Crowns Of Human Teeth Research Articles

Comparative evaluation of probiotic solutions on surface roughness and microhardness of different restorative materials and enamel.

This research study aimed to investigate the impact of probiotic mouthwash and kefir on the surface characteristics, specifically surface roughness and microhardness, of different restorative materials, as well as permanent and deciduous tooth enamels. Thirty disc-shaped specimens were prepared from composite resin (G-ænial Posterior (GP)), polyacid-modified composite resin (compomer) (Dyract-XP (DXP)), and resin-modified glass ionomer cement (Ionoseal (IS)). Additionally, thirty specimens of enamel were obtained from permanent teeth (PT) and thirty from deciduous teeth (DT) by embedding buccal and lingual sections, acquired through vertical sectioning of 15 permanent and 15 deciduous human tooth crowns in the mesiodistal orientation within acrylic resin blocks. The specimens were then categorized into three distinct groups and immersed for 14 days in one of the following solutions: distilled water, kefir or probiotic mouthwash. The mean surface roughness values of all specimens were assessed using an atomic force microscope, while the mean surface microhardness was measured using a Vickers hardness measuring instrument. The results revealed a statistically significant difference in mean surface roughness among the various restorative materials (p < 0.001). Among the restorative materials, the IS material exhibited notably higher mean surface roughness values than other restorative materials and tooth enamel, while no significant differences were observed between the PT and DT groups. Importantly, the main effect of the solutions under investigation was not statistically significant (p = 0.208). No significant difference was found between the surface roughness values of specimens subjected to the different solutions. When evaluating the effects of materials and solutions on microhardness, the main effects of material and solution variables and the influence of material-solution interactions were statistically significant (p < 0.001). Taken together, these results indicate that consistent use of kefir or probiotic mouthwashes may impact the surface properties of various restorative materials and tooth enamel.

Fluorine distribution from fluoride-releasing luting materials into human dentin

There are many kinds of dental luting materials (cements) in the market. Some luting materials are fluoride-releasing to prevent secondary caries. The purpose of this study was to evaluate the release of fluorine from fluoride-containing luting materials to adjacent dentin by in-air micro PIXE/PIGE (µPIXE/PIGE) system at Takasaki Advanced Radiation Research Institute. Each extracted human tooth crown was cut to expose a flat dentin surface. A 2-mm thick acrylic resin plate was cemented to each tooth using one of four fluoride-containing luting materials on the dentin surface: Fuji Luting EX (FL); Fuji I (FO); SA Luting plus (SA); and BeautiCem SA (BC). The specimens were sectioned and exposed to automated pH cycling (pH 4.5 and 7.0; simulate oral condition) for 4 or 8 weeks. After pH cycling, calcium and fluorine distributions were analyzed by the µPIXE/PIGE system with a 1.7-MeV 1H+ microbeam. The cumulative fluorine concentration (fluorine uptake) and calcium concentration in each specimen was calculated at a distance of 100 µm from the outermost surface. The results of our study indicated that FL had the highest concentration of fluorine uptake among all test materials in the 8-week group. The other three materials did not differ significantly from each other in terms of fluorine uptake. FL showed higher calcium content than SA in the 8-week group. Findings from this study suggest that the amount of fluorine penetration into dentin is likely to be dependent on the amount of fluoride released from each material, and also related to the amount of calcium present.

Intra- and Inter-population Variability in Mamelon Expression on Incisor Teeth

Although rounded protubernaces referred to as mamelons are observes commonly on the crowns of newly-emerged human incisor teeth, there have been very few systematic studies of their expression. The main aims of this study were to describe the nature and extent of variation of mamelon expression on permanent incisors within and between two different human populations, and to quantify the contributions of genetic and environmental influences to observed variability. Mamelon expression was scored according to a 12-grade system described by Fitzgerald et al (1983) using dental models of 104 indigenous Australians, as well as 287 singletons and 175 pairs of twins of European descent. Over 90% of all incisors displayed mamelons, akthough the pattern of expression differed significantly between maxillary and mandibular arches, tooth types and ethnic groups. There were no significant differences in expression between sexes of antimeric teeth. A three-mamelon form was most common on maxillary and mandibular central incisors in both ethnic groups, but different expressions were observed on lateral incisors. Percentage concordances for monozygotic twin pairs were higher generally than those for dizygotic twin pairs, indicating that genetic factors play a role in determining the mamelon expression.

The Relationship between Crown Size and Complexity in Two Collections

Many studies show human tooth crown sizeincreases with increasing crown complexity (i.e., extracusps, tubercles or grooves). Plio-Pleistocene hominidtooth size reduction has also incurred reduction incomplexity, which plays into many theories that attemptto explain this well known, sustained odontometricreduction. We correlated various types of tooth complexitywith measured tooth size in two collections: the widelyused ASU dental models (238 MD and BL dimensionsof 119 teeth involved in 19 post-incisor model plaques),and in Newton Plantation slave remains from Barbados(736 dimensions of 368 teeth from ca. 100 individualsconsisting of 8 post-canine types: mandibular premolarsand molars, and maxillary molars). Significant positivecorrelations show crown size and crown complexitydecrease together, thus either type of data might serve todocument this decline. However the degree and pattern ofthis positive correlation was distinct in the two samples.

Global variation in human tooth crown and root morphology - anthropological and forensic applications - 1

Global variation in human tooth crown and root morphology - anthropological and forensic applications - 1

Global variation in human tooth crown and root morphology - anthropological and forensic applications - 2

Global variation in human tooth crown and root morphology - anthropological and forensic applications - 2

Book Review: Human Tooth Crown and Root Morphology and Dental Morphology for Anthropology: An Illustrated Manual

Book Review: Human Tooth Crown and Root Morphology and Dental Morphology for Anthropology: An Illustrated Manual

Postradiation Matrix Metalloproteinase-20 Expression and Its Impact on Dental Micromorphology and Radiation-Related Caries

Recent evidence suggests that head-and-neck radiotherapy (HNRT) increases active forms of matrix metalloproteinase-20 (MMP-20) in human tooth crowns, degrading the dentin-enamel junction (DEJ) and leading to enamel delamination, which is a pivotal step in the formation of radiation-related caries (RRC). Additional participation of enzymatic degradation of organic matrix components in caries progression was attributed to MMP-20 in dentin. Therefore, the current study tested the hypothesis that MMP-20 is overexpressed in the DEJ, dentin-pulp complex components, and carious dentin of post-HNRT patients, leading to detectable micromorphological changes to the enamel and dentin. Thirty-six teeth were studied, including 19 post-HNRT specimens and 17 nonirradiated controls. Optical light microscopy was used to investigate the micromorphological components of the DEJ, dentin-pulp complex components, and carious dentin. The samples were divided into 2 subgroups: nondemineralized ground sections (n = 20) and demineralized histological sections (n = 16). In addition, immunohistochemical analysis using the immunoperoxidase technique was conducted to semiquantitatively assess MMP-20 expression in the DEJ, dentin-pulp complex components, and carious dentin. No apparent damage to the DEJ microstructure or other dentin-pulp complex components was observed and no statistically significant differences were detected in MMP-20 expression (p > 0.05) between the irradiated and control groups. This study rejected the hypothesis that MMP-20 is overexpressed in the DEJ, dentin-pulp complex components, and carious dentin of post-HNRT patients, leading to detectable micromorphological changes. Hence, direct effects of radiation may not be regarded as an independent factor to explain aggressive clinical patterns of RRC.

Peroxide dental bleaching via laser microchannels and tooth color measurements.

The aim of this study was to use microchannels drilled by an Er:YAG laser into a human tooth through the enamel into the dentin for direct injection of hydrogen peroxide (HP) to produce a minimally invasive, rapid, tooth bleaching effect. The experiments were conducted in vitro. Five microchannels with a diameter of ?200???m and a depth of ?2??mm were drilled through the palatal side of a human tooth crown using the microbeam of an Er:YAG-laser with a wavelength of 2.94???m. After injection of an aqueous solution of 31%-HP through the microchannels, the tooth color was evaluated using a VITA shade guide and International Commission on Illumination L*ab color parameters. A tooth model used for the evaluation of the distribution of HP concentration was created and the amount of HP which can be injected into tooth dentin to bleach it safely was estimated. Injection of 1.5±0.1??mm3 of 31%-HP into the tooth led to noticeable bleaching within 3 h and significant improvement of tooth color within 24 h.

Extracts of irradiated mature human tooth crowns contain MMP-20 protein and activity

ObjectivesWe recently demonstrated a significant correlation between enamel delamination and tooth-level radiation dose in oral cancer patients. Since radiation can induce the synthesis and activation of matrix metalloproteinases, we hypothesized that irradiated teeth may contain active matrix metalloproteinases. Materials and methodsExtracted teeth from oral cancer patients treated with radiotherapy and from healthy subjects were compared. Extracted mature third molars from healthy subjects were irradiated in vitro and/or incubated for 0–6 months at 37°C. All teeth were then pulverized, extracted, and extracts subjected to proteomic and enzymatic analyses. ResultsScreening of irradiated crown extracts using mass spectrometry identified MMP-20 (enamelysin) which is expressed developmentally in dentine and enamel but believed to be removed prior to tooth eruption. MMP-20 was composed of catalytically active forms at Mr=43, 41, 24 and 22kDa and was immunolocalized predominantly to the morphological dentine enamel junction. The proportion of different sized MMP-20 forms changed with incubation and irradiation. While the pattern was not altered directly by irradiation of healthy teeth with 70Gy, subsequent incubation at 37°C for 3–6 months with or without prior irradiation caused the proportion of Mr=24–22kDa MMP-20 bands to increase dramatically. Extracts of teeth from oral cancer patients who received >70Gy radiation also contained relatively more 24 and 22kDa MMP-20 than those of healthy age-related teeth. ConclusionMMP-20 is a radiation-resistant component of mature tooth crowns enriched in the dentine–enamel. We speculate that MMP-20 catalyzed degradation of organic matrix at this site could lead to enamel delamination associated with oral cancer radiotherapy.

Spectrophotometric analysis of crown discoloration induced by MTA- and ZnOE-based sealers

Crown discoloration can be induced by root canal sealer remnants following root canal treatment.Objective:The aim of this study was to evaluate chromatic alterations in human tooth crowns induced by a Mineral Trioxide Aggregate-based sealer (MTA Fillapex® and a commonly used ZnOE-based sealer (Roth-811). The tested null hypothesis was that the application of the materials did not induce clinically perceptible crown discoloration (Ho: CIE color difference ΔE<3.7).Material and Methods:Forty five fully developed, intact, mandibular third molars were sectioned 1 mm below the cemento-enamel junction. The pulp chambers were chemomechanically debrided via the cervical access. The specimens were randomly assigned into three groups Group 1: MTA Fillapex, Group 2: Roth 811, Group 3: Negative control (unfilled) and immersed in individually marked vials containing distilled water up to the cervix (37±1º C). The spectral reflectance lines were recorded by utilizing a UV-VIS spectrophotometer equipped with integration sphere in the visual spectrum at baseline, 1 week, 1 and 3 months after material placement. Data were transformed into values of the CIE L*a*b* color system and the corresponding ΔE values were calculated. Statistical analysis was performed using two-way mixed ANOVA models, at p=0.05 level of significance. Results:A statistically significant increase in a* and b* chromatic parameters of the MTA Fillapex Group was measured. However, ΔE values did not exceed the human eye perceptibility threshold (set at ΔE<3.7) during the experimental period (ΔEt3=2.88). In Roth-811 Group, a statistically significant decrease in L* and a statistically significant increase in a* and b* chromatic parameters was measured, during all observation periods. Resultant ΔE values exceeded the human eye perceptibility threshold after 1 week (ΔEt1=5.65).Conclusions:Application of MTA Fillapex in tooth crowns resulted in minimal color alterations, while Roth 811 induced severe discoloration, in vitro. It could be suggested that, in terms of aesthetics, the use of MTA Fillapex appears to be favorable.

Modification of the mechanical and chemical properties of dental enamel using Er laser radiation with sub-ablative energy density

AbstractLasers can be successfully used for the modification of biological tissues. In dentistry, an increase in strength and the chemical properties of enamel with a laser in order to prevent tooth decay appears to be quite promising. We investigated microhardness and acid resistance of human tooth enamelEnamel of the tooth crown was investigatedThe measured microhardness of intact enamel of human tooth crown wasIn this paper it was found that sub-ablative YLF:Er laser radiation modifies the intact enamel in such a way that the enamel microhardness increases and can exceed the intact enamel microhardness by 20%. Laser-treated enamel can resist abrasive impact during a time equivalent to 3 years of standard dental hygiene. Laser-treated enamel can resist an external aggressive medium containing 37.5% phosphoric acid significantly longer than intact enamel. The observed improvement in the mechanical and chemical properties of the enamel can be explained by a significant reduction in enamel porosity after laser radiation impact.

Crack arrest within teeth at the dentinoenamel junction caused by elastic modulus mismatch

Enamel and dentin compose the crowns of human teeth. They are joined at the dentinoenamel junction (DEJ) which is a very strong and well-bonded interface unlikely to fail within healthy teeth despite the formation of multiple cracks within enamel during a lifetime of exposure to masticatory forces. These cracks commonly are arrested when reaching the DEJ. The phenomenon of crack arrest at the DEJ is described in many publications but there is little consensus on the underlying cause and mechanism. Explanations range from the DEJ having a larger toughness than both enamel and dentin up to the assumption that not the DEJ itself causes crack arrest but the so-called mantle dentin, a thin material layer close to the DEJ that is somewhat softer than the bulk dentin. In this study we conducted 3-point bending experiments with bending bars consisting of the DEJ and surrounding enamel and dentin to investigate crack propagation and arrest within the DEJ region. Calculated stress intensities around crack tips were found to be highly influenced by the elastic modulus mismatch between enamel and dentin and hence, the phenomenon of crack arrest at the DEJ could be explained accordingly via this elastic modulus mismatch.

3D variations in human crown dentin tubule orientation: A phase-contrast microtomography study

Tubules dominate the microstructure of dentin, and in crowns of human teeth they are surrounded by thick mineralized peritubular cuffs of high stiffness. Here we examine the three-dimensional (3D) arrangement of tubules in relation to enamel on the buccal and lingual aspects of intact premolars and molars. Specifically we investigate the angular orientation of tubules relative to the plane of the junction of dentin with enamel (DEJ) by means of wet, non-destructive and high-resolution phase-contrast (coherent) tomography. Enamel capped dentin samples (n=16), cut from the buccal and lingual surfaces of upper and lower premolar and molar teeth, were imaged in water by high-resolution synchrotron-based phase-contrast X-ray radiography. Reconstructed 3D virtual images were co-aligned with respect to the DEJ plane. The average tubule orientation was determined at increasing distances from the DEJ, based on integrated projections onto orthogonal virtual planes. The angle and curl of the tubules were determined every 100 microm to a depth of 1.4mm beneath the DEJ. Most tubules do not extend at right angles from the DEJ. Even when they do, tubules always change their orientations substantially within the first half-millimeter zone beneath the DEJ, both on the buccal and lingual aspects of premolar and molar teeth. Tubules also tend to curl and twist within this zone. Student t-tests indicate that lower teeth seem to have greater tilts in the tubule orientations relative to the DEJ normal with an average angle of 42 degrees (+/-2.0 degrees), whereas upper teeth exhibit a smaller change of orientation, with an average of 32 degrees (+/-2.1 degrees). Tubules are a central characteristic of dentin, with important implications on how it is arranged and what the properties are. Knowing about the path that tubules follow is important for various reasons, ranging form improving control over restorative procedures to understanding or simulating the mechanical properties of teeth. At increasing depths of dentin beneath enamel, tubules are significantly tilted relative to the DEJ norm, which may be important to understand clinical challenges such as sensitivity, effectiveness of bonding techniques or prediction of possible paths for bacterial invasion. Our data show dissimilar average tubule angles of upper versus lower teeth with respect to the DEJ which presumably contributes to different shear responses of the tissue under function. The degree to which this may warrant improved restoratives or new adhesive techniques to enhance adhesive restorations merits further investigation.

Neutron activation analysis of Ca, Cl, K, Mg, Mn, Na, P, and Sr contents in the crowns of human permanent teeth

The effect of age and gender on chemical element contents in intact crowns of permanent teeth of 84 apparently healthy 15–55 year old women (n = 38) and men (n = 46) was investigated. Mass fractions of Ca, Cl, K, Mg, Mn, Na, P, and Sr in crowns were determined by instrumental neutron activation analysis using short-lived radionuclides. Mean values (M ± SEΜ) for female and male combined were (on dry weight basis): 350 ± 5 g/kg, 2920 ± 150 mg/kg, 839 ± 80 mg/kg, 4880 ± 240 mg/kg, 3.20 ± 0.30 mg/kg, 6240 ± 140 mg/kg, 181 ± 4 g/kg, and 293 ± 24 mg/kg respectively. A statistically significant decrease of Sr (P ≤ 0.01) and increase of Na (P ≤ 0.01) content in the tooth crowns with age was found for women. Sex-related comparison did not show any differences.

Fluorine uptake into the human tooth from a thin layer of F-releasing material

Using the proton induced gamma-ray emission (PIGE) method (TIARA, Japan), we have studied fluorine (F) distribution in the human tooth under various conditions. Here, we report F uptake into the human tooth from a thin layer of F-releasing low viscous resin (FLVR). Crowns of human teeth were horizontally cut and the dentin of the cut surface was first covered with four kinds of FLVR (FL-Bond, Reactmer Bond, Xeno Bond, and Protect Liner F; thickness, 50–150 μm) according to the manufacturers’ instructions. Non-F-releasing and F-releasing filling resins were also hardened, on the cut surfaces of crowns covered with four kinds of FLVR thin layers. The type of the non-F-releasing filling materials used was LITE FIL IIP: G1-A (FL-Bond and LITE FIL IIP), G2-A (Reactmer Bond and LITE FIL IIP), G3-A (Xeno Bond and LITE FIL IIP), and G4-A (Protect Liner F and LITE FIL IIP). The types of F-releasing filling materials used were G1-B (FL-Bond and Beautifil), G2-B (Reactmer Bond and Reactmer Paste), G3-B (Xeno Bond and Xeno CF Paste), and G4-B (Protect Liner F and Teethmate F-1). Treatment and measurements of specimens were the same as previously reported [H. Yamamoto, M. Nomahci, K. Yasuda, Y. Iwami, S. Ebisu, N. Yamamoto, T. Sakai, T. Kamiya, Nucl. Instr. and Meth. B 210 (2003) 388]. F uptake from specimens following one month of application was estimated from 2-D maps. F penetration was observed in all teeth of G1-A–G4-A groups. The maximum values of F concentration in each tooth and F penetration depth were larger for larger F concentrations in FLVR. FLVR was useful for the F uptake into the tooth, and the F distribution near the thin layer of FLVR depended on the materials used. Between G1-A and G1-B or G4-A and G4-B, the F uptake was significantly different. We were able to obtain fundamental data, which were useful for the analysis of F transportation relating to prevention of caries.

Relations Between Shape, Materials Properties, and Function in Biological Materials Using Laser Speckle Interferometry: In situ Tooth Deformation

The manner in which stiff biological objects, such as whole bones and teeth, deform under load can provide direct insight into their in vivo functions, while highlighting the relations between their structure and materials properties. A new approach for studying the mechanical functions of such objects, using as an example the crowns of human teeth, is developed. Tooth-crown deformation under a compressive load is determined in water using laser speckle interferometry. The deformation patterns are analyzed using a novel procedure that reveals the relative magnitudes of 3D displacements of the outer surface. Nanometer-scale deformations of natural teeth were compared to deformations of identical acrylic replicas, in order to differentiate between contributions of the structure–material properties from contributions of morphology. It is shown that human premolars deform in a manner that is largely controlled by shape; in natural teeth, the enamel cap appears to displace mainly as a rigid body, undergoing moderate deformation. These observations contribute to the understanding of whole-tooth performance under load. The approach for analyzing the deformation of loaded whole objects is directly applicable to the study of many stiff biological specimens, including comparisons between normal and altered (repaired or genetically modified) bones.

Structure and mechanical properties of the soft zone separating bulk dentin and enamel in crowns of human teeth: Insight into tooth function

The 200–300 μm soft zone of dentin, found beneath enamel in crowns of human teeth, is thought to fulfill important roles in tooth function, but little is known about its structure–mechanical relations. Scanning electron microscopy images of fracture surfaces showed that near the dentino-enamel junction (DEJ), a porous reticulate matrix of intertubular-dentin contains tubules with no peritubular lining. Peritubular-dentin however is found at some distance from the DEJ, and it gradually thickens with increasing depth into the bulk dentin. Concurrently, tighter packing of the collagen fibers is observed with a gradual increase in mineral deposits on and between the fibers. This structurally graded zone is known to be softer when tested for micro-hardness. It undergoes greater strain compared to bulk dentin, when measured using Moiré interferometry. We investigated the deformation and stiffness of this zone by means of non-contact laser-speckle interferometry (ESPI), and nanometer-scale deformations were tracked during compression-testing performed in water. We report a significantly reduced stiffness of this zone compared to bulk dentin, with mid-buccal regions of teeth averaging 3.5 GPa compared with 9.7 GPa in mid-lingual regions. Our results support and expand upon the hypothesis that the durability of the whole tooth relies upon a bucco-lingual asymmetric matching of stiffness by means of an interphase: a cushioning soft layer between enamel and bulk dentin.

Sexual dimorphism in modern human permanent teeth

On average, males possess larger tooth crowns than females in contemporary human populations, although the degree of dimorphism varies within different populations. In previous studies, different amounts of either enamel or dentine were implicated as the cause of this dimorphism. In this study, we attempt to determine the nature of sexual dimorphism in the crowns of permanent modern human teeth and to determine if two contrasting tooth types (permanent third molars and canines) show identical patterns of dimorphism in enamel and dentine distribution. We estimated the relative contributions of both enamel and dentine to total crown size, from buccolingual sections of teeth. Our sample consisted of a total of 144 mandibular permanent third molars and 25 permanent mandibular canines of known sex. We show that sexual dimorphism is likely due, in part, to the presence of relatively more dentine in the crowns of male teeth. However, whatever the underlying cause, dimorphism in both tooth root and tooth crown size should produce measurable dimorphism in tooth weight, though this has not been previously explored. Therefore, we provide some preliminary data that indicate the usefulness of wet tooth weight as a measure of sexual dimorphism. Both male permanent third molars and canines are significantly heavier than those of females. The weight dimorphism reported here for both classes of teeth may prove a useful finding for future forensic studies. In particular, weights of canines may be more useful as a means of sexing modern human skeletal material than linear or area measurements of teeth.

The contributions of craniofacial growth to clinical orthodontics

Balanced facial form and functions are derived from a harmonious integration of the various components of the craniofacial complex. These components grow and develop throughout life in a sequential, predictable, and orderly fashion, albeit with a wide range of variation in the amount and timing of growth. The knowledge of growth-related changes is essential in planning orthodontic treatment. It is important to understand and anticipate the amount and relative rate of growth in different parts of the face, especially during childhood and adolescence. The orthodontist needs to assess the developmental status of the individual and estimate the remaining growth to plan treatment. Incremental growth curves made on linear measurements from longitudinal cephalometric radiographs have demonstrated that all facial dimensions have varying relative rates of growth and show small prepubertal and postpubertal growth spurts. 1 The pubertal spurt in facial dimensions was found to coincide with the spurt in skeletal growth, as reflected by body height, lasting 3 to 4 years. It is apparently of shorter duration and occurs earlier in females than in males. To determine the time of the peak growth period in facial dimensions for an individual, several maturity indicators have been tested. The closest relationship was found with skeletal maturation, which can be readily assessed from hand and wrist radiographs. In many cases orthodontic treatment should commence before the onset or early during the pubertal spurt in order to take advantage of the accelerated growth period. Individual variability in amount and rate of growth is fairly large, related mainly to heredity (familial potential), gender, and ethnic background. In addition, growth is a life-long process. The face of an adult male continues to become progressively more orthognathic. 2 The nose grows downward and forward, while the commissure of the lips moves down with lengthening