Effect of tooth preparation on LDF signals from pulp

Laser Doppler flowmeters (LDF) have been used to record pulpal blood flow from enamel surface. But, in many conditions, enamel and dentin have been destroyed and the signal record from dentin may be different from that obtained from intact enamel.

Objective: to investigate the effect of removing enamel and dentin on the LDF signal recorded from the pulp chamber in vitro.

Methods: Observations were made on 12 non-carious, first premolar teeth that had been extracted for orthodontic reasons. The apical 2/3 of the root was removed with a diamond bur and the remaining pulp tissue was removed with a barbed broach. A nylon cannula (diameter 1mm) was inserted into the pulp chamber and perfused with 1% v/v human blood diluted with normal saline at a rate of 0.1 ml/s using a motorized syringe. LDF signals were recorded with Moor laser Doppler Flowmeter (type MBF3D) from the center of the buccal surface of the crown. Recordings were made from the enamel surface and at steps of 0.5 mm as tooth substance was removed until the pulp chamber as exposed at 2.5 mm.

Result: The mean±SD of LDF recorded from the pulp chamber (1,000±0.00) was significantly greater than all others (p<0.001) and the value obtained at 0 mm (83.04±81.49) was significantly smaller than all others (p<0.05). The mean±SD at 2.0 mm (190.92±55.47) was significantly greater than those at 0, 0.5, 1.0 (83.04±81.49, 132.37±46.33, 142.77±65.65, consecutively), but not significant different with those at 1.5 mm (156.67±47.51).

Conclusion: Reducing the thickness of enamel and dentin caused the blood flow signal recorded from the tooth surface to increase in vitro.