Which of the following is a characteristic of Wickham's striae?

Wickham's striae are distinctive white lines seen in oral lichen planus, a condition that affects the mucous membranes. A defining characteristic of these striae is hyperparakeratosis, which refers to an abnormal retention of keratin in the stratum corneum of the oral epithelium. In lichen planus, this hyperparakeratosis occurs alongside an inflammatory process, contributing to the formation of these white striae.

The other options do not accurately describe the characteristics of Wickham's striae. A smooth surface is not typical, as the affected areas may have an irregular texture due to the underlying condition. The ground glass appearance usually refers to a specific type of dental radiographic finding, not related to Wickham's striae. Prominent pain can be associated with lichen planus, but typically, Wickham’s striae themselves are not painful; they are more of a clinical finding rather than a symptomatic feature. Thus, hyperparakeratosis is the key characteristic that best describes Wickham's striae in the context of oral lichen planus.