Why are partial-coverage restorations considered weaker?

Partial-coverage restorations are considered weaker primarily because they do not completely encircle the tooth. This lack of full encirclement means that the restoration only provides support and coverage to certain parts of the tooth structure, rather than distributing forces evenly across the entire tooth. As a result, they may not provide the same level of protection against fractures or failures compared to full-coverage restorations, which encase the entire tooth.

The design of partial-coverage restorations can make them more susceptible to stresses that may lead to chipping or cracking when the tooth experiences biting forces. Additionally, the remaining portions of the tooth are left exposed and can be more vulnerable to decay and other forms of damage. In contrast, full-coverage restorations encompass the entire tooth, offering superior strength and stability as they can better withstand the forces of mastication, thereby enhancing the longevity of the dental restoration.

Understanding that the structural integrity provided by the complete encirclement of full-coverage restorations juxtaposes the more limited support of partial-coverage helps clarify why the latter is generally deemed weaker.