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Biomedical subjects

R B Price

Publications and source records attributed to R B Price.

At least 19 recordsLinked to original sources
PubMed2006

Cloning and functional expression of voltage-gated ion channel subunits from cnidocytes of the Portuguese Man O'War Physalia physalis.

Cnidocytes were dissociated from the tentacles of the Portuguese Man O'War Physalia physalis using heat treatment, and purified using density centrifugation. Visual observation confirmed that these cnidocytes contained a nucleus, a cnidocyst and an apical stereocilium, confirming that the cells were intact. A cnidocyte-specific amplified cDNA library was then prepared using RNA isolated from the cnidocytes, and screened for voltage-gated ion channel subunits using conventional molecular cloning techniques. A variety of channel proteins were identified and full-length sequence obtained for two of them, a Ca(2+) channel beta subunit (PpCa(V)beta) and a Shaker-like K(+) channel (PpK(V)1). The location of the transcripts was confirmed by RT-PCR of total RNA isolated from individually selected and rinsed cnidocytes. The functional properties of these two channel proteins were characterized electrophysiologically using heterologous expression. PpCa(V)beta modulates currents carried by both cnidarian and mammalian alpha(1) subunits although the specifics of the modulation differ. PpK(V)1 produces fast transient outward currents that have properties typical of other Shaker channels. The possible role of these channel proteins in the behavior of cnidocytes is discussed.

Amino Acid Sequence↗
PubMed2001

Effect of package weight on the total amount of die stone used annually in a dental school.

PURPOSE: This study compared the total amount of Type IV dental stone (die stone) used annually by dental students when they were supplied with either 70-g or 140-g preweighed packages of die stone. MATERIALS AND METHODS: In September 1994, all the bulk containers of die stone were removed from the student dental clinic and laboratories and replaced by 70-g preweighed packages of die stone (Silky-Rock; Whip Mix, Louisville, KY). At the end of August 1998, all 70-g packages of die stone were removed from the student dental clinic and laboratories. The average annual number of 70-g packages of preweighed die stone used by the students from 1994 to 1998 was calculated. From September 1998 to the end of August 1999, only 140-g preweighed packages of die stone (Silky-Rock) were supplied to the students. The number of the 140-g packages of preweighed die stone and total weight used by students during this period were calculated and compared with the average annual number of 70-g preweighed packages of die stone used during the 1994-1998 period. RESULTS: From September 1994 to August 1998, the students used an annual average of 4060 +/- SD 250 of the 70-g packages (284.2 +/- 17.5 kg per annum). From September 1998 to August 1999, the students used 3360 of the 140-g packages (470.4 kg). CONCLUSIONS: Although the students used in total 700 fewer of the 140-g die stone packages per annum than the annual average number of 70-g packages, they used 186.2 kg (65.5%) more die stone when supplied with the 140-g packages.

Calcium Sulfate↗
PubMed2000

Margin adaptation of indirect composite inlays fabricated on flexible dies.

STATEMENT OF PROBLEM: Indirect composite restorations can be made in 1 appointment using a flexible die. Interactions between different impression materials and flexible die materials may affect the accuracy of fit and margin adaptation of the restoration. PURPOSE: This study compared the margin adaptation of composite inlays made using the following 5 impression/flexible die material combinations; condensation silicone/polyvinyl siloxane (CS/PVS), wash viscosity polyvinyl siloxane/medium or heavy viscosity polyvinyl siloxane (PVS/PVS), irreversible hydrocolloid impression/medium viscosity polyvinyl siloxane (IH/PVS), wash viscosity polyvinyl siloxane impression/polyether (PVS/PE), with composite inlays made using a control system of a wash viscosity polyvinyl siloxane impression and a type IV stone die. MATERIAL AND METHODS: For each test and control system, 10 impressions were made of a class II composite inlay preparation in a metal master die. One die was made from each impression and one composite inlay was made and finished on each die (a total of 60 inlays). Inlays were placed on the master die and the margin opening at the buccal, distal, and gingival sites was recorded with a measuring microscope (x40 magnification). RESULTS: The overall mean +/- SD margin openings of inlays made from the systems were as follows: PVS wash/PVS heavy viscosity 149.5 +/- 107. 4 microm; PVS wash/PVS medium viscosity 87.4 +/- 63.0 microm; IH/PVS medium viscosity 76.7 +/- 48.9 microm; CS/PVS 73.3 +/- 48.7 microm, PVS wash viscosity/PE 64.0 +/- 44.3 microm, PVS wash viscosity/stone 53.9 +/- 48.3 microm. Composite inlays made using the PVS wash viscosity/PVS heavy viscosity system had significantly larger distal, gingival, and overall mean margin openings than all other inlays (ANOVA and Fisher PLSD test; P =.05). The separating medium required between some impression and die materials did not work consistently. Composite inlays fabricated on dies made of material different than the impression material had mean buccal, distal, gingival, and overall margin openings < or =100 microm. CONCLUSION: Composite inlays made on the CS/PVS, IH/PVS medium viscosity, PVS wash viscosity/PE flexible dies, and control PVS wash viscosity/stone dies had statistically similar (P =.05) mean buccal, distal, gingival, and overall mean margin openings that were < or =100 microm. Composite inlays made on dies that were made of the same type of material as the impression material (PVS/PVS) had mean gingival margin openings >100 microm that were significantly larger than all other systems tested (P =.05).

Alginates↗
PubMed2000

Effect of distance on the power density from two light guides.

PURPOSE: This study determined the effect of distance on the power density from standard and Turbo light guides (Demetron/Kerr, Danbury, Connecticut). MATERIALS AND METHODS: Power density was measured from 0 to 10 mm away from the tip of standard 8-mm curved light guides and 13/8-mm Turbo curved light guides. To determine the effect of distance on power density, a polynomial regression line was fitted. The Kolmogorov-Smirnov (K-S) statistic and the Wilcoxon rank sum (WR) tests were used to determine if there was a difference in the rate at which the power density decreased for the standard and Turbo light guides as the distance from the tip increased. Photographs of the light dispersion from each tip were also taken. RESULTS: At 0 mm, the mean (+/- SD) power density from the two standard light guides was 743 +/- 6.1 mW/cm2 and from the four Turbo light guides was 1128 +/- 22.1 mW/cm2. As the distance from the tip of the light-guide tip increased, the power density decreased, but the rate of decrease was greater from the Turbo light guides than from the standard light guides. At 6 mm the power density from the standard light guides fell to 372 mW/cm2 (50% of the original value) and the power density from the Turbo light guides fell to 263 mW/cm2 (23% of the original value). Both the K-S statistic and the WR sum test indicated that the distribution of light intensities was significantly different from the two light guides (WR p-value = .0246, K-S p-value < .0001). The two estimated polynomials intersected at 3.66 mm, and the 95% prediction intervals intersected at about 2.8 and 4.8 mm. Therefore, beyond 5 mm away from the tip of the light guide, the standard light guides gave higher power density readings than the Turbo light guides. Photographs showed that the light dispersed at a wider angle from the Turbo light guides than from the standard light guide. CLINICAL SIGNIFICANCE: The design of the light guide of a light curing unit affects light dispersion, power density, and ultimately the dentist's ability to properly cure composite. For these reasons, manufacturers should report the power density at the tip of the light guide and 6 mm from the tip of the light guide, since significant differences exist between light guide designs.

Dental Cavity Preparation↗
PubMed2000

Effects of composite thickness on the shear bond strength to dentin.

The manufacturers of some condensable posterior composites claim that their products can be placed in bulk and light-cured in 5-mm-thick increments. This study compared the shear bond strengths of three composite resins when bonded to dentin in 2- and 5-mm-thick increments. Overall the bond strengths were adversely affected by the composite thickness (p < 0.0001). The shear bond strength of each composite tested was much lower when polymerized in a 5-mm increment than in a 2-mm increment of composite (p < or = 0.0005). The two condensable composites tested had a lower bond strength than the conventional composite when polymerized in a 5-mm bulk increment (p < or = 0.01).

Analysis of Variance↗
PubMed2000

The pH of tooth-whitening products.

Tooth whitening products may be in contact with intraoral structures for several hours or they may be used daily to whiten the teeth. Consequently, these products should have a relatively neutral pH to minimize potential damage. This study measured the pH of 26 commercially available tooth-whitening products. The pH of the different whitening products ranged from 3.67 (highly acidic) to 11.13 (highly basic). The dentist-supervised home-bleaching products had a mean pH of 6.48 (range 5.66 to 7.35). The over-the-counter whitening products had a mean pH of 8.22 (range 5.09 to 11.13), and the whitening toothpastes had a mean pH of 6.83 (range 4.22 to 8.35). The 3 in-office bleaching products had a pH between 3.67 and 6.53. One-way ANOVA showed that there was a significant difference between the 4 product categories. The most basic pH of all the products tested was 11.13 for the whitening gel of Natural White-Rapid White. The most acidic pH of all products tested was 3.67 for Opalescence Xtra 35% hydrogen peroxide in-office bleach. The Least-Squares-Means test showed that the over-the-counter category had a pH significantly different from the other categories (p < 0.05).

Carbamide Peroxide↗
PubMed2000

Interchangeability of semiadjustable articulators after 2 to 7 years of use.

PURPOSE: The purpose of this study was to test the interchangeability of articulators that had been in use from 2 to 7 years and compare these results with the interchangeability of the same articulators 1 year earlier. MATERIALS AND METHODS: Forty-six Whip Mix model #2240 articulators (Whip Mix Corporation, Louisville, KY) that were in clinical use from 2 to 7 years were checked for interchangeability using the Whip Mix #2245 check system. The horizontal tolerance of the check system was 94 microm. Articulators were also evaluated in the vertical dimension at 4 predetermined locations around the check system cylinders using 26-microm-thick shimstock. Vertical discrepancies between the cylinders were recorded as the thickness of 0, 1, 2, or more than 2 pieces of shimstock. Interchangeability results were compared with those determined 1 year previously using the same evaluation methods using the Exact McNemar's Test of Agreement (alpha = 0.05). RESULTS: Using the Whip Mix 2245 check system, 35 (76%) articulators were interchangeable after 2 to 7 years of use. This compares to 38 (83%) that were interchangeable upon evaluation 1 year earlier. The decrease in interchangeability was not significant (p =.4531). Forty-three (94%) of the articulators had vertical discrepancies of 52 microm or less at the initial evaluation. One year later, 45 (98%) of the articulators had vertical discrepancies of 52 microm or less. After 1 year, there were significant differences in the amount of vertical space between the cylinders only at the right side (p =.014). CONCLUSION: The Whip Mix model #2240 articulator can remain interchangeable during clinical use for 7 years, but should be routinely checked for calibration.

Calibration↗
PubMed2000

Light energy transmission through cured resin composite and human dentin.

OBJECTIVE: This study determined the amount of light energy transmitted through various densities of cured resin composite and human dentin when 2 different light intensities were used. METHOD AND MATERIALS: The maximum light energy (mW/cm2) transmitted through disks (0.46 to 5.85 mm thick) of 7 resin composites and human dentin was measured when either a Standard or a Turbo light guide was attached to a curing light. The effects of the 2 light guides, the specimen thickness, and type of specimen dentin on light energy transmission were determined. RESULTS: The mean light energy reading at the surface of the specimens was 682.1 mW/cm2 with the Standard light guide and 1,014 mW/cm2 with the Turbo light guide. For all the specimens, there was an exponential decrease in light energy transmitted as the specimen thickness increased. The analysis of covariance showed that the specimen, thickness, and light guide all had a statistically significant effect. Significantly more light energy (about 42%) was transmitted through the specimens when the Turbo light guide was used. CONCLUSION: When the Turbo light guide was used, about 42% more light energy was transmitted through the cured composite specimens. There was an exponential decrease in the light energy transmitted through 7 resin composites and dentin as the specimen thickness increased.

Analysis of Variance↗
PubMed2000

Effect of stepped light exposure on the volumetric polymerization shrinkage and bulk modulus of dental composites and an unfilled resin.

PURPOSE: To compare the volumetric polymerization shrinkage and dynamic bulk modulus of five resins and an experimental unfilled resin polymerized with a stepped power light and with a conventional one step curing light. MATERIALS AND METHODS: Parallel sided glass rings 5 mm in diameter and 2 mm high were etched for 5 min with hydrofluoric acid and silanated. The density and volume of the rings were calculated before they were filled with either SureFil, AEliteflo, Pertac II, Z100, or an experimental unfilled resin. When cured, the resin was bonded to the glass ring which produced a mold with a configuration C-factor of approximately 0.8. The resin was cured for 40 s on each side using either a one step curing light or a stepped power curing light. After curing, the specimens were weighed in air and in water to calculate their final density and volumetric shrinkage. Ten samples were made using each light system and for each resin (total of 100 samples). The bulk modulus was determined for each resin using an ultrasonic method, and the percentage filler contents were determined by thermogravimetric analysis. RESULTS: The mean +/- SD volumetric polymerization shrinkage values ranged from 3.10 +/- 1.19% for SureFil using the one step light to 12.35 +/- 1.38% for the unfilled resin using the stepped power curing light. Student-Newman-Keuls post hoc test separated the 10 different materials into three significant groups at P= 0.05. The unfilled resin exhibited the highest volumetric shrinkage followed by the flowable composite (AEliteflo). For all materials tested, there was no significant difference in the volumetric shrinkage values when the resin was cured with the one step or the stepped power curing light. There was no significant difference in the volumetric shrinkage values for the hybrid composites (Pertac II, Z100, and SureFil). The volumetric shrinkage values were highly sensitive to filler weight (P < 0.001). Except for Z100, there was no difference in the specific gravity values and velocities of the longitudinal and shear waves and bulk modulus when the one step and stepped power curing lights were used. The bulk modulus values ranged from 6.30 +/- 0.19 GPa for unfilled resin, to 17.10 +/- 1.09 GPa for Z100. Curing with the one step or the stepped curing light had no significant effect on the modulus values for any resin with the exception of Z100, P = 0.05. The bulk modulus values were highly sensitive to filler weight, and higher modulus values were associated with increased filler weight (P < 0.001). There was no significant difference between the bulk modulus of Pertac II and SureFil (P = 0.05).

Acid Etching, Dental↗
PubMed2000

Effect of stepped vs. continuous light curing exposure on bond strengths to dentin.

PURPOSE: To compare the 10-min and 24-hr shear bond strengths of three dentin bonding systems, polymerized with either a standard (Optilux 401) light for 60 s, or a stepped curing light (Elipar Highlight) that delivered a low light intensity for 10 s followed by high intensity for 50 s. MATERIALS AND METHODS: Three bonding systems were used to bond two resin-based composites (RBC) to dentin at 34 degrees +/- 2C using the two curing lights. Single Bond (SB) and Prime & Bond 2.1 (P&B) were used with Z100 RBC, and EBS bonding system was used with Pertac II RBC. Ten specimens from each combination were debonded at 37 degrees +/- 1C 10 min after starting to light cure the bonding system. Ten other specimens were stored in water at 37 degrees +/- 1C for 24 hrs before debonding at 37 degrees +/- 1C (total 120 teeth). RESULTS: The 10-min mean shear bond strengths were: Standard Cure; EBS 11.9 +/- 2.9 MPa, SB 14.6 +/- 2.2 MPa, P&B 14.7 +/- 4.2 MPa: Stepped Curing; EBS 7.4 +/- 2.1 MPa, SB 13.0 +/- 3.6 MPa, P&B 15.6 +/- 4.8 MPa. The 24-hr mean shear bond strengths were: Standard Cure; EBS 14.8 +/- 5.1 MPa, SB 25.1 +/- 3.3 MPa, P&B 25.2 +/- 8.8 MPa: Stepped Curing; EBS 15.1 +/- 4.6 MPa, SB 21.9 +/- 5.9 MPa, P&B 17.3 +/- 9.2 MPa. Three way ANOVA showed significant main effects for light, bonding system and time and no 2- or 3-way interaction effects at P = 0.01. The Least-Squares Means test with Sidak's adjustment for Multiple Comparisons showed that the bond strengths obtained using the standard light were significantly greater than the bond strengths obtained using the stepped curing light (P < 0.01). The 24-hr bond strengths were significantly greater (P < 0.01) than the 10-min bond strengths. The bond strengths obtained with EBS were significantly less than SB and P&B (P < 0.01), but there were no significant differences between SB and PB (P = 0.9752).

Adhesiveness↗
PubMed1999

Long-term reliability of semiadjustable articulator interchangeability.

PURPOSE: Interchangeability between articulators allows mounted casts to be accurately transferred from one articulator to another. The purpose of this study was to evaluate the interchangeability of Whip-Mix model #2240 articulators (Whip-Mix Corporation, Louisville, KY) that had been in clinical use for between 1 and 6 years. MATERIALS AND METHODS: Forty-six Whip-Mix model #2240 articulators that had been in clinical use by students, practitioners, or laboratory technicians for between 1 and 6 years were evaluated for interchangeability using the Whip-Mix #2245 check system. The horizontal tolerance of the check system was 94 microns. The articulators were also evaluated in the vertical dimension at four locations around the check system cylinders using 26-micron shimstock. Vertical discrepancies between the cylinders were recorded as the thickness of 0, 1, 2, or more than 2 pieces of shimstock. RESULTS: Thirty-eight of the articulators (83%) passed the test for interchangeability. These articulators were interchangeable with other Whip-Mix model #2240 articulators fabricated over a 5 1/2-year period (December 1990 to August 1996). In the vertical dimension, most articulators had discrepancies < or = 26 microns. Three articulators (6.5%) had vertical discrepancies greater than 52 microns. CONCLUSIONS: (1) Eighty-three percent of Whip-Mix model #2240 articulators that had been in clinical use for between 1 and 6 years remained interchangeable within a tolerance of 94 microns in the horizontal dimension. (2) Only three articulators in this study (6.5%) had a vertical discrepancy at any location between the cylinders greater than 52 microns. (3) The model #2240 articulator has the potential to remain interchangeable during clinical use.

Dental Articulators↗
PubMed1999

In vitro comparison of 10-minute versus 24-hour shear bond strengths of six dentin bonding systems.

OBJECTIVE: Early bond strengths produced by dentin bonding systems should be sufficient to resist the polymerization shrinkage of resin composite. This study compared the 10-minute and 24-hour shear bond strengths of six dentin bonding systems: One-Step (OS), PermaQuik (PQ), Prime & Bond 2.1 (PB), Scotchbond Multi-Purpose (SBMP), Single Bond (SB), and Tenure Quik with Fluoride (TQ). METHOD AND MATERIALS: Each bonding system was used to bond composite to visibly moist dentin at 34 degrees C +/- 2 degrees C. The specimens were debonded at 37 degrees C +/- 1 degree C 10 minutes after the start of light curing of the bonding system, and the results were compared with the 24-hour bond strengths. The mode of failure was recorded. RESULTS: The 10-minute mean shear bond strengths were: OS, 16.4; PQ, 14.3; SB, 14.0; PB, 12.7; TQ, 10.7; and SBMP, 9.3 MPa. The 24-hour mean shear bond strengths were OS, 23.3; PB, 20.8; SB, 20.3; PQ, 19.4; TQ, 11.2; and SBMP, 10.0 MPa. The 10-minute mean shear bond strengths of OS, PQ, PB, and SB bonding systems were significantly less than the 24-hour values. More dentinal fractures and mixed failures were observed with OS, PQ, and PB. Systems with higher bond strengths had more resin penetration into the lateral dentinal branches. CONCLUSION: The 10-minute mean shear bond strengths were all less than 17 MPa, and the 10-minute bond strengths were less than the 24-hour values.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1999

Esthetic restoration of a single-tooth dental implant using a subepithelial connective tissue graft: a case report with 3-year follow-up.

This case report describes the use of a subepithelial connective tissue graft to restore the gingival papillae and augment ridge soft tissues adjacent to a dental implant. The patient was referred for periodontic and prosthodontic evaluation after the placement of an implant--with the implant head 6.5 mm below the adjacent cementoenamel junction--in an area of inadequate bone volume with deficient interproximal papillae and ridge soft tissues. The resulting esthetic defect was restored by means of a combined technique that used a subepithelial connective tissue graft and an emergence profile-contoured crown. A 3-year clinical follow-up with complete regeneration of the gingival papillae is described.

Adult↗
PubMed1998

Comparison of the surface detail reproduction of flexible die material systems.

STATEMENT OF PROBLEM: Flexible die materials have been introduced to facilitate the fabrication of indirect provisional or definitive restorations in 1 appointment. PURPOSE: This study compared the surface detail reproduction of 7 potential flexible die materials when used in combination with 7 elastomeric impression materials. METHODS: Surface detail reproduction of 17 impression material/flexible die material systems was compared with a control system containing an elastomeric impression material and a Type IV dental stone. Test dies of each system were prepared in a random order with the American Dental Association apparatus for testing detail reproduction, compatibility, and dimensional stability. RESULTS: One flexible die system had better surface detail reproduction than the control stone die, other systems had similar or worse reproduction. Surface detail reproduction was adversely affected when a separator was required between the impression and flexible die material. CONCLUSIONS: Impregum F die material with Extrude Light impression material produced better surface detail reproduction than the control dies. Impregum F impressions were incompatible with Blu-Mousse, Impregum F, or Imprint die materials. Polyvinyl siloxane impressions were incompatible with polyvinyl siloxane dies unless a separator was used. When a separator was used, the surface detail reproduction was not as good as the control die system or the Extrude Light impression material/Impregum F die material combination.

Analysis of Variance↗
PubMed1998

A review of preweighed, packaged die stone versus bulk die stone use in a dental school.

PURPOSE: This study compared the quantity of preweighed, packaged die stone use to bulk die stone use by dental students. MATERIALS AND METHODS: Starting in September 1994, all the bulk die stone was removed from the dental clinic, and only preweighed packages of die stone (Silky-Rock, Whip Mix) were available to students. At the end of August 1995 and August 1997, the amount of preweighed die stone used by the students was determined and compared with the amount of bulk die stone (DieKeen, Modern Materials) used during the period of September 1993 to August 1994. RESULTS: Between September 1994 and August 1997, the students used 42% less per annum of the preweighed, packaged die stone than the previous annual use of bulk die stone. The laboratories were much cleaner when the preweighed packages were used, and fewer cleaning staff were required. The environment was also cleaner for the laboratory staff, who used to fill the bulk containers with gypsum products. CONCLUSIONS: Students used 42% less die stone per annum when using the preweighed packages.

Calcium Sulfate↗
PubMed1995

Effects of home bleaching on the tissues of the oral cavity.

Eight subjects used a 10 per cent carbamide peroxide (Opalesence) home bleaching system in a mouthguard for 14 nights. Their periodontal health was assessed by measuring gingival crevicular fluid flow with a Periotron 6000, and subjects were given a questionnaire to assess the effects of the bleaching system. There was no significant change in the gingival crevicular fluid flow, recession, bleeding index or plaque index of any patient during the treatment phase. All treated teeth were lightened, and mild transient tooth sensitivity was common to all participants. One subject experienced internal tooth discoloration, possibly due to marginal leakage around an amalgam restoration.

Adult↗