information.The RMS was measured at(0.32±0.09)mm.Utilization of digital segmented screw path transfer guides assisted in the satisfactory reduction surgery of three pa-tients with comminuted mandibular fractures.Conclusion CBCT scanning of FDM-printed preoperative models accurately captures screw path position and orientation information,enabling digital transfer of screw paths and providing a novel method for precise design of digital surgical guides.

BACKGROUND:It is necessary to carry out multiple operations to remove the scar in patients with large area of scar, and whether the scar tissue can be recycled has become the focus of the study. OBJECTIVE:To compare the tissue structure, biomechanical properties and biocompatibility of the acel ular dermal matrix of mature scar tissue and normal skin. METHODS:The acel ular dermal matrix was prepared from the human mature scar tissue and the normal skin around the scar. Subsequently, histological and scanning electron microscope observations were performed, and biomechanical properties were detected using universal tensile testing machine. Then, the acel ular dermal matrix from mature scar tissue and normal skin was co-cultured with fibroblasts for 10 days, respectively, and the cel growth curve was drawn. Additional y, the acel ular dermal matrix from mature scar tissue and normal skin was subcutaneously implanted into the dorsal tissue of Sprague-Dawley rats, respectively and histological observation was conducted at 4, 8 and 12 weeks after implantation. RESULTS AND CONCLUSION:There were many gaps but no cel ular components in the acel ular dermal matrix, in both two groups. Col agen fibers of the acel ular dermal matrix derived from mature scar were looser than that of the normal skin, and arranged slightly irregularly;the biomechanical properties of the acel ular dermal matrix derived from mature scar were similar to that of the normal skin, which exhibited appropriate flexibility and strength. There was no significant difference in the growth state of the two kinds of acel ular dermal matrix, and the growth curve was basical y consistent. After 4 weeks of implantation, more inflammatory cel s infiltration could be found in the mature scar group, and in contrast, only a few inflammatory cel s infiltration appeared in the normal skin group, These inflammatory reactions disappeared with time in both two groups. Besides, col agen fibers arranged in neat, and smal vessels grew into the implants in both two groups. In conclusion, the tissue structure, biomechanical properties and biocompatibility of the acel ular dermal matrix derived from scar tissue are almost consistent with those of the human normal skin.