What type of defect is considered the best use for an onlay graft?

An onlay graft is particularly effective for a 5-wall defect because this type of defect provides a well-defined space with maximal surrounding bone support. In a 5-wall defect, the graft has the opportunity to be well-integrated and stabilized, which is crucial for successful osseointegration and bone regeneration. The surrounding walls create a containment area that minimizes the risk of graft displacement and allows for proper vascularization, which is important for healing and effective bone filling.

While various types of defects (1-wall, 3-wall, and 4-wall) might also benefit from grafting techniques, they lack the encasement that a 5-wall defect provides. The more walls present, the better the ability of the graft to maintain its position and promote healing, making the 5-wall defect the ideal scenario for utilizing an onlay graft effectively. Therefore, this choice highlights the importance of defect morphology in determining the best grafting approach.