Effect of data leakage in brain MRI classification using 2D convolutional neural networks

In recent years, 2D convolutional neural networks (CNNs) have been extensively used to diagnose neurological diseases from magnetic resonance imaging (MRI) data due to their potential to discern subtle and intricate patterns. Despite the high performances reported in numerous studies, developing CNN models with good generalization abilities is still a challenging task due to possible data leakage introduced during cross-validation (CV). In this study, we quantitatively assessed the effect of a data leakage caused by 3D MRI data splitting based on a 2D slice-level using three 2D CNN models to classify patients with Alzheimer’s disease (AD) and Parkinson’s disease (PD). Our experiments showed that slice-level CV erroneously boosted the average slice level accuracy on the test set by 30% on Open Access Series of Imaging Studies (OASIS), 29% on Alzheimer’s Disease Neuroimaging Initiative (ADNI), 48% on Parkinson’s Progression Markers Initiative (PPMI) and 55% on a local de-novo PD Versilia dataset. Further tests on a randomly labeled OASIS-derived dataset produced about 96% of (erroneous) accuracy (slice-level split) and 50% accuracy (subject-level split), as expected from a randomized experiment. Overall, the extent of the effect of an erroneous slice-based CV is severe, especially for small datasets

The first archaeological case of permanent teeth fusion in Europe

Abstract Teeth fusion is a developmental anomaly characterized by the union of two and, more rarely, three adjacent teeth. The fusion is caused by the physical pressure between two adjacent teeth during their development due to congenital, inherited, acquired or idiopathic factors. Nowadays, fused teeth occur with a frequency ratio between 0.1% and 1% in permanent dentition and 0.5% and 2.5% in primary dentition, and with an equal distribution between males and females. Fused teeth are a rare clinical finding, so there are not standardized clinical protocols and each case should be treated independently. This condition is rare in archaeological populations, likely due to taphonomic processes that cause the lack of information, as well as for the general low occurrence of the defect itself. In the European archaeological literature, there are no reports of two permanent fused teeth so far. Therefore, the present paper represents the first case study of two fused permanent incisors in the past Europe populations as this anomaly has been recognized in an adult man buried in the Longobard cemetery of Guidizzolo (VI?VII century A.D., northern Italy)

In vitro 2D and 3D roughness and spectrophotometric and gloss analyses of ceramic materials after polishing with different prophylactic pastes

Statement of problem: The effect of prophylactic polishing pastes on composite resin materials has been extensively investigated, but little is known about their effect on ceramic materials. Purpose: The purpose of this in vitro study was to evaluate the effect of prophylactic polishing pastes on the 2D and 3D roughness, translucency, and gloss of different ceramic materials. Material and methods: A total of 120 flat specimens (thickness: 2 mm) obtained from computer-aided design and computer-aided manufacturing (CAD-CAM) blocks of leucite glass-ceramic (Empress CAD), lithium disilicate glass-ceramic (e.max CAD), and zirconia (Zenostar MT) were glazed and sintered. Forty specimens from each material were then divided into 4 groups and polished with Cleanic fine, Nupro fine, or Proxyt fine pastes, leaving the control group untreated. The specimens were polished for 2 minutes with a prophylaxis cup mounted on a handpiece, applying a constant load of 3.9 N at 2000 rpm. Surface roughness was measured by using a contact profilometer and a 3D optical profilometer. The translucency parameter and gloss value were calculated by using a spectrophotometer and a glossmeter. One specimen per group was observed by scanning electron microscopy at 7200 magnification. Differences in means were compared by using 2-way ANOVA followed by the Tukey honestly significant difference (HSD) test (\u3b1=.05). Results: The 2D roughness of Empress was lower than that of e.max (P<.05) and was increased by using Cleanic fine and Nupro fine pastes (P<.05). The translucency parameter values of Empress and Zenostar decreased with the use of Nupro fine paste (P<.05). Zenostar showed the lowest translucency (P<.05). The effect of prophylactic polishing pastes on gloss was minimal (P>.05). The gloss of Empress was higher than that of Zenostar and e.max (P<.05). The Pearson correlation showed that gloss and surface roughness were correlated (P<.001). Conclusions: Polishing procedures can alter the surface of a ceramic restoration

Digital bar prototype technique for full-arch rehabilitation on implants

Background and Overview: The aim of the authors in this case report was to describe a new approach to using the digital bar prototype technique for complete digital full-arch implant rehabilitation. Two combinable structures were used during the same visit as prototypes to simultaneously test the implant locations and the prosthetic parameters. Then the structures were joined together to form the final prosthesis. Case Description: After the implant integration with the immediate provisional restoration, 3 sets of digital impressions were obtained to obtain a master digital model (MDM). A stereolithographic model with implant analogs was printed on the basis of the MDM. A titanium bar with implant connections and a functional resin structure were milled on the basis of the MDM and used as prototypes. To check the accuracy of the implant impression, the titanium prototype was tried in, and clinical and radiographic tests were performed. Then the resin prototype was slid into the positional prototype and fitted to the patient, and the esthetic and occlusal properties were evaluated and refined. Definitive restoration was obtained by luting the 2 prototypes together and finalizing the prosthesis with pink resin. Conclusions and Practical Implications: The prototypes allowed the clinician to simultaneously verify the accuracy of the digital impressions and test the prosthetic parameters in 1 visit. Moreover, they were used to create the final restoration. The digital bar prototype technique also allowed for the reduction of clinical and laboratory time in a full-arch rehabilitation on implants. Nevertheless, obtaining a full-arch impression in an edentulous arch can be challenging, and further studies are necessary to evaluate the long-term success of this technique

Manufacturing of Metal Frameworks for Full-Arch Dental Restoration on Implants: A Comparison between Milling and a Novel Hybrid Technology

Purpose: To determine the trueness and precision of frameworks manufactured with a selective laser melting/milling hybrid technique (SLM/m) and conventional milling by comparing the implant-platform/framework interface with those of the original computer-aided design (CAD). Materials and Methods: Using a virtual 6-implant-supported full-arch framework CAD drawing, 27 titanium replicas were manufactured by 3 independent manufacturing centers (n = 9/center) using a hybrid SLM/m technology (labs 1 and 2) or the conventional milling technique (lab 3). Using an opto-mechanical coordinate measuring machine, the frameworks\u2019 misfit distribution and patterns were analyzed, and the position error between paired platform positions within each framework was evaluated to calculate the misfit tendency for each group. A multilevel analysis using a mixed-effects model was conducted (\u3b1 = 0.05). The trueness was evaluated as the dimensional difference from the original, while the precision as the dimensional difference from a repeated scan. Results: The 3 dimensional misfits differed significantly among the 3 groups, with the milled group exhibiting the least accurate outcome (p = 0.005). The mean 3D positioning errors ranged from 8 to 16 \ub5m and from 9 to 22 \ub5m for the SLM/m technique (labs 1 and 2, respectively), and from 20 to 35 \ub5m for conventional milling (lab 3). Regarding the misfit distribution pattern, the misfit increased with the distance between paired platform positions in all groups. Conclusions: All groups had 3D misfits well within the error limits reported in the literature. The 3D misfits of new hybrid (SLM/milling) and conventional (milling) procedures differed significantly among them, with the milling technique the less accurate and precise. The largest errors in all groups were found between the most distant implants, resulting in a correlation between the framework span and the inaccuracies

Manufacturing of Metal Frameworks for Full-Arch Dental Restoration on Implants: A Comparison between Milling and a Novel Hybrid Technology

Purpose: To determine the trueness and precision of frameworks manufactured with a selective laser melting/milling hybrid technique (SLM/m) and conventional milling by comparing the implant-platform/framework interface with those of the original computer-aided design (CAD). Materials and Methods: Using a virtual 6-implant-supported full-arch framework CAD drawing, 27 titanium replicas were manufactured by 3 independent manufacturing centers (n = 9/center) using a hybrid SLM/m technology (labs 1 and 2) or the conventional milling technique (lab 3). Using an opto-mechanical coordinate measuring machine, the frameworks\u2019 misfit distribution and patterns were analyzed, and the position error between paired platform positions within each framework was evaluated to calculate the misfit tendency for each group. A multilevel analysis using a mixed-effects model was conducted (\u3b1 = 0.05). The trueness was evaluated as the dimensional difference from the original, while the precision as the dimensional difference from a repeated scan. Results: The 3 dimensional misfits differed significantly among the 3 groups, with the milled group exhibiting the least accurate outcome (p = 0.005). The mean 3D positioning errors ranged from 8 to 16 \ub5m and from 9 to 22 \ub5m for the SLM/m technique (labs 1 and 2, respectively), and from 20 to 35 \ub5m for conventional milling (lab 3). Regarding the misfit distribution pattern, the misfit increased with the distance between paired platform positions in all groups. Conclusions: All groups had 3D misfits well within the error limits reported in the literature. The 3D misfits of new hybrid (SLM/milling) and conventional (milling) procedures differed significantly among them, with the milling technique the less accurate and precise. The largest errors in all groups were found between the most distant implants, resulting in a correlation between the framework span and the inaccuracies