Development of an ultrasonic device to detect early demineralized lesions and establishment of clinical criteria for these diagnoses

龋齿的发病特点是牙齿表面有白色斑点或染色。然而，估计这些病变的龋齿活动是困难的，因为我们没有工具来识别哪些病变正在脱矿、停滞或再矿化。为了检测龋齿对牙釉质和牙根的影响，我们研制了一种无创、无损的超声波探牙仪。该超声波传感器检测系统由用于传感的振动压电元件、用于获取齿面频率特性的压电检测元件和用于将传感器定位在齿面上的轻臂组成。在知情同意的情况下收集拔除的牙齿，用乳酸-CMC凝胶(6%，pH 4.5)制备脱矿牙釉质标本。超声波传感器被加载到这些牙齿表面，并扫描以绘制频率特性图。在共振法中，表面特性用振荡的频移来表示。研制的超声传感器的检测元件在临床上足够小。通过对四组釉质标本的测量，早期釉质龋损以脱矿化的时间依赖方式的振荡的低频移位表现得非常明显。通过对10颗拔除牙齿的表面扫描，该检测系统能够区分牙釉质和牙根上的声音或龋损、牙石沉积、染色、釉质表面的白色斑点和裂缝。然而，当探索具有重叠损伤的复杂表面时，需要额外的信息。我们的新感官探测仪采用超声共振法，被发现是一种强大的工具，可以估计龋齿的初始变化和进展程度。

The onset of dental caries is characterized by white-spots or staining on tooth surfaces. However, estimation of caries activities of these lesions is difficult because we have no tool for recognition which lesion is demineralizing, arresting or re-mineralizing. For detection of the initial changes of the tooth surface affected by dental caries on the enamel and root, we developed a noninvasive, nondestructive dental explorer employing ultrasonic sensor technology. The ultrasonic sensor detection system consists of an oscillating piezoelectric element for sensing, a piezoelectric detective element to obtain frequency characteristics of the tooth surface, and a lightweight arm for positioning the sensor on the tooth surface. Extracted teeth were collected with informed consent and demineralized enamel specimens were prepared with lactate-CMC gel (6%, pH 4.5). The ultrasonic sensor was loaded on these tooth surfaces and scanned for drawing a map of the frequency characteristics. The surface characteristics were represented by the frequency shifts of oscillation in the resonance method. The detecting element of the developed ultrasonic sensor was sufficiently small in the clinic. By measurements using four sets of enamel specimens, early lesions of enamel caries were dearly represented by low frequency shifts of oscillation in a demineralized time-dependent manner. By scanning surfaces of ten extracted teeth, this detection system was able to distinguish sound or caries lesions on the enamel and roots, calculus depositions, staining, white spots and cracks on the enamel surface. However, additional information was need when exploring complex surfaces with overlapping lesions. Our new sensory explorer employing the ultrasonic resonance method was found to be a powerful tool for estimating initial change and degree of progression of dental caries.