Three-dimensional treatment planning of orthognathic surgery in the era of virtual imaging

Virtual surgical planning in orthognathic surgery: a dental hospital's 10-year experience

PURPOSE

The primary objective of this study was to evaluate how the utilization of virtual surgical planning (VSP) and the epidemiological profile of patients undergoing orthognathic surgery (OGS) have changed in the past decade.

METHODS

The records of patients who had undergone orthognathic surgery at a national dental hospital were reviewed. Trends in VSP, epidemiological data, presentation of dentofacial deformity, and management details were recorded.

RESULTS

A total of 1184 patients were included in this study. The majority of the patients seeking treatment in this dental hospital were young Chinese adults with dentofacial deformities requiring bimaxillary surgeries. Most patients presented with a skeletal Class III pattern (79.0%), and asymmetry was diagnosed in 80.8% of all cases.

CONCLUSION

There was an initial slow pick-up rate for VSP, but this rapidly increased to a high adoption rate of 98.7-100% between 2019 and 2021. Together with an increasing body of evidence suggesting greater accuracy in VSP, utilization in this technology can be enhanced with greater familiarity with the technology and improvements in the VSP services.

The online attention analysis on orthognathic surgery research

OBJECTIVES

Altmetrics is one of the fields of bibliometrics that seeks to assess the impact and interest of a given subject through Internet users. The aim of this study is to make an altmetric analysis of the orthognathic surgery literature.

METHODS

A literature search was conducted using Dimensions app up to December 2023. A list of the 100 most mentioned articles on the topic was compiled. A Google Trends search was performed with same strategy to visualize important data regarding internet search. Charts and tables were created using Microsoft Excel and VOSviewer software to allow bibliometric visualization.

RESULTS

There was a very poor correlation between the number of mentions and the number of citations (r = 0.0202). Most articles discussed on technical innovations associated to orthognathic surgery, majority related to virtual planning (n = 26). Other topics considered interesting to internet readers were complications (n = 18), surgical technique (n = 14), and psychological aspects/quality of life (n = 13).

CONCLUSION

Online interest in orthognathic surgery closely aligns with the level of academic interest but is also influenced by factors such as location and economic status. The internet is a powerful tool for disseminating scientific research to a broad audience, making it more accessible and engaging than traditional academic channels.

Does orthognathic surgery affect mandibular condyle position? A retrospective study

PURPOSE

The aim of this study is to analyze mandibular condyle position changes after bilateral sagittal split osteotomy (BSSO) and bimaxillary orthognathic surgery in patients operated at a single department by two surgeons in 2013-2022. Compared were groups of mandibular advancement vs setback and bimaxillary vs BSSO.

METHODS

Ninety-nine subjects were included. Inclusion criteria were patients who underwent one of the BSSO or bimaxillary surgery and had CT scans performed before and after surgery. Preoperative CT scans were performed 1 day before surgery and postoperative CT scans 6-12 months afterwards. Changes in mandibular condyle position were measured in axial and sagittal planes.

RESULTS

CT condylar position measurements indicated significant postoperative changes in AB angle bilaterally (p =  < 0.001). In mandibular advancement and setback comparison, values were significantly lower in ABL angle values in the setback group (p = 0.011326) and significantly higher in FDR in the advancement group (p = 0.005795). There were no statistically significant changes found in BSSO and bimaxillary group comparison.

CONCLUSION

Within the limitations of this study, it can be concluded that orthognathic surgery does have a moderate effect on position of the condyles, especially condylar rotation in transversal axis.

Emerging Trends in Virtual Surgical Planning for Orthognathic Surgery: A Global Overview of Research and Publication Patterns

PURPOSE

Anticipating trends and pursuing innovative ideas are imperative for the advancement of science. The objective of this study was to conduct a bibliometric analysis of 3-dimensional virtual simulation in orthognathic surgery, explore its implications for clinical practice, and identify future publication trends through digital tools.

METHODS

This study employed a retrospective bibliometric analysis using data obtained from the Web of Science database. The search strategy focused on articles related to orthognathic surgery and virtual simulation techniques. RStudio and bibliometrix tools were used to data mining. The independent variables retrieved from digital analysis were the emerging themes related to virtual planning in orthognathic surgery. The trends that we identified were facial esthetics, digital workflow, personalized treatments, and complex cases. The primary outcome variable was the number of publications dedicated to virtual simulation in orthognathic surgery, along with secondary outcomes such as citation rates, language of publication, country of origin, institutional affiliations, and emerging research themes. Covariates included variables related to publication characteristics, author affiliations, and geographic distribution of publications. Publication analyses over time involved descriptive statistics, regression analysis, Pearson correlation tests, and graphical representation techniques. Statistical significance was set at a 95% confidence interval (P value < .05).

RESULTS

A comprehensive analysis of 987 articles reveals the impact of included authors, with a mean h-index of 62 (SD = 18.4). The analysis further illuminates a discernible upward trend in publications on this subject, showcasing a linear pattern with a notable R2 value of 0.88 (P = .021). English remains the predominant language of publication, accounting for 97.97% of articles, while contributions hailed from a diverse spectrum of 56 countries. Interestingly, a moderate correlation emerges between publication numbers and gross domestic product per capita (r = 0.30, P = .044) and total area (r = 0.30, P = .032), whereas a more substantial correlation is evident with total population (r = 0.61, P = .034). Notably, the most cited article amassed 254 citations. Furthermore, a Pearson correlation coefficient of 0.97 underscores the correlation between citation density and the year of publication.

CONCLUSION

The bibliometric indicators provided insights for evaluating research productivity and the quality of research output. Emerging themes included facial esthetics, 3-dimensional printing, and the utilization of custom-made templates and implants. This study holds relevance for maxillofacial surgeons, academics, and researchers alike.

On the use of intraoperative 3D-RX C-arm imaging in orthognathic surgery: a prospective non-consecutive case series study

CONTEXT

Segment and osteosynthesis malposition resulting in patients' complaints (mainly about asymmetries) are encountered in orthofacial/orthognathic surgery.

OBJECTIVE, DESIGN, AND SETTING

We planned to investigate the usefulness of intraoperative three-dimensional (3D) imaging concerning positioning and fixation of bone segments and osteosynthesis in orthognathic/orthofacial surgery. We performed a prospective study of non-consecutive cases. All patients receiving a bimaxillary osteotomy, genioplasty, and their combinations were included in the study from May 2016 to May 2020. Unilateral and bilateral sagittal split osteotomies were excluded. There were no gender and age limitations. All were intraoperatively examined using the BV Pulsera 3D-RX System (Philips Medical, Eindhoven, The Netherlands). The outcome variables were the percentage of revisions of segment positioning and osteosynthesis. Predictor variables were age, gender, type of surgery, timing (pre- and post-imaging), and surgeon experience (senior vs assistant).

RESULTS

Forty female and twenty-two male patients were included (mean age 25.25 years ± 7.52 and 29.1 years ± 12.6 respectively). We evaluated 27 genioplasties and 34 Le Fort "type-I" osteotomies. Indications for segment repositioning and redo-osteosynthesis increased after intraoperative imaging as compared to operator's clinical judgment before intraoperative imaging (95% confidence interval; p < .001 and p = .002 respectively).

CONCLUSION

Suboptimal positioning and fixation of bone segments or osteosynthesis were more apparent with 3D imaging. In addition, some satisfactory cases were also revised for an optimal outcome. As a result, surgeons were prompted to more revisions than judged necessary without intraoperative imaging.

Three-dimensional positioning of the maxilla using novel intermediate splints in maxilla-first orthognathic surgery for correction of skeletal class III deformity

OBJECTIVES

Successful orthognathic surgery requires accurate transfer of the intraoperative surgical plan. This study aimed to (1) evaluate the surgical error of a novel intermediate splint in positioning the maxilla during maxilla-first orthognathic surgery and (2) determine factors influencing surgical error.

MATERIALS AND METHODS

This prospective study examined 83 patients who consecutively underwent Le Fort I osteotomy for correction of skeletal class III deformity using a novel intermediate splint and a bilateral sagittal split osteotomy. Surgical error was the outcome variable, measured as the difference in postoperative translational and rotational maxillary position from the virtual plan. Measures included asymmetry, need and amount for mandibular opening during fabrication of intermediate splints, and planned and achieved skeletal movement.

RESULTS

Mean errors in translation for vertical, sagittal, and transversal dimensions were 1.0 ± 0.7 mm, 1.0 ± 0.6 mm, and 0.7 ± 0.6 mm, respectively; degrees in rotation for yaw, roll, and pitch were 0.8 ± 0.6, 0.6 ± 0.4, and 1.6 ± 1.1, respectively. The transverse error was smaller than sagittal and vertical errors; error for pitch was larger than roll and yaw (both p < 0.001). Error for sagittal, transverse, and roll positioning was affected by the achieved skeletal movement (roll, p < 0.05; pitch and yaw, p < 0.001). Surgical error of pitch positioning was affected by planned and achieved skeletal movement (both p < 0.001).

CONCLUSIONS

Using the novel intermediate splint when performing Le Fort I osteotomy allowed for accurate positioning of the maxilla.

CLINICAL RELEVANCE

The novel intermediate splint for maxillary positioning can be reliably used in clinical routines.

Can a Point-of-Care 3D Printing Workflow Produce Accurate and Successful Results for Craniomaxillofacial Trauma?

BACKGROUND

Computer-aided design and manufacturing (CAD/CAM) is having a profound impact on craniomaxillofacial surgery, and point-of-care (POC) solutions for repairing facial trauma are starting to emerge.

PURPOSE

The purpose of this study was to demonstrate the success and accuracy of a POC 3D printing workflow for craniomaxillofacial trauma.

STUDY DESIGN, SETTING, SAMPLE

A retrospective cohort study was undertaken to analyze subjects presenting to a level 1 trauma center after sustaining facial trauma and were then treated using the POC 3D printing workflow. Subjects were excluded if they were not treated with the POC 3D printing workflow, were lost to follow-up, or if clinical data were incomplete.

PREDICTOR VARIABLE

Predictor variables included the cause of trauma (mechanism), location of the mandibular fracture, type of fracture, mandibular severity score, and repair error (ie, root mean square error (RMSE) value for planned vs actual outcome).

MAIN OUTCOME VARIABLE(S)

The primary outcome variables were case success and case error. Success was defined as clinical and radiographic evidence of bony stability at 3 months. Case accuracy was calculated overlaying preoperative plan data to postoperative data generating a numerical value (RMSE value, mm).

COVARIATES

Covariates included age (years), gender (male/female), surgery time (mins), and CAD/CAM time (preoperative).

ANALYSES

Descriptive statistics were calculated for each variable. Dependence between rates or counts was established using the Wilcoxon rank sum or Fisher's exact test. Linear regression model was computed to discern how predictor variables influence RMSE. A P value < .05 was considered statistically significant.

RESULTS

The sample included 27 subjects (19 male/8 female). The average age of all subjects was 46.4 ± 18.0 years. Common mechanisms of injury were assault (33%) and self-inflicted gunshots (SIGSW; 30%), and the average severity score for mandible injury was (13.5 ± 3.3). Ninety-three percent of cases were deemed successful. The average repair accuracy (RMSE value) was 3.4 ± 1.8 mm. A linear regression model indicated those injured by a fall (β-coefficient 1.99; P = .010), motor vehicle collision (β-coefficient 1.49; P = .043), or SIGSW (β-coefficient 2.82; P < .001) correlated with RMSE.

CONCLUSION AND RELEVANCE

In-house CAD/CAM technologies can be utilized at the POC to repair complex facial trauma accurately and successfully.

Development of occlusal canting identifying tool: verification, reliability and validation assessment

INTRODUCTION

Occlusal cant (OC) is a malocclusion trait that lacks accurate clinical assessment methods. The occlusal canting identifying tool (OCIT) was invented and patented as a clinical tool to accurately identify and quantify the degree of maxillary OC. This study aimed to 1) develop a prototype of the OCIT, 2) verify the functionality of the OCIT and 3) assess the validity and reliability of the OCIT.

MATERIALS AND METHODS

A patented OCIT design was revised, and the dimensions were finalized, followed by a three-dimensional conceptual prototype design that was reviewed and approved by the inventors. Verification was performed using a digital angle gauge to determine the accuracy of the bubble level as well as the angle between the bite plate and the protractor. For laboratory validation, 40 orthodontists measured the simulated OC at (0°, 2°, 4°, 6° and 8°) on five phantom heads using the OCIT. A reliability assessment of the tool was performed in three occasions by one orthodontist using the same laboratory settings.

RESULTS

The OCIT was prototyped from a medical-grade stainless steel alloy (316 L). Verification assessment revealed that the accuracy error of the bubble level (0.316° ± 0.028°) was statistically significant but clinically insignificant, while that of the angle between the bite plate and protractor (0.100° ± 0.050°) was statistically insignificant. Validation assessment showed high validity of the OCIT with no statistically significant difference between the OCIT and the reference values, having more errors in identifying smaller OC degrees compared to larger OC degrees. The intraclass correlation coefficient indicated the high reliability of the OCIT.

CONCLUSION

The OCIT was verified and proven to be a valid and reliable clinical tool that accurately evaluates the degree of OC.

Applications of Cone Beam Computed Tomography Scans in Dental Medicine and Potential Medicolegal Issues

A cone beam central tomography (CBCT) scan produces images in orthogonal and non-orthogonal with great spatial resolution. When a dental health care practitioner (DHP) orders a CBCT scan, they should consider if it is truly indicated, as CBCT scans carry up to four times the dosage of radiation compared to panoramic radiographs. Any diagnostic imaging obtained of a patient should include a formal interpretive report commenting on the findings within the imaging. Ordering of limited field of view (FOV) CBCT scans and failing to report on abnormal findings present outside of the region of interest (ROI) is a potential medicolegal issue.

Virtual surgical planning in craniomaxillofacial surgery: a structured review

Craniomaxillofacial (CMF) surgery is a challenging and very demanding field that involves the treatment of congenital and acquired conditions of the face and head. Due to the complexity of the head and facial region, various tools and techniques were developed and utilized to aid surgical procedures and optimize results. Virtual Surgical Planning (VSP) has revolutionized the way craniomaxillofacial surgeries are planned and executed. It uses 3D imaging computer software to visualize and simulate a surgical procedure. Numerous studies were published on the usage of VSP in craniomaxillofacial surgery. However, the researchers found inconsistency in the previous literature which prompted the development of this review. This paper aims to provide a comprehensive review of the findings of the studies by conducting an integrated approach to synthesize the literature related to the use of VSP in craniomaxillofacial surgery. Twenty-nine related articles were selected as a sample and synthesized thoroughly. These papers were grouped assigning to the four subdisciplines of craniomaxillofacial surgery: orthognathic surgery, reconstructive surgery, trauma surgery and implant surgery. The following variables - treatment time, the accuracy of VSP, clinical outcome, cost, and cost-effectiveness - were also examined. Results revealed that VSP offers advantages in craniomaxillofacial surgery over the traditional method in terms of duration, predictability and clinical outcomes. However, the cost aspect was not discussed in most papers. This structured literature review will thus provide current findings and trends and recommendations for future research on the usage of VSP in craniomaxillofacial surgery.

Understanding the Complexities of Cast Post Retention: A Comprehensive Review of Influential Factors

This comprehensive review delves into the intricate landscape of cast post retention in restorative dentistry, encompassing historical perspectives, contemporary techniques, and future directions. Examining factors ranging from tooth-related considerations to prosthesis-related dynamics, the review provides a detailed analysis of clinical techniques, including step-by-step procedures, common challenges, and innovative advancements. Technological breakthroughs, such as digital impressions, computer-aided design and computer-aided manufacturing (CAD/CAM) technology, three-dimensional (3D) printing, and finite element analysis, are explored for their transformative impact on precision and customization. The discussion extends to the promising future of cast post retention, emphasising emerging materials, the integration of artificial intelligence in treatment planning, and patient-specific approaches. Implications for clinical practice underscore the importance of individualised treatment planning and the adoption of advanced technologies. Recommendations for future research advocate for comprehensive long-term clinical studies, investigations into AI-driven treatment planning, and a focus on patient outcomes and satisfaction. This review consolidates existing knowledge and anticipates a future marked by enhanced precision, individualised care, and improved long-term success in cast post-retained restorations.

Clinical Analysis of Patients who Underwent Reoperation After Orthognathic Surgery: A 14-Year Retrospective Study

PURPOSE

The purpose of this study was to analyze the patients clinically who underwent reoperation after certain Orthognathic procedures, and to assess the reoperation rate. Furthermore, the authors also evaluated the incidence of intraoperative and postoperative complications that led to the need for reoperation.

METHODS

Total 526 patients were selected who underwent Orthognathic surgery between July 2008 and February 2022 at the Department of Oral and Maxillofacial Surgery in Pusan National University Dental Hospital by single surgeon. All the patients information were extracted from electronic database of our university. Demographic, radiologic, intraoperative, and postoperative data were recorded and compiled.

RESULTS

Out of 526 patients, 265 (50.3%) were males and 261 (49.6%) were females. The total number of patients who showed complication is 89 (16.9%) and the patients who underwent reoperation are 17 (3.2%). The common complications that occurred were postoperative sensory disturbance (31; 5.8%), unwanted fractures (17; 3.2%), intraoperative nerve injury (11; 2%), wound dehiscence (11; 2%), infection (10; 1.9%), tooth injury (2; 0.3%), and others (18; 3.4%). The serious complications that led to reoperation include severe bleeding (6; 1.1%), unesthetic results (5; 0.9%), non-union of maxilla (4; 0.7%), and failed osteosynthesis (2; 0.3%). After 2018, all the orthognathic surgeries were performed with the help of virtual surgical planning. After application of virtual surgical planning, the number of patients with complications statistically decreased.

CONCLUSION

The present study showed that the reoperation rate after orthognathic surgery was low, this rate was more decreased after applying 3-dimensional virtual surgery and 3-dimensional printed plate, especially in unesthetic cases.

Surgical accuracy of CAD/CAM splints using virtual surgical planning in orthognathic surgery: policy implications for healthcare in Australia

BACKGROUND

This study examines post-surgical outcomes of maxillary position using virtual surgical planning (VSP) with computer designed and manufactured surgical splints, without the use of costly patient specific implants (PSI), in the treatment of routine nonsyndromic orthognathic patients. The cost of these personalized medical devices and their impact in the setting of cranio-maxillofacial surgery is currently under review by The Department of Health and Aged Care in Australia.

METHODS

This is a single-centre retrospective analysis of 49 patients who underwent bimaxillary orthognathic surgery by a single surgeon at Epworth Richmond Hospital (Victoria, Australia) over a period spanning 2016 to 2020. Patients were included in the study provided their surgery was facilitated using VSP with manufacture of computer designed occlusal splints.

RESULTS

Use of computer designed and manufactured splints were highly reliable in reproducing the virtual surgical plan, when using palatal plane, upper incisor angulation, and anterior upper facial height.

CONCLUSION

Use of computer designed and manufactured splints provide a method of leveraging the accuracy of VSP methods, without the additional costs associated with PSI. These findings may assist in appropriate resource allocation and case stratification in patients undergoing orthognathic surgery.

Patient-specific plates for facial fracture surgery: A retrospective case series

OBJECTIVES

Surgeons often encounter challenges when treating maxillofacial fractures using conventional methods that involve trimming or bending ready-made titanium plates for open reduction and internal fixation (ORIF) since it can be time-consuming, imprecise, and inconvenient. This retrospective case series aimed to introduce a novel bone reduction method that utilizes virtual planning, patient-specific surgical guides, and titanium plates.

METHODS

Seven patients with mandibular symphysis or subcondylar fractures resulting from facial trauma underwent cone-beam computed tomography (CBCT) or facial CT scans, and their medical histories were documented. Virtual surgery was conducted based on three-dimensional (3D) stereolithography images derived from CT scans using the FaceGide software (MegaGen, Daegu, Korea). ORIF was performed using patient-specific surgical guides and plates that were designed, printed, and milled. Radiographic, clinical, and occlusal evaluations were conducted at two weeks and six weeks postoperatively. Subsequently, 3D images from virtual surgery and postoperative CT scans were compared.

RESULTS

The comparison of 3D virtual surgery and postoperative images revealed minimal surface differences of less than 1 mm. T-scan evaluations indicated that there were no statistically significant differences between the two- and six-week postoperative assessments. Favorable clinical outcomes were observed.

CONCLUSION

This novel method demonstrated stable outcomes in terms of occlusion and healing, with no notable complications. Consequently, this approach may serve as a viable alternative to conventional methods.

CLINICAL SIGNIFICANCE

Facial fracture surgery that utilizes patient-specific surgical guides and plates within a digital workflow can facilitate meticulous surgical planning, reducing the risk of complications and minimizing operation time.

Accuracy of Patient-Specific Implants in Virtually Planned Segmental Le Fort I Osteotomies

(1) Background: In orthognathic surgery, segmental Le Fort I osteotomies are a valuable method to correct maxillary deformities or transversal discrepancies. However, these procedures are technically challenging, and osteosynthesis can be prone to error. (2) Methods: In this retrospective, monocentric cohort study, patients were enrolled who underwent a virtually planned segmental maxillary osteotomy during their combined treatment. Positioning and osteosynthesis were achieved by either a 3D-printed splint and conventional miniplates or patient-specific implants (PSI). The preoperative CT data, virtual planning data, and postoperative CBCT data were segmented. The deviation of all the segments from the desired virtually planned position was measured using the analysis function of IPS CaseDesigner. (3) Results: 28 Patients in the PSI Group and 22 in the conventional groups were included. The PSI group showed significantly lower deviation from the planned position anteroposteriorly (-0.63 ± 1.62 mm vs. -1.3 ± 2.54 mm) and craniocaudally (-1.39 ± 1.59 mm vs. -2.7 ± 3.1 mm). For rotational deviations, the pitch (0.64 ± 2.59° vs. 2.91 ± 4.08°), as well as the inward rotation of the lateral segments, was positively influenced by PSI. (4). Conclusions: The presented data show that patient-specific osteosynthesis significantly reduces deviations from the preoperative plan in virtually planned cases. Transversal expansions and vertical positioning can be addressed better.

Three-dimensional planning accuracy and follow-up of Le Fort I osteotomy in cleft lip/palate patients

OBJECTIVES

Our aim was to determine the accuracy of the three-dimensional (3D) virtual planning and stability of LeFort I osteotomy in cleft lip and/or palate patients (CLP) using a validated 3D method.

MATERIALS AND METHODS

Eight patients with a history of cleft lip/palate treated with LeFort I osteotomy for maxillary hypoplasia between January 2016 and April 2020 were included in this retrospective study. Three-dimensional virtual planning was performed using Proplan software then transferred to the operation theater via 3D printed occlusal wafers. The accuracy of the 3D planning and the 1-year stability of the maxilla were evaluated by means of a validated semiautomatic stepwise module in Amira software resulting into 3 linear measurements: anterior/posterior, medial/lateral, superior/inferior and 3 rotational measurements: pitch, roll, yaw.

RESULTS

The largest mean absolute difference (MAD) for accuracy assessment was found in the A/P direction (2.75mm±2.25 mm) and in pitch (3.23°±2.11°). For A/P translation, an error of >2 mm was observed in 5(62.5%), for S/I translation an error of >2 mm was observed in 4(50.0%) of the 8 patients, whereas for pitch 3 patients(37,5%) showed an error >4° At one year follow-up, the largest linear and rotational MAD was found in the A/P direction (1.20mm±0.92 mm) and in pitch (3.31°±2.31°).

CONCLUSIONS

Findings of this study show that 3D virtual computer-assisted orthognathic surgery enables an accurate repositioning of the hypoplastic maxilla in CLP patients. However, A/P translations and pitch rotations remain challenging to achieve during surgery. These movements were also found to be least stable at one year follow-up.

Stability of maxillary expansion osteotomy using patient-specific fixation implants without necessitating removable appliances: a retrospective analysis

OBJECTIVE

This study aimed to evaluate the long-term stability of surgical maxillary expansion using patient-specific fixation implants (PSFIs) without intraoral retention.

MATERIALS AND METHODS

Fifteen patients who had undergone segmented Le Fort I osteotomy and PSFIs with available preoperative (t0) early (t1) and 1-year follow-up computed tomography (CT) scans (t2) were evaluated. The early and 1-year 3D models were superimposed to transfer the bony landmarks; the distances between each pair of landmarks at the different time points were then measured. The distances between the canines and second molars were also measured directly on the CT scans.

RESULTS

The achieved maxillary expansions ranged from a median of 4.39 (2.00-6.27) mm at the greater palatine foramina to a median of 2.14 (1.56-2 > 83) mm at the canine level of the palatal bone. One year postoperatively, the changes in skeletal diameters ranged from a median of - 0.53 (- 1.65 to 0.41) mm at the greater palatine foramina (p = 0.12) to 0.17 (- 0.09 to 0.32) mm at the canine level of the palatal bone (p = 0.56). Changes in dental arch diameters ranged from a median of - 0.6 (- 2 to 0.00) mm between the second molars to - 1.3 (- 1.8 to - 0.25) mm between the canines (P < 0.05).

CONCLUSION

This study showed the stability of maxillary expansion osteotomy using PSFIs, even without postoperative intraoral retention.

CLINICAL RELEVANCE

PSFIs are a reliable method for the surgical treatment of transverse maxillary discrepancy. PFSIs are easy-to-use and improve surgical accuracy.

Morphological Variation of the Mandible in the Orthognathic Population-A Morphological Study Using Statistical Shape Modelling

The aim of this study was to investigate the value of 3D Statistical Shape Modelling for orthognathic surgery planning. The goal was to objectify shape variations in the orthognathic population and differences between male and female patients by means of a statistical shape modelling method. Pre-operative CBCT scans of patients for whom 3D Virtual Surgical Plans (3D VSP) were developed at the University Medical Center Groningen between 2019 and 2020 were included. Automatic segmentation algorithms were used to create 3D models of the mandibles, and the statistical shape model was built through principal component analysis. Unpaired t-tests were performed to compare the principal components of the male and female models. A total of 194 patients (130 females and 64 males) were included. The mandibular shape could be visually described by the first five principal components: (1) The height of the mandibular ramus and condyles, (2) the variation in the gonial angle of the mandible, (3) the width of the ramus and the anterior/posterior projection of the chin, (4) the lateral projection of the mandible's angle, and (5) the lateral slope of the ramus and the inter-condylar distance. The statistical test showed significant differences between male and female mandibular shapes in 10 principal components. This study demonstrates the feasibility of using statistical shape modelling to inform physicians about mandible shape variations and relevant differences between male and female mandibles. The information obtained from this study could be used to quantify masculine and feminine mandibular shape aspects and to improve surgical planning for mandibular shape manipulations.

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.

The Last 40 Years of Orthognathic Surgery: A Bibliometric Analysis

PURPOSE

Bibliometric analyses provide information on the effectiveness, performance, trends, and various other characteristics of research by using mathematical and statistical analysis methods for data related to scientific publications. This study aims to determine the focus of studies in the field of orthognathic surgery, map it, and present the results in a simplified manner through a comprehensive bibliometric analysis of the relevant literature.

METHODS

In this bibliometric analysis study, orthognathic surgery publications from 1980 to 2022 were retrieved from the Web of Science Core Collection database. The independent variables were co-citations, while the outcome variables included cross-country collaboration analysis, keyword analysis, co-citation analysis, and cluster analysis of the co-citation network. Covariates were the number of publications, number of citations, year range, centrality value, and silhouette value. The bibliometric analysis was conducted using CiteSpace, VOSviewer, and R-Studio software.

RESULTS

A total of 7,135 publications and 75,822 references were included in the analysis, and the annual growth rate of publications was 9.52%. The co-citation clustering analysis revealed that the orthognathic surgery literature was organized into 16 subject headings. Patient satisfaction was found to be the most widely published topic. The youngest clusters, representing new topics in the field, were virtual planning and examination of condylar changes after orthognathic surgery.

CONCLUSION

Bibliometric analysis methods were used to evaluate the 40-year history of the orthognathic surgery literature. The analysis identified the most influential publications, the topics in which the literature is divided, and hot spots in the field. By conducting similar bibliometric research studies in the future, the progress and future direction of the literature can be monitored based on evidence.

Prediction of orthognathic surgery plan from 3D cephalometric analysis via deep learning

BACKGROUND

Preoperative planning of orthognathic surgery is indispensable for achieving ideal surgical outcome regarding the occlusion and jaws' position. However, orthognathic surgery planning is sophisticated and highly experience-dependent, which requires comprehensive consideration of facial morphology and occlusal function. This study aimed to investigate a robust and automatic method based on deep learning to predict reposition vectors of jawbones in orthognathic surgery plan.

METHODS

A regression neural network named VSP transformer was developed based on Transformer architecture. Firstly, 3D cephalometric analysis was employed to quantify skeletal-facial morphology as input features. Next, input features were weighted using pretrained results to minimize bias resulted from multicollinearity. Through encoder-decoder blocks, ten landmark-based reposition vectors of jawbones were predicted. Permutation importance (PI) method was used to calculate contributions of each feature to final prediction to reveal interpretability of the proposed model.

RESULTS

VSP transformer model was developed with 383 samples and clinically tested with 49 prospectively collected samples. Our proposed model outperformed other four classic regression models in prediction accuracy. Mean absolute errors (MAE) of prediction were 1.41 mm in validation set and 1.34 mm in clinical test set. The interpretability results of the model were highly consistent with clinical knowledge and experience.

CONCLUSIONS

The developed model can predict reposition vectors of orthognathic surgery plan with high accuracy and good clinically practical-effectiveness. Moreover, the model was proved reliable because of its good interpretability.

An Overview of Clinical Conditions and a Systematic Review of Personalized TMJ Replacement

The temporomandibular joint (TMJ) is a complex structure in the cranio-maxillomandibular region. The pathological changes of the joint cause deficiencies at different levels, making its replacement necessary in some cases. The aim of this article is to analyze the current indications, treatment and criteria, and follow-up using a systematic review and case series. A systematic review was carried out, identifying the indications for the use of a customized TMJ prosthesis and evaluating criteria and validation in the international literature. After review and exclusion, 8 articles were included with a minimum follow-up of 12 months. The age of the subjects was between 18 and 47 years old. In 226 patients, 310 TMJ prostheses were installed, 168 bilaterally and 142 unilaterally. In most of the articles, a good condition in the follow-up was observed, with a reduction in pain and better conditions of mandibular movement and function. TMJ prosthesis and replacement is a protocolized, defined, stable, and predictable procedure. Indications and criteria must be evaluated by specialists and patients related to the pathology involved in TMJ deformity or degeneration. Randomized research with an accurate diagnosis and follow-up is necessary to obtain the best indication for this treatment.

Accuracy and safety of in-house surgeon-designed three-dimensional-printed patient-specific implants for wafer-less Le Fort I osteotomy

OBJECTIVES

The design and fabrication of three-dimensional (3D)-printed patient-specific implants (PSIs) for orthognathic surgery are customarily outsourced to commercial companies. We propose a protocol of designing PSIs and surgical guides by orthognathic surgeons-in-charge instead for wafer-less Le Fort I osteotomy. The aim of this prospective study was to evaluate the accuracy and post-operative complications of PSIs that are designed in-house for Le Fort I osteotomy.

MATERIALS AND METHODS

The post-operative cone beam computer tomography (CBCT) model of the maxilla was superimposed to the virtual surgical planning to compare the discrepancies of pre-determined landmarks, lines, and principal axes between the two models. Twenty-five patients (12 males, 13 females) were included.

RESULTS

The median linear deviations of the post-operative maxilla of the x, y, and z axes were 0.74 mm, 0.75 mm, and 0.72 mm, respectively. The deviations in the principal axes for pitch, yaw, and roll were 1.40°, 0.90°, and 0.60°, respectively. There were no post-operative complications related to the PSIs in the follow-up period.

CONCLUSIONS

The 3D-printed PSIs designed in-house for wafer-less Le Fort I osteotomy are accurate and safe.

CLINICAL RELEVANCE

Its clinical outcomes and accuracy are comparable to commercial PSIs for orthognathic surgery.

TRIAL REGISTRATION

Clinical trial registration number: HKUCTR-2113. Date of registration: 29 July 2016.

Consideration of root position in virtual tooth setup for extraction treatment: A comparative study of simulated and actual treatment results

Objective

The purpose of the present study was to compare the root positions in virtual tooth setups using only crowns in a simulated treatment with those achieved in the actual treatment.

Methods

Pre- and post-treatment intraoral and corresponding cone beam computed tomography (CBCT) scans were obtained from 15 patients who underwent orthodontic treatment with premolar extraction. A conventional virtual tooth setup was used for the treatment simulation. Pre- and post-treatment three-dimensional digital tooth models were fabricated by integrating the patients' intraoral and CBCT scans. The simulated root positions in the virtual setup were obtained by merging the crown in the virtual setup and root in the pre-treatment tooth model. The root positions of the simulated and actual post-treatment tooth models were compared.

Results

Differences in root positions between the simulated and actual models were > 1 mm in all teeth, and statistically significant differences were observed (p < 0.05), except for the maxillary lateral incisors. The differences in the inter-root angulation were > 1° in all teeth, and statistically significant differences were observed in the maxillary and mandibular canines.

Conclusions

The virtual tooth setup using only crown data showed errors over the clinical limits. The clinical application of a virtual setup using crowns and roots is necessary for accurate and precise treatment simulation, particularly in extraction treatment.

Accuracy of Segmented Le Fort I Osteotomy with Virtual Planning in Orthognathic Surgery Using Patient-Specific Implants: A Case Series

Background: When maxillary transversal expansion is needed, two protocols of treatment can be used: a maxillary orthodontic expansion followed by a classical bimaxillary osteotomy or a bimaxillary osteotomy with maxillary segmentation. The aim of this study was to assess the accuracy of segmented Le Fort I osteotomy using computer-aided orthognathic surgery and patient-specific titanium plates in patients who underwent a bimaxillary osteotomy for occlusal trouble with maxillary transversal insufficiencies. Methods: A virtual simulation of a Le Fort I osteotomy with maxillary segmentation, a sagittal split ramus osteotomy, and genioplasty (if needed) was conducted on a preoperative three-dimensional (3D) model of each patient’s skull using ProPlan CMF 3.0 software (Materialise, Leuven, Belgium). Computer-assisted osteotomy saw-and-drill guides and patient-specific implants (PSIs, titanium plates) were produced and used during the surgery. We chose to focus on the maxillary repositioning accuracy by comparing the preoperative virtual surgical planning and the postoperative 3D outcome skulls using surface superimpositions and 13 standard dental and bone landmarks. Errors between these preoperative and postoperative landmarks were calculated and compared to discover if segmental maxillary repositioning using PSIs was accurate enough to be safely used to treat transversal insufficiencies. Results: A total of 22 consecutive patients—15 females and 7 males, with a mean age of 27.4 years—who underwent bimaxillary computer-assisted orthognathic surgery with maxillary segmentation were enrolled in the study. All patients presented with occlusion trouble, 13 with Class III malocclusions (59%) and 9 (41%) with Class II malocclusions. A quantitative analysis revealed that, overall, the mean absolute discrepancies for the x-axis (transversal dimension), y-axis (anterior−posterior dimensions), and z-axis (vertical dimension) were 0.59 mm, 0.74 mm, and 0.56 mm, respectively. The total error rate of maxillary repositioning was 0.62 mm between the postoperative cone-beam computed tomography (CBCT) and the preoperatively planned 3D skull. According to the literature, precision in maxilla repositioning is defined by an error rate (clinically relevant) at each landmark of <2 mm and a total error of <2 mm for each patient. Conclusions: A high degree of accuracy between the virtual plan and the postoperative result was observed.

Three-Dimensional Comparison of the Maxillary Surfaces through ICP-Type Algorithm: Accuracy Evaluation of CAD/CAM Technologies in Orthognathic Surgery

PURPOSE

This retrospective study aims to compare the accuracy of two different CAD/CAM systems in orthognathic surgery. The novelty of this work lies in the method of evaluating the accuracy, i.e., using an Iterative Closest Point (ICP) algorithm, which matches a pair of 2D or 3D point clouds with unknown dependencies of the transition from scan s_(k) to scan s_(k+1).

METHODS

The study population was composed of ten patients who presented to the Maxillofacial Surgery Department of the University "Sapienza" of Rome for the evaluation and management of skeletal malocclusions. The patients were divided into two groups, depending on the technique used: group 1: splintless group (custom-made cutting guide and plates); group 2: splint group (using a 3D-printed splint). STL files were imported into Geomagic^® Control X™ software, which allows for comparison and analysis using an ICP algorithm. The RMSE parameter (3D error) was used to calculate the accuracy. In addition, data were compared in two different patient subgroups. The first subgroup only underwent a monobloc Le Fort I osteotomy (p-value = 0.02), and the second subgroup underwent a Le Fort I osteotomy associated with a segmental osteotomy of the maxilla (p-value = 0.23).

RESULTS

Group 1 showed a 3D error of 1.22 mm ± SD 0.456, while group 2 showed a 3D error of 1.63 mm ± SD 0.303. These results have allowed us to compare the accuracy of the two CAD/CAM systems (p-value = 0.09).

CONCLUSIONS

The ICP algorithm provided a reproducible method of comparison. The splintless method would seem more accurate (p-value = 0.02) in transferring the surgical programming into the operating room when only a Le Fort I osteotomy is to be performed.

An innovative universal protocol for orthognathic surgery three-dimensional virtual simulation

The aim of this technical note is to describe a protocol for three-dimensional virtual simulation of orthognathic surgery that has been designed to be easily implemented, without the need for any special clinical apparatus, software brand, or computed tomography sequence. The protocol comprises innovative concepts and simplified steps for image segmentation, creation of a composite skull, control of the condylar position, and sequencing of bimaxillary surgery. This protocol was applied by the developers in about 2000 cases performed between 2015 and 2022, and has become quite popular among local surgeons. Previous preliminary studies have shown that it meets the accuracy standards for clinical use, although further studies with larger numbers of patients are desirable for additional validation.

A review on the application of deep learning for CT reconstruction, bone segmentation and surgical planning in oral and maxillofacial surgery

Computer-assisted surgery (CAS) allows clinicians to personalize treatments and surgical interventions and has therefore become an increasingly popular treatment modality in maxillofacial surgery. The current maxillofacial CAS consists of three main steps: (1) CT image reconstruction, (2) bone segmentation, and (3) surgical planning. However, each of these three steps can introduce errors that can heavily affect the treatment outcome. As a consequence, tedious and time-consuming manual post-processing is often necessary to ensure that each step is performed adequately. One way to overcome this issue is by developing and implementing neural networks (NNs) within the maxillofacial CAS workflow. These learning algorithms can be trained to perform specific tasks without the need for explicitly defined rules. In recent years, an extremely large number of novel NN approaches have been proposed for a wide variety of applications, which makes it a difficult task to keep up with all relevant developments. This study therefore aimed to summarize and review all relevant NN approaches applied for CT image reconstruction, bone segmentation, and surgical planning. After full text screening, 76 publications were identified: 32 focusing on CT image reconstruction, 33 focusing on bone segmentation and 11 focusing on surgical planning. Generally, convolutional NNs were most widely used in the identified studies, although the multilayer perceptron was most commonly applied in surgical planning tasks. Moreover, the drawbacks of current approaches and promising research avenues are discussed.

An overview of three-dimensional imaging devices in dentistry

OBJECTIVE

To review four types of three-dimensional imaging devices: intraoral scanners, extraoral scanners, cone-beam computed tomography (CBCT), and facial scanners, in terms of their development, technologies, advantages, disadvantages, accuracy, influencing factors, and applications in dentistry.

METHODS

PubMed (National Library of Medicine) and Google Scholar databases were searched. Additionally, the scanner manufacturers' websites were accessed to obtain relevant data. Four authors independently selected the articles, books, and websites. To exclude duplicates and scrutinize the data, they were uploaded to Mendeley Data. In total, 135 articles, two books, and 17 websites were included.

RESULTS

Research and clinical practice have shown that oral and facial scanners and CBCT can be used widely in various areas of dentistry with high accuracy.

CONCLUSION

Although further advancement of these devices is desirable, there is no doubt that digital technology represents the future of dentistry. Furthermore, the combined use of different devices may bring dentistry into a new era. These four devices will play a significant role in clinical utility with high accuracy. The combined use of these devices should be explored further.

CLINICAL SIGNIFICANCE

The four devices will play a significant role in clinical use with high accuracy. The combined use of these devices should be explored further.

Custom made cutting guides and osteosynthesis plates versus CAD/CAM occlusal splints in positioning and fixation of the maxilla in orthognathic surgery: A prospective randomized study

The aim of this study is to compare the accuracy of maxilla positioning in orthognathic surgery with the use of custom-made devices (cutting guides and patient-fitted osteosynthesis plates) comparing to CAD/CAM splints. A prospective randomized study was performed. Patients with dentofacial deformities undergoing orthognathic surgery were compared, using customized guides (experimental group) vs. CAD/CAM surgical splints (control group) for the repositioning of the upper maxilla. Preoperative and postoperative CT scans were used to compare positioning and fixation of the maxilla in the three planes of space. A total of 30 patients were included in the study (15 patients in each study group). The mean error obtained with customized guides was 0.8 mm (range 0.1-1.9) in the anterior-posterior axis, 0.4 mm (range 0-1.4) in the vertical axis and 0.2 mm (range 0-1.1) in the horizontal axis. There were statistically significant differences in the anterior-posterior and vertical axes in favour of the customized implants, whereas there were no differences in the horizontal plane. Furthermore, there was a mean reduction of the operative time of 36.5 min in the experimental group. Within the limitations of the study it seems that patient specific surgical guides should be preferred when accuracy of repositioning of the maxilla and saving operative time are the priority.

Accuracy of a surface-based fusion method when integrating digital models and the cone beam computed tomography scans with metal artifacts

The aim of this study was to evaluate the intra- and inter-observer reliability of maxillary digital dental model integration into cone-beam computed tomography (CBCT) scans to reconstruct three-dimensional (3D) skeletodental models for orthognathic patients. This retrospective study consisted of CBCT and digital maxillary dentition images of 20 Class III orthognathic patients. After two repeated fusions of digital cast images with reconstructed CBCT images by a digital engineer and an orthodontist respectively, the 3D coordinate values of the canines, first molars, and central incisors were evaluated. The intra- and inter-observer reliability of 3D positions of maxillary teeth were compared using intraclass correlation coefficients (ICCs). Intra-observer reliability of x-, y-, and z-coordinate values of maxillary teeth showed significant and excellent agreement in an engineer (0.946 ≤ ICC ≤ 1.000) and an orthodontist (0.876 ≤ ICC ≤ 1.000). The inter-observer reliability of the y- and z-coordinates of each tooth was significantly excellent or good, but that of the x-coordinates showed insignificantly poor to moderate agreement. This study showed that the integration of maxillary digital models into CBCT scans was clinically reliable. However, considering the low inter-observer reliability on the x-coordinates of dentition, clinical experience and repeated learning are needed for accurate application of digital skeletodental model in orthognathic patients.

Evaluation of the Predictability and Accuracy of Orthognathic Surgery in the Era of Virtual Surgical Planning

Virtual surgical planning allows orthognathic surgeons to design a surgical plan preoperatively and establish a personalized surgical protocol. This study aims to validate the predictability and accuracy of orthognathic surgery through a comparison of the three-dimensional (3D) models of the virtual planning and postoperative CBCT using free software (3D Slicer) on 40 patients who underwent bimaxillary orthognathic surgery. The distances of point A, point B, pogonion (Pog), and the first upper and lower molars, both in each axis (x, y, and z) and in the 3D space, were analyzed. The median of the distances in the mediolateral direction was the lowest, while the highest differences were found at point A and Pog in the anteroposterior direction (0.83 mm and 0.78 mm, respectively). Vertical differences were higher in the maxilla than in the mandible. In conclusion, we found that orthognathic bimaxillary surgery using virtual surgical planning was more accurate when positioning the bone segments in the mediolateral direction, using the information provided by the splint, as well as when positioning the mandible compared to the maxilla.

Computer Aided Orthognathic Surgery: A General Method for Designing and Manufacturing Personalized Cutting/Repositioning Templates

Orthognathic surgery allows broad-spectrum deformity correction involving both aesthetic and functional aspects on the TMJ (temporo-mandibular joint) and on the facial skull district. The combination of Reverse Engineering (RE), Virtual Surgery Planning (VSP), Computer Aided Design (CAD), Additive Manufacturing (AM), and 3D visualization allows surgeons to plan, virtually, manipulations and the translation of the human parts in the operating room. This work’s aim was to define a methodology, in the form of a workflow, for surgery planning and for designing and manufacturing templates for orthognathic surgery. Along the workflow, the error chain was checked and the maximum error in virtual planning was evaluated. The three-dimensional reconstruction of the mandibular shape and bone fragment movements after segmentation allow complete planning of the surgery and, following the proposed method, the introduction of both the innovative evaluation of the transversal intercondylar distance variation after mandibular arch advancement/set and the possibility of use of standard plates to plan and realize a customized surgery. The procedure was adopted in one clinical case on a patient affected by a class III malocclusion with an associated open bite and right deviation of the mandible with expected good results. Compared with the methods from most recent literature, the presented method introduces two elements of novelty and improves surgery results by optimizing costs and operating time. A new era of collaboration among surgeons and engineer has begun and is now bringing several benefits in personalized surgery.

Shaping the Lower Jaw Border with Customized Cutting Guides: Development, Validation, and Application in Facial Gender-Affirming Surgery

Importance: Three-dimensional planning software is not standardized in facial gender-affirming surgery. Objective: To develop and validate surgical planning software to create cutting guides to contour the lower jaw border. Design, Setting, and Participants: A 3-year prospective case series study done in three phases: software development, validation, and surgical guide application. Ethics committee approval was obtained to enroll the patients (Clinical Research Ethics Committee, Hospital Costa del Sol, Marbella, Spain). Main Outcomes and Measures: Validation phase: degree of agreement between the planned and obtained results, modification of cephalometric parameters, and surgical times. Application phase: surgical technique description, complications, and patient-reported outcome measures. Results: The degree of agreement between the planned and obtained results was inframillimetric (0.31 ± 0.70 mm). The guides reduced the mandible to within feminine parameters (p < 0.05). Surgical times decreased by 10.96% with chin ostectomies (p < 0.05) and 23.06% with lower jaw border (angle-to-angle) surgeries (p < 0.001). In the application phase, revision surgery was required for 11 patients out of 260 (4.23%). Conclusions and Relevance: The use of cutting guides on the lower jaw border is effective, helps reach standard feminine parameters, and decreases surgical times.

Posterior Mandibular Segmental Split Osteotomy: A Novel Technique for Edentulous Space Reconstruction in Patients With Skeletal Class III Malocclusion

ABSTRACT

This study presents an innovative surgery that successfully improved the facial profile and occlusal function of a patient with a skeletal Class III malocclusion and posterior hypodontia. The patient had chief complaints of missing teeth and a protruded jaw. A novel 1-stage surgery referred to as posterior mandibular segmental split osteotomy combined with Le Fort I osteotomy and BSSRO was used because the patient wanted to save time and was worried about periodontal complications associated with other treatment methods. As a result, a satisfying facial profile and a Class I occlusion with a normal position of the posterior dentoalveolar segment of the mandible were achieved with no adverse effects. Thus, posterior mandibular segmental split osteotomy can be considered an effective treatment for skeletal Class III malocclusion with posterior hypodontia.

Computed tomography imaging superimposition protocols to assess outcomes in orthognathic surgery: a systematic review with comprehensive recommendations

OBJECTIVES

A systematic review was performed to analyze the current evidence on three-dimensional (3D) computed tomography (CT) superimposition protocols used to assess dentomaxillofacial changes after orthognathic and orthofacial surgery. Accuracy, reproducibility, and efficiency were evaluated.

METHODS

The search was divided into Main Search (PubMed, EMBASE, Cochrane Library, LILACS, and SciELO), Grey Literature search (Google Scholar and Open Grey), and Manual search. Thirteen studies were included. Of these, 10 reported data on accuracy, 10 on reproducibility and five on efficiency. Seven proposed or evaluated methods of voxel-based superimposition, three focused on the surface-based technique, one compared surface- and voxel-based superimposition protocols, one used the maximum mutual information algorithm, and one described a landmark-based superimposition method. Cone-beam computed tomography (CBCT) was the most common imaging technique, being used in 10 studies.

RESULTS

The accuracy of most methods was high, showing mean differences smaller than voxels' dimensions, ranging between 0.05 and 1.76 mm for translational accuracy, and 0.10-1.09° for rotational accuracy. The overall reproducibility was considered good as demonstrated by the small mean error (range: 0.01-0.26 mm) and high correlation coefficients (range: 0.53-1.00). Timing to complete virtual superimposition techniques ranged between a few seconds up to 40 min.

CONCLUSIONS

Voxel-based superimposition protocols presented the highest accuracy and reproducibility. Moreover, superimposition protocols that used automated processes and involved only one software were the most efficient.

Complications on maxilar impaction: A systematic review and meta-analysis

OBJECTIVES

Maxillary impactions are seen as an orthognathic surgical movement that increases the number of complications. The aim of this paper is to research literature on this topic, with special attention to avoiding of complications.

METHODS

A systematic review was carried out according to the PRISMA guidelines. The PROSPERO registration has been performed. A risk of bias assessment was carried out with RevMan and graphics were created. A total of 20 articles were included in this systematic review.

RESULTS

Some interesting and conclusive facts about maxillary impactions. Relapses are not common due to the higher bone contact. Bleeding is a common complication due to the location of palatal artery. Aesthetic and functional complications can arise, especially in the nasal region. Bimaxillary orthognathic surgeries has a higher incidence of complications.

CONCLUSIONS

Today it is not possible to confirm that maxillary impactions alone are responsible for a higher incidence of complications due to the complexity of the three-dimensional movements. Some surgical steps could be safer and cause fewer complications.

Three-dimensional analysis of condylar remodeling and skeletal relapse following LeFort-I osteotomy: A one-year follow-up bicenter study

The aim of the study was to quantify the postoperative condylar remodeling after Le Fort I surgery. Patients treated with a Le Fort I osteotomy were investigated. CBCT scans were acquired preoperatively, one week and one year postoperatively. A preoperative 3D cephalometric analysis was performed on the preoperative CBCT. Surgical movements were quantified using a voxel-registration based method (OrthoGnaticAnalyser). After rendering of the condyles from the CBCT, a volumetric analysis was performed. The correlation between the surgical movement of the maxilla and the postoperative condylar volume changes was determined with analysis of variance. RESULTS: A total of 45 subjects were included in this study. 47 of 90 condyles (52%) showed a mean volume reduction of 93 mm³ (4.9 volume-%) postoperatively. The maxilla was impacted in 12 patients (2.44 ± 2.49 mm) and extruded in 33 patients (1.78 ± 1.29 mm). The maxillary impaction group showed a volume reduction of 50 ± 122 mm³ and the extrusion group showed a mean volume gain of 21 ± 139 mm³ (p = 0.028). CONCLUSION: Clinicians should be aware of potential condylar remodeling following solitary Le Fort I osteotomies, particularly in female patients with maxillary impaction.

Soft-Tissue Simulation for Computational Planning of Orthognathic Surgery

Simulation technologies offer interesting opportunities for computer planning of orthognathic surgery. However, the methods used to date require tedious set up of simulation meshes based on patient imaging data, and they rely on complex simulation models that require long computations. In this work, we propose a modeling and simulation methodology that addresses model set up and runtime simulation in a holistic manner. We pay special attention to modeling the coupling of rigid-bone and soft-tissue components of the facial model, such that the resulting model is computationally simple yet accurate. The proposed simulation methodology has been evaluated on a cohort of 10 patients of orthognathic surgery, comparing quantitatively simulation results to post-operative scans. The results suggest that the proposed simulation methods admit the use of coarse simulation meshes, with planning computation times of less than 10 seconds in most cases, and with clinically viable accuracy.

The Use of Surgical Splints in Orthognathic Surgery: A Bibliometric Study

Introduction  Orthognathic surgeries require the use of surgical splints (SS) to stabilize the occlusion and the segments fixed with plates and screws. Technological advances in the field of computing and the possibility of generating three-dimensional (3D) images have brought different possibilities for making SS, which has generated greater predictability and customization of surgical plans. The bibliometric study can have a qualitative character through the scope of articles in a certain area of knowledge. It is a selection process that can track a topic or scientific production.

Methods  The present study aimed to carry out a bibliometric literature review, in order to assess the evolution of the use of SS and the different planning protocols in orthognathic surgery. The Scopus database was used, with the terms “splint” and “orthognathic surgery.”

Results  A total of 331 articles were found. These were exported to Rayyan for application of the inclusion and exclusion criteria and selection of articles. A total of 76 references were selected and exported to the VOSviewer application for the analysis of bibliometric data.

Conclusions  Orthognathic surgery was initially not associated with any computerized technological resource; however, it underwent updates between the years 2010 to 2012. These advances allowed surgical planning to become faster, cheaper, and more accurate.

Comparison of actual amount of movement with surgical treatment objective in the orthognathic maxillary repositioning

OBJECTIVE

To compare the postoperative position of the maxilla with the surgical treatment objectives (STO) in bimaxillary orthognathic surgery for evaluating the surgical accuracy and investigating the pattern and cause of the discrepancy.

METHODS

Patients undergoing conventional bimaxillary orthognathic surgery by a single oral and maxillofacial surgeon were enrolled. Utilizing the superimposition of preoperative and postoperative computed tomography images, the actual amounts of positional change of both the maxillary central incisor and first molars were compared with those of STO. All the patients were divided into two groups according to the actual discrepancy between STO and the postoperative position and factors that may affect surgical accuracy were analyzed.

RESULTS

In 62 cases, the absolute mean value of the positional difference between STO and the actual outcome was 2.20 mm (X-axis, 0.93 mm; Y-axis, 1.31 mm; and Z-axis, 1.09 mm) in the maxillary central incisor. The signed mean value of the central incisor was -0.07 mm, 0.79 mm, and -0.57 mm in the X-, Y-, and Z-axes, respectively, and the value in the Y- and Z-axes showed a statistically significant difference in comparison with STO (P<0.01). Age, sex, skeletal Angle classification, maxillary and mandibular profile, use of 3D virtual surgery, facial asymmetry, and yawing correction did not show a statistically significant correlation with surgical accuracy at the central incisor.

CONCLUSION

There was an acceptable range of discrepancy between postoperative maxillary position and STO after orthognathic surgery; however, there was a tendency for posterior and downward movement in the maxillary anterior teeth.

Three-Dimensional Analysis of Soft and Hard Tissue Changes following Orthognathic Surgery

Change in soft tissue in relation to that in hard tissue following orthognathic surgery was evaluated. Twenty-five patients were enrolled in the study. The diagnosis in all was jaw deformity (maxillary retrusion and mandibular protrusion) and all underwent a Le Fort I osteotomy and bilateral sagittal splitting ramus osteotomy. Three-dimensional (3D) computer-aided design (CAD) models (polygon models) of the hard and soft tissue of the maxilla and mandible were constructed and superimposed. Reference points were established on the pre- and postoperative hard and soft tissues. Specific elements of each reference point were divided into X, Y, and Z components, respectively, and the distances in each direction and 3D distance (normal distance) measured. The Wilcoxon signed-rank test was used to determine differences in the mean values for the distance moved of each element as the error between pre- and postoperatively. The results revealed statistically significant differences in the Y-direction in the maxilla and the X- and Z-directions in the mandible. A significant difference was also observed in the 3D distances of the maxilla and mandible. Little evidence was found of linearity between the amount of hard and soft tissue movement in the X- and Z-directions in the maxilla. This means that 3D movement in the maxilla was masked more by changes in the morphology of the soft tissue than in the mandible, making it less evident. The results of this study suggest that the 3D analysis method used enables changes in hard and soft tissues to be understood qualitatively, and that it can be used in diagnosis and treatment in orthognathic surgery. It may also be useful in simulation of morphological change in soft tissue.

Accuracy of 3-dimensional soft tissue prediction for orthognathic surgery in a Chinese population

OBJECTIVES

This study aims to determine the validity of a 3D planning software in predicting the soft tissue outcome of Chinese patients undergoing orthognathic surgery for correction of Skeletal III dentofacial deformity.

METHODS

Pre- and post-operative 3D facial stereophotogrammetric scans and cone beam computed tomography were taken for 10 Chinese patients who had underwent orthognathic surgery. The pre-operative 3D facial scan was integrated with the pre-operative CBCT using the ProPlan CMF software. The simulated soft tissue 3D face was then compared with the actual 3D facial scan obtained at least 6 months postoperatively. Two outcome measures were computed as follows (i) mean absolute difference between meshes (ii) percentage of points where the distance between the two meshes is 2mm or less.

RESULTS

The mean absolute difference between the predicted and actual soft tissue surface meshes for the full face and the 6 anatomic regions ranged from 0.72mm to 1.42 mm. The mean absolute distance between the meshes for all the anatomic regions were within 2 mm (p<0.05). The percentage of mesh points with less than 2mm error ranged from 72.5% to 92.5%. The accuracy of soft tissue prediction, assessed using mean absolute distance for the full face, was significantly correlated to the amount of sagittal surgical movement (r=0.707, p=0.022). The lower lip was also found to be the least accurate.

CONCLUSIONS

Using ProPlan CMF, the accuracy of 3D soft tissue predictions for bimaxillary orthognathic surgery in Chinese Skeletal III patients were clinically satisfactory.

Three-dimensional evaluation of long-term skeletal relapse following Le Fort I maxillary advancement surgery: a 2-year follow-up study

The aim of this study was to assess relapse following Le Fort I (LFI) maxillary advancement with superior or inferior repositioning at 2 years of follow-up. A total of 50 patients (26 female, 24 male; age range 15-56 years) with skeletal class II or III, who underwent bimaxillary surgery with LFI maxillary advancement in combination with either superior or inferior repositioning and also mandibular advancement/setback, were recruited. Preoperative (T0), immediate postoperative (T1), and 2-year postoperative (T2) cone beam computed tomography scans were acquired. Data were imported into a validated module to assess the skeletal movement (T0-T1) and relapse (T1-T2). Overall, the majority of the translational and rotational movements showed a relapse of <1 mm and <1°. Patients undergoing maxillary advancement with inferior repositioning in combination with mandibular advancement showed the highest amount of translational relapse in a superior (0.86 ± 0.85 mm, P < 0.0001) and posterior direction (-0.65 ± 1.11 mm, P < 0.0001). In relation to patients who received a bone graft, inferior repositioning with mandibular setback showed the highest maxillary relapse in a superior direction (1.20 ± 1.56 mm, P = 0.0719) with counterclockwise pitch rotation (2.15 ± 0.64°, P = 0.3759). Amongst the non-grafted procedures, superior repositioning with mandibular setback exhibited the highest relapse in a medial direction (1.38 ± 2.78 mm, P = 0.3981). Maxillary advancement was found to be a highly stable procedure with a lack of superoinferior stability in patients undergoing inferior repositioning.

Fully automatic brain tumor segmentation for 3D evaluation in augmented reality

OBJECTIVE

For currently available augmented reality workflows, 3D models need to be created with manual or semiautomatic segmentation, which is a time-consuming process. The authors created an automatic segmentation algorithm that generates 3D models of skin, brain, ventricles, and contrast-enhancing tumor from a single T1-weighted MR sequence and embedded this model into an automatic workflow for 3D evaluation of anatomical structures with augmented reality in a cloud environment. In this study, the authors validate the accuracy and efficiency of this automatic segmentation algorithm for brain tumors and compared it with a manually segmented ground truth set.

METHODS

Fifty contrast-enhanced T1-weighted sequences of patients with contrast-enhancing lesions measuring at least 5 cm3 were included. All slices of the ground truth set were manually segmented. The same scans were subsequently run in the cloud environment for automatic segmentation. Segmentation times were recorded. The accuracy of the algorithm was compared with that of manual segmentation and evaluated in terms of Sørensen-Dice similarity coefficient (DSC), average symmetric surface distance (ASSD), and 95th percentile of Hausdorff distance (HD95).

RESULTS

The mean ± SD computation time of the automatic segmentation algorithm was 753 ± 128 seconds. The mean ± SD DSC was 0.868 ± 0.07, ASSD was 1.31 ± 0.63 mm, and HD95 was 4.80 ± 3.18 mm. Meningioma (mean 0.89 and median 0.92) showed greater DSC than metastasis (mean 0.84 and median 0.85). Automatic segmentation had greater accuracy for measuring DSC (mean 0.86 and median 0.87) and HD95 (mean 3.62 mm and median 3.11 mm) of supratentorial metastasis than those of infratentorial metastasis (mean 0.82 and median 0.81 for DSC; mean 5.26 mm and median 4.72 mm for HD95).

CONCLUSIONS

The automatic cloud-based segmentation algorithm is reliable, accurate, and fast enough to aid neurosurgeons in everyday clinical practice by providing 3D augmented reality visualization of contrast-enhancing intracranial lesions measuring at least 5 cm3. The next steps involve incorporation of other sequences and improving accuracy with 3D fine-tuning in order to expand the scope of augmented reality workflow.