汎用デジタル機器を用いて製作した複製義歯 : 材料特性と臨床評価

目的：われわれが提案した汎用デジタル機器を用いた複製義歯製作法の有用性を示すために，使用するアクリロニトリル−ブタジエン−スチレン（ABS）共重合樹脂，ポリ乳酸（PLA）樹脂の細胞毒性試験，シリコーン印象材および常温重合レジンとの接着試験，使用感に関する主観的評価を行った．
方法：細胞毒性試験では，ABS樹脂とPLA樹脂の浸漬液を用いてマウスの線維芽細胞様細胞の細胞生存率を測定した．接着試験では，専用の保持体にそれぞれの試験片を固定し，シリコーン印象材および常温重合レジンを圧接した後に，万能試験機を用いて引張試験を行った．使用感の評価には，専用の評価票を作成し，PLA製の複製義歯を使用する術者に回答させた．
結果：細胞毒性試験では，ABS樹脂，PLA樹脂ともに72時間までの細胞生存率の低下は認められなかった．接着試験では，トレー用レジンと比較して両試料ともにシリコーン印象材への接着強さは低かった．常温重合レジンとの接着強さでは，PLA樹脂は低かったが，ABS樹脂では従来のトレー用レジンと同等の接着強さであった．術者による複製義歯使用感の評価結果としては，従来のアクリルレジン製の義歯とほとんど変わらない評価が得られた．
結論：三次元プリンターで製作した複製義歯における材料的，臨床的評価から本術式の有効性が示唆された．

Purpose: The purpose of this study was to investigate the validity of the process of duplicating complete dentures using general digital devices through the following tests: cytotoxicity test of materials used, adhesion test of materials to a silicone impression material and a self-curing resin, and questionnaires to operators on duplicate dentures in clinical situations.
Methods: The cell viability of mouse fibroblast-like cells in acrylonitrile- butadiene-styrene (ABS) and polylactic acid (PLA) were evaluated as a cytotoxicity test. The tensile strength between the silicone impression material/self-curing resin and ABS/ PLA specimen was measured as adhesive strength using a universal testing machine. Six practitioners who used duplicate PLA complete dentures in 7 patients were asked to evaluate the duplicate denture using the original questionnaire.
Results: The cytotoxicity test showed that the cell viabilities in ABS and PLA were similar to that in acrylic resin at the cell culture times of 24, 48 and 72 hours. The adhesion test showed that the adhesive strength between the ABS/PLA and silicone impression material was significantly lower than that between the conventional self-curing resin and silicone impression material. Although the adhesive strength between the PLA and self-curing resin was low, there was no significant difference between the ABS and self-curing resin. The results of the questionnaire showed that the duplicate denture made of PLA would be of similar value compared to the conventional duplicate denture made of acrylic resin.
Conclusions: The present study suggests that the duplicate complete dentures made by our proposed digital process are clinically effective.

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