bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of Gingival Swelling from Dental Casts by Generation of a Moire Pattern with Laser Light
Authors: Wouters F.R. , Jon-And C. , Abramson N. , Olsson L. , Frithiof L. , Soder P.-Ö. , Dirtoft I.
Published: November 2010

The aim of the study was to develop a sensitive measuring method enabling direct evaluation of gingival swelling to be made as registered on dental casts. On two separate occasions, when different degrees of severity of gingival inflammation were present in the same subject, reversible hydrocolloid impressions were taken of the mandible. The casts obtained were located successively in identical three-dimensional relationships in a field of interference fringes generated by two intersecting beams of collimated helium-neon laser light, and were photographed. The evaluation of the moiré pattern obtained directly by superimposition of the two images of the surface studied indicated that a decrease in gingival height of 0.38 mm in the direction of the camera had occurred between the two occasions. The use of a computer-based image-processing system considerably improved the visibility of the pattern. The reproducibility of the impression technique, as well as the relocation and superimposing techniques, proved satisfactory at the moiré resolution used (0.19 mm). The method has potential application in clinical experimental research, and therefore warrants further evaluation.
Comparison of Solution- and Gel-prepared Enamel Lesions-an in vitro pH-cycling Study
Authors: Damato F.A. , Strang R. , Stephen K.W.
Published: November 2010

A variety of methods has been employed to produce artificial caries-like enamel lesions. The aim of this paper was to use a pH-cycling regime to compare the de-/remineralization behavior of lesions prepared by two methods. Lesions were produced by use of either an acidified undialyzed gelatin system or a buffered solution. Enamel sections, each containing four lesions, were allocated to four groups (A, B, C, D) and subjected to a daily ph-cycling regime of 16-hour demineralization and eight-hour remineralization. Groups A & B contained gelatin-prepared lesions, whereas Groups C & D contained solution-prepared lesions. To the remineralizing solutions used in Groups B & D, 2 ppm fluoride was added. The mineral content in the lesions was assessed, by means of microradiography/microdensitometry, at baseline and at intervals for six weeks. The lesions in all four groups exhibited net demineralization. In terms of the total mineral lost from the lesion (the Δz parameter), the demineralization rates of the solution-prepared lesions were significantly greater than those of the corresponding gelatin-prepared lesions. All sections in the non-fluoride groups showed subsurface demineralization in initially sound enamel, whereas only one section in the fluoride groups showed an area of mineral loss. Laminations in the mineral content profiles were apparent only in Group D. The results of this study indicate that the method of lesion preparation affects the subsequent behavior of lesions when exposed to de- and remineralizing protocols.
Maturation in Developing Permanent Porcine Enamel
Authors: Kirkham J. , Robinson C. , Weatherell J.A. , Richards A. , Fejerskov O. , Josephsen K.
Published: November 2010

Mineral content per tissue volume was investigated in developing permanent porcine enamel and contrasted with weight-related data. Levels of mineralization were correlated directly with the histological appearance of the overlying enamel organ. Magnesium concentrations were measured at different stages of enamel development. Mineral levels rose from ~30% per volume of tissue during the secretory stage to -60% in mature tissue. This is much lower than final mineral levels in enamel of other species. Enamel containing low mineral levels was adjacent to tall secretory ameloblasts which had reduced in height by -50% at a point corresponding to the beginning of the maturation stage. Magnesium concentrations remained relatively constant throughout the secretory stage, at 0.2% Mg by weight. These rose by 3-4 times in the enamel of the maturation stage. The low levels of mineralization in the mature porcine enamel did not appear to be due to enamel pathology, and the possibility of porcine teeth erupting in an immature, partially porous condition is discussed.
Fluctuating Odontometric Asymmetry in an Urban South African Black Population
Authors: Kieser J.A. , Groeneveld H.T.
Published: November 2010

The magnitude of fluctuating odontometric asymmetry is reported for a group of 106 urban South African Blacks by use of re-scaled asymmetry values and Euclidean map analyses. When these results were contrasted with those reported for South African Caucasoids and Paraguayan Lengua Indians, Blacks were found to be significantly more asymmetric. It is suggested that the disproportionately high levels of dental asymmetry may be ascribed to the high disease and malnutrition burden of South African Blacks and to decreased individual buffering ability. The present study failed to support Garn's model of x-chromosomal odontogenetic buffering in females, and also failed to confirm significant arcadal differences in the magnitude of fluctuating odontometric asymmetry.
Effects of Age on the Ability of the Rat Temporomandibular Joint to Respond to Changing Functional Demands
Authors: Bouvier M.
Published: November 2010

This investigation examined the ability of the tissues of the temporomandibular joint (TMJ) to adapt to changing functional demands in young, growing rats compared with mature rats. Functional demands on the TMJ were varied by feeding diets with diffetvnt physical consistencies. The first group was fed a soft diet for the experimental period. The second group was fed a hard diet, and the third group was initially fed the soft diet, then switched to the hard diet at the mid-point of the experimental period. Gross dimensions of the condyle, mandible, and maxilla were measured with calipers. Thickness of the articular, proliferative, transitional, and hypetirophic zones of the condylar cartilage, and the amount of bone in the subcondylar region and condylar neck were measured on histological sections. Gross dimensions of the condyle were significantly smaller in the soft-diet group compared with the hard- and soft/hard-diet groups in both growing and mature rats. The individual zones of the condylar cartilage were also significantly narrower in the soft-diet group in both growing and mature rats. However, the soft/hard-diet group of mature rats showed only a significant reduction in the thickness of the articular zone of the condylar cartilage compared with the hard-diet group. There were also narrower proliferative and transitional zones in the mature rats fed a soft/hard diet. In contrast, all of these zones showed full recovery in the young rats fed a soft/hard diet. The data presented here suggest that increasing age may diminish the capacity of the TMJ to adapt to altered function and consequently may play a significant role in the development of degenerative joint disease.
Comparison of Fluoride Concentrations in Unstimulated whole Saliva Following the Use of a Fluoride Dentifrice and a Fluoride Rinse
Authors: Zero D.T. , Fu J. , Espeland M.A. , Featherstone J.D.B.
Published: November 2010

Recent evidence has suggested that the cariostatic effects of topical fluoride (F) are related to the presence of low concentrations of ionic F in the oral environment. The purpose of this study was to compare the retention of F in the oral environment over 24-hour periods after the use of a F dentifrice or a F rinse.

Groups of ten consenting adult subjects (age 18-52 years) brushed and/or rinsed (B/R) in a standardized manner twice per day in the morning (AM) and before bed (PM) with either a placebo dentifrice (8 ppm F), NaF dentifrice (1100 ppm F), or NaF rinse (225 ppm F). Experiments were performed with placebo dentifrice only (PD); F dentifrice only (FD); F dentifizce followed by F rinse (FD/FR); placebo dentifrice followed by F rinse (PD/FR); and F rinse followed by placebo dentifrice (FR/PD). Unstimulated whole saliva samples were collected at baseline and then at 0, 15, 30, and 45 min, 1, 2, and 8 hr after B/R in the AM, after B/R in the PM and upon rising the following morning. Salivary flow rate and F were determined for each sampling interval.

The results of this study suggest that: (1) F rinse may be a more effective way of delivering topical F than F dentifrice; (2) based on F retention, the combination of FD/FR was not more effective than FR only (PD/FR); (3) older individuals with gingival recession retained higher F levels; and (4) bedtime F application resulted in longer F retention than did daytime application, which may have important implications for enamel remineralization.
Dendritic Cells and Macrophages Expressing Class II Antigens in the Normal Rat Incisor Pulp
Authors: Jontell M. , Bergenholtz G. , Scheynius A. , Ambrose W.
Published: November 2010

This study has identified and characterized class II (Ia) antigen-expressing cells in the normal rat incisor pulp by immunohistochemistry and flow cytometry. Two types of la-expressing cells occurred: one with a pronounced dendritic appearance located primarily in the periphery of the pulp, and one with morphological characteristics similar to those of macrophages. The latter cells were mainly observed in the central portion of the pulp. A numerical ratio of 1 :4 was established between the two cell types. The existence of la-expressing cells suggests an inherent capacity of the pulp to process and present foreign antigens.
An in vitro Evaluation of the Prevention of Caries on Overdenture Abutments
Authors: Ettinger R.L. , Manderson D. , Wefel J.S. , Jensen M.E.
Published: November 2010

Teeth prepared as overdenture abutments are susceptible to caries, and it has been shown that brushing by itself is not sufficient to prevent this process. This study evaluated the preventive effect of a remineralization gel which has a low fluoride concentration and compared its effects with those of a phosphate fluoride gel (Karigel), which has a much higher concentration of fluoride. Twenty extracted anterior teeth from patients aged 50 to 70 years were prepared as for overdenture abutments. Each tooth was sectioned into three fragments. An acidified gel system was used to produce artificial caries lesions on the occlusal and root surfaces of each fragment. One fragment of each tooth was treated with the remineralizing gel, the second fragment with a high-fluoride gel, and the third fragment served as the control. Ten teeth were removed at two weeks and again at four weeks, and were sectioned and prepared for histological examination. The depth of the lesions was measured from standardized photomicrographs by means of a sonic digitizer. The conclusions were: (1) Lesions on the occlusal tended to be deeper than those on the root surfaces at four weeks but not at two weeks; and (2) the high-fluoride gel was more protective than the low-fluoride remineralizing solution at both time periods on the occlusal but not on the root surface.
Analytical and Physiological Variability of Salivary Microbial Counts
Authors: Bentley C. , Crawford J.J. , Broderius C.A.
Published: November 2010

Quantitation of mutans streptococci (MS) and Lactobacillus has been proposed as a method for the identification of patients at high risk for dental caries. The purpose of the present study was to investigate the analytical and physiological variability of this procedure. Variability due to specimen collection and processing was investigated by repeated sampling studies. Sample stability was investigated over storage periods of up to 72 hr at 5°C, room temperature, and 37°C. Physiological variability was investigated by performance of serial analyses on ten individuals, who collected six samples at intervals on a single day, and rising and noon samples on ten subsequent days. Sample collection, rather than sample processing, was found to be the major factor determining the imprecision of salivary microbial analysis in the majority of cases. However, individual subjects varied considerably in the consistency with which they provided saliva samples. Imprecision due to sample processing was relatively small, with coefficients of variation of 2.3% for MS counts and 2.1% for Lactobacillus counts. Samples were generally stable over a wide temperature range for at least 72 hours, although there was some loss of viability of lactobacilli on prolonged storage at room temperature or 37°C in one experiment. Rising samples yielded higher counts than samples collected after breakfast and toothbrushing. Day-to-day variability was considerable, with 95% confidence limits exceeding 1 log in 28% of data sets for MS count and 39% of data sets for Lactobacillus.
The Acute Effects of Smokeless Tobacco on Transport and Barrier Function of Buccal Mucosa
Authors: Tobey N.A. , Schreiner V.J. , Readling R.D. , Orlando R.C.
Published: November 2010

The acute effects of smokeless tobacco (ST) on buccal mucosal transport and barrier function were studied by means of in vivo and in vitro techniques. In humans, in vivo exposure to 0.5 g ST transiently increased the transmural electrical potential difference (PD). However, despite continued exposure, PD returned to baseline within 20 min. The mechanisms for these changes were explored by use of dog buccal mucosa mounted in Ussing chambers. Luminal exposure to a Ringer-extract of ST (EOST) increased PD and short-circuit current (Isc) and decreased electrical resistance (R), with changes reversible upon removal of EOST from the bath. Further, radioisotopic fluxes showed that the increase in Isc in EOST-exposed tissues was accompanied by increased absorption of electrolytes (Na, Cl, and other ions), and the decrease in R was accompanied by increased permeability to mannitol. Light microscopy of tissues exposed to EOST showed no morphological changes after exposure to 0.5 g of ST, but after exposure to 1.5-2.5 g of ST, dilated intercellular spaces were identified.

Contact of aqueous media with ST led to the release of electrolytes and other soluble compounds into solution. To determine the effect of electrolyte release on buccal function, we exposed mucosae luminally to a solution with ion composition and/or osmolality similar to EOST or to one with an EOST previously dialyzed against Ringer. Solutions with similar ion composition and/or osmolarity changed PD, Isc, and R in a manner similar to EOST, while dialyzed-EOST had no effect. In addition, luminal nicotine produced effects different from EOST, decreasing PD and Isc and increasing R. These results indicate that ST can acutely alter buccal transport and barrier function by creating, through electrolyte release, electrochemical and osmolar gradients across the tissue.
The Effect of Previous Diet on Plaque pH Response to Different Foods
Authors: Sgan-Cohen H.D. , Newbrun E. , Huber R. , Tenenbaum G. , Sela M.N.
Published: November 2010

In this study we investigated the effect of previous diet on the response of plaque pH to three test foods. The study population consisted of 11 dental students. Plaque pH was measured, by means of the touch electrode method, on the first two upper molars. The study was conducted at two sessions, one week apart. Subjects followed a 48-hour high-sugar diet before the first test session and a 48-hour low-sugar diet before the second test session. During both 48-hour periods, students refrained from all oral hygiene practices and fluoride utilization. At each session, three foods were ingested at one-hour intervals : cola, beer, and chocolate bar. pH measurements at baseline and at selected times after food ingestion were recorded and analyzed. Multivariate analysis of variance revealed significant independent effects of food, previous diet, and their interaction on plaque pH. After the same foods were ingested, plaque pH response after a previous high-sugar diet was significantly more acidic than after a previous low-sugar diet.
Composition and Buffer Capacity of Pooled Starved Plaque Fluid from Caries-free and Caries-susceptible Individuals
Authors: Margolis H.C. , Duckworth J.H. , Moreno E.C.
Published: November 2010

The composition of pooled starved plaque fluid from six population samples, grouped according to age (8-11, 12-16, 8-17, 18-22 years) and caries status (caries-free, CF, DMFS = 0; caries-susceptible, CS, DMFS > 10), was determined by means of ion chromatography. Prior to plaque collection, all subjects abstained from oral hygiene for 48 hours and fasted overnight. In addition, selected subjects also received a dental prophylaxis one week prior to plaque collection. Plaque samples from each group were pooled under mineral oil and centrifuged at 15, 000 g (ambient temperature) for 45 minutes. Supernatants were then analyzed for organic acids, inorganic anions, and mono- and divalent cations. Plaque fluid samples from CF and from the CS subgroups were also titrated with standard HCI for exploration of the inherent buffer capacity. The ions Na+ NH4 +, K+, Ca2+, Mg2+, C1-, phosphate, and carbonate were present in all samples analyzed. Formic, acetic, propionic, butyric, and trace amounts of isobutyric and isovaleric acids were detected, with acetic and propionic acids comprising between 85 and 94% of the total acids. Little (< 1 mmol/L) to no succinic or lactic acid was detected in starved plaque fluid. No apparent difference was detected in the composition and saturation status of pooled starved plaque fluid from CF and CS individuals. These results suggest that caries susceptibility is not necessarily correlated with the plaque fluid composition of pooled starved plaque. ln addition, no apparent difference in the inherent buffer capacities of these samples could be detected, consistent with the noted similarities in composition. It was also apparent from the titration studies that a significant buffering component is missing from our analyses; this missing component appears to be an effective buffer above pH 6.
Risk Factors for Dental Fluorosis in a Fluoridated Community
Authors: Osujp O.O. , Leake J.L. , Chipman M.L. , Nikiforuk G. , Locker D. , Levine N.
Published: November 2010

We conducted a case-control study to determine the sources of fluoride which are particular risk factors to dental fluorosis. Cases and non-cases were identified by the screening of 8-, 9-, and 10-year-old schoolchildren in the fluoridated community of East York, Ontario-Parents were interviewed about the child's first five years of residence and about diet and preventive caries practices. The Mantel-Haenszel odds ratio and associated chi-square tests were used to assess the association of fluorosis with several potential sources, controlling for other sources of fluoride and mother's education.

The prevalence of mild fluorosis [1-4 on the Thylstrup and Fejerskov (1978) Index] was 13%. Those who brushed their teeth before the age of 25 months had 11 times the odds of fluorosis compared with those beginning toothbrushing later; prolonged use of infant formula (≥ 13 months) was associated with 3.5 times the risk of fluorosis, compared with no, or shorter duration of, formula use. We estimate that these factors were responsible for 72% and 22%, respectively, of the cases in our population.

Dental fluorosis is not a public health problem in East York, but parents should be advised to supervise toothbrushing by children under 2 years of age.
Degenerative Changes in the Temporomandibular Joint in two Australian Aboriginal Populations
Authors: Richards L.C.
Published: November 2010

The frequency and severity of degenerative changes in the temporomandibular joints in two Australian Aboriginal populations with different patterns of tooth wear, craniofacial morphology, and temporomandibular joint morphology were examined. The incidence of degenerative changes differed between groups and between sexes and increased with age, ranging from zero in the youngest groups to 65% in the oldest, most severely affected group. Degenerative changes of the fossa were more frequent than condylar changes. Significant associations between degenerative changes and both the pattern of tooth wear and aspects of facial morphology were also evident.
Characterization of One Phenotype of Human Periodontal Granulation-tissue Fibroblasts
Authors: Larjava H. , Heino J. , Kähäri V.-M. , Krusius T. , Vuorio E.
Published: November 2010

Human granulation-tissue fibroblasts were cultured from oral chronic inflammatory lesions and compared with fibroblasts of healthy gingival connective tissue with respect to cell-surface sialoglycoproteins, and the synthesis of extracellular matrix components. Granulation-tissue fibroblasts exhibited a slower growth rate and larger size than their controls. Their cell-surface sialoglycoproteins resembled those of the control cells, except that the relative amount of glycoproteins in the 140-kd region was lower. The ratio of mRNAs for proαl(I) and proαl(III) collagen chains was decreased in granulation-tissue fibroblasts, although electrophoretic fractionation of the proteins did not reveal consistent differences in type I/type III collagen ratio. Granulation-tissue fibroblasts secreted into the culture medium a dermatan sulfate proteoglycan with a lower molecular weight. After digestion with chondroitinase ABC, the molecular weight of the core protein appeared to be identical with that of the control fibroblasts, suggesting a difference in the glycosylation of the core protein. These results support the theory that granulation-tissue fibroblasts represent a distinct phenotype of fibroblastic cells.
Studies on Sound and Carious Enamel with the Quantitative Acoustic Microscope
Authors: Peck S.D. , Rowe J.M. , Briggs G.A.D.
Published: November 2010

The scanning acoustic microscope gives strong contrast from small caries lesions in sections of human enamel. The uniqueness of the acoustic microscope lies in its ability to image elastic properties. In addition to revealing the extent and the shape of lesions, the microscope may also be used to measure the elastic properties point by point across an area of interest. Since enamel is anisotropic, measurements of the Rayleigh velocity and attenuation were made as a function of direction on a section of sound enamel. The velocity was greatest parallel to the prism axis, and the attenuation was least in this direction. Measurements of V(z) across a section through a lesion are presented. The variation of attenuation can be interpreted in terms of the development of demineralization, initially along prism boundaries and then along cross-striations. The variation of velocity indicates a substantial reduction of elastic stiffness in the lesion.
Purification of Lingual Amylase from Serous Glands of Rat Tongue and Characterization of Rat Lingual Amylase and Lingual Lipase
Authors: Field R.B. , Spielman A.I. , Hand A.R.
Published: November 2010

Lingual amylase and lingual lipase, two digestive enzymes that are secreted from lingual serous glands (von Ebner's), were simultaneously purified from rat lingual serous glands with hydrophobic chromatography used as the final step. This method, previously developed for the purification of lingual lipase, includes homogenization of rat lingual serous glands, 100,000 g centrifugation, ammonium sulfate precipitation of proteins, and extraction of lipids with acetone at -20°C, followed by hydrophobic chromatography on ethyl agarose or Agethane. Amylase was eluted after the elution of proteins that did not interact with the hydrophobic gel at pH 6.3. Lingual lipase was eluted with a solution containing micelles of taurodeoxycholate, monoolein, and oleic acid. Analysis of each of the purified enzymes by SDS polyacrylamide gel electrophoresis revealed one band at M, = 59,000 for amylase and one band at M, = 51, 000 for lingual lipase. Isoelectric focusing of amylase indicated a strong band at pl = 5.0 and two very faint bands at pl = 4.9 and 4.8, possibly isozymes or deamidated protein. Amino acid and hexosamine analyses were performed on the enzymes after electroelution from SDS-polyacrylamide gels. Both lingual lipase and lingual amylase had a high content of dicarboxylic (free and amide) amino acids. For lingual lipase and lingual amylase, the % molar ratios of aspartic acid/asparagine were 15.35 and 15.10, and the % molar ratios of glutamic acid/glutamine were 7.07 and 7.20, respectively. Lingual amylase was very similar to rat parotid, pancreatic, and mouse salivary amylases, except that it contained more proline (11.03% molar ratio). Although no hexosamines were detected in lingual amylase, lingual lipase contained 14 moles of hexosamines/mole, 10 moles of GlcNAc, and 4 moles of GaINAc, indicating that the enzyme undergoes both N-linked and 0-linked glycosylation.
Studies on Fluoride Concentrations in Human Submandibular/Sublingual Saliva and their Relation to Flow Rate and Plasma Fluoride Levels
Authors: Oliveby A. , Lagerlof F. , Ekstrand J. , Dawes C.
Published: November 2010

Submandibular/sublingual saliva and blood were collected from five subjects after ingestion of 1 mg fluoride as NaF. An individual collection device, made from a silicone impression material, was used to collect the saliva in 10-minute samples, before and during 2 hr after the fluoride intake. In two separate experiments on each individual, submandibular/sublingual saliva was collected continuously at different flow rates: without stimulation and with gustatory stimulation. Blood was also collected at intervals throughout the experiments. The concentration of fluoride in the submandibularlsublingual saliva was less than that in the plasma but independent of salivary flow rate. The ratio between the saliva and plasma fluoride concentrations at the peak of the mean plasma fluoride concentrations was 0.55 ± 0.13 and 0.69 ± 0.11 in the experiments on unstimulated and stimulated salivary flow rate, respectively. The total amount of the ingested fluoride dose that was excreted through the submandibular/sublingual glands during 130 min was highly correlated with the salivary flow rate. The fraction of the ingested fluoride dose excreted in 2 hr was 0.04 ± 0.02% in the unstimulated saliva and 0.15 ± 0.09% in the stimulated saliva.
The Influence of Polyacid Molecular Weight on Some Properties of Glass-ionomer Cements
Authors: Wilson A.D. , Hill R.G. , Warrens C.P. , Lewis B.G.
Published: November 2010

The influence of the molecular weight of the poly(acrylic acid) component on some properties of glass-ionomer cement has been investigated. The results can be explained by treatment of glass-ionomer cements as thermoplastic composites. Many of the concepts of polymer science can be applied successfully in a qualitative way to these cements, including the ideas of entanglements and reptation. Molecular weight of the polyacid had a pronounced influence on setting rate, acid erosion rate, toughness, fracture toughness, and wear resistance. The chain length of the polyacid was found to be an important parameter in formulation of a cement, and the higher the molecular weight, the better the properties. However, in practice the molecular weight is limited by viscosity, and some balance has to be achieved among concentration, molecular weight, and viscosity.
Prevention of Sucrose-induced Demineralization of Tooth Enamel by Chewing Sorbitol Gum
Authors: Kashket S. , Yaskell T. , Lopez L.R.
Published: November 2010

Measurements were made of the effect of chewing sorbitol gum on the intra-oral demineralization induced by rinsing with 10% sucrose solutions. Blocks of bovine enamel were covered with a layer of Streptococcus mutans IB1600, and mounted on palatal appliances that were worn by five subjects for defined periods of time. Enamel demineralization was determined by following changes in iodide penetrability (delta Ip) of the enamel surfaces. Delta Ip increased to a maximum of about 15 units between 30 and 45 min, while the pH of the S. mutans plaque dropped to below 4 by 15 min. Plaque pH returned to 4.9 by 60 min. Chewing sorbitol gum after the sucrose rinse minimized further increases in delta Ip and brought about a more rapid return of the S. mutans plaque pH toward neutrality. The effect of chewing gum was greater when chewing was initiated earlier so that, when gum was given at five min after the sucrose rinse, demineralization was only 37% of that obtained without gum. The findings confirm earlier reports on the effect of gum on plaque pH, and directly demonstrate the profound protective effects that chewing sorbitol gum can have on tooth enamel.
The Effects of Pellicle Formation on Streptococcal Adhesion to Human Enamel and Artificial Substrata with Various Surface Free-energies
Authors: Pratt-Terpstra I.H. , Weerkamp A.H. , Busscher H.J.
Published: November 2010

The influence of a pellicle on streptococcal adhesion was studied. A "ripened" two-hour salivary pellicle and an "early" five-minute salivary pellicle were formed on human enamel and artificial solid substrata with varying surface free-energies. Three strains of oral streptococci, also with widely different surface free-energies, were used for adhesion studies. Pellicle formation and streptococcal adhesion took place at a constant shear rate of 21 s-1. Adhesion of S. mitis BMS to bare and pellicle-covered enamel was low and not significantly affected by the presence of a pellicle (0.7 × 106 and 0.6 x 10 6 cells.cm-2, resp.), whereas the numbers of S. sanguis 12 and S. mutans NS adhering to bare enamel (4.2 x 106 cells.cm -2 and 13.8 x 106 cells.cm-2, resp.) were significantly reduced by the presence of a pellicle. This reduction was almost complete after only five minutes of salivary protein adsorption (1. 9 × 106 and 1.1 x 106 cells.cm-2 for S. sanguis and S. mutans, resp.) but further reduced for S. sanguis adhering to a ripened pellicle (0.7 × 106 cells.cm-2). The numbers of streptococci adhering at equilibrium to bare enamel could be fitted to a thermodynamically based model, which was previously described for bacterial adhesion to homogeneous artificial substrata. Streptococcal adhesion to artificial substrata exposed to saliva was low, and the differences among uncoated materials were markedly reduced even after only five minutes' exposure to saliva.
Oligomers with Pendant Isocyanate Groups as Adhesives for Dentin and Other Tissues
Authors: Lee C.H. , Brauer G.M.
Published: November 2010

Oligomers containing pendant isocyanate groups were synthesized from various vinyl monomers, m -isopropenyldimethylbenzyl isocyanate (TMI), and 2-isocyanatoethyl methacrylate (IEM). The liquids were characterized by their refractive indices, infrared spectra, and percentage of isocyanate groups in the molecule. Adhesive properties of these compounds were compared with those of oligomers prepared from methacrylate esters, IEM, and/or TMI which had been synthesized previously. Bond strengths of the sodium salt of ethylenediaminetetraacetic acid (Na2EDTA adjusted to pH 7.4) and glutaraldehyde-treated dentin cemented to composite resin with dilute solutions of the oligomers and then stored in water were determined by the procedure of Kemper and Kilian (1975). These adhesive compositions, especially formulations synthesized from vinyl monomers, adhered at least as well to dentin as did other dentin bonding agents. Oligomers synthesized with methacrylate esters bonded more strongly to bone than did other hard-tissue adhesives. These oligomeric compositions are also excellent soft-tissue adhesives. For example, they provide a strong bond between a collagenous substrate (such as calfskin) and cured denture-base resin. Provided that their biological properties prove satisfactory, these compositions could find many applications as hard-and soft-tissue adhesives in clinical dentistry.
Inhibition of Bacterial Growth under Composite Restorations Following GLUMA Pretreatment
Authors: Felton D. , Bergenholtz G. , Cox C.F.
Published: November 2010

The purpose of this investigation was to test in five adult monkeys the effects of a glutaraldehyde-containing dentin bonding agent, GLUMA, on bacterial colonization in Class V cavities restored with composite resin. Experimental groups consisted of immediate placement of GLUMA and composite resin as well as placement of GLUMA or Scotchbond (control) in acid-etched cavities that had been left open to the oral environment for 48 hours. Various procedures for pretreatment of the cavities were included. Tissue specimens were prepared for light microscopy for observation of bacterial presence and pulp tissue reactions after eight days and 90 days. Bacteria were not detected in any of the 54 cavities treated with GLUMA regardless of observation period or use of enamel-etching procedure prior to placement of composite resin. When cavities were restored with composite resin without prior GLUMA pretreatment or with Scotchbond, bacteria were present under the majority of restorations at both time intervals. Pulpal inflammation of varying extent and character was seen after eight days in teeth that had been previously infected. At 90 days, pulps showed repair and healing regardless of treatment protocol. Data indicate that GLUMA has a distinct in vivo antibacterial effect that seems to prevent bacterial growth in tooth/restoration interfaces.
Model of Mercury Vapor Transport from Amalgam Restorations in the Oral Cavity
Authors: Olsson S. , Berglund A. , Pohl L. , Bergman M.
Published: November 2010

A model of the oral cavity was used as the basis for a discussion of the conditions prevalent during the transport of mercury vapor from amalgam restorations via the saliva to the gas phase of the oral cavity during respiration or during pumping of air through the mouth. It was found that the mercury diffusion rate through the saliva layer is independent of the air flow rate through the oral cavity. Mercury appears to be transported as atoms both in the agueous phase of saliva and in the gas phase. The majority of the mercury atoms reaching the gas phase appears to originate directly from the surface of the amalgam restorations, passing through the saliva layer, while only a minority oiginates from mercury dissolved in the aqueous phase. The amount of mercury released per unit of time to the gas phase was shown to be independent of the air flow rate during respiration and pumping. Furthermore, the released mercury atoms are distributed partly to the gas phase, from which they are respired to the lungs and the environment, and partly to the saliva and the gastro-intestinal tract, by swallowing.
Arterial Blood Pressure Regulation of Pulpal Blood Flow as Determined by Laser Doppler
Authors: Sasano T. , Kuriwada S. , Sanjo D.
Published: November 2010

Dynamic changes of pulpal blood flow (PBF) and gingival blood flow (GBF) induced by intra-venous injection of two kinds of vasoactive drugs were observed in dogs by means of Laser Doppler Velocimetry. Intra-venous injection of norepinephrine caused PBF to increase, corresponding to the blood pressure (BP) increase, while GBF decreased. Orciprenaline sulfate caused PBF to decrease parallel to the BP decrease, as compared with a GBF increase. The effects of these vasoactive drugs lasted longer on GBF than on PBF and BP.

These results indicate that the regulation of blood flow in the dental pulp is more dependent on systemic blood pressure than on local vasoconstriction or vasodilation.
Assessment of Appearance Match by Visual Observation and Clinical Colorimetry
Authors: Johnston W.M. , Kao E.C.
Published: November 2010

Judgments of appearance matching by means of the visual criteria established by the United States Public Health Service (USPHS) and by means of an extended visual rating scale were determined for composite resin veneer restorations and their comparison teeth. Using a colorimeter of 45°/0° geometry and the CIELAB color order system, we used the color of the restorations and comparison teeth to calculate a color difference for every visual rating. Statistically significant relationships were found between each of the two visual rating systems and the color differences. The average CIELAB color difference of those ratings judged a match by the USPHS criteria was found to be 3. 7. However, the overlap in ranges of the color differences for those comparisons rated matches and mismatches indicates the importance of other factors in appearance matching, such as translucency and the effects of other surrounding visual stimuli. The extended visual rating scale offers no advantages to the more broadly defined criteria established by the USPHS.
The Concentration of Dietary Casein Required for Normal Mandibular Growth in the Rat
Authors: Bozzini C. , Barcelo A.C. , Alippi R.M. , Leal T.L. , Bozzini C.E.
Published: November 2010

To determine a suitable casein concentration for normal, undeformed mandibular growth, we placed weanling male rats on diets containing graded levels of casein between 0% and 30% for 19 days. Some weanlings were killed so that initial values could be established. Ten linear dimensions corresponding to the six skeletal units of the mandible were evaluated so that their growth rates at the end of the experimental period could be established. Other dimensions were also evaluated for study of the growth rate of the bone as a whole. The macroscopic growth of the mandible showed a sigmoidal relationship with dietary casein concentration, most of the measurements reaching a plateau at 20% casein. Within the skeletal units, four dimensions corresponding to the alveolar and symphyseal regions did not change with age and were not affected by the casein content of the diet. The remaining six dimensions-corresponding to condylar, coronoid, angular, and basal regions of the mandible-increased with age and were related positively to dietary casein concentration. Their growth patterns were not uniform, although all of them reached maximal values when the diet contained 20% casein. Therefore, deformation of the mandible appears to occur in rats fed diets with a casein concentration lower than 20%. It appears that a dietary casein concentration of 20% is required for normal, undeformed mandibular growth.
Effect of Etching Glass-ionomer Cements on Bond Strength to Composite Resin
Authors: Sheth J.J. , Jensen M.E. , Sheth P.J. , Versteeg J.
Published: November 2010

The use of glass-ionomer cement in restorative dentistry has seen a revival because of its capacity for being etched and bonded to composite resin. Past investigators compared an etched cement surface with an unetched surface that was set against a smooth surface. Clinically, however, a glassy smooth surface is not produced when the cement is used as a base. Using Scotchbond bonding resin, we developed this two-part study to evaluate the tensile bond strengths of P-30™ composite resin to several glass-ionomer cements that were (a) unetched but allowed to set in air and (b) etched for 30 s with orthophosphoric acid, and to compare them with the cohesive strength of the respective cement. Using a silver nitrate staining technique, we also evaluated the microleakage of class V cavities restored with Silux™ composite resin under a base of etched or unetched Ketac Bond® cement. Although there were significant differences among three cements between their cohesive strength and the resin bond strength after the two surface treatments (p<0.01), the bond to the unetched surface was generally similar to that of the etched surface of the cement. The remaining groups showed no statistical difference. The microleakage was similar in the two groups. SEM micrographs showed a rough topography of the unetched cement that resembled that of the etched surface. This in vitro study suggests that acid-etching a glass-ionomer base for resin-bonding may not be necessary for specific materials. Further clinical evaluation is recommended to validate this observation intra-orally.
In vitro Caries-inhibitory Properties of a Silver Cermet
Authors: Swift E.J.
Published: November 2010

Recurrent caries is one of the primary causes of failure of dental restorations. One method for reducing the frequency and severity of this problem is the use of fluoride-releasing restorative materials.

The glass-ionomer cements are a type of fluoride-releasing material. They have been used extensively in recent years for a variety of clinical applications. However, in comparison with other restorative materials such as amalgam and composite resins, glass ionomers have relatively poor physical properties. Sintering of silver particles to glass-ionomer powder is a means of improving these physical properties. The sintered material is called a silver-glass ionomer or silver cermet.

This study examined the in vitro caries-inhibitory potential of a silver cermet by means of two methods. First, long-term fluoride release was measured. Second, an artificial caries system was used for evaluation of caries inhibition by cermet restorations in extracted teeth.

In comparison with a standard glass-ionomer restorative material, fluoride release from the cermet material was significantly less throughout a 12-month period. The results from the artificial caries system indicated that this decreased fluoride release corresponded with a lesser degree of caries inhibition. Lesions around cermet restorations in both enamel and root surfaces were significantly more severe than those around conventional glass-ionomer restorations. However, in compartson with amalgam and composite resin restorations, the cermet did have some cariostatic activity.
Methodological Considerations Concerning the Use of Bruxcore Plates to Evaluate Nocturnal Bruxism
Authors: Pierce C.J. , Gale E.N.
Published: November 2010

The purpose of this study was to evaluate the Bruxcore Plate (BP) as a dependent measure of nocturnal bruxing activity. As part of a bruxism treatment study, we evaluated 100 nocturnal bruxers for bruxing activity before, during, and immediately after treatment and again at a six-month recall. The first 40 subjects wore both a BP and an EMG (electromyographic) unit for every night of each 14-night evaluation period (bcrseline; post-treatment; six-month recall). During the treatment period, these subjects wore the EMG unit but no Bruxcore Plates. Another 40 subjects wore the EMG unit and never used Bruxcore Plates. We evaluated a 20-subject no-treatment control group by two methods. Ten control subjects were evaluated with the EMG unit and the BP and another ten with the EMG unit alone. We hypothesized that the BP would not measure the same construct as an accepted EMG measure of bruxing activity, and that the BP would effect changes in EMG measured nocturnal bruxing activity.

The results supported the conclusions that the BP did not measure the same construct as the EMG measure, and that the BP did effect changes in nocturnal bruxing activity. Correlations of BP scores with EMG data for equivalent measurement periods were low or non-existent. For the control group and the massed practice (negative practice) treatment group, there were significant interaction effects for EMG-measured bruxing episodes per hour for BP vs. no-BP Groups, with respect to measurement periods (time). Interpretation of these results indicated that BP evaluation of nocturnal bruxing activity was confounded with measurable treatment effects.
Effect of an Acute Maternal Fluoride Dose on Fetal Plasma Fluoride Levels and Enamel Fluoride Uptake in Guinea Pigs
Authors: Bawden J.W. , Deaton T.G. , Koch G.G. , Crawford B.P.
Published: November 2010

We conducted this study to measure maternal plasma, fetal plasma, and fetal enamel fluoride concentrations for four hours following an oral F dose to near-term pregnant guinea pigs.

We placed female guinea pigs on de-ionized (Group I) or 3-ppm-F (Group II) drinking water prior to breeding and during gestation. On the 57th day of gestation, we administered a maternal dose of NaF solution (0.6 mg Flkg) by stomach tube. We collected samples of maternal plasma, fetal plasma, and fetal enamel at baseline, at 15 and 30 min, and at one, two, and four h after administration of the dose. We assayed samples for F using a modification of the micro-diffusion and ion-specific electrode method.

Group I mean baseline F values were: maternal plasma, 0.016; fetal plasma, 0.002 ; and fetal enamel, 7. 0 ppm. Group II mean values were: 0.055, 0.004, and 19.0 ppm. After the maternal fluoride dose, the mean maternal plasma [F] rose sharply for 30 to 60 min and declined to about 50% of peak values by four h. Fetal plasma [F] changed less in absolute values, but similarly to maternal changes relative to baseline. Fetal enamel mean [F] rose more in Group II than in Group I.

Baseline F status had an important effect on F uptake in fetal enamel following an actue maternal fluoride dose.
Amalgam Margin Breakdown Caused by Creep Fatigue Rupture
Authors: Williams P.T. , Cahoon J.R.
Published: November 2010

This study was designed to determine whether the mechanical cyclic stressing that occurs during normal mastication contributes to margin breakdown of dental amalgam restorations. The method used appears to duplicate the mechanical stresses developed in vivo during mastication, as the result of tooth flexing. We evaluated one low-copper alloy—NTD—and three high-copper alloys—Dispersalloy, Phasealloy, and Tytin. We prepared simple amalgam restorations in a cavity cenn-ally located in an aluminum beam. Each specimen received five periods of three-point cyclical loading (1.7 hertz, 4200 cycles at 37°C). The margin area was subjected to SEM examination prior to and at the completion of each period of cycling. At the beginning of each period of cycling, beam deflection was set to establish a maximum theoretical stress of I, 2, 4, 6, or 8 MPa. For all brands, cycling resulted in margin gap formation and surface wrinkling. Wrinkling in Dispersalloy occurred as a wide band of shallow wrinkles, whereas that in NTD occurred as a narrow band of deep wrinkles. At 21,000 cycles, very little void formation and fracturing had occurred in the Dispersalloy or NTD restorations. In contrast, the Phasealloy and Tytin restorations developed extensive fracturing even after 4200 cycles. Fracture surface analyses of Phasealloy and Tytin indicated that creep fatigue ruptacre was the fracture mechanism responsible for margin breakdown in these amalgam restorations, when subjected to cyclic compressive loading similar to that experienced during mastication.
Fractography of a bis-GMA Resin
Authors: Davis D.M. , Waters N.E.
Published: November 2010

The fracture behavior of a bis-GMA resin was studied by means of the double-torsion test. The fracture parameter measured was the stress-intensity factor. Fracture occurred in either a stick-slip (unstable) or continuous (stable) manner, depending upon the test conditions. When stick-slip propagation occurred, the fracture surfaces showed characteristic crack-arrest lines. The fracture surfaces were examined by use of a reflected-light optical microscope. The stress-intensity factor for crack initiation was found to be related to the size of the crack-arrest line which, in turn, could be related to the Dugdale model for plastic zone size. The evidence supported the concept that the behavior of the crack during propagation was controlled by the amount of plastic deformation occurring at the crack tip.