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Biomedical subjects

C M Russell

Publications and source records attributed to C M Russell.

At least 37 records · Page 2Linked to original sources
PubMed1997

Tetracycline demineralization of dentin: the effects of concentration and application time.

The current investigation was initiated to study the effect concentration and application time has on the rate of tetracycline demineralization of dentin. Buccal and lingual surfaces of extracted bovine molars were ground to a smooth flat dentin surface using wetted silicon carbide discs. Standardized depressions were made in the dentin surface with a #909-055 diamond round wheel. Fresh tetracycline HCl (TTC-HCl) (Flavine Int. Inc.) solutions, i.e., 0, 25, 50, 75, 100, 125 and 150 mg/ml were prepared. A 30% citric acid solution was used as a positive control. The pH of each solution was recorded. 7 microl of each solution were pipetted into a depression and remained undisturbed for 1, 3, or 5 min. At the end of each application time period a fresh #3 cotton pellet was placed in the depression, once every 20 s for 1 min, to soak up the solution. The 3 pellets were placed in a 2.00 ml of 18 M omega H2O sample. As a measure of the rate of demineralization, the parts per million calcium (ppm Ca++) found in each sample were determined using atomic absorption spectrophotometry. Two-way analysis of variance was used to determine effects of TTC-HCI concentration and time on the rate of demineralization. No significant differences were found in the mean ppm Ca++ released at 1-, 3- and 5-min application times for 0, 25, or 50 mg/ml TTC. No significant differences were found in the mean ppm Ca++ released (i) between 3- and 5-min application times for 75, 100, 125 and 150 mg/ml TTC-HCl solutions and (ii) between 75, 100, 125 and 150 mg/ml TTC-HCl solutions within either the 3- or 5-min application times. The mean ppm Ca++ released at 3- and 5-min application times for 75, 100, 125 and 150 mg/ml TTC-HCI solutions were all significantly greater than the respective readings at the 1-min application time. The mean ppm Ca++ recorded for the 30% citric acid solution for all 3 application times were 3 to 5.5 x greater than the highest mean ppm Ca++ recording for TTC-HCl. The results of this study show that a 3-min application time of 75 mg/ml TTC-HCl solution is equally as effective at demineralizing dentin as is higher concentrations and/or longer application times, but was far less effective than a 30% citric acid solution.

Animals↗
PubMed1997

Expression of connexin 43 in rat mandibular bone and periodontal ligament (PDL) cells during experimental tooth movement.

Bone remodeling in response to force requires the coordinated action of osteoblasts, osteoclasts, osteocytes, and periodontal ligament cells. Coordination among these cells may be mediated, in part, by cell-to-cell communication via gap junctions. This study tests the hypothesis that the regulation of expression of connexin 43, a gap junction protein, is part of the transduction mechanism between force as applied to bone during orthodontic tooth movement and bone remodeling. To test this hypothesis, we examined connexin 433 expression in a rat model system of experimental tooth movement. To establish the model, we extracted maxillary first molars to initiate supra-eruption of opposing mandibular molars. The rats were killed at 0, 6, 12, 24, and 48 hrs post-extraction. The mandibles were removed, demineralized, and embedded in paraffin. To localize connexin 43 protein and mRNA, we used a specific antibody for immunohistochemistry and a specific cDNA probe for in situ hybridization. Western and Northern blot analyses were used to assess the specificity of the connexin 43 antibody and cDNA probe, respectively. We found connexin 43 protein expressed by osteoclasts (++ ++) and periodontal ligament cells (++ +) in compression zones, and by osteoblasts (++ ++) and osteocytes (++ ++) in tension zones of the periodontal ligament. In addition, connexin 43 mRNA was found in some bone and periodontal ligament cells. Connexin 43 protein was found, by densitometric analysis, to be higher in the periodontal ligament after exposure to force compared with controls (P < 0.001). The number of osteocytes expressing connexin 43 48 hrs after molar extraction was also significantly greater in bone subjected to tension when compared with controls (P < 0.001). The results of this study support the hypothesis that connexin 43 plays a role in the coordination of events during experimentally induced alveolar bone remodeling.

Animals↗
PubMed1997

Effects of toothbrush design and brushing proficiency on plaque removal.

A single-blind, short-term cross-over clinical trial compared the plaque removal performance of three commercially available manual toothbrushes. A sample of 25 dental hygiene students, 19 to 42 years old, served as participants. On 3 separate occasions, participants were instructed to refrain from toothbrushing or flossing for 24 hours before clinical trials. A prebrushing plaque index using disclosing solution was performed on each participant. One of the 3 test brushes was then randomly dispensed to each participant, and they were allowed to brush for 90 seconds without the aid of a mirror. A postbrushing plaque index was then performed on each participant. This procedure was repeated 2 more times at 2-week intervals so that each participant was tested with all 3 toothbrushes. Previous studies of this kind using random participant samples have suggested that brush design does indeed affect the efficacy of plaque removal. This study used participants who were well versed on efficient toothbrushing technique to determine if improved brushing skills would overshadow advantages in toothbrush design. No significant differences in performance were detected between the test brushes for any of the three scored areas.

Adult↗
PubMed1996

Potential interference of leucite crystallization during porcelain thermal expansion measurement.

OBJECTIVES: The elevated temperatures and slow heating and cooling rates associated with a thermal expansion run provide a thermal treatment comparable to those previously shown to produce leucite crystallization in dental PFM porcelains. The purpose of this study was to determine whether the exposure of dental porcelains to the time-temperature profile of a thermal expansion run could result in leucite crystallization, a potential interference with the accurate determination of the thermal expansion coefficient. METHODS: A total of 112 thermal expansion specimens were prepared, 16 each of six commercially available body porcelains, as well as the "Component No. 1" (leucite-containing) frit of the Weinstein et al. (1962) patent. In a randomized design, the leucite contents of specimens subjected to a 3 degrees C/min thermal expansion run were compared to those of untreated controls. The leucite content of each specimen was determined via quantitative X-ray powder diffraction using an Al2O3 internal standard. One-tailed t-tests were applied to determine whether the dilatometer thermal treatment produced a statistically significant increase in leucite content. RESULTS: The heat treatment afforded by a 3 degrees C/min dilatometer run was not sufficient to induce measurable leucite crystallization in any of the porcelains examined in this study. SIGNIFICANCE: The crystallization of leucite during a dilatometer heating run can be ruled out as a possible interference with the determination of the coefficient of thermal expansion of dental porcelain.

Aluminum Silicates↗
PubMed1996

Spatial resolution in radiometric analysis of enamel loss. A pilot study.

This pilot study was undertaken to determine whether spatial resolution affects radiometric analyses aimed at detecting progressive enamel loss. Four teeth were weighed, attached to a positioning device, and evaluated with radiography. A 1 mm strip of enamel was removed from each tooth, and the teeth were weighted again and reexamined by radiography. This process was repeated five times until 1/2 mm of dentin was removed. The radiographs were digitized twice with 59 and 200 microns pixels at 8 bits, providing two series of images with the optical densities converted into 256 gray levels. Each series of images was adjusted for contrast variation. Regions of interest were drawn on the crowns, and cumulative percent histograms (CPHs) were calculated. Within a series of CPHs enamel reduction resulted in shifts in the CPHs that were directly proportional to the amount of enamel removed. CPH shifts associated with the smaller 59 microns pixels accounted for 68% of the variation in weights caused by enamel reduction, whereas the shifts associated with the larger 200 microns pixels accounted for 50%. The results indicate that pixel size does affect radiometric determinations of enamel reduction.

Dental Caries↗
PubMed1996

Tooth thickness at the furcation entrance of lower molars.

Better understanding of the furcation anatomy may serve to decrease the risk of pulpal injury during rotary odontoplasty, a procedure often used in conjunction with guided tissue regeneration. The purpose of this study was to determine (i) the tooth thickness about the furcation entrance of lower molars, and (ii) whether there is a relationship between tooth thickness and patient age. 40 mandibular 1st molars (M1) (mean age = 36.2; range 10-65 years) and 40 mandibular 2nd molars (M2) (mean age = 37.9; range 14-70 years) were collected. Age, gender and furcation involvement (if any) were noted for each tooth at the time of extraction. Teeth were sectioned in half, buccal-lingual, at the furcation entrance with a rotary diamond blade. A standardized linear reference scale was placed on each experimental section and an 8 x 10 in. photograph generated. The distance from the floor of the pulp chamber to 5 predetermined sites on the root surface was calculated. The data were expressed as (a) the mean of each site and (b) the mean of each tooth (the average of the 5 points of each tooth). Analysis of covariance failed to show a relationship between thickness measurements and gender or furcation involvement. Thus, the data was subjected to simple regression analysis to determine the relationship of age with tooth and cementum thickness. This study revealed that by site, the mean measurements ranged from 2.7-3.0 mm for both M1 and M2. The single least/greatest measurements of the 5 sites were for M1: 1.6/4.7 mm and for M2: 1.8/4.2 mm. By tooth, the average distance from the pulp to the root surface was 2.83 mm (+/- 0.49) for M1 and 2.88 mm (+/- 0.44) for M2. Regression analysis of tooth thickness with age was significant for M1 only. The maximum slope of the 5 sites was approximately 0.3 mm/10 years. No relationship was found between cementum thickness and age for either tooth group. The results of this study indicate that the majority of times the pulp is 1.6-4.2 mm from the root surface in the vicinity of the furcation entrance of lower 1st and 2nd molars. Although tooth thickness in this area may increase with age, the amount is not enough to forego judicious odontoplasty on older patients.

Adolescent↗
PubMed1996

The effects of acetone, ethanol, HEMA, and air on the stiffness of human decalcified dentin matrix.

During resin-bonding procedures, dentin surfaces are treated with acidic conditioners to remove the smear layer and decalcify the surface to expose the collagen fibrils of the underlying matrix. These decalcified surfaces are then either air-dried or treated with dehydrating solvents, procedures which may modify the physical properties of the dentin matrix. The purpose of this study was to evaluate the effects of dehydration on the stiffness of the decalcified dentin matrix. Small (8 x 1.7 x 0.9 mm) beams of dentin were prepared from mid-coronal dentin of extracted human molars. The ends were covered with varnish for protection, and the specimens were placed in 0.5 M EDTA for 5 days to decalcify. The stiffness was measured by both the cantilever technique and by conventional stress-strain testing. Specimens tested by the cantilever technique were sequentially exposed to water, acetone, alcohol, HEMA, and glutaraldehyde. Specimens tested by conventional stress-strain testing were exposed either to water, acetone, or HEMA, or were allowed to air-dry. The results indicate that the stiffness of decalcified human dentin matrix is very low (ca. 7 MPa), if the specimens are wet with water. As they are dehydrated, either chemically in water-miscible organic solvents or physically in air, the stiffness increases 20- to 38-fold at low strains or three- to six-fold at high strains. These increases in modulus were rapidly reversed by rehydration in water. Exposure to glutaraldehyde also produced an increase in stiffness that was not reversible when the specimens were placed back in water.

Acetone↗
PubMed1996

Digital enhancement of radiographs: can it improve caries diagnosis?

Unlike traditional radiographs, digital images are electronically alterable and offer the potential for enhancing diagnostic information. The authors conducted a small-scale study to examine differences in clinicians' diagnoses of caries using traditional radiographs and digitized images vs. microscopic diagnosis. Two general dentists and one oral-maxillofacial radiologist scored the images for caries. This study suggests that digital enhancements may aid some clinicians in caries diagnosis.

Dental Caries↗
PubMed1996

Assessing the effects of 10 percent carbamide peroxide on oral soft tissues.

To examine the effects of a 10 percent carbamide peroxide bleaching gel on the oral soft tissues, the authors conducted a prospective, double-blind, placebo-controlled clinical investigation. Fifty-two patients completed a two-week treatment regimen, applying either a placebo or a 10 percent carbamide peroxide gel in a soft tray for eight hours a day. Clinicians examined the participants' oral soft tissues at baseline and one week, two weeks and six weeks after the first treatment. The examiners recorded the Silness and Löe plaque and gingival indexes, nonmarginal gingival index and nongingival oral mucosal index at each examination. The data collected at these intervals did not indicate that any soft tissue damage had occurred as a result of the bleaching regimen.

Adult↗
PubMed1996

Porous polysulfone coated with platelet-derived growth factor-BB stimulates proliferation of human periodontal ligament fibroblasts.

The purpose of this study was to investigate if the treatment of porous polysulfone (PPSF) with various concentrations of platelet-derived growth factor-BB (PDGF-BB) would stimulate the proliferation of the adherent human periodontal ligament fibroblasts (HPDLF) in culture. Sterilized PPSF cylinders were immersed in an Eagle's minimum essential medium supplemented with 0.5% fetal bovine serum and 1% penicillin/streptomycin containing either 0, 10, 20, or 50 ng/ml of PDGF-BB for 24 hours. After 24 hours, the PPSF cylinders were removed and allowed to dry then placed in culture plates for each time point. Pooled HPDLF (8 x 10(4)) and 3H-thymidine in medium were pipetted into each well to cover the treated and control PPSF cylinders and plates were then incubated. At 1, 4, and 10 days the PPSF cylinders were removed and macromolecular precipitation was performed. Incorporation of 3H-thymidine was measured and a 2-way ANOVA with repeated measures was performed. In addition, determination of binding and release was performed using I125-PDGF-BB treated PPSF at 0, 2, 12, and 24 hours, and at 4 and 10 days. Results showed that the effects on HPDLF were significant for dose (P = 0.0012; F = 5.74) and time (P = 0.0001; F = 40.83). At 4 days, the percent increases above the control for the doses 10, 20, and 50 ng/ml were 192%, 310%, and 162% respectively. In conclusion, our findings suggest that treating PPSF with PDGF-BB results in a significant increase in the proliferation of HPDLF cells adherent to PPSF.

Analysis of Variance↗
PubMed1995

Bond strength versus dentine structure: a modelling approach.

Bond strengths of a hypothetical hydrophilic dentine-bonding agent were calculated as a function of dentine depth and resin strength to evaluate the importance of several variables in a simple model. The tested hypothesis was that the total bond strength was the sum of the strengths of resin tags, hybrid layer and surface adhesion. Each of these three variables has a range of values that can influence its relative contribution. The resulting calculations indicate the potential for higher bond strengths to deep dentine than to superficial dentine in non-vital dentine and the importance of resin strength in the development of strong bonds. Comparison of the calculated bonds with published values indicated that they were within the same order of magnitude. Such theoretical modelling of dentine bonding can identify the relative importance of variables involved in the substrate, resins and surface adhesion.

Acid Etching, Dental↗
PubMed1995

Shear bond strength and quantitative microleakage of a multipurpose dental adhesive system resin bonded to dentin.

The shear bond strengths of a dental bonding system used in conjunction with a composite resin bonded to dentin were determined 1 minute after irradiation and after storage in saline at 37 degrees C for 24 hours, 1 week without and with temperature cycling, and 4 weeks without and with temperature cycling. The quantitative microleakage of class V preparations in cementum (dentin) restored with the system was determined by a spectrophotometric dye-recovery method. Excellent shear bond strengths ranging from 13.9 MPa (1 minute) to 19.5 MPa (1 week) were obtained. The shear bond strengths and quantitative microleakage of the multipurpose dental adhesive system compared favorably with the data obtained from other dental bonding systems under similar experimental conditions.

Analysis of Variance↗
PubMed1995

Tensile properties of resin-infiltrated demineralized human dentin.

The ability of adhesive resins to restore the physical properties of demineralized dentin has not been well-documented. The unfilled resins that are used for adhesion have relatively low moduli of elasticity and limited ability to increase dentin stiffness, although they may increase the ultimate tensile strength of dentin. This study tested the hypothesis that resin infiltration of demineralized dentin can restore its tensile properties to those of mineralized dentin. Small (ca. 0.5 mm thick x 0.5 mm wide) specimens of demineralized human dentin were infiltrated with one of five different dentin bonding resins over many hours, to determine how these resins altered the tensile properties of dentin. Tensile stress and strain were measured in these and control (mineralized and demineralized) specimens until their ultimate failure. The results indicate that some adhesive resins, after infiltrating demineralized dentin, can restore and even exceed the ultimate tensile strength of mineralized dentin. These resins increased the modulus of elasticity of resin-infiltrated dentin to values equal to or greater than those of the resins but far below those of mineralized dentin. Although the conditions in this experiment were far removed from the manufacturer's recommendations or clinical practice, the results support the potential of resin infiltration for reinforcing dentin.

Acid Etching, Dental↗
PubMed1995

Tensile bond strength and SEM evaluation of caries-affected dentin using dentin adhesives.

Tensile bond strength measurements are commonly used for the evaluation of dentin adhesive systems. Most tests are performed using extracted non-carious human or bovine dentin. However, the adhesion of resins to caries-affected dentin is still unclear. The objectives of this study were to test the hypothesis that bonding to caries-affected dentin is inferior to bonding to normal dentin, and that the quality of the hybrid layer plays a major role in creating good adhesion. We used a micro-tensile bond strength test to compare test bond strengths made to either caries-affected dentin or normal dentin, using three commercial adhesive systems (All Bond 2, Scotchbond Multi-Purpose, and Clearfil Liner Bond II). For scanning electron microscopy, the polished interfaces between the adhesive bond and dentin were subjected to brief exposure to 10% phosphoric acid solution and 5% sodium hypochlorite, so that the quality of the hybrid layers could be observed. Bonding to normal dentin with either All Bond 2 (26.9 +/- 8.8 MPa) or Clearfil Liner Bond II (29.5 +/- 10.9 MPa) showed tensile bond strengths higher than those to caries-affected dentin (13.0 +/- 3.6 MPa and 14.0 +/- 4.3 MPa, respectively). The tensile bond strengths obtained with Scotchbond Multi-Purpose were similar in normal and caries-affected dentin (20.3 +/- 5.5 MPa and 18.5 +/- 4.0 MPa, respectively). The hybrid layers created by All Bond 2 in normal dentin and by Clearfil Liner Bond II in normal or caries-affected dentin showed phosphoric acid and sodium hypochlorite resistance, whereas the hybrid layers created by All Bond 2 in caries-affected dentin and those created by Scotchbond Multi-Purpose to normal and caries-affected dentin showed partial susceptibility to the acid and sodium hypochlorite treatment. The results indicate that the strength of adhesion to dentin depends upon both the adhesive system used and the type of dentin. Moreover, the quality of the hybrid layer may not always contribute significantly to tensile bond strength.

Analysis of Variance↗
PubMed1995

Laboratory evaluation of the Gluma 3-step bonding system.

PURPOSE: To determine in vitro (1) the shear bond strengths (SBS) of the modified Gluma system to enamel and dentin; (2) the qualitative and the quantitative microleakage (ML) of Class V preparations on the cemento-enamel junction (CEJ) and in dentin, respectively, restored with the Gluma system; and (3) the effect of the system's components on enamel and dentin by scanning electron microscopy. MATERIALS AND METHODS: Seventy-five extracted human maxillary permanent central incisors and 75 permanent first and second molars were embedded in brass tooth cups with cold-cure acrylic resin. The facial surfaces of the anterior and the occlusal surfaces of the molar teeth were ground wet on 180- followed by 600-grit silicon carbide paper. Demarcated sites on the surfaces were treated according to the manufacturer's instructions and Pekafill composite was bonded to the treated surfaces. Fifteen specimens prepared on enamel were removed 1 minute after cure (A) and the SBS determined. The remaining specimens were removed 15 minutes after final cure, stored in saline at 37 degrees C for 24 hours (B), for 1 week without (C) and with temperature cycling (D), and for 4 weeks (E). Similar regimens were used for dentin, groups F, G, H, I and J. The SBS were determined and expressed in MPa. The data were analyzed by ANOVA, Student-Newman-Keuls and t-tests. For the qualitative ML evaluation, Class V cavities were prepared on the CEJ of 30 human premolars and restored with Gluma/Pekafill. After thermocycling in 0.5% basic fuchsin, the teeth were sectioned and ranked according to the degree of microleakage. Class V cavities were prepared on the facial root surfaces of 15 human premolars and restored. The ML was determined quantitatively by a spectrophotometric dye-recovery method and expressed as microgram dye/restoration. RESULTS: The mean +/- SD of the SBS in MPa were: A: 14.6 +/- 2.2; B: 21.2 +/- 1.6; C: 20.5 +/- 1.4; D: 24.2 +/- 2.0; E: 22.8 +/- 3.7; F: 7.0 +/- 2.0; G: 16.1 +/- 4.0; H: 15.6 +/- 3.7; I: 10.9 +/- 3.3; J: 14.4 +/- 3.3. The quantitative ML was 1.00 +/- 0.39 microgram dye/restoration. The lowest SBS were obtained on specimens tested after 1 minute. Temperature cycling had a significantly adverse effect on the SBS to dentin (P = 0.0003). Etch patterns conducive to bonding were produced on the enamel. The resin system penetrated into the dentin tubules.

Analysis of Variance↗