CAD-CAM 數位義齒之人工齒列與基底材在加速老化及不同溶液浸泡下之顏色穩定性評估

Abstract

目的： 本研究旨在評估不同製程之義齒樹脂材料與市售人工齒列，於模擬口腔熱老化及日常飲品浸泡環境下之顏色穩定性，並探討製程方式、浸泡介質、義齒組成區域、人工齒列與義齒基底交界處，以及表面壓克力染劑處理對色差變化之影響。 材料與方法： 本研究選用傳統熱聚合、電腦輔助設計與電腦輔助製造（computer-aided design and computer-aided manufacturing，簡稱CAD-CAM）減法銑削及加法積層製造之義齒樹脂材料，並搭配市售人工齒列製作樣本。所有樣本先進行 55°C 蒸餾水熱老化 5 天後，再分別浸泡於咖啡、茶、柳橙汁及蒸餾水中28天，以模擬日常飲品造成之外源性染色。樣本依不同材料製程、人工齒列與義齒基底區域、平滑中央區域與交界處，以及是否施加壓克力染劑進行分組比較。 利用標準化影像擷取流程測量各組色彩變化，並依據CIELAB色彩空間測量其顏色變化 ΔE*ab 評估顏色穩定性，臨床可接受閾值設定為 ΔE*ab = 3.7。統計分析採用Wilcoxon符號排序、Mann-Whitney 及Kruskal-Wallis檢定，顯著水準設定為 p < 0.05，若Kruskal-Wallis檢定結果顯示各組間存在顯著差異，則進一步採用事後成對比較。 結果： 影像色彩擷取結果顯示，攝影設備具有良好穩定性（ICC = 0.8918），多數操作者之自我一致性亦表現良好；然而，不同操作者間之一致性僅達中等程度（ICC = 0.43358），顯示手動選點仍可能受到主觀判斷影響。所有實驗組別經熱老化後皆較初始狀態產生顯著色差變化（p < 0.0001），表示即使無外源性色素存在，熱與水分環境仍足以影響義齒樹脂材料之光學表現。不同製程材料間之顏色穩定性亦存在差異，整體而言，CAD-CAM 減法銑削材料表現最穩定，傳統熱聚合材料次之，加法積層製造材料較易產生明顯變色，其中部分加法積層製造組之 ΔE*ab 超過臨床可接受範圍（ΔE*ab > 3.7）。 不同浸泡介質對材料變色程度具有顯著影響，多數材料呈現咖啡與茶造成之色差最大，柳橙汁次之，蒸餾水最低之趨勢。咖啡與茶組多數試體之ΔE*ab超過臨床可接受閾值，柳橙汁組則多接近或略低於臨床可接受範圍，蒸餾水組之色差變化最小。 人工齒列與義齒基底在咖啡與茶介質中呈現不同變色反應，人工齒列區域普遍較義齒基底區域出現較大色差變化（p < 0.05）。此外，人工齒列與義齒基底交界處之色差值普遍高於平滑中央區域，且於咖啡與茶組中特別明顯（p < 0.05），顯示交界處可能因表面粗糙等因素而成為顏色劇烈變化之高風險區域。施加壓克力染劑之試體於部分咖啡、茶及柳橙汁組中呈現較低色差值（p < 0.05），顯示表面染劑在高染色風險環境下可能具有降低色素附著與滲透之保護效果。 結論： 本研究顯示，義齒材料之長期顏色穩定性受到熱老化、浸泡介質、材料製程、義齒組成區域、交界處形態及表面處理方式等多重因素共同影響。CAD-CAM 減法銑削材料整體具有較佳顏色穩定性，而加法積層製造材料對熱老化與外源性色素較為敏感。咖啡與茶為造成義齒材料變色之主要日常飲品介質，人工齒列與義齒基底交界處則為臨床上較易發生顏色劣化之區域。表面壓克力染劑於高染色風險環境下可能具有一定保護效果，未來仍需進一步結合表面粗糙度與微觀結構分析，以釐清其抗染色機制與臨床應用價值。

Purpose: This study aimed to evaluate the color stability of denture base resin materials fabricated using different manufacturing techniques and commercially available artificial denture teeth under simulated oral thermal aging and daily beverage immersion conditions. The effects of manufacturing technique, immersion medium, denture component region, tooth–denture base junction, and surface acrylic staining treatment on color change were investigated. Materials and Methods: Denture resin materials fabricated by conventional heat-polymerization, CAD-CAM subtractive milling, and additive manufacturing were used in combination with commercially available artificial denture teeth to prepare the specimens. All specimens were first subjected to thermal aging in distilled water at 55°C for 5 days, followed by immersion in coffee, tea, orange juice, or distilled water for 28 days to simulate extrinsic staining caused by daily beverages. The specimens were compared according to manufacturing technique, denture tooth and denture base regions, smooth central area and junction area, and the presence or absence of acrylic stain application. Color changes were measured using a standardized image acquisition protocol and evaluated according to the CIELAB color space using ΔEab. The clinically acceptable threshold was set at ΔEab = 3.7. Statistical analyses were performed using the Wilcoxon signed-rank test, Mann-Whitney U test, and Kruskal-Wallis test, with the significance level set at p < 0.05. When significant differences were detected by the Kruskal-Wallis test, post hoc pairwise comparisons were further conducted. Results: The image-based color acquisition showed good stability of the photographic setup (ICC = 0.8918), and most operators demonstrated good intra-rater reliability. However, the inter-rater reliability was only moderate (ICC = 0.43358), indicating that manual point selection may still be influenced by subjective judgment. All experimental groups showed significant color changes after thermal aging compared with the initial condition (p < 0.0001), suggesting that heat and moisture alone can affect the optical properties of denture resin materials even in the absence of extrinsic pigments. Differences in color stability were also observed among manufacturing techniques. Overall, CAD-CAM subtractive milled materials showed the best color stability, followed by conventional heat-polymerized materials, whereas additively manufactured materials were more prone to obvious color changes. Some additively manufactured groups exceeded the clinically acceptable threshold (ΔE*ab > 3.7). The immersion medium significantly affected the degree of discoloration. In most materials, coffee and tea produced the greatest color changes, followed by orange juice, while distilled water resulted in the lowest color change. Most specimens immersed in coffee and tea exceeded the clinically acceptable threshold, whereas those immersed in orange juice were generally close to or slightly below the acceptable range, and those immersed in distilled water showed the least discoloration. Denture teeth and denture base regions exhibited different staining responses in coffee and tea. The denture tooth region generally showed greater color changes than the denture base region (p < 0.05). In addition, the tooth-denture base junction generally exhibited higher ΔE*ab values than the smooth central area, especially in the coffee and tea groups (p < 0.05), indicating that the junction may be a high-risk area for pronounced color changes, possibly due to factors such as surface roughness. Specimens with acrylic stain showed lower color changes in some coffee, tea, and ornge juice groups (p < 0.05), suggesting that surface staining may provide a protective effect by reducing pigment adhesion and penetration under high-staining-risk conditions. Conclusion: The long-term color stability of denture materials is influenced by multiple factors, including thermal aging, immersion medium, manufacturing technique, denture component region, junction morphology, and surface treatment. CAD-CAM subtractive milled materials demonstrated better overall color stability, whereas additively manufactured materials were more sensitive to thermal aging and extrinsic staining. Coffee and tea were the major daily beverage media associated with denture material discoloration, and the tooth-denture base junction was identified as a clinically vulnerable area for esthetic deterioration. Surface acrylic staining may provide a certain protective effect under high-staining-risk conditions. Further studies incorporating surface roughness and microstructural analyses are needed to clarify its anti-staining mechanism and clinical applicability.