bluuebunny/crossref_metadata_2025_split huggingface dataset:
Variables Affecting Measurements of Vertical Occlusal Force
Authors: Fields H.W. , Proffit W.R. , Case J.C. , Vig K.W.L. 
Published: November 2010

Previous studies of occlusal force have provided conflicting results. The purpose of these studies was to determine whether the extent of vertical opening, contralateral occlusal support, or head posture influenced vertical occlusal forces during swallowing, simulated chewing, and maximum biting effort. Three samples of subjects with normal vertical facial proportions - one each of children, adolescents, and young adults - were evaluated to determine the effects of changes in small (2.5 vs. 6.0 mm) vertical separation of the first molars. A sample of young adults was used to evaluate changes in large (10-40 mm) vertical openings, and a sample of adolescents was used to investigate the effect of contralateral support and head posture. All between-group comparisons were evaluated using non-parametric statistics. For the small vertical openings, there was significantly more vertical occlusal force at 6.0 than 2.5 mm in children during swallowing and chewing but not during maximum biting effort. In adults, there was significantly more force during swallowing at 6.0 than at 2.5 mm separation, but no differences in chewing or maximum biting. Increasingly large vertical openings resulted in a progressive increase in maximum bite force to a maximum at about 20 mm, followed by a decrease and then a second increase to near-maximum force at about 40 mm for young adults. There were no significant differences in vertical force with or without contralateral support or between flexed, normal, and extended head postures at either of the small openings.
A Comparison of Some of the Permeability Characteristics of Intact and Tape-stripped Hamster Cheek Pouches in vitro
Authors: Reid C.O. , Hardcastle J. , Smith C.J. 
Published: November 2010

Cheek pouches were removed from anesthetized hamsters and were either tape-stripped or left intact and then mounted in Ussing chambers, where they were bathed in Krebs-Ringer bicarbonate saline. A potential difference could be measured across all pouches and was stable for over an hour across the unstripped pouches. The electrical resistance across the unstripped pouches was high (8960 Ω.cm2), whereas the resistance across the tape-stripped pouches was significantly lower (p<0.01), suggesting that these pouches are likely to be more permeable than the unstripped pouches. Reflection coefficients of urea, ethanol, and glycerol were derived by means of streaming potentials. Values for intact pouches were all close to 1 and for tape-stripped pouches were 0.938, 0.822, and 0.509, respectively. Permeability coefficients for urea and ethanol across intact and tape-stripped pouches were, respectively, 12.5 × 10-9 cm/min; 27.6 x 10-9 cm/min; 2325 × 10 -9 cmlmin ; and 28471 × 10-9 cmlmin. The hamster cheek pouch has a high electrical resistance; it is an impermeable structure in which the keratin layer appears to provide a major barrier to the passage of water, ions, and certain solutes.
Demonstration of Structural Variation in Rat Incisor Dentin as Determined by the X-ray Laue Method
Authors: Mishima H. , Sakae T. 
Published: November 2010

Rat incisor dentin was studied by an x-ray micro-Laue method to investigate the relationship between crystal orientation and structural variation in the dentin. The results showed that crystal orientation was very poor in the labial dentin, but that the crystals were well-oriented in the lingual dentin. In the lingual dentin, the axis of crystal orientation was parallel to the tooth axis. It is suggested that the difference in crystal orientation between the lingual and labial dentin is due to the different mode of calcification between the two.
A Numerical Model of Temporomandibular Joint Loading
Authors: Smith D.M. , McLachlan K.R. , McCall W.D. 
Published: November 2010

A numerical model of the mandible, its articulating surfaces, and the forces exerted by the primary masticatory muscles has been developed for the purpose of investigating loading of the temporomandibular joint. Evidence is presented which shows that the temporomandibular joint is a load-bearing joint over the normal functional range of bite-force positions and angles. In this investigation, temporomandibular joint loads were found to vary from a maximum appositional force of 60% of the bite force (when bite forces were applied to the incisors) to a distracting force of about 5% of the bite force (when applied to the distal surfaces of the third molars). TMJ loads tended to reach a minimum as a result of vertically directed bite forces positioned at the second molars. A range of conditions in which bite forces were directed parallel to or within approximately 20° of the mid-sagittal plane was found to be conducive to stability of the temporomandibular joint. This stability included symmetry in the direction and in the magnitude of condylar loads as well as the presence of small forces tending to appose the condyle and articular eminence. TMJ loads tended to reach a maximum in response to mediolaterally directed bite forces. This result is consistent with the fact that no muscle of mastication exhibits a spatial orientation in which the muscle fibers are predominantly mediolateral in direction.
Establishment of an Improved Implantation Technique for Hamster Mucous Membrane Irritation Testing
Authors: Roy M. , Wishe H.I. 
Published: November 2010

Biological evaluation procedures for the acceptance of new dental materials include testing for mucous membrane irritation and inflammation, with the hamster cheek pouch used as a model system. Previous reports have indicated both a low 14-day implant retention rate and poor differentiation between positive and negative controls, requiring the establishment of a new standard procedure for hamster cheek pouch implantations. Groups of 10 female golden Syrian hamsters were implanted with uniform discs (6 mm in diameter and 1 mm thick) of white base-plate gutta percha (GP), gray welding-rod polyvinyl chloride (PVC), low-density polyethylene (LDPE), or test alloys, under Nembutal anesthesia. Each animal's right cheek pouch was everted and cleaned, and the implant was loosely placed at the bottom of the pouch. The pouch was closed by a double-suture technique. Contralateral (left) cheek pouches served as controls for the physical state of each animal. A collar (cable tie) was placed tightly around the animal's neck at a level between the sutures and the implant. Cheek pouches were assessed after 14 days. Implants were kept in contact with oral mucosa longer using the double-suture-plus-collar technique than in hamsters without collars (14-day retention rates of 48.0% and 6.7%, respectively). Average severity indices (ASI) of 5.4 and 1.7 were obtained for PVC and GP, respectively, as compared with 1.6 for contralateral control pouches. LDPE was not a suitable negative control material (ASI = 2.6). Positive and negative controls were clearly delineated when PVC and GP were the control materials.
Metronidazole Concentrations in Human Plasma, Saliva, and Gingival Crevice Fluid after a Single Dose
Authors: Van Oosten M.A.C. , Notten F.J.W. , Mikx F.H.M. 
Published: November 2010

Metronidazole concentrations were estimated in four human volunteers after a single dose of 750 mg taken orally. Samples of blood, saliva, and gingival crevice fluid were collected before intake and during the following 24 hours. The concentrations of metronidazole in plasma and saliva were measured by high-performance liquid chromatography (HPLC). The concentrations in gingival fluid were estimated by a capillary agar-diffusion assay. The results of the metronidazole measurements as obtained by both methods were significantly correlated. The peak concentrations of metronidazole in plasma and saliva were in the same range, 8.7-13.8 μ g/mL, and similar concentrations were found in the gingival fluid samples. It is concluded that metronidazole taken orally has similar pharmacokinetics in both saliva and plasma, and that a single oral dose of 750 mg metronidazole leads to a concentration of the drug in the gingival crevice fluid that exceeds the minimal inhibitory concentration for most anaerobic oral micro-organisms.
Effects of Water-soluble Components of Cheese on Experimental Caries in Humans
Authors: Silva M.F. de A. , Burgess R.C. , Sandham H.J. , Jenkins G.N. 
Published: November 2010

The effect of water-soluble components of extra-old Cheddar cheese on experimental caries was tested by means of the seven-day intraoral cariogenicity test (ICT). Two bovine enamel blocks were placed in each buccal flange of the dental appliances of five volunteers. One side of each appliance (experimental) was dipped in a 25% water extract of the cheese for five min, while the other side (control) was dipped in de-ionized water. Immediately thereafter, the appliance was returned to the subject's mouth, and two 60-second rinses with 10% sucrose were performed. These procedures were repeated six times per day. The cheese-extract dippings reduced the cariogenicity of the sucrose by an average of 55.7% (p<0.01), as assessed by enamel microhardness. Neither the mean resting pH nor the mean minimum pH in response to sucrose was significantly different between the experimental and control sides. The concentration of calcium was significantly higher in plaque from the experimental side (32.44 μg/mg) as compared with the control side (19.36 μg/mg, p<0.01). The concentration of plaque phosphorus was higher on the experimental side (12.90 μg/mg) than on the control side (9.61 μg/mg); however, the difference was not statistically significant. These results show that cheese has one or more water-soluble components which reduce experimental caries in human subjects.
Nerve Interactions in Salivary Glands
Authors: Emmelin N. 
Published: November 2010

In the salivary reflex, not only secretory cells are activated, but also myo-epithelial cells are contracted to support these cells and promote the flow of saliva, and blood vessels dilate to meet the increased demands of the tissues. The various effector cells often receive nerves from both parts of the autonomic system, and interactions may occur when the nerves act on the same type of effector, or on different types of effectors.While in an experiment electrical stimulation of the sympathetic trunk may decrease a parasympathetic salivary flow by causing marked vasoconstriction, this does not occur in the salivary reflex, since the vasoconstrictors do not take part. On the contrary, the normal sympathetic vasoconstrictor tone of the resting gland is easily overcome by activity in parasympathetic vasodilator nerves when secretion starts. Pronounced synergism can be demonstrated between sympathetic and parasympathetic secretory nerves. In dogs, for instance, in which sympathetic secretion is β-adrenoceptor-mediated, this is marked in the case of fluid secretion. In rats and rabbits, in which β-receptors elicit secretion of amylase, the potentiating interaction among the nerves is striking when amylase secretion is considered. Even the random release of acetylcholine from the post-ganglionic parasympathetic axons, by itself insufficient to evoke secretion, can increase the sympathetic effects. Motor nerves interact with secretory nerves by causing myo-epithelial contraction, mechanically promoting secretion. Interactions between the nerves in their long-term regulatory function on the sensitivity of the acinar secretory and myo-epithelial cells can also be demonstrated.
Developmental Changes in the Volumes, Protein, and Some Electrolyte Concentrations of Male and Female Rat Submandibular Saliva Secreted in Response to Methoxamine and Pilocarpine
Authors: Abe K. , Hidaka S. , Ishibashi K. , Yanabu M. , Kamogashira K. , Itoh T. , Matsumoto M. 
Published: November 2010

Saliva secreted in response to methoxamine and pilocarpine was collected from the cannulated ducts of the submandibular glands of male and female rats at weekly intervals from two to 10 weeks of age. It was analyzed for volume and for concentrations of protein, potassium, calcium, and inorganic phosphate. Following the collection of saliva, the submandibular glands were removed and weighed. The wet weights of the glands increased substantially up to seven weeks of age and then reached almost plateau values in both sexes. The salivary volumes secreted in response to both agents in both sexes were positively correlated with the gland weights, except that after five to six weeks of age there was no correlation between gland weight and methoxamine-stimulated salivary volume. The concentrations of protein, potassium, and inorganic phosphate were inversely related to the flow rates only at relatively low rates of flow. The concentration of calcium was positively correlated with the protein concentration and was independent of the nature of the stimulus and of sex differences during postnatal development.
Altered Sympathetic-Salivary Gland Development: Delayed Response to Postnatal Castration
Authors: Melvin J.E. , Hamill R.W. 
Published: November 2010

These studies defined the normal and hormonally altered development of activity for tyrosine hydroxylase (T-OH), the rate-limiting enzyme in catecholamine biosynthesis (Levitt et al., 1965), and choline acetyltransferase activity (CAT) in the male rat superior cervical ganglion (SCG). Additionally, salivary gland weight was monitored. Two distinct developmental plateaus for postsynaptic T-OH activity exist. The first plateau represents the prepubertal level, which is significantly lower than the second postpubertal plateau. In contrast, presynaptic CAT activity displayed only a single plateau, commencing at approximately 45 days of age.The effects of postnatal castration (at 10 or 11 days of age) on the submandibular gland and T-OH activity were delayed until after puberty. No change in T-OH activity was seen at two and four post-operative weeks between control and castrated animals; however, T-OH activity was significantly less in castrated animals at 12 and 16 post-operative weeks. Testosterone replacement reversed the effect of castration on T-OH activity. Conversely, CAT activity in the SCG was unchanged by postnatal castration for at least 16 post-operative weeks, the longest time point studied. The failure of castrated animals to display the normal developmental increase in T-OH activity following puberty was comparable with the effect of castration on the development of submandibular salivary gland weight.These results suggest that in postpubertal male rats, development of T-OH activity in the superior cervical ganglion is influenced by testosterone. The parallel effects of castration on submandibular gland weight imply that testosterone regulates T-OH activity via an indirect mechanism. In contrast to noradrenergic enzyme activity and target tissue size, the ontogeny of presynaptic CAT activity appears to be insensitive to testosterone levels.
The Effects of Tenotomy on the Morphology of the Rabbit Digastric Muscle
Authors: Waryjas R.J. , Muhl Z.F. 
Published: November 2010

The digastric muscles of 17 New Zealand White rabbits were subjected to tenotomy. A sham operation was performed on six animals. Groups of three or four animals were killed at one hour, one day, 10 days, 30 days, and 60 days after the tenotomy. There was evidence of tendon regeneration by 10 days, and by 30 days the tendon appeared normal macroscopically. The tendon was normal in microscopic appearance in the animals examined at 60 days. Muscle belly length and fascicle length decreased after the tenotomy, and the angle of pinnation increased. Sarcomere lengths underwent a transient decrease within one hour of the tenotomy, but then were as long as or longer than those in the sham-operated group. A biomechanical analysis suggests that the net result of the morphological changes produced by the tenotomy leads to a reduction in force capability of only about 12%. The shorter belly and fascicle lengths, however, may diminish the effective range over which effective force can be exerted.
Hard Tissue Barrier Formation in Pulpotomized Monkey Teeth Capped with Cyanoacrylate or Calcium Hydroxide for 10 and 60 Minutes
Authors: Cvek M. , Granath L. , Cleaton-Jones P. , Austin J. 
Published: November 2010

Monkey incisor teeth were pulpotomized in groups of 10. After physiological hemostasis, the pulps of group I were covered with isobutyl cyanoacrylate, and those of groups II and III with calcium hydroxide for 10 and 60 minutes, respectively, whereafter this compound was washed away and the wound surfaces covered with Teflon. In group IV, calcium hydroxide was used as a positive control, and Teflon as a negative control in group V. The animals were killed after 12 weeks and the teeth removed in tissue blocks. The material was processed and evaluated histologically with respect to location and continuity of a hard tissue barrier, type of newly formed hard tissue, state of the pulp, and presence of stainable bacteria in the coronal cavity. Seven of nine teeth in group I showed a hard tissue barrier. The corresponding figure for group II was eight out of 10 teeth. All teeth in groups III and IV had a barrier. The incidence of a continuous barrier increased from group I through group IV, as did the incidence of its location below the level of the original wound surface. The condition of the pulp was related to the presence of bacteria and the continuity of the barrier to the presence of inflammation. There was no bridging in group V. The results support the theory that a low-grade irritation is responsible for the formation of a hard tissue barrier in exposed pulps.
Verification of Theoretical Modeling of Heat Transmission in Teeth by in vivo Experiments
Authors: Spierings Th. A. M. , Peters M.C.R.B. , Bosman F. , Plasschaert A.J.M. 
Published: November 2010

A theoretical axisymmetric tooth model, simulating the conditions involved in the drinking of a liquid of a certain temperature, was compared with results of a similar in vivo experiment. The temperature changes as a result of one draught of a hot/cold liquid were recorded within the model as well as in the surrounding environment. The experimental data obtained were compared with the calculated results for the theoretical model as determined by the Finite Element Analysis. The temperatures recorded experimentally agreed reasonably with the calculated results. It can be concluded that the assumptions which have been made concerning the described thermal loading conditions lead to a good approximation of the physical reality.
Effect of Acid Type on Kinetics and Mechanism of Dental Enamel Demineralization
Authors: Patel M.V. , Fox J.L. , Higuchi W.I. 
Published: November 2010

The influence of acid type (pKa effects) of weak organic acid buffers on dissolution kinetics of dental enamel was critically examined for rigorous testing of the behavioral validity of the physical model of Patel et al. (1987). Quantitative evaluation of this model indicated that monitoring initial dissolution rates was a viable approach to critical testing of the model. Initial dissolution rates were determined in 0.1 mol/L acetate (pKa = 4.77), benzoate (pKa = 4.20), and salicylate (pKa = 2.98) buffers (pH = 4.50, μ = 0.50), with ground bovine enamel blocks of known surface area mounted in a rotating disk apparatus. The Levich theory was used to study dependence of dissolution rates on stirring rates in these buffers. The experimental data were analyzed by the physical model which includes pKa effects, complexation of the buffer anion with the other ions, surface kinetics, simultaneous diffusion and equilibrium of all species in enamel pores, diffusion layer thickness, and bulk solution composition. The KIAp [ a10Ca2 + a6 PO34-a2OH-] governing the dissolution reaction and the surface resistance factor were deduced from the model. Dissolution kinetics was also followed in these buffers in the presence of calcium or phosphate common ions. In effect, by conducting both the stirring rate studies and common ion experiments, we derived the driving force function independently by these two techniques. The results obtained in this study were consistent with the model, indicating that pKa effects on the dissolution of dental enamel can be accountedfor quantitatively by the model, and it was found that weak acids do not influence either the apparent solubility or the surface reaction process of bovine dental enamel.
Corrosion of Ferromagnetic Alloys used for Magnetic Retention of Overdentures
Authors: Vrijhoef M.M.A. , Mezger P.R. , Van der Zel J.M. , Greener E.H. 
Published: November 2010

Three ferromagnetic casting alloys intendedfor use with magnetically retained overdentures (compositions in wt%: #1, Pd 50, Co 47, Ga 2, Pt 1 ; #2, Pd 60, Co 37, Ga 2, Pt 2; #3, Pd 49, Co 46, Ga 2, Pt 2) were investigated. A 0.9% saline solution and an artificial saliva (Meyer) were used for evaluation of the electrochemical corrosion behavior of these alloys, utilizing standard potentiodynamic techniques. All alloys investigated possessed a good corrosion resistance in the potential range of the oral environment (from - -100 to 300 mV versus SCE). In addition, alloys #1 and 3 appeared to be susceptible to pitting above +300 mV (SCE), while #2 was resistant to pitting and was found to passivate in 0.9% saline solution.
Surface Characterization of Amalgams Using X-ray Photoelectron Spectroscopy
Authors: Hanawa T. , Takahashi H. , Ota M. , Pinizzotto R.F. , Ferracane J.L. , Okabe T. 
Published: November 2010

This study is the first to report on the use of x-ray photoelectron spectroscopy (XPS or ESCA) for studying the surface films (less than 10 nm thick) of aged amalgams. The concentrations and electron binding energies of the elements on the surfaces of four different amalgams aged for 20 min, one day, seven days, and 30 days were determined quantitatively. For comparison, the bulk compositions of the amalgams aged for seven days were also determined after removal of approximately 5 nm of material from the surface by argon-ion-sputtering. The XPS data revealed that the surface films of aged zinc-containing amalgams were not a simple oxide but were primarily composed of a (hydrated) tin and zinc oxy-hydroxide, whereas, in the zinc-free amalgams, the surface films were primarily a tin oxide. The concentration of mercury in this thin surface film after aging was depleted. This suggests that tin and/or zinc preferentially diffused to the surface and combined with oxygen, forming a surface film and diluting the mercury concentration in the surface. Another probable explanation for the depleted mercury is that a minimal amount of mercury in the surface film evaporated during the aging.