WO2002032338A2

WO2002032338A2 - Dental impression material utilizing ruthenium catalyst

Info

Publication number: WO2002032338A2
Application number: PCT/US2001/024004
Authority: WO
Inventors: Christos Angeletakis; Mingfei Chen
Original assignee: Kerr Corp
Current assignee: Kerr Corp
Priority date: 2000-10-17
Filing date: 2001-07-31
Publication date: 2002-04-25
Anticipated expiration: 2003-04-17
Also published as: CA2425485A1; AU2001280925A1; BR0114679A; WO2002032338A3; CN1469730A; ATE344004T1; DE60124290D1; MXPA03003449A; JP2004513892A; EP1326574B1; EP1326574A2; DE60124290T2; US6455029B1

Abstract

A composition for use as a dental impression material including a polymerizable telechelic oligomer or polymer curable by ring-opening metathesis polymerization, a filler system, and a ruthenium carbene complex catalyst, whereby the catalyst initiates ring-opening metathesis polymerization of the composition. The invention includes a paste/paste system in which a base paste includes the polymerizable telechelic oligomer or polymer and a filler system and in which a catalyst paste includes the catalyst dissolved in an inert solvent and a filler system. The telechelic oligomer or polymer may be, for example, a polydimethylsiloxane end-functionalized with norbornyl groups. The catalyst may be, for example, a ruthenium carbene complex with a ligand having a basicity higher than tricyclohexylphosphine. The composition of the present invention exhibits reduced sensitivity to sulfur impurities.

Description

DENTAL IMPRESSION MATERIAL UTILIZING RUTHENIUM CATALYST

Field of the Invention

This invention relates to dental impression materials. Background of the Invention

Impression materials used in dentistry are one of several types of

elastomers, such as polysulfϊdes, condensation silicones, polyethers or polyvinyl

siloxanes (addition-curable silicones). These materials are normally two-paste systems

that are mixed immediately before use, then placed in contact with the tooth structure.

Mixing of the two pastes initiates a chemical reaction that results in the formation of the

elastic rubber impression material after setting, thereby forming a negative impression

of the tooth structure involved. The addition-curable silicones, which exhibit fast

curing speeds and low shrinkages, typically use a platinum-containing hydrosilation

catalyst. This type of catalyst necessitates the use of silicon-containing oligomers,

which are generally expensive. Also, the platinum-based catalyst can be inactivated by sulfur-containing impurities present in the latex gloves ordinarily used by dentists, as well as by certain medicaments used in the oral cavity. In addition, there may be

undesirable hydrogen evolution from the decomposition of the hydrosiloxane cross-

linkers that are present in the systems. This may increase the time and effort necessary

to take an impression with these materials because extra precautionary steps have to be taken.

In view of these drawbacks, there is a need for dental impression

materials that do not exhibit the various sensitivity problems described above. Summary of the Invention

The present invention provides a composition for use as a dental

impression material. The composition comprises a polymerizable telechelic oligomer or

polymer curable by ring-opening metathesis polymerization (ROMP), a filler system,

and a ruthenium carbene complex catalyst, whereby the catalyst initiates the ring-

opening metathesis polymerization of the composition. In an embodiment of the

invention, the composition is a paste/paste system in which a base paste includes the

polymerizable telechelic oligomer or polymer and a filler system and in which a catalyst

paste includes the catalyst dissolved in an inert solvent and a filler system. In one

example of the invention, the telechelic oligomer or polymer is a polydimethylsiloxane

end-functionalized with norbornyl groups and having between 5 and 5000

dimethylsiloxane units, and the catalyst is a ruthenium carbene complex with at least

one of the ligands having a basicity higher than tricyclohexylphosphine. The

composition of the present invention exhibits reduced sensitivity to sulfur impurities. Detailed Description of the Invention

The present invention provides formulations for dental impression

materials using a telechelic resin system that is cured by ROMP with the aid of a catalyst based on a ruthenium complex. The composition of the present invention

comprises a catalyst paste and base paste in intimate admixture with one another in a

paste/paste system. Curing is obtained by a ROMP reaction using a ruthenium carbene

as a catalyst. Generally, in this system, the catalyst paste comprises a ruthenium

catalyst for initiating polymerization, a solvent for the catalyst that is miscible or

dispersible with the base paste, and fillers for optimizing viscosity for the application of

the paste and for reinforcement of the cured material. Fillers for non-reinforcing

purposes can always also be used. The base paste generally comprises a polymerizable ■

oligomer and/or polymer resin system that is curable via the ROMP mechanism, and

fillers as described above for the catalyst paste.

The type of oligomers and/or polymers that may be used in the present

invention include telechelic (end functionalized) polymers with any of a variety of

backbones, as long as the chain ends are functionalized with reactive by ROMP groups,

such as norbornyl groups. For example, the resin may be a telechelic polydimethyl-

siloxane terminated with norbornyl groups according the following structure:

where n=5-5000, for example 27-1590. Other examples of telechelic polysiloxanes are

those having the following structure:

where n=5-5000, such as 27-1590;

Rι»

where R₃, R₄=C,-C₁₈hydrocarbon, and m=0-2; and

For an alternative example, the resin may be polytetrahydrofuran-polyethylene oxide

copolymer terminated with norbornyl groups. As yet another alternative example, the resin may be a norbornyl carboxylate terminated polybutadiene.

The catalysts useful in the present invention include the ruthenium

carbene complexes. The parent benzylidene ruthenium complex A, with the following

structure, exhibits high air and water stability:

PCy₃

A The ring-opening metathesis activity of the parent complex A can be increased by

substituting a saturated imidazole ligand for a tricyclohexylphosphine ligand. The

ligands may be 4,5-dihydroimidazol-2-ylidenes, which have the following general

structure:

These substituted ligands have a basicity higher than that of tricyclohexylphosphine, as

indicated by a higher pKa, which is believed to contribute to the higher activity.

Ruthenium complex B, a derivative of complex A and having the structure shown

below, is a substituted ruthenium carbene complex including such a ligand:

B Other derivatives of parent complex Ά. can also be used in the resin system of the

composition of the present invention, such as substituted ruthenium carbene complexes

C and D having the following structures:

D

The catalyst component of the dental impression material is formulated by dissolving

the ruthenium carbene complex in an inert solvent. The solvent, or diluent, is chosen

such that the solvent and the complex are miscible (soluble) or dispersible with the base

pastes, and such that the solvent does not interfere with the reaction. The solvent may be, for example, 3-phenyl-heptamethyl-trisiloxane.

The fillers useful in the composition of the present invention include

reinforcing and/or non-reinforcing (extending) fillers. Suitable reinforcing fillers

include precipitated silicas, fumed silica, calcium silicate (Wbllastonite), crystalline

silica, and the like. The addition of reinforcing filler improves the mechanical strength,

such as tensile and tear strengths, of the cured composition. Suitable non-reinforcing

fillers include diatomaceous earth, aluminas, magnesias, titanium dioxide, zirconium

silicate, calcium carbonate, metallic oxides, and the like. Surface-treated fillers may

also be used. Typical surface treatments include silanization and the like. In accordance with the present invention, mixtures of fillers with different particle sizes

may be used. A bimodal filler system blended with sub-micron (< l ^m) and micron-

sized particles (2-10μm) of close particle size distribution is used as a varying filler

loading to provide dental impression materials with low, medium or high consistency,

as defined by ISO Specification No. 4823 (2nd. Ed. 1992), suitable for use in all dental

impression techniques. The filler may be present in amounts of from about 15 wt.% to

about 50 wt.% of the composition. To adjust the consistency of the two-paste

embodiment of the present invention to achieve either a low, medium or high

consistency composition, the sub-micron sized filler and/or the micron sized filler may

be adjusted in one or both of the catalyst and base pastes. The higher the consistency

desired, the more beneficial it is to increase the sub-micron filler to a greater extent than

the increase in the micron sized filler, whereby the sub-micron filler particles are

worked into the interstitial spaces between micronized particles during mixing.

By way of example only and not limitation, the composition may

comprise the polymerizable resin in an amount of about 5wt.% to about 95wt.%, the

sub-micron sized filler in an amount up to about 10 wt.%, the micron sized filler in an

amount of about 10wt.% to about 60wt.%, and the catalyst in an amount of about

0.001wt.% to about lwt.%. The composition of the present may further include

optional additives known to one skilled in the art, such as pigments, that do not interfere

with the reaction.

EXAMPLE

A telechelic polydimethylsiloxane terminated with norbornyl groups was

synthesized according to the following scheme:

A three-neck round bottom flask equipped with a mechanical stirrer, a condenser and N₂

inlet-outlet was charged with 360.0 g silanol terminated poly(dimethyl siloxane) (DMS-

S27, n=243, from Gelest Corp.) and 4.85 g triethylamine containing 1% 4-(N,N-

dimethyl)amino-pyridine. A quantity of 9.02 g of 2-(5-norbor-2-enyl)-ethyl-

dimethylchlorosilane was added dropwise to the flask with stirring. After the addition,

the reaction temperature was raised to 70 °C, and stirring was continued for 4 hours at

that temperature. Then, 2 mL methanol was added to the mixture and stirring was

continued for 1 hour longer. The reaction mixture was next diluted with 500 mL of

hexanes and filtered to remove the white salt. The hexane solution was washed three

times with 1% HC1 and three times with deionized water. The solution was then dried

over Na₂SO₄. After evaporation of the solvent under vacuum, a clear liquid product was

obtained. This compound 1, having n=243 (average), exhibited the following infrared

peaks (cm^"1): 2963, 1411, 1260, 1020, 800, and 702.

A second compound was produced following the same procedure as

above, but this time using a silanol terminated poly(dimethyl siloxane) having n=27 (average). These two resulting compounds were then mixed and compounded with

fillers and dispersed in a three-roll mill to form a suspension. This suspension is

referred to as the base component, or base paste, and its composition is detailed in Table

1.

TABLE 1

Two catalyst pastes were then formulated by dissolving in 3-phenyl-

heptamethyl-trisiloxane the ruthenium carbene complex A and B, respectively, each

catalyst complex having been obtained from Strem Chemicals Inc., Newburyport, MA.

The solutions were then compounded with fillers and dispersed in a three-roll mill to

form suspensions. These suspensions are referred to as the catalyst components, or

catalyst pastes, and are further described in Table 2.

TABLE 2

For comparative purposes, the test base paste composition was combined

with each of the test catalyst paste compositions in a base to catalyst ratio of 10:1 and

mixed by spatulation. Separately, for use in the comparison, catalyst and base pastes

were prepared for an addition-curable silicone composition using a platinum-containing

hydrosilation catalyst. The comparative control base paste and control catalyst paste

compositions are detailed in Tables 3 and 4, respectively.

TABLE 3

TABLE 4

The control pastes were combined in a base paste to catalyst paste ratio of 1 : 1.

Both the test compositions and control compositions are classified as type 2 or 3 impression materials, meaning that they have low to medium consistency, as

defined by ISO Specification No. 4823. The physical properties of the cured

compositions were determined using ISO Specification No. 4823 for evaluation of work time, set time, mixed consistency, dimensional change, strain and compression and

deformation recovery. The results are given below in Table 5.

Table 5 also includes the results of a test devised to determine the

relative sensitivity of these formulations to residual sulfur compound containing

surfaces, such as latex gloves used by dentists. The sulfiir sensitivity test comprised

preparing a 1% solution of an approximately 30%/70% mixture of mono- and di-octyl

tin bis (2-ethylhexylthioglycolate) esters in hexane. A microbrush was dipped in this

solution, and the solution was painted on the edge of a 3x6 inch dental impression

mixing pad. The control base paste and the control catalyst paste were mixed in a 1 :1

ratio (0.5g/0.5g) and the test base paste and the test catalyst paste were mixed in a 10:1

ratio (1.0 g/O.lg), each by spatulation for 20 seconds, and each mixture was partially

placed on top of the area of the pad where the hexane solution was painted on. After the

bulk of the material had set, as indicated by set time and recovery from deformation, the

mixture was lifted off the pad, and the area that was in contact with the painted area was checked to see if it had also set. The materials were checked 10 minutes after

placement on the pad to ascertain whether setting was achieved at the sulfur contact area

after the bulk material had already set. The results of this sulfur sensitivity test, along

with the physical properties set forth in ISO Specification No. 4823 are set forth in

Table 5.

¹² TABLE 5

From the data in Table 5, it is shown that the materials of the present invention pass the

requirements of ISO specification 4823 for Type 2 and/or 3 dental impression materials,

including requirements for compatibility with gypsum and detail reproduction.

In addition, the test impression materials exhibited a reduction in

sensitivity to sulfiir impurities. The test impression material of the present invention

incorporating the complex B catalyst exhibited significantly reduced sulfur sensitivity,

as indicated by its ability to fully set at surfaces in contact with a sulfur impurity. The test impression material of the present invention utilizing the complex A catalyst at least

partially set at the contact surface after 10 minutes, although it did not fully set within 20 minutes after placement. In contra&c, the control impression material utilizing the

platinum complex catalyst did not set at all at the contact surface within 20 minutes of

contacting the sulfur impurity. As defined in ISO specification 4823, a material has set

when it develops a recovery from deformation of between 96.5% and 100%. Thus,

while the bulk of the impression material may fully set within 10 minutes in each of the

test and control materials, surfaces in contact with sulfur impurities may be prevented

from setting due to the sulfur deactivating the catalyst, possibly by a chelation

mechanism. The parent benzylidene ruthenium complex A caused a reduction in sulfur

sensitivity, and the high ring-opening metathesis active ruthenium carbene complexes

having substituted imidazole ligands exhibited the highest reduction in sulfur sensitivity

during polymerization, as indicated by the full setting of the material at the contacting

surface. Thus, compositions of the present invention including a ruthenium carbene

complex with a ligand having a basicity higher than that of tricyclonexylphosphine can achieve a recovery after deformation of at least 96.5% within 20 minutes of contacting a

thin film of an oxidizable sulfur-containing compound.

While the present invention has been illustrated by the description of an

embodiment thereof, and while the embodiment has been described in considerable

detail, it is not intended to restrict or in any way limit the scope of the appended claims

to such detail. Additional advantages and modifications will readily appear to those

skilled in the art. The invention in its broader aspects is therefore not limited to the

specific details, representative methods and illustrative examples shown and described.

Accordingly, departures may be made from such details without departing from the scope or spirit of applicant's general inventive concept.

WHAT IS CLAIMED IS:

Claims

1. A composition for use as a dental impression material, comprising:

a polymerizable resin comprising a telechelic oligomer or polymer curable by

ring-opening metathesis polymerization;

a filler system; and

a ruthenium carbene complex catalyst, wherein the catalyst is capable of

initiating the ring-opening metathesis polymerization of the composition.

2. The composition of claim 1, wherein the polymerizable resin is telechelic

polydimethylsiloxane end-functionalized with norbonyl groups and having between about 5 and about 5000 dimethylsiloxane units.

3. The composition of claim 2, wherein the polydimethylsiloxane includes between

about 27 and about 1590 dimethylsiloxane units.

4. The composition of claim 1, wherein the polymerizable resin is a telechelic

polysiloxane having the following structure:

where n=5-5O00,

R₁₍ R₂=C_rCi₈ hydrocarbon or CH₂CH₂-j-CH₂CHθ -R₄

where R₃,

and

drocarbon

5. The composition of claim 1, wherein the polymerizable resin is telechelic

polytetrahydrofuran-polyethylene oxide end-fuctionalized with norbonyl groups.

6. The composition of claim 1, wherein the composition comprises about 5 wt.% to

about 95 wt.% of the polymerizable resin.

7. The composition of claim 1, wherein the filler system is bimodal, including a

sub-micron sized filler component and a micron sized filler component.

8. The composition of claim 7, wherein the composition comprises up to about 10

wt.% sub-micron sized filler and about 10 wt.% to about 60 wt.% micron sized filler.

9. The composition of claim 1, wherein the catalyst is a benzylidene ruthenium

complex of the formula:

wherein Cy is cyclohexyl and Ph is phenyl.

10. The composition of claim 1, wherein the catalyst is a 4,5-dihydroimidazol-2-

ylidene-substituted ruthenium carbene complex.

11. The composition of claim 1 , wherein the catalyst is a ruthenium carbene

complex with one ligand having a basicity higher than tricyclohexylphosphine.

12. The composition of claim 11 , wherein the complex is of the formula:

B

wherein Cy is cyclohexyl, Ph is phenyl and R is mesityl.

13. The composition of claim 11 , wherein the complex is of the formula:

wherein Cy is cyclohexyl, Ph is phenyl and R is mesityl.

14. The composition of claim 11 , wherein the complex is of the formula:

D wherein Cy is cyclohexyl, Ph is phenyl and R is mesityl.

15. The composition of claim 1 , wherein the composition achieves a recovery after

deformation of at least 96.5% within 20 minutes of contacting a film of an oxidizable

sulfiir-containing compound.

16. The composition of claim 1 wherein the composition comprises about 0.001wt.% to about lwt.% of the catalyst.

17. A composition for use as a dental impression material, comprising:

a base paste including a polymerizable resin that is a telechelic oligomer or

polymer curable by ring-opening metathesis polymerization and a filler system; and

a catalyst paste including a ruthenium carbene complex catalyst dissolved in a

solvent which is miscible with the base paste, and a filler system, wherein the catalyst is

capable of initiating the ring-opening metathesis polymerization of the composition.

18. The composition of claim 17, wherein the ratio of the base paste to the catalyst

paste in the composition is in the range of about 10:1 to about 1:10.

19. The composition of claim 17, wherein the polymerizable resin is telechelic

polydimethylsiloxane end-functionalized with norbonyl groups and having between

about 5 and about 5000 dimethylsiloxane units.

20. The composition of claim 19, wherein the polydimethylsiloxane includes

between about 27 and about 1590 dimethylsiloxane units.

21. The composition of claim 17, wherein the polymerizable resin is a telechelic

polysiloxane having the following structure:

where n=5-5000

where R₃,

and

22. The composition of claim 17, wherein the polymerizable resin is telechelic

polytetrahydrofuran-polyethylene oxide end-fuctionalized with norbonyl groups.

23. The composition of claim 17, wherein the composition comprises about 5 wt.%

to about 95 wt.% of the polymerizable resin.

24. The composition of claim 17, wherein the filler system in each of the base paste

and the catalyst paste is bimodal, including a sub-micron sized filler component and a

micron sized filler component.

25. The composition of claim 24, wherein the composition comprises up to about 10

26. The composition of claim 17, wherein the catalyst is a benzylidene ruthenium

complex of the formula:

wherein Cy is cyclohexyl and Ph is phenyl.

27. The composition of claim 17, wherein the catalyst is a 4,5-dihydroimidazol-2-

ylidene-substituted ruthenium carbene complex.

28. The composition of claim 17, wherein the catalyst is a ruthenium carbene

complex with one ligand having a basicity higher than tricyclohexylphosphine.

29. The composition of claim 28, wherein the complex is of the formula:

B

wherein Cy is cyclohexyl, Ph is phenyl and R is mesityl.

30. The composition of claim 28, wherein the complex is of the formula:

PCy₂

wherein Cy is cyclohexyl, Ph is phenyl and R is mesityl.

31. The composition of claim 28, wherein the complex is of the foimula:

wherein Cy is cyclohexyl, Ph is phenyl and R is mesityl.

32. The composition of claim 17, wherein the composition achieves a recovery after

sulfur-containing compound.

33. The composition of claim 17 wherein the composition comprises about

0.001wt.% to about lwt.% of the catalyst.

34. A composition for use as a d 2e3ntal impression material, comprising:

a base paste including a telechelic polysiloxane curable by ring-opening

metathesis polymerization and a filler system; and

a catalyst paste including a substituted ruthenium carbene complex with a

substituted ligand having a basicity higher than tricyclohexylphosphine, the complex

dissolved in a solvent which is miscible with the base paste, and a filler system,

wherein the catalyst is capable of initiating the ring-opening metathesis

polymerization of the composition, and

wherein the composition achieves a recovery after deformation of at least 96.5%

within 20 minutes of contacting a solution of 1 % or less of an oxidizable sulfur-

containing compound in hexane.