Enamel Prisms Research Articles

Research of the structure of the mineral component of tooth enamel in connective tissue dysplasia by densitometry and atomic force microscopy in the early postpartum ontogenesis period

To give a quantitative and qualitative characteristic of the structure of the enamel's mineral component structure of impacted teeth with or without connective tissue dysplasia in different periods of early postnatal human ontogenesis using densitometry and atomic force microscopy. The study involved 120 males with and without connective tissue dysplasia (CTD), which were divided into 3 equal subgroups (60 people with CTD and 60 people without CTD), 20 people in each, according to age: 15-20, 21-30, 31-40 years old. Each of the examined was removed either 3.8 or 4.8 tooth. To study the inorganic component of tooth enamel, a densitometric assessment of enamel's optical density was carried out using computed tomography in the Kodak Dental Systems software (Trophy 2000) and preparation of thin sections of tooth samples 3.8 or 4.8 for atomic force microscopy (AFM) according to the methods of Omsk State Medical University. The structure of tooth enamel in connective tissue dysplasia in the early postpartum period of ontogenesis is characterized by pronounced polymorphisms and an insufficient level of maturity. The ordering and orientation of the enamel prisms are disturbed due to insufficient packing density and a large distance between the enamel prisms at the age of 15-20, 21-30. The established changes indicate the incomplete nature of amelogenesis with connective tissue dysplasia at the indicated ages. In case of connective tissue dysplasia in the early postnatal period of ontogenesis, an incomplete amelogenesis is observed. This process is manifested by lower values of the mineral component's optical density, low packing of enamel prisms, a large distance between enamel prisms and their irregular shape.

Comparative scanning electron microscope analysis of the enamel of permanent human, bovine and porcine teeth.

BackgroundBovine and porcine teeth are often used in in vitro experiments as substitutes of human teeth.ObjectivesThe aim of the present study was to perform a comparative analysis of enamel morphology of permanent human, bovine and porcine teeth under the scanning electron microscope.MethodsAs many as 10 human, 10 bovine, and 10 porcine teeth were studied. All the teeth were sectioned and the halves were randomly divided into 2 groups according to the examined tissue (vestibular enamel at the mid-height of the dental crown and in the cervical area). Human and bovine enamel was etched for 15 sec and porcine enamel for 30 sec. The scanning electron microscope analysis was performed. The length and width of enamel prisms were determined with the “Met-Ilo” 1.1 computer program.ResultsAll enamel samples revealed the same etching pattern—Silverstone's type 2. Bovine enamel showed a similar porosity and the amount of interprismatic enamel compared to human enamel while the amount and width of interprismatic enamel bands in porcine enamel were evidently greater. The shape of the porcine prisms was visually similar to human prisms, although dimensions were significantly different. However, bovine prisms differed in form and appeared to be distinctly elongated.ConclusionsReported findings indicate that the results of experimental studies carried out on bovine and porcine enamel should not be compared with the results obtained on human enamel.

The study of infiltration and microabrasion effects on the tooth surface structure on chemical model of focal enamel demineralization

Objective: to create in vitro model of local enamel demineralization (LED) and to compare the morphological changes in the enamel microstructure after infiltration and microabrasion treatment. Materials and methods. A solution of hydrochloric acid in decreasing concentrations was used to create LED model: 0.3% HCl for 48 hours, 0.15% HCl for 120 hours, 0.1% HCl for 48 hours and 0.05% HCl for 96 hours at room temperature. Using scanning electron microscopy (SEM), we studied a microstructure of the surface and sagittal sections of intact teeth, as well as teeth with artificial LED before and after treatment by infiltration and microabrasion. Results. The tooth surface in the artificial LED zone is characterized by areas with partially and completely demineralized interprismatic substrate. In the partially demineralized zone, channels are formed after dissolution of the enamel prisms structure. In zones with complete demineralization of the crystalline structure, the organic matrices looks like a smooth surface. After microabrasion, the tooth surface represents an even prism layer with prism sheaths forming arcuate excavations. Infiltration of the LED region modifies the tooth surface into a flat field without pores and microcracks, completely covering the lesion with an infiltrant. Conclusion. The proposed method of enamel processing with hydrochloric acid solutions of a decreasing concentration allows LED formation within enamel layer for teeth with various caries resistance. According to SEM data, LED treatment by microabrasion and infiltration effectively smoothes the tooth surface and eliminates defects. After microabrasion, excavations in the area of enamel prism sheaths are preserved on the surface.

Effect of cavosurface angle beveling on the exposure angle of enamel prisms in different cavity sizes.

The quality of the micromechanical retention between the enamel prisms exposed through acid etching and adhesive system can be influenced by the relationship between the angle of the exposed enamel prisms and the external surface/restorative material. Therefore, the aim of the present study was to determine the influence of the enamel cavosurface beveling in different cavity sizes on the angle relation between enamel prisms and the restorative material. For this research, 30 human permanent molars were used and divided into three groups according the isthmus aperture of class I cavities (1/4, 1/3, and 1/2 of the intercuspal distance). Cavosurface angle beveling was performed in each tooth buccal or palatal/lingual side, and a resin composite restoration was placed. Each restored tooth was sectioned in buccal/palatal direction followed by analysis in scanning electron microscope. Means of the angles observed between enamel prisms and the restorative material were registered and statistically analyzed by Kruskal-Wallis test. Results showed higher mean angle values for beveled groups when comparing with the values observed in the unbeveled margins (p < .05) regardless of the isthmus aperture, being 1/4 (beveled = 48.36°; unbeveled = 20.71°), 1/3 (beveled = 39.75°; unbeveled = 29.15°), and 1/2 (beveled = 37.02°; unbeveled = 26.34°). It was also observed that in some unbeveled cavities, there were the presence of laterally exposed enamel prisms (0°), mainly in more conservative cavities. It was concluded that the presence of higher angles values occurred in the samples with beveled margins, without presence of laterally exposed enamel prisms.

In vitro remineralization of enamel white spot lesions with a carrier-based amorphous calcium phosphate delivery system.

To achieve in vitro remineralization of enamel white spot lesions (WSLs) via a mesoporous delivery system of amorphous calcium phosphate (ACP) precursors. Amine-functionalized expanded pore mesoporous silica (aMSN) was loaded with polyacrylic acid-stabilized amorphous calcium phosphate (PAA-ACP) to develop a carrier-based delivery system (PAA-ACP@aMSN). Thirty-six artificial WSLs samples were created and randomly assigned to three treatments: artificial saliva solution (negative control, n = 12), casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) slurry (n = 12), and PAA-ACP@aMSN slurry (n = 12). Surface microhardness, Raman intensity, and color were measured before/after artificial demineralization and after remineralization treatments to evaluate the remineralization level of each sample. SEM images were taken on the surface and cross-section of samples to observe microstructure changes. The surface microhardness recovery ratio (%SMHRR), Raman intensity change ratio (%ICR), and color recovery ratio (%CRR) were not significantly different between CPP-ACP and PAA-ACP@aMSN groups (P > 0.05), but both of them had significantly higher %SMHRR, %ICR, and %CRR values than negative control (P < 0.01). SEM images showed that apparent enamel prism imprints and inter-prism gaps in negative control were masked by mineral deposition in the PAA-ACP@aMSN and CPP-ACP groups. PAA-ACP@aMSN has an ability to remineralize enamel WSLs. The carrier-based amorphous calcium phosphate delivery system has great potential to serve as a remineralizing agent for the treatment of WSLs.

The Effect of Hydroxyapatite from Various Toothpastes on Tooth Enamel

The process of re-demineralisation is governed by the degree of mineral saturation of oral fluids. Due to positive changes in conditions, remineralisation can become the predominant process leading to the healing of injuries. To improve remineralisation, it is necessary to increase the concentration of calcium and fluoride in oral fluids. For this purpose, fluorides have traditionally been used in varied forms and concurrently, the cariostatic mechanism can be explained by increasing the force of fluorapatites. The aim of this paper was to demonstrate the importance of using toothpastes containing hydroxyapatite on tooth enamel and how to operate at microscopic level by sealing the enamel and enamel prism defects etched by acid. The specimens obtained from extracted teeth were treated with different types of toothpastes containing hydroxyapatite: Biorepair, Sensodyne Repair &amp; Protect and Lacalut White &amp; Repair. We treated the teeth with the aforementioned toothpastes, followed the study under SEM microscope. We compared the control sample with the treated sample, and then the treated samples were compared to each other. All three toothpastes used had the expected result, making a protective layer on the surface of the etched enamel, but in this study, the Sensodyne toothpaste seems to be the most effective.

Prevalence of Molar Incisors Hypomineralisation (MIH) in primary school children

Introduction: Molar Incisor Hypomineralisation (MIH) is an enamel defect with white, yellow or black colour due to minerals insufficient during tooth development. The abnormality of prismatic enamel structures and tooth hypersensitivity on patients with MIH may disturb the success rate of restoration. The objective of this research was to determine the prevalence of MIH in primary school children. Methods: A cross-sectional study with purposive sampling on 619 primary school children at Pasteur Urban Village of Bandung City, Indonesia. All dentition were scored using the European Association of Paediatric Dentist (EAPD) MIH scoring sheet, and oral hygiene status assessment with simplified OHI. All data were descriptively described using distribution table. Results: Distribution of MIH on total of 619 children were scored as follows: 0,1,1a, 2, 2a, 3, 4, 5, 6, 7, 8, 9,10 (0 = free enamel defect; 6, 7, and 8 = alteration to non MIH; 1 -5 and 9 -10 = MIH) with frequencies 417(67.36%), 39(6.30%), 60(.65%), 13(2.10%), 0(0.00%), 7(1.13%), 0(0.00%), 4(0.65%), 0(0.00%), 26(4.20%), 58(9.36%), 0(0.00%), and 49(7.91%) respectively. Conclusion: Prevalence of children with MIH in primary school is quite high (19% (118 out of 619 participants)). The highest prevalence is found at the 11 years old group with 49 participants (36.84%), while the prevalence in boys (83 (62.4%)) is found to be higher than girls (50 (37.59%)).Keywords: Prevalence, Molar Incisor Hypomineralisation (MIH), primary school children

A Novel AMELX Mutation, Its Phenotypic Features, and Skewed X Inactivation

Amelogenesis imperfecta (AI) is a group of genetic disorders of defective dental enamel. Mutation of AMELX encoding amelogenin on the X chromosome is a major cause of AI. Here we report a Chinese family with hypoplastic and hypomineralized AI. Whole exome analysis revealed a novel mutation c.185delC in exon 5 of AMELX causing the frame shift p.Pro62ArgfsTer47 (or p.Pro62Argfs*47). By sequencing of polymerase chain reaction products and T-vector clones, the mutation was confirmed as homozygous in the proband, hemizygous in her father, and heterozygous in her mother. The proband and her father had small and yellowish teeth with thin and rough enamel that was radiographically indistinguishable from the underlying dentin. Scanning electronic microscopy of 1 maternal tooth showed cracks and exposed loosely packed enamel prisms in affected areas. Consistent with a 25:75 skewing of X inactivation in the peripheral blood DNA as measured by androgen receptor allele methylation, the surface of the mother’s tooth had alternating vertical ridges of transparent normal and white chalky enamel in a 34:66 ratio. In summary, this study provides one of the few phenotypic comparisons of hemizygous and homozygous AMELX mutations and suggests that the skewing of X inactivation in AI contributes to the phenotypic variations in heterozygous carriers of X-linked AI.

Chitosan-bioglass complexes promote subsurface remineralisation of incipient human carious enamel lesions

ObjectivesTo test the in vitro subsurface remineralisation efficacy of chitosan-bioglass complex on artificial white spot lesions.Methods: 64 artificial enamel white spot lesions were created by acidic gel and equally separated for static and 7d pH-cycling models. In each model, samples were assigned to 4 groups: (1) bioglass application on chitosan pre-treated lesions (CB); (2) chitosan-bioglass slurry (CBS); (3) "standard" remineralisation solution (RS - positive control); (4) deionised water (NC - negative control). Before each treatment using remineralising agents, 3-minute pellicle was formed on lesions' surfaces. Mineral content changes, surface and subsurface microhardness and ultrastructure were evaluated by Raman intensity mapping, Knoop microhardness and scanning electron microscopy, respectively. Data were statistically analysed using one-way ANOVA with Tukey's test (p < 0.05 is considered as significant). ResultsChitosan-bioglass complexing was found to exhibit greater mineral regain and recovery of surface and subsurface microhardness compared to "standard" remineralisation solution and control groups, after static and dynamic pH-cycling remineralisation for 7 days (p < 0.05). Specifically, dense precipitations with Ca/P ratios similar to that in pure hydroxyapatite (HA) were observed on surfaces and subsurfaces which filled the porosities in the dynamic pH-cycling group, leaving no prismatic enamel structure exposed. ConclusionsChitosan-bioglass complex is positive in promoting subsurface mineral deposition in spite of the presence of a short-term salivary pellicle. Clinical significance chitosan-bioglass complexing may provide an alternative clinical strategy in remineralising early enamel carious lesions as well as desensitizing exposed porous vital dental tissues clinically.

Using image compression to quantify enamel complexity

In mammals, complexity of enamel prism decussation has long been recognized as a reflection of biomechanical demands placed upon teeth. Crisscrossing prisms or bundles of prisms, known as decussation, have been demonstrated to limit crack propagation through tooth enamel, and help maintain overall functional integrity of a tooth; therefore, prism decussation tends to appear more frequently and with more complexity in animals that must break down hard foods and/or who place other high loads upon their teeth. Hunter‐Schreger bands are alternating bundles of prisms with common orientations that decussate with respect to adjacent bands. The more severe the loading regime of a tooth that a species experiences, the more complex its decussation and Hunter‐Schreger banding patterns tend to be. Species whose diets primarily create abrasive wear on teeth and who are at low risk of cracking have simple enamel whose prisms all run in parallel fashion from dentine to surface, referred to as radial enamel.In order to assess the biomechanics of teeth and microstructural adaptations to loading both within extant and fossil taxa, it would be useful to have a simple quantitative measurement that could assess overall complexity of enamel decussation. However, previous studies of enamel complexity tend to be descriptive and are often so complex in terms of their discussion of prism pathways that such studies are of limited use when comparing large numbers of teeth and/or species.The objective of this study is to solve this problem using modern, commonly available computer algorithms to find a way to quickly and easily quantify enamel complexity from histological images of teeth. Specifically, we use image compression ratio as a proxy variable for identifying tooth complexity. This ratio reflects the compressed size of a standard .jpg image as compared to an original, uncompressed .tif image (in our case generated by a digital microscopy system), and has been used successfully by prior studies to quantify complexity of tooth cusp relief.We here apply the compression ratio method to two‐dimensional photomicrographic images of tooth thin‐sections taken in circularly polarized light (CPL). CPL creates visual contrast in complex teeth by highlighting regions of differing prism orientations with different colors in the final image. We captured 90 images of teeth with varying decussation complexity in CPL, then deleted non‐enamel components of the image (dentine, artifacts, etc.) using digital image processing software. The original .tif images were then compressed to .jpg format, and the compression ratio (.jpg size / .tif size, in bytes) was analyzed statistically in comparison with subjectively assigned “complexity” categories. The compression ratio of radial enamel images was significantly different from images of decussating enamel. Moreover, we found a significant correlation between compression ratio and our complexity categories. These data suggest that image compression ratio is useful for comparing overall complexity of dental enamel in mammals.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Erosive potential of medication on human enamel and posterior remineralization capacity

Introduction: Changes in lifestyle have been reported as one of the greatest causes of dental erosion. Nevertheless the intake of potentially erosive medication might be other important factor contributing to the rise in prevalence of this condition [1]. The increased occurrence of some chronic respiratory diseases (such as asthma), allergic states and other recurrent common conditions (as cough, cold or flu) has led to frequent medicine prescription that might be potentially erosive to the teeth [2]. This study’s goals were to compare the erosive potential of two medicines commonly prescribed for chronic respiratory diseases, and to determine the enamel capacity for remineralization after their application. Materials and methods: Ethical approval was obtained. Sixty-six human enamel samples were randomly assigned to 6 groups (n = 11): Ven (Ventilan®), Ven-F (Ventilan® with fluoride varnish), Cla (Claritine®), Cla-F (Claritine® with fluoride varnish), C (control) and C-F (control with fluoride varnish). The samples in groups Ven, Cla, and C were exposed to the respective medicines or distilled water (3x 1min/day during 5 days) followed by remineralization in artificial saliva. In groups Ven-F, Cla-F and C-F, fluoride varnish (Profluorid®) was applied after the medicine exposure. Two 5-day cycles were performed. The enamel surface was analyzed by magnifying stereomicroscope (prevalence of erosive lesions), scanning electron microscopy (SEM) and surface hardness (SH). One-way ANOVA was used (α = 0.05) for the analysis. Results: Groups Ven and Cla revealed 93 and 66% prevalence of erosive lesions, respectively, and significant lower SH than C (p < .001). Ven-F and Cla-F, with lesion prevalences of 30 and 23%, respectively, showed significant lower SH than C-F (p < .001) or even C (p < .001), but significantly higher than the non-fluorinated counterparts (p < .001). Cla showed the lowest SH, and even fluorinated couldn’t overcome the SH of Ven (p > .05) (Figure 1). The two medicines showed clear evidence of enamel surface damage on SEM micrographs, with cracks, craters and enamel prisms’ exposure, being the most common features encountered (Figures 2 and 3). Figure 1. SH values in VHN (±sd). Figure 2. Ven group (×3.000) Figure 3. Cla group (×3.000). Discussion and conclusions: Under the conditions of this study, Claritine® treated samples showed lower prevalence of erosion lesions than Ventilan®. Regarding the SH, Claritine® seemed to have higher erosive potential, and to hold the lowest potential for remineralization.

ЩІЛЬНІСТЬ ПРИЛЯГАННЯ РЕСТАВРАЦІЙНОГО МАТЕРІАЛУ ДО ЕМАЛІ ЗУБІВ З РІЗНИМ ФОРМУВАННЯМ КРАЮ КАРІОЗНОЇ ПОРОЖНИНИ

Introduction. At present, the question of the influence of carious cavity edge design on the density of the adherence of restorative material to the enamel remains discursive; there is some confusion in the open access publications on this topic. Objectives. To study the density of the adherence of restorative material to the enamel of teeth depending on the design of the formation of carious cavity edge. Materials and methods. The research was carried out using 30 intact third molars extracted upon clinical indications. The samples were divided into three groups, 10 in each, depending on the formation of carious cavities of the 1st class according to Black classification. In group I a classical carious cavity with even, straight-edged walls without the formation of the bevel (folds) of the enamel was formed. In group II, the outer beveling of enamel was made at an angle of 45o to the enamel-dentine border. In group III, the cavity was formed with an internal beveling of enamel. Carious cavities were restored with micro-hybrid composite light cured material LATELUX (PE LATUS, Kharkiv). One-time vertical mechanical load with a force of 98.07 N was performed on restoration, and treated with thermocycled in a mode of 200 cycles at a temperature from 5 °C to 55 °C with an exposure of 60 seconds at each temperature. The teeth were separated in a medio-distal direction through a center of restoration with diamond disks, placed in a column of a raster electron microscope with a low vacuum chamber REM 102, and the contact area of the restoration with solid tissues of the teeth was studied, the density of their adherence, and the present gaps were measured and expressed in micrometers (μm) Results. Electron diffraction pattern of the samples of group I showed that the density of the adherence of the restorative material to the enamel of the carious cavity was different throughout: sometimes thick, sometimes the space in the contact area was determined. Moreover, the space was formed between the adhesive layer of the material and enamel. The space size averaged 7.90 ± 0.73 μm (95% CI: 6.3: 9.5). Enamel prisms adjoined in the area of contact with the material partly linear, longitudinal along its axis or transversely, obliquely with a slanted body. In the samples of group II restorative material was evenly in contact with the layer of adhesive, adherence of which to the enamel edge of the carious cavity was dense almost throughout. But in some areas there was a violation of the contact of the enamel with the adhesive layer, there were cracks 2.76 ± 0.52 μm (95% CI: 1.6: 3.9). Enamel prisms in the area of contact with the material were located more transversely to their axis, obliquely with a slanted body. In the samples of group III, the adherence of the restorative material to the enamel of the carious cavity was not dense almost throughout. The restorative material had a uniform contact with the adhesive. At the same time, there was a breach of contact in the form of cracks of 16.50 ± 0.89 (95% CI: 14.6: 18.4) μm observed between adhesive and enamel. Enamel prisms in the zone of contact with the material were linear, longitudinal along its axis. Conclusions. The greatest density of the adherence of restorative material to the enamel of teeth occurs when forming the outer beveling of the enamel edge in the carious cavities of the 1st class according to Black classification.

Enamel mineralization and compositional time-resolution in human teeth evaluated via histologically-defined LA-ICPMS profiles

Abstract Mammalian dental enamel is a key archive for the reconstruction of past environments. Sequentially mineralizing enamel provides continuous, several year-long records, which spatially-resolved sampling can ‘read’ at seasonal or higher time resolution. Yet it remains underexplored how much an initially incorporated compositional signal is overprinted by the two-stage enamel mineralization process, which affects the finally achievable time-resolution. We report results of a systematic investigation into histologically-defined compositional profiles from human enamel obtained by laser-ablation inductively-coupled-plasma mass spectrometry (LA-ICPMS). Sr/Ca, Zn/Ca, Ba/Ca and Pb/Ca are investigated as commonly-utilized proxies of (palaeo)diet, mineralization and/or pollution in modern and archaeological samples. Our modern human teeth are from unequivocally breast-fed and formula-fed individuals, respectively. By focusing on two profiles that are time-equivalent yet topographically different, namely the enamel-dentine junction (EDJ) vs. enamel prisms (P), we evaluate the compositional effect of enamel secretion vs. maturation on elemental proxies throughout enamel thickness. These two broadly orthogonal orientations are compared with the connecting Neonatal/Retzius (NNL/R) profiles that represent nominal isogrowth events during enamel secretion, which – if later maturation had no effect – should show invariant compositional signals across enamel. However, we find that all NNL/R profiles record systematically varying compositions across enamel, with Sr/Ca always decreasing by 30–80% and Zn/Ca increasing near-exponentially 20–35 times towards outer enamel. As such they can be used to benchmark the extent of enamel maturation. Since all prism profiles reveal signals similar to NNL/R for Sr, Zn and in part Ba, this unequivocally demonstrates that P-orientations are equally overprinted by maturation, in all cases with increasing intensity towards outer enamel. EDJ and P profiles do not match one-another despite representing coeval secretion time, and we infer that the highest degree of initial signal variability can be retrieved along the EDJ (approx. ≤ 100 μm) where maturation had the least effect. Using a simple two-component mixing model we show that during maturation only a moderate increase (1.3–1.9×) in discrimination against Sr is required to explain the Sr/Ca patterns. The Zn/Ca increase on the other hand is interpreted to reflect the Zn-binding motifs of the enzymes MMP-20 (matrix metalloproteinase-20) and KLK-4 (kallikrein-4) active during enamel secretion and maturation, which may preferentially imprint a Zn compositional signal in maturing enamel. In the case of Ba/Ca we find no systematic patterns analogous to that of Sr and Zn in modern samples. Moreover, cryptic diagenesis affecting Ba in otherwise well-preserved fossil teeth argues for caution when using Ba/Ca to infer nutritional signals without additional elemental/isotopic corroboration. Unlike all other investigated elements, Pb/Ca shows broadly similar EDJ-P profiles, and nearly invariant R-signals across enamel, which may reflect the affinity of Pb to both organic molecules and inorganic apatite during enamel mineralization. Overall our results reveal the element-specific behaviour of Sr, Zn, Ba and Pb during enamel mineralization.

Bending Fibers of Hydroxyapatite for Ordered Parallel Architecture in Bovine Tooth Enamel

The nanometer-scale bending structure in the enamel–dentin interfacial region of bovine teeth was clarified using detailed electron micrographs. We found that enamel prisms of width ∼5–10 μm in the enamel are regarded as a bundle of nanometer-scale hydroxyapatite (HA) fibers of width ∼20–30 nm that are connected to the enamel–dentin interface. The radial arrangements of HA fibers elongated in the c-axis were formed on the dentin surface at the boundary. The orientation adjustment of the HA fibers was observed through stepwise bending with a gradual change of the c direction in the ordered parallel array of the enamel prisms. Our observation suggests that the crystallographic ordering in the enamel layer originates from the growth-induced orientation of HA crystals in the interfacial region.

Three-dimensional assessment of proximal contact enamel using optical coherence tomography

ObjectiveThe purpose of this study was to detect and investigate the association of enamel microcracks with demineralization at proximal contact areas of premolars, using 3D swept-source optical coherence tomography (SS-OCT). MethodsExtracted maxillary and mandibular premolars (n=50 each), without any visible tooth cracks, were examined for demineralization of interproximal contact areas, using the International Caries Detection and Assessment System (ICDAS). SS-OCT was used to evaluate demineralization and detect microcracks. Demineralization progression was divided into 4 types by depth: 0 for sound enamel and Type I, II, and III for enamel demineralization penetrating into the outer third, the middle third, and the inner third of the enamel thickness, respectively. Enamel microcracks were classified according to the predominant crack pattern: Type O, no cracks; Type A, subsurface microdefects; Type B, enamel microcrack running along the direction of the enamel prism; Type C, enamel microcrack running transverse to the enamel prism direction; and Type D, a combination of patterns A, B, and C. SS-OCT findings were confirmed by confocal laser scanning microscopy observation. ResultsMicrocracks confined within the superficial enamel in proximal contact areas were seen as bright lines on SS-OCT. There were significant positive correlations among ICDAS codes, demineralization levels, and microcrack distribution (p≤0.001). The mesial side of maxillary premolars showed significantly more demineralization (n=36) and microcracks (n=27) than that of the mandibular premolars (n=20 and n=14, respectively; p<0.001). SignificanceThe presence of microcracks within the superficial enamel in proximal contact areas could be determined using SS-OCT, and correlated with the level of demineralization. 3D SS-OCT is a valuable diagnostic tool for comprehensive assessment of microstructural changes related to enamel demineralization and crack development.

Clinical and morphological characteristics of enamel during pigment hypoplasia of tooth tissues.

Background. Dystrophic changes in enamel and dentin occur as a result of metabolic disturbances in the hard tissues of the tooth and are characterized by its insufficient formation and mineralization, or excessive accumulation of pigments in the form of spots. The accumulation of pigment (qualitative and quantitative) is irreversible, that is, pigmentary dystrophy has no reverse development and remains in the enamel for life. Objectivе. To analyze the structural changes in tooth enamel in case of pigmentary dystrophy. Methods. After extraction, the teeth were embedded with Epon-812 epoxy. After polymerization, the obtained block was cut with a separating disk on thin sections 0.25 mm thick, an aluminum layer was applied to the preparations in vacuum and examined on a scanning electron microscope REM - 102E with an accelerating voltage of 30 kV. Results. It has been established that in case of chronic discolorites the enamel is partially fragmented, the phenomena of lysis of the enamel are determined. Lacunae are observed on the enamel-dentin border. Enamel preparations with congenital discolorations revealed a thickening of enamel prisms, mosaic expressiveness of Retzius lines. In exogenous pigmentary dystrophy, the main changes are established on the enamel surface. The phenomena of focal fragmentation, diffuse thinning of enamel prisms (atrophic changes) were observed. In endogenous pigmental dystrophy, the main changes are determined by the enamel-dentin boundary. Prisms are thinned and fragmented. Conclusion. Congenital dystrophy of pigment has a diffuse nature and affects the entire thickness of the enamel, which is caused by disorders in the process of histogenesis. With acquired discolorites, the localization of pathological changes depends on the etiology - endogenous, or exogenous. In endogenous pigmental dystrophy, morphological changes are found in the surface layers of enamel, developing as a result of disruption of the tertiary mineralization process, which create favorable conditions for the penetration of pigments by reducing the content of inorganic substances. In endogenous pigmental dystrophy, major changes develop in the deep layers of enamel adjacent to the dentine-enamel border. The source of pigment in this case is enamel spindles, which have a low content of inorganic substances and penetrate into the enamel on 1/3 of its thickness.

Relationships Between Enamel Prism Decussation and Organization of the Ameloblast Layer in Rodent Incisors.

Rodent enamel microstructure has been extensively investigated, primarily on the basis of 2D electronic microscopy data. The nature and dynamics of the ameloblasts (the enamel-secreting cells) have also been well studied. However, critical issues still remain surrounding exactly how the ameloblasts produce the astonishing microstructural complexity of enamel, and how this subtle architecture evolved through time. In this article, we used a new methodology based on confocal laser microscopy to reconstruct the enamel microstructure of rodent incisors in three dimensions (3D) with the ameloblasts in situ. We proposed interpretations regarding the possible relationships between the workings of the ameloblasts and the resulting enamel prisms, especially how the phenomenon of decussation is generated. Finally, we were able to represent the two main types of modern rodent incisor microstructures (uniserial and multiserial decussations), as a set of parameters that have been entered into the 3D enamel simulation software Simulenam to generate 3D models that can be digitally manipulated. Associating 2D data of incisor enamel microstructure of fossil rodents and Simulenam, it was then possible to better understand how the various decussation parameters evolved through time and gave rise to the two modern microstructure types from the same ancestral type (pauciserial). This study also confirmed that rodent and artiodactyl enamel do not share the same mechanism of decussation formation. Anat Rec, 302:1195-1209, 2019. © 2018 Wiley Periodicals, Inc.

Analysis of the Optical Properties of Medieval Enamel

The purpose of the study was to investigate the differences in the optical properties of samples of intact, abraded, and reduced enamel. The optical properties of medieval enamel were compared to the results obtained from studies of enamel of contemporary populations in order to investigate the structural changes of enamel due to the effect of diagenesis (destructive changes, which affect interred bone). Reduced enamel (artificially removed superficial layer of the enamel) was used as a comparative sample for the study of abraded enamel. The dental material was obtained from the medieval cemetery of Stara Torina located in northern Serbia. Micro-morphological analysis was conducted using a polarized light microscope. Based on the results, we can demonstrate that 1) the birefringence value of the mature medieval enamel sample ranges from 0.3 to 0.4, which means that medieval enamel has retained its optical properties, although some changes in the inorganic components were found; 2) the matrure intact enamel and abraded enamel have a negative optical sign, which is the same as that found in immature enamel; and 3) the mature reduced enamel changes its optical sign due to the phenomena of bending of the surface enamel prisms from 0.7 mm to 0.9 mm. This change of the optical sign results from a rise in temperature during the reduction process and from a diffusion of "non-oriented" molecules. The increased pressure on the enamel during the reduction process causes the bending of the surface part of the enamel prisms. The presence of the pigmentation and carious changes in the abraded enamel and ground enamel also indicated the process of diffusion of different molecules, which occurred while the enamel was buried in the soil, as well as during the lifetime of the individual.

Digital enhancement of dental enamel microstructure images from intact teeth.

Dental enamel is formed by rod-like structures, the enamel prisms. Groups of prisms are packed together in successive horizontal layers of alternating directions, known as Hunter-Schreger bands (HSBs). HSBs are the major microstructural characteristic of mammalian enamel. The pattern of HSBs can vary among mammalian species and this variability may provide relevant information regarding the species life history and taxon identification. In human HSBs can be used as a biometric-based parameter for personal identification in automated systems. The analysis of HSBs has been hampered by technical difficulties. The low contrast between light and dark bands and variations in light intensity may hinder the observation of HSBs in digital images. This article describes a simple and efficient computational procedure that greatly enhances the contrast and minimizes the differences in the intensity of illumination in HSBs images. Its use can significantly increase the quality and the number of HSBs that can be recorded in intact teeth.

Effects of regional enamel and prism orientations on bovine enamel bond strength and cohesive strength.

This study investigated the regional microtensile bond strength (MTBS) and cohesive strength of bovine enamel. The crowns of bovine incisors were sectioned, either horizontally along incisal and cervical thirds to produce horizontal and tangential segments, or longitudinally along the midline to produce longitudinal segments. Half of the horizontal and longitudinal segments were prepared using a 45° bevel. Then, the differently sectioned enamel surfaces were treated with one- or two-step self-etch adhesives (Clearfil SE Bond or Clearfil S3 Bond) and a composite resin (Clearfil Majesty) was placed. Resin-bonded enamel samples were cut into beams for use in the MTBS tests. Labial horizontal and longitudinal segments of pure enamel beams were prepared for cohesive strength tests. Enamel microstructures were analyzed by scanning electron microscopy. Three-way anova followed by Tukey's post-hoc HSD multiple comparisons procedure showed that a 45° bevel cut did not statistically significantly improve enamel MTBS, which varied with the different regions. The longitudinally sectioned resin-bonded enamel samples had the lowest MTBS, and the horizontal enamel cohesive strength was weaker than that of the longitudinal enamel. The scanning electron microscopy fractographs indicated that rows of parallel prisms were detached from the fractured surfaces. In conclusion, the regional enamel MTBS and the cohesive strength are strongly related to the enamel microstructures and prism orientations.