bluuebunny/crossref_metadata_2025 huggingface dataset:
Shear vs. Tensile Bond Strength of Resin Composite Bonded to Ceramic
Authors: Della Bona A. , van Noort R.
Published: January 2009

Since the mode of failure of resin composites bonded to ceramics has frequently been reported to be cohesive fracture of either ceramic or resin composite rather than separation at the adhesive interface, this study was designed to question the validity of shear bond strength tests. The reasons for such a failure mode are identified and an alternative tensile bond strength test evaluated. Three configurations (A, conventional; B, reversed; and C, all composite) of the cylinder-on-disc design were produced for shear bond strength testing. Two-dimensional finite element stress analysis (FEA) was carried out to determine qualitatively the stress distribution for the three configurations. A tensile bond strength test was designed and used to evaluate two ceramic repair systems, one using hydrofluoric acid (HF) and the other acidulated phosphate fluoride (APF). Results from the shear bond strength tests and FEA showed that this particular test has as its inherent feature the measurement of the strength of the base material rather than the strength of the adhesive interface. In the tensile test, failure invariably occurred in the adhesive layer, with HF and APF showing a similar ability to improve the bond of resin composite to ceramic. It is concluded that the tensile bond strength test is more appropriate for evaluating the adhesive capabilities of resin composites to ceramics.
Cytotoxic Interactive Effects of Dentin Bonding Components on Mouse Fibroblasts
Authors: Ratanasathien S. , Wataha J.C. , Hanks C.T. , Dennison J.B.
Published: January 2009

Previous studies have shown a wide range of pulpal reactions to dentin bonding systems and a poor correlation between in vitro and in vivo toxicity of dentin bonding agents. Because dentin bonding agents are composed of multiple components which may diffuse through dentin, we hypothesized that these components may cause cytotoxicity through interactive (synergistic) effects. We investigated the cytotoxicities of four dentin bonding components-HEMA, Bis-GMA, TEGDMA, and UDMA-and interactive effects for three binary combinations of the dentin bonding components-HEMA and Bis-GMA, Bis-GMA and TEGDMA, and TEGDMA and UDMA. Cytotoxicities to Balb/c 3T3 mouse fibroblasts were measured by the MTT assay. Concentrations which caused 50% toxicity compared with controls (TC50 values) were compared, and the interactive effects were determined by evaluation of the differences between observed and expected MTT activities of the cells. The ranks of toxicity of the dentin bonding components in terms of TC50 values were as follows: Bis-GMA > UDMA > TEGDMA >>> HEMA (least toxic) after 24- and 72-hour exposures. As binary combinations, the three combinations of dentin bonding components interacted in three ways—synergism, additivism, and antagonism-which were influenced by the concentrations of both components. The longer period of exposure resulted in a significant increase in the cytotoxicity of the dentin bonding components and combinations. The findings indicate that both exposure time and the interactions between the dentin bonding components may be important parameters in determining the cytotoxicity of dentin bonding agents in vivo.
Bacterial Colonization on Titanium, Hydroxyapatite, and Amalgam Surfaces in vivo
Authors: Leonhardt A. , Olsson J. , Dahlén G.
Published: January 2009

A study was conducted to evaluate qualitative and quantitative differences in bacterial colonization on titanium, hydroxyapatite, and amalgam surfaces in vivo. Six healthy adult individuals participated in the study. Two pieces each of titanium, hydroxyapatite, and amalgam of similar size were placed in cobalt-chromium splints and kept intra-orally in each individual for 10 min, and 1, 3, 6, 24, and 72 hrs. After removal of the splints, the pieces were rinsed in PBS and transferred to transport medium. After being vortexed, the samples were inoculated on selective and non-selective media for analyses of various facultative and anaerobic bacteria. During the experiment, total viable count increased on all surfaces. The investigated bacterial groups constituted, on average, approximately 60 to 99% of the total viable count on all three types of surfaces in each of the experiments, except in the 10-minute samples, when they constituted around 20 to 30%. Various streptococcal species predominated and usually constituted > 50% of total viable count. Similar colonization patterns of Streptococcus spp., Actinomyces naeslundii, Neisseria spp., Hemophilus parainfluenzae, Fusobacterium spp., and black-pigmented Prevotella spp. were seen at all three types of surfaces. No significant differences among the materials regarding colonization of investigated bacteria were found during the study period. This study failed to show any qualitative and quantitative differences in bacterial colonization among these materials. Titanium, hydroxyapatite, and amalgam do not seem to have a marked influence on the early colonization pattern in vivo.
Effect of Sucrose Monolaurate on Acid Production, Levels of Glycolytic Intermediates, and Enzyme Activities of Streptococcus mutans NCTC 10449
Authors: Iwami Y. , Schachtele C.F. , Yamada T.
Published: January 2009

We studied the mechanism by which the antimicrobial compound sucrose monolaurate inhibits Streptococcus mutans NCTC 10449 by determining its effect on the rate of acid production from glucose and sucrose and the intracellular and extracellular levels of glycolytic intermediates. Sucrose monolaurate was more effective than either sodium laurate or sodium fluoride in inhibiting acid production at pH 7.0 from glucose. Inhibition of acid production was the same when either glucose or sucrose was the carbon source and in the presence or absence of oxygen. Quantitative analysis of various glycolytic intermediates revealed that the steps inhibited by sucrose monolaurate were the reactions catalyzed by phosphofructokinase and glyceraldehyde 3-phosphate dehydrogenase and/or phosphoglycerate kinase. Since the activities of these enzymes in cell-free extracts were not decreased by the addition of sucrose monolaurate, the inhibition of acid production could not be ascribed to direct effects on the enzymes. A decrease in the rate of acid production with corresponding elevations in the extracellular levels of glycolytic intermediates indicates that sucrose monolaurate inhibits S. mutans by altering the permeability of the cell membrane, which causes a loss of important metabolites.
Sumter Smith Arnim, DDS, PhD (1904-1990): A Pioneer in Preventive Dentistry
Authors: Christen Arden G.
Published: January 2009

This article reviews the life story and contributions of Sumter Smith Arnim (1904-1990), a noted author, lecturer, teacher, and researcher in preventive dentistry. Following in the footsteps of Levi Spear Parmly, MD, DDS (1790-1859), and Charles C. Bass, MD (1875-1975), Arnim developed and popularized a wide range of preventive concepts and practices, especially dental plaque control via mechanical means. Today, these innovative ideas and techniques continue to have an impact on oral health research, the practice of dentistry, and the teaching of oral hygiene to dental patients. This article traces both the development of these oral health concepts and Arnim's study of dental plaque ("microcosm"), which he characterized by means of phase-contrast microscopy and cinemicrography.
Effect of Growth Hormone on the Distribution of Decorin and Biglycan during Odontogenesis in the Rat Incisor
Authors: Zhang C.Z. , Li H. , Bartold P.M. , Young W.G. , Waters M.J.
Published: January 2009

Previous studies have shown that growth hormone can influence the expression of N-acetylgalactosamine-containing molecules in the extracellular matrix of developing rat incisors. N-acetylgalactosamine is a principal component of proteoglycans containing chondroitin sulfate and dermatan sulfate, as well as of some glycoproteins. Since chondroitin sulfate proteoglycans are identifiable components in enamel, dentin, and cementum, we have tested the hypothesis that growth hormone modulates their expression in developing rat incisors. The distribution of the chondroitin-sulfate-rich proteoglycans, decorin and biglycan, was investigated. We used the Lewis dwarf rat as a model because their circulating growth hormone levels are markedly reduced. Polyclonal antibodies against decorin and biglycan were used to localize these two proteoglycans. Semi-quantitative assessments of the staining patterns and intensities were made for each proteoglycan within compartments of the developing teeth. In normal Lewis rats, decorin and biglycan differentially expressed throughout the enamel organ, dental papilla, and dental follicle. Decorin displayed a wide distribution throughout all three regions and was closely associated with different cellular components. In contrast, biglycan showed little association with cells and was identified in the predentin and osteoid matrices. The expression of both proteoglycans was dramatically decreased in the growth-hormone-deficient animals. Administration of growth hormone to the dwarf rats markedly elevated the expression of both proteoglycans, approximating the distribution and intensity of staining seen in normal animals. These findings confirm that growth hormone status can modulate the expression of decorin and biglycan, and hence matrix deposition, in the rat tooth.
The Role of Sensory Information in the Control of Rhythmic Open-Close Movements in Humans
Authors: van der Bilt A. , Weijnen EG , Ottenhoff F.A.M. , van der Glas H.W. , Bosman F.
Published: January 2009

Chewing requires a low level of muscle activity for jaw movement. Additional muscle activity is required to overcome the resistance of the food. The additional muscle activity consists of two contributions, an anticipating contribution before food contact and a peripherally induced contribution, about 23 ms after food contact. The amounts of both contributions depend on the information about food resistance obtained in preceding chewing cycles. It is not known whether this information is preserved if the resistance is absent during only a limited number of chewing cycles. Our aim was to investigate the extent to which information about food resistance obtained during chewing is used during subsequent cycles to generate anticipating and peripherally induced muscle activity. Subjects made rhythmic open-close movements at their natural chewing frequency, controlled by a metronome. Food resistance was simulated by an external force acting on the jaw in a downward direction during part of the closing movement. Jaw movement and surface EMG of the masseter and suprahyoid muscles were recorded during experiments in which sequences of at least 20 cycles with the force were alternated with a small, random number (from 1 to 10) of cycles without the force. The amount of anticipating muscle activity as well as the peripherally induced muscle activity in the first cycle with the force gradually decreased as a function of the number of preceding forceless cycles. About 30% of the additional muscle activity had an anticipatory origin, whereas the rest of the activity was evoked by the force regardless of the number of preceding forceless cycles.
Absence of Parasympathetic Vasodilatation in Cat Dental Pulp
Authors: Sasano T. , Shoji N. , Kuriwada S. , Sanjo D. , Izumi H. , Karital K.
Published: January 2009

The existence and nature of parasympathetic nerve fibers in the dental pulp have long been a subject for discussion; indeed, vasodilator responses mediated by such nerve fibers have yet to be conclusively demonstrated in the dental pulp. This study was designed to determine whether parasympathetic vasodilator mechanisms do or do not exist in the cat dental pulp. Dynamic changes in pulpal blood flow (PBF), with mandibular lip blood flow (LBF) recorded as a control, were investigated in cat mandibular canine teeth by means of laser Doppler velocimetry. Peripheral trigeminal afferents (see below) were stimulated electrically to confirm that somato-parasympathetic reflex vasodilatation could be induced. The peripheral cut ends of the facial and glossopharyngeal nerve roots, which have been reported to contain parasympathetic nerve fibers to the oral tissues, were then stimulated intracranially. Electrical stimulation of trigeminal afferents (in the infra-orbital nerve or the maxillary buccal gingiva) caused no change in PBF but did increase ipsilateral LBF. Neither facial nor glossopharyngeal nerve root stimulation caused a PBF increase, though both elicited increases in ipsilateral LBF. The vasodilator responses in the lip were sensitive to ganglion blockade (with hexamethonium), indicating vasodilatation via activation of parasympathetic vasodilator fibers. In contrast, intracranial stimulation of the trigeminal nerve root induced increases in both PBF and LBF which were reduced by pre-treatment with tripelennamine, indicating antidromic vasodilatation via the trigeminal sensory nerve. These results suggest that a parasympathetic vasodilator mechanism is not present in feline dental pulp.
Characterization of GlucosyltransferaseB, GtfC, and GtfD in Solution and on the Surface of Hydroxyapatite
Authors: Venkitaraman A.R. , Vacca-Smith A.M. , Kopec L.K. , Bowen W.H.
Published: January 2009

GlucosyltransferaseB, GtfC, and GtfD were purified by hydroxyapatite column chromatography, followed by ultrafiltration from the culture supernatant fluids of three Streptococcus milleri constructs (gift from Dr. H.K. Kuramitsu) which harbored individual gtf genes of Streptococcus mutans GS5. GtfB, GtfC, and GtfD were enzymatically active both in solution and in an experimental pellicle (HA-CWS-Gtf) formed by adsorbing Gtf onto the surface of clarified human whole saliva (CWS)-coated hydroxyapatite (HA). The Km values for sucrose for all three enzymes were lower when the enzyme was adsorbed to a surface, compared with when it was in solution. In solution phase assays, and in the absence of primer dextran, glucan production was enhanced 75% when both GtfB and GtfD were present in the reaction mixture, compared with the sum of the individual enzyme activities (p < 0.005). This enhancement did not occur when GtfC was additionally present, or when the GtfB + GtfD enzyme pair was adsorbed onto HA-CWS. In additional experiments, glucan formed by GtfB or GtfC, but not by GtfD, on a HA-CWS-Gtf surface increased adherence of Streptococcus mutans GS5 and Streptococcus sobrinus 6715 by seven- to nine-fold compared with adherence when no glucan was present on the pellicle surface (p < 0.001). Further, treatment of the HA-CWS-GtfB-glucan or HA-CWS-GtfC-glucan pellicle with a-1,6 dextranase significantly reduced adherence of both streptococcal strains (p < 0.001). These results show that GtfB, GtfC, and GtfD are enzymatically active in an adsorbed state and that the nature of their product glucan can influence the adherence of cariogenic oral streptococci to an experimental pellicle.
Scanning Electron Microscope Observations of CO2 Laser Effects on Dental Enamel
Authors: McCormack S.M. , Fried D. , Featherstone J.D.B. , Glena R.E. , Seka W.
Published: January 2009

Studies of the effects of carbon dioxide (CO2) lasers on dental enamel have demonstrated that surface changes can be produced at low fluences (< 10 J/cm2) if wavelengths are used which are efficiently absorbed by the hard tissues. In this study, scanning electron microscopy (SEM) was used to characterize the wavelength dependence of surface changes in dental enamel after exposure to an extensive range of CO2 laser conditions. Bovine and human enamel were irradiated by a tunable, pulsed CO2 laser (9.3, 9.6, 10.3, 10.6 μm), with 5, 25, or 100 pulses, at absorbed fluences of 2, 5, 10, or 20 J/cm2, and pulse widths of 50, 100, 200, 500 us. SEM micrographs revealed evidence of melting, crystal fusion, and exfoliation in a wavelength-dependent manner. Crystal fusion occurred at absorbed fluences as low as 5 J/cm2 per pulse at 9.3, 9.6, and 10.3 μm, in contrast to no crystal fusion at 10.6 pm (≤ 20 J/cm2). Longer pulses at constant fluence conditions decreased the extent of surface melting and crystal fusion. The total number of laser pulses delivered to the tissue did not significantly affect surface changes as long as a minimum of 5 to 10 pulses was used. Within the four easily accessible wavelengths of the CO2 laser, there are dramatic differences in the observed surface changes of dental hard tissue.
The Site-specificity of Supragingival Calculus Deposition on the Lingual Surfaces of the Six Permanent Lower Anterior Teeth in Humans and the Effects of Age, Sex, Gum-chewing Habits, and the Time Since the Last Prophylaxis on Calculus Scores
Authors: Macpherson L.M.D. , Girardin D.C. , Hughes N.J. , Stephen K.W. , Dawes C.
Published: January 2009

The hypotheses to be tested were: (i) that chewing sugar-free gum frequently and for long periods would be associated with higher amounts of supragingival calculus, and (ii) that there would be no site-specificity of calculus deposition on the lingual surfaces of the 6 lower anterior teeth. Subjects, 436 in Glasgow and 191 in Winnipeg, were scored for calculus at mesial, lingual, and distal sites on the lingual surface of each of the 6 lower anterior teeth, by the Volpe-Manhold method. They also answered questions on the time since the last prophylaxis, the frequency of gum chewing, the type of gum chewed, and the length of a typical gum-chewing episode. A subset (233) of the Glasgow subjects were scaled and re-scored for calculus 3 months later. When the data for the logarithmic transformations of the initial calculus scores were subjected to stepwise multiple-regression analysis, the only factor which correlated significantly with initial calculus scores in both cities was the time since the last prophylaxis. In the Glasgow subjects scored 3 months after a prophylaxis, there was a negative correlation between chewing sugar-free gum and calculus scores, whereas in the Winnipeg subjects, age and the chewing of sucrose-containing and sugar-free gum were positively correlated with calculus scores. Thus, the results were contradictory with respect to the first-tested hypothesis. The calculus distribution patterns were very similar in the subset of Glasgow subjects and the Winnipeg subjects, with the amounts on the lateral incisors and canines averaging 70.2% and 44.5%, respectively, of those on the central incisors. Thus, the second hypothesis was disproved.
The Influence of Bur Blade Concentricity on High-speed Tooth-cutting Interactions: A Video-rate Confocal Microscopic Study
Authors: Watson T.F. , Cook R.J.
Published: January 2009

This study aimed to determine the degree of eccentricity between different tungsten carbide bur manufacturing techniques and to study the effect of bur inaccuracy on dental enamel. Error in bur concentricity may arise from malalignment of the steel shaft and carbide head in a two-piece construction bur. Cutting blades rotate at multiple radii from the shaft axis, potentially producing vibrations and damage to the cut substrate. Techniques now allow for the manufacture of one-piece tungsten carbide burs with strength adequate to withstand lateral loading. A comparison of tungsten carbide dental cutting tools revealed the true extent of concentricity errors. Variation in alignment of the cutting head and shaft in the two-part constructions incurred between 20 and 50 μm of additional axial error. High-speed cutting interactions with dental enamel between carbide burs were studied by means of a video-rate confocal microscope. A cutting stage fitted to a Tandem Scanning Microscope (TSM) allowed for real-time dynamic image acquisition. Images were captured and retrieved by means of a low-light-level camera recording directly to S-VHS videotape. Videotape showing the interactions of high-speed rotary cutting instruments (at 120,000 rpm) were taken under simulated normal wet-cutting environments, and the consequent damage to the tooth tissue was observed as it occurred. Concentrically engineered bur types produced a superior quality cut surface at the entry, exit, and advancing front aspects of a cavity, as well as less subsurface cracking. Imaging of the coolant water film local to recent cutting operations showed regular spherical cutting debris of 6 to 18 um diameter from the concentric tools, whereas the less-well-engineered burs produced ragged, irregular chips, with 25-40 um diameter debris, indicating far more aggressive cutting actions. This study has shown that there is reduced substrate damage with high-concentricity carbide burs.
Salivary Levels of Suspected Periodontal Pathogens in Relation to Periodontal Status and Treatment
Authors: von Troil-Lindén B. , Torkko H. , Alaluusua S. , Jousimies-Somer H. , Asikainen S.
Published: January 2009

The primary ecological niche for suspected periodontal pathogens seems to be the subgingival area, even though periodontal pathogens are also frequently recovered from saliva. The interrelationship of different periodontal conditions and the salivary levels of suspected periodontal pathogens is not known. In the present study, salivary levels of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Campylobacter rectus, and Peptostreptococcus micros were determined by bacterial culture and related to clinical periodontal status in 40 subjects with either advanced, moderate, or initial/no periodontitis. Culture-positive subjects harbored the 5 bacterial species in mean numbers ranging from 2 x 105 to 6 x 107 colony-forming units (CFU)/mL saliva. A. actinomycetemcomitans was found in none and P. gingivalis in one of the subjects with initial periodontitis, whereas both species were found in 33% and 44%, respectively, of the subjects with moderate periodontitis and in 60% and 40%, respectively, of the subjects with advanced periodontitis. The mean numbers of CFU/mL of P. intermedia, C. rectus and P. micros were significantly higher in subjects with advanced periodontitis than in subjects with initial/no periodontitis. Ten patients with advanced periodontitis were treated mechanically and with adjunctive systemic metronidazole, and were re-examined 1 and 6 months after treatment. Periodontal treatment eradicated or significantly reduced the levels of salivary periodontal pathogens for half a year, whereas in untreated subjects, the levels and the detection frequencies generally remained fairly stable. In conclusion, the results showed that the salivary levels of periodontal pathogens reflect the periodontal status of the patient.
Simultaneous Detection of Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis by a Rapid PCR Method
Authors: Wahlfors J. , Meurman J.H. , Väisänen P. , Alakuijala P. , Korhonen A. , Torkko H. , Janne J.
Published: January 2009

The identification of periodontal pathogens by conventional methods is time-consuming and difficult. Therefore, a multiplex PCR method for simultaneous detection of Actinobacillus actinomycetemcomitans (A.a.) and Porphyromonas gingivalis (P.g.) was developed for rapid and easy determination of these risk-indicator bacteria in human periodontal disease. The PCR primers were designed to hybridize to various regions of 16S rRNA genes, and a hot-start technique was used to obtain maximum sensitivity and specificity. This method can detect both of these bacteria in subgingival plaque samples at concentrations as low as 5 to 50 cells per sample. The sensitivity, however, was even 10 times better when the bacteria were analyzed in a water suspension. Since the only step between sample collection and the actual analysis is a brief centrifugation of the patient sample, the detection can be readily carried out in four hours. The performance of the method was studied with 36 patient samples. The results showed that the PCR method detected A.a. (44% vs. 25%, respectively) and P.g. (56% vs. 42%, respectively) more often than the conventional culture in plaque samples. Thus, our multiplex PCR method is rapid and more effective than conventional protocols in detecting these periodontal pathogens.
Concise Review: Saliva and Growth Factors: The Fountain of Youth Resides in Us All
Authors: Zelles T. , Purushotham K.R. , Macauley S.P. , Oxford G.E. , Humphreys-Beher M.G.
Published: January 2009

The predominant focus of research dealing with saliva revolves around the role in the maintenance of oral health through a number of physiological and biological properties of constituent proteins. An ever-expanding literature exists indicating that the salivary glands additionally synthesize, and secrete into saliva, a wide range of growth factors. Animal studies with epidermal growth factor have provided evidence for a role in both oral and systemic health, through the promotion of wound healing rates. Thus, the ability to manipulate their rates of synthesis and absorption from saliva holds the potential to enhance tissue regeneration and homeostasis.
Bovine Enamel Organ Cells Express Tissue Non-specific Alkaline Phosphatase mRNA
Authors: Yuan Z.A. , Golub E.E. , Collier P.M. , Gibson C.W.
Published: January 2009

Alkaline phosphatase (AP) is expressed at high levels in all mineralizing tissues, and the isoform identified in developing enamel has biochemical properties similar to that found in bone. While the bone AP is referred to as the liver/bone/kidney or tissue non-specific (TNS) form, other APs are highly specific for tissue of expression. To determine unequivocally the AP isoform made by enamel organ cells, we constructed a fetal bovine enamel organ cDNA library, which yielded eight AP cDNA clones. In each case, the DNA sequence was homologous to the partial cDNA reported for bovine kidney AP (Garattini et al., 1987). It is concluded that enamel organ cells express the TNS-AP isoform. The extended 3' untranslated region of the cDNA has considerable homology to human TNS-AP, and the conservation of sequence suggests that the 3' end may have a role in post-transcriptional regulation of expression.
Michael Buonocore and the Eastman Dental Center: A Historic Perspective on Sealants
Authors: Handelman Stanley L. , Shey Zia
Published: January 2009

Dr. Michael Buonocore is known for his innovative research on the preparation of the enamel surface with a weak acid to enhance adhesion of an organic plastic chemical sealant and the polymerization in situ of a sealant with ultraviolet light. His co-workers at Eastman Dental Center aided and extended his research findings. The purpose of his original research was the development of a sealant to prevent occlusal caries on posterior teeth. However, the major impact of his work has been the development of adhesive restorative techniques. Although it has been demonstrated that (i) bacteria tend to die out and caries does not progress if early caries lesions are inadvertently sealed, (ii) sealant retention rates are favorable, and (iii) sealants are cost-effective, the use of sealants by the profession is still far short of early expectations.
Cariogenicity Depends More on Diet than the Prevailing Mutans Streptococcal Species
Authors: van Palenstein Helderman W.H. , Matee M.I.N. , van der Hoeven J.S. , Mikx F.H.M.
Published: January 2009

This review aims to compare the occurrence and distribution of mutans streptococci in Africa, Europe, and North America and in addition will try to offer explanations for existing relationships among salivary mutans streptococci counts, dietary patterns, and dental caries. The literature reveals that salivary mutans streptococci counts in child populations of the three continents are comparable. The distribution of mutans streptococci species, with a predominance of S. mutans followed by S. sobrinus, and the virtual absence of other mutans streptococci species are also comparable. Although it is widely believed that diet has an important effect on mutans streptococci counts, this review provides evidence that this does not hold true when variations in dietary patterns are moderate, as they normally are in real-life situations. Since the diets of the child populations in the three continents vary moderately, a strong dietary-induced effect on salivary mutans streptococci counts cannot be expected. The observed analogous salivary mutans streptococci counts in these child populations are thus 'not surprising' but are in accordance with the conceptual expectation. The differences in caries experience in children of the three continents cannot be explained by the prevailing mutans streptococci species but instead should be attributed to differences in the cariogenicity of the various diets. The fact that the cariogenicity of the diet determines the development of dental caries while hardly affecting the mutans streptococci counts explains the limited value of the latter as an indicator of dental caries. The reviewed literature shows that mutans streptococci are ubiquitous in children aged 7 years and older in Africa, Europe, and North America. Mutans streptococci should therefore be considered as belonging to the indigenous microflora of the human mouth.
Sleep Bruxism: Validity of Clinical Research Diagnostic Criteria in a Controlled Polysomnographic Study
Authors: Lavigne G.J. , Rompre P.H. , Montplaisir J.Y.
Published: January 2009

The clinical validity of diagnostic criteria for sleep orofacial motor activity-more specifically, bruxism-has never been tested. Polysomnographic recordings from 18 bruxers and 18 asymptomatic subjects, selected according to American Sleep Disorders Association criteria, were analyzed (1) to discriminate sleep bruxism from other orofacial motor activities and (2) to calculate sensitivity, specificity, and predictive values of research criteria. Clinical observations and reports revealed that all 18 bruxers reported frequent tooth-grinding during sleep. Tooth wear was noted in 16 out of 18 bruxers and jaw discomfort reported by six of them. These findings were present in none of the controls. The analysis of polysomnographic data showed that the asymptomatic subjects presented a mean of 1.7 ± 0.3 bruxism episodes per hour of sleep (sustained or repetitive bursting activity in jaw closer muscles), while bruxers had a significantly higher level of activity: 5.4 ± 0.6. Controls exhibited 4.6 ± 0.3 bruxism bursts per episode and 6.2 (from 0 to 23) bruxism bursts per hour of sleep, whereas bruxers showed, respectively, 7.0 ± 0.7 and 36.1 (5.8 to 108). Bruxism-like episodes with at least two grinding sounds were noted in 14 of the 18 bruxers and in one control. The two groups exhibited no difference in any of the sleep parameters. Based on the present findings, the following polysomnographic diagnostic cut-off criteria are suggested: (1) more than 4 bruxism episodes per hour, (2) more than 6 bruxism bursts per episode and/or 25 bruxism bursts per hour of sleep, and (3) at least 2 episodes with grinding sounds. When the polysomnographic bruxism-related variables were combined under logistic regression, the clinical diagnosis was correctly predicted in 81.3% of the controls and 83.3% of the bruxers. The validity of these clinical research criteria needs now to be challenged in a larger population, over time, and in subjects presenting various levels of severity of sleep bruxism.
Inflammatory Lesions of the Tooth Pulp Induce Changes in Brainstem Neurons of the Rat Trigeminal Subnucleus Oralis
Authors: Tomeck C.D. , Kwan C.L. , Hu J.W.
Published: January 2009

Neuroplastic changes are known to occur in the CNS in response to injury of peripheral nerves. Previous investigation has demonstrated neuroplasticity in second-order neurons of the subnucleus oralis (SO) of the trigeminal (V) nuclear complex in association with aseptic injury to the tooth pulp. A question arises, therefore, as to whether similar changes occur in response to injury associated with inflammation induced by tooth pulp infection. The effects of tooth pulp infection on the mechanoreceptive fields (RFs) of SO neurons were examined in rats. Infection was established by exposure and removal of the coronal pulp of the mandibular first molar, which was left open to the oral environment for 7 (n = 5) or 28 (n = 6) days. Neurons in SO were then electrophysiologically characterized in chloralose/urethane-anesthetized rats. The RF and the response properties of 118 low-threshold mechanoreceptive (LTM) neurons from seven-day-old rats and 149 LTM neurons from 28-day-old rats were compared with those of 204 LTM neurons tested in 11 untreated (control) rats. Significant differences were noted in RF size and location when control, seven-day-old, and 28-day-old groups were compared. Radiographic examination revealed inconsistencies among examiners in the interpretation of periapical lesions < 2 mm in diameter and general agreement in the identification of periapical lesions > 2 mm in diameter. Histological examination of teeth with pulp exposure revealed superficial necrosis and inflammation without periapical extension in the seven-day-old animals and total pulp necrosis with periapical inflammation, abscess formation, and alveolar bone resorption in the 28-day-old animals. The results indicate that neuroplastic changes in LTM oralis neurons can develop subsequent to tooth pulp infection and that there may be a correlation between the incidence of these changes and the extension of the attending inflammation from the pulp to the dental supporting tissues.
Interleukin (IL)-1β, IL-6, Tumor Necrosis Factor-α, Epidermal Growth Factor, and β2-Microglobulin Levels Are Elevated in Gingival Crevicular Fluid during Human Orthodontic Tooth Movement
Authors: Uematsu S. , Mogi M. , Deguchi T.
Published: January 2009

Bone remodeling is a complex process regulated by several mediators. Recent work has revealed that cytokines and growth factors have significant effects on bone cell metabolism. However, little information is available concerning the production of cytokines during orthodontic tooth movement in human subjects, and there is no non-invasive model for determining the production of cytokines. Therefore, the purpose of this study was to identify and quantify the various cytokines in human gingival crevicular fluid (GCF), and to investigate the changes in their levels during orthodontic tooth movement. Twelve patients (mean age, 14.4 years) were used as subjects. An upper canine of each patient having one treatment for distal movement served as the experimental tooth, whereas the contralateral and antagonistic canines were used as controls. The GCF around the experimental and the two control teeth was taken from each subject immediately before activation, and at 1, 24, and 168 hr after the initiation of tooth movement. Cytokine levels were determined by ELISAs. The concentrations of interleukin (IL)-1β, IL-6, tumor necrosis factor-a, epidermal growth factor, and β2-microglobulin were significantly higher in the experimental group than in the controls at 24 hr after the experiment was initiated. All the cytokines remained at baseline levels throughout the experiment for the two control groups. In contrast to cytokine alteration, the amount of total protein in the GCF exhibited a gradual increase, but no significant difference was observed between the control and experimental groups. Since all cytokines in GCF play an important role in the bone remodeling processes in vitro, the present results indicate that the changes in cytokines in GCF are associated with orthodontic tooth movement.
Regulation of Mucous Acinar Exocrine Secretion with Age
Authors: Culp D.J. , Richardson L.A.
Published: January 2009

Denny and co-workers (Navazesh et al., 1992) recently reported decreased concentrations of MG1 and MG2 mucins in resting and stimulated whole human saliva with age. The current study was therefore conducted to examine whether there is a corresponding attenuation with age in stimulus-secretion coupling regulating mucous cell exocrine secretion. We utilized an in vitro model system, isolated rat sublingual acini, to evaluate the regulation of mucous cell exocrine secretion. Rat sublingual glands are similar to human sublingual and minor mucous glands, both histologically and in terms of their pattern of innervation, which is predominantly parasympathetic. Mucin secretion is thus activated primarily by muscarinic cholinergic agonist and to a lesser extent by vasoactive intestinal peptide (VIP), which is co-localized with acetylcholine in parasympathetic nerve terminals. We isolated sublingual mucous acini from five-month-old and 24-month-old rats and compared the concentration responses for mucin secretion induced by VIP and the muscarinic agonist, arecaidine propargyl ester (APE). Concentration-response curves for VIP were nearly identical for mucous acini from the five-month-old and 24-month-old animals. Values for basal secretion, maximal secretion, and EC50 (= 200 nmol/L VIP) were statistically equivalent between both age groups. Concentration-response curves for APE were also very similar between age groups, with no statistically significant difference in basal secretion or EC50 values (= 50 nmol/L APE). Maximal secretion was slightly less but statistically different for 24-month-old vs. five-month-old animals, 158% vs. 169% above basal secretion, respectively. Collectively, we found no substantial age-related changes in the secretory responsiveness of salivary mucous cells.
Immunoreactivity of Tenascin-C in Dentin Matrix in Dentinogenesis Imperfecta Associated with Osteogenesis Imperfecta
Authors: Lukinmaa P.-L. , Allemanni G. , Waltimo J. , Zardi L.
Published: January 2009

Osteogenesis imperfecta (01) is a heterogeneous group of heritable connective tissue disorders, assigned to different mutations in type I collagen genes. A variety of structural abnormalities of dentin have been described in dentinogenesis imperfecta (DI) associated with OI. To clarify further the constitution of the dentin matrix in 01, we immunostained frozen and paraffin sections of deciduous teeth from four patients, each from a different family, with two monoclonal antibodies (MAbs) to the matrix glycoprotein tenascin-C (TN-C). One of the MAbs recognizes an epitope common to all TN-C isoforms (BC-4), and the other is specific for a splicing variant (BC-2). Normal teeth, oral mucosa, and skin were analyzed for comparison. Staining patterns with the two MAbs did not differ markedly. Normal dentin matrix and odontoblasts were lacking reactivity, but the pulp stained clearly. TN-C reactivity was present in the dentin matrix of all teeth obtained from two patients with different OI phenotypes and DI, and in one out of three teeth from one patient who also had DI. The reactivity was distributed in layers, but the staining patterns varied from one patient to another and from tooth to tooth. Intratubular staining seen in a tooth from the patient with clinically and histologically normal teeth was comparable with that present in normal deciduous teeth. The variation in TN-C expression suggests that, besides genetic heterogeneity, epigenetic factors could influence the composition of the dentin matrix in OI.
Evaluation of Sodium Fluorescein for Quantitative Diagnosis of Root Caries
Authors: van der Veen M.H. , Tsuda H. , Arends J. , ten Bosch J.J.
Published: January 2009

The diagnosis of root caries, in particular the judgment of the activity of a visually observed lesion, is difficult. Quantitative determination of lesion severity would allow the lesion to be monitored with time, so that an indication of lesion activity could be obtained. This paper describes a step in the development of a method that provides such a quantitative determination. Specifically, fluorescein sodium salt is used as a penetrating dye, the subject of study being the relationship between dye concentration and porosity in demineralized root dentin. Fourteen human third molars were demineralized in vitro (lactic acid CMC-gel, pH 5; in each of 6 groups for 4, 7, 11, 14, 18, and 21 days). Fluorescein sodium salt (0.2 g/L) was applied for 2 min. Thin slices (± 130 um) were cut from the root surfaces without water cooling. The dye fluorescence radiance in the demineralized dentin was determined by means of a micro-Raman spectroscope and compared with the mineral loss profiles measured with transverse microradiography (TMR). The TMR data were corrected for the difference in measurement area between the two measurement systems. Corrected TMR profiles were compared with the corresponding fluorescence scans, showing linear correspondence. The correlation coefficient was r = 0.96. We conclude that, after uptake of fluorescein sodium salt for 2 min, the dye concentration in an artificially produced root-surface caries lesion is proportional to the amount of mineral lost from that lesion.
Long-term Use of Nicotine Chewing Gum and Mercury Exposure from Dental Amalgam Fillings
Authors: Sällsten G. , Thorén J. , BarregÅrd L. , Schütz A. , Skarping G.
Published: January 2009

In experimental studies, chewing gum has been shown to increase the release rate of mercury vapor from dental amalgam fillings. The aim of the present study was to investigate the influence of long-term frequent chewing on mercury levels in plasma and urine. Mercury levels in plasma (P-Hg) and urine (U-Hg), and urinary cotinine were examined in 18 subjects who regularly used nicotine chewing gum, and in 19 referents. Age and number of amalgam surfaces were similar in the two groups. Total mercury concentrations in plasma and urine were determined by means of cold vapor atomic absorption spectrometry. Urinary cotinine was determined by gas chromatography-mass spectrometry. The chewers had been using 10 (median) pieces of gum per day for the past 27 (median) months. P-Hg and U-Hg levels were significantly higher in the chewers (27 nmol/L and 6.5 nmol/mmol creatinine) than in the referents (4.9 nmol/L and 1.2 nmol/mmol creatinine). In both groups, significant correlations were found between P-Hg or U-Hg on the one hand and the number of amalgam surfaces on the other. In the chewers, no correlations were found between P-Hg or U-Hg and chewing time per day or cotinine in urine. Cotinine in urine increased with the number of pieces of chewing gum used. The impact of excessive chewing on mercury levels was considerable.
New Surface-active Comonomer for Adhesive Bonding
Authors: Bowen R.L. , Bennett P.S. , Groh R.J. , Farahani M. , Eichmiller EC
Published: January 2009

Previous studies have indicated that chemical and physical characteristics of aromatic amines can be influenced by the nature of their substituents. The experimental question examined in the present study relates to the effects of replacing specific hydrogen atoms with methyl groups in a surface-active comonomer utilized in adhesive bonding protocols. N-2-propionic acid-N-3-(2-hydroxy-l-methacryloxy)propyl-3,5-dimethylaniline sodium salt (N35A) was synthesized by an addition reaction of glycidyl methacrylate with the sodium salt of N-(3,5-dimethylphenyl)alanine, which was formed by alkaline hydrolysis of ethyl-N-(3,5-dimethylphenyl)alanate that was prepared by condensation of ethyl-2-bromopropionate with 3,5-dimethylaniline. 1H and 13C NMR spectra and analysis by mass spectroscopy were consistent with N35A after it had been recrystallized from acetone. Color stability and adhesion-promoting capability of N35A were compared with those of N-2-acetic acid-N-3-(2-hydroxy-l-methacryloxy)propyl-4-methylanaline sodium salt (Na-NTG-GMA), the latter being widely used in commercial bonding formulations. Both N35A and Na-NTG-GMA polymerized within a few minutes at 23°C when dissolved in aliquots from a stock solution containing benzene 85 wt%, ethanol 14 wt%, and benzoyl peroxide 1.0 wt%; but with each at 0.018 molal concentration, the N35A suspension was more color-stable than that of the Na-NTG-GMA. In the protocol used, shear bond strengths of a hybrid composite to human dentin with N35A were 30.2 MPa, SD = 7.5 MPa, and with Na-NTG-GMA, 29.7 MPa, SD = 11.8 MPa (n = 7 each; t test, p = 0.93).
Ins and Outs of Antimicrobial Resistance: Era of the Drug Pumps
Authors: Jenkinson Howard F.
Published: January 2009

Over the past five years, concerns have heightened over the escalating numbers of pathogenic micro-organisms isolated that are resistant to many antibiotics and drugs. This phenomenon poses major problems in the treatment of patients with hospital- or community-acquired infections caused by bacteria, fungi, or parasitic organisms. Microbial cells have acquired resistances to specific antibiotics and drugs by mechanisms that include antibiotic inactivation, target alteration, or drug exclusion. More recently, the importance of another mechanism, that of drug expulsion, has been recognized as contributing significantly to antibiotic and drug resistance in microbes. Drug expulsion, mediated by membrane-associated drug efflux pumps, can protect cells from a range of toxic compounds and therefore may confer single-step multidrug resistance. It is imperative that new drugs be designed or discovered that will poison the pumps or bypass the efflux mechanisms.
Analysis of Tempering Stresses in Metal-Ceramic Disks
Authors: DeHoff P.H. , Anusavice K.J. , Vontivillu S.B.
Published: January 2009

Previous studies showed that residual compressive stresses induced by thermal tempering retarded the growth of surface cracks in bilayered porcelain disks. The objectives of the present study were: (1) to determine whether thermal tempering by air blasting reduces the length of cracks induced by microhardness indentation in metal-ceramic disks, and (2) to use visco-elastic finite element analyses to calculate transient and residual stresses in metal-ceramic disks. Ni-Cr-Be disks, 16 mm in diameter and 0.3 mm in thickness, were prepared with a 0.5-mm-thick layer of opaque porcelain and a 1.5-mm-thick layer of body porcelain. Metal-porcelain combinations were selected to provide a range of thermal contraction mismatch values. The disks were fired to the maturing temperature of body porcelain and then were subjected to three cooling procedures: (1) slow cooling in a furnace (SC), (2) cooling in air (FC), and (3) air tempering (T) by blasting the surface of the body porcelain with compressed air. The lengths of cracks induced in the surface of the body porcelain by a microhardness indenter were measured immediately after indentation at 20 points along diametral lines. The results of Tukey's multiple-contrast analyses indicated that the mean crack lengths of air-tempered specimens were significantly smaller (p ≤ 0.05) than the crack lengths of the fast-cooled and slow-cooled groups. Except for one case, there were no statistically significant differences in the mean crack lengths between FC and SC specimens independent of thermal contraction mismatch. Residual tensile stresses were calculated for SC and FC specimens for all thermal contraction mismatch cases, with the largest values being associated with combinations containing the body porcelain with the smaller contraction coefficient. Calculations by use of the model confirmed that tempering induces large residual compressive stresses in the surface of body porcelain for all of the thermal contraction mismatch cases included in this study.