3D-printed Cast Research Articles

Accuracy Analysis of Digital Models from Intraoral Scanners and 3D-Printed Casts in Children and Teenagers.

The aim was to analyze the accuracy of digital models and 3D-printed casts from full-arch digital impressions using two intraoral scanners (iTeroTM and PrimescanTM). A crossover reliability study was designed, scanning children and teenagers with iTeroTM and PrimescanTM. Accuracy was evaluated by measuring intercanine, intermolar, and ipsilateral canine-molar distances intraorally and comparing these measurements with those from plaster casts, digital models obtained with intraoral scanners, and 3D-printed casts. A paired comparison and a general linear model with a one-way repeated measures ANOVA procedure were carried out with a confidence level of 95% (p ≤ 0.05). A total of 51 subjects were analyzed (mean age 12.35 ± 2.57). Statistical differences (p < 0.05) were found in the upper and lower arch regarding accuracy in comparison to intraoral measurements, except for the iTeroTM-printed cast and canine-molar upper right and intercanine lower distances (p > 0.05 for all comparisons). Regarding a comparison between reproduction methods, the plaster cast oversized the intercanine upper distance in comparison with both intraoral scanners' digital models and the PrimescanTM-printed cast (p = 0.001), but there were no differences in the lower arch (p > 0.05 for all comparisons). Intraoral scanners reproduce tooth structures with similar accuracy to conventional methods.

Impact of groove-and-tongue parameters on the bonding behavior between 3d-printed UHP-SHCC and cast normal concrete

The utilization of 3D-printed formworks represents a significant advancement in traditional construction practices, offering the potential to enhance structural capacity and effectively address reinforcement challenges in 3D concrete printing. Ensuring strong bonding between formwork and cast concrete is critical for structural integrity. In this study, 11 composite specimens with varying groove-and-tongue parameters including the layer number, spacing, length, and thickness of tongues undergo splitting tests. Results reveal that increasing the tongue’s layer number enhances the interfacial splitting tensile strength, whereas tongue spacing has minimal impact on interfacial strength, and a thicker tongue negatively affects the interfacial splitting tensile strength. An optimized groove-and-tongue configuration can significantly increase the interfacial splitting tensile strength from 2.10 MPa to 3.66 MPa, with a maximum increase rate of 70.4% and achieving a higher value (20.8%) than that of fully cast normal concrete. A splitting tensile strength model is proposed, with predictions aligning well with experimental results.

A Comparative Evaluation of Real-Time Guided Dynamic Navigation and Conventional Techniques for Post Space Preparation During Post Endodontic Management: An In Vitro Study.

The three-dimensional (3D) dynamic navigation system (DNS; Navident, ClaroNav Technology, Toronto, ON) is a revolutionary technique in endodontics that offers superior precision and efficiency compared to existing techniques for post space preparation. The aim is to evaluate and contrast the efficacy and efficiency of the DNS with conventional post space preparation techniques. This assessment considers severalparameters, notably canal deviation (global coronal and apical deviation and angular deflection), duration of the procedure, and total volumetric loss of instrumented root canal and volumetric loss of instrumented root canal above 4 mm from the apex. Freshly extracted maxillary central incisors were chosen for this study. A total sample size of 60 (n) was included. The extracted teeth samples were divided into two groups: 3D DNS (group I; n = 30)and conventional techniques (group II; n = 30). The samples were taken, and 50% of the crown structure was reduced for post space preparation to ensure standardization between thetwo groups. The samples were root canal-treated and mounted in a 3D-printed maxillary cast. Preoperative micro-computed tomography (micro-CT) and cone-beam computed tomography (CBCT) were taken for both groups.For group I, post space preparation was conducted with the DNS, which provided comprehensive guidance. The procedure was stopped when post space preparation was 4 mm short of the apex, as indicated in the system display. For group II, post space preparation was done without the guidance of DNS. Time taken for the procedure was assessed using a timer; canal deviation was evaluated using CBCT analysis, and volumetric loss was estimated using micro-CT analysis. The dynamic navigation group achieves significantly more precise outcomes in post space preparation than the conventional technique. The DNS group has significantly lesser global coronal and apical deviation and angular deflection compared to the conventional group (p < 0.05). The DNS group has reduced the volumetric loss of instrumented root canals compared to the conventional group (p < 0.05). Furthermore, the DNS group requires significantlyless time than the conventional method, with a mean difference of about 10.567 minutes (p < 0.05). Implementing dynamic navigation improves precision in post space preparation, with a notable reduction in canal deviation and volumetric loss and a decrease in procedure time compared to the conventional method.

Development of favipiravir dry powders for intranasal delivery: An integrated cocrystal and particle engineering approach via spray freeze drying

The therapeutic potential of pharmaceutical cocrystals in intranasal applications remains largely unexplored despite progressive advancements in cocrystal research. We present the application of spray freeze drying (SFD) in successful fabrication of a favipiravir-pyridinecarboxamide cocrystal nasal powder formulation for potential treatment of broad-spectrum antiviral infections. Preliminary screening via mechanochemistry revealed that favipiravir (FAV) can cocrystallize with isonicotinamide (INA), but not nicotinamide (NCT) and picolinamide (PIC) notwithstanding their structural similarity. The cocrystal formation was characterized by differential scanning calorimetry, Fourier-transform infrared spectroscopy, and unit cell determination through Rietveld refinement of powder X-ray analysis. FAV-INA crystalized in a monoclinic space group P21/c with a unit cell volume of 1223.54(3) Å3, accommodating one FAV molecule and one INA molecule in the asymmetric unit. The cocrystal was further reproduced as intranasal dry powders by SFD, of which the morphology, particle size, in vitro drug release, and nasal deposition were assessed. The non-porous flake shaped FAV-INA powders exhibited a mean particle size of 19.79 ± 2.61 μm, rendering its suitability for intranasal delivery. Compared with raw FAV, FAV-INA displayed a 3-fold higher cumulative fraction of drug permeated in Franz diffusion cells at 45 min (p = 0.001). Dose fraction of FAV-INA deposited in the nasal fraction of a customized 3D-printed nasal cast reached over 80 %, whereas the fine particle fraction remained below 6 % at a flow rate of 15 L/min, suggesting high nasal deposition whilst minimal lung deposition. FAV-INA was safe in RPMI 2650 nasal and SH-SY5Y neuroblastoma cells without any in vitro cytotoxicity observed. This study demonstrated that combining the merits of cocrystallization and particle engineering via SFD can propel the development of advanced dry powder formulations for intranasal drug delivery.

Rivastigmine nasal spray for the treatment of Alzheimer’s Disease: Olfactory deposition and brain delivery

Alzheimer’s disease (AD) is characterized by a gradual decline in cognitive function and memory impairment, significantly impacting the daily lives of patients. Rivastigmine (RHT), a cholinesterase inhibitor, is used to treat mild to moderate AD via oral administration. However, oral administration is associated with slow absorption rate and severe systemic side effects. RHT nasal spray (RHT-ns), as a nose-to-brain delivery system, is more promising for AD management due to its efficient brain delivery and reduced peripheral exposure. This study constructed RHT-ns for enhancing AD treatment efficacy, and meanwhile the correlation between drug olfactory deposition and drug entering into the brain was explored. A 3D-printed nasal cast was employed to quantify the drug olfactory deposition. Brain delivery of RHT-ns was quantified using fluorescence tracking and Desorption Electrospray Ionization Mass Spectrometry (DESI-MS) analysis, which showed a good correlation to the olfactory deposition. F2 (containing 1% (w/v) viscosity modifier Avicel® RC-591) with high olfactory deposition and drug brain delivery was further investigated for pharmacodynamics study. F2 exhibited superiority in AD treatment over the commercially available oral formulation. In summary, the present study showed the successful development of RHT-ns with improved olfactory deposition and enhanced brain delivery. It might provide new insight into the design and development of nose-to-brain systems for the treatment of AD.

Custom-made 3D-printed boot as a model of disuse-induced atrophy in murine skeletal muscle.

Skeletal muscle atrophy is characterized by a decrease in muscle mass and strength caused by an imbalance in protein synthesis and degradation. This process naturally occurs upon reduced or absent physical activity, often related to illness, forced bed rest, or unhealthy lifestyles. Currently, no treatment is available for atrophy, and it can only be prevented by overloading exercise, causing severe problems for patients who cannot exercise due to chronic diseases, disabilities, or being bedridden. The two murine models commonly used to induce muscle atrophy are hindlimb suspension and ankle joint immobilization, both of which come with criticalities. The lack of treatments and the relevance of this atrophic process require a unilateral, safe, and robust model to induce muscle atrophy. In this work, we designed and developed a 3D-printed cast to be used for the study of disuse skeletal muscle atrophy. Applying two halves of the cast is non-invasive, producing little to no swelling or skin damage. The application of the cast induces, in 2-weeks immobilized leg, the activation of atrophy-related genes, causing a muscle weight loss up to 25% in the gastrocnemius muscle, and 31% in the soleus muscle of the immobilized leg compared to the control leg. The cross-sectional area of the fibers is decreased by 31% and 34% respectively, with a peculiar effect on fiber types. In the immobilized gastrocnemius, absolute muscle force is reduced by 38%, while normalized force is reduced by 16%. The contralateral leg did not show signs of overload or hypertrophy when compared to free roaming littermates, offering a good internal control over the immobilized limb. Upon removing the cast, the mice effectively recovered mass and force in 3 weeks.

Mechanical Properties of 3D-Printed Carbon Fiber-Reinforced Cement Mortar

The 3D printing process is different from traditional construction methods of formwork casting due to the use of additive manufacturing. This study develops a suitable 3D-printed carbon fiber-reinforced cement mortar (CFRCM) considering the extrudability, fluidity, setting time, and buildability of the CFRCM. The difference in compressive strength and flexural strength between 3D-printed specimens and conventional cast specimens was investigated by varying the amount of carbon fiber added (carbon fiber to cement ratio, 2.5 vol.‰, 5 vol.‰, 7.5 vol.‰, and 10 vol.‰) and the curing times (7th day and 28th day). The results of the experiments indicate that the addition of 6 wt.% cement accelerators to the cementitious mortar allows for a controlled initial setting time of approximately half an hour. The fluidity of the CFRCM was controlled by adjusting the dosage of the superplasticizer. When the slump was in the range of 150 mm to 190 mm, the carbon fiber to cement ratio 2.5 vol.‰ could be incorporated into the cementitious mortar, enabling the printing of hollow cylinders with a height of up to 750 mm. Comparing the 3D-printed specimens with the traditionally cast specimens, it was found that the addition of a carbon fiber to cement ratio of 7.5 vol.‰, and 10 vol.‰ resulted in the optimal compressive strength and flexural strength, respectively.

Interfacial bonding performance of 3D-printed Ultra-High Performance Strain-Hardening Cementitious Composites (UHP-SHCC) and cast normal concrete

Using 3D-printed elements as permanent formwork for structural members is an efficient way to integrate 3D printing technology in the traditional construction field which could also enhance structural capacity and possibly address the reinforcement challenge during 3D concrete printing. The bonding performance between 3D-printed formwork and post-cast concrete is crucial for maintaining the overall mechanical performance of the structures. This study experimentally investigates the interfacial bonding properties between 3D-printed Ultra-High Performance Strain-Hardening Cementitious Composites (UHP-SHCC) permanent formwork and post-cast normal concrete (NC). Three groups of prismatic composite specimens with smooth, grooved, and 3D-printed interfaces are subjected to the splitting tensile test to evaluate the interfacial bonding. A fully cast normal concrete specimen is also tested as a reference for comparison. The failure modes, splitting tensile strength, and effective bonding area ratio of normal concrete are analyzed and discussed. Results reveal that the splitting tensile strength of interfaces with grooved and 3D-printed preparation is significantly higher than that of the smooth interface, with an increase of 92.2%–114.8 %.

Density-Based Topological Optimization of 3D-Printed Casts for Fracture Treatment with Freefem Software

Abstract 3D printed plastic casts can be used for healing bone fractures. The main requirements for these cases are: they should be light, require little printing time, have good mechanical properties, and ensure proper skin ventilation. We present a density-based topology optimization algorithm for obtaining optimal cast shapes that fulfil these requirements. The algorithm uses a linear stress model and simplified boundary conditions to model the contact problems. The cast shapes were optimized against the influence of several sharp corners. The parametric studies showed that the mass of optimized casts was reduced by 20 %–25 % in comparison with original industrial casts, and the printing time is reduced by 1.4–1.7 h for the largest cast. A major model drawback is the use of 3D numerical volume to model the density distribution. The density distribution should be homogenized across the cast layer. The overhang problem should also be addressed. We also suggest that the cast producers collect more experimental data on the cast breakages for a better calibration of the numerical model.

What Are the Key Anatomical Features for the Success of Nose-to-Brain Delivery? A Study of Powder Deposition in 3D-Printed Nasal Casts.

Nose-to-brain delivery is a promising way to improve the treatment of central nervous system disorders, as it allows the bypassing of the blood-brain barrier. However, it is still largely unknown how the anatomy of the nose can influence the treatment outcome. In this work, we used 3D printing to produce nasal replicas based on 11 different CT scans presenting various anatomical features. Then, for each anatomy and using the Design of Experiments methodology, we characterised the amount of a powder deposited in the olfactory region of the replica as a function of multiple parameters (choice of the nostril, device, orientation angle, and the presence or not of a concomitant inspiration flow). We found that, for each anatomy, the maximum amount of powder that can be deposited in the olfactory region is directly proportional to the total area of this region. More precisely, the results show that, whatever the instillation strategy, if the total area of the olfactory region is below 1500 mm2, no more than 25% of an instilled powder can reach this region. On the other hand, if the total area of the olfactory region is above 3000 mm2, the deposition efficiency reaches 50% with the optimal choice of parameters, whatever the other anatomical characteristics of the nasal cavity. Finally, if the relative difference between the areas of the two sides of the internal nasal valve is larger than 20%, it becomes important to carefully choose the side of instillation. This work, by predicting the amount of powder reaching the olfactory region, provides a tool to evaluate the adequacy of nose-to-brain treatment for a given patient. While the conclusions should be confirmed via in vivo studies, it is a first step towards personalised treatment of neurological pathologies.

Three-dimensional printed cast assisted screw fixation of calcaneal fractures: a prospective study

BackgroundTreatment of displaced intra-articular calcaneal fractures (DIACFs) with percutaneous screw fixation remains defective in some aspects. A novel three-dimensional (3D) printed cast was devised to assist screw placement. This study assessed the radiological and functional outcomes of 3D-printed cast assisted screw fixation for patients with DIACFs.MethodsPatients with unilateral Sanders type II or III DIACFs admitted to a single-centre hospital underwent either 3D-printed cast assisted screw fixation (3D group) or minimally invasive plate fixation (control group) from September 2020 to November 2022. All patients were assessed at one, two, three, and six months of follow-up. Comparison between groups was conducted in operative duration, fluoroscopic times, radiographic measurements of the calcaneus, and the American Orthopaedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot Score.ResultsA total of 32 patients were enrolled (19 in the 3D group versus 13 in the control group). Significant differences were detected between the 3D group and control group in operative duration (53.63±8.95 min, 95.08±8.31 min, P <0.001), fluoroscopic times (7.37±1.21, 16.85±1.57, P <0.001). At a follow-up of six months, the 3D group showed better restoration than the control group in calcaneal width, height, Bohler angle, and AOFAS Ankle-Hindfoot scores (all P <0.001). No significant differences were shown in calcaneal length and Gissane angle (P >0.05). No wound-related complications occurred in either group.ConclusionThe 3D-printed cast assisted screw fixation has shown superiority over minimally invasive plate fixation in the operative duration, fluoroscopic exposure, morphological restoration of the calcaneus, and functional outcomes in the treatment of DIACFs.

A technique to convert a 3D printed cast used in the fabrication of an interim implant-supported crown into a definitive cast capturing the acquired emergence profile.

An esthetic peri-implant soft tissue contour is a critical element of the success of implant restorations in the esthetic zone. Once the optimal transmucosal soft tissue profile is formed, it needs to be accurately replicated on the master cast. This clinical technique involves the utilization of a silicone putty positioning index placed in the patient's mouth to accurately duplicate the external contour of teeth and soft tissue. By combining this positioning index with the implant-supported interim crown, the 3D-printed initial cast, which was used to fabricate the interim crown, can be conveniently and efficiently transformed into a definitive master cast.

Dimensional Accuracy of 3D-Printed, Digital and Conventional Stone Dental Cast of Dentate Patients Using Arch and Teeth Measurements

Aim: This study aimed to compare the conventional, digital, and three-dimensional (3D)-printed casts in terms of their accuracy in quantifying arch and teeth measurements. Materials and Methods: The conventional casts were prepared using polyether dental impressions. Digital impressions of the typodont reference casts were accomplished using an intra-oral scanner. The digital casts were first converted to stereolithography (STL) files which were then edited, and printed using an SLA printer and photo-polymer resin material. The measurements of the first two groups were completed using a digital caliper, while an imaging software was used to measure digital casts. The occlusocervial (OC) height and mesiodistal (MD) width of canines, second premolars (PMs), and molars of each jaw were measured. Additionally, intercanine width (ICW) and intermolar width (IMW) were also measured. Results: Overall, the lowest OC measurement errors were observed for 3D-printed casts for the upper canine, lower canine, and lower molar (0.003±0.01 mm). Similarly, the lowest MD measurement errors were observed for 3D-printed casts for upper canine, upper PM, and lower PM (0.002±0.01 mm). The ICW and IMW measurement errors for the 3D-printed casts were significantly lower (p &lt; 0.01) for the upper ICW (0.011±0.01 mm) and lower IMW (0.017±0.01 mm) than the other two groups. Compared to the conventional and digital casts, the lower ICW (0.013±0.01 mm) and upper IMW (0.017±0.01 mm) measurement errors observed for the 3D-printed casts were also lower, but non-significantly (p &gt; 0.01). Conclusions: 3D-printed casts presented the lowest OC, MD, ICW, and IMW measurement errors, than the conventional and digital casts. The highest measurement errors were associated with the digital casts.

Poster 120: Understanding the Biological Basis of Contracture Using a Mouse Model of Single Hindlimb Immobilization-Induced Fibrosis

Poster 120: Understanding the Biological Basis of Contracture Using a Mouse Model of Single Hindlimb Immobilization-Induced Fibrosis

Effective nose-to-brain drug delivery using a combination system targeting the olfactory region in monkeys

The nose-to-brain (N2B) pathway has garnered attention because it transports drugs directly into the brain. Although recent studies have suggested the necessity of selective drug administration to the olfactory region for effective N2B drug delivery, the importance of delivering the formulation to the olfactory region and the detailed pathway involved in drug uptake in primates brain remain unclear. Here, we developed a combination system for N2B drug delivery comprising a proprietary mucoadhesive powder formulation and a dedicated nasal device (N2B-system) and evaluated it for nasal drug delivery to the brain in cynomolgus monkeys. This N2B-system demonstrated a much greater formulation distribution ratio in the olfactory region in an in vitro experiment using a 3D-printed nasal cast and in vivo experiment using cynomolgus monkeys, as compared to that in other nasal drug delivery systems that comprise of a proprietary nasal powder device developed for nasal absorption and vaccination and a commercially available liquid spray. Additionally, Texas Red-labeled dextran (TR-DEX, 3 kDa) was administered using the N2B-system to estimate the drug transition pathway from the nasal cavity to the brain. TR-DEX preferentially localized to the olfactory epithelium and reached the olfactory bulb through the cribriform foramina. Moreover, domperidone, a model drug with poor blood-brain barrier permeability, was administered to assess the brain uptake of medicine after olfactory region-selective administration by using the N2B-system. Domperidone accumulation in the brain was evaluated using positron emission tomography with intravenously administered [18F]fallypride based on competitive inhibition of the dopamine D2 receptor (D2R). Compared to other systems, the N2B-system significantly increased D2R occupancy and domperidone uptake in the D2R-expressing brain regions. The current study reveals that the olfactory region of the nasal cavity is a suitable target for efficient nasal drug delivery to the brain in cynomolgus monkeys. Thus, the N2B-system, which targets the olfactory region, provides an efficient approach for developing effective technology for nasal drug delivery to the brain in humans.

Ray-tracing images for melting PCM bridges in microgravity

A ray-tracing algorithm is developed to obtain synthetic images for tracking the melting of the phase change material (PCM) n-octadecane in a liquid bridge configuration. The translucent nature of the solid n-octadecane is modelled through a sigmoid function which provides a distance-dependent illumination intensity throughout the solid. The code is validated against two types of experiments: front shapes made of 3D-printed PLA and cast front shapes of solid n-octadecane. Comparison with these experiments allows the numerical constants involved in the model to be tuned to appropriate values. For application to the MarPCM microgravity experiment (Porter et al., 2023), the current study provides the expected images of the solid/liquid front obtained by the optical diagnosis module for three different values of the dimensionless volume (defined with respect to a perfect cylinder), V=0.9, 1, and 1.1, and two applied temperature differences, ΔT=5 and 30K. The solid/liquid front shapes are obtained numerically from a two-dimensional axisymmetric code as in Varas et al. (2021). The results reveal a strong dependence of image quality on the liquid fraction L. Visual inspection leads to the conclusion that, below L≈60%, an accurate determination of the front location may be difficult, particularly for the relatively shallow layer of liquid near the thermocapillary interface.

In vitro Evaluation of Paliperidone Palmitate Loaded Cubosomes Effective for Nasal-to-Brain Delivery.

This work aimed to develop chitosan-coated cubosomal nanoparticles intended for nose-to-brain delivery of paliperidone palmitate. They were compared with standard and cationic cubosomal nanoparticles. This comparison relies on numerous classical in vitro tests and powder deposition within a 3D-printed nasal cast. Cubosomal nanoparticles were prepared by a Bottom-up method followed by a spray drying process. We evaluated their particle size, polydispersity index, zeta-potential, encapsulation efficiency, drug loading, mucoaffinity properties and morphology. The RPMI 2650 cell line was used to assess the cytotoxicity and cellular permeation. An in vitro deposition test within a nasal cast completed these measurements. The selected chitosan-coated cubosomal nanoparticles loaded with paliperidone palmitate had a size of 305.7 ± 22.54 nm, their polydispersity index was 0.166 ± 0.022 and their zeta potential was +42.4 ± 0.2 mV. This formulation had a drug loading of 70% and an encapsulation efficiency of 99.7 ± 0.1%. Its affinity with mucins was characterized by a ΔZP of 20.93 ± 0.31. Its apparent permeability coefficient thought the RPMI 2650 cell line was 3.00E-05 ± 0.24E-05 cm/s. After instillation in a 3D-printed nasal cast, the fraction of the injected powder deposited in the olfactory region reached 51.47 ± 9.30% in the right nostril and 41.20 ± 4.59% in the left nostril, respectively. The chitosan coated cubosomal formulation seems to be the most promising formulation for nose-to-brain delivery. Indeed, it has a high mucoaffinity and a significantly higher apparent permeability coefficient than the two other formulations. Finally, it reaches well the olfactory region.

Development and evaluation of a portable and soft 3D-printed cast for laparoscopic choledochojejunostomy model in surgical training

BackgroundLaparoscopic choledochojejunostomy (LCJ) is an essential basic skill for biliary surgeons. Therefore, we established a convenient and effective LCJ 3D printing model to evaluate whether the model could simulate the actual operation situation and determine its effectiveness and validity in surgical training.MethodsA 3D printing dry laboratory model was established to simulate LCJ. The face and content validity of the model were evaluated by six experienced biliary surgeons based on 5-point Likert scale questionnaires. A total of 15 surgeons with different levels of experience performed LCJ on the model and evaluated the structural validity of the model using the objective structured assessment of technical skills (OSATS). Simultaneously, the operation time of each surgery was also recorded. A study was also performed to further evaluate the learning curve of residents.ResultsThe operating space score of the model was 4.83 ± 0.41 points. The impression score of bile duct and intestinal canal was 4.33 ± 0.52 and 4.17 ± 0.41 points, respectively. The tactile sensation score of bile duct suture and intestinal canal suture was 4.00 ± 0.63 and 3.83 ± 0.41points, respectively. The OSATS score for model operation in the attending group was 29.20 ± 0.45 points, which was significantly higher than that in the fellow group (26.80 ± 1.10, P = 0.007) and the resident group (19.80 ± 1.30, P < 0.001). In addition, there was a statistical difference in operation time among surgeons of different experience levels (P < 0.05). Residents could significantly improve the surgical score and shorten the time of LCJ through repeated training.ConclusionsThe 3D printing LCJ model can simulate the real operation scenes and distinguish surgeons with different levels of experience. The model is expected to be one of the training methods for biliary tract surgery in the future.

Development of computational fluid dynamics methodology for characterization of exhalation delivery system performance in a nasal airway with Draf-III surgery

Computational fluid dynamics (CFD) has been used to investigate the intranasal deposition of corticosteroid sprays. CFD Lagrangian tracking models terminate particle motion once particles come into contact with a surface (“trap” boundary condition) and disregard the liquid film buildup on the mucosal surfaces of the sinonasal cavity walls. However, the interaction between spray droplets and the mucosal surface is critical for corticosteroid delivery using the exhalation delivery system (EDS) nasal spray device. Droplets coalesce on sinonasal walls, forming a thin “wall-film” on which droplets spread along the surface, splash, and/or break into secondary particles, depending on impact energy. To advance nasal drug delivery modeling, three CFD models of fluticasone propionate deposition using the EDS device in a Draf III post-surgical geometry were developed: (1) using traditional “trap” boundary conditions; (2) using “wall-film” boundary conditions and one-way coupling; and (3) using “wall-film” boundary conditions with two-way coupling (to account for the high-mass loading in the near-nozzle spray field). Contour plots and data sets for each CFD model were qualitatively compared with physical models in the same geometry (visualized in a 3D-printed sinonasal cast). The CFD simulations showed that EDS delivers fluticasone to all sinonasal regions, including areas superiorly and posteriorly in the sinonasal cavity. In addition, deposition improved and more closely correlated with physical experiments as the CFD model complexity evolved. “Wall-film” modeling of EDS delivery demonstrated increased surface coverage compared to the “trap” model. The “wall-film/two-way coupling” model demonstrated substantially higher deposition in the remote frontal and maxillary sinuses, agreeing with physical cast experiments. In conclusion, CFD simulation of EDS delivery using the “wall-film” boundary/two-way coupling model appears to most accurately represent observations from physical model experiments in the same geometry.

Comparative analysis of intaglio surface trueness of cement-retained implant-supported prostheses generated by a cast-free digital workflow and a three-dimensionally printed cast workflow

Statement of problemComparative analysis of the accuracy of the prostheses produced by a cast-free digital workflow and 3-dimensional (3D) printing cast workflow is lacking. PurposeThe purpose of the present investigation was to compare the intaglio surface trueness of implant-supported prostheses fabricated by using 3 different digital workflows: cast-free computer-aided design (CAD), 3D printed cast CAD (direct insert), and 3D printed cast CAD (indirect insert). Material and methodsThe laboratory data of 11 partially edentulous arches for prosthetic implant treatment were obtained. Three different workflows were tested to produce the cement-retained prostheses: cast-free CAD (Group CF), 3D printed cast CAD with direct insert (Group PD), and 3D printed cast CAD with indirect insert (Group PI). The intaglio surfaces of the prosthesis CAD data from Groups CF, PD, and PI were superimposed with 3D printed prosthesis scan data from Group CF to measure 3D surface deviation. Using the prosthesis CAD data from Group CF as a reference, those from Groups PD and PI were compared by superimposition analysis. The root mean square (RMS) estimates, positive average deviations, and negative average deviations were measured. The Kruskal-Wallis test and Dunn test with Bonferroni correction, and the Wilcoxon rank sum test were used for statistical analyses (α=.05). ResultsSignificant differences were found among the 3 groups when the 3D printed prosthesis scan data were referenced (P<.05). Group CF showed the lowest RMS, positive average deviation, and negative deviation values, while Group PI showed the highest values. Significant differences in the RMS, positive average deviation, and negative average deviation values were found between Groups PD and PI when the prosthesis CAD data (Group CF) were referenced (P<.05). ConclusionsAmong the 3 different workflows tested, the prostheses generated from the cast-free CAD flow showed significantly lower intaglio surface deviation than those generated from the 3D printed cast CAD flows, regardless of the insertion method of the implant replicas.