| To be human is to smile. The smile is the natural expression of happiness around the world, an expression that is instantly and universally understood. It transcends all cultural differences and has never gone out of fashion. Why then, if the smile is such a universal and timeless human expression, do we as a profession have such a hard time talking about it in a precise and clinical way?
We have classified and measured virtually every other aspect of the world around us down to a science, except the human smile. In fact, we don't even have a generally accepted definition of what a smile is. What the profession needs, and what this article proposes, is a system for analysing our patients' smiles. Without such systems, how can we hope to inspire confidence in our patients and build aesthetic dentistry into a widely respected part of the dental profession?
For comparison, look at the field of architecture. The structural principals that an architect uses are applied in exactly the same way across the world. While each building looks different, just as each patient's smile looks different, the underlying principles that go into erecting buildings are always the same. They follow a natural set of laws, the laws of physics, that do not change. Having a fundamental set of principles that are commonly accepted allows architects to collaborate on projects and discuss new techniques with colleagues from anywhere in the world. While this has been possible in the field of general dentistry for years, we fall short when it comes to being able to discuss our patients' smiles.
As patients come to us wanting to improve their smiles we need a systematic way of discussing their smile with them. Too often the conversation between a dentist and their patient quickly breaks down into the purely subjective and unscientific level of "I just don't like my smile" or, "I want a smile like Robert Redford." At this point, we're at a loss as a profession to break down the different elements of a smile and discuss these with our patients and colleagues in an objective, methodical scientific way.
Classification
of a Smile
The Static
Smile
The Dynamic
Smile
There are striking variations in the amount of movement that exists in the normal smile from one person to another. A maximum spontaneous smile results in movement of the Commissure from 7 to 22 mm. Likewise, the average direction of movement of the Commissure is 40 degrees from the horizontal (range 24 to 38 degrees); the direction of movement of most smiles is to the helix-scalp junction. A large difference when comparing the left side to the right side may exist in the extent of movement but there is a relatively slight discrepancy in the actual direction of movement when comparing left to right.
Styles of
a Smile
There are millions of different smiles, essentially each individually characteristic. Nevertheless there are three basic smile patterns that can be identified:
1. The Commissure Smile (67%) in which the corners of the mouth are first pulled up and outward followed by the levators of the upper lips contracting to show the upper teeth.
2. The Cuspid Smile (31%) in which the levator labii superioris are dominant. They contract first, exposing the canine teeth, and then the corners of the mouth contract secondarily to pull the lips upward and outward.
3. The Complex Smile (2%) in which all the levators of the upper lips, the elevators of the corners of the mouth, and the depressors of the lower lips contracts simultaneously, showing all the upper and lower teeth simultaneously.
Although the
basis for the smile styles are neuromuscular, individuals can
usually employ all smile styles. Often a smile has been programmed
by habit. Restoring the smile can give the individual new confidence
and can often change their neuromuscular programming. 5
Stages of
a Smile
There are four stages in a smile cycle:
| Stage
I. |
Lips
closed |
| Stage
II. |
Resting
display |
| Stage
III. |
Natural
Smile (3/4) |
| Stage
IV. |
Expanded
smile (full) |
Of course, smiles will range and are unique to each individual. Many smiles do not differ much from a Natural Smile to an Expanded Smile. In these cases, treatment can often be restricted to the maxillary or mandibular anterior front six teeth. Other smiles have a very apparent discrepancy in display between these two zones. Here then, the treatment plan to aesthetically improve one's smile must be extended.
Types
of a Smile
There are five variations in which dental and/or periodontal tissues
are displayed in the smile zone:
Type 1. Maxillary
only
Type 2. Maxillary
and over 3 mm gingiva
Type 3. Mandibular
only
Type 4. Maxillary
and Mandibular
Type 5. Neither
Maxillary or Mandibular
The author suggests that above delineated categories can be systematically combined to create a standardization of terms to objectively describe various smiles. Both patients and dentists would benefit from a nomenclature that is recognizable by definition (i.e. the most common smile would be Commissure Smile, Stage III, Type 1)
However, there are often individuals who will vary their neuromuscular smile patterns by having a very animated lip pattern. This can most often be seen in changes as the smile pattern goes from a restricted Stage III to a fully expanded Stage IV smile.
Summary
Although 'smile therapy' is in its infancy, already society has placed a great demand on dentists to evaluate and treat their smiles. The author has presented a smile classification scheme and a vocabulary system that will aid in discussion between patient and dentist and the profession at large.
References
1. Young,
S. (1992) The Cambridge Encyclopedia of Human Evolution
2. Kingdon, J. (1992) The Cambridge Encyclopedia of Human Evolution
3. Ekman, P. (1973) Darwin and facial expressions; a century of
research in review New York: Academic Press
4. Rubin, L. R. (1974) The anatomy of a smile: Its importance
in the treatment of facial paralysis. Plast. Reconstr. Surg. 53:
384
5. Manktelow, R. T. (1993) The Shape of a Normal Smile: Implications
for Facial Paralysis Reconstruction. Plast. Reconstr. Surg. 93:
4
6. Janzen, E. K. (1977) A balanced smile - A most important treatment
objective. Am J. Orthod. 72: 359
|
