Contemporary Correction of Dentofacial Anomalies: A Clinical Assessment.

Contemporary computer-assisted technologies can support the surgical team in the treatment of patients affected by dentofacial deformities. Based on own experiences of 350 patients that received orthognathic surgery by the same team from 2007 to 2015, this clinical review is intended to give an overview of the results and risks related to the surgical correction of dentofacial anomalies. Different clinical and technological innovations that can contribute to improve the planning and transfer of corrective dentofacial surgery are discussed as well. However, despite the presence of modern technologies, a patient-specific approach and solid craftsmanship remain the key factors in this elective surgery.

RapidSplint: virtual splint generation for orthognathic surgery - results of a pilot series.

BACKGROUND: Within the domain of craniomaxillofacial surgery, orthognathic surgery is a special field dedicated to the correction of dentofacial anomalies resulting from skeletal malocclusion. Generally, in such cases, an interdisciplinary orthodontic and surgical treatment approach is required. After initial orthodontic alignment of the dental arches, skeletal discrepancies of the jaws can be corrected by distinct surgical strategies and procedures in order to achieve correct occlusal relations, as well as facial balance and harmony within individualized treatment concepts. To transfer the preoperative surgical planning and reposition the mobilized dental arches with optimal occlusal relations, surgical splints are typically used. For this purpose, different strategies have been described which use one or more splints. Traditionally, these splints are manufactured by a dental technician based on patient-specific dental casts; however, computer-assisted technologies have gained increasing importance with respect to preoperative planning and its subsequent surgical transfer. METHODS: In a pilot study of 10 patients undergoing orthognathic corrections by a one-splint strategy, two final occlusal splints were produced for each patient and compared with respect to their clinical usability. One splint was manufactured in the traditional way by a dental technician according to the preoperative surgical planning. After performing a CBCT scan of the patient's dental casts, a second splint was designed virtually by an engineer and surgeon working together, according to the desired final occlusion. For this purpose, RapidSplint, a custom-made software platform, was used. After post-processing and conversion of the datasets into .stl files, the splints were fabricated by the PolyJet procedure using photo polymerization. During surgery, both splints were inserted after mobilization of the dental arches then compared with respect to their clinical usability according to the occlusal fitting. RESULTS: Using the workflow described above, virtual splints could be designed and manufactured for all patients in this pilot study. Eight of 10 virtual splints could be used clinically to achieve and maintain final occlusion after orthognathic surgery. In two cases virtual splints were not usable due to insufficient occlusal fitting, and even two of the traditional splints were not clinically usable. In five patients where both types of splints were available, their occlusal fitting was assessed as being equivalent, and in one case the virtual splint showed even better occlusal fitting than the traditional splint. In one case where no traditional splint was available, the virtual splint proved to be helpful in achieving the final occlusion. CONCLUSIONS: In this pilot study it was demonstrated that clinically usable splints for orthognathic surgery can be produced by computer-assisted technology. Virtual splint design was realized by RapidSplint®, an in-house software platform which might contribute in future to shorten preoperative workflows for the production of orthognathic surgical splints.

Virtual planning for craniomaxillofacial surgery--7 years of experience.

Contemporary computer-assisted surgery systems more and more allow for virtual simulation of even complex surgical procedures with increasingly realistic predictions. Preoperative workflows are established and different commercially software solutions are available. Potential and feasibility of virtual craniomaxillofacial surgery as an additional planning tool was assessed retrospectively by comparing predictions and surgical results. Since 2006 virtual simulation has been performed in selected patient cases affected by complex craniomaxillofacial disorders (n = 8) in addition to standard surgical planning based on patient specific 3d-models. Virtual planning could be performed for all levels of the craniomaxillofacial framework within a reasonable preoperative workflow. Simulation of even complex skeletal displacements corresponded well with the real surgical result and soft tissue simulation proved to be helpful. In combination with classic 3d-models showing the underlying skeletal pathology virtual simulation improved planning and transfer of craniomaxillofacial corrections. Additional work and expenses may be justified by increased possibilities of visualisation, information, instruction and documentation in selected craniomaxillofacial procedures.

Craniomaxillofacial surgery planning based on 3D models derived from Cone-Beam CT data.

INTRODUCTION: Individual planning of complex maxillofacial corrections may require 3D models which can be manufactured based on DICOM datasets. The gold standard for image acquisition is still high-resolution multi-slice computed tomography (MSCT). However, appropriate datasets for model fabrication can be acquired by modern Cone-Beam CT (CBCT) devices that have been developed specifically for maxillofacial imaging. The clinical utility of individual models fabricated on the basis of CBCT datasets was assessed. METHODS: In five patients affected by different deficiencies of the maxillofacial skeleton, preoperative imaging was performed with ILUMA CBCT. Segmentation of hard tissues was performed manually by thresholding. Corresponding STL datasets were created and exported to an industrial service provider (Alphaform, Munich, Germany) specializing in rapid prototyping, and 3D models were fabricated by the selective laser sintering (SLS) technique. For variance analysis, landmark measurements were performed on both virtual and 3D models. Subsequently, maxillofacial surgery was performed according to the model-based planning. RESULTS: All CBCT-based DICOM datasets could be used for individual model fabrication. Detailed reproduction of individual anatomy was achieved and a topographic survey showed no relevant aberrance between the virtual and real models. The CBCT-based 3D models were therefore used for planning and transfer of different maxillofacial procedures. CONCLUSIONS: CBCT-based datasets can be used for the fabrication of surgical 3D models if the correct threshold is set. Preoperative workflow and patient comfort is improved in terms of the fast-track concept by using this "in-house" imaging technique.

A noncontact laser-guided system for endoscopic computer-assisted sinus surgery.

The limited size of the nose leads to frequent instrument changes in navigated endonasal sinus surgery. Tracked instruments provide limited accuracy, and the pointer gives no navigation information during tissue removal. To overcome information loss, laser triangulation was integrated into navigation information. Accuracy and reliability of the laser-assisted distance-measuring system were evaluated within the distance of 0 and 20 mm. System accuracy of the laser endoscope was compared with a standard pointer using registration via bone screws and surface matching. Accuracy of the laser was 0.12 mm ± 0.12 mm with a reliability of 0.2 mm. The system accuracy of the laser endoscope was 0.59 mm ± 0.16 mm using bone screw registration and 0.64 mm ± 0.22 mm using surface matching. Additionally, laser endoscope is more accurate compared with the pointer using bone screw registration. Overall, navigation information was successfully integrated into an endoscope by laser triangulation with encouraging results.

Overlay visualization in endoscopic ENT surgery.

PURPOSE: In endoscopic ENT surgery, the identification and localization of target structures is challenging-depth information is missing, relevant tissues could be hidden behind opaque material and image distortion affects the instrument handling. In this paper, a novel overlay visualization is presented that supports the surgeon by superimposing planning and navigation information on the endoscopic image. METHOD: Target regions, which have been identified in preoperative CT data, are superimposed on the endoscopic image, allowing the use of guiding lines for distance visualization. To match the overlay information with the geometrically distorted endoscopic images, a new intraoperative calibration procedure has been developed. RESULTS: The accuracy of this new method has been verified by cadaver studies. Clinical evaluation in three paranasal sinus interventions was performed to show the intraoperative assistance and practicability with promising results. CONCLUSION: The new techniques safely support the surgeon in locating target structures in the paranasal sinuses with little change in the actual workflow.

Computer-aided manufacturing technologies for guided implant placement.

Implant treatment increasingly focuses on the reduction of treatment time and postoperative impairment. The improvement of 3D dental diagnosis by ConeBeam computed tomography allows detailed preparation for the surgical placement of dental implants under prosthetic considerations. While the first generation of implant planning software used high-contrast multislice computed tomography, software that has been specifically designed for ConeBeam computed tomography is now available. Implant placement can be performed using surgical guides or under the control of optical tracking systems. Surgical guides are more commonly used in private office owing to their availability. The accuracy for both techniques is clinically acceptable for achieving implant placement in critical anatomical indications. When using prefabricated superstructures and in flapless surgery, special abutments or an adjusted workflow are still necessary to compensate misfits of between 150 and 600 microm. The proposition to ensure proper implant placement by dentists with limited surgical experience through the use of surgical guides is unlikely to be successful, because there is also a specific learning curve for guided implant placement. Current and future development will continue to decrease the classical laboratory-technician work and will integrate the fabrication of superstructures with virtual treatment planning from the start.

The influence of body mass index, age, implants, and dental restorations on image quality of cone beam computed tomography.

OBJECTIVE: The aim was to determine the influence of patient age, gender, body mass index (BMI), amount of dental restorations, and implants on image quality of cone-beam computerized tomography (CBCT). METHODS: Fifty CBCT scans of a preretail version of Galileos (Sirona, Germany) were investigated retrospectively by 4 observers regarding image quality of 6 anatomic structures, pathologic findings detection, subjective exposure quality, and artifacts. Patient age, BMI, gender, amount of dental restorations, and implants were recorded and statistically tested for correlations to image quality. RESULTS: A negative effect on image quality was found statistically significantly correlated with age and the amount of dental restorations. None of the investigated image features were garbled by any of the investigated influence factors. CONCLUSIONS: Age and the amount of dental restorations appear to have a negative impact on CBCT image quality, whereas gender and BMI do not. Image quality of mental foramen, mandibular canal, and nasal floor are affected negatively by age but not by the amount of dental restorations. Further studies are required to elucidate influence factors on CBCT image quality.

Comparison of cone-beam volumetric imaging and combined plain radiographs for localization of the mandibular canal before removal of impacted lower third molars.

OBJECTIVE: The removal of third molars requires information about the relative position of the root tips and the mandibular nerve. The diagnostic value of conventional radiologic procedures using a panoramic radiograph and symmetrical PA cephalometric radiograph (PAN&PA) was compared with that of a cone-beam volumetric imaging (CBVI) device (Galileos; Sirona, Bensheim, Germany). STUDY DESIGN: Six observers evaluated 30 PAN&PA and 30 CBVI for the position of root tips. Diagnostic information was rated from 1 to 5 (excellent to poor). RESULTS: With PAN&PA, 3 times more scans showed nondetectable information for horizontal position compared with CBVI. The diagnostic information in the vertical dimension received a median rating of 2 (good) for CBVI and for PAN & PA; for the horizontal dimension, CBVI received a median rating of 2 (good), compared with a significantly worse median rating of 3 (sufficient) for PAN & PA (P = .000). The variance was highest for the horizontal dimension with PAN & PA (1.27). CONCLUSION: These findings indicate that cone-beam technology improves the localization of third molar for presurgical planning.

Diagnostic quality of panoramic views obtained by a newly developed digital volume tomography device for maxillofacial imaging.

OBJECTIVE: To compare the diagnostic quality of 2-dimensional panoramic views generated from imaging data acquired by a newly developed cone beam machine with the diagnostic quality of conventional digital orthopantomograms (OPTs). METHOD AND MATERIALS: Thirty panoramic views reconstructed from digital volume tomograms (DVT) obtained by the pre-retail version of Galileos (Sirona Dental Systems), a newly developed compact cone beam device, were compared with 30 OPT images acquired by Orthophos XG Plus (Sirona Dental Systems). Diagnostic quality was assessed by 3 observers on criteria regarding detection of diagnosis-related findings, image quality, and visualization of anatomic structures in the maxillomandibular area. Wilcoxon rank sum test was applied for paired comparison. RESULTS: Statistical analysis showed no significant difference in diagnostic quality between both imaging modes using a calculation model based on 10 weighted criteria (P = .629). There was especially no statistically significant difference in the assessment of diagnosis-related findings detection (P = .163). Image quality of DVT panoramic views was significantly lower than that of OPT. Except for mandibular canal and alveolar ridge gingiva, all evaluated anatomic structures were visualized better by DVT. Intraclass correlation coefficients were consistently higher in the DVT group for all criteria but 2, although the difference was not statistically significant (P = .374). CONCLUSIONS: DVT panoramic views perform better in diagnosis of specific lesions, whereas OPTs provide a better image quality for a general overview of the maxillomandibular area. The diagnostic quality of both imaging modes is, however, equal.

Geometric accuracy of a newly developed cone-beam device for maxillofacial imaging.

OBJECTIVE: The aim of this study was to determine the geometric accuracy of scans obtained with a newly developed cone-beam computed tomography (CBCT) device in comparison with a multidetector row computed tomography (MDCT) scanner. STUDY DESIGN: Cone-beam scans were obtained with the preretail version of a newly developed compact size device with a scan volume of 15 x 15 x 15 cm. Conventional CT scans for comparison were performed with a 6-detector row CT scanner. To determine distance accuracy, 100 measurements were performed on radiopaque markers on a dry human skull. To determine volume accuracy, 25 measurements were carried out on a geometric phantom. Commercially available software was used for three-dimensional visualization and measurements on imaging data. RESULTS: Mean absolute measurement error (AME) for linear distances was 0.26 mm (+/-0.18 mm) for the CBCT device and 0.18 mm (+/-0.17 mm) for the MDCT device (P = .196 in paired t test). The average absolute percentage error (APE) was 0.98% (+/-0.73%) and 1.26% (+/-1.50%), respectively (P = .485 in paired t test). Linear regression analysis showed a positive correlation between AME and distance length (R = 0.628; P = .004) for CBCT-based measurements. Average AME in volume measurements was 1.78 mL (+/-0.99 mL) for the CBCT device and 1.23 mL (+/-0.93 mL) for the MDCT device. The average APE was 6.01% (+/-1.49%) and 4.42% (+/-1.99%), respectively. CONCLUSIONS: The results indicate that the evaluated cone-beam device provides satisfactory information about linear distances and volumes. Multidetector row computed tomography scans proved slightly more accurate in both measurement categories. The difference may be considered as not relevant for the majority of clinical applications.

Range of curvilinear distraction devices required for treatment of mandibular deformities.

PURPOSE: The purpose of this study was to determine the range of fixed trajectory curvilinear distraction devices required to correct a variety of severe mandibular deformities. MATERIALS AND METHODS: Preoperative computed tomography (CT) scans from 18 patients with mandibular deformities were imported into a CT-based software program (Osteoplan). Three-dimensional virtual models of the individual skulls were made with landmarks to track movements. An ideal treatment plan was created for each patient. Upper and lower boundaries for the dimensions of curvilinear distractors were established based on manufacturing and geometric constraints. Then, anatomically acceptable distractor attachment points were identified on the models using proximal and distal grids. Treatment plans were simulated for a series of distractors with varying radii of curvature, elongations (arc-length of device), and placements along the grids. The outcomes using these distractors were compared with the ideal treatment plans. Discrepancies were quantified in millimeters by comparing landmarks in the simulated versus ideal movements. RESULTS: Approximately 400,000 simulated 3-dimensional movements, based on the distractor parameters and variations in placement were computationally evaluated for the 18 cases. It was determined that, by varying distractor placement, a family of 5 distractors, with 3, 5, 7, and 10 cm radii of curvature and a straight-line device, could be used to treat all 18 cases to within 1.8 mm of error. CONCLUSIONS: The results of this study indicate that a family of 5 curvilinear distractors may suffice to treat a broad range of mandibular deformities.