Search  in
INVITED REVIEW
NUMBER 2 YEAR 2003
Facial Beauty and the Maxilla
1 London School of Facial Orthotropics, Royal Dental College, Aarhus, Denmark

Correspondence to:
John Mew,
Braylsham Castle, Broad Oak, Heathfield, Sussex, TN218TY
We naturally associate facial beauty with straight teeth. Indeed many people assume that if the teeth are aligned by orthodontics, or good crown and bridge-work the facial appearance will automatically improve. However, it is not as simple as that, and most of us have encountered people who have had the very best dental or orthodontic treatment but finish with an unpleasing smile.

RECOGNITION

It is not always easy to see what is wrong; perhaps they show too much gum or maybe the smile doesn't fit the mouth. Some orthognathic surgeons and clinicians develop the ability to judge by eye what should be done and experienced orthodontists may be able to assess this from plaster models of the teeth but what advice can be given to the less experienced? Is beauty in the eye of the beholder or are there some general rules that can be applied?
The maxilla is one of the crucial elements in facial beauty. Anatomically it provides the support for the mid-face and if it is forward then the patient will have 'good bone structure' and attractive eyes1. If it is back they will be flat faced and appear to have a large nose. The eye is especially vulnerable and if the maxilla is down or back, the outer canthous of the eye will drop. This can easily be recognised because it will give the patient a sleepy look and some of the white sclera of the eye may be visible below the iris. This always looks unattractive and is a reliable sign of severe maxillary retrusion.
How do the surgeons decide where to place the facial bones for the greatest aesthetic effect? They use very complex 'work ups' but they also rely on their own judgement. In an effort to discover what people find attractive, psychologists have used frontal photographs to assess facial appearance. Horizontal and vertical lines are drawn across the facial features and from these specific rules for ideal facial proportion have been created. Surgeons and orthodontists find it easier to assess a profile view and Lucker and Graber2 suggested that psychologists should rely more on lateral views.
Work by psychologists3 has suggested that symmetry and averageness provide the ideal face but many individual beauties fall outside these parameters, being noticeably more prognathic. Beauty Queens have both their jaws substantially further forward than the rest of us and Platou and Zachrisson4 found that prognathic faces have straighter teeth. Does this mean that we should place our patients teeth further forward or would this re-create the toothy appearance that the non-extraction orthodontist Edward Angle was criticized for? We need some simple rules to help us.
Many years ago Bjork5 used metal implants to demonstrate that the direction of growth of the maxilla varies "individually from almost purely sagittal to purely vertical" The effect of this on the facial appearance can be dramatic, and vertical growth is usually associated with increasing malocclusion. When this occurs the bony orbit also drops, causing the Frankfort Plane to tilt down, rendering this plane of dubious value for reference purposes.
In the past it was thought that the base of the skull was more or less immutable but more recent work has shown that the Saddle Angle (Nasion-Sella-Basion) like the Frankfort plane also varies widely, both between individuals6 and within the same individual over time7. This has required some radical re-thinking about the diagnosis of dento-facial relationships which have traditionally been related to the Sella Nasion plane. Patients with vertically growing faces adopt a head posture with their head tilted back, possibly to improve their airway8. As a result the SN plane tilts upwards sometimes quite steeply. This makes the Maxilla appear further forward that it really is and misleads many clinicians into considering the face to be 'convex' when in reality it is retruded. Retractive headgear in this situation can severely damage a face.
All that is required to convince a clinician that this is true is to superimpose such a face onto the cranial vault of any good-looking individual in possession of all 32 teeth. Many cases diagnosed as 'bimaxillary' protrusions or 'convex faces' are in fact 'bi-dental' protrusions with the maxilla placed distally and the teeth and alveolus forward.
Prosthedontists will often be guided by the position of the upper lip when positioning the central incisors. They ask the patient to say a suitable phrase or pronounce the letter 'M' and place the teeth a predetermined distance below the upper lip. Most orthodontists use lines dropped from the upper face such as McNamara's Nasion Vertical or from below such as Rickett's 'Aesthetic Line'. However the former is unreliable if the Sella Nasion plane is tipped up and the latter if the mandible has hinged down and back. Some orthodontists use a measurement they call the 'Indicator Line'. This measures the distance between the upper left central incisor and the tip of the nose. It sounds unlikely but it is relatively independent of the changes in the Sella Nasion and Frankfort planes and is a help in locating the maxilla in relation to the cranial vault. It appears that large noses are mainly due to the maxilla falling back.
Prosthetists, and crown and bridge experts, unlike orthodontists, are not as free to place the teeth in ideal positions and usually accept the supporting skeletal structure as it is. Orthodontists have the additional option of moving bone, either by orthopedics or surgery, and use slightly different guidelines although they all recognise that ultimately the teeth need to be in a position of balance between the lips, the tongue and the opposing teeth.
The work of Proffit and his colleagues9 (2000) would suggest that if the teeth are in contact for more than four hours each day they will intrude or if out of contact for more than eight hours each day they will erupt. Clearly these figures will vary between individuals but the height of everyone's occlusion must depend on a combination of the force and the period of time that the teeth are in contact. The work of Kiliaridis and Kalebo10 has shown that strong muscles of mastication can encourage horizontal growth in both forward and lateral dimensions. This would suggest that we should encourage our patients to keep their mouths closed, eat hard foods and perhaps chew hard gum.

FACIAL CORRECTION

Surgeons such as the Americans Bruce Epker and Larry Wolford learnt long ago that to improve a prominent lower jaw it is often better to move the maxilla forward than take the mandible back. Interestingly much orthognathic surgery for retruded mandibles now involves the upper as well as the lower jaw, both of which are taken forward. While the teeth can be moved forward with appliances, orthodontists have found it difficult to move the maxilla in any direction other than downwards. Most clinicians are aware of this problem and avoid mechanics that will lengthen the face. The orthodontic suppliers say they are now selling fewer retractive headgears and more forward pull headgears but a disappointingly high number of cases still finish with a proportionately longer face than before treatment. This is particularly true if the facial height was increased prior to treatment. Faure11 found that in this group of patients "The period of the treatment is concomitant with esthetic facial loss".
There is hope that 'Functional' appliances may help in these situations and certainly some encouraging results have been seen with the Clark Twin Block and the Herbst but although they bring the mandible forward they tend to retract the maxilla and increase vertical height. At times there is a reduction of facial height but out of retention this seems to revert and often the gonial angle will actually increase. Intrusive forces applied through high pull headgear have shown some promise but also have a retrusive effect on the maxilla and the high forces necessary have been associated with worrying levels of root resorbtion12.
The work of Baccetti and his colleagues13 partly based on McNamara's original experience with monkeys would suggest that after the age of seven or eight it becomes progressively more difficult to change the form or position of the maxilla. Most dental orthopaedics is done after this age and should perhaps be encouraged earlier.
If the position of the maxilla could easily be recognised and controlled then a wide range of new orthodontic possibilities would open up. The research quoted above would suggest that these would include, good-looking forward growing faces, long-term stability and room for 32 teeth. Discovering the cause and cure of vertical facial growth undoubtedly deserves a high priority in our future research projects.
REFERENCES

1 Peck, H. & Peck,S. 1970 "A concept of facial aesthetics". Angle Orhtodontist. 40: 119-127
2 Lucker G, and Graber. L. 1980 Physiognomic features and facial appearance judgements in children. Journal of Psychology. 104:261-268.
3 Perrett. D. I. May. K A and Yoshikawa. S. 1994 Facial shape and judgements of female attractiveness: preferences for not average characteristics. Nature Magazine 368:239-242.
4 Platou, C. & Zachrisson, B.U. 1983. "Incisor position in Scandinavian children with ideal occlusion." American Journal of Orthodontics. 83:341-352.
5 Bjork, A. "Sutural growth of the upper face studied by the implant method." Acta Odont Scand. 24:109-127. 1966.
6 Trenouth, M.J and Timms DJ. Relationship of the functional oropharynx to craniofacial morpho;ogy. 1999. A random sample of 82 Brithish schoolchildren. The Angle Orthodontist. 69:419-423.
7 Singh, G.D., McNamara J.A. and Lozanoff, S. 1997 "Thin-plate spline analysis of the cranial base in subjects with Class III malocclusion". European Journal of Orthodontics. 19: 341-353.
8 Vig,P.S. Sarver,D.M. Hall,D.J.& Warren,B.N. 1981 "Quantitative evaluation of airflow in relation to facial morphology". American Journal of Orthodontics. 79; 273-272.
9 Proffit,W R, Bailey, L'T J, Phillips, C & Turvey,T A. 2000 Long-term stability of surgical open -bite correction by Le Fort osteotomy. Angle Orthodontist 70: 112117
10 Kiliaridis. S, & Kalebo, P. 1991. "Masseta muscle thickness measured by ultrasonography and its relation to muscle morphology". Journal of Dental Research. 70:1262-1265.
11 Faure, J. 1998. "Esthetic Prejudice and its evolution in severe anteroposterior and vertical dysmorphoses". Revue D'Orthopedie Dento Faciale. 32: 275-295.
12 Kurol,J., Owman-Moll,P and Lundgren,D. 1996. "Time related root resorption after application of a controlled continuous orthodontic force". American Journal of Orthodontics and Dentofacial Orthopedics. 110: 303-310.
13 Baccetti T, Franchi L, Cameron GC,and McNamara JA.2001. Treatment Timing for Rapid Maxillary Expansion. Angle Orthodontist, Vol 71, No 5.



"Victor Babes" Publishing House "Victor Babes" University of Medicine and Pharmacy Romanian Academy of Medical Sciences National Council of Scientific Research in Higher Education (B+) Index Copernicus
Journals Master List
Embase Journal List Timisoara Medical Scientific Association
 
ISSN: 1583-526X (Online Edition)
Copyright © 2002-2019 Timisoara Medical Journal. All rights reserved.