# Clinical Applications of Low-Intensity Pulsed Ultrasound and Its Underlying Mechanisms in Dentistry
## 4 LIPUS Contributes to the Stability of Implants via Facilitating Osseointegration  
Dental implants have been widely applied in the mandible and the maxilla. However, a lack of osseointegration may result in implant looseness and the stability of implants depends on the surrounding bone and the bone implant interface (BII) [74]. Less alveolar bone and osteoporosis may also lead to implant failure. Furthermore, building a secure surface between the implant and surrounding bone is a slow process [75]. At present, there are numerous studies exploring new technology to improve and promote osteoporosis of dental implants. Ultrasound techniques had been proven that can stimulate dental implants' osteoporosis and the spread of ultrasonic waves in dental implants can be led by the structure of implants [76; 77]. Due to the excellent performance in osseointegration and soft tissue healing, LIPUS attracted broad attention in the context of implants [78]. LIPUS was found to contribute to peri-implant bone volume at any time and promote the contact between bone and implants from the fourth week [79]. Besides, the combined application of LIPUS and low-magnitude high-frequency (LMHF) loading can also enhance the osteogenic activity of peri-implant bone and osseointegration can be observed in about the fourth week after implanting [80]. Actually, in the studies of rabbits, pigs, and rats, LIPUS was also demonstrated as effective to enhance osseointegration. Since the jaws of rabbits, pigs, and rats are thin, it's difficult to build a model of animal maxillofacial implants. So, most of the studies used dental implants in the tibial model to evaluate the effect of osseointegration. Using LIPUS in a rabbit tibial model with dental implants imbedded, the bone area values, the bone volume values, and the bone-implant contact values were all increased significantly while the increase of bone area values and bone volume values was earlier than that of bone-implant contact volume [81]. Besides, the fibrillar calcified layer and trabecular bone around the dental implant in  
Figure 5: LIPUS inhibits further exacerbation of OITRR by affecting the ratio of RANKL and OPG. During OITRR, the ratio of RANKL/OPG is high. The RANKL binds to RANK which exists in the osteoclast precursor and then the osteoclast precursor differentiates into osteoclasts. The growing osteoclasts lead to OITRR further aggravation. Through using LIPUS, the ratio of RANKL/OPG decreases which contributes to osteoclast apoptosis. rabbits with LIPUS occurring earlier than in rabbits without LIPUS. Further, the maximal pull-out strength and stiffness were more preeminent on the side with LIPUS, which suggested that the combination of dental implants and bone is excellent [75]. Similarly, in the pig model, LIPUS can also promote bone formation and bone-implant contact surface healing [82]. Interestingly, a rat model was built with dental implants in the maxillary first molars extraction sockets successfully. In this study, LIPUS played a significant role in promoting the dental implant osseointegration of \(\alpha\)calcitonin gene-related peptide (\(\alpha\)CGRP) positive rats while cutting no ice in \(\alpha\)CGRP negative rats. This consequence indicated that LIPUS may promote local neurons to generate \(\alpha\)CGRP to enhance dental implant osseointegration [83]. In addition to animal studies, the human study also declared that LIPUS contributed to dental implant osseointegration. Through fractal dimension (FD) analysis, dental implants with LIPUS had better stability and the side which was closer to LIPUS showed more new bone formation [84]. In addition to dental implants, miniscrew implants (MSIs) are also needed in orthodontic treatment. MSIs can be implanted into the alveolar bone to pull tooth movement [85]. However, the success rate of implanting MSIs is about 86.5%, which is lower than dental implants [86]. The surrounding bone metabolism of MSIs is one of reasons for MSI failures [87].