The crucial characteristic of dental waxes for ensuring dimensional accuracy of the wax pattern is a low coefficient of thermal expansion.

- Dental waxes are used to create precise patterns that will later be cast into restorative materials.
- During the waxing, investing, and casting processes, temperature changes occur.
- If the wax expands or contracts significantly with temperature variations, the dimensional accuracy of the wax pattern will be compromised, leading to ill-fitting dental restorations.
- Therefore, a low coefficient of thermal expansion is essential to minimize size changes due to temperature fluctuations and ensure the wax pattern remains true to the desired dimensions.

Other options:
- High melting point helps maintain pattern integrity at elevated temperatures but is not directly related to dimensional accuracy during temperature changes.
- Good flow at oral temperature facilitates adaptation but does not prevent dimensional changes once the wax cools.
- High ductility relates to the wax's ability to withstand deformation without cracking but does not affect dimensional stability caused by thermal expansion.

In summary, minimizing dimensional changes caused by heating or cooling through a low coefficient of thermal expansion is the key requirement for dental waxes used in pattern fabrication.

Reference: Craig, R.G. *Restorative Dental Materials*, 13th Edition, Chapter 4 – Wax and Waxes for Dental Applications, Page 89.