Why should wax patterns not be left on the bench for a long time?

Wax patterns should not be left on the bench for a long time primarily because of the risk of distortion. Wax is a material that can easily change shape and lose its designed form when exposed to various environmental factors such as temperature changes or prolonged handling.

If wax patterns are allowed to sit for an extended period, they may warm up due to ambient conditions or from the heat generated by handling, which can lead to deformation. Distortion in the wax pattern can adversely affect the accuracy of prosthetic restorations, ultimately compromising their fit and function when manufactured.

While loss of elasticity, risk of contamination, and poor impression quality are all considerations in dentistry, they do not directly address the immediate structural integrity and shape retention of wax patterns as distortion does. Therefore, maintaining the integrity of the wax pattern by minimizing the time it spends unprotected on the bench is crucial for achieving precision in dental restorations.