The anatomy of the smile

Orthodonic FAQ's

You might have heard the phrase ‘beauty is power and a smile is its sword’ – it’s not a lie! A genuine smile can be infectious – it is a universal language, appreciated worldwide which transcends nations, creed and colour. We use our smiles instinctively; however, do we fully understand what makes it up?

The Anatomy of the Smile

AProportion of upper incisors shown
Ideally you should have four upper incisor teeth which appear in the smile zone. The two larger incisors in the middle are called central incisors while the smaller ones on either side are called lateral incisors. 100% of all four upper incisors should be on display when you smile. It is characteristic of the aging process that people show less of their incisors with time, so a greater amount of incisors shown is usually associated with youthfulness. As a general rule, males show less of their upper incisors and more of their lowers than females. The extent of incisor display is affected by tooth alignment, colour, tooth dimensions and how confident you are when you part your lips.

BAmount of gum on display
A small amount of gum display is acceptable, if your gums are pink and healthy. Your gums can be an indication of healthiness and youth, provided they are not receding, swollen, bleeding or discoloured. An assessment of the relative height of the gum margin and the quantity/quality of the gum tissue is made subconsciously by every person observing your smile - excessive gum display is known as a “gummy smile”, while no gum display is sometimes called a “stiff upper lip”!

CThe smile arc
This is defined as the relationship of the curvature made by the edges of the upper teeth (the curved red line) with the curvature of the lower lip (the curved blue line). The ideal smile arc has the two curves in a close parallel relationship with each other. Careful planning by an orthodontist can allow movement and alignment of the front teeth to create harmony with the lower lip for your ideal smile arc.

DNegative space or buccal corridors
This is the small black space visible at the corner of the mouth, which is primarily dependant on the broadness of the smile and the shape of the mouth. These spaces are supposed to be present in all smiles, however, too little or too much can have a significant effect on the balance of a smile.

E“Broadness of the smile” Dental archform
The broader the smile, the better! A broad smile is determined by the width of the upper arch (when your teeth are in line they form a wide arched shape). Some people have narrow or collapsed arches, so when they smile you can’t see a lot of teeth. In the ideal scenario, you should be able to see the upper pre-molars on both sides of the buccal corridors described earlier. Americans and Africans are known to have broader smiles than Europeans, because of their wider skeletal forms. It’s important to know that jaw expansion using orthodontic devices can produce a broader smile, but only within biological limits!

Other factors that contribute to the balance of a smile are:

Upper lip length, lip shape and size and lip animation – these should all be
in balance.

The slope formed by the teeth when you bite together should be straight. If this slope bends to either side, it is considered to be an unattractive or lopsided feature. The shape of the Incisal edges is important because chipped or worn teeth are considered unfavourable.

The dental and facial midlines are not always coincident (in line with each other) but can be considered harmonious if they are close – you might need plastic surgery and not orthodontics, to make these lines coincident. It is more important for the upper midline to be coincident with the facial midline, because this is more noticeable.

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