Tooth Mineralization Research Articles

Effect of Ions Released and pH of Two Glass Ionomer Cements in Human Gingival Fibroblasts

Conventional glass ionomer cements are used as dental provisional restorative materials, which present several advantages such as adhesion to the tooth mineral phase among others. On the other hand, the knowledge about biological property of glass ionomers shows various approaches and results. In this work, it was studied the in vitro biological response of human gingival fibroblasts in contact with commercial cements of glass ionomer: Mirafil® and Ionglass® and with their extracts, according to ISO 10993. The extracts of the cements, in which the cells were cultured, were adjusted at different concentrations ranging 0.1% to 100%. The cellular metabolic activity of gingival fibroblasts was measured using the Alamar Blue® reagent. The results showed a significant effect on the cellular metabolic activity correlated with the concentration of liberated ions (Al³+ and Ca²+) for both ionomers, as well as the pH variations of the culture media. This could mean that the cellular metabolic activity is substantially influenced by ions and pH of the cell culture.

Alkaline Phosphatase Replacement Therapy for Hypophosphatasia in Development and Practice.

Hypophosphatasia (HPP) is an inherited disorder that affects bone and tooth mineralization characterized by low serum alkaline phosphatase. HPP is caused by loss-of-function mutations in the ALPL gene encoding the protein, tissue-nonspecific alkaline phosphatase (TNSALP). TNSALP is expressed by mineralizing cells of the skeleton and dentition and is associated with the mineralization process. Generalized reduction of activity of the TNSALP leads to accumulation of its substrates, including inorganic pyrophosphate (PPi) that inhibits physiological mineralization. This leads to defective skeletal mineralization, with manifestations including rickets, osteomalacia, fractures, and bone pain, all of which can result in multi-systemic complications with significant morbidity, as well as mortality in severe cases. Dental manifestations are nearly universal among affected individuals and feature most prominently premature loss of deciduous teeth. Management of HPP has been limited to supportive care until the introduction of a TNSALP enzyme replacement therapy (ERT), asfotase alfa (AA). AA ERT has proven to be transformative, improving survival in severely affected infants and increasing overall quality of life in children and adults with HPP. This chapter provides an overview of TNSALP expression and functions, summarizes HPP clinical types and pathologies, discusses early attempts at therapies for HPP, summarizes development of HPP mouse models, reviews design and validation of AA ERT, and provides up-to-date accounts of AA ERT efficacy in clinical trials and case reports, including therapeutic response, adverse effects, limitations, and potential future directions in therapy.

Differences in surface roughness of enamel after whey-extract application and CPP-ACP in post extracoronal-tooth bleaching

Demineralization is a process of partial or full tooth mineral loss which caused by acidic environment, for example the side effect of extracoronal bleaching treatment. Demineralization increases enamel surface roughness which leads plaque accumulation. Whey extract and calcium phosphopeptide-amorphous calcium phophate (CPP-ACP) contain calcium and phosphate that can stop the demineralization through remineralization process. This study aimed to determine the differences of enamel surface roughness after whey extract and CPP-ACP application post- extracoronal bleaching. Experimental laboratory with pre- and post-test control group design was performed on 24 first maxillary premolars which devided into 3 groups. On group I, specimens were immersed in artificial saliva. Specimens in group II were immersed in whey extract meanwhile specimens were immersed in CPP-ACP on group III. Whey extract and CPP-ACP immersions were conducted 10 minutes every 12 hours for 15 days. The enamel surface roughness test was performed twice, after extracoronal bleaching treatment and after 15 days remineralization agent application. This study result indicated significant differences between group I and group II and between group I and group III (p<0.05), but there was no significant difference between group II and group III (p>0.05). This study showed whey extract decreased more enamel surface roughness than CPP-ACP but the difference was not significant statistically. So, whey extract and CPP-ACP showed similar remineralization potential.

Expression and function of Slc34 sodium-phosphate co-transporters in skeleton and teeth.

Under normal physiological condition, the biomineralization process is limited to skeletal tissues and teeth and occurs throughout the individual's life. Biomineralization is an actively regulated process involving the progressive mineralization of the extracellular matrix secreted by osteoblasts in bone or odontoblasts and ameloblasts in tooth. Although the detailed molecular mechanisms underlying the formation of calcium-phosphate apatite crystals are still debated, it is suggested that calcium and phosphate may need to be transported across the membrane of the mineralizing cell, suggesting a pivotal role of phosphate transporters in bone and tooth mineralization. In this context, this short review describes the current knowledge on the role of Slc34 Na+-phosphate transporters in skeletal and tooth mineralization.

Biomimetic transformation of polyphosphate microparticles during restoration of damaged teeth

ObjectiveIn the present study, we investigated the fusion process between amorphous microparticles of the calcium salt of the physiological polymer comprising orthophosphate units, of inorganic polyphosphate (polyP), and enamel. MethodsThis polymer was incorporated as an ingredient into toothpaste and the fusion process was studied by electron microscopy and by synchrotron-based X-ray tomography microscopy (SRXTM) techniques. ResultsThe data showed that toothpaste, supplemented with the amorphous Ca-polyP microparticles (aCa-polyP-MP), not only reseals tooth defects on enamel, like carious lesions, and dentin, including exposed dentinal tubules, but also has the potential to induce re-mineralization in the enamel and dentin regions. The formation of a regeneration mineralic zone on the tooth surface induced by aCa-polyP-MP was enhanced upon exposure to artificial saliva, as demonstrated by SRXTM. Energy dispersive X-ray analysis revealed an increase in the calcium/phosphorus atomic ratio of the enamel deposits to values characteristic for the particles during the treatment with polyP applied in the toothpaste, indicating a fusion of the particles with the tooth mineral. SignificanceOur results suggest that toothpaste enriched with aCa-polyP-MP is a promising biomimetic material for accelerating enamel and dentin restoration.

Full-scale Raman imaging for dental caries detection

Early detection of dental caries is critical for avoiding more invasive and advanced treatment at a later stage. However, currently available techniques are unsatisfactory for early detection. Raman spectroscopy is known to have both high sensitivity and specificity in the analysis of mineral content in a tooth; but translating Raman spectroscopy to clinical caries detection remains a challenge. In this study, we report a full-scale Raman imaging system that can provide fast full-scale (~7 mm in diameter) tooth mineral analysis which could be feasible for clinical application. The results show that the Raman imaging system could not only confirm carious lesions that are obvious to the naked eye but also identify those which are not conclusive to traditional visual examination and probing.

Tooth Mineralization: A Technical Note on the Moorrees-Fanning-Hunt Standards

One of the largest, longitudinal studies of tooth mineralization is that described by Moorrees, Fanning and Hunt (J Dent Res, 1963) based on children growing up in Boston, Massachusetts, and Yellow Springs, Ohio. This short communication provides tables of the means and standard deviations, by sex, in order to make the data more accessible and usable than the graphic form of the information in the original article. Characteristics of the study and applications are discussed.

The Genetics of Odontogenesis: Implications in Dental Anthropology and Palæo-Odontology

Palaeoanthropology and forensic odontology rely significantly upon detailed dental morphology that is ultimately the phenotypic expression of the underlying genotype and developmental phenomena. Odontogenesis is the consequence of a complex series of molecular interactions controlled by epigenetic signals acting on embryonic epithelial-mesenchymal tissues of ectodermal, neural crest and mesodermal origin. Of the estimated 24,847 genes of the human genome (Pearson, 2003) some 200 or more genes have been directly or indirectly involved in tooth development (http://bite-it.helsinki.fi). The loci of these genes on the 22 pairs of autosomes and the pair of sex chromosomes are being identified by their mutations that give rise to phenotypic dental abnormalities. The sequential cascades of stages from initiation through the bud, cap, bell, mineralization, root formation and eruption of teeth are all under genetic control but subject to environmental influences. Identification of specific genes with clinical phenotypes provides invaluable clues to familial, racial and evolutionary affinities, all of jurisprudential, heredity and evolutionary significance to odontologists. Combining the genetics of odontogenesis with forensic evidence and palaeoanthropological fossil data provides an unparalled source of information on heredity, environmental and evolutionary events through teeth, the most durable of all biological structures after death. It is paradoxical that teeth are most susceptible to decay during life, but postmortem are the last structures to disintegrate. Teeth truly tell tales of the living and the dead.

Dental Age: Effects of Estimating Different Events During Mineralization

The extent of tooth mineralization affords apractical method for assessing an individual’s biologicalage. Dental age is useful for evaluating a child’sgrowth status, and for assessing the ages of subjects inanthropological, forensic, and medicolegal settings.Historically, some data have been collected from serialstudies (e.g., Stuart’s Harvard Study, and the BurlingtonStudy) while most studies are cross-sectional, where eachchild is examined just once. Serial and cross-sectionalstudies traditionally have been used to estimate differentsorts of information, namely the onset at a stage and theaverage age in a stage, respectively. This paper discussesthe differences of the analyses, and then presents anempirical comparison of two large sets of data on thelower third molar in American whites, showing how theconventional uses of serial data—that estimate the onsetof an event—precede the age of occurrence derived fromcross-sectional data (age at stage). Inter-group differencesfor tooth stages can exceed one year, so it is important torecognize the nature of the ‘standards’ available in theliterature.

Primary Tooth Mineralization and Exfoliation Ages Calculated from the Moorrees-Fanning-Hunt Study

Staging of the formation of teeth and shedding of the primary teeth are particularly useful for age estimation of archaeological and forensic specimens, as well as for gauging whether a child’s tempo of maturation is progressing within normal limits. Staging can be done using radiographs or with direct inspection of dental remains. Standards for the primary dentition are scarce, but obviously needed for young children. This note provides tables, by sex, of the normative ages of the mineralization of three mandibular tooth types (c, m1, m2) as well as of root resorption and times of shedding of these tooth types. The data are transformed from charts developed by Moorrees, Fanning and Hunt (1963 Am J Phys Anthropol 21:99-108). Conversion to numeric form is intended to aid in using these data for statistical comparisons.

The development of the mammalian dentition as a complex adaptive system

General characteristics of Complex Adaptive Systems include self-adaptation and or-ganisation, emergence, multitasking, robustness, critical phases, diversity and compatibility with such statistical models as Thresholds and Scale Free Networks. The aim was to investigate wheth-er dental development exhibits the general and statistical characteristics of a Complex Adaptive System, by examining data on normal and abnormal dental development. The findings were that self-adaptation and organisation occur while interactions between genes, epigenetic and environmental factors lead to the emergence of cells, tooth germs and mineralised teeth. Multitasking occurs as signalling pathways act simultaneously and reiteratively during initiation and morphogenesis. Tooth germs that do not attain a critical threshold during development may undergo apoptosis. Diversity is evident in tooth number, size, shape and mineralisation. Statistical investigation shows that males have significantly larger teeth and higher prevalences of megadontia and supernumerary teeth (p<0.05), supporting Brook’s Threshold Model which is further developed here to include shape. Image Analysis of tooth dimensions showed they followed a Power Law distribution, with the first 8 of 34 factors in upper lateral inci-sors accounting for 94.4% of the total variation. In conclusion, the development of the dentition shows the general and statistical characteristics of a Complex Adaptive System.

Evolution of dental tissue mineralization: an analysis of the jawed vertebrate SPARC and SPARC-L families

BackgroundThe molecular bases explaining the diversity of dental tissue mineralization across gnathostomes are still poorly understood. Odontodes, such as teeth and body denticles, are serial structures that develop through deployment of a gene regulatory network shared between all gnathostomes. Dentin, the inner odontode mineralized tissue, is produced by odontoblasts and appears well-conserved through evolution. In contrast, the odontode hypermineralized external layer (enamel or enameloid) produced by ameloblasts of epithelial origin, shows extensive structural variations. As EMP (Enamel Matrix Protein) genes are as yet only found in osteichthyans where they play a major role in the mineralization of teeth and others skeletal organs, our understanding of the molecular mechanisms leading to the mineralized odontode matrices in chondrichthyans remains virtually unknown.ResultsWe undertook a phylogenetic analysis of the SPARC/SPARC-L gene family, from which the EMPs are supposed to have arisen, and examined the expression patterns of its members and of major fibrillar collagens in the spotted catshark Scyliorhinus canicula, the thornback ray Raja clavata, and the clawed frog Xenopus tropicalis. Our phylogenetic analyses reveal that the single chondrichthyan SPARC-L gene is co-orthologous to the osteichthyan SPARC-L1 and SPARC-L2 paralogues. In all three species, odontoblasts co-express SPARC and collagens. In contrast, ameloblasts do not strongly express collagen genes but exhibit strikingly similar SPARC-L and EMP expression patterns at their maturation stage, in the examined chondrichthyan and osteichthyan species, respectively.ConclusionsA well-conserved odontoblastic collagen/SPARC module across gnathostomes further confirms dentin homology. Members of the SPARC-L clade evolved faster than their SPARC paralogues, both in terms of protein sequence and gene duplication. We uncover an osteichthyan-specific duplication that produced SPARC-L1 (subsequently lost in pipidae frogs) and SPARC-L2 (independently lost in teleosts and tetrapods).Our results suggest the ameloblastic expression of the single chondrichthyan SPARC-L gene at the maturation stage reflects the ancestral gnathostome situation, and provide new evidence in favor of the homology of enamel and enameloids in all gnathostomes.

Tooth mineralization and histology patterns in extinct and extant snaggletooth sharks, Hemipristis (Carcharhiniformes, Hemigaleidae)-Evolutionary significance or ecological adaptation?

Shark jaws exhibit teeth that are arranged into distinct series and files and display great diversities in shapes and structures, which not only is related to their function (grasping, cutting, crushing) during feeding, but also bear a strong phylogenetic signal. So far, most research on the relationship between shark teeth and feeding ecology and systematics focused on the external tooth morphology only. Although the tooth histology of sharks has been examined since the early 19th century, its functional and systematic implications are still ambiguous. Shark teeth normally consist of either a porous, cellular dentine, osteodentine (in lamniform sharks and some batoids) or a dense layer of orthodentine (known from different sharks). Sharks of the order Carcharhiniformes, comprising ca. 60% of all extant shark species, are known to have orthodont teeth, with a single exception—the snaggletooth shark, Hemipristis elongata. High resolution micro-CT images of jaws and teeth from selected carcharhiniform sharks (including extant and fossil snaggletooth sharks) and tooth sections of teeth of Hemipristis, other carcharhiniform and lamniform sharks, have revealed that (1) Hemipristis is indeed the only carcharhiniform shark filling its pulp cavity with osteodentine in addition to orthodentine, (2) the tooth histology of Hemipristis elongata differs from the osteodont histotype, which evolved in lamniform sharks and conversely represents a modified orthodonty, and (3) this modified orthodonty was already present in extinct Hemipristis species but the mineralization sequence has changed over time. Our results clearly show the presence of a third tooth histotype—the pseudoosteodont histotype, which is present in Hemipristis. The unique tooth histology of lamniform sharks might provide a phylogenetic signal for this group, but more research is necessary to understand the phylogenetic importance of tooth histology in sharks in general.

СТРУКТУРА ЗУБНЫХ ЗАЧАТКОВ И ОСОБЕННОСТИ МИНЕРАЛЬНОГО ОБМЕНА ПРИ ВИБРАЦИОННОМ ВОЗДЕЙСТВИИ В ЭКСПЕРИМЕНТЕ

Object. Vibration exposure is the most common adverse technogenic factor in the work and living conditions of many people. A significant impact on the state of the oral cavity have many socio-hygienic factors; the nature of their impact, their variability depends on the individual, the environmental situation in the region, the social conditions of people, as well as their professional activities. The undeniable fact is that production factors have an impact on both somatic health and dental status. These circumstances explain the importance of studying the development of the structure of dental rudiments, taking into account the mineral metabolism in the conditions of various anthropogenic influences, including the action of General industrial vibration.
 Purpose of the study. Explore features of the histogenesis of teeth based on mineral metabolism during vibrational excitation.
 Materials and methods. Wistar rats was performed with a vibration 9 to day 18 of pregnancy. We studied the morphology of the tooth germs in the fetus. Analytical studies of the mineral composition of the liver were performed by IRS-nuclear laboratory NGO "CBM" (Moscow) in the method of Dr. A.V. Skalniy. In the liver, the concentration female elements: Ca, Cd, Cu, Fe, Mg, P, Pb, Se, Zn.
 Results. The features in the structure of tooth germs and mineral metabolism in the mother-fetus system with vibrational excitation. Identified structural changes reveal a violation of microcirculation, the development of hypoxia in the tissues of the tooth germ and accelerated dentinogenesis. Change the concentration of minerals in the body - significantly reduces the concentration of essential elements of Ca, Fe, Mg and significantly increased the content of Cu, Cd, Pb.
 Conclusion. The observed changes in the morphology of tooth germs and mineral metabolism, are a reflection of altered homeostasis system the mother-fetus arising under the influence of vibration exposure.

Взаємозв’язок між інтенсивністю карієсу, структурно-функціональною резистентністю емалі та гігієною порожнини рота у дітей із карієсом оклюзійної поверхні жувальної групи зубів

Summary. The article describes the relationship between caries intensity, oral hygiene and enamel resistance during the period of secondary mineralization of teeth is an actual task, the solution of which will be the basis for the justification of caries prevention.The aim of the study – to assess the relationship between caries intensity, oral hygiene and enamel resistance during the period of secondary mineralization of the teeth.Materials and Methods. 156 children were examined, among them 76 were between 12 and 15 years of age and 80 children aged 16 to 18 years. To assess the odor of caries of chewing teeth, the intensity of the KPV index and intensity levels according criteria were determined. The condition of hygiene of the oral cavity was estimated using the hygienic index Green-Vermilion. Structural-functional resistance was determined by the TER-test Okushko V. R., Kosareva L. I. (1983).Results and Discussion. As a result of our research, we found that with an increase in the intensity of the carious process in children of both groups of the study deterioration of the hygienic state of the oral cavity according to the OHI-S index. Also between this index and TER-test there is a strong correlation relationship. When TER-test increases the value of OHI-S index enlarges.Conclusions. Unsatisfactory level of hygiene of the oral cavity, especially during the period of active mineralization of the enamel, contributes to reducing the resistance of the enamel, which plays a significant role in the development of caries in children of the study group.

Strontium isotope evidence for human mobility in the Neolithic of northern Greece

Strontium isotope ratios are widely used in archaeology to differentiate between local and non-local populations. Herein, strontium isotope ratios of 36 human tooth enamels from seven archaeological sites spanning the Early to Late Neolithic of northern Greece (7th–5th millennia B.C.E.) were analysed with the aim of providing new information relating to the movement of humans across the region. Local bioavailable 87Sr/86Sr signals were established using tooth enamel from 26 domestic animals from the same Neolithic sites. 87Sr/86Sr values of faunal enamel correlate well with predicted strontium isotope ratios of the local geology. This is consistent with animal management occurring at a local level, although at Late Neolithic sites strontium isotope values became more varied, potentially indicating changing herding practices. The strontium isotope analysis of human tooth enamel likewise suggests limited population movement within the Neolithic of northern Greece. Almost all individuals sampled exhibited 87Sr/86Sr values consistent with having spent their early life (during the period of tooth mineralisation) in the local area, although movement could have occurred between isotopically homogeneous areas. The strontium isotope ratios of only three individuals lay outside of the local bioavailable 87Sr/86Sr range and these individuals are interpreted as having spent their early lives in a region with a more radiogenic biologically available 87Sr/86Sr. Mobility patterns determined using Sr isotope analysis supports the current evidence for movement and exchange observed through studies of pottery circulation. Suggesting limited movement in the Early and Middle Neolithic and greater movement in the Late Neolithic.

Overexpressed Sirt1 in MSCs Promotes Dentin Formation in Bmi1-Deficient Mice

Sirt1 promotes odontoblastic gene expression in human dental pulp cells, whereas the inhibition of Sirt1 downregulates the expression of those genes. To investigate whether the overexpression of Sirt1 in mesenchymal stem cells (MSCs) driven by Prx1 promoter could rescue the dentin formation defects in Bmi1-deficient (Bmi1−/−) mice, we established the MSCs overexpressing Sirt1 in Bmi1 knockout mice (Sirt1TGBmi1−/−). First, we used Prx1-Cre/ROSAnTnG mice to demonstrate that Prx1 linage cells exist mainly in the pulp horns at 4 wk of age. Second, we found that 4-wk-old Sirt1TG mice had increased tooth volume as compared with wild-type (WT) littermates. The expression level of Sirt1 was significantly higher in dental papilla mesenchymal cells of Sirt1TG mice than WT mice. Furthermore, we demonstrated that the tooth mineralization, dental volume, dentin sialoprotein–immunopositive areas, odontoblastic gene expression, and percentage of proliferating BrdU-positive cells were significantly elevated in the Sirt1TG mice and dramatically reduced in the Bmi1–/– mice versus the WT littermates at 4 wk of age. However, the areas of predentin and the percentage of TUNEL-positive apoptotic cells were significantly reduced in the Sirt1TG mice but dramatically increased in the Bmi1−/− mice as compared with the WT littermates. All these parameters were rescued in the Sirt1TGBmi1−/− mice versus the Bmi1−/− mice. Finally, by using dental papilla mesenchymal cells, we found that the overexpression of Sirt1 rescued the reduced cell proliferation and differentiation and increased the cell apoptosis caused by Bmi1 deficiency, which was associated with increased p53 deacetylation. Therefore, this study indicates that Sirt1 is a potential therapeutic target for promoting dentin formation in an anabolic approach to the treatment of dental developmental defects.

Quantitative reconstruction of seasonality from stable isotopes in teeth

Seasonal variation in rainfall and temperature are major determinants of ecosystem structure and productivity and influence physical processes such as erosion rates and glaciation. By extension, seasonality can drive evolutionary change, and is hypothesized to have influenced early human subsistence and technological development. Rainfall patterns are reflected by oxygen isotope ratios (δ18O values) in mammalian tooth enamel, which records environmental chemistry as reflected by blood chemistry during mineralization. Fossilized herbivore molars are commonly used to study paleoseasonality, since temporal variation in precipitation δ18O results in spatial variation in tooth mineral δ18O. However, this approach has been hampered by incomplete knowledge of isotope incorporation during tooth mineralization. Here we test a new synchrotron-based mineralization model and demonstrate its potential to quantitatively reconstruct original seasonal input histories under a Bayesian computational framework. To accomplish this, we first integrate the mineralization model with blood water oxygen isotope turnover to produce high-resolution spatial δ18O predictions. We test these predictions using fine-scaled tooth enamel phosphate δ18O measurements (n = 109 locations sampled in a 2D grid format) in a sheep (Ovis aries) subjected to a controlled water switch (switch δ18O magnitude of 12‰). Tooth mineralization, blood oxygen turnover and isotopic measurements demonstrate that enamel secretion and maturation waves advance at nonlinear rates with distinct geometries. Final enamel isotopic composition may be influenced by isotopic shifts during enamel maturation from amorphous precursors. We combine these observations to produce a Bayesian inverse model for reconstructing water δ18O inputs from tooth isotopic measurements. The system accurately reproduces the controlled switch of the experimental animal and reveals transient documented meteorological events that were unplanned during the experiment. A simulation approach shows that given appropriate priors and search methodologies, this system also reconstructs precipitation histories at different latitudes with striking fidelity. We show that in some contexts even simple sampling approaches (i.e. 1D transects) can yield accurate reconstructions of seasonality. Finally, we refine our mineralization model further by exploring the possible extent of isotopic resetting during mineral phase transitions. This work demonstrates that tooth isotopic measurements can be employed to reconstruct past seasonal isotopic variation in rainfall quantitatively, allowing exploration of the relationships among climate, earth history and evolution.

Responses to spaceflight of mouse mandibular bone and teeth

ObjectiveTo determine if spaceflight and microgravity affect non-weight bearing bones and development and mineralization of teeth, reasoning that combining an organ and a cellular level approach can lead to greater insights about these effects. DesignMandibles and incisors of mice flown on the US STS-135 space shuttle mission and the Russian Bion-M1 satellite were studied using micro-computed tomography and immunohistochemistry. Ground controls were mice housed in standard vivarium cages and flight habitats. ResultsIncisor length was greater in the 13-day STS-135 flight mice than in either control group. Initial incisor mineralization occurred more posteriorly, and incisor, enamel and dentin volumes and enamel and dentin thicknesses were greater in the 30-day Bion-M1 flight and habitat control mice than in vivarium control mice. Mandibular bone volume (BV) was increased in STS-135 flight and habitat groups and decreased in Bion-M1 flight and habitat groups compared to vivarium controls. No significant histological alterations occurred, but changes were seen in the bone and tooth proteins dentin sialoprotein, amelogenin and the type II regulatory subunit of protein kinase A. The percentage of sclerostin positive osteocytes was greatest in flight mice, and greater in STS-135 flight and habitat control mice than in the corresponding Bion-M1 groups. TRAP staining, representing osteoclastic bone remodeling, differed between the two flights and corresponded with changes in BV.Interpretation of the findings was limited by a small number of flight mice, different sex and ages of the mice in the two missions, and different habitats and diets. ConclusionsMicrogravity has measurable effects on mandibular bone physiology and incisor development and mineralization. The results also showed that the habitat had an effect either in flight or ground control samples, as demonstrated by the changes in BV and apparent slowing of incisor eruption. Therefore, developing appropriate habitats is critical for future spaceflight missions.

Interrelationships Between Morphometric, Densitometric, and Mechanical Properties of Teeth in 5-Month-Old Polish Merino Sheep.

Interrelationships between morphological, densitometric, and mechanical properties of deciduous mandibular teeth (incisors, canine, second premolar) were investigated. To perform morphometric, densitometric, and mechanical analyses, teeth were obtained from 5-month-old sheep. Measurements of mean volumetric tooth mineral density and total tooth volume were performed using quantitative computed tomography. Microcomputed tomography was used to measure total enamel volume, volumetric enamel mineral density, total dentin volume, and volumetric dentin mineral density. Maximum elastic strength and ultimate force of teeth were determined using 3-point bending and compression tests. Pearson correlation coefficients were determined between all investigated variables. Mutual dependence was observed between morphological and mechanical properties of the investigated teeth. The highest number of positive correlations of the investigated parameters was stated in first incisor indicating its superior predictive value of tooth quality and masticatory organ function in sheep. Positive correlations of the volumetric dentin mineral density in second premolar with final body weight may indicate predictive value of this parameter in relation with growth rate in sheep. Evaluation of deciduous tooth properties may prove helpful for breeding selection and further reproduction of sheep possessing favorable traits of teeth and better masticatory organ function, leading to improved performance and economic efficiency of the flock.