bluuebunny/crossref_metadata_2025 huggingface dataset:
How Much Is Too Much: Educational Loans and College Graduation
Authors: Zhan Min , Xiang Xiaoling , Elliott William
Published: January 2017

This study examines the association between educational loans and college graduation rates, with a focus on differences by race and ethnicity. Data come from the 1997 National Longitudinal Survey of Youth. Results from the event history analyses indicate that educational loans are positively related to college graduation rates, but only up to a point (about US$19,753). Although this nonlinear relationship holds true among White, Black, and Hispanic students, there are differences in the level of loans where its effect turns negative on graduate rates. There is little evidence overall that educational loans reduce racial and ethnic disparities in college graduation.
Factors Limiting Dental Diagnosis: A Conceptual Overview
Authors: Webber R.L.
Published: January 2017

Recent technological advances, particularly those dealing with information acquisition and management, have created opportunities in dental diagnosis and therapy which can be realized fully only through a systematic analysis of all relevant factors. For diagnostic systems, these include: (1) delineation of the task to be accomplished; (2) determination of a rational strategy for sampling pertinent data; and (3) assessment of performance obtainable from real components relative to that produced theoretically by an ideal system operating under the same constraints. The sequence of consideration of these factors is also important, because each is unilaterally constrained by those preceding. The perspective so obtained suggests that future development is likely to be determined more by the conceptualization of problems for which new tools can be designed than by the application of new technology in old ways.
Laser Effects On Dental Hard Tissues
Authors: Featherstone J.D.B. , Nelson D.G.A.
Published: January 2017

The use of lasers in dentistry has been considered for over 20 years. Higher-energy density lasers were shown to fuse enamel but were potentially unsafe. Subsequently, low-energy density laser radiation was shown to affect artificial caries lesion formation.

Recent studies have shown that carbon dioxide lasers can successfully be used at low-energy densities to fuse enamel, dentin, and apatite. Our studies have shown that specific wavelengths are highly efficient. These wavelengths are directly related to the infrared absorption regions of apatite. We have conducted studies with enamel and dentin, using pulsed CO2 laser radiation in the 9.32-μm to 10.49-μm region with energy densities in the 10 to 50 J.cm-2 range. This laser treatment caused surface fusion and inhibition of subsequent lesion progression and markedly improved the bonding strength of a composite resin to dentin. Similar studies have shown no pulpal damage or permanent deleterious effect on soft tissues.

This improved understanding of the scientific rationale for the interaction of CO2 lasers with teeth can lead to several clinical applications. This will depend, however, on the development of a technology to direct a specific frequency laser beam precisely to a desired site.
General Aspects of Optical Methods in Dentistry
Authors: Ten Bosch J.J.
Published: January 2017

Optical methods may be considered first in relation to vision. At wavelengths and power levels common in vision, optical radiation is harmless, and therefore only diagnostic use can be expected; for treatment uses, other wavelengths and/or higher power levels are needed. Because human vision is of high quality and the most important channel of information, optical methods are only useful as a supplement to it. This supplement is most useful when light properties are employed which are not used by vision: wavelength selection, coherence, and quantification. This leads to the use of fluorescence, holography, and instrumental measurement of contrasts and color, respectively. Applications of such use in dental diagnosis are summarized. Optical methods for treatment include the well-known curing of polymeric materials, photodynamic therapy of tumors and, potentially, laser fusion of enamel and dentin.
The Caries Lesion Under the Scanning Acoustic Microscope
Authors: Peck S.D. , Briggs G.A.D.
Published: January 2017

The scanning acoustic microscope can be used to obtain images of caries lesions in longitudinal sections of human enamel. The contrast in the acoustic images is unique in that it arises from changes in the elastic properties across the surface of a specimen. The contrast depends sensitively on the distance between the specimen and the focal plane of the lens, and this can be exploited to reveal features of interest. Comparison of an acoustic micrograph, a polarized light micrograph, and a microradiograph of a caries lesion reveals that the elastic properties of enamel are strongly dependent on the level of mineralization within the tissue. Acoustic micrographs show regions similar to those seen with the other techniques, but with greater sensitivity to small changes in mineralization.
The Elastic Properties of a Human Mandible
Authors: Ashman R.B. , Van Buskirk W.C.
Published: January 2017

This paper is a report on a study of the elastic properties of the human mandible. Using a continuous-wave ultrasound technique, we determined the elastic constants of ten small specimens taken from various locations within a single mandible. Seven of the nine independent orthotropic elastic constants were determined for each specimen. The data indicate that human mandibular bone is elastically homogeneous but anisotropic. In the elastic properties it exhibits, it is similar to, if slightly less stiff than, human and canine femora. Indeed, elastically it seems like a long bone bent into the shape of a horseshoe.
Computer-Based Reconstruction and Temporal Subtraction of Radiographs
Authors: Ruttimann U.E.
Published: January 2017

The most important physical parameter limiting the diagnostic performance achieved with radiographic images is the signal-to-noise ratio (SNR). In most dental applications, the normal anatomical structures contribute to a background pattern in the image that is limiting the SNR attainable. Hence, the projection direction of radiographs is a fundamental determinant of the SNR. The acquisition of a basis set of projection images obtained from a plurality of spatially registered sampling directions permits the reconstruction of any desired slice lying within a limited volume by tomosynthesis. Alternatively, the multi-projection strategy permits synthesis of any arbitrary radiographic image whose projection direction lies within the cone spanned by the basis projection directions. This feature can be used to synthesize a desired image at the proper projection angle required for meaningful subtraction from a previously obtained radiograph, and thus to suppress anatomy-related background variations.
Nuclear Medicine Techniques for the Detection of Active Alveolar Bone Loss
Authors: Jeffcoat M.K. , Williams R.C. , Kaplan M.L. , Goldhaber P.
Published: January 2017

The use of bone-seeking radiopharmaceutical uptake (BSRU) as an indicator of periodontal disease activity was assessed in untreated beagles with naturally occurring periodontal disease, and in beagles treated with the non-steroidal anti-inflammatory drug, flurbiprofen. In untreated beagles, a single uptake measurement was indicative of the rate of bone loss subsequently determined by sequential radiographs. Beagles treated with flurbiprofen demonstrated a significant decrease in rate of bone loss and a corresponding decrease in BSRU. Transfer of this technology to untreated human subjects with moderate to severe periodontal disease also showed a positive correlation between a single measurement of BSRU and the rate of bone loss determined from sequential radiographs. Analysis of these data shows that a single BSRU examination may be indicative of periodontal disease activity.
Telemetric Methods Using Ion-Specific Electrodes
Authors: Jensen M.E.
Published: January 2017

The use of telemetric methods for obtaining data from the human oral cavity has increased dramatically T over the last two decades. Measurement of intra-oral pH from plaque or saliva has been the most common application of ion-specific telemetry in dental research. Economics and technical problems such as durability requirements have led to wire-telemetric approaches for most clinical studies. However, limitation of subject mobility by the wire connection has led to further development of radio-telemetric methods. The use of custom-fabricated FM transmitters with ion-sensitive field effect transistors (ISFETS) has allowed for increased subject mobility during measurement of the activities of hydrogen, calcium, fluoride, and other ions of dental interest. Data can be transmitted to a small pocket receiver/recorder as digital data and later transcribed by means of a tape reader. Applications of ion-specific telemetry are described as well as possible future developments, including glucose measurement with enzyme-linked electrodes such as glucose-oxidase-coated gates on ISFETS. An intra-oral device for storage of these data within the appliance will be described. Although not yet evaluated in human subjects, this approach may eliminate the need for carrying a receiver/recorder for data collection and may have a wide variety of applications for intra-oral ion-specific measurement. Possible uses of this technology for diagnosis and therapeutics in dentistry may be limited to "special" patient populations, but it is likely to provide a wealth of information to research investigators and may suggest new therapeutic approaches toward dental diseases.
Epithelial-Mesenchymal Junctional Area in an Early Stage of Odontogenesis in Macaca Fuscata
Authors: Sawada T. , Yanagisawa T. , Takuma S.
Published: January 2017

The epithelial-mesenchymal junctional area in tooth germs of one- and three-year-old Japanese monkeys was studied with electron microscopy.

The plasma membranes at the distal ends of inner enamel epithelium cells were relatively even, and were associated with basement membrane. A large number of filaments, which were 15 nm in diameter and up to 2 μm in length, were present, extending perpendicularly from the basement membrane toward the dental papilla, forming an unique fibrillar layer. The distal cytoplasm of the cell contained rather few vesicles and granules which were positive for the acid phosphatase reaction. The distal ends of differentiating ameloblasts showed irregular undulations and numerous small processes which penetrated through the basement membrane and fibrillar layer. Following an increase of the undulations, the fibrillar layer and the basement membrane were engulfed by the cells and removed from the surface of pre-dentin. Large irregular bodies, which were filled with the filaments of the disintegrating fibrillar layer, were observed frequently. The distal cytoplasm contained a large number of coated pits, coated vesicles, and acid-phosphatase-positive granules. The fibrillar layer then disappeared, being replaced by collagen fibrils in the pre-dentin, which was in the stage of early mineralization.

These results indicate that the fibrillar layer is removed by the differentiating ameloblasts and degraded through an engulfing system which is formed by the cell surfaces.
Relating Developing Surface To Adult Ultrastructure in Chiropteran Enamel By Sem
Authors: Lester K.S. , Boyde A.
Published: January 2017

The developmental basis for a newly discovered feature of adult Chiropteran (bat) enamel has been explored. Developing enamel surfaces of tooth germs of Chalinolobus gouldii have been examined after either plasma-ashing or NaOCI immersion to remove cellular material superficial to the surface. Maintenance of dimensional stability of the anorganic surface was promoted either by prior embedding in methacrylate for plasma-ashing or by subsequent critical-point-drying for wet preparation. Stereo-pair scanning electron micrographs were analyzed in a stereo-comparator and profiles reconstructed in directions parallel with the electron beam.

A novel feature of the developing surface is described which accounts for the additional crystallite discontinuity line (minor boundary plane) found in the central cervical region of each horseshoe-shaped prism in what is essentially a Pattern 2 enamel. The feature is a consistent groove in the more superficial part of the developing floor wall of the Tomes' process depression, reflecting the absence of the most prominent parts of the developing enamel at the border between adjacent (Pattern 2) pits in the direction of their longitudinal alignment. The existence of a cervical floor groove was predicted from earlier observations of adult material as a result of our previously having constructed three-dimensional models utilizing the stereo-sketch approach. The present observations satisfactorily complete a conceptual cycle involving initial description of a new feature of adult bat enamel; prediction of the necessary developmental basis for it; and finally, analysis and confirmation of that developmental feature.
Function of Amelogenins in Porcine Enamel Mineralization During the Secretory Stage of Amelogenesis
Authors: Aoba T. , Tanabe T. , Moreno E.C.
Published: January 2017

The purpose of this investigation was to study the properties of amelogenins present in the secretory stage of amelogenesis of porcine enamel, and to explore their possible role in enamel formation. Interest was focused on three species of amelogenins having different properties regarding localization in the forming enamel, solubility, adsorption affinity onto hydroxyapatite (HA), and inhibitory activity of HA growth. The results suggest that the secreted 25-kilo-Dalton (kDa) parent amelogenin may directly regulate the growth kinetics and the habit of forming crystals through selective adsorption onto specific crystal surfaces. The observed constant distribution of 20-kDa amelogenin during the secretory stage of amelogenesis may be explained by steady-state conditions of two degradation processes: from the 25-kDa to the 20-kDa species; and, subsequently, from the 20-kDa to the 13-kDa and 11-kDa species. The former process could be crucial to induction of a slow growth of the crystals in directions of width and thickness, as observed following the initial, preferential growth parallel to the long-axis direction. Possible modulation of this slow growth by the presence of 20-kDa amelogenin as a weak inhibitor or a space-filling matrix through the secretory stage is still a very open question. The concentration gradient of the soluble amelogenins from the inner to the outer enamel would promote the diffusion toward the ameloblasts and the removal of the amelogenins by the cells. It should be pointed out that the soluble moieties (13 kDa and 11 kDa) in the fluid may also play a regulatory function with respect to the driving force for crystal growth through a weak Ca-binding, thus reducing the ionic calcium activity.
Isolation of Two Bovine Amelogenin Peptides and Their Amino Acid Sequences
Authors: Yeh J.-H. , Takagi T. , Sasaki S.
Published: January 2017

Two peptide fractions of bovine amelogenin having a highly aggregative property to form polymers were purified by chromatography, SDS-polyacrylamide gel electrophoresis, and HPLC. Amino acid sequences of purified peptides were determined by automated Edman degradation. One peptide was found to be composed of 63 amino acid residues having a molecular weight of 7105, and the other of 86 residues having that of 9683. The sequence of the smaller peptide was identical to the C-terminal 63 residues of the amelogenin molecule of 170 residues previously reported, but the larger contained eight residues which are absent in the amelogenin sequence. There is a possibility that the latter peptide might be synthesized independently from mRNA spliced at different positions.
New Artefacts for Old: An Alternative Method of Preparing Hard and Soft Tissue Interfaces of Developing Enamel
Authors: Fearnhead R.W. , Pang M. , Mok N. , Kawasaki K.
Published: January 2017

Serial sections (each from 150 to 200 μm thick) of porcine molar tooth germs within their bony crypts, rodent incisor teeth (in situ), and human extracted teeth were cut with a thin rotating diamond-impregnated disc, without prior embedding. Some specimens were cut unfixed, at room temperature (21°C) or frozen (-70°C), some in fixative, and others cut after fixation. A variety of routine fixatives has been tried, and in general the preservation of hard/soft tissue interfaces is best achieved when fixation precedes cutting. Several histological and histochemical methods have also been tried successfully. The damaged surface layers of the specimens brought about by the cutting disc can be removed after staining, if the section is embedded in a thin sheet of Epon and then thinned by being polished. The method provides a novel way of studying hard/soft tissue junctions.
Bonding Agents and Adhesives
Authors: Phillips R.W.
Published: January 2017

Development of molecules which will adhere to tooth structure is a high-priority area of dental research. Although enamel and dentin present formidable obstacles to adhesive mechanisms, there is substantial progress in the formulation of agents which are already altering certain procedures, such as the conservative restoration of the erosion lesion. These materials are evaluated with particular attention to dentin bond agents and the glass-ionomer system. The latter is of particular interest due to its proved biocompatibility, fluoride leach, and bonding capability. The exact status of dentin bond agents based on phosphonates remains controversial, and the possible reasons for the divergent data are discussed.
Bonding Agents and Adhesives: Reactor Response
Authors: Bowen R.L.
Published: January 2017

Adhesive materials must form multiple bonds with sound tooth substrates for maximum adhesion. Adhesive resins can be applied in incremental layers to bond composite materials to enamel and dentin. Hardening shrinkage and stress concentrations are factors that have detrimental effects on adhesive bonding with resins and composites. Improvements in dimensional stability of composites can therefore allow for better bonding and sealing of preventive and restorative materials.
Casting Metals: Reactor Response
Authors: Tesk J.A.
Published: January 2017

A commentary on the paper given by Dr. Asgar is presented. Agreement with that paper's contents on the trend toward palladium-based and other lower-cost alloys is rendered. However, with a view toward future competitiveness and quality of prosthetic restorations, this commentary looks for the application of new and emerging technologies. To implement these developments, the National Institute of Dental Research is urged to find avenues to support applications for dentistry in selected instances, despite adverse reviews from an entrenched establishment.
Research On Dental Amalgam: 1982-1986
Authors: Mahler D.B.
Published: January 2017

This paper is a five-year review of selected research papers on dental amalgam which were published during the years 1982 through 1986. Papers presented at scientific dental meetings are also included. During the past five years, clarification of amalgam metallurgy has been made, and a few innovative modifications have been recommended. The addition of palladium, indium, and selenium to dental amalgam has been suggested, but commercial applications have yet to be made. The mechanical property of creep has been studied more extensively, while the applicability of fracture toughness tests has been examined. More work has been done on the microleakage of amalgam restorations, with certain alloy factors showing an influence on this problem. Most in vitro investigations on the use of cavity varnish or resin films beneath amalgam restorations show reduced microleakage. Additionally, many electrochemical investigations were conducted. A most significant finding was that amalgam does not appear to break down in vivo as much as in vitro tests would indicate, the buffering action of saliva being protective in this regard. The marginal fracture evaluation of clinical amalgam restorations is still being used as a major clinical performance criterion, and measuring techniques for this failure mode have been improved. Measurements of metallic ion loss from amalgam were made with instruments of high sensitivity, but no evidence has been found to associate this loss with any disease entity. The rare presence of an allergy to mercury appears to be the only contra-indication for the use of amalgam as a dental restoration. Further research on dental amalgam can lead to improved clinical performance of this most useful restorative material.
Research on Oral Diseases and Its Impact On Dental Education and Practice
Authors: Löe H.
Published: January 2017

In recent years advances in dental research have marked the integration of dental science into the mainstream of biomedical research, with dental investigators employing the same cell and molecular biology techniques that have revolutionized the biosciences. Examples include the isolation and cloning of genes essential to the development of teeth and bones, discoveries of numerous extracellular factors that guide the growth and differentiation of cells and aid in tissue repair and regeneration, the development of a technique for producing human monoclonal antibodies, and the use of recombinant DNA techniques to generate mutant forms of oral bacteria. At the same time, dental research continues to make strides in more traditional pursuits. Thus, we are seeing continued advances in dental diagnostics, in the generation of new materials and methods for restorations and replacements of natural teeth, and an increase in approaches aimed at preventing or reversing the major dental diseases: dental caries and the periodontal diseases. Recent epidemiological studies highlight the gains that have been made in the oral health status of Americans and are helping shape the research agenda of the National Institute of Dental Research in the years ahead. Greater emphasis will be put on the oral health problems of adults and older Americans and those of any age who are at high risk for oral problems. Advances in research, evident in changing patterns of disease, have become the major force for change in dental education and practice. Future practitioners will need a broader intellectual preparation that will enable them to diagnose and treat a wide range of oral tissue conditions. Many dental schools are showing their willingness and ability to rise to the challenge of changing demands, assuring a promising future for the "new dentistry".
Light and Electron Microscopic Studies of Experimentally-Induced Pathologic Changes in the Rat Periodontal Tissue
Authors: Ijuhin N.
Published: January 2017

Morphological changes in periodontal tissues following topical application of lipopolysaccharide (LPS) or prostaglandin E2 (PGE2) were examined in Wistar rats by light and electron microscopy. Ultrastructural demonstration of acid phosphatase and immunohistochemical localization of lysozyme in these tissues were also studied. The number of osteoclasts along the alveolar bone facing the periodontal ligament was counted.

After topical application of LPS, degeneration and necrosis of the junctional epithelial cells, gingival fibroblasts, and alveolar osteoblasts were observed, as were increased bone resorption by osteoclasts and enhanced phagocytosis of collagen fibrils by fibroblasts. LPS appears to traverse easily through the junctional epithelium into the underlying gingival connective tissues. There it can cause destruction of deeper periodontal tissues by activating alveolar bone resorption and by enhancing the phagocytosis of collagen fibrils. PGE2 topically applied induced similar morphological changes. Possible participation of PGE2 in the induction of these LPS-related changes is discussed.
Fimbriae From the Oral Anaerobe Bacteroides Gingivalis: A Screening of Clinical Isolates From Various Places
Authors: Suzuki Y. , Yoshimura F. , Tani H. , Suzuki T.
Published: January 2017

Clinical isolates of Bacteroides gingivalis from several different locations were screened for the presence of fimbriae, primarily by immunological methods. About 60% of the strains tested had fimbriae as determined by agglutination with rabbit anti-fimbriae sera, and about two-thirds reacted with the anti-fimbrilin sera. The high detection rate of fimbriae implies that B. gingivalis fimbriae may play an important role in the adherence of this organism to host cells. These studies also suggest that not all strains share fimbriae cross-reactive with the fimbriae of B. gingivalis 381. The non-reactive strains may be devoid of fimbriae or may have fimbriae of different antigenic types.
Neutrophil Functions in Patients with Severe Periodontal Disease
Authors: Katsuragi Y. , Matsuda N. , Nakamura M. , Murayama Y.
Published: January 2017

Recently several investigators have reported that neutrophil functions were depressed or defective in localized and generalized juvenile periodontitis. It has also been shown that patients with adult periodontitis exhibit no such abnormalities. Concerning rapidly progressing periodontitis, only a few reports have been provided. The purpose of the present study was to compare various neutrophil functions in patients with rapidly progressing periodontitis (RPP), generalized adult periodontitis (AP), and in periodontally healthy or control subjects.

Neutrophils and monocytes were obtained from heparinized peripheral blood of 13 RPP, 16 AP, and 18 control subjects. Cells were isolated by Percoll® discontinuous density gradient centrifugation. Neutrophil phagocytosis was examined by use of FITC-labeled bacteria, and the number of EA rosette-forming cells was determined. Random migration and chemotaxis of neutrophils and monocytes were evaluated with the Boyden chamber. In addition, opsonizing activity of plasma, effects of plasma on phagocytosis and chemotaxis, and lysosomal enzyme secretion were also determined.

Neutrophil phagocytosis was markedly depressed in RPP compared with AP and those with normal periodontal tissue. The number of phagocytizing neutrophils was decreased and seemed to be correlated with the number of EA rosette-forming cells. Random migration and chemotaxis of neutrophils and monocytes were not significantly different among these three study groups. No differences in other neutrophil functions could be found.

From these results, it was clear that neutrophil phagocytosis in RPP patients was depressed. These results suggest that neutrophil abnormalities may lead to decreased resistance to periodontal infections in adults with rapidly progressing forms of periodontal disease.
The Function of Gingival Lymphocytes on the Establishment of Human Periodontitis
Authors: Okada H. , Shimabukuro Y. , Kassai Y. , Ito H. , Matsuo T. , Ebisu S. , Harada Y.
Published: January 2017

Human periodontitis has been confirmed to be an IgG plasma cell-rich lesion. However, we also detected many T cells, both CD4-positive and CD8-positive cells, in periodontal lesions. Some of these T cells expressed HLA-DR (la-like) antigen on their surfaces, and the proportion of HLA-DR+ cells was approximately equal in both CD4+ and CD8+ cell populations (Okada et al., 1983, 1984). Consequently, both helper and suppressor T cells were believed to participate in the establishment of periodontal lesions.

On the other hand, B cells were thought to be activated polyclonally in periodontal lesions, because a variety of periodontal florae possessed polyclonal B-cell-activating activity. We demonstrated that Actinomyces viscosus T14V stimulated mouse spleen B cells polyclonally and induced many IgM-producing cells but few IgG-producing cells. Moreover, IgG-producing cells were differentiated from only surface IgG-positive B cells but not from surface IgG-negative B cells-namely, surface IgM- or IgA-positive B cells (Harada et al., 1988). These results suggested that memory B cells, which had already been primed with appropriate antigens, might migrate into periodontal lesions, and then be activated polyclonally and develop into IgG-producing cells.

The periodontal lesion could, therefore, be induced by the interactions of immunoregulatory mechanisms of T cells and polyclonal B cell activity of periodontal florae. In fact, L3T4-positive T cells (helper-inducer T cells) enhanced IgG synthesis of mouse spleen B cells which had been activated with T-independent B cell activators such as LPS and A. viscosus preparations (Okada et al., 1987; Ito et al., 1988). We hypothesized from the above results that autoreactive T cells recognized the increasing self-MHC class II(Ia) antigen on B cells which had been activated with polyclonal B cell activators, and then produced soluble factors, which could enhance IgG synthesis of these B cells. Autoreactive T cells as well as PBAs, thus, may play an important role in the establishment of the IgG plasma cell-rich periodontal lesion.
Effects of Culture Supernatants of Leukocytes from Periodontal Patients on Monocyte-Mediated Hydroxyapatite Resorption
Authors: Marumoto Y. , Sato I. , Ikeda K.
Published: January 2017

In this study, the effects of culture supernatants on various activities of the monocyte, as a bone-resorbing cell, were compared between peripheral blood leukocyte (PBL) cultures from patients with periodontal disease and those from subjects with a clinically healthy periodontium. We have reported that normal human monocytes in vitro induce the release of calcium from synthetic hydroxyapatite particles and that the activity is enhanced by supernatants from cultures of stimulated or non-stimulated peripheral blood leukocytes.

Monocytes from both patients and healthy subjects induced the release of calcium from hydroxyapatite particles (HA) to an equal degree. This activity of monocytes from healthy subjects showed a statistically significant increase by addition of supernatants from stimulated or unstimulated cultures of peripheral blood leukocytes from periodontitis patients. This increase was greater than that seen with supernatants from cells of healthy controls. The Nitro Blue Tetrazolium reduction activity and [3H]-thymidine incorporation of monocytes were also increased by addition of the supernatants from leukocyte cultures from either patients or healthy controls, but no significant difference was noted in the increase.

These results suggest that the HA-resorbing activity of monocytes was enhanced by factors from cultured leukocytes. Furthermore, these studies showed that production of these factors by peripheral mononuclear cells from patients with periodontal disease was greater than that seen with cells from normal subjects.
Crestal Alveolar Bone Change in Patients with Periodontitis as Observed by Subtraction Radiography: An Overview
Authors: Hausmann E. , Dunford R. , Christersson L. , Allen K. , Wikesjo U.
Published: January 2017

Subtraction radiography is a highly sensitive and useful technique for detecting crestal alveolar bone changes in patients. Utilizing this technique, researchers have demonstrated that 9% of crestal sites lose bone over a six-month period in untreated subjects with periodontitis. On the order of 10-13% of crestal sites were found to lose bone three months post-periodontal therapy which included surgery. Non-surgical therapy resulted in 0.5-2% of crestal sites with bone loss. Subtraction requires radiographs which have closely approximating projection geometry. Presently available technology for taking standardized radiographs based on an occlusal stent system is adequate for obtaining interpretable subtraction images.
Prevalence of Juvenile Periodontitis Among Students at Nagasaki University
Authors: Kowashi Y.
Published: January 2017

The prevalence of juvenile periodontitis was examined among 641 students aged 19 to 28 years at Nagasaki University. Of all 1520 students in their sophomore year at the university, they were randomly selected for examination in this study. Bitewing radiographs were taken on 49 subjects who had a probing pocket depth of 4 mm or more on six representative teeth (#16, 21, 24, 36, 41, and 44). Individuals who exhibited bone loss on the bitewing radiographs were taken for further clinical and full-mouth radiographic examination. Three subjects among the 641 adolescents had vertical bone destruction of 3 mm or more from the cemento-enamel junction on first molars and incisors, for a prevalence rate of 0.47%.
The Concentration of Salivary Steroid Hormones and the Prevalence of Gingivitis at Puberty
Authors: Morishita M. , Aoyama H. , Tokumoto K. , Iwamoto Y.
Published: January 2017

Gingival conditions of 1323 junior high schoolchildren aged 12-15 were examined, and 132 children who had either healthy gingivae or severe gingivitis were called to the clinic. More precise examination of gingivitis was performed by assessment of Jackson's gingivitis index (G.I.), probing depth (P.D.), and bleeding on probing. Whole saliva was collected, and the salivary concentrations of estradiol, progesterone, and testosterone were determined by radioimmunoassay. Subgingival bacterial plaque was sampled from 36 children, and total bacterial counts and morphological differentiation were performed under a phase-contrast microscope. For statistical analysis, both males and females were divided into two groups according to the concentration of each sex hormone and subgrouped by the results of clinical examinations. Chi-square analysis using 2-by-2 tables was performed to determine the relation between salivary steroid hormone levels and gingival inflammation.

The results suggest that unbalanced secretion of certain hormones might be one of the factors promoting gingivitis at puberty.
Periodontal Treatment by Local Drug Delivery Using Resorbable Base Material
Authors: Noguchi T. , Fukuda M. , Ishikawa I.
Published: January 2017

The effects of local drug delivery to the subgingival plaque flora using resorbable base material were evaluated by the study of microbial composition in periodontal pockets and clinical manifestations of disease.

In vitro, the drug used in this study was released within 24 hr from the hydroxypropylcellulose (HPC) strips. In vivo release of the drug from strips was also measured in nine patients who had, contralaterally, deep pockets of more than 5 mm. A tetracycline (TC)-containing HPC strip was inserted in one pocket, and a blank strip without TC was inserted in the other pocket. The amount of TC in the gingival crevicular fluid (GCF) 24 hr after insertion of the strip was significantly higher than that of the control.

Ten subjects, who had at least three pockets greater than 4 mm in depth, were selected from 50 volunteers after an initial examination. HPC strips containing TC, chlorhexidine (CH), and control (base material) were inserted into each pocket three times a week. Clinical and microbiological changes ascertained by darkfield microscopy were monitored over three weeks. Reduction of both probing depth and bleeding-on-probing was observed only in the pockets in which TC was administered. Changes of microbial composition of subgingival plaque were, however, found in both TC- and CH-treated pockets. The percentages of spirochetes and motile rods were remarkably reduced in these pockets.
Hypocalcification and Hypoplasia in Primary Teeth of Pre-School Children from Different Ethnic Groups in South Africa
Authors: Hargreaves J.A. , Cleaton-Jones P.E. , Roberts G.J. , Williams S.D.L.
Published: January 2017

A study was completed in 1985/86 which examined the dental health of pre-school children from different ethnic groups and communities in South Africa: rural black, urban black, urban colored, urban Indian, and urban white. Enamel defects were recorded in primary teeth by use of the HHI, an index developed to measure hypocalcification and hypoplasia of enamel. The findings showed that colored children had the greatest number of enamel defects. The teeth most commonly affected were the maxillary anterior teeth and mandibular molar teeth. It is suggested that further epidemiological studies utilizing the HHI should be undertaken in pre-school children, especially from developing countries, to gain more information on the causes of enamel defects in the primary dentition and the possible use of such findings to predict nutritional health of individuals.
Developmental Enamel Defects in Primary Teeth in Children with Cerebral Palsy, Mental Retardation, or Hearing Defects: A Review
Authors: Bhat M. , Nelson K.B.
Published: January 2017

Developmental enamel defects in primary teeth have been found at least twice as frequently in children with cerebral palsy or mental retardation as in control children, and frequently also in children with sensori-neural hearing deficits. The developing tooth germ is sensitive to a range of systemic disturbances, some of which may also affect neurologic development. Because the enamel cannot recover once it is damaged, it may provide a repository of information on the timing and nature of insults potentially affecting other ectodermally derived structures, including the brain. This paper reviews the literature on developmental defects of enamel in primary teeth, asking whether these might be useful as biological markers of the timing and in some cases the nature of insults. Among systemic factors related to development of enamel that might also have implications for neurologic development are certain genetic disorders including tuberous sclerosis, premature birth, neonatal nutritional disturbances (especially hypocalcemia), viral infections (such as rubella and cytomegalovirus during gestation), thyroid disorders, and maternal diabetes. It is concluded that further research is warranted concerning whether developmental defects of dental enamel can be useful markers for the timing of intra-uterine or perinatal events associated with certain neurologic and sensory disorders of children.
Fluoride and Enamel Defects
Authors: Horowitz H.S.
Published: January 2017

The concentration of fluoride in drinking water is the major determinant of the prevalence and severity of dental fluorosis in a community. Fluorosis is more prevalent and discernible in permanent teeth than in primary teeth; the intensity can range from barely perceptible, whitish striations in enamel to confluent pitting and dark staining. The traditional belief is that fluorosis is produced only during the secretory stages of ameloblastic activity. Some recent reports suggest that the maturation stages of enamel development are as important as or even more important than the secretory stages as the time when fluorosis can be produced. The question of timing remains unresolved. Many questions also remain about general and individual physiologic variations in relation to susceptibility to dental fluorosis.

Good criteria for differential diagnosis exist to distinguish dental fluorosis from non-fluoride enamel opacities. An increasing number of reports indicates that the prevalence of fluorosis may be increasing among children in fluoridated and non-fluoridated communities. Reasons for the increases may relate to misuse of dietary fluoride supplements, ingestion of fluoride toothpastes, or increasing amounts of fluoride in foods or the atmosphere. The intensity of the increased fluorosis is in the milder categories and is not generally unsightly. It should be recognized that a small amount of fluorosis may be an alternative to a greater prevalence of dental caries, a disease that may produce cosmetic problems and sequelae worse than those produced by fluorosis.
Changes in Dental Fluorosis Following an Adjustment to the Fluoride Concentration of Hong Kong's Water Supplies
Authors: Evans R.W.
Published: January 2017

In June, 1978, the fluoride concentration in Hong Kong water supplies was reduced from 1.0 to 0.7 mg/ L. The objectives of this study were (1) to determine whether, as a result of this minor adjustment, a consequent reduction in the prevalence and severity of dental fluorosis came about, and (2) to determine whether dental fluorosis develops during enamel secretion and primary mineralization or during the maturation stage of enamel development. Dental fluorosis was assessed by Dean's community fluorosis index (CFI) on upper central incisors in 2382 children aged from 7 (exposed to 0.7 mg/L only) to 13 years. The children were selected from four districts served with drinking water by four different water treatment stations. Differences in the distributions of dental fluorosis scores across ages were significant in all districts. The susceptibility to fluoride was assessed statistically through a series of analyses whereby the fluoride concentration in the drinking water (both coincident with enamel secretion and periods of enamel maturation) was correlated with CFI. It was concluded (1) that CFI values were reduced following a minor adjustment to the fluoride concentration in drinking water, (2) that dental fluorosis develops during the maturation stage of enamel development, (3) that the development of dental fluorosis may occur over a period of 16 to 24 months, commencing from 12 to 32 months following enamel secretion, and (4) that Dean's index is a suitable instrument for monitoring the effects on dental fluorosis of minor adjustments to the fluoride concentration in drinking water.
Enamel Hypomineralization Viewed From the Pattern of Progressive Mineralization of Human and Monkey Developing Enamel
Authors: Suga S.
Published: January 2017

Microradiograms and their computer-aided image analysis of ground sections of the developing enamel of human permanent third molars and monkey permanent teeth (Macaca fuscata) indicate that the mode of progressive mineralization of enamel is completely different between the matrix formation and maturation stages. During the former stage, the enamel matrix is slightly mineralized. During the latter stage, which takes a much longer period than the previous stage, the increase in the secondary mineralization takes place first slightly, from the surface toward the inner layer, and then heavily, from the inner layer toward the surface. The narrow outer layer mineralizes very slowly during the middle and late stages of maturation, but finally achieves the highest mineralization of the entire enamel layer. The very narrow innermost layer mineralizes slowly without expanding its width. The former three processes seem to be under the direct control of the ameloblasts. Hypoplastic areas which appear during the matrix formation stages are not necessarily accompanied by hypomineralization. Dysfunction of the cells immediately after the completion of matrix formation appears to cause hypomineralization throughout the entire width of matrix except for the innermost layer. Disorders of the cells occurring during the middle and/or the late stage of maturation—due to chronic metabolic disturbances, such as fluorosis—induced hypomineralization localized mainly at the outer layer. The hypomineralized enamel is not necessarily accompanied by hypoplasia. The process of enamel mineralization is not necessarily fully synchronized with that of tooth eruption. Therefore, the narrow outer layer, especially in the fissure and cervical regions, is sometimes hypomineralized even after the teeth have erupted normally.
Enamel Proteases in Secretory and Maturation Enamel of Rats Ingesting 0 and 100 ppm Fluoride in Drinking Water
Authors: Denbesten P.K. , Heffernan L.M.
Published: January 2017

Dental enamel formed during ingestion of high levels of fluoride in drinking water has an increased organic content in the maturation stage, which may be due to a delay in the breakdown of amelogenins during the early-maturation stage of enamel formation. This delay in the breakdown of amelogenins in fluorosed enamel suggests an effect of fluoride on enamel proteases which hydrolyze the early secreted enamel proteins. In this study, we compared the proteases present in fluorosed and control secretory-stage and maturation-stage enamel. Enamel was demineralized and separated in SDS gels containing 0.1% gelatin. After incubation in 100 mmol/L Tris-HCI, pH 8, with 10 mmol/L CaCl2, the gels were stained with Coomassie Blue, and proteases were seen as clear zones of degraded gelatin. Similar bands of proteolytic activity were seen in fluorosed and in control enamel. In the maturation stage, more proteases were present than in the secretory stage of enamel formation. Less digestion of gelatin substrate occurred in several proteases found in the fluorosed maturation-stage enamel as compared with the control maturation-stage enamel. This suggests that the amount of protease secreted or the activity of the proteases may be altered in fluorosed maturation-stage enamel.
Macroscopic and Scanning Electron Microscopic Appearance and Hardness Values of Developmental Defects in Human Permanent Tooth Enamel
Authors: Suckling G.W. , Nelson D.G.A. , Patel M.J.
Published: January 2017

Defects present in 12 human permanent teeth were classified on the basis of their macroscopic appearance as hypoplasia (three teeth), diffuse opacities (three teeth), white demarcated opacities (one tooth but two defects), or yellow demarcated opacities (five teeth but six defects). The hardness values and SEM appearance of the defective enamel were determined after the teeth were sectioned through the lesion(s) and were distinctive for each type of defect. The thin enamel of the hypoplastic lesions was either opaque (with reduced hardness values) or translucent (with near-normal hardness values and sometimes a change in prism orientation external to an incremental line). The enamel of the diffuse and demarcated opacities was of normal thickness. The changes in the macroscopic and SEM appearance, and the reduced hardness values of the diffuse patchy opacities, were restricted to the outer 150 μm of the enamel. The demarcated opacities varied in position and depth, and in places had a clearly marked boundary with the adjacent normal enamel. Hardness values were related to color change, with yellow lesions being softer than white. Although prism direction was normal within demarcated opacities, prism outlines were less distinct. The findings suggest that temporary and permanent dysfunction of ameloblasts can occur in both secretory and maturation phases, influencing the final appearance of the lesion.
The Ultrastructure of Spindles and Tufts in Human Dental Enamel
Authors: Palamara J. , Phakey P.P. , Rachinger W.A. , Orams H.J.
Published: January 2017

A transmission electron microscope (TEM) study was made of spindles and tufts as identified in the light microscope, from samples prepared by selected-area argon-ion-beam thinning. Spindles in human dental enamel were found to be continuous with dentinal tubules across the dentin-enamel junction (DEJ) and usually appeared at the DEJ as electron-lucent, empty channels nearly circular in cross-section. The spindles were found to cross prism boundaries, branched rarely, and some were occasionally found to be occluded or partially occluded with small needle-like crystals (-5 nm width and -70 nm length), granular material (-1.5 nm diameter) and/or amorphous material. Near the DEJ, the majority of spindles had a diameter less than 2 μm, while in the prismatic enamel away from the DEJ, spindles with a diameter greater than 2 μm were generally found. Spindle varicosity was characterized by an enlargement of their diameter. Tufts started at the DEJ and were not associated with dentinal tubules. Two types of ultrastructure were observed in the TEM: (i) disrupted regions of enamel incorporating large voids (up to -0.1 μm in diameter), or, more commonly, (ii) channels within the enamel occluded or partially occluded, with small needle-like crystals and granular and/or amorphous material similar to that found in the enamel spindles. It was concluded that spindles and tufts represent areas of hypomineralization with increased void volume and partial remineralization.