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[Application of computer-aided virtual mandibular position in the simultaneous treatment of children with temporomandibular joint ankylosis and jaw deformity].

OBJECTIVE
To evaluate the feasibility of computer-aided design virtual mandibular position in the simultaneous treatment of children with temporomandibular joint ankylosis (TMJA) and jaw deformity.


METHODS
The children with unilateral TMJA were surgically treated from January 2016 to June 2017 in the Department of Oral and Maxillofacial Surgery. The image data of jaw and dentition were imported into the computer software to simulate the surgical procedure. An osteotomy of the affected side was performed to remove ankylosed bone mass. Then the mandible was rotated around the unaffected condyle to eliminate the chin deviation by the virtual plan. An open bite was thus created on the affected side to provide space for vertical midfacial growth. In the virtual mandibular position, the affected ramus was reconstructed with costochondral grafting. Finally, digital occlusal splint was designed and prefabricated by 3D printing. During surgery, temporomandibular joint ankylosis was released and mandibular position was guided in place by the digital occlusal splint. In the new mandibular position, costochondral grafting was completed. After the surgery, the occlusal splint was wired to the mandibular dentition and would be gradually adjusted by grinding off the maxillary side to promote downward growth of the maxilla until the open bite was eliminated. The ramus height and chin deviation were measured before and one week after the surgery to validate the method. Comparisons of the measurements were made by means of a repeatedmeasures analysis of variance (ANOVA) (P=0.05). Pairwise multiple comparisons were conducted using the Bonferroni correction (P=0.05).


RESULTS
Five patients were included in this study. Under the guidance of the digital occlusal splint, the mandible could reach the preoperative designed position smoothly in all the cases. The chin deviations were (0.58±0.20) mm in the virtual plan before surgery, and (0.70±0.27) mm after surgery, which were not significant statistically (P>0.05). The ramus heights on the affected side were (48.19±3.20) mm in the virtual plan before surgery, and (48.17±3.62) mm after surgery, which were not significant statistically (P>0.05).


CONCLUSION
It is feasible and reliable in the simultaneous treatment of TMJA with jaw deformity under the guidance of virtual mandibular position.