Enamel Band Research Articles

甘肃秦安安湾的托氏原互棱齿象(Protanancus tobieni)化石及其剖面<br>Protanancus tobieni from the Anwan Section, Qinan County, Gansu Province

详细记述了1976年甘肃秦安安湾剖面第三系地层中发现的一件托氏原互棱齿象(Protanancus tobieni)标本。该材料保存有完整的下颌并带有m3和下门齿，以及完整的左上门齿，与宁夏同心丁家二沟中中新世的托氏原互棱齿象具有相同的特征，可以归为同一种。托氏原互棱齿象的下颌联合部特别伸长；上门齿粗壮，向外分，具宽的釉质带；下门齿扁平，截面为双凹的同心层结构；m3副齿柱具三叶雏形，主副齿柱有初步的伪互棱齿(pseudo-anancody)特征。以上特征可以将其归为原互棱齿象属，而不是此前所认为的变齿象属。并且，其副齿柱三叶和主副齿柱伪互棱齿特征的发育程度比该属的已知各种都弱，又具有下门齿横截面双凹形这一自近裔特征，因而与已知的原互棱齿象各种均不相同，可以确定为一有效种。通过对秦安安湾剖面的考察，推测其可能发育有中新统的连续沉积。剖面以棕红色泥质粉砂岩和泥岩为主，中下段夹有砂砾岩、细砂岩、以及灰绿色泥灰岩透镜体，表明在新近纪的早期，该地区的沉积环境以洪泛平原的河漫滩与河道沉积为主，推测该地区在这一时期的环境较为湿润，含有大量水体。剖面的上段出现较多的钙质结核层，说明在新近纪的中期之后，该地区经历了多次干旱化的过程。 We report a specimen of Protanancus tobieni discovered in 1976 from the Anwan Section, Qinan County, Gansu Province, including a complete mandible with lower incisors and a complete left upper incisor. The material can be referred to the same species as P. tobieni from the middle Miocene Dingjiaergou locality, Ningxia Hui Autonomous Region, because they show almost identical characters. The mandibular symphysis is extremely elongated; the upper incisor is robust with a broad enamel band; the lower incisor is flattened with a biconcave, concentrated-laminated cross-section; and the m3 shows posttrite ornamentation and pseudo-anancody. The above features indicate that the specimen is referable to Protanancus rather than Amebelodon, as it has been previously assigned. Furthermore, P. tobieni shows relatively poor posttrite ornamentation and pseudo-anancody; the lower incisor has a biconcave cross-section —an autapomorphy. These features distinguish it from other known species of Protanancus, and thus support the validity of P. tobieni as a distinct species. Based on the field survey, we infer that the Anwan Section records continuously from the lower to the upper Miocene. The lithology is primarily composed of brownish-red sandy-mudstones and mudstones. The middle and lower members of the section are intercalated with glutenite, sandstone, and grayish-green marl lenses, which represent channel deposits developed on the flood plain; this reflects a fairly humid environment with a large aquatic environmental component, which existed during the early period of the Neogene. The upper member of the section contains numerous layers of calcareous muddy granules, demonstrating a multi-acidification process of environmental evolution that occurred after the middle Neogene.

Enamel malformations associated with a defined dentin sialophosphoprotein mutation in two families

Wang S‐K, Chan H‐C, Rajderkar S, Milkovich RN, Uston KA, Kim J‐W, Simmer JP, Hu JC‐C. Enamel malformations associated with a defined dentin sialophosphoprotein mutation in two families. Eur J Oral Sci 2011; 119 (Suppl. 1): 158–167. © 2011 Eur J Oral SciDentin sialophosphoprotein (DSPP) mutations cause dentin dysplasia type II (DD‐II) and dentinogenesis imperfecta types II and III (DGI‐II and DGI‐III, respectively). We identified two kindreds with DGI‐II who exhibited vertical bands of hypoplastic enamel. Both families had a previously reported DSPP mutation that segregated with the disease phenotype. Oral photographs and dental radiographs of four affected and one unaffected participant in one family and of the proband in the second family were used to document the dental phenotypes. We aligned the 33 unique allelic DSPP sequences showing variable patterns of insertions and deletions (indels), generated a merged dentin phosphoprotein (DPP) sequence that includes sequences from all DSPP length haplotypes, and mapped the known DSPP mutations in this context. Analyses of the DSPP sequence changes and their probable effects on protein expression, as well as published findings of the dental phenotype in Dspp null mice, support the hypothesis that all DSPP mutations cause pathology through dominant‐negative effects. Noting that Dspp is transiently expressed by mouse pre‐ameloblasts during formation of the dentino–enamel junction, we hypothesize that DSPP dominant‐negative effects potentially cause cellular pathology in pre‐ameloblasts that, in turn, causes enamel defects. We conclude that enamel defects can be part of the dental phenotype caused by DSPP mutations, although DSPP is not critical for dental enamel formation.

The microstructure of enamel, dentine and cementum in advanced Taeniodonta (Mammalia) with comments on their dietary adaptations

ABSTRACT The cheek teeth of Ectoganus and Stylinodon, the most derived genera of Taeniodonta following recent phylogenies, show various morphological and microstructural characteristics that are unusual for herbivores of their size. Their continuously growing premolars and molars have blunt occlusal surfaces without shearing facets and enamel is restricted to the lingual and buccal sides of the teeth. The anterior and posterior walls of the teeth are covered with a thick layer of cementum to which the periodontal ligament is attached. The enamel band is relatively thin. The schmelzmuster is one-layered and features weakly developed Hunter-Schreger bands that are only recognizable in longitudinal section. In cross-section, the enamel prisms show a ‘keyhole pattern’ with an incomplete prism sheath. There is no interprismatic matrix. The microstructure of the dentine has the regular mammalian pattern and shows no special similarity to that of xenarthrans. Taeniodonts seem to have used their hypsodont cheek teeth almost exclusively for squeezing and some crushing of food and only to a minor degree for grinding. Weakly developed Hunter-Schreger bands indicate only light loading during mastication.

A New Species of Water Vole from the Early Pleistocene of Southern Europe

In the Early Pleistocene Red Lower Unit of the Sima del Elefante site (Sierra de Atapuerca karst complex, Burgos, Spain), levels TE9–TE13, dental and mandibular remains of an arvicoline are referred to as the new species Arvicola jacobaeus sp. nov. The new species has medium-sized hypselodont molars, with abundant cementum in the re-entrant folds, and thick enamel band with differentiation of the Mimomys-type. The occlusal morphology of M3 is simple. The dental morphology of the new species resembles that of Arvicola sapidus, though smaller. It is more derived, in size and morphology than the Middle Pleistocene species Arvicola mosbachensis. The morphologic affinities among Arvicola jacobaeus, Arvicola terrestris, and A. sapidus suggest a common ancestry. A preliminary phylogenetic analysis corroborates that Mimomys savini is the sister group of the Arvicola clade.

Tooth Morphology in Fossil and Extant Lagomorpha (Mammalia) Reflects Different Mastication Patterns

The functional interpretation of the cheek teeth and the mastication cycle of Lagomorpha are deduced from various aspects of tooth morphology of fossil and extant species. Mastication is composed of an almost orthal shearing and transverse grinding in a lingual direction. Shearing blades are not only indicated by facets but as well by thickened enamel. A primary shearing blade (PSB) inherited from stem lagomorphs occurs in all examined species. It can be correlated with facets 1 and 5 (sensu Crompton 1971) and occurs in very few mammals; it is conspicuously absent in the sister-taxon Rodentia. A secondary shearing blade (SSB) occurs in derived Ochotonidae and two basal Leporidae (Romerolagus and Pronolagus) as a convergent pattern. In fossil ochotonids from Europe, the “lagicone structure” is gradually reduced in favor of the SSB. Thus, ochotonids strengthen the shearing ability, whereas most leporids favor the grinding function realized by the partial crenulation of the enamel band of the re-entrant folds. For the mastication cycle, the distinct phases were recognized, related to phase I of the tribosphenic model. The first movement (phase Ia) is directed almost orthally, the second (phase Ib) lingually. Only in Lepus europaeus was an additional phase detected, which might correspond to phase II.

The fossil suidae from the Plio-Pleistocene Chiwondo Beds of northern Malawi, Africa

ABSTRACT The fossil suids from the Chiwondo Beds in northern Malawi constitute four separate assemblages that may be used for internal and external biostratigraphic correlation. Pig remains occur in two stratigraphic units. Unit 2 contains Notochoerus jaegeri. The younger stratigraphic unit 3A can be subdivided by the suid fauna into an older zone 3A-1 containing Notochoerus euilus and zone 3A-2 with more advanced forms such as Notochoerus scotti and early Metridiochoerus andrewsi. Unit 3B contains advanced M. andrewsi and M. compactus. Bushpig and warthog remains have also been recovered but their stratigraphic position could not be determined. A method of documenting the structural density of enamel bands on the occlusal surface of suid cheek teeth can be used to correlate the Chiwondo Beds suids with similar species from elsewhere in sub-Saharan Africa and thereby for estimating the age of the two hominins discovered by the Hominid Corridor Research Project.

Automated biometrics-based personal identification of the Hunter–Schreger bands of dental enamel

The use of automated biometrics-based personal identification systems is a ubiquitous procedure in present times. Biometrics has certain limitations, such as in cases when bodies are decomposed, burned, or only small fragments of calcified tissues remain. Dental enamel is the most mineralized tissue of organisms and resists post-mortem degradation. It is characterized by layers of prisms of regularly alternating directions, known as Hunter-Schreger bands (HSB). In this article, we show that the pattern variation of the HSB, referred here as toothprint, can be used as a biometric-based parameter for personal identification in automated systems.

Infrared Absorption Bands of Enamel and Dentin Tissues from Human and Bovine Teeth

The chemical components present in the hard tissue such as water, phosphate, carbonate and organic material strongly absorb infrared radiation. The research in dentistry area has a fundamental interest in identifying the chemical origin of all the bands present in the infrared region to study the chemical and thermal action on the hard dental tissues. To improve this technique it is important to identify chemical alterations in the tissues and characterize their properties in a more natural form. Transmission and reflection spectra in the infrared range from 2.5 µm to 25 µm of the enamel and dentin tissues from human and bovine teeth were acquired. Sliced samples were used for the transmission spectra, polished blocks and natural surfaces for the reflection spectra. Tissue spectra were registered between 4000 and 400 cm−1 in a FTIR Spectrometer. No differences were found between the mineral matrix of human and bovine tissues, only differences in intensity among bands were observed. Regarding the organic matrix, the bands observed in the dentin were not observed in the enamel tissue and, as the same, the bands observed in the enamel tissue were not observed in the dentin tissue with a significant intensity. Using infrared spectroscopy of sliced samples or blocks forms it is possible to characterize the chemical and optical alterations produced in the dental hard tissues by either thermal or chemical treatment, or an association of the two treatments, Therefore this technique can be used in dental research that study the effect of laser irradiation on hard tissues and the acid attack produced by intraoral bacteria.

Food-specialization and structural parameters of dental patterns of Arvicolinae (Rodentia, Mammalia)

In this study it is demonstrated that food-specialization of different species of voles and lemmings is reflected in their dental patterns. The subfamily of Arvicolinae was chosen because the basic structure of the occlusal patterns of their molars is very stereotypical and thus their modifications can be attributed to differences in function. The properties of their M2 occlusal patterns are expressed by structural parameters such as pattern density, relative enamel surface and orientation of the enamel edges. Marked differences were found between grass- and moss-feeding species on the one hand as well as root-feeding species on the other. Differences of construction of walls of plant cells of the firmness tissues determine the kind of food-disintegration. The grass- and moss-feeders have evolved a dentition with high pattern density, low relative enamel surface and a high degree of orientation of the enamel bands. The root-feeders have a dentition with low pattern density, high relative enamel surface and a low degree of orientation. Species, which often feed on seeds or have a wide range of diet, are located between them.

Répartition et évolution des Arvicola Lacépède, 1799 (Rodentia, Mammalia) au cours du Pléistocène moyen et supérieur en France et en Ligurie [Distribution and evolution of Arvicola Lacepede, 1799 (Rodentia, Mammalia) from France and Liguria during the middle and the upper Pleistocene

A study of Arvicola (Rodentia, Mammalia) populations of France (Gaudry, Vaufrey, Suard, l'Eglise, Artenac, Moula-Guercy, Lazaret and Gigny) and Liguria (Arma delle Manie) has allowed to systematic and evolution specifications of this genus at the end of the middle Pleistocene and the start of the upper Pleistocene. The enamel thickness shows temporal and geographic variations wich allow to state precisely the biochronological sequence framework. The migration of Arvicola from Northern Europe, during a cols stage dating back to the end of the middle Pleistocene, in the East and the South-East of France should explain the large variation observed in the relative thickness of the enamel band.

Developmental defects of enamel in humans with hereditary epidermolysis bullosa

Developmental defects of enamel are often reported as a feature of the more severe forms of epidermolysis bullosa (EB). The purpose of this investigation was to determine the prevalence and character of enamel defects in each of the major hereditary EB types. Clinical evaluations were made on 237 individuals representing all of the major EB types and 58 unaffected individuals. All EB cases were categorized by phenotype, mode of inheritance and skin biopsy. The frequency of individuals having developmental enamel defects ranged from 8.6% in recessive dystrophic EB to 100% in junctional EB; 27.5% of the control population had these defects. Generalized hypoplasia characterized by either severe pitting and/or thin enamel was seen in all junctional EB cases but not in any other EB type. There was a tendency for the severe Herlitz form of junctional EB to have thin enamel while non-Herlitz junctional EB cases had less severe pitting and generally no reduction in enamel thickness. The prevalence of individuals with hypoplastic enamel bands was greater in the EB population (9.7%) than controls (1.9%). Thus individuals with simplex and dominant dystrophic EB typically have enamel defects that are similar in frequency and distribution to those of unaffected individuals. Developmental defects of enamel are a consistent feature of junctional EB, although the clinical expression is highly variable.

Relationship of Cranial and Dental Features to Direction of Mastication in Tuco-Tucos (Rodentia: Ctenomys)

Cranial morphology and dental features (orientation of enamel bands and of tooth scars) were examined in osteological specimens of four species of Ctenomys ( C. magellanicus, C. maulinus, C. mendocinus , and C. opimus ) with the objective of understanding possible relationships between skull morphology, chewing direction, and subterranean lifestyle. Similarity of skull shape suggested that the four species studied chew in the same direction. Orientation of tooth scars and of enamel bands on the upper cheek teeth predicted an oblique angle of chewing, ca. −55 to −60°. In comparison to pocket gophers, the broadest-skulled Ctenomys are about as narrow as the narrowest-skulled geomyids. We suggest that broad skulls are not requisite for a fossorial lifestyle. Rather, skull morphology in subterranean rodents might be related to reception of substrate-borne vibrations.

Biophysical Analyses of Sequential Bands of Enamel Related to Ruffle-ended and Smooth-ended Maturation Ameloblasts

During amelogenesis in the rat incisor, modulating ruffle-ended (RA) and smooth-ended (SA) ameloblasts are distributed as bands in the enamel organ of the maturation zone. This distribution of the two cell types has been shown to be precisely correlated with a banding of the underlying enamel, as shown by staining and other cyclical indicators (Takano et al., 1982a,b). Several biophysical approaches have been taken here to characterize the enamel bands sequentially and to determine whether the appearance of such bands is attributable to differences in inorganic composition possibly related to RA and SA. Sprague-Dawley rats were decapitated under ether anesthesia, lower incisors were dissected from surrounding alveolar bone, and enamel organs were wiped from the teeth with moistened gauze. Analyses were performed on either the surface of intact enamel or on individual strips of enamel dissected from the tooth surface, by use of the translucent bands that appear during drying as reference marks for the positions of the overlying cell type. X-ray diffraction (XRD), infrared spectroscopy (IR), x-ray photoelectron spectroscopy (XPS), and wave-length-dispersive electron probe x-ray micro-analysis (WDS) all failed to detect significant differences between analysis areas; data were characteristic of enamel apatite having typical XRD maxima (hkl = 002, 211, 112, 300), IR absorption bands (PO4(3-) and CO3(2-], XPS Ca and P binding energies (Ca2p = 350.5, 346.9 eV; P2p = 133.7, 132.7 eV), and WDS Ca/P molar ratios (1.33-1.49).(ABSTRACT TRUNCATED AT 250 WORDS)

X-ray crystallographic studies as to the calcification in the Hunter-Schreger bands of human enamel.

By analyzing integrated intensities of X-ray diffraction patterns and X-ray diffractograms obtained from the two zones of the Hunter-Schreger bands, it was deduced that the ratio of the sums of the integrated intensities and the degree of preferred orientation of the crystal aggregates in both zones of the bands were almost the same in value, but the fiber axes of the two zones were oriented in different directions. From these experimental observations and a consideration of the effect of the orientation of the enamel prisms relative to the incident X-ray beam, it is concluded that the two zones of the bands were calcified evenly and the light and dark zones on the microradiographs were caused by the difference in the orientation of enamel prisms.

Prediction of Direction of Chewing from Cranial and Dental Characters in Thomomys Pocket Gophers

Three lines of evidence were used independently to predict directionality of chewing in the nine extant species of Thomomys pocket gophers. Cranial morphometrics identified T. bulbivorus and T. bottae as having the broadest (platycephalic morphology) and narrowest (dolichocephalic) skulls, respectively, in the genus. Using Merriam's (1895) skull-shape approach, chewing in T. bulbivorus was predicted to be transverse/oblique, whereas T. bottae was expected to chew propalinally. Orientation of tooth scars and enamel bands suggested that all nine Thomomys species studied chew propalinally. To determine whether skull morphology or dental features were better indicators of directionality of chewing, live specimens of T. bulbivorus and T. bottae were collected and their chewing modes evaluated by external observation and cineradiography both species (and presumably all members of the genus) chew propalinally. Therefore, dental features better reflect masticatory mode than does skull morphology.

Use of backscattered electron imaging on developed radioautographic emulsions: Application to viewing rat incisor enamel maturation pattern following 45calcium injection

AbstractBackscattered electron imaging (BEI) can be used to obtain compositional contrast in biological structures because it detects differences in concentration of elements with different atomic number. Rat incisor enamel shows a banded pattern in the maturation zone when radioautography is used to reveal the location of injected 45Ca at the enamel surface. The bands of developed silver grains in the photographic emulsion that coats the enamel surface are ideal for atomic number contrast. The purpose of this study was to use BEI to analyze the radioautographic pattern with SEM resolution. One‐month‐old rats were injected with 45Ca and sacrificed at early (1 min, 5 min, 30 min), intermediate (4 h, 8 h), and late (1 day, 4 days) time intervals after injection. Whole incisors were dissected, the enamel organs were removed, and the enamel surface was coated with photographic emulsion and processed for radioautography. These radioautographed teeth were examined with a JEOL JSM‐840 SEM equipped with a JEOL backscatter annular‐type detector. At the early time intervals, light microscopic examination showed five or six broad black bands running obliquely across the teeth. These were separated by narrow white bands of unlabeled enamel. BEI resolved the presence of a delicate subbanding pattern within each dark band. At the intermediate time intervals, although the incisal bands persisted, only a diffusely blackened apical area was seen by light microscopy. BEI resolved bands in this apical region, but these showed no subbanding pattern. At the late time intervals, both light microscopy and BEI showed no banding, and the enamel was uniformly labeled. The significantly improved resolution obtained with BEI on surface radioautographs has revealed a previously undetected substructure in the 45Ca‐labeled banding pattern seen in enamel maturation.

Ultrastructure of altered rat enamel beneath fluoride-induced cysts.

The effect of a single injection of sodium fluoride (60 mg/kg) on the development of rat molar enamel beneath fluoride-induced subameloblastic cysts was studied by transmission electron microscopy using undecalcified sections. Three bands of altered enamel were identified and defined as the cyst surface band, the hypoplastic band, and the hypercalcified band. The irregular cyst surface band, not previously described, was found to have two components: electron-dense enamel globules and organic spherules. The electron-dense globules consisted of small, randomly arranged crystals (confirmed by selected area electron diffraction) occurring within a stippled organic matrix. The organic spherules have staining properties similar to stippled material and lack a crystalline component. They may be a form of organic material being extruded from the underlying developing enamel. The critical role of normal matrix production and ameloblast Tomes' process structure on the development of the crystal orientation and rod pattern is discussed.

機能性モノマーと歯質への接着 人工物と生体のハイブリッド化

Several new monomers which are effective to give adhesion to tooth substrates have been discussed based on the concept that monomers with hydrophobic and hydrophilic groups have biocompatibility with the tissues and promote the interpenetration of monomers into the substrates. The bond strength between dentin treated with 10 % citric acid and 3 % ferric chloride and 4-META/MMA-TBB resin was 18 MPa, but it decreased to 6 MPa when dentin was etched with phosphoric or citric acid. Ferric chloride in citric acid prevents the denaturation of collagen during the demineralization. Control of the higher structure of collagen is very important to get good bond to the dentin. The monomers interpenetrated into dentin or enamel and polymerized was confirmed by SEM observation on partially demineralized specimen of the bonded tissue. A HCl insoluble dentin or enamel band modified by the interpenetration in the subsurface of the tissue was identified. The band is a resin reinforced dentin or enamel and has better resistance against decalcification than the original. The band is a hybrid of natural tissues with biocompatible artificial materials.

Autoradiographic evidence of cyclical entry of calcium into maturing enamel of the rat incisor tooth

Adult rats were injected intraperitoneally with radioactive calcium and allowed to survive for periods up to 60 min. Animals were then killed and the upper incisors were removed. Soft tissue was removed from the teeth by dissection and with Clorox. Teeth were then coated with photographic emulsion and, after 17 days, the emulsion on the specimens was developed. Black bands of reduced silver indicated areas of radioactivity where calcium had entered the enamel. These bands were separated by narrower bands of non-radioactive enamel. It was judged that calcium did not gain entry into the enamel in these areas of enamel at this particular time. The patterns made by the bands of calcium entry and restriction were similar to patterns which show where striated border and non-striated border maturation ameloblasts cover the maturing enamel. Maturation ameloblasts with a striated border cover a larger area of the maturing enamel than do maturation ameloblasts without a striated border. It is considered that the maturation ameloblasts with a striated border are engaged in calcium entry into the maturing enamel.

Observations with scanning and transmission electron microscopy on the structure of human surface enamel

The approximal surfaces of 71 partially erupted and unerupted molars and premolars were examined by scanning electron microscopy (SEM) and ultrasections of enamel specimens taken from the 16 approximal surfaces of eight teeth were examined by transmission electron microscopy (TEM). By SEM, bands of prism-end depressions most commonly alternated with bands of smooth enamel, although perikymata-spacing varied and areas occurred where the enamel was all smooth or all pitted and where perikymata were weak or absent. Many teeth showed other pits and outcrops, 5–60 μm dia, particularly near the enamel-cementum junction, which was contrarily sometimes completely smooth, and on marginal ridges and occlusal surfaces. By TEM, smooth surfaces consisted of crystals perpendicular to the outer enamel contour. Small pits were associated with the ends of prisms reaching the enamel surface. Striae of Retzius, varying from simple gaps between rows of crystals to more severe disturbances of structure, could be followed from within the enamel to the surface; sometimes a row of small outcrops, decreasing in size, was seen on the surface. Within these semi-spherical, or possibly cylindrical, structures, crystals were radially orientated. The variation in surface structure is accounted for by variations in the pattern of cessation of amcloblastic activity. Attention is drawn to the diurnal rhythm of enamel formation indicated by prism cross-striations and to the approximately 8-day periodicity of the striae of Retzius. A possible explanation of the striae is an imperfect synchronization of two or more circadian rhythms, ameloblast activity and general body activity for example, only one of which is exactly 24 hr. If separation of the two rhythms became too great, an incremental deposit would be delayed for the remainder of the cycle, possibly up to one day. until synchrony was restored. Such a mechanism has an electronic analogue in the cyclic “slipping” which can occur when an oscillator is imperfectly synchronized with a trigger signal.