Periodontal disease is an inflammatory condition that alters the periodontium, resulting in destruction of the alveolar bone; without treatment the condition may lead to tooth loss. Dental implants are an alternative for substitution of naturally lost teeth as they have high success rates; however, some factors are related to its failure. Peri-implantitis (PI) is a pathological condition that affects the tissues surrounding dental implants and has been reported as the major cause of implant failure; PI and periodontal diseases are characterized by tissue inflammation and bone damage. In homeostasis conditions, reactive oxygen species (ROS) have been shown to be involved in cell maintenance, signal transduction, and repair of all tissues, but ROS overaccumulation leads to oxidative stress, which generates cell damage and tissue destruction; likewise, antioxidants protect against the destructive effects of ROS by turning free radicals into waste products. The main purpose of this review was to determine some aspects of inflammatory responses and oxidative stress and analyze their relationship with the lack of osseointegration and PI.