Interim restoration enamel fracture is most predictable due to:

Interim restorations are typically designed to serve as temporary solutions while the final restorations are being fabricated. The predictability of enamel fracture in interim restorations can often be attributed to the presence of missing proximal contacts. When proximal contacts are compromised or absent, the stability of the tooth structure is affected. This lack of support can lead to increased movement and stress on the restoration, making it more susceptible to failure, including enamel fractures.

Additionally, missing proximal contacts can result in an improper distribution of forces during normal function, further increasing the likelihood of enamel damage. This situation is particularly problematic in posterior restorations, where forces during chewing are concentrated.

While factors like marginal fit, occlusal load, and whether the interim restoration is partial coverage can contribute to the overall performance and longevity of an interim restoration, the absence of proximal contacts most directly correlates with the predictability of enamel fracture. This emphasizes the importance of ensuring that interim restorations maintain proper proximal contacts to enhance their mechanical stability and reduce the risk of complications during the interim period.