With the advances of titanium three-dimensional (3D) printing, creating complex, yet accurate, custom-made implants used for reconstructive and replacement surgeries has become a possibility. This is evident in orthognathic surgery, where sections of the mandible or the entire mandible are reconstructed or replaced with a patientspecific mandibular implant. One of the processes involved in the design of such an implant is the virtual 3D reconstruction of the affected region. This is often achieved by either making use of the symmetric characteristic of the mandible or by comparing the mandible to a database of other similar mandibles. This approach can become problematic when the desired symmetry features are not available or when no similar mandible is found on the database. It is proposed that this problem can be overcome by retrospectively investigating the morphology of the mandible and determining the respective cephalometric variables to better understand its geometric properties and relationships. The aim of this study is to reproduce published cephalometric analyses, but for the South African population. Secondly, to incorporate observed variation and relationships into statistical shape models that would enable estimates of an individual’s healthy mandibular shape from partial observations. The cephalometric measures will be analysed statistically in order to determine correlations and dimorphism. The output from this would serve to inform and validate the statistical shape models. The ability of the resulting shape model to estimate healthy geometry is to be investigated by presenting sparse/partial input from known, non-pathological datasets, which should give an indication of whether or not the shape model is suitable for approximating the healthy form of partial, real-world cases for the purposes of deformity correction and implant design. At least one case study will discuss the entire process from diagnosis, through implant design, to surgery. It is expected that the results of this study will allow surgeons and biomedical engineers to quickly and accurately design and evaluate new patient-specific implants to improve patient outcomes.

1. The Study of Mandible Morphology
towards Implant Design for the
South African Population
Presenter: Sven Delport
Collaborator: Johan van der Merwe

2. Introduction
Technimark:
• 1996
• Product development
– Concept
– Prototyping
– Testing
– Manufacturing
1

3. Introduction
Energade Off-centre
Nozzle Cap
Addis Comfi-Grip Range
Lawn Star Edge Trimmer
2

4. Introduction
Medical Device Design:
• 2015
• Implant product development
• Patient-specific
– 3D anatomical models
– Implant design
3

5. Case Study
• October 2015
• CRPM at the CUT
4

6. Case Study
5

7. Case Study
3-matic
• Symmetry
did not work
• Mandible
fitment
• Export point
cloud
SolidWorks
• Parametric
modelling
• Export STL
Surgeon
• Feedback
• Apply
changes
6

8. Morphology Study
• Bigger picture
Mandible
Morphology
Study
Statistical
Shape
Modelling
Patient-specific
Implant Design
7

9. Co
Morphology Study
• Morphology
– Study of form and structure
*Reproduced from Bayome et al. (2013)
MSP
FHP
Med Co Lat Co
Go
FHP
Go
Co
Me
Sigmoid
8

10. Morphology Study
• Compare statistical differences
– White, black, coloured (race)
– Male and female (gender)
• Left and right symmetry
– Paired t-test
• Correlation and relationship between
variables
– Regression curves
9

11. Statistical Shape Modelling
• Model variation within a given set of
similar objects
• Train model on morphological data
– Estimate individual’s healthy or missing
geometry from sparse input
• Validate model
– Use partial input not in training set
– Compare RMS error between actual and
estimated
10

12. Statistical Shape Modelling
*Reproduced from Zachow et al. (2005)
Hypoplastic
mandible Mean mandible
shape
Adaptation of shape model
to healthy part of mandible
Template for
implant design
11

13. Patient-specific Implant Design
1. Take CT scan
2. Convert to 3D model
3. Apply SSM
4. Produce adapted 3D model
5. Design patient-specific implant
12

14. Conclusion
• Design of patient-specific mandibular
implants
– Statistically accurate
– Quick
– Unique to SA population
– Proudly South African
13