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Biomedical subjects

R P Christensen

Publications and source records attributed to R P Christensen.

At least 19 recordsLinked to original sources
PubMed2001

The role of pit-and-fissure discoloration in caries assessment.

Occlusal dental caries often is not apparent using traditional diagnostic techniques. The clinical significance of pit-and-fissure discoloration in the absence of dietary and habit substances was examined. The study included 462 extracted teeth (216 with obvious pit-and-fissure discoloration, 216 with subtle discoloration, and 30 with no discoloration); 130 clinical teeth with varying degrees of pit-and-fissure discoloration; and 159 teeth in young adults, which had sealants placed > or = 10 years. All teeth studied were excavated very conservatively using air abrasion and/or the uniquely small H1 004 carbide bur. Presence of caries and its depth and extent were recorded, photographed, and measured with a custom made calibrated probe. Of the 721 teeth with discolored pits and fissures studied (432 extracted teeth and 289 clinical teeth), 660 (92%) had two or more of the four clinical criteria used to define dental caries in this study. Sixty-four percent of the lesions were > 2 mm in depth and 27% were > 3 mm in depth. Of the 159 teeth sealed for > or = 10 years, 47 (92%) were carious, and 26% had large, deep carious lesions penetrating > 3 mm. These data indicate: more effective methods are needed to diagnose pit-and-fissure caries and presence of pit-and-fissure discoloration in the absence of substances causing extrinsic staining should be a strong warning for clinicians to examine carefully for dental caries.

Adult↗
PubMed1999

Resin polymerization problems--are they caused by resin curing lights, resin formulations, or both?

Negative effects of rapid, high-intensity resin curing have been predicted for both argon lasers and plasma-arc curing lights. To address these questions, six different resin restorative materials were cured with 14 different resin curing lights representing differences in intensities ranging from 400 mW/cm2 to 1,900 mW/cm2; delivery modes using constant, ramped, and stepped methods; cure times ranging from 1 second to 40 seconds; and spot sizes of 6.7 mm to 10.9 mm. Two lasers, five plasma-arc lights, and seven halogen lights were used. Shrinkage, modulus, heat generation, strain, and physical changes on the teeth and resins during strain testing were documented. Results showed effects associated with lights were not statistically significant, but resin formulation was highly significant. Microfill resins had the least shrinkage and the lowest modulus. An autocure resin had shrinkage and modulus as high as or higher than the light-cured hybrid resins. Lasers and plasma-arc lights produced the highest heat increases on the surface (up to 21 degrees C) and within the resin restorations (up to 14 degrees C), and the halogen lights produced the most heat within the pulp chamber (up to 2 degrees C). Strain within the tooth was least with Heliomolar and greatest with Z100 Restorative and BISFIL II autocure resin. Clinical effects of strain relief were evident as white lines at the tooth-resin interface and cracks in enamel adjacent to the margins. This work implicates resin formulation, rather than light type or curing mode, as the important factor in polymerization problems. Lower light intensity and use of ramped and stepped curing modes did not provide significant lowering of shrinkage, modulus, or strain, and did not prevent enamel cracking adjacent to margins and formation of "white line" defects at the margins. Until materials with lower shrinkage and modulus are available, use of low-viscosity surface sealants as a final step in resin placement is suggested to seal defects.

Acrylic Resins↗
PubMed1994

Disinfection regimen.

Explore the source record for details and available documents.

Dental High-Speed Equipment↗
PubMed1993

Practice costs are up--how do we pay the bills?

Dentistry today is exciting, vibrant, stimulating and demanding, but the costs to run a dental practice are extremely high. Constant planning and thought are necessary to allow optimum service to patients and provide adequate income. Specific cost-control measures are offered.

Cost Control↗
PubMed1993

Maintaining infection control during restorative procedures.

This report has listed criteria, example products, and pertinent information to aid clinicians in performing infection control procedures using products and techniques with verified efficacy. The goal is to provide optimal protection of clinicians and patients from cross-contamination in the dental environment. Subjects reviewed were face masks, eye protection, gloves, hand antiseptics, uniforms, vaccines, instrument cleaning, sterilization, environmental surface management, and contaminated waste management. The criteria proposed and the products listed were not intended to be all-inclusive or absolute. The omission of a product from this article or from the examples of products that did meet the criteria listed is not intended to disparage the product. No endorsement or approval of any product is made or intended by the author, editors, or publisher. The intent is to provide some direction at this time. Many new products and concepts now in development will bring changes in the future. The products referenced have been evaluated by independent researchers and clinicians in laboratory and clinical-use tests, and data are available upon request to support all recommendations.

Anti-Infective Agents, Local↗
PubMed1989

Antimicrobial activity of environmental surface disinfectants in the absence and presence of bioburden.

Thirty-nine products representing six categories of disinfectants (alcohols, chlorines, dilute glutaraldehydes, iodophors, phenolics, and quaternary ammonium compounds) were first tested in the absence of bioburden, using four test methods with five test organisms. Products that performed best were retested with the same methods and organisms in the presence of both serum and whole blood, using 3- and 10-minute contact times. Only products containing high ethyl alcohol had consistently high antimicrobial activity regardless of the test method, test organism, or contact time used both in the absence and presence of bioburden. Although these specific formulations demonstrated ability to penetrate and inactivate high concentrations of microorganisms within heavy bioburden, optimum disinfection of environmental surfaces is highly formulation dependent. Other products tested showed deficiencies that contraindicate their use as environmental surface disinfectants in clinical dental settings.

Alcohols↗
PubMed1988

A suspension method to determine reuse life of chemical disinfectants during clinical use.

In-use testing of disinfectants is necessary to ensure efficacy over time. The current official procedure for testing disinfectants, the Association of Official Analytical Chemists (AOAC) use-dilution method, cannot be adapted to repeated sampling techniques of use-life testing. It is therefore necessary to use an alternative method when evaluating the activity of a disinfectant under actual use. The Clinical Research Associates (CRA) suspension method was developed to fill this need. It consists of adding 0.5 ml of a standard culture to 5.0 ml of test disinfectant and sampling the mixture after 10 min for surviving bacteria. When this test was compared with the AOAC use-dilution method under a simulated use situation, the two methods were generally equivalent in identifying disinfectant inactivation. In addition, the CRA method was less time consuming, easier to perform, and less variable than the AOAC method. Use of the CRA method in a clinical study demonstrated the need for reuse claims to be based on clinical use studies rather than on laboratory testing only.

Disinfectants↗
PubMed1986

SEM low magnification stereoscopic technique for mapping surface contours: application to measurement of volume differences in human teeth due to polishing.

SEM stereogrammetry with a low magnification mosaic of pictures is used to measure the elevation of many individual points. This random array of elevations is then connected into a triangular mesh, from which a contour map of elevation is drawn for the entire surface. Maps of surfaces before and after removal of material are used to determine the volume removed. The method is applicable to many circumstances of wear, erosion or deformation of surfaces. It is applied here to the erosion of human teeth due to dental polishing.

Dental Polishing↗
PubMed1984

Determination of rpm, time, and load used in oral prophylaxis polishing in vivo.

Clinically relevant values for revolutions per minute (rpm), time, and load should be used when one evaluates effects of abrasive slurries on teeth. However, in the past, these variables have not been measured in vivo to determine clinical means. This study describes an instrument and computer software which monitored rpm, time, and load used by 29 clinicians during routine oral prophylaxes performed on 76 patients. Grand means and standard deviations determined for the three variables were: rpm, mean = 2571 (s = 739): time per tooth surface, mean = 4.5 sec (s = 2.9); and load, mean = 145 g (s = 66). Mean rpm, time, and load used on facial and lingual surfaces of the 32 teeth were also determined. Statistical tests showed that rpm was not altered significantly by tooth location, surface, or type and amount of deposit, but time was affected significantly by tooth location, surface, and amount of calculus; load was affected by tooth location, surface, and amount and intensity of stain.

Computers↗
PubMedDate not supplied

Clinical observations of porcelain veneers: a three-year report.

One hundred and sixty-five Cerinate porcelain veneers were placed by 11 private practice clinicians from diverse locations throughout the USA. The veneers were evaluated over a 3-year service period using Kodachrome photographs and grading of clinical characteristics by evaluators. The following factors were evaluated: (1) esthetics; (2) margin fit; (3) margin discoloration; (4) breakage; (5) gingival irritation; (6) patient acceptance; and (7) caries. Specific characteristics and their evaluations over three years were: (1) Esthetics started out excellent and remained that way; (2) Margin fit was acceptable at the beginning of the study and was actually perceived to improve, perhaps related to cement at the margins wearing and smoothing; (3) Margin discoloration started very low and became slightly worse; (4) Breakage was present during each of the 3 years, and 13 percent of veneers had some breakage after 3 years. Changes in clinical procedures are suggested in this paper to diminish this problem; (5) Gingival irritation was minimal throughout the study; (6) Patient acceptance was excellent at the beginning of the study and improved; and (7) Dental caries involvement was minimal, with only one veneered tooth showing caries involvement. Over the 3-year period, the veneers provided excellent service overall.

Dental Debonding↗