Anatomy of a Smile

Medically Reviewed by: Ross W. Nash, DDS

A bright, attractive smile creates a winning first impression. Without saying a word, your smile can convey a confident, optimistic and friendly personality. An esthetically pleasing smile is an attractive quality that lures people to you, making them respond positively.

Aside from the physical effects of your smile, it also can have major psychological and emotional influences on your personality. If you are self-conscious and unhappy about your smile, it can seriously affect how others perceive you, making you appear timid, hesitant, withdrawn, sad and/or angry. You may feel unattractive, inadequate and insecure.

Fortunately, advances in cosmetic dentistry allow a growing number of people to benefit from smile makeovers capable of transforming their dental characteristics to produce dramatic results with positive influences on their lives.

Smile Design Principles

The principles involved in a smile makeover are known as smile design. Combined, they influence the overall esthetic impact of an individual’s smile. The principles of smile design are divided into four parts:

Facial Esthetics: Facial and muscular considerations vary from patient to patient and are studied through visual and photographic analysis. They include how the lips frame your smile when you speak, smile or laugh.

Gingival (Gum) Esthetics: The health and appearance of your gums are essential elements in smile design. Excessive gingival display (gummy smile), uneven gum contours, inflammation and exposed root surfaces are common gingival-based esthetic complaints that detract from your smile’s appeal.

Microesthetics: This involves the subtle characteristics that make your teeth look the way they do, such as how they reflect light and unique marks or colorations. The ideal restoration is one with qualities closely resembling those of natural teeth. The anatomy of natural teeth is unique from person-to-person and specific to each tooth.

Macroesthetics: This analyzes the relationships and proportions between front teeth, surrounding tissue landmarks and facial characteristics, in order to ensure natural and attractive restorative care and smile makeover treatment. Working in collaboration, your cosmetic dentist and dental laboratory technician combine their technical and artistic abilities to create a natural and esthetically pleasing appearance in which the shapes, sizes and arrangement of individual teeth blend with and complement your particular features.

Components of a Smile

Smile esthetics involve applying certain rules, tools and strategies to the assessment of teeth and gum conditions in order for your dentist to decide on cosmetic and restorative procedures to correct and/or enhance your appearance.

Some key components of a “pleasing” smile include:

Lips

The lips have been compared to a frame that sets off the image of your smile, encompassing your teeth and gums. Enhancing or correcting the shape, fullness and symmetry of your lips can make your smile seem fuller.

For optimal esthetics, your facial features should line up to your teeth and lip lines. When your lips form a broad smile, an imaginary line can be drawn through the corners of the mouth, from one side to the other. The amount of upper front (maxillary anterior) tooth revealed below this line helps create a vibrant, youthful image. In a youthful smile, the upper front teeth should fill between 75 to 100 percent of the space between your upper and lower lips in a full smile.

Midline

The starting point of any smile design is the facial midline, an imaginary vertical line drawn between the front two upper teeth. For optimal esthetic value, the facial midline should be in the middle of the face.

Prominent facial features – such as the eyes, nose and chin – can be misleading when locating the midline. For instance, your eyes may be at slightly different levels, or your nose may be off-center, lessening their usefulness when trying to find the midline. A more accurate approach to determining the facial midline focuses on two facial landmarks: a point between the eyebrows and the Cupid’s bow in the center of the upper lip. By drawing a line between these landmarks, dentists can locate the position of the facial midline while also determining the midline’s direction.

Whenever possible, the midline between the upper front teeth (central incisors) should coincide with the facial midline. In cases where this is not possible, the midline between the central incisors should be perpendicular to the imaginary line that could be drawn through the corners of the mouth.

Smile Line

Your smile line is the line created by the top of your lower lip. In an ideal smile line, the edges of your upper teeth should be parallel to your lower lip when you smile. The bottom of your lower lip should have the same line as the gums of your lower jaw. This should always be a standard, regardless of the size or shape of your smile. Once your dentist has determined the orientation of your smile line, he or she can design its curve, or shape, and determine the length of your new restorations.

Teeth

Attractive smiles have various things in common, such as teeth that are white, unstained, straight, evenly spaced with no gaps between them and not crowded or overlapping.

When you smile, your top teeth show fully in a good proportion to your gums. The line where the gums and teeth meet is smooth and even. The smile line of the upper teeth follows the curve of the lower lip. The midline of the upper front teeth ideally is in the center of the face. “Tooth reveal” is a term that describes the amount of tooth structure that shows during different views and lip positions.

Other significant considerations for teeth that influence a person’s smile include:

Incisal (Biting) Embrasures: The spaces between the edges of the teeth (embrasure spaces) follow a pattern that develops between the central incisors and then progress sideways. These silhouette patterns, created by the edges and separations between the upper front teeth against the darker background of the mouth, help accentuate an attractive smile. The size and volume of the incisal embrasures between teeth increase as the teeth move away from the midline.

Color: Typically, the upper central incisors are the lightest and brightest teeth in your smile. The upper side teeth are similar in color (hue) to that of the central incisors, but generally slightly lower in brightness (value). The canines (third teeth from midline) have greater intensity or saturation of color (chroma). First and second premolars (teeth behind canines), which are lighter and brighter than the canines, are similar in color to that of the lateral incisors.

When evaluating the color of your teeth, your dentist examines how closely matched your upper and lower teeth appear. Both sets of teeth should look similar and complement your hair, skin and eye color. For best results, color/shade reproduction in anterior restorative and cosmetic treatment should come close to natural esthetics, rather than merely opting for the lightest, brightest shades. Shade guides are used to evaluate optimal color prior to teeth whitening.

Tooth Proportion: Most people perceive a pleasing smile as one in which the two central front teeth are dominant and have a width-to-length ratio of 75 to 80 percent. This proportion guides the length and width of other teeth in the esthetic zone (the section of upper and lower teeth that show when you smile), making your smile appear balanced or symmetrical.

Long teeth equate to a younger-looking smile. Over the years, normal wear and tear has a shortening or aging effect on your teeth and overall appearance. Teeth length also may play a role in facial contouring. For instance, long, square-shaped teeth on a plump, round face creates a slimming effect.

Tooth Texture and Characterization: Cosmetic dentists can use their artistic skill and clinical experience to characterize restorations to create a more feminine (meaning, smaller, smoother, oval- or round-shaped) or masculine (meaning, larger, square-shaped, blunt) appearance. Apart from matching or enhancing the look, feel and function of your natural teeth, cosmetic dentists also can correct imperfections, such as chips or cracks.

Teeth Angulation: Your teeth should have a symmetrical appearance in the front and a balanced appearance in the back. Teeth should not jut out too much or be set too far in; they should not be crooked, overgrown or uneven. When the upper front teeth tip toward the midline, the overall esthetic effect is a harmonious one in relation to the lower lip and, more importantly, to the midline.

Proper occlusion: the relationship between your upper (maxillary) and lower (mandibular) teeth when they come into contact when you bite, chew or bring your jaws together – is critical. In addition to affecting your looks, the way your teeth’s chewing surfaces come together also impacts your other teeth, gums, neck and head, jaw muscles and joints and your overall oral health.

Incisal Edge Position

The incisal edge position – how far down/long the top two middle teeth are – sets the stage for the proportions of the rest of your smile and smile line. Apart from serving an important esthetic function, the incisal edge position is vital to proper function, in addition to speech and making sounds that start with “F” and “V”, for example.

Gum (Gingival) Tissue

Gum tissue should look healthy (meaning, no red, puffy or bleeding gums). Gingival contour is the shape or form of the gums around the necks of the teeth. The “ideal” smile should not show more than three millimeters of gums between the top of your tooth and the bottom of your upper lip. The shape of the gums of the lower incisors and the upper laterals should be a symmetrical half-oval or half-circular shape. The upper centrals and canines should show a more oval, or elliptical, shape to the gums.

Buccal Corridor

The buccal corridor is the dark space visible between the corners of the mouth and the upper teeth. Research indicates that, under most circumstances, individuals with considerably smaller buccal corridors (broader smiles) are thought to have the “best” or “most attractive” smiles. Women, in general, have significantly broader smiles, increased tooth arcs and reduced tooth/lip arc differences than men.

Emergence Profile

A tooth’s emergence profile is the angle at which the tooth emerges from the gums when viewed from the side. This can affect the fullness of a person’s smile, as well as provide lip and cheek support. Greater fullness avoids a caved-in look to the face, giving a more youthful and attractive appearance.

Other Smile Anatomy Considerations

A smile’s impact cannot be determined just by the beauty of individual teeth and gums. Each patient is unique, varying by age, sex, looks, personality traits, and esthetic needs and expectations.

The “ideal” smile also must take into account individual considerations such as facial features, skin tone, hair color, and how the size, color and condition of your teeth, as well as gum tissue and lips, fit in with your overall physical appearance. In addition, occlusal and functional considerations may influence the smile design in both natural and restored teeth, and may affect the longevity of cosmetic treatment.

Macroesthetic concepts provide only guidelines and reference points for beginning esthetic evaluation, planning and treatment. The artistic component of dentistry – especially for cosmetic dentistry – can be applied and perfected by dentists who understand the rules, tools and strategies of smile design. With today’s modern technology, such as digital imaging, lasers, whitening procedures and the like, dentists can create smile design makeovers with procedures and techniques that range from minimally invasive whitening and composite bonding, to porcelain veneers, crowns and dental implants. Additionally, they can use soft tissue augmentation via dermal filling agents to correct facial aspects such as thin lips and asymmetrical facial appearances to increase a smile’s attractiveness. Advances in dental spa dentistry and sedation dentistry make it possible to do these procedures with less patient anxiety and pain.

Yet smile makeovers, like beauty, ultimately are in the eyes of the beholder. Just because they can be done does not mean they need to or should be done. The esthetics of cosmetic dentistry are highly subjective in nature and practice, and in many cases, when they do not cause physical, mental and/or psychological damage, are best left to the discretion of the individual patient, who may think that his or her unique dental quirks are characteristics to be embraced rather than “corrected.”

[updated July 24, 2019]

About the Reviewer

Dr. Ross Nash is a contributor to Better Vision Guide, authoring the Ask the Expert section which is geared towards answering common consumer questions related to a wide variety of dentistry topics. Dr. Nash is one of only 46 Accredited Fellows in the American Academy of Cosmetic Dentistry, meaning he has acquired extraordinary skills in the area of esthetic and cosmetic dentistry. He is the founder of the Nash Institute for Dental Learning and Cosmetic Dentistry of the Carolinas, his private practice located in Huntersville, North Carolina.

Dr. Nash is a well-respected dentist in his field and regularly invited to speak about esthetic dentistry around the globe. He is also the dentist-of-choice for many of his dental peers when it comes to managing their own dental care.