The applications of flexible electronics in dental, oral, and craniofacial medicine

Dental, oral, and craniofacial diseases jeopardize health and reduce the quality of life. Accessing disease-related signals in advance is beneficial to prevent the occurrence or progression of those diseases. However, the inconvenience of periodical in-hospital examinations and the difficulty of sustaining daily health monitoring challenge personal compliance and possibly lead to limited prevention or treatment. Medical flexible electronics are electric devices fabricated on soft and extensible substrates to fit the human skin and enable non-invasive continuous monitoring of biophysical/biochemical signals. They provide the possibility of long-term, continuous, comfortable, and wireless healthcare monitoring and are expected to alleviate time and economic consumption by avoiding in-hospital examinations and treatment. Therefore, flexible electronics have emerged for early diagnosis and disease monitoring in stomatology. It is noteworthy that special biophysical/biochemical characteristics and the environment of dental, oral, and craniofacial areas bring distinct challenges that flexible electronics need to address ingeniously to ensure their stability, selectivity, and sensitivity. This review summaries flexible electronics and their specificity when used in dental, oral, and craniofacial applications, including monitoring saliva or cavity-gas related biosignals, sensing the mechanical fluctuation from facial muscle/respiratory activities or orthodontic forces, and executing special functions in the prevention or postoperative recovery of relevant diseases. Furthermore, after analyzing current challenges and proposing potential solutions, the “5I” principles of imperceptibility, intelligence, individualization, integration, and inexpensiveness are presented to help guide the future development of flexible electronics and promote their commercialization for dental, oral, and craniofacial medicine.