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This study aimed to investigate the effects of a peer-led oral health intervention based on the Health Belief Model and the Social Cognitive Theory on improving oral health among Hong Kong adolescents. The study adopted a cluster-randomized controlled trial design, and 1184 students in 12 schools were randomized to intervention or control groups. After baseline assessment, the intervention group received a peer-led theory-based oral health intervention, while the control group received booklets for oral health promotion. Self-reported brushing and flossing, Health Belief Model/Social Cognitive Theory constructs, and oral health–related quality of life (OHRQoL) were measured at baseline, 6 months, and 12 months, and dental plaque accumulation and caries status were measured at baseline and 12 months. The trial was registered at https://www.clinicaltrials.gov (NCT03694496). Brushing, flossing, and OHRQoL improved more in the experimental group than in the control group at the 6-month follow-up compared with baseline (p <.001). The mean gain score difference was.81 for brushing,.47 for flossing, and -2.51 for OHRQoL. At the 12-month follow-up, the mean gain score of brushing frequency, plaque index, caries status, and OHRQoL were.18, −.28, −.32, and −2.79, respectively, which all sustained the significant difference (p <.001). Our findings suggested that the Health Belief Model combined with Social Cognitive Theory in a peer-led intervention is effective to increase self-reported brushing frequency and improve oral hygiene status and OHRQoL among adolescents. [ABSTRACT FROM AUTHOR]

The transplantation of stem cells/tissue constructs into root canal space is a promising strategy for regenerating lost pulp tissue. However, the root canal system, which is cone shaped with a taper from the larger coronal end to the smaller apical end, limits the vascular supply and, therefore, the regenerative capacity. The current study aimed to fabricate built-in microchannels with different tapers to explore various approaches to endothelialize these microchannels. The fluidic microchannels with varying tapers (parallel, 0.04, and 0.06) were fabricated within gelatin methacryloyl (GelMA) hydrogel (with or without stem cell from the apical papilla [SCAP] encapsulation) of different concentrations (5%, 7.5%, and 10% [w/v]). Green fluorescent protein–expressing human umbilical vein endothelial cells (HUVECs-GFP) were seeded alone or with SCAPs in coculture into these microchannels. Angiogenic sprouting was assessed by fluorescence and a confocal microscope and ImageJ software (National Institutes of Health, Bethesda, MD). Immunostaining was conducted to illustrate monolayer formation. Data were statistically analyzed by 1-way/2-way analysis of variance. HUVEC-only inoculation formed an endothelial monolayer inside the microchannel without angiogenic sprouting. HUVECs-GFP/SCAPs cocultured at a 1:1 ratio produced the longest sprouting compared with the other 3 ratios. The average length of the sprouting in the 0.04 taper microchannel was significantly longer compared with that in the parallel and 0.06 taper microchannels. Significant differences in HUVEC-GFP sprouting were observed in 5% GelMA hydrogel. Encapsulation of SCAPs within hydrogel further stimulated the sprouting of HUVECs. The coculture of SCAPs and HUVECs-GFP at a ratio of 1:1 in 0.04 taper fluidic microchannels fabricated with 5% (w/v) GelMA hydrogel with SCAPs encapsulated was found to be the optimal condition to enhance angiogenesis inside tapered microchannels. [ABSTRACT FROM AUTHOR]

Control measures aiming for removing droplets generated during dental treatments have been attracted increasing attention after COVID-19 pandemic, but the emission characteristics of droplets around the source (namely, the mouth) have still not been fully understood. The present study investigated experimentally the emission characteristics of droplets around mouth during typical dental treatments. A manikin being treated by portable dental instruments simulated the dental treatments, while the laser light scattering technique and particle image velocimetry (PIV) technique were employed to perform the measurements. The peak mass fraction of droplets occurs around the droplet size from 20 μm to 100 μm, while the mass fraction of droplets with the diameter less than 200 μm accounts for over 80 %. By fitting with the Rosin-Rammler equation, the mean size of droplets (d ‾) are 54.96 and 98.93, and the size distribution parameter (n) are 1.35 and 1.58, respectively, for the process of air-powder-polishing and ultrasonic scaling. The dominant emission direction of droplets is towards the dummy' head and chest. The emitted droplets formed approximately a cone shape, and its angle varied from 25° to 83° for different conditions. The maximum velocity of droplets at the location near the dummy's mouth exceeds 1.0 m/s for most conditions. The injecting flow rate and treated tooth position are the major factors influencing the emission direction, angle, and velocity. It is expected that the results can further increase our understanding of emission characteristics of droplets and provide accurate initial conditions for CFD simulations. • Emission characteristics of droplets during typical dental treatments were tested. • Mass fraction of droplets with the diameter less than 100 μm accounted for over 80 %. • Cone angle of emitted droplets varied from 37° to 71° for different conditions. • Maximum velocity of emitted droplets exceeded 1.0 m/s for most conditions. • Flow rate and tooth position determined considerably the emission characteristics. [ABSTRACT FROM AUTHOR]

Abstract In order to improve the effectiveness of a local exhaust ventilation system, an attempt is the changed hood geometry by adding a plate. The near fields of a simple exhaust and the annular slotted hoods with different slot widths are measured by a 2D-particle image velocimetry (PIV) system. The time-averaged velocity fields show that the slotted-hood designs enhance the capture velocities beyond half a diameter (0.5D) downstream the hood. The relative velocity increase coefficient (IC) along the hypothetical boundaries in the near fields was proposed to compared with the simple exhaust and determine the effect of slot width on the capture velocity enhancement, the IC for different slot widths is approximately 109%–130%. To predict the velocity at downstream of the hood for a given slot width and velocity, a unimodal-skewed distribution model was developed with a correlation coefficient of approximately 94%. Regarding turbulence statistics, the influence of the plate only involves the near hood region. The higher-order statistics also show no obvious differences between slotted hoods with different slot widths. In general, this study not only motivates us to design and improve the performance of LEV systems for forced advection problems by adding a baffle plate, but also provides benchmark flow data for a follow-up numerical simulation study. Highlights • 2D-PIV experiments testing annular slotted hoods with different slot widths were conducted. • The capture velocity is increased under the positive effect of the plate. • Empirically derived centerline velocity equations were obtained. • The slot width modifies the turbulent intensity distribution. [ABSTRACT FROM AUTHOR]

People spend most of their lives in buildings and unavoidably perceive the sound in their surroundings. The understanding of the human perceptual dimensions of sound is important for obtaining the occupant-oriented decision-making in future building designs. This paper presented a systematic review of the studies analyzing the human perceptual dimensions of sound. Studies that used of principal component analysis (PCA) or factor analysis (FA) for the semantic differential method (SDM) applications of the subjective measurements of the human perceptions of sound were identified in the study selection process and included in the quantitative analysis. Forty-five eligible studies covered a wide range of sounds in the general indoor environment, including machines, building facilities, human voices, human activities, transportations, and the urban environment. The meta-analysis of the factor analysis integrated the data from the 39 individual studies and generated the evidence-based results of the review. Three major perceptual dimensions of sound were found to be ”Evaluation,” ”Potency,” and ”Activity” which referred to the human general judgment, the sensitivity to the magnitude, and the sensation of the temporal and spectral compositions of the perceived sound respectively. It implied that not only the energy level but also the energy distribution of the stimulations in the environment affects our perceptions. The review also provided insights into the selection of the suitable perceptions, the suggestions on the SDM applications, and the acoustics index development for the quantification of the psychological impacts of sound on the occupants in the indoor and outdoor environment. This research provides directions for future psychoacoustics studies to analyze the correlations between the objective stimulations and the human perceptions. [ABSTRACT FROM AUTHOR]

Background/purpose There is a need to comprehensively investigate the relationship between tooth eruption and obesity. The study aimed to investigate the relationship between erupted permanent tooth number and obesity among 12-year-old children in a population-based study. Materials and methods A random sample of 806 12-year-old schoolchildren in Hong Kong was recruited. Oral examinations were conducted and the eruption status of the permanent teeth was assessed. Body height, body weight, waist circumference (WC), hip circumference, and triceps skinfold thickness (TRSKF) were measured to assess the adiposity statuses [weight-height ratio (W/H) and body mass index (BMI) for general obesity; WC and waist-hip ratio (WHR) for central obesity; and TRSKF for peripheral obesity]. The relationships between erupted permanent tooth number and adiposity statuses were examined in bivariate analysis and analysis of covariance. Results The response rate was 82.9% ( n = 668/806). Three hundred and forty-six (50.9%) children had 28 teeth erupted. Second molars had the highest rate of noneruption (17.5–35.8%). The mean number and standard deviation (SD) of erupted permanent tooth were 26.4 (2.4). The mean value and SD were 31.1 (6.3) for W/H, 19.8 (3.7) for BMI, 70.4 (9.4) for WC, 0.82 (0.06) for WHR, and 11.8 (4.5) for TRSKF, respectively. After accounting for sociodemographic factors, analysis of covariance identified that W/H, BMI, WC, and WHR were positively associated with the number of erupted permanent teeth (P < 0.01). Conclusion Erupted permanent tooth number was positively associated with obesity (general and central) among a population-based sample of 12-year-old children in Hong Kong. [ABSTRACT FROM AUTHOR]

Given the difficulty of experimental measurement of respiratory airflow and dispersion through a face mask, accurate numerical simulation is an important method to increase the understanding of the health effect of face masks and to develop high-performance ones. The objective of this study is to develop such an accurate modeling framework based on computational fluid dynamics (CFD) theory and method. For model validation, the flow characteristics through the face mask were tested experimentally, and the air speed and exhaled pollutant concentration in the breathing zone were measured with human subjects. The influence of gird division, time step size, and turbulence model on simulation accuracy were investigated. The result shows that the viscous resistance coefficient and inertial resistance coefficient of face masks (surgical masks) were 3.65 × 109 and 1.69 × 106, respectively. The cell size on the surface of face masks should not be larger than 1.0 mm; the height of the first layer cells near the face masks should not be larger than 0.1 mm; and the time step sizes discretizing the breathing and coughing periods should not be more than 0.01 s and 0.001 s, respectively. The results given by LES model show closer agreement with the experimental data than RANS models, with approximately 10% relative deviation for the air speed near the face mask. Overall, the SST k-ω model performs the best among the RANS models, especially for the air speed. The findings obtained form a CFD modeling framework for an accurate prediction of airflow and dispersion problems involving face masks. [Display omitted] • Comprehensive validation of face mask simulation including penetration and leakage. • Grid division, cell size, and cell distribution on and around face masks recommended. • Time step sizes should not be more than 0.01 s (breathing) and 0.001 s (coughing). • LES model is more accurate than RANS models for airflow and dispersion prediction. • SST k-ω model performs the best among the RANS models, especially for air speed. [ABSTRACT FROM AUTHOR]

Background: Many countries have recently experienced a rapid increase in the demand for forensic age estimates of unaccompanied minors. Hong Kong is a major tourist and business center where there has been an increase in the number of people intercepted with false travel documents. An accurate estimation of age is only possible when a dataset for age estimation that has been derived from the corresponding ethnic population. Thus, the aim of this study was to develop and validate a Reference Data Set (RDS) for dental age estimation for southern Chinese.Materials and Methods: A total of 2306 subjects were selected from the patient archives of a large dental hospital and the chronological age for each subject was recorded. This age was assigned to each specific stage of dental development for each tooth to create a RDS. To validate this RDS, a further 484 subjects were randomly chosen from the patient archives and their dental age was assessed based on the scores from the RDS. Dental age was estimated using meta-analysis command corresponding to random effects statistical model. Chronological age (CA) and Dental Age (DA) were compared using the paired t-test.Results: The overall difference between the chronological and dental age (CA-DA) was 0.05 years (2.6 weeks) for males and 0.03 years (1.6 weeks) for females. The paired t-test indicated that there was no statistically significant difference between the chronological and dental age (p > 0.05).Conclusion: The validated southern Chinese reference dataset based on dental maturation accurately estimated the chronological age. [ABSTRACT FROM AUTHOR]

The infection risk assessment associated with the contaminant inhalation can provide a scientific basis for formulating mitigation measures. Previous studies on the breathing zone are primarily based on the assumption of the steady formation and homogeneous property, while it might not be applicable for short-term events. Large-eddy simulation (LES) is employed in the present study, as well as two computational thermal manikins with detailed facial features and transient breathing conditions. Exposure risks in eight commonly used monitor points are compared in short-term events and under steady-state conditions. Three representative physical distances between room occupants are investigated, namely 0.35 m, 1.0 m, and 1.5 m. Based on the statistical difference in the contaminant distribution at a short physical distance, the breathing zone could be identified from the time-averaged concentration field. The results highlight that the previously defined breathing zone ignores unsteady airflow characteristics, significantly impacting the exposure risk estimation in short-term events. Owing to the substantial temporal variation of the contaminant in the identified breathing zone, the instant exposure risk analysis in short-term events should consider its turbulence intensity and concentration fluctuation characteristic. Overall, instead of using the identified breathing zone. Point_A, Point_B, and Point_C should be employed to evaluate infection risk in short-term events. The localized method with direct interference on the respiratory airflow should be recommended in short-term events. • Breathing zone is examined in short-term events and under steady-state conditions. • Formation of the breathing zone should be treated as unsteady in short-term events. • Instant exposure risk in short-term events can significantly vary with time. • Point_E, at the nose tip, is not optimal to represent the inhaled concentration. • Localized ventilation and physical barriers should be highly recommended. [ABSTRACT FROM AUTHOR]

Background/purpose Dental anxiety is closely related to one's past experience in dental clinics. However, little is known about what clinical, environmental, and psychological aspects provoke anxiety in dental patients. Extending on previous work in The Netherlands which explored anxiety provoking stimuli, the objective of the study was to develop a Dental Anxiety Provoking Scale (DAPS) that measures the degree to which anxiety was provoked by dental stimuli and to identify the underlying factor structure of the DAPS. Materials and methods Four hundred and sixty study participants were recruited from two universities in Hong Kong. Each participant completed a self-administrated questionnaire that included a 73-item measure of dental anxiety provoking stimuli, and a four-item dental anxiety scale. Results Results of exploratory and confirmatory factor analyses showed that the DAPS has seven factors, namely, dental check-up, injection, scale and drill, surgery, empathy, perceived lack of control, and clinic environment, and has 27 items. Results of structural equation modeling showed that three factors of the DAPS; dental check-up, surgery, and clinic environment, had a significant effect on dental anxiety score. The Cronbach α values ranged from 0.76 to 0.92 while the composite reliability values ranged from 0.78 to 0.93. The average variance extracted (AVE) values ranged from 0.55 to 0.81. The minimum AVE value was greater than the square of correlation value for each pair of factors. Conclusion The study developed and validated the DAPS covering a wide range of dental anxiety provoking stimuli, findings were concise enough to be used in clinical based studies. [ABSTRACT FROM AUTHOR]

Objectives To evaluate the effects of various chemical surface modifications on adhesion between zirconia and resin adhesive. Material and methods Pre-sintered zirconia discs were sectioned from commercial cylindrical blocks and polished with abrasive papers under running tap water. All the discs were randomly divided into five study groups according to the methods of surface treatment, including: the control group (fully sintered, without any modification), group S (fully sintered and sandblasted with silica coated alumina particles), group HN (fully sintered and etched with a blend of mineral acid solution at 100 °C for 25 min), group HF (fully sintered and etched with 48% hydrofluoric acid solution at 100 °C for 25 min), and group Si (coated with silica particles and then fully sintered). The mean value of surface roughness was evaluated before further treatment. Resin stubs (3.6 mm in diameter and 3 mm in height) were adhered and light cured on each zirconia disc after the application of a silane coupling agent. In each group, all the samples were further divided into three subgroups with each n =12, one for the measurement of initial adhesion strength (shear bond) value and the other two were tested after thermal cycling for 10,000 and 20,000 cycles, respectively. The results were analyzed with two-way ANOVA and Turkey HSD ( p <0.05). XRD technique was utilized in the examination of zirconia surface crystallinity. The morphological appearance of zirconia surface after surface treatment was observed with SEM. Results The control group showed the lowest initial shear bond strength (SBS) value (16.8±2.4 MPa) and did not survive the aging treatments. All the investigated surface treatments improved resin zirconia bond strength significantly, the group S displaying the highest initial value of 25.1±2.7 MPa. However, the highest resistance to the aging effects of thermal cycling was found in group Si. It was further shown in the XRD examination that only the grit-blasting caused the crystalline transformation from tetragonal phase to monoclinic phase (T→M). On the other hand, such a phase transformation could not be detected in all the other four groups. Significance Resin zirconia adhesion could be effectively improved by both HF etching and silica coating on zirconia surface, without leading to a T→M crystalline phase transformation. [ABSTRACT FROM AUTHOR]

Abstract: Background: Estimation of age of an individual can be performed by evaluating the pattern of dental development. A dataset for age estimation based on the dental maturity of a French–Canadian population was published over 35 years ago and has become the most widely accepted dataset. The applicability of this dataset has been tested on different population groups. Aim: To estimate the observed differences between Chronological age (CA) and Dental age (DA) when the French Canadian dataset was used to estimate the age of different population groups. Materials and methods: A systematic search of literature for papers utilizing the French Canadian dataset for age estimation was performed. All language articles from PubMed, Embase and Cochrane databases were electronically searched for terms ‘Demirjian’ and ‘Dental age’ published between January 1973 and December 2011. A hand search of articles was also conducted. Results: A total of 274 studies were identified from which 34 studies were included for qualitative analysis and 12 studies were included for quantitative assessment and meta-analysis. When synthesizing the estimation results from different population groups, on average, the Demirjian dataset overestimated the age of females by 0.65 years (−0.10 years to +2.82 years) and males by 0.60 years (−0.23 years to +3.04 years). Conclusion: The French Canadian dataset overestimates the age of the subjects by more than six months and hence this dataset should be used only with considerable caution when estimating age of group of subjects of any global population. [Copyright &y& Elsevier]

The exposure risk of droplets and aerosols emitted from the oral cavity to the dental professionals and patients has received more attention especially the ongoing outbreak of COVID-19. The aim of this study is to address the question about how the use of the high-volume evacuation (HVE) alters the risk profiles compared with the situation only personal protective equipment (PPE). The risk profiles of the different situations were analyzed in terms of droplet velocity, flow field characteristics, and particle removal efficiency. The ultrasonic scaling with suction was performed in the mock-up experimental dental clinic, and the instantaneous moment when the HVE acted on the droplets was visualized using a laser light scattering technique. From the results of the velocity profiles, the hypothesis about the moderate effect of the HVE on high-velocity small droplets near the mannequin's mouth had been firstly proven in this study. The suction can be characterized as low-threshold equipment to bring substantial benefits to reduce the area of the contaminated region. Once the cooperation of suction, the pair of vortexes that were in the face shield area of the dental professional would be eliminated, removing the high-level contaminated region near the breathing area of dental professionals. Compared with the low and medium volume evacuation, the particle removal efficiency of the HVE was more stable at 60%. The research will provide references to the HVE recommendation in the dentistry clinical practice guidelines. • Proving the hypothesis about the moderate effect of HVE on high-velocity droplets. • Suction can be characterized as low-threshold equipment to bring substantial benefits. • Altering the risk profiles by eliminating the pair of vortexes in the face shield area. • The particle removal efficiency of the HVE was more stable at 60%. • The research would provide references to the dentistry clinical practice guidelines. [ABSTRACT FROM AUTHOR]

• The laser light scattering method has been proposed in a mock-up dental clinic. • Fallow time was calculated by the decay curves of suspended particles. • Fallow time was in the range of 27–35 min without any mitigation measures. • The cooperation of HVE[IO] can help to reduce the fallow time by 3–11 min. In time, dental health care has slowly expanded beyond emergency treatment to treat oral diseases. How to reduce the cross-transmission risk in dental surgery has raised much more attention. Considering the lack of consistency of fallow time (FT) in its necessity and duration, the highly sensitive laser light scattering method has been proposed to visualize the airborne lifetime and decay rate of suspended particles in the dental surgery environment. The FT is defined as when the number of suspended particles drops to the level that the next patient can safely enter after the aerosol-generating procedures (AGPs). The ultrasonic scaling was performed in the mock-up experimental dental clinic with 6 air changes per hour (ACH), and the instantaneous moments of the droplets were recorded by a high-speed camera. Without any mitigation measures, the estimated FT in the single dental surgery environment with 6 ACH was in the range of 27–35 min, significantly affecting the number of daily dental services. Despite the cooperation of high-volume evacuation (HVE [IO]) cannot eliminate the FT to zero minutes, the equipment could reduce the required FT by 3–11 min for the suspended particles reducing the baseline levels. Owing to the longer airborne lifetime of suspended particles, the relevant protection equipment, especially respiratory protection, is quite essential in dental surgery. The obtained results of this study will provide evidence to establish the revised FT in dental surgery guidelines and protect the health and wellbeing of urban dwellers. [ABSTRACT FROM AUTHOR]

Objective: To investigate the longitudinal association between obesity and dental caries among adolescents.Study Design: The present cohort study was conducted among a random sample of 12-year-old adolescents in Hong Kong. Two rounds of follow-up were performed when the participants were aged 15 and 18 years. A total of 668 participants were included at age 12 years, and 282 of them completed all 3 phases of data collection. Body mass index, waist circumference, waist-to-hip (WHR) ratio, waist-to-height ratio, and triceps skinfold thickness were measured as indices of obesity. Dental caries were assessed by the number of decayed, missing, and filled permanent teeth (DMFT).Results: The percentage of underweight adolescents increased significantly from 6.0% to 23.8% during the observation period (P <.001). Body mass index, waist circumference, waist-to-hip ratio, and waist-to-height ratio were related to frequency of tooth brushing at age 15 and 18 years. The prevalence of dental caries was 25.5%, 53.2%, and 62.1% at 12, 15 and 18 years, respectively. At age 18 years, mean DMFT of participants whose WHR at age 15 years was below the median value was 0.707 times (ie, 29.3%) lower than the DMFT of those whose WHR was above the median (P = .028). Participants with greater DMFT at age 15 demonstrated significantly increased probability of having WHR above the median (OR 1.135; 95% CI 1.01-1.28; P = .041) at age 18 years.Conclusion: There is longitudinal association between central obesity and dental caries experience among adolescents aged 15-18 years. [ABSTRACT FROM AUTHOR]