伝統的手法とCAD/CAM技術によって製作された義歯の適合性の比較

Comparison of Fit of Dentures Fabricated by Traditional Techniques Versus CAD/CAM Technology.

抄録

目的:

3つの方法で製作された義歯床の収縮率を比較すること。CAD/CAM、圧縮成形、射出成形の3つの方法で製作した義歯床の収縮率を比較する。また、アーチの形態と口蓋の深さの影響も検証した。

PURPOSE: To compare the shrinkage of denture bases fabricated by three methods: CAD/CAM, compression molding, and injection molding. The effect of arch form and palate depth was also tested.

材料および方法:

電子ビーム溶解法（EBM）により，テーパー型，卵型，角型アーチと浅い口蓋，中くらいの口蓋，深い口蓋の組み合わせで9個のチタンキャストを作製した．各鋳造体から3個のポリビニルシロキサン印象材を作製し，各製造法とも27個の義歯を作製した．圧縮成形義歯はLucitone 199 poly methyl methacrylate（PMMA），射出成形義歯はIvobase社のHybrid Pink PMMAで作製した．CAD/CAMでは，Avadent社のLight PMMAを用いて義歯床を設計し，削り出した．義歯とマスターキャストの隙間を測定するために，義歯のインタリオにシリコーン複製材を入れ，チタン製のマスターキャストを加圧して装着し，シリコンをトリミングして回収した．1つの義歯につき3回測定し，合計243回測定した．各測定値は，重量を測定し，各歯列の表面積に合わせ，各歯列の平均値と標準偏差を算出した．

MATERIALS AND METHODS: Nine titanium casts, representing combinations of tapered, ovoid, and square arch forms and shallow, medium, and deep palate depths, were fabricated using electron beam melting (EBM) technology. For each base fabrication method, three poly(vinyl siloxane) impressions were made from each cast, 27 dentures for each method. Compression-molded dentures were fabricated using Lucitone 199 poly methyl methacrylate (PMMA), and injection molded dentures with Ivobase's Hybrid Pink PMMA. For CAD/CAM, denture bases were designed and milled by Avadent using their Light PMMA. To quantify the space between the denture and the master cast, silicone duplicating material was placed in the intaglio of the dentures, the titanium master cast was seated under pressure, and the silicone was then trimmed and recovered. Three silicone measurements per denture were recorded, for a total of 243 measurements. Each silicone measurement was weighed and adjusted to the surface area of the respective arch, giving an average and standard deviation for each denture.

結果:

製造方法の比較により，統計的に有意な差が認められた（p=0.0001）．平均値の比を用いると，圧縮成形は射出成形およびCAD/CAMに比べて平均41～47％スペースが大きかった．アーチ/口蓋形状の比較では，統計的に有意な差（p=0.023）が認められ，浅い口蓋形状は圧縮成形でより多くのスペースが確保された．卵形の浅い形態では、CAD/CAMと圧縮成形が射出成形よりもスペースが広いことが示された。

RESULTS: Comparison of manufacturing methods showed a statistically significant difference (p = 0.0001). Using a ratio of the means, compression molding had on average 41% to 47% more space than injection molding and CAD/CAM. Comparison of arch/palate forms showed a statistically significant difference (p = 0.023), with shallow palate forms having more space with compression molding. The ovoid shallow form showed CAD/CAM and compression molding had more space than injection molding.

結論:

全体として，射出成形とCAD/CAMによる作製法は同じように適合度の高い義歯を作製し，どちらも圧縮成形よりも適合度が高かった．浅い口蓋は中口蓋や深口蓋よりも収縮の影響を受けやすいと思われる．浅い卵形アーチは，CAD/CAMや圧縮成形に比べ，射出成形の使用が有効であるように思われた．

CONCLUSION: Overall, injection molding and CAD/CAM fabrication methods produced equally well-fitting dentures, with both having a better fit than compression molding. Shallow palates appear to be more affected by shrinkage than medium or deep palates. Shallow ovoid arch forms appear to benefit from the use of injection molding compared to CAD/CAM and compression molding.