Stable, cationically polymerizable/crosslinkable dental compositions having high filler contents

Abstract

Stable, highly filled cationic dental compositions useful for the production of dental prostheses and dental restoration materials contain: (1) at least one compound which is reactive cationically when activated, advantageously at least one UV-and cationically reactive oxirane-functionalized silicone;

• • (2) at least one dental filler, advantageously SiO₂; (3) at least one organic polymer or copolymer dispersant having an amine index less than or equal to 100 mg of potassium hydroxide per gram of dispersant, advantageously a polyurethane/acrylate copolymer or alkylammonium salt thereof; (4) at least one cationic photoinitiator, advantageously iodonium borate; and (5) optionally, at least one photosensitizer.

Description

BACKGROUND OF THE INVENTION 1. Technical Field of the Invention The present invention relates to dental compositions. More precisely, the dental compositions according to the present invention are useful for producing dental prostheses and for dental restoration. 2. Description of Background and / or Related and / or Prior Art The conventional dental compositions are typically epoxy resins or photopolymerizable silicones or free-radically polymerizable acrylate resins. These compositions further include particulate reinforcing fillers (e.g., of hydrophobicized silica), photoinitiators and optionally photosensitizers in the case of cationic compositions or free-radical initiators for the free-radical compositions, and indeed other functional additives such as pigments or stabilizers. After they have been mixed, these compositions are shaped and then photocrosslinked to a mass whose structure is like that of the teeth. The fact that the filler is composed of very fine particles (≈0....

AI Technical Summary

Benefits of technology

These dispersants make it possible to fluidify the material without opacifying it, while retaining very substantial stability in the compositions. As a result of this attribute of the invention it is possible to use very high levels of treated filler of very low particle size, namely ≧50%.

This technical solution is all the more advantageous in being economically viable and easy to implement.

It is likewise of interest to observe that this composition provides satisfaction in terms of limiting the shrinkage after polymerization / crosslinking, which is entirely appreciable in dental application.

Problems solved by technology

This is because the absorption capacity of the resin is limited.

The result is that the filler levels of such compositions rarely reach more than 45% by volume.

This is therefore to the detriment of the mechanical reinforcement function assigned to the particulate filler.

This particulate filler may also interact with the reactive functions of the (photo)polymerizable / crosslinkable species and may therefore underlie problems of instability of the dental composition.

These resins have the drawback of not being perfectly transparent to the actinic activating radiation of the UV-visible actinic polymerization, which is detrimental to the reaction kinetics and hence limits the possibilities of obtaining very thick photocrosslinked materials.

Silicone formulations of this kind are therefore unstable on storage of the compositions.

This is because the R—[—CO—(CH2)5—O—]n—PO3H2 dispersants are not suitable for the cationic compositions, in particular since they contain a significant acid residue, RPO3H2, which reacts in the presence of oxirane functions and is detrimental to the stability of the composition.

It is therefore apparent that the prior art provides no satisfactory solution to the twin problem of stabilizing dental compositions based on units which are polymerizable cationically under UV (oxiranes, for example) and dispersing sizable amounts of fillers in the resin.

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