Facial-keys-To-Orthodontic II Arnett y Bergman

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Facial keys to orthodontic diagnosis and treatment planningpart I I

G. William Arnett, DDS, and Robert T. Bergman, DDS, MS

Santa Barbara, Calif.

This is Part II of a two-part article. Part I was published in the AMERICAN JOURNAL

OF ORTHODONTICS AND DENTOFACIAL ORTHOPEDICS, Vol. 103, No. 4. Part I

discussed the problem of accurate orthodontic diagnosis. Part II discusses the solution to the

orthodontic diagnostic problem. (AM J ORTHOD DENTOFAC ORTHOP 1993:103:395-411.)

Nineteen facial traits were selected for this examination (Table I). Two views of the

patient are used for identification of problems in three planes of space:

I. Frontal

A. Relaxed lip

B. Functional analysis

1. Closed lip

2. Smile

II. Profile

A. Relaxed lip

FRONTAL VIEW

Natural head posture, centric relation, and relaxed lip posture are used to accurately

assess the frontal view.

Outline form and symmetry (Fig. 1)

General outline form and asymmetries are noted.1 The widest dimension of the face is the

zygomatic width (Fig. 1). The bigonial width is approximately 30% less than the bizygomatic

dimension. Farkas1,2 has established normal values for height and width. The height to width

proportion is 1.3:1 for females and 1.35:1 for males. An alternative to measuring height and

width is to artistically describe the face. Faces are wide or narrow, short or long, round or oval,

square or rectangular.

The important question when assessing these dimensions is: Will orthodontic and/or

surgical care necessary for bite correction correct or accentuate existing height and width

imbalance? An example of orthodontic correction of height-width imbalance is the use of biteopening mechanics to lengthen the face during bite correction. An example of surgical

correction is maxillary impaction to shorten the long face.

The extremes of disproportion are short and wide or long and narrow. Short, square facial

outlines are indicative of deep bite Class II malocclusion, vertical maxillary deficiency, and in

some cases, masseteric hyperplasia. Long, narrow faces are associated with vertical maxillary

excess or mandibular protrusion with dental interferences leading to open bite. The bizygomatic

dimension is often deficient (cheekbone deficiency) in combination with maxillary retrusion.

The bigonial dimension may be deficient in combination with mandibular retrusion.

Height and width disproportion is corrected in two ways:


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1. Maxillary or mandibular surgery is used simultaneously to correct the bite and to

lengthen or shorten the facial height.

2. Augmentation or reduction of the facial height or width.

Examples of the latter are chin lengthening to increase facial height (H to Me'),

cheekbone augmentation to increase the bizygomatic width (Zy to Zy), or augmentation of the

mandibular angles to increase the bigonial dimension (Go' to Go'). Buccal lipectomies can help

reduce excessive width in the submalar cheek areas.

As a general rule, the maxilla should rarely be moved up and back. This movement

decreases lip support, increases the nasolabial folds, decreases incisor exposure, and can make

the facial outline appear short and wide. These changes give the appearance of premature facial

aging.

The most common to least common sites of facial asymmetry are chin, mandibular

angles, and cheekbones. The maxilla is rarely in skeletal asymmetry. Asymmetries can occurwith any growth abnormality but are strongly associated with unilateral condylar hyperplasia.

Correction of asymmetries are accomplished with (1) cant correction or midline

movement of the maxilla and mandible simultaneous with occlusal correction or (2)

augmentation or reduction of the skeletal surfaces. Examples of the latter include unilateral

cheekbone, angle, or body augmentation. A common asymmetry correction is chin shifting to

the right or left to center the chin on the facial midline.

Facial level (Fig. 2)

To examine facial levels a reliable horizontal landmark line is necessary. With the patient

in natural head posture,3 the pupils are assessed for level with the horizon. If the pupils are

level, they are used as the horizontal reference line and adjacent structures are measured relative

to this line (Fig. 2). Structures compared with the pupil line are (1) upper canine level, (2) lower

canine level, and (3) chin and jaw level.

Mandibular deviations commonly have upper and lower occlusal cants with chin and jaw

line canting associated. Deviations from level should be noted and correction integrated into the

overall bite treatment plan. If bimaxillary surgery is contemplated, occlusal cant is corrected

routinely at surgery. If one jaw surgery is contemplated, the occlusal cant can be neglected

unless it is esthetically problematic. When problematic, either orthodontic tooth movement or

bimaxillary surgery must be used to correct the cant.

If the pupils, in natural head posture, are not level to the horizon, a constructed frontal

horizontal reference line is used (Fig. 3). This line is visualized as follows:

1. Frontal natural head posture.

2. Horizontal line parallel to the horizon through the pupil area.

3. Assess other structures relative to this line (Fig. 3).

Midline alignments (Fig. 4)


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Midlines are assessed with uppermost condyle position and first tooth contact. If occlusal

slides alter joint position, no reliable midline assessment can be made. The relative positions of

soft tissue landmarks (nasal bridge, nasal tip, filtrum, chin point) and dental midline landmarks

(upper incisor midline, lower incisor midline) are noted. Needed changes are incorporated into

the surgical/orthodontic treatment plan to position these structures on the vertical midline of the

face. Filtrum is usually a reliable midline structure and can be used as the basis for midlineassessment most often. When the pupils are level in natural head posture, a vertical line through

filtrum midpoint is used to assess other hard and soft tissue midline structures (Fig. 4). If the

pupils are not level, a vertical line through filtrum midpoint, perpendicular to postural

horizontal, is used to assess midline structures (Fig. 5). With the evaluation of skeletal or dental

midlines, etiologic factors are assigned.

Dental midline shifts are the result of multiple dental factors including:

1. Spaces

2. Tooth rotations

3. Missing teeth

4. Buccally or lingually positioned teeth

5. Crowns or fillings which change tooth mass

6. Congenital tooth mass difference from left to right

Model examination is used to distinguish dental midline shift etiologic factors (spaces,

rotations). Dental midline shifts are treated orthodontically. Asymmetric premolar extractions

may be necessary to align dental and skeletal midlines. Skeletal midline shifts are not corrected

orthodontically, surgery is employed. When the dental and skeletal midlines deviate together,

the etiologic factor is usually skeletal, and surgery is used to correct (i.e., chin and lower incisor

midline are 3 mm to the left). Stability, periodontal health, and facial balance are optimized

when dental shifts the result of skeletal deviation are treated with surgical, rather than

orthodontic, tooth movement. Attempts to orthodontically correct the bite when the etiologic

factor is skeletal can produce buccal plate violation and gingival recession.4,5

Facial one thirds (Fig. 6)

The face divides vertically into thirds from hairline to midbrow, midbrow to subnasale,

and subnasale to soft tissue menton (Fig. 6). The thirds are within a range of 55 to 65 mm,

vertically.1 The hairline is variable, and the upper third is frequently low range. Increased lower

one-third height is frequently found with vertical maxillary excess and Class III malocclusions

(lack of interdigitation opens vertical height). Decreased lower one-third height is associated

with vertical maxillary deficiency and mandibular retrusion deep bites. Production of correct

proportion influences the choice of surgical procedure used to correct the occlusion (i.e.,

maxillary impaction to correct Class II malocclusion associated with long lower one-third rather

than mandibular advancement). The equality of the middle and the lower thirds should not be

used as the determining factor in facial height changes. The appearance of the landmarks

(incisor exposure, interlabial gap) within the lower third are more important in assessing

balance than are the equality of the middle and the lower thirds.


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Lower one-third evaluation (Figs. 7 through 9)

This area of facial analysis is extremely important in surgical orthodontic diagnosis and

treatment planning. The importance of relaxed lip position for these measurements cannot be

overemphasized.

Upper and lower lip lengths (Fig. 7). The lips are measured independently in a relaxed

position (Fig. 7). The normal length from subnasale to upper lip inferior is 19 to 22 mm.1 If the

upper lip is anatomically short ( 18 mm or less), an increased interlabial gap and incisor

exposure is seen with a normal lower face height. This should not be confused with vertical

maxillary excess (increased interlabial gap, increased upper incisor exposure, increased lower

one-third facial height).

The lower lip is measured from lower lip superior to soft tissue menton and normally

measures in a range of 38 to 44 mm.1 Anatomic short lower lip is sometimes associated with

Class II malocclusion and is verified by cephalometric measurement of the lower anterior dental

height (lower incisor tip to hard tissue menton; women, 40 mm 2 mm, and men, 44 mm 2mm).6 Anatomic short lower lip should not be confused with a short lower lip secondary to

posture (upper incisor interferences) seen in Class II deep bite cases with normal anterior dental

height. Anatomic short lower lip can be lengthened with a lengthening genioplasty.

Anatomic long lower lip can be associated with Class III malocclusions. This should be

verified with the cephalometric anterior dental height measurement. A closed lip position will

produce a long lower lip in combination with increased lower facial height (vertical maxillary

excess and Class III) as the lip elongates to close. The closed lip length is misleading and should

not be used for treatment planning. The normal ratio of upper to lower lip is 1:2.1 Proportionate

lips harmonize regardless of length; disproportionate lips may need length modification to

appear in balance. Lip measurements identify normal or abnormal soft tissue length that can be

related to dentoskeletal length normalcy, excess, or deficiency.

Lip redundancy is seen in cases of vertical maxillary deficiency and mandibular retrusion

with deep bite and, rarely, long lip lengths. To accurately assess lip lengths with redundant lips,

the patient's bite must be opened until the lips separate (Fig. 7).1 This is best accomplished with

a pink base plate wax bite used to open the bite on centric relation (no translation).1 The face is

examined in that posture, and vertical skeletal increases are planned.

Upper tooth to lip relationship (Fig. 8). The distance from upper lip inferior to maxillary

incisal edge is measured (Fig. 8). The normal range is 1 to 5 mm.1 Women show more within

this range. Surgical and orthodontic vertical changes are based primarily on this measurement

(i.e., postsurgical incisor exposure range of 1 to 5 mm).

Conditions of disharmony are produced by four variables:

1. Increased or decreased anatomic upper lip length (infrequently).

2. Increased or decreased maxillary skeletal length (frequently).

3. Thick upper lips expose less incisor than thin upper lips, all other factors being equal.

4. The angle of view changes the amount of incisor visible to the viewer. The threevariables that contribute to the angle of view are (1) the patient's height, (2) the observer's


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height, and (3) the distance from the facial surface of the upper lip to the incisive edge

(increased lip thickness reveals less relative tooth exposure).

Overimpaction of upper incisor teeth leads to the appearance of premature aging,

especially in conjunction with maxillary retraction. This type of surgical movement is rarely

indicated. Posterior movement of the maxillary incisors is indicated only for true maxillaryprotrusion. Orthodontic overretraction, which is used to occlusally correct mandibular retrusion,

produces premature aging of the face.

Interlabial gap (Fig. 9). With the lips relaxed, a space of 1 to 5 mm1 between upper lip

inferior and lower lip superior is present (Fig. 9). Females show a larger gap within the normal

range. This measurement is also dependent on lip lengths and vertical dentoskeletal height.

Increases in interlabial gap are seen with anatomic short upper lip, vertical maxillary

excess, and mandibular protrusion with open bite secondary to cusp interferences. Decreased

interlabial gap is found with vertical maxillary deficiency, anatomically long upper lip (natural

change with aging, especially in males), and mandibular retrusion with deep bite. Abnormalitiesshould be considered when planning skeletal changes. An anatomically short upper lip should

be recognized as a soft tissue problem and should not be treated by excessively shortening the

maxilla. This can lead to a short, round facial outline.

Closed lip position. Even though an understanding of relaxed lip position is essential, an

understanding of closed lip position adds support to diagnostic patterns. The closed lip position

also reveals disharmony between skeletal and soft tissue lengths.

Increased mentalis contraction (mentalis strain), lip strain, and alar base narrowing are

observed in vertical skeletal excess, anatomic short upper lip and some cases of mandibular

protrusion with open bite.

Lip redundancy is seen with vertical maxillary deficiency and mandibular retrusion with

deep bite. With balanced lip and skeletal lengths, the lips should ideally close from a relaxed,

separated position without lip, mentalis, or alar base strain. The maxilla should not be impacted

to idealize the short upper lip closure unless the facial outline will tolerate such a change.

Smile position lip level. When examining the smile posture, different lip elevations are

observed in normal and abnormal skeletal patterns. Ideal exposure with smile is three-quarters

of the crown height to 2 mm of gingiva, females more than males.1 Variability in gingival

exposure is related to (1) lip length, (2) vertical maxillary length, (3) maxillary anatomic crown

length, and (4) magnitude of lip elevation with smile.

Excess gingival exposure may be caused by a short upper lip, vertical maxillary excess,

short clinical crown, and/or large lip elevation with smiling. Because of etiologic variability,

surgical shortening of the maxilla is indicated only when excess gingival exposure is found in

combination with increased interlabial gap, increased tooth exposure, increased lower face

height, and/or mentalis strain.

Deficient exposure etiologic factors include a long upper lip, vertical maxillary

deficiency, and/or minimal smile lip elevation. Decreased incisor exposure is treated with

maxillary lengthening when found in combination with decreased interlabial gap-lip

redundancy, short lower one-third face height, and normal upper lip length.


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When impacting or lengthening the maxilla on the basis of reposed incisor exposure,

gingival smile exposure should also be considered. For example, if the patient has normal smile

gingival exposure (1 to 2 mm) and the incisors are lengthened to treat decreased relaxed lip

incisor exposure, excessive smile gingival exposure will result.

Particular care should be taken with short clinical crowns. A 3 to 4 mm repose incisorexposure may expose unacceptable amounts of gingiva when smiling because of short maxillary

incisor crowns. This situation is properly treated by placing normal length crowns (veneers) on

the maxillary incisors and treatment planning from the repose and smile perspective. The

"gingival smile" is never treated to ideal at the expense of underexposing the incisors in the

relaxed lip position.

PROFILE VIEW

Natural head posture, centric relation, and relaxed lips are used to accurately assess

profile.1

Profile angle (Fig. 10)

This angle is formed by connecting soft tissue glabella, subnasale, and soft tissue

pogonion (Fig. 10).7,8 General harmony of the forehead, midface, and lower face is appraised

with this angle. Maxillary and mandibular basal bone anteroposterior discrepancies are easily

visualized. Class I occlusion presents a total facial angle range of 165 to 175.1 Class II angles

are less than 165, and Class III are greater than 175. Skeletal discrepancies producing Class II

angulation include maxillary protrusion (rare), vertical maxillary excess (common), and

mandibular retrusion (common). Class III skeletal patterns include maxillary retrusion

(common), vertical maxillary deficiency (rare), and mandibular protrusion (common).

Surgical procedures should generally address the cosmetic imbalance established with

this angle. The profile angle is the most important key to the need for anteroposterior surgical

correction. When values are less than 165 or greater than 175, skeletal malocclusions needing

surgery are probably the cause. Angles at the extreme of normal (greater than 175 or less than

165) are usually caused by skeletal disharmony. Soft tissue thickness differences are not

capable of causing these extreme angle changes.

Nasolabial angle (Fig. 11)

This angle is formed by the intersection of the upper lip anterior and columella at

subnasale (Fig. 11). This angle can change noticeably with orthodontic and surgical proceduresthat alter the anteroposterior position or inclination of the maxillary anterior teeth.9-11 All

procedures should place this angle in the cosmetically desirable range of 85 to 105.1 Female

patients will usually be more obtuse within this range. Factors to be considered in treatment

planning to correctly achieve this angle are as follows:

1. Existing angle.

2. Tilting versus bodily movement of maxillary teeth (orthodontic and surgical) and

predicted effect on the existing lip position.


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3. Estimation of lip tension present. Tense lips may move more posteriorly with tooth and

basal bone movement and less anteriorly. Flaccid lips may move less with posterior tooth and

basal bone movement and less with anterior.12-14

4. Anteroposterior lip thickness. Thin lips (6 to 10 mm)9,12,13 may move more with

tooth retraction movement than thick lips (12 to 20 mm).12-14

5. The magnitude of the mandibular retrusion (overjet). The larger the overjet distance,

the more retraction of the maxillary incisors will be necessary, thus opening the nasolabial

angle.9-11

6. The following factors affect the anteroposterior movement of incisor teeth after

extractions: Amount of anterior crowding, spaces, tooth mass proportion (upper versus lower),

posterior rotations, curve of Spee (upper versus lower), and anchorage (headgear, Class II

elastics).

7. Extraction versus nonextraction.

8. Extraction pattern (first versus second premolars).

If the nasolabial angle is open (approximately 105), retraction of anterior teeth

orthodontically and surgically should be avoided in treatment planning. Likewise, a long nose

will become adversely prominent with lip retraction. Present limited knowledge of how lips

respond to anteroposterior movement of the teeth dictates a conservative approach when large

movements are contemplated. Crowding dictates the need for extraction, facial balance

influences which teeth are extracted and how spaces are closed.

Surgical movement of the maxilla also affects the nasolabial angle. The same factors that

affect orthodontic change should be analyzed when considering maxillary movement. As a

general rule, the maxilla should not be moved posteriorly in treating dentofacial deformities,

especially in combination with superior repositioning. This creates nasal elongation, alar base

depression, and opening of the nasolabial angle, all of which create facial premature aging.

Inadvertent maxillary retraction occurs with isolated LeFort surgery when the VTO x-ray film is

taken with the condyles on the eminence rather than seated in the fossa.

Maxillary sulcus contour (Fig. 12)

Normally this sulcus is gently curved15 and gives information regarding upper lip tension

(Fig. 12). With lip tension, the sulcus contour flattens. Flaccid lips form an accentuated curvewith the vermilion lip area showing an accentuation of curve.12 The flaccid lip generally is

thick (12 to 20 mm from anterior vermilion to labial incisor) giving the lip (i.e., headgear with

Class II elastics or functional appliance treatment) the appearance of being too far forward

relative to the teeth.12 The maxilla should not be retracted significantly when a deeply curved,

thick lip is present since this produces poor lip support and cosmetics. If possible, the maxilla

should be moved forward into a thick, curved lip to improve lip support.

Mandibular sulcus contour (Fig. 13)

This contour is a gentle curve15 (Fig. 13) and can indicate lip tension. When deeply

curved, the lower lip is flaccid in character (Class II, vertical maxillary deficiency). The deepcurve is usually secondary to maxillary incisor impingement in the case of deep bite Class II


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and vertical maxillary deficiency. When flattened, the lower lip demonstrates tension of tissues

(Class III). Surgical procedures that correct the basal bone generally will improve the

mandibular sulcus angle (i.e., deep contour associated with deep bite Class II malocclusion or

flatness associated with mandibular protrusion).

Orbital rim (Fig. 14)

The orbital rim is an anteroposterior indicator of maxillary position. Deficient orbital rims

may correlate positionally with a retruded maxillary position because the osseous structures are

often deficient as groups, rather than in isolation. The globe normally is positioned 2 to 4 mm

anterior to the orbital rim (Fig. 14).1 The surgical maxillary versus mandibular decision is

influenced by the orbital rim position. Deficient orbital rims dictate maxillary advancement, all

other factors being equal.

Cheekbone contour (Figs. 15 and 16)

Cheekbone assessment requires frontal and profile examination simultaneously (Figs. 15and 16). Cheekbone contour (CC) correlates with maxillary anteroposterior position, frequently

the cheekbone contour is deficient in combination with maxillary retrusion. Deficient

cheekbones may correlate positionally with a retruded maxillary position because the osseous

structures are often deficient as groups, rather than in isolation. Cheekbone contour is used as

one of the main indicators of maxillary retrusion. This area should have an apex at the

cheekbone point (CP) and not appear flat. The CP is located 20 to 25 mm inferior and 5 to 10

mm anterior to the outer canthus (OC) of the eye when viewed in profile (Fig. 15). When

viewed frontally the CP is 20 to 25 mm inferior and 5 to 10 mm lateral to the OC (Fig. 16). It

should be noted that true mandibular prognathism can show mild malar flatness as a relative

observation to the extreme chin protrusion. True maxillary hypoplasia often is associated with

true malar deficiency.

Nasal base-lip contour (Figs. 15 and 16)

The nasal base-lip contour (Nb-LC) line requires frontal and profile examination

simultaneously (Figs. 15 and 16). The line is the continuation of the cheekbone contour line.

This area is an indicator of maxillary and mandibular skeletal anteroposterior position. Normal

position is indicated by the maxilla point (MxP) directly behind the alar base. The MxP is the

most anterior point on the continuum of the cheekbone-nasal-lip contour and is an indication of

maxillary anteroposterior position.

Maxillary retrusion is indicated by a straight or concave contour at MxP (Fig. 17). When

this anatomic area is concave or flat, maxillary advancement is necessary.

Mandibular protrusion interrupts the nasal base-lip line in the length of the upper lip (Fig.

18). When the line is interrupted within the height of the upper lip a mandibular setback may be

indicated.

Nasal projection (Fig. 19)

The nasal projection (NP) measured horizontally from subnasale to nasal tip is normally

16 to 20 mm (Fig. 19).1 Nasal projection is an indicator of maxillary anteroposterior position.

This length becomes particularly important when contemplating anterior movement of the


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maxilla. Decreased nasal projection contraindicates maxillary advancement. With a Class III

malocclusion, short nose, and all other factors equal, mandibular setback is indicated.

Throat length and contour (Fig. 20)

The distance from the neck-throat junction to the soft tissue menton should be noted (Fig.

20). No millimeter measurement is necessary, but a planned mandibular setback will change this

length. The predicted esthetic result should produce a normal appearing length without sagging.

A patient with a short, sagging throat length is not a good candidate for mandibular setback. A

long, straight throat length is amenable to mandibular setback. Often a mandibular setback is

necessary with chin augmentation to balance lips with chin and maintain throat length. Suction

lipectomy is a useful adjunct for controlling submental sag with setbacks or when isolated fat

accumulation is present.

Subnasale-pogonion line (Sn-Pg') (Fig. 21)

Burstone reported that the upper lip is in front of the Sn-Pg' line by 3.5 mm 1.4 mm,and the lower lip is in front of the line by 2.2 mm 1.6 mm.16

The relationship of the lips to the Sn-Pg' line is an important aid in orthodontic soft tissue

analysis and treatment. Tooth movement changes the relationship of the lips to the Sn-Pg' line

and therefore the esthetic result. All tooth movements should be assessed in regard to the

anticipated lip change to the Sn-Pg' line. Extractions should be avoided when they move the

teeth and create retraction of the lips (dished-in) behind this line (Fig. 22). On the other hand, if

unravelling the crowding with extractions allows for lip balance to the Sn-Pg' line, the

extractions are esthetically acceptable.

The relationship of the lips to this line is affected by the following factors:

1. Skeletal relationship: When anterior or posterior skeletal disharmony exists, producing

overjet abnormalities (positive or negative), the Sn-Pg' has no validity.

2. Incisor inclinations: With a Class I skeletal pattern, the upper and lower incisors must

be at proper overjet and axial inclination to produce proper protrusion of the lips relative to the

Sn-Pg' line.

3. Lip thickness: The lip relationship to the Sn-Pg' line is dependent on lip thickness. The

Burstone relationship16 is true only if the lips are the same thickness, all other factors being

ideal. Class I incisors (upper incisor in front of lower incisor) produce Class I lips (upper lip infront of lower lip) only if the lips are of equal thickness.

This line is also used when planning surgery on the VTO (Fig. 23). The Sn-Pg' line is

ideally drawn to the lips through subnasale. If Pg' is significantly posterior to the line, a chin

augmentation is indicated. Female chins are softer relative to this line.

SOFT TISSUE CHARACTERISTICS OF COMMON SKELETAL DEFORMITIES

With the 19 facial keys, 8 pure skeletal deformities with predictable soft tissue

appearances can be defined. The greater magnitude of the skeletal deformity the more distinct

the soft tissue pattern. Skeletal deformities may occur in combination (i.e., vertical maxillary

excess with mandibular prognathism) and facial traits are therefore blended. In all cases, facial


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traits are helpful in diagnosing skeletal problems. The eight uncombined or pure or unmixed

anteroposterior facial-skeletal types are as follows:

A. Class I facial and dental (facial angle Class I) (Fig. 24)

1. Vertical maxillary excess (Table II)

2. Vertical maxillary deficiency (Table III)B. Class II facial and dental (facial angle Class II) (Fig. 25)

3. Maxillary protrusion (Table IV)

4. Vertical maxillary excess (Table II)

5. Mandibular retrusion (Table V)

C. Class III facial and dental (facial angle Class III) (Fig. 26)

6. Maxillary retrusion (Table VI)

7. Vertical maxillary deficiency (Table III)

8. Mandibular protrusion (Table VII)

Knowing the eight unmixed skeletal patterns is helpful in organizing facial analysis

information into a cohesive, meaningful whole. Without facial analysis, distinguishing the

skeletal source of the malocclusion can be difficult. Facial trait identification and categorization

leads to a differential diagnosis of skeletal patterns (Table VIII Class II, Table IX Class III).

Cephalometric analysis has been shown to be ineffective in this regard. The advantage of a

diagnosis based on facial traits is important. Skeletal malocclusions have profound soft tissue

imbalance that patients expect to be corrected. Facial based treatment planning ensures that

facial change will be correct, whereas cephalometrics have been shown to be unreliable.

ORTHODONTIC PREPARATION FOR SURGERY

Facial and dental discrepancies may not be proportionate because of dental

compensations to the anteroposterior skeletal malalignment.17 Dental compensations are incisoraxial inclination changes in response to increased or decreased overjet. Mandibular retrusion

and, occasionally, vertical maxillary excess are associated with lower incisor flaring and upper

incisor up-righting. Mandibular protrusion, maxillary retrusion and vertical maxillary deficiency

are associated with upper incisor flaring and lower incisor uprighting.

Extraction patterns and mechanics are aimed at removing dental compensations before

surgery. Compensation removal leads to better facial results. An example of this is a 10 mm

skeletal mandibular retrusion. Incisor dental compensations to the overjet may decrease the 10

mm overjet to 5 mm. If the mandible is advanced with the compensations present, the chin

deficiency is still 5 mm. In contrast, when dental compensations are removed, the 10 mm

overjet and 10 mm chin retrusion are simultaneously and totally corrected with surgical

advancement.

Inappropriate orthodontic preparation (e.g., upper first premolar extractions, headgear and

Class II elastics to treat a skeletal mandibular retrusion) distorts the equality of the dental and

facial problems far more than dental compensations. In an attempt to correct the bite without

surgery, the dental discrepancy becomes much less than the facial discrepancy magnitude.

Subsequently, if surgery is used for dental correction, the soft tissue problem is only minimally

corrected. This problem leads to the conclusion that surgery should be planned from the

beginning to obtain optimal facial changes with bite correction.17,18 Extractions should be

planned around factors including, most importantly, crowding, periodontal needs, and facial


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must be followed when determining surgical orthodontic plans. For this purpose 19 key traits

have been described.

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