International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B5. Istanbul 2004
the four impression taking Pn
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Figure 13. Shoulder total error
3.2 Conclusions
The analysis of those technological parameters yielded the
following geometrical conclusions for shoulder and knife edge
arrangements:
1. The number of dies, that is, whether several adjacent dies
were tested or just one, did not influence the distortion
tendencies per die in any of the impression taking procedures.
2. The model dies made without preparation and those made
with grooves were significantly taller than the original object,
whereas those made with place holders were practically
identical in height with the original die .
3. The bottom circles of the models and their middle circles
showed significant differences in diameter for each method, that
is, the cylindrical parts of all model dies were getting narrower
towards the top. The extent of narrowing was the lowest for
impressions made with a Fuji spearating foil and with a Plicafol
foil. The most pronounced narrowing, i.c., a significantly
shorter middle diameter than in all the other cases, was found
for the impressions made without any place holding or grooves.
4. The total width of dies was diminished in all models made by
any of the methods; they did so the most drastically for the
unprepared and for the grooved impressions.
5. In the case of shoulder dics, the diameter of shoulders also
diminished; the least so in cases where some place holder was
used.
4. SUMMARY
In this series of experiments, we have compared four different
dental impression taking technologies using geometrical data
obtained by a photogrammetrical method. From the analysis of
those data, the following points became clear:
Impressions taken without preparation and those
prepared with grooves are unfaithful to the original: the model
dies we got from casting those impressions were taller and
thinner than the original dies. This suggests that grooves do not
sufficiently allow for the outflow of surplus correction
material. The shape and size of the original metal die was
faithfully reproduced by the use of impressions made with place
holding foils; but no significant difference was found in
accuracy between the two such technologies involved in the
experiment.
5. REFERENCES
1. Bopp, H. — Krauss, H. (1978): An orientation and calibration
method for non topographic applications, Photogrammetric
Engineering and Remote Sensing, Vol. 44, no. 9, pp. 1191-
1196.
2. Detrekôi, À. — Fekete, K. — Toth, Z. — Alhusain, O. — Juhdsz,
A. — Stuber, I. — Rakusz, A. (2002): Representing the Human
Vascular System with the Use of X-ray Pictures, International
Archives of Photogrammetry and Remote Sensing Vol. XXXII.
Part B5 Comission V, Corfu, Greece, pp. 247-249.
3. Fekete, K. (1996): Developing the surface model of human
gums, International Archives of Photogrammetry and Remote
Sensing Vol. XXXI Part B5, Vienna, pp. 160-166.
4. Kaán, B. — Fekete, K. — Somogyi, E. — Kaan, M. — Fejérdy,
P. (2002): An examination of the modelling ability of two-time
two-phase silicon impression taking procedures, with a
specially designed tool and method, Hungarian Dental
Association Arkôvy Conference Word Dental Congress,
Vienna, p. 39.
5. Krauss, K. (1998): Fotogrammetria (university textbook),
Tetria Kiadó, Budapest.
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