In vitro optical detection of simulated blood pulse in a human tooth pulp model

Area of Science:

• Biomedical Optics
• Dental Research
• Physiology

Background:

• Noninvasive optical methods like photoplethysmography are used for organ blood pulse detection.
• Their application for human dental pulp vitality testing is proposed but lacks mechanistic understanding within closed pulp chambers.
• The influence of non-pulpal blood flow sources on optical signals is unknown.

Purpose of the Study:

• To develop a device for optical detection of pulpal blood pulse.
• To investigate the influence of parameters, including simulated gingival blood flow (GBF), on optical pulpal blood pulse signals.

Main Methods:

• Pulsed human erythrocyte suspensions (HES) through flexible/rigid tubes within extracted molars in a tooth-gingiva model.
• Simulated GBF using HES pulsed around the tooth.
• Introduced red (625 nm) and infrared (940 nm) light, detecting transmitted signal amplitude.
• Tested shielding materials (rubber dam, foils) and analyzed data nonparametrically.

Main Results:

• Optical signals detected for HES and lysed HES, but not with air, water, or non-particulate hemoglobin.
• Signal amplitude varied with tube rigidity and light wavelength (IR higher in flexible, red higher in rigid tubes).
• GBF significantly impacted signals; wavelength-dependent shielding (940 nm effective, 625 nm negligible) was observed.

Conclusions:

• Optical detection of pulpal blood pulse is achievable in rigid pulp chamber environments.
• Gingival blood flow (GBF) can interfere with pulpal signals, necessitating wavelength-specific shielding.
• Optical methods show potential for pulp vitality testing if signal differentiation is improved.