Effect of Thermo-Mechanical Cycling on The Vertical Marginal Gap of Different CAD/CAM Crowns (In-vitro Study).

Document Type : Original Article

Authors

1 Crown and bridge department Faculty of Dentistry, al Azhar university

2 Crown and bridge department, Faculty of dentistry, Al-Azhar university

3 Department of Crown and Bridge, Faculty of Dental Medicine, Al-Azhar University in Cairo-Egypt.

Abstract

Objective: To evaluate the effect of Thermo-mechanical cycling on the vertical marginal gap of different CAD/CAM crowns.
Materials and Methods: A maxillary first premolar tooth was selected, and the tooth was prepared using a CNC; the machine was adjusted to reduce the tooth to fulfill the criteria of all ceramic crown designs. Special mold fabrication responsible for tooth mounting and replication. The tooth was duplicated twenty-one times with epoxy resin materials with a specially designed tray, paired with the special mold to give twenty-one identical epoxy dies. Then, twenty-one CAD/CAM crowns were fabricated and divided into three groups (n = 7) according to the material used: IPS emax CAD (LD), Vita ENAMIC (VE), and Tetric CAD. All samples were cemented with a universal bond (Tetric N bond) and adhesive resin cement (Variolink Esthetic DC). The vertical marginal gap was recorded with a digital microscope. Subsequently, all samples were Thermo-mechanical cycled TMC (5 °C to 55 °C, 30s, 75,000 cycles). Then, the vertical marginal gap was re-evaluated.
Results: The vertical marginal gap showed no significant difference between the tested groups before TMC; LD (28.04±8.21µm) had the highest value, followed by VE (26.66±8.1µm) and Tetric CAD (21.18±2.97µm); however, the vertical marginal gap showed a significant difference between the tested groups after TMC the highest mean value was recorded in VE (38.76±8.39 µm), followed by Tetric CAD (34.91±8.73µm), with the lowest value recorded in LD (15.39±1.99).
Conclusions: Thermo-mechanical cycling affected the vertical marginal gap of all tested materials.

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Al-Azhar Journal of Dental Science
Volume 28, Issue 3 - Serial Number 3
July - Restorative Dentistry Issue (Removable Prosthodontics, Fixed Prosthodontics, Endodontics, Dental Biomaterials, Operative Dentistry)
July 2025
Pages 387-392

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