ORCID Profile
0000-0001-8668-7744
Current Organisation
University of Adelaide
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: S. Karger AG
Date: 2009
DOI: 10.1159/000242406
Abstract: Two metaphors are presented to highlight concepts that could lead to a paradigm shift in dental studies of twins. The first, derived from the Song of Solomon in the Bible, refers to teeth as being twins. This viewpoint emphasises that each tooth should be viewed as a paired structure, not only with its antimere (within the same arch) but also with its isomer (in the opposing arch). The other metaphor provided by Waddington in 1957 is visual and involves 'an epigenetic landscape' that represents the processes of decision-making by cells during development. It likens the different stages of cellular decision-making to a ball rolling down an undulating landscape of interconnecting hills and valleys. This viewpoint helps to explain how distinct differences in dental phenotypes may arise both within and between monozygotic (MZ) co-twins due to relatively minor temporospatial effects during development. Measurements of maximum mesiodistal diameters of teeth in a pair of MZ twins, using calipers and also 2D and 3D imaging systems, have demonstrated that differences in dental crown size occur between antimeric pairs and between corresponding teeth of MZ co-twins. By defining new dental phenotypes that provide more comprehensive descriptions of tooth size and shape, and by drawing on the metaphors described, we are confident of providing new insights into the reasons for observed similarities and differences within, and between, the dentitions of twins. Our approaches will focus on multivariate analyses that take into account the paired arrangement of teeth and also explore epigenetic, as well as genetic and environmental, sources of variation.
Publisher: Oxford University Press (OUP)
Date: 11-10-2023
DOI: 10.1093/EJO/CJAD061
Publisher: Elsevier BV
Date: 10-2023
Publisher: S. Karger AG
Date: 2009
DOI: 10.1159/000242401
Abstract: This study is part of a larger investigation of genetic and environmental influences on primary tooth emergence in Australian twins. Our aims were to describe patterns of emergence asymmetry, including directional and fluctuating components (DA, FA), and to test for a genetic basis to observed asymmetry. The study s le consisted of 131 twin pairs. Using one randomly-selected twin from each pair, dental asymmetry was examined by analysing the number of days between emergence of antimeres (Delta), with dates of emergence provided through parental recording. Scatterplots were used for assessment of DA and FA, followed by paired t-tests to detect significant differences in mean Delta from zero (evidence of DA). FA was assessed by calculating means and variances of the absolute value of Delta. A range of intervals (0, 7, 14, 21, 28 days) was used to define symmetrical emergence of antimeres. Although a trend in left-side advancement for tooth emergence was detected, this was not statistically significant. Relatively low levels of FA were noted through -out the primary dentition, with maxillary and mandibular lateral inisors displaying the highest values, but no evidence of a genetic influence on FA was noted. Around 50% of all antimeric pairs of primary teeth were found to emerge within 14 days of each other, although time differences of more than 50 days were noted in some cases. Studies of dental asymmetry provide insights into the biological basis of lateralisation in humans and the results can also assist clinicians to discriminate between normal and abnormal developmental patterns.
Publisher: Wiley
Date: 19-02-2020
DOI: 10.1002/AJPA.24019
Publisher: Oxford University Press (OUP)
Date: 20-10-2023
DOI: 10.1093/EJO/CJAD054
Publisher: MDPI AG
Date: 02-06-2022
Abstract: This study aims to expand our understanding of the genetic architecture of crown morphology in the human diphyodont dentition. Here, we present bivariate genetic correlation estimates for deciduous and permanent molar traits and evaluate the patterns of pleiotropy within (e.g., m1–m2) and between (e.g., m2–M1) dentitions. Morphology was observed and scored from dental models representing participants of an Australian twin and family study (deciduous n = 290, permanent n = 339). Data collection followed Arizona State University Dental Anthropology System standards. Genetic correlation estimates were generated using maximum likelihood variance components analysis in SOLAR v.8.1.1. Approximately 23% of deciduous variance components models and 30% of permanent variance components models yielded significant genetic correlation estimates. By comparison, over half (56%) of deciduous–permanent homologues (e.g., m2 hypocone–M1 hypocone) were significantly genetically correlated. It is generally assumed that the deciduous and permanent molars represent members of a meristic molar field emerging from the primary dental lamina. However, stronger genetic integration among m2–M1/M2 homologues than among paired deciduous traits suggests the m2 represents the anterior-most member of a “true” molar field. The results indicate genetic factors act at distinct points throughout development to generate homologous molar form, starting with the m2, which is later replaced by a permanent premolariform crown.
Publisher: Elsevier BV
Date: 02-2023
DOI: 10.1016/J.JOMS.2022.10.014
Abstract: Osteonecrosis of the jaws (ONJ) occurs in patients on antiresorptive drugs for osteoporosis with the risk with oral bisphosphonates being known to be of the order of 0.1 to 0.3% while the risk for patients on denosumab for osteoporosis is not known. The aim of this study was to determine the risk of developing ONJ in a consecutive series of patients on denosumab for osteoporosis having dental extractions. A prospective cohort study of patients on denosumab for osteoporosis having dental extractions in the period January 1, 2017 and June 30, 2021 were compared to a control group not on antiresorptives. Detailed demographic records including length of time on antiresorptives and CTX values were obtained. Comparison to further define risk factors was made between those patients developing ONJ to those who didn't. The treatment group included 427 patients who were on denosumab for osteoporosis they collectively underwent 561 episodes of dental treatment involving extractions for a total of 1081 extractions, with 10 developing ONJ (risk 2.3%). The control group consisted of 299 patients who were not taking denosumab they collectively underwent 315 episodes of dental treatment for a total of 669 extractions, and none of them developed ONJ. There were significant differences in age and sex, but not medical comorbidities between the treatment and control groups. Within the treatment group, there were no significant differences in any of these characteristics between those who did, and those who didn't, develop ONJ. Within the treatment group, the number of extractions modified the risk of developing ONJ (odds ratio, 1.35 confidence interval, 1.1-1.7). Of the 76 patients who had extractions between 6 and 7 months after the last denosumab injection, none developed ONJ. The risk of ONJ in patients on denosumab for osteoporosis is a magnitude greater than for patients on the oral bisphosphonates 2.3% v 0 - 0.3%, which is 7.7 times more likely. Number of extractions and early resumption of the next dose of denosumab increases the risk of ONJ.
Publisher: Elsevier BV
Date: 09-2021
DOI: 10.1016/J.ARCHORALBIO.2021.105168
Abstract: This study presents a quantitative genetic analysis of human anterior dental morphology in a longitudinal s le of known genealogy. The primary aim of this work is to generate a suite of genetic correlations within and between deciduous and permanent characters to access patterns of integration across the diphyodont dental complex. Data were recorded from casted tooth crowns representing participants of a long-term Australian twin and family study (deciduous n = 290, permanent n = 339). Morphological trait expression was observed and scored following Arizona State University Dental Anthropology System standards. Bivariate genetic correlations were estimated using maximum likelihood variance decomposition models in SOLAR v.8.1.1. Genetic correlation estimates indicate high levels of integration between antimeres but low to moderate levels among traits within a tooth row. Only 9% of deciduous model comparisons were significant, while pleiotropy was indicated for one third of permanent trait pairs. Canine characters stood out as strongly integrated, especially in the deciduous dentition. For homologous characters across dentitions (e.g., deciduous i Patterns of genetic correlation suggest a morphological canine module that spans the primary and secondary dentition. Results also point to the existence of a genetic mechanism conserving morphology across the diphyodont dental complex, such that paired deciduous and permanent traits are more strongly integrated than characters within in idual tooth rows/teeth.
Publisher: Springer Science and Business Media LLC
Date: 14-05-2020
DOI: 10.1038/S41598-020-64747-1
Abstract: Humans are host to a multitude of microorganisms that rapidly populate the body at birth, subject to a complex interplay that is dependent on host genetics, lifestyle, and environment. The host-associated microbiome, including the oral microbiome, presents itself in a complex ecosystem important to health and disease. As the most common chronic disease globally, dental caries is induced by host-microbial dysbiosis in children and adults. Multiple biological and environmental factors are likely to impact disease predisposition, onset, progression, and severity, yet longitudinal studies able to capture these influences are missing. To investigate how host genetics and environment influenced the oral microbial communities over time, we profiled supragingival plaque microbiomes of dizygotic and monozygotic twins during 3 visits over 12-months. Dental plaque DNA s les were lified by targeting the 16S rRNA gene V4 region, and microbial findings were correlated with clinical, diet and genetic metadata. We observed that the oral microbiome variances were shaped primarily by the environment when compared to host genetics. Among the environmental factors shaping microbial changes of our subjects, significant metadata included age of the subject, and the age by which subjects initiated brushing habits, and the types of actions post-brushing. Relevant heritability of the microbiome included Actinomyces and Capnocytophaga in monozygotic twins and Kingella in dizygotic twins. Corynebacterium and Veillonella abundances were associated with age, whereas Aggregatibacter was associated with younger subjects. Streptococcus abundance showed an inverse association over time, and Selenomonas abundances increased with brushing frequency per day. Unraveling the exact biological mechanisms in caries has the potential to reveal novel host-microbial biomarkers, pathways, and targets important to effective preventive measures, and early disease control in children.
Publisher: Elsevier BV
Date: 09-2015
DOI: 10.1016/J.ARCHORALBIO.2015.06.010
Abstract: The aim of this study was to investigate the prevalence of selected dental variations in association with infraocclusion, as well as determining the effects of infraocclusion on dental development and tooth size, in singletons and twins. Two s les were analysed. The first s le comprised 1454 panoramic radiographs of singleton boys and girls aged 8-11 years. The second s le comprised dental models of 202 pairs of monozygotic and dizygotic twins aged 8-11 years. Adobe Photoshop CS5 was used to construct reference lines and measure the extent of infraocclusion (in mm) of primary molars on the panoramic radiographs and on 2D images obtained from the dental models. The panoramic radiographs were examined for the presence of selected dental variations and to assess dental development following the Demirjian and Willems systems. The twins' dental models were measured to assess mesiodistal crown widths. In the singleton s le there was a significant association of canines in an altered position during eruption and the lateral incisor complex (agenesis and/or small tooth size) with infraocclusion (P<0.001), but there was no significant association between infraocclusion and agenesis of premolars. Dental age assessment revealed that dental development was delayed in in iduals with infraocclusion compared to controls. The primary mandibular canines were significantly smaller in size in the infraoccluded group (P<0.05). The presence of other dental variations in association with infraocclusion, as well as delayed dental development and reduced tooth size, suggests the presence of a pleiotropic effect. The underlying aetiological factors may be genetic and/or epigenetic.
Publisher: Research Square Platform LLC
Date: 13-07-2022
DOI: 10.21203/RS.3.RS-477787/V1
Abstract: Antibiotic overuse has promoted the spread of antimicrobial resistance (AMR) with significant health and economic consequences. Surveillance of resistance reservoirs, like the rarely explored oral microbiome, is necessary to combat AMR. We characterised the development of the paediatric oral resistome and investigated its role in dental caries in 221 twin children s led over the first decade of life. From 535 oral metagenomes, we identified 309 antimicrobial resistance genes (ARGs), which significantly clustered by age, with the influence of host genetics on antimicrobial resistance increasing over time. Our results suggest the mobilisation potential of ARGs increased with age as Tn916 transposase was co-located with more species and ARGs as children grew. Dental caries compared to health was associated with a depletion of ARGs and species, which was reversed when restored. Our results highlight the dynamic nature of the paediatric oral resistome, and its potential role in transmission of AMR and dysbiosis.
Publisher: Springer Science and Business Media LLC
Date: 09-03-2023
DOI: 10.1038/S41467-023-36781-W
Abstract: Antibiotic overuse has promoted the spread of antimicrobial resistance (AMR) with significant health and economic consequences. Genome sequencing reveals the widespread presence of antimicrobial resistance genes (ARGs) in erse microbial environments. Hence, surveillance of resistance reservoirs, like the rarely explored oral microbiome, is necessary to combat AMR. Here, we characterise the development of the paediatric oral resistome and investigate its role in dental caries in 221 twin children (124 females and 97 males) s led at three time points over the first decade of life. From 530 oral metagenomes, we identify 309 ARGs, which significantly cluster by age, with host genetic effects detected from infancy onwards. Our results suggest potential mobilisation of ARGs increases with age as the AMR associated mobile genetic element, Tn 916 transposase was co-located with more species and ARGs in older children. We find a depletion of ARGs and species in dental caries compared to health. This trend reverses in restored teeth. Here we show the paediatric oral resistome is an inherent and dynamic component of the oral microbiome, with a potential role in transmission of AMR and dysbiosis.
No related grants have been discovered for Toby Hughes.