title: Marginal Accuracy of Castings Fabricated with Ringless Casting Investment System and Metal Ring Casting Investment System: A Comparative Study.
abstract: BACKGROUND
  The thermal expansion of the investment can be restricted by the metal casting ring because the thermal expansion of the ring is less than that of the investment. The ringless casting procedure is in use in clinical dentistry, though there is little scientific data to support its use in fixed partial dentures. In this study, marginal discrepancy of castings produced with the ringless casting technique and the conventional technique using the metal rings were compared.
  
  
  METHODS
  A total of 30 wax patterns were fabricated directly on a metal die. Optical stereomicroscope was used to measure the marginal discrepancy between the metal die and wax patterns. A total of 15 castings were invested using Bellavest T phosphate-bonded investment with the ringless technique and 15 were invested with the same investment with a metal ring; 30 castings were produced using a nickel-chromium ceramo-metal alloy. The internal surface of the castings was not modified and seated with finger pressure. The vertical marginal discrepancy was measured using an optical stereomicroscope at a magnification of 100x. The data obtained were statistically analyzed using students t-test (paired t-test and unpaired t-test).
  
  
  RESULTS
  The castings of the ringless technique provided less vertical marginal discrepancy (240.56 ± 45.81 μ) than the castings produced with the conventional metal ring technique (281.98± 53.05 μ). The difference was statistically significant.
  
  
  CONCLUSIONS
  The ringless casting technique had produced better marginal accuracy compared with conventional casting technique. Ringless casting system can be used routinely for clinical purpose.
authors.affiliation: Lecturer, Department of Prosthodontics and Crown and Bridge Government Dental College and Research Institute, Bengaluru Karnataka, India, Phone: +917676708707, e-mail: drmallis@gmail.com.
authors.forename: M
authors.initials: M
authors.lastname: Kalavathi
authors.affiliation: College of Dental Science, Davangere, Karnataka, India.
authors.forename: Bhuvana
authors.initials: B
authors.lastname: Sachin
authors.affiliation: Department of Prosthodontics, College of Dental Sciences Davangere, Karnataka, India.
authors.forename: B G
authors.initials: BG
authors.lastname: Prasanna
authors.affiliation: Department of Prosthodontics, College of Dental Sciences Davangere, Karnataka, India.
authors.forename: T V
authors.initials: TV
authors.lastname: Shreeharsha
authors.affiliation: Department of Prosthodontics, College of Dental Sciences Davangere, Karnataka, India.
authors.forename: B
authors.initials: B
authors.lastname: Praveen
authors.affiliation: Department of Prosthodontics, Yenepoya Dental College Yenepoya University, Mangaluru, Karnataka, India.
authors.forename: Mallikarjuna
authors.initials: M
authors.lastname: Ragher
mesh_terms: D003734:Dental Casting Investment; D003735:Dental Casting Technique
chemical_list: D003734:Dental Casting Investment
keywords: Marginal accuracy; Phosphate-bonded investment; Ringless casting; Thermal expansion.