JPS63255210A - Production of dental restoration material - Google Patents

Abstract

PURPOSE:To obtain the titled restoration material having short cure time and high crushing strength, harmless to dentine and firmly adhesive to the deficient part of dentine, by curing and crushing uncured calcium phosphate powder and mixing the crushed product with uncured calcium phosphate powder. CONSTITUTION:A calcium phosphate material (e.g. alpha- or beta-tricalcium phosphate and tetracalcium phosphate) is cured by hydration reaction under acidic condition and the produced calcium hydrate apatite is crushed to powder for seed crystal (having an average particle diameter of 3-100mum). The obtained powder is added to uncured calcium phosphate powder in an amount of 15-30wt.% based on the whole composition. The restoration material produced by the above process is preferably used in combination with a fluoride (preferably acidic calcium fluoride) at a Ca/F gram-atom ratio of 4.2-60. The formation of secondary dentine and the prevention of secondary caries can be expected by the combined use of the fluoride.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method of manufacturing a dental restorative material.

(Conventional technology) Dental restorative materials have traditionally included luting cements such as zinc phosphate cement, cements that can be applied to surfaces such as polycarboxylate cements and glass ionomer cements, and cements for root canal treatment. Root canal filling materials and the like have been proposed. However, the properties of these materials are clearly different from that of teeth, and they do not blend well with the tooth structure, so gaps are likely to form between the tooth structure and the restoration (filling material), causing the restoration to fall off (peeling off) and break. These materials are prone to breakage and have an extremely high possibility of secondary caries.Furthermore, these materials are insufficient in terms of toxicity to living organisms (pulp irritation, etc.) and operability.

On the other hand, the material obtained by kneading calcium phosphate materials with acid is preferable as a material because it is close to tooth structure, but the strength of the material obtained by simply kneading it with acid is 200 kg.
Only about f/c 2 can be obtained, which is extremely insufficient.

Therefore, with the aim of improving both biocompatibility and strength, dental restorative materials have been developed that combine inorganic materials such as apatite and α-tricalcium phosphate with a polymer of unsaturated carboxylic acid as a hardening agent. (Unexamined Japanese Patent Publication No. 58-8360
No. 5, No. 61-83107).

(Problems to be Solved by the Invention) However, even with dental restorative materials using polymers of unsaturated carboxylic acids as described above, depending on the application, biotoxicity is insufficient, which poses an important problem, and furthermore, a relatively large amount of polymerization may occur. Because it requires materials, there remain problems such as shrinkage during polymerization, short operating time, and deterioration of physical properties due to saliva.

Furthermore, when apatite is used, a decrease in physical properties (such as crushing strength) is unavoidable.

(Means for Solving the Problems) As a result of extensive research in order to overcome the drawbacks of the above-mentioned dental cement compositions, the present inventors found that fluoride was added to calcium phosphate-based materials, such as α-tricalcium phosphate. We discovered that by curing the α-calcium phosphate powder that had been added and hardened with acid, and using this as a seed crystal to harden the powder, we were able to shorten the hardening time and significantly increase the crushing strength. Based on this, the present invention has been completed.

That is, the present invention provides a method for producing a dental restorative material, which comprises curing unhardened calcium phosphate powder with an acid aqueous solution, and mixing a pulverized product of the hardened product with the unhardened calcium phosphate powder.

In the method of the present invention, the calcium phosphate material is first
It is hardened by a water utilization reaction under acidic conditions to produce calcium hydroxide apatite, which is used as a powder for seed crystals.

As the calcium phosphate material, α- and β-tricalcium phosphate, dicalcium phosphate, calcium phosphate, calcium phosphate, etc. are used.

Fluoride is preferably used in combination with this calcium phosphate material. Such fluorides include alkali metal salts of hydrofluoric acid such as sodium fluoride, lithium fluoride, potassium fluoride, cesium fluoride, and rubidium fluoride, ammonium fluoride, and acidic ammonium fluoride (NH
4F-HF), calcium fluoride, titanium fluoride, tin fluoride, etc. Slightly soluble fluorides can also be used, and fluorides of different metals are also preferably used, but especially calcium fluoride and acidic fluorides can be used. Ammonium fluoride is preferably used.

When using fluoride in this way, it is preferable to add Ca/F so that the gram atom ratio is 4.2 to 60.

The pH of the kneading solution used to harden the powder of this calcium phosphate material is preferably 3.5 to 6.5. As the kneading solution, for example, a 1M citric acid solution adjusted to pH 5 with ammonia wood is used, but glycolic acid, phosphorus A water-soluble acid such as acid or malic acid may be used.

At this time, the weight ratio of powder (P)/mixture (L) was 3.1.
It is preferable to carry out the reaction in the range of ~4.0. The powder and the kneading liquid react gently, and the pH immediately after kneading becomes neutral and crystal growth is observed. It was found that this substance had been transformed into fluoroapatite after 8 hours when fluoride was used in combination.

The apatite crystals thus obtained are crushed to uniform particle size and mixed with calcium phosphate powder to form the powder part of the dental restorative material of the present invention.

The particle size of the powder obtained by crushing and hardening apatite crystals in the powder part made of this mixture is not particularly limited, but the average particle size is 3 to loop pm, and the content is 0.1 in the mixture.
~50% by weight, preferably 15-30% by weight.

Further, as the calcium phosphate obtained by crushing this apatite crystal and hardening it as a seed crystal, the same calcium phosphate as used in the preparation of the above-mentioned apatite crystal can be used.

The powder mixture of calcium phosphate thus obtained contains:
Zinc oxide, calcium oxide, silicon oxide, magnesium oxide, etc. may be added. Zinc oxide is particularly effective in improving fluidity, and a small amount of zinc oxide is added to areas where fluidity is expected such as root canal filling. This allows you to change the consistency at will.

The calcium phosphate powder mixture thus obtained can then be kneaded in a conventional manner and used for dental restorations.

In this case, it is preferable to use fluoride in combination as in the case of preparing the seed crystals, and it is preferable to use the same acid used to prepare the seed crystals as the kneading liquid.
The above seed crystal-containing composition is kneaded so that L=3.1 to 6. It was found that the hardened material created by kneading transforms into fluoroapatite over time.

The hardening time of the dental restorative material obtained in this way after kneading is 1/2 to 1/2 that of the case where seed crystals are not used.
4, the compressive strength is improved by 2 to 3 times.

(Effects of the invention) The dental restorative material obtained by the method of the present invention has a short curing time, and the crushing strength of the hardened material has been increased to about 700 kgf/c2. It has the excellent effect of closely adhering to the defective area and metastasizing to apatite, which resembles tooth structure, within one hour.

In addition, the dental restorative material obtained by the method of the present invention is different from the conventional powder-liquid type, as crystal seeds of kneaded hardened material are added to the powder, so it hardens quickly and crystal growth progresses rapidly. The restorative material and tooth structure adhere to each other in a crystal structure and become homogeneous. Therefore, it is possible to block external stimuli and prevent bacterial invasion.

Furthermore, in the method of the present invention, the formation of secondary dentin and the prevention of secondary caries can be expected by incorporating fluorine into the restorative material. In addition, dentinal tubule exudate, 1 body fluid, etc. (saliva)
The strength is improved.

Furthermore, by appropriately adding a small amount of zinc oxide or the like to the calcium phosphate powder, the operability can be improved, and it can be widely applied to the field of orthopedics, such as alveolar bone repair materials and ridge formation.

(Example) Next, the present invention will be explained in more detail based on examples.

Example 1 α-tricalcium phosphate (α-TCP) of Ca
F20.13aol,NH4F-)(FO,20a
1.0g of powder mixed with ol was adjusted to pH 5 with aqueous ammonia.
,0.23 dl of a citric acid aqueous solution having a concentration of 1,0+++ol adjusted to 0.0 was used for curing. This hardened raw material was pulverized to an average particle size of 70ILm, and α-TCP powder 1. Mix 0.3g to Og and adjust the pH to 5.0 with aqueous ammonia.
The mixture was kneaded and hardened with i.

Example 2 1.0 g of α-TCP powder was cured with 0.24 d of an aqueous glycolic acid solution of 1.5 mol/gj adjusted to pH 4.0 with aqueous ammonia. This hardened product was pulverized to an average particle size of TOgm, and 0.0 gm was obtained per 1.0 g of a-TCP powder.
1, which was mixed with 2g and adjusted to pH 4.0 with ammonia water.
The mixture was kneaded with a 5 mol aqueous citric acid solution o, z+m and hardened.

Comparative Example 1 1.3 g of α-TCP powder was kneaded with 0.29 ml of a 1.0 mol 15 degree citric acid aqueous solution adjusted to pH 5.0 with aqueous ammonia and hardened.

Comparative Example 2 a-T CP 1. osol with CaF2 0.
1.3g of powder mixed with 13aol, N H4F-HFO, 20aol was adjusted to pH 5.0 with aqueous ammonia.
Prepared 1, (1■01 concentration citric acid aqueous solution 0.29d
The mixture was kneaded and hardened.

The physical properties and solidification time of the cured products obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were measured, and the results are shown in Table 1 below.

From the results in Table 1, compared to the one obtained in Comparative Example 1.2, the one obtained in Example 1.2 had an extremely short solidification time, good adhesive strength, and significantly higher crushing strength and Knoop hardness. I understand.

Claims (1)

[Claims] A method for producing a dental restorative material, which comprises curing unhardened calcium phosphate powder with an acid aqueous solution, and mixing a pulverized product of the hardened product with the unhardened calcium phosphate powder.