【発明の詳細な説明】[Detailed description of the invention]
産業上の利用分野
本発明は、熱可塑性樹脂の圧縮成形法により義
歯床を製作する改良された方法に関する。
従来の技術
本発明者らは、さきに熱可塑性樹脂の圧縮成形
法による義歯床の製作法を開発し、特許出願を行
なつた（特開昭58−1439号）。その方法は、下部
フラスコ内の石こう型の上に熱可塑性樹脂材料を
のせて加熱軟化させ、ついで上部フラスコ内の石
こう型をその上に合わせて圧縮成形を行ない義歯
床を製作する方法である。
本発明者は、研究の結果、上記圧縮成形法にお
いて、フラスコ内の石こう型の上に熱可塑性樹脂
材料をのせて熱風で軟化させる場合には、石こう
型の熱伝導性が低いため、熱風の当る表面のみが
軟化し、樹脂材料内部もしくは、石こう型と接触
した樹脂面は軟化しにくく、均一な軟化状態が得
られず、不均一な軟化状態で圧縮成形を行うと、
樹脂の十分な流動が得られないため、充填性の良
好な義歯床が得られないという欠点を有すること
がわかつた。
発明が解決しようとする問題点
本発明の目的は、上記欠点を改良し安定的に均
一な軟化状態が得られ、良好な結果、すなわち、
人工歯が強固に植えられ、凹みがなく、良好な充
填性を有する義歯床が得られる方法を提供するこ
とである。
問題を解決するための手段
本発明の特徴とするところは、下部フラスコ内
の石膏型の上に熱可塑性樹脂材料をのせて加熱軟
化させ、ついで上部フラスコ内の石膏型をその上
に合わせて圧縮成形を行ない義歯床を製作する方
法において、該熱可塑性樹脂材料を3μm以上の波
長を主体とする遠赤外線で加熱することにある。
本発明において使用される熱可塑性樹脂として
は該成形方法で熱的に劣化を起さず、かつ適度な
粘度を有し、良好な賦型性をもち、歯肉に近似し
た色に着色が可能で、適度な剛性と耐湿性を有
し、かつ使用時にストレスクラツクを起さない強
靱性を備えた樹脂であることが要求される。した
がつて、ポリスチレン、ポリメチルメタクリレー
ト、ポリメチルペンテン−１、透明ナイロン、ポ
リカーボネート、ポリアリレート、ポリエステル
カーボネート、ポリエチレンテレフタレート、透
明ABS、ポリサルホン系樹脂などが使用される
が、特にポリサルホン、ポリエーテルサルホンな
どポリサルホン系の樹脂が耐湿性、剛性、耐スト
レスクラツキング性などにすぐれており、好まし
い。本発明で好ましい態様として使用されるポリ
サルホン系樹脂はアリーレン単位がエーテルおよ
びスルホン結合と共に無秩序にまたは秩序正しく
位置するポリアリーレンポリエーテルポリサルホ
ンとして定義される。たとえば
の構造を有するUCC製ポリサルホンUdel
や
FIELD OF INDUSTRIAL APPLICATION The present invention relates to an improved method for producing denture bases by compression molding of thermoplastic resins. Prior Art The present inventors previously developed a method for manufacturing a denture base by compression molding a thermoplastic resin, and filed a patent application (Japanese Patent Application Laid-open No. 1439/1983). The method is to place a thermoplastic resin material on top of the plaster mold in the lower flask and heat it to soften it, then fit the plaster mold in the upper flask over it and perform compression molding to produce a denture base. As a result of research, the present inventor found that in the above-mentioned compression molding method, when placing a thermoplastic resin material on top of a plaster mold in a flask and softening it with hot air, since the thermal conductivity of the plaster mold is low, Only the surface that comes into contact with the resin material softens, and the inside of the resin material or the resin surface that comes into contact with the plaster mold is difficult to soften, and if a uniform softened state is not obtained and compression molding is performed in an unevenly softened state,
It has been found that this method has the disadvantage that a denture base with good filling properties cannot be obtained because the resin cannot flow sufficiently. Problems to be Solved by the Invention An object of the present invention is to improve the above-mentioned drawbacks, to obtain a stable and uniform softened state, and to achieve good results, namely:
To provide a method for obtaining a denture base in which artificial teeth are firmly planted, without dents, and having good filling properties. Means for Solving the Problem The present invention is characterized in that a thermoplastic resin material is placed on top of the plaster mold in the lower flask, heated and softened, and then the plaster mold in the upper flask is placed over it and compressed. In the method of manufacturing a denture base by molding, the thermoplastic resin material is heated with far infrared rays mainly having a wavelength of 3 μm or more. The thermoplastic resin used in the present invention is one that does not undergo thermal deterioration during the molding method, has an appropriate viscosity, has good moldability, and can be colored to resemble the color of the gums. The resin is required to have appropriate rigidity, moisture resistance, and toughness that does not cause stress cracks during use. Therefore, polystyrene, polymethyl methacrylate, polymethylpentene-1, transparent nylon, polycarbonate, polyarylate, polyester carbonate, polyethylene terephthalate, transparent ABS, polysulfone resins, etc. are used, but in particular polysulfone, polyethersulfone Polysulfone resins such as Polysulfone resins are preferred because they have excellent moisture resistance, rigidity, and stress cracking resistance. The polysulfone resin used as a preferred embodiment in the present invention is defined as a polyarylene polyether polysulfone in which arylene units are located in a disordered or ordered manner with ether and sulfone bonds. for example UCC polysulfone Udel with the structure
【式】の構造を有
するICI製のポリエーテルサルホンVlctrex
が
挙げられる。
本発明に使用される熱可塑性樹脂材料の形状は
特に限定されない。該熱可塑性樹脂からなる粒
状、板状、棒状いずれでもよいが、歯列弓に近似
のＵ字状または周縁に歯列弓に近似のＵ字状の肉
厚部を有する板状の場合に、より安定的に均一な
軟化状態が得られ、良好な義歯床が得られ好まし
い。
本発明において使用される3μm以上の波長を主
体とする遠赤外線は、例えば金属発熱線をセラミ
ツクの内部に埋めこんだ遠赤外線ヒータ、暗赤外
線ヒータと呼ばれているヒータなどを適用し、得
ることができる。
日本碍子社製のインフラスタイン（商品名）な
どがそれに該当する。
一般に熱可塑性樹脂の加熱に使用されている赤
外線ヒータ（赤外線ランプ等）は、その波長が
0.75〜2μm程度で可視光の波長に近く、近赤外線
と呼ばれているが、このような波長の赤外線で
は、該熱可塑性樹脂が前記圧縮成形に適した十分
な軟化状態をとり得ず、良好な義歯床が得られな
い。
本発明において使用される遠赤外線はさらにそ
の波長が３〜10μmの時一層該樹脂の加熱効果が
高く、短時間で圧縮成形に適した軟化状態が安定
的に得られるため好ましい。
さらに、上記遠赤外線の輻射に、熱風循環によ
る加熱方式を併用することによつて一層安定的、
効果的な加熱軟化が可能となるため、より好まし
い。
作 用
本発明は熱可塑性樹脂材料を用いて圧縮成形で
義歯床を得る際、該熱可塑性樹脂材料を3μm以
上、好ましくは３〜10μmの波長を主体とする遠
赤外線で加熱することにより、放射される遠赤外
線の波長と該樹脂の赤外線吸収特性がよく対応し
ているため、熱吸収性に優れ、短時間で該圧縮成
形に適した軟化状態が得られるものと推定され
る。
以下、実施例により本発明を具体的に説明する
が、これは好適な態様の例示であつて本発明は実
施例の範囲に限定されるものではない。
実施例
義歯床ワツクス模型の埋設されたフラスコを加
熱し、ワツクスを軟化、流ろうさせた後、フラス
コ下部の石膏型上に義歯床形成用として、ポリエ
ーテルサルホン（ICI製Victrex
4100G）の歯肉
様に着色されたＵ字型成形品を位置させ、遠赤外
線の放射により該Ｕ字型成形品を加熱軟化させ
た。
遠赤外線は該Ｕ字型成形品の上方10cmの位置
に、日本碍子社製 インフラスタインＡヒータ
（３〜7μmを主体とする遠赤外線）を２つ水平に
取付け、表面温度550℃に設定し、５分間放射さ
せた。
該成形品を軟化させた後、圧縮成形機にかけて
圧縮成形し、その後自然冷却させた。冷却後、上
下フラスコを分離し、石膏型を分割し、義歯床成
形品を取り出した。
該義歯床成形品はずみずみまで完全に樹脂が充
填されており、肉厚部においてもひけが認められ
ず、義歯床ワツクス模型に忠実な肉厚、寸法を有
する良好なものであつた。
比較例 １
実施例の遠赤外ヒータ用いるかわりに遠赤線ラ
ンプ真空理工(株)社製 ゴールドイメージ炉
RHL−Ｐ（1.15〜2.0μmにピーク値をもつ赤外線）
を用いて実施例と同様の成形を行なつたが、20分
間加熱してもＵ字型成形品の軟化が不十分であ
り、圧縮成形後義歯床成形品を取り出したとこ
ろ、樹脂の充填性が不十分であり、充填不足の成
形品しか得られなかつた。
比較例 ２
実施例の遠赤外ヒータを用いるかわりに350℃
の熱風を使用する以外は実施例と同様の成形を行
なつたが、熱風の当る表面が軟化するが、樹脂材
料内部もしくは石こう型と接触した樹脂面が軟化
しにくく、圧縮成形後義歯床を取り出したところ
充填不足とともに溶融むらにもとずく外観不良現
象が認められた。
発明の効果
以上に述べたように、本発明は熱可塑性樹脂を
3μm以上の波長を主体とする遠赤外線で加熱軟化
させ、圧縮成形で義歯床を得る方法であるので以
下の効果を有する。
(1) 該熱可塑性樹脂材料が表面のみならず内部ま
で均一に短時間に加熱されるため、樹脂の過熱
劣化、軟化不足に基く変色、物性低下、充填不
足、ひけなどの不良現象が発生せず、安定的に
均一な義歯床成形品が効率よく得られる。
(2) 該樹脂材料が位置する下石膏型も均一に加熱
されるため、石膏型全体を適正温度に維持させ
ることができ、石膏型の強度、石膏型と該樹脂
材料との密着性、成形後の分離性などが、場所
による大きな性質のバラツキなく成形でき、よ
り安定的に歪の少ない義歯床が得られるという
効果も有する。
(3) 石膏型を内蔵する金属製フラスコは、該遠赤
外線の吸収が少ないためと思われるが高温熱風
で加熱する場合に比べ、温度の上昇が小さい。
したがつて、該樹脂材料が圧縮成形に適した十
分な軟化状態にあつても、金属製フラスコの温
度が低いため、取扱いが極めて容易であり、作
業性、安全性が飛躍的に向上するという効果も
奏する。One example is polyether sulfone Vlctrex manufactured by ICI, which has the structure of [Formula]. The shape of the thermoplastic resin material used in the present invention is not particularly limited. The thermoplastic resin may be in the form of particles, plates, or rods, but in the case of a U-shape similar to a dental arch or a plate having a thick U-shape similar to a dental arch on the periphery, It is preferable because a more stable and uniform softening state can be obtained and a good denture base can be obtained. The far infrared rays mainly having a wavelength of 3 μm or more used in the present invention can be obtained by applying, for example, a far infrared heater in which a metal heating wire is embedded inside ceramic, a heater called a dark infrared heater, etc. I can do it. Infrastein (product name) manufactured by Nippon Insulators falls under this category. The wavelength of infrared heaters (infrared lamps, etc.) generally used to heat thermoplastic resins is
It has a wavelength of about 0.75 to 2 μm, which is close to the wavelength of visible light, and is called near-infrared rays. However, with infrared rays of such a wavelength, the thermoplastic resin cannot be softened sufficiently to be suitable for compression molding, and it is not good. A suitable denture base cannot be obtained. The far infrared rays used in the present invention have a wavelength of 3 to 10 μm, which is preferable because the heating effect on the resin is even higher and a softened state suitable for compression molding can be stably obtained in a short time. Furthermore, by combining the above-mentioned far-infrared radiation with a heating method using hot air circulation, the
This is more preferable because it enables effective heating and softening. Function The present invention, when obtaining a denture base by compression molding using a thermoplastic resin material, heats the thermoplastic resin material with far infrared rays mainly having a wavelength of 3 μm or more, preferably 3 to 10 μm. Since the wavelength of the far infrared rays used in the resin corresponds well with the infrared absorption characteristics of the resin, it is presumed that the resin has excellent heat absorption properties and that a softened state suitable for the compression molding can be obtained in a short time. Hereinafter, the present invention will be specifically explained with reference to Examples, but these are merely illustrative of preferred embodiments, and the present invention is not limited to the scope of the Examples. Example After heating the flask in which the denture base wax model was embedded to soften and flow the wax, polyether sulfone (Victrex 4100G manufactured by ICI) was placed on the plaster mold at the bottom of the flask for denture base formation. A colored U-shaped molded product was placed in the same position, and the U-shaped molded product was heated and softened by far-infrared radiation. For far infrared rays, two Infrastein A heaters manufactured by Nippon Insulators (far infrared rays mainly in the range of 3 to 7 μm) were installed horizontally at a position 10 cm above the U-shaped molded product, and the surface temperature was set at 550°C. It was allowed to irradiate for 5 minutes. After softening the molded product, it was compression molded using a compression molding machine, and then allowed to cool naturally. After cooling, the upper and lower flasks were separated, the plaster mold was divided, and the denture base molded product was taken out. The denture base molded product was completely filled with resin from top to bottom, no sink marks were observed even in the thick wall part, and the product had a good wall thickness and dimensions that were faithful to the denture base wax model. Comparative Example 1 Instead of using the far-infrared heater of the example, a far-infrared lamp was used, and a gold image furnace manufactured by Shinku Riko Co., Ltd.
RHL-P (infrared rays with a peak value between 1.15 and 2.0 μm)
Molding was carried out in the same manner as in the example using the same molding method as in the example, but even after heating for 20 minutes, the U-shaped molded product was not sufficiently softened, and when the denture base molded product was taken out after compression molding, the filling properties of the resin were was insufficient, and only molded products with insufficient filling could be obtained. Comparative example 2 350℃ instead of using the far infrared heater of the example
Molding was carried out in the same manner as in Example except that hot air of When taken out, poor appearance was observed due to insufficient filling and uneven melting. Effects of the Invention As stated above, the present invention uses thermoplastic resin.
This is a method of heating and softening with far infrared rays mainly having a wavelength of 3 μm or more and obtaining a denture base by compression molding, so it has the following effects. (1) Since the thermoplastic resin material is heated not only on the surface but also inside the material uniformly and in a short time, defects such as overheating deterioration of the resin, discoloration due to insufficient softening, deterioration of physical properties, insufficient filling, and sink marks occur. Therefore, a stable and uniform denture base molded product can be obtained efficiently. (2) Since the lower plaster mold where the resin material is located is also heated uniformly, the entire plaster mold can be maintained at an appropriate temperature, which improves the strength of the plaster mold, the adhesion between the plaster mold and the resin material, and the moldability. It also has the effect that it can be molded without large variations in properties depending on location, such as subsequent separation, and that a more stable denture base with less distortion can be obtained. (3) A metal flask with a built-in plaster mold has a smaller temperature rise than when heated with high-temperature hot air, probably because it absorbs less of the far-infrared rays.
Therefore, even when the resin material is in a sufficiently softened state suitable for compression molding, the temperature of the metal flask is low, making it extremely easy to handle, dramatically improving workability and safety. It is also effective.