新世代義歯床用材料の表面粗さと洗浄後の色調変化に及ぼす研磨剤および義歯洗浄剤の影響

Effect of polishing and denture cleansers on the surface roughness of new-generation denture base materials and their color change after cleansing.

抄録

目的:

アディティブ法，サブトラクティブ法および従来法で作製された新世代義歯床用材料の表面粗さ（R）に及ぼす研磨および義歯洗浄剤の影響と洗浄後の色調変化を評価する．

PURPOSE: To evaluate the effect of polishing and denture cleansers on the surface roughness (R ) of new-generation denture base materials that are additively, subtractively, and conventionally fabricated, while also assessing their color change after cleansing.

材料および方法:

5種類の義歯床材料（サブトラクティブ法で作製したナノグラフェン強化プレポリメチルメタクリレート（PMMA）（SM-GC），サブトラクティブ法で作製したプレポリメチルメタクリレート（PMMA）（SM-PM），アディティブ法で作製した2種類の義歯床用レジン（AM-DT，AM-ND），およびヒートポリマー法で作製したPMMA（CV）（n=30）から150個の円板状試験片（Ø10×2mm）を作製した．試料のRは通常のラボ研磨の前後で測定し，色座標は研磨後に測定した．次に、試料を義歯洗浄剤に基づいて3つのサブグループに分けた：蒸留水、1％次亜塩素酸ナトリウム（NaOCl）、および発泡性錠剤（n＝10）。20日間にわたり9回の洗浄を行った後、R座標と色座標を再測定した。CIEDE2000 式を用いて色差（ΔE ）を算出した。二元配置分散分析（ANOVA）を使用して、洗浄前（n = 30）と洗浄後（n = 10）のR値を分析し、反復測定ANOVAを使用して、各義歯洗浄剤（n = 10）内の材料-点ペアのRを分析した。 義歯洗浄後のΔEデータも二元配置分散分析（n = 10）を使用して分析した（α = 0.05）。

MATERIAL AND METHODS: One hundred and fifty disk-shaped specimens (Ø10 × 2 mm) were prepared from five denture base materials (one subtractively manufactured nanographene-reinforced prepolymerized polymethylmethacrylate (PMMA) (SM-GC), one subtractively manufactured prepolymerized PMMA (SM-PM), two additively manufactured denture base resins (AM-DT and AM-ND), and one heat-polymerized PMMA (CV) (n = 30). The R of the specimens was measured before and after conventional laboratory polishing, while color coordinates were measured after polishing. Specimens were then divided into three subgroups based on the denture cleanser: distilled water, 1% sodium hypochlorite (NaOCl), and effervescent tablet (n = 10). The R and color coordinates were remeasured after nine cleansing cycles over a period of 20 days. The CIEDE2000 formula was used to calculate the color differences (ΔE ). Two-way analysis of variance (ANOVA) was used to analyze the R values before (n = 30) and after (n = 10) cleansing, while repeated measures ANOVA was used to analyze the R of material-time point pairs within each denture cleanser (n = 10). ΔE data after denture cleansing was also analyzed by using two-way ANOVA (n = 10) (α = 0.05).

結果:

研磨前のRは各材料間で有意差があった．SM-GCとSM-PMのR値が最も低く、AM-NDのR値が最も高かった（P<0.001）。研磨により、すべての材料のRが有意に減少し（P<0.001）、研磨後は材料間のRの差は有意ではなかった（P≥0.072）。義歯洗浄剤にかかわらず、異なる時点を考慮すると、AM-DT、AM-ND、CVのRは研磨前が最も高かった（P<0.001）。洗浄後は、洗浄剤にかかわらず、AM-NDがすべての材料の中で最も高いRを示した（P≦0.017）。AM-DTは蒸留水を用いた場合、SM-PMよりもRが高く（P = 0.040）、NaOClを用いた場合、SM-GC、SM-PM、CVよりもRが高かった（P<0.001）。洗浄剤の種類はAM-DT、AM-ND、CVのRに有意な影響を与えた。AM-DTでは、NaOClが最も高いRを示し、錠剤が最も低いRを示した（P≦0.042）。AM-NDでは、蒸留水が最も低いRを示した（P≦0.024）。CVでは、錠剤は蒸留水よりも低いRを示した（P=0.009）。色の変化は材料によって異なっていた。蒸留水を用いた場合、SM-GCはSM-PMおよびAM-DTよりもΔEが高かった（P≦0.034）。NaOClを使用した場合、AM-NDはSM-GC、SM-PMおよびAM-DTよりもΔEが高く、CVおよびSM-GCはSM-PMおよびAM-DTよりもΔEが高かった（P≦0.039）。最後に、錠剤を使用した場合、AM-NDとCVは最も高いΔEを示したが、AM-DTはSM-GCよりも低いΔEを示した（P≦0.015）。

RESULTS: Before polishing, R varied significantly among the materials. SM-GC and SM-PM had the lowest and AM-ND the highest R values (P < 0.001). Polishing significantly reduced R of all materials (P < 0.001), and after polishing, R differences among materials were nonsignificant (P ≥ 0.072). Regardless of the denture cleanser, the R of AM-DT, AM-ND, and CV was the highest before polishing when different time points were considered (P < 0.001). After cleansing, AM-ND had the highest R of all the materials, regardless of the cleanser (P ≤ 0.017). AM-DT had higher R than SM-PM when distilled water (P = 0.040) and higher R than SM-GC, SM-PM, and CV when NaOCl was used (P < 0.001). The type of cleanser significantly influenced the R of AM-DT, AM-ND, and CV. For AM-DT, NaOCl led to the highest R and the tablet led to the lowest R (P ≤ 0.042), while for AM-ND, distilled water led to the lowest R (P ≤ 0.024). For CV, the tablet led to lower R than distilled water (P = 0.009). Color change varied among the materials. When distilled water was used, SM-GC had higher ΔE than SM-PM and AM-DT (P ≤ 0.034). When NaOCl was used, AM-ND had higher ΔE than SM-GC, SM-PM, and AM-DT, while CV and SM-GC had higher ΔE than SM-PM and AM-DT (P ≤ 0.039). Finally, when the tablet was used, AM-ND and CV had the highest ΔE , while AM-DT had lower ΔE than SM-GC (P ≤ 0.015).

結論:

試験した材料は、研磨前には許容できない表面粗さ（>0.2μm）を有していた。研磨後の粗さは有意に減少した（<0.2μm）。義歯洗浄剤は材料の表面粗さに有意な影響を与えず、粗さは洗浄後も臨床的に許容できる粗さ（<0.2μm）であった。既報の色調閾値を考慮すると、AM-NDとCVは義歯洗浄剤にかかわらず許容できない色調変化を示し、SM-GC、SM-PM、AM-DTは発泡性錠剤により知覚できるが許容できる色調変化を示した。

CONCLUSIONS: The tested materials had unacceptable surface roughness (>0.2 μm) before polishing. Roughness decreased significantly after polishing (<0.2 μm). Denture cleansers did not significantly affect the surface roughness of the materials, and roughness remained clinically acceptable after cleansing (<0.2 μm). Considering previously reported color thresholds, AM-ND and CV had unacceptable color change regardless of the denture cleanser, and the effervescent tablet led to perceptible, but acceptable color change for SM-GC, SM-PM, and AM-DT.