Pulpal blood flow (PBF) in immatured permanent incisors after luxation injuries was measured with a laser Doppler flowmetry (LDF). Applications of the LDF for studying revascularization of the injured pulp and for the early diagnosis of the pulpal vitality are discussed in this paper.
Periodic fluctuations synchronous with heartbeat were present in all of the PBF signals of the vital permanent incisors in healthy children (n=11). For detecting the heartbeat synchronous fluctuations, PBF in the luxated upper central incisors was recorded simultaneously with an electrocardiogram (ECG) in two patients aged 6 y 5 m and 8 y 11 m. The PBF and ECG waveforms were analyzed using a power spectrum analysis and spectral peaks in the PBF signals corresponding to the heartbeat frequency were examined. This method presents advantages for assessing blood flow recovery in a luxated tooth because the PBF value is easily affected by the crown color, probe position, thickness of the enamel and dentin, etc. and these factors reduce the reliability of the net PBF values. One of the luxated teeth which regained sensitivity to electric pulp testing five months after the injury showed heartbeat synchronous fluctuations in the PBF signal in the early stage of the healing (one month after the injury). In contrast, the other luxated tooth which did not show heartbeat synchronous fluctuations in the PBF signals was diagnosed as pulpal necrosis nine months after the injury. Evidence for such a conclusion was found in increasing apical radiolucency. The tooth never responded to the electric pulp testings which were carried out during the follow-up period.
It is proposed that a reliable method for the early diagnosis of the pulpal vitality in luxated teeth would be to measure the blood flow with the LDF and to assess the heartbeat synchronous fluctuations in the signals through power spectrum analysis.