Londono J, Ghasemi S, Lawand G, Dashti M. Evaluation of the golden proportion in the natural dentition: a systematic review and meta-analysis. J Prosthet Dent 2021; doi: 10.1016/j.prosdent.2021.07.020. Online ahead of print.

Golden proportions, means and percentages may be irrelevant

The assessment of facial aesthetics is an important element in diagnosis and treatment planning in restorative dentistry. 'Smile design' are current dental buzzwords, and without doubt, an attractive smile can improve self-confidence. Despite the fact that beauty is in the eye of the beholder and extremely subjective, there have been frequent attempts to define perfect tooth and facial ratios mathematically. Hopefully, outcomes may then be enhanced and misunderstandings alleviated by the application of a standard formula.

The Golden Proportion (1:1.618, denoted by the Greek letter phi) was first mooted as being relevant to tooth relationships in the 1970s. It was proposed that the upper lateral incisor should be 0.618 of the width of the neighbouring central incisor and also 0.618 of the visible width of the neighbouring canine. Others have suggested a 'recurring (a)esthetic dental proportion' (RED), stating that the reduction in visible width of the teeth remains constant from the midline distally. The golden mean or golden percentage has also been proposed in which, within the inter-canine width, the central incisors occupy 50%, the lateral incisors 30% and the canines 20%. Variations in these ratios may be related to ethnicity and sex, but the evidence is conflicting. Methods of measurement of clinical dimensions have included computer imaging, casts and 'intra-oral assessments'. The authors suggest that there is no evidence for the dominance of the Golden Proportion in the natural dentition and they carried out a systematic review of the literature.

Of the populations studied, the Golden Proportion was not common and was not found in the natural dentition of the majority of individuals with an aesthetically pleasing smile. The Golden Proportion is thus irrelevant. If the ratio is not used in treatment planning, then 'patients will not have visible abnormalities in their prosthesis'. Similarly, the study did not find a relationship between inter-canine distance and other parameters. Although the tooth width ratio of the lateral incisor to the central incisor did not differ between men and women, the study found that the tooth width ratio of the canine to the lateral incisor was larger in men than women.

Proportions need to be chosen which are harmonious with the face, and complex cultural and ethnic preferences need to be considered when designing smiles. Studies on the factors which determine an aesthetically pleasing smile are lacking. Measurements may be important but should only be used as a preliminary guide. If a pleasing smile is to be quantified to a number, then further studies are required, which take into account ethnic and cultural differences.