The Golden Proportion

18 October, 2011 / Infocus
 

Phi, the divine proportion, the magic ratio, the golden cut and the sacred geometry are just some of the names given to the number 1.618033988749895. This occurs throughout nature and parts organised in this proportion are said to display greatest beauty and ultimate efficiency in function. It has been found in all aspects of our world from the spirals of galaxies and the harmony of music, to the breeding of rabbits and stock market rises and falls.

Proportion is an important aspect of good aesthetics and is regularly used consciously and subconsciously by dentists. Many have tried to measure beauty and set ‘golden’ rules but by far the most cited is the ‘golden proportion’. This was first mentioned in the dental literature in 1978 and subsequently there have been many studies regarding the use of the golden proportion in various aspects of dental aesthetics.

More recent studies have challenged the ‘golden proportion’ and suggesting the golden proportion is not a single value but rather like a range2. Whatever your opinion, these are interesting and potentially very useful concepts which every dentist should be aware of.

The most well known relationship is the proportion between teeth widths. A golden proportion is present between the widths of the eight anterior teeth when viewed from straight on (not the actual width). The width of the central incisor is 1.61 larger than the lateral incisor which is 1.61 larger than the canine etc. This has uses in determining space requirements for incisor replacements.

Interestingly, there is also a relationship between the width of these anterior teeth, known as the anterior aesthetic segment, and the width of the smile. These buccal corridors provide a ‘back drop’ for the anterior aesthetic segment and is said to be most aesthetically pleasing when in golden proportion. These areas of darkness or neutrality, sometimes known as negative space, are useful in orthodontics and an important factor in giving prosthesis a natural appearance. The picture above demonstrates this relationship.

When specifically looking at central incisors their dimensions can be established using the golden rectangle. The width of two central incisors is in golden proportion to their height (black rectangle above). This is useful when reconstructing the smile, for example in patients suffering from significant gingival recession anteriorly. The golden rectangle can be used when constructing a gingival veneer to determine where to place the gingival margin and how much tooth to show. The golden rectangle is also found in many day to day shapes including playing cards, credit cards and windows.

Another use is the positioning of the incisal line when constructing prosthesis. In a relaxed face, with a free way space, the ‘chin to lip line’ (larger) is in golden proportion to the ‘base of nose to lip line’ (smaller).

There are several ‘golden proportion’ tools available to the clinician including a disposable plastic/paper gauge3. This comes in a variety of sizes to fit central incisors from 7-10mm in width. Additionally, software3 is available for download which overlays golden proportion grids onto digital clinical photos to show the most aesthetically pleasing dimensions of the central, lateral, canine and pre-molar teeth.

These proportions are tools and not goals. They are a useful guide and should be used as part of a full aesthetic assessment. Chiche4 describes the four factors of aesthetic composition: frame and reference, proportion and idealism, symmetry and perspective and illusion.

A technique using frames is used by artists to draw heads. They draw within a measured general frame and then refine this with measured inner frames and reference points. Teeth interact with three frames: the face, lips and gingival4.

This concept of the golden decagon has been applied to faces by the mathematician and plastic surgeon Marquardt5. He designed face masks which fit these ratios and can be digitally placed over clinical photographs to determine how close a face is to the average.

A good example of this is that the width of the base of the nose compared to the width of the mouth should be 1:1.618.

It seems that facial attractiveness is founded in averageness and proportion. Clearly beauty is not average though and many studies have shown that the beautiful face is often distinctive by two or more striking features that fall out of the average such as beautiful eyes or perfect teeth.

When a patient attends the FACE clinic with an aesthetic concern we use these guiding principles to help us decide where the discrepancy lies and therefore what are the treatment options. These may range from non-surgical treatments such as botulinum toxins and fillers to orthognathic surgery to address the soft tissues and any underlying skeletal disproportion.

Facial plastic aesthetic procedures such as otoplasty, rhinoplasty rhytydectomy (face-lifting) and brow-lifting are often the key to providing facial harmony and rejuvenation.

As a group of surgeons and affiliated dentists we are convinced that by working together we can provide the highest standards of care and the best outcomes for our patients. We think that the dentition is the key stone to the face.

The FACE team are committed to education and collaborative working. We run regular educational evenings for GDPs and GMPs. Our next course will focus on non-surgical treatments and will cover the use of botulinun toxins and dermal fillers.

It will run on Saturday 29 and Sunday 30 October. We look forward to meeting you there. To book please contactby email or by phone on 07850 929 322.

The FACE team consults every Friday afternoon at BMI Ross Hall Hospital and by appointment in various dental practises within the West of Scotland.

Appointments with Mr Jeff Downie or Mr Mark Devlin can be arranged by contacting the BMI call line on 0141 810 3151.

References

1.Levin EI. Dental aesthetics and the golden proportion. The journal of prosthetic dentistry. 1978; 40(3):

244-52.

2.Bukhary SM et al. the influence of varying maxillary lateral incisor dimensions on perceived smile aesthetics. British Dental Journal. 2007;203(12):687-93.

3. Levin EI. The updated application of the golden proportion to dental aesthetics. Aesthetic dentistry today. 2011; 5(3): 22-27.

4. Chiche G, Pinault A. Esthetics of Anteior Fixed Prosthodontics. Quintessence books. 1994.

5. Marquardt SR: The Golden Decagon and Human Facial Beauty. J Clin Orthod 2002, 36:339-347

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