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Objective: This study aimed to present three indicators that represent the proximal contact area gap change under intercuspal occlusion and to see if and how these indicators influence food impaction with tight proximal contact. Materials and Methods: Ninety volunteers were recruited for bite force measurement and intraoral scanning. Three‐dimensional surface data and buccal bite data were obtained for 60 impacted and 60 non‐impacted teeth. The scanning data were imported into the Geomagic Studio 2013 to measure three indicators, which included the gap change maximum (Δdm, μm), the buccolingual position of Δdm (P), and the gap expanded buccolingual range (S, mm). The difference between two groups of three indicators and their relationship with food impaction with tight proximal contact were analyzed by the t test, the Pearson chi‐squared test, the nonparametric Mann–Whitney U test, and the binary logistic regression analysis (a = 0.05). Results: All indicators (Δdm, P, and S) were statistically different (p < 0.001, p = 0.002, and p < 0.001) in the impacted and non‐impacted groups. Food impaction with tight proximal contact was affected by Δdm and S (p < 0.001, p = 0.039), but not by P (p = 0.409). Conclusion: The excessive increase of the gap change maximum and the gap expanded buccolingual range under bite force promoted the occurrence of food impaction with tight proximal contact. Clinical Significance: The use of intraoral scanning to measure the characteristics of the proximal contact area gap change under bite force may help to deepen our understanding of the pathogenesis of food impaction with tight proximal contact. Importantly it can provide a reference basis for individualizing and quantifying occlusal adjustment treatment. [ABSTRACT FROM AUTHOR]

The part with lattice structures generally consists of a framework and lattice structures. Since its slices contain the large-area contours of the framework and some small and discrete contours of the lattice structures, using the scanning strategy recommended by the SLM machine supplier may result in material and shape defects, especially in the case of lattice structures. Therefore, this article proposes a rectangular ring area-partition (RRAP) combined with a 67°-interval rotating scanning strategy for the framework and a parallel line (PL) combined with a 67°-interval rotating scanning strategy for the lattice structures. To study the influence of scanning strategy on the produced samples from the aspects of tensile strength and deformation, the self-developed scanning strategies and existing scanning strategies are used to fabricate 316L samples. The results showed that the 316L solid samples using the RRAP scanning strategy could improve the tensile strength and reduce the deformation. The 316L lattice sandwich panels that adopted the PL scanning strategy can obtain the smallest deviation value of the top surface. Moreover, the effectiveness of the proposed scanning strategies was proven in SLM experiments on two parts that have lattice structures. [ABSTRACT FROM AUTHOR]

Objectives: This study aimed to develop a structured light scanning system with a planar mirror to enhance the digital full‐arch implant impression accuracy and to compare it with photogrammetry and intraoral scanner methods. Materials and Methods: An edentulous maxillary stone cast with six scan bodies was scanned as the reference model using a laboratory scanner. Three scanning modalities were compared (n = 10): (1) self‐developed structured light scanning with a mirror (SSLS); (2) intraoral scanner (IOS); and (3) photogrammetry system (PG). The scanners were stopped for 1 min after each scan. Six scan bodies were analysed within each scan model. Linear deviations between the scan bodies (1–2, 1–3, 1–4, 1–5, and 1–6) and 3D mucosal deviations were established. The overall deviation was calculated as the mean of all linear deviations. "Trueness" represented the discrepancy between the test and reference files, while "precision" denoted the consistency among the test files. Kruskal–Wallis and Mann–Whitney U tests were used for statistical analyses. Results: Significant overall linear discrepancies were noted among the SSLS, PG, and IOS groups (p <.001). SSLS showed the best overall trueness and precision (6.6, 5.7 μm), followed by PG (58.4, 6.8 μm) and IOS (214.6, 329.1 μm). For the 3D mucosal deviation, the trueness (p <.001) and precision (p <.001) of the SSLS group were significantly better than those of the IOS group. Conclusions: The SSLS exhibited higher accuracy in determining the implant positions than the PG and IOS. Additionally, it demonstrated better accuracy in capturing the mucosa than IOS. [ABSTRACT FROM AUTHOR]

(1) Background: Various 3D printers are available for dental practice; however, a comprehensive accuracy evaluation method to effectively guide practitioners is lacking. This in vitro study aimed to propose an optimized method to evaluate the spatial trueness of a 3D-printed dental model made of photopolymer resin based on a special structurized dental model, and provide the preliminary evaluation results of six 3D printers. (2) Methods: A structurized dental model comprising several geometrical configurations was designed based on dental crown and arch measurement data reported in previous studies. Ninety-six feature sizes can be directly measured on this original model with minimized manual measurement errors. Six types of photo-curing 3D printers, including Objet30 Pro using the Polyjet technique, Projet 3510 HD Plus using the Multijet technique, Perfactory DDP and DLP 800d using the DLP technique, Form2 and Form3 using the SLA technique, and each printer's respective 3D-printable dental model materials, were used to fabricate one set of physical models each. Regarding the feature sizes of the simulated dental crowns and dental arches, linear measurements were recorded. The scanned digital models were compared with the design data, and 3D form errors (including overall 3D deviation; flatness, parallelism, and perpendicularity errors) were measured. (3) Results: The lowest overall 3D deviation, flatness, parallelism, and perpendicularity errors were noted for the models printed using the Objet30 Pro (overall value: 45 μm), Form3 (0.061 ± 0.019 mm), Objet30 Pro (0.138 ± 0.068°), and Projet 3510 HD Plus (0.095 ± 0.070°), respectively. In color difference maps, different deformation patterns were observed in the printed models. The feature size proved most accurate for the Objet30 Pro fabricated models (occlusal plane error: 0.02 ± 0.36%, occlusogingival direction error: −0.06 ± 0.09%). (4) Conclusions: The authors investigated a novel evaluation approach for the spatial trueness of a 3D-printed dental model made of photopolymer resin based on a structurized dental model. This method can objectively and comprehensively evaluate the spatial trueness of 3D-printed dental models and has a good repeatability and generalizability. [ABSTRACT FROM AUTHOR]

Periodontal tissue infection is a chronic destructive inflammatory disease caused by bacteria including anaerobes and facultative anaerobes. Traditional mechanical debridement and antibiotic treatments are not effective at removing biofilm from the root surface, resulting in recurrent disease. Antimicrobial photodynamic therapy (aPDT) is a promising bactericidal method, but it is limited by oxygen content. Here, an oxygen‐free cationic polymer (HQRB‐SS‐Dex) containing the photosensitizer rose bengal (RB) and dextran is proposed. It releases both 1O2 and HO•, and it exhibits strong antibacterial efficiency against periodontal pathogenic bacteria under irradiation. The positively charged quaternary ammonium polymer and dextran of HQRB‐SS‐Dex facilitate adherence to the bacterial surface and penetration of the bacterial biofilm to permit efficient use of reactive oxygen species. Disulfide bonds make the complex biodegradable, which improves biosafety. This work presents a unique branched cationic polymer for oxygen‐free aPDT, with potential application to the treatment of periodontal infection. [ABSTRACT FROM AUTHOR]

Simultaneous measurements of atmospheric volatile organic compounds (VOCs), conventional gases and meteorological parameters were performed at an urban site in Jinan, East China, in June 2021 to explore the formation and evolution mechanisms of summertime ozone (O3) pollution events. O3 Episode Ⅰ, O3 Episode II, and non-O3 episodes were identified based on the China Ambient Air Quality Standards and the differences in precursor concentrations. The O3 concentrations in Episode I and Episode II were 145.4 μg/m3 and 166.4 μg/m3, respectively, which were significantly higher than that in non-O3 episode (90 μg/m3). For O3 precursors, VOCs and NOx concentrations increased by 48% and 34% in Episode I, and decreased by 21% and 27% in Episode II compared to non-O3 episode days. The analysis of the m,p-xylene to ethylbenzene ratio (X/E) and OH exposure demonstrated that the aging of the air masses in Episode II was significantly higher than the other two episodes, and the differences could not be explained by localized photochemical consumption. Therefore, we speculate that the high O3 concentrations in Episode II were driven by the regional transport of O3 and its precursors. Backward trajectory simulations indicated that the air masses during Episode II were concentrated from the south. In contrast, the combination of high precursor concentrations and favorable meteorological conditions (high temperatures and low humidity) led to an excess of O3 in Episode I. Positive matrix factorization (PMF) model results indicated that increased emissions from combustion and gasoline vehicle exhausts contributed to the elevated concentrations of VOCs in Episode I, and solvent usage may be an important contributor to O3 formation. The results of this study emphasize the importance of strengthening regional joint control of O3 and its precursors with neighboring cities, especially in the south, which is crucial for Jinan to mitigate O3 pollution. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In severe service environments, the presence of high local residual stress, significant organizational gradient, and nonlinear changes in material properties often leads to stress corrosion cracking (SCC) in dissimilar metal welded (DMW) joints. To accurately predict the crack growth rate, researching the initiation and propagation behavior of SCC cracks in DMW joints under residual stress (RS) is one of the most important methods to ensure the safe operation of nuclear power plants. Using the extended finite element method (XFEM), the crack propagation behaviors in DMW joints under different RS states are predicted and compared. The effects of RS, crack location, and initial crack length on crack propagation behavior are investigated. The crack in a DMW joint without RS deflects to the material of low yield strength. High residual stress urges the crack growing direction to deflect toward the material of high yield strength. Young's modulus has little impact on the crack deflection paths. The distance between the specimen symmetric line and the boundary line has little effect on the crack initiation and propagation within the RS field. A long initial crack is more likely to initiate and propagate than a short crack. To a long crack and the crack that is far from the interface of two materials, the impact of residual stress on the crack propagation path is significant when it is located in a material with high yield strength, while when the initial crack is located in the material with low yield strength, RS has a great influence on the deflection of a short crack growth direction on the condition that the crack is adjacent to the interface. [ABSTRACT FROM AUTHOR]

Purpose: To research and develop a novel virtual articulator system (the PN-300) based on computer binocular vision, raster scanning, and simulation technology and to conduct a preliminary evaluation of its accuracy.Materials and Methods: Two digital cameras were used to build the trajectory-tracking part of the virtual articulator system, and cameras combined with a projection module were used to form the scanning part of the system. The most prominent feature of the PN-300 is its ability to simultaneously obtain the 3D data of the subject's teeth and the movement trajectory of the mandible relative to the maxilla. The PN-300 recorded the linear, circular, and rectangular quadrilateral movements of a high-accuracy 3D electronic translation stage. The accuracy of measurement of the inclination of incisal guidance derived from the PN-300 based on the PROTAR evo7 articulator was also estimated.Results: The measurement error was below 100 μm for the linear and circular movements, and the angle error was within 0.2 degrees for the rectangular quadrilateral movements. The error of inclination of protrusive incisal guidance was 1.51 ± 0.68 degrees, and for incisal guidance was 0.82 ± 0.55 degrees. Trajectories and incisal 3D data obtained by the PN-300 were combined with data from plaster models and CBCT to simulate mandibular movement and to calculate the trajectories of the condyle.Conclusion: The PN-300 achieved a good accuracy for recording mandibular movement and can be expected to calculate the movement of the condyle. [ABSTRACT FROM AUTHOR]

Purpose: To compare the accuracy of occlusal wear facet morphology designed using different bite registration methods for mandibular first molar crowns. Materials and methods: The posterior teeth and intraoral intercuspal occlusions of 12 participants were scanned. The abutment shape of the mandibular first molars for complete crowns was virtually designed, and the anatomic coping design method was used to design crowns. In the anatomic coping design, digital wax patterns were constructed by elevating the wear facets on the original surface of the first molars and then adjusting the facets with 2 types of virtual occlusions determined by buccal bite registration (BBR) or segmented tooth registration (STR) methods, where the displacement of teeth under bite force was considered (STR) or not (BBR). The occlusal distance between the original wear facets and the antagonists as well as 3D deviations between the facets on the designed crowns and on the surfaces of the original teeth were measured. Paired‐samples t‐test was used to analyze the results (α = 0.05). Results: Regarding occlusal distance, the mean 3D deviation and the root mean square (RMS) values of BBR were greater than those of the STR groups (p < 0.001 and p = 0.008). The mean 3D deviations of the crowns of the BBR and STR groups were 0.19 ±0.04 mm and 0.14 ±0.06 mm, respectively and the RMS values were 0.22 ±0.03 mm and 0.18 ±0.04 mm (p < 0.001), respectively. Conclusions: The morphology of occlusal wear facets of mandibular first molar crowns designed with the occlusion constructed using the segmented tooth registration method are more coincident with the original morphology. [ABSTRACT FROM AUTHOR]

Purpose: To compare the accuracies of three intraoral scanners for shade determination function in vitro, and to preliminarily investigate the shade‐matching characteristics of the three intraoral scanners. Materials and Methods: The shade of the middle third region of each shade tab on the Vita Classical A1‐D4 shade guide (VC) was measured with a spectrophotometer (Vita Easyshade V, VE) and three intraoral scanners, including CEREC Omnicam (OM), 3Shape TRIOS 3 (T3), and TRIOS 4 (T4). A conversion table between VC values and CIELAB values was established from the database of VE to analyze the trueness. The reproducibility of the instruments was then compared by repeating the measurements five times. Results: The mean color difference for each instrument was highest in the OM, followed by the T4, and lowest in the T3 and VE, respectively. The L* and a* value for OM, and the b* value for T4, were significantly different from those for VE (p <0.05). The reproducibility of the instrument was highest in the VE (Fleiss' kappa: 0.95), followed by the T3 (Fleiss' kappa: 0.89), T4 (Fleiss' kappa: 0.87), and OM (Fleiss' kappa: 0.78). Conclusions: Of the three intraoral scanners, the trueness was best on the T3. The reproducibility of all the instruments was excellent. [ABSTRACT FROM AUTHOR]

Purpose: To design and fabricate zirconia bars with porous surfaces using stereolithography and evaluate their surface characteristics and flexural strengths. Materials and Methods: Five groups of zirconia bars (20 mm × 4 mm × 2 mm) with interconnected porous surfaces were designed and manufactured: (i) 400‐µm pore size and 50% porosity (D400‐P50 group), (ii) 400‐µm pore size and 30% porosity (D400‐P30 group), (iii) 200‐µm pore size and 50% porosity (D200‐P50 group), (iv) 200‐µm pore size and 30% porosity (D200‐P30 group), and (v) 100‐µm pore size and 30% porosity (D100‐P30 group). Zirconia bars without a porous surface (NP) were used as controls. The surface topographies and pore structures were investigated using scanning electron microscopy and three‐dimensional laser microscopy. The printed porosity was calculated using the Archimedes method. Fifteen specimens from each group were subjected to a three‐point bending test according to the ISO 6872:2015 standard. A Weibull analysis was performed, and the fractured surfaces were examined using scanning electron microscopy. Results: Zirconia bars with porous surfaces were designed and successfully manufactured. The designed pore size, porosity, and shape of the printed pores were approximately achieved for all the porous surfaces. The flexural strength of the control group was significantly higher than those of the groups with porous surfaces (p < 0.001). For the same porosity, groups with a pore size of 400 µm exhibited a lower flexural strength than the other groups (p<0.001). Additionally, for the same pore‐size design, the flexural strengths of group D400‐P50 and D400‐P30 exhibited no significant differences (p = 0.150), while the flexural strengths of D200‐P30 were significantly higher than that of the D200‐P50 group (p = 0.043). The control group and D400‐P50 group had higher Weibull moduli than the other groups. The fractography of the specimens with porous surfaces indicated more than one crack origin, mainly owing to defects, including pores and cracks. Conclusion: Zirconia bars with porous surfaces were successfully designed and fabricated using the stereolithography technique. Although porous surfaces may be advantageous for osteogenesis, the porous‐surface design can reduce the flexural strength of the printed zirconia bars. By reducing the pore size, controlling the porosity, and improving the printing accuracy, a higher strength can be achieved. [ABSTRACT FROM AUTHOR]

Background: Precise occlusal design of implant-supported fixed prostheses is difficult to achieve by the conventional wax-up method, often requiring chairside adjustments. The computer-aided design (CAD) method is promising. This study aims to compare the occlusal contacts and clearance of posterior implant-supported single crowns designed by the CAD and conventional methods. Methods: Sample size calculation indicated fourteen samples per group. Two sets of type-IV plaster casts with a single implant analog inserted in the posterior teeth region were mounted as master casts in a mechanical articulator in maximal intercuspal position (MIP). Seven working cast sets were obtained from each master cast by a closed tray technique, and mounted in MIP. Two implant-supported single crowns were designed with an occlusal clearance to achieve light occlusal contact in each working cast set by CAD and conventional method, separately. For the CAD group, the crown was designed in digital models obtained by scanning the working casts. For the conventional group, wax-up of the crown was prepared on the working casts and scanned to generate a STL file. In the working and master casts, mean and minimum occlusal clearances in the designed occlusal contact area of the both finished prostheses were calculated using the occlusal clearance (OC) and occlusal record (OR) method. The prostheses' occlusion was evaluated in master casts. Results: For the evaluation in the working casts, both design methods had similar mean occlusal clearances by the OC method (195.4 ± 43.8 vs. 179.8 ± 41.8 μm; P = 0.300), while CAD group resulted in a significantly larger minimum occlusal clearance in the designed occlusal contact area (139.5 ± 52.3 vs. 99.8 ± 43.8 μm; P = 0.043). Both design methods had similar mean and minimum occlusal clearances by the OR method (P > 0.05). For the evaluation in the master casts, both design techniques had similar mean and minimum occlusal clearances, number and distribution of occlusal contacts, and lateral interference ratios (P > 0.05). Conclusion: Occlusal contact and clearance of posterior implant-supported single crowns designed by the CAD method can be at least as good as those designed by the conventional wax-up method. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the physical and mechanical properties of zirconia ceramic manufactured with stereolithography and to quantitatively analyze the internal and marginal adaptation of the zirconia ceramic dental crowns.Materials and Methods: A resin-based zirconia suspension with a solid content of 45 vol% was prepared. Zirconia dental crowns (n = 5) for the maxillary right first molar were designed and manufactured. Physical and mechanical properties-including density, sintering shrinkage, flexural strength, Weibull parameters, phase composition, and microstructure-of the stereolithography-manufactured zirconia crowns were evaluated. A three-dimensional subtractive analysis technique was used to evaluate the internal and marginal adaptation.Results: The stereolithography-manufactured zirconia (n = 22) achieved a flexural strength of 812 ± 128 MPa and a Weibull modulus of 7.44. Quantitative analysis of the fabricated zirconia crowns showed a cement space of 63.40 ± 6.54 μm in the occlusal area, 135.08 ± 10.55 μm in the axial area, and 169.58 ± 18.13 μm in the marginal area.Conclusion: Within the limits of this study, the strength of the stereolithography-manufactured zirconia was adequate for fabricating dental crowns. However, internal and marginal adaptation are not yet ideal for clinical application. [ABSTRACT FROM AUTHOR]

As an important anthropogenic source of volatile organic compounds (VOCs), industrial emissions have a significant impact on air quality and human health. In this study, the characteristics, chemical reactivities, and health risks of VOCs around an industrial park in Zibo were analyzed at two sampling sites. The results showed that the concentrations of total VOCs at Dongzhang Community (DZ) and Special School (SS) sites were 113.12 ppb and 139.40 ppb, respectively, with oxygenated VOCs (OVOCs) as the most abundant species, accounting for 42–45%, followed by alkanes (19.3–19.6%). Diurnal variation of OVOCs exhibited noticeable peaks at 3:00, which may be related to the nighttime sneaky emissions of some enterprises. OVOCs were the species with the highest photochemical activity, with an average contribution of 56.5% to OH radical loss rate and 57% to ozone generation. In addition, OVOCs contributed 40% to secondary organic aerosol formation potential at both sites, second only to aromatics (55%). Acrolein and 1,2-dichloropropane presented the highest non-cancer and cancer risks to human health. The results highlight the importance of OVOCs in some industrial areas. [ABSTRACT FROM AUTHOR]

The purpose of this study was to compare the accuracy of digital dental casts from plaster cast scanning (PCS), impression scanning (IPS), intraoral scanning (IOS), and cone-beam computed tomography (CBCT) scanning (CCS) methods. The maxillary and mandibular dental casts of 15 patients who needed CBCT scans for oral examination or treatment were digitized via four methods. 12 linear distance measurements of all digital dental casts were selected and acquired with software and compared to those of the reference plaster cast to evaluate the dimensional accuracy. Three-dimensional deviation analysis of the IPS, IOS and CCS groups with respect to the reference PCS group was performed to evaluate the morphological accuracy. The discrepancy in linear distances between the digital dental casts and reference plaster casts was statistically significant (p < 0.01). The dimensional accuracies of the PCS (0.06 ± 0.12 mm) and IPS (0.03 ± 0.05 mm) casts were better than those of the IOS (0.37 ± 0.30 mm) and CCS (0.54 ± 0.40 mm) casts. The one-sample t test showed that there were statistically significant differences between the discrepancies in 8 of the linear distances for the PCS group and 9 of the linear distances for the IPS group between the digital dental casts and reference plaster casts, with an ideal error of 0.00 (p < 0.05). The sequence of morphological accuracy from good to poor was maxillary and mandibular IPS, mandibular IOS; maxillary IOS; and maxillary and mandibular CCS. The accuracy of the digital dental casts from the PCS and IPS methods was greater than that of IOS and CCS methods. Although accuracy of the digital dental cast from IOS was low, it satisfied the clinical requirements for fixed restorations in small units. The accuracy of the digital dental cast from CCS was poorest and could only be used for procedures with lower accuracy requirements. [ABSTRACT FROM AUTHOR]

The authors of this study aimed to compare the treatment outcomes and time efficiency between digital and conventional complete denture restorations and propose suggestions for clinical use. The authors used digital (functionally suitable digital complete denture [FSD]) and conventional complete denture restorations to make 2 dentures each for 10 edentulous patients. All the operations of both techniques before denture delivery were completed in the first 4 visits, and then 2 dentures were delivered successively for the patients. The clinical and laboratory times were recorded to evaluate the time efficiency; treatment outcomes were evaluated via scoring the denture satisfaction of the dentist and patients in a double-blind manner. The satisfaction scores of FSDs (7.6-9.6 [dentist's scores], 8.4-10 [patients' scores]) were higher than those of conventional dentures (7.2-9.7 [dentist's score], 7.4-9.8 [patients' scores]), but there were no significant differences. The clinical and laboratory operation times of the FSD group were less than those of the conventional group, saving an average of 28.0 minutes and 64.3 minutes in the clinic and laboratory, respectively. FSD technology can improve the efficiency of clinical and laboratory operations and shorten the manufacturing cycle of dentures. The occlusion stability of FSDs was statistically better than that of traditional dentures, but there was no statistical difference in other clinical indicators. FSD technology is low cost and easy to operate and has several applications. Compared with conventional complete denture restoration technology, FSDs can save time and have a comparable clinical effect. This clinical trial was registered at the Chinese Clinical Trial Registry. The registration number is ChiCTR1900021722. [ABSTRACT FROM AUTHOR]

Manufacturability analysis is a critical step before manufacturing to reduce costs and risks. It is used widely in conventional manufacturing (CM) processes. However, to the best of our knowledge, there is no natural method to evaluate the manufacturability of additive manufacturing (AM) processes that have more uncertainty-derived risks and costs than CM processes. A clear definition of the manufacturability of AM processes has not been established, and there is no standard to check whether a component is manufactured successfully by an AM process, particularly for porous complex components. This study introduces the development of a new machine learning-based method to solve the problem mentioned above. It is based on the statistical measurement of experimental samples. The proposed method can be used to perform the manufacturability analysis for periodic cellular structures printed by a selective laser melting (SLM) process. A novel definition of the manufacturability of the SLM-ed periodic cellular structure was proposed. Experimental results indicate that the developed learning model (ANN model) can achieve up to 94% classification accuracy and 96% prediction accuracy, which satisfies the application requirements of the AM industry. Moreover, the developed model can be adapted for the manufacturability analysis of different AM processes. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the internal adaptations of cast crowns made from resin patterns produced using three different computer-aided design/computer-assisted manufacturing technologies.Materials and Methods: A full-crown abutment made of zirconia was digitized using an intraoral scanner, and the design of the crown was finished on the digital model. Resin patterns were fabricated using a fused deposition modeling (FDM) 3D printer (LT group), a digital light projection (DLP) 3D printer (EV group), or a five-axis milling machine (ZT group). All patterns were cast in cobalt-chromium alloy crowns. Crowns made from traditional handmade wax patterns (HM group) were used as controls. Each group contained 10 samples. The internal gaps of the patterns were analyzed using a 3D replica method and optical digitization. The results were compared using Kruskal-Wallis analysis of variance (ANOVA), a one-sample t test, and signed rank test (α = .05).Results: For the LT group, the marginal and axial gaps were significantly larger than in the other three groups (P < .05), but the occlusal adaptation did not reveal a significant difference (P > .05). In the ZT group, the axial gap was slightly smaller than in the HM group (P < .0083). All the means of gaps in all areas in the four groups were less than 150 μm.Conclusion: Casting crowns using casting patterns made from all three CAD/CAM systems could not produce the prescribed parameters, but the crowns showed clinically acceptable internal adaptations. [ABSTRACT FROM AUTHOR]

To compare the accuracy of visual and instrumental methods for tooth-color matching based on three attributes in the Munsell color system and to investigate the characteristics of intraoral scanners for tooth-color matching. Shades of the cervical, middle, and incisal third region of 130 maxillary anterior teeth were matched visually by an experienced prosthodontist (EP) using Vita classical A1-D4 (VC) and Vita System 3D-Master (V3D) shade guides, and digitally by a spectrophotometer (Vita Easyshade V, VE) and two intraoral scanners (3Shape TRIOS 3, T3; TRIOS 4, T4). VE was used as a reference. The reproducibility of the three test groups was examined by repeating the measurements in triplicate. The overall trueness of the three test groups (from high to low) was T3 > EP > T4 for VC values (p < 0.01), and T3, EP > T4 (p < 0.01) for V3D. The trueness of T3 in incisal regions was lower than cervical and middle regions. When hue or lightness was correct, the mismatched chroma in test groups was smaller than VE (p < 0.01). The repeatability of EP was the poorest (p < 0.01). The color-matching trueness of T3 was higher than EP and T4. The reproducibility of intraoral scanners was better than visual methodology. [ABSTRACT FROM AUTHOR]

Purpose: To compare the accuracy of chairside, fused deposition modeling (FDM) three‐dimensional (3D)‐printed surgical guides with that of stereolithographic guides for implant placement in single edentulous sites within a clinical setting. Materials and Methods: A total of 28 participants with 30 single posterior edentulous sites were included. The sites were randomized into a FDM 3D‐printed surgical guide group (test) or stereolithographic guide group (control) of equal size (n = 15). In both groups, digital implant planning was performed using data from cone beam‐computed tomography and intraoral scans. The test group's surgical guides were fabricated using a chairside, FDM 3D‐printer; those in the control group were fabricated using a light‐curing 3D‐printer. Postoperative intraoral scans were used to obtain the 3D position of the implants. Compared to preoperative design, the angular, 3D, mesiodistal, buccolingual and apicocoronal deviations at the implant shoulder and apex were recorded. Results: The workflow for the design and chairside fabrication of implant guides was established. The mean angular deviations of the test and control group were (4.23 ± 2.38) ° and (4.13 ± 2.42) ° (p >.05), respectively. The respective 3D deviations at the implant shoulder were (0.70 ± 0.44) mm and (0.55 ± 0.27) mm (p >.05); those at the implant apex were (1.25 ± 0.61) mm and (1.11 ± 0.54) mm (p >.05). The mesiodistal, buccolingual, and apicocoronal deviations at the implant shoulder and apex did not significantly differ between the groups (p >.05). Conclusions: Implants for single posterior edentulous spaces were placed as accurately with the test guide as with the control. Further research under more complex situations involving multiple missing teeth is needed. [ABSTRACT FROM AUTHOR]

Purpose: To establish a direct digital method for determining and recording edentulous maxillomandibular relationship using a custom‐made jaw movement tracking system and evaluate its accuracy. Materials and methods: A novel jaw tracking system was used to record the trajectory of habitual opening‐closing jaw movement, and mandibular rest position (MRP) in 10 edentulous patients. 3D surface scanning was performed on the conventional maxillomandibular impressions and facial structures of patients in MRP. The multisource data were registered using a custom‐made recording tool. A plane parallel to the ala‐tragus and horizontal lines was constructed 2 mm above the MRP, and its vertical position was used to determine the vertical relationship. The intersections of the trajectory passing through the plane were located, and their density distributions were analyzed. The coordinates of highest density, which presented the highest repeatability of jaw movement, were used to construct the digital maxillomandibular relationship (test group). The maxillomandibular relationship of the new complete dentures with artificial teeth in the intercuspal position was defined as the control group. The displacements of the anterior reference point and 3D deviations of the entire mandibular arch were measured and compared between the test and control groups using a Wilcoxon signed‐ranks test and a one‐sample t‐test, respectively. Results: With reference to the centric relationship position, the maximum displacements of the anterior reference points were in the horizontal anteroposterior direction for both groups, and there were no significant differences. Compared to the control group, the 3D deviations of the entire mandibular arch in the test group were significant (95% confidence interval: 0.76 mm to 1.35 mm, p < 0.001). Conclusions: By analyzing the individual trajectory features obtained by the in‐house developed jaw tracking system, a digital method for determining and recording edentulous maxillomandibular relationships was established; however, the accuracy needs to be further improved. [ABSTRACT FROM AUTHOR]

Purpose: This in vitro study aims to explore the effects of selective laser melting (SLM) process parameters on the accuracy of the intaglio surface of cobalt–chromium alloy (Co–Cr), commercially pure titanium (CP Ti) and titanium alloy (Ti–6Al–4V) maxillary removable partial denture (RPD) frameworks and optimize these process parameters. Design/methodology/approach: Maxillary RPD framework specimens designed on a benchmark model were built. The process parameters, including contour scan speed and laser power, infill scan speed and laser power, hatch space, build orientation and metallic powder type, were arranged through the Taguchi design. Three-dimensional deviations of the clasps area, connector area and overall area of maxillary RPD frameworks were analyzed by using root mean square (RMS) as a metric. One-way analyses of variance with the above RMSs as the dependent variable were carried out (α = 0.05). Findings: Maxillary RPD frameworks built horizontally had a more accurate intaglio surface than those built at other orientation angles; CP Ti or Ti–6Al–4V maxillary RPD frameworks had a more accurate intaglio surface than Co–Cr ones; the Maxillary RPD framework built with a higher infill scan speed and lower infill laser power had the more accurate intaglio surface than the one built with other levels of these two process parameters. Originality/value: A novel benchmark model for evaluating the accuracy of the intaglio surface of maxillary RPD frameworks manufactured by SLM is proposed. The accuracy of the intaglio surface of maxillary RPD frameworks can be improved by adjusting SLM process parameters. The optimal setting of process parameters concerning the accuracy of the intaglio surface of maxillary RPD frameworks was given. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to explore the application of computer-aided design and rapid prototyping (CAD/RP) for removable partial denture (RPD) frameworks and evaluate the fitness of the technique for clinical application.Materials and Methods: Three-dimensional (3D) images of dentition defects were obtained using a lab scanner. The RPD frameworks were designed using commercial dental software and manufactured using selective laser melting (SLM). A total of 15 cases of RPD prostheses were selected, wherein each patient received two types of RPD frameworks, prepared by CAD/RP and investment casting. Primary evaluation of the CAD/RP framework was performed by visual inspection. The gap between the occlusal rest and the relevant rest seat was then replaced using silicone, and the specimens were observed and measured. Paired t test was used to compare the average thickness and distributed thickness between the CAD/RP and investment casting frameworks. Analysis of variance test was used to compare the difference in thickness among different zones.Results: The RPD framework was designed and directly manufactured using the SLM technique. CAD/RP frameworks may meet the clinical requirements with satisfactory retention and stability and no undesired rotation. Although the average gap between the occlusal rest and the corresponding rest seat of the CAD/RP frameworks was slightly larger than that of the investment casting frameworks (P < .05), it was acceptable for clinical application.Conclusion: RPD frameworks can be designed and fabricated directly using digital techniques with acceptable results in clinical application. [ABSTRACT FROM AUTHOR]

Objective. Restoring the correct masticatory function of partially edentulous patient is a challenging task primarily due to the complex tooth morphology between individuals. Although some deep learning-based approaches have been proposed for dental restorations, most of them do not consider the influence of dental biological characteristics for the occlusal surface reconstruction. Description. In this article, we propose a novel dual discriminator adversarial learning network to address these challenges. In particular, this network architecture integrates two models: a dilated convolutional-based generative model and a dual global-local discriminative model. While the generative model adopts dilated convolution layers to generate a feature representation that preserves clear tissue structure, the dual discriminative model makes use of two discriminators to jointly distinguish whether the input is real or fake. While the global discriminator focuses on the missing teeth and adjacent teeth to assess whether it is coherent as a whole, the local discriminator aims only at the defective teeth to ensure the local consistency of the generated dental crown. Results. Experiments on 1000 real-world patient dental samples demonstrate the effectiveness of our method. For quantitative comparison, the image quality metrics are used to measure the similarity of the generated occlusal surface, and the root mean square between the generated result and the target crown calculated by our method is 0.114 mm. In qualitative analysis, the proposed approach can generate more reasonable dental biological morphology. Conclusion. The results demonstrate that our method significantly outperforms the state-of-the-art methods in occlusal surface reconstruction. Importantly, the designed occlusal surface has enough anatomical morphology of natural teeth and superior clinical application value. [ABSTRACT FROM AUTHOR]

Purpose: To analyze the accuracy of transferring casts in maximal intercuspal position to a virtual articulator by using transfer plates in the laboratory scanner before and after occlusal optimization. Material and methods: Five sets of standard dental casts were mounted on a mechanical articulator in maximal intercuspal position. The number and position of occlusal contacts were determined with 12‐μm articulating foil. After a calibration process according to the manufacturer's instructions, the mountings were transferred to a virtual articulator using the transfer plates in a laboratory scanner. The occlusion of the digital casts was determined before and after the occlusal optimization process. Then, the sensitivity and positive predictive value were determined by comparing the occlusal contact points in the virtual articulator with those in the mechanical articulator. To evaluate trueness, the occlusal surface of the maxillary teeth in the mechanical articulator was recorded by polyvinyl siloxane occlusal record in maximal intercuspal position and retained on the mandibular arch. The trueness was calculated as the deviation between the occlusal surface of the maxillary teeth in the mechanical articulator and the virtual articulator. To evaluate precision, one set of the casts was scanned 10 times. And the deviation of the interarch position of the maxillary arches when superimposing the mandibular arches of every 2 different scans was calculated. Results: The sensitivity before occlusal optimization (0.14 ± 0.15) was significantly lower than that after occlusal optimization (0.82 ± 0.10) (p = 0.003). However, there was no significant difference between the positive predictive value before (0.80 ± 0.45) and after (0.81 ± 0.09) occlusal optimization (p = 0.952). The trueness before (91.0 ± 10.7 µm) and after (75.4 ± 25.2 µm) occlusal optimization had no significant difference (p = 0.249). The precision before occlusal optimization (11.6 ± 3.8 µm) was significantly superior to that after occlusal optimization (75.6 ± 39.2 µm) (p < 0.001). Conclusions: The accuracy of transferring casts in maximal intercuspal position to a virtual articulator using transfer plates in the laboratory scanner could be improved after occlusal optimization and can meet the clinical needs for occlusal design and analysis of prostheses. [ABSTRACT FROM AUTHOR]

Restoring the correct masticatory function of broken teeth is the basis of dental crown prosthesis rehabilitation. However, it is a challenging task primarily due to the complex and personalized morphology of the occlusal surface. In this article, we address this problem by designing a new two-stage generative adversarial network (GAN) to reconstruct a dental crown surface in the data-driven perspective. Specifically, in the first stage, a conditional GAN (CGAN) is designed to learn the inherent relationship between the defective tooth and the target crown, which can solve the problem of the occlusal relationship restoration. In the second stage, an improved CGAN is further devised by considering an occlusal groove parsing network (GroNet) and an occlusal fingerprint constraint to enforce the generator to enrich the functional characteristics of the occlusal surface. Experimental results demonstrate that the proposed framework significantly outperforms the state-of-the-art deep learning methods in functional occlusal surface reconstruction using a real-world patient database. Moreover, the standard deviation (SD) and root mean square (RMS) between the generated occlusal surface and the target crown calculated by our method are both less than 0.161 mm. Importantly, the designed dental crown have enough anatomical morphology and higher clinical applicability. [ABSTRACT FROM AUTHOR]

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 DR 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 DM between the pairs of concaves were measured as test values. Variable differences between DR and DM 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. [ABSTRACT FROM AUTHOR]

Purpose: To investigate a computer-aided design/computer-aided manufacturing (CAD/CAM) process for producing one-piece removable partial dentures (RPDs) and to evaluate their fits in vitro.Materials and Methods: A total of 15 one-piece RPDs were designed using dental CAD and reverse engineering software and then fabricated with polyetheretherketone (PEEK) using CAM. The gaps between RPDs and casts were measured and compared with traditional cast framework RPDs.Results: Gaps were lower for one-piece PEEK RPDs compared to traditional RPDs.Conclusion: One-piece RPDs can be manufactured by CAD/CAM, and their fits were better than those of traditional RPDs. [ABSTRACT FROM AUTHOR]

Restoring the normal masticatory function of broken teeth is a challenging task primarily due to the defect location and size of a patient’s teeth. In recent years, although some representative image-to-image transformation methods (e.g. Pix2Pix) can be potentially applicable to restore the missing crown surface, most of them fail to generate dental inlay surface with realistic crown details (e.g. occlusal groove) that are critical to the restoration of defective teeth with varying shapes. In this article, we design a computer-aided Deep Adversarial-driven dental Inlay reStoration (DAIS) framework to automatically reconstruct a realistic surface for a defective tooth. Specifically, DAIS consists of a Wasserstein generative adversarial network (WGAN) with a specially designed loss measurement, and a new local-global discriminator mechanism. The local discriminator focuses on missing regions to ensure the local consistency of a generated occlusal surface, while the global discriminator aims at defective teeth and adjacent teeth to assess if it is coherent as a whole. Experimental results demonstrate that DAIS is highly efficient to deal with a large area of missing teeth in arbitrary shapes and generate realistic occlusal surface completion. Moreover, the designed watertight inlay prostheses have enough anatomical morphology, thus providing higher clinical applicability compared with more state-of-the-art methods. [ABSTRACT FROM AUTHOR]

Common impressions cannot accurately duplicate the dental occlusion under occlusal force due to tooth displacement and mandibular deformation. To establish new methods to construct virtual intercuspal occlusion and assess their construction accuracy. The intraoral occlusal contacts of posterior teeth of 15 subjects were recorded with 8 μm and 100 μm articulating paper, respectively, and the marked teeth and buccal bite data were scanned with an intraoral scanner. The virtual dental occlusions were separately determined by buccal bite registration (BBR) method, and 3 new methods, namely segmented tooth registration (STR), occlusal contact areas (marked by 8 μm articulating paper) registration (OCR) and mixing registration (MR) methods. With the intraoral contact areas marked by 100 μm articulating paper set as reference and contact areas of the 4 virtual occlusions as tests, sensitivity, positive predictive value (PPV) and the ratio of overlapping areas were calculated. Kruskal‐Wallis test or 1‐way ANOVA was used to analyse the difference among groups. The sensitivity ranged from 0.69 to 0.94 and the PPV from 0.67 to 0.90. Sensitivity of OCR group and PPV of STR and OCR groups were different from that of BBR group at overlapping threshold of 50% (P =.028,.028 and.006). There was statistical difference of the ratio of overlapping areas over reference areas, and the values of STR and OCR groups were higher than that of BBR group (P =.045 and.021). The ability of STR and OCR methods to construct virtual intercuspal occlusion was better than BBR method. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the effect of different residual dentitions on the dynamic adjustment of wear facet morphology on a single mandibular first molar crown with a virtual articulator. Materials and Methods: Gypsum casts (N = 12) of natural full dentitions were mounted on an articulator and scanned. The mandibular right first molar (#46) was prepared and a copy of the tooth before it was prepared and used to design the crown. The wear facets on the original #46 were selected and elevated by 0.3 mm in the occlusal direction to generate high points. The #46 with high points was segmented to create a digital wax pattern. Then different teeth were virtually removed to generate 4 types of residual dentitions: Type I (no teeth), Type II (adjacent teeth), Type III (ipsilateral posterior teeth and canine), and Type IV (all teeth). The crowns were adjusted dynamically with different residual teeth to guide mandibular movement of the virtual articulator. Three‐dimensional deviations, negative and positive volumes between crowns and wear facets on the original #46 were analyzed. The Kruskal‐Wallis test was used to analyze the results. Results: The mean deviation values and positive volumes decreased with the decrease in residual teeth, and the negative volumes showed an opposite trend. The mean deviation values, root mean square, and positive volumes were not significantly different. The negative volume of the crowns of Type I was different from that of Type IV (p = 0.031). Conclusions: Residual dentition affects the dynamic adjustment of wear facet morphology. When there are insufficient residual teeth, mandibular movements should be accurately measured. [ABSTRACT FROM AUTHOR]

The tooth defect is a frequently occurring disease within the field of dental clinic. However, the traditional manual restoration for the defective tooth needs an especially long treatment time, and dental computer aided design and manufacture (CAD/CAM) systems fail to restore the personalized anatomical features of natural teeth. Aiming to address the shortcomings of existed methods, this article proposes an intelligent network model for designing tooth crown surface based on conditional generative adversarial networks. Then, the data set for training the network model is constructed via generating depth maps of 3D tooth models scanned by the intraoral. Through adversarial training, the network model is able to generate tooth occlusal surface under the constraint of the space occlusal relationship, the perceptual loss, and occlusal groove filter loss. Finally, we carry out the assessment experiments for the quality of the occlusal surface and the occlusal relationship with the opposing tooth. The experimental results demonstrate that our method can automatically reconstruct the personalized anatomical features on occlusal surface and shorten the treatment time while restoring the full functionality of the defective tooth. [ABSTRACT FROM AUTHOR]

Poly-ε-caprolactone (PCL) is a promising synthetic material in bone tissue engineering (BTE). Particularly, the introduction of rapid prototyping (RP) represents the possibility of manufacturing PCL scaffolds with customized appearances and structures. Bio-Oss is a natural bone mineral matrix with significant osteogenic effects; however, it has limitations in being constructed and maintained into specific shapes and sites. In this study, we used RP and fabricated a hollow-structured cage-shaped PCL scaffold loaded with Bio-Oss to form a hybrid scaffold for BTE. Moreover, we adopted NaOH surface treatment to improve PCL hydrophilicity and enhance cell adhesion. The results showed that the NaOH-treated hybrid scaffold could enhance the osteogenesis of human bone marrow-derived mesenchymal stem cells (hBMMSCs) both in vitro and in vivo. Altogether, we reveal a novel hybrid scaffold that not only possesses osteoinductive function to promote bone formation but can also be fabricated into specific forms. This scaffold design may have great application potential in bone tissue engineering. [ABSTRACT FROM AUTHOR]

Technological innovation, which can be classified into major and minor innovation, enables firms to gain competitive and sustainable advantage in the changing environment. R&D investment and financial resources are recognized as two critical factors for fostering technological innovation. Based on a panel dataset of 257 listed Chinese high-tech manufacturing firms over the period of 2008–2015, we explored the effect of R&D intensity on technological innovation and the moderating role of free cash flow using negative binormal regression models. Our results reveal that the relationship between R&D intensity and technological innovation (both major and minor innovation) follows an inverted U pattern in which technological innovation increases with R&D intensity at decreasing rates and falls gradually after R&D intensity exceeds a threshold. Our results also indicate that free cash flow plays a moderating role in the relationship between R&D intensity and major innovation but not in the relationship between R&D intensity and minor innovation. Our study draws attention to the improvement of R&D investment efficiency in high-tech manufacturing firms and sheds light on the importance of holding cash in major innovation-oriented firms. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to establish a chair-side design and production method for a tooth-supported fixed implant guide and to evaluate its accuracy. Design/methodology/approach: Three-dimensional (3D) data of the alveolar ridge, adjacent teeth and antagonistic teeth were acquired from models of the edentulous area of 30 patients. The implant guides were then constructed using self-developed computer-aided design software and chair-side fused deposition modelling 3D-printing and positioned on a dental model. A model scanner was used to acquire 3D data of the positioned implant guides, and the overall error was then evaluated. Findings: The overall error was 0.599 ± 0.146 mm (n = 30). One-way ANOVA revealed no statistical differences among the 30 implant guides. The gap between the occlusal surface of the teeth covering and the tissue surface of the implant guide was measured. The maximum gap after positioning of the implant guide was 0.341 mm (mean, 0.179 ± 0.019 mm). The implanted axes of the printed implant guide and designed guide were compared in terms of overall, lateral and angular error, which were 0.104 ± 0.004 mm, 0.097 ± 0.003 mm, and 2.053° ± 0.017°, respectively. Originality/value: The results of this study demonstrated that the accuracy of a new chair-side tooth-supported fixed implant guide can satisfy clinical requirements. [ABSTRACT FROM AUTHOR]

The abnormal occlusal contact can disrupt the coordination and health of the oral jaw system. Therefore, the dynamic adjustment of the occlusal surface is of great significance for assessing the status of occlusal contact and clarifying jaw factors of stomatognathic system diseases. To solve this problem, a trajectory subtraction algorithm based on screw theory to improve the accuracy of the occlusal movement trajectory is proposed in our paper. Driving by the relative trajectory, a virtual dynamic occlusal adjustment system is developed to realize 3D occlusal movement simulating, automatic occluding relation detection, and automatic occlusal adjustment. Furthermore, we adapt an active occlusal adjustment method based on Laplacian deformation to increase the contact areas of the occlusal surface, which can aid dentists to realize the automatic adjustment of the non-interference regions. As a consequence, the proposed subtraction algorithm is feasible and the root-mean-square is 0.097 mm, and the adjusted occlusal surface is more consistent with the natural occlusal morphology. Graphical abstract ᅟ. [ABSTRACT FROM AUTHOR]

Objective: To quantitatively evaluate maxillary complete dentures fabricated from polylactic acid (PLA) using fused deposition modelling (FDM) technology. Methods: A digital maxillary complete denture was prepared based on a standard maxillary edentulous plaster model. The PLA pattern was printed by a FDM machine, with 5 repetitions, while another 5 wax patterns were printed as control group, using a high accuracy three-dimensional (3D) wax printer. The patterns were scanned with a 3D scanner. A light-body silicone film was made after each denture pattern had been totally seated on the plaster model, and was scanned to determine its thickness, which reflected the 3D space between the plaster model and the tissue surface of the denture pattern. The overall area was separated into four parts: primary stress-bearing area, secondary stress-bearing area, border seal area and relief area, and the average deviation of these four parts were measured. The values were analyzed by independent t-test. Results: The overall mean value and standard deviation of space between PLA denture patterns and plaster model was 0.277 ± 0.021 mm, while that of the wax denture patterns was 0.279 ± 0.045 mm, which showed a good fit overall. No statistically significant (푃 > 0.05) difference was observed between the PLA patterns and wax patterns. Conclusions: The adaptation of the PLA pattern of maxillary complete denture printed by FDM technology is comparable to that prepared by wax printer, and can satisfy the accuracy requirements. [ABSTRACT FROM AUTHOR]

The conventional technique for the fabrication of complete dentures is complex, with a long fabrication process and difficult-to-control restoration quality. In recent years, digital complete denture design has become a research focus. Digital complete denture tooth arrangement is a challenging issue that is difficult to efficiently implement under the constraints of complex tooth arrangement rules and the patient’s individualized functional aesthetics. The present study proposes a complete denture automatic tooth arrangement method driven by a reconfigurable rule; it uses four typical operators, including a position operator, a scaling operator, a posture operator, and a contact operator, to establish the constraint mapping association between the teeth and the constraint set of the individual patient. By using the process reorganization of different constraint operators, this method can flexibly implement different clinical tooth arrangement rules. When combined with a virtual occlusion algorithm based on progressive iterative Laplacian deformation, the proposed method can achieve automatic and individual tooth arrangement. Finally, the experimental results verify that the proposed method is flexible and efficient. [ABSTRACT FROM AUTHOR]

Abstract: A removable complete denture is still the main selection for edentulous patients. Over the last 5 years, digital technologies for producing complete dentures have rapidly developed. Nevertheless, the design method for the baseplate has become the bottleneck of digital complete denture technology development. In this study, we report a novel method for the generation of esthetic gingiva and polished surfaces of complete dentures that are driven by the feature curve, which can be conveniently modified using the gingival shape factor. A solid modeling method based on Poisson surface reconstruction is used to generate a high‐quality baseplate solid. This method can aid dentists to realize the rapid design process of personalized esthetic baseplate. Finally, the experimental results verify that the method of digital design for the baseplate proposed is efficient and accurate (standard deviation <0.01 mm). [ABSTRACT FROM AUTHOR]

With the development of 3-dimensional (3D) scanning technologies in dentistry, high accuracy optical scanning data from the crown and cone beam computed tomography data from the root can be acquired easily. In many dental fields, especially in digital orthodontics, it is useful to fuse the data from the crown and the root. However, the manual fusion method is complex and difficult. A novel automatic fusion method for 2-source data from the crown and the root was researched, and its accuracy was evaluated in this study. An occlusal splint with several alumina ceramic spheres was fabricated using heat-curing resin. A multipoint (center of each sphere) alignment method was performed to achieve rapid registration of the crown data from optical scanning and the root data from cone beam computed tomography. The segmentation algorithm based on heuristic search was adopted to perform extraction and segmentation of the crown from whole optical scanning data. The level set algorithm and the marching cubes (MC) algorithm were used to reconstruct digital imaging and communications in medicine data into a 3D model. A novel multisource data fusion algorithm, which is based on iterative Laplacian deformation (ILD), was researched and applied to achieve automatic fusion. Finally, the 3D errors of the method were evaluated. The 3 groups of typical tooth data were automatically fused within 2 seconds. The mean standard deviation was less than 0.02 mm. The novel method can aid the construction of a high-quality 3D model of complete teeth to enable orthodontists to safely, reliably, and visually plan tooth alignment programs. [ABSTRACT FROM AUTHOR]

With the development of 3D printing and computer graphics technology, mouth rehabilitation has increasingly adopted digital methods. This research proposes a new method to transform the appearance of facial model after complete denture prosthesis. A feature template with few feature points is first constructed according to the facial muscle anatomy and facial deformation after complete denture prosthesis. Next, the traditional as-rigid-as-possible (ARAP) method is optimised by clustering based on facial muscles. The optimised ARAP method is then used for real-time and interactive simulations. Finally, by classifying the degrees of elasticity in the model with additional weights, the simulation can be customised to the skin of individual patients. Different degrees of elastic deformation and post-operative models are superimposed for match analysis. Compared with our previous study, the error is reduced by 24.05%. Results show that our method can deform facial models accurately and efficiently. [ABSTRACT FROM AUTHOR]

Purpose To investigate the biomechanical performance of different osseointegration patterns between cortical bone and implants using finite element analysis. Materials and Methods Fifteen finite element models were constructed of the mandibular fixed prosthesis supported by implants. Masticatory loads (200 N axial, 100 N oblique, 40 N horizontal) were applied. The cortical bone/implant interface was divided equally into four layers: upper, upper-middle, lower-middle, and lower. The bone stress and implant displacement were calculated for 5 degrees of uniform integration (0, 20%, 40%, 60%, and 100%) and 10 integration patterns. Results The stress was concentrated in the bone margin and gradually decreased as osseointegration progressed, when the integrated and nonintegrated areas were alternated on the bone-implant surface. Compared with full integration, the integration of only the lower-middle layer or lower half layers significantly decreased von Mises, tensile, and compressive stresses in cortical bone under oblique and horizontal loads, and these patterns did not induce higher stress in the cancellous bone. For the integration of only the upper or upper-middle layer, stress in the cortical and cancellous bones significantly increased and was considerably higher than in the case of nonintegration. In addition, the maximum stress in the cortical bone was sensitive to the quantity of integrated nodes at the bone margin; lower quantity was associated with higher stress. There was no significant difference in the displacement of implants among 15 models. Conclusions Integration patterns of cortical bone significantly affect stress distribution in peri-implant bone. The integration of only the lower-middle or lower half layers helps to increase the load-bearing capacity of peri-implant bone and decrease the risk of overloading, while upper integration may further increase the risk of bone resorption. [ABSTRACT FROM AUTHOR]

Objective: Developments in digital technology have permitted researchers to study mandibular movements. Here, the accuracy of a real-time, computerized, binocular, three-dimensional (3D) trajectory-tracking device for recording functional mandibular movements was evaluated. Methods: An occlusal splint without the occlusal region was created based on a plaster cast of the lower dentition. The splint was rigidly connected with a target on its labial side and seated on the cast. The cast was then rigidly attached to the stage of a high-precision triaxial electronic translator, which was used to move the target-cast-stage complex. Half-circular movements (5.00-mm radius) in three planes (XOY, XOZ, YOZ) and linear movements along the x-axis were performed at 5.00 mm/s. All trajectory points were recorded with the binocular 3D trajectory-tracking device and fitted to arcs or lines, respectively, with the Imageware software. To analyze the accuracy of the trajectory-tracking device, the mean distances between the trajectory points and the fitted arcs or lines were measured, and the mean differences between the lengths of the fitted arcs’ radii and a set value (5.00 mm) were then calculated. A one-way analysis of variance was used to evaluate the spatial consistency of the recording accuracy in three different planes. Results: The mean distances between the trajectory points and fitted arcs or lines were 0.076 ± 0.033 mm or 0.089 ± 0.014 mm. The mean difference between the lengths of the fitted arcs’ radii and the set value (5.00 mm) was 0.025 ± 0.071 mm. A one-way ANOVA showed that the recording errors in three different planes were not statistically significant. Conclusion: These results suggest that the device can record certain movements at 5.00 mm/s, which is similar to the speed of functional mandibular movements. In addition, the recordings had an error of <0.1 mm and good spatial consistency. Thus, the device meets some of the requirements necessary for recording human mandibular movements. [ABSTRACT FROM AUTHOR]

Purpose The use of removable complete dentures is a selectable restorative procedure for edentulous patients. To improve the fabrication quality and efficiency of removable complete dentures, this paper aims to introduce a new method to fabricate customized wax complete dentures with additive manufacturing. This process uses complementary digital technologies, and allows faster and better manufacture of complete dentures.Design/methodology/approach In the study, a dental scanner was used to obtain surface data from edentulous casts and rims made by the dentist. A parameterized three-dimensional graphic database of artificial teeth was pre-established. Specialized computer-aided design software was used to set up the artificial dentition and design the esthetic gingiva and base plate. A selective laser sintering machine was used to transfer the data from stereolithography files into a wax base plate with location holes for each artificial tooth.Findings Under this method, a set of wax base plates with 28 location holes available for the placement of the artificial teeth were designed and fabricated within 6 h. The try-in wax dentures fitted the patient’s mouth well, besides occlusion relationships. Then, the occlusion relationships can be adjusted manually to achieve a balanced centric occlusion.Originality/value This method can be used to design and fabricate wax try-in removable complete dentures semi-automatically and rapidly; however, the algorithm for the occlusion contact design needs to be improved. [ABSTRACT FROM AUTHOR]