Occlusal Area Research Articles

Evaluation of fit and accuracy of single crowns fabricated from self-glazed zirconia compared with milled zirconia

Statement of problemSelf-glazed zirconia is a novel dental material fabricated with a combination of subtractive and additive manufacturing techniques. However, how the marginal and internal fit of these restorations compare with conventionally fabricated zirconia is unclear. PurposeThe purpose of this in vitro study was to evaluate the marginal and internal fit and internal accuracy of single crowns made from self-glazed zirconia compared with those made from milled zirconia. Material and methodsA metal die was scanned, and a crown was designed using a computer-aided-design program. The computer-aided-manufacturing milling method (conventional technique) was used to produce 10 zirconia crowns, and additive manufacturing was used to produce 10 self-glazed zirconia crowns. Internal and marginal fit measurements were made by using the silicone replica method; marginal fit was also measured by using the direct-view technique. An independent t test was performed to compare both types of crowns and test the null hypothesis (α=.05). ResultsFor the occlusal, internal, and total mean distances, significant differences were found between self-glazed and milled zirconia crowns (P<.001). With the direct-view technique, a significant difference (P=.004) between the 2 techniques was found in the marginal area. The accuracy for the axial and occlusal areas combined for self-glazed and milled zirconia was 27 μm and 49 μm, respectively. ConclusionsBoth techniques produced crowns with clinically acceptable marginal and internal fit. The self-glazed zirconia crowns had higher accuracy of internal fit than milled zirconia crowns.

Accurate light field depth estimation under occlusion

Epipolar plane images (EPIs) have advantages in light field depth estimation, but the current EPI-based methods only use one aspect of the information related to the line or its surroundings in EPIs. Moreover, most current methods merely extract the depth map of the target view, ignoring the depth information from other views. To fully utilize the available information, we first introduce a novel data cost by comprehensively utilizing the characteristics of pixel consistency on the line and region difference around the line in EPIs to improve the robustness against occlusion and noise. Then, we put forward a multi-view depth integration strategy that copes with weak texture and occlusion areas. Finally, an edging preserving filter is applied to further refine the depth map. Experiments on synthetic and real light field datasets show that the proposed method outperforms the state-of-the-art light field depth estimation algorithms, especially in the presence of occluded pixels.

Microleakage of Class II Bulk-Fill Resin Composite Restorations Cured with Light-Emitting Diode versus Quartz Tungsten-Halogen Light: An In Vitro Study in Human Teeth

Background: Resin composites undergo a certain degree of shrinkage when light-cured with different light sources available on the market, resulting in microleakage of dental restorations. The aim of the present study was to assess microleakage of class II restorations with bulk-fill resin composites cured with LED (light-emitting diode) and QTH (quartz tungsten-halogen light) units, both in cervical and occlusal areas of cavity preparations. Materials and Methods: In the present in vitro experimental study, a total of 30 human molar teeth were used, in which 60 class II cavities were prepared (mesial and distal) and restored with Filtek bulk fill resin composite. Restorations were equally distributed in 3 groups according to type of curing light: A, QTH (Litex 680A Dentamerica®); B, LED (Bluephase N® 3rd generation); and C, LED (Valo® 3rd generation). Each group was further subdivided into subgroups 1 and 2 according to IV-A or IV-B resin composite color. Restored teeth were subjected to 20,000 thermal cycles between 5° and 55 °C, then immersed in 1M silver nitrate solution for 24 h. Subsequently, the teeth were sectioned mesiodistally to obtain samples for observation under stereomicroscope in order to determine microleakage degree. Kruskal-Wallis H and Mann-Whitney U statistical tests were applied with a significance level of 5% (p < 0.05). Results: No statistically significant differences were found in the degree of microleakage of bulk-fill resin composites light-cured with LED and QTH units for both occlusal (p > 0.05) and cervical areas (p > 0.05). Additionally, no significant differences were found when comparing microleakage between occlusal and cervical areas (p > 0.05), regardless of lamp type. In addition, significant differences in microleakage degree were found between bulk-fill resins with IV-A and IV-B shades when they were light-cured with QTH at cervical level (p = 0.023). However, there were no significant differences when comparing these bulk-fill resin composite shades at occlusal level with LED (p > 0.05) and QTH (p > 0.05) units. Conclusions: Class II restorations with bulk-fill resin composite in IV-A and IV-B shades light-cured with third generation LED lamp and QTH showed no significant differences in microleakage when compared in both occlusal and cervical areas. On the other hand, significantly more microleakage was found at the cervical level when a darker shade of resin composite was used and light-cured with the QTH unit.

Light Field View Synthesis Using the Focal Stack and All-in-Focus Image.

Light field reconstruction and synthesis algorithms are essential for improving the lower spatial resolution for hand-held plenoptic cameras. Previous light field synthesis algorithms produce blurred regions around depth discontinuities, especially for stereo-based algorithms, where no information is available to fill the occluded areas in the light field image. In this paper, we propose a light field synthesis algorithm that uses the focal stack images and the all-in-focus image to synthesize a 9 × 9 sub-aperture view light field image. Our approach uses depth from defocus to estimate a depth map. Then, we use the depth map and the all-in-focus image to synthesize the sub-aperture views, and their corresponding depth maps by mimicking the apparent shifting of the central image according to the depth values. We handle the occluded regions in the synthesized sub-aperture views by filling them with the information recovered from the focal stack images. We also show that, if the depth levels in the image are known, we can synthesize a high-accuracy light field image with just five focal stack images. The accuracy of our approach is compared with three state-of-the-art algorithms: one non-learning and two CNN-based approaches, and the results show that our algorithm outperforms all three in terms of PSNR and SSIM metrics.

An Algorithm for Single View Occlusion Area Detection in Binocular Stereo Matching

Occlusion area detection is a crucial step affecting the performance of the binocular stereo matching algorithm, but the traditional method of occlusion area detection has two major problems, including left–right consistency detection (LRC). First, these algorithms must obtain the left and right disparity maps with precision. Second, these algorithms cannot detect the occlusion region at the image’s borders. We propose the single view occlusion area detective (SVOAD) algorithm to detect these occlusion areas and better deal with them. The SVOAD can detect the area of occlusion from a single image, thereby reducing the computational cost. Additionally, the algorithm can detect the occlusion region in all image regions. This paper also improves the guided filter so that it works better with the end-to-end neural network and makes the SVOAD algorithm work better.

Back-Projection Imaging for Synthetic Aperture Radar with Topography Occlusion

When synthetic aperture radar (SAR) is conducting remote sensing or terrain mapping, its radar beam is inevitably occluded by the variations in the under-test topography. Although back-projection algorithm (BPA) can theoretically directly solve the imaging problems of topography variations that most current SAR imaging algorithms cannot handle, these BPAs only solve the phase focusing of SAR echo signal, and do not consider the mismatch of SAR imaging results caused by topography occlusion. To solve the mis-imaging issue of the occluded area generated by BPA under the case of topography variation, a topography-based BPA (Topo-BPA) is proposed in this paper. Firstly, a new beam occlusion judgment algorithm based on spherical wave assumption is proposed, and its core is depression angle interpolation and depression angle updating. Then, the proposed Topo-BPA embeds the proposed beam occlusion judgment algorithm before the classical BPA, which not only did not reduce the focus depth of BPA, but improved the imaging accuracy of classical BPA. Finally, numerical experiments have demonstrated the superiority of the Topo-BPA’s performance in comparison with classical BPA.

An In Vitro Comparison of Zirconia and Hybrid Ceramic Crowns With Heavy Chamfer and Shoulder Finish Lines.

Purpose This in vitro study aimed to compare the marginal fit and internal adaptation of computer-aided designed and computer-aided manufactured (CAD-CAM) zirconia and hybrid ceramic crowns on heavy chamfer and shoulder finish line designs using silicon replica method. Materials and methods Forty die samples were divided into four groups of 10 dies each. Out of 40 diecasts scanned, zirconia crowns were milled on 20 casts (10 prepared with shoulder and 10 prepared with heavy chamfer finish line design), whilehybrid ceramic crowns were milled on the rest of the 20 casts. After milling crowns, the silicone replica technique measured the marginal fit and internal adaptation. Results The heavy chamfer finish line design provided a better marginal fit than the shoulder finish line design for zirconia and hybrid ceramic crowns. Hybrid ceramic crowns had a better marginal fit and internal adaptation than zirconia crowns, both at heavy chamfer and shoulder finish line design. The gap at the margin was less than the axial and occlusal walls, and the maximum gap was observed in the occlusal area. In addition, the marginal gap was less than the internal gap, which showed a positive correlation with each other. Conclusion The study concluded that the difference in CAD-CAM materials and finish line designs influences marginal fit and crown restoration's internal adaptation.A heavy chamfer finish line design provides a better marginal fit for zirconia and hybrid ceramic crowns than a shoulder finish line design. Hybrid ceramic crowns have a better marginal fit and internal adaptation than zirconia crowns in heavy chamfer and shoulder finish lines.

Fit analysis of stereolithography-manufactured three-unit resin prosthesis with different 3D-printing build orientations and layer thicknesses

Statement of problemPrinting conditions can affect the fit of a 3-dimensionally (3D) printed prosthesis. Therefore, it is important to determine the optimal printing conditions for stereolithography (SLA)-manufactured prostheses. PurposeThe purpose of this study was to analyze the fit according to the build orientations and layer thicknesses in SLA-manufactured 3-unit resin prostheses. Material and methodsSLA 3D printed prostheses were produced in 5 build orientations (0, 30, 45, 60, and 90 degrees) and 2 layer thicknesses (50 and 100 μm). Milled prostheses were fabricated from the same design. The mounted prostheses on the master model were scanned with microcomputed tomography (μCT). Data were processed with the NRecon software program. For quantitative analysis, marginal and internal fits were measured by using the imageJ software program in terms of the following metrics: absolute marginal discrepancy, marginal gap, cervical area, midaxial wall area, line-angle area, and occlusal area. Internal gap volume was also measured with the CTAn software program. For statistical analysis, ANOVA and Tukey HSD tests were used (α=.05). For qualitative analysis, μCT cross-sections were compared among groups, and intaglio surfaces were imaged with a scanning electron microscope. ResultsA layer thickness of 50 μm with build orientations of 45 and 60 degrees exhibited smaller mean gap values (P<.05) than the other conditions for all measurements except line-angle area and occlusal area. The scanning electron microscope images showed voids on the intaglio surfaces for the 0- and 90-degree groups. ConclusionsFor SLA 3D printed resin prostheses, a difference in fit occurred based on the printing conditions, although both 3D printed and milled prostheses showed a clinically acceptable fit. When an SLA 3D printed prosthesis is manufactured under appropriate conditions, a clinically acceptable fit can be obtained.

A new method to retrieve rainfall intensity level from rain-contaminated X-band marine radar image

ABSTRACT In this study, a new methodcombining wave-number energy spectrum (WES) and Genetic algorithm-back propagation neural network (GA-BPNN) isproposed to retrieve the rainfall intensity level from rain-contaminated X-bandmarine radar image. Since the intensity of spatialrainfall can be reflected by the distribution of energy in the wavenumberfrequency domain, the obtained WES is divided into three wavenumber segments(low, medium and high wavenumber segments), and the ratio of the wavenumber ineach wavenumber segment to the total wavenumber is calculated separately as the characteristicparameters. Based on the excellent networkconvergence speed and data prediction accuracy of the GA-BPNN, these calculatedparameters are input into the constructed GA-BPNN for training to complete thetask of rainfall intensity level retrieval. The proposed method is tested usingdata collected at the ocean observation station of Haitan Island in PingtanCounty. Referring to the actual rainfallintensity synchronously recorded by the rain gauge, the retrieval accuracy ofthe proposed method is 97.4%, which is 4.3% higher than that of back propagation neural network (BPNN) not optimizedby Geneticalgorithm(GA). In addition, compared with theretrieval performance of the ratio of zero intensity to echo (RZE) method basedon the occlusion area of radar image, the retrievalaccuracy of the proposed method is improved by about 12.9%.

Occlusion of faces by sanitary masks improves facial attractiveness of other races.

Recent studies provide mixed results regarding whether the perception of facial attractiveness is increased or decreased by partial occlusion with a sanitary mask. One set of studies demonstrated that occluding the bottom half of a face increased facial attractiveness. This effect is thought to occur because the occluded area is interpolated by an average facial representation that is perceived as attractive. However, several groups of studies showed that partial occlusion can increase or decrease perceived attractiveness depending on the attractiveness of the original (unoccluded) face, due to regression to the mean. To reconcile this inconsistency, we propose that the occluded area is interpolated not by an average facial representation, but by a template of moderate attractiveness, shaped by the distribution of each viewer's experience. This hypothesis predicts an interaction between occlusion and the attractiveness of the original face so that occluded attractive faces are rated as less attractive, while occluded unattractive faces are rated as more attractive. To examine this hypothesis, the present study used attractiveness-rating tasks with mask-free versus masked faces in own-race and other-races categories. Viewers were familiar with own-race faces and unfamiliar with other-races faces. If moderate-attractiveness interpolation were the explanatory factor, the interaction between the occlusion and the attractiveness of the original face should be found only in the rating of own-race faces. Consistent with this hypothesis, the interaction between the occlusion and the attractiveness of the original faces was significant only for the own-race faces. Specifically, wearing a sanitary mask decreased the facial attractiveness of attractive faces in the own-race, while it increased the attractiveness regardless of the level of facial attractiveness in other-races. These findings suggest that the occluded area of own-race faces is interpolated by a facial template of moderate attractiveness. The other-races template could be developed using familiar exemplars such as celebrities. Thus, interpolation by such a template should result in elevated attractiveness relative to that by an own-race template. Accordingly, the apparent inconsistency in the literature regarding the effect of partial occlusion on physical attractiveness can be explained in terms of differences in the template involving interpolation of the occluded area.

Comparative assessment of the remineralization characteristics of nano-hydroxyapatite extracted from fish scales and eggshells.

Dentine hypersensitivity (DH) is a common concern in dentistry that has the potential to restrict daily activities and harm a person's quality of life. In this study, the remineralization characteristics of nano-hydroxyapatite (nHAp) extracted from waste eggshells and fish scales were comparatively assessed. The extraction methods used to obtain nHAp from both fish scales and eggshells are also described. The effect of the extraction process and bio-waste source on the physicochemical characteristics of the nHAp such as Ca/P ratio, functional groups, crystallinity and phase change, and surface morphology are presented in the study. The remineralization properties were evaluated using dentine models (n = 15). A field scanning electron microscope was used to evaluate the effectiveness of the dentine tubules occlusion. The percentage occluded area for all the specimens was evaluated statistically using a one-way analysis of variance (α = 0.05). The results showed that there were variations in the physicochemical characteristics of the nHAp extracted, including the crystallinity, particle size, and surface morphology, and buffering effects against citric acids. The EnHAp extracted from eggshells had higher crystallinity, superior buffering effects, and smaller particle size compared to the nHAp extracted from fish scales, making it a more favourable material for remineralization of teeth. The statistical evidence showed that there were statistically significant differences in the dentine occluding properties measured in the nHAp (p < 0.001). The highest mean % occluded area was measured with the EnHAp group. The findings of this study provide insights into the use of bio-waste materials for the development of sustainable and effective products for oral health care.

From Front to Rear: 3D Semantic Scene Completion Through Planar Convolution and Attention-Based Network

Semantic Scene Completion (SSC) aims to reconstruct complete 3D scenes with precise voxel-wise semantics from the single-view incomplete input data, a crucial but highly challenging problem for scene understanding. Although SSC has seen significant progress due to the introduction of 2D semantic priors in recent years, the occluded parts, especially the rear-view of the scenes, are still poorly completed and segmented. To ameliorate this issue, we propose a novel deep learning framework for 3D SSC, named Planar Convolution and Attention-based Network (PCANet), to effectively extend high-precision predictions of the front-view surface to the rear-view occluded areas. Specifically, we decompose the traditional convolutional layer into three successive planar convolutions to form a Planar Convolution Residual (PCR) block, which maintains the planar features of the 3D scene. Afterward, the Planar Attention Module (PAM) is proposed to capture three different planar attentions and harvest the global context from the front surface to the rear occluded areas to improve the overall accuracy. Extensive experiments on the real NYU and NYUCAD datasets and the synthetic SUNCG-RGBD dataset demonstrate that our proposed framework can generate high-quality SSC results in both front and rear views and outperforms the state-of-the-art approaches trained in an end-to-end manner without additional data.

Anti-local occlusion intelligent classification method based on MobileNet for hazardous waste

Anti-local occlusion intelligent classification methods based on MobileNet and VTM for hazardous waste are investigated in this paper. Three image datasets with ten kinds of hazardous waste and 5,000.0 samples are constructed, which include the image dataset with without occlusion, the image dataset with 15% occlusion, and the image dataset with random occlusion. Based on them, the MobileNet and VTM intelligent classification model are constructed, trained, and tested, respectively. It can be seen from testing results that the classification accuracies of VTM and MobileNet are very high for the image dataset with without occlusion. But as occlusion area on images go up or randomly changes, the classification accuracies of VTM and MobileNet go down for 15% and random occlusion cases. The testing results show that classification accuracy of MobileNet model is better than that of VTM model for hazardous waste with or without occlusion.

SMod: Scene-Specific-Prior–Based Moving Object Detection for Airport Apron Surveillance Systems

The detection of moving objects in airport apron surveillance encounters serious detection defects, which reflects that the classification is biased toward the background. In this article, we propose a new method, scene-specific-prior–based moving object detection (SMod), to detect the moving object by the use of the prior knowledge specific to the airport apron. We find that the airport apron is made of concrete and has a special gray–white color distribution. Therefore, first, we use a dual-mode Gaussian distribution to fit the color distribution of the airport apron. Further analysis shows that this fitted distribution also reflects the probability of a detection defect, which occurs when the aircraft and occluded apron area share a similar color distribution. Based on this, second, we present a scene-specific prior model based on the dual-mode distribution, where pixels with a larger detection defect probability are more likely to be classified as the foreground, so that the prior model is able to bias the classification to the foreground. As a result, the detection defect in the airport apron can be compensated for. Third, the prior model is used in conjunction with an apron model and an object model to detect a moving object within a Bayesian framework. Next, we conduct comparison experiments on the airport ground video surveillance benchmark to verify the effectiveness of the proposed algorithm. Finally, we demonstrate the application of SMod in an airport apron surveillance system.

A Lightweight Road Detection Algorithm Based on Multiscale Convolutional Attention Network and Coupled Decoder Head

Automatic road detection from remote sensing images has always been a significant research topic. It is of great value to many practical applications. However, there are still some problems need to be solved. First of all, most of existing road detection methods are inefficient because of the sequential processing of the decoder head. Secondly, some existing methods are unable to detect occluded road areas effectively. For this reason, we focus on the speed and occlusion problems in road detection network, and propose a new lightweight road detection method based on multi-scale convolution attention network (MSCAN) and coupled decoder head, LRDNet. In particular, LRDNet adopt multi-scale convolution attention network with large receptive field for feature extraction to solve the occlusion problem, and decode the road surface, road edge and road centerline in a coupled way to improve the speed of road detection and ensure that the road surface detection results have fewer burrs at the road edge. We have performed several experiments on the RNBD dataset. Compared with some state-of-the-art methods, the experimental results prove the validity of the proposed LRDNet. The code will be released soon on the site of https://github.com/dyl96/LRDNet.

Occlusion-Aware Motion Planning for Autonomous Driving

Motion planning of autonomous vehicles is still challenging in urban road environments with occlusions. In this work, with the view of safety, comfort and efficiency, we present a motion planning framework that enables autonomous vehicles to navigate safely in urban road with occlusions. Our solution mainly includes three parts: local path planning, trajectory planning and speed planning. First, based on the improved Artificial Potential Field to generate the local path, then the optimal trajectory is solved in the S-L coordinate with the local path as the reference line. Finally, the potential risk probability of the occluded area is incorporated into the incomplete information static game framework and implement speed planning based on the game results and the proposed vehicle "safe driving" to complete the collision avoidance between the autonomous vehicle and visible or obscured dynamic traffic participants. Through simulation verification in common traffic scenarios and a comparison with some existing methods, the proposed method is proven to enable autonomous vehicles to navigate safely in traffic scenarios with occlusions and improve the driving efficiency and comfort of autonomous vehicles.

Application of Routine Echocardiography Combined with Contrast-Enhanced Echocardiography in the Diagnosis of Endomyocardial Fibrosis.

In China, endomyocardial fibrosis (EMF) is a type of restrictive cardiomyopathy that is rare and easy to be misdiagnosed. Our aim was to examine the value of routine echocardiography (RE) combined with contrast-enhanced echocardiography (CEE) in EMF diagnosis. We studied 16 EMF patients retrospectively, from 2012 to 2022. All patients underwent RE, from which 11 underwent CEE. We divided the patients into three groups: biventricular EMF (Bi-EMF), right ventricular EMF (RV-EMF), and left ventricular EMF (LV-EMF) based on different lesion locations. We also analyzed the clinical and conventional ultrasound characteristics of the three groups of patients and examined the ventricle opacification (VO) and myocardial contrast echocardiography (MCE) characteristics of patients who underwent CEE. All patients with EMF subtypes had the following ultrasound findings: apical occlusion on one or both sides, corresponding atrial dilatation, atrioventricular valve regurgitation in varying degrees, and cardiac diastolic dysfunction. Of the subjects, 69% had apical thrombus calcification and 81% had mild pericardial effusion. RV-EMF patients had statistically significant right atrial enlargement compared with the other two groups (p < 0.05), moderate or severe tricuspid regurgitation, and inferior vena cava (IVC) dilation. LV-EMF patients had statistically significant left atrial enlargement compared with the other two groups (p < 0.05), elevated pulmonary artery systolic pressure (PASP), and 60% of LV-EMF patients had moderate or severe mitral regurgitation. Bi-EMF patients had bilateral atrial enlargement, an IVC collapsibility index <50%, and elevated PASP. CEE was performed in 11 patients, whose ventricle opacification showed no contrast filling in the apical occluded area and the heart chambers presented the "mushroom sign" during diastole. Their myocardial contrast echocardiography (MCE) showed delayed perfusion in the thickened fibrotic endomyocardium (TFE) of the apical and subvalvular regions and perfusion defect in the apical thrombus. The number and location of thrombus determined by the MCE combined with RE were the same as those detected by cardiac magnetic resonance imaging (CMR). MCE shows that the position and range of TFE are similar to CMR. EMF has characteristic RE presentation, and different EMF subtypes have unique characteristics. CEE can better display heart structure, ventricular wall motion, and tissue perfusion compared to RE. A combination of RE and CEE can make the EMF diagnosis more accurate, thereby allowing early treatment for EMF patients.

The comparison of the accuracy of temporary crowns fabricated with several 3D printers and a milling machine.

The purpose of this in vitro study was to compare the accuracy of various 3D printers and a milling machine. The die model was designed using CAD (Autodesk Inventor 2018 sp3). The 30 µm cement space was given to the die and the ideal crown of the mandibular left first molar was designed using CAD (ExoCAD). The crowns were produced using the milling machine (Imes-icore 250i) and the 3D printers (Zenith U, Zenith D, W11) and they were divided into four groups. In all groups, the interior of each crown was scanned (Identica blue) and superimposed (Geomagic Control X) with the previously designed die. The difference between the die and the actual crown was measured at specific points. The Kruskal-Wallis test, the Mann-Whitney test, and Bonferroni's method were performed with a statistical analysis software (P < .008 in inter-group comparison P < .001 in intra-group comparison). In all groups, the center of the occlusal area and the anti-rotational dimple area showed significantly greater difference and the marginal area showed the smallest difference comparatively. The mean value of the difference in each area and the sum of the differences were higher in order of W11, Imes-icore 250i, Zenith D, and Zenith U. The digital light processing (DLP) method shows higher accuracy compared to the sereolithography (SLA) method using the same resin material.

Association between occlusal support and cognitive impairment in older Chinese adults: a community-based study.

The loss of occlusal support due to tooth loss is associated with systemic diseases. However, there was little about the association between occlusal support and cognitive impairment. The cross-sectional study aimed to investigate their association. Cognitive function was assessed and diagnosed in 1,225 community-dwelling adults aged 60 years or older in Jing'an District, Shanghai. Participants were diagnosed with mild cognitive impairment (MCI) by Peterson's criteria, or dementia, according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition. We determined the number of functional occlusal supporting areas according to Eichner classifications. We used multivariate logistic regression models to analyze the relationship between occlusal support and cognitive impairment and mediation effect models to analyze the mediation effect of age. Six hundred sixty participants were diagnosed with cognitive impairment, averaging 79.92 years old. After adjusting age, sex, education level, cigarette smoking, alcohol drinking, cardiovascular disease, and diabetes, individuals with poor occlusal support had an OR of 3.674 (95%CI 1.141-11.829) for cognitive impairment compared to those with good occlusal support. Age mediated 66.53% of the association between the number of functional occlusal supporting areas and cognitive impairment. In this study, cognitive impairment was significantly associated with the number of missing teeth, functional occlusal areas, and Eichner classifications with older community residents. Occlusal support should be a significant concern for people with cognitive impairment.

The effect of occlusal reduction and different CAD-CAM materials on stress distribution in endocrown restorations: A three-dimensional finite element analysis

Aim: The aim of this study was to examine the effects of various preparation types and restorative materials on endocrown restorations applied to endodontically treated maxillary first molars and the stress distribution on the related tissues. Methodology: A three-dimensional (3D) image of a previously extracted intact tooth was obtained with CBCT. The resulting .dicom files were imported into Mimics. Enamel, dentine, and pulp were separated and extracted as an STL file. Four groups were determined and prepared in SolidWorks. The 3D images were imported into the relevant finite element analysis software (ABAQUS, 2020 Dassault Systems Simulation Corp., Johnston, RI, USA), and a load of 600 N was applied at the occlusal area of each model in the axial direction. Models were divided into three groups according to material type: Vita Suprinity (VS; VITA Zahnfabrik, Bad Sackingen, Germany), Cerasmart (CS; GC Corp., Tokyo, Japan), and Shofu Block HC (SB; Shofu, Kyoto, Japan). The type of cement used was RelyX ARC (3M ESPE, MN, USA). Results: Regardless of the results, stress on any tissue or restoration did not exceed the strength limits. In models with cusp preparation, the stress on the dental tissues was lower. Higher stress was generally observed in groups in which the lingual area was healthy. On the other hand, stress occurring in zirconia-reinforced glass ceramics (VS) is higher than in ceramic materials with a resin matrix (CS, SB). It has been determined that the stress transmitted to the supporting tissues is lower. Conclusion: Endocrown restorations can be used in the restoration of endodontically treated first molars. In addition, when endocrown restoration is applied to molars with only one healthy area and excessive loss of coronal structure, reducing the cusp is beneficial in terms of the distribution of stress on healthy tissues. How to cite this article: Tolu Gİ, Güntekin N, Mohammadi R, Demirel MG. The effect of occlusal reduction and different CAD-CAM materials on stress distribution in endocrown restorations: A three-dimensional finite element analysis. Int Dent Res 2022;12(Suppl.1):22-8. https://doi.org/10.5577/intdentres.461