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: Dental
[{'content': 'Successful alignment of the permanent incisors to overcome the incisor liability depends upon: \nSelect and explain. \nA. Leeway space of Nance, B. Broadbent phenomenon, C. Increased intercanine width, D. Increased intermolar width', 'role': 'user'}, {'content': 'Answer: C \nExplanation: For incisors to erupt in normal alignment, there is an obligate space requirement in the anterior part\xa0of both the arches which is termed as incisor liability. The total sum of the mesiodistal width of four\xa0permanent incisors is larger than that of primary incisors by 7.6 mm in maxilla and 6 mm in mandible\xa0(Wayne). This obligate space is provided by:\n\nInterdental physiologic spacing in the primary incisor region: 4 mm in maxillary arch; 3 mm in\xa0mandibular arch.\nIncrease in the intercanine arch width: Signiﬁcant amount of growth occurs with the eruption of\xa0incisors and canines.\nIncrease in the anterior length of the dental arches: Permanent incisors erupt labial to the primary\xa0incisors to obtain an added space of 2-3 mm.\nChange in inclination of permanent incisors: Primary teeth are upright, but permanent teeth incline to the labial surface, thus decreasing the inter-incisal angle from about 150o in the\xa0deciduous dentition to 123o in the permanent dentition. This increases the arch perimeter.\n\nTextbook of Orthodontics, Gurkeerat Singh, 2nd ed\xa0Page 45-46', 'role': 'assistant'}]