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Biomedical subjects

W C Outhwaite

Publications and source records attributed to W C Outhwaite.

10 recordsLinked to original sources
PubMed1983

A clinical comparison of dentinal slot retention with metallic pin retention.

Twenty-two pairs of extensive amalgam restorations were placed in 19 patients. One amalgam of each pair had self-threading pin retention, and the other had dentinal slot retention. Evaluations were done at baseline, at one, and two years. After two years, 17 pairs of amalgams were available for evaluations. The data obtained can be summarized as follows: 100% (17) of the slot-retained amalgams were clinically acceptable, whereas 94.1% (16) of the pin-retained amalgams were acceptable. It can be concluded that, in clinical usage, dentinal slot retention is as effective as self-threading pin retention in extensive amalgam restorations.

Adult↗
PubMed1982

Slots vs pins: a comparison of retention under simulated chewing stresses.

The specimens of composite resin retained by pins exhibited significantly lower cycle life than did all other groups. At low loads, the pins and slots are comparable (when composite resin is used), but there is a dramatic decrease in the life of restorations retained with pins as the load is increased. At the 30-micrometer end point, the composite restorations retained with pins failed at a mean of 250 cycles, whereas the composite restorations retained with a slot failed at 250,000 cycles - a 1000X increase in cycle life. In general, cycle life of composite resin retained with a slot is comparable to or greater than that of amalgam retained with a slot or pins. Whether the life difference between the pin- and slot- retained amalgam restoration is clinically significant is not known; however, the baseline for a clinical study of the two types of retention for definitive amalgam restorations has been completed and will be reported in the future.

Composite Resins↗
PubMed1978

Dentin permeability: changes produced by iontophoresis.

Iontophoretic currents (0--1.0 mA) were applied to dentin disks prepared from human third molars. A negative electrode increased 125I-permeation 10X, while a positive electrode increased 14C-lidocaine 8X. Iontophoresis appears promising as a method to increase the permeation of dentin by ionized substances of therapeutic interest.

Carbon Radioisotopes↗
PubMed1977

Rate of permeation of isotopes through human dentin, in vitro.

A simple in vitro method has been described for quantitatively measuring the rate at which isotopically labeled substances permeate through dentin in occlusal cavity preparations. The presence or absence of pulp tissue had only a minor effect on the kinetics of permeation. As the dentin was made thinner there was a resulting increase in the rate of iodide permeation. The relative rates of permeation were 3H2O greater than 131I greater than 99mTc greater than 14C-urea, a sequence that follows the molecular dimensions of these substances.

Carbon Radioisotopes↗
PubMedDate not supplied

Magnification--an interesting optical property of dentin.

Disks of dentin taken from extracted human teeth demonstrated the optical property of the magnification/reduction effect. When images were transmitted from a pulpal-to-occlusal direction, the images were magnified. When the disks were inverted, the images were reduced in size. The images were slightly distorted but clear. When these disks were decalcified or dehydrated, they still possessed the same magnification/reduction effect property. The clear image transmission is attributed to the passage of light along the dentinal tubules; the magnification is the result of their divergence from the pulpal to the occlusal direction. The degree of tubule divergence was determined to correspond closely with the proportion of magnification and of reduction. In calcified sections, an individual tubule would act as a light-pipe, conducting light as it reflects internally off the dentin walls. Decalcified disks may demonstrate a fiberoptic effect. The magnification of an image is the result of the divergence of hundreds of thousands of minute light conductors.

Decalcification Technique↗