title: In vitro assessment of the marginal and internal fits of interim implant restorations fabricated with different methods.
abstract: BACKGROUND
  The fit of an interim implant restoration (IIR) is important for the effective treatment of patients with partial edentulism. However, no clinical trials have evaluated the marginal and internal fittings achieved with various fabrication methods.
  
  
  OBJECTIVE
  The purpose of this in vitro study was to evaluate and compare the marginal and internal discrepancies in IIRs produced with 3 different methods.
  
  
  METHODS
  Partially edentulous maxillary and mandibular casts from a transfer abutment were used. Prostheses were prepared by applying wax to the implant abutment. Shapes were copied using putty. IIRs were fabricated from poly(methyl methacrylate) for a conventional system with thermoplastic resin (CTR, n=40), a 4-axial milling machine with a crown-designed standard template library for a subtractive manufacturing system with Pekkton milling (SPM, n=40), and a 3-dimensional printer for an additive manufacturing system with digital light processing (ADL, n=40). The marginal and internal discrepancies were evaluated in each group using the silicone replica technique. The space between the abutment and the intaglio surface of the prosthesis was evaluated with a digital microscope (×160 magnification). Results were analyzed with nonparametric 2-way analysis of variance using rank-transformed values and Tukey post hoc test (α=.05).
  
  
  RESULTS
  The fabricated IIRs were significantly different at all points (P<.001). Moreover, ADL was superior to CTR and SPM. IIRs were significantly different only at the intermarginal discrepancy (the vertical discrepancy between the crown and the point where the margin becomes round and changes to the axial wall), the axiogingival discrepancy (the vertical discrepancy between the internal surface and the axial wall adjacent to the gingival wall of the abutment), and the occlusal discrepancy (the vertical discrepancy between the occlusal wall of the abutment and the internal surface; this discrepancy comprises the internal discrepancy; P<.001). No significant differences were found among the IIRs at the marginal discrepancy (the vertical discrepancy between the abutment margin and the crown; P>.111) and the axio-occlusal discrepancy (the vertical discrepancy between the axial wall adjacent to the occlusal wall of the abutment and the internal surface; this discrepancy comprises the internal discrepancy; P>.257).
  
  
  CONCLUSIONS
  ADL was superior to the other 2 fabrication methods. However, all 3 methods were suitable because they produced a marginal fit which was within the clinically acceptable range.
authors.affiliation: Doctoral student, Department of Dental Laboratory Science and Engineering, College of Health Science, Korea University, Seoul, South Korea.
authors.forename: Jin-Young
authors.initials: JY
authors.lastname: Park
authors.affiliation: Doctoral student, Department of Dental Laboratory Science and Engineering, College of Health Science, Korea University, Seoul, South Korea.
authors.forename: Il-Do
authors.initials: ID
authors.lastname: Jeong
authors.affiliation: Master student, Department of Dental Laboratory Science and Engineering, College of Health Science, Korea University, Seoul, South Korea.
authors.forename: Jae-Jun
authors.initials: JJ
authors.lastname: Lee
authors.affiliation: Doctoral student, Department of Dental Laboratory Science and Engineering, College of Health Science, Korea University, Seoul, South Korea.
authors.forename: So-Yeon
authors.initials: SY
authors.lastname: Bae
authors.affiliation: Professor, Department of Dental Laboratory Science and Engineering, College of Health Science, Korea University, Seoul, South Korea.
authors.forename: Ji-Hwan
authors.initials: JH
authors.lastname: Kim
authors.affiliation: Professor, Department of Dental Laboratory Science and Engineering, College of Health Science, Korea University, Seoul, South Korea. Electronic address: kuc2842@korea.ac.kr.
authors.forename: Woong-Chul
authors.initials: WC
authors.lastname: Kim
mesh_terms: D000044:Dental Abutments; D003735:Dental Casting Technique; D059605:Dental Implant-Abutment Design; D018772:Dental Marginal Adaptation; D017267:Dental Prosthesis Design / Q000379:methods*; D003833:Denture, Partial, Temporary; D006801:Humans; D066298:In Vitro Techniques