Department of Conservative Dentistry and Periodontology, University Medical Center Regensburg, University of Regensburg, Regensburg, Germany.
Private practice, Amberg, Germany.
Clin Oral Investig. 2019 Mar;23(3):1121-1132. doi: 10.1007/s00784-018-2530-y. Epub 2018 Jun 29.
Due to severe limitations of dental pulp sensitivity tests, the direct recording of pulsed blood flow, using photoplethysmography (PPG), has been proposed. In vivo evaluation is methodologically difficult and in vitro models have hitherto been adversely influenced by shortcomings in emulating the in vivo situation. Consequently, the aim of this study was to test an improved data acquisition system and to use this configuration for recording pulsed blood in a new model.
We introduced a PPG signal detection system by recording signals under different blood flow conditions at two wavelengths (625 and 940 nm). Pulsed blood flow signals were measured using an in vitro model, containing a molar with a glass pulp and a resin socket, which closely resembled in vivo conditions with regard to volumetric blood flow, pulp anatomy, and surrounding tissue.
The detection system showed improved signal strength without stronger blanketing of noise. On the tooth surface, it was possible to detect signals emanating from pulsed blood flow from the glass pulp and from surrounding tissue at 625 nm. At 940 nm, pulp derived signals were recorded, without interference signals from surrounding tissue.
The PPG-based method has the potential to detect pulsed blood flow in small volumes in the pulp and (at 625 nm) also in adjacent tissues.
The results show the need for clear differentiation of the spatial origins of blood flow signals of any vitality test method to be applied to teeth.
由于牙髓敏感性测试存在严重限制，因此提出了使用光体积描记法（PPG）直接记录脉冲血流。体内评估在方法学上具有挑战性，而体外模型迄今为止一直受到模拟体内情况的缺陷的不利影响。因此，本研究的目的是测试改进的数据采集系统，并使用该配置在新模型中记录脉冲血流。
我们通过在两个波长（625nm 和 940nm）下记录不同血流条件下的信号，引入了一种 PPG 信号检测系统。使用包含玻璃牙髓和树脂插座的体外模型测量脉冲血流信号，该模型在体积血流、牙髓解剖和周围组织方面与体内情况非常相似。
检测系统显示信号强度增强，而噪声的屏蔽作用减弱。在牙齿表面，在 625nm 处可以检测到来自玻璃牙髓和周围组织的脉冲血流发出的信号。在 940nm 处，可以记录到来自牙髓的信号，而不会受到周围组织的干扰信号。
基于 PPG 的方法有可能检测到牙髓中较小体积的脉冲血流，并且（在 625nm 处）还可以检测到相邻组织中的脉冲血流。
结果表明，任何应用于牙齿的活力测试方法都需要明确区分血流信号的空间来源。
