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Biomedical subjects

E H Greener

Publications and source records attributed to E H Greener.

At least 73 records · Page 4Linked to original sources
PubMed1986

Physical properties of periodontal dressing materials.

The purpose of this study was to develop standardized reproducible testing methods for evaluating physical properties of periodontal dressing materials. Three commercial compositions (Coe-Pak, Coe-Pak Hard & Fast Set and WondrPak) were studied. Working and setting times were determined by observing the continuous changes in viscosity via the oscillating rheometer. The 24-h and 1-week tensile and shear adhesive bonds to enamel were studied by luting orthodontic lingual cleats with a standard film thickness to the orientated labial surfaces of extracted incisors and pulling them to failure. Dimensional change was studied over a period of 24 h using a linear variable differential transformer (LVDT). The developed testing modalities have greater precision than those previously reported. The concept of 'bench time' was developed during which certain materials cannot be handled immediately after mixing.

Adhesiveness↗
PubMed1985

Effect of oxygen on the corrosion of dental amalgam.

The anodic and cathodic polarization of five dental amalgams were determined as a function of oxygen concentration in Ringer's solution and artificial saliva. The results indicate an anodic polarization behaviour dependent on Cl ion concentration and a corrosion potential determined primarily by oxygen concentration. At high oxygen concentrations the corrosion rates of traditional and copper enriched amalgams were equivalent.

Copper↗
PubMed1985

The electrochemical activity of the oral cavity--a new approach.

In order to develop model systems for studying and understanding corrosion phenomena in the oral cavity the electrochemical nature of the oral cavity must be known. Accordingly, the PH and oxidation potential Eh (SCE) were measured in vivo in nine patients utilizing microelectrode techniques. Three of the patients had periodontal therapy and three had received minimal dental care. Sampling was always performed at five specific sites and in periodontal pockets greater than 4 mm when available. In the five sites common to all subjects the oxidation potential ranged from -58 to +212 mV (SCE) and the pH ranged from 6.1 to 7.9. For patients undergoing periodontal therapy the pH/potential clustered around acidic pH (6.6) and an oxidation potential range of 270 mV, whereas minimal dental care revealed a pH range from 6.3 to 7.9 and a small range (57 mV) of oxidation potential. Differences in pH and oxidation potential are related to site of measurement, periodontal health of patient and nature and quantity of restorations present.

Adult↗
PubMed1984

The hardness of composites as a function of temperature.

The microhardness of conventional, posterior and microfil composites were measured as a function of temperature in an aqueous environment. With the exception of one posterior composite and two microfils, the composites suffered dramatic decreases in hardness (of the order of 30-50%) over temperature intervals corresponding to that encountered in oral service. In those systems which did not display hardness changes, interactions between glass and matrix as well as enhanced filler packing may be important.

Chemical Phenomena↗
PubMed1984

Fourier transform infrared analysis of degree of polymerization in unfilled resins--methods comparison.

Two methods of transmission Fourier Transform Infrared analysis were compared to determine the degree of polymerization (DP) in unfilled Bis-GMA-based dental resins. Diluent concentration, curing mode, and activator type were investigated. DP ranged from 55-72% and was highest for the most diluted resins. The effects of polymerization activation mode and type were insignificant. DP was slightly enhanced in the bulk of the resin, as determined by a KBr-pellet technique, in comparison with results from a thin film method, but both techniques seem to provide useful and reproducible results for dental resins.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1982

The creep compliance of dental amalgam in the stress range of 20-80 MPa.

The continuous compressive creep curves of four distinct types of one-week-old dental amalgam were monitored for one day on a specially designed mini-specimen creep apparatus. Creep conditions included three different applied constant stress levels (20, 40, and 80 MPa), and temperatures ranging from 0 degrees C to 60 degrees C. To compensate for changing dimensions at high creep strains, the data was converted to terms of compressive creep compliance. For all types of dental amalgam, compressive creep increased both with increased applied stress and with increased test temperature. The two high copper systems evaluated appear to approach a steady-state creep condition up to the highest temperatures tested, but the two conventional amalgams appear to change their creep exponent precipitously at temperatures above 45 degrees C.

Dental Amalgam↗
PubMed1982

Tensile creep of dental amalgam.

Rather than the usual compressive dental creep, various types of one week old dental amalgams were continuously monitored in tensile creep. Testing was done at 37, 45 and 50 degrees C, in a specially designed apparatus capable of 0 to 60 degrees C while maintaining a constant true tensile stress of 17 MPa. For the first time, the classical four stages of creep were observed at elevated temperatures in the low Cu amalgams, including creep rupture. The high Cu systems displayed only transient creep up to 50 degrees C and no rupture. Approximately one half the stress was needed in tension to provide the equivalent creep in compression.

Copper↗