What is the primary factor impacting retention in posterior tooth restorations?

The primary factor impacting retention in posterior tooth restorations is margin design. A well-designed margin plays a crucial role in ensuring that the restoration adequately hugs the tooth structure. This allows for better mechanical retention and can influence how well the restoration stays in place. Proper margin design also minimizes the risk of plaque accumulation and helps facilitate an effective seal between the restoration and the tooth, reducing the likelihood of secondary caries.

In contrast, cusp height and wall height also contribute to retention but are not as central as margin design. Cusp height primarily affects the occlusal function and aesthetic of the restoration, rather than its ability to remain securely bonded to the tooth. Wall height is significant for providing adequate support and resistance against forces during mastication, but again, the margin is what directly impacts how well the restoration is held in place within the tooth structure. Hence, focusing on margin design is essential when considering retention in posterior tooth restorations.