Clinical Follow-up Study of Traumatized Teeth Using Transmitted-Light Plethysmography

Objectives: Transmitted-light plethysmography (TLP) is an optical technique to detect blood volume change. Previously, we reported clinical applicability of the prototype TLP system (J. Morita. Mfg. Corp) to detect pulpal blood flow from traumatized teeth. This study investigated prognosis after dental trauma in terms of pulpal circulation and nerve response. Methods: TLP data were recorded from traumatized young permanent and deciduous teeth of patients aged 4-12 years which didn't respond to electric pulp testing (EPT). The observation periods ranged from 6-24 months after trauma. The resin caps of each tooth were made to support light emitting diode (LED) and photodiode. Teeth were illuminated from palatal side with 525nm LED. Light transmission was recorded at labial side by photodiode. Quantifying the pulpal circulation, amplitudes of plethysmogram (AC; Alternate current) and transmitted light intensity (DC; direct current) were measured to derive AC/DC values in percentage. We classified TLP data under four following groups according to pulse shape characteristics; (a) clear pulse waves as healthy teeth, (b) noisy pulse waves, (c) sometimes detectable, (d) not detectable. As a control, TLP and EPT data of healthy teeth were also recorded. Results: At early stage of trauma, although AC/DC values were significantly lower and pulse shapes weren't clearer than that of control, TLP was detected. During the follow-up, sensory threshold eventually recovered in most cases followed by long-time observation of TLP. Pulse shapes were becoming clearer. As for deciduous teeth, recovery of EPT tended to delay compared with permanent teeth, TLP was easily detectable. Conclusion: Recovery of pulpal circulation was observed before the nerve response. The change of AC/DC values and pulse shape characteristics might reflect the healing process of pulp vascular system. TLP was found to provide the effective information for pulp viability. This research was supported by Grant-in-Aid for Young Scientists (B) #21791843.