Dental Midline
The vertical line between the two upper central incisors and its aesthetic importance.
The dental midline is the imaginary vertical line between the two upper central incisors. Ideally, it coincides with the facial midline (center of the face, defined by the philtrum of the upper lip). Research shows that midline deviations up to 2mm are generally not noticeable to non-dental observers, while deviations greater than 4mm are readily detected. More important than perfect midline coincidence is midline perpendicularity — the midline must be perpendicular to the interpupillary line (horizontal line connecting the eyes). A vertical midline that's slightly off-center appears natural, while a canted (tilted) midline is immediately noticeable and disturbing. In orthodontic treatment and prosthetic rehabilitation, achieving a perpendicular midline takes priority over centering it perfectly. The lower dental midline is less critical aesthetically and often doesn't align with the upper.