Emmy Shaheen

Three-dimensional printed final occlusal splint for orthognathic surgery: design and validation

Orthognathic surgery is indicated for the treatment of significant skeletal malocclusion and is normally prepared using conventional face bows combined with two-dimensional cephalometric analysis and manually made splints. With recent developments in oral imaging, more orthognathic surgeries are being planned using three-dimensional computer-aided design and manufacturing (3D CAD/CAM) software. The purpose of this study was to present a protocol for the design and 3D printing of final digital occlusal splints based on 3D planning of orthognathic surgery and to validate the accuracy of these splints. The 3D virtual planning was performed in PROPLAN software (Materialise). The required data were then exported into 3-matic software (Materialise) to design the splints, which were 3D printed in biocompatible material using an Objet Connex 350 printer (Stratasys). To validate the accuracy of the splints, the cases of 20 patients undergoing orthognathic surgery were analysed. The splints were assessed clinically and quantitatively by comparing the printed splints to the conventional analogue set-up (clinical standard) and recording the absolute distance errors of three landmarks. The mean absolute distance error was 0.4mm (standard deviation 0.17mm), which falls within clinically accepted error margins. The absolute distance error ranged from 0.12 to 0.88mm.

Validation of cone beam computed tomography–based tooth printing using different three-dimensional printing technologies

OBJECTIVE Our aim was to determine the accuracy of 3-dimensional reconstructed models of teeth compared with the natural teeth by using 4 different 3-dimensional printers. STUDY DESIGN This in vitro study was carried out using 2 intact, dry adult human mandibles, which were scanned with cone beam computed tomography. Premolars were selected for this study. Dimensional differences between natural teeth and the printed models were evaluated directly by using volumetric differences and indirectly through optical scanning. Analysis of variance, Pearson correlation, and Bland Altman plots were applied for statistical analysis. RESULTS Volumetric measurements from natural teeth and fabricated models, either by the direct method (the Archimedes principle) or by the indirect method (optical scanning), showed no statistical differences. The mean volume difference ranged between 3.1 mm(3) (0.7%) and 4.4 mm(3) (1.9%) for the direct measurement, and between -1.3 mm(3) (-0.6%) and 11.9 mm(3) (+5.9%) for the optical scan. A surface part comparison analysis showed that 90% of the values revealed a distance deviation within the interval 0 to 0.25 mm. CONCLUSIONS Current results showed a high accuracy of all printed models of teeth compared with natural teeth. This outcome opens perspectives for clinical use of cost-effective 3-dimensional printed teeth for surgical procedures, such as tooth autotransplantation.

Design and application of a structured phantom for detection performance comparison between breast tomosynthesis and digital mammography.

This paper introduces and applies a structured phantom with inserted target objects for the comparison of detection performance of digital breast tomosynthesis (DBT) against 2D full field digital mammography (FFDM). The phantom consists of a 48 mm thick breast-shaped polymethyl methacrylate (PMMA) container filled with water and PMMA spheres of different diameters. Three-dimensionally (3D) printed spiculated masses (diameter range: 3.8-9.7 mm) and non-spiculated masses (1.6-6.2 mm) along with microcalcifications (90-250 µm) were inserted as targets. Reproducibility of the phantom application was studied on a single system using 30 acquisitions. Next, the phantom was evaluated on five different combined FFDM & DBT systems and target detection was compared for FFDM and DBT modes. Ten phantom images in both FFDM and DBT modes were acquired on these 5 systems using automatic exposure control. Five readers evaluated target detectability. Images were read with the four-alternative forced-choice (4-AFC) paradigm, with always one segment including a target and 3 normal background segments. The percentage of correct responses (PC) was assessed based on 10 trials of each reader for each object type, size and imaging modality. Additionally, detection threshold diameters at 62.5 PC were assessed via non-linear regression fitting of the psychometric curve. The reproducibility study showed no significant differences in PC values. Evaluation of target detection in FFDM showed that microcalcification detection thresholds ranged between 110 and 118 µm and were similar compared to the detection in DBT (range of 106-158 µm). In DBT, detection of both mass types increased significantly (p  =  0.0001 and p  =  0.0002 for non-spiculated and spiculated masses respectively) compared to FFDM, achieving almost 100% detection for all spiculated mass diameters. In conclusion, a structured phantom with inserted targets was able to show evidence for detectability differences between FFDM and DBT modes for five commercial systems. This phantom has potential for application in task-based assessment at acceptance and commissioning testing of DBT systems.This paper introduces and applies a structured phantom with target objects for the comparison of detection performance of digital breast tomosynthesis (DBT) against full field digital mammography (FFDM). The phantom consists of a 48 mm thick breast-shaped polymethyl methacrylate (PMMA) container filled with water and PMMA spheres of different diameters. Three-dimensionally (3D) printed spiculated masses (diameter range: 3.8-9.7 mm) and non-spiculated masses (1.6-6.2 mm) along with microcalcifications (90-250 µm) were inserted as targets. Reproducibility of the phantom application was studied on a single system using 30 acquisitions. Next, the phantom was evaluated on five different combined FFDM & DBT systems and target detection was compared for FFDM and DBT modes. Ten phantom images in both FFDM and DBT modes were acquired on these 5 systems using automatic exposure control (AEC). Five readers evaluated target detectability. Images were read with the four-alternative forced-choice (4-AFC) paradigm, with always one segment including a target and 3 normal background segments. The percentage of correct responses (PC) was assessed based on 10 trials of each reader for each object type, size and modality. Additionally, detection threshold diameters at 62.5 PC were assessed via non-linear regression fitting of the psychometric curve. The reproducibility study showed no significant differences in PC values. Evaluation of target detection in FFDM showed that microcalcification detection thresholds ranged between 110 and 118 µm and were similar compared to the detection in DBT (range of 106-158 µm). In DBT, detection of both mass types increased significantly (p=0.0001 and p=0.0002 for non-spiculated and spiculated masses respectively) compared to FFDM, achieving almost 100% detection for all spiculated mass diameters. In conclusion, a structured phantom with inserted targets was able to show evidence for detectability differences between FFDM and DBT modes for five commercial systems. This phantom has potential for application in task-based assessment at acceptance and commissioning testing of DBT systems.

CBCT-gebaseerde tandautotransplantatie voor elementvervanging na trauma of bij agenesie bij kinderen

Autotransplantatie van gebitselementen vormt een waardevolle behandeloptie bij jonge kinderen met ontbrekende elementen door trauma of agenesie. Het betreft een meer biologische benadering, met een esthetisch bevredigend resultaat tegen aanvaardbare kosten. Toch blijkt uit de literatuur dat het risico op mislukking reeel blijft. Om de kans op mislukken tot een minimum te beperken, wordt een multidisciplinaire aanpak voorgesteld met nauwe samenwerking tussen kindertandarts, chirurg, orthodontist, radioloog en restauratief tandarts. Essentieel daarbij is dat een grondig klinisch en radiologisch onderzoek moet leiden tot de juiste indicatiestelling en een patientspecifiek behandelingsplan. Cruciaal is ook de overleving van het donorelement en meer in het bijzonder de levensvatbaarheid van de parodontale ligamentcellen, die na transplantatie een biologisch ontwikkelproces en succesvolle overleving van het transplantaat kunnen garanderen. Om dit te realiseren werd meer dan tien jaar geleden aan de Universiteit van Leuven een behandeling ontwikkeld op basis van driedimensionale CBCT-gebaseerde planning en perioperatief gebruik van een tandreplica. Inmiddels wordt deze specifieke multidisciplinaire behandelingsaanpak steeds vaker aangeboden als alternatieve therapie bij elementvervanging bij het jonge kind. Deze behandeling wordt in dit hoofdstuk toegelicht, waarbij ook korte- en langetermijnresultaten getoond worden.

Three-dimensional planning accuracy and follow-up protocol in orthognathic surgery: a validation study

The purpose of the study was to propose and validate a three-dimensional (3D) tool for the assessment of orthognathic surgery planning accuracy and postoperative follow-up. A total of 15 patients (four male, 11 female; mean age 29.6 years) with skeletal class II and III, who underwent bimaxillary surgery were recruited for the study. All patients had preoperative computed tomography (CT), and cone-beam computerized tomography (CBCT) scans 1-6 weeks and 6 months postoperatively. The data was exported to a customized stepwise module developed in Amira software resulting in the accuracy being presented as translational and rotational differences between the planning and the actual outcome. To evaluate the reliability of the proposed method, intra-class correlation coefficient (ICC) was applied at a 95% confidence interval on the translational and rotational output of two observers. The inter- and intra-observer reliability were found to be high (ICC range: 0.94-0.98) with mean variability of less than 0.4mm and 0.7° for translational and rotational movements for both planning accuracy and follow-up protocols. The study provides a reliable, quantitative and time-efficient method for evaluating the accuracy of virtual surgical planning and postoperative follow-up.

Condylar changes after orthognathic surgery for class III dentofacial deformity: a systematic review

After orthognathic surgery for class II dentofacial deformity, remodelling of the mandibular condyle will take place. In a number of cases, this may evolve towards a phenomenon of condylar resorption. Yet, studies on the occurrence of this complication after the correction of a class III deformity are scarce. A systematic review of the literature was performed with the aim of identifying reports on condylar resorption or remodelling after orthognathic surgery for class III dentofacial deformity. A search of the international databases yielded 12 eligible studies. Eight studies reported some degree of postoperative condylar remodelling, while symptoms of condylar resorption were only described in a limited group of patients. Thus, the literature may show evidence of condylar remodelling after orthognathic treatment of class III patients, and anecdotal reports of condylar resorption exist. The small sample sizes, heterogeneity in methods and outcomes, and use of two-dimensional radiographs indicate the need for updated long-term research. In the future, the use of cone beam computed tomography data for volumetric and morphological condylar analysis in combination with three-dimensional cephalometry may provide the opportunity to further elucidate this phenomenon and better characterize its aetiology.

Driedimensionaal printen voor orale en maxillofaciale toepassingen

Door de opkomst van driedimensionale beeldvorming is het mogelijk om beelden niet alleen te gebruiken voor hun diagnostische waarde, maar kan er ook een virtuele planning van de chirurgische ingrepen gemaakt worden. Naast het bestuderen van de chirurgische noden met behulp van softwareprogramma’s voor 3D-planningen en het inschatten van mogelijke complicatierisico’s kunnen er ook eventuele hulpmiddelen geprint worden die de chirurg kunnen helpen tijdens de operatie. De mogelijkheid om driedimensionaal te printen zorgt voor een grote sprong voorwaarts in orale en maxillofaciale toepassingen.