Effects of Cement Cleaning Methods on Marginal Adaptation of Zirconia Coping

Objectives: Timing of cement removal may affect crown marginal integrity and gingival health. However, the cement removal timing has not been well studied. Our objective is to evaluate the effects of different cement removal techniques on the marginal adaptation of zirconia coping.
Methods: Pre-prepared maxillary first molar typodonts with deep chamfer (n=20) were used to fabricate stone dies. Zirconia copings were manufactured via the CAD/CAM system and randomly divided into two groups. Each coping was cemented on a corresponding prepared typodont with resin-modified glass ionomer cement under an axial load of 5 kg. Excess cement was removed in two different methods. Group A: excess cement was wiped off using a microbrush immediately after crown seating. Group B: excess cement was peeled off with an explorer when the initial set was obtained (rubbery phase). The cemented copings were embedded and sectioned in mesiodistal and faciolingual directions to obtain 20 measuring points per specimen. Marginal gap (MG), vertical marginal discrepancy (VMD), horizontal marginal discrepancy (HMD), and absolute marginal discrepancy (AMD) were measured and analyzed morphometrically. A Student’s t-test was performed to compare the groups.
Results: Group A showed a mean of 21.7 µm (±15.1) for MG, 36.3 µm (±20.5) for VMD , 23.7 µm (±20.1) for HMD, and 45.3 µm (±20.9) for AMD. Group B exhibited a mean (SD) of 34.2 µm (±13.3) for MG, 53.7 µm (±34.3) for VMD, 25.6 µm (±22.0) for HMD, and 64.1 µm (±33.4) for AMD. Significant differences were observed in MG, VMD, and AMD between the groups. HMD was similar between the groups.
Conclusions: Both cleaning methods provided clinically acceptable marginal adaptation of zirconia coping (<100µm). However, the wiping-off cleaning method presented better adaptations overall compared with the peeling-off method.