bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Optical 3-D Device for the Detection of Wear
Authors: Mehl A. , Gloger W. , Kunzelmann K.-H. , Hickel R.
Published: January 2009

For the clinical performance of new dental restorative materials to be accurately assessed, the three-dimensional anatomical changes of the functional surfaces of the restoration must be elucidated over time. To this end, a highly accurate 3-D optical scanner has been developed that utilizes the principles of triangulation and a reference-free automated 3-D superimposition software. The aim of this study was to assess the accuracy and the precision of the new system with and without referenced positioning. Additionally, the ability of the system to determine wear of posterior fillings three-dimensionally has been shown. Gypsum replicas of restored teeth were evaluated. The tooth surfaces were scanned with a resolution of 250,000 surface points within a measuring time of 20 to 40 sec. The results show that the precision and accuracy of 3-D data acquisition depend on the surface inclination. Up to an angle of 60°, the precision is better than 3 μm, and the accuracy is better than 6 μm. If exact repositioning of the object before and after occlusal loading is possible, e.g., with in vitro studies, differences on the surface can be determined with a precision of 2.2 μm. In reference-free measurements, which are a necessity in clinical studies, the 3-D data acquisition in combination with the automatic matching program can detect wear with an accuracy of 10 um. The application of this measuring device for the detection of wear of a composite filling functioning in the mouth has been shown. Since this measuring technique is automated, and measurements of high accuracy can be attained in a short period of time, this system offers the possibility for complex analyses of three-dimensional wear to be conducted on a large number of samples in clinical studies.
Distribution of Fluoride in the Oral Cavity after Application of a Bioadhesive Fluoride-releasing Tablet
Authors: Bottenberg P. , Bultmann C. , Gräber H.G.
Published: January 2009

Bioadhesive fluoride tablets are fluoride-releasing devices that can be applied to the oral mucosa by the patient and release fluoride for several hours. From earlier research, it is known that a single fluoride source in the mouth can lead to an uneven distribution of fluoride in the oral cavity. In this study, fluoride concentrations were determined at different sites of the oral cavities of 13 healthy human volunteers after the application of a bioadhesive fluoride tablet containing 0.5 mg fluoride. The sites were: (1) labial surfaces of the upper central incisors, (2) lingual surfaces of the lower central incisors, (3) labial surface of the first upper left molar, and (4) labial surface of the lower right first molar. The tablet was fixed either centrally on the palate or in the lower labial sulcus in two consecutive experiments. Saliva was sampled with polyethylene sponges 5, 10, 20, 30, 60, 120, 180, and 240 minutes after tablet insertion. Fluoride was determined electrochemically. It could be shown that the area under the curve (AUC) values were significantly (p < 0.05) higher after tablet insertion in the lower labial sulcus at sampling site 1, a trend (p = 0.06) could be calculated for sampling sites 2 and 3, and no difference was found at sampling site 4. Fluoride could be detected in concentrations above 0.01 mmol.L-1 at all sampling sites after tablet insertion in the lower labial sulcus. This location seems to be a more appropriate tablet location than the palate.
Longitudinal Analysis of the Association of Human Salivary Antimicrobial Agents with Caries Increment and Cariogenic Micro-organisms: A Two-year Cohort Study
Authors: Kirstilä V. , Häkkinen P. , Jentsch H. , Vilja P. , Tenovuo J.
Published: January 2009

Previous studies of the possible associations of salivary antimicrobial agents with dental caries have given controversial results, obviously mainly because almost all studies have been cross-sectional. Our aim was to find out, in a two-year longitudinal follow-up study, the associations among selected salivary non-immune and immune antimicrobial variables, cariogenic bacteria, and caries increment. The study population was comprised of 63 subjects, all of whom had their 13th birthday during the first study year. In addition to a comprehensive dental examination at baseline and after 2 yrs, paraffin-stimulated whole saliva samples were collected in a standardized way at six-month intervals. Saliva samples were analyzed for flow rate, buffer effect, lysozyme, lactoferrin, total peroxidase activity, hypothiocyanite, thiocyanate, agglutination rate, and total and specific anti-S. mutans IgA and IgG, as well as for numbers of total and mutans streptococci, lactobacilli, and total anaerobic bacteria. Cluster analysis and Spearman-Rank correlation coefficients were used to explore possible associations between and among the studied variables. During the two-year period, a statistically significant increase was observed in flow rate, thiocyanate, agglutination rate, anti-S. mutans IgA antibodies, lactobacilli, and total anaerobes, whereas lysozyme, lactoferrin, and total and anti- S.mutans IgG antibodies declined significantly. Based on various analyses, it can be concluded that, at baseline, total IgG and hypothiocyanite had an inverse relationship with subsequent two-year caries increment, anti-S. mutans IgG antibodies increased with caries development, and mutans streptococci and lactobacilli correlated positively with both baseline caries and caries increment. Total anaerobic microflora was consistently more abundant among caries-free individuals. In spite of the above associations, we conclude that none of the single antimicrobial agents as such has sufficiently strong power to have diagnostic significance in vivo with respect to future caries.
Functional Properties of Jaw and Tongue Muscles in Rats Fed a Liquid Diet after Being Weaned
Authors: Liu Z.J. , Ikeda K. , Harada S. , Kasahara Y. , Ito G.
Published: January 2009

Decreased masticatory demands due to liquid or soft diets cause a reduction in the growth of craniofacial bones and in the development of feeding musculature, but the effects on masticatory function and jaw/tongue muscle activities are unclear. The present study was undertaken to test the hypotheses that a liquid diet feeding after weaning affects the critical-period programming of mastication and the motor performances of jaw and tongue muscles. Thirty-six male Wistar rats were divided into two equals groups at weaning and fed either a solid (solid-diet group) or a liquid (liquid-diet group) diet until they reached 50 days of age. Electromyograms (EMG) of the masseter, medial pterygoid, temporalis, anterior digastric, styloglossus, and genioglossus were recorded while animals were naturally ingesting ordinary pellets, apple cubes, and a liquid diet. It was found that: (1) a more irregular chewing rhythm, a shorter chewing sequence, and a longer chewing cycle were found in the liquid-diet group, but there were no differences observed during lapping/licking between the two groups; (2) during the chewing cycles, the EMG onset of each muscle in relation to that of the masseter in the liquid-diet group was similar to that in the lapping/licking cycles in both groups; (3) the activities of jaw elevators (masseter, medial pterygoid, and temporalis) during the chewing cycles were significantly higher in the liquid-diet group; and (4) the increase in the EMG activities of jaw elevators during pellet chewing compared with apple cube chewing was significantly weaker in the liquid-diet group, whereas such an enhancement was found simultaneously in the styloglossus in the solid-diet group, and in the anterior digastric in the liquid-diet group. These findings verify that: (1) the motor output of jaw and tongue muscles may be altered in rats fed a liquid diet after being weaned; (2) the feeding of a liquid diet to rats after being weaned may obstruct the functional transition from suckling to mastication; and (3) jaw elevators that develop without motor learning of mastication are inefficiency when performing functionally.
Purification, Characterization, and Cloning of Enamel Matrix Serine Proteinase 1
Authors: Simmer J.P. , Fukae M. , Tanabe T. , Yamakoshi Y. , Uchida T. , Xue J. , Margolis H.C. , Shimizu M. , DeHart B.C. , Hu C.-C. , Bartlett J.D.
Published: January 2009

The maturation of dental enamel succeeds the degradation of organic matrix. Inhibition studies have shown that this degradation is accomplished by a serine-type proteinase. To isolate and characterize cDNA clones encoding this proteinase, we used two degenerate primer approaches to amplify part of the coding region using polymerase chain-reaction (PCR). First, we purified the proteinase from porcine transition-stage enamel matrix and characterized it by partial protein sequencing. The enzyme was isolated from the neutral soluble enamel extract by successive ammonium sulfate precipitations, hydroxyapatite HPLC, reverse-phase HPLC, DEAE ion exchange, and affinity chromatography with a Benzamidine Sepharose 6B column. The intact protein and lysylendopeptidase-generated cleavage products were characterized by amino acid sequence analyses. Degenerate oligonucleotide primers encoding two of the polypeptide sequences were synthesized. In a complementary strategy, degenerate oligonucleotide primers were designed against highly conserved active-site regions of chymotrypsin-like proteinases. Both approaches yielded PCR amplification products that served as probes for screening a porcine enamel organ epithelia-specific cDNA library. The longest full-length clone is 1133 nucleotides and encodes a preproprotein of 254 amino acids. We designate this protein enamel matrix serine proteinase 1 or EMSP1. The active protein has 224 amino acids, an isotope-averaged molecular mass of 24.1 kDa, and an isoelectric point of 6.0. Multiple-tissue Northern analysis indicates that EMSP1 is a tooth-specific protein. Gelatin enzymography shows a dramatic increase in EMSP1 activity in the transition-stage enamel matrix. EMSP1 is most homologous to kallikriens and trypsins.
Threshold for Bone Resorption Induced by Continuous and Intermittent Pressure in the Rat Hard Palate
Authors: Sato T. , Hara T. , Mori S. , Shirai H. , Minagi S.
Published: January 2009

Osteoclastic bone resorption under the denture base has been considered to be influenced by mechanical force exerted through the denture base. However, no scientific evidence has been shown concerning whether osteoclastic bone resorption is a pressure-threshold-regulated phenomenon or merely a proportionally pressure-dependent phenomenon. In this study, a clear statistical criterion as an objective standard for the evaluation of histopathological bone resorption was established, and the relationship between the amount of continuous or intermittent compressive pressure exerted on the rat hard palate and induced osteoclastic bone resorption was studied based on this criterion. Eighty-five male rats of the Wistar strain, 15 weeks of age, were fitted with experimental dentures which were designed to exert a defined amount of continuous or intermittent compressive pressure on the intermolar region of the hard palate. No bone resorption was observed when continuous compressive pressure was << 1.96 kPa or when intermittent compressive pressure was << 9.8 kPa. In contrast, continuous compressive pressure ≧ 6.86 kPa or intermittent compressive pressure ≧ 19.6 kPa caused significant bone resorption in all rats studied. From these results, it was revealed that osteoclastic bone resorption under the denture base was a pressure-threshold-regulated phenomenon, and that the thresholds exist for the induction of bone resorption under the denture base by both continuous and intermittent compressive pressure, respectively. It was also clearly revealed from the results that the threshold for continuous compressive pressure is lower than that for intermittent compressive pressure.
Effects of Aged Fluoride-containing Restorative Materials on Recurrent Root Caries
Authors: Hsu C.-Y.S. , Donly K.J. , Drake D.R. , Wefel J.S.
Published: January 2009

Accumulated evidence has illustrated that secondary caries is the major reason for the failure of amalgam and resin composite restorations. The purpose of this study was to assess the cariostatic effects of aged fluoride-containing restorative materials on the formation of secondary root caries. Fifty sound human molars were selected and randomly assigned to five material groups: non-fluoride-containing amalgam (NA), fluoride-containing amalgam (FA), non-fluoride-containing composite (NC), fluoride-containing composite (FC), and glass-ionomer cement (GIC). After standardized class V cavity preparations and placement of restorations, teeth within each group were randomly divided into two subgroups, "non-aged" and "aged". The aged subgroup was immersed in an inorganic buffer solution for 2 wks before being thermocycled. After being thermocycled and subjected to four cycles of caries formation in a bacterial model system, the teeth were sectioned. Depths of outer lesions and areas of lesions on the cavity walls were measured by polarized light microscopy. The results showed that the FA and GIC groups, whether aged or not, had significantly smaller outer lesion depth than the non-fluoride-containing NA and NC groups. After aging, the FA group demonstrated significantly greater lesion depth (p = 0.0002), while the GIC group exhibited no significant changes in lesion depths. The NA group had a greater wall lesion area than the NC group, while both demonstrated no significant changes following 2 weeks of aging. The FA and GIC groups had similar inhibition areas along the cavity walls, whereas both inhibition areas increased significantly after the aging process. It is concluded that the fluoride-containing amalgam and the glass-ionomer cement, even after a two-week aging process, can still elicit a significant preventive effect on recurrent root caries in an in vitro bacterial model system.
Oral Streptococci... Products of Their Environment
Authors: Burne R.A.
Published: January 2009

Microbial biofilms form on oral surfaces. These biofilms usually exist in dynamic equilibria with host defenses and are compatible with maintenance of the integrity of the target tissues. Disease occurs when the composition and the metabolic activities of complex communities in biofilms are perturbed. These ecologically driven changes in oral biofilms result in increases in the proportions of pathogenic micro-organisms, which possess enzymatic and structural determinants that may render them more virulent than organisms associated with oral health. This brief review focuses on key environmental influences, and genetic and physiologic aspects of bacteria associated with the formation of dental caries, and attempts to identify some areas of oral microbiology in which interdisciplinary efforts will be essential for dissection of the molecular events controlling the development and persistence of pathogenic plaques. The focus is on strategies to enhance fundamental knowledge of oral biofilm composition, structure, and activities, with the rationale that broadly effective therapeutic strategies targeted at plaque physiology, or at biofilm development and persistence, can arise from such knowledge.
Flow Cytometry Analysis of Gingival and Periodontal Ligament Cells
Authors: Kuru L. , Parkar M.H. , Griffiths G.S. , Newman H.N. , Olsen I.
Published: January 2009

Gingival and periodontal ligament (PDL) fibroblasts are the major cellular components of periodontal soft connective tissues, but the precise differences between these cells are not yet known. In the present study, we have therefore examined the phenotypic and functional features of the cells obtained from gingival and PDL biopsy samples. Spindle-shaped cells characteristic of fibroblasts were the main cell type observed in vitro, although epithelial cells were also present in primary gingival cell cultures. Flow cytometry was used to measure the size and granularity of the cultured cells, and showed that the gingival fibroblasts were smaller and less granular compared with the PDL cells. The expression of certain key extracellular matrix (ECM) proteins, fibronectin, collagen type I, and tenascin was measured by flow cytometry. Analysis of the fluorescence profiles of these cultures showed that the majority of cells expressed fibronectin and that the average fluorescence intensity of this antigen in the PDL cells was higher than that in the gingival fibroblasts. Moreover, the fibronectin-positive PDL cells apparently comprised two subpopulations which expressed fibronectin at different levels, suggesting that the cells in the PDL cultures were functionally heterogeneous. The level of collagen type I was also found to be up-regulated in the PDL compared with the gingival cells and, as with fibronectin, was expressed at two different levels by subsets of the PDL cells. In contrast, tenascin was expressed at very similar levels by both the gingival fibroblasts and PDL cells. In addition, measurement of alkaline phosphatase, a marker enzyme for mineralized tissue-forming cells, showed that the PDL cells had higher activity than the gingival fibroblasts and that the alkaline phosphatase activity in the PDL cells was far more markedly up-regulated by dexamethasone. Our findings demonstrate that, despite their similar spindle-shaped appearance, fibroblasts derived from gingival and PDL tissues appear to display distinct functional activities which are likely to play a vital part in the maintenance of tissue integrity and regenerative processes.
A Five-year Multi-practice Clinical Study on Posterior Resin-bonded Bridges
Authors: De Kanter R.J.A.M. , Creugers N.H.J. , Verzijden C.W.G.J.M. , Van't Hof M.A.
Published: January 2009

Previous clinical observations have revealed that resin-bonded bridges for posterior tooth replacements are less retentive than anterior resin-bonded bridges. Improved bonding procedures and preparation designs, however, may have a positive effect on the functional durability of these restorations. The present study reports the final analysis of a randomized controlled clinical trial in which different designs of posterior resin-bonded bridges were evaluated for a period of at least 5 years. The operational hypothesis was that the bonding system and the preparation design used in posterior resin-bonded bridges have an influence on the survival and clinical functioning of these restorations. Survival in this study was defined at two levels: (1) 'complete' survival (survival without any debonding), and (2) 'functional' survival (survival including loss of retention on one occasion and successful rebonding of the original RBB without further debonding). With regard to 'complete' survival, no significant differences were found between the bonding systems used for adherence of the restorations to abutment teeth (etching/Clearfil F2, sandblasting/Panavia EX, and silica-coating/Microfill Pontic C). The variable 'preparation form' (conventional preparation form vs. modified preparation form) for complete survival was statistically in favor of the modified preparation form (62% vs. 46%), but did not influence the functional survival. With regard to 'functional' survival, the combination of silica coating and Microfill Pontic C was more retentive than the other bonding systems (90% survival vs. 72% and 75%, p < 0.01). Factor location was found to be highly significant for both survival levels [Cox's PH model, p = 0.0002 (Cox, 1972)]: The five-year 'complete' survival rates were 65% for maxillary restorations and 40% for mandibular restorations, while the five-year 'functional' survival rates were 89% and 68%, respectively. It is concluded that preparation of grooves in abutment teeth for posterior resin-bonded bridges is beneficial to their chance of survival. Resin-bonded bridges placed in the maxilla have a better prognosis than those made in the mandible. The bonding systems used in this study appear to have no influence on the chance of failure. In rebonded posterior resin-bonded bridges, the bonding system silica-coating/Microfill Pontic C was more retentive than the other systems tested.
Mercury in Biological Fluids after Amalgam Removal
Authors: Sandborgh-Englund G. , Elinder C.-G. , Langworth S. , Schütz A. , Ekstrand J.
Published: January 2009

Dental amalgam is the major source of inorganic mercury (Hg) exposure in the general population. The objective of the present study was to obtain data on changes in Hg levels in blood, plasma, and urine following removal of all amalgam fillings during one dental session in 12 healthy subjects. The mean number of amalgam surfaces was 18 (range, 13 to 34). Frequent blood sampling and 24-hour urine collections were performed up to 115 days after amalgam removal, and in eight subjects additional samples of plasma and urine were collected up to three years after amalgam removal. A transient increase of Hg concentrations in blood and plasma was observed within 48 hours after amalgam removal. In plasma, the peak concentrations significantly exceeded the pre-removal plasma Hg levels by, on average, 32% (1.3 nmol/L; range, 0.1 to 4.2). No increase in the urinary Hg excretion rate was apparent after amalgam removal. An exponential decline of Hg was seen in all media. Sixty days after the amalgam removal, the Hg levels in blood, plasma, and urine had declined to approximately 60% of the pre-removal levels. In seven subjects, who were followed for up to three years, the half-lives of Hg in plasma and urine were calculated. In plasma, a bi-exponential model was applied, and the half-life was estimated at median 88 days (range, 21 to 121). The kinetics of Hg in urine (nmol/24 hrs) fit a mono-exponential model with a median half-life of 46 days (range, 35 to 67). It is concluded that the process of removing amalgam fillings can have a considerable impact on Hg levels in biological fluids. After removal, there was a considerable decline in the Hg levels of blood, plasma, and urine, which slowly approached those of subjects without any history of amalgam fillings.
Comparison between Er:YAG Laser and Conventional Technique for Root Caries Treatment in vitro
Authors: Aoki A. , Ishikawa I. , Yamada T. , Otsuki M. , Watanabe H. , Tagami J. , Ando Y. , Yamamoto H.
Published: January 2009

Effective ablation of dental hard tissues by means of the erbium-doped:yttrium-aluminum garnet (Er:YAG) laser has been reported recently, and its application to caries removal and cavity preparation has been expected. However, few studies have investigated the capability of the Er:YAG laser to treat caries. In the present study, the effectiveness of caries removal by using an Er:YAG laser in vitro was compared with that of conventional mechanical treatment. Thirty-one extracted human teeth with root caries were used. Half of the caries in each tooth was treated with the Er:YAG laser, and the other was removed with a conventional bur or was left untreated as a control. Laser treatment was performed by means of a combination of contact and non-contact irradiation modes with cooling water spray, with a new fiber delivery and contact probe system. Conventional bur treatment was conducted by means of a low-speed micromotor. Measurements of the time required for caries removal, histopathological observations of decalcified serial sections, scanning electron microscope (SEM) observations, and hardness measurements of the treated cavity-floor dentin were performed for each treatment. Due to the careful irradiation technique, a longer treatment time was required for the complete removal of carious dentin by the Er:YAG laser. However, the Er:YAG laser ablated carious dentin effectively with minimal thermal damage to the surrounding intact dentin, and removed infected and softened carious dentin to the same degree as the bur treatment. In addition, a lower degree of vibration was noted with the Er:YAG laser treatment. The SEM examination revealed characteristic micro-irregularities of the lased dentin surface. Our results show that the Er:YAG laser system is promising as a new technical modality for caries treatment.
Activation of the Immune System and Systemic Immune-Complex Deposits in Brown Norway Rats with Dental Amalgam Restorations
Authors: Hultman P. , Lindh U. , Horsted-Bindslev P.
Published: January 2009

Dental amalgam restorations are a significant source of mercury exposure in the human population, but their potential to cause systemic health effects is highly disputed. We examined effects on the immune system by giving genetically mercury-susceptible Brown Norway (BN) rats and mercury-resistant Lewis (LE) rats silver amalgam restorations in 4 molars of the upper jaw, causing a body burden similar to that described in human amalgam-bearers (from 250 to 375 mg amalgam/kg body weight). BN rats with amalgam restorations, compared with control rats given composite resinous restorations, developed a rapid activation of the immune system, with a maximum 12-fold increase of the plasma IgE concentration after 3 wks (p < 0.001; Mann-Whitney's test). LE rats receiving amalgam restorations showed no significant increase of plasma IgE (p > 0.05). After 12 wks, BN rats with amalgam restorations showed significantly increased (p < 0.05) titers of immune-complex (IC) deposits in the renal glomeruli and in the vessel walls of internal organs. These rats also showed a significant (p < 0.05), from six- to 130-fold, increase in tissue mercury concentration in the concentration order kidney > spleen > cerebrum occipital lobe > cerebellum > liver > thymus, and the tissue silver concentration was significantly (p < 0.05) increased from three- to 11-fold. Amalgam-implanted BN rats showed a significant (p < 0.05) increase in copper concentration in the kidney and spleen, and in kidney selenium concentration. We conclude that dental amalgam restorations release substantial amounts of their elements, which accumulate in the organs and which, in genetically susceptible rats, give rise to activation of the immune system and systemic IC deposits.
Effects of Dopaminergic Drugs, Occlusal Disharmonies, and Chronic Stress on Non-functional Masticatory Activity in the Rat, Assessed by Incisal Attrition
Authors: Gómez EM , Areso M.P. , Giralt M.T. , Sainz B. , García-Vallejo P.
Published: January 2009

Observational methods and the recording of nonspecific jaw movements or masticatory muscle activity have been used to evaluate oral parafunctional movements in animal models of bruxism. In this study, we have used a new approach in which the non-functional masticatory activity in the rat was assessed by the measurement of incisal attrition, with the aim of investigating the role of diverse factors involved in the etiology of bruxism. We quantified the attrition rate weekly by making superficial notches in the lower incisors and measuring the distances to the incisor edges. Repeated stimulation of the dopaminergic system with apomorphine led to an enhancement of the non-functional masticatory activity (p < 0.0001). The severity of the apomorphine-induced oral behavior was positively correlated (rs = 0.69, p < 0.01) with an increase in the incisal attrition rate (20.9%, p < 0.0001). Apomorphine-induced non-functional masticatory activity was strongly enhanced by the placement of an acrylic cap on both lower incisors (306%, p < 0.0001), but not by the cutting of a lower incisor. Repeated cocaine administration also increased the attrition rate (22.5%, p < 0.0001). However, neither chronic blockade of dopaminergic receptors with haloperidol, nor its withdrawal, modified attrition. In addition, since emotional disturbances are considered to be causal factors of bruxism, we tested whether experimental stress might accelerate tooth wear. Exposure to two different chronic stress regimes did not induce significant changes in incisal attrition. Moreover, exposure to chronic stress after the withdrawal of chronic haloperidol treatment did not alter attrition either. These results partially support the role of the central dopaminergic system in bruxism and suggest that stress, in general, may not be a relevant factor in tooth wear.
A Novel Organ Culture Method to Study the Function of Human Odontoblasts in vitro: Gelatinase Expression by Odontoblasts is Differentially Regulated by TGF-β1
Authors: Tjäderhane L. , Salo T. , Larjava H. , Larmas M. , Overall C.M.
Published: January 2009

Odontoblasts cannot be cultured by traditional cell culture methods, thus restricting in vitro studies. Here we present an organ culture method for human odonto-blasts that utilizes the pulp chamber as a culture crucible. Crowns of human third molars were dissected, pulp was gently removed, and the odontoblasts attached to and in the walls of the pulp chambers were cultured in serum-free OPTI-MEM medium, or DMEM/Ham's F12 medium containing 10% serum. Pulp tissues were cultured separately. Cell content and morphology were analyzed by SEM, and the removed pulps were examined by light microscopy. Proteins secreted into the medium with or without TGF-β1 supplementation were metabolically labeled with [35S]methionine, and the total protein content was assessed by TCA precipitation and SDS-PAGE/fluorography. To assess the role of gelatinolytic enzymes on dentin matrix remodeling, we used enzymography to analyze the effect of TGF-β1 on gelatinase A and B expression. SEM revealed odontoblasts in pulp chambers after 5 days of culture, with only few or no fibroblasts, and no alterations in the odontoblast cell morphology or differences between the cells cultured in serum-free and serum-containing media. Rarely were any odontoblasts present in pulp tissue. Radiolabeling revealed protein synthesis and secretion until day 6 in both the odontoblast and pulp cultures, with no marked differences between TGF-β1-treated and control cultures. The level of gelatinase A remained constant up to 7 days, while gelatinase B expression was always low and decreased with time in culture. However, gelatinase B levels were markedly increased upon TGF-β1 treatment of cells and remained high to day 7. The results suggest that this method provides a novel technique for the study of human odontoblasts in vitro and that odontoblasts can be cultured even in serum-free conditions.
Changes in the Expression of Extracellular Matrix (ECM) and Matrix Metalloproteinases (MMP) of Proliferating Rat Parotid Acinar Cells
Authors: Broverman R.L. , Nguyen K.-H.T. , da Silveira A. , Brinkley L.L. , Macauley S.P. , Zeng T. , Yamamoto H. , Tarnuzzer R.W. , Schultz G.S. , Kerr M. , Humphreys-Beher M.G.
Published: January 2009

Tissue morphogenesis, development, and maintenance of function are mediated by signals generated through the composition of the extracellular matrix. The regulation of the composition of matrix is determined by enzymes specific for their degradation, the matrix metalloproteinases. Chronic injections of the β-adrenergic receptor agonist, isoproterenol, result in a non-neoplastic hypertrophy and hyperplasia of the rat parotid gland. The activity of matrix metalloproteinases, as measured by gelatin zymography and enzymatic digestion of Azocoll® substrates by gland lysates, decreased significantly (P < 0.05) following 24 hrs of agonist treatment, and slowly recovered to control values by 6 days of treatment. Daily administration of the broad-spectrum matrix metalloproteinase inhibitor Galardin® for 3 days in combination with isoproterenol resulted in enhanced gland hypertrophy compared with that produced by isoproterenol alone. Given alone, Galardin® also caused hypertrophy. The relative abundance of mRNA for the extracellular matrix molecules, collagens I and III and fibronectin, declined rapidly following the initiation of β-agonist treatment in vivo, while laminin B1 and B2 mRNA levels increased initially before declining below control levels. These changes in patterns of mRNA levels also were observed in the concentrations of glandular protein when Western dot blot analysis of collagens I and III and laminin, respectively, was used. The importance of laminin, in vivo, was demonstrated by co-injection of anti-laminin antibody along with isoproterenol, which resulted in the inhibition of β-agonist-induced parotid gland hypertrophy and hyperplasia. These data suggest that modulation of the ECM is associated with isoproterenol-induced salivary gland hypertrophy and hyperplasia. It is likely that this modulation of the ECM takes place through transcriptional regulation of some ECM genes and regulation of matrix-degrading enzyme activity.
Laminin y2 Expression is Developmentally Regulated during Murine Tooth Morphogenesis and is Intense in Ameloblasts
Authors: Sahlberg C. , Hormia M. , Airenne T. , Thesleffl I.
Published: January 2009

Mutations in the laminin y2 gene cause junctional epidermolysis bullosa, and enamel hypoplasias are frequently seen in these patients. Laminin γ 2 is one of the three polypeptide chains forming the basement membrane glycoprotein laminin-5. We have localized the expression of the laminin y 2 gene by in situ hybridization during mouse tooth development from early morphogenesis to completion of crown development. The expression was restricted to epithelial cells. During the early morphogenesis of the tooth germ, laminin y 2 was expressed by the outer dental epithelium and by the stellate reticulum cells. No expression was detected in the cells of the inner dental epithelium giving rise to ameloblasts. The pre-ameloblasts remained negative during the early bell stage, but, interestingly, expression was very prominently upregulated as the cells differentiated into ameloblasts. This upregulation appeared to coincide with the start of enamel matrix secretion. The ameloblasts expressed laminin γ2 intensely throughout the period of active enamel deposition. The expression continued at a lower level in the maturation-stage ameloblasts covering the enamel surface. Immunolocalization of laminin-5 with polyclonal antibodies indicated that the protein formed a continuous lining at the basal surfaces of the cells expressing the laminin y 2 transcripts. We suggest that the role of laminin-5 during enamel formation may be to strengthen the anchorage of the ameloblasts to the enamel matrix, and that the pathogenesis of enamel hypoplasias in cases of laminin-5 mutations could be associated with detachment of the ameloblast cell layer from the enamel surface.
Synthetic Integrin-binding Peptides Promote Adhesion and Proliferation of Human Periodontal Ligament Cells in vitro
Authors: Grzesik W.J. , Ivanov B. , Robey F.A. , Southerland J. , Yamauchi M.
Published: January 2009

Periodontal ligament (PDL) cells have been shown to express several integrins (αv, α5, β1, β3) that use RGD (arginine-glycine-aspartic Acid)-dependent mechanisms for the recognition and binding of their ligands. The objective of this study was to evaluate the effects of certain integrin-binding cyclic and linear synthetic RGD-containing peptides on PDL cells' adhesion, proliferation, and de novo protein synthesis in vitro. Fifth passages of normal human PDL cells established from teeth extracted from patients (ages 12 to 14) for orthodontic reasons were used for all experiments. Synthetic peptides containing the EPRGDNYR sequence in two different spatial conformations (linear and cyclic) were covalently attached to bovine serum albumin (BSA). Type I collagen, EPRGDNYR-BSA conjugates, 1:1 mixtures of type I collagen and conjugates, as well as BSA (a negative control) were coated on bacteriological plastic and evaluated for their attachment-promoting activities. In addition, the effects of these substrates on cell proliferation were evaluated by [3H]thymidine incorporation by the PDL cells. For attachment and spreading, the cyclic forms of EPRGDNYR-BSA conjugate and type I collagen were most potent, followed by linear EPRGDNYR-BSA conjugate. The effects of all collagen/conjugate mixtures were equivalent to that of type I collagen except for the collagen/linear EPRGDNYR-BSA mixture, which was less potent. The cyclic EPRGDNYR-BSA conjugate was the most effective substrate to stimulate cell proliferation, and it was followed in potency by the linear peptide-BSA conjugate. Collagen alone did not stimulate [3H]thymidine incorporation above the control level. Mixtures of collagen with all of the conjugates showed stimulatory effects similar to that of the cyclic peptide-BSA conjugate. No significant differences in de novo protein synthesis were detected. These results suggest that the synthetic RGD-containing peptides attached to a carrier are potent ligands for the human PDL cells, and that they could provide a basis for the development of new strategies aimed at the regeneration of the periodontium.
Structural Integrity of Resin-modified Glass Ionomers as Affected by the Delay or Omission of Light Activation
Authors: de Gee A.J. , Leloup G. , Werner A. , Vreven J. , Davidson C.L.
Published: January 2009

Since light activation of resin-modified glass ionomers as a means of polymerizing the HEMA is usually done shortly after mixing occurs, the acid-base reaction will proceed mainly within a formed HEMA-polymer matrix. Delaying or omitting light activation may alter the structure and consequently its integrity. The aim of this study was to investigate the effect on the structural integrity of Fuji II LC, Photac-Fil, and Vitremer by delaying or omitting light initiation as compared with the integrity when light activation is performed 2 min after mixing occurs. We evaluated integrity by three-body wear experiments, conducted 8 hrs after sample preparation, to establish the integrity in the early phase of hardening, as well as after 1 wk and after 4 mos, to follow the materials throughout the process of maturation. When light activation was delayed for 1 hr, the structural integrity of Fuji II LC and Photac-Fil improved significantly in the early stages of hardening. In the case of Vitremer, an hour's delay of light activation significantly decreased integrity, which declined further when light activation was omitted. Fuji II LC was not affected by the omission of light activation, while Photac-Fil was markedly weakened. After 4 mos of aging, most of the samples of each product which had been cured by the different methods attained equal integrity, with the exception of the non-light-activated Vitremer samples, which remained weaker. We concluded that the structural integrity of resin-modified glass-ionomer cements benefits from a chemical integration of the polyalkenoate and poly-HEMA networks, as in Vitremer. Improvement in the structural integrity in the early phase for cements with a mechanical entanglement of the matrices, as in Fuji II LC and Photac-Fil, requires an acid-base reaction, a considerable portion of which may take place before activation of the HEMA polymerization.
Serum or Growth Factor Deprivation Induces the Expression of Alkaline Phosphatase in Human Gingival Fibroblasts
Authors: Abe T. , Hara Y. , Abe Y. , Aida Y. , Maeda K.
Published: January 2009

We have previously reported that the increased expression of alkaline phosphatase (ALP) activity is a phenotypic characteristic of gingival fibroblasts present in chronic inflammatory periodontal lesions. We hypothesized that ALP might be induced in gingival fibroblasts by environmental factors. In the present study, we investigated the factors influencing the induction of ALP expression in fibroblasts derived from healthy human gingiva. The withdrawal of serum from confluent cultures of fibroblasts increased the number of cells positive for ALP activity and protein, without their proliferation. Suramin, a growth factor antagonist, induced ALP expression in cells cultured with serum. Serum re-addition or exposure to platelet-derived growth factor-AB and/or insulin-like growth factor I suppressed ALP induction and caused cell growth. ALP-positive cells could survive for up to 6 weeks after serum deprivation, a condition inducing cell death via apoptosis. These results demonstrate that serum or growth factor deprivation induces the expression of ALP in gingival fibroblasts. ALP expression is negatively correlated with cell growth and accompanied by a change into serum-growth-factor-independent survival.
Salivary Secretions: Narcolepsy and Central Nervous System Stimulants
Authors: Nordgarden H. , Lamkin M. , Oppenheim EG , Storhaug K. , Jensen J.L.
Published: January 2009

In an ongoing attempt to develop a model to study the influence of various diseases and drugs on saliva, we studied persons with narcolepsy treated with central nervous system stimulants. The aim was to study the secretion of salivary proteins in narcolepsy in the presence and absence of central nervous system stimulants. For this purpose, two proteins synthesized in acinar cells, acidic proline-rich proteins (PRPs) and statherin, were selected. Persons with narcolepsy treated with central nervous system stimulants only were included, n = 12, ages 14 to 68, seven females. Citric-acid-stimulated parotid and submandibular/sublingual saliva samples were collected from these persons during medication, after a drug-free period of one week, at least two weeks after the drug had been re-introduced, and from a matched healthy control group. PRP and statherin concentrations were determined by means of reversed-phase and anion exchange chromatography, respectively. Both concentration and output of statherins and PRPs were increased in persons with narcolepsy receiving central nervous system stimulants compared with healthy control individuals. When the drug was withdrawn, salivary flow rates were not influenced. In contrast, withdrawal of the drug led to a significantly decreased secretion of PRPs and statherin. The reduced protein secretion may reflect decreased adrenergic activation in narcolepsy, to be reversed by treatment with central nervous system stimulants. It can be concluded that measurements of both salivary fluid and salivary proteins may be necessary for an overall evaluation of the effects of a given drug or disease on salivary secretion.
Psychophysiological Assessment of Stress in Chronic Pain: Comparisons of Stressful Stimuli and of Response Systems
Authors: Ohrbach R. , Blascovich J. , Gale E.N. , McCall W.D. , Dworkin S.F.
Published: January 2009

Due to disparate findings across the published studies, the stress-hyperactivity hypothesis has never been fully accepted as a causal mechanism for chronic muscle pain. Two recent comprehensive reviews of the psychophysiological studies of chronic pain came to opposite conclusions about the viability of the hypothesis, which stemmed from differing importance placed on the experimental methodology: the adequacy of stress manipulation. The present study tested the hypotheses that the adequacy of stress manipulation is influenced by stress stimuli type, degree of personal relevance, and selection of criterion for verification of stress experience, and that these factors have a measurable impact on the related physiological responses in a manner that is consistent with a theory of stress applicable to clinical stress disorders. The three factors investigated were: task (imagery, reaction time), relevance (high, low), and manipulation criterion (autonomic, self-report). The tasks were presented to 16 chronic pain patients while muscle, electrodermal, and self-report responses were recorded. Reaction-time tasks and high-relevance conditions led to high muscle and electrodermal responses. Only the high-relevance imagery, however, produced high self-reported distress. Consistent with other research, the present overall data demonstrated differing physiological profiles for different stimuli types. More importantly, these data suggest that the manipulation type and the manipulation criterion influence outcomes of experimental tests of stress on physiological systems, which may directly lead to contrasting conclusions about causal relations between stress and chronic pain conditions.
Anthropology, Tooth Wear, and Occlusion ab origine
Authors: Young William George
Published: January 2009

The purpose of this essay is to emphasize that Anthropology, the study of man in his environments, is a potent tool for scientific discovery and inspiration in dental science. It attempts to capture flashes of creative anthropological insight which have illuminated studies of tooth wear and occlusion in the past. While it documents contributions, understandings, and misunderstandings from Australian and New Zealand dentists, it is not a hagiography. The real saint of this essay is the Australian aborigine. For when men and women are understood in their environments, much is learned from them which challenges preconceptions of our dental science culture. The essay concludes that new, contemporary Australian culture needs to be studied by anthropological approaches if we are to understand how dental erosion is exacerbating tooth wear and damaging the occlusions of contemporary Australians. Much remains to be discovered about contemporary lifestyles, habits, and diets that lead to dental erosion, the principal cause of contemporary tooth wear in this part of the world.
Rheological Properties of Elastomeric Impression Materials Before and During Setting
Authors: McCabe J.F. , Arikawa H.
Published: January 2009

In this study, we examined the rheological properties of elastomeric impression materials, both before and during setting, to assess the clinical significance of certain key characteristics such as viscosity, pseudo-plasticity, and the rate of development of elasticity. The hypothesis to be tested was that monitoring the change in tan 8 is the most appropriate means of monitoring the setting characteristics of elastomers. The loss tangent (tan 8) and the dynamic viscosity (η') for five impression materials (both unmixed pastes and mixed/setting materials) were measured by means of a controlled-stress rheometer in a cone/plate configuration. For unmixed pastes, tests were performed at various frequencies (0.1 to 10 Hz) and torques (from 1 to 50 x 10-4 Nm), while testing on setting materials was performed at constant frequency (1 Hz) and torque (3 x 10-3 Nm). Most base and catalyst pastes were pseudoplastic before being mixed. Immediately after being mixed, the polyether (tan 8 = 9.85) and polysulfide (tan 8 = 9.54) elastomers showed tan 8 markedly higher than those of other mixed materials (tan 8 = 4.96 to 3.01). The poly-vinylsiloxane elastomers showed lower initial tan 8, which rapidly reduced even further with time. This suggests that these materials should be used as soon as possible after being mixed. The polyether elastomer had a comparatively long induction period during which the tan 8 remained at a high value. These characteristics are thought to be key factors in controlling clinical efficacy and therefore support the hypothesis that monitoring tan 8 is an appropriate method for evaluating the setting characteristics of elastomers. One limitation was that the controlled-stress rheometer was unable to monitor rheological properties through to completion of setting.