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
A 25 year old female patient is unhappy with her smile. Which of the following could be the reason for the patient’s chief complaint? 
Select and explain. 
A. Reverse smile arc, B. Narrow buccal corridor, C. Roll of esthetic line, D. Both 1 and 3
A: Reverse smile arc
Answer: A: Reverse smile arc 
Explanation: The smile arc is defined as the contour of the incisal edges of the maxillary anterior teeth relative to the curvature of the lower lip during a social smile. For best appearance, the contour of these teeth should match that of the lower lip. If the lip and dental contours match, they are said to be consonant. In a “nonconsonant” smile arc, the maxillary incisal edges are either flat or reversed relative to the curvature of the lower lip. A flattened smile arc is less attractive in both males and females.