Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-03-01
2001-11-06
Moore, Margaret G. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S588000
Reexamination Certificate
active
06313190
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
There is a need in many proceedings in dental medicine and dental technique for materials which pass over from a viscous state to a particularly hard final state. Especially for the keying, fixing, positioning, repair, transfer and remounting, there is the demand on a high final hardness of the material used. One of the most important fields of application is the bite impression.
2. Description of the Related Art
For the bite impression, the positional relation of both jaws the one to the other has to be precisely fixed. The resulting bite impression serves as a base for the work of the dental laboratory technician to transfer the bite situation specific to the patient to the pattern situation. Bite impressions are made by the dentist in almost all fields. An appropriate bite impression material has to meet the following requirements.
For a precise impression, it is important that the material does not allow any displacement in vertical and horizontal direction. Therefore, a particularly high final hardness and a low elasticity of the material is a main requirement. Moreover, the high hardness is a condition for a good processing of the impression with a milling cutter or a scalpel. For a checking of the right bite impression in the patient's mouth, it is desirable to be able to break off excess material purposefully. For the impression, a particularly short retention time in the mouth as well as a sufficient whole processing time are required to avoid a displacement of the jaws during the setting phase. The dimensions of the material may not vary during the transport from the dental pratice to the dental laboratory and later on. The user wants an easy handling when metering, mixing and applying as well as a storage stability as long as possible.
It is known to use addition cross-linking silicones for bite impressions; they have a higher final hardness and a lower strain compared with the silicones usually used in dental medicine.
The products on the market reach a Shore A final hardness of 70 to 90.
Therefore, for the indication bite impression a substantial increase of the final hardness or of the modulus of elasticity is desirable for a better precision.
The A-silicone which will be described below, which has a particularly high final hardness, brings substantial advantages for example for the following indications
sprayable material for bite impressions
material for the coating of the biting fork or of the impressing plates for impression
keying material, for example for intraoral support peg impressions
transfer of brackets in orthodontics
remounting of ceramic, cast or plastic fillings to grind in the occlusion on the pattern
underlining silicone which becomes hard
pattern material for the fabrication of inlays/onlays.
The above mentioned known addition cross-linking silicones are made of two components which chemically cross-link over a noble metal catalyzed hydrosilylation.
The A and B components are adjustable in various viscosities (fluid, moderately fluid, viscous, kneadable) and mixture ratios (generally 1:1). The mixing of the A and B components may be completed according to weight and volume and is carried out by appropriate metering and mixing devices as, for example, extruded length metering and manual mixing, cartridge system with static mixer and electrically/mechanically operated mixing apparatus. After having metered and mixed the A and B components, the resulting homogeneously mixed paste is applied during the whole processing time with appropriate aids into the patient's mouth. After the curing of the material (retention time in the mouth), it is removed from the patient's mouth and further processed as required.
According to the state of the art, bite impression materials on the base of addition cross-linking silicones have the following raw material composition
a) organopolysiloxanes with two or more vinyl groups in the molecuie and a viscosity between 100 and 350 000 MPA·s,
b) organopolysiloxanes of the general formula:
CH
2
═CH—SiR
2
O—(SiR
2
O)
n
—SiR
2
—CH═CH—CH
2
,
“R” meaning similar or different monovalent, eventually substituted hydrocarbon rests, free from aliphatic multiple compounds, and “n” an integral number with a value from 10 to 20,
c) low molecular vinyl and ethoxyl group containing MQ-resins,
d) organohydrogenpolysiloxanes (SiH cross-linking agent) with two or more SiH groups in the molecule,
e) catalysts for the acceleration of the hydrosilylation reaction,
f) dyestuff,
g) reinforcing filling material (optionally also surface treated, precipitated and pyrogenically fabricated),
h) compounds made of polydimethylsiloxanes and a.m. reinforcing filling material,
i) non-reinforcing filling material (optionally also surface treated).
From EP-A-0 522 341 we know a transparent material on the base of addition cross-linking polysiloxanes which is preferably used for the bite impression in dental technique to allow a checking of the adjustments or positions because of their transparentness, for example by light polymerization. According to this, the object is at ambient temperatures hardenable compositions on the base of polysiloxane which cross-link according to the addition process and which contain, besides organopolysiloxanes with two or more vinyl groups in the molecule, organohydrogenpolysiloxanes with two or several Si-H-groups in the molecule, a catalyst for the acceleration of the addition reaction and, eventually, dyestuff, whereby the latter prejudice the desired transparentness, still compounds of microdispersed, active filling material in silicone oil, short-chain organopolysiloxanes with two or several vinyl groups in the molecule and optionally a low molecular vinyl and ethoxyl group containing QM-resin, in which organopoiysiloxanes with two or more vinyl groups in the molecule are homogenously soluble, which has first a vinyl group content of 0.5∝8 mMol/g and second which is made of SiO
{fraction (4/2)}
-, RO
½
- and R
3
SiO
½
units and R is a methyl, vinyl, phenyl and ethyl group and has a ethoxyl group content of less than 4 mMol/g, whereby the organohydrogenpolysiloxanes with two or several Si-H-groups in the molecule are contained in the base paste and the catalyst for the acceleration of the addition reaction in the catalyst paste. Base and catalyst paste should stand out for a high temperature stability with respect to viscosity. The bite impressions fabricated with this mass should have a high hardness, a high transparentness and resistance to tearing for a low strain. The QM-resins which are set in here must be so low molecular that they are transparently soluble in the vinyl end stopped polydimethylsiloxanes so as to obtain the desired transparentness of the bite impressions. The products which are obtained here do not have a high Shore D hardness (10 to 19) and a high modulus of elasticity (about 5 to 9 Mpa).
SUMMARY OF THE INVENTION
The present invention aims at creating addition cross-linking two-component silicone materials with a high Shore D hardness and a high modulus of elasticity and thus at obtaining compositions of addition cross-linking two-component silicone materials which can be used particularly advantageously in dental medicine and dental technique when vulcanized because of their high Shore D hardness and their high modulus of elasticity compared to the known A-silicones for various problem definitions which are not yet solved in a satisfying way.
The Shore D hardness required here of more than 35 and the modulus of elasticity of more than 20 MPa shall be reached while maintaining the other mechanical properties and the working properties with respect to appropriately processable viscosities/consistencies with the a.m. metering and mixing systems, quick setting behaviour, flexibility, workability, removability, flow behaviour during the processing time and eventually smooth surface finish. The formulation of the contents will have a sufficient storage stability in the corresponding primary packing, for
Bublewitz Alexander
Reber Jens-Peter
Friedrich Kueffner
Kettenbach GmbH & Co. KG
Moore Margaret G.
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