Assessment of Enamel Demineralisation and Remineralisation using Terahertz Pulsed Imaging

D. CHURCHLEY¹, F. LIPPERT², A. BUTLER¹, A. PORTIERI³, and R.J.M. LYNCH¹, ¹GlaxoSmithKline Consumer Healthcare, Weybridge, England, ²Indiana University School of Dentistry, Indianapolis, IN, ³TeraView Ltd, Cambridge, England

Objective

Transverse micro-radiography (TMR) is the “gold standard” for measuring mineral changes in enamel; however, it is destructive in nature. The aim of this study was to compare Terahertz Pulsed Imaging (TPI), a non-destructive technique, with TMR for measuring mineral changes in enamel.

Methods 

Lesions with diverse mineral characteristics were created in bovine and human enamel blocks (n=48 per enamel type) using three demineralising systems (MeC, Carbopol C907 & HEC).  Specimens were assigned to two treatment groups (n=24 per enamel type per group): Group 1: remineralisation for 5 days (1.5mM CaCl₂.2H₂O, 0.9mM KH₂PO₄, 20mM HEPES and 130mM KCl) Group 2: demineralisation for 2 days (50mM acetic acid, 2.25mM CaCl₂.2H₂O, 1.35mM KH₂PO₄, 130mM KCl and 5ppm F).  Lesions were imaged using a TPI imaga 1000. Reflection data were used to generate lesion mineral profiles.   Lesions were also radiographed.  For both techniques the integrated mineral loss (ΔZ), lesion depth (L), change in mineral content (ΔM), and change in lesion depth (ΔL) were calculated. Pearson correlation coefficients were calculated for the combined data set as well as by enamel type, treatment and lesion type.

Results

The table shows the Pearson correlation coefficients.  There is generally a good association (Pearson coefficients ≥ 0.70) between TPI and TMR measurements for most variables.

Variable	Combined	Enamel Type		Treatment		Lesion Type
		Bovine	Human	Demin	Remin	MeC	C907	HEC
ΔZ(baseline)	0.66	0.69	0.65	0.59	0.81	0.28	0.74	0.47
ΔZ(post-treatment)	0.84	0.92	0.71	0.78	0.83	0.82	0.82	0.77
ΔM	0.75	0.84	0.58	0.55	0.52	0.80	0.72	0.70
L(baseline)	0.79	0.77	0.80	0.76	0.87	0.19	0.75	0.20
L(post-treatment)	0.88	0.95	0.77	0.75	0.73	0.97	0.87	0.78
ΔL	0.84	0.93	0.65	0.49	0.51	0.94	0.80	0.82

Conclusion 

Whilst these initial findings demonstrate that TPI could be a useful technique for the non-destructive assessment of enamel mineral changes; further evaluation is required.

This study was performed using TeraView's Imaga 1000 system (TeraView, Cambridge, UK) 

Full Article: https://iadr.confex.com/iadr/14iags/webprogram/Paper189313.html