Photoacoustic imaging of gingival inflammation using low-cost near-infrared diode laser

Periodontal disease and dental caries are the most common health issues encountered in dental practice. A new technique for detecting periodontitis is photoacoustic imaging (PAI) with a low-cost diode laser modality. This study investigates the capability of a PAI system in detecting gingival inflammation by using an animal model. The modeling of gingival inflammation in this study used Sprague-Dawley rats, which were divided into the following four groups: healthy, incipient inflammation (7 days of inflammation induction), moderate inflammation (14 days of inflammation induction), and advanced inflammation (21 days of inflammation induction). A custom-built PAI, which comprised a near-infrared diode laser, a condenser microphone, and a mechanical system in the form of a computer numerical control (CNC), was used for imaging samples. The imaging source was a continuous-wave diode laser, whose intensity was modulated in this study by adjusting the duty cycle of the laser exposure. The laser modulation frequency and duty cycle were 13 kHz and 50 %, respectively, to image gingiva in a PAI system. The photoacoustic (PA) intensities of gingiva in the advanced inflammation, moderate inflammation, incipient inflammation, and healthy groups were 104.37, 97.57, 91.27, and 64.37 dB, respectively. Analysis of PA images showed that the inflammation groups produced PA with higher intensity than the healthy group. The study shows that a simple PAI system can be used to distinguish between healthy and inflamed gingiva.