Background Precise preoperative knowledge of the mandibular canal (MC) variations and alveolar bone dimensions are vital elements for a successful dental implant. Thus, this study aimed to describe the three-dimensional morphology of the MC and alveolar bone dimensions, followed by a comparison of the variables in edentulous mandibular posterior sides with contralateral dentulous sides among adult Chinese individuals. Such variations were also studied in relation to gender and age. Material and Methods Cone-beam computed tomography (CBCT) was used for the morphometric analysis of the MC and alveolar bone dimensions in this cross-sectional study that analyzed retrospectively gathered data. Records of 112 individuals (56 males and 56 females) who had one edentulous mandibular posterior side and one dentulous side were included in the analysis. The MC position, length (MCL), and diameter (MCD) along with superior bone height (SBH) and bone width (BW) of the alveolar bone ridge were assessed. Results The MCD was lower at first ( p = 0.016) and second ( p = 0.079) molars on the edentulous sides. The SBH, BW1mm, and BW3mm were significantly lower on the edentulous than dentulous sides ( p < 0.05). However, there were no significant differences in the MC position or MCL and the incidence of bifid MC for dentulous and edentulous sides. Gender was a significant parameter for MCL, SBH, and BW, while no significant differences were observed in all variables on both sides in relation to age. Conclusions The position of the MC remains relatively constant regardless of losing teeth or increasing age. However, the MC position and MCL show differences in relation to gender. Alveolar bone dimensions are highly affected by dentate status followed by gender. Therefore, such variations should be considered by surgeons for successful surgical procedures in the posterior mandible. Key words: Mandibular canal, Bifid mandibular canal, edentulous mandible, alveolar bone dimension.

Background Implant periapical lesion (IPL), as a peri-implant disease originating from implant apex, maintains coronal osseointegration in the early stage. With the understanding to IPL increasingly deepened, IPL classification based on different elements was proposed although there still lacks an overall classification system. This study, aiming to systematically integrate the available data published in the literature on IPL associated with histopathology, proposed a comprehensive classification framework and treatment decision tree for IPL. Methods and findings English articles on the topic of “implant periapical lesion”, “retrograde peri-implantitis” and “apical peri-implantitis” were searched on PubMed, Embase and Web of Science from 1992 to 2021, and citation retrieval was performed for critical articles. Definite histopathology and radiology of IPL are indispensable criteria for including the article in the literature. The protocol was registered in PROSPERO (CRD42022378001). A total of 509 papers identified, 28 studies were included in this review. In only one retrospective study, 37 of 39 IPL were reported to be at the inflammatory or abscess stage. 27 cases (37 implants) were reported, including acute non-suppurative (1/37, developed to chronic granuloma), chronic granuloma (5/37), acute suppurated (2/37), chronic suppurated-fistulized (6/37), implant periapical cyst (21/37), poor bone healing (2/37), foreign body reaction (1/37). Antibiotics alone did not appear to be effective, and the consequence of surgical debridement required cautious interpretation because of the heterogeneity of lesion course and operation. Implant apicoectomy and marsupialization were predictable approaches in some cases. Conclusions The diversiform nature of IPL in the case reports confirms the need for such histopathological classification, which may enhance the comparison and management of different category.