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The single-function agents with wide-spectrum activity which tend to disturb the ecological balance of oral cavity cannot satisfy dental treatment need. A multi-functional agent with specifically targeted killing property and in situ remineralization is warranted for caries management. A novel multi-functional agent (8DSS-C8-P-113) consisting of three domains, i.e., a non-specific antimicrobial peptide (AMP) (P-113), a competence stimulating peptide (C8), and an enhancing remineralization domain (8DSS), is fabricated and evaluated in this study. The findings demonstrates that 2 μM mL−1 of 8DSS-C8-P-113 eliminates planktonic Streptococcus mutans (S. mutans) without disrupting the oral normal flora. At a concentration of 8 μM mL−1, it exhibits the ability to prevent S. mutans' adhesion. Furthermore, 8DSS-C8-P-113 self-assembles a hydrogel state at the higher concentration of 16 μM mL−1. This hydrogel self-adheres on the tooth surface, resisting acid attack, eradicating S. mutans’ biofilm, and inducing mineralization in order to facilitate the repair of demineralized dental hard tissue. Its significant effectiveness in reducing the severity of dental caries is also demonstrated in vivo in a rat model. This study suggests that the multi-functional bioactive AMP 8DSS-C8-P-113 is a promising agent to specifically target pathogen, prevent tooth demineralization, and effectively induce in situ bio-mimic remineralization for the management of dental caries.

Objectives: To investigate the association of salivary and gingival crevicular fluid (GCF) biomarkers with periodontal status and obesity in children and adolescents. Data/sources: A literature search up to July 2023 was conducted through PubMed, Web of Science, Embase, ProQuest Medical Database, ProQuest SciTech Premium Collection, and the Cochrane Library. Observational studies comparing salivary and GCF biomarkers in children and adolescents with compromised periodontal status and/or obesity were included for data extraction. A meta-analysis was performed to estimate the overall standardised mean difference. Study selection: Fifteen observational studies met the inclusion criteria and were included in this systematic review. Meta-analysis was only applicable in synthesising the dyadic relationship between GCF biomarkers and obesity. The results demonstrated that children and adolescents with obesity had significantly higher GCF levels of tumour necrosis factor-alpha (SMD:0.56; 95% CI:0.07, 1.04), adiponectin (SMD:0.33; 95% CI:0.06, 0.60), leptin (SMD:0.52; 95% CI:0.15, 0.90), and interleukin-1 beta (SMD:0.71; 95% CI:0.44, 0.99) than those with normal weight. Conclusion: To date, no study has well addressed the triadic association between salivary or GCF biomarkers, periodontal status, and obesity among children and adolescents. Further in-depth, high-quality studies are required to investigate these associations. Clinical significance: Periodontal disease and obesity are growing public health crises worldwide. Their relationship has been intensively studied. Investigating the salivary or GCF biomarkers alterations could help better understand the relationship between periodontal disease and obesity, which would assist in tailoring future oral health promotion programs.

Developmental changes of facial shape are commonly investigated through geometric morphometrics. A limitation with this approach is the inability to investigate patterns of morphological changes at local scale. This could be addressed through quantifying the deformation required to deform one shape to another. This study aimed to investigate changes in mean, rate and variance of facial shape at local scale using geometric morphometrics through deformation perspective. A total of 2112 Europeans 3 to 40 years old from the three-dimensional Facial Norms project were included. Shape and rate trajectories from partial least-squares regressions revealed that the developmentally protrusive nasal bridge was due to local expansion in surrounding tissues as opposed to shape changes in nasal bridge per se. Local expansion of the supraorbital region, in particular the medial part in males, resulted in the sloping forehead and deep-situated eyes with development. Facial shape variation increased nonlinearly with age (p < 0.05), with features having larger rate of change becoming more developmentally diversified. In summary, our deformation perspective facilitates unravelling morphogenetic processes underlying shape changes. Our extended analytical scope inspires novel measures worthy of consideration while establishing facial growth charts. The analytical framework in this study is broadly applicable for analysis of shape changes in general.

Abstract Various materials are used in bone tissue engineering (BTE). Graphene oxide (GO) is a good candidate for BTE due to its antibacterial activity and biocompatibility. In this study, an innovative biomaterial consists of GO, agarose and hydroxyapatite (HA) was synthesized using electrophoresis system. The characterization of the synthesized biomaterial showed that needle-like crystals with high purity were formed after 10 mA/10 h of electrophoresis treatment. Furthermore, the calcium-phosphate ratio was similar to thermodynamically stable HA. In the synthesized biomaterial with addition of 1.0 wt% of GO, the colony forming units test showed significantly less Staphylococcus aureus. Initial attachment of MC3T3-E1 cells on the synthesized biomaterial was observed which showed the safety of the synthesized biomaterial for cell viability. This study showed that the synthesized biomaterial is a promising material that can be used in BTE.

Conventional dental materials lack of the hierarchical architecture of enamel that exhibits excellent intrinsic-extrinsic mechanical properties. Moreover, restorative failures frequently occur due to physical and chemical mismatch between artificial materials and native dental hard tissue followed by recurrent caries which is caused by sugar-fermenting, acidogenic bacteria invasion of the defective cite. In order to resolve the limitations of the conventional dental materials, the aim of this study was to establish a non-cell-based biomimetic strategy to fabricate a novel bioactive material with enamel-like structure and antibacterial adhesion property. The evaporation-based, bottom-up and self-assembly method with layer-by-layer technique were used to form a large-area fluorapatite crystal layer containing antibacterial components. The multilayered structure was constructed by hydrothermal growth of the fluorapatite crystal layer and highly conformal adsorption to the crystal surface of a polyelectrolyte matrix film. Characterization and mechanical assessment demonstrated that the synthesized bioactive material resembled the native enamel in chemical components, mechanical properties and crystallographic structure. Antibacterial and cytocompatibility evaluation demonstrated that this material had the antibacterial adhesion property and biocompatibility. In combination with the molecular dynamics simulations to reveal the effects of variables on the crystallization mechanism, this study brings new prospects for the synthesis of enamel-inspired materials.

The durability of the resin–dentin bonding interface is a key issue in clinical esthetic dentistry. Inspired by the extraordinary bioadhesive properties of marine mussels in a wet environment, we designed and synthetized N-2-(3,4-dihydroxylphenyl) acrylamide (DAA) according to the functional domain of mussel adhesive proteins. DAA’s properties of collagen cross-linking, collagenase inhibition, inducing collagen mineralization in vitro, and as a novel prime monomer for clinical dentin adhesion use, its optimal parameters, and effect on the adhesive longevity and the bonding interface’s integrity and mineralization, were evaluated in vitro and in vivo. The results showed that oxide DAA can inhibit the activity of collagenase and cross collagen fibers to improve the anti-enzymatic hydrolysis of collagen fibers and induce intrafibrillar and interfibrillar collagen mineralization. As a primer used in the etch-rinse tooth adhesive system, oxide DAA can improve the durability and integrity of the bonding interface by anti-degradation and mineralization of the exposed collagen matrix. Oxidized DAA (OX-DAA) is a promising primer for improving dentin durability; using 5% OX-DAA ethanol solution and treating the etched dentin surface for 30 s is the optimal choice when used as a primer in the etch-rinse tooth adhesive system.

Abstract Background Accurate appraisal of burden of adolescents and young adults (AYAs) cancers is crucial to informing resource allocation and policy making. We report on the latest estimates of burden of AYA cancers in 204 countries and territories between 1990 and 2019 in association with socio-demographic index (SDI). Patients and methods Estimates from the Global Burden of Disease study 2019 were used to analyse incidence, mortality, and disability-adjusted life years (DALYs) due to AYA cancers at global, regional, and national levels by sex. Association between AYA cancer burden and SDI were investigated. Burdens of AYA cancers were contextualized in comparison with childhood and older adult cancers. All estimates are reported as counts and age-standardized rates per 100,000 person-years. Results In 2019, there were 1.2 million incident cases, 0.4 million deaths, and 23.5 million DALYs due to AYA cancers globally. The highest age-standardized incidence rate occurred in Western Europe (75.3 [Females] and 67.4 [Males] per 100,000 person-years). Age-standardized death (23.2 [Females] and 13.9 [Males] per 100,000 person-years) and DALY (1328.3 [Females] and 1059.2 [Males] per 100,000 person-years) rates were highest in Oceania. Increasing SDI was associated with a higher age-standardized incidence rate. An inverted U-shaped association was identified between SDI and death and DALY rates. AYA cancers collectively is the second leading cause of non-communicable diseases-related deaths globally in 2019. DALYs of AYA cancers ranked the second globally and the first in low and low-middle SDI locations when compared with that of childhood and older adult cancers. Conclusion The global burden of AYA cancers is substantial and disproportionally affect populations in limited-resource settings. Capacity building for AYA cancers is essential in promoting equity and population health worldwide.

Dental caries is a major public health problem. Streptococcus mutans (S. mutans) are the main etiologic pathogens in dental caries and cause tooth hard tissue demineralization. To prevent dental caries, it is important to inhibit S. mutans and induce tooth remineralization. In this study, we combined a self-assembled lysozyme with polyphemusin I (PI) to form a multi-functional membrane for inhibiting S. mutans and inducing remineralization. The normal enamel coated with lysozyme nanofilm could adsorb significant more PI. After combining with PI, the coated enamel could kill more S. mutans and had the superior ability in inhibiting biofilm formation. In addition, the coated enamel combined with PI could prevent the loss of calcium and phosphate ions. In the pH cycling, the coated enamel regenerated more crystals than normal enamel did. The coated enamel combined with PI had a significant lower lesion depth (72.45 ± 4.07 μm) compared to normal enamel combined with PI (93.30 ± 7.64 μm) after S. mutans demineralization. Moreover, the lysozyme nanofilm and PI had good biocompatibility. Accordingly, the formed multi-functional membrane could be a promising strategy for preventing dental caries.

Abstract Background To investigate changes in facial morphology during the first six months of orthodontic treatment among adult females receiving orthodontic treatment. Methods 43 adult females receiving orthodontic treatment were randomly recruited. 3D facial images were taken at baseline (T0), three months (T1), and six months (T2) after treatment initiation. Spatially dense facial landmarks were digitized to allow for sufficient details in characterization of facial features. 3D geometric morphometrics and multivariate statistics were used to investigate changes in mean and variance of facial shape and facial form associated with treatment. Results We observed statistically significant changes in facial shape across the three treatment stages (p = 0.0022). Pairwise comparisons suggested significant changes from T0 to T1 (p = 0.0045) and from T0 to T2 (p = 0.0072). Heatmap visualization indicated that the buccal and temporal region were invaginated while the labial region became protruded with treatment. The magnitude of shape change was 0.009, 0.004, and 0.010 from T0 to T1, T1 to T2, and T0 to T2, respectively, in unit of Procrustes distance. The average magnitude of change per-landmark was 1.32 mm, 0.21 mm, and 1.34 mm, respectively. Changes in mean facial form were not statistically significant (p = 0.1143). No changes in variance of facial shape were observed across treatment stages (p > 0.05). Conclusion Rate of facial changes was twice as fast during the first three months as that during fourth to sixth month. Buccal and temporal region became invaginated while labial region became protruded with treatment.

Abstract Background Biting objects was a parafunctional oral habit among children with special care needs. Chewing or biting toothbrushes could expedite the process of toothbrush wear. However, few studies evaluated the deterioration levels of toothbrushes used by children with special needs. This study aimed to assess the deterioration level of toothbrushes used by children with special care needs, and collect parents’ feedbacks to improve the design of children’s toothbrushes. Methods The cross-sectional study recruited 277 children who had special care needs. Children’s toothbrushing behaviors, background information, and parents’ comments on toothbrushes were obtained. Toothbrush deterioration was assessed by bristle wear and bite mark scores. Higher scores indicated severe deterioration. Results Three hundred twenty-one toothbrushes were collected. Children who used 2 to 6 toothbrushes in a 3-month period showed higher toothbrush deterioration scores than children who used a single toothbrush. Over 40% children’s toothbrushes presented excessive wear. Excessive wear was associated with social skills and parents’ education background. Distinct bite marks tended to exist on toothbrushes which had been used by children who showed challenging behaviors during toothbrushing (OR = 1.96, 95%CI1.15–3.32, p

Abstract Background Oral health belief is a prerequisite of changing oral health behaviors especially during adolescence. However, there is a paucity of well-established questionnaire for use among adolescents. This study aimed to develop and validate an instrument to evaluate adolescents’ beliefs about oral health behaviors using health belief model. Methods A preliminary 43-item questionnaire was developed by an expert panel. Then the questionnaire was finalized by decreasing the number of items to 35 by analyzing the results from face validity and factor analysis from 421 Hong Kong secondary school students. The content validity were evaluated by a panel of 2 behavioral scientists, 2 dentists, 2 schoolteachers and 10 adolescents. The construct validity of the questionnaire was assessed by performing exploratory factor analysis (EFA) and confirmatory factor analysis (CFA). The Cronbach’s alpha coefficient, item-total correlation and intraclass coefficient were used to test its reliability. In addition, to confirm its applicability, multiple regression analysis and path analysis were used to evaluate the possibility of HBM as predictors for oral health behaviors and oral hygiene status. Results The initial analysis extracted six factors that jointly accounted for 62.47% of the variance observed. Based on CFA, the final version of the questionnaire consisted of 35 items and the data of the final version fitted the model well. The Cronbach’s alpha coefficient for the subscale (> 0.7), item-total correlations (0.47–0.91) and the intraclass coefficient (0.82–0.91) were all above acceptable thresholds. The results of multiple regression analysis and path analysis confirmed its ability to predict oral health behaviors and status. Conclusions The present findings indicate satisfactory validity, reliability and applicability of the proposed Oral Health Behavior Questionnaire for Adolescents based on the Health Belief Model (OHBQAHBM) for measuring oral health beliefs of adolescents. This questionnaire can be used as an instrument to measure oral health beliefs and predict oral health behavior and oral hygiene status of adolescents.

Abstract Background There is a lack of cohort studies on the influence factors of oral health-related quality of life (OHRQoL). This study aimed to follow subjects from age 12 to 18 to analyse the sociodemographic and clinical factors that may influence OHRQoL. Methods This cohort study selected a representative sample from Hong Kong. Periodontal status and caries were examined according to WHO criteria. Four orthodontic indices were used to assess malocclusion. Child Perceptions Questionnaires (CPQ11–14) with 8 items (CPQ11–14-ISF: 8) and 37 items were used to assess OHRQoL at age 12 and age 15, respectively; Oral Health Impact Profile (OHIP-14) was used to assess OHRQoL at age 18. Wilcoxon signed ranks test and Friedman’s test were used to analyse the age-related change of OHRQoL and malocclusion from age 12 to 18. Generalized estimating equations were used to analyse the influence factors of OHRQoL and to calculate adjusted risk ratio (RR). Results Subjects recruited in this study were 589 (305 females, 284 males), 364 (186 females, 178 males) and 300 (165 females, 135 males) at age 12, 15 and 18, respectively. Among them, 331 subjects (172 females, 159 males) were followed from age 12 to 15, and 118 subjects (106 females, 82 males) were followed from age 12 to 18. Subjects had less severe malocclusion at age 12 than at ages 15 and 18 (p = 0.000, measured by Dental Aesthetic Index). Age, periodontal status, and malocclusion had an effect on OHRQoL. When compared with OHRQoL at age 12, worse OHRQoL was observed at age 15 (adjusted RR = 1.06, 95%CI = 1.01–1.12, p = 0.032), but not at age 18 (adjusted RR = 1.01, 95%CI = 0.95–1.08, p = 0.759). Unhealthy periodontal conditions had a negative effect on OHRQoL (adjusted RR = 1.14, 95%CI = 1.04–1.25, p = 0.007). Only severe malocclusions had a negative effect on OHRQoL; a more severe malocclusion was associated with a higher effect on OHRQoL (adjusted RR = 1.09, 95%CI = 1.01–1.18, p = 0.032 for severe malocclusion, and adjusted RR = 1.17, 95%CI = 1.07–1.28, p = 0.001 for very severe malocclusion measured by Dental Aesthetic Index). Conclusion Age, periodontal status, and malocclusion had an influence on OHRQoL from age 12 to 18. When clinicians attempt to improve subjects’ OHRQoL, it is necessary to consider these factors.

The oral cavity is an environment with diverse bacteria; thus, antibacterial materials are crucial for treating and preventing dental diseases. There is a high demand for materials with an enamel-like architecture because of the high failure rate of dental restorations, due to the physical differences between dental materials and enamel. However, recreating the distinctive apatite composition and hierarchical architecture of enamel is challenging. The aim of this study was to synthesize a novel material with an enamel-like structure and antibacterial ability. We established a non-cell biomimetic method of evaporation-based bottom-up self-assembly combined with a layer-by-layer technique and introduced an antibacterial agent (graphene oxide) to fabricate a biofunctional material with an enamel-like architecture and antibacterial ability. Specifically, enamel-like graphene oxide-hydroxyapatite crystals, formed on a customized mineralization template, were assembled into an enamel-like prismatic structure with a highly organized orientation preferentially along the c-axis through evaporation-based bottom-up self-assembly. With the aid of layer-by-layer absorption, we then fabricated a bulk macroscopic multilayered biofunctional material with a hierarchical enamel-like architecture. This enamel-inspired biomaterial could effectively resolve the problem in dental restoration and brings new prospects for the synthesis of other enamel-inspired biomaterials.

Abstract Background Dental age estimation can assist in the identification of victims following natural disasters and it can also help to solve birth date disputes in individuals involved in criminal activities. A reference dataset (RDS) has been developed from the dental development of 2306 subjects of southern Han Chinese origin and subsequently validated. This study aimed to test the applicability of the southern Han Chinese dental maturation RDS on three distinct East Asian population groups. Methods A total of 953 dental panoramic radiographs of subjects aged 2 to 24 years were obtained from Philippines, Thailand and Japan. The staging of dental development was conducted according to Anglo-Canadian classification system. The dental age (DA) was calculated using six methods; one un-weighted average and five weighted average (n-tds, sd-tds, se-tds, 1/sd-tds, 1/se-tds) methods based on the scores of the southern Han Chinese RDS. Statistical significance was set at p

Abstract Background There is a need to comprehensively investigate the relationship between tooth eruption and infant growth to explain the theory of tooth emergence. This study aimed to investigate the association between infant growth during the first year of life and the emergence of the permanent teeth. Methods A random sample of 668, 12-year-old students was recruited from a birth cohort. Erupted permanent tooth number was recorded. The association of infant growth (growth trajectories and growth rates) and permanent tooth emergence was examined through logistic regression analyses. The regression model was adjusted by potential confounders including gender, gestational age, mode of delivery, type of feeding, parental education, and health status. Results The response rate was 76.9% (n = 514). Two hundred and forty-five (47.7%) children had all 28 permanent teeth erupted. Infants who had higher birth weight z-scores and those who had grown slowly during the first three months of life were more likely to have complete permanent teeth emergence at their 12-year-old in both unadjusted (p 0.05). Conclusion Birth weight and infant growth during the first three months of life might be associated with permanent tooth emergence at their 12 years of age. This association may be applied in the assessment of risk for dental caries or malocclusion.

Background. Pericytes play an important role in forming functional blood vessels and establishing stable and effective microcirculation, which is crucial for vascular tissue engineering. The slow ex vivo expansion rate, limited proliferative capacity, and variability of tissue-specific phenotypes would hinder experimental studies and clinical translation of primary pericytes. In this study, the angiogenic and pericyte functions of stem cells from human exfoliated deciduous teeth (SHEDs) and postnatal human dental pulp stem cells (DPSCs) were investigated. Methods. Osteogenic and adipogenic induction assays were performed to evaluate the mesenchymal potential of SHEDs, DPSCs, and pericytes. An in vitro Matrigel angiogenesis assay was conducted to reveal the ability of SHEDs, DPSCs, and pericytes to stabilize vascular-like structures. Quantitative real-time polymerase chain reaction (RT-qPCR) was performed to evaluate mRNA expression. Flow cytometry, western blotting, and immunostaining were used to assess the protein expression. Wound healing and transwell assays were performed to evaluate the migration ability of SHEDs, DPSCs, and pericytes. Results. The osteogenic and adipogenic induction assays showed that SHEDs, DPSCs, and pericytes exhibited similar stem cell characteristics. The mRNA expression levels of PDGFR-β, α-SMA, NG2, and DEMSIN in SHEDs and DPSCs cultured in EC medium were significantly higher than those in the control groups on day 7 (P0.05). Conclusion. The SHEDs and DPSCs display a profile similar to that of pericytes. Our study lays a solid theoretical foundation for the clinical use of dental pulp stem cells as a potential candidate to replace pericytes.

Aim To assess the longitudinal association between adolescents’ and their mothers’ dental fear. Study Design A longitudinal questionnaire survey study. Methods A randomized sample of 12-year-old adolescents were selected from local Hong Kong schools. Adolescents and their mothers self-completed the Modified Dental Anxiety Scale (MDAS). The sociodemographic background of the mothers and the oral health habits of the adolescents were also collected and these measurements were repeated at 15- and 18-years-old. Non-parametric tests (Mann–Whitney U test/Kruskall Wallis test) were used to test associations between MDAS dental fear items and independent variables. Logistic regression (adjusted for family’s sociodemographic background and adolescent’s oral health habits) was performed to evaluate the longitudinal association between adolescents’ and mothers’ dental fear. Results A total of 212 mother-child pairs were recruited at baseline (12-year-old adolescents). In the first and second follow-ups (15- and 18-years-old), 195 and 182 mother-child pairs completed the survey. Significant associations between mother’s and child’s scores in “feeling about having their teeth scraped and polished”, “having teeth drilled”, and ‘having an injection in the gum’ were found when adolescents were 12- years-old (P < 0.01) and 18-years-old (P < 0.05), but not at 15-years-old. Conclusion Adolescents’ and mothers’ dental fear is associated at 12-years-old and 18-years-old, but not at 15-years-old, which is likely specific to the Hong Kong context but may be extrapolated to other industrialized countries with caution.

BACKGROUND:In the clinical dental consultation, multi-party configurations predominate with the presence of parents/ primary caregivers in pediatric dentistry adding another layer of complexity. In managing child oral healthcare, parents/ primary caregivers are critical, especially in dental caries prevention. This study aimed (1) to identify the structure of oral health literacy (OHL) talk in interpreter-mediated pediatric dentistry and (2) to analyze interpreter contributions to the communication strategies: patient-centered direct interpreting (PC-DI), patient-centered mediated interpreting (PC-MI), clinician-centered direct interpreting (CC-DI), and clinician-centered mediated interpreting (CC-MI). METHODS:Visual text analysis (VTA) of video recorded pediatric clinical consultations in Hong Kong utilized Discursis™ software to illustrate temporal and topical structures and their distribution across turns-at-talk. Conversation analysis (CA) was applied to analyze turn-taking of the identified OHL talk qualitatively. The mixed-method approach of combining VTA and CA was applied to analyze the patterns and features of the recorded OHL talk. RESULTS:The conceptual recurrences of the 77 transcribed video recordings were plotted visually. CC- and PC-OHL talk were identified by the recurrence patterns of monochromatic and multi-colored triangular clusters formed by off-diagonal boxes, respectively. CA of interpreter-mediated turns supported earlier findings regarding patterns of MI in multilingual adult dental consultations; however, the role of the interpreter in parent/ primary caregiver education and patient management was more distinctive in the pediatric dentistry. CONCLUSIONS:The mixed-method approach assisted in unpacking the complexities of the multi-party interactions, supported identification of effective communication strategies, and illustrated the roles of the dental professionals in initiating CC- and PC-OHL talk in pediatric dentistry. The intervention showed the implication of the professional education of evidence-based practices for clinicians in balancing agenda management and the communicative dimension of OHL with the help of VTA and CA in multilingual consultations.

Abstract Background Socio-economic status, health awareness, and dietary habits have been reported as common risk factors of dental caries and obesity. The present study aimed to explore shared mediators between caries and obesity and to estimate the effects of caries-related factors on adiposity. Methods This was a cross-sectional study among adolescents aged 18 years. The study was nested in a population-representative cohort of Chinese in Hong Kong. The number of decayed, missing, and filled permanent teeth (DMFT) was recorded during the oral examinations. Body Mass Index (BMI), Waist Circumference (WC), Waist-Hip-Ratio (WHR), Waist-Height-Ratio (WHtR), and Triceps Skinfold Thickness (TRSKF) were used as adiposity indices. Data on socio-economic status, oral health behavior (tooth brushing habit, use of fluoride toothpaste, dental flossing habit, and mouth rinse habit), and dietary record (frequency and amount of different food) were collected through self-completed questionnaires. Chi-square tests and binary logistic regressions were used for analysis. Results Three hundred eighty-three participants were included. The mean (standard deviation, SD) of BMI, WC, WHR, WHtR, TRSKF, and DMFT were 21.26 (3.72), 69.11 (9.25), 0.77 (0.06), 0.42 (0.05), 15.72 (6.33), and 2.06 (2.43), respectively. Males were more likely to be overweight/obese than females. Various factors including gender, parental employment status, mouth rinse habit, frequency and amount of meat intake, frequency of oil intake, use of fluoride toothpaste, and DMFT were found significant (p

Abstract Background There is no consensus opinion regarding the association between obesity and periodontal diseases among children and adolescents in the literature. Methods A prospective observational cohort study was conducted in a Hong Kong cohort at age 12, 15 and 18. CPI and various obesity indices including BMI, WC, WHR, WHtR, and TRSKF were recorded during each wave of data collection. Information on socioeconomic status and oral health behaviors were collected through self-completed questionnaires. Results Two hundred and eighty-two (male: 122 and female: 160) participants completed all three rounds of data collection. Prevalence of overweight/obesity was 27.0, 19.1, and 14.2% at 12, 15, and 18 years, respectively. 19.9% participants had healthy periodontal conditions at age 12. While the percentage dropped to 10.3% at 15 years and 5.7% at 18 years. The proportion of 15-year-old adolescents who brushed teeth more than twice a day was significantly higher among participants belonging to the lower BMI, WC, WHR, and WHtR category (P

Abstract Background Young adulthood is a time when subjects transform their role from a dependent child to an independent social identity. This cross-sectional study aimed to analyze the sociodemographic and clinical factors that may influence the OHRQoL of 18-year-old young adults. Methods A representative sample was selected from Hong Kong. Periodontal status and caries were examined according to WHO criteria. Four orthodontic indices were used to assess malocclusion. The oral health impact profile (OHIP-14) was used to measure OHRQoL. Adjusted OR was calculated by ordinal logistic regression. Results A total of 300 eligible subjects (165 females, 135 males) were recruited. Females had more severe caries than males; however, gender was not a significant factor of OHRQoL. Household income affected OHRQoL more than parents’ education did: household income had effects on physical pain, psychological discomfort, psychological disability, and the total OHIP; while parents’ education had some effects on functional limitation, physical pain and psychological discomfort. As for clinical factors, unhealthy periodontal conditions were more prevalent than caries (94.67% vs. 59.00%); however, both of them showed no effect on OHRQoL. Malocclusion had a negative effect on OHRQoL; the most affected subscales were psychological discomfort and psychological disability. Conclusion In this study, family ecosocial factors and malocclusion had an effect on OHRQoL. Among the family ecosocial factors, it was household income that had the most effect on OHRQoL. Malocclusion mainly affected the subscales of psychological discomfort and psychological disability. Gender, periodontal status and caries had no effect on young adults’ OHRQoL.

Abstract Background The development of primary dentition can be affected by oral sucking habits. Therefore, this study aims to investigate the association of nutritive and non-nutritive sucking habits with primary dentition development. Methods One thousand one hundred and fourteen children aged 2 to 5 years old in Hong Kong were recruited in a cross-sectional study. Information on their nutritive (e.g. breastfeeding and bottle feeding) and non-nutritive sucking habits (e.g. pacifier use and thumb/digit sucking) was collected via questionnaires. The children’s primary occlusions were examined in three dimensions. Results Children who were breastfed for more than 6 months had a lower proportion of daily pacifier use (p

Abstract Background The accuracy of estimated age should depend on the reference data sets (RDS) from which the maturity scores or Ages of Attainment (AoA) were obtained. This study aimed to test the accuracy of age estimation from three different population specific dental reference datasets (RDS). Methods Two hundred and sixty six dental panoramic radiographs of subjects belonging to southern Chinese ethnicity were scored and dental age (DA) was estimated from three reference datasets: French-Canadian, United Kingdom (UK) Caucasian and southern Chinese. Statistical significance was set at p 0.05). The southern Chinese RDS estimated the age of 80% of subjects within ±12 months range, and 90% of subjects within ±18 months range (p

Abstract Background Several hypotheses on factors that influence oral health-related quality of life (OHRQoL) have been proposed but a consensus has not been reached. This cross-sectional study aimed to analyse the sociodemographic and clinical factors that may influence the OHRQoL of 15-year-old children. Methods A representative sample was selected from Hong Kong. Periodontal status and caries were examined according to WHO criteria. Four orthodontic indices were used to assess malocclusion. Child Perception Questionnaire (CPQ11–14, 37 items) including four domains, namely oral symptoms (OS), functional limitations (FL), emotional well-being (EWB), and social well-being (SWB), was used to measure OHRQoL. Adjusted OR was calculated by ordinal logistic regression. Results A total of 364 eligible subjects (186 girls, 178 boys) were recruited. The prevalence of caries was higher in girls than in boys (P = 0.013). Compared with girls, boys tended to have a better experience in the domains of EWB, SWB and the total CPQ (adjusted OR = 0.46, 0.59 and 0.61, respectively). Unhealthy periodontal conditions were more prevalent than caries (92.6% vs. 52.7%); moreover, periodontal conditions with CPI scores of 2 had a negative effect on the domain of SWB and the total CPQ (adjusted OR = 1.76 and 1.71, respectively). Only the most severe malocclusion showed an effect on the domain of FL and the total CPQ (adjusted OR = 1.55 and 2.10, respectively). Little effect of family ecosocial factors and caries was found on CPQ scores. Conclusion In this study, gender, periodontal status, and malocclusion showed an effect on OHRQoL after adjusting for potential confounders. Boys had less caries and better OHRQoL than girls did. Unhealthy periodontal conditions led to worse social welfares and OHRQoL. The most severe level of malocclusion caused oral functional limitations, hence worse OHRQoL.

Graphene oxide (GO) is an emerging luminescent carbon nanomaterial with the ability to foster hydroxyapatite (HA). A specially designed electrophoresis system can be used to accelerate the mineralization process. The aim of this study was to promote HA crystal growth on demineralized dentin using a GO incorporated electrophoresis system. GO was successfully synthesized by carbonization of citric acid and its presence was confirmed by Fourier transform infrared and UV-visible spectrophotometry evaluation. Dentin slices were placed in demineralized solution and divided into control (without the electrophoresis system) and experimental group. Demineralized dentin slices in the experimental group were remineralized using the electrophoresis system for 8 h/1.0 mA, with one subgroup treated without GO and the other with GO. Energy dispersive spectroscopy evaluation showed that the calcium/phosphate ratio of the crystal formed in control and experimental group with addition of GO was close to natural hydroxyapatite. However, scanning electron microscopy evaluation showed that the exposed dentinal tubules were occluded with rod-like crystals, which is similar to native enamel morphology, in the experimental group with addition of GO compared to the flake-like crystal in the control group. Mechanical evaluation revealed that the nanohardness and modulus of remineralized dentin were significantly higher in the experimental group. In conclusion, GO is a promising material to remineralize dentin and the introduction of an electrophoresis system can accelerate its process.

The distinct architecture of native enamel gives it its exquisite appearance and excellent intrinsic-extrinsic fracture toughening properties. However, damage to the enamel is irreversible. At present, the clinical treatment for enamel lesion is an invasive method; besides, its limitations, caused by the chemical and physical difference between restorative materials and dental hard tissue, makes the restorative effects far from ideal. With more investigations on the mechanism of amelogenesis, biomimetic mineralization techniques for enamel regeneration have been well developed, which hold great promise as a non-invasive strategy for enamel restoration. This review disclosed the chemical and physical mechanism of amelogenesis; meanwhile, it overviewed and summarized studies involving the regeneration of enamel microstructure in cell-free biomineralization approaches, which could bring new prospects for resolving the challenges in enamel regeneration.

Abstract Background Oral health-related quality of life (OHRQoL) could be affected not only by oral health but also by demographic and ecosocial factors. This research aimed to analyze the sociodemographic and clinical factors that may influence the OHRQoL of 12-year-old children. Methods A representative sample was selected from Hong Kong. Periodontal status and caries were examined according to WHO criteria. Four orthodontic indices were used to assess malocclusion. Child Perception Questionnaires (CPQ11–14-ISF:8 and CPQ11–14-RSF:8) including four domains, namely oral symptoms (OS), functional limitations (FL), emotional well-being (EWB), and social well-being (SWB), were used to measure OHRQoL. Adjusted OR was calculated by ordinal logistic regression. Results Totally 589 eligible subjects (305 females, 284 males) were recruited. Males tended to rank higher in OS domain but lower in EWB domain (adjusted OR = 1.89 and 0.67). Mother’s education was linked more closely with children’s CPQ scores. Higher education levels were associated with better quality of life (adjusted OR = 0.45 and 0.37). Household income showed no effect on CPQ scores. Unhealthy periodontal conditions had a negative effect on EWB and total CPQ (adjusted OR = 1.61 and 1.63). High caries experience only had a negative effect on SWB (adjusted OR = 1.60). Malocclusion affected FL, EWB, SWB and total CPQ: all malocclusion severities affected SWB; only severe malocclusions affected FL, EWB and total CPQ. Conclusion Males were more tolerant of oral symptoms than females were. Higher levels of mother’s education led to better OHRQoL of their children. Unhealthy periodontal conditions affected emotional well-being, while high caries experience affected social well-being. All malocclusion severities had an effect on social well-being; severe malocclusion further caused functional limitations, worse emotional well-being, and hence worse OHRQoL.

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

Faculty of Dentistry of the University of Hong Kong has introduced innovative blended problem-based learning (PBL) with the aid of 3D electronic models (e-models) to Bachelor of Dental Surgery (BDS) curriculum. Statistical results of pre- and post-semester questionnaire surveys illustrated compatibility of e-models in PBL settings. The students’ importance ratings of two objectives “Complete assigned tasks on time” and “Active listener”, and twenty-two facilitator evaluation items including critical thinking and group problem-solving skills had increased significantly. The students’ PBL preparation behavior, attentions to problem understanding, problem analysis, and learning resource quality were also found to be related to online support of e-models and its software. Qualitative analysis of open-ended questions with visual text analytic software “Leximancer” improved validity of statistical results. Using e-model functions in treatment planning, problem analysis and giving instructions provided a method of informative communication. Therefore, it is critical for the faculty to continuously provide facilitator training and quality online e-model resources to the students.

Background: Although lung cancer incidence and mortality have been declining since the 1990s, the extent to which such progress has been made is unequal across population segments. Updated epidemiologic data on trends and patterns of disparities are lacking.Methods: Data on lung cancer cases and deaths during 1974 to 2015 were extracted from the Surveillance, Epidemiology, and End Results program. Age-standardized lung cancer incidence and mortality and their annual percent changes were calculated by histologic types, demographic variables, and tumor characteristics.Results: Lung cancer incidence decreased since 1990 (1990 to 2007: annual percent change, −0.9 [95% CI, −1.0%, −0.8%]; 2007 to 2015: −2.6 [−2.9%, −2.2%]). Among adults aged between 20 and 39 years, a higher incidence was observed among females during 1995 to 2011, after which a faster decline in female lung cancer incidence (males: −2.5% [−2.8%, −2.2%]; females: −3.1% [−4.7%, −1.5%]) resulted in a lower incidence among females. The white population had a higher incidence than the Black population for small cell carcinoma since 1987. Black females were the only group whose adenocarcinoma incidence plateaued since 2012 (−5.0% [−13.0%, 3.7%]). A higher incidence for squamous cell carcinoma was observed among Black males and females than among white males and females during 1974 to 2015. After circa 2005, octogenarians and older patients constituted the group with the highest lung cancer incidence. Incidence for localized and AJCC/TNM stage I lung cancer among octogenarians and older patients plateaued since 2009, while mortality continued to rise (localized: 1.4% [0.6%, 2.1%]; stage I: 6.7% [4.5%, 9.0%]).Conclusions: Lung cancer disparities prevail across population segments. Our findings inform effective approaches to eliminate lung cancer disparities by targeting at-risk populations.

BackgroundThorough understanding of developmental changes of human facial shape is lacking. The present study aimed to evaluate developmental shape changes of facial morphology based on a prospective, population-representative, Chinese cohort in Hong Kong.MethodsA population-representative sample of Chinese in Hong Kong was followed. Serial facial images of over 260 participants were obtained at age 12, 15, and 18 years. Facial landmarks were digitized and the corresponding coordinates were submitted for Generalized Procrustes Analysis. The resultant Procrustes shape coordinates, which captured shape information encoded by the facial landmarks, were then used for statistical shape analyses.ResultsSmall but significant developmental changes in mean facial shape were observed (p < 0.0001 for all pairwise comparisons). Significant age-related changes in the magnitude of variance of facial shape were also observed (p < 0.05). Phenotypic growth trajectories representing developmental shape changes were similar in size (p > 0.05) between sexes but differed in direction (p < 0.05) in shape space and trajectory shape (p < 0.05). The magnitude of shape differences between sexes remained constant from 12 to 18 years. Results of frontal facial shape analyses after removing the effect of allometry were similar to results obtained before removal of allometry. For lateral facial configurations, allometric trajectories among the age-by-sex groups were similar in slope (p > 0.05) but varied in directions in the multidimensional shape space.ConclusionsOur findings suggested significant age-related changes in facial shape and provided a dynamic view of developmental changes in sexual dimorphism of facial shape. Allometry contributed minimally to developmental changes in frontal facial shape. In addition, the allometric trajectories for lateral facial configurations were similar in rate of shape change but differed in their directions in shape space.

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.

Patients' perceived satisfaction is a key performance index of the quality health care service. Good communication has been found to increase patient's perceived satisfaction. The purpose of this study was to examine the impact of the prominent themes arising from clinician-patient conversations on the caregiver's perceived quality of communication during paediatric dental visits. 162 video recordings of clinical dental consultations for 62 cases attending the Paediatric Dentistry Clinic of The Prince Philip Dental Hospital in Hong Kong were captured and transcribed. The patients' demographic information and the caregiver's perceived quality of communication with the clinicians were recorded using the 16-item Dental Patient Feedback on Consultation skills questionnaires. Visual text analytics (Leximancer™) indicated five prominent themes 'disease / treatment', 'treatment procedure related instructions', 'preparation for examination', 'positive reinforcement / reassurance', and 'family / social history' from the clinician-patient conversation of the recorded videos, with 60.2% of the total variance in concept words in this study explained through principal components analysis. Significant variation in perceived quality of communication was noted in five variables regarding the prominent theme 'Positive reinforcement / reassurance': 'number of related words' (p = 0.002), 'number of related utterances' (p = 0.001), 'percentage of the related words in total number of words' (p = 0.005), 'percentage of the related utterances in total number of utterances' (p = 0.035) and 'percentage of time spent in total time duration' (p = 0.023). Clinicians were perceived to be more patient-centered and empathetic if a larger proportion of their conversation showed positive reinforcement and reassurance via using related key words. Care-giver's involvement, such as clinicians' mention of the parent, was also seen as critical to perceptions of quality clinical experience. The study reveals the potential of the application of visual text analytics software in clinical consultations with implications for professional development regarding clinicians' communication skills for improving patients' clinical experiences and treatment satisfaction.

Existing studies on facial growth were mostly cross-sectional in nature and only a limited number of facial measurements were investigated. The purposes of this study were to longitudinally investigate facial growth of Chinese in Hong Kong from 12 through 15 to 18 years of age and to compare the magnitude of growth changes between genders.Standardized frontal and lateral facial photographs were taken from 266 (149 females and 117 males) and 265 (145 females and 120 males) participants, respectively, at all three age levels. Linear and angular measurements, profile inclinations, and proportion indices were recorded. Statistical analyses were performed to investigate growth changes of facial features. Comparisons were made between genders in terms of the magnitude of growth changes from ages 12 to 15, 15 to 18, and 12 to 18 years. For the overall face, all linear measurements increased significantly (p < 0.05) except for height of the lower profile in females (p = 0.069) and width of the face in males (p = 0.648). In both genders, the increase in height of eye fissure was around 10% (p < 0.001). There was significant decrease in nasofrontal angle (p < 0.001) and increase in nasofacial angle (p < 0.001) in both genders and these changes were larger in males. Vermilion-total upper lip height index remained stable in females (p = 0.770) but increased in males (p = 0.020). Nasofrontal angle (effect size: 0.55) and lower vermilion contour index (effect size: 0.59) demonstrated large magnitude of gender difference in the amount of growth changes from 12 to 18 years.Growth changes of facial features and gender differences in the magnitude of facial growth were determined. The findings may benefit different clinical specialties and other nonclinical fields where facial growth are of interest.

While northern and southern Chinese are genetically correlated, there exists notable environmental differences in their living conditions. This study aimed to evaluate validity of the southern Chinese reference dataset for dental age estimation applied to northern Chinese. Dental panoramic tomographs of 437 northern Chinese aged 3 to 21 years were analysed. All the left maxillary and mandibular permanent teeth plus the 2 third molars on the right side were scored based on Demirjian’s classification of tooth development stages. Mean and standard error of dental age were obtained for each tooth development stage, followed by random effect meta-analysis for mean dental age estimation. Validity of the method was examined through measures of agreement (95% limits of agreement, standard error of measurement, and Lin’s concordance correlation coefficient) and measure of reliability (Intraclass correlation coefficient). On average, the estimated dental age overestimated chronological age by only around 1 month in both females and males. The Intraclass correlation coefficient values were 0.99 for both sexes, suggesting excellent reliability of the method. Reference dataset for dental age estimation developed on the basis of southern Chinese was applicable for use among the northern Chinese.

This paper reports the results of a four-part questionnaire survey to assess the effects of the sound of dental equipment on people′s perceptions and dental anxiety levels. The convenience sample for the survey comprised 230 dental students and 230 gender and age matched non-dental university students. The subjects were requested to complete the questionnaires themselves. The results show that the sound of dental equipment has a great influence on dental anxiety. Dental students, who are more familiar with the operation of this equipment, are less prone to anxiety when they hear its sound than their non-dental counterparts.

BackgroundNumerous facial photogrammetric studies have been published around the world. We aimed to critically review these studies so as to establish population norms for various angular and linear facial measurements; and to determine inter-ethnic/racial facial variations.Methods and findingsA comprehensive and systematic search of PubMed, ISI Web of Science, Embase, and Scopus was conducted to identify facial photogrammetric studies published before December, 2014. Subjects of eligible studies were either Africans, Asians or Caucasians. A Bayesian hierarchical random effects model was developed to estimate posterior means and 95% credible intervals (CrI) for each measurement by ethnicity/race. Linear contrasts were constructed to explore inter-ethnic/racial facial variations. We identified 38 eligible studies reporting 11 angular and 18 linear facial measurements. Risk of bias of the studies ranged from 0.06 to 0.66. At the significance level of 0.05, African males were found to have smaller nasofrontal angle (posterior mean difference: 8.1°, 95% CrI: 2.2°-13.5°) compared to Caucasian males and larger nasofacial angle (7.4°, 0.1°-13.2°) compared to Asian males. Nasolabial angle was more obtuse in Caucasian females than in African (17.4°, 0.2°-35.3°) and Asian (9.1°, 0.4°-17.3°) females. Additional inter-ethnic/racial variations were revealed when the level of statistical significance was set at 0.10.ConclusionsA comprehensive database for angular and linear facial measurements was established from existing studies using the statistical model and inter-ethnic/racial variations of facial features were observed. The results have implications for clinical practice and highlight the need and value for high quality photogrammetric studies.

This study investigated the softening and erosive effects of various paediatric over-the-counter (OTC) oral liquids on deciduous teeth. Twenty sectioned and polished deciduous enamel blocks were ground on the buccal surface (2 × 2 mm2) and randomly divided into five groups, immersed into four commercially-available paediatric OTC oral liquids (two for paracetamol, both sugared; and two for chlorpheniramine, one sugared and one sugar-free), with deionized water as control. The pH of the oral liquids ranged from 2.50 to 5.77. Each block was immersed into the test or control groups for 15 s, rinsed with deionized water, and Vickers micro-hardness (n = 5) was measured. After twenty cycles of immersion and hardness measurements, Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Spectrometry (EDS) were used to evaluate the surface morphology and chemistry of the tooth blocks, respectively. The pH values of the liquids were also recorded. Rapidly descending trends in the micro-hardness ratios of the four test groups were observed that were statistically different from the control group (p < 0.001). EDS showed an increase of Ca/C ratio after drug immersion, whereas SEM showed an enamel loss in all the test groups. Paediatric OTC oral liquids could significantly soften the enamel and render them more susceptible to caries, such that the formulation of the oral liquids is the major factor.

With cancer survival rate climbing up over the past three decades, quality of life for cancer patients has become an issue of major concern. Oral health plays an important part in one’s overall quality of life. However, oral health status can be severely hampered by side effects of cancer therapies including surgery, chemotherapy, radiotherapy, and hematopoietic stem cell transplantation. Moreover, prevention and treatment of these complications are often overlooked in clinical practice. The present paper aims at drawing health care professionals’ attention to oral complications associated with cancer therapy by giving a comprehensive review. Brief comments on contemporary cancer therapies will be given first, followed by detailed description of oral complications associated with cancer therapy. Finally, a summary of preventive strategies and treatment options for common oral complications including oral mucositis, oral infections, xerostomia, and dysgeusia will be given.

Current studies on the aetiology of developmental defects of enamel (DDE) are subject to recall bias because of the retrospective collection of information. Our objective was to investigate potential risk factors associated with the occurrence of DDE through a prospective cohort study.Using a random community sample of Hong Kong children born in 1997, we performed a cohort study in which the subjects' background information, medical and dental records were prospectively collected. A clinical examination to identify DDE was conducted in 2010 when the subjects were 12 years old. The central incisor, lateral incisor and first molar in each quadrant were chosen as the index teeth and were examined 'wet' by two trained and calibrated examiners using the modified FDI (DDE) Index.With a response rate of 74.9%, the 514 examined subjects had matched data for background information. Diffuse opacites were the most common type of DDE. Of the various possible aetiological factors considered, only experience of severe diseases during the period 0-3 years was associated with the occurrence of 'any defect' (p = 0.017) and diffuse opacities (p = 0.044). The children with experience of severe diseases before 3 years of age were 7.89 times more likely to be affected by 'any defect' compared with those who did not have the experience (OR 7.89; 95% CI 1.07, 58.14; p = 0.043). However, after adjusting for confounding factors, the association no longer existed.No variables could be identified as risk factors of DDE in this Hong Kong birth cohort.