Aesthetic deviation

Sir, I would like to join the discussion regarding the golden proportions in dental aesthetics.

I pay my respects to Dr E. Levin and also thank Dr A. Astakhov for his overview of golden proportion coefficients (BDJ 2008; 204: 419–420 and BDJ 2008; 205: 61, 637). It is hard to disagree with Dr Levin that perfect symmetry is very rare in nature. However, it can be observed through clinical practice that teeth forming a pair have exactly the same width. Moreover, the correlation of central incisors to lateral incisors in the dental arch is standard and the majority of people have teeth of standard width. Therefore, the natural asymmetry of the dental arch is due not to differences in the width of symmetrical teeth but rather to their positioning in the dental arch.

Ultimately, mathematics is the root of aesthetics. Therefore, employing ideal proportions will always help to improve the accuracy of a clinical assessment and management.

The method of dental arch calculation, to which there are no written references in English, uses ideal coefficients of the ratio of the front teeth widths. It can be used in addition to Dr Levin's method of visually assessing the correlation of the front teeth in the dental arch to the golden proportion.

My method is based on the coefficients of the correlation of the front teeth to each other. The coefficients are not the golden proportions themselves because golden proportions only work when you look at the patient face-on. These coefficients, on the other hand, can be used by the dentist in the working position with the help of a gauge. The working position does not allow the dentist to control the proportionality of teeth to each other. However, the coefficients allow the dentist to plan and build the front teeth such that once the work is finished, the teeth will be in line with the golden proportions when the patient isviewed face-on.

A human eye is inclined to optical illusions. One can perceive objects and spaces in different ways. A dental gauge permits measurements to an accuracy of up to 0.1 mm, which is the minimum for controlling teeth symmetry and proportionality. This easily compensates for optical illusions and makes inevitable mistakes in the dentist's work invisible to everyone.

For the upper jaw the ideal proportion for the central, lateral incisors and canines is 1.3 : 1.0 : 1.15. For the lower jaw the proportion for the central, lateral incisors and canines is 1.0 : 1.1 : 1.4. Using these coefficients one can:

• Check the proportionality and symmetry

• Identify a probable reason for disproportion and asymmetry

• Reconstruct the dental arch in symmetry and in golden proportions.

In Figure 1, the arch length between the canines is 29.9 mm. It is completely sufficient for standard incisor widths (8.5 mm and 6.5 mm). The space excess is divided proportionally between four incisors with a 1.3 coefficient.

Figure 1

Reconstruction of the upper front teeth with a 1.8 mm diastema

In Figure 2, the length of the front part of the dental arch is 3.8 mm shorter then the standard, while the incisors have standard widths (5.5 mm and 5.0 mm). The space deficiency is compensated by 0.5 mm on each canine and 2.0 mm on all incisors with a 1.1 coefficient. Now all incisors have a compromised width, but are proportional as between each other.

Figure 2

Reconstruction of the lower front teeth with crowding

Finally, when performing a restoration in a direct technique even with the ideal coefficients one will always still have some aesthetic deviation.