Orthodontics

Achieving Facial Harmony Through Orthodontics

Robert G. Keim, DDS, EdD, PhD

Copyright 2002 Journal of the California Dental Association.

Author: Robert G. Keim, DDS, EdD, PhD, is program director of advanced orthodontics and director of advanced specialty education at the University of Southern California School of Dentistry.

A substantial body of science allows the application of objective measurement techniques to augment a clinician’s subjective assessment of facial harmony and beauty. These techniques have found wide application in all clinical disciplines involved with the enhancement of facial beauty, including esthetic dentistry, plastic surgery, orthognathic surgery, and prosthodontics. This paper will explore the applications of those techniques to the field of orthodontics.

"All human growth studies sample a very heterogeneous population. Accordingly, it is biologically and statistically without meaning to try to establish ‘normal standards’ for human craniofacial growth when, for example, several parameters (distance, angles) are obtained from different samples of man." -- Moss 1982

"A person’s own craniofacial composite can be evaluated for what it is, and the nature of some of its morphological and morphogenetic relationships can be determined relative to standards for that individual rather than those for the population at large." -- Enlow 1982

"The psychological security obtained from manipulating numbers (ANB, mandibular plane angle, etc.) does a disservice for the clinician. ... To the patient, evaluation of his appearance is validity, not a number or some recipe for changing it. To dentists, such ‘scientific formulae’ have appeal because they are logical. It is harder to determine if such is valid." -- Hixon 1972

While the old adage "Beauty is in the eye of the beholder" is as true today as it was when the saying was first coined several hundred years ago, a substantial body of science has been established that allows the application of objective measurement techniques to augment a clinician’s subjective assessment of facial harmony and beauty. These techniques have found wide application in all clinical disciplines involved with the enhancement of facial beauty. The fields of esthetic dentistry, plastic surgery, orthognathic surgery, and prosthodontics have all found wide application for various studies relative to the assessment of facial esthetics. This paper will explore the applications of those techniques to the field of orthodontics.

Analysis of Facial Harmony

Hundreds of papers have been published presenting various cephalometric, anthropometric, and soft-tissue analyses of facial harmony, both frontal and lateral. No attempt will be made here to review all of these. Many of these present normative or average values for various parameters of facial or dental measurement. The assumption is that these average, or mean, values should be regarded as treatment goals. The problem encountered is that application of these normative values as treatment objectives -- "treating to the mean" -- may or may not result in an esthetically desirable outcome. Sarver¹ stated that "any analysis based on cephalometric or facial ‘normative’ values has one inherent weakness, and that is that beauty is not the norm." Indeed, if facial esthetics were regarded as falling along a normal distribution, i.e., on a bell curve, beauty would fall in the far-right portion of the curve. Average, or mean, appearance would fall squarely in the middle (Figure 1). Treating to the mean then is tantamount to striving for mediocrity. Clearly, any quantitative assessment of facial esthetics must be referenced specifically to the individual patient in question rather than toward any normative population values.

Recently, Marquardt² has explored the application of a "golden decagon matrix," derived from two- and three-dimensional geometric extrapolations of the classical "golden ratio," to the analysis of facial esthetics with remarkable results. Marquardt has developed a set of "facial masks" that can be superimposed over facial photographs, frontal or lateral, of individual patients for the assessment of the fit of their face to an idealized symmetry based on the golden decagon matrix (Figure 2). The applicability of the facial masks holds up across all races and both genders. While applications of Marquardt’s findings to clinical orthodontics have not yet been explored in the orthodontic literature, the prospect of their application, especially in the area of soft-tissue analysis, is intriguing.

Prior to the development of Marquardt’s facial masks, Fishman³ proposed the centrographic analysis as an individualized, non-numeric approach to the assessment of facial symmetry, facial harmony, and facial balance from the lateral aspect (Figure 3). Like Marquardt’s facial masks, Fishman’s centrographic analysis holds up across all race and gender lines. This analysis is essentially a qualitative assessment of the skeletal structures of the face, along with a qualitative soft-tissue assessment, done on an individualized basis without comparisons to any standardized or normative values. Application of this technique provides the operator with a reliable means of objectively evaluating facial balance without comparing the individual to any population norms.

In developing the technique of centrographic analysis, Fishman employed characteristics that were found to be "common to the human species."³ It is interesting to note that Marquardt has also suggested that identification of those facial attributes that contribute to facial beauty is essentially the identification of attributes that lead to the visual identification of "humanness."⁴ In centrographic analysis, "graphic relationships that represent facial balance and harmony have been identified and applied to case diagnosis and treatment planning."

The analysis is based on the principles of centroid geometry. In its application to the analysis of two-dimensional cephalometric radiographs, the relationships of the centroids of four of triangles, constructed in the cranium, upper face, lower face, and face overall, and various anatomic structures are appraised for harmony and symmetry.

Fishman’s analysis requires a minimal knowledge of cephalometric points and planes. Only five points are used: sella (S), nasion (N), basion (Ba), point A (A), pogonion (Pog), and gnathion (Gn). Five lines are drawn: A-Pog, S-N, N-Ba, Ba-A, and Ba-Gn. The intersection of a fifth line -- Na-Gn -- with the Ba-A line is marked. From these, the centroids of four anatomical triangles are constructed:

* The cranial centroid (CC), triangle Ba-S-N;

* The upper centroid (UC), triangle Ba-N-A;

* The lower centroid (LC), triangle Ba-A-Gn; and

* The facial centroid (FC), triangle Ba-N-Gn with the intersection of the N-Gn line with Ba-A serving as the upper anterior apex of the lowest triangle (Figure 4). The plane perpendicular to Ba-A through the facial centroid, termed the centroid plane, serves as the point of reference for analysis in the sagittal aspect (Figure 5). Individualized assessment of facial balance and symmetry is then accomplished by analyzing the relationships of these four centroids to Ba-A and the centroid plane.

Vertical skeletal harmony, or symmetry, is seen when the facial centroid is located directly on the Ba-A line. In situations where insufficient vertical development has occurred, the facial centroid will be located in the upper facial triangle. Likewise, excessive vertical development will result in the facial centroid being located in the lower facial triangle.

Horizontal skeletal imbalance is evaluated by assessing the anteroposterior positions of UC and LC to the centroid plane. An upper centroid located in front of the centroid plane is indicative of a protrusive maxilla and upper face. If that centroid is located posterior to the centroid plane, a maxillary retrusion is evident. Mandibular protrusion or retrusion is assessed in a similar fashion comparing LC to the centroid plane.

Dental characteristics of balanced facial form are also analyzed relative to the centroid plane (Figure 6). In a symmetrically harmonious face, the upper and lower molars will demonstrate a Class I relationship with the vertical centroid plane bisecting the distal root of the upper molar while appearing tangent to the distal surface of the lower first molar. Fishman notes that the occlusal plane of the molars should fall below the Ba-A plane.

In a symmetrically harmonious face, the incisal edge of the lower incisor will be found tangent to a line that originates from the lower centroid constructed parallel to the Ba-A line. The labial surface of the lower incisor is positioned horizontally so that it lies tangent to the A-Pog plane. When the upper incisor is in proper occlusion with the lower incisor, the A-Pog plane will bisect its crown. Also, with regards to angulation, when the upper incisor is in proper occlusion with the lower incisor, the extrapolated long axis of the upper incisor should pass through orbitale. The lower incisor is properly inclined when its long axis intersects Ba-Gn at a point "approximately a third of the distance of the symphyseal segment of the Ba-Gn plane."

By employing both Marquardt’s facial masks for lateral facial assessment and Fishman’s centrographic analysis to the underlying skeletal relationships, a much clearer analysis of individual profiles is possible without unfounded reliance on population norms. Superimposition of Marquardt’s lateral facial mask over Fishman’s template for a balanced and harmonious profile shows remarkable correlation between the two independent assessment modalities (Figure 7).

By combining the two modalities, it is possible to establish individualized treatment goals, both skeletal and soft-tissue profile.

Treatment

Regardless of what analyses a clinician uses for the assessment of facial symmetry and balance, the goal is to guide diagnostic and treatment planning decisions toward a successful, esthetic outcome. Treatment planning is a matter of identifying a specific list of problems, derived from clinical examination data and through analyses as the examples described above and others, then logically applying treatment modalities to address those problems. For example, a protrusive maxilla calls for headgear therapy in a growing individual or perhaps a combination of techniques including selective extractions. A similar situation in a nongrowing patient may well dictate a combination of orthodontic and surgical treatment modalities.

Just how much is possible in terms of orthodontic treatment? There are four basic approaches available to the orthodontist, to quote Sarver and colleagues:⁵

* Repositioning the teeth through orthodontic tooth movement;

* Redirecting facial growth through functional alteration or the use of strong modifying forces;

* Employing dentofacial orthopedics in which dentofacial (dentoalveolar) growth is altered through the use of strong modifying forces; and

* Utilizing surgical-orthodontic treatment.

Proffit and colleagues have proposed what they term an "envelope of discrepancy for the maxillary and mandibular arches in three planes of space."⁶ They note that "for any characteristic there are three ranges of correction: (1) a range of correction that can be accomplished by orthodontic tooth movement alone; (2) a larger range of correction that can be achieved by tooth movement plus functional or orthopedic treatment; and (3) a still larger range of correction that requires surgery as a part of the treatment plan." The range of correction by orthodontic means alone is about the same for adults as it is in children. As children become adults, the ability to achieve skeletal correction through orthopedic growth modification declines and vanishes. For the nongrowing individual, corrections of malocclusions greater than that possible through tooth movement alone require a combination of orthodontics and orthognathic surgery.

Since such an emphasis has been placed in this issue on the attainment of facial symmetry, it is of interest that the envelope of discrepancy is not symmetric. Greater corrections can be made by orthodontics and dentofacial orthopedics in the sagittal plane than in the transverse or vertical planes. A much greater degree of maxillary protrusion can be treated orthodontically than can a similar problem in the mandible. While not absolute limits, the guidelines in the next few paragraphs, suggested by Proffit and colleagues, serve as useful guides in answering the question posed above.⁶ "By orthodontic means alone, maxillary incisors can be retracted approximately 7 mm. They can be advanced only 2 mm. The same teeth can be extruded 4 mm, but only intruded 2 mm. In a growing individual, when orthodontic forces are combined with orthopedic and functional forces, the maxillary incisors can be retracted 12 mm, advanced 5 mm, extruded 6 mm, and intruded 5 mm. When surgery is performed in addition to orthodontics, as in a nongrowing patient, the maxillary incisor can be retracted 15 mm, advanced 10 mm, extruded 10 mm, and intruded 15 mm.

"In the mandible, the incisor can be retracted 3 mm by orthodontic tooth movement, advanced 5 mm, extruded 2 mm, and intruded 4 mm. Using orthodontics and orthopedics together, the incisor can be retracted 5 mm, advanced 10 mm, extruded 5 mm, and intruded 6 mm. When surgery is employed, the incisor can be retracted 25 mm (via mandibular set back), advanced 12 mm, extruded 15 mm and intruded 10 mm.

"The transverse envelope of discrepancy is much smaller than is the sagittal envelope. Orthodontically, maxillary premolars can be moved buccally 3 mm, palatally 2 mm, intruded 3 mm, and extruded 2 mm. Orthopedically, maxillary premolars can be moved buccally 4 mm, palatally 3 mm, intruded 4 mm, and extruded 3 mm. Surgically, they can be moved buccally 7 mm, palatally 4 mm, intruded 10 mm, and extruded 10 mm. Mandibular premolars have similar restraints with buccal movement of 2 mm, lingual 1 mm, intrusion of 3 mm, and extrusion of 2 mm being possible through orthodontics; 4 mm buccal, 2 mm lingual, 4 mm intrusion, and 4 mm extrusion possible through orthopedics. Surgery increases the possible values to 5 mm buccal, 3 mm lingual, 10 mm intrusion, and 10 mm extrusion. It is clear, as mentioned above, that the envelope of discrepancy is far from symmetric."

Numerous authors, including Holdaway,^7,8 Gencov,⁹ and Subtelny¹⁰ have explored the relationship of the change in lip and soft tissue position relative to the underlying tooth movements. While there is a little disagreement between the various authors, it is fairly safe to assume that the relationship is about 1:1 for the upper lip relative to change in sagittal position of the upper incisor. That is, if the upper incisor is retracted about 2 mm, the upper lip will move back a similar amount. This is important to bear in mind when employing either Fishman’s or Marquardt’s assessment of lip position in treatment planning for optimum facial harmony.

Conclusion

Facial beauty is an enigmatic phenomenon. Poets and lovers the world over would be aghast at the very thought of clinicians’ trying to objectively measure or assess the phenomenon. The abilities of clinicians to enhance an individual’s innate beauty depends on upon their understandings of the possibilities of variation in the individual’s own facial beauty. At least in general, dental professionals know what their technical limitations are relative to rearranging the hard and soft tissue of the mouth and face. They have a little better grasp on how to objectively assess facial harmony and complex symmetry. To what then do they compare their assessments, goals, and outcomes? Stated more plainly, to what do they compare their patient’s facial beauty? One thing is very clear, comparisons to any population normative values for any parameters of facial beauty and harmony are of little if any value. Perhaps Shakespeare took a more correct approach in his comparisons, "Shall I compare thee to a summer's day?"

References

1. Sarver DM, Esthetic Orthodontics and Orthognathic Surgery. Mosby-Yearbook, St Louis 1998, p 3.

2. Marquardt SR, The Facial Masks. Marquardt Beauty Analysis, http://www.beautyanalysis.com/index2_mba.htm, 2002.

3. Fishman LS, Individualized evaluation of facial form. Am J Orthod 111:510-7, 1997.

4. Marquardt SR, Archetype Theory. Marquardt Beauty Analysis, http://www.beautyanalysis.com/index2_mba.htm, 2002.

5. Sarver DM, Proffit WR, Ackerman JL. In, Graber TM, Vanarsdall RL, Orthodontics Current Principles and Techniques. Mosby-Yearbook, St Louis, 2000, p 7.

6. Sarver DM, Proffit WR, Ackerman JL. In, Graber TM, Vanarsdall RL, Orthodontics Current Principles and Techniques. Mosby-Yearbook, St Louis, 2000, p 6.

7. Holdaway RH, A soft-tissue cephalometric analysis ant its use in orthodontic treatment planning, Part I. Am J Orthod 84:1, 1983.

8. Holdaway RH, A soft-tissue cephalometric analysis and its use in orthodontic treatment planning, Part I. Am J Orthod 82:279, 1984.

9. Genecov JS et al, Development of the nose and soft tissue profile. Angle Orthodontist 60(3):191, 1990.

10. Subtelny JD, A longitudinal study of soft-tissue facial structures and their profile characteristics, defined in relation to underlying skeletal structures. Am J Orthod 45:7, 1959.

To request a printed copy of this article, please contact: Robert G. Keim, DDS, EdD, PhD,
9737 La Canada Way, Shadow Hills, CA 91040.

Legends

Figures 1a through o. Attractive deviations from the mean. Each of the models pictured received an average Lundstrom’s Facial Esthetics Scale rating of 1 (highly attractive) when evaluated by an independent team of raters. When analyzed by several different conventional cephalometric analyses, each of them displayed multiple scores that were greater than two standard deviations from the mean.

Figure 2. Marquardt’s Lateral Facial Mask.

Figure 3. Construction of cephalomorphic centroids.

Figure 4. Centroid plane.

Figure 5. Cephalomorphic dental harmony.

Figure 6. Superimposition of CGA over Lateral Facial Mask.