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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]

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]

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]

Brook AH, Smith JM. Hypoplastic enamel defects and environmental stress in a homogeneous Romano–British population. Eur J Oral Sci 2006; 114 (Suppl. 1): 370–374. © Eur J Oral Sci, 2006 --> This study investigated hypoplastic enamel defects in a well‐defined sample of Romano–Britons from the 3rd to the 5th century AD and compared the findings with a modern British sample investigated by the same authors. All 178 excavated skulls with intact dentitions were examined for hypoplastic defects using the Federation Dentaire International (FDI) Developmental Defects of Enamel Index criteria. Histopathological and microradiographic sections were prepared of 5 teeth. Hypoplastic defects were found in the teeth of 37% of skulls, with 25% having 4 or more teeth affected. The teeth most frequently involved were canines. Of the defects, 75% were horizontal grooves, 12.7% were pitting, and 7.1% were areas of missing enamel. The location of defects was 82% buccal, 16.5% lingual, and 1.2% occlusal. The reproducibility of diagnosis was 84%. Microscopic and microradiographic investigations showed areas of hypomineralization of enamel and wide zones of interglobular dentine related to the hypoplastic grooves. There was higher frequency, different morphology, and greater severity of hypoplastic enamel defects compared with the modern British sample. The defects may be related to repeated environmental stresses between the ages of 2 and 6 yr. Identified environmental stresses in these Romano–Britons, including high lead ingestion, poor nutrition, and recurrent infections, may be important etiological factors for the enamel defects. [ABSTRACT FROM AUTHOR]

This study investigated hypoplastic enamel defects in a well-defined sample of Romano–Britons from the 3rd to the 5th century AD and compared the findings with a modern British sample investigated by the same authors. All 178 excavated skulls with intact dentitions were examined for hypoplastic defects using the Federation Dentaire International (FDI) Developmental Defects of Enamel Index criteria. Histopathological and microradiographic sections were prepared of 5 teeth. Hypoplastic defects were found in the teeth of 37% of skulls, with 25% having 4 or more teeth affected. The teeth most frequently involved were canines. Of the defects, 75% were horizontal grooves, 12.7% were pitting, and 7.1% were areas of missing enamel. The location of defects was 82% buccal, 16.5% lingual, and 1.2% occlusal. The reproducibility of diagnosis was 84%. Microscopic and microradiographic investigations showed areas of hypomineralization of enamel and wide zones of interglobular dentine related to the hypoplastic grooves. There was higher frequency, different morphology, and greater severity of hypoplastic enamel defects compared with the modern British sample. The defects may be related to repeated environmental stresses between the ages of 2 and 6 yr. Identified environmental stresses in these Romano–Britons, including high lead ingestion, poor nutrition, and recurrent infections, may be important etiological factors for the enamel defects. [ABSTRACT FROM AUTHOR]

The complexity of patients cared for in modern ICUs, along with continuing advances in the technology of critical care and the escalating costs associated with providing that care, have been motivating factors for critical care practitioner to identify and implement “best” medical practices. Individual best practices are often determined based on their association with improvements in patient outcomes, increased efficiency and cost-effectiveness of medical care, or both. These practices should ideally be determined based on sound medical evidence obtained from rigorously performed clinical trials, the most rigorous being randomized controlled trials. However, such trials have often not been performed for many aspects of critical care medicine. Outcomes research is an emerging field which attempts, in part, to use variations in medical practices, as well as formal scientific investigations, to identify important associations between specific medical practices and clinical outcomes. This review focuses on two areas of mechanical ventilation, acute respiratory distress syndrome (ARDS) and weaning, to illustrate how outcomes research can be employed to facilitate decision making in the management of patients with respiratory failure. [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]

Mutations in the amelogenin gene, AMGX, are known to cause X-linked amelogenesis imperfecta (AIH1). We have used DNA single-strand conformational polymorphism analysis and DNA sequencing to diagnose this disorder unequivocally in two related boys aged 3 and 7 years, respectively, from a family in which an existing mutation in the amelogenin gene is segregating. [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 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 dental development. The aim of this study was to investigate this relationship further by comparing multiple crown parameters, including cusp numbers, between patients with mild hypodontia and controls. Digital images of dental casts of the permanent dentition from 28 Romanian subjects with mild hypodontia and 28 controls were used. Measurements of the vestibular and occlusal surfaces were performed using a 2D image analysis method. Seven dimensions were measured (mesio-distal, occluso-gingival, bucco-lingual, vestibular perimeter, vestibular area, occlusal perimeter and occlusal area) and cusps on premolars and first molars were counted. Multivariate analysis of variance was performed using SPSS V17 software. The results showed teeth in the hypodontia group were smaller than those of controls, with many measurements being significantly different (significance values varied from p=0.048 to p=0.0001). Lower first incisors and upper first premolar teeth presented the most reduced dimensions. Mesio-distal, bucco-lingual and occlusal area and perimeter dimensions were the most affected. Upper first molars presented the Carabelli trait in significantly less subjects in the hypodontia group than in controls. This variation was accompanied by a difference in tooth height. Lower premolars showed reduced cusp numbers in hypodontia subjects, accompanied by variation in tooth width or depth. In conclusion, this study demonstrated differences in multiple parameters of crown size and shape in patients with mild hypodontia compared to controls. The degree of these differences varied between different tooth types and dimensions. [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 article presents information on the growth of Cymbella Sp. which is found growing beneath layers of ice. The reason for the winter growth of Cymbella is linked to aquatic fauna. The absence of active aquatic fauna, which at other seasons of the year browse down algal felts and in many instances keep submerged aquatic macrophytes virtually epiphyte free. Various experimental studies have demonstrated the extent insect larvae and fish can have on the epiphytic flora of various macrophytes. In many instances removal of the algal epiflora from such plants can be rapid and almost complete.

Roof shingles are often colonized and discolored by blue-green and green algae. The former are mostly subaerial species and the latter are soil algae most frequently recovered from the atmosphere. [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]

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]

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]

Objective 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. Design Two samples were analysed. The first sample comprised 1454 panoramic radiographs of singleton boys and girls aged 8–11 years. The second sample 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. Results In the singleton sample 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 individuals with infraocclusion compared to controls. The primary mandibular canines were significantly smaller in size in the infraoccluded group ( P < 0.05). Conclusion 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. [ABSTRACT FROM AUTHOR]

Objectives: A priority research area in minimal intervention dentistry is the characterization of the early stages of dental erosion. The aim of this in vitro study was to assess the effect of short, repetitive erosive challenges to human enamel over 2 min at pH 1.5 and 3.0 under conditions simulating gastric regurgitation. Methods: Enamel surfaces were subjected to erosive challenges at pH 1.5 (Group 1, n = 10) and pH 3.0 (Group 2, n = 9) for periods of 30 s (stage 1), 60 s (stage 2) and 120 s (stage 3). Quantitative changes were assessed longitudinally by measuring the 3D average surface roughness (Sa) values using 3D confocal microscopy. Qualitative micrographic assessment of surface changes was also conducted by using environmental scanning electron microscopy. Results: Linear mixed model analysis showed significant effects of the pH values ( p < 0.001) and the stages (p < 0.001) on the observed Sa values. Post hoc tests showed significant increases in the Sa values between baseline and other stages in both groups (p < 0.01). The mean Sa values also increased significantly from stage 1 to stage 2 in Group 1 (p < 0.05). Micrographic analysis displayed severely etched enamel rods in Group 1, but only subtle changes in Group 2. Conclusions: The complexity of the enamel surface is influenced by both acid concentration (pH value) and duration of acid exposure during early stages of erosion. Erosion occurring under conditions simulating GORD can be detected in its initial stages, opening up the possibilities of early diagnosis and management of this condition. Clinical significance: Erosive tooth wear occurs progressively and insidiously, often creating complex treatment challenges. This emphasizes the need for early diagnosis and management in accordance with minimal intervention philosophy. Our findings provide a foundation for further research that could lead to the development of highlysensitive clinical diagnostic tools and preventive strategies. [ABSTRACT FROM AUTHOR]

The Craniofacial Biology Research Group in the School of Dentistry at The University of Adelaide is entering an exciting new phase of its studies of dental development and oral health in twins and their families. Studies of the teeth and faces of Australian twins have been continuing for nearly 30 years, with three major cohorts of twins recruited over that time, and currently we are working with twins aged 2 years old to adults. Cross-sectional data and records relating to teeth and faces of twins are available for around 300 pairs of teenage twins, as well as longitudinal data for 300 pairs of twins examined at three different stages of development, once with primary teeth, once at the mixed dentition stage, and then again when the permanent teeth had emerged. The third cohort of twins comprises over 600 pairs of twins recruited at around birth, together with other family members. The emphasis in this third group of twins has been to record the timing of emergence of the primary teeth and also to sample saliva and dental plaque to establish the timing of colonization of decay-forming bacteria in the mouth. Analyses have confirmed that genetic factors strongly influence variation in timing of primary tooth emergence. The research team is now beginning to carry out clinical examinations of the twins to see whether those who become colonized earlier with decay-forming bacteria develop dental decay at an earlier age. By making comparisons within and between monozygotic (MZ) and dizygotic (DZ) twin pairs and applying modern molecular approaches, we are now teasing out how genetic, epigenetic, and environmental factors interact to influence dental development and also oral health. [ABSTRACT FROM AUTHOR]

This study explores the impact of social inequality through a study of health and diet involving the analysis of skeletal remains and grave furnishings from the Roman period cemetery of Baldock, UK. Analysis revealed correlations between the presence of different types of grave furnishing with aspects of childhood health, and consistent differences in diet between individuals with different quantities and types offurnishings. These findings suggest that inequality may have had a considerable impact upon both health and diet at Baldock. The further observation ofpatterns in diet by sex and in grave furnishings by sex and age-at- death suggests that thesefactors may have played an important role in determining access to resources within the community at Baldock. [ABSTRACT FROM AUTHOR]

Abstract: Objective: To assess the reproducibility of a mobile non-contact camera-based digital imaging system (DIS) for measuring tooth colour under in vitro and in vivo conditions. Methods: One in vitro and two in vivo studies were performed using a mobile non-contact camera-based digital imaging system. In vitro study: two operators used the DIS to image 10 dry tooth specimens in a randomised order on three occasions. In vivo study 1: 25 subjects with two natural, normally aligned, upper central incisors had their teeth imaged using the DIS on four consecutive days by one operator to measure day-to-day variability. On one of the four test days, duplicate images were collected by three different operators to measure inter- and intra-operator variability. In vivo study 2: 11 subjects with two natural, normally aligned, upper central incisors had their teeth imaged using the DIS twice daily over three days within the same week to assess day-to-day variability. Three operators collected images from subjects in a randomised order to measure inter- and intra-operator variability. Results: Subject-to-subject variability was the largest source of variation within the data. Pairwise correlations and concordance coefficients were >0.7 for each operator, demonstrating good precision and excellent operator agreement in each of the studies. Intraclass correlation coefficients (ICCs) for each operator indicate that day-to-day reliability was good to excellent, where all ICC''s where >0.75 for each operator. Conclusion: The mobile non-contact camera-based digital imaging system was shown to be a reproducible means of measuring tooth colour in both in vitro and in vivo experiments. [Copyright &y& Elsevier]

Objective: To assess the reproducibility of a mobile non-contact camera-based digital imaging system (DIS) for measuring tooth colour under in vitro and in vivo conditions.Methods: One in vitro and two in vivo studies were performed using a mobile non-contact camera-based digital imaging system. In vitro study: two operators used the DIS to image 10 dry tooth specimens in a randomised order on three occasions. In vivo study 1:25 subjects with two natural, normally aligned, upper central incisors had their teeth imaged using the DIS on four consecutive days by one operator to measure day-to-day variability. On one of the four test days, duplicate images were collected by three different operators to measure inter- and intra-operator variability. In vivo study 2:11 subjects with two natural, normally aligned, upper central incisors had their teeth imaged using the DIS twice daily over three days within the same week to assess day-to-day variability. Three operators collected images from subjects in a randomised order to measure inter- and intra-operator variability.Results: Subject-to-subject variability was the largest source of variation within the data. Pairwise correlations and concordance coefficients were > 0.7 for each operator, demonstrating good precision and excellent operator agreement in each of the studies. Intraclass correlation coefficients (ICCs) for each operator indicate that day-to-day reliability was good to excellent, where all ICC's where > 0.75 for each operator.Conclusion: The mobile non-contact camera-based digital imaging system was shown to be a reproducible means of measuring tooth colour in both in vitro and in vivo experiments. [ABSTRACT FROM AUTHOR]

Elcock C, Smith RN, Simpson J, Abdellatif A, Bäckman B, Brook AH. Comparison of methods for measurement of hypoplastic lesions. Eur J Oral Sci 2006; 114 (Suppl. 1): 365–369 © Eur J Oral Sci, 2006 --> Enamel hypoplasia is a quantitative defect of enamel thickness. Methods previously used for its measurement have limitations in clinical studies. The aim of this study was to investigate new methods of measurement using image analysis. Lesions on 8 teeth affected by enamel hypoplasia were quantified from study models and impression surfaces using an image‐analysis system. The measurements made included lesion area and tooth surface area; from these the proportion of tooth surface area affected was calculated. For comparison, manual measurement was performed on impression surfaces and study models, using digital callipers. Images were also acquired of lesions on 12 exfoliated teeth, and the lesion area and total tooth area were calculated. For assessment of intra‐operator reliability, the +/– repeatability coefficient was calculated. Measurement of the surface of lesions direct from the exfoliated teeth gave the best results overall, followed by direct image analysis of the silicone impression. [ABSTRACT FROM AUTHOR]

Elcock C, Lath DL, Luty JD, Gallagher MG, Abdellatif A, Bäckman B, Brook AH. The new Enamel Defects Index: testing and expansion. Eur J Oral Sci 2006; 114 (Suppl. 1): 35–38 © Eur J Oral Sci, 2006 --> The Enamel Defects Index (EDI) was created based on three innovative principles: (i) a basic level of the three major categories of defects; (ii) more detailed subcategories of each major category; and (iii) each category scored independently as present [1] or absent [0], simplifying decision making. The aim of this investigation was to further test the index in a number of applications and to expand it to record defect subtype and treatment need. Testing was undertaken by operators with different levels of clinical experience. A computer‐assisted learning (CAL) package was developed for operator training and calibration. The index was also used on clinical photographs and high‐resolution digital images of exfoliated and extracted teeth. Scoring of photographs revealed substantial intra‐operator agreement. Training using the CAL package resulted in significant improvement in index use. Intra‐operator reproducibility was good to excellent, and interoperator reproducibility was good for buccal surfaces on digital images. Index expansion allowed information on defect subtype, location, and treatment need to be gathered readily. The EDI has high reproducibility and allows more rapid and accurate data collection from clinical and in vitro studies than the Fédération Dentaire Internationale Developmental Defects of Enamel index. [ABSTRACT FROM AUTHOR]

The Enamel Defects Index (EDI) was created based on three innovative principles: (i) a basic level of the three major categories of defects; (ii) more detailed subcategories of each major category; and (iii) each category scored independently as present [1] or absent [0], simplifying decision making. The aim of this investigation was to further test the index in a number of applications and to expand it to record defect subtype and treatment need. Testing was undertaken by operators with different levels of clinical experience. A computer-assisted learning (CAL) package was developed for operator training and calibration. The index was also used on clinical photographs and high-resolution digital images of exfoliated and extracted teeth. Scoring of photographs revealed substantial intra-operator agreement. Training using the CAL package resulted in significant improvement in index use. Intra-operator reproducibility was good to excellent, and interoperator reproducibility was good for buccal surfaces on digital images. Index expansion allowed information on defect subtype, location, and treatment need to be gathered readily. The EDI has high reproducibility and allows more rapid and accurate data collection from clinical and in vitro studies than the Fédération Dentaire Internationale Developmental Defects of Enamel index. [ABSTRACT FROM AUTHOR]

Enamel hypoplasia is a quantitative defect of enamel thickness. Methods previously used for its measurement have limitations in clinical studies. The aim of this study was to investigate new methods of measurement using image analysis. Lesions on 8 teeth affected by enamel hypoplasia were quantified from study models and impression surfaces using an image-analysis system. The measurements made included lesion area and tooth surface area; from these the proportion of tooth surface area affected was calculated. For comparison, manual measurement was performed on impression surfaces and study models, using digital callipers. Images were also acquired of lesions on 12 exfoliated teeth, and the lesion area and total tooth area were calculated. For assessment of intra-operator reliability, the +/– repeatability coefficient was calculated. Measurement of the surface of lesions direct from the exfoliated teeth gave the best results overall, followed by direct image analysis of the silicone impression. [ABSTRACT FROM AUTHOR]

Summary: Objective:: Identifying the patterning of congenitally absent teeth will contribute to understanding the aetiology of hypodontia. The aim of this study was to investigate patterns of hypodontia in a group of young adults in Sheffield, UK involving specific tooth types, gender differences and maxilla:mandible and left:right correlations. Methods:: The patients were 198 unrelated Caucasian young adults (86 males and 112 females) with non-syndromic hypodontia. Statistical methods included the multivariate techniques of cluster analysis and principal components analysis and associated display devices of circular dotplots and biplots. Autologistic regression was used to model the relationship of the presence or absence of a particular tooth to the status of other teeth. Results:: The results revealed distinct patterns of dependence. Common patterns included either third molars and second premolars missing in all quadrants and/or combinations of these two tooth types and the incisors. The gender of the patient and the severity of hypodontia did not have a significant effect on patterns of tooth type absence. If a tooth was missing, the odds ratios that the same tooth type in the horizontally or vertically opposite quadrant was also missing were some 20 times higher than if the tooth was present. For diagonally opposite quadrants the dependence was much weaker. Conclusions:: These statistical techniques are valuable for increasing understanding of hypodontia and identifying groups of patients for genetic studies. [Copyright &y& Elsevier]

Summary: Objective:: Fluctuating dental asymmetry as an indication of the effect of environmental insults during tooth development requires further investigation. The aim of this study was to assess asymmetry in tooth crown dimension for the increased range of parameters possible with image analysis compared to previous manual measurements. Methods:: Study models of 25 male and 25 female white Caucasian subjects were measured from buccal and occlusal views to determine mesio-distal, bucco-lingual, occluso-gingival and tooth surface area dimensions using image analysis. Method errors were assessed by the repeatability coefficient RC and asymmetry assessed calculating intra-class correlation coefficients between pairs of antimere teeth. Results:: The method errors calculated using RC were small. There was a high degree of symmetry with correlation coefficients with a range of 0.67–0.96 for linear measurements and 0.80–0.97 for tooth surface areas. No significant differences were found between the genders or between the upper and lower jaws. Asymmetry tended to follow a pattern in morphogenic tooth fields with the mesial tooth showing greater symmetry than the more distal. There were differences in the degree of symmetry among the variables measured with the mesio-distal dimension showing the greatest symmetry. Conclusions:: This new technique was reliable and readily applicable, providing also a greater range of measurements. While the asymmetry generally followed a similar pattern to earlier manual studies, there were variations in the degree of symmetry between different parameters. [Copyright &y& Elsevier]

• Crown morphology is moderately genetically integrated among deciduous teeth and among permanent teeth. • Paired deciduous-permanent homologues are more strongly genetically integrated than traits expressed within dentitions. • The same genes are recruited throughout development to yield morphologically similar phenotypes. • When present in deciduous teeth, clinically problematic traits will likely be expressed in permanent replacement teeth. This study presents a quantitative genetic analysis of human anterior dental morphology in a longitudinal sample 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 i1 shoveling and permanent I1 shoveling), ∼70% of model comparisons yielded significant genetic correlations. 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 individual tooth rows/teeth. [ABSTRACT FROM AUTHOR]

• A shape classification model based on quasi-conformal theory is proposed. • The surface geometry, anatomical landmarks and curvature differences of the shapes are all taken into account in our proposed method. • The classification accuracy for teeth with respect to ancestry and gender is significantly improved by our proposed method. Shape analysis is important in anthropology, bioarchaeology and forensic science for interpreting useful information from human remains. In particular, teeth are morphologically stable and hence well-suited for shape analysis. In this work, we propose a framework for tooth morphometry using quasi-conformal theory. Landmark-matching Teichmüller maps are used for establishing a 1-1 correspondence between tooth surfaces with prescribed anatomical landmarks. Then, a quasi-conformal statistical shape analysis model based on the Teichmüller mapping results is proposed for building a tooth classification scheme. We deploy our framework on a dataset of human premolars to analyze the tooth shape variation among genders and ancestries. Experimental results show that our method achieves much higher classification accuracy with respect to both gender and ancestry when compared to the existing methods. Furthermore, our model reveals the underlying tooth shape difference between different genders and ancestries in terms of the local geometric distortion and curvatures. In particular, our experiment suggests that the shape difference between genders is mostly captured by the conformal distortion but not the curvatures, while that between ancestries is captured by both of them. [ABSTRACT FROM AUTHOR]

Studies in rodents and humans have suggested that masculinisation of females and feminisation of males can occur between fetuses in utero due to hormonal diffusion. Opposite-sex twin pairs provide a useful model to study the effects of prenatal hormone diffusion on tooth size. The aim of this study is to determine whether primary and permanent tooth size is altered in females and/or males from opposite-sex dizygotic (OSDZ) twin pairs compared with same-sex monozygotic (SSMZ) or dizygotic (SSDZ) twins. Methods: Female sample: 44 OSDZ females, 39 SSDZ females, 52 MZ females; and male sample: 44 OSDZ males, 42 SSDZ males, 56 MZ males; aged from 4.1 to 16.5 years. Serial dental models of primary, mixed and permanent dentitions were used. Mesiodistal (MD) and buccolingual (BL) crown diameters, crown heights (CH) and intercuspal distances (IC) of upper central and lateral incisors, canines, second premolars, first and second molars and lower central and lateral incisors, canines, second premolars, first and second molars were measured to an accuracy of 0.1mm using 2D image analysis system. OSDZ females were consistently larger by approximately 1-3% in MD and BL dimensions for permanent teeth compared with other groups but CH and IC dimensions did not show the same pattern. No systematic trend was found in either dentition of the male groups. This effect may be related to circulating male hormones in utero. [ABSTRACT FROM AUTHOR]

Abstract: Aims: In studying aetiological interactions of genetic, epigenetic and environmental factors in normal and abnormal developments of the dentition, methods of measurement have often been limited to maximum mesio-distal and bucco-lingual crown diameters, obtained with hand-held calipers. While this approach has led to many important findings, there are potentially many other informative measurements that can be made to describe dental crown morphology. Advances in digital imaging and computer technology now offer the opportunity to define and measure new dental phenotypes in 3-D that have the potential to provide better anatomical discrimination and clearer insights into the underlying biological processes in dental development. Over recent years, image analysis in 2-D has proved to be a valuable addition to hand-measurement methods but a reliable and rapid 3-D method would increase greatly the morphological information obtainable from natural teeth and dental models. Additional measurements such as crown heights, surface contours, actual surface perimeters and areas, and tooth volumes would maximise our ability to discriminate between samples and to explore more deeply genetic and environmental contributions to observed variation. The research objectives were to investigate the limitations of existing methodologies and to develop and validate new methods for obtaining true 3-D measurements, including curvatures and volumes, in order to enhance discrimination to allow increased differentiation in studies of dental morphology and development. The validity of a new methodology for the 3-D measurement of teeth is compared against an established 2-D system. The intra- and inter-observer reliability of some additional measurements, made possible with a 3-D approach, are also tested. Methods and results: From each of 20 study models, the permanent upper right lateral and upper left central incisors were separated and imaged independently by two operators using 2-D image analysis and a 3-D image analysis system. The mesio-distal (MD), labio-lingual (LL) and inciso-gingival (IG) dimensions were recorded using our 2-D system and the same projected variables were also recorded using a newly developed 3-D system for comparison. Values of Pearson''s correlation coefficient between measurements obtained using the two techniques were significant at the 0.01 probability level for variables mesio-distal and incisal-gingival with labio-lingual significant at the 0.05 level for the upper left side only, confirming their comparability. For both 2-D and 3-D systems the intra- and inter-operator reliability was substantial or excellent for variables mesio-distal, labio-lingual, incisal-gingival actual and projected and actual surface area. The reliability was good for inter-operator reliability measurement of the labio-lingual dimension using 3-D. Conclusions: We have developed a new 3-D laser scanning system that enables additional dental phenotypes to be defined. It has been validated against an established 2-D system and shown to provide measurements with excellent reliability, both within and between operators. This new approach provides exciting possibilities for exploring normal and abnormal variations in dental morphology and development applicable to research on genetic and environmental factors. [Copyright &y& Elsevier]

Abstract: This paper reviews the concept of morphogenetic fields within the dentition that was first proposed by Butler (Butler PM. Studies of the mammalian dentition. Differentiation of the post-canine dentition. Proc Zool Soc Lond B 1939;109:1–36), then adapted for the human dentition by Dahlberg (Dahlberg AA. The changing dentition of man. J Am Dent Assoc 1945;32:676–90; Dahlberg AA. The dentition of the American Indian. In: Laughlin WS, editor. The Physical Anthropology of the American Indian. New York: Viking Fund Inc.; 1951. p. 138–76). The clone theory of dental development, proposed by Osborn (Osborn JW. Morphogenetic gradients: fields versus clones. In: Butler PM, Joysey KA, editors Development, function and evolution of teeth. London: Academic Press, 1978. p. 171–201), is then considered before these two important concepts are interpreted in the light of recent findings from molecular, cellular, genetic and theoretical and anthropological investigation. Sharpe (Sharpe PT. Homeobox genes and orofacial development. Connect Tissue Res 1995;32:17–25) put forward the concept of an odontogenic homeobox code to explain how different tooth classes are initiated in different parts of the oral cavity in response to molecular cues and the expression of specific groups of homeobox genes. Recently, Mitsiadis and Smith (Mitsiadis TA, Smith MM. How do genes make teeth to order through development? J Exp Zool (Mol Dev Evol) 2006; 306B:177–82.) proposed that the field, clone and homeobox code models could all be incorporated into a single model to explain dental patterning. We agree that these three models should be viewed as complementary rather than contradictory and propose that this unifying view can be extended into the clinical setting using findings on dental patterning in individuals with missing and extra teeth. The proposals are compatible with the unifying aetiological model developed by Brook (Brook AH. A unifying aetiological explanation for anomalies of tooth number and size. Archs Oral Biol 1984;29:373–78) based on human epidemiological and clinical findings. Indeed, this new synthesis can provide a sound foundation for clinical diagnosis, counselling and management of patients with various anomalies of dental development as well as suggesting hypotheses for future studies. [Copyright &y& Elsevier]

Abstract: Utilising data derived from twins and their families, different approaches can be applied to study genetic and environmental influences on human dental variation. The different methods have advantages and limitations and special features of the twinning process are important to consider. Model-fitting approaches have shown that different combinations of additive genetic variance (A), non-additive genetic variance (D), common environmental variance (C), and unique environmental variance (E) contribute to phenotypic variation within the dentition, reflecting different ontogenetic and phylogenetic influences. Epigenetic factors are also proposed as important in explaining differences in the dentitions of monozygotic co-twins. Heritability estimates are high for most tooth size variables, for Carabelli trait and for dental arch dimensions, moderate for intercuspal distances, and low for some occlusal traits. In addition to estimating the contributions of unmeasured genetic and environmental influences to phenotypic variation, structural equation models can also be used to test the effects of measured genetic and environmental factors. Whole-genome linkage analysis, association analysis of putative candidate genes, and whole genome association approaches, now offer exciting opportunities to locate key genes involved in human dental development. [Copyright &y& Elsevier]