Five Critical Criteria for Digital Smile Design

1. Width of central incisor: 8.5 mm

Adults go through a change in the length of anterior teeth with age due to wear. Width stays standard throughout an entire lifetime more or less. In his study on papilla proportions, Dr. Stephen Chu, showed that if we pick the central incisor width as 8.5 mm and a range of plus-minus 0.5 mm, 80 percent of the general population will fall within this range. Females usually had width 0.5 mm to 1mm less than males.

2. Height to width ratio of central incisor: 75 percent

The general esthetic shape of a well-proportioned central incisor would range between 70-80 percent. Female smiles generally have slightly slender and taller teeth proportion.

3. Papilla height: 40 percent

Chu and his group showed in their study that the interdental papilla of upper anterior teeth is 40 percent of the crown height.

4. Contact height: 4 mm, 3 mm and 2 mm

The contact areas between the maxillary anterior teeth should be designed to approximate the following measurements:

• Central-Central = 4 mm
• Central-Lateral = 3 mm
• Lateral-Canine = 2 mm

Correspondingly, the contact area proportion follows a 40-30-20 rule. The apical point of the contact between the maxillary anterior teeth is at the same horizontal plane. The incisal point of the contact progressively moves apically from central to lateral to canines.

5. Display of interdental papilla on smile

This is crucial for smile esthetics. Dr. Mark Hochman and colleagues  analyzed the display of the interdental papilla during maximum smiling and found that in 91 percent of the adult population the interdental papilla is visible. Even in low smiles interdental papilla was visible 87 percent of the time. There is also a correlation with age. The younger the patient, the more interdental papilla were visible on maximum smiling.

References

1. Chu, Stephen J., et al. "Papilla proportions in the maxillary anterior dentition." Int J Periodontics Restorative Dent 29.4 (2009): 385-93.

2. Hochman, Mark N., Stephen J. Chu, and Dennis P. Tarnow. "Maxillary Anterior Papilla Display During Smiling: A Clinical Study of the Interdental Smile Line." International Journal of Periodontics and Restorative Dentistry 32.4 (2012): 375.