This chapter describes through various clinical cases and a review of the literature the mechanisms leading to complications during and after the sinus grafting procedure (SFE). A clear understanding of those mechanisms contributes to more efficient treatments and prevents their recurrence. In the first part, the peroperative complications are reviewed with emphasizing on the clinical and practical aspects. The authors make a synthesis of the most predictable techniques for avoiding and resolving uneventful complications. Frequent complications such as membrane perforation and arterial bleeding are detailed, and appropriate solutions are proposed. The prevalence, detection, causes, and management of membrane perforations, the presence and morphology of septa, and the membrane thickness are presented. Arterial anatomy, bleeding, and hemostasis are described. Physiological and anatomical postoperative complications are discussed following a chronological order. The diagnostic tools and the appropriate treatment and approach are presented according to the severity of the alteration. The chronic sinusitis might in particular cause an osteitis resulting in implant loss in case of late diagnosis or inadequate therapy.