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A Modified Novel Technique for Condylar Positioning in Mandibular Bilateral Sagittal Split Osteotomy Using Computer-Assisted Designed and Computer-Assisted Manufactured Surgical Guides

Current techniques for orthognathic surgery after Le Fort I osteotomy and bilateral sagittal split osteotomy (BSSO) rely on intermediate and final occlusal splints for proper positioning of the dental arches without any control in positioning the condyle and ramus segments. Setting the 2 condyles in centric relation in the glenoid fossae at fixation is paramount for condylar function and the accuracy and stability of postoperative occlusion. Usually the 2 ramus segments are manually positioned and fixated in the final position according to the surgeon's experience. This report describes a novel technique to position the condyle and ramus segments in centric relation using skeletal guides designed by computer-assisted designed and computer-assisted manufactured (CAD-CAM) technology. The skeletal guides have a double-U shape designed to be tooth borne on the distal segment and bone borne on the proximal segment. The guides fit on the last molar crown and the anterior border of the ramus; using these reference points will position the mandibular arch and 2 ramus segments in ideal centric occlusion and centric relation. The condyle position in the sagittal, horizontal, and transverse planes was analyzed by computed tomography and differences in measurements were calculated. This technique confirms precise control of the condylar segment in centric relation with stable centric occlusion using CAD-CAM guides during BSSO.

[Orthognathic surgery of mandibular asymmetry: which results can we expect with and without chin wing? A cohort out of 51 cases]

INTRODUCTION

The aim of this retrospective cohort is to evaluate the amount of postsurgical correction of soft and hard tissues in patients with mandibular asymmetries and to compare the results with and without surgery of the lower mandibular contour (chin wing…).

MATERIAL AND METHOD

Mandibular asymmetries cases of three surgeons were systematically included. The angles of deviation of the chin, bi-commissural, bi-gonic and occlusal were measured on face photography and radiography. A pre and post-surgical comparison was performed and the amount of correction was analyzed via the Wilcoxon statistical test.

RESULTS

51 patients (44 women and 7 men) were included. After surgery, the correction is significant for all measurements with an improvement of 44 to 60% depending on the measured angles. No patient is normalized but the small initial mandibular asymmetries are the closest to normal after surgery. The correction of the bi-commissural angle is controlled without being optimal (60% correction). The difficulty remains the horizontalization of the bi-gonial plan which is only corrected at 45%. Patients with mandibular margin surgery (chin wing…) showed the greatest improvement in bi-gonial (p = 0.0142) and occlusal (p = 0.0154) angles.

CONCLUSION

If surgery allows a significant correction of facial dissymmetry, this is not complete. Surgical procedures on the lower edge of the mandible such as the chin wing could provide a better correction especially for bi-gonial and occlusal angles.

[Surgery First : prediction for skeletal objectives through structural analysis. Comparison of Sassouni and Delaire analysis]

INTRODUCTION

The purpose of this study was to compare two structural cephalometric analysis (Delaire and Sassouni) as surgical decision tools. These two analyses do not include dental compensation for skeletal discrepancies and have been proven reliable especially for the Sendai surgery first protocol developed by Sugawara.

MATERIAL AND METHOD

The two analysis were performed on 20 surgical cases and the proposed skeletal modifications were compared in order to measure the differences and see if those differences varied according to the facial type. For 10 cases the Virtual Surgical Planning (VSP) images obtained from Dolphin 11.95 Premium software (based on the presurgical CBCT and facial photographs) allowed a comparison of the two analyses as surgical decision indicators and to the realised surgical procedure. The VSP photographs obtained were graded by two panels: one professional and the other one non professional.

RESULTS

Sassouni's analysis favored more forward movements for the maxilla (ENA +5,45) as well as more vertical modifications (Me 1,595). The facial type did not appear to have a significant effect. The quality of Dolphin VSP prediction was judged rather reliable above average (3.7/6) by the panels. The VSP photographs obtained from the two analyses were presented to the panels as well as the VSP obtained from the actual surgery. The three facial outcomes: Sassouni, Delaire and "Surgery Realised" called Dolphin showed some potentially interesting differences. The small size of the sample did not show any significant findings (t test) but a special analysis revealed a valid difference between the three outcomes. The most aesthetic being Dolphin (surgery realised) 17.4 then Sassouni 16.6 (diff 0.8) and finally Delaire 14 (diff 2.6).

CONCLUSIONS

The two structural analysis Delaire and Sassouni did not give the same surgical objectives. Sassouni favored more forward movements for the maxilla as well as more vertical modifications. The Dolphin software appeared to be the quite reliable software to predict the facial outcomes of the surgery. The VSP photographs obtained using Sassouni's analysis were more balanced than when the Delaire analysis was followed (16.4/14 = +2.6). The VSP based on the actual surgery was judged to be even more aesthetic. This shows that beyond a cephalometric analysis the facial aesthetic details and the functional analysis are very important during the phase of surgical planning.