Microleakage of Lithium Disilicate Crown Margins Finished on Direct Restorative Materials

For some esthetic clinical situations, it is necessary to finish crown margins on direct restorative materials to preserve tissue integrity, bonding integrity, and biological width. The purpose of this research was to investigate microleakage at the interface between bonded lithium disilicate crowns and various direct restorative materials in a class III and class V position.

Class III or class V restorations were prepared on one side of extracted incisors with either Tetric EvoCeram, Tetric Evoceram Bulk, Fuji II LC, or Tetric Evoflow. The teeth were prepared for and received a lithium disilicate crown. After load fatiguing, the specimens were thermo-cycled with a fuchsin dye and sectioned. The depth and area of dye penetration were measured with a dimensional grid in micrometers using stereomicroscopy and reported as mean dye depth and area (μm) ± SD. The comparison of multiple categorical independent variables with ratio scale dependent variables was evaluated with an analysis of variance and Tukey's post hoc analysis.

A statistically significant higher dye penetration was noted for all treatment groups compared with the positive control (side opposite the restoration after sagittal sectioning was used as positive control) regardless of material or placement area (p<0.05). In comparing treatment groups, the Tetric EvoFlow experienced a statistically higher dye penetration than did the other treatment groups regardless of material or placement area (p<0.05). There was no statistically significant difference between the Tetric EvoCeram, Tetric Evoceram Bulk, and Fuji II LC materials regardless of placement area (p>0.05).

Within the limitations of this study, it can be concluded that flowable composite materials as finish lines that interact with resin cements could lead to exacerbated interfacial degradation. Finishing lithium disilicate all-ceramic crowns on flowable resin composite materials in the esthetic zone should be used with caution. If necessary, finishing lithium disilicate all-ceramic crowns on nanofilled resin composite or resin-modified glass ionomer materials seems to provide the least dye penetration depth and area.