title: Are different generations of CAD/CAM milling machines capable to produce restorations with similar quality?
abstract: BACKGROUND
  Different CAD/CAM machines' generation may impact the restoration overall quality. The present study evaluated the marginal fit of CAD/CAM restorations manufactured with different generations of CEREC milling unit systems.
  
  
  METHODS
  Sixteen typodont teeth were divided into two groups (n=8) according to the machine's generation assigned. These are control group (G1): Cerec AC with Bluecam/Cerec 3 milling unit and (G2): Cerec AC with Bluecam/MC XL Premium Package milling unit. Scanning of the preparation were performed and crowns were milled using the Vita Mark II blocks. Blocks were cemented using epoxy glue on the pulpal floor only and finger pressure applied for 1 min. Upon completion of the cementation step, misfits between the restoration and abutment were measured by microphotography and the silicone replica technique using light body silicon material on Mesial (M) and Distal (D) surfaces.
  
  
  RESULTS
  Mean and SDs of marginal gaps in micrometers were: G1/M: 94.90 (±38.52), G1/D: 88.53 (±44.87), G2/M: 85.65 (±29.89), G2/D: 95.28 (±28.13). Two-way ANOVA indicated no significant differences among different groups (P>0.05); surface area (P>0.05) and the interaction (P>0.05). Overall, G2 had greater margin gaps than G1, however, without statistical difference (P>0.05).
  
  
  CONCLUSIONS
  Difference in milling unit generation did not significantly affect the marginal fit. Marginal gap means were in the range of the clinical acceptance levels for both generations of Cerec milling units, regardless the teeth site area.Key words:CAD/CAM, margin, ceramics.
authors.affiliation: DDS, MS, PhD, Department of Comprehensive Care, School of Dental Medicine - Case Western Reserve University, 2124 Cornell Rd, Cleveland, 44106, USA.
authors.forename: Renato
authors.initials: R
authors.lastname: Roperto
authors.affiliation: DDS, MS, Department of Comprehensive Care, School of Dental Medicine - Case Western Reserve University, 2124 Cornell Rd, Cleveland, 44106, USA.
authors.forename: Hussein
authors.initials: H
authors.lastname: Assaf
authors.affiliation: DDS, MS, Department of Comprehensive Care, School of Dental Medicine - Case Western Reserve University, 2124 Cornell Rd, Cleveland, 44106, USA.
authors.forename: Thiago
authors.initials: T
authors.lastname: Soares-Porto
authors.affiliation: DDS, MS, MBA, Department of Comprehensive Care, School of Dental Medicine - Case Western Reserve University, 2124 Cornell Rd, Cleveland, 44106, USA.
authors.forename: Lisa
authors.initials: L
authors.lastname: Lang
authors.affiliation: DDS, MBA, Department of Comprehensive Care, School of Dental Medicine - Case Western Reserve University, 2124 Cornell Rd, Cleveland, 44106, USA.
authors.forename: Sorin
authors.initials: S
authors.lastname: Teich