Endodontic microsurgery is one effective method for preserving teeth affected by periapical disease, and is also an essential technique for treating difficult cases. However, due to the restricted operating space at the posterior site and the proximity of the root apex to the maxillary sinus, endodontic surgery in the posterior maxillary area represents great challenges. This article summarizes the anatomical relationship between the maxillary sinus and the maxillary posterior teeth, the influence on endodontic microsurgery, and the application of assistive techniques on maxillary posterior teeth, such as 3D-printed surgical guides and ultrasonic osteotomes. Literature review results show that the spatial relationship between the apex of maxillary posterior teeth and the maxillary sinus is usually divided into three categories: the apex enters the maxillary sinus; the apex contacts the bottom of the maxillary sinus; and there is a distance between the apex and the bottom of the maxillary sinus. CBCT should be performed before the operation, and the periapical state of the tooth and the maxillary sinus and the distance between the lesions and the sinus floor should be considered to evaluate the difficulty of the operation. Meanwhile, during surgery, equipment such as surgical guides, endoscopes and ultrasonic osteotomes should be used to ensure that the operation is safer, reliable, precise and less invasive, but the clinical popularity of ultrasonic osteotomes still needs further promotion. Moreover, high-quality clinical studies on the long-term effects of micro-apical surgery in the posterior maxillary area are still lacking.

Endodontic microsurgery is an important treatment for endodontic disease and maxillary sinusitis of endodontic origin of maxillary posterior teeth. However, endodontic microsurgery is challenging due to the close proximity between the maxillary posterior teeth and the maxillary sinus, which may lead to complications of mucosal perforation of the maxillary sinus floor. Endodontic microsurgery combined with maxillary sinus floor elevation is considered as a solution, namely natural tooth-related maxillary sinus floor elevation. The evaluation and design of natural tooth-related maxillary sinus floor elevation are closely related to local anatomic relationships. This article provides a systematic review of the anatomical considerations of endodontic microsurgery, namely natural tooth-related maxillary sinus floor elevation in the maxillary posterior region in terms of maxillary posterior teeth, alveolar ridge of the maxillary posterior region, and maxillary sinus. The literature review showed that a minimum of 3 mm of the root apex must be removed during endodontic microsurgery to eliminate the majority of apical ramification, lateral canals, and severe root curvatures. The height and thickness of alveolar ridge bone are important indicators for evaluating and designing endodontic microsurgery for maxillary posterior teeth. Maxillary sinus floor mucosa, maxillary sinus ostium, the proximity between maxillary posterior teeth and the maxillary sinus floor, maxillary sinus septa, posterior superior alveolar artery, and greater palatine artery, and possible maxillary sinus cysts are the main maxillary sinus-related considerations. When the maxillary sinus floor is below the line between the buccal and palatal roots, when the root apices contact or protrude into the maxillary sinus floor, or when the apical lesion is directly connected to the maxillary sinus mucosa, natural tooth-related maxillary sinus floor elevation is applicable. Anatomical considerations should be emphasized throughout endodontic microsurgery and natural tooth-related maxillary sinus floor elevation in the maxillary posterior region. Further studies are required to investigate the clinical design and difficulty assessment of natural tooth-related maxillary sinus floor elevation in different local anatomical relationships.

Inflammation is a protective response of the body to pathogens and injury. Hence, it is particularly important to explore the pathogenesis and key regulatory factors of inflammation. BMP9 is a unique member of the BMP family, which is widely known for its strong osteogenic potential and insensitivity to the inhibition of BMP3. Recently, several studies have reported an underlying pivotal link between BMP9 and inflammation. What is clear, though not well understood, is that BMP9 plays a role in inflammation in a carefully choreographed manner in different contexts. In this review, we have summarized current studies focusing on BMP9 and inflammation in various tissues and the latest advances in BMP9 expression, signal transduction, and crystal structure to better understand the relationship between BMP9 and inflammation. In addition, we also briefly summarized the inflammatory characteristics of some TGF-β superfamily members to provide better insights and ideas for the study of BMP9 and inflammation.