Evaluation of marginal/internal fit of chrome‑cobalt crowns: Direct laser metal sintering versus computer‑aided design and computer‑aided manufacturing

Abstract

Background and Purpose: The purpose of this study was to evaluate the internal and marginal fit of chrome cobalt (Co‑Cr) crowns were fabricated with laser sintering, computer‑aided design (CAD) and computer‑aided manufacturing, and conventional methods.

Materials and Methods: Polyamide master and working models were designed and fabricated. The models were initially designed with a software application for three‑dimensional (3D) CAD (Maya, Autodesk Inc.). All models were fabricated models were produced by a 3D printer (EOSINT P380 SLS, EOS). 128 1‑unit Co‑Cr fixed dental prostheses were fabricated with four different techniques: Conventional lost wax method, milled wax with lost‑wax method (MWLW), direct laser metal sintering (DLMS), and milled Co‑Cr (MCo‑Cr). The cement film thickness of the marginal and internal gaps was measured by an observer using a stereomicroscope after taking digital photos in ×24.

Results: Best fit rates according to mean and standard deviations of all measurements was in DLMS both in premolar (65.84) and molar (58.38) models in μm. A significant difference was found DLMS and the rest of fabrication techniques (P < 0.05). No significant difference was found between MCo‑CR and MWLW in all fabrication techniques both in premolar and molar models (P > 0.05).

Conclusion: DMLS was best fitting fabrication techniques for single crown based on the results.The best fit was found in marginal; the larger gap was found in occlusal.All groups were within the clinically acceptable misfit range.

Keywords: Chrome‑cobalt, computer‑aided design and computer‑aided manufacturing, internal fit, laser sintering, marginal fit, single crown