Alshali Ruwaida Z, Salim Nesreen A, Satterthwaite Julian D, Silikas Nick
School of Dentistry, The University of Manchester, Higher Cambridge Street, Manchester, UK; Department of Oral and Maxillofacial Rehabilitation, King Abdulaziz University, Jeddah, Saudi Arabia.
Prosthodontic Department, University of Jordan, Amman, Jordan.
J Dent. 2015 Feb;43(2):209-18. doi: 10.1016/j.jdent.2014.12.004. Epub 2014 Dec 13.
To measure bottom/top hardness ratio of bulk-fill and conventional resin-composite materials, and to assess hardness changes after dry and ethanol storage. Filler content and kinetics of thermal decomposition were also tested using thermogravimetric analysis (TGA).
Six bulk-fill (SureFil SDR, Venus bulk fill, X-tra base, Filtek bulk fill flowable, Sonic fill, and Tetric EvoCeram bulk-fill) and eight conventional resin-composite materials (Grandioso flow, Venus Diamond flow, X-flow, Filtek Supreme Ultra Flowable, Grandioso, Venus Diamond, TPH Spectrum, and Filtek Z250) were tested (n=5). Initial and 24h (post-cure dry storage) top and bottom microhardness values were measured. Microhardness was re-measured after the samples were stored in 75% ethanol/water solution. Thermal decomposition and filler content were assessed by TGA. Results were analysed using one-way ANOVA and paired sample t-test (α=0.05).
All materials showed significant increase of microhardness after 24h of dry storage which ranged from 100.1% to 9.1%. Bottom/top microhardness ratio >0.9 was exhibited by all materials. All materials showed significant decrease of microhardness after 24h of storage in 75% ethanol/water which ranged from 14.5% to 74.2%. The extent of post-irradiation hardness development was positively correlated to the extent of ethanol softening (R(2)=0.89, p<0.001). Initial thermal decomposition temperature assessed by TGA was variable and was correlated to ethanol softening.
Bulk-fill resin-composites exhibit comparable bottom/top hardness ratio to conventional materials at recommended manufacturer thickness. Hardness was affected to a variable extent by storage with variable inorganic filler content and initial thermal decomposition shown by TGA.
The manufacturer recommended depth of cure of bulk-fill resin-composites can be reached based on the microhardness method. Characterization of the primary polymer network of a resin-composite material should be considered when evaluating its stability in the aqueous oral environment.
测量大块充填和传统树脂复合材料的底部/顶部硬度比，并评估干燥和乙醇储存后的硬度变化。还使用热重分析（TGA）测试了填料含量和热分解动力学。
测试了六种大块充填材料（SureFil SDR、Venus bulk fill、X-tra base、Filtek bulk fill flowable、Sonic fill和Tetric EvoCeram bulk-fill）和八种传统树脂复合材料（Grandioso flow、Venus Diamond flow、X-flow、Filtek Supreme Ultra Flowable、Grandioso、Venus Diamond、TPH Spectrum和Filtek Z250）（n = 5）。测量了初始和24小时（固化后干燥储存）的顶部和底部显微硬度值。将样品储存在75%乙醇/水溶液中后重新测量显微硬度。通过TGA评估热分解和填料含量。使用单因素方差分析和配对样本t检验（α = 0.05）分析结果。
所有材料在干燥储存24小时后显微硬度均显著增加，增幅范围为100.1%至9.1%。所有材料的底部/顶部显微硬度比均>0.9。所有材料在75%乙醇/水溶液中储存24小时后显微硬度均显著降低，降幅范围为14.5%至74.2%。辐照后硬度发展程度与乙醇软化程度呈正相关（R(2)=0.89，p<0.001）。通过TGA评估的初始热分解温度各不相同，且与乙醇软化相关。
在制造商推荐的厚度下，大块充填树脂复合材料的底部/顶部硬度比与传统材料相当。硬度受储存的影响程度各不相同，无机填料含量不同，且TGA显示初始热分解情况也不同。
基于显微硬度方法可达到制造商推荐的大块充填树脂复合材料的固化深度。在评估树脂复合材料在口腔水性环境中的稳定性时，应考虑其初级聚合物网络的特性。
