In the current era of media-driven esthetic awareness, the bar has been raised regarding patients' esthetic expectations. To meet these demands, dental assistants not only need to recognize the fine elements of the esthetic principles of a natural smile, but also be able to communicate those principles to their patients. It is even more important that the entire dental team participate with a high level of knowledge and cohesiveness in esthetic practices.

For the patient, successfully attaining a natural-looking smile often involves waiting room educational materials, conversations with knowledgeable auxiliaries, consultations with the dentist, and beautifully constructed temporaries. To be truly effective, each step must be executed and aligned with a common understanding and awareness by the entire restorative team. One method to ensure consistency and quality in this team effort is to establish identifiable standards. The establishment of those standards must begin with effective training in tooth anatomy and the esthetic principles of a natural smile.

This article details 10 fundamentals of a natural-looking smile,¹ which will help dental assistants communicate with patients from the diagnostic phase of treatment through the successful completion of the desired results. Mastery of these fundamentals will help you guide patients through the creation of their new smiles. Further, this information will provide a means of more effective communication with supporting specialists and laboratory technicians.

The 10 Fundamental Components of a Natural Smile

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1. Long Axis

Being able to visualize the long axis is important for recognizing tooth position and understanding that the anatomical features of a tooth, such as the developmental lobes, developmental grooves, and vertical transitional line angles, must follow the long axis to appear natural. On a study cast, the long axis is drawn down the center of the tooth.

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2. Vertical Transition Line Angles

Vertical transition line angles define the transition from the labial surface at the mesial and distal lobes to the interproximal embrasures. Changes in their positions control the appearance of the width of the tooth.

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3. Developmental Grooves and Lobes

Each anterior tooth has 3 lobes divided by 2 developmental grooves. The length and depth of the developmental grooves dictate lobe position and prominence. Of the 3 labial lobes found on centrals and laterals, the central lobe is usually the longest and widest. The mesial lobe is the second longest and the narrowest. The distal lobe is the shortest and the second widest. While a large percentage of teeth exhibit the proportions described, much variation is found. Often the central lobe is depressed and the least prominent, and there also may be variations in the mesial and distal lobes.

Like the rest of the anterior teeth, cuspids have 3 lobes. The mesial lobe is second in length, second in prominence, and the narrowest of the lobes. It is smoothly convex in all directions, and blends at its gingival extremity with the central lobe. The central lobe extends from the tip of the cusp to the cervical line. It is the longest, widest, and most prominent of all anterior lobes. Because of its prominence, it forms a labial ridge that differentiates this tooth from the centrals and laterals. The distal lobe is separated from the central lobe in the incisal region by the distal labial developmental groove. The distal lobe is the shortest and the second widest of the lobes. It ends below the distal middle third in a fairly deep concavity.

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4. Primary Plane

The primary plane is a flat, slightly depressed area in the center of the incisal half of an anterior tooth that dictates symmetry. The mesiodistal width of the plane is dictated by the location of the mesial and distal developmental grooves.

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5. "S" Curve

The "S" curve is a subtle, depressed area on centrals and laterals that starts just distal to the long axis in the gingival one third and curves up in an elongated "S" or reverse "S" shape into the base of the central lobe. This anatomical feature is very subtle and defines the length of the mesial and distal lobes while giving the incisor a pleasing, flowing shape.

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6. Embrasures, Interdental Papilla, and Proximal Contacts

The incisal embrasures are one of the most telling components of an unnatural smile when improperly developed. The subtle variations in wear at the incisal edge create the appearance that the tooth has aged with the patient. In a case where all of the incisors are being reconstructed, this feature is controlled by the study cast or communication between the patient and the clinical staff about how youthful or mature the result should appear. In the case of a single-unit or unilateral restoration, the teeth on the opposite side should dictate the result. The proper placement of proximal contacts ensures healthy interdental papilla. This is dictated by the proper development of gingival embrasures for healthy soft-tissue response and esthetically correct incisal embrasures.

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7. Nine Rotational Axes

Each tooth has 9 rotational axes for communicating individual position within the arch. These rotational axes provide a method of positioning teeth by "rotating" them on a specific axis to accomplish a specific orientation of an area of the specific tooth. For example, we can rotate a tooth on its mesial-vertical axis to move the distal surface facially or lingually enhancing or deemphasizing the distal lobe and how light reflects from that surface.

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8. Three Esthetic Compositions

In the 1950s Dr. John Frush and colleagues defined the 3 most recurring tooth arrangements in natural smiles—basic, strong, and soft.² These compositions relate not only to the communication of denture tooth arrangements, but also any dental restoration.

Basic Esthetic Composition—A generic arrangement of anterior teeth can be used for most cases when there is no other reference, such as a preoperative model. (1) Centrals flat to the front of the mouth, on the occlusal plane and vertical in profile. (2) Laterals face on the curve of the arch, 1 mm to 2 mm shorter than the centrals and vertical in profile. (3) Cuspids on the curve of the arch, 1 mm to 3 mm shorter than the cen­trals, ro­tated out slightly at the gingival with the mesials rotated slightly out and the distals rotated in.

Strong Esthetic Composition—An arrangement of anterior teeth that can be used to create a stronger, more aggressive appearance. This composition is commonly used for men. (1) Centrals flat to the front of the mouth, one depressed slightly from the other, on the occlusal plane and vertical in profile. (2) Laterals on the curve of the arch, depressed from the centrals, mesials rotated in, 1 mm to 2 mm shorter than the centrals. (3) Cuspids on the curve of the arch, 1 mm to 3 mm shorter than the centrals, rotated out slightly at the gingival with the mesials rotated slightly out and the distals rotated in.

Soft Esthetic Composition—An arrangement of anterior teeth that can be used to create a softer, more delicate appearance. This composition is commonly used for women. (1) Centrals flat to the front of the mouth, one depressed slightly from the other, on the occlusal plane and vertical in profile. (2) Laterals on the curve of the arch, depressed at the neck, mesials rotated out, 1 mm to 2 mm shorter than the centrals. Rotate one lateral slightly to the distal on the labio–lingual axis and the other slightly to the mesial.

(3) Cuspids on the curve of the arch, 1 mm to 3 mm shorter than the centrals, rotated out slightly at the gingival with the mesials rotated slightly out and the distals rotated in.

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9. Gingival Tissues

Advancements in periodontal therapy have brought correction of asymmetrical gingival architecture into the mainstream of daily prosthodontic treatment. The illustration shows the arrangement of the gingival architecture in an esthetically pleasing smile. Study casts can be physically modified as part of the preoperative diagnostic workup and sent to a periodontist for guidance.

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10. Smile Line and Buccal Corridors

The relationship of the incisal edges to the lower lip and the triangular space between the cheek and the buccal surfaces of the posterior teeth create the smile line and the buccal corridors. The illustration shows these relationships in an esthetically pleasing smile.

Conclusion

Mastery of the fine elements of the esthetic principles of a natural-looking smile by the clinical team ensures the ability to orchestrate the evaluation and diagnosis of the existing esthetic situation and achieve predictable results with confidence. By using these fundamental components, dental assistants can help their patients achieve the smiles they desire. In addition, being able to communicate the details in a language used by dentists, specialists, and laboratory technicians will make your work easier.

Acknowledgment

All figures courtesy of PTC (Productivity Training Corporation), Morgan Hill, California.

Disclosure

Mr. Avery is a consultant for PTC.

References

1. Ness J. Anterior Anatomy and the Science of a Natural Smile. Morgan Hill, Calif: Productivity Training Corporation; 2006.
2. Frush JP. Dynesthetics Illustrated. Glendale, Calif: Swissedent Corp; 1975.