Solanum burchellii is sometimes called the tandpynbos (toothache bush) in Afrikaans. While the name may sound reassuring to the toothed one in distress, how the remedy works or should be applied is not clear from the name. A bit like correlation between two variables indicating a link, not its nature.
Trial and error attempts at alleviating the toothache of the day via the S. burchellii route might result in imaginable but unwelcome outcomes. Some of them possibly disastrous should the choice become desperation driven.
For if the fruit contains the cure, one may imagine that it should be applied in the mouth or ingested. Remember that Solanum fruits are often poisonous; more could possibly be finished off besides the agony!
The sparsely scattered, straight and rigid spines in picture share the general hairiness of the plant on their lower parts. Spines do serve the purpose of making people think twice about the plant that bears them (Le Roux, et al, 2005; iNaturalist; http://solanaceaesource.org).