Evaluation of a custom made anatomical guide for orthognathic surgery

Orthognathic surgery is a routinely used surgical technique for the correction of dento-facial deformities. During a Le Fort I orthognathic procedure the maxilla is surgically separated from the skull and the surgical positioning wafer is placed between the occlusal surfaces of the upper and lower dentition. However, the physiological response to general aesthesia results in loss of muscle tone in the mandible, which has a profound influence on the correct amount of maxillary advancement required. The expertise and visual judgement of the surgeon is relied upon to foresee and eliminate this potential source of error. However, this may not be possible to achieve in all cases, therefore there is a need for a device to guide the surgical position of the maxilla independent of the mandibular dentition. The aim of this study was to design and validate a custom made anatomical repositioning surgical framework for accurately repositioning the maxilla independently of the mandible during a Le Fort I osteotomy. A single plastic anatomical skull was scanned using a helical Computed Tomography (CT) scanner. Utilising 3D manipulation software, forty-three Le Fort I orthognathic surgery movements were planned. A custom made anatomical repositioning guide was designed and 3D printed for all movements. Each guide was used to reposition the maxilla of the physical skull and then laser scanned using a GOM blue light scanner. GOMinspect software was used to compare the planned and physical position of the repositioned maxilla. The results of the experiment were statistically evaluated.Orthognathic surgery is a routinely used surgical technique for the correction of dento-facial deformities. During a Le Fort I orthognathic procedure the maxilla is surgically separated from the skull and the surgical positioning wafer is placed between the occlusal surfaces of the upper and lower dentition. However, the physiological response to general aesthesia results in loss of muscle tone in the mandible, which has a profound influence on the correct amount of maxillary advancement required. The expertise and visual judgement of the surgeon is relied upon to foresee and eliminate this potential source of error. However, this may not be possible to achieve in all cases, therefore there is a need for a device to guide the surgical position of the maxilla independent of the mandibular dentition. The aim of this study was to design and validate a custom made anatomical repositioning surgical framework for accurately repositioning the maxilla independently of the mandible during a Le Fort I osteotomy. A single plastic anatomical skull was scanned using a helical Computed Tomography (CT) scanner. Utilising 3D manipulation software, forty-three Le Fort I orthognathic surgery movements were planned. A custom made anatomical repositioning guide was designed and 3D printed for all movements. Each guide was used to reposition the maxilla of the physical skull and then laser scanned using a GOM blue light scanner. GOMinspect software was used to compare the planned and physical position of the repositioned maxilla. The results of the experiment were statistically evaluated

Three-dimensional applications in orthodontics

Orthodontics as a specialty is going through a technological revolution. During the last 10 years there were more new developments in orthodontics than in the whole history of the specialty. One of the areas undergoing rapid progress is three-dimensional (3D) imaging. 3D Imaging allows for more precise evaluation of the airway. Patients displaying a Skeletal Class II had smaller airway volume while controlling for age, gender and size of face. The shape of the airway was different among individual with different antero-posterior jaw relationship. Airway volume among patients with different vertical jaw relationship displayed great variability. A good understanding of imaging concepts is important for the contemporary clinician. Most of the three-dimensional visual information is not liked yet to a clear diagnosis and prognosis classification. Visualization, measurement, creation of two-dimensional (2D) radiographs, segmentation, registration, superimposition and other quantitative analysis require specific training and specialized software in order to manipulate 3D files. In order to compare the newer 3D images with our current and historical databases, it is necessary to emulate 2D radiographs from 3D data. When we compared homologous landmark coordinates in digital and synthetic cephalograms, there was no systematic error. However when both modalities are used in the same individual the error of the method could produce clinically significant differences. A second area undergoing rapid progress is orthodontic digital models. These are qualitatively and quantitatively similar to conventional dental casts, but offer some advantages. One of these advantages is the possibility of register and superimpose them in space. The registration of digital orthodontic models to represent the patients' occlusion, as well as registration of final orthodontic models to the planned setup models was reliable. Finally, CAD/CAM technology allows for fabricating orthodontic appliances on a setup model of the planned correction. Based on a three-dimensional comparison of the planned tooth positions with the final ones, A fully customized lingual technique was very accurate in achieving the planned tooth positions in terms of translation and rotation. Digital orthodontics and digital dentistry have arrived: be part of i

Comparative TMJ imaging accuracy using iCAT cone beam computerized tomography.

A blinded observational cross-sectional in vitro study was conducted to compare the diagnostic accuracy of observers viewing images made using cone beam computerized tomography (CBCT), panoramic radiography and linear tomography. The sample consisted of 37 TMJ articulations from 30 human skulls demonstrating either normal condylar morphology (n=19) or erosion of the lateral pole (n=18). The articulations were imaged using corrected angle linear tomography, normal and TMJ specific panoramic radiography and CBCT. Images and 10 re-reads were presented to 10 observers. Multiple CBCT multi-planar images were presented both statically and interactively. Intra-observer reliability was determined by weighted kappa (Kw) and diagnostic accuracy by the fitted area under the ROC curve (Az). Means were compared using ANOVA (piÜ.05). Our results show CBCT images provide superior reliability and greater accuracy than corrected angle linear tomography and TMJ panoramic projections in the detection of condylar cortical erosion

Applications of Cone Beam Computed Tomography in Orthodontics and Endodontics

Stelt, P.F. van der [Promotor]Sanderink, G.C.H. [Copromotor

Computer-aided cephalometric landmark identification

Master'sMASTER OF ENGINEERIN

Interlandmark measurements from lodox statscan images with application to femoral neck anteversion assessment

Includes abstract.Includes bibliographical references.Clinicians often take measurements between anatomical landmarks on X-ray radiographs for diagnosis and treatment planning, for example in orthopaedics and orthodontics. X-ray images, however, overlap three-dimensional internal structures onto a two-dimensional plane during image formation. Depth information is therefore lost and measurements do not truly reflect spatial relationships. The main aim of this study was to develop an inter-landmark measurement tool for the Lodox Statscan digital radiography system. X-ray stereophotogrammetry was applied to Statscan images to enable three-dimensional point localization for inter-landmark measurement using two-dimensional radiographs. This technique requires images of the anatomical region of interest to be acquired from different perspectives as well as a suitable calibration tool to map image coordinates to real world coordinates. The Statscan is suited to the technique because it is capable of axial rotations for multiview imaging. Three-dimensional coordinate reconstruction and inter-landmark measurements were taken using a planar object and a dry pelvis specimen in order to assess the intra-observer measurement accuracy, reliability and precision. The system yielded average (X, Y, Z) coordinate reconstruction accuracy of (0.08 0.12 0.34) mm and resultant coordinate reconstruction accuracy within 0.4mm (range 0.3mm – 0.6mm). Inter-landmark measurements within 2mm for lengths and 1.80 for angles were obtained, with average accuracies of 0.4mm (range 0.0mm – 2.0 mm) and 0.30 (range 0.0 – 1.8)0 respectively. The results also showed excellent overall precision of (0.5mm, 0.10) and were highly reliable when all landmarks were completely visible in both images. Femoral neck anteversion measurement on Statscan images was also explored using 30 dry right adult femurs. This was done in order to assess the feasibility of the algorithm for a clinical application. For this investigation, four methods were tested to determine the optimal landmarks for measurement and the measurement process involved calculation of virtual landmarks. The method that yielded the best results produced all measurements within 10 of reference values and the measurements were highly reliable with very good precision within 0.10. The average accuracy was within 0.40 (range 0.10 –0.80).In conclusion, X-ray stereophotogrammetry enables accurate, reliable and precise inter-landmark measurements for the Lodox Statscan X-ray imaging system. The machine may therefore be used as an inter-landmark measurement tool for routine clinical applications

Issues in Contemporary Orthodontics

Issues in Contemporary Orthodontics is a contribution to the ongoing debate in orthodontics, a discipline of continuous evolution, drawing from new technology and collective experience, to better meet the needs of students, residents, and practitioners of orthodontics. The book provides a comprehensive view of the major issues in orthodontics that have featured in recent debates. Abroad variety of topics is covered, including the impact of malocclusion, risk management and treatment, and innovation in orthodontics

Airway Volume and Shape from Cone-Beam CT: Relationship to Facial Morphology

Cone beam computed tomography (CBCT) records of 62 non-growing patients were used to evaluate the pharyngeal airway volume (upper and lower components), and the shape of the airway, using semi-automatic segmentations to calculate real volumes instead of estimates based on linear measurements. The sample was divided according to anteroposterior jaw relationships and vertical proportions. There was a statistically significant relationship between the volume of the lower component and a-p jaw relationship, and between airway volume and both the size of the face and gender. No differences in airway volumes related to vertical facial proportions were observed. Skeletal Class II patients tended to display forward inclination of the airway, greater projection of the tongue into the airway, and narrower airways. Skeletal Class III patients usually had a vertically-oriented airway. This study is a pioneer in measuring real 3-D models and controlling for face size

Comparison of 3D facial soft tissue changes following Twin-block and Button & Bead appliances: a single centre randomised clinical trial.

Objectives To determine if the horizontal advancement of soft tissue pogonion was statistically significantly different following treatment with a Twinblock appliance and Button & Bead appliance. Method: Sixty-four children aged 10-14 years were recruited from the Birmingham Dental Hospital. Following randomization thirty-two patients were allocated to either the Twinblock or the Button & Bead appliance group. Records, including threedimensional facial soft tissue images (3dMD), were taken at the start (T0) and and at the end of functional appliance therapy (T1). Results: The overlying soft tissue changes followed the underlying skeletal and dental changes produced by the appliances. There were no statistically significant differences in upper lip movement between the two appliances. There was statistically significantly more anterior horizontal movement at pogonion (p=0.001) and B-point (p=0.012) in the Twinblock group compared to the Button & Bead group. Conclusion: As a result of Twinblock treatment there were minimal changes in upper lip position. In the Button & Bead group there was some retraction and lengthening of the upper lip, this could be clinically significant (>2mm) and mainly in the philtrum region. The horizontal anterior movement of the soft tissue chin region was statistically and clinically significantly greater in the Twinblock group compared to the Button & Bead group. The Button & Bead appliance produced a clinically significant vertical increase in chin and lower lip compared to the Twinblock