Development of a methodology for simulating seat back interaction using realistic body contours

Seat comfort is driven in part by the fit between the sitter and seat. Traditional anthropometric data provide little information about the size and shape of the torso that can be used for backrest design. This report introduces a methodology for using three-dimensional computer models of the human torso based on a statistical analysis of body shapes for conducting automated fit assessments. Surface scan data from 296 men and 417 women in a seated posture were analyzed to create a body shape model that can be adjusted to a range of postures spanning those typical of vehicle occupants. A parameterized finite-element model of an auto seat surface was created, along with custom software that generates body models and postures them in the seat. A simple simulation technique was developed to rapidly assess the fit of the torso relative to the seat back. Further refinement of the method will allow prediction of seat surface pressure distribution, which may be usefully related to subjective assessment of seat fit.The University of Michigan Transportation Research Institutehttp://deepblue.lib.umich.edu/bitstream/2027.42/89868/1/102814.pd

Ultrastructure of early amelogenesis in wildâ type, Amelxâ /â , and Enamâ /â mice: enamel ribbon initiation on dentin mineral and ribbon orientation by ameloblasts

IntroductionDental enamel is comprised of highly organized, oriented apatite crystals, but how they form is unclear.MethodsWe used focused ion beam (FIB) scanning electron microscopy (SEM) to investigate early enamel formation in 7â weekâ old incisors from wildâ type, Amelxâ /â , and Enamâ /â C56BL/6 mice. FIB surface imaging scans thicker samples so that the thin enamel ribbons do not pass as readily out of the plane of section, and generates serial images by a mill and view approach for computerized tomography.ResultsWe demonstrate that wildâ type enamel ribbons initiate on dentin mineral on the sides and tips of mineralized collagen fibers, and extend in clusters from dentin to the ameloblast membrane. The clustering suggested that groups of enamel ribbons were initiated and then extended by fingerâ like membrane processes as they retracted back into the ameloblast distal membrane. These findings support the conclusions that no organic nucleator is necessary for enamel ribbon initiation (although no ribbons form in the Enamâ /â mice), and that enamel ribbons elongate along the ameloblast membrane and orient in the direction of its retrograde movement. Tomographic reconstruction videos revealed a complex of ameloblast membrane processes and invaginations associated with intercellular junctions proximal to the mineralization front and also highlighted interproximal extracellular enamel matrix accumulations proximal to the interrod growth sites, which we propose are important for expanding the interrod matrix and extending interrod enamel ribbons. Amelxâ /â mice produce oriented enamel ribbons, but the ribbons fuse into fanâ like structures. The matrix does not expand sufficiently to support formation of the Tomes process or establish rod and interrod organization.ConclusionAmelogenin does not directly nucleate, shape, or orient enamel ribbons, but separates and supports the enamel ribbons, and expands the enamel matrix to accommodate continued ribbon elongation, retrograde ameloblast movement, and rod/interrod organization.This is the first report using focused ion beam microscopy to visualize enamel ribbons at high resolution as they form, which are shown to initiate on the underlying dentin crystals. This continuity between dentin and enamel mineral has been difficult to establish with conventional thin sectioning techniques and has been debated for many years. We converted serial images into movies that allowed us to better appreciate the complex infolding of cell membranes and intercellular compartmentalization that are integral to the complex mechanism of enamel biomineralization.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135052/1/mgg3253-sup-0002-FigS13-21.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135052/2/mgg3253-sup-0005-FigS41-51.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135052/3/mgg3253_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135052/4/mgg3253-sup-0003-FigS24-26.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135052/5/mgg3253-sup-0004-FigS29-40.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135052/6/mgg3253.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135052/7/mgg3253-sup-0001-FigS1-12.pd

Quantitative analysis of the core 2D arrangement and distribution of enamel rods in crossâ sections of mandibular mouse incisors

Considerable descriptive information about the overall organization of mouse mandibular incisor enamel is available but almost nothing is known about the quantitative characteristics of enamel rod arrangement and distribution in these teeth. This has important implications concerning cell movement during the secretory stage because each ameloblast makes one enamel rod. Knowing how many enamel rods are cut open in a crossâ section of the enamel layer could provide insights into understanding the dynamics of how groups of ameloblasts form the enamel layer. In this study, crossâ sections of fully mineralized enamel were cut on 24 mandibular mouse incisors, polished and etched, and imaged by scanning electron microscopy in backscatter mode. Montaged maps of the entire enamel layer were made at high magnification and the enamel rod profiles in each map were colorâ coded based upon rod category. Quantitative analyses of each color layer in the maps were then performed using standard routines available in imagej. The data indicated that that there were on average 7233 ± 575 enamel rod profiles per crossâ section in mandibular incisors of 7â weekâ old mice, with 70% located in the inner enamel layer, 27% located in the outer enamel layer, and 3% positioned near the mesial and lateral cementoenamel junctions. All enamel rod profiles showed progressive increases in tilt angles, some very large in magnitude, from the lateral to mesial sides of the enamel layer, whereas only minor variations in tilt angle were found relative to enamel thickness at given locations across the enamel layer. The decussation angle between alternating rows of rod profiles within the inner enamel layer was fairly constant from the lateral to central labial sides of the enamel layer, but it increased dramatically in the mesial region of the enamel layer. The packing density of all rod profiles decreased from lateral to central labial regions of the enamel layer and then in progressing mesially, decreased slightly (inner enamel, mesial tilt), increased slightly (outer enamel layer) or almost doubled in magnitude (inner enamel, lateral tilt). It was concluded that these variations in rod tilt angle and packing densities are adaptations that allow the tooth to maintain a sharp incisal edge and shovelâ shape as renewing segments formed by around 7200 ameloblasts are brought onto the occluding surface of the tooth by continuous renewal.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/147012/1/joa12912_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147012/2/joa12912.pd

Relationships between protein and mineral during enamel development in normal and genetically altered mice

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90093/1/EOS_871_sm_SupportingInformation.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/90093/2/j.1600-0722.2011.00871.x.pd

Enamel ribbons, surface nodules, and octacalcium phosphate in C57BL/6 Amelxâ /â mice and Amelx+/â lyonization

BackgroundAmelogenin is required for normal enamel formation and is the most abundant protein in developing enamel.MethodsAmelx+/+, Amelx+/â , and Amelxâ /â molars and incisors from C57BL/6 mice were characterized using RTâ PCR, Western blotting, dissecting and light microscopy, immunohistochemistry (IHC), transmission electron microscopy (TEM), scanning electron microscopy (SEM), backscattered SEM (bSEM), nanohardness testing, and Xâ ray diffraction.ResultsNo amelogenin protein was detected by Western blot analyses of enamel extracts from Amelxâ /â mice. Amelxâ /â incisor enamel averaged 20.3 ± 3.3 μm in thickness, or only 1/6th that of the wild type (122.3 ± 7.9 μm). Amelxâ /â incisor enamel nanohardness was 1.6 Gpa, less than half that of wildâ type enamel (3.6 Gpa). Amelx+/â incisors and molars showed vertical banding patterns unique to each tooth. IHC detected no amelogenin in Amelxâ /â enamel and varied levels of amelogenin in Amelx+/â incisors, which correlated positively with enamel thickness, strongly supporting lyonization as the cause of the variations in enamel thickness. TEM analyses showed characteristic mineral ribbons in Amelx+/+ and Amelxâ /â enamel extending from mineralized dentin collagen to the ameloblast. The Amelxâ /â enamel ribbons were not well separated by matrix and appeared to fuse together, forming plates. Xâ ray diffraction determined that the predominant mineral in Amelxâ /â enamel is octacalcium phosphate (not calcium hydroxyapatite). Amelxâ /â ameloblasts were similar to wildâ type ameloblasts except no Tomesâ processes extended into the thin enamel. Amelxâ /â and Amelx+/â molars both showed calcified nodules on their occlusal surfaces. Histology of D5 and D11 developing molars showed nodules forming during the maturation stage.ConclusionAmelogenin forms a resorbable matrix that separates and supports, but does not shape early secretoryâ stage enamel ribbons. Amelogenin may facilitate the conversion of enamel ribbons into hydroxyapatite by inhibiting the formation of octacalcium phosphate. Amelogenin is necessary for thickening the enamel layer, which helps maintain ribbon organization and development and maintenance of the Tomesâ process.We thoroughly characterized enamel formation in amelogenin null mice and determined that the mineral covering dentin in these animals is octacalcium phosphate. The initial enamel mineral has a ribbon shape, similar to the wild type. Thus, amelogenin is not required to shape the ribbons, as is currently thought, but is required to ensure that the final mineral phase is calcium hydroxyapatite.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134766/1/mgg3252_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134766/2/mgg3252-sup-0001-AppendixS1-21.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134766/3/mgg3252.pd

The Enamel Phenotype in Homozygous Fam83h Truncation Mice

BackgroundTruncation FAM83H mutations cause human autosomal dominant hypocalcified amelogenesis imperfecta (ADHCAI), an inherited disorder characterized by severe hardness defects in dental enamel. No enamel defects were observed in Fam83h null mice suggesting that Fam83h truncation mice would better replicate human mutations.MethodsWe generated and characterized a mouse model (Fam83hTr/Tr) expressing a truncated FAM83H protein (amino acids 1â 296), which recapitulated the ADHCAIâ causing human FAM83H p.Tyr297* mutation.ResultsDay 14 and 7â week Fam83hTr/Tr molars exhibited rough enamel surfaces and slender cusps resulting from hypoplastic enamel defects. The lateral third of the Fam83hTr/Tr incisor enamel layer was thinner, with surface roughness and altered enamel rod orientation, suggesting disturbed enamel matrix secretion. Regular electron density in mandibular incisor enamel indicated normal enamel maturation. Only mildly increased posteruption attrition of Fam83hTr/Tr molar enamel was observed at 7â weeks. Histologically, the Fam83hTr/Tr enamel organ, including ameloblasts, and enamel matrices at sequential stages of amelogenesis exhibited comparable morphology without overt abnormalities, except irregular and less evident ameloblast Tomes’ processes in specific areas.ConclusionsConsidering Fam83hâ /â mice showed no enamel phenotype, while Fam83hTr/Tr (p.Tyr297*) mice displayed obvious enamel malformations, we conclude that FAM83H truncation mutations causing ADHCAI in humans disturb amelogenesis through a neomorphic mechanism, rather than haploinsufficiency.FAM83H truncation mutations cause inherited enamel malformations in humans. Previously we showed that no enamel malformations are observed in Fam83h null mice. Here we demonstrate that truncation of FAM83H in mice causes enamel malformations. This figure shows how the lateral incisor enamel (on the left) is thinner in the Fam83h truncation mouse than it is in wild-type.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149571/1/mgg3724-sup-0004-DataS4.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149571/2/mgg3724-sup-0003-DataS3.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149571/3/mgg3724-sup-0001-DataS1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149571/4/mgg3724-sup-0002-DataS2.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149571/5/mgg3724_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149571/6/mgg3724.pd

Characterization of porcine dentin sialoprotein (DSP) and dentin sialophosphoprotein (DSPP) cDNA clones

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74726/1/j.1600-0722.2003.00009.x.pd

Critical roles for WDR72 in calcium transport and matrix protein removal during enamel maturation

Defects in WDR72 (WD repeat‐containing protein 72) cause autosomal recessive hypomaturation amelogenesis imperfecta. We generated and characterized Wdr72‐knockout/lacZ‐knockin mice to investigate the role of WDR72 in enamel formation. In all analyses, enamel formed by Wdr72 heterozygous mice was indistinguishable from wild‐type enamel. Without WDR72, enamel mineral density increased early during the maturation stage but soon arrested. The null enamel layer was only a tenth as hard as wild‐type enamel and underwent rapid attrition following eruption. Despite the failure to further mineralize enamel deposited during the secretory stage, ectopic mineral formed on the enamel surface and penetrated into the overlying soft tissue. While the proteins in the enamel matrix were successfully degraded, the digestion products remained inside the enamel. Interactome analysis of WDR72 protein revealed potential interactions with clathrin‐associated proteins and involvement in ameloblastic endocytosis. The maturation stage mandibular incisor enamel did not stain with methyl red, indicating that the enamel did not acidify beneath ruffle‐ended ameloblasts. Attachment of maturation ameloblasts to the enamel layer was weakened, and SLC24A4, a critical ameloblast calcium transporter, did not localize appropriately along the ameloblast distal membrane. Fewer blood vessels were observed in the papillary layer supporting ameloblasts. Specific WDR72 expression by maturation stage ameloblasts explained the observation that enamel thickness and rod decussation (established during the secretory stage) are normal in the Wdr72 null mice. We conclude that WDR72 serves critical functions specifically during the maturation stage of amelogenesis and is required for both protein removal and enamel mineralization.We generated knockout mice lacking the ability to make WDR72. Deletion of WDR72 caused retention of degraded enamel proteins within the mineral layer and significantly reduced mineralization. The null enamel layer was only a tenth as hard as wild‐type enamel and underwent rapid attrition following eruption. Attachment of maturation ameloblasts to the enamel layer was weakened, and SLC24A4, a critical ameloblast calcium transporter, did not localize appropriately along the ameloblast distal membrane. Interactome analysis of WDR72 protein revealed potential involvement in ameloblastic endocytosis.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/112233/1/mgg3143.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/112233/2/mgg3143-sup-0001-SuppInfo.pd

Electronic structure of REREAuMg and REREAgMg (RERE = Eu, Gd, Yb)

We have investigated the electronic structure of the equiatomic EuAuMg, GdAuMg, YbAuMg and GdAgMg intermetallics using x-ray photoelectron spectroscopy. The spectra revealed that the Yb and Eu are divalent while the Gd is trivalent. The spectral weight in the vicinity of the Fermi level is dominated by the mix of Mg $s$, Au/Ag $sp$ and $RE$ $spd$ bands, and not by the $RE$ $4f$. We also found that the Au and Ag $d$ bands are extraordinarily narrow, as if the noble metal atoms were impurities submerged in a low density $sp$ metal host. The experimental results were compared with band structure calculations, and we found good agreement provided that the spin-orbit interaction in the Au an Ag $d$ bands is included and correlation effects in an open $4f$ shell are accounted for using the local density approximation + Hubbard $U$ scheme. Nevertheless, limitations of such a mean-field scheme to explain excitation spectra are also evident.Comment: 4 pages, 3 figures, Brief Repor