Aim: This study examined the effect of cervical finish line preparation on the internal adaptation of all-ceramic crowns produced, using CAD CAM technology with two fabricated materials: IPs Emax and Zirconia-reinforced lithium silicate (Celtra Duo).
Methods: Two intact human premolars were collected with similar preparation dimensions, except for a (1.00 mm) on the margin. For sample standardization, 40 epoxy replicas of prepared premolar teeth were produced. Deep chamfer (DC group, n = 20) and knife-edge (KE group, n = 20) finish lines were used to split samples. Each group was divided into two subgroups according to fabricated material. Subgroup 1: lithium di silicate ceramic (n=10) and Subgroup 2: lithium silicate reinforced with zirconia (n=10). All crowns were CAD/CAM-made. All samples were aged by thermo-cycling after being bonded to a tooth, and the internal adaptation was measured using a stereomicroscope.
Results: The findings demonstrated an increase in the internal adaptation between vertical preparation (127.7±8.6) and deep chamfer (109.9±6.4), regardless of the material. In addition, regardless of methodology, the difference between E-max (119.6±16) and Celtra (118±5.7).
Conclusions: Vertical preparation may be an alternative to horizontal preparation and more conservative to sound tooth structure throughout the fabrication of fixed abutments to give a less intrusive option.
Key words: Internal adaptation, Vertical preparation, CAD/CAM technology, Zirconia reinforced lithium silicate (Celtra Duo), Epoxy.