Visualising Synthetic Dental Biofilm on Teeth

Using Micro-CT

Nina Vyas

School Of Dentistry

University Of Birmingham, UK

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Presentation Overview 1. Background: dental plaque and ultrasonic scaling

2. Methods

3. Image processing

a) Noise Reduction

b) Dual Energy Segmentation

4. Summary and future work

2

Plaque

Biofilm

Calculus

Ultrasonic

Scaling

http://tinyurl.com/n4mbbcf

http://tinyurl.com/ldj4lnt

http://tinyurl.com/mpu6465

3

Mechanical vibrations

Cavitation? [1, 2]

Micro-streaming?

[3]

http://tinyurl.com/k9pjq2t

4 [1] Walmsley et al. (1988) J. Clinical Periodonlotogy. [2] Walmsley et al. (2013) Clinical oral investigations [3] Khambay et al. (1999) J. Clinical Periodonlotogy

Why Micro-CT?

3D overview of biofilm localisation on tooth

See where ultrasonic scaler is most and least effective

Quick and easy

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Aims of project

1. Image an artificial biofilm on a tooth

using microCT

2. Use dual energy imaging and Dehist

software to segment artificial biofilm

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Methods

Sample Preparation Dual Energy

Scanning Noise

Reduction

Dual Energy

Segmentation

7

[5,6]

[4]

[4] Macedo et al. (2014), Int. Endodontic J. [5] http://www.skyscan.be/products/downloads.htm [6] Depypere et al. (2010)

Why Dual Energy?

Lighter elements absorb low energy x-rays

Heavier elements absorb high energy x-rays

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Low energy image: More noise but

can see hydrogel High energy image:

Less noise, cannot see hydrogel

‘Dehist’ Software

High Energy Low Energy

Dual Histogram

Segmented Image

Noise Included

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Noise Reduction

Mean Median Gaussian Blur

Minimum Removed Outliers

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Noise Reduction

Calculated Signal/Noise Ratio for each noise reduction technique

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Noise reduction

0

20

40

60

80

100

120

140

160

None Mean Gaussian Blur

Median Minimum Removed Outliers

Noise Reduction Technique

30 kV

40 kV

50 kV

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Sign

al/N

ois

e R

atio

Segmenting After Noise Reduction BEFORE AFTER

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Evaluating Accuracy of Dehist Created reference images using image subtraction

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Reference Segmentation

Evaluating Accuracy of Dehist

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Dual Energy Segmentations

40 kV, 50 kV

30 kV, 70 kV

Reference Segmentation

Calculated Sensitivity and Specificity

Evaluating Accuracy of Dehist

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0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.100.90

0.91

0.92

0.93

0.94

0.95

0.96

0.97

0.98

0.99

1.00

30 kV 70 kV

50 kV 70 kV

40 kV 70 kV

40 kV 80 kV

30 kV 50 kV

40 kV 50 kV

50 kV 80 kV

30 kV 80 kV

30 kV 40 kV

0.0 0.2 0.4 0.6 0.8 1.00.0

0.2

0.4

0.6

0.8

1.0

Se

nsitiv

ity

1-Specificity

S

en

sitiv

ity

1-Specificity

Future work

Image:

◦ Mineralised hydrogel

◦ Natural biofilm grown on teeth

◦ Biofilm disruption

Improve segmentation tools

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Conclusion Unique imaging of artificial biofilm using microCT

Using dual energy and Dehist software

Image processing to reduce noise in dual energy images

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Acknowledgments Dentistry

Professor Damien Walmsley

Dr Michael Sandholzer

Jonathan Robinson

Biomaterials

Dr Rachel Sammons

Chemical Engineering

Professor Liam Grover

Computer Science

Dr Hamid Dehghani

Funding Sources

Engineering and Physical Sciences Research Council

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References [1] Walmsley, A. D., Laird, W. R. E. & Williams, A. R. (1988) Dental plaque removal by cavitational activity during ultrasonic scaling. Journal of Clinical Periodonlotogy. 15, 539-543.

[2] Walmsley, A. D., Lea, S. C., Felver, B., King, D. C., & Price, G. J. (2013). Mapping cavitation activity around dental ultrasonic tips. Clinical oral investigations, 17(4), 1227-1234.

[3] Khambay B. S. , Walmsley AD. (1999) Acoustic microstreaming: detection and measurement around ultrasonic scalers. Journal of Clinical Periodonlotogy. 70, 626–631

[4] Macedo, R. G., Robinson, J. P., Verhaagen, B., Walmsley, A. D., Versluis, M., Cooper, P. R., & Sluis, L. W. M. (2014). A novel methodology providing insights into removal of biofilm mimicking hydrogel from lateral morphological features of the root canal during irrigation procedures. International endodontic journal.

[5] http://www.skyscan.be/products/downloads.htm

[6] Depypere, M., van Gastel, N., Nuyts, J., Laperre, K., Carmeliet, G., Maes, F., & Suetens, P. (2010). Dual energy microCT imaging of bone and vasculature inside bone. status: published.

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