bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Edge-losses in Reflectance Measurements of Pigmented Maxillofacial Elastomer
Authors: Johnston W.M. , Hesse N.S. , Davis B.K. , Seghi R.R.
Published: January 2009

Edge-losses occur during reflectance measurements of pigmented maxillofacial elastomer when light is scattered within a sample beyond that part of the surface exposed to the observation system of the optical device. A custom sample-holder is presented which redirects light that would not be measured during conventional reflectance measurement back into the sample. The amount of edge-loss occurring within thin layers of maxillofacial elastomer with tan pigment on black-and-white backings was found to depend on sample thickness, the backing, the beam size used during conventional reflectance measurement, and the optical term bS = (2KS + K2)1/2. Data analysis revealed a significant interaction among these four factors. Additionally, the edge-loss occurring during the tristimulus reflectance measurement of thick samples of maxillofacial elastomer with various concentrations of tan and black pigment was found to be linearly related to bS up to a limiting value, with no additional edge-loss occurring for bS values above this limiting value. Edge-loss is an important consideration during the matching of the optical characteristics of pigmented maxillofacial material to those of human skin.
Temporal and Compositional Characteristics of Salivary Protein Adsorption to Hydroxyapatite
Authors: Lamkin M.S. , Arancillo A.A. , Oppenheim E.G.
Published: January 2009

Salivary proteins bind to enamel surfaces and hydroxyapatite in a highly selective manner. Numerous studies have identified these proteins as primarily proline-rich proteins, cystatins, statherin, and histatins. Previously, the hydroxyapatite-binding potential of these proteins had been characterized in systems consisting of singly purified protein and adsorbent. The purpose of this study was to investigate the adsorption of each protein in the presence of complete salivary secretion. Proteins, shown to adsorb to hydroxyapatite, were purified, biotinylated, and added back to the remaining proteins to form a series of reconstituted secretions. The adsorption of each biotinylated protein in the reconstituted secretion to hydroxyapatite was then measured as a function of time. Results indicated that three different adsorption patterns occur. A simple hyperbolic pattern is characteristic of amylase, glycosylated proline-rich protein (PRG), and cystatin. A faster adsorption process is observed for PRP-3, PRP-4, PIF-f, and statherin. A more complex pattern, exhibiting a rapid phase followed by a slower phase, is characteristic of PRP-1, PRP-2, PIF-s, and histatins. These results suggest that there are different adsorption processes involved in the binding of salivary proteins to hydroxyapatite. Two possible mechanisms are direct adsorption of protein to hydroxyapatite and indirect adsorption of protein by interacting with other proteins already bound to hydroxyapatite.
The Moral Foundations of Scientific Ethics and Responsibility
Authors: Camenisch P.F.
Published: January 2009

Any significant involvement of AADR/IADR in ensuring responsible research among their members must be grounded in a widely accepted consensus that there are good moral reasons for such involvement. One important source of such reasons is AADR/IADR's identity as a scientific research, a professional, and a dental association. These identities and the commitments to society and to clients implicit in them generate several mutually reinforcing reasons for taking responsibility for the reliability of members' research. With regard to scientific research, these reasons arise from what it means to do such research, and from the various ways the larger society supports that activity. With regard to the professional dimension, the reasons arise from what it means to be a profession in this society and can be best seen in relation to the four major characteristics of professions. With regard to AADR/IADR's being a dental profession, such reasons arise from dental researchers' specific role in the dental family of professions' goal of delivering optimal care to the clients of practitioners. The clients' perspective, specifically the need to be able to trust that one will receive the best care possible, is a final source for such reasons. Two current issues, the sharing of findings and commercial/industrial support for research, give new urgency to this question of the Association's role in ensuring responsible research.
On Being a Scientist in a Rapidly Changing World
Authors: Mandel I.D.
Published: January 2009

The practice of biological science has changed dramatically since mid-century, reshaped not only by a rapid series of landmark discoveries, but also by governmental directives, institutional policies, and public attitudes. Until 1964, the major influences were the mentor, who provided direction and indoctrination into the culture of science, and in dentistry, the newly established NIDR, which fueled the research engine with an expanding research and training program. The 1965-74 period witnessed the advent of the Institutional Review Board, an increased social involvement of biological scientists, and a recognition of the need for biological and physical safeguards in the conduct of research. The most turbulent years were 1975-89, when there was a confluence of animal rights activism and regulation, growing concerns with scientific fraud and publication malpractice, and the stresses and strains (and opportunities) resulting from the rapid expansion of the academic-industrial complex. The current period is characterized by rapid pace, high volume, and an increased depth and breadth of knowledge-a major change in scale in the conduct of science. It is an exciting time but one in which ethical issues are multiplying. Attention must be paid.
Survey of Ethical Issues in Dental Research
Authors: Bebeau M.J. , Davis E.L.
Published: January 2009

The American Association for Dental Research (AADR) surveyed its leaders to determine their perceptions of the prevalence of problematic research practices and the possible roles AADR should play in promoting scientific integrity. Seventy-six of the 98 program chairs and Association officers (1990-1995) surveyed responded. In general, these respondents did not think that serious misconduct or sloppy science occurred more often in AADR than in other scientific disciplines. Overall, respondents rated practices that undermine the trustworthiness of science (falsifying or fabrication of research data, retaliation, failure to present negative results, failure to disclose involvement with commercial enterprises, failure to maintain research records, etc.) as more serious, but less prevalent, than practices considered disrespectful of the work of others (gift authorship, citing sources without reading them, dividing a project into many small units, etc.). All respondents said that they had observed each of the less serious problematic practices one or more times, whereas 10% reported having observed retaliation, 30% reported having observed falsification, and 54% reported having observed plagiarism one or more times. AADR leaders had observed many more instances of misconduct and other problematic research practices than had faculty surveyed by Swazey et al. (1993), supporting conclusions by Greenberg and Goldberg (1994) that status and years of experience are associated with more frequent observations of misconduct. With respect to the possible roles the AADR might play in promoting research integrity, 88% thought that AADR should develop ethics cases and materials for educational use, 78% thought that AADR should create a process for addressing allegations of misconduct, 72% thought that the Association should develop an ethics committee or consultation service, 55% thought it should create a yearly ethics symposium, and 45% thought that the AADR should develop a more specific code of ethics to complement the general code recently developed by the IADR.
Effects of Different Magnitudes of Tension-force on Alkaline Phosphatase Activity in Periodontal Ligament Cells
Authors: Yamaguchi M. , Shimizu N. , Shibata Y. , Abiko Y.
Published: January 2009

Alkaline phosphatase (ALP) activity is involved in the process of calcification in various mineralizing tissues, and it is found at much higher levels in the periodontal ligament (PDL) than in other connective tissues. Since the PDL lies between hard tissues and functions as a cushion mitigating mechanical stress, such as occlusal and orthodontic forces, this stress may modulate ALP activity in PDL cells, which themselves may affect adjacent alveolar bone metabolism. The objective of this study was to determine the level of ALP activity and the gene expression of liver/bone/kidney (L/B/K) ALP in human PDL fibroblasts in response to cyclic tension-forces. Human PDL cells were cultured on flexible-bottomed plates and placed on a Flexercell Strain Unit. Cells were flexed at 6 cycles/min (5 sec strain, 5 sec relaxation) at 6 levels of tension-force (9%, 12%, 15%, 18%, 21%, and 24% increase in surface area) for 5 days. There was no significant difference in cell proliferation between the cells subjected to the tension-force and the controls. There was a 10% and 42% decrease, respectively, in the ALP activity in PDL cells exposed to low (9%) and high (24%) tension-forces, and these decreases were dependent on the magnitude of the tension-force. The finding of inhibited ALP activity in response to tension-force was consistent with the observation that L/B/K ALP mRNA levels were decreased in response to cyclic tension-force. These results suggest that tension-force may affect PDL metabolism, depending on the functional role of ALP.
Functional Characteristics of Gingival and Periodontal Ligament Fibroblasts
Authors: Giannopoulou C. , Cimasoni G.
Published: January 2009

In periodontal surgery, healing after Guided Tissue Regeneration (GTR) may be explained by differences in functional activities of gingival and periodontal ligament fibroblasts (GF and PDLF). Several studies in vitro have supported this hypothesis, but much remains to be defined. In the present work, gingival and periodontal ligament fibroblasts derived from five healthy subjects were isolated and compared in vitro. The morphology of the cells was observed under scanning electron microscopy (SEM). Several extracellular matrix components (ECM) were studied to compare the effects on fibroblast attachment, proliferation, and protein synthesis. Several biochemical markers were examined in both cellular extract (CE) and conditioned medium (CM). We also examined the muscle differentiation markers alpha-smooth muscle actin, desmin, and smooth-muscle myosin. Finally, we studied the effects of epithelial cells on the proliferation and protein synthesis of the two types of fibroblasts. GF and PDLF appeared identical under the SEM. All ECM components enhanced attachment; however, while collagen types I and IV promoted the attachment of GF, gelatin, laminin, and vitronectin promoted that of PDLF. Most ECM components increased the proliferation rate of GF and the biosynthetic activity of PDLF. The biochemical markers were similarly distributed between the two cell types, except for alkaline phosphatase, which was detected only in the CE of PDLF. Both GF and PDLF strongly expressed alpha-smooth-muscle actin and were negative for desmin; only PDLF were positive for smooth-muscle myosin. Epithelial cells increased the proliferation of both GF and PDLF but had no effect on their biosynthetic activity. These in vitro results may better explain the in vivo functional differences between GF and PDLF.
Effects of Dexamethasone and Cell Proliferation on the Expression of Matrix Metalloproteinases in Human Mucosal Normal and Malignant Cells
Authors: Kylmäniemi M. , Oikarinen A. , Oikarinen K. , Salo T.
Published: January 2009

Matrix metalloproteinases (MMPs) have an important role in many biological processes, such as tumor metastasis, wound healing, and inflammation. The regulation of MMPs and their inhibitors is still not known in detail, and the aim of this study was to investigate the effects of dexamethasone on cultured oral benign and malignant cell lines. The expression of MMPs in culture was studied: in four gingival (GF) and one periodontal ligament (PLF) fibroblast cell lines; in six gingival keratinocyte (GK) cell lines; and in UNR (UNR-108, Rat Osteogenic sarcoma) and SCC (SCC-25, Human Tonque Squamous Cell Carcinoma) cell lines. In the GFs, PLFs, and UNR cells, only MMP-2 (72 kDa gelatinase) was detected by gelatin zymography, while in most of the GK cell lines only MMP-9 (92 kDa gelatinase) was observed. In confluent SCC cultures, both MMP-2 and MMP-9 were found, while only MMP-2 was seen in rapidly growing SCC cells, demonstrating that cell proliferation influenced gelatinase expression in these cells, but not in the other cell lines studied. Dexamethasone at concentrations of 10-5 mol/L and 10-7 mol/L decreased the production of gelatinases in the GFs and PLFs, but not in the GKs, SCC, or UNR cells. The expression of mRNAs for matrix metalloproteinases (MMP-1 [interstitial collagenase] and MMP-2) and their inhibitors (TIMP-1 and TIMP-2) was also studied in the GFs by Northern hybridization. Dexamethasone markedly decreased the amount of MMP-2 mRNA in the GFs. The mRNA level of MMP-1 decreased even more in the same GFs. The mRNA levels for TIMP-1 and TIMP-2 were also decreased by dexamethasone in the GFs. Cell proliferation influenced the degree to which dexamethasone decreased these mRNA levels. The results indicate that glucocorticoids decrease the levels of MMPs and TIMPs in oral fibroblastic cells, whereas they do not appear to affect the production of gelatinases in either normal or malignant oral epithelial cell lines.
A Regulatory Role in Mammalian Salivary Glands for 5-Hydroxytryptamine Receptors Coupled to Increased Cyclic AMP Production
Authors: Turner J.T. , Sullivan D.M. , Rovira I. , Camden J.M.
Published: January 2009

Although a functional role for serotonin (5-hydroxytryptamine, 5-HT) has been defined in the salivary glands of some lower species, relatively few data supporting a role for 5-HT in the regulation of mammalian salivary glands have been presented. Our initial results from polymerase chain reaction studies in cells of mammalian submandibular gland origin using consensus sequence primers from G protein-coupled receptors suggested the presence of mRNA for a 5-HT receptor in these cells. Based on this observation, the question of a role for 5-HT in mammalian submandibular gland function was re-addressed, using isolated, perfused rat submandibular glands and dispersed-cell aggregates from this gland. In perfused glands, 5-HT decreased the rate of saliva flow initiated by acetylcholine by about 50% and increased the amount of protein in the saliva two-fold. In dispersed-cell aggregates, 5-HT elicited a concentration-dependent increase in the accumulation of adenosine 3',5' monophosphate (cyclic AMP; EC50= 660 ± 110 nM). In addition, functional studies, as well as radioligand binding experiments, indicated that the effects of 5-HT are independent of beta-adrenoceptors. Accumulation of cAMP in gland cells was consistent with a direct action of 5-HT on adenylyl cyclase. Similar cyclic AMP responses to 5-HT were observed in cells isolated from mouse and opossum submandibular glands and rat sublingual and parotid glands. Our findings suggest the presence of a 5-HT receptor in mammalian salivary glands coupled to the stimulation of adenylyl cyclase and, at least in rat submandibular gland, involved in modifying the volume and protein content of saliva.
A Quantitative Morphological Comparison of Cat Lingual Nerve Repair Using Epineurial Sutures or Entubulation
Authors: Holland G.R. , Andrade D. , Smith K.G. , Lahl S. , Robinson P.P. , Pehowich E.
Published: January 2009

Since lingual nerves may be transected during a variety of oral surgical procedures, including third molar removal, we have investigated two possible methods of repair. Quantitative morphological observations were made on feline chorda tympani and lingual nerves proximal and distal to transection injuries repaired either by epineurial suturing or by insertion of the cut ends into a perforated silicon tube. Proximal to the repair, the most prominent difference was an increase in the number of myelinated axons in the lingual nerve following epineurial suturing but not entubulation. Proximal to the repair site, the number of non-myelinated axons increased in comparison with controls in both chorda tympani and lingual nerves after both procedures, though the difference was statistically significant only in the lingual nerve proximal to entubulation. Distal to the injury, both types of repair showed a reduction in the number, size, and sheath thickness of myelinated axons in comparison with unoperated controls, but the difference in numbers was statistically signficant only distal to repair by entubulation. The number of non-myelinated axons distal to the repair sites was much higher than that in controls, the difference being greater distal to entubulation repair. There were more axons per Remak bundle distal to entubulation repair than to epineurial suturing, suggesting, perhaps, that fewer axons would ultimately become myelinated. Though the morphological differences between the two repair techniques are not as striking as the parallel electrophysiological differences reported previously (Smith and Robinson, 1995a,b), they are consistent with them and support the conclusion that, for transected lingual and chorda tympani nerves, epineurial suturing is the preferred approach. Key words: lingual nerve, injury, oral surgery, taste.
Transmission Electron Microscopy of Cementum Crystals Correlated with Ca and F Distribution in Normal and Carious Human Root Surfaces
Authors: Tohda H. , Fejerskov O. , Yanagisawa T.
Published: January 2009

Root-surface caries, like enamel caries, develops as a subsurface type of mineral loss. Very little is known about the composition of the surface zone covering the body of the lesion, and the ultrastructure and composition of carious cementum are not known. The aim of this study was to correlate the ultrastructure and arrangement of the cementum crystals with the distribution of fluoride and calcium in root cementum from human teeth with sound, unexposed, or exposed root surfaces as well as in early stages of root-surface caries. Microradiographically, unexposed specimens showed a relatively homogeneous mineral distribution contrasting with the formation of an apparently highly mineralized surface layer in exposed and, in particular, in carious cementum. The electron-probe findings showed a substantial fluoride peak corresponding to the surface layers in carious tissues in particular, whereas the calcium profile in the surface did not reflect the apparent increase in mineralization. A substantial increase in size of the cementum crystals was found in specimens with formation of the fluoride-rich, well-mineralized surface zone. The crystal lattice intervals when observed along the (001) plane showed a hydroxyapatite spacing. The findings indicated that a significant crystal growth can be achieved in human cementum concomitant with fluoride accumulation.
Effects of Actinomyces Amphiphile on the Fluidity of Endothelial Cells: A Spin Label Study
Authors: Hamada Y.
Published: January 2009

Actinomyces amphiphile (AcA) is an amphipathic molecule produced by Actinomyces viscosus that exhibits several biological activities. The effect of AcA on the fluidity and permeability of the plasma membrane in human umbilical vein endothelial cells was analyzed by a spin label method with 5- and 16-stearic acid nitroxide labels (SAL). These labels help to visualize the fluidity at the shallow (5-SAL) and deep (16-SAL) portions of the lipid bilayer. Cells were incubated with and without AcA (control) at 37°C for 6 hours, and membrane fluidity was periodically measured. Another spin label, 4-(N, N-dimethyl-N-hexadecyl) ammonium-2, 2, 6, 6-tetramethyl-piperidine-l-oxyliodine (CAT-16), was also used to assess the physical state of the cell surface. The order parameter of 5-SAL was significantly lower in the cells incubated with AcA than in control cells after the six-hour incubation. The motion parameter of 16-SAL was significantly lower in AcA-treated cells than in controls after 4 and 6 hours of incubation. These findings indicated that the AcA increased the fluidity. There were no significant differences between the AcA-treated and control cells incubated for only 2 hours. In addition, there were no differences in CAT-16 measurements between AcA-treated and control cells. The release of endoplasmic lactate dehydrogenase (LDH) into the medium tended to increase in the AcA-treated vs. the control cells. LDH release increased in both a dose- and time-dependent manner, indicating that AcA increased the permeability of plasma membranes. These findings suggest that AcA alters the biophysical properties of the plasma membranes of endothelial cells, affecting membrane function.
Constant Composition Dissolution Kinetics Studies of Human Dentin
Authors: Paschalis E.P. , Tan J. , Nancollas G.H.
Published: January 2009

The Constant Composition (CC) method has been used to study the dissolution kinetics of whole powdered human dentin as a function of calcium phosphate concentration at relative undersaturations with respect to hydroxyapatite (σHAP), ranging from +0.8 to -2.8, ionic strength from 0.05 to 0.30 mol/L-1 in sodium chloride or potassium nitrate, pH 4.00 to 5.50, and molar calcium/phosphate ratio in the reaction solutions from 0.05 to 11.1. The results suggest that human dentin behaves as a mixture of at least two calcium phosphate phases, HAP-like and octacalcium phosphate-like, OCP-like. Significant dissolution took place in solutions that were even supersaturated with respect to HAP, and the rates exhibited a striking insensitivity to relative undersaturation, while influenced by ionic strength, pH, and molar calcium/phosphate ratio in the reaction solutions. Although the dissolution was retarded in the presence of magnesium ion, the reaction rate showed the same insensitivity to undersaturation with respect to calcium phosphate.
Comparative Study of the Chemotactic Responses of Periodontal Ligament Cells and Gingival Fibroblasts to Polypeptide Growth Factors
Authors: Nishimura F. , Terranova V.P.
Published: January 2009

Selective recruitment of periodontal ligament cells to a previously exposed root surface is believed to enhance periodontal regeneration. It has been hypothesized that competition from gingival fibroblasts may reduce the potential of periodontal regeneration. We compared the migratory responses of PDL cells and gingival fibroblasts to a variety of biologicals. Parallel experiments designed to examine the directed migration responses of both periodontal ligament cells (PDL cells) and gingival fibroblasts (GF) isolated from the same donors were conducted using Platelet Derived Growth Factor (PDGF), Insulin Like Growth Factor-I, -II (IGF-I, -II), Epidermal Growth Factor (EGF), Transforming Growth Factor-β (TGF-β), and the chemotactic factor derived from the conditioned culture media of PDL cells (termed PDL-CTX) as attractants.

Both PDL cells and GF exhibited dose-dependent migratory responses when challenged with PDGF, IGF-I, IGF-II, EGF, and TGF-β. However, when these cells were challenged with PDL-CTX, only PDL cells migrated in a specific dose-dependent manner, while GF were refractive to PDL-CTX stimulation. Additionally, concentrated conditioned culture media from cultures of gingival fibroblasts did not stimulate PDL cell migratory responses. In other experiments, antibody directed against PDGF, FGF, TGF-β, IGF-I, IGF-II, NGF, and EGF did not inhibit the PDL-CTX-elicited response in PDL cells.

Previous studies have suggested that success of periodontal therapy depends on the specific attachment, migration, and proliferation of selected periodontal ligament cells. The data presented in this manuscript suggest that both PDL cells and gingival fibroblasts respond to a multitude of growth factors. PDL-CTX was found to be PDL-cell-specific for directed migration. Thus, we conclude that any biological therapeutic regime for periodontal regeneration should include PDL-cell-specific agents.
Periodontal Ligament Cells are Chemotactic to Fibroblast Collagenase
Authors: Terranova V.P. , Nishimura F.
Published: January 2009

Periodontal ligament (PDL) cell motility and the passage of PDL cells along a root surface are important components of tissue remodeling during periodontal regeneration. Proteolytic enzymes, including fibroblast collagenase, have been demonstrated to play an important role in tissue remodeling. Previous studies have shown that PDL cells chemotactically respond to a variety of matrix and growth factors. We therefore studied the effects of type I collagen fragments and fibroblast collagenase on PDL cell migration, since PDL cells have been shown to adhere preferentially to partially demineralized root surfaces with exposed type I collagen. Gingival epithelial cells were used as a control cell population. We report that PDL cells but not gingival epithelial cells preferentially migrate in a dose-dependent manner to both fibroblast collagenase and to type I collagen degradation products. Epithelial cell migration to fibroblast collagenase and type I collagen fragments was observed. Antibody to type I collagen inhibited the type I collagen fragment-mediated migration. Collagenase pre-treatment of PDL cells enhanced PDL cell migration to type I collagen fragments. In other assays, enzyme inhibitors were shown to decrease the collagenase-mediated PDL cell motility. Epithelial cells were shown to migrate preferentially to 92-kDa type IV collagenase and type IV collagen degradation products. Antibody to type IV collagen inhibited type IV collagen-induced epithelial cell migration. Taken together, these data suggest a role for collagenase in the fine control of PDL cell migration in tissue remodeling during periodontal regeneration.
Electrical Stimulation of Masseter Muscles Maintains Condylar Cartilage in Long-term Organ Culture
Authors: Pirttiniemi P. , Kantomaa T.
Published: January 2009

When condylar cartilage is maintained under non-functional organ culture conditions, its phenotypic expression is altered to a premature form with less expression of the type II collagen characteristic of mature chondroblasts. The aim of this study was to examine whether, by electrical stimulation of the major masticatory muscle, the masseter muscle, chondrogenic expression could be maintained under organ culture conditions in which the jaws with the craniomandibular joint were cultured in one block. Sixty BALB/c mice of both sexes were divided randomly into three groups of equal size. Two groups were decapitated at the age of 5 days. The cranial base and mandible were dissected out in one block, and the explant was placed on its cut surface on a culture dish. The masseter muscles of the explants in one group were stimulated with an electric pulsing device delivering an AC current of a frequency of 0.7 Hz and an amplitude of 5V with hourly active and silent periods. Five experimental and five control explants were fixed after culture periods of 1, 3, 7, and 14 days. The mice in the third group were used as in vivo controls. By electrical stimulation of the masseter muscle, the phenotypic characteristics of the condylar chondroblasts, such as the deposition of type II collagen and the thickness of the cartilage layers, closely resembled the situation in vivo, while the controls in a non-functional environment gradually lost their characteristic form.
Jaw Muscle Orientation and Moment Arms of Long-face and Normal Adults
Authors: van Spronsen P.H. , Weijs W.A. , van Ginkel EC , Prahl-Andersen B.
Published: January 2009

Long-face subjects have strongly reduced bite forces relative to normal subjects. This difference cannot be fully explained by the reduced cross-sectional area of the jaw muscles. In this study, we investigated whether the orientation and moment arms of the jaw muscles of normal and long-face subjects are different, and if so, to what extent these differences contribute to the observed differences in maximum molar bite-force levels. Three MRI scan series with different orientations were made of the jaw muscles of 30 normal and 13 long-face subjects. These served as the basis for computer reconstructions of the external shape of the muscles. The spatial orientation of the jaw muscles was defined by the regression line through the centroids of the muscular cross-sections. The moment arms of the jaw muscles and the bite point of the first mandibular molar were measured with respect to the center of the ipsilateral condyle. The muscular variables-including angles, moment arms, and mechanical advantage-were analyzed with a discriminant analysis and a multivariate analysis of variance (MANOVA). Differences in the spatial orientation of the temporalis muscle and the anterior digastric muscle contributed most to the distinction of the normal and long-face group. With MANOVA, it was shown that the normal and long-face group did not significantly differ with respect to the jaw muscle moment arms and mechanical advantage data. Only small differences were found between the sagittal muscle angles of the masseter and anterior digastric muscles in the two groups. In both the normal and long-face group, the orientation and moment arm data of the right and left muscles differed significantly. It was concluded that the variation of the spatial orientation of the jaw muscles is small and does not significantly contribute to the explanation of the different molar bite-force levels of long-face and normal subjects. Therefore, it is tempting to assume that the jaw muscles of normal and long-face subjects are different with respect to the maximum force they can exert per unit of cross-sectional area.
Regional Strengths of Bonding Agents to Cervical Sclerotic Root Dentin
Authors: Yoshiyama M. , Sano H. , Ebisu S. , Tagami J. , Ciucchi B. , Carvalho R.M. , Johnson M.H. , Pashley D.H.
Published: January 2009

The regional bond strengths of three current-generation bonding systems (All Bond 2, Scotchbond MultiPurpose, and Clearfil Liner Bond 2) were measured in natural wedge-shaped defects in the cervical area of extracted human teeth. A microtensile testing method was used to compare the strengths of resin bonds made to occlusal margins with those made to gingival margins. Controls consisted of normal teeth which had artificial wedge-shaped defects, of the same depth and dimension, created with a high-speed bur. The results indicated that there were no regional differences in bond strength, although bonds made to natural lesions were from 20 to 45% lower than those made to normal dentin in artificially created wedge-shaped defects, depending on the bonding agent. Scanning electron microscopy revealed that Clearfil Liner Bond 2 created the thinnest hybrid layers, which were difficult to measure in the natural lesions. The natural lesions contained sclerotic dentin, whereas the artificial lesions were composed of normal dentin. Although the bond strengths to sclerotic dentin were lower than those to normal dentin, the absolute values ( ca. 16 to 17 MPa) were high relative to previous-generation bonding agents.
Effects of Flaw Size and Auto-glaze Treatment on Porcelain Strength
Authors: Griggs J.A. , Thompson J.Y. , Anusavice K.J.
Published: January 2009

The functional surfaces of porcelain restorations are often ground to adjust occlusion. This removes the surface glaze and introduces flaws. Re-firing the restoration before final placement produces a self-glaze layer on the surface that may reduce the extent of damage caused by grinding. The objectives of this study were to determine whether re-firing after grinding increases the strength of dental porcelain and to determine whether the effectiveness of this treatment was dependent on the initial flaw size. Six groups, each containing 12 disk specimens, were prepared from experimental body porcelain (No. 36, J.F. Jelenko & Co., Armonk, NY). The specimens were fired under vacuum, ground to a thickness of 1 mm with 240-grit SiC abrasive, and polished through 600-grit on the surface to be subjected to tensile stress. Control Group A consisted of 12 non-indented specimens. Flaws were induced in the remaining groups by means of a Vickers indenter under the following loads: 3.9 N (Group B), 7.8 N (Group C), 11.8 N (Group D), 15.7 N (Group E), and 19.6 N (Group F). Following indentation, half of the specimens from each group were re-fired. The flexure strength of each specimen was determined by means of a piston-on-three-ball biaxial fixture. The TTEST procedure of SAS (1985) indicated a significant difference between the mean strength values of glazed and non-glazed specimens in Group E only (p = 0.55, 0.24, 0.13, 0.07, 0.01, and 0.69 for Groups A to F, respectively). ANOVA with the GLM procedure of SAS (1985) revealed that the mean strength values of groups subjected to five indentation loads were not significantly different (p = 0.45 for glazed specimens and p = 1.00 for non-glazed specimens). These findings support those of Fairhurst et al. (1992) for specimens with smaller flaws that were induced by grinding with 1 um abrasive grit. The results of the current study indicate that re-firing of porcelain with large surface flaws does not significantly increase the flexural strength.
Interaction of Citric Acid with Hydroxyapatite: Surface Exchange of Ions and Precipitation of Calcium Citrate
Authors: Misra D.N.
Published: January 2009

The use of citric acid is efficacious and distinctive in the demineralization of dentinal root surfaces for periodontal regeneration and in the etching and conditioning of enamel or dentin for bonding restorative resins. To decipher the role of citric acid in these applications, it is important that one have a basic understanding of its interaction with synthetic hydroxyapatite. The uptake or removal of citrate ions from aqueous solutions of citric acid (4 to 100 mmol/L, 10 mL) by hydroxyapatite (1 g) was studied at 22°C after a given reaction period (from 3 hr to 11 days) by immediate spectrophotometric monitoring of the concentrations of the filtrates (214 nm). The concentrations of calcium, phosphate, and hydrogen ions were also determined in the same solutions. The interaction: (i) is a time-independent ionic-exchange process with the substrate when the initial acid concentrations are dilute (4 to 12.5 mmol/L), and (ii) is a reactive process that is time-dependent for higher acid concentrations. The exchange process shows an adsorption of about one citrate ion per (100) face of the unit cell of hydroxyapatite for a maximally exchanged surface. The curves representing the reactive process may be quantitatively or qualitatively explained on the basis of the supersaturation of the solutions with respect to calcium citrate and its slow precipitation. The physico-chemical analysis of the needle-shaped birefringent crystals of the precipitate from the supersaturated solutions confirms the precipitate to be Ca3(citrate) 2·4H2O.
Variations in the Social Impact of Oral Conditions Among Older Adults in South Australia, Ontario, and North Carolina
Authors: Slade G.D. , Spencer A.J. , Locker D. , Hunt R.J. , Strauss R.P. , Beck J.D.
Published: January 2009

Previous studies among older adults have demonstrated that oral disease frequently leads to dysfunction, discomfort, and disability. This study aimed to assess variations in the social impact of oral conditions among six strata of people aged 65 years and older: residents of metropolitan Adelaide and rural Mt Gambier, South Australia; residents of metropolitan Toronto-North York and non-metropolitan Simcoe-Sudbury counties, Ontario, Canada; and blacks and whites in the Piedmont region of North Carolina (NC), United States. Subjects were participants in three oral epidemiological studies of random samples of the elderly populations in the six strata. Some 1,642 participants completed a 49-item Oral Health Impact Profile (OHIP) questionnaire which asked about impacts caused by problems with the teeth, mouth, or dentures during the previous 12 months. The percentage of dentate people reporting impacts fairly often or very often was greatest among NC blacks for 41 of the OHIP items. Two summary variables of social impact were used as dependent variables in bivariate and multivariate least-squares regression analyses. Among dentate people, mean levels of social impact were greatest for NC blacks and lowest for NC whites, while people from South Australia and Ontario had intermediate levels of social impact (P < 0.01). Missing teeth, retained root fragments, root-surface decay, periodontal pockets, and problem-motivated dental visits were associated with higher levels of social impact (P < 0.05), although there persisted a two-fold difference in social impact across the six strata after adjustment for those factors. Among edentulous people, there was no statistically significant variation in social impact among strata. The findings suggest that there are social and cultural factors influencing oral health and its social impact, and that those factors differ most between dentate blacks and whites in NC.
Use of the Weibull Hazard Model to Estimate Age-specific Probability of Permanent Tooth Loss
Authors: Otani K. , Ohtaki M. , Fujita M.
Published: January 2009

In analysis of the probability of tooth loss with age, the exact time of tooth loss is often unknown, although it is clear whether a tooth remains or has been lost. That is, left censoring is inevitable during data sampling. This may provide a biased estimate if such data are dealt with by the product-limit method, which is a common method of survival analysis. To reduce such a bias in estimating the age-specific probability of tooth loss, we developed a survival analysis method taking left censoring into consideration. Four hundred and forty-six panoramic radiographs obtained in a daily clinical practice were used. The frequency of tooth loss with age was assumed to follow the Weibull hazard model, and a likelihood function taking left censoring into consideration was defined to estimate the probability of tooth loss. The estimate obtained from our method was compared with that from the product-limit method to examine whether the effect of left censoring was reduced. We found that the probability of tooth loss estimated by the product-limit method was biased by left-censored data, and that the bias was reduced when our method was used. A Monte Carlo simulation study, in which the true tooth loss time was given, also showed that our method provided an estimate closer to the true value. Our method is considered to be more accurate in estimating the probability of tooth loss, since it reduces the bias caused by left-censored data.
Trial Production of Titanium Orthodontic Brackets Fabricated by Metal Injection Molding (MIM) with Sintering
Authors: Deguchi T. , Ito M. , Obata A. , Koh Y. , Yamagishi T. , Oshida Y.
Published: January 2009

Safety and esthetics are two indispensable factors to consider when fabricating orthodontic brackets. However, these factors are not easily achieved when conventional techniques (including forging and casting) are used in the mass production of titanium brackets, albeit the brackets exhibit excellent biocompatibility. In the present study, orthodontic brackets were manufactured by metal powder injection molding with sintering. Brackets with three different base designs were made and subjected to compression shear tests for evaluation of their bonding strength to enamel substrate. The shapes given to the dimple of the base were spherical, oval, and grooved. The maximum shear forces for each type were 11.1 kgf, 7.6 kgf, and 18.5 kgf, respectively. The bonding strengths of the titanium bracket were equivalent to those obtained with conventional stainless steel brackets. Moreover, uniform distribution of Vickers hardness values (average, 240 ± 40 Hv) measured at three locations indicated that the titanium bracket was uniformly sintered. Accordingly, titanium brackets thus fabricated exhibit a potential for clinical application.
Microstructure and Segregation Behavior of Palladium in Silver-Copper-Palladium Alloys
Authors: Chen K.I. , Lin J.H. Chern , Ju C.P.
Published: January 2009

It has been reported that the addition of palladium can modify the microstructure and improve the properties of Ag-Cu eutectic alloy as well as admixed Cu-rich amalgam. The purpose of this work was to study the microstructure and segregation behavior of palladium in a series of Ag-Cu-Pd alloys. All microstructural and microchemical results consistently indicated a strong tendency for palladium to form the ordered Cu3Pd superlattice in the copper-rich phase of the present ternary alloys. Transmission electron microscopic examination indicated that, in addition to the large Cu-rich particles, numerous small (typically tens of nanometers) Cu-rich particles were distributed in the Ag-rich phase. In the alloys containing 10 and 15 wt% Pd, the Cu3Pd superlattice had an L1 2-type crystal structure. In the alloy containing 20 wt% Pd, the Cu 3Pd had a periodic (regular) APB structure. The solubility of palladium in the Cu-rich phase was always much larger than that in the Ag-rich phase. The ratio of the palladium concentration in the copper-rich phase to that in the silver-rich phase decreased with the overall palladium content.
Expression of Laminin 5, Fibronectin, and Epithelium-associated Integrins in Recurrent Aphthous Ulcers
Authors: Richards D.W. , MacPhail L.A. , Dekker N. , Greenspan D. , Greenspan J.S. , Lozada-Nur F. , Regezi J.A.
Published: January 2009

Recurrent aphthous ulceration (RAU) is characterized by an ulcerated lesion that persists longer than traumatic ulcers of similar size. This delayed healing phase of the lesion was investigated for extracellular matrix components and matrix receptors (integrins). The hypothesis tested was that aphthous ulcers may lack key extracellular matrix components, or their receptors, that are necessary for the migration of marginal keratinocytes from the ulcer edge. We immunocytochemically stained biopsy specimens of RAUs and non-involved mucosal specimens from HIV+ and non-infected individuals to investigate the presence and distribution of molecules reported to be associated with re-epithelialization of mucosal and cutaneous wounds. Fibronectin, laminin type 5 (kalinin), and integrin subunits β1, β4, a6, and av were consistently found at the margins of RAU, as they are in traumatic ulcers. The a5 and β6 subunits were not always present. We also found av in the intact stratified squamous epithelium adjacent to ulcers. Immunohistochemical stains showed disruption in the deposition of laminin 5 and an apparent lack of fibronectin at the edges of some ulcers. Although these tissue results do not determine which integrin subunits are paired with each other, they do show some alterations in their expression in RAU. Absence of one or more of these molecules at the migrating front may contribute to delayed epithelial regeneration. It is likely that the absence or inappropriate expression of keratinocyte integrins or their extracellular matrix receptors occurs after the causative factors (currently unknown) of the lesion are gone. The reason for the altered expression of these molecules may be related to the secretory products (including lymphokines and proteinases) of the lymphocytic infiltrate.
Expression of Bone Morphogenetic Proteins by Osteoinductive and Non-osteoinductive Human Osteosarcoma Cells
Authors: Raval P. , Hsu H.H.T. , Schneider D.J. , Sarras M.P. , Masuhara K. , Bonewald L.F. , Anderson H.C.
Published: January 2009

Freeze-dried Saos-2, human osteosarcoma cells, and extracts of Saos-2 cells contain all components necessary to induce ectopic new bone and marrow when implanted into athymic Nu/Nu nuce. On the other hand, human osteosarcoma cells of the U-2 OS strain failed to induce bone formation under the same experimental conditions. Our aim was to compare the relative expressions of known osteoinductive factors including bone morphogenetic proteins (BMPs) and transforming growth factor-β (TGF-β) in these two cell lines in an attempt to explain the unique bone-inducing ability of the Saos-2 cells. Saos-2 cells expressed mRNA for BMP-1, -2, -3, -4, -6, and TGF-β1. The non-osteoinductive U-2 OS cells expressed BMP-2, -4, -5, -6, and -7 as well as TGF-β1 mRNA, while levels of BMP-1 and BMP-3 mRNA were either not detectable or detectable at a very low level in U-2 OS cells. The presence of BMP-1 and -4 protein was confirmed in Saos-2 cells by immunofluorescence, and TGFβ protein was demonstrated by bioassay in both cell types. These findings suggest that Saos-2 cells are endowed qualitatively and quantitatively with sufficient amounts of many bone morphogenetic proteins-especially BMP-1, -3, and -4—to confer osteoinductivity upon these cells. However, the absence of osteoinductivity in U-2 OS cells, despite significant mRNA expression levels of several bone morphogenetic proteins, suggests that, even though expression of one or more bone morphogenetic proteins may be present, it may not necessarily be sufficient to confer osteoinductivity upon U-2 OS cells. U-2 OS cells may be non-osteoinductive because (1) they contain inhibitors to the BMPs or secrete inhibitory binding proteins, (2) they do not process BMPs correctly, or (3) the BMPs are inappropriately localized and sequestered within the U-2 OS cells. Saos 2 cells may be osteoinductive because (1) they uniquely express BMP-1, (2) they express an appropriate combination of interactive BMPs at appropriate levels, and/or (3) the Saos-2 cells elaborate as-yet-unidentified osteoinductive factor(s).
CD44-Hyaluronate Interaction Participates in the Adherence of T-lymphocytes to Gingival Fibroblasts
Authors: Murakami S. , Saho T. , Asari A. , Hino E. , Kasai D. , Shimabukuro Y. , Okada H.
Published: January 2009

It has already been clarified that peripheral blood T-lymphocytes which had been activated with phorbol 12-myristate 13-acetate (PMA) acquired the ability to bind to human gingival fibroblasts (HGF) and that the adherence was mediated by VLA integrins. However, these studies also raised the possibility that molecules other than VLA integrins should be involved in the adherence between T-lymphocytes and HGF. In this study, the possible involvement of CD44, a hyaluronate receptor, in heterotypic cell-cell interactions was investigated. It was confirmed that PMA-activated T-lymphocytes strongly adhered to plate-coated hyaluronate and that the hyaluronate binding was clearly inhibited by the addition of OS/37, a newly established mAb specific for the hyaluronate-binding epitope on CD44. Interestingly, OS/37 also blocked the HGF binding of the activated T-lymphocytes when the adherence to HGF was assessed at 4°C, at which temperature the adhesion of integrin molecules diminished, while that of CD44 functioned normally. Immunofluorescence staining revealed that hyaluronate was anchored along the cell surface of HGF. Furthermore, the binding of activated T-lymphocytes to HGF was significantly inhibited by the treatment of HGF with hyaluronidase. These results clearly demonstrated that CD44-hyaluronate interactions participated at least in part in the adhesiveness of T-lymphocytes to HGF.