| Background:With the rapid development of digital technique,the stimulation process of orthognathic model surgery went through the traditional one to the virtual one.With three-dimension data materials,the virtual model surgery makes the surgery plan much more accurate.Combining with the three-dimension printing technique,surgeons finally got rid of the fussy process of producing the hand-made occlusal splints,and achieved three-dimension print of the digital splints.Also,other facilities for the cutting and locating purposes generated gradually benefiting from the technique progress.Objective:To analysis the maxilla reposition accuracy of the cutting-locating guides and the digital occlusal splints in Lefort I osteotomies.Materials and Methods:This study evaluated 20 patients with dentofacial deformity involving maxilla between October 2017 and February 2019 at the Department of Dentofacial deformity,the Affiliated Stomatology Hospital,Zhejiang University School of Medicine.Patients were divided into two groups by the type of guides using during the surgery.The pre-surgery CBCT scans,three-dimension photography and dentition scan were collected within one month before the surgery.Virtual surgery simulation was performed by Dolphin imaging,and the design model was produced.The post-surgery CBCT scan was taken again within one week after the surgery.The design model,post-surgery CBCT were superimposed with pre-surgery CBCT according to the anterior skull to unify the orientation of these three materials.Separately,five landmarks(the contact point of the upper incisors,the cusp of left and right canine,the mesial-buccal cusp of left and right first molar)were marked and measurements were calculated according the coordinates of these landmarks.The movement deviation of each landmark,the whole maxilla,sagittal and transverse occlusal plane were compared between the surgery design and post-surgery CBCT.Result:1.For each landmark,there is no statistically significant differences between two groups.Refer to the average deviation,at mediolateral dimension(X axis),the digital splints performed better,while at the vertical dimension(Y axis),the cutting-locating guides exceed the digital splints(except U6R).But,neither of them had a pleasant effect at anteroposterior dimension(Z axis)or distance deviation in three-dimension.2.When calculating the deviation of the whole maxilla,although there were no statistically differences between two groups,the cutting-locating guides had lower average deviations than the digital splints in each dimension and distances in three-dimension.At the vertical dimension,the cutting-locating guides(0.60 ±0.45 mm)had lower deviation than the digital splints(0.88 ± 0.48 mm).As for the distance deviation in three-dimension,the cutting-locating guides(1.74 ± 0.97 mm)also had a better control than the digital splints(2.12 ± 0.91 mm).3.As for the sagittal occlusal plane control,these two groups had no significant differences.But for the control of sagittal anterior occlusal plane,the digital splints(2.66 ± 1.79°)surpassed the cutting-locating guides(3.05 ± 2.24°).When comes to the transverse occlusal plane,at U3 Canting,the digital splints(0.64 ± 0.28 mm)performed extremely better than the cutting-locating guides(1.31 ± 0.84 mm)with a significant difference(P = 0.044),although there is no significant difference at U6 Canting.Conclusion:The digital splints had a good control at mediolateral dimension and anterior occlusal plane,while the cutting-locating guides performed better in vertical dimension and distance deviation in three-dimension.Both of them need improvement in anteroposterior dimension control. |
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