Consortium-based genome-wide meta-analysis for childhood dental caries traits.

Prior studies suggest dental caries traits in children and adolescents are partially heritable, but there has been no large-scale consortium genome-wide association study (GWAS) to date. We therefore performed GWAS for caries in participants aged 2.5-18.0 years from nine contributing centres. Phenotype definitions were created for the presence or absence of treated or untreated caries, stratified by primary and permanent dentition. All studies tested for association between caries and genotype dosage and the results were combined using fixed-effects meta-analysis. Analysis included up to 19 003 individuals (7530 affected) for primary teeth and 13 353 individuals (5875 affected) for permanent teeth. Evidence for association with caries status was observed at rs1594318-C for primary teeth [intronic within ALLC, odds ratio (OR) 0.85, effect allele frequency (EAF) 0.60, P 4.13e-8] and rs7738851-A (intronic within NEDD9, OR 1.28, EAF 0.85, P 1.63e-8) for permanent teeth. Consortium-wide estimated heritability of caries was low [h2 of 1% (95% CI: 0%: 7%) and 6% (95% CI 0%: 13%) for primary and permanent dentitions, respectively] compared with corresponding within-study estimates [h2 of 28% (95% CI: 9%: 48%) and 17% (95% CI: 2%: 31%)] or previously published estimates. This study was designed to identify common genetic variants with modest effects which are consistent across different populations. We found few single variants associated with caries status under these assumptions. Phenotypic heterogeneity between cohorts and limited statistical power will have contributed; these findings could also reflect complexity not captured by our study design, such as genetic effects which are conditional on environmental exposure.

Dental development and craniofacial morphology in school-age children.

INTRODUCTION: The growth of the craniofacial complex is important for establishing a balanced relationship among the teeth, jaws, and other facial structures. However, there is still a lack of information about craniofacial parameters that are affected by the rate of dental development. The aim of this study was to investigate the association between dental development and craniofacial morphology in school-age children. METHODS: This study was embedded in the Generation R Study, Rotterdam, The Netherlands. In 3,896 children aged 8 to 11 years, dental development was assessed from panoramic radiographs and craniofacial morphology was assessed by combining cephalometric parameters into 9 uncorrelated principal components, each representing a distinct skeletal or dental craniofacial pattern. The statistical analysis was performed using linear and nonlinear regression model. RESULTS: Dental development was positively associated with the bimaxillary growth (ß = 0.04; 95% CI 0.01 to 0.08). Children with above-average dental development had a tendency toward Class II jaw relationship (ß = -0.08; 95% CI -0.13 to -0.04). Regarding dental parameters, the proclination increased for incisors and lips with advanced dental development (ß = 0.15 [95% CI 0.10 to 0.19] and ß = 0.13 [95% CI 0.09 to 0.17], respectively), but the incisor proclination remained more pronounced in children that had above-average dental development. CONCLUSIONS: The findings of this large population-based study show that dental development is associated with specific dental and skeletal cephalometric characteristics in school-age children. Further longitudinal studies are necessary to confirm the observed effects over time.

Ancestry and dental development: A geographic and genetic perspective.

OBJECTIVE: In this study, we investigated the influence of ancestry on dental development in the Generation R Study. METHODS: Information on geographic ancestry was available in 3,600 children (1,810 boys and 1,790 girls, mean age 9.81 ± 0.35 years) and information about genetic ancestry was available in 2,786 children (1,387 boys and 1,399 girls, mean age 9.82 ± 0.34 years). Dental development was assessed in all children using the Demirjian method. The associations of geographic ancestry (Cape Verdean, Moroccan, Turkish, Dutch Antillean, Surinamese Creole and Surinamese Hindustani vs Dutch as the reference group) and genetic content of ancestry (European, African or Asian) with dental development was analyzed using linear regression models. RESULTS: In a geographic perspective of ancestry, Moroccan (ß = 0.18; 95% CI: 0.07, 0.28), Turkish (ß = 0.22; 95% CI: 0.12, 0.32), Dutch Antillean (ß = 0.27; 95% CI: 0.12, 0.41), and Surinamese Creole (ß = 0.16; 95% CI: 0.03, 0.30) preceded Dutch children in dental development. Moreover, in a genetic perspective of ancestry, a higher proportion of European ancestry was associated with decelerated dental development (ß = -0.32; 95% CI: -.44, -.20). In contrast, a higher proportion of African ancestry (ß = 0.29; 95% CI: 0.16, 0.43) and a higher proportion of Asian ancestry (ß = 0.28; 95% CI: 0.09, 0.48) were associated with accelerated dental development. When investigating only European children, these effect estimates increased to twice as large in absolute value. CONCLUSION: Based on a geographic and genetic perspective, differences in dental development exist in a population of heterogeneous ancestry and should be considered when describing the physiological growth in children.

Dentofacial trauma and players' attitude towards mouthguard use in field hockey: a systematic review and meta-analysis.

BACKGROUND: Dentofacial injuries are a risk while playing field hockey. Wearing mouthguards is recommended. OBJECTIVE: To synthesise findings on the prevalence and characteristics of dentofacial injuries sustained by field hockey players. We also investigated the prevalence of regular mouthguard use and players' attitude towards use of mouthguard. MATERIAL AND METHODS: A literature search was performed using PubMed, EMBASE, OvidSP, Web of Science, Cochrane and Cinahl databases. Eligible studies were identified based on the title, abstract and full text of articles. If applicable, a random effects model was used to calculate the overall effect size; otherwise, pooled prevalence was reported. RESULTS: 11 studies were eligible for the analysis. The average proportion of field hockey players who had sustained at least one dentofacial injury varied from 12.7% (95% CI 8.5% to 17.0%) among junior and senior players to 45.2% (95% CI 39.3% to 51.0%) among elite players. We did not observe any significant differences with respect to gender. In the 2000s, a significantly higher proportion of players regularly wore a mouthguard, 84.5% (95% CI 69.3% to 99.7%) as compared with players 20 years ago, 31.4% (95% CI 22.7% to 40.1%). The most common complaints about the mouthguard were that it was unnecessary and uncomfortable. CONCLUSION: Dentofacial injuries pose a serious problem in field hockey and a substantial number of players do not regularly wear a mouthguard. Greater use of mouthguards would be expected to reduce dentofacial injuries in field hockey.

Patterns of orodental injury and mouthguard use in Dutch field hockey.

BACKGROUND: Orodental injuries in field hockey are a growing cause of concern that requires attention. OBJECTIVE: The objective of this cross-sectional study was to investigate the patterns of orodental injury, and the use of mouthguards in Dutch national field hockey. MATERIALS AND METHODS: In the period from 1 May to 31 July 2014, a 33-item questionnaire about orodental injury and mouthguard use was sent to 7 field hockey clubs in the Netherlands. Data were analysed using 2 multivariable logistic (non-)linear regression per outcome measurement: (1) orodental injury and (2) type of mouthguard. RESULTS: Out of 6585 players, 1299 (20%) responded sufficiently and were eligible for the study. In total, 214 hockey players (16%) experienced at least 1 orodental injury in their career. The injuries were less severe in athletes who wore a mouthguard during an accident than in those who did not, OR=2.1 to 3.3, p≤0.05. Players without mouthguard sustained broken and knocked out teeth more frequently, while players with a mouthguard had more lip cuts (p≤0.05). Players complained less about custom-made than about mouth-moulded mouthguards (p≤0.05). Also, males were more at risk for an orodental injury, OR=1.4 (95% CI 1.0 to 1.9), and were less likely to have a custom-made mouthguard, OR=0.7 (95% CI 0.6 to 0.9), than females. CONCLUSIONS: A substantial number of field hockey players suffers from orodental injury. Mouthguards should be included in prevention strategies as they are associated with less severe injuries and patterns of injury are to be taken into account when targeting specific groups.

The association between hypodontia and dental development.

OBJECTIVES: In this cross-sectional study, we aimed to investigate the pattern of hypodontia in the Dutch population and determine the association between hypodontia and dental development in children with and without hypodontia, applying three different standards, Dutch, French Canadian, and Belgian, to estimate dental age. METHODS: We used dental panoramic radiographs (DPRs) of 1488 children (773 boys and 715 girls), with a mean age of 9.76 years (SD = 0.24) participating in a population-based cohort study in Rotterdam, the Netherlands, born in 2002-2004, and 452 children (219 boys and 233 girls) with a mean age of 9.83 years (SD = 1.09) participating in a mixed-longitudinal, interdisciplinary population-based cohort study in Nijmegen, the Netherlands born in 1960-1968. RESULTS: The prevalence of hypodontia in the Generation R Study was 5.6 % (N = 84) and 5.1 % (N = 23) in the Nijmegen Growth Study. Linear regression analysis showed that children with hypodontia had a 0.37 [95 % CI (-0.53,-0.21)] to 0.52 [95 % CI (-0.76,-0.38)] years lower dental age than children without hypodontia. The ordinal regression analysis showed a delay in development of mandibular second premolars [1.68 years; 95 %CI (-1.90,-1.46)], mandibular first premolars [0.57 years; 95 % CI (-0.94,-0.20)], and mandibular second molars [0.47 years; 95 % CI (-0.84,-0.11)]. CONCLUSION: These findings suggest that children with hypodontia have a delayed dental development. CLINICAL RELEVANCE: The delay of dental development in children with hypodontia should be taken into consideration and therefore orthodontists should recognize that a later start of treatment in these patients may be necessary.

Craniofacial characteristics of children with mild hypodontia.

INTRODUCTION: The aim of our study was to evaluate the craniofacial characteristics of children with mild hypodontia using conventional and principal component (PC) analysis. METHODS: We used radiographic images of 124 children (8-12 years old) with up to 4 missing teeth (55 boys, 69 girls) and of 676 reference children (365 boys, 311 girls) from the Rotterdam Generation R Study and the Nijmegen Growth Study in The Netherlands. Fifteen cephalometric measurements of children with hypodontia were compared with those of the reference children. Moreover, cephalometric parameters were combined into standardized PC scores using PC analysis, and the components were compared between the 2 groups. RESULTS: PC analysis showed common dental characteristics for all types of hypodontia: a significant increase of the interincisal angle, and decreases of the maxillary and mandibular incisor angles. Other findings were consistent when both methods were applied: (1) anterior hypodontia was significantly associated with the high-angle (hyperdivergent) craniofacial pattern, (2) the tendency toward a Class III malocclusion was identified in maxillary hypodontia, and (3) we observed a significant reduction of lower posterior facial height in children with posterior and mandibular hypodontia. CONCLUSIONS: Our findings suggest that children with mild hypodontia have distinctive skeletal and dental features.

Secular trend of dental development in Dutch children.

Many studies have established dental age standards for different populations; however, very few studies have investigated whether dental development is stable over time on a population level. Therefore, the aim of this study was to analyze changes in dental maturity in Dutch children born between 1961 and 2004. We used 2,655 dental panoramic radiographs of 2- to 16-year-old Dutch children from studies performed in three major cities in the Netherlands. Based on a trend in children born between 1961 and 1994, we predicted that a child of a certain age and gender born in 1963 achieved the same dental maturity on average, 1.5 years later than a child of the same age born 40 years later. After adjusting for the birth year of a child in the analysis, the regression coefficient of the city variable was reduced by 56.6% and it remained statistically significant. The observed trend from 1961 to 1994 was extrapolated to 9- to 10-year-old children born in 2002-2004, and validation with the other samples of children with the same characteristics showed that 95.9%-96.8% of the children had dental maturity within the 95% of the predicted range. Dental maturity score was significantly and positively associated with the year of birth, gender, and age in Dutch children, indicating a trend in earlier dental development during the observation period, 1961-2004. These findings highlight the necessity of taking the year of birth into account when assessing dental development within a population with a wider time span.

The association between WNT10A variants and dental development in patients with isolated oligodontia.

In this study we aimed to determine the effect of WNT10A variants on dental development in patients with oligodontia. Forty-three (25 boys and 18 girls) individuals were eligible for this study. Stage of development for each present tooth was assessed using the Demirjian method. In case no corresponding tooth was present, regression equations were applied for dental age to be calculated. The ratio between length of root and length of crown was ascertained for each present tooth in all quadrants. All patients were physically examined by a clinical geneticist and DNA analysis of the WNT10A gene was performed. Linear regression models were applied to analyze the association between WNT10A variants and dental age. The same analysis was applied to study the association between WNT10A variants and root elongation for each present tooth. One ordinal regression model was applied to analyze the association between WNT10A variants and development of present maxillary and mandibular teeth. Thirty-six (84%) patients were detected with WNT10A variants of which six patients displayed evident ectodermal features. Dental age was 1.50 (95% confidence interval (CI): -2.59, -0.42) to 1.96 (95% CI: -3.76, -0.17) years lower in patients with WNT10A variants compared with patients without variants. The development of maxillary canine, maxillary second molar and mandibular second molar was statistically significantly delayed in patients with WNT10A variants compared with patients without variants. The impact of WNT10A variants on dental development increases with presence of the nonsense c.(321C>A p.(C107*)) variant and the number of missing teeth.

[Comparative analysis of linear morphometric parameters of the humane mandibula obtained by direct and indirect measurement].

BACKGROUND/AIM: Reconstruction of lost, damaged or distorted mandibular bone presents a challenge from the functional side, as well as from the esthetic point of view. The aim of this study was to determinate potential differences between values of the basic linear moprhometric parameters (LMPs) obtained by direct and indirect manual measurement of the same humane mandibles, with accuracy testing of indirect measurement, which are routinely used in every-day clinical practice. The results are essential for defining of parametric model of the "standard mandible" and virtual modeling of the humane mandible in future researches as well as in clinical medicine. METHODS: A total number of 12 dry bony mandibles of human adults were studied. According to the standard anatomical landmarks, 10 standard LPMs were measured on each mandible by different manual methods: directly by a sliding caliper with nonius, and indirectly using standard software on two-dimensional (2D) reconstructions of mandibular multislice computed tomography (MSCT) scans. The values obtained by the different measuring methods were matched for the same LMPs. RESULTS: Statistically significant differences between compared LMPs values obtained by different measuring methods, appeared in the gnathio-interdental distance (Gn-IdD), as well as in the gnathio-condylar distance (Gn-CoD), bilaterally. In both parameters, significantly higher mean values (with percent of difference) were obtained by direct versus indirect measurement: Gn-IdD (21.57%; 29.2 mm vs 22.9 mm; p = 0.004); Gn-CoD left side (14.1%; 122.7 mm vs 105.4 cm; p = 0.001); Gn-CoD right side (11.87%; 124.7 mm vs 109.9 mm; p = 0.009). CONCLUSION: According to the observed inaccuracy of indirect measurement, we recommended the use of a correction factor for calculation of both Gn-IdD and Gn-CoD real vales, in defining of parametric model of the "standard mandible" based on indirect morphometry on 2D reconstructions of mandibular MSCT scans. Additional studies with larger number of specimens and quantification of anatomical variations regarding to sex, age, dentition status and ethnic origin, additionally should increase measurement accuracy and consequently reliability of future parametric model of the human mandible.