Evaluation of fit for 3D printed retainers as compared to thermoform retainers

ABSTRACT EVALUATION OF FIT FOR 3D PRINTED RETAINERS AS COMPARED TO THERMOFORM RETAINERS By David Cole, D.M.D. A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Dentistry at Virginia Commonwealth University Thesis Directors: Eser Tüfekçi, D.D.S., M.S., Ph.D., M.S.H.A. Professor, Department of Orthodontics Sompop Bencharit, D.D.S., M.S., Ph.D. Associate Professor and Director of Digital Dentistry, Department of General Practice Introduction: Despite recent advances in three-dimensional (3D) printing, little information is available on 3D printed retainers Methods: Three reference models were used to fabricate traditional vacuum formed, commercially-available vacuum formed, and 3D printed retainers. For each model, three retainers were made using the three methods (a total of 27 retainers). To determine the trueness, the distances between the intaglio surface of the retainers and the occlusal surface of the reference models were measured using an engineering software. A small difference was indicative of a good fit. Results: Average differences of the traditional vacuum formed retainers ranged from 0.10 to 0.20mm. The commercially-available and 3D printed retainers had a range of 0.10 to 0.30mm and 0.10 to 0.40mm, respectively. Conclusions: The traditional vacuum formed retainers showed the least amount of deviation from the original reference models while the 3D printed retainers showed the greatest deviation

Whole-brain vasculature reconstruction at the single capillary level

The distinct organization of the brain’s vascular network ensures that it is adequately supplied with oxygen and nutrients. However, despite this fundamental role, a detailed reconstruction of the brain-wide vasculature at the capillary level remains elusive, due to insufficient image quality using the best available techniques. Here, we demonstrate a novel approach that improves vascular demarcation by combining CLARITY with a vascular staining approach that can fill the entire blood vessel lumen and imaging with light-sheet fluorescence microscopy. This method significantly improves image contrast, particularly in depth, thereby allowing reliable application of automatic segmentation algorithms, which play an increasingly important role in high-throughput imaging of the terabyte-sized datasets now routinely produced. Furthermore, our novel method is compatible with endogenous fluorescence, thus allowing simultaneous investigations of vasculature and genetically targeted neurons. We believe our new method will be valuable for future brain-wide investigations of the capillary network

Utilizing micro-computed tomography to evaluate bone structure surrounding dental implants: a comparison with histomorphometry

Although histology has proven to be a reliable method to evaluate the ossoeintegration of a dental implant, it is costly, time consuming, destructive, and limited to one or few sections. Microcomputed tomography (µCT) is fast and delivers three-dimensional information, but this technique has not been widely used and validated for histomorphometric parameters yet. This study compared µCT and histomorphometry by means of evaluating their accuracy in determining the bone response to two different implant materials. In total, 32 titanium (Ti) and 16 hydroxyapatite (HA) implants were installed in 16 lop-eared rabbits. After 2 and 4 weeks, the animals were scarified, and the samples retrieved. After embedding, the samples were scanned with µCT and analyzed three-dimensionally for bone area (BA) and bone-implant contact (BIC). Thereafter, all samples were sectioned and stained for histomorphometry. For the Ti implants, the mean BIC was 25.25 and 28.86% after 2 and 4 weeks, respectively, when measured by histomorphometry, while it was 24.11 and 24.53% when measured with µCT. BA was 35.4 and 31.97% after 2 and 4 weeks for histomorphometry and 29.06 and 27.65% for µCT. For the HA implants, the mean BIC was 28.49 and 42.51% after 2 and 4 weeks, respectively, when measured by histomorphometry, while it was 33.74 and 42.19% when measured with µCT. BA was 30.59 and 47.17% after 2 and 4 weeks for histomorphometry and 37.16 and 44.95% for µCT. Direct comparison showed that only the 2 weeks BA for the titanium implants was significantly different between µCT and histology (p = 0.008). Although the technique has its limitations, µCT corresponded well with histomorphometry and should be considered as a tool to evaluate bone structure around implants

Validity and sensitivity of a human cranial finite element model: Implications for comparative studies of biting performance

Finite element analysis (FEA) is a modelling technique increasingly used in anatomical studies investigating skeletal form and function. In the case of the cranium this approach has been applied to both living and fossil taxa to (for example) investigate how form relates to function or infer diet or behaviour. However, FE models of complex musculoskeletal structures always rely on simplified representations because it is impossible completely to image and represent every detail of skeletal morphology, variations in material properties and the complexities of loading at all spatial and temporal scales. The effects of necessary simplifications merit investigation. To this end, this study focuses on one aspect, model geometry, which is particularly pertinent to fossil material where taphonomic processes often destroy the finer details of anatomy or in models built from clinical CTs where the resolution is limited and anatomical details are lost. We manipulated the details of a finite element (FE) model of an adult human male cranium and examined the impact on model performance. First, using digital speckle interferometry, we directly measured strains from the infraorbital region and frontal process of the maxilla of the physical cranium under simplified loading conditions, simulating incisor biting. These measured strains were then compared with predicted values from FE models with simplified geometries that included modifications to model resolution, and how cancellous bone and the thin bones of the circum-nasal and maxillary regions were represented. Distributions of regions of relatively high and low principal strains and principal strain vector magnitudes and directions, predicted by the most detailed FE model, are generally similar to those achieved in vitro. Representing cancellous bone as solid cortical bone lowers strain magnitudes substantially but the mode of deformation of the FE model is relatively constant. In contrast, omitting thin plates of bone in the circum-nasal region affects both mode and magnitude of deformation. Our findings provide a useful frame of reference with regard to the effects of simplifications on the performance of FE models of the cranium and call for caution in the interpretation and comparison of FEA results

Three Dimensional Printing: Modern Medical Applications

3-D printing is an additive printing process based on inkjet printing principles. Using this technology, a variety of materials can be used to create a three-dimensional product. Currently this technology is expensive, however it is slowly becoming more affordable. 3-D printing has the potential to change the future of medical model production and prototyping, due to the beneficial products it can produce. The objective of this research study is to discover the technological advancements in 3-D printing that could greatly affect several aspects of the medical industry. The areas discussed include high-risk surgery, dentistry, and prosthetics. After conducting six interviews with medical professionals, it was discovered that 3-D printing is a viable technological source that all professionals are eager to use and implement into their medical line of work. 3-D printing is a revolutionary technology that has the possibility to positively affect the work of medical professionals, while enhancing the lives of others