title: Evaluation of the marginal fit of three margin designs of resin composite crowns using CAD/CAM.
abstract: OBJECTIVE
  To examine the marginal fit of resin composite crowns manufactured with the CEREC 3 system employing three different margin designs; bevel, chamfer and shoulder, by means of a replica technique and a luting agent.
  
  
  METHODS
  Three master casts were fabricated from an impression of a typodont molar tooth and a full-coverage crown prepared with a marginal finish of a bevel, a chamfer and a shoulder. Each cast was replicated 10 times (n=10). Scanning of the replicas and crown designing was performed using the CEREC Scan system. The crowns were milled from Paradigm MZ100 composite resin blocks. The marginal fit of the crowns was evaluated with a replica technique (Aquasil LV, Dentsply), and with a resin composite cement (RelyX Unicem, Aplicap) and measured with a travelling microscope. Statistical analysis was performed using two-way ANOVA.
  
  
  RESULTS
  For the replica technique the average marginal gaps recorded were: Bevel Group 105+/-34 microm, Chamfer Group 94+/-27 microm and Shoulder Group 91+/-22 microm. For the resin composite cement the average marginal gaps were: Bevel Group 102+/-28 microm, Chamfer Group 91+/-11 microm and Shoulder Group 77+/-8 microm. Two-way ANOVA analysis showed that there was no statistically significant difference between the three groups of finishing lines regardless of the cementation technique used.
  
  
  CONCLUSIONS
  The marginal gap of resin composite crowns manufactured with the CEREC 3 system is within the range of clinical acceptance, regardless of the finishing line prepared or the cementation technique used.
authors.affiliation: Department of Adult Dental Care, School of Clinical Dentistry, University of Sheffield, Claremont Crescent, Sheffield S10 2TA, UK. e.tsitrou@gmail.co.uk
authors.forename: Effrosyni A
authors.initials: EA
authors.lastname: Tsitrou
authors.forename: Simon E
authors.initials: SE
authors.lastname: Northeast
authors.forename: Richard
authors.initials: R
authors.lastname: van Noort
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D002516:Ceramics; D003188:Composite Resins / Q000737:chemistry*; D017076:Computer-Aided Design; D003442:Crowns; D018772:Dental Marginal Adaptation; D017267:Dental Prosthesis Design / Q000379:methods*; D011140:Polyurethanes / Q000737:chemistry*
chemical_list: D000180:Acrylic Resins; C029012:Composite Dental Resin; D003188:Composite Resins; D011140:Polyurethanes; C074543:Cerec