Microleakage of composite crowns luted on CAD/CAM-milled human molars: a new method for standardized in vitro tests
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To investigate debonding of full crowns made of CAD/CAM composites, CAD/CAM technology was applied to manufacture standardized test abutments to increase the reproducibility of human teeth used in in vitro studies.
Materials and methods
A virtual test abutment and the corresponding virtual crown were designed and two STL data sets were generated. Sixty-four human third molars and CAD/CAM blocks were milled using a CNC machine. Crowns of four different composite blocks (Lava Ultimate (LU), Brilliant Crios (BC), Cerasmart (CS), Experimental (EX)) were adhesively bonded with their corresponding luting system (LU: Scotchbond Universal/RelyX Ultimate; BC: One Coat 7 Universal/DuoCem; CS: G-PremioBond/G-Cem LinkForce; EX: Experimental-Bond/Experimental-Luting-Cement). Half of the specimens were chemical-cured (CC) and the others were light-cured (LC). Afterwards, specimens were artificially aged in a chewing simulator (WL-tec, 1 million cycles, 50–500 N, 2 Hz, 37 °C). Finally, a dye penetration test was used to detect debonding. For inspection, the specimens were sliced, and penetration depth was measured with a digital microscope. Data were analyzed with the Mann-Whitney U test.
No cases of total debonding were observed after cyclic loading. However, the LC specimens showed a significantly lower amount of leakage than the CC ones (p < 0.05). Furthermore, the CC specimens exhibited broad scattering. Only the LC-EX blocks showed no debonding. The CC-CS blocks showed the highest leakage and scattering of all tested specimens.
Natural human teeth can be manufactured by CAD/CAM technology in highly standardized test abutments for in vitro testing. For CAD/CAM composites, light curing should be performed.
The success of a restoration depends on the long-term sealing ability of the luting materials, which avoids debonding along with microleakage. For CAD/CAM composites, separate light curing of the adhesive and luting composite is highly recommended.
KeywordsCAD/CAM Debonding Composite Microleakage Adhesive cementation
The authors would like to thank the dental companies Coltene and Dental Milestones Guaranteed (DMG) for the donation of their materials for the study. In addition, we are thankful for the support of the dental technicians, Marc Richter and Ulf Neveling, for the extraordinary value for designing the STL data sets. Furthermore, we gratefully acknowledge the support of our biostatistician, Dr. Johannes Herrmann, for the statistical analysis.
The work was supported by the Department of Prosthodontics, Justus-Liebig-University in Giessen, Germany.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
This article does not contain any studies with human participants or animals performed by any of the authors.
For this type of study, formal consent is not required.
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