Apatite varieties in extant and fossil vertebrate mineralized tissues

A whole-pattern fitting of X-ray diffraction (XRD) patterns, including lattice-parameter and size–strain analysis, was elaborated and applied to a sample set of extant and fossil vertebrate tooth apatite. Recent and subfossil human tooth enamel and dentine, extant and fossil shark tooth enameloid, sarcopterygian and coelacanth tooth enamels were studied. As comparative materials, a modern coelacanth fish scale and a pharyngeal tooth of bony fish were used. It was found that the enamel apatite of human milk teeth had lattice parameter valuesa≃ 9.4 Å andc≃ 6.88 Å, which are close to the corresponding values of subfossil human teeth. The apatite of fossilized vertebrate teeth always has a loweralattice parameter (about 9.37 Å), while the lattice parametercappears to be more stable, being around 6.88 Å. The strain appears to be correlated with the lattice direction, being around ten times higher in the [hk0] direction. During fossilization, the strain diminished in the [00l] direction, but was random in the perpendicular [hk0] direction. The enamel tissues of vertebrates are built of two discrete crystallite series. About one-third of the human milk tooth enamel is composed of larger crystallites with dimensions of about 400 × 500 Å, and two-thirds of smaller crystallites with dimensions of about 50 × 150 Å. The latter range of dimensions is also characteristic for the crystallites forming the mineral part of human dentine and fish scales. Shark tooth enameloid is also built of two distinct series of apatite crystallites of different sizes and shapes. The larger crystallites (amounting to ∼15% of all crystallites) have approximate dimensions of 500 × 1000 Å, while the smaller ones are 400 × 500 Å. Both series are distinguishable in XRD patterns of modern, Jurassic and Devonian shark enamel.

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The Effect of Hydroxyapatite on the Remineralization of Dental Fissure Sealant

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.284-286.35 ◽

2005 ◽

Vol 284-286 ◽

pp. 35-38 ◽

Cited By ~ 2

Author(s):

S.W. Park ◽

Yong Keun Lee ◽

Yeon Ung Kim ◽

Min Chul Kim ◽

Kyoung Nam Kim ◽

...

Keyword(s):

Simulated Body Fluid ◽

Bonding Strength ◽

Body Fluid ◽

Tooth Enamel ◽

Human Tooth ◽

Curing Time ◽

Human Teeth ◽

Fissure Sealant ◽

Human Tooth Enamel ◽

Electronic Microscope

The purpose of this study is to investigate the remineralization of enamel in the human tooth by fissure sealant containing various amount of hydroxyapatite. Prior to remineralization experiments, the necessary requirements of the dental fissure sealant, the curing depth and the curing time, were measured with the content of the hydroxyapatite according to the standard of ISO 6874. Various amount of hydroxyapatite was mixed uniformly using sonicator up to 20 wt% to the fissure sealant. In spite both the curing time and the curing depth were decreased with increasing the content of hydroxyapatite, all samples were satisfied the ISO requirements. Remineralization experimental samples were produced by bonding fissure sealant containing various amount of hydroxyapatite to human tooth enamel using manufacturer’s information. After exposure to the simulated body fluid at 36.5oC for 4 weeks, the bonding strength and the surface morphology were examined using Instron and scanning electronic microscope, respectively. The bonding strength between the fissure sealant and the human teeth was drastically enhanced with the amount of hydroxyapatite. The remineralization zone could be observed along with the boundary of hydroxyapatite and fissure sealant using a scanning electronic microscope.

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Bond strength of adhesive systems to human tooth enamel

Brazilian Oral Research ◽

10.1590/s1806-83242007000100001 ◽

2007 ◽

Vol 21 (1) ◽

pp. 4-9 ◽

Cited By ~ 12

Author(s):

Thaís Cachuté Paradella ◽

Marcelo Fava

Keyword(s):

Bond Strength ◽

Shear Bond Strength ◽

Tooth Enamel ◽

Acrylic Resin ◽

Human Tooth ◽

Adhesive Systems ◽

Human Teeth ◽

Total Etching ◽

Type Of Fracture

The purpose of this study was to evaluate in vitro three adhesive systems: a total etching single-component system (G1 Prime & Bond 2.1), a self-etching primer (G2 Clearfil SE Bond), and a self-etching adhesive (G3 One Up Bond F), through shear bond strength to enamel of human teeth, evaluating the type of fracture through stereomicroscopy, following the ISO guidance on adhesive testing. Thirty sound premolars were bisected mesiodistally and the buccal and lingual surfaces were embedded in acrylic resin, polished up to 600-grit sandpapers, and randomly assigned to three experimental groups (n = 20). Composite resin cylinders were added to the tested surfaces. The specimens were kept in distilled water (37°C/24 h), thermocycled for 500 cycles (5°C-55°C) and submitted to shear testing at a crosshead speed of 0.5 mm/min. The type of fracture was analyzed under stereomicroscopy and the data were submitted to Anova, Tukey and Chi-squared (5%) statistical analyses. The mean adhesive strengths were G1: 18.13 ± 6.49 MPa, (55% of resin cohesive fractures); G2: 17.12 ± 5.80 MPa (90% of adhesive fractures); and G3: 10.47 ± 3.14 MPa (85% of adhesive fractures). In terms of bond strength, there were no significant differences between G1 and G2, and G3 was significantly different from the other groups. G1 presented a different type of fracture from that of G2 and G3. In conclusion, although the total etching and self-etching systems presented similar shear bond strength values, the types of fracture presented by them were different, which can have clinical implications.

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A method for mapping submicron-scale crystallographic order/disorder applied to human tooth enamel

Powder Diffraction ◽

10.1017/s0885715620000251 ◽

2020 ◽

Vol 35 (2) ◽

pp. 117-123

Author(s):

R. Free ◽

K. DeRocher ◽

R. Xu ◽

D. Joester ◽

S. R. Stock

Keyword(s):

Tooth Enamel ◽

Population Level ◽

Human Tooth ◽

Crystallographic Structure ◽

X Rays ◽

Enamel Microstructure ◽

Human Teeth ◽

Developmental Defects ◽

X Ray ◽

Submicron Scale

Tooth enamel, the outermost layer of human teeth, is a complex, hierarchically structured biocomposite. The details of this structure are important in multiple human health contexts, from understanding the progression of dental caries (tooth decay) to understanding the process of amelogenesis and related developmental defects. Enamel is composed primarily of long, nanoscale crystallites of hydroxyapatite that are bundled by the thousands to form micron-scale rods. Studies with transmission electron microscopy show the relationships between small groups of crystallites and X-ray diffraction characterize averages over many rods, but the direct measurement of variations in local crystallographic structure across and between enamel rods has been missing. Here, we describe a synchrotron X-ray-based experimental approach and a novel analysis method developed to address this gap in knowledge. A ~500-nm-wide beam of monochromatic X-rays in conjunction with a sample section only 1 μm in thickness enables 2D diffraction patterns to be collected from small well-separated volumes within the enamel microstructure but still probes enough crystallites (~300 per pattern) to extract population-level statistics on crystallographic features like lattice parameter, crystallite size, and orientation distributions. Furthermore, the development of a quantitative metric to characterize relative order and disorder based on the azimuthal autocorrelation of diffracted intensity enables these crystallographic measurements to be correlated with their location within the enamel microstructure (e.g., between rod and interrod regions). These methods represent a step forward in the characterization of human enamel and will elucidate the variation of the crystallographic structure across and between enamel rods for the first time.

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