Long term three dimensional tracking of orthodontic patients using registered cone beam CT and photogrammetry.
Boulanger P. Flores-Mir C. Ramirez JF. Mesa E. Branch JW.
Conference Proceedings: ... Annual International Conference of the IEEE Engineering in Medicine & Biology Society. 2009:3525-8, 2009.
AB The measurements from registered images obtained from Cone Beam Computed Tomography (CBCT) and a photogrammetric sensor are used to track three-dimensional shape variations of orthodontic patients before and after their treatments. The methodology consists of five main steps: (1) the patient's bone and skin shapes are measured in 3D using the fusion of images from a CBCT and a photogrammetric sensor. (2) The bone shape is extracted from the CBCT data using a standard marching cube algorithm. (3) The bone and skin shape measurements are registered using titanium targets located on the head of the patient. (4) Using a manual segmentation technique the head and lower jaw geometry are extracted separately to deal with jaw motion at the different record visits. (5) Using natural features of the upper head the two datasets are then registered with each other and then compared to evaluate bone, teeth, and skin displacements before and after treatments. This procedure is now used at the University of Alberta orthodontic clinic.
Tomographic volume evaluation of submandibular fossa in patients requiring dental implants.
Parnia F. Fard EM. Mahboub F. Hafezeqoran A. Gavgani FE.
Oral Surgery Oral Medicine Oral Pathology Oral Radiology & Endodontics. 109(1):e32-6, 2010 Jan.
AB OBJECTIVE: The aim of this study was to evaluate submandibular fossa volume from multislice CT scans of patients requiring endosseous implants. STUDY DESIGN: One hundred spiral computed tomographic (CT) preoperative examinations of patients requiring assessment the lower jaw before implant placement were retrospectively evaluated to determine anatomical variations in bone morphology in the submandibular fossa region. Reformatted cross-sectional images tangential to the mandibular dental arch and distal to the mental foramen border were selected. The deepest area of submandibular fossa or concavity depth was measured on all of the images. To measure the concavity depth, a tangent line was first derived to the lingual surface of the fossa and the deepest point was then selected by moving a perpendicular line across the tangent line. RESULTS: Within our sample we could classify the depth of the submandibular gland fossa as a function of the lingual concavity depth over a range up to a maximum value of 6.6 mm. Mandibular lingual concavity depth could be divided into 3 groups. A lingual concavity (depth > or =2 mm) was observed in 80% of the jaws. In 20% of the cases, there were flat depressions less than 2 mm in depth (Type I) and in 52% of the cases the concavities were 2 to 3 mm deep (Type II). About 28% of the examined regions showed significant concavities of more than 3 mm (Type III). The obtained distribution as a function of the depth did not reveal any dependence on age and gender of patients examined by this study (P > .05). CONCLUSION: Mandibles with any lingual concavity pose a potential increased risk of lingual cortical perforation during surgery, particularly endosseous implant placement. Cross-sectional imaging provides excellent delineation of mandibular anatomy and important information on the depth of the submandibular gland fossa in the preoperative assessment of the posterior mandible for dental implant fixture placement and other surgical procedures. Copyright 2010 Mosby, Inc. All rights reserved.
Comparison between cone-beam and multislice computed tomography depicting mandibular neurovascular canal structures.
Naitoh M. Nakahara K. Suenaga Y. Gotoh K. Kondo S. Ariji E.
Oral Surgery Oral Medicine Oral Pathology Oral Radiology & Endodontics. 109(1):e25-31, 2010 Jan.
AB OBJECTIVE: The most common diagnostic imaging modalities for cross-sectional imaging in dental implant planning are currently cone-beam computed tomography (CBCT) and multislice CT (MSCT). However, clinical differences between CBCT and MSCT in this task have not been fully clarified. In this investigation, the detection of fine anatomical structures in the mandible was assessed and compared between CBCT and MSCT images. STUDY DESIGN: The sample consisted of 28 patients who had undergone CBCT and MSCT. The bifid mandibular canal in the mandibular ramus, accessory mental and buccal foramina, and median and lateral lingual bony canals were observed in 2-D images, and the findings were compared between CBCT and MSCT. RESULTS: Four of 19 canals observed in CBCT were not observed in MSCT images. Three accessory mental foramina in 2 patients and 28 lateral lingual bony canals in 18 patients were observed consistently using the two methods. CONCLUSION: Depiction of fine anatomic features in the mandible associated with neurovascular structures is consistent between CBCT and MSCT images. Copyright 2010 Mosby, Inc. All rights reserved.
On cone-beam computed tomography artifacts induced by titanium implants.
Schulze RK. Berndt D. d'Hoedt B.
Clinical Oral Implants Research. 21(1):100-7, 2010 Jan.
AB OBJECTIVES: To briefly review the mathematical background of beam-hardening artifacts in cone-beam computed tomography (CBCT)-reconstruction and to investigate geometrical properties relevant for these reconstruction errors. By means of simulated and experimental results, beam-hardening effects caused by titanium implants are evaluated. MATERIALS AND METHODS: The geometrical and physical properties of the acquisition process of the projections used for 3D reconstruction are investigated and their effects on the CBCT images in the presence of titanium implants are derived. Beam-hardening effects are computed for a simplified polychromatic situation (three energy subsets of 80 and 110 kV) and compared with experimental results from a hard-plaster phantom containing two 'implants' (pure titanium rods; 4 mm diameter) exposed in two CBCT machines. RESULTS: Massive absorption within a typical implant body (diameter: 4 mm) was computed for the low-energy subset of both energies (80 kV: 99.7%; 110 kV: 90.9%), whereas the high-energy subsets are only marginally absorbed (80 kV: 14.8%; 110 kV: 11.3%). Accordingly, phantom data revealed drastically reduced gray values in artifact-affected regions (3DAccuitomo: -46% to -51%) or (3DExam: -55%) plus increased noise (+67% vs. +73%), when compared with unaffected regions. CONCLUSIONS: Our theoretical and experimental results prove massive beam-hardening artifacts for a typical implant diameter and typical energies of up-to-date CBCT machines. Meaningful artifact reduction has to be based on more sophisticated mathematical modeling of the actual physical image acquisition process rather than on postprocessing of the erroneous results obtained from the rather crude reconstruction algorithms used presently.
Accuracy and landmark error calculation using cone-beam computed tomography-generated cephalograms.
Grauer D. Cevidanes LS. Styner MA. Heulfe I. Harmon ET. Zhu H. Proffit WR.
Angle Orthodontist. 80(2):286-94, 2010 Mar.
AB OBJECTIVE: To evaluate systematic differences in landmark position between cone-beam computed tomography (CBCT)-generated cephalograms and conventional digital cephalograms and to estimate how much variability should be taken into account when both modalities are used within the same longitudinal study. MATERIALS AND METHODS: Landmarks on homologous cone-beam computed tomographic-generated cephalograms and conventional digital cephalograms of 46 patients were digitized, registered, and compared via the Hotelling T(2) test. RESULTS: There were no systematic differences between modalities in the position of most landmarks. Three landmarks showed statistically significant differences but did not reach clinical significance. A method for error calculation while combining both modalities in the same individual is presented. CONCLUSION: In a longitudinal follow-up for assessment of treatment outcomes and growth of one individual, the error due to the combination of the two modalities might be larger than previously estimated.
Accuracy of two stereolithographic guide systems for computer-aided implant placement: a computed tomography-based clinical comparative study.
Arisan V. Karabuda ZC. Ozdemir T.
Journal of Periodontology. 81(1):43-51, 2010 Jan.
AB BACKGROUND: Stereolithographic surgical guides provide significant benefits during the simultaneous placement of multiple implants with regard to the final prosthetic plan. However, deviation from the planning poses a significant risk. Deviations of implants that were placed by bone-, tooth-, and mucosa-supported stereolithographic surgical guides were examined in this study. METHODS: After enrolling 54 eligible patients, 294 implants were planned on cone-beam computerized tomography CB(CT)-derived images. Sixty guides, both single- and multiple-type, were produced using two commercial systems. Mucosa-supported guides were fixed with osteosynthesis screws. Implants were inserted, and at the end of osseointegration period, a new CB(CT) scan was performed. Preoperative planning was merged with the new CB(CT) data to identify the deviations between the planned and placed implants for each support type and manufacturer. The Kruskal-Wallis and Mann-Whitney U tests were used for comparison (P <0.05). RESULTS: There were no damage-related complications in any critical anatomy. Implants that were placed by bone-supported guides had the highest mean deviations (5.0 degrees +/- 1.66 degrees angular, and 1.70 +/- 0.52 mm and 1.99 +/- 0.64 mm for implant shoulder and tip, respectively), whereas the lowest deviations were measured in implants that were placed by mucosa-supported guides (2.9 degrees +/- 0.39 degrees angular, and 0.7 +/- 0.13 mm and 0.76 +/- 0.15 mm for implant shoulder and tip, respectively). CONCLUSIONS: Computer-aided planning and manufacturing surgical guides in accordance with CB(CT) images may help clinicians place implants. Rigid screw fixation of a single guide incorporating metal sleeves and a special drill kit further minimizes deviations.
Simultaneous modified oblique Le Fort III and segmentalized Le Fort I osteotomies.
Cheung LK. Ow A. Chua HD.
Journal of Oral & Maxillofacial Surgery. 68(4):915-23, 2010 Apr.
Reproducibility of 3 different tracing methods based on cone beam computed tomography in determining the anatomical position of the mandibular canal.
Gerlach NL. Meijer GJ. Maal TJ. Mulder J. Rangel FA. Borstlap WA. Berge SJ.
Journal of Oral & Maxillofacial Surgery. 68(4):811-7, 2010 Apr.
AB PURPOSE: To investigate the reproducibility of 3 different tracing methods to determine a reliable method to define the proper anatomical position of the mandibular canal based on cone beam computed tomography (CBCT) data. MATERIALS AND METHODS: Five dentate and 5 edentate patients were selected at random from the CBCT database. Two independent observers traced both the left and the right mandibular canal using 3-dimensional image-based planning software (Procera System NobelGuide; Nobel Biocare, Goteborg, Sweden). All mandibular canals were traced using 3 different methods. Method I was based on coronal views, also known as cross-sections. Panorama-like reconstructions were the starting point for method II. The third method combined methods I and II. RESULTS: With respect to interobserver reliability, no significant difference (P = .34) for the various methods was observed. The reproducibility was better in edentate than in dentate jaws (P = .0015). The difference between 2 tracings was the lowest for the combined method: within a range of 1.3 mm in 95% of the course of the canal. The most obvious deviations were mainly seen in the anterior part of the canal. CONCLUSIONS: The best reproducible method for mandibular canal tracing is the combined method III. Between observers, still a mean 95th percentile deviation threshold of 1.3 mm (SD 0.384) is noted, indicating that a safety zone of 1.7 mm should be respected. When planning surgery on CBCT-based data, surgeons should be aware of the obvious deviations located in the region of the anterior loop of the canal. 2010 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.
Treatment for ectopic third molar in the subcondylar region planned with cone beam computed tomography: a case report.
Bortoluzzi MC. Manfro R.
Journal of Oral & Maxillofacial Surgery. 68(4):870-2, 2010 Apr.