title: Fit of interim crowns fabricated using photopolymer-jetting 3D printing.
abstract: BACKGROUND
  The fit of interim crowns fabricated using 3-dimensional (3D) printing is unknown.
  
  
  OBJECTIVE
  The purpose of this in vitro study was to evaluate the fit of interim crowns fabricated using photopolymer-jetting 3D printing and to compare it with that of milling and compression molding methods.
  
  
  METHODS
  Twelve study models were fabricated by making an impression of a metal master model of the mandibular first molar. On each study model, interim crowns (N=36) were fabricated using compression molding (molding group, n=12), milling (milling group, n=12), and 3D polymer-jetting methods. The crowns were prepared as follows: molding group, overimpression technique; milling group, a 5-axis dental milling machine; and polymer-jetting group using a 3D printer. The fit of interim crowns was evaluated in the proximal, marginal, internal axial, and internal occlusal regions by using the image-superimposition and silicone-replica techniques. The Mann-Whitney U test and Kruskal-Wallis tests were used to compare the results among groups (α=.05).
  
  
  RESULTS
  Compared with the molding group, the milling and polymer-jetting groups showed more accurate results in the proximal and marginal regions (P<.001). In the axial regions, even though the mean discrepancy was smallest in the molding group, the data showed large deviations. In the occlusal region, the polymer-jetting group was the most accurate, and compared with the other groups, the milling group showed larger internal discrepancies (P<.001).
  
  
  CONCLUSIONS
  Polymer-jet 3D printing significantly enhanced the fit of interim crowns, particularly in the occlusal region.
authors.affiliation: Graduate student, Department of Prosthodontics, School of Dentistry, Kyungpook National University, Daegu, Republic of Korea.
authors.forename: Hang-Nga
authors.initials: HN
authors.lastname: Mai
authors.affiliation: Professor, Department of Prosthodontics, School of Dentistry, A3DI, Kyungpook National University, Daegu, Republic of Korea.
authors.forename: Kyu-Bok
authors.initials: KB
authors.lastname: Lee
authors.affiliation: Assistant Professor, Department of Prosthodontics, School of Dentistry, A3DI, Kyungpook National University, Daegu, Republic of Korea. Electronic address: deweylee@knu.ac.kr.
authors.forename: Du-Hyeong
authors.initials: DH
authors.lastname: Lee
mesh_terms: D003442:Crowns; D003761:Dental Impression Technique; D017267:Dental Prosthesis Design; D066298:In Vitro Techniques; D066330:Printing, Three-Dimensional