The main idea here is that muscle pain from the jaw muscles can be felt as toothache in specific teeth—a phenomenon known as referred pain from the masticatory muscles. In particular, the posterior portion of the temporalis and the upper part of the superficial masseter are the muscle regions most commonly associated with referred pain to the maxillary posterior teeth. When these muscle fibers are tense or harbor trigger points—often from clenching or grinding—they can send nociceptive signals that the brain interprets as pain in the back upper teeth. Why these two areas fit best: the posterior temporalis lies nearer the temples and the back of the maxilla, and its nociceptive input tends to be referred to the posterior maxillary dentition. The upper superficial head of the masseter sits over the zygomatic arch and also has referral patterns that align with the maxillary molar region. Together, they account for pain felt in the back upper teeth when the muscle is stressed. The other options are less likely because their referral patterns typically involve different regions. Anterior or middle temporalis areas tend to relate more to frontal or lateral regions rather than the posterior teeth, and the lower portion of the masseter is more associated with referred pain to the lower teeth. So, pain in the maxillary posterior teeth being deferred to the posterior temporalis and the upper superficial masseter best matches the known referral patterns for masticatory muscle pain.