Systematic three-dimensional analysis of wafer-based maxillary repositioning procedures in orthognathic surgery

Accuracy and influencing factors of maxillary and mandibular repositioning using pre-bent locking plates: a prospective study

In-house repositioning methods based on three-dimensional (3D)-printing technology and the use of pre-bent plates has been gaining popularity in orthognathic surgery. However, there remains room for further improvement in methods and investigations on clinical factors that affect accuracy. This single-centre, prospective study included 34 patients and aimed to evaluate the accuracy and factors influencing maxillary and mandibular repositioning using pre-bent locking plates. The plates were manually pre-bent on the 3D-printed models of the planned position, and their hole positions were scanned and reproduced intraoperatively with osteotomy guides. The accuracy of repositioning and plate-hole positioning was calculated in three axes with the set landmarks. The following clinical factors that affect repositioning accuracy were also verified: deviation of the plate-hole positioning, amount of planned movement, and amount of simulated bony interference. The median deviations of the repositioning and hole positioning between the preoperative plan and postoperative results were 0.26 mm and 0.23 mm, respectively, in the maxilla, and 0.69 mm and 0.36 mm, respectively, in the mandible, suggesting that the method was highly accurate, and the repositioning concept based on the plate hole and form matching was more effective in the maxilla. Results of the correlation test suggest that large amounts of bony interference and plate-hole positioning errors in the up/down direction could reduce mandibular repositioning accuracy.

Volumetric and Morphological Analysis of Mandibular Condyles of Angle Class 2 and 3 Malocclusion Patients

ABSTRACT

This study was conducted to provide diametric and volumetric data of mandibular condyles from patients with Angle class 2 and 3 malocclusions by semiautomatic segmentation based upon cone-beam computed tomography.Cone-beam computed tomography images of 79 patients were analyzed. By using the open-source software "ITK-SNAP", diametric and volumetric measurements of 158 mandibular condyles were performed. Descriptive statistics were calculated for all normally distributed variables. Correlations between patients with Angle class 2 and 3 were calculated with the independent Student t test. P values P < 0.05 were considered significant.Irrespective of the side, patients with class 2 malocclusion showed smaller mandibular condyles (right: 1.128 ± 0.504 cm3; left: 1.222 ± 0.596 cm3) than patients with class 3 (right: 1.504 ± 0.361 cm3; left: 1.493 ± 0.335 cm3). These results were reproducible also in accordance with the diametric measurement (class 2 right: 16.75 ± 2.72 mm; left: 17.04 ± 3.01 mm) (class 3 right: 18.24 ± 2.54 mm; left: 18.32 ± 2.13 mm). However, volumetric differences were highly statistically significant (right: P = 0.001; left: P = 0.018) while diametric differences were slightly significant for the right and not significant for the left side (right: P = 0.042; left: P = 0.053).Diametric and volumetric analyses offer important additional information based on 3D images of cone-beam computed tomography technology. Significant differences in diameter and volume of mandibular condyles could be assessed between different classes of malocclusion.

A volumetric study of mandibular condyles in orthognathic patients by semiautomatic segmentation

Purpose

This study was conducted to elucidate volumetric data of mandibular condyles of orthognathic patients by analyzing cone beam computed tomography images based upon semiautomatic segmentation.

Methods

Cone beam computed tomography images of 87 patients with malocclusions were analyzed in this retrospective study. Patients were between 17 and 53 years old and diagnosed with Angle class I, II, or III malocclusion. By using the validated open-source software “ITK-SNAP,” the volumetric measurements of 174 mandibular condyles were performed. Volumetric analysis was performed according to intra-subject side differences by paired Student t test. In accordance to inter-subject side, gender, age and type of malocclusion differences bivariate analysis and ANOVA were applied.

Results

The mean volume for the right condyle was 1.378 ± 0.447 cm³, with a maximum of 2.379 cm³ and a minimum of 0.121 cm³. The mean volume for the left side was 1.435 ± 0.474 cm³, with a maximum of 3.264 cm³ and a minimum of 0.109 cm³. Bivariate analysis indicated a highly significant inter-subject difference between the volume of the left and right mandibular condyles (p < 0.01). Females had a significantly smaller condyle volume than males (p < 0.05 left condyle; p < 0.01 right condyle).

Conclusion

The fact that shape and volume of mandibular condyles show a high susceptibility to pathological alterations and particularly malocclusions makes a precise knowledge about volumetric changes indispensable. Our results show that significant inter-subject differences in condyle volume could be found with respect to the side and gender. Larger volumes could be assessed for the left condyle and for male patients.

Improvement in accuracy of maxillary repositioning of Le Fort I osteotomy with Orthopilot™ Navigation System: evaluation of 30 patients

Traditional model surgery with facebow transfer is not very accurate. We aimed to demonstrate that the Orthopilot™ Navigation System improves the accuracy of maxillary repositioning during Le Fort I osteotomy. Thirty patients underwent Le Fort I osteotomy alone or associated to sagittal split osteotomy. The maxilla positioning was done in two phases. First, the maxilla was positioned with the traditional occlusal splint, the position ("without Orthopilot™") was recorded by the Orthopilot™. In the second phase, the Orthopilot™ was used to improve positioning; and the final position ("with Orthopilot™") was recorded, after osteosynthesis. Positioning data were compared with planned data. Positioning data with and without the Orthopilot™ were also compared. Accuracy was classified in distinct classes with three major criteria (conformity, non-conformity, failure) according to the discrepancies. Conformity rate was significantly greater with the Orthopilot™ (2 without the Orthopilot™ compared with 8 with the Orthopilot™; p=0.01). The failure rate was significantly lower with the Orthopilot™ (18 without Orthopilot™ compared with 7 with the Orthopilot™; p=0.002). Dispersions of discrepancies were usually lower in all directions with the Orthopilot™. Navigation reduced the risk of discrepancy without cancelling it, especially when large movements are planned. The Orthopilot™ therefore improved the accuracy of traditional occlusal splint during Le Fort I osteotomy.

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.

Volumetric analysis of MRONJ lesions by semiautomatic segmentation of CBCT images

PURPOSE

The purpose of this study was to evaluate potential differences in volumes of areas of osteolysis caused by medication-related osteonecrosis of the jaw (MRONJ) between the upper and lower jaw. We aim to analyze the clinical relevance of volumetric measurement of osteolytic lesions for surgical planning of MRONJ patients.

METHODS

Sixty-seven patients who were clinically and histopathologically diagnosed with MRONJ were retrospectively included in this study. Cone beam computed tomography (CBCT) images were evaluated according to localization, affected anatomical structures, and volumetric measurement of osteolytic lesions caused by MRONJ in appliance of CBCT datasets by using ITK-SNAP.

RESULTS

The most frequently affected localization is the mandible, whereas female patients show significantly more often lesions of the maxilla. The cortical bone was predominantly affected. Furthermore, the affection of teeth, sinus floor, inferior alveolar nerve canal, or even a pathological fracture of the mandible are infrequently existing. The volumetric measurements revealed a statistically significant greater absolute osteolysis volume in males.

CONCLUSIONS

Image analysis and volumetric measurements of osteolytic lesions of MRONJ patients is a helpful tool to further understand the clinical appearance and identify compromised anatomic landmarks. Volumetric analysis aids in pre-surgical planning and visualizes the individual extent of the disease for each patient.

Quantification of the inaccuracy of conventional articulator model surgery in Le Fort 1 osteotomy: evaluation of 30 patients controlled by the Orthopilot® navigation system

Occlusal splints are commonly used to position the maxilla during traditional orthognathic surgery. We aimed to quantify the inaccuracy of the maxillary positioning (in three dimensions) in traditional model surgery with the Orthopilot^® navigation system. Thirty Le Fort I osteotomies were made using a standard technique. The position of the maxilla was recorded by the navigation system and defined by three values of translation and three of rotation. The recorded data were compared with the planned data. The accuracy of positioning was classified in distinct classes with three major criteria (conformity, non-conformity, and failure) according to the discrepancy. The positioning of the maxilla was in conformity with operative planning in 3/30 of our Le Fort I osteotomies (95% CI 2% to 27%) and in failure in 22/30 (95% CI 54% to 88%). The dispersion of the discrepancy was more important in the sagittal plane, particularly for the sagittal rotation and for the back-front translation, which reflected greater inaccuracy in this plan. The frontal orientation of the maxilla was better controlled. The risk of maxillary malposition was proportional to the planned maxillary advancement.