Predictability and accuracy of maxillary repositioning during bimaxillary surgery using a three-dimensional positioning technique

Influence of the Inferior Turbinate on the Accuracy of Superior Maxillary Repositioning

Notably, many studies have focused on the bony interference in the maxillary segment when performing maxillary superior repositioning; however, few reports have described the interference with the inferior nasal turbinate. Therefore, the authors aimed to retrospectively analyze the soft tissue or bone tissue volume of the inferior nasal turbinate and the accuracy of maxillary superior repositioning in Le Fort I osteotomy (LF1). The authors included 83 patients with facial deformities who underwent conventional LF1 (maxillary molar elevation between 4.0 and 6.0 mm) with/without bilateral sagittal split ramus osteotomy. The ratio of the soft tissue of the inferior turbinate to that of the inferior nasal cavity was used to divide the participants into 2 subgroups (large and small ratio). Similarly, the bony tissue volume of the inferior turbinate was used to divide the participants into 2 subgroups (large and small bony tissues), and the planned or actual amount of superior repositioning was compared 3 dimensionally. In the soft tissue group, the subgroups showed no significant differences (P=0.934). However, the actual maxillary superior repositioning was significantly lower in the large bone group than in the planned maxillary elevation group (P<0.01). In cases where the maxillary molar needs to be elevated by >4 mm and the bone tissue of the inferior nasal turbinate is well developed, an adjunctive technique such as horseshoe osteotomy or partial inferior turbinate resection should be considered in addition to LF1 to avoid interference between the inferior nasal turbinate and the maxillary bone fragments.

Mandible-First Sequencing Increase Surgical Accuracy for Patients With Skeletal Class II Malocclusion Concomitant With Unstable Condyle-Fossa Relation

The aim of this study was to explore whether mandible-first sequencing increases the surgical accuracy in bimaxillary orthognathic surgery for patients with skeletal class II malocclusion concomitant with the unstable condyle-fossa relation. A retrospective evaluation of 19 patients who had undergone virtually planned double-splint orthognathic surgery with different operation sequences was performed: maxilla-first (n=9) or mandible-first (n=10) surgery. The centroid position, translational, and rotational differences in the maxilla were evaluated by comparing the virtual plans with actual results. The stability was assessed by comparing the actual results with the follow-up outcomes 6 months postoperatively. The accuracy of the maxilla centroid position was improved in mandible-first sequencing surgery: mandible-first 1.87±0.94 mm versus maxilla-first 2.70±0.75 mm ( P <0.05). Moreover, no significant difference was detected in the translational and orientational discrepancies between the 2 groups. Neither sequencing procedure differed in the overall stability: maxilla-first (1.48±1.13 mm) versus mandible-first (1.57±0.90 mm). This study indicated that the mandible-first surgery leads to a more accurate maxilla position than the maxilla-first surgery for patients with skeletal class II malocclusion concomitant with the unstable condyle-fossa relation.

Postoperative stability of bioresorbable plates made of 85:15 poly (L-lactide-co-glycolide) in Le Fort I osteotomy

OBJECTIVE

Recently, RapidSorb plates (DePuy Synthes) made of 85.15 poly (L-lactide-co-glycolide) have been used for orthognathic surgery; however, reports regarding their effectiveness are limited. We aimed to compare the postoperative stability of RapidSorb plates, RapidSorb combined with titanium (MOJ plates), and MOJ plates in patients who underwent Le Fort I osteotomy at Tokyo Medical and Dental University Hospital.

STUDY DESIGN

The use of RapidSorb in the maxilla is a load-sharing application and therefore constitutes an approved indication. Discrepancies in the maxillary positions were measured using postoperative computed tomography data at 1 week and 1 year using the centroid method 3-dimensionally. Treatment with RapidSorb alone showed a more vertical discrepancy in the maxilla treatment with MOJ and RapidSorb+MOJ. The RapidSorb4 group was subdivided into 2 groups (under and over 1.0-mm) based on the change in the maxillary centroid.

RESULTS

The bone gap at the lateral border of the piriform aperture was significantly larger in the over-1.0-mm group than in the 1.0-mm group.

CONCLUSIONS

The fixation of RapidSorb alone is not appropriate in load-bearing and unstable applications but is not contraindicated for load-sharing indications. Fixation with RapidSorb combined with MOJ was clinically effective, with results similar to titanium plate-only fixation regarding postoperative stability.

Accuracy of orthognathic surgery with customized titanium plates-Systematic review

This systematic review aimed to evaluate the accuracy of customized titanium plates in orthognathic surgery compared to standard outcome in virtual surgical planning. PRISMA and JBI guidelines were followed. Research protocol was registered in PROSPERO. Six databases and two gray literature repositories were used as sources of research articles. Descriptive clinical studies, that performed orthognathic surgery using custom titanium plates, were included. Risk of bias was assessed by "The Joanna-Briggs Institute Critical Appraisal tools for use in Systematic Reviews Checklist for Case Series". Of the 11,916 studies initially identified, seven met the eligibility criteria and were included. The studies were published between 2015 and 2019. Most of the studies (57%) had a low risk of bias, while one had a high risk of bias. Total sample included 74 patients with 63 bimaxillary surgeries and 11 unimaxillary surgeries. All studies showed acceptable accuracy within previously established clinical parameters. Although the eligible articles assessed the accuracy of the orthognathic surgery with respect to virtual planning, the wide variability of evaluation methodologies made it impossible to calculate a combined accuracy measure. It was not possible to perform a meta-analysis, so a pragmatic recommendation on the use of these plates is not possible.

The Accuracy of Maxillary Position Using a Computer-Aided Design/Computer-Aided Manufacturing Intermediate Splint Derived Via Surgical Simulation in Bimaxillary Orthognathic Surgery

PURPOSE

The purpose of this study was to assess the clinical interventions and the accuracy of maxillary reposition using a computer-aided design/computer-aided manufacturing (CAD/CAM) splint derived via surgical simulation.

MATERIALS AND METHODS

The retrospective study comprised 24 patients who underwent bimaxillary surgery. The patients were assigned to 1 of 2 groups by a way of maxillary repositioning. One group received conventional intermediate wafers and the other CAD/CAM wafers during Le Fort I osteotomy. We recorded operation time, blood loss, the operative accuracy. Accuracy was analyzed by 3-dimensional computed tomography images before and immediately after the operation. The evaluation points were the right maxillary first incisor (U1), the right maxillary second molar (M2-right), and the left maxillary second molar (M2-left).

RESULTS

The 2 groups did not differ significantly in operation time and blood losses. The vertical axis of U1 data differed significantly between the 2 groups (P = 0.008). None of the horizontal, vertical, or anteroposterior axis of M2-right data differed significantly, and anteroposterior axis of M2-left data differed significantly (P = 0.0296). The CAD/CAM group 3-dimensional distance errors were less than those of the conventional group for all points.

CONCLUSION

Placement of CAD/CAM splint allowed highly accurate repositioning; the accuracy exceeded that afforded by conventional model surgery using a facebow and articulator.

Accuracy of mandible-independent maxillary repositioning using pre-bent locking plates: a pilot study

The double splint method is considered the gold standard for maxillary repositioning, but the procedure is lengthy and prone to error. Recent splintless methods have shown high repositioning accuracy; however, high costs and technical demands make them inaccessible to many patients. Therefore, a new cost-effective method of mandible-independent maxillary repositioning using pre-bent locking plates is proposed. Plates are bent on maxillary models in the planned position prior to surgery. The locations of the plate holes are replicated during surgery using osteotomy guides made from thermoplastic resin sheets. Pre-bent plates are subsequently fitted onto the maxilla, and plate holes are properly set to reposition the maxilla. The purpose of this study was to evaluate the accuracy of this method for maxillary repositioning and the reproducibility of the plate holes. Fifteen orthognathic surgery patients were evaluated retrospectively by superimposing preoperative simulations over their postoperative computed tomography models. The median deviations in maxillary repositioning and plate hole positioning between the preoperative plan and postoperative results were 0.43mm (range 0-1.55mm) and 0.33mm (range 0-1.86mm), respectively. There was no significant correlation between these deviations, suggesting that the method presented here allows highly accurate and reliable mandible-independent maxillary repositioning.

Influence of the anatomical form of the posterior maxilla on the reliability of superior maxillary repositioning by Le Fort I osteotomy

Certain patients with facial deformities require superior repositioning of the maxilla via Le Fort I osteotomy; however, the magnitude of superior repositioning of the maxilla is often less than expected. In this study, the correlation between the accuracy of superior repositioning of the maxilla and the anatomical form of the maxillary posterior region was examined. Seventy-five patients who underwent Le Fort I osteotomy without forward movement of the maxilla but with superior repositioning of the maxilla were included in this study. The bone volume around the descending palatine artery (DPA), the angle of the junction between the pterygoid process and the tuberosity, and the distance between the upper second molar and the pterygoid process were measured via three-dimensional analysis. A significant negative correlation (r=-0.566) was found between the bone volume around the DPA and the ratio of repositioning (actual movement divided by expected movement). It is possible that the superior repositioning of the maxilla expected prior to surgery was not sufficiently attained because of the large volume of bone around the DPA. The results of this study show that in some patients, superior repositioning was not achieved at the expected level because of bone interference attributable to the anatomical form of the maxillary posterior region.

CAD/CAM splint based on soft tissue 3D simulation for treatment of facial asymmetry

BACKGROUND

Most cases of facial asymmetry involve yaw deformity, and determination of the yaw correction level is very difficult.

METHODS

We use three-dimensional soft tissue simulation to determine the yaw correction level. This three-dimensional simulation is based on the addition of cephalometric prediction to gradual yaw correction. Optimal yaw correction is determined visually, and an intermediate splint is fabricated with computer-aided design and computer-aided manufacturing. Application of positioning devices and the performance of horseshoe osteotomy are advisable.

RESULTS

With this procedure, accurate repositioning of jaws was confirmed and patients obtained fairly good facial contour.

CONCLUSIONS

This procedure is a promising method for a widespread, predictable treatment of facial asymmetry.

Maxillary single-jaw surgery combining Le Fort I and modified horseshoe osteotomies for the correction of maxillary excess

A modified technique of horseshoe osteotomy combined with Le Fort I osteotomy for superior and posterior repositioning of the maxilla is presented. Eight patients with maxillary excess associated with retrogenia or microgenia were treated with this technique in combination with genioplasty. The maxillary segment was repositioned a maximum of 5.0mm posteriorly and 7.0mm superiorly at point A. The mandible autorotated anterosuperiorly to achieve sound occlusion. Point B moved 2.0-10.0mm anteriorly and 5.0-10.0mm superiorly. The pogonion moved 7.0-17.0mm anteriorly in combination with genioplasty. All patients obtained sound occlusion and a good profile after the operation. Almost no skeletal relapse was observed during 1 year of postoperative follow-up. Patients with long faces with maxillary excess and retrogenia often have small, unstable condyles. In these cases, because surgical intervention to the ramus can result in postoperative progressive condylar resorption, maxillary single-jaw surgery with a horseshoe osteotomy, thereby avoiding ramus intervention, is a less invasive option.