title: The effect of different fabrication steps on the marginal adaptation of two types of glass-infiltrated ceramic crown copings fabricated by CAD/CAM technology.
abstract: OBJECTIVE
  Marginal adaptation is an important factor affecting the longevity of all-ceramic restorations, although the effects of different fabrication steps on marginal adaptation at various stages of fabrication are not fully understood. The purpose of this study was to assess with an in vitro model whether In-Ceram alumina (IA) or In-Ceram zirconia (IZ) copings produced by the CAD/CAM method would be clinically acceptable, and to evaluate the effect of each fabrication step (post-milling, post-trimming, and post-glass infiltration) on the marginal discrepancy of the coping.
  
  
  METHODS
  A melamine tooth was prepared, duplicated, poured with inlay wax, and then cast with metal to fabricate a master die. An InLab 3D system was used to scan the master die and to design and mill the copings. Thirty IA and IZ copings each were developed with thicknesses of 0.6 mm and a 30-μm thick computer luting space. Epoxy resin replicas of the master die were fabricated, and the vertical and horizontal marginal discrepancies were measured using a Micro-Vu optical microscope at three stages of the fabrication (post-milling, post-trimming, post-infiltration). One-way ANOVA was used to analyze the data between the three stages of fabrication for each marginal discrepancy, and a t-test was used to compare vertical and horizontal marginal discrepancies (after glass infiltration) between IZ and IA copings
  
  
  RESULTS
  There were no significant differences (p > 0.05) in the vertical marginal discrepancies (μm) between IA (36 ± 14) and IZ (40 ± 14) copings after glass infiltration. ANOVA (comparing three stages within horizontal marginal discrepancy for IZ copings) showed that post-milling (40 ± 26) > post-trimming (23 ± 11) = post-infiltration (19 ± 13). ANOVA (comparing three stages within vertical marginal discrepancy for IZ copings) showed that post-milling (53 ± 12) = post-trimming (47 ± 13) > post-infiltration (36 ± 14). ANOVA (comparing three stages within horizontal marginal discrepancy for IA copings) showed that post-milling (52 ± 28) > post-trimming (30 ± 16) > post-infiltration (30 ± 16). ANOVA (comparing three stages within vertical marginal discrepancy for IA copings) showed that post-milling (54 ± 13) = post-trimming (56 ± 26) > post-infiltration (40 ± 14).
  
  
  CONCLUSIONS
  There was no significant difference in the marginal adaptation of both material copings. After the trimming process, the glass infiltration firing cycle improved the vertical marginal discrepancy for both IZ and IA copings. Clinical implications. IA and IZ copings fabricated by CAD/CAM technology have an acceptable marginal fit as documented in the literature, and the glass infiltration process improves the marginal fit after machining.
authors.affiliation: Department of Prosthetic Dental Sciences, College of Dentistry, Taibah University, Madinah Munawwarah, Saudi Arabia. tghazzawi@taibahu.edu.sa
authors.forename: Tariq F
authors.initials: TF
authors.lastname: Alghazzawi
authors.forename: Perng-Ru
authors.initials: PR
authors.lastname: Liu
authors.forename: Milton E
authors.initials: ME
authors.lastname: Essig
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry; D017076:Computer-Aided Design; D003442:Crowns; D000044:Dental Abutments; D018772:Dental Marginal Adaptation; D003776:Dental Porcelain / Q000737:chemistry*; D017267:Dental Prosthesis Design; D004853:Epoxy Resins / Q000737:chemistry; D005898:Glass / Q000737:chemistry*; D006801:Humans; D008422:Materials Testing; D008853:Microscopy; D013499:Surface Properties; D015040:Zirconium / Q000737:chemistry
chemical_list: D004853:Epoxy Resins; C483026:In-Ceram Alumina; C485633:In-Ceram Zirconia; D003776:Dental Porcelain; D015040:Zirconium; D000537:Aluminum Oxide; C028541:zirconium oxide