Final answer:
A real cultured pearl may give a slightly gritty or squeaky feeling when rubbed against one's teeth due to its crystalline structure, while imitation pearls generally feel smooth. However, the tooth test is subjective, and professional appraisal is recommended for a definitive verification.
Step-by-step explanation:
Many pearl aficionados believe that a real pearl, including a cultured pearl, can be distinguished from an imitation by the sensation it gives when rubbed against one's teeth. If you lightly rub a pearl against the edge of your teeth, a real pearl typically gives a slightly gritty or squeaky feeling, due to the microscopic crystalline structure of the nacre, or mother-of-pearl, that it is made of. It is not a definitive test, and it should be done gently to avoid damaging the pearl or your teeth.
Imitation pearls, on the other hand, often feel smooth when rubbed against the teeth because they're usually made of glass or plastic and lack the natural texture of real nacre. Remember, this test is subjective and other factors such as pearl type, condition, and individual perception can affect the outcome. Therefore, a professional appraisal is always recommended if you require a definitive verification of a pearl's authenticity.