A learning curve in 3D virtual surgical planned orthognathic surgery.

OBJECTIVES: To assess the surgical accuracy of 3D virtual surgical planned orthognathic surgery and the influence of posterior impaction and magnitude of the planned movements on a possible learning curve. MATERIALS AND METHODS: This prospective cohort study included subjects who underwent bimaxillary surgery between 2016 and 2020 at the Department of Oral and Maxillofacial Surgery of the Radboud University Medical Center, Nijmegen. 3D virtual surgical planning (VSP) was performed with CBCT data and digitalized dentition data. By using voxel-based matching with pre- and postoperative CBCT data the maxillary movements were quantified in six degrees of freedom. The primary outcome variable, surgical accuracy, was defined as the difference between the planned and achieved maxillary movement. RESULTS: Based on 124 subjects, the surgical accuracy increased annually from 2016 to 2020 in terms of vertical translations (0.82 ± 0.28 mm; p = 0.038) and yaw rotations (0.68 ± 0.22°; p = 0.028). An increase in surgical accuracy was observed when combining all six degrees of freedom (p = 0.021) and specifically between 2016 and 2020 (p = 0.004). An unfavorable learning curve was seen with posterior impaction and with a greater magnitude of movements. CONCLUSION: The present study demonstrated a significant increase in surgical accuracy annually and therefore supports the presence of a learning curve. CLINICAL RELEVANCE: Cases with planned maxillary posterior impaction and/or a great magnitude of jaw movements should be transferred from the 3D VSP with extra care to obtain a satisfactory surgical accuracy.

Intraoral Scanning as an Alternative to Evaluate the Accuracy of Dental Implant Placements in Partially Edentate Situations: A Prospective Clinical Case Series.

(1) Background: For years, Cone-Beam Computed Tomography's (CBCT) have been the golden standard to evaluate implant placement accuracy. By validating Intraoral Scans (IOS) as an alternative to determine implant placement accuracy, a second CBCT could be avoided. (2) Methods: Using dynamic guided implant surgery, 23 implants were placed in 16 partially edentate patients. Preoperatively, both CBCT and IOS (Trios® 3) were obtained and subsequently imported into DTX Studio™ planning software to determine the ideal implant location. A CBCT scan and an IOS including scan abutments were acquired immediately after placement. Both postoperative CBCT and postoperative IOS were used to compare the achieved implant position with the planned implant position and were projected and analyzed using the Implant Position Orthogonal Projection (IPOP) method. (3) Results: Mean differences between the CBCT and IOS methods on the mesio−distal plane were 0.09 mm (p = 0.419) at the tip, 0.01 mm (p = 0.910) at the shoulder, −0.55° (p = 0.273) in angulation, and 0.2 mm (p = 0.280) in implant depth. Mean differences between both methods on the bucco-lingual/bucco-palatal plane were 0.25 mm (p = 0.000) at the tip, 0.12 mm (p = 0.011) at the shoulder, −0.81° (p = 0.002) in angulation, and 0.17 mm (p = 0.372) in implant depth. A statistical analysis was performed using a paired t-test. All mesiodistal deviations between the two methods showed no significant differences (p > 0.05). Buccolingual/buccopalatal deviations showed no significant difference in implant depth deviation. However, significant differences were found at the tip, shoulder, and angulation (p < 0.05). These values are of minimal clinical significance. (4) Conclusions: This study supports the hypothesis that a postoperative IOS is a valid alternative for determining implant placement accuracy.

Reproducibility of Manual Transfer of the Clinical Natural Head Position: Influence on the Soft Tissue and Hard Tissue Position of 3-Dimensional Virtual Surgical Planning.

PURPOSE: The purpose of this study was to assess the reproducibility of manually transferring the clinical natural head position (NHP) to the 3-dimensional (3D) virtual surgical planning and its subsequent influence on the soft tissue and maxillary hard tissue position. METHODS: A retrospective cohort study was set up. The study population consisted of subjects who underwent bimaxillary osteotomies between 2016 and 2020 at the Department of Oral and Maxillofacial Surgery in Radboud University Medical Centre (Nijmegen, the Netherlands). Cone beam computed tomography scans, dentition data, and clinical photographs were acquired 4 weeks before surgery. Two attempts (NHP1 and NHP2) were performed by a single examiner to manually transfer the NHP. 3D transformation matrices were used to quantify the transferred NHP in 3 degrees of freedom (pitch, roll, and yaw). Landmarks and surface-based matching were used to quantify the influence on the soft tissue and hard tissue positions in 6 degrees of freedom. The primary outcome variable was the reproducibility of manually aligning the NHP. The secondary and tertiary outcome variables were the effect of the reproducibility of the manually aligned NHP on the soft tissue and hard tissue displacements in the 3D virtual surgical planning. RESULTS: The study population consisted of 109 subjects: 37 males (33.9%) and 72 females (66.1%) with a mean age of 29.1 ± 10.3 years (range, 17.0 to 59.0). The manual transfer of pitch alignment (2.24 ± 1.64°; 95% confidence interval [CI], 1.93 to 2.55) was significantly less reproducible than the roll (0.56 ± 0.44°; 95% CI, 0.48 to 0.64; P < .001) and yaw (0.67 ± 0.92°; 95% CI, 0.50 to 0.85; P < .001). Subsequently, this alignment error influenced the position of the maxilla (incisal point) and soft tissue menton by 0.85 ± 0.86 mm and 1.01 ± 1.00 mm vertically and 0.78 ± 1.10 mm and 0.80 ± 1.18 mm sagittally. CONCLUSIONS: The present study demonstrated that the manual transfer of the NHP from the clinical situation to the virtual environment influenced the soft tissue and hard tissue position and that a more reproducible method of transferring the clinical NHP is recommended.

Author Correction: One-year postoperative skeletal stability of 3D planned bimaxillary osteotomies: maxilla-first versus mandible-first surgery.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Does Mandible-First Sequencing Increase Maxillary Surgical Accuracy in Bimaxillary Procedures?

PURPOSE: In bimaxillary procedures, it is important to know how the chosen sequence affects the surgical outcome. The purpose of this study was to explore whether the theoretical advantages of using the mandible-first procedure were supported by clinical data. MATERIALS AND METHODS: The authors performed a retrospective investigation on a cohort compiled from 3 published retrospective studies. The sample was composed of patients treated at the Radboud University Nijmegen Medical Centre (Nijmegen, the Netherlands) from 2010 to 2014 and the Odense University Hospital (Odense, Denmark) from 2011 to 2015. The inclusion criterion was bimaxillary surgery without maxillary segmentation. The exclusion criterion was lack of a virtual surgical plan. The primary outcome variable was surgical accuracy, defined as the mean difference between the obtained outcome and the virtual surgical plan. The primary predictor variable was the comparison between mandible-first and maxilla-first sequencing. Secondary predictors were inferior maxillary repositioning and counterclockwise (CCW) rotation. The confounding variable was the virtually planned reposition. Results were analyzed by mixed-model regression encompassing all variables, followed by a detailed analysis of positive results using 2-sample t tests. RESULTS: Overall, 145 patients were included for analysis (98 women; mean age, 28 years). Operating on the mandible first notably influenced maxillary positioning and placed the maxilla 1.5 mm posterior and with 1.4° of CCW rotation compared with virtual surgical planning. The interaction of surgical sequence with maxillary rotation showed similar surgical accuracy between maxilla-first surgery with clockwise rotation and mandible-first surgery with CCW rotation. Inferior maxillary repositioning resulted in the maxilla being placed 1.7 mm (maxilla-first sequence) and 2.0 mm (mandible-first sequence) posterior to the planned position. CONCLUSION: Surgical accuracy was considerably influenced by sequencing in bimaxillary procedures. It remains important to know how the chosen sequence affects the surgical outcome so that the virtual surgical plan can be adjusted accordingly.

One-year postoperative skeletal stability of 3D planned bimaxillary osteotomies: maxilla-first versus mandible-first surgery.

Orthognathic surgery is carried out to correct jaw deformities and to improve facial aesthetics. However, controversy surrounds whether the maxilla- or mandible-first surgery approach leads to better surgical outcomes. In our previous study, we have shown that in most instances, the maxilla-first surgical approach yielded closer concordance with the 3D virtual treatment plan than a mandibular-first procedure. However, the post-operative stability of each approach has not been investigated. Therefore, this one-year follow-up study was set-up and investigated the postoperative skeletal stability of the 3D planned translations and rotations after either the maxilla- or mandible-first surgery. In total, 106 patients who underwent bimaxillary surgery and had an individualized 3D virtual operation plans, received either maxilla-first (n = 53) or mandible-first (n = 53) surgery. 3D printed interocclusal splints were used during surgery to position the jaws. One year postoperatively a cone-beam computed tomography (CBCT) scan was made to assess the effects using the OrthoGnathicAnalyser. The mean sagittal, vertical and transverse relapse was less than 1.8 mm and no significant differences were found in relapse between the maxilla-first or the mandibular-first surgical procedure. Overall, this study shows that 3D virtual planning in combination with an optimised sequencing of osteotomies provides predictable long-term results in bimaxillary surgery.

Toward a higher accuracy in orthognathic surgery by using intraoperative computer navigation, 3D surgical guides, and/or customized osteosynthesis plates: A systematic review.

The aim of this study was to systematically review the accuracy of intraoperative computer navigation, three-dimensional surgical guides and customized osteosynthesis plates for the transfer of the virtual surgical plan to the patient in orthognathic surgery. A systematic review of the currently available publications was performed in databases MEDLINE, Embase, and Cochrane Library, using a PICOS search strategy, and reported according to PRISMA. The initial search yielded 3050 articles. In total, 16 studies were included for final quantitative analyses. The results of individual studies demonstrated a comparable accuracy in the transfer of planned surgical displacement of the jaws. A large variability was found with regard to the method of accuracy assessment and reported outcomes. The findings of this review show that these modern techniques have the potential to replace interocclusal splints in routine clinical practice in the future. We recommend that authors presenting new data on the accuracy of a technique should choose the method of accuracy assessment meticulously, acquiring postoperative imaging as soon as possible after surgery. They should report as much as possible, summarizing values or, ideally, even the raw data of the accuracy assessment in order to allow comparison with other techniques in a meta-analysis.

Achievability of 3D planned bimaxillary osteotomies: maxilla-first versus mandible-first surgery.

The present study was aimed to investigate the effects of sequencing a two-component surgical procedure for correcting malpositioned jaws (bimaxillary osteotomies); specifically, surgical repositioning of the upper jaw-maxilla, and the lower jaw-mandible. Within a population of 116 patients requiring bimaxillary osteotomies, the investigators analyzed whether there were statistically significant differences in postoperative outcome as measured by concordance with a preoperative digital 3D virtual treatment plan. In one group of subjects (n = 58), the maxillary surgical procedure preceded the mandibular surgery. In the second group (n = 58), the mandibular procedure preceded the maxillary surgical procedure. A semi-automated analysis tool (OrthoGnathicAnalyser) was applied to assess the concordance of the postoperative maxillary and mandibular position with the cone beam CT-based 3D virtual treatment planning in an effort to minimize observer variability. The results demonstrated that in most instances, the maxilla-first surgical approach yielded closer concordance with the 3D virtual treatment plan than a mandibular-first procedure. In selected circumstances, such as a planned counterclockwise rotation of both jaws, the mandible-first sequence resulted in more predictable displacements of the jaws.

A New 3D Tool for Assessing the Accuracy of Bimaxillary Surgery: The OrthoGnathicAnalyser.

AIM: The purpose of this study was to present and validate an innovative semi-automatic approach to quantify the accuracy of the surgical outcome in relation to 3D virtual orthognathic planning among patients who underwent bimaxillary surgery. MATERIAL AND METHOD: For the validation of this new semi-automatic approach, CBCT scans of ten patients who underwent bimaxillary surgery were acquired pre-operatively. Individualized 3D virtual operation plans were made for all patients prior to surgery. During surgery, the maxillary and mandibular segments were positioned as planned by using 3D milled interocclusal wafers. Consequently, post-operative CBCT scan were acquired. The 3D rendered pre- and postoperative virtual head models were aligned by voxel-based registration upon the anterior cranial base. To calculate the discrepancies between the 3D planning and the actual surgical outcome, the 3D planned maxillary and mandibular segments were segmented and superimposed upon the postoperative maxillary and mandibular segments. The translation matrices obtained from this registration process were translated into translational and rotational discrepancies between the 3D planning and the surgical outcome, by using the newly developed tool, the OrthoGnathicAnalyser. To evaluate the reproducibility of this method, the process was performed by two independent observers multiple times. RESULTS: Low intra-observer and inter-observer variations in measurement error (mean error < 0.25 mm) and high intraclass correlation coefficients (> 0.97) were found, supportive of the observer independent character of the OrthoGnathicAnalyser. The pitch of the maxilla and mandible showed the highest discrepancy between the 3D planning and the postoperative results, 2.72° and 2.75° respectively. CONCLUSION: This novel method provides a reproducible tool for the evaluation of bimaxillary surgery, making it possible to compare larger patient groups in an objective and time-efficient manner in order to optimize the current workflow in orthognathic surgery.

A new 3D approach to evaluate facial profile changes following BSSO.

The purpose of this study was to evaluate changes in the soft tissue facial profile in patients who underwent bilateral sagittal split osteotomy (BSSO) using 3D stereophotogrammetry and principal component analysis (PCA). Twenty-five female patients (mean age, 24 years; range: 18-26) who underwent BSSO and 70 female controls (mean age, 24 years; range: 18-26) participated in this prospective study. Three-dimensional photographs of all patients and controls were acquired. PCA was used to determine the unique morphological variations (UV) between the dysgnathic group and the control group. The most prominent facial morphologic difference between the dysgnathic group and the control group (UV1) was a clockwise rotation of the mandible and shortening of the lower part of the face, followed by a protrusion of the upper lip, retrusion of the mandible and over-accentuation of the labial-mental fold (UV2). The combination of UV1 and UV2 could be used to simulate a typical Class II facial profile and to automatically differentiate between the preoperative patients, postoperative patients and the control group. Based on the applied PCA method, this study demonstrated that BSSO advancement surgery could only provide a suboptimal improvement of the soft tissue facial profile in the majority of cases.

Three-dimensional facial simulation in bilateral sagittal split osteotomy: a validation study of 100 patients.

PURPOSE: Three-dimensional (3D) virtual planning of orthognathic surgery in combination with 3D soft tissue simulation allows the surgeon and the patient to assess the 3D soft tissue simulation. This study was conducted to validate the predictability of the mass tensor model soft tissue simulation algorithm combined with cone-beam computed tomographic (CBCT) imaging for patients who underwent mandibular advancement using a bilateral sagittal split osteotomy (BSSO). MATERIALS AND METHODS: One hundred patients were treated with a BSSO according to the Hunsuck modification. The pre- and postoperative CBCT scans were matched and the mandible was segmented and aligned. The 3D distance maps and 3D cephalometric analyses were used to calculate the differences between the soft tissue simulation and the actual postoperative results. Other study variables were age, gender, and amount of mandibular advancement or rotation. RESULTS: For the entire face, the mean absolute error was 0.9 ± 0.3 mm, the mean absolute 90th percentile was 1.9 mm, and for all 100 patients the absolute mean error was less than or equal to 2 mm. The subarea with the least accuracy was the lower lip area, with a mean absolute error of 1.2 ± 0.5 mm. No correlation could be found between the error of prediction and the amount of advancement or rotation of the mandible or age or gender of the patient. CONCLUSION: Overall, the soft tissue prediction algorithm combined with CBCT imaging is an accurate model for predicting soft tissue changes after mandibular advancement. Future studies will focus on validating the mass tensor model soft tissue algorithm for bimaxillary surgery.

Accuracy of three-dimensional soft tissue simulation in bimaxillary osteotomies.

The purpose of this study was to evaluate the accuracy of an algorithm based on the mass tensor model (MTM) for computerized 3D simulation of soft-tissue changes following bimaxillary osteotomy, and to identify patient and surgery-related factors that may affect the accuracy of the simulation. Sixty patients (mean age 26.0 years) who had undergone bimaxillary osteotomy, participated in this study. Cone beam CT scans were acquired pre- and one year postoperatively. The 3D rendered pre- and postoperative scans were matched. The maxilla and mandible were segmented and aligned to the postoperative position. 3D distance maps and cephalometric analyses were used to quantify the simulation error. The mean absolute error between the 3D simulation and the actual postoperative facial profile was 0.81 ± 0.22 mm for the face as a whole. The accuracy of the simulation (average absolute error ≤2 mm) for the whole face and for the upper lip, lower lip and chin subregions were 100%, 93%, 90% and 95%, respectively. The predictability was correlated with the magnitude of the maxillary and mandibular advancement, age and V-Y closure. It was concluded that the MTM-based soft tissue simulation for bimaxillary surgery was accurate for clinical use, though patients should be informed of possible variation in the predicted lip position.