Evaluation of a new device to measure dentin permeability

Objectives: To evaluate a new electronic device to measure dentin permeability (Lp).

Methods: The flowmeter ASL1600 (Sensirion, Switzerland) is a new electronic device based on a thermal chip that detects liquid mass flow from changes in thermal gradients. An initial test at 70 cm H₂0 was performed to compare fluid flow values of human acid-etched (H₃PO₄ 15sec) crown segments alternatively tested with the new Flowmeter and with the much older Flodec (DeMarco Engineering, Geneva, Switzerland). After flow rates were measured using the Flowmeter in 20 acid-etched crown segments, the flow rates were reevaluated with the Flodec. Fluid flow, expressed in µl/min, was recorded for 5 minutes for each specimen, after a steady permeability had been reached. 

Results: Dentin permeability values obtained by Flowmeter and Flodec were compared. Flodec gave values that were 19.7± 4% higher values compared to those recorded at the same pressure with the Sensirion.  However, the standard deviation of the flow rates of the Flodec were 5.6 times higher than the Flowmeter. When Flowmeter data were plotted against Flodec data, a significant correlation was found (r=0.91). 

Conclusions: The Sensirion solid-state device represents a simple, accurate, reliable instrument to measure the fluid flow rate across the dentine. It is less expensive than the Flodec device and should be more reliable because it contains no moving parts.  

Flodec Sensirion	Fluid flow (µL/min) at 70 cm H2O (mean ± SD, CV)
	Mean ± SD	% diff	CV	Difference
	3.05 ± 0.78	--	0.0066	4.13
	2.43 ± 0.55	19.8	0.016	--