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Biomedical subjects

C L Davidson

Publications and source records attributed to C L Davidson.

At least 127 records · Page 7Linked to original sources
PubMed1987

The relationship between test methodology and elastic behavior of composites.

Comparisons were made of the Young's moduli obtained with tests that impose static, low-frequency, or high-frequency elastic deformations on dental composite systems. The frequency of the imposed stress was reflected in the absolute value of Young's modulus. However, the values obtained at different test frequencies could be compared and understood by taking into account this frequency dependence. It was thus found that the composite structure largely determined the type of reaction to the imposed stress. The fundamental period test permitted the greatest differentiation in the elastic behavior of the investigated composites.

Composite Resins↗
PubMed1987

Setting stress in composite resin in relation to configuration of the restoration.

The setting stress in composite resins was studied as a function of restoration shape. The shape is described by the configuration factor, C, the ratio of the restoration's bonded to unbonded (free) surfaces. In an experimental set-up, the shape of the restoration was simulated by cylindrical forms of various dimensions. The shrinkage stress was measured continuously. It was shown that in most of the clinically relevant cavity configurations, the stress-relieving flow is not sufficient to preserve adhesion to dentin by dentin-bonding agents.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1987

Stiffness increase during the setting of dental composite resins.

Changes in the dynamic Young's modulus under flexure of self-cured and light-cured composite resins during setting were demonstrated to reflect accurately the condition of the curing composite resins. The rate of stiffness increase during setting varied considerably with the product, and the light-cured composite resins generally showed a faster rate of increase of stiffness. In the initial stage, the Young's moduli were very low, especially for the self-cured composite resins. This accounts for the damage (adhesion disruption and cross-linking interruption) that can be inflicted on a freshly placed composite resin filling that is not yet mechanically stabilized. Therefore, such fillings are vulnerable to aggressive distortion for at least 10 to 15 minutes after placement.

Composite Resins↗
PubMed1986

Toothbrush resistance and fluoride retention of sound, etched, fluoridated, and remineralized bovine enamel.

The wear resistance of tooth enamel that had undergone eight different treatments regarding the bonding procedure has been investigated. In comparison to sound enamel, the outer 3 microns of the etched-surface enamel show a decreased wear resistance against toothbrushing in vitro. Remineralization, either direct or preceded by acidified phosphated fluoride (APF) application, did not improve the wear resistance. The prophylactic effect of the APF treatment of etched enamel is considerable and is not lost after the soft, outer surface layer has worn off.

Acid Etching, Dental↗
PubMed1986

Test battery for metal allergy in dentistry.

Some alloys used in restorative dentistry may evoke an allergic contact stomatitis in certain persons. In order to protect patients from materials with undesired reactions, and considering corrosion characteristics of different alloys used, it is useful to devise an adequate patch test battery to include the most relevant metals. Dental alloys are composed of a combination of various metals. 12 different ions of frequent occurrence (Au3+, Pd2+, Zn2+, Mo6+, Sn2+, Ga3+, In3+, Co2+, Cr3+(6+), Ni2+, Fe2+(3+) and Si4+) were epicutaneously tested as the aqueous solution of the respective salt. The concentrations are given in g/100 ml and also in m.mole/l. The 12 different metal ion solutions were patch tested on patients in 3 groups: one group with a positive history of contact stomatitis (30 patients, group 1), one group with a positive history of contact dermatitis (16 patients, group 2), and a control group (17 persons, group 3). In contrast to the control group, a remarkable high percentage (11%) of positive skin reactions to Pd was found in groups 1 and 2. No allergic or irritant skin reactions were detected to Ga, Sn and Zn. No irritant reaction was observed at pH values as low as 1.5. In the case of SiCl4 (pH = 0.5), 41% positive irritant reactions were evoked. In the group with a positive history of contact dermatitis (group 1), a positive reaction was found more often (69%) than in the group with a positive history of contact stomatitis (30%) (group 2). The difference between these groups was mainly caused by reactions to Ni and Pd.(ABSTRACT TRUNCATED AT 250 WORDS)

Dental Alloys↗
PubMed1986

Effect of abrasion medium on wear of stress-bearing composites and amalgam in vitro.

Measurements of in vitro wear for several composite materials and an amalgam were conducted using a new device in which contact stress, moving speed, mutual slip, and third-body composition could be set. This preliminary study reports the results obtained with a fixed choice of contact stress, speed, and slip, but with different third-body media. With a Millet-seed/PMMA-beads mixture as a medium, the various types of restoratives showed a wear pattern and relative ranking comparable with that reported in clinical studies.

Composite Resins↗
PubMed1986

Occupational dermatology of the hand.

This article focuses on the various types and causes of occupational hand dermatitis. Salient features of several common occupations at risk for developing industrial hand dermatoses also are presented.

Female↗