bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of 2-(Methacryloxy)ethyl Phenyl Hydrogen Phosphate on Adhesion to Dentin
Authors: Wang T. , Nakabayashi N.
Published: November 2010

A variety of methacrylate-based materials has been developed with the capacity of adhering to dentin. This study investigated the effectiveness of 2-(methacryloxy)ethyl phenyl hydrogenphosphate (phenyl-P) for bonding 5% phenyl-P in methyl methacrylate (MMA) to dentinal surfaces. Polymerization of the phenyl-P/MMA monomer was initiated by partially oxidized tri-n-butyl borane catalyst (TBB). The mean tensile bond strength of 5% phenyl-P in MMA to dentin that was pre-treated with an aqueous solution of 10% citric acid/3% ferric chloride, abbreviated as 10-3, was found to be 10.5 MPa. Scanning electron microscope examination demonstrated the formation of a transitional or "hybrid" layer of resin-reinforced dentin, created by the intermingling and entanglement of polymerized resin with collagen bundles exposed by dentin pre-treatment with 10-3, an effective remover of the dentinal smear layer. This "hybrid" layer or zone was essential for high tensile bond strength to be attained. Phenyl-P was found to be effective in promoting monomer diffusion and impregnating monomer into demineralized dentinal surfaces. The formation of the "hybrid" layer of resin-reinforced dentin followed in situ resin polymerization initiated by partially oxidized tri-n-butyl borane (TBB). Ferric (Fe3+) ions deposited on dentinal surfaces from the 10-3 solution also acted to improve monomer diffusion and entanglement with demineralized dentin, and facilitated the formation of the "hybrid" layer/zone.
The Effect of Catalyst Structure on the Synthesis of a Dental Restorative Monomer
Authors: Farahani M. , Johnston A.D. , Bowen R.L.
Published: November 2010

The addition product of 2-hydroxyethyl methacrylate (HEMA) and pyromellitic dianhydride (PMDA), known as PMDM, is a mixture of two structural isomers. The para PMDM isomer-currently used in mediating adhesive bonding of restorative materials to hard tooth tissues-is a crystalline solid. The meta isomer is a liquid. In the synthesis of PMDM, the para isomer, which can be purified by crystallization, is usually present to the extent of only 50% of the product mixture. The effect of the amine catalyst structure was studied relative to its role in increasing the yield of the para isomer, either by a reduction in the amount of the meta isomer or by an increase in the extent of overall reaction. The chemical structure of the amine catalyst had an important role in the synthesis of PMDM and influenced the ratio of the isomers. Among aliphatic amines, especially noteworthy as catalysts that gave excellent yields of the para isomer in high purity were N,N-di-isopropyl-ethylamine and hexamethylenetetramine.
Adhesion to Dentin and Physical Properties of a Light-cured Glass-ionomer Liner/Base
Authors: Mitra S.B.
Published: November 2010

The objective of this study was to determine the adhesion to dentin and the physical properties of Vitrabond Light Cure Glass Ionomer Liner/Base and to compare these values with those of a conventional material, 3M Glass Ionomer Liner (3MGI). Shear bond strengths to bovine dentin after 24 h in distilled water were determined to be 12 ± 3 MPa for Vitrabond Liner/Base, while for 3MGI, bond strengths were 4 ± 2 MPa. The failure mode was cohesive in dentin or the ionomer. Immediate adhesion of the light-cured material was also significantly higher than that of the conventional glass-ionomer liner. Thermal cycling experiments showed that the bond of Vitrabond Liner/Base to dentin was a stable one. Adhesion studies carried out on human dentin showed high adhesion values as well. Compressive and diametral tensile strengths for Vitrabond Liner/Base were determined immediately after light curing and also after storage in water for 24 h, one week, one month, and seven months. There was no significant difference in the values of compressive and diametral tensile strengths obtained immediately after curing and after extended storage in water at 37°C.
Fatigue Strength of a Au-Pd Alloy/585 Solder Combination
Authors: Wiskott H.W.A. , Nicholls J.I. , Taggart R.
Published: November 2010

The S-N diagram (applied stress vs. cycles to failure) for the gold-palladium alloy/585 solder combination was generated. Au-Pd alloy specimens were cast, prepared for soldering, and joined with 585 solder. After milling and polishing of the joint, testing was carried out in a specially designed machine. This device loaded the cantilevered test specimen in a unidirectional mode at a rate of 70 strokes per minute. The applied tensile stress ranged between 294.2 and 686.5 MPa. Three specimens were cycled for each stress level until fracture occurred. The number of fatigue cycles to failure ranged from one cycle (stress level, 686.5 MPa) to 4.83 x 106 cycles (stress level, 294.2 MPa). On a logarithmic scale, the relationship between the applied stress and the number of cycles to failure was linear. Under the present (ideal) experimental conditions, the Au-Pd/ 585 solder combination behaved favorably on the high-cycle end of the diagram. However, no definite endurance limit could be detected within the stress range examined.
Effects of Fluoride and Chlorhexidine on the Microflora of Dental Root Surfaces and Progression of Root-surface Caries
Authors: Schaeken M.J.M. , Keltjens H.M.A.M. , Van Der Hoeven J.S.
Published: November 2010

The effects of fluoride and chlorhexidine varnishes on the microflora of dental root surfaces and on the progression of root-surface caries were studied. Forty-four patients, surgically treated for advanced periodontal disease, were distributed at random among three groups. All patients received a standardized preventive treatment. Furthermore, the dentition of the patients in the two experimental groups was treated, at three-month intervals, with chlorhexidine and fluoride varnish, respectively. Patients in the control group received no additional treatment.

In the experimental groups, plaque samples were collected from selected sound and carious root surfaces at baseline and at three, six, and nine months after the onset of the study. The presence of root-surface caries was scored at baseline and after one year. In addition, the texture, depth, and color of the root-surface lesions were monitored.

Mutans streptococci on root surfaces were suppressed significantly (p<0.05) during the whole experimental period in the chlorhexidine varnish group, but not in the fluoride varnish group. A non-significant increase in the number of Actinomyces viscosus/naeslundii was noted after treatment with chlorhexidine and fluoride varnish.

The increase in the number of decayed and filled root surfaces after one year was significantly lower in the experimental groups than in the control group. After treatment with chlorhexidine varnish, significantly more initial root-surface lesions had hardened than in the other groups.
Acid Profile in Carious Dentin
Authors: Hojo S. , Takahashi N. , Yamada T.
Published: November 2010

Organic acids in carious dentin from 69 permanent teeth were analyzed by gas chromatography. Lactate, acetate, propionate, and butyrate were detected in most samples, and limited amounts of isobutyrate, valerate, isovalerate, caproate, and isocaproate were occasionally detected. Lactate, acetate, and propionate were major acids and altogether accounted for about 90% of total acid in most samples of carious dentin. However, the proportion of these three acids varied among the samples. Some samples contained over 85% lactate, while others contained mainly acetate and propionate. A high percentage of acetate was usually accompanied by an appreciable amount of propionate. All seven samples in carious dentin under fillings or restorations had little lactate, but a high percentage of acetate plus propionate. The differences in acid profiles of carious dentin may reflect differences in the microbial ecology of carious dentin, and a stage of progress of dentin caries or a type of dentin caries.
An Experimental Study in Dogs of Transseptal Fiber Arrangement between Teeth which have Emerged in Rotated or Non-rotated Positions
Authors: Kusters S.T. , Kuijpers-Jagtman A.M. , Maltha J.C.
Published: November 2010

Transseptal fibers of the periodontal ligament are thought to play a role in relapse after orthodontic derotation. The aim of this study was to compare the location of the attachment site and the arrangement of the transseptal fibers in rotated emerged and non-rotated emerged teeth. In five dogs, unilaterally, the first upper premolars were replaced into a rotated position, before emergence. Histological evaluation showed that transseptal fibers developed in the experimental as well as in the control specimens. In all cases, transseptal fibers bridged the shortest distance between two adjacent teeth. It was concluded that the attachment site of the transseptal fibers was not determined by the tooth anatomy itself, but by the tooth position and its orientation in the dental arch during transseptal fiber development.
Chemical and Molecular Weight Analyses of Prosthodontic Soft Polymers
Authors: Jones D.W. , Hall G.C. , Sutow E.J. , Langman M.F. , Robertson K.N.
Published: November 2010

A number of studies have been made investigating the properties of dental prosthodontic soft polymer materials. In such materials, which are used as short-term denture soft liners, the polymer component is complexed with one or more plasticizers. This lowers the glass transition temperature, Tg, of the polymer by allowing greater chain mobility and produces a more flexible material. Little information is available relating to the polymer components of such soft-lining materials. The chemical composition and molecular-weight distribution of a polymer help to determine its ability to form a plasticized soft polymer-gel. In the present work, both pyrolysis depolymerization/gas chromatography (GC) and size exclusion chromatography (SEC) have been used to characterize 11 commercial polymer powders. By use of SEC and polymer standards having a narrow molecular-weight range, it has been possible for accurate molecular-weight distributions to be determined for all 11 powders. The peak molecular weights were found to be between 1.79 x 105 and 3.28 x 105. These values are above the molecular weight at which chain entanglement occurs. The polydispersity ratios (Mw/Mn) were between 2.09 and 4.48. Methacrylate polymers can be readily decomposed thermally to their constituent monomers, which, once recovered, can be analyzed by gas chromatography. The simple pyrolysis apparatus used in the present study was easily assembled and was capable of producing both qualitative and quantitative results. None of the commercial polymers analyzed gave methacrylate decomposition products with pendant chains greater than ethyl (-CH2-CH3). All of the commercial polymers successfully studied by the pyrolysis test method proved to be poly(ethyl [100-79%]/methyl [0-21%] methacrylate) polymers or co-polymers.
Refractive-index-adjustable Fillers for Visible-light-cured Dental Resin Composites: Preparation of TiO 2-SiO2 Glass Powder by the Sol-gel Process
Authors: Suzuki H. , Taira M. , Wakasa K. , Yamaki M.
Published: November 2010

New fillers have been prepared for visible-light-cured (VL) dental resin composites with the refractive index adjustable to that of the resin phase. These SiO2 glass powders containing TiO2 up to 20 wt% were formed by heating to 1000°C ground gels made from a mixture of Ti[OCH(CH3)2] 4 and Si(OC2H5)4· With increasing TiO2 content, the refractive index of the prepared powder increased linearly, while the optical transmittance at 467 nm decreased linearly. The experimentally formulated VL-cured resin composites, consisting of (TEGDMA and Bis-GMA) monomer mixture and TiO2-SiO2 glass filler, had greater transmittance when the refractive index of the filler matched that of the monomer mixture, resulting in a greater degree of monomer conversion upon irradiation with VL.
Single-dose Concentrations of Tinidazole in Gingival Crevicular Fluid, Serum, and Gingival Tissue in Adults with Periodontitis
Authors: Liew V. , Mack G. , Tseng P. , Cvejic M. , Hayden M. , Buchanan N.
Published: November 2010

Previous studies have shown that metronidazole is effective in the treatment of subgingival microflora associated with destructive periodontitis. The aim of this study was to determine whether tinidazole, a close analogue of metronidazole, would reach sufficient concentrations in serum, gingival crevicular fluid, and gingival tissue, to inhibit putative periodontopathic bacteria.

Ten adult patients with moderate to advanced periodontitis took a single 2-g dose of tinidazole orally. Samples were assayed by high-performance liquid chromatography. The concentrations of tinidazole in serum and GCF were in a similar range (3.2-46.5 μg/mL). Tinidazole was not detected in the GCF in three of the patients. The drug was found in gingival tissue obtained at two h (0.17 ± 0.14 μg/mg) and six h (0.15 ± 0.18 μg/mg) after oral administration. The mean concentration of tinidazole in serum at 24 h (13 ± 3.0 μg/mL) is greater than the minimum inhibitory concentration for anaerobic bacteria as reported by others. The present data suggest that a single 2-g oral dose of tinidazole may lead to the presence of potentially bactericidal levels of tinidazole for up to 24 h in the periodontal pockets of some patients with periodontitis.
Dentinal Fluid Movement Associated with Loading of Restorations
Authors: Hirata K. , Nakashima M. , Sekine I. , Mukouyama Y. , Kimura K.
Published: November 2010

Post-operative biting sensitivity is a significant clinical problem after placement of posterior resin composites and may be due to dentinal fluid movement. The occlusal surfaces of extracted teeth were filled with amalgam (control) or various posterior resin composites, and the movement of the dentinal fluid induced by the loading of the restorations was studied. In addition, the firing of pulpal nerves induced by the loading of class 5 resin composite restorations in canine teeth of dogs was also investigated.

When the entire cavity was etched with an acid gel and then filled with resin composite, dentinal fluid movement in response to loading was significantly (p<0.01) greater than in the amalgam-filled or unoperated controls. The dog canine tooth filled with resin composite showed firing of pulpal nerves when loaded.

These results suggest that the movement of dentinal fluid induced by masticatory pressure on resin composite restorations may elicit biting sensitivity.
Dental Fluorosis and Fluoride Exposure in Western Australia
Authors: Riordan P.J. , Banks J.A.
Published: November 2010

Dental fluorosis in children is reported from many locations, and its prevalence may be increasing. This study aimed to measure fluorosis in 12-year-olds in fluoridated and non-fluoridated areas of Western Australia and to relate this to exposure. School dental clinics in Perth (F- 0.8 mg/L) and the Bunbury area (F- <0.2 mg/L) were the sampling units. Parents provided data on residence in fluoridated areas and on use of supplements and toothpaste. Exposure to water and supplemental fluoride between birth and four years was calculated. Clinical examinations (upper left central incisor) based on the TF classification of fluorosis (which requires teeth to be dried) were conducted for 338 children in Perth and 321 in the Bunbury region. Re-examinations (n = 50) gave a weighted kappa of 0.78. Contingency analysis estimated bivariate relationships, and multiple logistic regression estimated odds ratios (OR) for risk factors. Fluorosis prevalence in the Perth region was 0.40, and in the Bunbury region 0.33 (χ2 = 3.69, df = 1, p = 0.055). Prevalence was 0.44 in children with fluoride exposure equivalent to optimal water fluoridation and 0.20 among those with the lowest exposure (χ 2 = 35.99, df = 1, p = 0.0001). Increasing exposure was associated with higher fluorosis prevalence and higher TF scores, but overall, 27.3% of participants had TF score 1 (barely discernible), and only 9.4% had TF score ≥2. The odds of fluorosis were greatest for use of fluoride supplements in accordance with recommendations (OR = 4.63, 95% CI 1.97, 10.90) and extended residence in an area with fluoridated water (OR = 4.06, 95% CI 2.55, 6.44). All toothpaste-related variables had ORs > 1, but none was statistically significant, suggesting recall error. The findings suggest that supplement use by some children in 1978-82 provided too much fluoride, and that a small number of persons have undesirable fluorosis.
Water and Abrasive Effects on Three-body Wear of Composites
Authors: Sarrett D.C. , Söderholm K.-J.M. , Batich C.D.
Published: November 2010

The degrees of in vitro three-body wear resistance of a hybrid, a small-particle, and a microfilled composite were determined after water storage for up to 24 months. The hybrid composite was the most wear-resistant, while the microfilled composite showed the most wear. The hybrid composite showed no loss of wear resistance as a result of water storage. The small-particle composite showed a decrease in wear resistance after water storage only when tested with silicon carbide abrasive. The wear resistance of the microfilled composite decreased following water storage when tested with either a soft (CaCO3) or a hard (SiC) abrasive. For all composites, the soft abrasive was not capable of causing preferential wear of the polymer matrix, as observed on in vivo specimens. Instead, the filler particles became flattened, with minimal loss of interparticle substance. The hard abrasive did cause preferential wear of the matrix. All composites absorbed water and leached silicon during water storage, indicating that the filler-polymer bond was attacked by hydrolytic degradation. Scanning electron microscopic evaluation of the three-body wear specimens indicated that the in vitro wear method did not duplicate in vivo wear conditions (e.g., the hard abrasive caused excessive wear and chipping of the filler particles in vitro, a pattern that was not usually observed in vivo). Filler-polymer de-bonding was observed on in vivo specimens of all the composites, while it was found only on the in vitro microfilled composite specimens. These findings suggest that filler dislodging is a complex process that cannot be simulated with the in vitro wear method used in this study, not even after prolonged water storage.
Vibrational Analysis by Raman Spectroscopy of the Interface Between Dental Adhesive Resin and Dentin
Authors: Suzuki M. , Kato H. , Wakumoto S.
Published: November 2010

The Raman microprobe technique was applied for analysis of the molecular components at the adhesive interface between 4-META/MMA-TBB resin and dentin. The Raman spectra showed that the 4-META molecules in monomer solution were mostly hydrolyzed into 4-MET molecules, which were then co-polymerized with MMA molecules to form resin and resin-reinforced dentin layers. On the basis of line analysis by the Raman microprobe, resin molecules were estimated to penetrate 6 μm into the dentin from the interface. Raman intensity studies indicated that the concentration of 4-MET molecular units in the resin-reinforced dentin was more than four times the concentration in the original monomer solution. This demonstrated the excellent infiltration ability of 4-MET monomer into dentin substrate in situ.
Effects of Salivary Film Velocity on pH Changes in an Artificial Plaque Containing Streptococcus oralis, After Exposure to Sucrose
Authors: Macpherson L.M.D. , Dawes C.
Published: November 2010

Results from a computer model suggest that following exposure of dental plaque to sucrose, the rate of clearance of acids from plaque into the overlying salivary film will be greatly retarded at low film velocities. This was investigated with an in vitro technique in which artificial plaque containing S. oralis cells was exposed to 10% sucrose for one min. The pH at the proximal (P) and distal (D) undersurfaces of the plaque (0.5 or 1.5 mm thick) was then monitored during the passage of a 0.1-mm-thick film of a sucrose-free solution over the surface. Over the range of salivary film velocities that have been estimated to occur in vivo (0.8-8 mm/min), lower minimum pH values and increased times for the pH to recover toward neutrality occurred at the lower salivary film velocity. Lower pH values were also reached with the 0.5- than with the 1.5-mm-thick plaque. P/D pH gradients, with a lower pH distally, developed at film velocities of 0.8 and 8 mm/min, and the gradients were much more pronounced at the lower velocity. No P/D pH gradients developed when the film velocity was 86.2 mm/min. Incorporation of dead S. oralis cells into the plaque at percentages up to 57% reduced the extent of the pH fall and prolonged the recovery of the pH toward neutrality. The results support the prediction that, other factors being equal, plaque located in regions of the mouth with low salivary film velocity will achieve pH values lower than those of plaque of identical dimensions and microbial composition located in areas where salivary film velocity is high.
Changes in Strains of Mutans Streptococci Induced by Treatment with Chlorhexidine Varnish
Authors: Kozai K. , Wang D.S. , Sandham H.J. , Phillips H.I.
Published: November 2010

Isolates of mutans streptococci were obtained from the dental plaque of ten subjects before and after the subjects had been free of detectable mutans streptococci for a mean period of 14.6 weeks (range, from two to 36 weeks). The mutans streptococci had been rendered undetectable by chlorhexidine varnish treatment. Examination of the restriction endonuclease analysis (REA) patterns of the isolates revealed that all ten subjects had one strain (REA type) after re-appearance of the mutans streptococci that was identical to one that had been present before the varnish treatment. In six of the ten subjects, only one strain was detected both before and after treatment. Each of the other four subjects appeared to gain a new strain after treatment; one of the four appeared to lose one strain, and another, four strains. The ability of strains to persist after the period of undetectability seemed unrelated to their resistance to chlorhexidine or to their ability to exhibit insoluble glucan-mediated adhesion. In the subjects harboring multiple REA types, one-seventh of the tooth surfaces sampled harbored two strains simultaneously, suggesting an inability of either strain to exclude the other aggressively. Overall, the study indicated that every subject receiving chlorhexidine varnish therapy had a primary strain of mutans streptococcus that re-emerged after treatment. In contrast, secondary strains were highly susceptible to being lost or gained.
Effect of Transferrin on the Growth of Porphyromonas gingivalis
Authors: Inoshita E. , Iwakura K. , Amano A. , Tamagawa H. , Shizukuishi S.
Published: November 2010

This study describes the effect of transferrin as an iron source on the growth of Porphyromonas (formally Bacteroides) gingivalis. Bacterial growth was monitored spectrophotometrically. All strains of P. gingivalis tested grew well in medium containing transferrin. The growth of P. gingivalis depended not only on the concentration of transferrin, but also on the iron saturation level of the protein. However, growth was not stimulated with either the ferrous or ferric iron salts tested. The addition of dipyridyl to the medium containing transferrin suppressed the growth of P. gingivalis, which also did not show species-specificity for human transferrin. Transferrin-binding activity was found in P. gingivalis by solid-phase assay with peroxidase-conjugated human transferrin. These results suggest that P. gingivalis may be capable of utilizing transferrin as an iron source for growth in vivo.
Cell Attachment Activity of Cementum Proteins and Mechanism of Endotoxin Inhibition
Authors: Olson S. , Arzate H. , Narayanan A.S. , Page R.C.
Published: November 2010

Cementum occupies a unique anatomical location where soft connective tissues of the periodontium are attached to root surfaces. Cell attachment properties of proteins present in cementum were studied. Human and bovine cementum were extracted with 0.5 mol/L CH3COOH followed by 4 mol/L guanidine, and proteins were separated by ion-exchange chromatography and SDS-polyacrylamide gel electrophoresis. Cells were labeled with radioactive amino acids and added to tissue-culture plastic plates incubated with cementum proteins, and attachment was measured. Results showed that cementum proteins promoted the attachment of smooth muscle cells, endothelial cells, and fibroblasts, but not epithelial cells. Fibroblasts attached more efficiently than other cell types, and they manifested spreading with re-organization of actin filaments. No attachment occurred to plates incubated with endotoxin from A. actinomycetemcomitans. Fewer fibroblasts attached to plates treated with cementum proteins in the presence of endotoxin, but cells pre-treated with endotoxin attached normally. Attachment was not inhibited when plates were incubated first with attachment proteins and then with endotoxin; however, it was decreased when endotoxin or bovine serum albumin preceded cementum proteins. Cementum proteins with Mr 68,000, 61,000, 55,000, and 36,000 (p68, p61, p55, and p36, respectively) manifested attachment activity, while protein(s) with Mr 23,000-24,000 did not. Western blots revealed that guanidine extracts contained three bands cross-reacting with anti-bovine sialoprotein-II antibody, but the p61, p55, and p36 were negative. We conclude that cementum contains bovine sialoprotein-II and at least four other fibroblast attachment proteins, and that they do not support epithelial cell attachment. Endotoxin did not mediate fibroblast attachment, but it non-specifically inhibited attachment by blocking binding sites for cementum attachment proteins.
Influence of the Solubility Parameter of Intermediary Resin on the Effectiveness of the Gluma Bonding System
Authors: Asmussen E. , Hansen E.K. , Peutzfeldt A.
Published: November 2010

The aim of the present study was to investigate the effect of the solubility parameter of the intermediary resin in the Gluma system on the bonding to dentin. The solubility parameter of the resins was varied between 18.8 x 103 and 21.1 x 103 J1/2/m 3/2 by varying the composition of the resin. The efficacy of the bonding system was determined by measurements of marginal gaps formed by polymerization contraction of a restorative resin in dentin cavities treated with the bonding system. The bonding system had maximum efficacy at a solubility parameter of the intermediary resin of 8 = 20.0 x 103 J1/2/m3/2. This finding corroborates a concept of bonding to dentin that involves a mechanical interlocking by interpenetrating resins.
Scanning and Contact Microradiographic Study of the Effect of Degree of Saturation on the Rate of Enamel Demineralization
Authors: Gao X.J. , Elliott J.C. , Anderson P.
Published: November 2010

The effect of degree of saturation with respect to hydroxyapatite (DSHA) on enamel section demineralization was studied by contact and scanning microradiography (CMR and SMR). Two aspects were studied: (1) the effect of different values of DSHA at constant pH, and (2) the effect of constant DSHA with variable pH. In the pH range (2.5 - 4.5) and time scale (0-120 h) studied, the DSHA was more important in determining the rate of enamel lesion progression than was the pH.
The Effect of Partial Coating with Hydroxyapatite on Bone Remodeling in Relation to Porous-coated Titanium-alloy Dental Implants in the Dog
Authors: Pilliar R.M. , Deporter D.A. , Watson P.A. , Pharoah M. , Chipman M. , Valiquette N. , Carter S. , De Groot K.
Published: November 2010

For inhibition of crestal bone resorption due to stress shielding and disuse atrophy, an hydroxyapatite (HA) plasma coating was added to the coronal portion of partially porous-coated endosseous dental implants. These implants, as well as control non-HA-coated implants were placed in healed mandibular premolar extraction sites in dogs for a 72-week period of function. Histological examination showed that both implant designs became securely fixed by bone ingrowth into the porous-coated apical region of the implants. The plasma-sprayed HA coating resulted in significantly greater bone height formation and maintenance next to the coronal portion of the implant compared with non-HA-coated implants of similar design. In addition, significant resorption of the 20-to-50-μm-thick plasma-sprayed HA coating occurred over the 18-month period of function.
Evaluation of New Gingival Retraction Agents
Authors: Bowles W.H. , Tardy S.J. , Vahadi A.
Published: November 2010

Current gingival retraction agents are not without undesirable side-effects; there appears to be no ideal gingival retraction agent. Several sympathomimetic amines, capable of producing local vasoconstriction with minimal systemic side-effects, are available as non-prescription nasal decongestants and eye washes. The purpose of this study was to evaluate the efficacy of three of these agents for gingival tissue displacement.

Mongrel dogs were used as experimental subjects, in which pulse rate and blood pressure were monitored electronically. Visine® (tetrahydrozoline HCl, 0.05%), Afrin® (oxymetazoline, 0. 05%), and Neosynephrine®(phenylephrine HCl, 0.25%) were the commercial products studied as gingival retraction agents. Plain, untreated cord was used as a mechanical control, and as a vehicle for the three experimental agents. Commercially available cords impregnated with both racemic epinephrine (8%) and alum were also used as standard retraction agents with which the test solutions were compared.

Visine and Afrin produced tissue displacement greater than that of any of the other agents; Neosynephrine, epinephrine, and alum were more effective than the untreated mechanical control. Cardiovascular changes included a slight increase in systolic pressure in the Neosynephrine group, and a slightly lower mean arterial pressure and pulse rate in all three experimental groups.
The Effect of Low-level Laser Treatment on Maxillary Arch Dimensions after Palatal Surgery on Beagle Dogs
Authors: De Braekt M.M.H. In , Van Alphen F.A.M. , Kuijpers-Jagtman A.M. , Maltha J.C.
Published: November 2010

The effect of low-level laser treatment on maxillary arch dimensions after palatal surgery was investigated in Beagle dogs at an age of 12 weeks. A total of 30 dogs was used, and they were assigned to either a control group (Group C, n = 6) or one of two experimental groups (Group L, n = 12; and group LL, n = 12).

After Von Langenbeck's palatal repair in the two experimental groups, denuded bony areas in the LL group were irradiated with a continuous Ga-As-Al laser beam (830 nm) and energy output set at 30 mW. A dosage of 1 J/cm2 wound surface area was used. Treatment was carried out three times a week, with a total of ten treatments. The animals of the L group served as non-treated control animals. Dental casts were made of all animals of all groups at regular intervals until they reached 25 weeks of age. Maxillary arch dimensions were studied.

Dental arch dimensions in the deciduous dentition of both experimental groups were not disturbed by surgery, but after eruption of permanent teeth, mainly transvere maxillary arch dimensions in the premolar region increased less in both experimental groups than in the control group. It was concluded that low-level laser treatment under the conditions used in this study did not decrease the adverse iatrogenic effects of palatal surgery on maxillary arch dimensions.
Solvent Degradation and Reduced Fracture Toughness in Aged Composites
Authors: Ferracane J.L. , Marker V.A.
Published: November 2010

Quartz- and barium-glass-filled composites aged for more than one year in ethanol experienced a significant reduction in fracture toughness (KIc), essentially identical to that experienced after two months of aging. This reduction is mainly attributed to a softening of the resin matrix, but cracking within the resin and at the filler/ matrix interface, as revealed by SEM microscopy, may also have contributed. No significant cracking could be seen in the composites aged in water. Composites post-cured at temperatures approaching their glass-transition temperature also experienced a reduction in KIc after alcohol storage. Storage in water for one year had little effect on the KIc of composites cured at oral temperatures, but a significant increase was observed for those post-cured at elevated temperatures. This increase is difficult to explain, but appears to involve a filler/matrix interfacial phenomenon, because it was not observed in the unfilled resin. The results of this study demonstrate that an alteration in the fracture resistance and some degradation of the filler/matrix interface, as has been observed clinically, occur after long-term exposure of dental composites to certain solvents used as food-simulating liquids.
A Light and Electron Microscopic Anterograde WGA-HRP Tracing Study on the Sensory Innervation of Junctional and Sulcular Epithelium in the Rat Molar
Authors: Kondo T. , Ayasaka N. , Nagata E. , Tanaka T.
Published: November 2010

The sensory innervation of junctional and oral sulcular epithelium was investigated by use of anterograde transport of wheat-germ agglutinin-horseradish peroxidase from the trigeminal ganglion. By light microscopy, labeled intra-epithelial nerve fibers were observed forming a dense plexus in the apical two-thirds of the junctional epithelium, with some fibers located near the enamel space. Occasional fibers extended coronally to the sulcus bottom. By electron microscopy, labeled intra-epithelial axon terminals or varicosities were demonstrated to be in close contact with both junctional epithelial cells and neutrophils. These varicosities, which were occasionally surrounded by the cytoplasmic processes of epithelial cells or neutrophils, frequently contained large granular and small clear vesicles. In contrast to the junctional epithelium, the oral sulcular epithelium was sparsely innervated, except for the transition region between the oral sulcular epithelium and the junctional epithelium, where a dense innervation by labeled intraepithelial fibers was found. These fibers extended as far as the stratum spinosum. Electron microscopy revealed mitochondria-filled profiles of varicosities between epithelial cells. This study shows differences in the distribution and ultrastructure of sensory nerves between the junctional and oral sulcular epithelia, and further provides morphological evidence that sensory nerves in the junctional epithelium come into contact not only with epithelial cells but also with neutrophils.
The Occurrence of Interglobular Dentin in Incisors of Hypophosphatemic Mice Fed a High-calcium and High-phosphate Diet
Authors: Abe K. , Masatomi Y. , Nakajima Y. , Shintani S. , Moriwaki Y. , Sobue S. , Ooshima T.
Published: November 2010

The incisor dentin of hypophosphatemic (Hyp) mice was examined histopathologically to determine whether the multiple occurrences of interglobular dentin would be influenced by the serum phosphate level. Both normal and Hyp mice (12 weeks of age) were divided into two groups. The mice in one group were given a control diet (1.42% Ca, 1.16% P) and the other a high-calcium and high-phosphate diet (2.00% Ca, 3.00% P) for 30 days. Blood was collected from the mice every fifth day for measurement of the calcium and phosphate concentrations in serum. Both ground and decalcified cross-sections were prepared from incisors from the mandible and maxilla for microscopic examination. The levels of serum Ca and P were almost constant in normal mice, regardless of diet. On the other hand, serum P levels in Hyp mice fed the control diet were significantly lower than those in normal mice. The ten days' feeding of the high-Ca/-P diet significantly elevated the serum P level in Hyp mice, and it reached a level similar to that of the normal mice. However, histopathological examination showed no significant changes in incisor dentin of Hyp mice fed the high-Ca/-P diet, and interglobular dentin still occurred. These results suggest that the multiple formations of interglobular dentin, which is the most outstanding feature of X-linked hypophosphatemic vitamin-D-resistant rickets, are not influenced in Hyp mice by the short-time normalization of the serum phosphate level.
Effectiveness of Oxide Films in Reducing Mercury Release from Amalgams
Authors: Ferracane J.L. , Hanawa T. , Okabe T.
Published: November 2010

The release of mercury from four freshly-triturated amalgams into air, argon, and moist air environments was quantitated at three different temperatures. Although a measurable amount of mercury was released from dental amalgam, the evaporation rate was immediately reduced by several phenomena, the most important being the formation of an oxide film on the surface. This hypothesis was supported by the fact that release rates were elevated in an inert argon environment, but declined dramatically once air was introduced and oxidation could occur. The further amalgamation of "free" mercury, as well as the presence of water vapor, also contributed to the reduced release rates observed during aging. Mercury release was reduced to a negligible level within three to four hours after trituration. Only one of the amalgams, Tytin, demonstrated a thermal dependence for mercury release in air. The results of this study suggest that the exposure to mercury vapor from a freshly placed amalgam restoration would be negligible in consideration of the normal estimated daily intake from all other sources.
The Effect of an Experimental Chewable Antiplaque Preparation Containing Chlorhexidine on Plaque and Gingival Index Scores
Authors: Nuuja T.T. , Murtomaa H.T. , Meurman J.H. , Pesonen T.J.
Published: November 2010

This clinical cross-over trial investigated the effects of a chewable preparation containing chorhexidine-fluoride-xylitol, xylitol control tablets, or chlorhexidine mouthwash, twice daily, on plaque and gingival index scores of subjects refraining from mechanical cleaning of their teeth. Both preparations containing chlorhexidine were found to be efficient antiplaque agents when compared with the control. There was no statistically significant difference between the tablet preparation and conventional chlorhexidine rinsings with respect to the recorded parameters. Thus, an efficient antiplaque preparation can be made in tablet form, which may have advantages in instances where use of mouthwash solutions is impracticable.
pH Regulation by Streptococcus mutans
Authors: Dashper S.G. , Reynolds E.C.
Published: November 2010

The intracellular pH (pH i) optimum for glycolysis in Streptococcus mutans Ingbritt was determined to be 7.0 by use of the ionophore gramicidin for manipulation of pHi. Glycolytic activity decreased to zero as the pHi was lowered from 7.0 to 5.0. In contrast, glycolysis had an extracellular pH (pHo) optimum of 6.0 with a much broader profile. The relative insensitivity of glycolysis to the lowering of pHo was attributed to the ability of S. mutans to maintain a transmembrane pH gradient (ApH, inside more alkaline) at low pHo. At a pHo of 5.0, glycolyzing cells of S. mutans maintained a ΔpH of1.37 ± 0.09 units. The maintenance of thisΔpH was dependent on the concentration of potassium ions in the extracellular medium. Potassium was rapidly taken up by glycolyzing cells of S. mutans at a rate of 70 nmol/mg dry weight/min. This uptake was dependent on the presence of both ATP and a proton motive-force (Δp). The addition of N-N'dicyclohexylcarbodiimide (DCCD) to glycolyzing cells of S. mutans caused a partial collapse ofthe ΔpH. Growth of S. mutans at pHo 5.5 in continuous culture resulted in the maintenance of a ApH larger than that produced by cells grown at pH o 7.0. These results suggest the presence of a proton-translocating F1Fo ATPase in S. mutans whose activity is regulated by the intracellular pH and transmembrane electrical potential (Δψ). The production of an artificial Δp of 124 mV across the cell membrane of S. mutans did not result in proton movement through the F 1Fo-ATPase coupled to ATP synthesis. This suggests that ATP synthesis is not driven by the low Δp values obtained under physiological conditions in S. mutans. Therefore, the major role of the F1 Fo-ATPase is likely to be in pHi regulation. The extracellular concentration of sodium had no effect on ΔpH maintenance in glycolyzing cells, whereas the addition of 500 μmol/L fluoride caused a significant fall in pHi. S. mutans was able to grow in the absence of a Δp, indicating that the transmembrane circulation of protons is not obligatory for growth of this organism.
Restriction Endonuclease-fragment Polymorphisms of Oral Viridans Streptococci, Compared by Conventional and Field-inversion Gel Electrophoresis
Authors: Rudney J.D. , Neuvar E.K. , Soberay A.H.
Published: November 2010

Oral streptococci formerly classified as Streptococcus sanguis or Streptococcus mitis have recently been divided into four species. Two additional species have also been proposed for this group. Each species is genetically distinct, but they have many traits in common, which makes it difficult for clinical isolates to be identified by phenotypic tests. Genotypic comparison may provide an alternative approach. This study used DNA fingerprint analysis for comparison of genotypes of 21 reference strains-classified as Streptococcus gordonii, Streptococcus sanguis, Streptococcus oralis, "Streptococcus parasanguis", or "Streptococcus crista" in previous DNA hybridization studies-and 17 clinical and laboratory strains placed in those groups on the basis of phenotypic tests. HinDIII and PuuII digests were run in conventional horizontal agarose gels. SfiI digests of reference strains and two laboratory strains were run in field-inversion gels. Fingerprint patterns were compared by visual examination, cluster analysis of densitometric traces, and lane-matching software. Only two "S. crista" strains and two parent mutant lineages showed fingerprint patterns that were identical by visual examination. Fingerprint patterns of all other strains were unique. Cluster analysis results could not be considered valid, since replicate lanes in different gels were not grouped together. HinDIII and PvuII digests contained too many bands for correct matching by lane-matching software. SfiI digests were correctly matched by computer, with the same results as visual examination. Results indicate that the diversity of strains within these streptococcal species was too great to permit species identification by DNA fingerprint patterns. This genotypic diversity suggests that isolates from unrelated hosts may have been separate for long periods of time. Fingerprint patterns were useful for strain identification, and this may facilitate studies of the ecology and transmission of oral streptococci. Field-inversion electrophoresis of SfiI digests may be particularly suitable for that purpose, since computers can be used for comparison of large numbers of strains.
The Role of Albumin in Developing Rodent Dental Enamel: A Possible Explanation for White Spot Hypoplasia
Authors: Robinson C. , Kirkham J. , Brookes S.J. , Shore R.C.
Published: November 2010

The uptake of serum albumin by maturation-stage rodent enamel and the resulting effects on the growth of enamel crystallites were investigated in vitro. Albumin uptake was demonstrated by means of gel electrophoresis and confirmed by Western blotting with use of monoclonal antibodies. Measurement of crystal size was carried out by direct TEM measurement of enamel crystallite outlines after incubations in metastable solutions of calcium phosphate. The ability of endogenous enamel enzymes to degrade albumin was investigated by substrate-specific zymography. The results showed that albumin could be taken up by maturation-stage enamel and produce inhibition of crystallite growth. There was no detectable proteolytic activity in the enamel against albumin substrate, which suggests that albumin entering enamel by extravasation in vivo may produce incomplete tissue maturation, resulting in a white, opaque appearance on eruption.
Comparison of Whole Saliva Flow Rates and Mucin Concentrations in Healthy Caucasian Young and Aged Adults
Authors: Navazesh M. , Mulligan R.A. , Kipnis V. , Denny P.A. , Denny P.C.
Published: November 2010

Unstimulated and chewing-stimulated whole saliva samples were obtained from 42 healthy Caucasians; 21 were between 18 and 35 years of age, and 21 between 65 and 83 years of age. The unstimulated salivary flow rate was significantly lower in the aged group, but the stimulated flow rate was significantly higher in the aged than in the young group. Both groups showed significantly increased flow during salivary stimulation. MG1 and MG2 concentrations in unstimulated and stimulated saliva samples were significantly lower in the aged group. There were no significant correlations between salivary flow rates and MG1 and MG2 concentrations.
A Fluoride Dose-response Evaluation in an Anticaries Clinical Trial
Authors: Marks R.G. , D'Agostino R. , Moorhead J.E. , Conti A.J. , Cancro L.
Published: November 2010

This study evaluated the dose-response relationship between four increasing levels of fluoride from 1000 to 2500 ppm F as sodium monofluorophosphate (MFP) and three-year dental caries increments, as measured by DMFS, DMFT, and DFS-A on 4424 schoolchildren. The results indicated consistent linear decreases in all three dental indices as the dose level increased to 2500 ppm F MFP, with slopes (average reductions) of 0.32 in DMFS for an increase of 1000 ppm F, 0.13 in DMFT, and 0.17 in DFS-A when all children were evaluated, p < 0.03 for each index. For children 11 years and older at baseline, the slopes quadrupled, p < 0.01 for each index. Age and baseline DMFS were shown to be the most important covariates to control for in the statistical models. No differences in adverse reactions, or other safety problems, were observed at the different dose levels.
Progression of Approximal Caries in Relation to Iatrogenic Preparation Damage
Authors: Qvist V. , Johannessen L. , Bruun M.
Published: November 2010

The aim of the present study was to evaluate the effect of iatrogenic preparation damage on the need for operative caries treatment of approximal surfaces, adjacent to Class II amalgam restorations.

The material was collected by 77 dentists from the Public Dental Child Health Service in Denmark. It consisted of die-stone models of 187 first-time Class II preparations, adjacent to 190 unfilled approximal surfaces of 58 primary and 132 permanent teeth. The cavity preparations were performed in children between 4 and 17 years of age. They were all filled with amalgam. Information about operative treatment and exfoliation or extraction of the preparation teeth and the adjacent teeth during the following seven years was obtained from the patients' records.

sStereomicroscopic examination of the models revealed preparation damage on 64% of the unfilled approximal surfaces in primary teeth and on 69% of the corresponding test surfaces in permanent teeth. During the observation period, operative treatment was performed on 10% of the undamaged test surfaces in primary teeth and on 35% of the damaged ones (p < 0.05). The corresponding figures for test surfaces in permanent teeth were 6% and 15% (p < 0.05). It is concluded that iatrogenic preparation damage is a frequent side-effect of operative intervention with approximal caries lesions, and represents a dental health problem, since the damage increases caries progression and the perceived need for restorative therapy of the adjacent teeth.