Abigail Lauer

Evaluation of the accuracy of 7 digital scanners: An in vitro analysis based on 3-dimensional comparisons

Statement of problem. As digital impressions become more common and more digital impression systems are released onto the market, it is essential to systematically and objectively evaluate their accuracy. Purpose. The purpose of this in vitro study was to evaluate and compare the trueness and precision of 6 intraoral scanners and 1 laboratory scanner in both sextant and complete‐arch scenarios. Furthermore, time of scanning was evaluated and correlated with trueness and precision. Material and methods. A custom complete‐arch model was fabricated with a refractive index similar to that of tooth structure. Seven digital impression systems were used to scan the custom model for both posterior sextant and complete arch scenarios. Analysis was performed using 3‐dimensional metrology software to measure discrepancies between the master model and experimental casts. Results. Of the intraoral scanners, the Planscan was found to have the best trueness and precision while the 3Shape Trios was found to have the poorest for sextant scanning (P<.001). The order of trueness for complete arch scanning was as follows: 3Shape D800 >iTero >3Shape TRIOS 3 >Carestream 3500 >Planscan >CEREC Omnicam >CEREC Bluecam. The order of precision for complete‐arch scanning was as follows: CS3500 >iTero >3Shape D800 >3Shape TRIOS 3 >CEREC Omnicam >Planscan >CEREC Bluecam. For the secondary outcome evaluating the effect time has on trueness and precision, the complete‐ arch scan time was highly correlated with both trueness (r=0.771) and precision (r=0.771). Conclusions. For sextant scanning, the Planscan was found to be the most precise and true scanner. For complete‐arch scanning, the 3Shape Trios was found to have the best balance of speed and accuracy.

Differences in Right Ventricular Functional Changes during Treatment between Systemic Sclerosis-Associated Pulmonary Arterial Hypertension and Idiopathic Pulmonary Arterial Hypertension.

Rationale: Patients with systemic sclerosis‐associated pulmonary arterial hypertension (SSc‐PAH) continue to have an unacceptably high mortality rate despite the progress achieved with pulmonary arterial vasodilator therapies. Objectives: We sought to determine whether SSc‐PAH is a clinically distinct pulmonary vascular disease phenotype when compared with idiopathic pulmonary arterial hypertension (IPAH) on the basis of progression of echocardiographic right ventricular (RV) dysfunction. Methods: Retrospective analysis of echocardiographic data in 13 patients with SSc‐PAH and 11 patients with IPAH was used to delineate the progression of RV dysfunction during single or combination pulmonary arterial vasodilator therapy. All patients had right heart catheterization‐confirmed pulmonary arterial hypertension as well as complete baseline (at the time of diagnosis) and follow‐up (most recent) echocardiograms. We excluded patients with significant scleroderma‐associated interstitial lung disease. Adjusting for time of follow‐up and disease duration, we performed mixed model regression analyses comparing the changes between the two groups for different echocardiographic variables: tricuspid annular plane systolic excursion, tricuspid regurgitation jet velocity, right atrial area, and RV diameter. Results: The mean ages for the SSc‐PAH and IPAH groups were 60.8 and 48.2 years, respectively. The mean follow‐up periods for the two groups were 3.8 and 1.95 years, respectively. Tricuspid annular plane systolic excursion did not improve in patients with SSc‐PAH, whereas it increased in the patients with IPAH (−0.38 mm, P = 0.87; vs. +5.6 mm, P = 0.02). The other echocardiographic variables showed a trend toward worsening in the SSc‐PAH group and improvement in the IPAH group. Conclusions: Our results indicate that, in patients with SSc‐PAH, echocardiographic RV function does not improve over time compared with that of patients with IPAH, despite institution of pulmonary artery vasodilator therapies.

Restoration of Kv7 Channel-Mediated Inhibition Reduces Cued-Reinstatement of Cocaine Seeking

Cocaine addicts display increased sensitivity to drug-associated cues, due in part to changes in the prelimbic prefrontal cortex (PL-PFC). The cellular mechanisms underlying cue-induced reinstatement of cocaine seeking remain unknown. Reinforcement learning for addictive drugs may produce persistent maladaptations in intrinsic excitability within sparse subsets of PFC pyramidal neurons. Using a model of relapse in male rats, we sampled >600 neurons to examine spike frequency adaptation (SFA) and afterhyperpolarizations (AHPs), two systems that attenuate low-frequency inputs to regulate neuronal synchronization. We observed that training to self-administer cocaine or nondrug (sucrose) reinforcers decreased SFA and AHPs in a subpopulation of PL-PFC neurons. Only with cocaine did the resulting hyperexcitability persist through extinction training and increase during reinstatement. In neurons with intact SFA, dopamine enhanced excitability by inhibiting Kv7 potassium channels that mediate SFA. However, dopamine effects were occluded in neurons from cocaine-experienced rats, where SFA and AHPs were reduced. Pharmacological stabilization of Kv7 channels with retigabine restored SFA and Kv7 channel function in neuroadapted cells. When microinjected bilaterally into the PL-PFC 10 min before reinstatement testing, retigabine reduced cue-induced reinstatement of cocaine seeking. Last, using cFos-GFP transgenic rats, we found that the loss of SFA correlated with the expression of cFos-GFP following both extinction and re-exposure to drug-associated cues. Together, these data suggest that cocaine self-administration desensitizes inhibitory Kv7 channels in a subpopulation of PL-PFC neurons. This subpopulation of neurons may represent a persistent neural ensemble responsible for driving drug seeking in response to cues. SIGNIFICANCE STATEMENT Long after the cessation of drug use, cues associated with cocaine still elicit drug-seeking behavior, in part by activation of the prelimbic prefrontal cortex (PL-PFC). The underlying cellular mechanisms governing these activated neurons remain unclear. Using a rat model of relapse to cocaine seeking, we identified a population of PL-PFC neurons that become hyperexcitable following chronic cocaine self-administration. These neurons show persistent loss of spike frequency adaptation, reduced afterhyperpolarizations, decreased sensitivity to dopamine, and reduced Kv7 channel-mediated inhibition. Stabilization of Kv7 channel function with retigabine normalized neuronal excitability, restored Kv7 channel currents, and reduced drug-seeking behavior when administered into the PL-PFC before reinstatement. These data highlight a persistent adaptation in a subset of PL-PFC neurons that may contribute to relapse vulnerability.

Sensitivity of diffusion MRI to perilesional reactive astrogliosis in focal ischemia

Reactive astrogliosis is a response to injury in the central nervous system that plays an essential role in inflammation and tissue repair. It is characterized by hypertrophy of astrocytes, alterations in astrocyte gene expression and astrocyte proliferation. Reactive astrogliosis occurs in multiple neuropathologies, including stroke, traumatic brain injury and Alzheimers disease, and it has been proposed as a possible source of the changes in diffusion magnetic resonance imaging (dMRI) metrics observed with these diseases. In this study, the sensitivity of dMRI to reactive astrogliosis was tested in an animal model of focal acute and subacute ischemia induced by the vasoconstricting peptide, endothelin‐1. Reactive astrogliosis in perilesional cortex was quantified by calculating the astrocyte surface density as determined with a glial fibrillary acidic protein (GFAP) antibody, whereas perilesional diffusion changes were measured in vivo with diffusional kurtosis imaging. We found substantial changes in the surface density of GFAP‐positive astrocyte processes and modest changes in dMRI metrics in the perilesional motor cortex following stroke. Although there are time point‐specific correlations between dMRI and histological measures, there is no definitive evidence for a causal relationship.

Effect of imperceptible vibratory noise applied to wrist skin on fingertip touch evoked potentials – an EEG study

Random vibration applied to skin can change the sense of touch. Specifically, low amplitude white‐noise vibration can improve fingertip touch perception. In fact, fingertip touch sensation can improve even when imperceptible random vibration is applied to other remote upper extremity areas such as wrist, dorsum of the hand, or forearm. As such, vibration can be used to manipulate sensory feedback and improve dexterity, particularly during neurological rehabilitation. Nonetheless, the neurological bases for remote vibration enhanced sensory feedback are yet poorly understood. This study examined how imperceptible random vibration applied to the wrist changes cortical activity for fingertip sensation. We measured somatosensory evoked potentials to assess peak‐to‐peak response to light touch of the index fingertip with applied wrist vibration versus without. We observed increased peak‐to‐peak somatosensory evoked potentials with wrist vibration, especially with increased amplitude of the later component for the somatosensory, motor, and premotor cortex with wrist vibration. These findings corroborate an enhanced cortical‐level sensory response motivated by vibration. It is possible that the cortical modulation observed here is the result of the establishment of transient networks for improved perception.

Evaluation of the effect scan pattern has on the trueness and precision of six intraoral digital impression systems

OBJECTIVE Clinicians have been slow to adopt digital impression technologies due possibly to perceived technique sensitivities involved in data acquisition. This research has two aims: determine whether scan pattern and sequence affects the accuracy of the three-dimensional (3D) model created from this digital impression and to compare the 5 imaging systems with regards to their scanning accuracy for sextant impressions. MATERIALS AND METHODS Six digital intraoral impression systems were used to scan a typodont sextant with optical properties similar to natural teeth. The impressions were taken using five different scan patterns and the resulting digital models were overlayed on a master digital model to determine the accuracy of each scanner performing each scan pattern. Furthermore, regardless of scan pattern, each digital impression system was evaluated for accuracy to the other systems in this same manner. RESULTS No differences of significance were noted in the accuracy of 3D models created using six distinct scan patterns with one exception involving the CEREC Omnicam. Planmeca Planscan was determined to be the truest scanner while 3Shape Trios was determined to be the most precise for sextant impression making. CONCLUSIONS Scan pattern does not significantly affect the accuracy of the resulting digital model for sextant scanning. CLINICAL SIGNIFICANCE Companies who make digital impression systems often recommend a scan pattern specific for their system. However, every clinical scanning scenario is different and may require a different approach. Knowing how important scan pattern is with regards to accuracy would be helpful for guiding a growing number of practitioners who are utilizing this technology.