Abutment height matters - but not always: the role of prosthetic retention type in peri-implant marginal bone loss.

Peri-implant marginal bone loss (MBL) is influenced by multiple prosthetic variables, yet evidence on abutment height remains inconsistent. This review proposes that this inconsistency arises from a failure to stratify evidence by prosthetic retention type. In screw-retained restorations, micromovement at the abutment-crown interface is mechanically unavoidable. Abutment height determines the proximity of this mobile interface to the crestal bone. Multiple clinical studies have reported greater MBL with shorter abutments, and reclassification of studies from four recent systematic reviews by retention type revealed that this association holds specifically in screw-retained configurations, where longer abutments consistently yielded more favorable outcomes. In cement-retained restorations, the abutment and crown are bonded into a unified complex, substantially reducing interface micromovement. Abutment height, therefore, loses its mechanical relevance. Instead, the transmucosal profile geometry-specifically the contour angle within the 2-mm zone adjacent to the bone crest-emerges as the primary determinant of MBL. Profile angles below approximately 20°, with concave or straight contours, have been associated with favorable peri-implant outcomes, though this value represents a pragmatic clinical target rather than an absolute threshold. These findings call for retention-specific prosthetic strategies: taller abutments should be prioritized in screw-retained restorations, whereas in cement-retained restorations, greater emphasis should be placed on optimizing the transmucosal contour design.