Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
2001-02-02
2003-05-20
Moore, Margaret G. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
C528S015000, C528S031000, C523S118000, C523S120000, C524S588000, C526S279000
Reexamination Certificate
active
06566479
ABSTRACT:
FIELD OF APPLICATION
The invention pertains to a relining for prostheses on the basis of silicone and an adhesive for a durable bond between the plastic of the prosthesis and the silicone.
When bonding silicones with plastics, in particular in dentistry the problem is to obtain a stable, durable, and stable bond. Thus, the dental prosthesis is provided with a relining material of the relining in order to maintain the functional efficiency of dental prostheses due to changes of the prosthesis support.
With regard to materials science, hard and soft-remaining materials used for relining a dental prosthesis should have a good adhesion to the plastic of the prosthesis, a sufficient dimensional stability, a low water absorption, a high abrasion resistance under oral conditions and a smooth surface. With regard to clinical practice, demands for biocompatibility, freedom from odour and taste, resistance to fungi and bacteria, colour fastness, an aesthetic appearance and a high ease of cleaning are added. An additional demand is the fast execution of relining including the functional shaping in the so-called direct relining method in one operating step at the dentist without any detour via a dentistry laboratory.
Further, a good processability with dental instruments such as, e.g., milling cutters, scalpels, polishing disks is highly important.
By a good processability there is understood that the cured relining material can be routed with rotating instruments, i.e., slipping off with the milling cutter, an erasing effect or a breakaway of larger silicone parts will not occur.
As relining materials natural rubber, polyvinyl compounds, fluorocarbon elastomers, hard and soft-remaining acrylic acid derivatives and silicones have been known in the prior art.
The known soft-remaining materials inhere drawbacks such as a short shelf live, an insufficient adhesion to the base of the prosthesis, embrittlement, discolouration and others. Of the proposed materials, acrylic acid with plasticizers and silicones are used most frequently for the soft-remaining relining. However, the common characteristics of acrylic acid derivatives are unsatisfactory. Although said derivatives provide a very good binding and consequently adhesion to the prosthesis plastics due to the similar composition thereof, the plasticizer contained therein, however, will diffuse out over time which will result in embrittlement, dimensional changes and porosity of the relining material. In addition, due to the toxic effect of the monomer components on the mucous membrane acrylic acid derivatives can be used only restrictedly for the direct relining method within the mouth of the patient. The indirect relining brings about a laboratory operating step with possible sources of error, a second treatment attendance, and the patient has to manage without his prosthesis for a longer time.
Recently, hardening (meth)acrylic acid derivatives have normally been used for the hard relining. Although they bond well to the prosthesis plastics, they are used nearly exclusively for the indirect relining method due to the drawbacks described above. In addition, when using said materials in the direct relining method a removal from the mouth without any difficulty, e.g., with partial prosthesis, would be endangered due to the inflow of material into cavities.
Regarding the requirements on a relining material in the direct process, silicones are most suited. However, the adhesion thereof to the prosthesis plastic of poly methyl methacrylate turned out to be extremely unsatisfactory. According to the prior art, a reduction of this unwanted effect is achieved by mechanical retentions and the use of adhesion promoters consisting of a mixture of acrylooxyalkylsilanes, e.g., methacryloxypropyltrimethoxysilane. However, the bond strengths obtainable thereby are still below 100 Ncm
−2
.
From DE-A-39 02 817 it is known that the adhesion of addition crosslinking silicones to the prosthesis plastic by adding from 10 to 50% by weight of a powdery methacrylate (co)polymer as a filler to a heat-curing vinylsilicone mass of the addition polymerization type can result in bond strengths of up to 200 Ncm
−2
. However, due to the high amount of methacrylate plastic the typical properties of the silicone important for relining materials such as the permanent flexibility and the water-repellent effect are partially lost so that a durability of only six months can be specified for such a relining material.
DE-A-39 11 520 describes a permanently durable and soft-remaining relining on the basis of silicone rubber. Here, the adhesion between the prosthesis plastic and the silicone is achieved by vulcanizing the silicone on a steel reinforcement at 200° C. and subsequently applying the prosthesis plastic and the teeth on the steel basis. A drawback in this process are the high required temperatures and the required expenditures in equipment.
In PCT/EP 950 13 13 and DE-A-195 39 653 two-component polyurethane adhesives with an addition of organohydrogenpolysiloxanes for the durable bonding of prosthesis plastics with addition-crosslinking silicones are described.
Said system provides good adhesive bonds which inhere, however, all known drawbacks of a two-component system as compared with a one-component system: higher expenditures in time for mixing both components homogeneously and higher expenditures in time due to the necessary reaction times of both components reacting with each other, the risk of mixing inhomogeneities, wrong metering and the incorporation of air.
Moreover, with two-component polyurethane systems there is the risk of foaming and gassing depending on the air humidity of the environment.
EP-A-0 632 060 describes the use of silicone-modified acrylic copolymers having mean molecular weights from 5,000 to 1,000,000 g/mol as one-component adhesive (constituent part of commercial product 1, see table 1-4) which is manufactured by the copolymerisation of methyl meth-acrylate with allyl methacrylate and the subsequent platinum-catalysed hydrosilylation of the prepared copolymer containing allyl groups with a hydrogen polydimethylsiloxane.
However, the amount of syntheses for this adhesive is high.
On the one hand the copolymerisation catalysts interfere with the platinum-catalysed hydrosilylation, and on the other hand the consumed platinum catalyst has to be removed from the product after the hydrosilylation in order to avoid stability problems due to the development of hydrogen.
According to EP-A-0 614 655, the adhesive force obtainable with this adhesive results in a bond between the PMMA plastic and the appropriate relining silicone (constituent part of commercial product 1).
The fracture stress values of this adhesive bond as determined in the tensile test are between 67 and 75 N/cm
2
(see table 2a). The fracture pattern demonstrates a pure cohesive failure in the silicon, however, from the above-mentioned fracture stress it can be concluded that the tear strength of the relining silicone according to EP-A-0 614 655 (constituent part of commercial product 1) has comparatively low values such that a high tear strength and the tear propagation resistance for the employed relining silicone is ensured only insufficiently to resist the permanent load of the chewing motion in a long-term relining.
Further, the relining silicone of commercial product 1 on the basis of EP-A-0 614 655 demonstrates a very high (not user-friendly) resistance to a manually implied force during the discharge from a cartridge. (See table 1, comparative tests.)
Favourably the relining silicone is metered and mixed by means of a hand-operated discharge gun from a cartridge having a static mixer. Here, it is important that the required resistance to a manually implied force necessary to discharge the relining silicone be as low as possible in order to ensure a user-friendly operation.
Under the mentioned conditions the relining silicone according to EP-A-0 614 655 (see commercial product 1) does not present a sufficiently long pot life such that the mimic motions of the pat
Bublewitz Alexander
Reber Jens-Peter
Kettenbach GmbH & Co. KG
Moore Margaret G.
LandOfFree
Relining for prostheses and process the manufacturing thereof does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Relining for prostheses and process the manufacturing thereof, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Relining for prostheses and process the manufacturing thereof will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3001034