If patients complain about sudden ill-fitting occlusal sensation(acute malocclusion), a dentist has to consider many possible causes about that. Acute malocclusion is characterized its sudden onset and mainly can be caused by teeth and its related structure problem. But we always keep on mind that acute malocclusion also can be caused by temporomandibular disorders In this 3 cases of acute malocclusion, evaluating by patient history, clinical and radiographic findings, we diagnosed them as 1. Lateral pterygoid muscle spasm, 2.. Retrodiscitis, 3. Osteoarthritis. Through this non-odontogenic acute malocclusion cases, we emphasize the key of diagnosis is on comprehensive and careful patient history taking and clinical examination.