bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effects of Airborne Fluorides on Oral Conditions in Morocco
Authors: Haikel Y. , Cahen P.M. , Turlot J.C. , Frank R.M.
Published: November 2010

The purpose of this study was to determine the prevalence and severity of dental caries and dental fluorosis, as well as various other oral conditions, in 2378 subjects (ages seven to 60) living in the fluoridated area of Khouribga and the non-fluoridated area of Beni Mellal, Morocco. The community index of dental fluorosis (CFI) ranged from 1.99 to 2.80 in the high-fluoride area: Over 90% of the population was affected, and more than one-third of the subjects showed moderate dental fluorosis. However, in Beni Mellal, more than 96% of the dentate subjects examined were free of dental fluorosis, and the CFI of 0.02 was considered not significant. Significant differences were observed between the two areas with respect to caries prevalence. DMFT and DMFS indices were markedly lower in the fluorosis area of Khouribga. The oral conditions of subjects appeared to be better in Khouribga, where the gingival and calculus indices were significantly lower than in Beni Mellal. The analyses of covariance showed no significant differences in plaque accumulation (PI) between the Khouribga and Beni Mellal samples. However, a close statistical correlation was found between PI and GI in Beni Mellal and Khouribga.
Effects of Thyroxine and Dexamethasone on Rat Submandibular Glands
Authors: Sagulin G.-B. , Roomans G.M.
Published: November 2010

Glucocorticoids and thyroxine are known to have a marked effect on the flow rate and protein composition of rat parotid saliva in hormonally intact animals. In the present study, the effects of a one-week treatment of male rats with dexamethasone and thyroxine were studied by electron microscopy and x-ray micro-analysis, and by measurement of the flow rate and determination of the chemical composition of pilocarpine-induced submandibular saliva. Thyroxine had the most extensive effects on the submandibular gland. The acinar cells were enlarged and filled with mucus; the cellular calcium concentration was significantly increased. The flow rate of the submandibular saliva was significantly reduced compared with that in saline-injected control animals. Thyroxine caused an increase in the concentrations of protein, total calcium, and potassium in the saliva. Dexamethasone had no significant effects on gland ultrastructure or on the elemental composition of the acinar cells; flow rate was not affected, but the concentrations of protein, calcium, and potassium were significantly increased. The effects of dexamethasone and thyroxine on the flow rate and protein composition of pilocarpine-induced rat submandibular saliva differ from those reported earlier for rat parotid saliva after simultaneous stimulation with pilocarpine and isoproterenol.
Demonstration of Physiological Barrier Between Pulpal Odontoblasts and its Perturbation Following Routine Restorative Procedures: A Horseradish Peroxidase Tracing Study in the Rat
Authors: Turner D.F. , Marfurt C.F. , Sattelberg C.
Published: November 2010

Vascular injection of the macromolecular tracer, horseradish peroxidase (HRP), was used to study the permeability of the odontoblast cell layer in developing and mature rat molar teeth, and to investigate the effect of cavity preparations on the permeability of this epithelioid cell layer in adult animals. HRP injected into the vascular system of normal animals 28 days of age and older was localized histochemically (from 5 to 90 min after injection) throughout the extracellular spaces of the maxillary dental pulps; however, the tracer did not penetrate beyond the tight junctions at the apical region of the odontoblast cell layer, and was absent from the predentin and dentin. In contrast, HRP injected into very young neonatal animals (e.g., day 3) resulted in free passage of HRP between odontoblasts and into the overlying predentin and dentin. When Class V cavities had been prepared in adult maxillary molars after HRP was injected into the blood stream, HRP reaction product penetrated the predentin and dentin immediately beneath the cavity preparation; however, adjacent, un-traumatized areas of predentin and dentin in the operated teeth were devoid of reaction product. These results provide evidence that: (1) a physiological barrier develops between the distal segments of odontoblast cell bodies in normal rat molar teeth between days 15 and 28 of postnatal life, and this barrier prevents the passage of macromolecules from the pulp into the predentin and dentin; and (2) this barrier is perturbed following routine restorative procedures in adult animals.
Effects of Carbohydrate Pulses and pH on Population Shifts within Oral Microbial Communities in vitro
Authors: Bradshaw D.J. , McKee A.S. , Marsh P.D.
Published: November 2010

A mixed culture chemostat system was used to distinguish between the effects of carbohydrate availability per se and the low pH generated from carbohydrate metabolism on the proportions of bacteria within microbial communities. Nine oral bacteria were grown at pH 7 and pulsed with glucose on ten consecutive days. In one chemostat, the pH was maintained automatically at 7 throughout the experimental period, while in the other, pH control was discontinued for six hours after each pulse. Glucose pulses at neutral pH had little effect on the composition of the microflora. Only the proportions of A. viscosus and V. dispar increased; L. casei and S. mutans remained at low levels (0.2% and 1.0%, respectively). Acetate and propionate were the predominant end-products of metabolism; lactate levels were low. In contrast, when pH was allowed to fall after each glucose pulse, the composition of the microflora altered dramatically. The amounts of L. casei and S. mutans increased both as a proportion of the total count and in absolute numbers, as did V. dispar, whereas the amounts of the other Gram-negative organisms (B. intermedius, F. nucleatum, and N. subflava) and S. sanguis were considerably reduced. Lactate formed a major portion of the metabolic end-products. Successive glucose pulses resulted in both amplified changes in the microflora and a steadily greater rate and final extent of acid production. This is in agreement with the reported shifts in the oral microflora in vivo in response to frequent carbohydrate intake. Analysis of the data strongly suggests that the pH generated from carbohydrate metabolism, rather than carbohydrate availability per se, is responsible for the widely reported shifts in composition and metabolism of the oral microflora in vivo.
The Effect of Thermal History on Porcelain Expansion Behavior
Authors: Fairhurst C.W. , Hashinger D.T. , Twiggs S.W.
Published: November 2010

Porcelain-fused-to-metal restorations are fired several hundred degrees above the glass-transition temperature and cooled rapidly through the glass-transition temperature range. Thermal expansion data from room temperature to above the glass-transition temperature range are important for the thermal expansion of the porcelain to be matched to the alloy.

The effect of heating rate during measurement of thermal expansion was determined for NBS SRM 710 glass and four commercial opaque and body porcelain products. Thermal expansion data were obtained at heating rates of from 3 to 30°C/min after the porcelain was cooled at the same rate. By use of the Moynihan equation (where Tg systematically increases in temperature with an increase in cooling/heating rate), the glass-transition temperatures (Tg) derived from these data were shown to be related to the heating rate.
Possible Roles of Partial Sequences at N- and C-termini of Amelogenin in Protein-Enamel Mineral Interaction
Authors: Aoba T. , Moreno E.C. , Kresak M. , Tanabe T.
Published: November 2010

The purpose of this study was to assess the functional significance of homologous sequences of mammalian amelogenins at their N- and C-termini. A porcine 5-kDa fragment corresponding to the N-terminal 45 residues of amelogenins was purified from the secretory enamel. The decapeptide TDKTKREEVD corresponding to the C-terminal 10 residues of amelogenins was synthesized according to conventional solid-phase procedures. The inhibitory activity of both moieties on apatite crystal growth was determined in a supersaturated solution having an ionic composition similar to that of the fluid phase separated from porcine secretory enamel. The 5-kDa amelogenin fragment was sparingly soluble in neutral solutions and (in condensed forms because of aggregation) showed no significant inhibition of crystal growth, whereas the fragment molecules pre-adsorbed onto the seed crystals yielded modest inhibition of hydroxyapatite precipitation. However, their inhibitory activity was significantly lower than that of parent porcine amelogenin (25-kDa molecular mass). The high solubility of synthesized decapeptide allowed us to determine the adsorption isotherm onto hydroxyapatite at 37°C, at an ionic strength similar to that of the enamel fluid. The obtained adsorption isotherm was described by a Langmuir model; the adsorption affinity and the maximum adsorption sites were 6.2 mL/μmol and 0.53 μmol/m2, respectively. As expected from the low adsorption affinity, the peptide showed a much weaker inhibition of apatite crystal growth than the parent amelogenin. All the foregoing results suggest that the adsorption onto apatite crystals and any inhibition of crystal growth by the amelogenin macromolecules cannot be associated with either partial molecular sequence, but may be determined by the whole molecular structure, including both segments at the N- and C-termini.
Modeling of Jaw-Head-Neck Dynamics during Whiplash
Authors: Schneider K. , Zernicke R.F. , Clark G.
Published: November 2010

Clinicians report signs and symptoms of temporomandibular joint (TMJ) disorders in many patients who have experienced automobile rear-end collisions involving neck hyperextension (whiplash). In order for relationships between TMJ disorders and rear-end collisions to be explored, the dynamic response of the jaw to hyperextension of the neck associated with automobile rear-end collisions needs to be quantified. To achieve this goal, we extended an existing head-neck model by adding a movable jaw, and performed preliminary computer simulations of the jaw movements during rear-end collisions at 6. 71 ms-1 (75 mph) and 13.41 ms -1 (30 mph). The initial computer simulations produced promising kinematic and dynamic results, such as: relative angle between the head and jaw (jaw-opening angle), predicted TMJ torques, and displacement and linear acceleration of the jaw's center of mass. However, the absolute values and time course of our results must be viewed with caution, since the jaw model has not yet been validated with experimental data. Nevertheless, the modeling approach, detailed in this study, shows good promise for eventually providing quantitative dynamic information about the jaw-head-neck system during impulsive loading.
A Cytochemical Study of Horseradish Peroxidase Uptake in Rat Junctional Epithelium
Authors: Ayasaka N. , Tanaka T.
Published: November 2010

The uptake of horseradish peroxidase (HRP) was studied in rat junctional epithelium (JE). Intravenous HRP (12.5 mg, 25 mg, or 50 mg) was only endocytosed by the entire JE (particularly by the coronal portion of the JE). Although HRP uptake was negligible at a concentration of 12.5 mg, marked uptake was observed at concentrations of 25 mg and 50 mg. However, there was no difference in the HRP uptake by the JE between the concentrations of 25 mg and 50 mg. By electron microscopy HRP was detected in the organellae (micropinocytotic vesicles, intracytoplasmic vacuoles, dense bodies, and multivesicular bodies) in the junetional epithelial cells (JE cells). HRPpositive micropinocytotic vesicles were detected in all JE cells. However, intracytoplasmic vacuoles, which are characteristically observed in JE cells, were not always positive for HRP. Numerous HRPnegative vactioles were detected in the JE cells. The number of HRPpositive organellae in the coronal portion of the JE was pronounced, compared with those in ather portians. These findings provided evidence that the entire JE, especially its coronal portion, has endocytotic ability by micropinocytotic vesicles, rather than intracytoplasmic vacuoles, for foreign substances.
Microscopic and Crystallographic Examinations of the Teeth of the X-linked Hypophosphatemic Mouse
Authors: Abe K. , Ooshima T. , Masatomi Y. , Sobue S. , Moriwaki Y.
Published: November 2010

Teeth from the C57BLl6J-Hyp mouse (Hyp mouse) were examined histologically, radiographically, and crystallographically. Microscopic examinations of the ground sections, the decalcified and H-E-stained sections, and the contact microradiograms of molars and incisors from the Hyp mouse showed several abnormalities-such as large pulp chamber, wide predentin, thin dentin at the pulp floor, and multiple occurrences of interglobular dentin. Powder and microbeam x-ray diffraction analyses showed that the crystallinity of hydroxyapatite in incisor globular dentin from the Hyp mouse was higher than that in incisor dentin from the normal mouse. On the other hand, the findings of transmission electron microscopy demonstrated that the sizes of hydroxyapatite crystals of globular dentin in the Hyp incisor were larger than those in normal incisor dentin. These results demonstrated that the findings in Hyp mouse teeth were in accord with those of human XLH teeth.
Output from Visible-light Activation Units and Depth of Cure of Light-activated Composites
Authors: McCabe J.F. , Carrick T.E.
Published: November 2010

A simple and reproducible method for monitoring the intensity of radiation from composite light-activation units has been developed. The method depends upon the use of a cadmium sulfide photo-conductive cell, the electrical resistance of which varies with the amount of light falling upon its surface. Filters were used for selection of the wavelength of light that is thought to be most effective in activating polymerization. The use of broad-band wavelength filters failed to give results for light intensity that correlated with depth of cure. Narrow-band interference filters, having a band width of only 10 nm and being selective within the wavelength range of from 460 to 480 nm, produced results for light intensity that correlated with depth of cure.

The depths of cure for various types of composite material were measured with use of a penetrometer that enabled the thickness of unpolymerized material at the base of the test mould to be determined. The depth of cure was inversely proportional to the attenuation of light caused by the composite resin at 470 nm. The relationship between depth of cure and light intensity at 470 nm was not a simple linear one over all intensity values. Above a certain critical value of intensity (about 550 lux for a 3.5-mm aperture in these experiments), the depth of cure appeared to be almost independent of intensity. Below this critical value, depth of cure fell markedly with decreasing intensity.
Maximum Bond Strength of Dental Luting Cement to Amalgam Alloy
Authors: Mojon P. , Hawbolt E.B. , MacEntee M.I. , Belser U.C.
Published: November 2010

Although dental amalgam is used frequently under artificial crowns for restoration of severely damaged teeth, there is little information available on the bond between luting cements and this alloy. This study was designed for determination of the strength of the bond between a dental amalgam alloy and three crown-luting cements.

Cylinders of dental amalgam were joined in pairs, with use of a zinc-phosphate, a glass-ionomer, and an acrylic-adhesive resin cement. The tensile-fracture stress of 45 samples of each cement was measured with a universal testing machine, and subjected to a Weibull analysis. The fractured surfaces were examined under low magnification with use of a light microscope, and at low and high magnifications with use of a scanning electron microscope, for evaluation of the appearance of the fractured joints.

The Weibull analysis demonstrated that the adhesive resin cement provided a stronger and more predictable bond than either the zinc-phosphate or the glass-ionomer cement. The appearance of the fractured surfaces gave no indication of the strength of the joints, a feature that is common to brittle materials.

The results suggest that crowns placed on teeth offering a large amalgam-alloy surface could be retained more predictably with an adhesive resin cement.
Comparison of Jaw-muscle Bite-force Cross-sections Obtained by Means of Magnetic Resonance Imaging and High-resolution CT Scanning
Authors: van Spronsen P.H. , Weijs W.A. , Valk J. , Prahl-Andersen B. , van Ginkel F.C.
Published: November 2010

Cross-sectional areas of the jaw muscles were determined by means of magnetic resonance imaging (MRI) in 12 healthy adult male subjects. These findings were compared with the cross-sectional areas of the jaw muscles of the same subjects, obtained by means of computer tomography (CT) in a previous study (Weijs and Hillen, 1985).

Significant correlations (r>0.7) were found between the CT and MRI cross-sections of the masseter, medial pterygoid, and temporalis muscles. The low correlation between the CT and MRI cross-sections of the lateral pterygoid muscle could be explained by the different imaging techniques (slice thickness) of MRI and CT scanning.

CT and MRI cross-sectional areas of the masseter and medial pterygoid muscle (but not the temporalis muscle) showed highly positive and significant correlations with the maximal voluntary bite force.

In living subjects, the cross-sections of the masseter and medial pterygoid muscles can be visualized with CT and MRI. Compared with CT, MRI has some advantages, such as the absence of adverse effects (no radiation) and the excellent soft-tissue imaging. Furthermore, a series of frontal, horizontal, sagittal, and angulated MRI scans can be made without modification of the patient's position, facilitating reconstruction of the jaw muscles.
Dental Caries in Adult and Elderly Chinese
Authors: Luan W.-M. , Baelum V. , Chen X. , Fejerskov O.
Published: November 2010

This paper reports on a study of dental caries conducted among 1744 urban and rural Chinese (from 20 to 80 years old), who were selected by means of a systematic srratifzed sampling procedure. The prevalence of one or more decayed or filled teeth ranged from 48 to 90% in urban residents, and from 51 to 97% in rural residents, depending on age. The mean number of decayed or filled teeth ranged from 1.2 (± 1.9) among 20-29-year-olds, to 6.2 (± 5.5) among 70+-yearolds, and was highest among rural residents. Among 20-29-year-olds, the main components of the DFT were enamel lesions and fillings. Among 30-49-year-olds, the DFT consisted mainly of enamel lesions and filled teeth, as well as teeth with lesions involving the pulpal tissues. In subjects over the age of 50 years, lesions involving pulpal tissues were the predominant type, followed by root-surface lesions. In subjects below the age of 50 years, most of the caries experience derived from coronal surfaces, particularly occlusal surfaces. Root-surface caries was predominantly a feature of persons aged 50 years and above. Despite a large number of surfaces being at risk of root-surface caries, less than 10% of the surfaces were so affected. Although cross-sectional in nature, these data indicate that when the oral hygiene standards are poor, caries lesions continue to develop and progress throughout life. With age, dental caries becomes a substantial oral health problem in this population of adult and elderly Chinese, despite the availability of some dental services.
Structural Relationship Between Human Salivary Histatins
Authors: Troxler R.F. , Offner G.D. , Xu T. , Vanderspek J.C. , Oppenheim F.G.
Published: November 2010

Histatins are a group of electrophoretically distinct histidine-rich polypeptides with microbicidal activity found in human parotid and submandibular gland secretions. Recently, we have shown that histatins 1, 3, and 5 are homologous proteins that consist of 38, 32, and 24 amino acid residues, respectively, and that these polypeptides kill the pathogenic yeast, Candida albicans. We now describe the isolation and structural characterization of histatins 2, 4, 6, and 7-12, the remaining members of this group of polypeptides. Histatin 2 was found to be identical to the carboxyl terminal 26 residues of histatin 1; histatin 4 was found to be identical to the carboxyl terminal 20 residues of histatin 3; and histatin 6 was found to be identical to histatin 5, but contained an additional carboxyl terminal arginine residue. The amino acid sequences of histatins 7-12 formally correspond to residues 12-24, 13-24, 12-25, 13-25, 5-11, and 5-12, respectively, of histatin 3, but could also arise proteolytically from histatin 5 or 6. These results establish, for the first time, the complete structural relationships between all members of this group of microbicidal proteins in human parotid saliva. The relationship of histatins to one another is discussed in the context of their genetic origin, biosynthesis and secretion into the oral cavity, and potential as reagents in anti-candidal studies.
Fracture-mechanics Parameters of the Composite-Enamel Bond
Authors: De Groot R. , Van Elst H.C. , Peters M.C.R.B.
Published: November 2010

In a previous study, the critical values of the opening mode stress intensity factor (K1 ), its equivalent, the strain energy-release rate (G1 ), and the J integral (J1 ) (in the elastic case being equal to that of G1 ) were determined for resin composite.

In this study, the strength of the composite-tooth interface was investigated. The critical values of K1 and J1 were measured with single-edge notched-bend (SENB) specimens of resin composite bonded to enamel, with the notch at midspan at the bonded interface. Due to enamel's anisotropy, the values of K1c and J1c to be used in a fracture-mechanics application for failure prediction of a structure depend on the enamel prism orientation relative to the adhesive interface. Where interfacial failure is to be expected, the following values for J 1c and K1c can be used: Silux, J1c = 145 ± 35 Jm-2 and K1c = 0.84 ± 0.16 MNm-3/2; P-30, J1c = 163 ± 13 Jm-2 and K1c = 1.02 ± 0.07 MNm-3/2. Where enamel failure is expected or where the failure mode cannot be predicted, the following values can be applied: Silux, J 1c = 89 ± 15 Jm-2 and K1c = 0.84 ± 0.16 MNm-3/2; P-30, J1c = 89 ± 15 Jm-2 and K 1c = 0.75 ± 0.10 MNm-3/2.
Studies of Human Gastric Mucosa After Application of 0.42% Fluoride Gel
Authors: Spak C.-J. , Sjöstedt S. , Eleborg L. , Veress B. , Perbeck L. , Ekstrand J.
Published: November 2010

Dental prophylaxis with APF gels (1.23%) may cause gastric distress as a side-effect. This gastric irritation is probably due to a direct toxic effect of fluoride (F), swallowed in conjunction with the treatment, on the gastric mucosa. The aim of the present study was to investigate whether-and to what extent-a dental treatment with 3 g of a 0.42%-F gel could affect the gastric mucosa due to inadvertent swallowing of the gel. Ten subjects underwent a control gastroscopy, and two weeks later, a second gastroscopy was performed two h after a F gel treatment. During the gastroscopy, the mucosa was examined and the injuries graded according to an arbitrary scale. Four biopsies of the antral and corpus regions of the stomach were taken and evaluated histologically. The mean (± SD) amount of F retained after the application was 5.1 ± 2.1 mg, i.e., 40% of the applied amount of F. Petechiae and erosions were found in the mucosa in seven of the ten patients. The histopathological evaluation revealed changes in nine of ten patients, with the surface epithelium as the most affected component of the mucosa. The present study clearly shows that a treatment with a F gel of rather low F concentration may result in injuries to the gastric mucosa. The importance of current recommended guidelines so that the amount of F swallowed during a gel application can be minimized is emphasized. From a toxicological standpoint, the use of a low-F gel instead of a 1.23%-F gel in small children is recommended for avoidance of adverse gastric effects.
Sorbitol Adaptation of Dental Plaque in People with Low and Normal Salivary-secretion Rates
Authors: Kalfas S. , Svensater G. , Birkhed D. , Edwardsson S.
Published: November 2010

Caries-related bacteriological and biochemical factors were studied in 12 persons with low and 11 persons with normal salivary-secretion rates before and after a four-week period of frequent mouthrinses with 10% sorbitol solution (adaptation period). After the adaptation period, an increase in total numbers of sorbitol-fermenting bacteria and mutans streptococci was found in plaque samples from both groups. The pH drop in dental plaque in situ after a mouthrinse with sorbitol was more pronounced after the adaptation period, especially in the group with the low salivary-secretion rate. Increased acid production in plaque from sorbitol was also observed in the two groups in vitro. The composition of the fermentation end-products was affected by the sorbitol exposure. It is suggested that in subjects with diminished natural protection against caries development, such as patients with low salivary-secretion rate, a cariogenic potential of sorbitol should be considered when this polyol is included in products that might be used frequently.
The Clinical Effects of a Mouthrinse Containing 0.1% Octenidine
Authors: Beiswanger B.B. , Mallatt M.E. , Mau M.S. , Jackson R.D. , Hennon D.K.
Published: November 2010

The purpose of this three-month clinical trial was to evaluate the effects of a 0.1 % octenidine mouthrinse on plaque, gingivitis, extrinsic dental stain, and the oral soft tissues. A total of 451 adult volunteer subjects was initiated into the study and given baseline dental examinations. The subjects were stratified into two balanced groups according to gender, plaque, and gingivitis scores. The subjects then received a dental prophylaxis and were provided with dentifrice, toothbrushes, and either a mouth rinse containing 0.1 % octenidine dihydrochloride as the active ingredient or a similar placebo mouthrinse. Subjects were instructed to rinse with their assigned product for 30 s twice each day. Examinations were repeated at six weeks (soft-tissue assessment, gingivitis) and three months (soft tissues, plaque, gingivitis, dental stain). The results showed that the group rinsing with 0.1% octenidine had significantly less plaque (39%), gingivitis (50%), and bleeding sites (60%) than the group using the control product, but had significantly higher stain formation and experienced longer prophylaxis times to remove the stain. The oral soft-tissue examinations revealed no differences in the groups in either the numbers or types of lesions noted.
Monomer Composition and Bond Strength of Light-cured 4-META Opaque Resin
Authors: Yoshida K. , Matsumura H. , Atsuta M.
Published: November 2010

A light-cured opaque resin was prepared with 4-(2-methacryloxyethoxycarbonyl) phthalic anhydride (4-META), bifunctional methacrylates, and titanium dioxide (TiO2). The relation between monomer composition and bond strength was examined with seven methacrylate monomers. Methyl methacrylate (MMA) was useful as a solvent of 4-META. However, it was not sufficiently cured by photo-initiator. The bond strength of a triethyleneglycol dimethacrylate (TEGDMA)-based composition was superior to other monomer-based compositions after repeated thermocycles. 1,6-bis(methacryloxy-2-ethoxycarbonyl-amino)-2,4,4-trimethylhexane (UDMA) effectively provided viscosity to the composition. The prepared opaque resin consisted of 4-META/ MMA-TEGDMA primer, TEGDMA-UDMA-based monomer, and titanium dioxide. This opaque resin bonded strongly to alumina-blasted cobalt-chromium alloy. The light-cured 4-META opaque resin may be useful for bonding prosthodontic composite to metal frameworks.
Mutans Streptococci in Plaque from Margins of Amalgam, Composite, and Glass-ionomer Restorations
Authors: Svanberg M. , Mjör I.A. , Ørstavik D.
Published: November 2010

Levels of mutans streptococci in plaque samples from margins of Class II amalgam (Dispersalloy), composite (P-10), and glass-ionomer (Ketac Silver) restorations were compared. Fifty-one children, each having one of the restorations in a permanent first molar, were part of an inter-individual comparison, giving 17 restorations of each material. The age of the children, the age of the restorations, and the salivary levels of mutans streptococci were comparable in the three groups. Another seven children-each having both a composite and a glass-ionomer restoration of the same age placed on contralateral premolar or molar teeth-were part of an intra-individual comparison.

The percentage mutans streptococci of total CFU count in plaque was higher on composite (mean 13.7) and amalgam (mean 4.3) than on glass-ionomer (mean 1.1) restorations in the inter-individual comparison, and higher on composite (mean 4.2) than on glass-ionomer (mean 0.4) restorations in the intra-individual comparison. In both comparisons, the differences in values between samples from glass-ionomer restorations and samples from composite or amalgam restorations were statistically significant (p<0.05).
The Effect of Plaque Thickness on Progression of Artificial Caries Lesion Formation in situ
Authors: Mellberg J.R. , Petrou I.D. , Grote N.E.
Published: November 2010

Eighty thin enamel sections with artificially-fonned caries lesions were implanted in the buccal surfaces of molars (in the removable partial dentures of ten subjects) and covered with a steel mesh for plaque accumulation to occur. The mesh was placed in contact with the enamel surface in half the lesions and 0.5 mm above the lesions in the other half, thus facilitating formation of thin and thick plaque samples. Following two-week use of a non-fluoride dentifrice, the lesions were analyzed for mineral change by quantitative microradiography. Significant mineral was lost from lesions in both groups, but the loss was twice as large in the thick-plaque group. These findings are important to in vivo remineralization models, since they show that plaque thickness should be controlled for minimization of variation.
Effect of Dietary Components on the Indigenous Oral Bacterial Flora of BALB/c Mice
Authors: Blais J.-F. , Lavoie M.C.
Published: November 2010

Diet is recognized as one of the most important factors affecting the equilibrium of the oral bacterial flora. Studies related to dental caries development have focused mainly on the effect of carbohydrates. In the present work, using swabbing coupled with an immuno-colony-blot assay, we followed the indigenous oral bacterial populations of BALB/c mice fed diets with different concentrations of sucrose, starch, proteins, lipids, vitamins, and minerals for a period of 14 days. The results indicate that although high-sucrose diet favored an increase of the proportion of S . faecalis, only variations in the protein and the starch concentrations significantly influenced the composition of the indigenous oral bacterial populations of BALB/c mice. With low-protein diets, the proportion of Lactobacillus murinus decreased, that of Streptococcus faecalis increased, while that of Staphylococcus aureus was relatively stable. A diet containing a high proportion of starch (65%) resulted in a significant increase in the population of S. faecalis, while that of S. aureus decreased proportionally. With the same diets used as in vitro culture media, growth of L. murinus was the fastest at high protein concentrations, while that of S. faecalis was not affected by the protein concentrations. These results indicate a direct effect of dietary protein content on the indigenous oral bacterial populations of BALB/c mice.
Endocytosis in Odontoclasts and Osteoclasts Using Microperoxidase as a Tracer
Authors: Tanaka T. , Morioka T. , Ayasaka N. , Jima T. , Kondo T.
Published: November 2010

Microperoxidase (MP, a peptide tracer) was intravenously injected into rats after six days of tooth movement by the Waldo method. Bone resorption was seen along the distal bone surface of the inter-radicular septum of the upper first molar, and tooth root resorption occurred along the mesial and distal surfaces of the distal root of the same molar. Odontoclasts were smaller in size and numbers than osteoclasts, but had the same organelles [multiple nuclei, ruffled borders (RB), clear zones, vacuoles, mitochondria, and specific granules] as osteoclasts. MP was deposited on the resorbed area through the clear zone and was transported into the vacuoles along the channels of the RB. The uptake of MP by odontoclasts was small, compared with that by osteoclasts. Collagen fibrils were found in the channels of the RB but were not detected in the vacuoles. Instead, filament-like structures were seen in the vacuoles and were located very near the collagen fibrils in the channels. Fibroblasts outside the resorbed lacunae had endocytosed collagen. In contrast, some cells close to odontoclasts (osteoclasts) in the dentin (bone)-resorbed lacunae had not endocytosed any collagen fibrils.

These findings suggest (1) that odontoclasts resorb the dentin or cementum just as osteoclasts do in bone resorption, (2) that the resorbed area connects with the extracellular spaces of the odontoclasts or osteoclasts, and (3) that the organic components (e.g., collagen ftbrils) of dentin or cementum are endocytosed through the channels of the RB in the same manner as that for MP. However, the endocytotic ability of odontoclasts appears inferior to that of osteoclasts.
Release of Organic Matrix Components from Bovine Incisor Roots during in vitro Lesion Formation
Authors: Klont B. , Ten Cate J.M.
Published: November 2010

The solubilization of organic matrix components during demineralization of powdered and intact root sections from adult bovine incisors was investigated. Root powder was demineralized with 0.1 mol/L acetic acid, pH 4.0, at 4°C and 37°C. Surfaces of intact root sections were subjected to 0.1 mol/L acetic acid, pH 4.0 (for production of erosive lesions), or to 0.1 mol/L lactic acid, 0.2 mmol/L methane hydroxy diphosphonate, pH 5.0 (for production of subsurface lesions at 37°C). The solubilized organic material was analyzed for collagen, total noncollagenous protein (NCP), organic phosphate (Po), and proteoglycans (PGs), which were measured as chondroitin 4-sulfate (C-4-S). For root powder, a maximal release of NCPs and PGs was found only after neutralization of the extraction mixture. For both temperatures tested, the average amounts of liberated noncollagenous components (NCCs) were the same, i.e., 0.68 μg [NCP - Po], 0.11 μm Po, and 0.10 μg C-4-S per μmol released calcium. The amino acid composition of the NCP fraction revealed relatively high amounts of aspartic acid and serine. These fzndings indicate that the NCCs were easily liberated from the tissue, and that the NCP fraction consisted mainly of phosphoprotein. Demineralization of intact root sections resulted in average amounts of solubilized NCCs of 0.21 μg [NCP- Po], <0.01 μg Po, and <0.01 μg C-4-S per μmol released calcium, independent of incubation time and lesion type. The amino acid composition of all NCP fractions was virtually the same, high in glutamic acid, but lower in aspartic acid and serine when compared with the neutralized powder extracts. For both demineralization solutions, the amounts of solubilized collagen were 0.07 and 0.16 μg per μmol released calcium after three and 28 days of incubation, respectively. Our experiments indicate that phosphoprotein and proteoglycans may be released from root surfaces during the periods of neutral pH that follow acid demineralization.
Jaw Muscle Activity in Relation to the Direction and Point of Application of Bite Force
Authors: Van Eijden T.M.G.J.
Published: November 2010

This study examined the way the masseter and the anterior and posterior temporal muscles of human subjects were activated when a bite force of constant magnitude was exerted at different teeth in different defined directions. Subjects were instructed to produce a bite force of a particular magnitude (250 N) and direction (vertical, anterior, lateral, posterior, or medial) using a three-component force transducer and a feedback method. Simultaneously, the EMG activity of the muscles was registered with use of surface electrodes. Unilateral bite forces were produced at the right canine, second premolar, and second molar. In addition, a bilateral vertical premolar bite was examined for comparison of activity levels of the muscles of both sides. The results showed that, on average, the activities of the right and left side muscles did not differ in a bilateral vertical bite. Moreover, in a unilateral vertical bite, there were no significant right-left differences. For all bite force directions, more muscle activity was required for production of a constant bite force at the anterior side of the dental arch than at the posterior side. An exception to this rule was the activity of the posterior temporal muscle in a posteriorly directed bite. There was a close relationship between the direction of bite force and jaw muscle activity. Variations in activity were small for the anterior temporal muscle and large for the posterior temporal and masseter muscles. All muscles that were studied were always active, even in directions in which they could be expected to act antagonistically.
Risk Factors for Tooth Loss Over a 28-year Period
Authors: Burt B.A. , Ismail A.I. , Morrison E.C. , Beltran E.D.
Published: November 2010

Over 500 residents of Tecumseh, Michigan, were dentally examined in 1959 as part of a community-wide health study. In 1987, the dental examinations were repeated, with use of the same criteria as in 1959, for 167 dentate persons from the original group. Another 28 reported by telephone that they had become edentulous since 1959. This report uses a historical cohort analysis for exploration of the risk factors for tooth loss, both total and partial, over the 28-year period. Over that time, the edentulous lost an average of 18.0 teeth (95% confidence interval 15.5, 20. 7), whereas the age-matched 90 dentate persons lost only 3.2 (2.2, 4.2) teeth each. Descriptive data showed the edentulous to have higher baseline scores for plaque, calculus, and gingivitis, and a higher proportion of them smoked, though only loss of periodontal attachment (LPA) of 4 mm or more, early loss of first molars, and educational attainment were significant risk factors in regression analysis. Odds ratios for these three variables were 4.0 (1.2, 12.8), 2.0 (1.3, 3.1), and 0.6 (0.4, 0.9), respectively. The strongest risk factors for partial tooth loss among 116 dentate persons were baseline gingivitis (which was correlated with LPA of 4 mm or more) and the baseline number of teeth present, with odds ratios of 2.4 (1.2, 5.2) and 0. 8 (0. 7, 1.0), respectively. While the analysis had to be carried out without caries data, it was concluded that total tooth loss is a social-behavioral issue as much as it is disease-related. Social-behavioral factors were less clearly related to partial tooth loss in dentate persons; oral disease characteristics were the most prominent risk factors for partial tooth loss.
A Histological Comparison in the Dog of Porous-coated vs. Threaded Dental Implants
Authors: Deporter D.A. , Watson P.A. , Pilliar R.M. , Chipmani M.L. , Valiquette N.
Published: November 2010

The histological findings of an 18-month trial, in the dog, of a partially porous-coated endosseous dental implant made of Ti-6Al-4V, with a truncated conical shape, are described and compared with those for a cylindrical, threaded, endosseous implant made of commercially pure Ti. Six beagle dogs each received two porous-coated implants on one side of the mandible and two threaded implants on the contralateral side. Each set of two implants supported a two-unit fixed bridge for an 18-month functional period.

Methylmethacrylate sections of both the buccolingual and mesiodistal aspects of each implant were examined qualitatively and by computer-assisted morphometry. The morphometric measurements were used for determination of the length of implant surface in direct contact with bone on each aspect of each implant. The data were expressed both as an absolute length and as a fraction of the maximum length available for contact (contact length fraction or CLF). On the buccal and lingual aspects of the implants, both the absolute lengths and CLF were significantly smaller for the porous-coated design. For the mesial and distal aspects, the absolute lengths and CLF were less for the porous-coated design, but the differences were not significant. However, when the absolute contact length was related to the corresponding vertical bone height, significant differences were observed, the absolute contact length being greater for any given bone height for the porous-coated design. Taken together, the data suggest that shorter implants may be used with the porous-coated design.
Evaluation of Mutagenicity of Restorative Dental Materials Using the Ames Salmonella/Microsome Test
Authors: Li Y. , Noblitt T.W. , Dunipace A.J. , Stookey G.K.
Published: November 2010

Compounds of five commercially available dental material kits were examined for mutagenic potential by use of the Ames Salmonella/microsome test. Dimethyl sulfoxide (DMSO) was used as the solvent for all materials, except MONO-LOK2 Primer and Right-On Activator, which were dissolved in 95% ethanol. The Tenure, Fuji, and Gluma materials were initially screened at 2 mg (solids) or 2 μL (liquids) per plate, without S9 (Aroclor 1254-induced rat liver microsomes), and dose-response studies were conducted for those materials showing potential mutagenicity. The components of three dental kits, MONO-LOK2, Right-On, and Gluma, were further examined, both with and without S9 activation, at doses of 0.2, 4, 20, 100, 500, and 2500 μg (nL for liquid components) per plate. The data showed no mutagenic potential for the components of Fuji Glass Ionomer (Type III), Tenure Dentin Bonding System, and MONO-LOK2 kits, or Right-On Paste. However, Gluma 3, a component of the Gluma/Lumifor Bonding System, exhibited mutagenic activity in a dose-response manner. The mutagenicity of Gluma 3 was demonstrated in repeated experiments. Gluma 4 and the resin of the Gluma dental kit, as well as Right-On Activator, caused a slight increase in the number of revertants, and judgment regarding their mutagenicity could not be made conclusively. The results of this study indicate that some commercial dental materials may not have been adequately tested for mutagenicity, and that a reliable test program for evaluation of mutagenicity of dental materials is needed so that their safe use in dental practice can be ensured.
Assessment of Loosely-bound and Firmly-bound Fluoride Uptake by Tooth Enamel from Topically Applied Fluoride Treatments
Authors: Sieck B. , Takagi S. , Chow L.C.
Published: November 2010

The amounts of loosely-bound fluoride (F) deposited on human enamel by two topical F treatments were measured with use of a constant-composition F washing method. Enamel biopsies conducted before treatment and after the washing were used for determination of the firmly-bound F uptake. The results showed that (1) the washing system did not remove F from untreated enamel surface, (2) a four-minute application of an acidulated phosphate fluoride (APF) gel deposited 27.2 (2.4) (mean, S.E.) μg of loosely-bound Fper cm2 of enamel surface and 186 (111) ppm of firmly-bound F in the outer 10 μm of enamel, and (3) a four-minute application of a pH-2.1 dicalcium phosphate dihydrate (DCPD)-forming solution followed by APF produced 44.9 (3.1) μg/cm2 of loosely-bound F and 1280 (354) ppm of firmly-bound F in the outer 10 μm of enamel. The results showed that the DCPD pre-treatment effectively enhanced the enamel reactivity with F, so that the DCPD-APF treated enamel acquired greater amounts of both loosely-bound F and firmly-bound F than did samples treated with APF alone.
The Possible Role of Oral Epithelial Cells in Tissue-type Plasminogen Activator-related Fibrinolysis in Human Saliva
Authors: Sindet-Pedersen S. , Gram J. , Jespersen J.
Published: November 2010

We studied the fibrinolytic activities of the following subfractions of unstimulated human whole saliva on plasminogen-rich fibrin plates: (1) submandibular saliva, (2) parotid saliva, and (3) smears of buccal epithelial cells from ten healthy males. A cell-bound plasminogen activator could be demonstrated in the sediments of all three subfractions of whole saliva. The incorporation of antibodies (goat IgG) against human two-chain tissue-type plasminogen activator (t-PA) could quench the assessed fibrinolytic activities, whereas additional experiments suggested the absence of urokinase-like and F XII-dependent activators of fibrinolysis. The determinations in growth medium from buccal-epithelial cell culture of t-PA antigen by means of enzyme-linked immunosorbent assay showed the presence of t-PA.

These clinical and experimental findings suggest that buccal-epithelial cells produce t-PA, while the activity of t-PA in parotid and submandibular saliva is very low.
Transverse Development of the Human Jaws Between the Ages of 8.5 and 15.5 Years, Studied Longitudinally With Use of Implants
Authors: Korn E.L. , Baumrind S.
Published: November 2010

We report longitudinal data on the transverse widening of the maxilla and mandible from a sample of normal subjects (11 males and 20 females) with metallic implants of the Bjork type. Data were from measurements on lateral and frontal (posterior-anterior) cephalograms generated at annual intervals between the ages of 8.5 and 15.5 years (although data were not available for all subjects at all time points).

The maxillary data were, in general, similar to those reported by Bjork and Skieller (1974, 1977) for a smaller sample of slightly younger boys. During the age interval studied, transverse widening was greater in the more posterior part of the palate. [The mean annual rate of change in the posterior-most (zygomatic) region was 0.43 mm, sd = 0.18 mm; p < 0.001.] Although the rate of palatal widening was not large in absolute terms, widening appeared to continue throughout the age interval under study, and there was no evidence to support the conventionally accepted idea that palatal growth in the transverse dimension tapers off substantially or even ceases during the age interval under observation.

Evidence of statistically significant widening of the mandibular arch by means of transverse rotation of the osseous matrix was noted in nine of the 29 subjects for whom three-dimensional mandibular information was available. For these nine subjects, the estimated annual increase in mandibular arch angle ranged from 0.52 degrees to 1.40 degrees. As far as we are aware, this is the first report of mandibular matrix rotation in the transverse direction from a sample of subjects with metallic implants. The finding that spontaneous changes in this dimension are relatively common raises the possibility that classical attitudes concerning the immutability of osseous relationships in the symphyseal region during growth may be inappropriate.