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Purpose: To establish a recording method for edentulous jaw relations and to perform quantitative accuracy evaluation in vitro., Materials and Methods: Maxillary and mandibular edentulous arch models and complete dentures were mounted on an articulator, simulating protrusion (A), left and right laterotrusion (B and C), and small opening jaw relations (D), aided by metal foil wax record. Using the tracking system, 3D trajectories of targets were recorded from intercuspation to A, B, C, and D, then used to rehabilitate digital arch relations of A, B, C, and D in the test group. Axial model surfaces were pasted with six pairs of positioning cylinders. The center points of the bottom surfaces of the cylinders in A, B, C, and D were measured to rehabilitate digital arch relations in the control group. With the maxilla as the common area, arch relations of the test group were registered in the control group; 3D deviations of the mandible were calculated, and displacements in horizontal left/right, horizontal anterior/posterior, and vertical directions were analyzed., Results: 3D deviations of the mandible in A, B, C, and D were 131 ± 39 μm, 133 ± 44 μm, 120 ± 51 μm, and 112 ± 52 μm, respectively. Mean absolute values of displacements of the mandible were less than 200 μm., Conclusion: By using the optical jaw tracking system, the accuracy of jaw relation records as measured on an articulator was acceptable for clinical demand. Further investigations among patients are required to clinically verify the results of this study.

Purpose: The scanning of plaster models for three-dimensional (3D) construction requires their rigid fixation in the intercuspal position. Factors such as installation, motion, and scanning procedures influenced the accuracy of this method, which ultimately influence the results. Therefore, the present study attempted to provide an optimal and accurate method with less complex procedures and a more accessible equipment for determining the intercuspal relation in the 3D occlusal construction of dental models., Methods: A pair of plastic mounting plates that could be directly attached to a mechanical articulator was designed and 3D printed. Nine axial hemispherical concaves were introduced on the axial surface of each plate. The rigidly fixed maxillary and mandibular dental models were scanned directly. The distances D R between nine pairs of concaves on both mounting plates adhered to the maxillary and mandibular sections of the articulator were measured using the three-coordinate measuring machine Faro Edge as the reference. The present study comprised seven test groups varying in number and location. Assessing the reference points from each of the seven groups performed the 3D construction. The Geomagic Studio software was used to construct the concaves of digital casts, and the distances D M between the pairs of concaves were measured as test values. Variable differences between D R and D M were analyzed., Results: An optimum distribution scheme was obtained for reference point registration by quantitatively evaluating accuracy levels of the 3D constructions of different reference point distribution patterns. This scheme can serve as a reference for related studies and dental clinic operations., Conclusions: Three-dimensional construction of the intercuspal relation during scanning of the maxillary and mandibular models with an accuracy of 0.046 mm ± 0.009 mm can be achieved using the improved design of mounting plates., (© 2021. The Author(s).)

Statement of Problem: The triple-scan method for assessing the 3D adaptation of dental restorations has been introduced and reported to be reliable. However, the suitability of using a dental laboratory scanner in the triple-scan method has not been evaluated., Purpose: The purpose of this in vitro study was to evaluate the suitability of the triple-scan method using a dental laboratory scanner to assess the 3D adaptation zirconia crowns., Material and Methods: A zirconia abutment and a zirconia crown were fabricated, and the abutment was fixed in a custom-made base. The crown was seated onto the abutment with the interposition of light-body silicone impression material between them. The triple-scan method was performed by using a dental laboratory scanner, and the mean cement-gap thickness was calculated. The seating and digitalization process was repeated 10 times, and after each digitalization, the light-body silicone layer was stabilized by applying heavy-body silicone impression material over it. Cement-gap thickness was measured on cross-sections of the aligned scan data sets and of the physical silicone replica. The results were assessed by using the paired t test and the Bland-Altman method (α=.05)., Results: Mean 3D cement-gap thickness assessed by the triple-scan method reported small dispersion with a coefficient of variation of 5.6% for the occlusal area, 1.9% for the axial area, and 6.4% for the margin area. Cement gap thickness measured at corresponding locations in the aligned scan data sets and in the physical silicone replica reported no significant difference (P=.326) and good agreement., Conclusions: The cement gap was accurately duplicated in scan data sets. The triple-scan method by using a dental laboratory scanner is suitable for assessing the 3D adaptation of zirconia crowns., (Copyright © 2020 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Purpose: The aim of this in vitro study was to evaluate the three-dimensional trueness and margin quality of monolithic zirconia restorations fabricated by additive 3D gel deposition, compared with those by subtractive milling., Methods: Ten single crowns and ten 4-unit FPDs of different occlusal geometries and margin thickness were fabricated by additive 3D gel deposition (additive group) and subtractive milling (subtractive group). An intraoral scanner was used to digitalize the restorations. 3D deviation analysis was applied and root mean square (RMS) was used to assess the trueness. Margin quality was characterized using optical stereomicroscopy and 3D laser scanning microscopy., Results: For single crowns with shallow fossae and grooves and normal margin, RMS value of additive group and subtractive group showed no significant difference in external surface, while additive group showed higher RMS value in intaglio surface. As for 4-unit FPDs with deep fossae and grooves and thin margin, RMS value of additive group in external surface was significantly lower than that of subtractive group and in intaglio surface there was no significant difference between two groups. With a 0.5 mm chamfer design, single crowns in additive group showed flawless margin with a smooth contour line, whereas minor flaws could be observed in 4-unit FPDs with thin margin. In subtractive group, restorations showed minor flaws or defects of various number and severity., Conclusions: Monolithic zirconia restorations fabricated by additive 3D gel deposition have comparable trueness and better margin quality than those fabricated by subtractive milling. Besides it is more capable of enabling complex geometry., Competing Interests: Declaration of Competing Interests None., (Copyright © 2020. Published by Elsevier Ltd.)

Purpose: To compare the accuracy of a chairside fused deposition modeling (FDM) 3D-printed surgical template with that of a light-cured template for implant placement., Materials and Methods: Twenty standard mandibular resin models with missing teeth 36 and 46 were selected. Surgical templates were fabricated using a chairside FDM 3D-printer (test group) or a light-curing 3D printer (control group) (n = 20/group). Forty implants were placed by a clinician blinded to group allocation. The angular, 3D, mesiodistal, buccolingual, and apicocoronal deviations at the implant base and tip between preoperative design and postoperative implant position were recorded., Results: The mean angular (test vs control groups: 3.22° ± 1.55° vs 2.74° ± 1.24°, p = 0.343) and 3D deviations at the implant base (test vs control groups: 0.41 ± 0.13 mm vs 0.35 ± 0.11 mm, p = 0.127) and tip (test vs control groups: 0.91 ± 0.34 mm vs 0.75 ± 0.28 mm, p = 0.150) were similar. The mesiodistal, buccolingual, and apicocoronal deviations at the implant base and tip also did not differ significantly between groups (p > 0.05)., Conclusions: For single tooth gap indications, implant placement with an FDM 3D-printed surgical template was as accurate as that with a light-cured template, and more efficient., (Copyright © 2019 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.)

Statement of Problem: In computer-aided design and computer-aided manufacturing (CAD-CAM) dentistry, the correlation method is an efficient way to design complete crowns. However, the occlusal relationship and patient satisfaction with prostheses fabricated using this method remain unclear., Purpose: The purpose of this clinical trial was to compare the occlusion of monolithic zirconia crowns designed using the correlation and library methods., Material and Methods: Twenty-three teeth of 21 participants received 2 monolithic zirconia crowns designed by using the correlation or the library method. Defective teeth were scanned using an intraoral scanner to obtain references and working casts from before and after the preparation. Before cementation, the occlusal relationship of both crowns and patient satisfaction were evaluated, and the occlusal adjustment time was recorded., Results: The correlation method resulted in less lateral occlusal interference of the crowns than the library method (P<.01). The occlusal adjustment times of the correlation and library conditions were 455.8 ±357.1 seconds and 575.3 ±488.0 seconds, respectively (P>.05). Relative occlusal force was significantly higher in the correlation than in the library condition and was related to before preparation relative occlusal force (r=0.706, P<.01). The visual analog score before occlusal adjustment was higher in the correlation than in the library condition (P<.05). The occlusal contacts, occlusal contact distributions, and number of occlusal contacts did not differ between conditions (P>.05)., Conclusions: Better eccentric occlusion and reduced lateral occlusal interference were obtained when the correlation method was used to design crowns. The correlation method yielded higher relative occlusal force, which helped to restore the original occlusal force., (Copyright © 2018 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Reducing the diameter of silver nanowires has been proven to be an effective way to improve their optoelectronic performance by lessening light attenuation. The state-of-the-art silver nanowires are typically around 20 nm in diameter. Herein we report a modified polyol synthesis of silver nanowires with average diameters as thin as 13 nm and aspect ratios up to 3000. The success of this synthesis is based on the employment of benzoin-derived radicals in the polyol approach and does not require high-pressure conditions. The strong reducing power of radicals allows the reduction of silver precursors to occur at relatively low temperatures, wherein the lateral growth of silver nanowires is restrained because of efficient surface passivation. The optoelectronic performance of as-prepared 13 nm silver nanowires presents a sheet resistance of 28 Ω sq -1 at a transmittance of 95% with a haze factor of ∼1.2%, comparable to that of commercial indium tin oxide (ITO).

Objectives: The effects of different surface treatments on cyclic fatigue strengths of computer-aided design and computer-aided manufacturing (CAD/CAM) zirconia implants and its mechanisms were evaluated., Material and Methods: One-piece cylindrical screw-type zirconia (Y-TZP) implants with diameters of 4.1-mm were fabricated using CAD/CAM technique; they were divided into four groups according to the type of surface treatment: (i) sintering (control group, CTRL), (ii) sandblasting (SB), (iii) sandblasting and etching with an experimental hot etching solution (SB-ST), and (iv) sandblasting and etching with hydrofluoric acid (SB-HF). The surface morphology and roughness of the implants were evaluated. Tetragonal to monoclinic transformation was measured on the surface by micro Raman spectroscopy. Static and fatigue tests were carried out at room temperature following the ISO 14801:2014 Standard. The cyclic fatigue strength of each group was determined using the staircase method. Specimens that survived the fatigue test were statically loaded to measure the residual fracture strength., Results: Among the four groups, SB-HF exhibited the highest surface roughness. Compared with the CTRL group, the surface monoclinic content was higher after all three types of surface treatments, amongst which, SB-HF had the highest content (39.14%), significantly more than the other three groups (P < 0.01). The cyclic fatigue strengths of CTRL, SB, SB-ST, and SB-HF implants were 530 N, 662.5 N, 705 N, and 555 N, respectively. The fracture strength after fatigue loading was higher than that before fatigue loading with no significant difference (P＞0.05)., Conclusions: SB and SB-ST remarkably enhanced the fatigue resistance of zirconia implants, while SB-HF did not. One-piece 4.1-mm diameter CAD/CAM zirconia implants have sufficient durability for application in dental implants., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The present study aimed to establish and evaluate a method for recording edentulous jaw relations digitally without occlusal bases, using a handheld scanner and specially designed headgear. The headgear maintained the mandibular position. Ten edentulous patients' upper (U) and lower edentulous jaw models (L) were prepared and scanned. A handheld scanner was used to capture the labial alveolar ridge mucosa relations in the upper and lower anterior arches directly (Dr). U and L were registered to Dr (test group). Complete dentures of patients in the intercuspal position were used to construct the relationship between U and L (control group). Differences in jaw relations in the test and control groups, in terms of vertical difference, displacement and rotation of the anterior and posterior, and displacement and rotation of the left and right were assessed using the Hotelling's T 2 test. The differences in the mean values and the mean of the absolute values of the jaw relations between groups were not statistically significant (P = 0.331) and significant (P = 0.016), respectively. Our findings show that it is possible to make digital recording of edentulous jaw relations by using a handheld scanner and headgear.

In this work, we report a new, general synthetic approach that uses heat driven benzoin radicals to grow ultrathin copper nanowires with tunable diameters. This is the first time carbon organic radicals have been used as a reducing agent in metal nanowire synthesis. In-situ temperature dependent electron paramagnetic resonance (EPR) spectroscopic studies show that the active reducing agent is the free radicals produced by benzoins under elevated temperature. Furthermore, the reducing power of benzoin can be readily tuned by symmetrically decorating functional groups on the two benzene rings. When the aromatic rings are modified with electron donating (withdrawing) groups, the reducing power is promoted (suppressed). The controllable reactivity gives the carbon organic radical great potential as a versatile reducing agent that can be generalized in other metallic nanowire syntheses.

Copper is uniquely active for the electrocatalytic reduction of carbon dioxide (CO 2 ) to products beyond carbon monoxide, such as methane (CH 4 ) and ethylene (C 2 H 4 ). Therefore, understanding selectivity trends for CO 2 electrocatalysis on copper surfaces is critical for developing more efficient catalysts for CO 2 conversion to higher order products. Herein, we investigate the electrocatalytic activity of ultrathin (diameter ∼20 nm) 5-fold twinned copper nanowires (Cu NWs) for CO 2 reduction. These Cu NW catalysts were found to exhibit high CH 4 selectivity over other carbon products, reaching 55% Faradaic efficiency (FE) at -1.25 V versus reversible hydrogen electrode while other products were produced with less than 5% FE. This selectivity was found to be sensitive to morphological changes in the nanowire catalyst observed over the course of electrolysis. Wrapping the wires with graphene oxide was found to be a successful strategy for preserving both the morphology and reaction selectivity of the Cu NWs. These results suggest that product selectivity on Cu NWs is highly dependent on morphological features and that hydrocarbon selectivity can be manipulated by structural evolution or the prevention thereof.

Statement of Problem: Limited information is available regarding the influence of object translucency on the scanning accuracy of a powder-free intraoral scanner., Purpose: The purpose of this in vitro study was to evaluate the scanning accuracy of a confocal microscopy principle powder-free intraoral scanner on ceramic copings and to analyze the relationship between scanning accuracy and object translucency., Methods: Six slice specimens (12×10 mm) and 6 offset copings (1.00-mm thickness) were made from different translucent homogeneous ceramic blocks (CEREC Blocs, S0-M to S5-M, highest to lowest translucency). The primary sintered zirconia offset coping was produced in the same way as the control. Optical parameters related to the translucency of each slice were measured with a spectrophotometer. Three-dimensional (3D) datasets of the surface morphology of offset copings were obtained by using the intraoral scanner. The same white wax resin bases were used for registration. Quantitative parameters of scanning trueness and precision were measured. One-way ANOVA was used to analyze the values of each parameter among the 6 ceramic blocks. Bivariate correlation was used to analyze the relationships between each parameter of scanning accuracy and translucency (α=.05)., Results: Translucent copings showed a positive 3D bias (S0-M to S5-M: 0.149 ±0.038 mm to 0.068 ±0.020 mm), a narrower collar diameter (Dd=-0.067 mm), larger convergence angle (ΔΦ=2.79 degrees), and larger curvature radius of the internal gingivoaxial corner (Δρ=0.236 mm). The smaller the percentage sum of scattering and absorption, the greater was the occurrence of scanning bias (r=-0.918) and curvature (r=-0.935) decrease., Conclusions: Use of the tested powder-free intraoral scanner, higher translucency objects (greater translucency than S1-M/A1C) resulted in lower scanning accuracy and morphological changes. Therefore, more suitable methods of measurement are still required., (Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

A dental defect is one of the most common oral diseases, and it often requires a full crown restoration. In this clinical operation, the dentist must manually prepare the affected tooth for the full crown so that it has a convergence angle between 4° and 10°, no undercuts, and uniform and even shoulder widths and depths using a high speed diamond bur in the patient׳s mouth within one hour, which is a difficult task that requires visual-manual operation. The quality of the tooth preparation has an important effect on the success rate of the subsequent prosthodontic treatment. This study involved research into digital modeling technology for full dental crown tooth preparation. First, the margin line of the tooth preparation was designed using a semi-automatic interactive process. Second, the inserting direction was automatically computed. Then, the characteristic parameters and the constraints on the tooth preparation were defined for the model. Next, the shoulder and axial surface of the tooth preparation were formed using parametric modeling. Finally, the implicit surface of a radial basis function was used to construct the tooth preparation׳s occlusal surface. The experimental results verified that the method of digital modeling for full crown preparation proposed in this study can quickly and accurately implement personalized designs of various parameters, such as the shoulder width and the convergence angle; it provides a digital design tool for full crown preparation., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

In complete-denture restoration of edentulous jaws, the following information is needed: functional impression of edentulous jaws, jaw relationship and facial fullness, parameters of individual mandibular movement, etc. Traditional clinical methods in obtaining these data, which depend greatly on practitioners' clinical experience and skills, are subjective, complicated and low efficient. With the development of the digital restoration of edentulous jaws, a variety of equipment for three-dimensional scan have been applied in acquiring three-dimensional source data concerning the needed information, which greatly simplifies the process of data obtaining, reduces the dependence on operational skills and subjective experience, improves efficiency and efficacy of diagnosis and treatment, and standardizes the restoration process.

With the accelerated aging of world population, complete denture prosthesis plays an increasingly important role in mouth rehabilitation. In addition to recovering stomatognathic system function, restoring the appearance of a third of the area under the face has become a great challenge in complete denture prosthesis. This study analyzes the interactive relationship between the appearance of a third of the area under the face and complete denture, and proposes a new method to predict facial deformation after complete denture prosthesis. Firstly, to improve computational efficiency, the feature template is constructed to replace the deformed facial region. Secondly, a forecast model of elastic deformation is constructed using BP neural network and predicts elastic deformation amount because of the inhomogeneous, anisotropic and nonlinear material properties of soft tissue. Finally, a new feature template is calculated using deformation amount, and the deformation of preoperative model is simulated using Laplacian deformation technique. The average error rates of different hidden layer nodes in the neural network are analysed. Deformation and postoperative models are superimposed for match analysis. Experimental results show that this method can predict facial soft tissue deformation quickly and accurately., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Purpose: The aim of the present study was to evaluate the feasibility of the design and fabrication of a novel arch bar using 3-dimensional printing. Furthermore, the study assessed its use in a preliminary clinical study of intermaxillary fixation., Patients and Methods: Seven patients who met the inclusion criteria were enrolled in the present study. Plaster dental casts were created of each patient and scanned using cone-beam computed tomography to obtain digital casts. Computer-aided design software was then used to complete the virtual building of the arch bars, which were manufactured using 3-dimensional printing and a cobalt-chrome alloy. The clinical results were observed after the arch bars were fixed to the dentition with steel wires., Results: The arch bar contacted the dentition with a "surface-to-surface" pattern. The utility of these novel arch bars was verified by successfully fitting them to the dental arches of the patients. All the patients achieved their desired occlusion., Conclusion: The results of the present study have illustrated that this digital method is feasible for constructing a novel arch bar, showing promise for clinical use., (Copyright © 2015 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.)

The aim of this study was to evaluate the surface roughness and wettability of dentin following ultrashort pulsed laser ablation with different levels of fluence and pulse overlap (PO). Twenty-five extracted human teeth crowns were cut longitudinally into slices of approximately 1.5-mm thick and randomly divided into nine groups of five. Samples in groups 1 to 8 were ablated with an ultrashort pulsed laser through a galvanometric scanning system. Samples in group 9 were prepared using a mechanical rotary instrument. The surface roughness of samples from each group was then measured using a three-dimensional profile measurement laser microscope, and wettability was evaluated by measuring the contact angle of a drop of water on the prepared dentin surface using an optical contact angle measuring device. The results showed that both laser fluence and PO had an effect on dentin surface roughness. Specifically, a higher PO decreased dentin surface roughness and reduced the effect of high-laser fluence on decreasing the surface roughness in some groups. Furthermore, all ablated dentin showed a contact angle of approximately 0 deg, meaning that laser ablation significantly improved wettability. Adjustment of ultrashort pulsed laser parameters can, therefore,significantly alter dentin surface roughness and wettability.

Introduction: The aim of this study was to evaluate the morphological changes and quantitatively assess the roughness of dentin after the ablation with a Ytterbium-Doped Potassium Yttrium Tungstate (YB: KYW) thin-disk femtosecond pulsed laser of different fluences, scanning speeds and scanning distances., Method: Twelve extracted human premolars were sectioned into crowns and roots along the cementum-enamel junction, and then the crowns were cut longitudinally into sheets about 1.5 mm thick with a cutting machine. The dentin samples were fixed on a stage at focus plane. The laser beam was irradiated onto the samples through a galvanometric scanning system, so rectangular movement could be achieved. After ablation, the samples were examined with a scanning electron microscope and laser three-dimensional profile measurement microscope for morphology and roughness study.With increasing laser fluence, dentin samples exhibited more melting and resolidification of dentin as well as debris-like structure and occluded parts of dentinal tubules., Results: When at the scanning speed of 2400mm/s and scanning distance of 24μm, the surface roughness of dentin ablated with femtosecond pulsed laser decreased significantly and varied between values of dentin surface roughness grinded with two kinds of diamond burs with different grits. When at the scanning speed of 1200mm/s and scanning distance of 12μm, the surface roughness decreased slightly, and the surface roughness of dentin ablated with femtosecond pulsed laser was almost equal to that grinded with a low grit diamond bur., Conclusion: This study showed that increased laser influence may lead to more collateral damage and lower dentin surface roughness, while scanning speed and scanning distance were also negatively correlated with surface roughness. Adequate parameters should be chosen to achieve therapeutic benefits, and different parameters can result in diverse ablation results.

Objective: To reconstruct the centric relation of upper and lower edentulous dental models with two methods, to compare the reconstruction accuracy of the vertical and horizontal distance, and to provide some references to computer aided design and computer aided manufacture for complete denture., Methods: Dental models and rims made from five edentulous patients in clinical were obtained.Each model was stocked with 10 identical size positioning cylinders (20 cylinders on each pair models) on 5 side-surfaces of basement. Twelve center point pairs were paired between upper and lower models from 20 cylinder bottoms. The vertical and horizontal distances of 12 center point pairs were regarded as the evaluation items. Firstly, upper and lower models and rims were scanned separately. Then, models and rims (fixed in centric relation respectively with positioning articulator and rubber banding) were scanned.In software, all the data were registered to reconstruct centric relation based on common region. Digital models were measured with software tools, and real models were measured with a contact measurement arm. The differences of the homologous items between two methods were analyzed with paired-t test., Results: The vertical distance errors for dental articulator positioning method was (0.356 ± 0.200) mm and that of the rubber band method was (0.382 ± 0.299) mm, and paired-t test between the two methods showed no significant differences (P > 0.05). The horizontal errors were (0.010 ± 0.411) mm and (0.104 ± 0.476) mm, and paired-t test showed significant differences (P < 0.05)., Conclusions: Comparing with rubber band method, dental articulator positioning can significantly increases three-dimensional reconstruction accuracy of edentulous jaw gypsum models' horizontal relation.

Background: This paper introduces a method to digitally design a virtual model of a tooth preparation of the mandibular first molar, by using the commercial three-dimensional (3D) computer-aided design software packages Geomagic and Imageware, and using the model as an input to automatic tooth preparing system., Methods: The procedure included acquisition of 3D data from dentate casts and digital modeling of the shape of the tooth preparation components, such as the margin, occlusal surface, and axial surface. The completed model data were stored as stereolithography (STL) files, which were used in a tooth preparation system to help to plan the trajectory. Meanwhile, the required mathematical models in the design process were introduced., Results: The method was used to make an individualized tooth preparation of the mandibular first molar. The entire process took 15min., Discussion: Using the method presented, a straightforward 3D shape of a full crown can be obtained to meet clinical needs prior to tooth preparation., (© 2013 Published by Elsevier Ltd.)