Why is a short crown considered as a contraindication for partial coverage restoration?

A short crown is considered a contraindication for partial coverage restoration primarily due to its inferior retentive and resistant features. When a crown is short, there is limited surface area available for bonding and retention, which is crucial in ensuring that the crown remains securely in place within the oral cavity during function. Adequate height and surface area on the preparation allow for better adhesion and resistance to dislodgement forces that a restoration may face during biting and chewing.

Partial coverage restorations, such as onlays or inlays, rely heavily on the tooth structure for retention. In cases where the crown is shorter than optimal, there is not enough circumferential support for the restoration, which can lead to the risk of failure due to displacement or fracture. Hence, the restorations may not be as effective or durable, necessitating a requirement for a longer crown to allow for sufficient retention and stability.