Successful bone augmentation relies on primary wound closure. The labial frenum is a soft tissue that connects the lip to the alveolar mucosa or gingiva. However, the frenum may exert biomechanical forces to the wound edge, causing wound instability. The aim of this study is to review the frenum composition and classifications and to understand the significance of the frenum in wound stability upon bone regeneration. Together with a manual search, an electronic search was conducted through three online databases on studies published until September 2022. A total of 300 articles were identified, and 9 studies were included in this review. Two of the included studies discovered that 35% to 37.5% of the labial frenum had muscle fibers. Other studies showed that the labial frenum was mainly composed of connective tissue with elastic fibers. There are two widely used classifications for the frenum based on its morphology and attachment position. No studies specifically evaluated the impact of the frenum on bone regeneration, but the frenum location intercorrelated with the amount of keratinized tissue, which could influence wound stability. A modified frenum classification for the edentulous ridge and a decision diagram to manage the frenum is proposed for research and evidence-based practice.
