The dental disease is a common disease for a human. Screening and visual diagnosis that are currently performed in clinics possibly cost a lot in various manners. Along with the progress of the Internet of Things (IoT) and artificial intelligence, the internet-based intelligent system have shown great potential in applying home-based healthcare. Therefore, a smart dental health-IoT system based on intelligent hardware, deep learning, and mobile terminal is proposed in this paper, aiming at exploring the feasibility of its application on in-home dental healthcare. Moreover, a smart dental device is designed and developed in this study to perform the image acquisition of teeth. Based on the data set of 12 600 clinical images collected by the proposed device from 10 private dental clinics, an automatic diagnosis model trained by MASK R-CNN is developed for the detection and classification of 7 different dental diseases including decayed tooth, dental plaque, uorosis, and periodontal disease, with the diagnosis accuracy of them reaching up to 90%, along with high sensitivity and high specificity. Following the one-month test in ten clinics, compared with that last month when the platform was not used, the mean diagnosis time reduces by 37.5% for each patient, helping explain the increase in the number of treated patients by 18.4%. Furthermore, application software (APPs) on mobile terminal for client side and for dentist side are implemented to provide service of pre-examination, consultation, appointment, and evaluation.