Case: Dental Bridge

We use a case of the dental bridge for discussing quality during the AM process of a metal dental prosthesis. The value chain is used structure to discuss quality issues in this particular case. This page gives a summary, whereas the full document can be downloaded here.

dentalbridgecustomized

The dental bridge, customized for topology optimization

amvaluechain Design Machine Materials Process Post-processing Metrology & Maintenance Services: A Quality Management System for AM

Keywords: Dental bridge, quality in dentistry

Content

  1. Product description
  2. Requirements
  3. Material certifications
  4. Design
  5. Machine & process parameters
  6. Post processing
  7. Maintenance & metrology

1. Product description

A dental bridge is a fixed dental restoration which is used to replace a missing tooth. The bridge itself is a series of artificial teeth, which can be placed on adjacent teeth.

2. Requirements

Requirements for a dental bridge are the following:

  • The aesthetics should be similar to the natural teeth of the patient
    • In terms of shape
    • In terms of colouring
  • Mastication of a patient should remain comfortable
  • Phonation of a patient should remain comfortable

These requirements account for all dental prosthetics: crowns, bridges, frameworks, inlays, dentures and more (NVQ for Nurses, 2009). To meet these requirements, the following quality aspects need to be assessed during the manufacturing process. These quality aspects can be referred to as the process window.

3. Material certifications

The material need the required biocompatibility and properties. For titanium and cobalt chrome, the certifications listed in the table below are required.

Material certifications
Certifications Summary of description
ISO 22674:2006 Classifies metallic materials that are suitable for the fabrication of dental appliances and restorations
ISO 9693-1 Specifies test methods for determining the compatibility of metallic and ceramic materials used for dental restorations by testing the composite structure.
ASTM F2924 AM specific standard for Ti6Al4V alloys
ASTM F1472 The use of Ti6Al4V alloys for surgical implant applications
ISO 5832-3:1996 The use of Ti6Al4V alloys for surgical implant applications
ASTM F136 The use of Ti6Al4V alloys for surgical implant applications

4. Design

For design of the dental bridge, we use the structure, as presented in the AM value chain, considering of four main steps and several sub-steps:

  • Original part
    • Definition of geometry (CAD)
    • Definition of load cases and constraints
    • Part requirements
    • Analysis of original component
  • Topology optimisation
    • Optimisation parameters
    • Assessment of results
    • Assessment of mesh sensitivity study
  • Part re-design
    • Materialise 3-Matic software
    • Regularise, smooth, and replace unwanted aspects
    • Re-mesh
    • Add substructures
  • Final verification
    • Re-mesh
    • Analyse under design loads
    • Verify adequacy of solution

See the full document for the design description.

5. Machine & process parameters

Are described in the full document

6. Post-processing

  • In order to obtain a final part it is necessary to develop these steps:
  • Remove part from the build platform
  • Remove supports
  • Sandblasting the surface
  • Clean the part to ensure that there is not dust
  • Machine the holes and the surfaces to fit with other parts.

7. Maintenance & metrology

  • Check the scanned file and design by designer
  • Manual checking dimensions by using a model
  • Visual colour check against colour standard.
  • Visual inspection by operator

For generic dental quality issues, we refer you to the chapter 'dental'.