This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
[{'content': 'Radiograph shows: \nSelect and explain. \nA. Dentinal dysplasia, B. Regional odontodysplasia, C. Dentinogenesis imperfecta, D. None', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Clinical\xa0 Features:\xa0The teeth affected by odontodysplasia\xa0exhibit either a\xa0delay or a total failure in eruption.\xa0Their\xa0shape is markedly altered,\xa0 being generally very irregular in appearance, often with evidence of defective mineralization.\nRadiographic\xa0 Features:\xa0The radiographs are uniquely\xa0characteristic, showing a marked reduction in radiodensity so\xa0that the teeth assume a ‘ghost’ appearance.\xa0Both the enamel and dentin appear\xa0very\xa0thin\xa0and\xa0the\xa0pulp\xa0chamber is exceedingly large. The enamel layer often is not\xa0evident.\nKey Concept\nThe unusually large pulp, thin enamel\xa0and dentin are evident.\nRef: Shafer’s Ed 7th Pg 59', 'role': 'assistant'}]