Note: Descriptions are shown in the official language in which they were submitted.
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-``` HOECHST AKTIENGESELLSCXAFT HOE 93/F 018 Dr. MA/we
Liquefied gas formulation for te~ting the vitality o~
teeth,
The matter of the vitality of teeth i8 of decisive
importance in the context o recording dental finding~
and planning dental treatment. The most requent causes
o toothache are carious deect~, hyperemias o the pulp
(marrow organ of the tooth), pulpitis or gangrene. Since
the treatment o the dierent diseases varie~, pulp
diagnostics (testing o vitali~y) is o decisive import-
ance. In the case of deep-seated caries, it is important
to retain the vitality wi~ich still exists (for example by
direct or i~direct capping). In the case of crowning, it
is important to determine devitalized teeth, since
devitalized side teeth have an excessive risk of fracture
and devitalized front teeth should be provided with a
core construction of metal before crowning. Difficulties
also oten occur with arowned teeth. Since diagnosis by
X-ray is made dificult here, testing of vitality is of
great importance.
The pulp regenerates dentine as a reaction to external
influences and ~timuli and thus maintains the vitality of
the pulp tissue.
The vitality of dental pulp i~ equated with the intact
metaboli~m of cells and the ability to regenerate dent-
ine. Direct evaluation of thie function ia not po~oible,i.e. vitality can be checked only indirectly.
In practice, the vitality of pulp is evaluated by check-
ing ~ensitivity. An establi~hed clinical method i~ the
U~8 o~ thermal stimuli. In this proc0dure, these ~timuli
are given to the tooth ~urface and lead, via a ehift in
the dentine Sluid, to excitation of the 0en~itive nerve3
o~ the pulp and thers~ore to a pain ~ensation.
Pulp ~enaltivity i~ chiefly t~ted with low temperature
stimuli. Thie te~t is reliable, ~ince tha ~tlmulus
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threshold for low temperature stimuli in pulp tissue is
low. On the other hand, in most case~ the pulp tissue i~
relatively insensitive to (brief) cooling, 80 that there
is no fear of permanent tissue damage.
The use o~ R12 (dichlorodi~luoromethane) is outst~ndingly
suitable and has been tried and tested for years for thi3
test.
To test the vitality of a tooth, this i8 brought into
contact with a $oam pellet or cotton wool swab which has
been sprayed beforehand with R12 liquefied under pres-
eure. AB a re~ult of the drop in temperature on the tooth
surface, the temperature in the region of the pulp falls,
which means that the stimulus threshold for low tempera-
ture stimuli is exceeded. However, like all completely
halogenated chlorofluorocarbons (CFC~), R12 has a high
resistance to biotic and abiotic degradation. CFCs are
not destroyed in the lower atmosphere and therefore rise
to the stratosphere. It is assumed that they are then
cleaved by W radi~tion and contribute to the degradation
of the ozone molecules via free radicale.
It has now been ~ound that R227 (1,1,1,2,3,3,3-hepta-
fluoropropane, 2-hydroheptafluoropropane), by itself or
as a mixture with up to 50% by weight of R134a (1,1,1,2-
tetrafluoroethane) ia a suitable eubetitute or R12. R227
and R134a ar~ both non-combustible. ~inca the~e compounds
contain hydrogen in the molecule, ~n contra~t to com-
pletely halogenated chloro~luorocarbons, their life in
the atmo~phere and therefore their contribution to the
indirect greenhoune e~ect i~ signi~icantly reduced.
Since they are chlorine-free, they do not contribute
toward ozone degradation. ~hi~ mean~ that the in~luence
on the atmo~phere is minimized.
~he preeent invention relate~ to a liguefied gae ~ormula-
tion ~or te~ting the ~itality o~ t~eth, which ~ompri~es
2-hydroh~pta~luoropropane (R227) lique~ied under
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pre~sure.
The usual epray can~ of aluminum are de~igned for a test
pressure of 18 bar. For safety reason~, however, they
~hould be filled only with products having a vapor
pressure at 50C of not more than 12 bar, i.e. 2/3 of the
test pressure.
R227 has a vapor pressure of only 9.22 bar at 50C. On
the other hand, the corresponding pressure of R134a is
already 12.77 bar. R134a therefore can be u~ed only as a
mixture with at least 50% by weight of R227 as a "pres-
sure reducer". The ~apor pre~ure of a mixture of 50% by
weight of R134a and 50% by weight of R227 i~ 10.8 bar at
50C, i.e. even if the spray cans are filled under an
atmo~pheric pres~ure of 1 bar, the total preseure in the
cans is only 11.8 bar, i.e. iB still of an admiesible
value.
~he invention therefore furthermore relate~ to a lique-
~ied ga~ formulation for testing the vitality of teeth,
which comprises at lea~t 50% by weight of 2-hydrohepta-
fluoropropane (R227) liguefied under pre~sure and notmore than 50% by weight of 1,1,1,2-tetrafluoroethane
(R134a) liquefied under pressure. The liquefied gaB
formulation preferably comprises 50 - 99% by weight of
R227, the remainder e~eentially being R134a. In particu-
lar, the liguefisd gas formulation compri~es 50 - 95% by
weight of R227, above all 50 - 90% by weight of R227, the
remainder in each case essentially being R134a.
Com~aratiYe ~tudie~ ~how that R12, when applied to a
measurement probe (thermocouple) wrapped in cotton wool,
lower~ the temperaturo to -36C, i.e. about 10C below
the boiling point of R12, within 20 - 25 eeconde. Sur-
prisingly, it has now been found that R227 lowers the
temperature to only about -16C, i.e. down to about the
boiling point of R227, within 15 second0. A mixture of
50% by weight each of R227 and R134a reaches a
temp~ratur~ of -26.5C, which al80 only corresponds to
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approximately the boiling point of this mixture, within
15 seconds. Considerably less icing on the mea~urement
probe therefore occurs both with pure R227 and with its
mixture with R134a than when R12 is employed.
Thes2 studies sugge~t that R227 and mixtures thareof with
not mora than 50~ by weight o R134a will cau~e a lower-
ing of the tamperature on the tooth surface (when applied
via a cotton wool swab or foam pellet or sprayed directly
onto the tooth) which is ~uff~cient to exceed the pain
limit of a vital tooth.
R227 and it~ mixtures mentioned with R134a therefore
allow gentler but ~ust as effective testing of the
vitality of teeth in comparison with the R12 employed to
date for this purpose. Damage to the enamel and the
surrounding ti~sue is prevented or minimized by the
higher temperature, in comparison with R12, as are the
effects following accidental spraying onto the mucou~
membrane.
With R227 and it~ mixtures with R134a, the doctor can
adjust to the individual pain limit of the patient by
starting with pure R227 and elowly increasing the content
of R134a and therefore slowly lower$ng the temperature on
the tooth. The higher the R134a content, the lower the
temperature generated on the tooth. In other word~, a
considerably gentler diagno~i~ can be parformed than with
R12.
The vitality can also be t0~ted by direct spraying onto
I the tooth u~ing pure R227 or R227 containing ~mall
I amount~ of R134a. However, it i~ preferable to u~e an
application aid (for example a cotton wool ~wab or foam
pellst), as $8 the case with mixture~ with higher con-
tents of R134a.
Overall, R227 and it~ mixtures with R134a have the
following advantage~ over R12: They are chlorine-Eree and
therefore do not contribute toward ozone degradation.
Their vapor pressure i~ 80 low that it i~ not nece~sary
to f$11 the ~pray can~ under v~cuum. Beaause the
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temperature generated by them on the tooth i~ not ~o low,
they are gentler to UBe. By suitable choice of the R134a
content, te~ting of vitality can be adapted to the
individual pain limit of the patient.
Mixtures with increas~ng contents of R134a can he em-
ployed here, starting at 1-5~ by weight, then 5-10~ by
weight, then 10-20% by weight, then 20-30~ by weight,
then 30-40~ by weight and then 40-50% by weight of R134a,
the remainder in each case being essentially R227.
10 The following example~ illustrate the invention. `
Comparison Example --
A thermocouple wae connected to a digital temperature ~ ;
display apparatus. The thermocouple was wrapped in a
cotton wool pellet (3 cm high and 4-5 cm thick). A --
15 pressurized ga~ can filled with R12 was fixed on a stand. ~--
The diatance between the spray head and the thermocouple
was 10 cm; the thermocouple was ad~u~ted centrally in the
cotton wool pellet. R12 was sprayed o~to the cotton wool
pellet at room temperature for about 5 seconds. Within 20
20 - 25 second~, counted from the ~tart of spraying, the - -~
temperature dropped to -36C. Severe icing occurred on
the cotton wool pellet. --
Example 1
~he procedure was ae in the Compari~on Example, except
that inetead of R12, R227 wa~ now ~prayed onto the cotton
wool pellet. Within 15 ~econd~, counted from the ~tart of
spraying, the temperature dropp0d to -16C, only ~light
icing occurring on the cotton wool pellet.
~xampls 2
Th~ procedure wa~ a~ in the Compari~on ~xample, except
that inetead of R12, a mixture of 50% by weight o~ R227
and 50% by weight o~ R134a wa~ now ~pray~d onto tha
cotton wool pellet. Within 15 ~econd~, counting from the
~tart o~ ~praying, the tempoxature dropped to -26.5C,
only moderat~ icing o¢curring on the cotton wool pellet.
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Example 3
The procedure wa~ a~ in the Comparison Example, except
that instead of R12, a mixture of 90% by weight of R227
and 10% by weight of R134a was now sprayed onto the
cotton wool pellet. Within 15 seconds, counting from the
start of spraying, the temperature dropped to -20C, only
slight icing occurring on the cotton wool pellet.
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