bluuebunny/crossref_metadata_2025 huggingface dataset:
Inhibition of Streptococcus mutans Adsorption to Hydroxyapatite by Low-molecular-weight Chitosans
Authors: Tarsi R. , Muzzarelli R.A.A. , Guzmàn C.A. , Pruzzo C.
Published: January 2009

The role of Streptococcus mutans in the initiation of dental caries has been recognized and attributed, at least in part, to its ability to colonize the tooth surface. Therefore, factors which prevent S. mutans attachment to hydroxyapatite (HA) are of considerable interest for the prophylaxis of this infectious disease. Chitosan, a chitin derivative by N-deacetylation, is an interesting candidate in this respect, since it stimulates the ordered regeneration of oral soft tissues, prevents the deleterious action of organic acid, and exhibits bactericidal action against several pathogens. In the present work, the efficacy of a low-molecular-weight chitosan (LMWC) and its derivatives N-carboxymethyl chitosan (NCMC) and imidazolyl chitosan (IMIC) in preventing S. mutans attachment to HA beads was assessed. The effects of chitosan on both sucrose-dependent and -independent adherence were evaluated. In both cases, when saliva-coated or uncoated HA beads were treated with any of the chitosans, a reduction in S. mutans adsorption ranging from 47 to 66% was observed. When HA beads were coated with saliva after the treatment with chitosan, neither carbohydrate caused a statistically significant reduction in S. mutans adsorption, suggesting that saliva deposition restores HA binding properties. Bacteria grown in the presence of chitosan sub-minimal inhibitory concentrations (sub-MICs) ranging from 12 to 500 ug mL-1 adsorbed poorly to HA and exhibited a lower affinity toward xylene than untreated controls. In the presence of chitosan sub-MICs up to 60 ug mL-1, an increase in the percentage of detached bacteria from two- to nine-fold was observed. The desorptive effect of chitosan was weaker when S. mutans had adhered to saliva-coated HA in the presence of sucrose. These results demonstrate that the presence of minor amounts of modified chitosans prevents S. mutans adsorption to HA and suggest that colonization of the tooth surface might be impaired by the use of toothpastes, mouthrinses, or chewing gums containing any of the tested polysaccharides.
Morphometry of the Cranial Base in Subjects with Class III Malocclusion
Authors: Singh G.D. , McNamara J.A. , Lozanoff S.
Published: January 2009

The significance of the cranial base in the development of Class III malocclusion remains uncertain. The purpose of this study was to determine whether the form of the cranial base differs between prepubertal Class I and Class III subjects. Lateral cephalographs of 73 children of European-American descent aged between 5 and 11 years with Class III malocclusion were compared with those of their counterparts with a normal, Class I molar occlusion. The cephalographs were traced, checked, and subdivided into seven age- and sex-matched groups. Average geometries, scaled to an equivalent size, were generated based on 13 craniofacial landmarks by means of Procrustes analysis, and these configurations were statistically tested for equivalence. Bivariate and multivariate analyses utilizing 5 linear and angular measurements were undertaken to corroborate the Procrustes analysis. Graphical analysis, utilizing thin-plate spline and finite element methods, was performed for localization of differences in cranial base morphology. Results indicated that cranial base morphology differed statistically for all age-wise comparisons. Graphical analysis revealed that the greatest differences in morphology occurred in the posterior cranial base region, which generally consisted of horizontal compression, vertical expansion, and size contraction. The sphenoidal region displayed expansion, while the anterior regions showed shearing and local increases in size. It is concluded that the shape of the cranial base differs in subjects with Class III malocclusion compared with the normal Class I configuration, due in part to deficient orthocephalization, or failure of the cranial base to flatten during development.
Effects of Calcium and Calmodulin on the Binding of Rat Parotid Secretion Granules to the Plasma Membrane
Authors: Watkins D.T. , Cooperstein S.J.
Published: January 2009

Since numerous studies suggest that Ca++and calmodulin may modulate the fusion of secretion granules to the plasma membrane which takes place in exocytosis, we have examined the role of calcium and calmodulin in the binding of isolated parotid secretion granules to plasma membrane vesicles.125I-labeled inside-out plasma membrane vesicles were incubated with secretion granules, the mixture was layered over 20% sucrose, the gradient was centrifuged, and the amount of125I in the granule pellet was determined. Addition of Ca++(20 nM to 10 pM) produced a concentration-dependent increase in the binding of125I-labeled plasma membrane vesicles to the secretion granules, reaching a maximum value at 10 μM free Ca++; half-maximal binding occurred at 400 nM. Neither right-side-out parotid plasma membrane vesicles nor inside-out pancreatic islet plasma membrane vesicles bound to granules in the presence of 1 μM Ca++. Calmodulin produced a concentration-dependent increase in binding above that of Ca++alone, and this effect was inhibited by the calmodulin antagonists, trifluoperazine and calmidazolium. Incubation of secretion granules with octadecylrhodamine B (R18)-loaded inside-out plasma membrane vesicles and 2 pM Ca++ caused de-quenching of fluorescence, indicating that the lipids in the granule membrane and the plasma membrane had intermixed. Added calmodulin increased the fluorescence two-fold above that with Ca++alone. These results suggest that Ca++and calmodulin may play a role in parotid gland exocytosis by modulating the interaction between the secretion granules and plasma membrane.
Cloning and Expression Analysis of the Bovine Dentin Matrix Acidic Phosphoprotein Gene
Authors: Hirst K.L. , Ibaraki-O'Connor K. , Young M.F. , Dixon M.J.
Published: January 2009

The dentin matrix acidic phosphoprotein gene has been mapped to human chromosome 4q21 and mouse chromosome 5q21. Expression studies have implicated a role for this gene in the mineralization of dentin. In the current investigation, a cDNA encoding bovine dentin matrix acidic phosphoprotein has been cloned and sequenced. A comparison of the bovine gene with its rat counterpart has indicated that the genes are conserved (67.4% identity; 79.5% similarity), particularly in the region of presumed functional elements such as the hydrophobic signal peptide sequence, the cell attachment Arg-Gly-Asp tripeptide, and numerous serine residues which are likely candidates for phosphorylation. Zoo blot analysis further indicated that a similar gene is found in all mammalian species tested, but not in chicks. However, Northern analysis has indicated that in the cow the message is detectable at high levels in fetal bovine brain and cultured long bone as well as in odontoblasts. These results support a potential role for dentin matrix acidic phosphoprotein in dentinogenesis.
An Estimation of the Size Distribution of Amalgam Particles in Dental Treatment Waste
Authors: Letzel H. , de Boer EA , Van T Hof M.A.
Published: January 2009

Regulations have been adopted in several countries of the European Union which prescribe that dental treatment waste water must be discharged via an amalgam separator device. Since the effectivity of the device strongly depends on the size of the amalgam waste particles, this size was evaluated in waste water samples from eight dental offices. Per sample, all solid particles were separated from the waste water by pressure filtration, then dried and divided into six fractions by being sieved over five sieves with decreasing mesh width. Of the particles in each fraction, the density was determined by picnometry, the mass by weighing, and the area and width by image analysis. For this analysis, width was defined as the dimension perpendicular to the length of the particles. By combining the density, area, and width determinations of all fractions, we obtained mass distributions per waste particle width of the samples. The proportional amalgam mass of the distributions was estimated with the measured density of the particle fractions and with a number of assumptions for the density of amalgam particles only and of other waste particles only. Each waste sample has its own characteristics with respect to the mass and density of the particle fractions. The size distribution of waste particles has a bimodal shape and consists of a distribution of small (width, 2 to 90 pm) and large particles (width, 160 to 5500 μm). For small particles with a width up to 60 μm, the influence of the assumptions on the estimation of the proportion amalgam of the waste mass distribution is minor when compared with the sampling error. By averaging the estimations over the samples, one can estimate the weight of amalgam particles with a width < 10 μm and < 50 μm, respectively, between 4 and 15% and between 15 and 30%. The smallest particles comprising 5% of the amalgam mass have an estimated width of up to 5 to 15 pm.
Effects of Food Texture and Sample Thickness on Mandibular Movement and Hardness Assessment during Biting in Man
Authors: Peyron M.A. , Maskawi K. , Woda A. , Tanguay R. , Lund J.P.
Published: January 2009

This study was designed to investigate the relationship among jaw movements, physical characteristics of food, and sensory perception of hardness in man. Vertical movements of the mandible were recorded with an infrared tracking device in humans during biting on two test foods, carrot and cheese. Samples of standard length (2 cm) and width (2 cm) were prepared in three different thicknesses (0.5, 1.0, and 1.5 cm). Nine subjects were asked to perform two types of bite with their incisor teeth. In the first, they cut through the food, then stopped and spat out the pieces (bite alone); in the second, biting was followed by mastication and swallowing (bite+chew). The 12 conditions (thickness x3, food x2, and bite x2) were presented in a random order within each block, and blocks were repeated five times (60 trials per subject). Subjects also estimated the hardness of the samples twice for each condition on visual analogue scales (VAS) 100 mm long. The duration, vertical amplitude, and maximum vertical velocity of the mandible during biting were calculated by computer for the three phases of the movements (opening, and fast and slow closing). Multilevel statistical models were used for data analysis. The estimated hardness scores associated with the first bite of thin carrot (59.0 VAS units) was significantly greater than for cheese (16.8 VAS units). The type of bite had no significant effect on these scores, but the estimate of hardness was significantly greater for the thickest sample (+13.3 VAS units). Food type had its strongest effect on the slow-closing phase. In particular, the peak velocity that followed the fracturing of the food sample was much greater for carrot than for cheese (thin, 34.1 mm.s-1 vs. 26.6 mm.s-1), and the difference between foods increased with thickness. The amplitude of opening was significantly greater for the thickest sample than for the other two. There were no significant relationships between VAS scores and the movement parameters. These results suggest that, when humans bite food: (1) changing the thickness of food has a greater effect on movement parameters than changing from soft to hard food, (2) the parameters of biting change little if biting is followed by mastication, (3) hardness perception is dependent on the thickness of food, (4) hardness perception is not different when food is removed from the mouth than when it is chewed and swallowed, and (5) there is no relationship between any of the parameters of movement that change with food type and the perceived hardness of food.
The Selective Capsaicin Antagonist Capsazepine Abolishes the Antinociceptive Action of Eugenol and Guaiacol
Authors: Ohkubo T. , Shibata M.
Published: January 2009

The dental phenolic medicaments, eugenol and guaiacol, are partly similar in chemical structure to capsaicin, the pungent constituent of chili peppers, which selectively activates sensory neurons via a specific receptor. We have previously demonstrated that these phenolic compounds show capsaicin-like action. In the present study, an attempt was made to investigate the possibility that these compounds interact with the same cellular site as capsaicin, by using capsazepine, a selective and competitive anta-gonist of capsaicin. Intrathecal (i.t.) treatment with eugenol (12.5 to 50 μg), guaiacol (25 to 150 ug), or capsaicin (1 to 4 ug) for 24 h dose-dependently inhibited the formalin-induced nociceptive response. Capsazepine (5, 10 μg, i.t.) shifted these dose-response curves in parallel to the right. Similarly, capsazepine abolished antinociceptive effects of eugenol (50 μg), guaiacol (150 μg), or capsaicin (2 μg) in the acetic acid writhing test. These results suggest that eugenol and guaiacol may exert their antinociceptive effects via the capsaicin receptor located on sensory terminals in the spinal cord.
Activation and Novel Processing of Matrix Metalloproteinases by a Thiol-proteinase from the Oral Anaerobe Porphyromonas gingivalis
Authors: DeCarlo A.A. , Windsor L.J. , Bodden M.K. , Harber G.J. , Birkedal-Hansen B. , Birkedal-Hansen H.
Published: January 2009

A critical outcome of periodontal disease is degradation of the collagenous periodontal ligament that connects teeth to bone in the dental arch. Periodontal diseases occur in response to bacterial colonization of the teeth, but their molecular pathogenesis is still speculative. One family of enzymes, known as the matrix metalloproteinases (MMPs), has been implicated in the degradation of the periodontal ligament. MMPs, which are also suspected to play a role in many other physiologic and pathologic remodeling processes, can be secreted by epithelial cells surrounding the teeth and are found in relative abundance in tissues and fluids near periodontally diseased sites. Since most MMPs are secreted as inactive zymogens which may be activated by limited proteolysis, it has been suggested that proteinases expressed by the infecting periodontal pathogens might activate latent host MMPs to initiate or accelerate degradation of the collagenous periodontal ligament. The aim of this work was to examine interactions between purified host MMPs and bacterial proteinase. In this article, we demonstrate that a proteinase isolated from the periodontopathogen Porphyromonas gingivalis can activate MMP-1, MMP-3, and MMP-9 and can catalyze the superactivation of MMP-1 by MMP-3. Activation of these MMPs is demonstrated to result from initital hydrolysis within their propeptide. Also, for MMP-1 and MMP-9, the P. gingivalis proteinase cleaves the MMP propeptide following a lysine residue at a previously unreported site which, for both MMPs, is one residue NH2-terminal to the known autocatalytic cleavage site. These data describe a mode of virulence for the periodontopathogen Porphyromonas gingivalis that involves activation of host-degradative enzymes.
The Association Among Occlusal Contacts, Clenching Effort, and Bite Force Distribution in Man
Authors: Kikuchi M. , Korioth T.W.P. , Hannam A.G.
Published: January 2009

The contact area during habitual biting can vary according to the activity of the jaw musculature. Forceful masticatory muscle activity may also induce deformations of the dento-alveolar tissues and the supporting skeleton, yielding various tooth loads despite an apparently even distribution of tooth contacts. To investigate this variability, we measured bite forces simultaneously at multiple dental sites during maximum-effort clenching tasks. In each of four healthy adults with complete natural dentitions, four strain-gauge transducers in the right side of an acrylic maxillary appliance occluded with the lower canine, second premolar, and first and second molars. These, and matching contralateral contacts, were balanced by means of articulating paper and a force monitor (type F appliance). Bite forces were recorded when the subjects, without visual feedback, clenched maximally on the appliance. Similar recordings were made when contralateral molar and all contralateral contacts were removed (type R and type U appliances, respectively). Although the relation between individual forces often changed during the initial increase in force, it was generally constant around the maximum. The maximum forces at the four dental locations varied in distribution between subjects, but were characterized by posteriorly increasing forces. Forces in the anterior region (especially at the canine) significantly increased (up to 10 times) when clenching took place on unilateral contacts only (type U) as compared with fully balanced ones (type F). Bite force distribution thus changed with biting strength and the location of occlusal contacts. Increased force in the canine region during unilateral clenching seems related to the pattern of jaw muscle co-activation and the physical properties of the craniomandibular and dental supporting tissues which induce complex deformations of the lower jaw.
Capsaicin-sensitive Aδ Fibers in Cat Tooth Pulp
Authors: Ikeda H. , Tokita Y. , Suda H.
Published: January 2009

How close a correlation there is between the conduction velocity and receptive properties of pulpal nerve fibers is still unclear. Our specific aims were to confirm whether: (1) capsaicin affects not only polymodal C fibers but A8 fibers as well, and (2) Aδ polymodal nociceptors exist in the tooth pulp. A total of 139 functional single cat tooth pulp nerve fibers was isolated for analysis, of which 21 were Ap, 37 C, and 81 AS fibers. The A8 fibers were divided into two groups: One (n = 38) consisted of those fibers whose conduction velocities were more than 2.0 m/s both inside and outside the tooth pulp, and the other (n = 43) consisted of those fibers whose intrapulpal conduction velocities were less than 2.0 m/s, with extrapulpal conduction velocities greater than 2.0 m/s. We used 82 fibers to record the neural response following the topical application of capsaicin for 60 min at increasing concentrations (1 nM, 100 nM, 10 μM) through thin dentin. Six of 25 slow Aδ, 10/20 C, and no Ap (0/11) or fast AS (0/26) fibers responded to 1 nM or 100 nM of capsaicin. When the three concentrations of capsaicin solution were applied in turn, the electrical threshold and latency of Aβ and fast AS fibers did not change, whereas those of slow AS and C fibers gradually increased. In 0/11 Ap, 0/26 fast AS, 13/25 slow AS, and 18/20 C fibers, the conduction was blocked reversibly or irreversibly following the application of 10 uM of capsaicin. The amplitude of the late component of antidromic action potential of fast AS fibers decreased after the capsaicin application. No neural discharge could be recorded from 19 (3 Aβ, 5 fast AS, 6 slow AS, and 5C) fibers following the application of a single high concentration of capsaicin (10 μM). A single low concentration of capsaicin (100 nM) activated only some slow-conducting fibers (0/4 Ap, 0/4 FAS, 3/6 SAS, and 4/6 C). Response properties recorded from the remaining 18 fibers (3 Ap, 3 fast AS, 6 slow Aδ, and 6 C) were not changed following the application of the control vehicle. These results confirm that a low concentration of capsaicin has an excitatory effect on the response of slow pulpal AS as well as C fibers, and that a high concentration of capsaicin blocks the conduction of slow Aδ and C fibers as well as the terminals of fast AS fibers in the pulp.
Localization of Nerve Cells in the Developing Rat Tooth
Authors: Luukko K. , Sainio K. , Sariola H. , Saarma M. , Thesleff I.
Published: January 2009

Earlier studies have shown that mammalian tooth formation can take place in the absence of peripheral nerve fibers. This has been taken to indicate that neurons are not needed for mammalian tooth development. However, our recent localization of peripherin, which is a neuronal cell marker, has suggested that neuronal cell bodies may be associated with developing teeth. In this study, we have analyzed in vivo and in vitro the presence of neuronal cells in developing rat tooth germs. When E14 and E16 rat first molars (thickening of presumptive dental epithelium and bud-stage tooth germ, respectively) were cultured in vitro, peripheral trigeminal axons degenerated. However, with antibodies against peripherin and L1 neural cell adhesion protein, we detected neuronal cell bodies and their axons in the explants. Next, the expression of neurofilament light-chain (NF-L) mRNAs was studied by in situ hybridization of embryonic E12 first branchial arches and tooth germs from initiation to completion of crown morphogenesis (E13, five-day post-natal teeth). NF-L transcripts were first seen at the bud stage (E15) next to the dental epithelium at the buccal side of the tooth germ. At the cap stage (E18), NF-L mRNAs were located under the oral epithelium at some distance from dental epithelium. These expression patterns correlate to the previous localization of peripherin-positive cells and suggest that NF-L expression also revealed neuronal cells. Taken together, these results demonstrate that, in addition to projections of peripheral neurons, neuronal cells are associated with the developing teeth. Hence, it is possible that neuronal cells may participate in the regulation of mammalian tooth formation.
Expression of Connexin 43 in Rat Mandibular Bone and Periodontal Ligament (PDL) Cells during Experimental Tooth Movement
Authors: Su M. , Borke J.L. , Donahue H.J. , Li Z. , Warshawsky N.M. , Russell C.M. , Lewis J.E.
Published: January 2009

Bone remodeling in response to force requires the coordinated action of osteoblasts, osteoclasts, osteocytes, and periodontal ligament cells. Coordination among these cells may be mediated, in part, by cell-to-cell communication via gap junctions. This study tests the hypothesis that the regulation of expression of connexin 43, a gap junction protein, is part of the transduction mechanism between force as applied to bone during orthodontic tooth movement and bone remodeling. To test this hypothesis, we examined connexin 43 expression in a rat model system of experimental tooth movement. To establish the model, we extracted maxillary first molars to initiate supra-eruption of opposing mandibular molars. The rats were killed at 0, 6, 12, 24, and 48 hrs post-extraction. The mandibles were removed, demineralized, and embedded in paraffin. To localize connexin 43 protein and mRNA, we used a specific antibody for immunohistochemistry and a specific cDNA probe for in situ hybridization. Western and Northern blot analyses were used to assess the specificity of the connexin 43 antibody and cDNA probe, respectively. We found connexin 43 protein expressed by osteoclasts (++++) and periodontal ligament cells (+++) in compression zones, and by osteoblasts (++++) and osteocytes (++++) in tension zones of the periodontal ligament. In addition, connexin 43 mRNA was found in some bone and periodontal ligament cells. Connexin 43 protein was found, by densitometric analysis, to be higher in the periodontal ligament after exposure to force compared with controls (P < 0.001). The number of osteocytes expressing connexin 43 48 hrs after molar extraction was also significantly greater in bone subjected to tension when compared with controls (P < 0.001). The results of this study support the hypothesis that connexin 43 plays a role in the coordination of events during experimentally induced alveolar bone remodeling.
In vitro Cellular Aging Stimulates Interleukin-1β Production in Stretched Human Periodontal-ligament-derived Cells
Authors: Shimizu N. , Goseki T. , Yamaguchi M. , Iwasawa T. , Takiguchi H. , Abiko Y.
Published: January 2009

Although the severity of periodontal disease is known to be affected by host age, the pathological role of aging in periodontal disease, and especially that attributable to trauma from occlusion, has not been well-characterized. Interleukin (IL)-1β is a key mediator involved in periodontal diseases, a potent stimulator of bone resorption. Furthermore, it is produced by human periodontal ligament (PDL) cells in response to mechanical stress. To investigate the age-related changes in the biosynthetic capacity of IL-1β in PDL cells, we examined the effects of in vitro cellular aging with mechanical stress on IL-1β protein and gene expression by human PDL cells. Human PDL cells (young = 5th or 6th passage; old = 18-20th passage) were cultured on flexible-bottomed culture plates, and the cells were deformed at 6 cycles per min at 2 steps of tension force for 1 to 5 days. We found a two-fold increase in IL-lp production by old PDL cells subjected to mechanical tension compared with that by young PDL cells, although the constitutive levels of IL-1β were similar in both the young and old PDL cells. This increase was tension-dependent. IL-1β mRNA was also detected in both the cell types under basal conditions, and its expression was further enhanced by application of mechanical tension by use of reverse-transcription-polymerase chain-reaction (RT-PCR) and in situ hybridization methods. The increase in signal rate was higher in the old cells than in the young cells. IL-1β-converting enzyme mRNA remained unchanged. It is possible that a large amount of IL-1β produced by PDL cells from an aged host in response to mechanical force may be positively related to the accleration of alveolar bone resorption.
Identification of Bacteroides forsythus in Subgingival Dental Plaque with the Aid of a Rapid PCR Method
Authors: Meurman J.H. , Wahlfors J. , Korhonen A. , Alakuijala P. , Väisänen P. , Torkko H. , Janne J.
Published: January 2009

Bacteroides forsythus has been shown to be prevalent among patients with periodontitis. Conventional microbiological methods used to identify this bacterium, however, are laborious and time-consuming and are therefore not well-suited for screening purposes. We have developed a polymerase chain-reaction (PCR) method which is rapid, specific, and simple to perform and does not require other sample pre-treatment except a brief centrifugation. This method was applied to the detection of B. forsythus in subgingival plaque of 58 periodontitis patients. When compared with the results of conventional culturing, the PCR method always confirmed the culture-positive results, while none of the PCR negative samples was shown to be culture-positive. The PCR method appeared to give more than double the number of samples positive for B. forsythus than culturing (89.7% vs. 37.9%). The analysis requires less than 4 hrs to perform, and is specific only to B. forsythus and sensitive enough to detect fewer than 5 bacteria.
In vitro Wear of Composite with Varied Cure, Filler Level, and Filler Treatment
Authors: Condon J.R. , Ferracane J.L.
Published: January 2009

For the clinical wear of composite filling materials to be reduced, compositional factors such as degree of cure, filler level, and silanation level should be optimized. An oral-wear-simulating machine was used to explore the effects of these factors on abrasion and attrition wear as well as on opposing enamel wear. The composites were made from Sr glass (1-2 μm avg) and a 50/50 Bis-GMA/TEGDMA resin. Series I (A-D, E) were light-cured (Triad II) for 9, 12, 25, and 40 sec/side to produce degree of cure (DC) as measured by FTIR of 56, 60, 61, and 63%, respectively. E received an additional heat cure (120°C for 10 min) to reach a DC of 66%. Series II (D, F-I) were filled to 62, 53, 48, 37, and 28 vol%, respectively. In series III (D, J-M), the portion of fillers treated with a silane coupler (MPS) was 100, 80, 60, 40, and 20%, respectively. Samples were cycled 50,000 times against an enamel antagonist in a poppy seed/PMMA slurry in the oral wear simulator to produce abrasion (load = 20 N) and attrition (load = 70 N) simultaneously. Wear depth (μm; n = 5) was measured by profilometry. Results for each series were analyzed by ANOVA/Tukey's (p ≤0.05). The wear depths did reflect cure values, though only the abrasion difference for E < A was significant. Greater wear was correlated with lower filler levels (r2 = 0.88; p < 0.05), significantly increasing below 48 vol% (G). Wear increased linearly as the percent of silane-treated fillers was reduced (r2 = 0.99; p < 0.05). Abrasion and attrition did not differ significantly for any composite. Wear of the opposing enamel was largely unchanged by these factors. Compositional factors including degree of cure, filler level, and silanation directly affected the wear resistance of dental composites evaluated in an oral wear simulator.
Craniofacial and TMJ Effects after Glutamate and TRH Microsphere Implantation in Proximity to Trigeminal Motoneurons of Growing Rats
Authors: Byrd K.E. , Sukay M.J. , Dieterle M.W. , Yang L. , Marting T.C. , Teomim D. , Domb A.J.
Published: January 2009

The sequelae of sustained, in vivo delivery of two important neurotransmitter substances, glutamate and thyrotropin-releasing hormone (TRH), upon craniofacial growth and development have previously not been investigated. Our purpose was to document and compare the relative effects of glutamate and TRH microspheres stereotactically placed in proximity to trigeminal motoneurons within the trigeminal motor nucleus. The following null hypotheses were tested: (1) TRH microspheres in proximity to trigeminal motoneurons have no significant effect upon the craniofacial skeleton, and (2) there are no significant differences between the relative effects of chronic, long-term delivery of glutamate and TRH upon the neuromusculoskeletal system of growing rats. Forty male Sprague-Dawley rats were divided into 4 experimental groups (glutamate microspheres, TRH microspheres, blank microspheres, sham surgeries) and underwent stereotactic neurosurgery at 35 days; 5 rats of each group were killed at 14 and 21 days for data collection. Histology revealed that implants were clustered in the pontine reticular formation, close to the ventrolateral tegmental nucleus. Both glutamate and TRH rats had implant-side deviation of their facial skeleton and snout regions; 4 x 2 ANOVA and post hoc t-tests revealed significant (P ≤ 0.05, 0.01) differences between groups and sides for motoneuron count, muscle weight, and osteometric data. TRH rats also demonstrated larger implant-side TMJ discs and mandibular fossae in comparison with the other groups. The stated null hypotheses were therefore rejected.
Intermittent Parathyroid Hormone Administration Stimulates Bone Formation in the Mandibles of Aged Ovariectomized Rats
Authors: Miller S.C. , Hunziker J. , Mecham M. , Wronski T.J.
Published: January 2009

Intermittent administration of parathyroid hormone (PTH) is known to stimulate bone formation in many skeletal sites and is being investigated as a possible therapeutic agent for the treatment of osteopenic conditions, including post-menopausal osteoporosis. The purpose of this study was to determine the ability of PTH to stimulate bone formation in the mandibles of aged ovariectomized (Ovx) rats, and the results are compared with a site in the appendicular skeleton (humerus). The Ovx rat is a useful model of estrogen deficiency, replicating many aspects of post-menopausal osteoporosis. Female rats were ovariectomized or sham-operated, and one year later a group of the ovariectomized rats was treated with the 1-34 fragment of human PTH daily, five days a week for 10 weeks. During the experiment, the animals were given fluorochrome bone markers for histomorphometry. More than one year after ovariectomy or sham surgery, there were few differences in the histomorphometric indices of bone formation in the humerus or mandible. PTH treatment had no effect on dentin formation, measured in the mandibular incisor; however, most indices of bone formation-including the double-labeled surface, mineralizing surface, mineral appositional rate, new bone area, and surface-referent bone formation rates-were substantially greater in the PTH-treated group compared with both the Ovx and the Sham controls measured at the periosteal and endocortical surfaces of the humerus and the periosteal and cancellous bone surfaces of the mandible. In addition, bone formation at the alveolar crest, particularly on the buccal side, was greater in the PTH-treated group. The results from this study demonstrate that systemic intermittent PTH treatment stimulates bone formation in the mandibles in aged, estrogen-deficient animals.
Solubility Control of Thin Calcium-phosphate Coating with Rapid Heating
Authors: Yoshinari M. , Watanabe Y. , Ohtsuka Y. , Derand T.
Published: January 2009

The thin calcium-phosphate (Ca-P) coatings produced by the ion-beam-mixing method instead of the plasma-spraying method have been found to be amorphous, resulting in films that easily dissolved in simulated body fluid. These coatings crystalized with conventional heat treatment in an electric furnace but tended to crack easily. Therefore, the purpose of this study was to find a suitable heat treatment that controls the solubility of Ca-P coatings without weakening their adhesion to titanium (Ti) substrate. Thin coatings (approximately 1 μm) were coated onto Ti substrates, followed by heat treatment in a conventional furnace and rapid heating by infrared radiation and laser radiation. X-ray diffraction analysis revealed untreated films to be amorphous but to become crystalline after being heated in a furnace at 500°C, heated rapidly with infrared radiation higher than 600°C and with laser radiation at output power of 10W. We evaluated solubility by estimating the film thickness after immersion in simulated body fluid for 5 weeks: Untreated films dissolved within 1 day. Coatings treated with infrared radiation at 600°C dissolved minimally. Cracks were observed in coatings subjected to infrared radiation at 800°C and furnace-heated at 500°C. Coatings treated with laser radiation tended to dissolve easily, with non-uniform surface degradation. X-ray photoelectron spectroscopy analysis at the interface between the coating and the Ti substrate showed that cracks were the result of decreased Ca-implanted layers and too much growth of Ti-P compounds. No difference was recognized in the Ti-oxidation state among specimens. These data indicate that rapid, homogeneous, and comparatively low-temperature heating, such as defocused infrared radiation, controls Ca-P solubility and ensures the adherence of the coatings to the substrate.
The Effects of Maturity and Dehydration Shrinkage on Resin-modified Glass-ionomer Restorations
Authors: Sidhu S.K. , Sherriff M. , Watson T.E.
Published: January 2009

The dimensional change, including hygroscopic change, of adhesive dental materials is a clinically important topic, since excessive changes could cause debonding from tooth structure. The water balance of glass-ionomer cements arises mainly from their sensitivity to the environment; depending on the surroundings, they can gain or lose water, either of which can be potentially damaging. These effects become less noticeable as the cement ages. The effects of maturity of the newer resin-modified glass-ionomer materials and their responses to changes in moisture are unknown. Using confocal microscopy, we examined the effects of dehydration stress on the glass-ionomer/tooth interface in specimens of various degrees of maturity. Wedge-shaped cervical cavities in extracted teeth were restored with one of three resin-modified glass-ionomer restorative materials. The control specimens were restored with a conventional glass ionomer. The samples were left to mature, then sectioned and examined at 1 day, 1 wk, 1 mo, 3 mos, 6 mos, and 1 yr. After being sectioned, each specimen was examined immediately with a confocal microscope with water-immersion objectives so that the subsurface interfacial characteristics could be studied. The specimen was then allowed to dehydrate under the microscope, with further examinations at 15, 30, and 60 min. Generally, gap formation at the interface occurred within 15 min of dehydration. All materials showed a different pattern of gap change with maturity, probably due to the different setting mechanisms involved. All of them were susceptible to dehydration shrinkage up to 3 mos of maturity. At 6 mos and 1 yr, Fuji II and Fuji II LC showed insensitivity to dehydration. Vitremer and Photac-Fil showed less sensitivity to dehydration at 1 yr than at 6 mos. The results of this study of the maturing polymerized resin-modified cements have potential clinical implications in the handling of these materials; the addition of resin has not significantly reduced the glass ionomer's susceptibility to dehydration problems.
Human Neutrophil Collagenase MMP-8 in Peri-implant Sulcus Fluid and its Inhibition by Clodronate
Authors: Teronen O. , Konttinen Y.T. , Lindqvist C. , Salo T. , Ingman T. , Lauhio A. , Ding Y. , Santavirta S. , Sorsa T.
Published: January 2009

The exact molecular mechanisms of the loosening of a dental implant are not well-known. The characteristics of implant sulci are similar to those of periodontal sulci regarding gingival crevicular fluid (GCF) and peri-implant sulcular fluid (PISF). Proteolytic enzymes, matrix metalloproteinases (MMPs), participate in peri-implant tissue remodeling. Clodronate is a well-tolerated bisphosphonate-group drug currently used in bone-resorption-related diseases in humans. The mechanisms of bisphosphonate action are not clarified. Collagenase activity in diseased PISF was significantly higher than in the clinically healthy group. Immunoblotting disclosed that diseased PISF contained increased immunoreactives MMP-8 compared with the healthy PISF. The residual latent collagenase activity in the diseased PISF was activated by gold thioglucose and inhibited completely by 100 pM of doxycycline closely resembling pure neutrophil collagenase (MMP-8). The presence of MMP-8 in diseased but not in clinically healthy PISF may prove to be a useful biochemical indicator to monitor peri-implant health and disease. Pure human neutrophil collagenase (MMP-8) and the MMP-8 present in PISF and in the GCF of both loosening implants and periodontitis-affected teeth were efficiently inhibited in vitro by clodronate (50% inhibition [IC50] was achieved by 150 uM of clodronate), an osteoactive, antiresorptive bisphosphonate. Furthermore, the new finding suggests an extended and hitherto-undescribed potential for clodronate in preventing the loosening of both implants and teeth, based on a dual beneficial effect: prevention of both bone resorption/osteolysis and of soft tissue/dental ligament destruction. Potential new therapeutic indications based on the collagenase-inhibiting effect of clodronate provide potential new therapeutic indications for a variety of diseases involving connective tissue breakdown, such as periodontal disease, arthritides, and tumor invasion.
Extracellular 37-kDa Antigenic Protein from Actinobacillus actinomycetemcomitans Induces TNF-α, IL-1β, and IL-6 in Murine Macrophages
Authors: Tani Y. , Tani M. , Kato I.
Published: January 2009

The extracellular antigens of Actinobacillus actinomycetemcomitans Y4 (serotype b) contain a 37-kDa protein which is a major target for IgGs from patients suffering from severe alveolar bone loss. Since the 37-kDa protein has not been studied sufficiently, our investigation focused on its characteristics, e.g., its localization, specificity, and whether it directly stimulates macrophages to produce cytokines. The 37-kDa protein was purified from the culture supernatant of the Y4 strain by means of chromatofocusing and gel filtration. The 37-kDa protein is a unique glycoprotein which forms immune complexes with monoclonal antibodies against rhamnose-fucose polysaccharide. Patients with A. actinomycetemcomitans-associated periodontitis had higher antibody titers to the purified 37-kDa protein than healthy subjects (p < 0.001). Anti-37-kDa protein antibodies recognized a 37-kDa band in the cytosolic, ribosomal, and total membrane fractions from Y4 cells. Extracellular substances from other strains of A. actinomycetemcomitans (serotypes a and c) also reacted in the Western blots, but Haemophilus spp. or several periodontopathic bacteria did not. These results suggested that the 37-kDa protein is a cytosolic protein that is passed through the cell membrane, and its protein portion is specific for A. actinomycetemcomitans but common to serotypes. This protein induced IL-1β, IL-6, and TNF-a release from murine macrophages. The IL-6-inducing activity of the 37-kDa protein was higher than that of LPS. These findings suggested that the 37-kDa protein which is released from live cells plays a role in A. actinomycetemcomitans- associated periodontitis, as antigen inducing the release of inflammatory cytokines which are associated with alveolar bone loss.
Expression of TGF-β Superfamily Receptors in Dental Pulp
Authors: Toyono T. , Nakashima M. , Kuhara S. , Akamine A.
Published: January 2009

Transforming growth factor-β (TGF-β) superfamily members and their cell-surface receptors may play inductive and/or regulatory roles in tooth development and repair. It will be important to identify the complete set of TGF-β superfamily receptors, to examine their temporal and spatial localization during tooth development, and to elucidate the cascade of molecular events of tooth formation induced by the TGF-β superfamily. In this report, we have cloned the cDNAs encoding potential receptors for TGF-β superfamily members in rat incisor pulp and bovine adult pulp which are regarded as embryonic and adult pulp, respectively. We analyzed poly (A)+ RNA from rat incisor pulp and bovine adult pulp by reverse-transcriptase/polymerase chain-reaction (RT-PCR), using degenerate primers corresponding to the most conserved amino acid sequences in the intracellular serine/threonine kinase of type I or type II receptors. Each amplified cDNA encoding activin receptor-like kinase-1 (ALK-1), ALK-2, ALK-3 (bone morphogenetic protein receptor type IA, BMPR-IA), ALK-4 (Bl), ALK-5, ALK-6 (BMPR-IB), and BMPR-II (BMP type II receptor) was found to be in dental pulp. Northern blot analysis further detected TGF-β type II receptor (TβR-II) mRNA transcript in addition to the above-identified receptors. These results provide the first evidence of multiple type I and type II receptors for TGF-βs, activins, and BMPs expressed in embryonic and adult pulp, implicating diverse function in tooth development and pulp tissue repair.
Craniofacial Growth in Short Children Born Small for Gestational Age: Effect of Growth Hormone Treatment
Authors: Van Erum R. , Mulier M. , Carels C. , Verbeke G. , De Zegher F.
Published: January 2009

The effects of growth hormone (GH) therapy in children have yet to be completely catalogued. In the present study, the effect of high-dose GH treatment on craniofacial growth was evaluated once yearly in 21 pre-pubertal, non-GH-deficient children born small for gestational age. These children were randomly allocated to be either untreated or treated with GH at a daily subcutaneous dose of 0.2 or 0.3 IU/kg for 2 yrs. The group consisted of 12 girls and 9 boys with a mean age of 5.1 yr (range, 2 to 8 yr), bone age of 3.4 yr, and height SDS of -3.6. At the start of the study, all children showed an overall delay of craniofacial growth. This cohort of short children born small for gestational age showed a small SNB angle and a large ANB angle; all other angular measurements were within normal range. GH treatment accelerated growth in several craniofacial components, especially the posterior total facial height, the cranial base length, and the overall mandibular length. The increase of the mandibular length increased the SNB angle; no other angular measurements were affected. Age at start of treatment differently influenced the increase in posterior and total cranial base length, the increase in mandibular corpus length, and the position of the mandible in relation to the cranial base. Although GH treatment for 2 yrs led to a craniofacial growth acceleration, the position of the mandible in relation to the cranial base and the craniofacial size in lateral aspect were not normalized in the majority of the GH-treated children. No signs of disproportional growth were evidenced after 2 yrs of high-dose GH treatment. In conclusion, short pre-pubertal SGA children display an overall delay of linear craniofacial growth and a retrognathic mandible. High-dose GH treatment over 2 yrs leads to craniofacial catch-up growth, which is pronounced in regions where interstitial cartilage is involved and results in a less convex face in profile.
Isolation of Enterobacteriaceae from the Mouth and Potential Association with Malodor
Authors: Goldberg S. , Cardash H. , Browning H. , Sahly H. , Rosenberg M.
Published: January 2009

Bad breath is a common phenomenon, usually the result of bacterial metabolism in the oral cavity. It is generally accepted that Gram-negative bacteria are responsible for this problem, largely through degradation of proteinaceous substances. In initial experiments, screening of malodorous isolates following outgrowth of samples obtained from saliva, periodontal pockets, and the tongue dorsum yielded enterobacterial isolates. Clinical studies were conducted to examine the prevalence of such bacteria in four different populations: orthodontic patients, malodor clinic patients, complete-denture wearers, and a healthy young population. The prevalence of Enterobacteriaceae in the oral cavities of the denture-wearing population was very high (48.0%) as compared with the other groups: 27.1% in the malodor clinic patients, 16.4% in the normal population, and 13% among orthodontic patients. Isolates of Klebsiella and Enterobacter emitted foul odors in vitro which resembled bad breath, with concomitant production of volatile sulfides and cadaverine, both compounds related to bad breath. When incubated on a sterile denture, enterobacterial isolates produced typical denture foul odor. Isolates exhibited cell-surface hydrophobic properties when tested for adhesion to acryl and aggregation with ammonium sulphate. The results, taken together, suggest that Klebsiella and related Enterobacteriaceae may play a role in denture malodor.
A Novel System of Human Submandibular/Sublingual Saliva Collection
Authors: Wolff A. , Begleiter A. , Moskona D.
Published: January 2009

The assessment of submandibular/sublingual (sm/sl) saliva is a procedure of increasing significance. However, the collection of these fluids by traditional techniques is difficult and therefore often neglected. To collect sm/sl saliva, we have assembled a novel, universal system consisting of four parts-collecting tubing, a buffering chamber, a storing tube, and a suction device. Submandibular/sublingual saliva samples were collected from ten healthy and ten xerostomic individuals. The system showed intra-examiner reproducibility of 0.92 for healthy and 0.89 for xerostomic subjects, and inter-examiner reproducibility of 0.93 for normal subjects and 0.80 for xerostomic individuals. The flow rates obtained by the present collecting set-up were similar to those measured by all known previous methods that were published during the last 40 years. The system was also efficient, in that more than 90% of the fluid that entered the system was eventually collected in the storing tube for analysis. The system appears to collect relatively pure sm/sl fluids, since contamination of the collected sample by a stimulant solution swabbed repeatedly over the tongue during saliva collection was minimal. The system is reliable, safe, practical, and comfortable for the patient.