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Impact of Preparation Thickness and Restorative Material on the Marginal Fit of CAD-CAM Complete Crowns
Éric Arnold Dos Santos Brito1, Thayara Coelho Metzker2, Ingrid Bandeira Sanches2
1Postgraduate Program in Oral Rehabilitation at the School of Dentistry of Ribeirão Preto, University of São Paulo (FORP-USP), Ribeirão Preto, São Paulo, Brazil.
Statement Of Problem:
A lack of consensus exists on whether the preparation thickness and choice of restorative material can affect the marginal adaptation of complete CAD-CAM crowns.
Purpose:
To evaluate the impact of preparation thickness and restorative material on the marginal adaptation of CAD-CAM complete crowns.
Materials And Methods:
Two human mandibular right second molars were prepared with the following characteristics: conventional preparation (CP)-1.0 mm chamfer, 2 mm reduction of the occlusal surface, ~6° convergence angle, and 1.5 mm axial reduction; ultrathin preparation (UFP)-0.5 mm finish line, 0.7 mm reduction of the occlusal and axial surface. The teeth were scanned using an intraoral scanner (IOs), and the crowns were designed and milled. Ten crowns were produced in each group (n = 10): feldspathic ceramic (FC), resin composite (RC), lithium silicate ceramic reinforced with zirconia (LSZ), and lithium disilicate ceramic (LDS). The marginal gap was analyzed at 4 points using a stereomicroscope. Data analysis used two-way analysis of variance (ANOVA) and the Tukey test (α = 0.05).
Results:
CP (65.00 ± 16.62 to 84.22 ± 20.87 µm) showed the lowest marginal discrepancy values, with a statistical difference from UFP (110.40 ± 28.64 to 183.83 ± 40.23 µm). In the CP group, there was no statistically significant difference between the materials. In the UFP, there was a difference between FC and RC compared to LSZ and LDS.
Conclusions:
The preparation's thickness impacted the marginal adaptation of CAD-CAM full crowns, and the CP showed a lower discrepancy compared to the ultrathin preparation. The performance of the materials in the CP was similar. However, there was better marginal adaptation of FC crowns and RCs in ultrathin preparations.
