[The war on technicians and its origins -- an odontological battle of authorization]. / Teknikerkrigen og dens optakt -- en odontologisk autorisationsbatalje.

From 1798 to 1916 dentistry was placed under the medical profession as a special studied subject--dentists were so to say authorized quacks. Doctors in dental practice were inviolable, but there were great problems with unauthorized groups of technicians and barbers, who ilegally gave dental treatment and acquired official permission to the lucrative transaction: to make false teeth. The fight which was basically for economic reasons but had also a professional background. It was not until 1916 with the first dental law that dentists were given their own professional status, but the quarrels with the unauthorized technicians continued until 1979.

Fluoride release from amalgam restorations lined with a silver-reinforced glass ionomer.

This study evaluated the amount of fluoride released from amalgam restorations lined with a silver-reinforced glass ionomer. Thirty human extracted molars were divided into three groups of 10 teeth each. Group 1: Class V cavities were made on the facial surfaces and restored with Dispersalloy amalgam. Group 2: Same as Group 1 except 1 mm of GC Lining glass ionomer cement (GIC) was placed on the axial wall before amalgam insertion. Group 3: Same as Group 2 except 1 mm of Miracle Mix silver-reinforced glass ionomer cement (GIC) was placed on the axial wall before amalgam insertion. Before any treatment, all samples were placed in polyethylene vials with 4 ml of deionized water and thermocycled (100x) for baseline fluoride release levels. After restoration, each tooth was replaced in a vial with 4 ml of deionized water. At weekly intervals, each tooth was removed from its aqueous medium and transferred to another vial containing 4 ml of deionized water. Fluoride release was measured four times at weekly intervals with an Orion #9609 fluoride-ion electrode. At 1 and 4 weeks, Miracle Mix released significantly more fluoride than GC Lining (P less than 0.0001).

Fluoride release from glass ionomer-lined amalgam restorations.

This study evaluated the amount of fluoride released from glass ionomer-lined amalgam restorations. 50 human extracted molars were divided into five groups of 10 teeth each. Group 1: No restorations. Group 2: Class V cavities (2 x 2 x 7 mm) were made on the facial and lingual surfaces and restored with Dispersalloy amalgam. Group 3: Same as Group 2 except 1 mm of Ketac-Bond glass ionomer cement (GIC) was placed on the axial wall before amalgam insertion. Group 4: Same as Group 2 except 1 mm of Chelon-Silver glass ionomer cement (GIC) was placed on the axial wall before amalgam insertion. Group 5: Same as Group 2 except 1 mm of Ketac-Silver GIC was used before amalgam insertion. Before any treatment, all samples were placed in polyethylene vials with 4 ml of deionized water and thermocycled (100x) for baseline fluoride release levels. After restoration, each tooth was placed in a vial with 4 ml of fresh deionized water. At weekly intervals, each tooth was removed from its aqueous medium and transferred to another vial containing 4 ml of deionized water. Fluoride release was measured four times at weekly intervals with an Orion #9609 fluoride-ion electrode. At one week, Ketac-Bond released significantly more fluoride than Ketac-Silver (P less than 0.01) which released significantly more fluoride than Chelon-Silver (P less than 0.01). At four weeks, there was no significant difference in fluoride release between Chelon-Silver and Ketac-Silver, but Ketac-Bond released significantly more fluoride than either of the other materials (P less than 0.01).

Current source density analysis of linear and non-linear components of the primate electroretinogram.

1. We have used the method of current source density analysis to locate the generators of harmonic electroretinogram (ERG) responses to contrast-modulated pattern and uniform-field stimuli in the primate retina. 2. Sinusoidal steady-state analysis was used, with a stimulus temporal frequency of 8 Hz. Fundamental and second-harmonic response components were measured for the uniform-field response. The second harmonic of the average of contrast-reversal pattern responses obtained at a series of spatial phases was also determined in the same experiments. In addition, retinal tissue resistance was measured. All of these measurements were obtained at a series of equally spaced depths in the retina. 3. Retinal resistivity was not observed to vary systematically with depth. In addition, any plausible undetected inhomogeneities of resistivity with depth were found to slightly affect the relative magnitudes of estimated current sources and sinks, but to have little effect on their localization. 4. In a given penetration, the phase lag of each harmonic component was relatively constant with depth in most cases; however the magnitude of this phase lag sometimes varied in different penetrations. To compare data from different penetrations, the constant phase lag for each harmonic was estimated, and the response data phase-shifted so as to bring all data into a standard (cosine) phase. 5. The resulting current source density analyses were found to be quite consistent in overall form for different penetrations and in different animals. These data were averaged to obtain a final estimate of the depth profiles for generators of different ERG components. 6. The uniform-field fundamental response was found to have a predominant source-sink pair in the distal half of the retina (receptor layer to outer plexiform layer). The pattern (second-harmonic) response generators had a quite different depth profile, consisting mainly of a source-sink pair in the proximal 20% of the retina (encompassing the nerve fibre layer to the middle of the inner plexiform layer). The uniform-field second-harmonic response showed a current source density (CSD) depth profile with multiple sources/sinks, as if it contained contributions from the other two.

Characteristics of rod driven off-responses in cat ganglion cells.

The off-response of dark adapted cat ganglion cells shows a tripartite response-intensity function in the optic nerve response (ONR) as well as in extracellular recordings of single cells. While responses increase when stimuli of low or high intensities are increased, the rod driven off-response shows a strong decrease (dip) for intermediate intensities before the cone part of the function starts to rise. In contrast, on-responses increase monotonically or stay at a maximum. The dip in the response-intensity function of the off-response has a constant shape with test lights of increasing as well as of decreasing irradiance. The action spectrum of the descending part of the function peaks at 500 nm, indicating that a rod driven mechanism is responsible for the response reduction reflected by the dip. Changing the stimulus diameter from 24 deg to a 1 deg test field centred on a ganglion cell's receptive field has minimal effect on the response reduction. This points to a temporal rather than a spatial mechanism being responsible for the dip.

Remote pattern reversal reduces the proximal negative response of the goldfish retina.

1. Using the eyecup preparation, proximal negative responses (PNR) to small test spots of different irradiance were recorded with (a) a stationary peripheral black and white grating surrounding the test spot, and (b) with contrast reversal of the same grating. In the latter case, the PNR-amplitude was reduced by a magnitude that was dependent on the frequency of contrast reversal. The reduction was maximum (approximately 50%) for a frequency of 8-10 Hz. 2. The attenuation was constant for PNR-amplitudes greater than half the maximum value, but increased for smaller responses. The fact that the intensity-response curve was not merely shifted towards higher values on the log intensity axis, indicates that the suppression was an effect neither of stray light nor of adaptive processes in the distal retina. 3. The effect of a single shift of the grating (by half a cycle) on the PNR was studied at different delays between grating shift and test spot presentation. Strong suppression of the PNR was found for delays between 100 ms (shift preceding test spot) and -50 ms (test spot preceding grating shift), with a maximum at about 30 ms. 4. This long-range effect of peripheral transient stimulation is of inhibitory nature, and probably related to Werblin's windmill effect.