Method for applying photographic resists to otherwise incompatible substrates

A method for applying photographic resists to otherwise incompatible substrates, such as a baking enamel paint surface, is described wherein the uncured enamel paint surface is coated with a non-curing lacquer which is, in turn, coated with a partially cured lacquer. The non-curing lacquer adheres to the enamel and a photo resist material satisfactorily adheres to the partially cured lacquer. Once normal photo etching techniques are employed the lacquer coats can be easily removed from the enamel leaving the photo etched image. In the case of edge lighted instrument panels, a coat of uncured enamel is placed over the cured enamel followed by the lacquer coats and the photo resists which is exposed and developed. Once the etched uncured enamel is cured, the lacquer coats are removed leaving an etched panel

Evaluation of the esthetic properties of developmental defects of enamel: a spectrophotometric clinical study

Objectives. Detailed clinical quantification of optical properties of developmental defect of enamel is possible with spectropho- tometric evaluation. Developmental defects of enamel (DDE) are daily encountered in clinical practice. DDE are an alteration in quality and quantity of the enamel, caused by disruption and/or damage to the enamel organ during amelogenesis. Methods. Several clinical indices have been developed to categorize enamel defects based on their nature, appearance, microscopic features, or cause. A sample of 39 permanent teeth presenting DDE on labial surface was examined using the DDE Modified Index and SpectroShade evaluation. The spectrophotometric approach quantifies L∗ (luminosity), a∗ (quantity of green-red), and b∗ (quantity of blue- yellow) of different DDE. Conclusions. SpectroShade evaluation of the optical properties of the enamel defect enhances clinical understanding of severity and extent of the defect and characterizes the enamel alteration in terms of color discrepancy and surface characterization

Intraspecific variation in M1 enamel development in modern humans: implications for human evolution

The timing and sequence of enamel development, as well as enamel thickness, was documented for individual cusps (protoconid, hypoconid,metaconid, entoconid) in 15 unworn permanent lower first molars (M1s) from a sample of modern human juveniles. These data were compared with previously published data for modern and fossil species reported in the literature. Crown formation in all teeth was initiated in the protoconid and completed in the hypoconid. These cusps had significantly longer formation times (2.91 and 2.96 yrs, respectively) than the metaconid and entoconid (2.52 and 2.38 yrs, respectively), as well as thicker enamel, and each represented between 92e95% of the total crown formation time. Rates of enamel secretion in all cusps increased significantly from 2.97 mm in the inner enamel to 4.47 mm in the outer enamel. Two cusps of one individual were studied in more detail and did not follow this typical trajectory. Rather, there was a sharp decrease in the middle of enamel formation and then a slow recovery of secretion rates from the mid to outer enamel. This anomalous trajectory of enamel formation is discussed in the context of other nondental tissue responses to illness. Neither secretion rates nor periodicity differed significantly when compared between the cusps of each molar. Differences in cusp formation times, initiation, and completion suggest a relationship between the rates of enamel formation and enamel thickness. This fits with expectations about the mechanics of the chewing cycle and general lower molar morphology. A comparison with similar data for some nonhuman primates and fossil hominoids suggests this relationship may hold true across several primate taxa. Other aspects of enamel growth differed between this human sample and certain fossil species. The lower molars formed slowly over a longer period of time, which may reflect the extended growth period of modern humans. The methodological approach adopted in this study is discussed in the context of that used in other studies

Prevention of the disrupted enamel phenotype in Slc4a4-null mice using explant organ culture maintained in a living host kidney capsule.

Slc4a4-null mice are a model of proximal renal tubular acidosis (pRTA). Slc4a4 encodes the electrogenic sodium base transporter NBCe1 that is involved in transcellular base transport and pH regulation during amelogenesis. Patients with mutations in the SLC4A4 gene and Slc4a4-null mice present with dysplastic enamel, amongst other pathologies. Loss of NBCe1 function leads to local abnormalities in enamel matrix pH regulation. Loss of NBCe1 function also results in systemic acidemic blood pH. Whether local changes in enamel pH and/or a decrease in systemic pH are the cause of the abnormal enamel phenotype is currently unknown. In the present study we addressed this question by explanting fetal wild-type and Slc4a4-null mandibles into healthy host kidney capsules to study enamel formation in the absence of systemic acidemia. Mandibular E11.5 explants from NBCe1-/- mice, maintained in host kidney capsules for 70 days, resulted in teeth with enamel and dentin with morphological and mineralization properties similar to cultured NBCe1+/+ mandibles grown under identical conditions. Ameloblasts express a number of proteins involved in dynamic changes in H+/base transport during amelogenesis. Despite the capacity of ameloblasts to dynamically modulate the local pH of the enamel matrix, at least in the NBCe1-/- mice, the systemic pH also appears to contribute to the enamel phenotype. Extrapolating these data to humans, our findings suggest that in patients with NBCe1 mutations, correction of the systemic metabolic acidosis at a sufficiently early time point may lead to amelioration of enamel abnormalities

New regression formula to estimate the prenatal crown formation time of human deciduous central incisors derived from a Roman imperial sample (Velia, Salerno, Italy, I-II cent. CE)

The characterization and quantification of human dental enamel microstructure, in both permanent and deciduous teeth, allows us to document crucial growth parameters and to identify stressful events, thus contributing to the reconstruction of the past life history of an individual. Most studies to date have focused on the more accessible post-natal portion of the deciduous dental enamel, even though the analysis of prenatal enamel is pivotal in understanding fetal growth, and reveals information about the mother's health status during pregnancy. This contribution reports new data describing the prenatal enamel development of 18 central deciduous incisors from the Imperial Roman necropolis of Velia (I-II century CE, Salerno, Italy). Histomorphometrical analysis was performed to collect data on prenatal crown formation times, daily secretion rates and enamel extension rates. Results for the Velia sample allowed us to derive a new regression formula, using a robust statistical approach, that describes the average rates of deciduous enamel formation. This can now be used as a reference for pre-industrial populations. The same regression formula, even when daily incremental markings are difficult to visualize, may provide a clue to predicting the proportion of infants born full term and pre-term in an archaeological series

A two-stage ceramic tile grout sealing process using a high power diode laser Part I: Grout development and materials characteristics

Work has been conducted using a 60 W-cw high power diode laser (HPDL) in order to determine the feasibility and characteristics of sealing the void between adjoining ceramic tiles with a specially developed grout material having an impermeable enamel surface glaze. A two-stage process has been developed using a new grout material which consists of two distinct components: an amalgamated compound substrate and a glazed enamel surface; the amalgamated compound seal providing a tough, heat resistant bulk substrate, whilst the enamel provides an impervious surface. HPDL processing has resulted in crack free seals produced in normal atmospheric conditions. The basic process phenomena are investigated and the laser effects in terms of seal morphology, composition and microstructure are presented. Also, the resultant heat affects are analysed and described, as well as the effects of the shield gases, O2 and Ar, during laser processing. Tiles were successfully sealed with power densities as low as 500 W/cm2 and at rates up to 600 mm/min. Contact angle measurements revealed that due to the wettability characteristics of the amalgamated oxide compound grout (AOCG), laser surface treatment was necessary in order to alter the surface from a polycrystalline to a semi-amorphous structure, thus allowing the enamel to adhere. Bonding of the enamel to the AOCG and the ceramic tiles was identified as being principally due to van der Waals forces, and on a very small scale, some of the base AOCG material dissolving into the glaze

Coaxial anode improves sensitivity of gas radiation counters

Anode wire itself is enclosed by three segments. Two on ends are rejector segments, and middle one is primary charge-detecting segment. Anode wire is made from tungsten and is surrounded by enamel insulation. Enamel is covered by segments of vapor-deposited gold. At one point in center segment, gold layer makes direct contact with anode wire

Meeting report: a hard look at the state of enamel research.

The Encouraging Novel Amelogenesis Models and Ex vivo cell Lines (ENAMEL) Development workshop was held on 23 June 2017 at the Bethesda headquarters of the National Institute of Dental and Craniofacial Research (NIDCR). Discussion topics included model organisms, stem cells/cell lines, and tissues/3D cell culture/organoids. Scientists from a number of disciplines, representing institutions from across the United States, gathered to discuss advances in our understanding of enamel, as well as future directions for the field

Adsorption of aminefluorides on human enamel

Changes in surface characteristics of ground and polished human enamel after adsorption of two types of aminefluorides (AmF 297 and AmF 335) have been studied. After adsorption of aminefluorides from solutions with concentrations up to 10 mM for 2 min followed by rinsing of the surface with distilled water, contact angle measurements were carried out to yield surface free energies and ellipsometry was performed to yield the adsorbed layer thickness. In a separate experiment on powdered enamel, set up in an analogous way, zeta potential changes after adsorption of aminefluorides were determined in a 10 mM potassium phosphate buffer at pH 7·0. Surface free energies decreased from 88 erg·cm−2 to 52 erg·cm−2 and 35 erg·cm−1 after adsorption of AmF 297 and AmF 335 respectively at c = 1 mM. Increasing the aminefluoride concentration in solution did not affect the values obtained. Zeta potentials, originally −36 mV, became positive after adsorption, while ellipsometry indicated the buildup of adsorbed layers with a thickness between 3 run and 12 nm. All three types of experiments indicated that both AmF 297 and AmF 335 form an adsorbed monolayer on ground and polished enamel at a concentration of 1 mM. Negligible additional adsorption takes place at higher concentrations under the present experimental circumstances. In vivo, adsorbed aminefluoride layers will be rapidly covered by adsorbed protein layers, shielding both the adsorbed aminefluoride layer as well as its physicochemical characteristics. This effect has been studied in vivo by measuring surface free energy changes of ground and polished enamel, with AmF 297 and AmF 335 adsorbed at c = 2·5 mM as a function of the time, these samples were carried by test persons in partial dentures. On both types of AmF-coated enamel the surface free energies increased within 30 min to values approaching the one obtained previously for pellicle-coated ground and polished enamel (110 ± 9 erg·cm−2)