Accuracy and reliability of lower dental arch reconstructions

Introduction: In the literature, there is information regarding the accuracy of models generated by conventional impression materials and intraoral scanners, but data on the accuracy of 3D models generated from cone-beam computed tomography (CBCT) is still lacking.Aim: The aim of this article is to investigate and compare the accuracy of tooth reconstructions made on 3D models generated from CBCT and intraoral scanning, as well as on plaster models from conventional impression materials, to the results of intraoral measurements using a digital caliper.Materials and Methods: The study included a total of 38 individuals (16 males and 22 females). After the initial examination, we scheduled appointments for the approved participants to undergo clinical procedures and imaging studies in the following sequence: 1. placement of composite markers; 2. physical measurements; 3. intraoral scanning; 4. CBCT; 5. capturing a conventional impression; 6. removal of composite markers. Following are the laboratory and measurement stages for the study: 7. casting gypsum models; 8. measurements on gypsum models; 9. converting the DICOM files from CBCT scans to STL files; 10. conducting measurements on digital models from CBCT and intraoral scanning.Results: Results from the reliability assessment of the researcher’s measurements for the studied modalities indicate a correlation coefficient ranging from moderate to excellent with very high statistical significance. Concerning accuracy, differences are observed between individual modalities. Conclusion: In summary, conventional methods and materials still outperform intraoral scanners in terms of the accuracy of the obtained reconstructions. 3D models generated from CBCT scans are generally the least satisfactory among the tested modalities, with deviations typically within clinically acceptable values

The residual STL volume as a metric to evaluate accuracy and reproducibility of anatomic models for 3D printing: application in the validation of 3D-printable models of maxillofacial bone from reduced radiation dose CT images.

BackgroundThe effects of reduced radiation dose CT for the generation of maxillofacial bone STL models for 3D printing is currently unknown. Images of two full-face transplantation patients scanned with non-contrast 320-detector row CT were reconstructed at fractions of the acquisition radiation dose using noise simulation software and both filtered back-projection (FBP) and Adaptive Iterative Dose Reduction 3D (AIDR3D). The maxillofacial bone STL model segmented with thresholding from AIDR3D images at 100 % dose was considered the reference. For all other dose/reconstruction method combinations, a "residual STL volume" was calculated as the topologic subtraction of the STL model derived from that dataset from the reference and correlated to radiation dose.ResultsThe residual volume decreased with increasing radiation dose and was lower for AIDR3D compared to FBP reconstructions at all doses. As a fraction of the reference STL volume, the residual volume decreased from 2.9 % (20 % dose) to 1.4 % (50 % dose) in patient 1, and from 4.1 % to 1.9 %, respectively in patient 2 for AIDR3D reconstructions. For FBP reconstructions it decreased from 3.3 % (20 % dose) to 1.0 % (100 % dose) in patient 1, and from 5.5 % to 1.6 %, respectively in patient 2. Its morphology resembled a thin shell on the osseous surface with average thickness <0.1 mm.ConclusionThe residual volume, a topological difference metric of STL models of tissue depicted in DICOM images supports that reduction of CT dose by up to 80 % of the clinical acquisition in conjunction with iterative reconstruction yields maxillofacial bone models accurate for 3D printing

Pterygoid implant: Option for rehabilitation of the atrophic posterior maxilla

Background: The anatomy of the atrophic posterior maxilla presents many limitations to implant placement. Factors affecting implant placements include poor bone quality and quantity, location of maxillary sinus. Posterior cantilevers on implant prostheses produce complications, such as prosthesis fracture, screw loosening, loss of osseointegration, and crestal bone loss. Pterygoid implants are an alternative to grafting solutions for posterior maxillary rehabilitation. Aim: This systematic review describes various implant treatment options for posterior maxillary rehabilitation. It highlights the use of pterygoid implants as a graftless solution with its anatomy, technique of placement, and advantages. Conclusion: Pterygoid implants have high success rates, less bone loss, and good acceptance by patients thus being an excellent alternative to treat patients with severely atrophic maxilla. Clinical Significance: Pterygoid implants avoid the need for sinus lifts and grafting procedures. They allow anchorage in the posterior atrophied/resorbed maxilla, achieving proper stability, and high rates of long-term succ

THREE-DIMENSIONAL MODEL PRINTING IN ORAL AND MAXILLOFACIAL RECONSTRUCTIVE SURGERY: COMPARISON OF THREE-DIMENSIONAL MODELS AND MULTISLICE COMPUTED TOMOGRAPHY SCANS

Objective: The objective of this study is to compare fabrication of commonly used three-dimensional (3D) models with original multislice computed tomography (MSCT) scan data for accuracy and precision in reconstruction surgery.Methods: MSCT data from 10 samples are processed and manufactured to be 3D models. Both groups are then measured and analyzed for the purpose of comparison.Results: The average mandibular measurement difference between 3D models and MSCT scans is 0.26 mm more <2%. The final results of the comparison reveal high accuracy in 3D models compared to MSCT scan data.Conclusion: The 3D model could be considered as surgical guidance for maxillofacial reconstruction surgery since it yields highly accurate results

Factors influencing CAD/CAM accuracy in fibula free flap mandibular reconstruction

La tecnologia CAD/CAM (Computer-Aided Design/Computer-Aided Manufacturing) ha migliorato sia i risultati funzionali che morfologici nella chirurgia ricostruttiva mandibolare. L\u2019obiettivo del nostro studio \ue8 stato quello di valutare questo tipo di tecnologia ed i fattori che possono influenzare la sua precisione. Un totale di 26 casi di ricostruzione mandibolare con lembo libero di fibula, utilizzando tecnologia CAD/CAM sono stati operati presso l\u2019Unit\ue0 Maxillofacciale della Fondazione IRCCS Ca\u2019 Granda Ospedale Maggiore Policlinico di Milano, da giugno 2014 a febbraio 2018. Abbiamo valutato l\u2019accuratezza confrontando i files STL di pianificazione chirurgica virtuale (obiettivo pianificato) con il file STL di una scansione TC postoperatoria precoce (risultato postoperatorio ottenuto). Entrambi i file STL sono stati importati su Geomagic Studio 2016 (Geomagic Gmbh). In base alla posizione della placca di ricostruzione (punto di riferimento fisso), abbiamo confrontato la deviazione sul condilo sinistro, gonion sinistro, gnathion, gonion destro e condilo destro, per calcolare l\u2019errore medio di deviazione. L\u2019errore medio di deviazione varia da 0,6 mm a 2,2 mm. Solo 2 dei 26 casi analizzati avevano un errore medio uguale o superiore a 2 mm (7,7%). L\u2019area mediana (symphysis-gnathion) ha mostrato una variazione pi\uf9 bassa (1,05 \ub1 0,92 mm) mentre l\u2019area di gonion ha mostrato maggiore variazione (la variazione media del gonion destro e sinistro era rispettivamente di 1,6 mm e 1,46 mm). Nessuno dei possibili fattori (tempi di ricostruzione, malignit\ue0 o benignit\ue0, sito o dimensione del difetto) che potrebbero influenzare la precisione del CAD/CAM, ha mostrato un\u2019influenza significativa. La tecnologia CAD/CAM nella ricostruzione microvascolare dei difetti mandibolari mediante lembo libero di fibula minimizza gli errori umani ed \ue8 considerato come un intervento chirurgico indipendente dall\u2019operatore con alto grado di accuratezza e riproducibilit\ue0.Computer-aided design/computer-aided manufacturing (CAD/CAM) technology has im-proved the functional and morphological results of mandibular reconstructive surgery. The purpose of this study was to objectively assess this technology and factors affecting its accuracy.Fibula free flap mandibular reconstruction was performed in 26 cases us-ing CAD/CAM technology at the Maxillofacial Unit of Fondazione IRCCS Ca\u2019 Gran-da Ospedale Maggiore Policlinico, Milan, between June 2014 and February 2018. We evaluated the technology\u2019s accuracy by comparing the virtual surgical planning STL file (planned-target mesh) with the STL file from an early postoperative CT scan (postopera-tive-achievement mesh) in each case. The STL files were imported into Geomagic Studio 2016 (Geomagic GmbH). According to the position of the reconstruction plate (fixed reference point), we assessed deviations at the right condyle, right gonion, gnathion, left gonion and left condyle, calculating mean, minimum and maximum error values.Mean error values ranged from 0.6 to 2.2 mm; they were 65 2 mm in only 2 (7.7%) cases. The midline area (symphysis-gnathion) showed the least variation (1.05 \ub1 0.92 mm), and the gonion area showed the greatest variation (right and left means of 1.6 and 1.46 mm, respectively). Among all possible factors that could affect CADCAM accuracy, nothing showed significant influence, including the timing of reconstruction, site and size of the defect and malignancy status. CAD/CAM technology has a high degree of accuracy and reproducibility for microvascular reconstruction of mandibular defects using fibula free flaps, regardless of the defect site and length, use of a single- or double-barrel graft or timing of reconstructio

Stress-strain analysis of skull implant

Lebeční implantáty se používají jako náhrady částí lebečních kosti, které v důsledku zranění nebo nemoci ztratili svou funkci. Důležitým faktorem, který ovlivňuje funkci celé soustavy implantátu, jsou jeho mechanické projevy. Tato práce stručně shrnuje současné znalosti v oblasti rekonstrukce lebečních defektů a popisuje srovnání různých tvarů stěn implantátu vytvořených z různých materiálů, na základě deformační napěťové analýzy modelu neurocrania s umístěným implantátem, zatíženým nitrolebečním tlakem a vnějším zatížením.Cranial implants are used as a substitute for parts of cranial bones that lost its function due to trauma or disease. An important factor, that influences function of the cranial implant structure, is its mechanical behavior. This thesis briefly summarizes current knowledge in the field of cranial defect reconstruction and provides comparison of different types of materials and implant wall shapes, based on stress-strain analysis of Computer Tomography based neurocranial model with placed implant and loaded by intracranial pressure and external load.

Study of medical image data transformation techniques and compatibility analysis for 3D printing

Various applications exist for additive manufacturing (AM) and reverse engineering (RE) within the medical sector. One of the significant challenges identified in the literature is the accuracy of 3D printed medical models compared to their original CAD models. Some studies have reported that 3D printed models are accurate, while others claim the opposite. This thesis aims to highlight the medical applications of AM and RE, study medical image reconstruction techniques into a 3D printable file format, and the deviations of a 3D printed model using RE. A case study on a human femur bone was conducted through medical imaging, 3D printing, and RE for comparative deviation analysis. In addition, another medical application of RE has been presented, which is for solid modelling. Segmentation was done using opensource software for trial and training purposes, while the experiment was done using commercial software. The femur model was 3D printed using an industrial FDM printer. Three different non-contact 3D scanners were investigated for the RE process. Post-processing of the point cloud was done in the VX Elements software environment, while mesh analysis was conducted in MeshLab. The scanning performance was measured using the VX Inspect environment and MeshLab. Both relative and absolute metrics were used to determine the deviation of the scanned models from the reference mesh. The scanners' range of deviations was approximately from -0.375 mm to 0.388 mm (range of about 0.763mm) with an average RMS of about 0.22 mm. The results showed that the mean deviation of the 3D printed model (based on 3D scanning) has an average range of about 0.46mm, with an average mean value of about 0.16 mm