CAD-CAM pressure-exerting device to create an ovate pontic for an implant-supported fixed partial denture.

This article presents a digital approach to fabricating a computer-aided design and computer-aided manufacturing (CAD-CAM) ovate pontic creating device for an implant-supported fixed partial denture. Intraoral digital scanning was done after osseointegration, and the pontic was designed as 2 separate parts, with the fixed part connecting the coronal part of the restoration and an ovate former shaping the pontic area. A mechanical spring was placed between the 2 parts to exert consistent pressure on the ovate former. An ovate pontic can be individually created rapidly and precisely as designed with this novel CAD-CAM device. This technology can be used to personalize the gingival morphology, improve esthetics, and minimize discomfort during the procedure.

Optical properties of monolithic zirconia fabricated with nanoparticle jetting.

STATEMENT OF PROBLEM: Excellent optical properties are essential for esthetic dental materials. However, the translucency and color masking ability of zirconia fabricated with nanoparticle jetting (NPJ), a type of printed zirconia, are unknown. PURPOSE: The purpose of this in vitro study was to evaluate the translucency and color masking ability of zirconia fabricated using NPJ. MATERIAL AND METHODS: A total of 90 specimens with thicknesses of 1.5, 1.0, and 0.5 mm were fabricated using high translucent milled zirconia (HT), low translucent milled zirconia (LT), and NPJ. CIELab values (L*, a*, and b*) of the specimens over 7 backgrounds, black, white, VitaB1, VitaA2, VitaA4, gold alloy (Au), and titanium (Ti), were obtained using a spectral radiometer. The relative translucency parameter (RTP) and color difference (∆E) of specimens over VitaB1, VitaA4, Au, and Ti were determined using VitaA2 as the control with the CIEDE2000 color difference equation. The normality of the data distribution was determined using the Shapiro-Wilk test. Differences among groups were analyzed using 2-way analysis of variance and the Student-Newman-Keuls (SNK) post hoc test (α=.05). The ∆E of specimens was analyzed according to perceptibility (∆E=0.8) and acceptability (∆E=1.8) thresholds using the 1 sample t test. The correlation between RTP and ∆E and RTP/∆E and thickness was examined using the Pearson correlation analysis. RESULTS: Statistically significant differences were observed in translucency and color masking ability among HT, LT, and NPJ (P<.05). The RTP value was the lowest for zirconia fabricated with NPJ (P<.001) and highest for HT (P<.001). Monolithic zirconia fabricated with NPJ had lower ∆E values than those of HT and LT for the same thickness and background (P<.05). A positive correlation was found in RTP and ∆E (P<.001). A negative correlation was observed in RTP and thickness (P<.001) and ∆E and thickness across a constant background (P<.001). CONCLUSIONS: Zirconia fabricated with NPJ was less translucent and had a greater color masking ability for discolored backgrounds than HT and LT.

Development and accuracy assessment of a crown lengthening surgery robot for use in the esthetic zone: An in vitro study.

STATEMENT OF PROBLEM: Crown lengthening surgery has been widely used to enhance the health and esthetics of anterior teeth, and its accuracy significantly influences surgical outcomes. However, the feasibility and accuracy of a robot system for crown lengthening surgery remains unknown. PURPOSE: The purpose of this in vitro study was to develop a crown lengthening surgery robot and evaluate its accuracy. MATERIAL AND METHODS: A robotic crown lengthening surgery system consisting of a robotic arm, a robotic software system, and an optical tracking device was designed. Intraoral scanning and cone beam computed tomography (CBCT) were performed on 18 artificial dentition models. The data were imported into the planning software program to synthesize a surgical path for gingivectomy and alveolectomy. Subsequently, a robotic arm equipped with a high-speed handpiece was used to perform these surgical procedures. Postoperatively, the models were rescanned for evaluation, with the accuracy (trueness ±precision) of the surgical outcomes of gingivectomy and alveolectomy being assessed from the trajectories in the highest, lowest, and overall regions. Differences between groups were analyzed by using the independent sample t test and the Levene test (α=.05). RESULTS: Crown lengthening surgery was feasible in vitro using the robot developed in this study. The overall robot-assisted crown lengthening surgery accuracy (trueness ±precision) of gingivectomy (0.23 ±0.08 mm) was significantly higher than that of alveolectomy (0.33 ±0.11 mm) (P<.05). CONCLUSIONS: Robot-assisted crown lengthening surgery had acceptable accuracy generally and can be considered a feasible treatment option.

Higher greenspace exposure is associated with a decreased risk of childhood asthma in Shanghai - A megacity in China.

Inconsistent evidence exists about whether exposure to greenspace benefits childhood asthma. Previous studies have only focused on residential or school greenspace, and no research has combined greenspace exposures at both homes and schools to determine their link with childhood asthma. A population-based cross-sectional study was conducted among 16,605 children during 2019 in Shanghai, China. Self-reported questionnaires were used to collect information on childhood asthma and demographic, socioeconomic and behavioural factors. Environmental data including ambient temperature, particulate matter with aerodynamic diameter less than 1 µm (PM1), enhanced vegetation index (EVI), and normalized difference vegetation index (NDVI) were collected from satellite data. Binomial generalized linear models with a logit link were carried out to evaluate the association between greenspace exposure and children's asthma, as well as the effect modifiers. An interquartile range increment of whole greenspace (NDVI500, NDVI250, EVI500, and EVI250) exposure was associated with a reduced odds ratio of children's asthma (0.88, 95% CI: 0.78, 0.99; 0.89, 95% CI: 0.79, 1.01; 0.87, 95% CI: 0.77, 0.99; and 0.88, 95% CI: 0.78, 0.99, respectively) after controlling potential confounders. Low temperature, low PM1, males, vaginal delivery, suburban/rural area, and without family history of allergy appeared to enhance the greenspace-asthma association. Increased greenspace exposure was associated with a lower risk of childhood asthma, and the association was modified by a range of socio-environmental factors. These findings add to the body of evidence on the benefits of biodiversity and supporting the promotion of urban greenspace to protect children's health.

Trueness of 4 sectional-cast digital methods for transferring the interocclusal relationship in complete mouth rehabilitation.

STATEMENT OF PROBLEM: An accurate digital workflow for transferring the interocclusal relationship from complete arch diagnostic interim restorations to complete arch tooth preparations is essential in complete mouth rehabilitation. However, research on the accuracy of digital cross-mounting methods is lacking. PURPOSE: The purpose of this in vitro study was to compare the trueness of 4 sectional-cast digital cross-mounting methods in transferring the interocclusal relationship for complete mouth rehabilitation. MATERIAL AND METHODS: Maxillary and mandibular anatomic typodonts were used to build complete arch tooth preparations and diagnostic interim restorations for complete mouth rehabilitation in vitro. Four sectional casts were designed: an anterior cast (AR), a posterior cast (PO), a unilateral cast (UL), and a tripod cast (TR). Both extraoral scanning (EOS) and intraoral scanning (IOS) were used to obtain intermediate digital sectional casts, which were cross-registered with diagnostic interim restorations and definitive casts to transfer the interocclusal relationship. Trueness was determined by assessing tooth distance deviation and mandibular 3-dimensional (3D) deviation. Differences among the 4 sectional-cast methods were analyzed with the Kruskal-Wallis test, and differences between the 2 scanning methods were analyzed with the Mann-Whitney U test (α=.05). RESULTS: Significant differences in the trueness of interocclusal relationship transfer were observed among the 4 sectional-cast methods (P<.05). Regarding tooth overall distance deviation, TR-EOS found no statistically significant difference compared with PO-EOS (P>.05), but TR-EOS had half the overall distance deviation of PO-EOS. Both TR-EOS and PO-EOS had smaller deviations than the AR-EOS and UL-EOS groups (P<.05). TR-IOS had a smaller distance deviation than the AR-IOS, PO-IOS, and UL-IOS groups (P<.05). The overall distance deviation of EOS was significantly smaller than that of IOS in the TR and PO groups (P<.05). Regarding mandibular 3D deviation, TR-EOS found no statistically significant difference but had half the root mean square (RMS) of 3D deviation compared with the PO-EOS groups (P>.05). Both TR-EOS and PO-EOS groups had a smaller RMS than the AR-EOS and groups (P<.05). The TR-IOS group had a smaller RMS than the AR-IOS, PO-IOS, and UL-IOS groups (P<.05). The 3D deviation of EOS was significantly smaller than that of IOS in the PO group (P<.05). CONCLUSIONS: Both EOS and IOS with the tripod sectional-cast digital method accurately transferred the interocclusal relationship for complete mouth rehabilitation.

Effect of build angle on the dimensional accuracy of monolithic zirconia crowns fabricated with the nanoparticle jetting technique.

STATEMENT OF PROBLEM: The build angle is an essential parameter in additive manufacturing. Its effect on the dimensional accuracy of zirconia restorations fabricated using the nanoparticle jetting (NPJ) technique is unknown. PURPOSE: The purpose of this in vitro study was to evaluate the effect of the build angle on the dimensional accuracy of monolithic zirconia complete crowns fabricated by using NPJ. MATERIAL AND METHODS: Standardized artificial right maxillary incisors and mandibular first molars were prepared for ceramic complete crowns. In total, 100 monolithic zirconia crowns were fabricated using NPJ at build angles of 0, 45, 90, 135, and 180 degrees (n=10/angle for incisors and molars). The dimensional accuracies in the external, marginal, and intaglio regions were determined by superimposing the scanned data and computer-aided design data on the crowns. Root mean square (RMS) values were used to analyze the accuracy of the zirconia crowns overall and at the external, marginal, and intaglio surfaces. The Shapiro-Wilk test was used to examine the normality of data distribution. Differences among test groups were assessed using a 1-way analysis of variance and the post hoc least significant difference test (α=.05). RESULTS: Significant differences were found in the accuracy of monolithic zirconia incisor and molar complete crowns in the external, marginal, and intaglio regions among the 5 build angles (P<.05). For incisors, the external RMS value was lowest for a build angle of 45 degrees (18.2 ±3.0 µm), the marginal and intaglio RMS values were lowest for a build angle of 135 degrees (47.4 ±10.7 and 26.5 ±6.1 µm, respectively), and the overall RMS values did not differ significantly among the 5 build angles (P>.05). For molars, build angles of 0 degrees and 180 degrees yielded the lowest RMS values overall (22.3 ±1.5 and 21.8 ±3.2 µm, respectively) and in the external (23.2 ±2.9 and 22.3 ±2.5 µm, respectively) and intaglio (22.2 ±3.7 and 21.2 ±4.6 µm, respectively) regions. No significant difference was observed in the marginal area among the 5 build angles (P>.05). The overall RMS values reflecting dimensional accuracy for the 5 build angles were between 23.5 and 26.7 µm for incisors and 21.8 and 26.2 µm for molars. CONCLUSIONS: The dimensional accuracy of monolithic zirconia crowns fabricated by using NPJ was affected by the build angle and was within clinically acceptable limits.

Dimensional accuracy and clinical adaptation of monolithic zirconia crowns fabricated with the nanoparticle jetting technique.

STATEMENT OF PROBLEM: The nanoparticle jetting (NPJ) technique is a recently developed additive manufacturing method that may have useful dental applications. The manufacturing accuracy and clinical adaptation of zirconia monolithic crowns fabricated with NPJ are unknown. PURPOSE: The purpose of this in vitro study was to compare the dimensional accuracy and clinical adaptation of zirconia crowns fabricated with NPJ and those fabricated with subtractive manufacturing (SM) and digital light processing (DLP). MATERIAL AND METHODS: Five standardized typodont right mandibular first molars were prepared for ceramic complete crowns, and 30 zirconia monolithic crowns were fabricated using SM, DLP, and NPJ (n=10) with a completely digital workflow. The dimensional accuracy at the external, intaglio, and marginal areas was determined by superimposing the scanned data and computer-aided design data of the crowns (n=10). Occlusal, axial, and marginal adaptations were evaluated by using a nondestructive silicone replica and dual scanning method. The 3-dimensional discrepancy was evaluated to determine clinical adaptation. Differences among test groups were analyzed by using a MANOVA and the post hoc least significant difference test for normally distributed data or the Kruskal-Wallis test with Bonferroni correction for nonnormally distributed data (α=.05). RESULTS: Significant differences were found in the dimensional accuracy and clinical adaptation among the groups (P<.001). The NPJ group had a lower overall root mean square (RMS) value for dimensional accuracy (22.9 ±1.4 µm) than the SM (27.3 ±5.0 µm) and DLP (36.4 ±5.9 µm) groups (P<.001). The NPJ group had a lower external RMS value (23.0 ±3.0 µm) than the SM group (28.9 ±5.4 µm) (P<.001) and equivalent marginal and intaglio RMS values than the SM group. The DLP group had larger external (33.3 ±4.3 µm), intaglio (36.1 ±10.7 µm), and marginal (79.4 ±12.9 µm) deviations than the NPJ and SM groups (P<.001). With regard to clinical adaptation, the marginal discrepancy was smaller in the NPJ group (63.9 ±27.3 µm) than in the SM group (70.8 ±27.5 µm) (P<.001). No significant differences were found between the SM and NPJ groups in terms of the occlusal (87.2 ±25.5 and 80.5 ±24.2 µm, respectively) and axial (39.1 ±19.7 and 38.4 ±13.7 µm, respectively) discrepancies. The DLP group had larger occlusal (239.0 ±60.1 µm), axial (84.9 ±29.1 µm), and marginal (140.4 ±84.3 µm) discrepancies than the NPJ and SM groups (P<.001). CONCLUSIONS: Monolithic zirconia crowns fabricated using NPJ have higher dimensional accuracy and clinical adaptation than those fabricated using SM or DLP.

Three-point sectional-cast digital method for transferring the interocclusal relationship for full-mouth rehabilitation of worn dentition.

For full-mouth rehabilitation of worn dentition, "diagnostic" interim restorations are required to reestablish the interocclusal relationship. It is important but challenging to transfer the interocclusal relationship and to map the basic form and contour of interim restorations to the final restorations. Alignment of interim restorations and working casts is difficult when using digital workflows because of a lack of consistent hard tissue reference points. The digital workflow presented in this study used a "3-point sectional-cast digital cross-mounting method" to transfer the interocclusal relationship during full-mouth rehabilitation. An intermediate cast was made with three interim restorations: one on an incisor and two on molars. The interocclusal relationship and occlusal morphologies of the diagnostic interim prostheses were transferred and aligned to working casts using the 3-point sectional casts.

Association of childhood asthma with intra-day and inter-day temperature variability in Shanghai, China.

OBJECTIVES: Short-term temperature variability (TV) is associated with the exacerbation of asthma, but little is known about the relative effects of intra- and inter-day TV. We aimed to assess the relative impacts of intra- and inter-day TV on childhood asthma and to explore the modification effects by season. METHODS: A quasi-Poisson generalized linear regression model combined with a distributed lag nonlinear model was adopted to evaluate the nonlinear and lagged effects of TV on childhood asthma in Shanghai from 2009 to 2017. Intra- and inter-day TV was measured with diurnal temperature range (DTR) and temperature changes between neighboring days (TCN), respectively. RESULTS: Increased DTR was associated with the elevated relative risk (RR) of daily outpatient visits for childhood asthma (DOVCA) in both the whole year (RRlag0-14 for the 99th percentile: 1.264, 95% confidence interval (CI): 1.052, 1.518) and cold season (RRlag0-12 for the 99th percentile: 1.411, 95% CI: 1.053, 1.889). Higher TCN in the warm season was associated with the increased RR of DOVCA (RRlag0-14 for the 99th percentile: 2.964, 95% CI: 1.636, 5.373). The number and fraction of DOVCA attributed to an interquartile range (IQR) increase of TCN were higher than those attributed to DTR in both the whole year period and warm season. However, the number and fraction of DOVCA attributed to an IQR increase of DTR were greater than those attributed to TCN in the cold season. CONCLUSIONS: Our results provide novel evidence that both intra- and inter-day TV might be a trigger of childhood asthma. Higher DTR appeared to have greater impacts on childhood asthma in the cold season while an increase in TCN seemed to have bigger effects in the warm season.

Environmental Exposure and Childhood Atopic Dermatitis in Shanghai: A Season-Stratified Time-Series Analysis.

BACKGROUND: Childhood atopic dermatitis (AD) is an inflammatory skin disease which sometimes predisposes to allergies. Environmental factors (low humidity, irritants, etc.) are prominent causative triggers of AD. OBJECTIVES: This study aims to explore the effects of both meteorological factors and air pollutants on childhood AD, and the modification effects by season in Shanghai, China. METHODS: Quasi-Poisson generalized linear regression model, combined with a distributed lag nonlinear model was used to examine the nonlinear and lagged effects of environmental factors on childhood AD from 2009 to 2017 in Shanghai. We also performed a season-stratified analysis to determine the modification effects of environmental exposure by season on childhood AD. RESULTS: There were 1,043,240 outpatient visits for childhood AD in total, at 3 major pediatric hospitals. Low temperature and relative humidity (RH), and high daily temperature difference (DTD) and air pollutants (i.e., NO2) increased the relative risks (RRs) of outpatient visits for childhood AD in the whole year. In the cold season, an increased risk of outpatient visits for childhood AD was associated with low RH (RR 2.26, 95% CI 1.69-3.02) and high NO2 (1.11, 95% CI 1.06-1.17). In the warm season, outpatient visits for childhood AD were associated with low temperature (3.49, 95% CI 3.22-3.77), low RH (1.89, 95% CI 1.74-2.06), high DTD (1.41, 95% CI 1.31-1.53), and high NO2 (1.05, 95% CI 1.03-1.06). CONCLUSIONS: This study suggests that environmental exposure may be a key trigger for outpatient visits for childhood AD with apparent seasonal effects. Tailored preventive strategies to avoid environmental triggers of childhood AD should be developed.

Accuracy of three digital scanning methods for complete-arch tooth preparation: An in vitro comparison.

STATEMENT OF PROBLEM: The accuracy of digital scanning for complete dental arch and implant-supported complete-arch restorations has been reported. However, research addressing the accuracy of digital scanning methods for complete-arch tooth preparation is lacking. PURPOSE: The purpose of this in vitro study was to compare the accuracy of intraoral scanning, impression scanning, and cast scanning for complete-arch preparation. MATERIAL AND METHODS: Maxillary and mandibular jaw typodonts with 28 teeth prepared for complete crowns were used as reference casts and digitized as reference data sets with a desktop scanner. Three digital scanning methods were applied. First, the reference casts were each scanned 10 times with an intraoral scanner to generate the intraoral scanning group data sets. Second, the reference casts were each captured 10 times by using polyvinyl siloxane impression material, and the impressions were scanned with a desktop scanner to generate the impression scanning group data sets. Third, the impressions obtained in the impression scanning group were used to make gypsum casts which were then digitized with a desktop scanner to generate the cast scanning group data sets. Accuracy was determined by trueness and precision. Three-dimensional deviations of the prepared arches and anterior and posterior segments were measured from root mean square values and depicted on color-difference maps. Differences among test groups were analyzed by using a 1-way ANOVA and the post hoc Bonferroni test for normally distributed data or the Kruskal-Wallis test with Bonferroni correction for non-normally distributed data (α=.05). RESULTS: The trueness of the maxillary arch was significantly higher in the impression scanning group than in the cast scanning and intraoral scanning groups (P<.05), but no significant differences were found among the 3 groups of the mandibular arch (P>.05). The precision of both arches was significantly higher in the impression scanning and intraoral scanning groups than in the cast scanning group (P<.05). Color maps showed horizontal symmetrical displacement in the intraoral scanning group relative to the reference data sets and within-group unilateral distal-end distortion. Irregular arch deformations were noted in the impression scanning group, and buccal and occlusal expansion occurred in the anterior-posterior direction in the cast scanning group. Pooled data for anterior teeth indicated that the trueness was lowest in the intraoral scanning group; however, that for the maxillary anterior teeth did not differ, while that for the mandibular anterior teeth differed significantly among groups (P<.05). For the posterior teeth, deviation was the lowest in the impression scanning group, and significant differences were noted in both arches among the 3 groups (P<.05). CONCLUSIONS: Of the methods tested, impression scanning was the most accurate for the creation of a digital cast of a complete prepared arch.

Breastfeeding duration modified the effects of neonatal and familial risk factors on childhood asthma and allergy: a population-based study.

BACKGROUND: Childhood asthma and allergic diseases are a significant global problem. There are inconsistent findings on the associations of delivery mode, the number of children in the household and breastfeeding with childhood asthma and allergic diseases. We assessed these associations and examined whether breastfeeding modified the effects of neonatal and familial risk factors on childhood asthma and allergic diseases. METHODS: A population-based cross-sectional study was conducted in Shanghai, China. A total of 17 primary schools were randomly selected from 13 districts of Shanghai in this study. The International Study of Asthma and Allergies in Childhood questionnaire was adopted to assess the childhood asthma and allergic diseases. Multivariable logistic regression models were used to evaluate the associations between neonatal and familial factors and childhood asthma and allergic diseases, and to examine the modification effects of breastfeeding on the associations assessed. RESULTS: Of 10,464 primary school children aged 6-11 years, the overall prevalence of childhood asthma, allergic rhinitis, urticaria, food allergy and drug allergy was 13.9, 22.7, 15.3, 8.1 and 4.6%, respectively. Male sex, high socioeconomic status, cesarean section delivery, only one child in the household and having family history of allergy were associated with increased odds ratio (OR) of childhood asthma and allergic diseases while longer breastfeeding duration (> 6 months) was inversely associated with these diseases. Longer breastfeeding duration also attenuated the OR of neonatal and familial risk factors on childhood asthma and allergic diseases. For instance, the adjusted OR of childhood asthma in the group of vaginal delivery and breastfeeding duration > 6 months was lowest (0.78, 95% confidence interval: 0.66, 0.92). CONCLUSIONS: Longer breastfeeding duration was inversely associated with childhood asthma and allergic diseases, and also reduced the OR of neonatal and familial risk factors on these diseases. Giving the prevalence of childhood asthma and allergic diseases is rapidly rising across the globe, these findings may have important clinical and public health implications.

Understanding the effects of metal pre-exposure on the sensitivity of zebrafish larvae to metal toxicity: A toxicokinetics-toxicodynamics approach.

Organisms are increasingly tolerant to metal toxicity in the natural ecosystems, which did not match the results of the environmental risk assessment (ERA) of metals based on toxicity data from organisms in the laboratory. Studies have described the effects of pre-exposure to metals on metal toxicity tolerance in terms of the toxicokinetic (TK) process; however, the toxicodynamic (TD) process may be more susceptible to metal pre-exposure. Therefore, to determine whether pre-exposure to low concentrations of silver (Ag) or cadmium (Cd) affects the metal TK and TD processes of zebrafish (Danio rerio) larvae, we investigated four TK-TD model parameters that control tolerance and sensitivity to metal toxicity on the survival. Our results showed that the killing rate (ks) of larvae exposed to high Cd concentrations was significantly lower following pre-exposure to 10 µg/L Cd than that of larvaenot pre-exposed. However, the ks for high Ag concentrations was significantly higher in zebrafish larvae following pre-exposure to 2 µg/L Ag than in larvae not pre-exposed. In other words, a one-day pre-exposure to 2 µg/L Ag rendered the larvae more sensitive to Ag during a subsequent 4-day exposure to higher Ag concentrations, whereas a one-day pre-exposure to 10 µg/L Cd rendered the larvae more tolerance to Cd during a subsequent 4-day exposure to higher Cd concentrations. Our results further the current understanding of toxic metal tolerance mechanisms, both in TK and TD processes, and they will guide future laboratory studies to assess actual pre-exposure scenarios that occur in natural environments. Thus, our study can help reduce uncertainty in testing and improve ecological management concerning metal risk assessments.

Learner behaviors in synchronous online prosthodontic education during the 2020 COVID-19 pandemic.

STATEMENT OF PROBLEM: Synchronous online prosthodontic courses became a popular learning mode during the 2020 COVID-19 pandemic crisis. Nonetheless, the extent of learner participation and completion of these courses remains unknown. PURPOSE: The purpose of this study was to assess learner behaviors in synchronous online prosthodontic continuing education lectures in China during the 2020 COVID-19 pandemic. MATERIAL AND METHODS: All live online prosthodontic courses held by an online dental school in China from February to May 2020 were retrieved. The no-cost lectures could be accessed anonymously and viewed repeatedly on the day of broadcast. Learning behavior data (teacher speaking time, audience total, timing of first visit to the online classroom, viewing time, and completion rate) were obtained. Learning progress was calculated by dividing viewing time by teacher speaking time. When a learner progressed through 95% of a lecture, the lecture was considered completed. RESULTS: A total of 41 781 learners participated in 18 online prosthodontic courses, which had a mean duration of 77.2 ±15.8 minutes. For each lecture, 2321 ±1454 participants attended, with 510 ±404 participants completing each session. There were 13 098 participants (31.35%) who viewed the lectures for less than 1 minute. Approximately half of the participants viewed the lectures for less than 10 minutes, with their learning progress failing to pass 10%. The average completion rate was 21.97%, with variation in completion rate dependent on when a learner first visited the online classroom. Significant differences were found among the lecture completion rates and the timing of the first visit to the online classroom (P<.001). CONCLUSIONS: Synchronous online prosthodontic education courses in China had a high number of participants but low learning progress and completion rates during the 2020 COVID-19 pandemic.

An auxiliary device for screw-retained fixed implant restorations which prevents extrusion of cement into screw-access openings.

For screw-retained fixed implant prostheses, the cement that extrudes onto the margin can be easily removed, but the cement that may intrude into the screw-access opening (SAO) during the extraoral bonding process is difficult to eliminate. This article presents a manufactured auxiliary device that is applied to the extraoral bonding process of screw-retained fixed implant prostheses. This device will prevent excess cement from being left in the SAO.

The Effect of Build Orientation on the Dimensional Accuracy of 3D-Printed Mandibular Complete Dentures Manufactured with a Multijet 3D Printer.

PURPOSE: To compare the dimensional accuracy of 3D-printed mandibular complete dentures with different build orientations. MATERIAL AND METHODS: A mandibular complete denture was digitized as a virtual reference file. The reference file was 3D-printed at the 0°, 45°, and 90° build orientations with a MultiJet 3D printer (Projet MJP 3600 Dental, 3D systems, Rock Hill, SC). A total of 27 complete dentures were 3D-printed with 9 samples for each orientation. All printed dentures were digitized and separated into teeth, denture extension and intaglio test surfaces. The dimensional accuracy (in root mean square, RMS) was evaluated by comparing whole denture and 3 test surfaces with the reference file. One-way analysis of variance (ANOVA) and a Post-Hoc all pairs Bonferroni test were used to determine statistical differences (α = 0.05). RESULTS: For the dimensional accuracy on whole denture, the 45° build orientation group showed the smallest RMS (0.170 ± 0.043 mm) than those of the 0° build orientation group (0.185 ± 0.060 mm, p < 0.001) and 90° build orientation group (0.183 ± 0.044 mm, p < 0.001). For the dimensional accuracy on the teeth, denture extension and intaglio test surfaces, the 45° build orientation group also show the smallest RMS values (0.140 ± 0.044 mm at teeth surface, 0.176 ± 0.058 mm at denture extension and 0.207 ± 0.006 mm at intaglio surface). The 0°and 90° build orientation groups had similar accuracy at the teeth (0.149 ± 0.056 mm versus 0.154 ± 0.056 mm, p = 0.164) and denture extension surfaces (0.200 ±0.025 mm vs 0.196 ± 0.013 mm, p = 1.000). However, 0° build orientation group (0.228 ± 0.010 mm) has significantly higher RMS values then those of 90° build orientation group (0.218 ± 0.057 mm) in the intaglio surface (p = 0.032). The teeth surfaces were most accurate in each build orientation groups, while the intaglio surfaces were least accurate. CONCLUSIONS: The build orientation affected the dimensional accuracy of 3D-printed mandibular complete dentures, and the 45° build orientation resulted in the most accurate 3D-printed denture from a MultiJet 3D printer.

Digital Duplication and 3D Printing for Implant Overdenture Fabrication.

This technical report describes a workflow to fabricate an implant overdenture via digital duplication of an interim complete removable dental prosthesis and additive manufacturing (3D printing). An edentulous patient was provided with an interim maxillary denture after implant placement. After 4 months of healing, the existing interim denture was scanned, duplicated via 3D printing, and used to make the final impression, record the maxillomandibular interocclusal relationship, and transfer the esthetic information to the definitive implant overdenture. The framework of the implant overdenture was digitally designed and manufactured using a direct metal printing (DMP) system. This digital duplication workflow facilitated the implant overdenture fabrication with favorable clinical outcomes.

Integrating Facial and Intraoral Scans for Digital Esthetic and Occlusal Design: A Technical Report.

The provisional prosthesis is a prerequisite for prosthodontic rehabilitation. The purpose of this technique was to register facial and intraoral scans predictably. A 3D virtual patient was created through facial scans, intraoral scans, digital face-bow transfer, and digital cross-articulation technique. This virtual patient allowed predictable positioning of intraoral scans to a virtual articulator by using digital face-bow transfer. The resulting virtual patient facilitated the design of definitive prostheses following a facially generated treatment planning principle. In addition, the virtual articulator was used to improve occlusal design on the definitive prostheses and reduce the need for intraoral adjustment.

Season-stratified effects of meteorological factors on childhood asthma in Shanghai, China.

OBJECTIVES: There has been increasing interest in identifying the adverse effects of ambient environmental factors on asthma exacerbations (AE), but season-stratified effects of meteorological factors on childhood asthma remain unclear. We explored the season-stratified effects of meteorological factors on childhood AE in Shanghai, China. METHODS: Poisson generalized linear regression model combined with a distributed lag nonlinear model was used to examine the lagged and nonlinear effects of meteorological factors on childhood AE after adjustment for putative confounders. We also performed a season-stratified analysis to determine whether the season modified the relationship between meteorological factors and childhood AE. RESULTS: There were 23,103 emergency department visits (EDVs) for childhood AE, including 15,466 boys and 7637 girls during 2008-2017. Most meteorological factors (e.g., temperature, diurnal temperature range (DTR), relative humidity (RH) and wind speed (WS)) were significantly associated with EDVs for childhood AE, even after adjustment for the confounding effects of air pollutants. In the whole year, extreme cold, moderate heat, higher DTR, lower RH and WS increased the relative risk (RR) for childhood AE. In the cold season, lower RH and wind speed increased the risks of childhood AE (RRlag0-28 for the 5th percentile (p5) of RH: 9.744, 95% CI: 3.567, 26.616; RRlag0-28 for the p5 of wind speed: 10.671, 95% CI: 1.096, 103.879). In the warm season, higher temperature and DTR, lower RH and WS increased the RR for childhood AE (RRlag0-5 for the p95 of temperature: 1.871, 95% CI: 1.246, 2.810; RRlag0-2 for the p95 of DTR: 1.146, 95% CI: 1.010, 1.300; RRlag0-5 for the p5 of RH: 1.931, 95% CI: 1.191, 3.128; RRlag0-2 for the p5 of WS: 1.311, 95% CI: 1.005, 1.709). CONCLUSIONS: Extreme meteorological factors appeared to be triggers of EDVs for childhood AE in Shanghai and the effects modified by season. These findings provide evidence for developing season-specific and tailored strategies to prevent and control childhood AE.

Fine Particulate Matter (PM2.5) upregulates expression of Inflammasome NLRP1 via ROS/NF-κB signaling in HaCaT Cells.

Skin, as the major organ of a human body, is constantly exposed to PM2.5 stimulation, which may exert specific toxic influences on the physiology of skin. This study aims to investigate the effect of PM2.5 on the formation of inflammasomes in skin cells and to explore the potential mechanism linking PM2.5 and skin inflammation. Changes in mRNA and protein levels of inflammasome-related genes were detected by real-time PCR and western blot in human immortalized epidermal cells (HaCaT) treated with PM2.5 at multiple concentrations for 24 hours. The expression of NLRP1 was increased significantly both in mRNA and protein levels after PM2.5 exposure while the elevated secretory protein level of IL-1ß in cell culture was detected by ELISA, which is one of the main downstream factors of NLRP1. In addition, the upregulation of NLRP1 and IL-1ß could be reversed by NF-κB inhibitor indicating that PM2.5 may promote NLRP1 expression through activating NF-κB pathway. Furthermore, high ROS level was also found in cells treated with PM2.5 and inhibition of ROS could also reverse NK-κB production stimulated by PM2.5 that means ROS is involved in this skin inflammation process.