Lo Giudice G, Cicciù M, Cervino G, Lizio A, Visco A M
Department of Oral Disease, University of Messina, Via Consolare Valeria 98100 Messina, IT, Italy.
Indian J Dent Res. 2012 Nov-Dec;23(6):763-9. doi: 10.4103/0970-9290.111256.
The aim of this study is to investigate the presence and the extent of a possible marginal gap after the interposition of a flowable composite between the composite restoration and the dental structures (enamel and cementum). This technique is also used to eliminate the infiltration in a zone of the cavity preparation that is frequently at a risk of secondary decay.
Fifteen human premolars extracted for orthodontic reasons were used for the study. A cavity with mesial and distal margin in enamel and cementum was realized in every tooth. The cavities were then restored with an adhesive system (ScotchBond 3MÔ) and composite (Filtek Supreme 3MÔ); and, a fine layer of flowable composite was applied in the distal margin of each cavity. Scanning electron microscopy (SEM) in secondary electron imaging (S.E.I.) modality was used for the study and identifying the marginal gaps in the composite restorations. Data was investigated on the mesial and distal margin of each cavity at the restoration-enamel interface, and at the restoration-cementum interface. The interfaces were divided in four groups: Group A (enamel/composite); Group B (enamel/flow/composite); Group C (cementum/composite); and, Group D (cementum/flow/composite).
By the comparison of the gap's average width found in each group, it is evidenced that the average width of the gap increases when the interface moves from the coronal to the radicular end (Group A 0,1 ± 0,4 μm Vs Group C 12,3 ± 11,6 μm; Group B 0,2 ± 0,8 μm Vs Group D 2,8 ± 6,6 μm). Correlating the measurements of the marginal gap's average width among the Group A and Group B, no significant variations were obtained; and instead, on comparing Group C with Group D, the gap's average width decreases.
The interposition of a low elastic modulus composite between the adhesive layer and the composite resin allows an improvement of the cementum-restoration interface by the means of a lower shrinkage stress during polymerization.
本研究旨在调查在复合树脂修复体与牙体结构（釉质和牙骨质）之间置入可流动复合树脂后可能存在的边缘间隙及其程度。该技术还用于消除窝洞预备中经常存在继发龋风险区域的微渗漏。
本研究使用了15颗因正畸原因拔除的人类前磨牙。每颗牙齿制备一个近中及远中边缘位于釉质和牙骨质的窝洞。然后用粘结系统（3M™ ScotchBond）和复合树脂（3M™ Filtek Supreme）修复窝洞；并且，在每个窝洞的远中边缘涂抹一层薄的可流动复合树脂。采用扫描电子显微镜（SEM）的二次电子成像（S.E.I.）模式进行研究并确定复合树脂修复体中的边缘间隙。在修复体 - 釉质界面和修复体 - 牙骨质界面，对每个窝洞的近中及远中边缘的数据进行研究。这些界面分为四组：A组（釉质/复合树脂）；B组（釉质/可流动材料/复合树脂）；C组（牙骨质/复合树脂）；D组（牙骨质/可流动材料/复合树脂）。
通过比较每组中发现的间隙平均宽度，结果表明当界面从冠方移向根方时，间隙平均宽度增加（A组0.1±0.4μm对C组12.3±11.6μm；B组0.2±0.8μm对D组2.8±6.6μm）。比较A组和B组边缘间隙平均宽度的测量值，未发现显著差异；相反，比较C组和D组时，间隙平均宽度减小。
在粘结层和复合树脂之间置入低弹性模量的复合树脂，可通过聚合过程中较低的收缩应力改善牙骨质 - 修复体界面。
