Anatomical considerations for natural tooth-related maxillary sinus floor elevation of maxillary posterior teeth

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.