Crown Form Research Articles

GINGIVAL BIOTYPE- AN APPRAISAL IN THE ESTHETIC ZONE

The interface between the restoration and the gingival tissue seems to have a great influence on the final outcome of various treatments. Therefore, the aim of this study was to evaluate the correlation between different morphometric parameters with the thickness of buccal gingiva at the cemento- enamel junction. In 60 periodontally healthy subjects, the six maxillary anterior teeth were examined. Clinical parameters included the gingival thickness, crown width/crown length ratio (CW/ CL), gingival width (GW), papillary height and transparency of the periodontal probe through the gingival sulcus (TRAN). A positive correlation was found between the gingival thickness (GT) and the crown width/ crown length (CW/CL) ratio as well as the papillary height (PH). A weak negative correlation was found between the transparency of probe TRAN and gingival width (GW) with the gingival thickness (GT). Thus, crown form (CW/CL) and papillary height are helpful indicators to determine the gingival thickness at the cemento- enamel junction. The transparency of probe method is subjective and cannot be relied upon for clinical application.

Gingival Phenotypes Amongst Male Dental Students at Kulliyyah of Dentistry, IIUM, Malaysia

The aim of the present study was to investigate the periodontal phenotypes among young Malay males with different gingival biotypes. Forty-seven systemically and periodontally healthy young Malay males participated in this study, where 25.5% were diagnosed with thin gingival biotype and 74.5% of thick biotype. The periodontal phenotypes were measured through clinical parameters presented by the gingival thickness (GT), gingival width (GW), papilla height (PH), and crown width/crown length ratio (CW/CL). Three clusters were identified through K-means cluster ing analysis based on the parameters of the periodontal phenotypes. Cluster 1 represents narrow crown form and the average CW/CL, GW, PH and PD were 0.69, 2.92, 4.55 and 2.16 mm, respectively. Cluster 2 displayed an average of 0.76, 4.29, 4.96 and 2.14 mm for CW/CL, GW, PH and PD, respectively. Cluster 3 represents wide crown form and the average displayed for CW/CL, GW, PH and PD were 0.80, 4.85, 3.73 and 2.23 mm, respectively. There were significant differences between the three clusters (p<0.05) with respect to the GW, PH and CW/CL. This study demonstrates the difference in gingival phenotypes between young Malay males. The GW has a signiϑicant positive linear correlation (p><0.05) with CW/CL and negatively correlated with PH.><0.05) with respect to the GW, PH and CW/CL. This study demonstrates the difference in gingival phenotypes between young Malay males. The GW has a significant positive linear correlation (p<0.05) with CW/CL and negatively correlated with PH.><0.05) with CW/CL and negatively correlated with PH.

Neighbourhood‐mediated shifts in tree biomass allocation drive overyielding in tropical species mixtures

Variations in crown forms promote canopy space-use and productivity in mixed-species forests. However, we have a limited understanding on how this response is mediated by changes in within-tree biomass allocation. Here, we explored the role of changes in tree allometry, biomass allocation and architecture in shaping diversity-productivity relationships (DPRs) in the oldest tropical tree diversity experiment. We conducted whole-tree destructive biomass measurements and terrestrial laser scanning. Spatially explicit models were built at the tree level to investigate the effects of tree size and local neighbourhood conditions. Results were then upscaled to the stand level, and mixture effects were explored using a bootstrapping procedure. Biomass allocation and architecture substantially changed in mixtures, which resulted from both tree-size effects and neighbourhood-mediated plasticity. Shifts in biomass allocation among branch orders explained substantial shares of the observed overyielding. By contrast, root-to-shoot ratios, as well as the allometric relationships between tree basal area and aboveground biomass, were little affected by the local neighbourhood. Our results suggest that generic allometric equations can be used to estimate forest aboveground biomass overyielding from diameter inventory data. Overall, we demonstrate that shifts in tree biomass allocation are mediated by the local neighbourhood and promote DPRs in tropical forests.

Effect of gingival phenotype on the maintenance of periodontal health: An American Academy of Periodontology best evidence review.

Gingival thickness, keratinized tissue width, and bone morphotype are three important parameters used to categorize periodontal phenotypes. These elements all play an important role in the maintenance of periodontal health. The aim of this review is to explore the importance of converting thin phenotype into a thick phenotype for periodontal health maintenance. Three clinically relevant focused questions were defined to understand the role of gingival phenotype around teeth. 1) What are the factors affecting gingival phenotype (e.g., age, sex, dental arch, race, crown forms, etc.)? 2) Is there a difference between thin versus thick gingival phenotype in terms of gingival health? 3) Does the conversion of gingivae from a thin to thick gingival phenotype in sites without mucogingival defects help with periodontal health maintenance? Extensive electronic and manual literature search identified a total of 1,129 citations. After title, abstract, and full-text screenings, 30 articles were included in the present review. Twenty-five studies met the inclusion criteria and provided data for focused question 1. It was found that periodontal phenotype varies among different individuals and different areas of the mouth within the same individual. Asian individuals tend to have thinner gingival phenotype compared with white subjects. Eleven studies met the inclusion criteria for the focused question 2. Prevalence and severity of gingival recession was higher at the sites with thin gingiva compared with the sites with thicker gingiva. No studies provided data for focused question 3. Available evidence indicates that subjects with thin and narrow gingiva tend to have more gingival recession compared with those with thick and wide gingiva. Currently, there is no published evidence to support conversion of thin to thick gingival phenotype in sites without gingival recession or mucogingival deformity.

Relationships between the upper central incisor crown forms and degree of labial inclination, overbite, and overjet in Japanese young adults.

PURPOSEThe present study aimed to investigate the relationships between the crown form of the upper central incisor and their labial inclination, overbite, and overjet.MATERIALS AND METHODSMaxillary and mandibular casts of 169 healthy dentitions were subjected to 3D dental scanning, and analyzed using CAD software. The crown forms were divided into tapered, square, and ovoid based on the mesiodistal dimensions at 20% of the crown height to that at 40%. The degree of labial inclination of the upper central incisor was defined as the angle between the occlusal plane and the line connecting the incisal edge and tooth cervix. The incisal edges of the right upper and lower central incisor that in contact with lines parallel to the occlusal plane were used to determine the overbite and overjet. One-way ANOVA was performed to compare the labial inclination, overbite, and overjet among the crown forms.RESULTSThe crown forms were classified into three types; crown forms with a 20%/40% dimension ratio of 1.00±0.01 were defined as square, >1.01 as tapered, and <0.99 as ovoid. The labial inclination degree was the greatest in tapered and the least in square. Both overbite and overjet in tapered and ovoid were higher than those in square.CONCLUSIONUpper central incisor crown forms were related to their labial inclination, overbite, and overjet. It was suggested that the labial inclination, overbite, and overjet should be taken into consideration for the prosthetic treatment or restoring the front teeth crowns.

Штамбова культура ліщини (фундука) (Corylus maxima Mill.) на деревоподібних підщепах

The authors have proved the hazel cultivation efficiency in the world and Ukraine. The expediency of this crop growing on the rootstock has been substantiated on the basis of the expedionary inspections of the hazel bole plants revealed in Ukraine. The problems of the grafted plants bole height have been considered, the crown forms, their formation technology recommended as well as the trees planting plans in the orchard. The bole height has proved to influence not only the habit but also sprouting formation of the under the conditions of such an orchard exploitation period. It appeared that hen creating hazel industrial orchards on its tree-like rootstocks it is important to elaborate the crown forms and bole height the parameters of which would ensure high productivity, limit the crown habit and enable to mechanize the fruits collection. The spherical and spindle-like crowns are proposed that are formed on a certain bole height, the latter form differing from the former by a less frit branches amount orientated concerning the row area (5-8). Hazel industrial orchards with the bole culture at present it is mainly are recommended to be established using the planting plan 7-6 х 6-4 m. But when choosing a concrete plan, first of all, the cultivar vigour should be taken into account like under the as well as the crown form, bole height and the fact that this orchard practically does not need irrigation. It is possible to foresee with great probability that the habit parameters of a bush-tree crown can be regulated by the bole height like concerning other fruit crops. However, the final conclusion cannot be made so far because of the lack of the facts as regards cultivars. Besides, it is a bush-tree that is studied and such sign as early-ripening occurs in those constructions in different ways. The necessity is stressed of improving the technology of the hazel grafted planting trees reproduction.

Growth performance of Acacia mangium provenances in Parung Panjang, Bogor and its correlation with physical and mechanical wood properties

Wood quality and growth are two important parameters that need to be analyzed for the utilization and selection of superior genotypes. The objective of this research was to investigate the ten provenances growth characteristics and their physical and mechanical properties of Acacia mangium at Parung Panjang, Bogor. The provenance trial was arranged in three blocks of a randomized completely blocks design. In every provenance, 18 trees were sampled resulting in a total of 180 trees in each block representing each provenance measured for their total height, clear bole height, stem diameter at breast height, stem form, branching system, and crown form. Three individual trees were selected randomly from each provenance for wood properties traits, i.e. moisture content, density, modulus of elasticity (MOE) and modulus of rapture (MOR). Significant differences among provenances were detected for stem diameter, clear bole height, branching system and crown form, while total height and stem form revealed not significantly different. Most of growth parameters was not significantly correlated with physical and mechanical wood traits, except for MOR, it revealed significant correlation with the total tree height, stem form, and branching system. Generally, some growth characteristics were not a good indicator for selecting the best provenance in wood properties. The best growth performance was revealed by Kiriwo/Serisa WP, Bimadebun Village, and Balimo District, but from wood quality, the superior provenance was revealed by Bimadebun Village with the lower moisture content, the highest wood density, the highest MOE and MOR. The Bimadebun Village provenance is potential to be developed as provenance seed stand, especialy for solid (contruction) wood.

Application of strip crown form in aesthetic restoration of mandibular deciduous incisors in severe childhood caries

Objective To explore the feasibility and effectiveness of aesthetic restoration of caries of mandibular deciduous incisors with strip crown form of maxillary deciduous incisors. Methods A total of 64 patients (202 teeth) with symmetrical caries of bilateral mandibular central incisors or lateral incisors were randomly selected. The opposite maxillary incisors were restored with strip crowns form and the opposite incisors were restored with resin composite. The effects of the two methods and the incidence of complications were compared three months, six months and twelve months after treatment. Results Three months after treatment, there was no significant difference in the success rate between the two groups. Six months after treatment, there was significant difference in the marginal adaptation between the two groups (χ2=3.919, P =0.048); 12 months after treatment, there was significant difference in the restoration integrity of the two groups and the incidence of secondary caries (χ2=5.027, P=0.025; secondary caries χ2=4.369, P=0.037 ). Conclusions The strip crown form of maxillary primary incisors can be used for aesthetic restoration of caries of mandibular primary incisors, and its effect is better than that of direct resin filling. The strip crown form for mandibular primary incisors needs to be developed and produced urgently. Key words: Incisor; Child; Dental caries; Composite resins; Deciduous mandibular incisors; Strip crown form

Vegetative parameters of sweet cherry (Cerasus avium L.) cultivars in two training systems

Hungarian sweet cherry production has been changed recently. Thanks to the favourable selling prices many new plantations were established in the last years. In the new orchards mainly spindle canopy are trained, although many type of crown forms are used all over the world. In our study slender spindle and bush canopy were evaluated with three cultivars (‘Petrus’, ‘Vera’, ‘Carmen’) grafted on Prunus mahaleb rootstock. Vigor of the 3-4 years old trees showed spectacular differences. The highest vigor with Spanish bush was found for cv. ‘Vera’, but on slender spindle canopy the thickness values were medium. Meanwhile cv. ‘Petrus’ showed the highest trunk thickness with spindle canopy, but the lowest with Spanish bush. On spindle canopy cv. ‘Carmen’ presented the highest ramification ability, but its 2-3 years old twigs started to bald very early, which can be considered an unfavorable phenomenon. Bush canopy still can be described with strong vegetative growth on 3-4 years old trees, as vigor of spindle trees are more moderate.

Testing of the narrow crowned Norway spruce ideotype (Picea abies f. pendula) and the hybrids with normal crown form (pyramidalis) in multisite comparative trials

The study aims to analyse the stability of the narrow crowned Norway spruce (pendula form) compared to the normal spruce form (pyramidalis form) and the hybrids of the two forms, in 5 field trials (Comandău, Lepşa 1&2, Ilva Mică and Voineasa) located in the Romanian Carpathians. Trees height (Th), breast height diameter (Dbh), height growth of the last year, crown diameter (Cd), number of branches per whorl (Nbw) and dominant branch diameter (Dbd) traits were measured and survival rate (Sr) was determined, at 20 years old. Also, branches finesse (Bf), trees volume (Tv) and trees slenderness (Ts) were calculated. In order to compare the wood density (Cwd) there were collected cores. In all trials ANOVA revealed significant (p < 0.05) differences between the two forms of spruce and the hybrids (mainly between those that have a different crown form mother), especially for the stability and quality traits. Factorial ANOVA revealed a high influence (p < 0.001) of the locality and also a significant influence (p < 0.05) of the locality × spruce form interaction. The factor “form” was significant for some traits involved in Norway spruce stability (Ts, Cd, Nbw). The pendula trees present higher values for Sr, Dbh and Tv, and lower values for Ts, Cd, Nbw, Dbd and Bf, compared to pyramidalis spruce form, which showed a higher stability. Heritability was in generally low (h2 < 0.4), with exceptions of Ts which presents a medium rate of heritage. For the same trait, different heritability was registered in different environmental conditions. The Cwd was higher only with 2% for the pendula form in Lepşa trial, while in Comandău trial the pyramidalis registered a higher value (7%). In the new breeding programme, the selection strategy may be pursued with the pendula trees selection based on Ts and branches traits.

Adaptability of Narrow-Crowned Norway Spruce Ideotype (Picea abies (L.) Karst. pendula Form) in 25 Years Half-Sib Comparative Trials in the Eastern Carpathians

This study analysed the stability of the narrow-crowned Norway spruce (pendula form) compared with the classic form of spruce (pyramidalis form) in two half-sib field trials located in the Romanian Carpathians. From eight natural populations, representative of three of the four large spruce spread areas in Romania, open-pollinated seeds from 48 trees (24 pendula ideotype and 24 pyramidalis form) were collected to install the Maneciu and Soveja trials. In these trials, at age 25 years, measurements were performed for the following traits: tree height, breast height diameter, crown diameter, number of branches per whorl and dominant branch diameter. Some important traits were calculated: average volume per tree, trees’ slenderness, crown slenderness and branches’ finesse. Pearson’s simple correlations between the analysed traits were calculated and also the correlations between traits and geographic and climatic gradients of provenances’ origin. In addition, cores were collected to compare the wood density of the two forms of spruce. In both trials, but especially in the limitative environmental conditions of the Soveja trial, the narrow crowned form of Norway spruce (Picea abies f. pendula) presented more favourable average results than the normal crown spruce form for the most important stand stability traits: trees’ slenderness, wood density, branches’ diameter and branches’ finesse. Between spruce crown forms, in both trials, no significant differences were observed for the growth traits, but between trials, higher results resulted in optimal environmental conditions of the Măneciu test (+89% for the trees’ volume). The trees from different provenances and with specific forms of the crown reacted differently to the changing of the testing site, which required the adoption of maximum caution for decisions regarding the transfer of forest reproductive materials. The correlations between the analysed traits converge towards the adoption of a two-step breeding strategy, starting by selection of narrow crowned trees after stability traits.

Комплексна оцінка декоративності рослин культиварів Thuja Occidentalis L.

Основна екологічна роль в озелененні міст належить деревним рослинам. З декоративними насадженнями тісно пов'язані функціональне зонування міських територій, система транспортних та пішохідних магістралей, прокладення інженерних комунікацій. На сьогодні важливу роль відіграють ті деревні види рослин, які здатні виконувати одночасно декілька функцій: стійкість до умов зростання, не втрачати декоративність впродовж року, відновлювати крону після обрізки. До таких деревних рослин належать рослини Th. occidentalis L. та її декоративні культивари, які вирізняються різноманітністю габітусу крони, будовою та забарвленням хвої, невибагливістю до родючості ґрунту, тіньовитривалістю. Представлено результати комплексної оцінки декоративності рослин культиварів Thuja occidentalis L. в умовах м. Києва за розробленою інтегральною шкалою А. С. Власенко, яка не містить показників зимостійкості, морозостійкості, посухостійкості та жаростійкості рослин. Оцінку декоративних ознак деревних рослин здійснювали за чотирма основними блоками. Перший – це оцінка загальної декоративності рослини, яка включає період декоративності, декоративні ознаки крони (форма, щільність, фактура) та тривалість квітування та облистнення. Другий блок – це оцінка декоративності кори, її фактури та забарвлення. Третій – це оцінка декоративності хвої за формою, розмірами, забарвленням і сезонністю її змін. Четвертий – це оцінка декоративності генеративних органів, яка ґрунтується на розмірах, забарвленні, рясності мегастробілів, а також формі, величині, забарвленні та рясності шишок. Дослідними об'єктами були рослини Th. occidentalis та її культивари, а саме: Th. oc. 'Wagneriana', Th. oc. 'Wareana Lutescens', Th. oc. 'Ericoides', Th. oc. 'Ellwangeriana', Th. ос. 'Lutescens', Th. ос. 'Columna', Th. oc. 'Globosa', Th. oc. 'Spiralis', Th. oc. 'Smaragd'. Аналіз декоративних властивостей представників виду туя західна свідчить про перспективність та доцільність подальшого розширеного введення досліджуваних видів у зелені насадження м. Києва під час створення садово-паркових об'єктів.

Quantitative genetic analyses of postcanine morphological crown variation

This article presents estimates of narrow-sense heritability and bivariate genetic correlation for 14 tooth crown morphological variants scored on permanent premolars, first molars, and second molars. The objective is to inform data collection and analytical practices in dental biodistance and to provide insights on the development of molar crowns as integrated structures. African American dental casts from the Menegaz-Bock collection were recorded for the Arizona State University Dental Anthropology System. Estimates of narrow-sense heritability and genetic correlation were generated using SOLAR v.8.1.1, which included assessment of age, sex, and birth year as covariates. Both continuous scale and dichotomized estimates are provided. Heritability estimates were nonsignificant for the majority of variables; however, for variables yielding significant estimates, values were moderate to high in magnitude and comparable to previous studies. Comparing left and right-side heritability estimates suggests directional asymmetry in the expression of environmental variance, something not seen in anterior tooth traits. Genetic correlations were moderate among antimeres and metameres and low for different traits scored on the same tooth crown. Although several negative correlations were noted, few reached statistical significance. Results affirm some of the current data cleaning and analytical practices in dental biodistance, but others are called into question. These include the pooling of males and females and combining left and right-side data into a single dataset. In comparison to anterior tooth crown traits, postcanine heritabilities were more often non-significant; however, those traits with significant heritability also tended to produce higher estimates. Genetic correlations were unremarkable, in part, because they were underpowered. However, M1 results may provide insight into the complex relationship between genes, environment, and development in determining ultimate crown form.

Growth and quality of Fagus sylvatica saplings depend on seed source, site, and browsing intensity

AbstractLocal climate and ungulate browsing are two major factors that affect tree regeneration and genetic adaptation in Central European forests. Owing to climate change and increasing ungulate numbers, the abiotic and biotic environments of trees are changing remarkably, making it necessary to investigate the separate and joint effects of seed source (i.e., location of tree population origin) and ungulate herbivory. We used a common garden experiment to study the growth and morphology of Fagus sylvatica saplings from 77 Swiss seed sources. The experiment was set up at two sites and included a clipping treatment (i.e., terminal shoot clipped at two intensities) applied before budburst to simulate winter ungulate browsing. We studied F. sylvatica sapling growth and morphology before and two years after clipping. Measured growth traits included sapling height, stem diameter, and biomass. Morphological traits included multi‐stemming, stem and crown form, stem quality, and reaction to clipping. Seed source, test site, and simulated leader browsing were all important in determining the growth and quality of F. sylvatica saplings. The effects of seed source on growth and quality indicate that F. sylvatica possesses a large pool of diverse genotypes across Switzerland and thus has the potential to adapt to local conditions through gene flow. Growth and morphology differed significantly between the two test sites, indicating that local environments should be considered carefully when a new plantation is established. The effect of the single simulated browsing event disappeared over time for the growth traits, owing to growth compensation. However, sapling quality decreased after clipping, suggesting that browsing may lead to persistent quality losses in production forests. Neither the growth nor the morphological reaction after clipping depended on the effect of population, meaning that resilience to browsing was independent of seed source. Consequently, interactions with ungulate browsing do not have to be taken into account when selecting F. sylvatica populations for particular climatic and site conditions.

Spectroscopic and thermal properties of stannadithiane compounds bearing endocyclic ether and lactone groups.

Four related stannadithiane compounds containing different endocyclic functional groups -including ether (1), diether (2), lactone (3), and spirolactone (4)- were prepared. The conformational landscape has been fully determined for the 8-membered representative (compound 1) resulting in a distorted crown form with the butyl chains adopting an extended conformation. The infrared and Raman spectra of stannadithiane species have been measured and interpreted, aided by quantum chemical calculations and potential energy surface analysis. Special attention has been devoted to the analysis of the vibrational features of the heterocyclic moieties. The characteristic νas(SnS) and νs(SnS) stretching modes of the SnS2endo-cyclic group were clearly observed in the Raman spectra at around 340 and 315 cm-1, respectively. The exo-cyclic ν(SnC) stretching modes were found near 590 and 565 cm-1 for the antisymmetric and symmetric motions, respectively. Thermal behavior for compounds 2-4 has been determined by thermogravimetric methods.

Morphological variation of Cedrela odorata (Meliaceae): contrast between natural and managed populations

Background and Aims: Cedrela odorata (Spanish cedar) is a tropical tree native to America with an important international trade market. In this study, the morphological variation of C. odorata was compared among three conditions: logging, plantations, and natural populations, with the objective to evaluate the current condition of managed populations after harvesting and in plantations, in contrast to relatively well-preserved populations.Methods: Two sites were chosen for each condition. The population density and four morphological attributes were measured: diameter at breast height, height, angle of branch insertion and crown form. A multivariate approach was used to compare the morphological variation among conditions (generalized discriminant factors analysis) and determine total variation distributed among size classes (cluster analysis), as well as assignment of these classes to each condition (canonical correspondence analysis).Key results: Four significantly different size classes were identified among all populations with specific association to condition. Strongest correlations were between highest trees with natural populations and small trees with plantations. Forest management, including harvesting and plantation conditions, reduced the phenotypical variation and modified the dasometrical attributes of C. odorata. The logging of the better shaped phenotypes increased the smaller size trees frequency compared to commercial size individuals, and changed the forest composition favoring small categories.Conclusions: The forest exploitation generates homogenization in median height-class and the plantation in lower height-class. In both cases, the harvestable trees are scarce, even after 20 years of management; and they are non-existent in plantations of 15 years. These results suggest that the removal of the highest trees, as well as forest plantations, are not being effective to wood production since they do not reach commercial sizes in the time of recovery or projected growth.

Внутрішньовидова диференціація abies alba Mill. за структурою деревини

Вивчено особливості формування річного приросту ялиці білої з прямоволокнистою та хвилясто-завилькуватою структурою деревини. Розглянуто відмінності абсолютних значень ширини ранньої та пізньої деревини на 40 модельних деревах у шести деревостанах. Встановлено, що ширина ранньої деревини ялиці білої змінюється в середньому від 0,5 до 2,0 мм. Різке збільшення ширини ранньої деревини пов'язано з локальними екологічними чинниками. Абсолютні значення ширини пізньої деревини у прямоволокнистій структурі характеризуються меншими значеннями, ніж у екземплярів із хвилясто-завилькуватою структурою. Середні значення ширини річного кільця прямоволокнистої деревини ялиці білої змінюються в межах від 2,36 до 3,53 мм, а в дерев із хвилясто-завилькуватою деревиною – 3,98–5,74 мм. Встановлено істотну різницю в середніх значеннях ширини річного кільця, що властива для мінімальних та максимальних значень. Середня ширина річного кільця у хвилясто-завилькуватій деревині ялиці білої становить 5,74 мм, а ширина річного кільця змінюється від 1,05 до 11,57 мм. Однофакторним дисперсійним аналізом ширини річного кільця деревини ялиці білої в чотирьох деревостанах встановлено статистично значущу різницю між показниками макроструктури у прямоволокнистій та хвилясто-завилькуватій деревині. Рівень значущості між досліджуваними деревами з прямоволокнистою та хвилясто-завилькуватою деревиною становив р&lt;0,05.&#x0D;

Localized Asymmetry in Human Dental Crown Form—an Interesting Case

A case of a 20-year-old female is described in which the premolars and molars on the right side of the arch display altered crown proportions and altered occlusal morphology. There is no evidence of an orofacial congenital disorder or history of trauma. It is argued that the asymmetrical expression of crown form does not fall within the normal range of variation but has resulted from a localized disruption in cellular function within the developing tooth germs, probably upsetting the folding of the internal enamel epithelia. This has produced crowns that have rounded cuspal outlines and reduced intercuspal distances. Superimposed space constraints in the mandible may have also led to compression of the lower molar crowns mesiodistally and affected their root formation.

A Geometric Morphometric Analysis of the Crown Form of the Maxillary Central Incisor in Humans

Dental traits have been studied over a long period and grossly evaluated using standard reference plaques. However, grading by subjective observation may result in inter-observer measurement errors. We aimed to analyze crown models three-dimensionally to assess the morphology of the lingual surface termed shovel shape. Micro-CT scanned data of 38 maxillary central incisors stored at two different laboratories were used to create crown models of the outer enamel surface (OES) and the dentinoenamel junction (DEJ). Original crown data were evaluated according to the grade of shoveling into weak and strong groups. Homologous models consisting of the same number of data points were created and the distance matrices between tooth models of OES and DEJ were respectively analyzed by using multidimensional scaling analysis (MDS) and principal component analysis. Student’s t-test was used to compare corresponding scores between the two groups based on shovel-shape. The results of a t-test in the OES model indicated significant differences between the two groups. In contrast, the result in the DEJ model did not reveal a statistically significant difference. Our results indicate that geometric morphometric analysis of micro-CT scanned tooth crowns represents a powerful solution for the objective shape assessment of human teeth.

Crown damage and the mortality of tropical trees.

What causes individual tree death in tropical forests remains a major gap in our understanding of the biology of tropical trees and leads to significant uncertainty in predicting global carbon cycle dynamics. We measured individual characteristics (diameter at breast height, wood density, growth rate, crown illumination and crown form) and environmental conditions (soil fertility and habitat suitability) for 26 425 trees ≥ 10 cm diameter at breast height belonging to 416 species in a 52-ha plot in Lambir Hills National Park, Malaysia. We used structural equationmodels to investigate the relationships among the different factors and tree mortality. Crown form (a proxy for mechanical damage and other stresses) and prior growth were the two most important factors related to mortality. The effect of all variables on mortality (except habitat suitability) was substantially greater than expected by chance. Tree death is the result of interactions between factors, including direct and indirect effects. Crown form/damage and prior growth mediated most of the effect of tree size, wood density, fertility and habitat suitability on mortality. Large-scale assessment of crown form or status may result in improved prediction of individual tree death at the landscape scale.