t 1991 European Orthodontics Society
European Journal of Orthodontics 13 (1991) 343-350
The aesthetic analysis of the face Neville M. Bass Department of Child Dental Health, The London Hospital Medical College, University of London, UK An analysis of the facial soft tissues is presented which permits aesthetic considerations of facial harmony and balance to be measured, and assessed quantitatively. The assessment is carried out in a practical and straight-forward manner, avoiding the measurement of angles. The visually determined Aesthetic Horizonal Line is used as the reference line, with more reliability than the Natural Head Position and more relevance to the soft tissues than Frankfort Horizontal. The analysis accurately predicts the correct position of the mandible so that the extent of orthopaedic or surgical correction necessary can be evaluated. The ideal position and angulation of the maxillary incisors are determined and established as treatment goals, to give optimal exposure of the dentition in expressive behaviour. Comparison of before and after treatment cephalograms permits quantitative assessment of aesthetic change. SUMMARY
Orthodontics today has moved beyond the stage of simple tooth alignment to a more holistic approach, taking facial appearance in its entirety into consideration. Ideal occlusion by itself is no longer an acceptable end result of treatment, but must be in association with optimal facial aesthetics. Edward H. Angle stated 'The mouth is a most potent factor in making or marring the beauty and character of the face' (Angle, 1907); and 80 years later, this still holds true. Studies of eye movement show that in a face-to-face situation, the eyes primarily scan the other person's eyes and the area of the mouth with little time spent in observation of other facial features (Morris, 1982). In the developed countries in the world of the 1990's, much greater emphasis, perhaps regrettably, has to be placed in an individual's appearance as social, professional, and business interactions become ever more numerous and more fleeting. The disturbance of facial harmony and the aesthetic balance between the dental and facial structures as a result of inadequately planned orthodontic therapy in adolescence may well compromise an individual's ability to communicate effectively in a lifetime of interpersonal contacts. At best, their fullest potential may never be attained; at worst they may be psychologically harmed by the effects of orthodontic treatment. Today's orthodontist
has a responsibility to the patient extending well beyond the confines of the oral cavity. Modern techniques in orthodontics and dento-facial orthopaedics fortunately allow much greater control and precision over the position of the teeth within the face and, in the growing individual, over the development of the jaws themselves. These enable the orthodontist to treat the patient with ah enhanced level of sophistication and without the necessity to compromise facial aesthetics in order to comply with gnathological goals. At the same time the effort required of the clinician has been significantly reduced and treatment times shortened. For example, a twophase approach to the Class II malocclusion (Bass, 1976, 1982, 1983a,b) using a prefabricated modular orthopaedic appliance system (Bass, 1987, 1988) in the first phase, followed by a Straight Wire Edgewise system (Andrews, 1976) in the second phase, permits rapid and efficient treatment to be carried out, generally in 20 months overall, without the compromise and risk of deterioration in facial appearance which may result from a single orthodontic phase. Subject and method
Cephalometric analysis In order to provide the optimum in facial aesthetics for a patient, it is necessary prior to
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Introduction
344
The aesthetic horizontal Harmony and balance in the facial appearance of an individual cannot be related simply to a set of statistical norms for a population group,
particularly when these norms are based on the measurement of hard tissue morphological features, many of which are some distance from the dento-facial area. It is more effective to relate primarily to soft tissue features in the dento-facial area of the individual patient. A balanced and harmonious facial appearance is a most complex phenomenon and essentially can be described as a 'visual experience' of the onlooker. For this reason, in the Analysis to be described, the patient's face on the cephalogram is orientated around the Aesthetic Horizontal Line, a horizontal axis pre-determined by the observer, looking at the face from the side (Bass, 1987). Methods The radiograph must be taken with adequate filtration of the beam to permit full visualization of the soft tissues. Prior to placing the patient in the cephalostat and taking the headfilm, the tilt of the patient's head is carefully adjusted until it gives the correct visual impression of being horizontally positioned (Fig. 1). A radiopaque horizontal marker is then fixed to the side of the face with double-sided adhesive tape 1 cm square (Fig. 2). The marker is constructed from a 4-cm length of 0.9-mm wire, glued to a small spirit level tube. With a little practice the levelling of the patient's head and fixing the marker becomes a
Figure 1 (a) The patient's head in the Aesthetic Horizontal position. Note the balanced visual appearance of the head and face, (b) The head appears to be tilted downwards, (c) The head appears to be tilted upwards.
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treatment, to have meaningful diagnostic criteria related to aesthetics, to give a basis for treatment decisions and the monitoring of treatment effects. This information can be obtained readily from the cephalometric headfilm with a small modification to the radiographic technique. Although many of the cephalometric analyses in current use give considerable data about the morphological relationships of the head and face and even aesthetic relationships (Holdaway, 1983), the ability of contemporary orthopaedic appliances to alter the rates and directions of growth of different parts of the dento-facial complex (Pancherz et al, 1989) gives rise to a need for additional diagnostic information from the headfilm. This information has been carefully identified by the author in his clinical practice over the past 15 years and many different analyses tried out in an empirical way during that time. This article represents the summation of this clinical research, and presents an effective and straightforward means of evaluating the facial profile, and the optimum position of the dentition within the face.
N. M. BASS
345
AESTHETIC ANALYSIS OF THE FACE
in addition to the clinician's usual analysis, the aesthetic analysis can be made.
Figure 2 The radiopaque horizontal marker, constructed from a 4 cm length of 0.9 mm wire, glued to a small spiritlevel tube ('water bubble'), is fixed on the side of the face with 1 cm 2 double-sided tape (photomount) prior to placing patient in cephalostat. The subsequent position of the head is then not important.
1. Visually level the patient's face. 2. Mark two points horizontally 4 cm apart on the face with an alcohol soluble ink. A fine black pen used for drawing on overhead projection plastic sheet is ideal for this purpose. The horizontal marks are placed using a conventional spirit level. 3. The patient is instructed to avoid washing the marks until after the headfilm is taken, which could be up to a week later (Although the ink is not water soluble, it can be removed by vigorous washing with soap and water). 4. In the radiographic department, a 4-cm 0.9-mm wire is placed across the two marks and held with double-sided sticky tape. A spirit level is no longer necessary at this stage. The radiograph is then taken in the usual way, with no necessity to level the head. The soft tissues should be in a relaxed position for the exposure. Once taken, the headfilm carries a line indicating the aesthetic horizontal which is subsequently used as a reference line to orientate the features in the face. A tracing is made and,
Error of the method The Aesthetic Horizontal Line is highly reproducible (Fig. 6). Analysis of repeat pairs of. radiographs of 82 subjects randomly selected, approximately 6 months apart, taken by 4 different assistants (including 2 trainees) showed 85 per cent to have a variation of 2.5 degrees or less, when superimposed on NSL (Table 1). From a clinical standpoint, this is well within acceptable limits of accuracy. The error of the method was calculated using the Dahlberg formula 2(11-1)
(Dahlberg, 1940) where d is the difference between the two measurements and n is the sample size. The Method Error of 1.36 degrees and Variance of 1.85 degrees compare favourably with previous reported studies of Natural Head Posture, which gave Method Errors of 2.25 degrees (Siersbaek-Nielsen and Solow, 1982), 3.20 degrees (Sandham, 1988), 2.18 degrees (Cole, 1988), and 2.34 degrees (Cooke and Wei, 1990).
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rapid routine for most assistants. The Aesthetic Line can be quickly checked, if necessary, by bringing the patient to the orthodontist prior to the radiographic exposure. If this should be inconvenient due to distance or time complications, e.g. in a hospital environment, an alternative method is as follows.
The horizontal reference line The Frankfort horizontal plane cannot be used to judge soft tissue facial aesthetics as it is based on hard tissue structures in the skull, which show considerable individual variation, particularly in the position of Porion. The variance of intra-cranial reference planes has been shown to range between 25 and 35 degrees (Cooke and Wei, 1988). Quite obviously, the vertical relationship of the ears cannot be used to assess the soft tissue profile. Although the 'Natural Head Posture' (Moorrees and Kean, 1958; Solow and Tallgren, 1971) has been used in many studies of the profile and in cephalometric analysis, this has also several drawbacks. It may vary with ambient temperature, the psychological demeanour of the patient or the patency of the airway (Solow et al., 1984) and it is also time consuming to assess properly if it is to be reproducible (Siersbaek-Nielsen & Solow, 1982). Furthermore, it does not fully equate to the aesthetic consideration of the profile, some individuals characteristically holding the head up or down, rather than level.
346
N . M. BASS
Table 1 Angular difference of Aesthetic Horizontal marker with reference to NSL in 82 paired radiographs. [Radiographs repeated at mostly 6-month intervals by four different assistants and cases selected at random.] Variation
Number of cases
0° 0.5° 1° 1.5° 2° 2.5° 3° 3.5° 4° 4.5° 5°
14 9 25 7 11 4 6 I
3 0 2
Mean Error 1.4°. Error of Method 1.36°. Variance 1.85°
The aesthetic analysis on the headfilm The position of soft tissue pogonion is a key factor in the harmonious profile and this has been shown to be as prominent in females as in males (Scheiderman et al., 1980). In females, •however, the lips are slightly more forward giving the impression of a more recessive chin (Spradley et al., 1981). Consideration of a variety of attractive faces in profile will make it apparent that the position of soft tissue nasion or glabella has little or no influence on the harmony and balance of the lower facial third; an individual with a receding or sloping forehead does not look more harmonious with a receding chin and similarly an individual with a prominent brow does not have a better balanced facial appearance with a protrusive mandible. It is more logical to assess the aesthetics of the dento-facial structures from a closer point and subnasale (Sn) has been chosen for this. This is defined as 'the point at which the nasal septum merges with the upper lip in the midsagittal plane'. Practically, it can be taken as the deepest point on the curve where the outline of the nose joins the lip. In the aesthetic analysis, the visual appearance of the soft tissues is a primary considera-
Tracing procedure (Fig. 3) Step 1 Extend the Aesthetic Horizontal Line (AH) through horizontal marker. Step 2 Bisect the horizontal distance from Point A to subnasale (Sn) and obtain Point V. Step 3 Chin line. A. Draw a line perpendicular to AH through Point V. This gives the posterior limit for a harmonious soft tissue chin position. Behind this, the chin looks retrusive. B. Draw a line perpendicular to AH through Subnasale. This is the anterior limit of the chin for a balanced profile. Anterior to this, the chin looks protrusive. Step4 Lip position (Caucasian). The slope of the upper lip should lie on or slightly in front of the perpendicular to AH from subnasale ('lip line') with the most anterior part of the upper lip 1-2 mm in front and the most anterior part of the lower lip 0-1 mm behind the line. Step 5 Maxillary Incisor Position (Caucasian). Bisect the horizontal distance between points A and V (to give one-quarter the thickness of the upper lip) and drop a perpendicular. The middle third of the labial surface of the maxillary central incisor should lie tangent to this line. This ensures that the teeth are well displayed during expression, without appearing to be too proclined or retroclined. This also places the roots in the correct angulation, assuming an average crown-root angle. However, there is considerable variation, up to 42 degrees in some cases (Bryant et al., 1984), between the labial surface and the root long axis and it is unwise to rely too heavily on root position in determining the aesthetic appearance of the incisors. The incisal edge should lie 2-3 mm below stomion for maximum exposure of the teeth during expressive behaviour, without an excess of gingival tissue showing. Note that the position of the lips and
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The method is thus highly reproducible and the horizontal line is easily and rapidly set up and taught to ancillary staff.
tion—these are ultimately the features of maximum significance to the patient. The thickness of the soft tissue drape of the facial skeleton varies between individuals and the analysis therefore seeks to compare the patient with themselves, rather than a group norm.
347
AESTHETIC ANALYSIS OF THE FACE
AESTHETIC HORIZONTAL
STEP 3
STEP1
STEP 2
\ \
'i-2mm
STEP 5 STEP 4 Figure 3 Steps in making the aesthetic analysis. I. Extend the Aesthetic Horizontal (AH) Line through the marker on the headfilm. 2. Find Point A and subnasale (Sn) and bisect the horizontal distance to obtain Point V. (The two points do not have to be at the same vertical height). 3. The Chin Line. A perpendicular to the Aesthetic Horizontal Line through Point V gives the posterior limit for a harmonious soft tissue chin position. The Lip Line. The perpendicular through Point Sn gives the anterior limit for the chin position. The chin has a range of approximately 8-10 mm within which it will appear well balanced. 4. The position of the lips is related to the Lip Line. In the Caucasian face, the slope of the upper lips should be on or slightly in front of the Lip Line. The most anterior part should be 1-2 mm in front of the line. The most anterior part of the lower lip should be 0-1 mm behind the line. 5. Maxillary Incisor Position (Caucasian). The analysis allows the maxillary incisors to be precisely placed as a basis for establishing optimum aesthetics of the smile. The distance between Point A and Point V is bisected and a perpendicular dropped. The middle third of the labial surface of the central incisor should be at a tangent to this line, with the incisal edge 2-3 mm below Stomion. 6. The Visualized Treatment Objective (VTO) to determine the need, or otherwise, for orthopaedic or surgical advancement (or retraction) of the chin.
maxillary incisors are more forward in the Oriental and Negro face. (A modified analysis is available, but it is beyond the scope of this paper.) Step 6. Determination of need for orthopaedic advancement of mandible. If positioning of the maxillary incisors in Step 5 leaves an overjet and if soft tissue pogonion is too far back, as assessed in Step 3, then orthopaedic correction of the mandibular position is indicated. A Visual Treatment Objective (VTO) can be constructed with the chin in the new position, using the methods described by
Ricketts (1960), Holdaway (1984), and others. With efficient orthopaedics, the change in mandibular position usually occurs as approximately 1 mm of growth down the facial axis per month of treatment, but with little or no forward growth in the mid-face. The final lower incisor position in relation to APC and the final lip position in relation to Ricketts E-Plane (1968) or the profile line of Merrifield (1966) can then be assessed. After a little experience, the construction of a V.T.O. will usually be found unnecessary, as the new mandib-
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STEP 6
N. M. BASS
ular position is easy to visualise and the monitoring of treatment changes will provide more accurate additional information during the progress of the case. Comparison of serial cephalometric records is carried out by transferring the Aesthetic Horizontal to subsequent radiographs with reference to stable anatomical structures within the anterior cranial base. Discussion
(a
Figure 4 Facial changes with incisor retraction, (a) Prior to treatment, (b) After Edgewise therapy involving retraction of the upper, incisor roots. Note the recessive appearance of the naso-labial area and the falling back of the upper lip. The Aesthetic Analysis indicates that few cases require palatal root movement of the incisors, if optimum aesthetics are to be provided.
FigureS Illustrative case. (A) Prior to treatment at 12 years 10 months. Mandible is recessive. Arrow indicates ideal position for soft tissue chin, on chin line. (B) After 9 months of treatment with Bass orthopaedic appliance system. Chin has developed forward substantially, up to chin line. Patient now displays a harmonious facial profile and dental relationships are overcorrected. Occlusion is ready for final correction with Straight Wire Edgewise therapy. (The overall treatment duration was 21 months.) (C) 18 years 9 months. Approximately 3 years out of maxillary retention. Note the well positioned chin and balanced facial appearance. (D) Intra-oral photographs at the three stages. The maxillary dentition is in the ideal location for optimum display in expressive behaviour, in the position determined by the Aesthetic Analysis. (All photographs and radiographs taken in retruded centric relation.)
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It will be noted that the Aesthetic Analysis uses the position of the maxillary incisors as a key to setting up treatment objectives, rather than the traditional starting point of the mandibular incisors. This radical departure is possible only when treatment includes a first orthopaedic phase to enhance mandibular growth (or a surgical orthodontic technique in the non-growing patient) to allow optimal facial aesthetics
to be obtained. The slope of the upper lip and the naso-labial angle (Lo and Hunter, 1982) are critical factors in the appearance of the face and a two-phase approach permits these to be fully respected by avoiding the over-retraction of the maxillary incisors with the consequent unattractive falling back of the upper lip (Roos, 1977). The great majority of Class II division 1 cases have the roots of the maxillary incisors in more or less the correct position within the alveolar crest prior to treatment, even with overjets of 10-15 mm and the Aesthetic Analysis will show few cases with a need for substantial apical retraction of the incisors. Indeed, if the roots of the upper incisors are moved back to any significant extent, it can usually be assumed that excessive retraction of the upper lip will take place and that subsequent alveolar remodelling will result in an artificial and recessive appearance of the subnasal area (Fig. 4). However, it must also be said that not every case exhibiting an overjet will require an orthopaedic phase. The clinician must guard against
349
AESTHETIC ANALYSIS OF THE FACE
H.L. 12 YEARS 10 MONTHS
^--
European Journal of Orthodontics 13 (1991) 343-350
The aesthetic analysis of the face Neville M. Bass Department of Child Dental Health, The London Hospital Medical College, University of London, UK An analysis of the facial soft tissues is presented which permits aesthetic considerations of facial harmony and balance to be measured, and assessed quantitatively. The assessment is carried out in a practical and straight-forward manner, avoiding the measurement of angles. The visually determined Aesthetic Horizonal Line is used as the reference line, with more reliability than the Natural Head Position and more relevance to the soft tissues than Frankfort Horizontal. The analysis accurately predicts the correct position of the mandible so that the extent of orthopaedic or surgical correction necessary can be evaluated. The ideal position and angulation of the maxillary incisors are determined and established as treatment goals, to give optimal exposure of the dentition in expressive behaviour. Comparison of before and after treatment cephalograms permits quantitative assessment of aesthetic change. SUMMARY
Orthodontics today has moved beyond the stage of simple tooth alignment to a more holistic approach, taking facial appearance in its entirety into consideration. Ideal occlusion by itself is no longer an acceptable end result of treatment, but must be in association with optimal facial aesthetics. Edward H. Angle stated 'The mouth is a most potent factor in making or marring the beauty and character of the face' (Angle, 1907); and 80 years later, this still holds true. Studies of eye movement show that in a face-to-face situation, the eyes primarily scan the other person's eyes and the area of the mouth with little time spent in observation of other facial features (Morris, 1982). In the developed countries in the world of the 1990's, much greater emphasis, perhaps regrettably, has to be placed in an individual's appearance as social, professional, and business interactions become ever more numerous and more fleeting. The disturbance of facial harmony and the aesthetic balance between the dental and facial structures as a result of inadequately planned orthodontic therapy in adolescence may well compromise an individual's ability to communicate effectively in a lifetime of interpersonal contacts. At best, their fullest potential may never be attained; at worst they may be psychologically harmed by the effects of orthodontic treatment. Today's orthodontist
has a responsibility to the patient extending well beyond the confines of the oral cavity. Modern techniques in orthodontics and dento-facial orthopaedics fortunately allow much greater control and precision over the position of the teeth within the face and, in the growing individual, over the development of the jaws themselves. These enable the orthodontist to treat the patient with ah enhanced level of sophistication and without the necessity to compromise facial aesthetics in order to comply with gnathological goals. At the same time the effort required of the clinician has been significantly reduced and treatment times shortened. For example, a twophase approach to the Class II malocclusion (Bass, 1976, 1982, 1983a,b) using a prefabricated modular orthopaedic appliance system (Bass, 1987, 1988) in the first phase, followed by a Straight Wire Edgewise system (Andrews, 1976) in the second phase, permits rapid and efficient treatment to be carried out, generally in 20 months overall, without the compromise and risk of deterioration in facial appearance which may result from a single orthodontic phase. Subject and method
Cephalometric analysis In order to provide the optimum in facial aesthetics for a patient, it is necessary prior to
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Introduction
344
The aesthetic horizontal Harmony and balance in the facial appearance of an individual cannot be related simply to a set of statistical norms for a population group,
particularly when these norms are based on the measurement of hard tissue morphological features, many of which are some distance from the dento-facial area. It is more effective to relate primarily to soft tissue features in the dento-facial area of the individual patient. A balanced and harmonious facial appearance is a most complex phenomenon and essentially can be described as a 'visual experience' of the onlooker. For this reason, in the Analysis to be described, the patient's face on the cephalogram is orientated around the Aesthetic Horizontal Line, a horizontal axis pre-determined by the observer, looking at the face from the side (Bass, 1987). Methods The radiograph must be taken with adequate filtration of the beam to permit full visualization of the soft tissues. Prior to placing the patient in the cephalostat and taking the headfilm, the tilt of the patient's head is carefully adjusted until it gives the correct visual impression of being horizontally positioned (Fig. 1). A radiopaque horizontal marker is then fixed to the side of the face with double-sided adhesive tape 1 cm square (Fig. 2). The marker is constructed from a 4-cm length of 0.9-mm wire, glued to a small spirit level tube. With a little practice the levelling of the patient's head and fixing the marker becomes a
Figure 1 (a) The patient's head in the Aesthetic Horizontal position. Note the balanced visual appearance of the head and face, (b) The head appears to be tilted downwards, (c) The head appears to be tilted upwards.
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treatment, to have meaningful diagnostic criteria related to aesthetics, to give a basis for treatment decisions and the monitoring of treatment effects. This information can be obtained readily from the cephalometric headfilm with a small modification to the radiographic technique. Although many of the cephalometric analyses in current use give considerable data about the morphological relationships of the head and face and even aesthetic relationships (Holdaway, 1983), the ability of contemporary orthopaedic appliances to alter the rates and directions of growth of different parts of the dento-facial complex (Pancherz et al, 1989) gives rise to a need for additional diagnostic information from the headfilm. This information has been carefully identified by the author in his clinical practice over the past 15 years and many different analyses tried out in an empirical way during that time. This article represents the summation of this clinical research, and presents an effective and straightforward means of evaluating the facial profile, and the optimum position of the dentition within the face.
N. M. BASS
345
AESTHETIC ANALYSIS OF THE FACE
in addition to the clinician's usual analysis, the aesthetic analysis can be made.
Figure 2 The radiopaque horizontal marker, constructed from a 4 cm length of 0.9 mm wire, glued to a small spiritlevel tube ('water bubble'), is fixed on the side of the face with 1 cm 2 double-sided tape (photomount) prior to placing patient in cephalostat. The subsequent position of the head is then not important.
1. Visually level the patient's face. 2. Mark two points horizontally 4 cm apart on the face with an alcohol soluble ink. A fine black pen used for drawing on overhead projection plastic sheet is ideal for this purpose. The horizontal marks are placed using a conventional spirit level. 3. The patient is instructed to avoid washing the marks until after the headfilm is taken, which could be up to a week later (Although the ink is not water soluble, it can be removed by vigorous washing with soap and water). 4. In the radiographic department, a 4-cm 0.9-mm wire is placed across the two marks and held with double-sided sticky tape. A spirit level is no longer necessary at this stage. The radiograph is then taken in the usual way, with no necessity to level the head. The soft tissues should be in a relaxed position for the exposure. Once taken, the headfilm carries a line indicating the aesthetic horizontal which is subsequently used as a reference line to orientate the features in the face. A tracing is made and,
Error of the method The Aesthetic Horizontal Line is highly reproducible (Fig. 6). Analysis of repeat pairs of. radiographs of 82 subjects randomly selected, approximately 6 months apart, taken by 4 different assistants (including 2 trainees) showed 85 per cent to have a variation of 2.5 degrees or less, when superimposed on NSL (Table 1). From a clinical standpoint, this is well within acceptable limits of accuracy. The error of the method was calculated using the Dahlberg formula 2(11-1)
(Dahlberg, 1940) where d is the difference between the two measurements and n is the sample size. The Method Error of 1.36 degrees and Variance of 1.85 degrees compare favourably with previous reported studies of Natural Head Posture, which gave Method Errors of 2.25 degrees (Siersbaek-Nielsen and Solow, 1982), 3.20 degrees (Sandham, 1988), 2.18 degrees (Cole, 1988), and 2.34 degrees (Cooke and Wei, 1990).
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rapid routine for most assistants. The Aesthetic Line can be quickly checked, if necessary, by bringing the patient to the orthodontist prior to the radiographic exposure. If this should be inconvenient due to distance or time complications, e.g. in a hospital environment, an alternative method is as follows.
The horizontal reference line The Frankfort horizontal plane cannot be used to judge soft tissue facial aesthetics as it is based on hard tissue structures in the skull, which show considerable individual variation, particularly in the position of Porion. The variance of intra-cranial reference planes has been shown to range between 25 and 35 degrees (Cooke and Wei, 1988). Quite obviously, the vertical relationship of the ears cannot be used to assess the soft tissue profile. Although the 'Natural Head Posture' (Moorrees and Kean, 1958; Solow and Tallgren, 1971) has been used in many studies of the profile and in cephalometric analysis, this has also several drawbacks. It may vary with ambient temperature, the psychological demeanour of the patient or the patency of the airway (Solow et al., 1984) and it is also time consuming to assess properly if it is to be reproducible (Siersbaek-Nielsen & Solow, 1982). Furthermore, it does not fully equate to the aesthetic consideration of the profile, some individuals characteristically holding the head up or down, rather than level.
346
N . M. BASS
Table 1 Angular difference of Aesthetic Horizontal marker with reference to NSL in 82 paired radiographs. [Radiographs repeated at mostly 6-month intervals by four different assistants and cases selected at random.] Variation
Number of cases
0° 0.5° 1° 1.5° 2° 2.5° 3° 3.5° 4° 4.5° 5°
14 9 25 7 11 4 6 I
3 0 2
Mean Error 1.4°. Error of Method 1.36°. Variance 1.85°
The aesthetic analysis on the headfilm The position of soft tissue pogonion is a key factor in the harmonious profile and this has been shown to be as prominent in females as in males (Scheiderman et al., 1980). In females, •however, the lips are slightly more forward giving the impression of a more recessive chin (Spradley et al., 1981). Consideration of a variety of attractive faces in profile will make it apparent that the position of soft tissue nasion or glabella has little or no influence on the harmony and balance of the lower facial third; an individual with a receding or sloping forehead does not look more harmonious with a receding chin and similarly an individual with a prominent brow does not have a better balanced facial appearance with a protrusive mandible. It is more logical to assess the aesthetics of the dento-facial structures from a closer point and subnasale (Sn) has been chosen for this. This is defined as 'the point at which the nasal septum merges with the upper lip in the midsagittal plane'. Practically, it can be taken as the deepest point on the curve where the outline of the nose joins the lip. In the aesthetic analysis, the visual appearance of the soft tissues is a primary considera-
Tracing procedure (Fig. 3) Step 1 Extend the Aesthetic Horizontal Line (AH) through horizontal marker. Step 2 Bisect the horizontal distance from Point A to subnasale (Sn) and obtain Point V. Step 3 Chin line. A. Draw a line perpendicular to AH through Point V. This gives the posterior limit for a harmonious soft tissue chin position. Behind this, the chin looks retrusive. B. Draw a line perpendicular to AH through Subnasale. This is the anterior limit of the chin for a balanced profile. Anterior to this, the chin looks protrusive. Step4 Lip position (Caucasian). The slope of the upper lip should lie on or slightly in front of the perpendicular to AH from subnasale ('lip line') with the most anterior part of the upper lip 1-2 mm in front and the most anterior part of the lower lip 0-1 mm behind the line. Step 5 Maxillary Incisor Position (Caucasian). Bisect the horizontal distance between points A and V (to give one-quarter the thickness of the upper lip) and drop a perpendicular. The middle third of the labial surface of the maxillary central incisor should lie tangent to this line. This ensures that the teeth are well displayed during expression, without appearing to be too proclined or retroclined. This also places the roots in the correct angulation, assuming an average crown-root angle. However, there is considerable variation, up to 42 degrees in some cases (Bryant et al., 1984), between the labial surface and the root long axis and it is unwise to rely too heavily on root position in determining the aesthetic appearance of the incisors. The incisal edge should lie 2-3 mm below stomion for maximum exposure of the teeth during expressive behaviour, without an excess of gingival tissue showing. Note that the position of the lips and
Downloaded from by guest on December 19, 2014
The method is thus highly reproducible and the horizontal line is easily and rapidly set up and taught to ancillary staff.
tion—these are ultimately the features of maximum significance to the patient. The thickness of the soft tissue drape of the facial skeleton varies between individuals and the analysis therefore seeks to compare the patient with themselves, rather than a group norm.
347
AESTHETIC ANALYSIS OF THE FACE
AESTHETIC HORIZONTAL
STEP 3
STEP1
STEP 2
\ \
'i-2mm
STEP 5 STEP 4 Figure 3 Steps in making the aesthetic analysis. I. Extend the Aesthetic Horizontal (AH) Line through the marker on the headfilm. 2. Find Point A and subnasale (Sn) and bisect the horizontal distance to obtain Point V. (The two points do not have to be at the same vertical height). 3. The Chin Line. A perpendicular to the Aesthetic Horizontal Line through Point V gives the posterior limit for a harmonious soft tissue chin position. The Lip Line. The perpendicular through Point Sn gives the anterior limit for the chin position. The chin has a range of approximately 8-10 mm within which it will appear well balanced. 4. The position of the lips is related to the Lip Line. In the Caucasian face, the slope of the upper lips should be on or slightly in front of the Lip Line. The most anterior part should be 1-2 mm in front of the line. The most anterior part of the lower lip should be 0-1 mm behind the line. 5. Maxillary Incisor Position (Caucasian). The analysis allows the maxillary incisors to be precisely placed as a basis for establishing optimum aesthetics of the smile. The distance between Point A and Point V is bisected and a perpendicular dropped. The middle third of the labial surface of the central incisor should be at a tangent to this line, with the incisal edge 2-3 mm below Stomion. 6. The Visualized Treatment Objective (VTO) to determine the need, or otherwise, for orthopaedic or surgical advancement (or retraction) of the chin.
maxillary incisors are more forward in the Oriental and Negro face. (A modified analysis is available, but it is beyond the scope of this paper.) Step 6. Determination of need for orthopaedic advancement of mandible. If positioning of the maxillary incisors in Step 5 leaves an overjet and if soft tissue pogonion is too far back, as assessed in Step 3, then orthopaedic correction of the mandibular position is indicated. A Visual Treatment Objective (VTO) can be constructed with the chin in the new position, using the methods described by
Ricketts (1960), Holdaway (1984), and others. With efficient orthopaedics, the change in mandibular position usually occurs as approximately 1 mm of growth down the facial axis per month of treatment, but with little or no forward growth in the mid-face. The final lower incisor position in relation to APC and the final lip position in relation to Ricketts E-Plane (1968) or the profile line of Merrifield (1966) can then be assessed. After a little experience, the construction of a V.T.O. will usually be found unnecessary, as the new mandib-
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STEP 6
N. M. BASS
ular position is easy to visualise and the monitoring of treatment changes will provide more accurate additional information during the progress of the case. Comparison of serial cephalometric records is carried out by transferring the Aesthetic Horizontal to subsequent radiographs with reference to stable anatomical structures within the anterior cranial base. Discussion
(a
Figure 4 Facial changes with incisor retraction, (a) Prior to treatment, (b) After Edgewise therapy involving retraction of the upper, incisor roots. Note the recessive appearance of the naso-labial area and the falling back of the upper lip. The Aesthetic Analysis indicates that few cases require palatal root movement of the incisors, if optimum aesthetics are to be provided.
FigureS Illustrative case. (A) Prior to treatment at 12 years 10 months. Mandible is recessive. Arrow indicates ideal position for soft tissue chin, on chin line. (B) After 9 months of treatment with Bass orthopaedic appliance system. Chin has developed forward substantially, up to chin line. Patient now displays a harmonious facial profile and dental relationships are overcorrected. Occlusion is ready for final correction with Straight Wire Edgewise therapy. (The overall treatment duration was 21 months.) (C) 18 years 9 months. Approximately 3 years out of maxillary retention. Note the well positioned chin and balanced facial appearance. (D) Intra-oral photographs at the three stages. The maxillary dentition is in the ideal location for optimum display in expressive behaviour, in the position determined by the Aesthetic Analysis. (All photographs and radiographs taken in retruded centric relation.)
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It will be noted that the Aesthetic Analysis uses the position of the maxillary incisors as a key to setting up treatment objectives, rather than the traditional starting point of the mandibular incisors. This radical departure is possible only when treatment includes a first orthopaedic phase to enhance mandibular growth (or a surgical orthodontic technique in the non-growing patient) to allow optimal facial aesthetics
to be obtained. The slope of the upper lip and the naso-labial angle (Lo and Hunter, 1982) are critical factors in the appearance of the face and a two-phase approach permits these to be fully respected by avoiding the over-retraction of the maxillary incisors with the consequent unattractive falling back of the upper lip (Roos, 1977). The great majority of Class II division 1 cases have the roots of the maxillary incisors in more or less the correct position within the alveolar crest prior to treatment, even with overjets of 10-15 mm and the Aesthetic Analysis will show few cases with a need for substantial apical retraction of the incisors. Indeed, if the roots of the upper incisors are moved back to any significant extent, it can usually be assumed that excessive retraction of the upper lip will take place and that subsequent alveolar remodelling will result in an artificial and recessive appearance of the subnasal area (Fig. 4). However, it must also be said that not every case exhibiting an overjet will require an orthopaedic phase. The clinician must guard against
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AESTHETIC ANALYSIS OF THE FACE
H.L. 12 YEARS 10 MONTHS
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