最近導入されたダイヤモンド回転器具の性能と有効性。切削性、表面処理、洗浄性

Performance and efficacy of a recently introduced diamond rotary instrument: Cutting, surface preparation, and cleanability.

抄録

問題提起:

新規の回転式器具の切削効率と有効性，表面粗さ，および洗浄性の評価が不足している．

STATEMENT OF PROBLEM: Evaluation of the cutting efficiency and effectiveness, surface roughness, and cleanability of a novel rotary instrument is lacking.

目的:

本研究の目的は，コランダム微小球を含む最近導入されたダイヤモンド回転器具と従来の器具の切削効率と有効性を，歯の準備後の各器具の発熱量，表面粗さ，清掃性を評価することによって比較することである．

PURPOSE: The purpose of this in vitro study was to compare the cutting efficiency and effectiveness of a recently introduced diamond rotary instrument containing corundum microspheres with conventional instruments by evaluating the heat generated, surface roughness, and cleanability of each instrument after tooth preparations.

材料および方法:

健全な臼歯部（n=225）を用い，3種類のダイヤモンド歯科用回転器具（試験器具（TI），基準器具（RI），NTI器具（NI））の発熱量を測定し，切削効率と効果を評価した．30本の窩洞標本（27 mm）を作製し，歯髄室内に挿入した熱電対から熱変化量（ΔT）を測定した．ベニア調製後の象牙質基材の表面粗さは，走査型白色光干渉計と走査型電子顕微鏡の画像処理により求めた．また，TIとRIの清掃性を，グラム陽性またはグラム陰性の口腔内病原体で器具を汚染した後，従来の3つの消毒プロトコルの有効性を比較することによって判定した．熱変化量，表面粗さ，コロニー形成単位の平均値と標準偏差を95%信頼水準で算出し，1-way ANOVAを用いて統計的有意性を判定した（α=.05）．

MATERIAL AND METHODS: Sound molars (n=225) were used to evaluate cutting efficiency and effectiveness by measuring the heat generated by 3 diamond dental rotary instruments: test instrument (TI), reference instrument (RI), and NTI instrument (NI). Thirty cavity preparations (27 mm) were prepared, and the thermal change (ΔT) was determined from a thermocouple inserted in the pulp chamber. The surface roughness of the dentin substrate was determined after veneer preparations using scanning white-light interferometry and scanning electron microscope imaging. The cleanability of TI and RI was also determined by comparing the efficacy of 3 conventional disinfection protocols after contaminating the instrument with Gram-positive or Gram-negative oral pathogens. The mean and standard deviation values for thermal change, surface roughness, and colony forming units were calculated at a 95% confidence level, and 1-way ANOVA was used to determine statistical significance (α=.05).

結果:

NI装置が最も低い平均ΔT（1.47 ℃）を示した。TI (1.77 °C)とRI (1.85 °C)のグループは、統計的に類似した平均値を示した(P>.05)。表面粗さは，TI群が最も小さく（1.68μm），次いでRI群（1.87μm）であった（P<.001）．NIは最も高い表面粗さ（2.17μm）を示した（P<.001）．使用した消毒プロトコルは，生物種や洗浄液への曝露時間にかかわらず，RI群よりもTI群でより効果的であった（P<.001）．

RESULTS: The NI instrument had the lowest mean ΔT (1.47 °C). The TI (1.77 °C) and RI (1.85 °C) groups showed statistically similar means (P>.05). The TI presented the lowest surface roughness (1.68 μm), followed by the RI (1.87 μm) (P<.001). The NI resulted in the highest surface roughness (2.17 μm) (P<.001). The disinfection protocols used were more effective on the TI group than on the RI group regardless of organisms and time exposed to the cleaning solution (P<.001).

結論:

新型ダイヤモンドインスツルメントは，従来のダイヤモンドインスツルメントと比較して，同等の切削効率と有効性を示した．しかし，新型インスツルメントは，従来のダイヤモンド回転式インスツルメントと比較して，より滑らかな歯質形成が可能であり，洗浄が容易であった．

CONCLUSIONS: The novel diamond instrument demonstrated similar cutting efficiency and effectiveness when compared with conventional diamond instruments. However, the novel instrument produced smoother tooth preparations and was easier to clean than the conventional diamond rotary instruments.