Developing haptic caries simulation for dental education

Background: Treating tooth decay (caries), an essential skill for dental students to learn, relies largely on tactile investigation. Most dental schools use plastic or extracted teeth to teach caries removal and cavity design. However, plastic teeth cannot replicate the ‘feel’ of caries, limiting the available practice exercises to manual dexterity rather than cavity design guided by pathology. Virtual haptic simulation is emerging as a viable adjunct to traditional methods, with potential to simulate dental tissues and pathology. Aim: To develop virtual haptic caries simulations, enabling students to practice the tactile and cognitive aspects of caries removal and cavity design in a controlled environment on the Moog Simodont Dental Trainer. Methods: Custom software was written to enable the creation of blocks containing unique variations of caries. Each block was produced with segment data to enable automatic marking of students’ attempts. This caries block generation process enabled the creation of a large library of disparate carious models calling for a unique solution for each case. Results: A library of caries blocks was built. The blocks hold varying shape, depth and amount of caries within a simulated tooth consisting of enamel, dentine and pulp tissue. The design of the block encouraged the user to follow correct clinical protocols to treat the lesion, while preserving the maximum amount of healthy tissue. Conclusions: We present a novel haptic caries simulation encouraging correct clinical technique based on tactile sensation and realistic disease patterns. The exercises provide a safe environment for novice dental students to practice caries removal

Development of haptic caries simulation for dental education

Background: Treating tooth decay (caries removal) is an essential skill for dental students to learn. The process relies heavily on the dentist's ability to evaluate the state of the dental tissue being probed, a judgement made largely based on tactile investigation. Currently, most dental schools use plastic or extracted teeth to teach caries removal. Replication of the ‘feel’ of caries is not available in plastic teeth, and while extracted teeth may hold some value, most extracted teeth do not reflect a realistic carious lesion, appropriate for caries removal. Aim: To develop haptic caries simulations, allowing students to practice the tactile aspects of caries removal in a controlled environment on the Moog Simodont Dental Trainer. Materials and methods: Early work found that, due to the anisotropic nature of dentine and tooth decay, cone beam CT data of carious teeth would not provide a realistic simulation of carious lesions. It was decided to produce the caries programmatically, allowing for full control of all variables. Custom software was created to enable the creation of blocks containing unique variations of caries. Each block is produced with segment data to enable automatic marking. Results: A library of 'caries blocks' has been built. The blocks hold varying shape, depth and amount of caries within a simulated ‘tooth’ consisting of enamel, dentine and pulp tissue, allowing the student to practice on an unseen case every time. The design of the block encourages the user to follow typical pathological patterns to remove the lesion, while retaining the maximum amount of enamel, as is considered good practice. Each block contains segment information allowing for automatic objective marking. Conclusions: Simulated carious blocks can provide a safe environment for novice dental students to practice caries removal based on tactile sensation. The caries block generation process enables the creation of a large library of disparate carious models calling for a unique solution for each case

Investigating three methods of assessing the clinically relevant trueness of two intraoral scanners

Aims Intraoral scanners (IOS) are used for a wide range of treatments. Most IOSs produce data appropriate for local work, such as crowns, but evidence suggests that full-arch scans result in more erroneous scans, which may affect the fit of clinical appliances. There are no standardized methods for assessing the quality of IOSs. Though many studies have investigated the accuracy of scanners, one may find the reported values are difficult to interpret in a clinical context. Materials and methods This study investigated the trueness of two IOSs, using three metrics. The clinical value of each metric is discussed. A dentate model was scanned 10 times using two intraoral scanners. Three methods were used to assess the trueness of the scans against a scan produced in a laboratory scanner. Results The mean unsigned distance deviation between a laboratory scan and the Primescan scans was 0.016(±0.006)mm. The mean unsigned distance deviation between the laboratory scan and the Omnicam scans was 0.116(±0.01)mm. The arch width between molars was 55.44mm for the Solutionix scan. The arch width of the Primescan was 55.439(±0.075)mm, while the Omnicam reported 54.672(±0.065)mm. The mean proportion of the Primescan scans deviating beyond 0.1mm when compared against the Solutionix was 0.7(±2.0)%. The equivalent for the Omnicam was 42.1(±2.5)%. Conclusions All methods indicated significantly different results between the scanners. The Primescan produced truer scans than the Omnicam, regardless of measurement method. The intermolar-width and proportion beyond 0.1mm methods may give more clinically relevant insight into the trueness of scan data than current gold-standard methods

Modern meson--exchange potential and superfluid neutron star crust matter

In this work we study properties of neutron star crusts, where matter is expected to consist of nuclei surrounded by superfluid neutrons and a homogeneous background of relativistic electrons. The nuclei are disposed in a Coulomb lattice, and it is believed that the structure of the lattice influences considerably the specific heat of the neutronic matter inside the crust of a neutron star. Using a modern meson--exchange potential in the framework of a local--density approximation we calculate the neutronic specific heat accounting for various shapes of the Coulomb lattice, from spherical to non--spherical nuclear shapes. We find that a realistic nucleon--nucleon potential leads to a significant increase in the neutronic specific heat with respect to that obtained assuming a uniform neutron distribution. The increase is largest for the non--spherical phase of the crust. These results may have consequences for the thermal history of young neutron stars.Comment: Revtex, 5 pages, 4 figures included as uuencoded p

Muons and emissivities of neutrinos in neutron star cores

In this work we consider the role of muons in various URCA processes relevant for neutrino emissions in the core region of neutron stars. The calculations are done for $\beta$--stable nuclear matter with and without muons. We find muons to appear at densities $\rho = 0.15$ fm$^{-3}$, slightly around the saturation density for nuclear matter $\rho_0 =0.16$ fm$^{-3}$. The direct URCA processes for nucleons are forbidden for densities below $\rho = 0.5$ fm$^{-3}$, however the modified URCA processes with muons $(n+N\rightarrow p+N +\mu +\overline{\nu}_{\mu}, p+N+\mu \rightarrow n+N+\nu_{\mu}$), where $N$ is a nucleon, result in neutrino emissivities comparable to those from $(n+N\rightarrow p+N +e +\overline{\nu}_e, p+N+e \rightarrow n+N+\nu_e$). This opens up for further possibilities to explain the rapid cooling of neutrons stars. Superconducting protons reduce however these emissivities at densities below $0.4$ fm$^{-3}$.Comment: 14 pages, Revtex style, 3 uuencoded figs include

Effect of Intraduodenal Bile and Na-Taurodeoxycholate on Exocrine Pancreatic Secretion and on Plasma Levels of Secretin, Pancreatic Polypeptide, and Gastrin in Man

The effect of intraduodenally administered cattle bile (CB) and Na-taurodeoxycholate (TDC) on basal pancreatic secretion and plasma levels of secretin, pancreatic polypeptide (PP), and gastrin were investigated on two separate days in 10 fasting volunteers. Doses of 2-6 g CB and 20&600 mg TDC were given intraduodenally at 65-min intervals. Volume, bicarbonate, lipase, trypsin, amylase, and bilirubin were measured in 10-min fractions of duodenal juice, and GI peptides determined by radioimmunoassay. CB and TDC enhanced significantly and dose-dependently volume, bicarbonate and enzyme secretion, and plasma secretin and PP levels. In contrast, plasma gastrin showed only a marginal increase. We conclude that the hydrokinetic effect of intraduodenal CB and TDC is at least partially mediated by secretin. Gastrin could be ruled out as a mediator of the ecbolic effect, whereas other GI peptides, primarily CCK, and/or neural mechanisms must be considered possible mediators. Both pathways may also play a role in the PP release

Asymmetric nuclear matter and neutron star properties

In this work we calculate the total mass, radius, moment of inertia, and surface gravitational redshift for neutron stars using various equations of state (EOS). Modern meson-exchange potential models are used to evaluate the $G$-matrix for asymmetric nuclear matter. We calculate both a non-relativistic and a relativistic EOS. Of importance here is the fact that relativistic Brueckner-Hartree-Fock calculations for symmetric nuclear matter fit the empirical data, which are not reproduced by non-relativistic calculations. Relativistic effects are known to be important at high densities, giving an increased repulsion. This leads to a stiffer EOS compared to the EOS derived with a non-relativistic approach. Both the non-relativistic and the relativistic EOS yield moments of inertia and redshifts in agreement with the accepted values. The relativistic EOS yields, however, too large mass and radius. The implications are discussed.Comment: Revtex, 16 pages, 6 figures include

The LeVe CPAP System for Oxygen-Efficient CPAP Respiratory Support: Development and Pilot Evaluation

Background: The COVID-19 pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has placed a significant demand on healthcare providers (HCPs) to provide respiratory support for patients with moderate to severe symptoms. Continuous Positive Airway Pressure (CPAP) non-invasive ventilation can help patients with moderate symptoms to avoid the need for invasive ventilation in intensive care. However, existing CPAP systems can be complex (and thus expensive) or require high levels of oxygen, limiting their use in resource-stretched environments. Technical Development + Testing: The LeVe (“Light”) CPAP system was developed using principles of frugal innovation to produce a solution of low complexity and high resource efficiency. The LeVe system exploits the air flow dynamics of electric fan blowers which are inherently suited to delivery of positive pressure at appropriate flow rates for CPAP. Laboratory evaluation demonstrated that performance of the LeVe system was equivalent to other commercially available systems used to deliver CPAP, achieving a 10 cm H2O target pressure within 2.4% RMS error and 50–70% FiO2 dependent with 10 L/min oxygen from a commercial concentrator. Pilot Evaluation: The LeVe CPAP system was tested to evaluate safety and acceptability in a group of ten healthy volunteers at Mengo Hospital in Kampala, Uganda. The study demonstrated that the system can be used safely without inducing hypoxia or hypercapnia and that its use was well-tolerated by users, with no adverse events reported. Conclusions: To provide respiratory support for the high patient numbers associated with the COVID-19 pandemic, healthcare providers require resource efficient solutions. We have shown that this can be achieved through frugal engineering of a CPAP ventilation system, in a system which is safe for use and well-tolerated in healthy volunteers. This approach may also benefit other respiratory conditions which often go unaddressed in Low and Middle Income Countries (LMICs) for want of context-appropriate technology designed for the limited oxygen resources available

Formation of superdense hadronic matter in high energy heavy-ion collisions

We present the detail of a newly developed relativistic transport model (ART 1.0) for high energy heavy-ion collisions. Using this model, we first study the general collision dynamics between heavy ions at the AGS energies. We then show that in central collisions there exists a large volume of sufficiently long-lived superdense hadronic matter whose local baryon and energy densities exceed the critical densities for the hadronic matter to quark-gluon plasma transition. The size and lifetime of this matter are found to depend strongly on the equation of state. We also investigate the degree and time scale of thermalization as well as the radial flow during the expansion of the superdense hadronic matter. The flow velocity profile and the temperature of the hadronic matter at freeze-out are extracted. The transverse momentum and rapidity distributions of protons, pions and kaons calculated with and without the mean field are compared with each other and also with the preliminary data from the E866/E802 collaboration to search for experimental observables that are sensitive to the equation of state. It is found that these inclusive, single particle observables depend weakly on the equation of state. The difference between results obtained with and without the nuclear mean field is only about 20\%. The baryon transverse collective flow in the reaction plane is also analyzed. It is shown that both the flow parameter and the strength of the ``bounce-off'' effect are very sensitive to the equation of state. In particular, a soft equation of state with a compressibility of 200 MeV results in an increase of the flow parameter by a factor of 2.5 compared to the cascade case without the mean field. This large effect makes it possible to distinguish the predictions from different theoretical models and to detect the signaturesComment: 55 pages, latex, + 39 figures available upon reques

Superfluidity in beta-stable neutron star matter

In this work we present results for pairing gaps in $\beta$--stable neutron star matter with electrons and muons using a relativistic Dirac--Brueckner--Hartree--Fock approach, starting with modern meson--exchange models for the nucleon--nucleon interaction. Results are given for superconducting $^1S_0$ protons and $^3P_2$ and $^1D_2$ neutron superfluids. A comparison is made with recent non--relativistic calculations and the implications for neutron star cooling are discussed.Comment: 7 pages, RevTex latex style, 3 figs include