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With diagnostic and therapeutic advances, over 80% of children diagnosed with cancer become long-term survivors. As the number of childhood cancer survivors (CCS) continues to increase, dental practitioners become more likely to have CCS among their patients. CCS may develop late complications from damage caused by their cancer treatment to endocrine, cardiovascular, musculoskeletal, and other organ systems. These complications may surface decades after the completion of treatment. Adverse outcomes of childhood cancer treatment frequently involve oral and craniofacial structures including the dentition. Tooth development, salivary gland function, craniofacial growth, and temporomandibular joint function may be disturbed, increasing oral health risks in these individuals. Moreover, CCS are at risk of developing subsequent malignancies, which may manifest in or near the oral cavity. It is important that dental practitioners are aware of the childhood cancer history of their patients and have knowledge of potential late complications. Therefore, this narrative review aims to inform dental practitioners of late oral complications of cancer treatment modalities commonly used in pediatric oncology. Furthermore, selected common non-oral late sequelae of cancer therapy that could have an impact on oral health and on delivering dental care will be discussed. [ABSTRACT FROM AUTHOR]

Background and objective The genetic basis of dentoalveolar characteristics has been investigated by several studies, however, the findings are equivocal. The objective of this systematic review and meta-analysis was to evaluate the heritability of dental arches and occlusal parameters in different stages of human dentition. Search methods Electronic databases PubMed, Embase, Scopus, Web of Science, and Dentistry and Oral Science Source were searched up to August 2023 without the restriction of language or publication date. Selection criteria Empirical studies investigating the heritability of dentoalveolar parameters among twins and siblings were included in the review. Data collection and analysis Study selection, data extraction, and risk of bias assessment were performed independently and in duplicate by two authors and a third author resolved conflicts if needed. Joanna Briggs Institute's critical appraisal tool was used to evaluate the risk of bias among studies and the certainty of evidence was assessed using the Grading of Recommendation, Assessment, Development, and Evaluation (GRADE) criteria. Results Twenty-eight studies were included in the systematic review, of which 15 studies reporting heritability coefficients in the permanent dentition stages were deemed suitable for the meta-analysis. Random-effects meta-analyses showed high heritability estimates for maxillary intermolar width (0.52), maxillary intercanine width (0.54), mandibular intermolar width (0.55), mandibular intercanine width (0.55), maxillary arch length (0.76), mandibular arch length (0.57), and palatal depth (0.56). The heritability estimates for the occlusal parameters varied considerably, with relatively moderate values for crossbite (0.46) and overbite (0.44) and low values for buccal segment relationship (0.32), overjet (0.22), and rotation and displacement of teeth (0.16). However, the certainty of evidence for most of the outcomes was low according to the GRADE criteria. Conclusions Based on the available evidence, it can be concluded that the dental arch dimensions have a high heritability while the occlusal parameters demonstrate a moderate to low heritability. Registration PROSPERO (CRD42022358442). [ABSTRACT FROM AUTHOR]

Genealogical samples that couple dental data and documented relatedness information provide unique opportunities to examine the biological foundations of tooth variation. Over the past century, these resources have been critical for examining the various factors that influence dental phenotypes—the same traits that anthropologists regularly apply to reconstructions of past phenomena. Genealogical samples are uniquely suited to test long‐standing assumptions underlying bioanthropological practice, for example, biodistance and phylogenetic analysis, which commonly reference aspects of tooth size and form as proxies for latent genetic information. This article provides an overview of published genealogical research, with a focus on the practical implications of quantitative genetic and environmental studies of (non)human primate dentitions. To highlight the utility of genealogical samples for understanding the influence of specific non‐genetic factors on dental characters, we also present novel data on gestational hormone effects in opposite‐sex dizygotic twin pairs as a test of the twin testosterone transfer (TTT) hypothesis. This article discusses fruitful next steps in genealogical dental research, as well as important ethical considerations surrounding the use of associated datasets, which are sensitive in nature. As we forge ahead in an age of phenomics, genealogical samples are likely to play a key role in generating comprehensive genotype–phenotype maps of the dentition and in refining bioanthropological methods. [ABSTRACT FROM AUTHOR]

The aims of this study are to determine the oral health status of a rare sample of 19th-century migrant settlers to South Australia, how oral conditions may have influenced their general health, and how the oral health of this group compares with contemporaneous samples in Australia, New Zealand, and Britain. Dentitions of 18 adults and 22 subadults were investigated using non-destructive methods (micro-CT, macroscopic, radiographic). Extensive carious lesions were identified in seventeen adults and four subadults, and from this group one subadult and sixteen adults had antemortem tooth loss. Sixteen adults showed evidence of periodontal disease. Enamel hypoplastic (EH) defects were identified in fourteen adults and nine subadults. Many individuals with dental defects also had skeletal signs of comorbidities. South Australian individuals had the same percentage of carious lesions as the British sample (53%), more than other historic Australian samples, but less than a contemporary New Zealand sample. Over 50% of individuals from all the historic cemeteries had EH defects, suggesting systemic health insults during dental development were common during the 19th century. The overall oral health of the South Australian settlers was poor but, in some categories, (tooth wear, periapical abscess, periodontal disease), better than the other historic samples. [ABSTRACT FROM AUTHOR]

Archaeological investigation of the dentoalveolar complex in situ within a human skull requires detailed measurements using non‐invasive techniques. Standard macroscopic and radiographic methods have limitations but large volume micro‐computed tomography (LV micro‐CT) scanning has the potential to acquire data at high resolution in microns. In this study, archaeological specimens are analyzed using three‐dimensional data visualization software from LV micro‐CT scans with the aims of (1) determining whether LV micro‐CT can act as a single technique to provide detailed analysis of the dentoalveolar complex and (2) how findings from the LV micro‐CT technique compare with standard methods. These aims are explored by measuring a range of human skull specimens from a rare archaeological sample requiring non‐invasive methods, for multiple dental and alveolar bone health categories. The LV micro‐CT technique was the only method to provide a full range of detailed measurements across all categories studied. A combination of macroscopic and radiographic techniques covered a number of categories, but the use of multiple methods was more time consuming, did not provide the same level of accuracy, and did not include all measurements. There were high levels of reproducibility for intra‐operator scoring and good inter‐operator agreement from four operators with one operator whose results were outliers. As a further investigation of the potential of the LV micro‐CT technique, an additional individual, a fragile, fragmented skull of an infant was studied. This investigation confirms the value of LV micro‐CT scanning as a non‐invasive, accurate, single technique for the extensive analysis of the dentoalveolar complex within archaeological skulls, which also allows the relationship of different tissues to be studied in situ. [ABSTRACT FROM AUTHOR]

Objective: Chronic periodontal disease (CP) is a multifactorial infectious and inflammatory disease that occurs due to the challenge between the immune response of the host and specific periodontal bacteria, and that can lead to tooth loss due to damage inflicted to the supporting tissue. The current study investigates the genotypes of the GSTM1 and GSTT1 genes, along with the allelic frequency of the single nucleotide polymorphism [SNP; rs1695] in the GSTP1 gene and correlates them individually or in various combinations with the incidence of CP. Methods: A total of 203 clinically confirmed CP patients and 201 control subjects were enrolled from Multan and Dera Ghazi Khan Districts in Pakistan from April to July 2022. Multiplex Polymerase Chain Reaction (PCR) and tetra-primer amplification refractory mutation system–polymerase chain reaction (T-ARMS–PCR) approaches were applied to determine the genotypes of the studied GSTs. The association of rs1695 in GSTP1 with CP was studied both individually and in various combinations with GSTM1 and T1. Results: The absence of GSTM1, the presence of GSTT1 and the presence of the mutant allele (G) at rs1695 in GSTP1 were found to be significantly associated with CP. Patients aged between 10 and 30 years were more affected by CP. Conclusion: Our results indicate that the genotypes of the analyzed GSTs affect the levels of protection from oxidative stress and may therefore influence the disease progression in CP. [ABSTRACT FROM AUTHOR]

(1) Background: Hypodontia has a multifactorial aetiology, in which genetic factors are a major component. Associated with this congenital absence, the formed teeth may show differences in size and shape, which may vary with the specific genetic variants and with the location of the missing teeth. The aims of the present study were to investigate a specific variant of MSX1, derive morphometric tooth measurements in a sample of patients with isolated maxillary lateral incisor agenesis and matched controls, and model the findings. (2) Methods: Genotyping of the MSX1 rs8670 genetic variant and morphometric measurements with a 2D image analysis method were performed for 26 hypodontia patients and 26 matched controls. (3) Results: The risk of upper lateral incisor agenesis was 6.9 times higher when the T allele was present. The morphometric parameters showed significant differences between hypodontia patients and controls and between the unilateral and bilateral agenesis cases. The most affected crown dimension in the hypodontia patients was the bucco-lingual dimension. In crown shape there was significant variation the Carabelli trait in upper first molars. (4) Conclusions: The MSX1 rs8670 variant was associated with variations in morphological outcomes. The new findings for compensatory interactions between the maxillary incisors indicate that epigenetic and environmental factors interact with this genetic variant. A single-level directional complex interactive network model incorporates the variations seen in this study. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate whether the genetic, epigenetic and environmental factors that give rise to supernumeraries in the maxillary incisor region and larger dimensions of the adjacent maxillary incisors are also associated with variations in the morphology of the mandibular incisors. If so, this would contribute to understanding the distribution and interactions of factors during dental development and how these can be modelled. The sample consisted of 34 patients with supernumerary teeth in the maxillary anterior region, matched for gender, age and White Caucasian ethnicity with 34 control subjects. The average ages of the supernumerary and control groups were 12.8 and 12.2 years, respectively. Study models of all subjects were constructed and imaged using a previously validated system. Using custom software, each of the mandibular incisor teeth were measured to obtain 17 parameters from the labial view and 17 from the occlusal view. Principal component analysis (PCA) was used to summarize the measurements into a smaller set representing distinct features of the clinical crowns, followed by a comparison between the supernumerary and control groups using 2-way ANOVA. Seven factors of tooth size of the mandibular central incisors and six factors of the mandibular lateral incisors were identified as major features of the clinical crowns. All parameters of both mandibular incisors were greater in the supernumerary group than in the control, with three of these, located in the incisal and cervical regions of the mandibular lateral incisors, being statistically significantly larger. The findings of this study indicate that the aetiological factors associated with supernumerary teeth in the maxillary anterior region also affect tooth crown dimensions of mandibular incisors. This new evidence enhances several models of the interactions of genetic, epigenetic and environmental components of dental development and supports a multi-model approach to increase understanding of this process and its variations. [ABSTRACT FROM AUTHOR]

Background: Chemotherapy treatment of cancer in children can influence formation of normal tissues, leading to irreversible changes in their structure and function. Tooth formation is susceptible to several types of chemotherapy that induce irreversible changes in the structure of enamel, dentin and dental root morphology. These changes can make the teeth more prone to fracture or to caries when they have erupted. Recent studies report successful treatment of brain tumors with the alkylating drug temozolomide (TMZ) in combination with veliparib (VLP) in a glioblastoma in vivo mouse model. Whether these drugs also affect tooth formation is unknown. Aim: In this study the effect of TMZ/VLP on incisor formation was investigated in tissue sections of jaws from mice and compared with mice not treated with these drugs. Materials and method: The following aspects were studied using immunohistochemistry of specific protein markers including: (1) proliferation (by protein expression of proliferation marker Ki67) (2) a protein involved in paracellular ion transport (expression of tight junction (TJ) protein claudin-1) and (3) in transcellular passage of ions across the dental epithelium (expression of Na+, K+ 2Cl- cotransporter/NKCC1). Results: Chemotherapy with TMZ/VLP strongly reduced immunostaining for claudin-1 in distal parts of maturation ameloblasts. No gross changes were found in the treated mice, either in cell proliferation in the dental epithelium at the cervical loop or in the immunostaining pattern for NKCC1 in (non-ameloblastic) dental epithelium. The salivary glands in the treated mice contained strongly reduced immunostaining for NKCC1 in the basolateral membranes of acinar cells. Discussion/Conclusions: Based on the reduction of claudin-1 immunostaining in ameloblasts, TMZ/VLP may potentially influence forming enamel by changes in the structure of TJs structures in maturation ameloblasts, structures that are crucial for the selective passage of ions through the intercellular space between neighboring ameloblasts. The strongly reduced basolateral NKCC1 staining seen in fully-grown salivary glands of TMZ/VLP-treated mice suggests that TMZ/VLF could also influence ion transport in adult saliva by the salivary gland epithelium. This may cause treated children to be more susceptible to caries. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The British colony of South Australia, established in 1836, offered a fresh start to migrants hoping for a better life. A cohort of settlers buried in a section of St Mary's Anglican Church Cemetery (1847–1927) allocated for government funded burials was investigated to determine their health, with a focus on skeletal manifestations associated with metabolic deficiencies. Findings of St Mary's sample were compared with those published for contemporary skeletal samples from two British cemeteries, St Martin's, Birmingham, and St Peter's, Wolverhampton, to explore similarities and differences. To investigate the changing economic background of the St Mary's cohort, which may have influenced the location of their burial within the cemetery, the number and demographic profile of government funded burials and those in privately funded leased plots were compared. The study sample consisted of the skeletal remains of 65 individuals (20 adults, 45 subadults) from St Mary's Cemetery 'free ground' section. The bones and teeth of individuals in this cohort showed evidence of pathological manifestations, including areas of abnormal porosity in bone cortices in 9 adults and 12 subadults and flaring of metaphyses (one subadult) and costochondral junctions of the ribs (one subadult). Porous lesions of orbital roof bones (Types 3 to 4) were seen on three subadults. Macroscopic examination of teeth identified enamel hypoplastic defects and micro-CT scans showed areas of interglobular dentine. Comparison of St Mary's findings with the British samples revealed that prevalences of manifestations associated with vitamin C deficiency were higher at St Mary's and manifestations associated with vitamin D deficiency were lower respectively. The location of burial pattern at St Mary's Cemetery, from the mid-1840s to1860s, showed differences in the economic status of migrants. This pattern changed from the 1870s, which reflected improvements in the local economy and the economic recovery of the colony. [ABSTRACT FROM AUTHOR]

Objectives: This study generates a series of narrow‐sense heritability estimates for crown morphology of the deciduous and permanent dentition with two overarching aims. The first is to test the hypothesis that deciduous teeth provide a more faithful reflection of genetic information than their permanent successors. The second is to use quantitative genetic methods to evaluate assumptions underlying common data collection and analysis practices in biodistance research. Materials and Methods: Dental morphology data were collected from longitudinal dental casts representing Australian twins and families using Arizona State Dental Anthropology System standards. Polygenic models and estimates of narrow‐sense heritability were generated using SOLAR v.8.1.1. Each model considered age, sex, and age/sex interaction as covariates. Results: Heritability estimates significantly differed from zero for the majority of morphological crown characters. Most estimates fell within the 0.4–0.8 range typically observed for crown morphology. Mean heritability was stable across the dental complex, but for paired homologues, permanent traits often yielded higher estimates than their deciduous counterparts. Results indicate directional asymmetry in environmental influence for crown morphology and inform biodistance "best practices" related to data collection and treatment. Conclusions: Overall, results for this sample support the use of crown morphology as a proxy for genetic variation in evolutionary research. This includes the deciduous dentition, which justifies the expansion of efforts to incorporate subadults into reconstructions of past microevolutionary processes. Results do not indicate that deciduous phenotypes more closely approximate underlying genotype, at least for deciduous/permanent homologues. [ABSTRACT FROM AUTHOR]

Highlights • Discordance in dental expression within and between twin pairs provides evidence of epigenetic and environmental effects during development. • A unique twin sample has provided the data for this study. • Hypodontia is expressed as a group of variations within dental development. • Compensatory interactions between developing maxillary anterior teeth has been confirmed. • Some, but not all, of the original findings of Sofaer et al. (1971) have been confirmed. Abstract Objectives The objective of this study was to revisit the topic of compensatory interactions between maxillary anterior teeth during development advanced by Sofaer et al. (1971). We addressed the hypotheses listed by Sofaer and colleagues using data derived from our Australian twin sample to investigate whether final tooth size in permanent maxillary central incisors and canines showed evidence of developmental compensation for adjacent missing or microdont lateral incisors. Such compensation is one factor interacting in the complex system of dental development. Materials and methods A 2D image analysis system was used to measure crown height from the labial view, labiopalatal crown width from the incisal view, and mesiodistal crown width from both the labial (MDl) and incisal (MDi) views of the permanent maxillary central incisors and canines on the dental study model of twins enrolled in a longitudinal study of dental development. Results Developmental variations of maxillary lateral incisors influence the morphogenesis of the adjacent teeth. For example, individuals with one missing lateral incisor and one lateral incisor of average dimensions, had significantly larger central incisors than the control group for the MDl and MDi dimensions (p < 0.05). Of the 7 monozygotic twin pairs, 6 were discordant in maxillary anterior hypodontia and microdontia, and 13 out of 14 dizygotic twin pairs were discordant. Conclusions This study provides further evidence of developmental interactions in the maxillary anterior region, partially supporting Sofaer and colleagues' hypotheses. These interactions are part of a complex adaptive system involving genetic, epigenetic and environmental factors. [ABSTRACT FROM AUTHOR]

Objectives: This study aimed to investigate size and shape variation of human premolars between Indigenous Australians and Australians of European ancestry, and to assess whether sex and ancestry could be differentiated between these groups using 3D geometric morphometrics. Materials and Methods: Seventy dental casts from each group, equally subdivided by sex, were scanned using a structured-light scanner. The 3D meshes of upper and lower premolars were processed using geometric morphometric methods. Seventy-two landmarks were recorded for upper premolars and 50 landmarks for lower premolars. For each tooth type, two-way ANOVA was used to assess group differences in centroid size. Shape variations were explored using principal component analysis and visualized using 3D morphing. Two-way Procrustes ANOVA was applied to test group differences for ancestry and sex, and a "leave-one-out" discriminant function was applied to assess group assignment. Results: Centroid size and shape did not display significant difference between the sexes. Centroid size was larger in Indigenous Australians for upper premolars and lower second premolars compared to the Australians of European ancestry. Significant shape variation was noted between the two ancestral groups for upper premolars and the lower first premolar. Correct group assignment of individual teeth to their ancestral groups ranged between 80.0 and 92.8% for upper premolars and 60.0 and 75.7% for lower premolars. Discussion: Our findings provide evidence of significant size and shape variation in human premolars between the two ancestral groups. High classification rates based on shape analysis of upper premolars highlight potential application of geometric morphometrics in anthropological, bioarcheological and forensic contexts. [ABSTRACT FROM AUTHOR]

Many representations of the movement of healthcare knowledge through society exist, and multiple models for the translation of evidence into policy and practice have been articulated. Most are linear or cyclical and very few come close to reflecting the dense and intricate relationships, systems and politics of organizations and the processes required to enact sustainable improvements. We illustrate how using complexity and network concepts can better inform knowledge translation (KT) and argue that changing the way we think and talk about KT could enhance the creation and movement of knowledge throughout those systems needing to develop and utilise it. From our theoretical refinement, we propose that KT is a complex network composed of five interdependent sub-networks, or clusters, of key processes (problem identification [PI], knowledge creation [KC], knowledge synthesis [KS], implementation [I], and evaluation [E]) that interact dynamically in different ways at different times across one or more sectors (community; health; government; education; research for example). We call this the KT Complexity Network, defined as a network that optimises the effective, appropriate and timely creation and movement of knowledge to those who need it in order to improve what they do. Activation within and throughout any one of these processes and systems depends upon the agents promoting the change, successfully working across and between multiple systems and clusters. The case is presented for moving to a way of thinking about KT using complexity and network concepts. This extends the thinking that is developing around integrated KT approaches. There are a number of policy and practice implications that need to be considered in light of this shift in thinking. [ABSTRACT FROM AUTHOR]

Objective The associations seen clinically between variations in tooth number, size and shape reflect the repetitive genetic interactions occurring between the epithelium and mesenchyme during the initiation and morphogenetic stages of the Complex Adaptive System that is dental development. The aim of this study was to investigate the clinical relationship further by comparing multiple crown parameters, including cusp numbers, between patients with mild hypodontia and controls in a Romanian sample. Design Digital images of dental casts of the permanent dentition from 28 patients with mild hypodontia and 28 controls were used. Measurements from the vestibular and occlusal surfaces were performed using a 2D image analysis method and cusps, including the Carabelli trait, were counted. Two-way analysis of variance was performed. Results The dimensions of the mild hypodontia group had smaller values than the controls, with many measurements being significantly different (significance values varied from p = 0.049 to p = 0.001 ). The most affected regions were the upper and lower anterior region in both sexes. Mesio-distal, bucco-lingual and occlusal area and perimeter dimensions were affected. Females from the hypodontia group had significantly less tricuspidated lower premolars when compared with the control group. Carabelli cusps were present in the hypodontia group less frequently, the difference being highly significant ( p = 0.0002 ) in women. Conclusions The hypodontia patients presented with reduced crown dimensions and shape compared with controls. This is the first published study to demonstrate smaller cusp numbers in patients with hypodontia than in controls. The findings are compatible with a model of dental development as a Complex Adaptive System incorporating associations between tooth number, size and shape. [ABSTRACT FROM AUTHOR]

Mutations in human and in mouse orthologous genes Amelx and Enam result in a diverse range of enamel defects. In this study we aimed to investigate the phenotype-genotype correlation between the mutants and the wild-type controls in mouse models of amelogenesis imperfecta using novel measurement approaches. Ten hemi-mandibles and incisors were dissected from each group of AmelxWT, AmelxX/Y64H, AmelxY/Y64H, AmelxY64H/Y64H, and EnamWT, EnamRgsc395 heterozygous and EnamRgsc395 homozygous mice. Their macro-morphology, colour and micro-topography were assessed using bespoke 2D and 3D image analysis systems and customized colour and whiteness algorithms. The novel methods identified significant differences (p ≤ 0.05) between the Amelx groups for mandible and incisor size and enamel colour and between the Enam groups for incisor size and enamel colour. The AmelxWT mice had the largest mandibles and incisors, followed in descending order of size by the AmelxX/Y64H, AmelxY/Y64H and AmelxY64H/Y64H mice. Within the Enam groups the EnamWT incisors were largest and the EnamRgsc395 heterozygous mice were smallest. The effect on tooth morphology was also reflected by the severity of the enamel defects in the colour and whiteness assessment. Amelogenin affected mandible morphology and incisor enamel formation, while enamelin only affected incisors, supporting the multifunctional role of amelogenin. The enamelin mutation was associated with earlier forming enamel defects. The study supported the critical involvement of amelogenin and enamelin in enamel mineralization. Copyright © 2012 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

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 cllls2D 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. [ABSTRACT FROM AUTHOR]

Background: Three-dimensional measurement of dental morphology is providing new variables and shape information not available previously, and the reliability of these data has proved to be substantial. Accurate superimposition of 2D and 3D data-sets has several applications in dental research when making comparisons of similar structures. For example, two data-sets of the same object can be superimposed to highlight differences apparent in limited region(s) of the tooth crown. When significant regions represented by the two data-sets are identical, registration of the images can be achieved by standard superimposition methods. However, for comparisons of crown morphologies between monozygotic and dizygotic co-twins, the data sets are similar but not identical so a new approach to superimposition has been developed. Aim: To develop a non 'best fit' (Synetic) method for the 3D superimposition of non-similar objects that forms one comparable interface providing enhanced methodology for the analysis of differences within the dentition of twins. Method: A minimised least-squares registration approach is followed by diffusion based registration to provide global minimisation between points that is not based on a best fit algorithm. This process is linear and therefore the method ensures uniqueness of the superimposition. Results: Initial results indicate a reliable method producing only one output as opposed to best fit approaches that may generate a different output each time. Conclusion: Diffusion-based registration offers a more reliable approach to superimposing non-identical objects, such as the tooth crowns of monozygotic co-twins, than conventional best fit methods. [ABSTRACT FROM AUTHOR]

This randomized controlled trial compared the effects of outreach placement with traditional, exclusively dental school-based clinical experience on students' confidence in providing treatment for patients presenting with common dental problems. Senior dental students (n=49) were allocated at random to existing dental school-based clinics or placement in primary care clinics to work supervised by local dentists. At baseline, students self-rated their global confidence on a five-point scale. These measures were repeated at follow-up, augmented by a transition judgment and a then-test of confidence (asking students to look back and re-rate their pre-placement confidence). Groups were comparable at baseline. Follow-up scores for global confidence were similar between groups. The outreach group scored higher in the transition judgment (mean 3.7, SD 0.9) than the control group (mean 3.1, SD 1.1, P=0.05). In the then-test, on reflection, the outreach group considered their baseline ratings of confidence were overoptimistic (mean then-test scores 3.2, SD 0.9 and baseline 3.7, SD 0.5) while the control group thought theirs were accurate (mean then-test scores 3.8, SD 0.7 and baseline 3.6, SD 0.8, P=0.01). The findings suggest dental outreach training in primary care settings is more effective than dental school training alone in improving students' confidence in tackling clinical situations. The measurement of change in confidence is complicated by shifts in students' internal scales arising from insights gained on outreach. [ABSTRACT FROM AUTHOR]