Deep Enamel Research Articles

Occlusal caries detection by using a cone-beam CT with different voxel resolutions and a digital intraoral sensor

This study assessed in vitro the diagnostic ability of intraoral digital CCD sensor images and CBCT images at different voxel resolutions in the detection of occlusal caries. The study sample consisted of 130 mandibular molars (61 sound and 69 diseased). Digital intraoral images and CBCT images were obtained at 0.1-mm, 0.2-mm, and 0.3-mm voxel sizes. All images were evaluated separately by 4 observers, and evaluations were repeated after a 4-week interval. Weighted kappa coefficients were calculated to assess intra- and interobserver agreement for each image set, and scores were compared with the histological gold. For the estimation of nonparametric imaging modality effects and tests of hypotheses, SAS 9.0 and SAS macros were used for F1_LD_F1 factorial design. An a priori level of significance of P equals .05 was used. High intra- and interobserver agreements were obtained (Kappa value range: 0.825 to 0.948 for intraobserver agreement and 0.700 to 0.903 for interobserver agreement). Estimated relative treatment effects (RTE) ranged from 0.26 to 0.85, which varied with caries level and imaging modality. Differences between RTE values obtained with ultra-resolution and high- and low-resolution images were not statistically significant for all caries levels. Comparing 3D and intraoral imaging modalities among caries levels showed that imaging modality performance was different for deep enamel, superficial dentine, and deep dentine; however, imaging modality performance was not statistically different for healthy and superficial enamel caries groups. At all voxel sizes, CBCT images can be considered a tool for use in the diagnosis of occlusal caries.

Cross-Sectional Hardness of Enamel from Human Teeth at Different Posteruptive Ages

This study evaluated, by cross-sectional hardness (CSH), enamel maturation at different depths in sound human teeth at different posteruptive ages (12 per age group): unerupted (molars; control), 2–3 years (premolars), 4–10 years (premolars) and >10 years (molars). Cross-sectional Knoop hardness was measured at 10, 30, 50, 70, 90, 110, 220 and 330 mm depth from the surface. The data were subjected to two-way ANOVA followed by Bonferroni’s pairwise tests (a = 0.05). The CSH significantly increased with posteruptive age, indicating that the time of exposure in the oral cavity might result in deep enamel maturation.

Dynamics of tooth erosion in adolescents: A 3-year longitudinal study

The aim of the present study was to estimate the prevalence, incidence and progression of tooth erosion on both mouth and tooth level over a 3-year period in a sample of adolescents. The study also aimed to investigate age, gender and socio-economic influences. Tooth erosion was recorded three times with 1.5 years intervals in a sample of 622 children, aged 10-12 years at baseline. Tooth erosion was present in 30.4% of the 11-year-olds, and 44.2% in 15-year-olds. Deep enamel or dentin was eroded in 1.8% of the 11-year-olds and in 23.8% of the 15-year-olds. Significantly more boys than girls showed tooth erosion as did children from a low socio-economic background compared with other children. The incidence of new tooth surfaces exhibiting erosion, in erosion-free children, decreased significantly with age, while the progression in children with erosion did not change. The incidence of tooth erosion in upper incisors and lower first molars decreased significantly with age. In upper incisors, a statistical significant relationship between SES and incidence was found, with lower incidences for higher SES. For first molars, only a relationship between gender and incidence was found, with a lower incidence for girls. The incidence of new tooth surfaces exhibiting erosion, in erosion-free children, decreased significantly with age. In children with tooth erosion the condition progressed steadily. On tooth level the incidence decreased significantly with age for upper incisors and lower first molars. There was a difference in influence of background variables on the incidence of tooth erosion between molars and upper incisors.

Putting a Face on Ancient Apes

![Figure][1] CREDIT: COURTESY PNAS When workers dug up a fossil while building a dump for a country house in the hills west of Barcelona, Spain, a half-dozen years ago, they had no idea that they had uncovered a treasure trove of fossils. Among them was a new species of ape that lived 11.9 million years ago, according to a report in the current issue of the Proceedings of the National Academy of Sciences . The discovery literally puts a face on a type of Miocene ape that may have given rise to African apes—gorillas, chimpanzees, bonobos, and humans—says paleontologist Salvador Moya-Sola of the Institut Catala de Paleontologia in Barcelona. The new ape, called Anoiapithecus brevirostris , may offer clues about whether apes in Eurasia or Africa gave rise to great ape lineages, says Moya-Sola. The jaw has traits that could tie it to later African apes: a deep upper palate and thick tooth enamel. The relatively flat midface and high-crowned canines are also reminiscent of hominids, the offshoot that led to modern humans. But the authors also acknowledge that the traits could have arisen independently both in Europe and in Africa. This ape would have been an evolutionary dead end if, as most scientists believe, great apes emerged in Africa. [1]: pending:yes

A Longitudinal Study of Tooth Erosion in Adolescents

Incidence studies on tooth erosion among adolescents are scarce. This longitudinal study aimed at estimating the prevalence, incidence, progression, and distribution of erosion in young adolescents over a 1.5-year period. Erosion at baseline was present in 32.2% of the 622 children (mean age, 11.9 +/- 0.9 yrs) and increased to 42.8% over 1.5 yrs. The prevalence of deep enamel or dentin erosion increased from 1.8% to 13.3%. It was hypothesized that more boys will suffer from erosion than girls. At baseline, no difference was found (p = 0.139), whereas 1.5 yrs later, more boys showed erosion than girls (p = 0.026). Of the erosion-free children, 24.2% developed erosion. Progression of erosion in terms of lesion depth and/or in number of lesions was 61.0% and was found more frequently in boys than in girls (p = 0.034). The distribution of erosion showed a predominance of occlusal surfaces of molars, especially the mesiobuccal cusp top, and palatal surfaces of upper anterior teeth.

Relationship between resin bonding strength and time on deep enamel after bleaching treatment

To study the effect of pre-restoration bleaching treatment on tensile strength of resin bonding agents to deep enamel and its duration, and to estimate the optimal timing of porcelain veneers bonding operation after bleaching treatment. A total of 96 extracted human permanent teeth were allocated into 6 groups, 16 teeth for each. In 5 study groups, 80 teeth were bleached using 35% hydrogen peroxide activated by cold light. Right after bleaching and at 1, 4, 7, and 14 days after bleaching, the teeth were prepared with removal of 0.6 to 0.8 mm depth of enamel respectively. And then each study group was divided into two subgroups and bonded with resin bonding agents A (One-step plus) and B (Single bond). In the control group, 16 unbleached teeth were divided into two subgroups and bonded with the two bonding agents respectively. The tensile bonding strength was measured. The tensile strength was [(17.79 +/- 3.53) and (19.41 +/- 3.37) MPa], [(17.50 +/- 4.29) and (19.66 +/- 3.48) MPa], and [(18.39 +/- 3.58) and (19.53 +/- 3.21) MPa] right after bleaching 0 day, 1 day, and 4 days, which were significantly smaller (about 30%) than that of the control group [(25.94 +/- 4.88) and (28.02 +/- 4.36) MPa] (P < 0.001). At 7 days after bleaching the tensile strength [(22.46 +/- 3.98) and (23.74 +/- 5.04) MPa] reached 87% and 85% of that in the control(P > 0.01). At 14 days after bleaching treatment, the strength [(26.03 +/- 4.47) and (27.88 +/- 4.78) MPa] reached the same level as that in the control (P > 0.01). There was no significant difference in bonding tensile strength between the two resin bonding agents. The bonding strength of resin bonding agents to deep enamel was low during 2 weeks after bleaching treatment. It is suggested that porcelain veneer bonding operation should be performed till 2 weeks after bleaching treatment.

How do enamelysin and kallikrein 4 process the 32‐kDa enamelin?

The activities of two proteases--enamelysin (MMP-20) and kallikrein 4 (KLK4)--are necessary for dental enamel to achieve its high degree of mineralization. We hypothesize that the selected enamel protein cleavage products which accumulate in the secretory-stage enamel matrix do so because they are resistant to further cleavage by MMP-20. Later, they are degraded by KLK4. The 32-kDa enamelin is the only domain of the parent protein that accumulates in the deeper enamel. Our objective was to identify the cleavage sites of 32-kDa enamelin that are generated by proteolysis with MMP-20 and KLK4. Enamelysin, KLK4, the major amelogenin isoform (P173), and the 32-kDa enamelin were isolated from developing porcine enamel. P173 and the 32-kDa enamelin were incubated with MMP-20 or KLK4 for up to 48 h. Then, the 32-kDa enamelin digestion products were fractionated by reverse-phase high-performance liquid chromatography (RP-HPLC) and characterized by Edman sequencing, amino acid analysis, and mass spectrometry. Enamelysin cleaved the 32-kDa enamelin only after it was deglycosylated. Kallikrein 4 digestion of the 32-kDa enamelin generated nine major cleavage products, six of which were successfully characterized. After 12 h of digestion with KLK4, all of the 32-kDa enamelin had been cleaved, but some cleavage products persisted after 48 h of digestion.

The progression of tooth erosion in a cohort of adolescents of mixed ethnicity.

To establish the prevalence of tooth erosion in a sample of 12-year-old children and to monitor changes over the subsequent 2 years. A random sample of 1753 children aged 12 years was drawn from all 62 state maintained schools in Leicestershire. A total of 1308 were re-examined 2 years later. Erosion was recorded on incisors and first molars using an erosion index based upon that from the Children's Dental Health in the United Kingdom 1993 survey. A score was also allocated to each subject according to the most advanced lesion in the mouth. Erosion was present in 56.3% of subjects at age 12 and 64.1% at age 14. Deep enamel or dentine was eroded in 4.9% and 13.1% of subjects, respectively, at the same ages. One hundred and sixty-one (12.3%) children who were erosion-free at 12 years of age developed erosion over the subsequent 2 years. Boys had more erosion than girls, as did white compared to Asian children. Associations were found between erosion experience and social deprivation. New erosive lesions developed in 12.3% of the subjects between the ages of 12 and 14 years. New or more advanced lesions were seen in 27% of the children over the 2 years of the study. Males, white children and social deprivation were significantly associated with erosion experience.

Enamelin Compartmentalization in Developing Porcine Enamel

The tissue compartmentalization of enamelin-processing products has been investigated in developing pig enamel using a sequential extraction procedure. Only trace amounts of enamelin-pr ocessing products were detected in simulated enamel fluid extracts, suggesting that enamelins are not solublized in the matrix to any great extent. Subsequent phosphate buffer extraction desorbed and extracted several enamelin-processing products that were presumably bound to the mineral phase. A 35-kD processing product dominated the phosphate extract, suggesting that enamelin processing leads to an accumulation of this mineral- bound molecule. Dissociative extraction with urea subsequently extracted the remainder of the enamelin-processing products present. This material was presumably present in the tissue in an aggregated insoluble state. Several enamelin-processing products were only extracted by specific extraction procedures, suggesting that different enamelin-processing products are differentially compartmentalized. This may indicate that specific enamelin-processing products have different functions. In contrast to amelogenins, which are processed in the deeper tissue to generate products having a low affinity for the mineral, enamelin processing appears to produce products (those enamelins desorbed by phosphate buffer) that have a high affinity for the mineral. These products, appearing in the deeper enamel layers, may serve to influence crystal growth kinetics in the absence of any mineral-binding amelogenins.

Enamel Ultrastructure of Cattle from the Quaternary Period in India

The present paper examines tooth enamel of three species of cattle, Bos acutifrons, Bos namadicus and Bos indicus, which are supposed to have been phylogenetically related and belong to the Quaternary period. It aims to show whether in a short geological time span of 2myrs, the changing environs that cattle were exposed to during the Early Holocene have caused any microstructural changes in their tooth enamel.Mammalian teeth exhibit a very complex arrangement of prisms in the enamel. The prisms are bundles of hydroxyapatite crystallites, arrangement of which is genetically determined and subject to evolutionary change. Hypsodonty or high crowned molars are such examples where concomitant masticatory stress factors near the enamel-dentin junction (EDJ) are known to have affected and altered the enamel microstructure in several large mammalian genera. Modified radial enamel in the deep enamel layer in some ungulates, including cattle, is an adaptive response to these stress factors which appeared much earlier (Tertiary) in the evolutionary history of these large mammals.The cattle enamel analysed here revealed several levels of structural complexity indicating its functional designations. The schmelzmuster in cattle are formed of three enamel types: radial enamel (outer enamel), Hunter-Schreger Bands (mid enamel), and modified radial enamel (inner enamel). There is an increase through time in the percentage of Hunter-Schreger Bands (HSB), which cover up to about 68% of the entire enamel surface among recent cattle. The modified radial enamel and radial enamel do have a receding trend in the Holocene, compared to their Pleistocene ancestors.

Enamel Matrix Serine Proteinase 1: Stage-Specific Expression and Molecular Modeling

Enamel proteins are cleaved by proteinases soon after their secretion by ameloblasts. Intact proteins concentrate in the outer enamel at or near the growing tips of the enamel crystallites while cleavage products accumulate in the deeper enamel. In the transition and early maturation stages there is a dramatic increase in proteolytic activity. This activity, coupled with the diminished secretory and increased reabsorptive functions of ameloblasts, leads to a precipitous fall in the amount of enamel protein in the matrix. Recently we have cloned and characterized an mRNA encoding a tooth-specific serine proteinase designated enamel matrix serine proteinase 1 (EMSP1) [Simmer et al., JDR (1998) 77: 377]. EMSP1 can be detected in the inner enamel during the secretory stage and its activity increases sharply during the transition stage. Stage-specific Northern blot analysis demonstrates this increase is accompanied by a parallel increase in the amount EMSP1 mRNA. A 3-dimensional computer model of EMSP1, based upon the crystal structure of bovine trypsin, has been generated and analyzed. All six disulfide bridges as well as the active site are conserved. Changes in the peptide binding region and the specificity pocket suggest that interaction of the proteinase with protein substrates is altered, potentially causing a shift in substrate specificity. The calcium binding region of trypsin is thoroughly modified suggesting that the calcium independence of EMSP1 activity is due to an inability to bind calcium. The three potential N-linked gly-cosylation sites, N104, N139 and N184, are in surface accessible positions away from the active site.

Cloning and characterization of porcine enamelin mRNAs.

Dental enamel forms by matrix-mediated biomineralization. The components of the developing enamel matrix are generally specific for that matrix. The primary structures of three enamel proteins-amelogenin, tuftelin, and sheathlin (ameloblastin/amelin)-have been derived from cDNA sequences. Here we report the cloning and characterization of mRNA encoding a fourth enamel protein: enamelin. The longest porcine enamelin cDNA clone has 3907 nucleotides, exclusive of the poly(A) tail. The primary structure of the secreted protein is 1104 amino acids in length. Without post-translational modifications, the secreted protein has an isotope-averaged molecular mass of 124.3 kDa and an isoelectric point of 6.5. Polymerase chain-reaction phenotyping of enamelin cDNA suggests that porcine enamelin transcripts are not alternatively spliced and use a single polyadenylation/cleavage site. Immunohistochemical and Western blot analyses with an affinity-purified antipeptide antibody specific for the enamelin carboxyl terminus demonstrate that enamelin is synthesized and secreted by secretory-phase ameloblasts. The parent protein is a 186-kDa glycoprotein that concentrates along the secretory face of the ameloblast Tomes' process. Intact enamelin and proteolytic cleavage products containing its carboxyl terminus are limited to the most superficial layer of the developing enamel matrix, while other enamelin cleavage products are observed in deeper enamel.

Hunter-Schreger band orientation in interproximal enamel of modern human molars with complex morphological traits

A recent paper concerning characteristic groove-shaped wear in interproximal attritional facets of Neandertal posterior teeth correlated groove formation with deep enamel structural traits (Villa & Giacobini, 1995). Further studies were carried out on modern human teeth in order to evaluate a possible correlation between deep enamel structure and some crown complex morphological features.

Enamel microstructure in lemuridae (mammalia, primates): Assessment of variability

This study describes the molar enamel microstructure of seven lemurid primates: Hapalemur griseus, Varecia variegata, Lemur catta, Lemur macaco, Lemur fulvus rufus, Lemur fulvus fulvus, and Lemur fulvus albifrons. Contrary to earlier accounts, which reported little or no prism decussation in lemurid enamel, both Lemur and Varecia molars contain a prominent inner layer of decussating prisms (Hunter-Schreger bands), in addition to an outer radial prism layer, and a thin, nonprismatic enamel surface layer. In contrast, Hapalemur enamel consists entirely of radial and, near the surface, nonprismatic enamel. In addition, for all species, prism packing patterns differ according to depth from the tooth surface, and for all species but Varecia (which also has the thinnest enamel of any lemurid), average prism area increases from the enamel-dentine junction to the surface; this may be a developmental solution to the problem of accommodating a larger outer surface area with enamel deposited from a fixed number of cells. Finally, contradicting some previous reports, Pattern 1 prisms predominate only in the most superficial prismatic enamel. In the deeper enamel, prism cross-sections include both closed (Pattern 1) and arc-shaped (Pattern 2 or, most commonly, Pattern 3). This sequence of depth-related pattern change is repeated in all taxa. It should also be emphasized that all taxa can exhibit all three prism patterns in their mature enamel. The high degree of quantitative and qualitative variation in prism size, shape, and packing suggests that these features should be used cautiously in phylogenetic studies. Hapalemur is distinguished from the other lemurids by unique, medially constricted or rectangular prism cross-sections at an intermediate depth and the absence of prism decussation, but, without further assessment of character polarity, these differences do not clarify lemurid phylogenetic relations. Some characters of enamel microstructure may represent synapomorphies of Lemuridae, or of clades within Lemuridae, but homoplasty is likely to be common. Homoplasy of enamel characters may reflect functional constraints.

Alkali-soluble and insoluble fluoride in erupted and unerupted human enamel from a high fluoride area with a low fluorosis score

The amounts of fluoroapatite and ‘CaF 2-like’ fluoride (F) were determined in enamel of unerupted and erupted teeth that had been exposed in vivo to 1.8–2.6 parts/10 6 F in the drinking water and to brushing with F dentifrice at least once a day, and occasionally to a F mouth-rinse (0.022% F). Enamel was sampled by acid-etching and the F levels were measured with an adapted F ion-selective electrode. More F was built into the deeper enamel in the high-F area than in a similar low-F area. Unerupted enamel did not etch significantly ( p > 0.05) deeper than erupted enamel. No significant differences ( p > 0.05) were found in the F concentrations amongst the following: alkali-washed erupted, unwashed erupted, alkali-washed unerupted and unwashed unerupted at the outer most enamel (approx. 6 μm). However the erupted enamel (alkali-washed or not) showed higher F levels than unerupted enamel (alkali-washed or not) between approx. 6 μm and greater than 100 μm. The increase of F for this high-F area was about 100% in the deeper enamel while for a low-F area it was approx. 78% in the most outer enamel with no increase after a depth of about 20 μm. In contrast to a similar low-F area (water F < 0.10 parts/10 6), no significant ‘CaF 2-like’ F could be detected in erupted or unerupted enamel for the high-F area.

Progression of approximal caries in primary molars and the effect of Duraphat treatment.

The progression of caries lesions over a 2-yr period was studied in 3-6-yr-olds. All 468 children included in the study lived in an area during 1977-85 (Malmö, Sweden) with a low fluoride concentration (0.2 ppm) in the drinking water. Radiographs were taken with a standardized periodic identical technique. Caries lesions were scored on the distal surface of the first and on the mesial surface of the second primary molars (maximum 8 per child) according to Gröndahl et al. Half of the children were treated semiannually with a fluoride varnish (Duraphat). In all, 421 surfaces with caries at baseline were available at the 1-yr examination and 369 at the 2-yr examination. After 1 yr, 34.1% of the shallow enamel lesions remained unchanged, while a progression was seen in 60.9%. 5.1% had been restored. The corresponding figures after 2 yr were 20.6, 52.1 and 27.3%. Of the deeper enamel lesions at baseline, 28.8% remained unchanged after 1 yr and 13.7% after 2 yr. Of the lesions extending into the dentin, 81.5% had been restored after 1 yr and all after 2 yr. When evaluating the effect of Duraphat, only the percentage of individuals with one or more superficial enamel lesions showing progression was determined. After 1 yr, 51.2% in the Duraphat (n = 41) and 82.8% in the control group (n = 29) showed progression (restored surfaces included). The corresponding figures after 2 yr were 66.7 (n = 42) and 91.2% (n = 34). The differences after both 1 yr and 2 yr were statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo Study of Slow-Release Fluoride Resin and Enamel Uptake

The purpose of this study was to investigate in vivo enamel fluoride uptake of a slow-release boron trifluoride BIS-GMA resin material. Study subjects were orthodontic patients with at least one pair of permanent bicuspid teeth indicated for extraction. The material was applied to the buccal surface of the test tooth 1 month prior to extraction; the contralateral tooth served as the control tooth. Following extraction, the resin was removed by soaking in acetone for 36 h and polishing with a sodium bicarbonate slurry. Prior scanning electron microscopic studies have shown that this cleaning procedure effectively removes all residual resin. Enamel fluoride analyses were completed for 12 pairs of teeth from 9 subjects. The mean differences in enamel fluoride concentrations between the treated and control teeth were significantly different from zero at the 0.01 level. At each successive depth, the absolute mean amount of fluoride uptake by the test teeth was fairly constant; however, the proportional mean amount or percent increase in fluoride concentration resulting from treatment became greater in the deeper enamel layers. The data suggest that this material has the potential to provide an effective means of introducing substantial amounts of permanently bound fluoride into surface enamel, even into the deeper layers.

Crystal-associated matrix components in rat incisor enamel. An electron-microscopic study.

Sections of glutaraldehyde-OsO4-fixed, plastic-embedded rat incisor enamel were left untreated, stained, decalcified (1% formic acid in 10% sodium citrate), or decalcified-stained. The presence of apatite crystals was monitored with electron diffraction. After brief decalcification and staining, apatite crystals and matrix components were visualized in the same field. The ghost was continuous with crystal fragments, and the coat appeared as a dense line next to crystals and ghosts. Position of ghosts and crystals at the ameloblast-enamel junction (AEJ) of the secretion zone suggested that there may be a lag of no more than 1/5 min between the elaboration of ghost and crystal. A major change in enamel morphology occurs between the AEJ and the deep enamel of the secretion zone. The ghost becomes thinner, the coat more pronounced, and the crystal enlarges. There is only little change from the deep secretion to the maturation zone enamel.

The frequency of bitewing radiographs

A model for use in analyzing the implications of different rates of caries incidence and progression for the timing of bitewing radiographs was developed. Estimates of progression rates and incidence patterns were derived from an analysis of serial bitewing radiographs. A time schedule for taking the next radiographs was determined so that carious lesions would be detected before radiolucencies reach the inner half of the dentin. For asymptomatic persons with extensive exposure to fluorides and no unrestored enamel lesions on the last radiographs, bitewing films could be scheduled every 2.5 to 3 years. For persons with little exposure to fluorides or with many early enamel lesions or at least one deep enamel lesion that has not been restored, radiographs should be performed every 6 months to 1 year.

The effects of different demineraliz1ng agents on human enamel surfaces studied by scanning electron microscopy

Natural surfaces of enamel, as well as surfaces cut and polished in different planes relative to prism direction, were etched with either formic, lactic or hydrochloric acids, or with ethylene diamine tetra-acetic acid (EDTA) and then examined in a scanning electron microscope. The natural surface of enamel was less severely affected than deeper enamel and surfaces prepared in a plane perpendicular to prism direction were more seriously damaged than those cut in a plane parallel with prism direction. All of the acids used preferentially dissolved the axial portions of prism heads so that etched surfaces transverse to prisms had a honeycomb appearance; etched surfaces parallel with prism direction showed troughs and ridges. In contrast to acid-etching, EDTA etching preferentially dissolved the peripheral regions of prisms leaving the axial parts relatively unaffected. It is concluded that the orientation of crystallites relative to the direction of attack, together with compositional variations within the enamel structure, contribute to the pattern of etching. The pattern of breakdown resulting from acid-etching resembles the pattern seen in caries more closely than does that produced by EDTA. The pattern produced by acid, however, can only be considered to reproduce a very advanced stage of the disease process.