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9 • Orthodontics I: Development, Assessment and Treatment Planning
227
Nickel Allergies
In patients with a confirmed severe hypersensitivity to
nickel, nickel-free brackets and wires should be used; in
some cases, clear aligner therapy may be considered as an
alternative.
Latex Allergy
Latex-free gloves, elastomeric separators, modules/chain,
intraoral elastics and headgear components should be used.
Bleeding Diatheses
If extractions are necessary, special medical arrangements
will need to be in place.
Behavioural/Learning Difficulties
These will influence the aims and scope of treatment possible.
Extractions alone may produce an improvement in dental
aesthetics and facilitate tooth-cleaning measures.
Arthritis or Osteoporosis/Bisphosphonates
Because juvenile or adult-onset rheumatoid arthritis often
requires management with chronic steroid administration,
lengthy orthodontic treatment is inadvisable due to the
increased possibility of periodontal problems arising.
Oral doses of prostaglandin inhibitors or resorptioninhibiting agents (bisphosphonates) may be administered
to adults being treated for arthritis or osteoporosis, respectively; as tooth movement may be affected, advice
should be sought from the treating physician. Orthodontic treatment and extractions are contraindicated if
bisphosphonates are given intravenously due to the osteonecrosis risk.
Dental History
The nature, extent and frequency of previous dental treatment together with the level of patient co-operation should
be recorded, along with details of daily oral hygiene practices. A history of early loss of primary teeth, incisor
trauma, enamel hypoplasia, absent teeth or TMJ problems
should be noted. If orthodontic treatment has been carried
out previously, details relating to extractions and appliance
type should be recorded. If treatment was abandoned, the
patient must be questioned carefully for the reasons.
Social History
The ease with which regular appointments can be attended
and any forthcoming events that may influence attendance
should be noted as both affect compliance with treatment.
CLINICAL EXAMINATION
Before the child patient takes a seat in the dental chair, it
is often worthwhile to attempt to estimate their chronological age from their height and general level of physical
maturity. This may give some indication of future growth
potential. If the patient is accompanied by a parent, obvious familial malocclusion traits may be observed. The
purpose of the clinical examination is to assess and record
facial, dental, occlusal and related functional aspects of a
patient in order to request appropriate diagnostic aids. An
extraoral followed by an intraoral examination should be
performed.
Extraoral Examination
The skeletal pattern, soft tissues of the lips, tongue position
during swallowing, speech, temporomandibular joints and
mandibular path of closure should be assessed and the
presence of any habits noted.
The relationship of the mandible to the maxilla should
be assessed in all three planes of space: anteroposteriorly,
vertically and laterally. Before proceeding, it is important to
ensure that:
n
the patient is seated upright with the head in the natural
postural position or with the Frankfort plane (a line joining the upper border of the external auditory meatus to
the inferior aspect of the bony orbit) horizontal; natural
head posture may be obtained by asking the patient to
look straight ahead focusing on the horizon
n
the lips are in repose
n
the teeth are in centric occlusion.
Anteroposterior Plane
The relationship of the dento-alveolar parts of the mandible
to those of the maxilla and their relationship to the cranial
base in the anteroposterior plane is assessed by observing
the patient in profile. Three means may be used.
n
Drop a perpendicular from soft tissue nasion (zero-meridian line): the upper lip should lie on or slightly ahead
and the chin point slightly behind where the skeletal pattern is class I.
n
Palpate the soft tissue profile over the apices of the upper
and lower incisors in the midline, which allows the following classification to be made (Fig. 9.7).
Class I: the mandible lies 2–3 mm behind the maxilla.
Class II: the mandible is retruded in relation to the maxilla.
Class III: the mandible is protruded in relation to the maxilla.
No indication is given as to where a skeletal discrepancy
may lie as the classification reflects solely the position of
the mandible and the maxilla relative to each other.
As this method is not always reliable because of variation in
lip thickness, palpation of the alveolar bases intraorally
in the same locations has been claimed to give a better
assessment. In essence, any significant discrepancy in
the anteroposterior dental base relationship should be
investigated more thoroughly by taking and analysing a
lateral cephalometric film (see later).
n
The angle of facial convexity (upper (mid-eyebrow to
base of nose) to lower (base of nose to chin point); mean
12° 1 4°) may also be assessed allowing the following
classification: average (class I or straight), increased
(class II or convex) or decreased (class III or concave).
Vertical Plane
Two assessments of the vertical relationship of the face
should be made (Fig. 9.8).
Assessment of lower facial height. In a well-balanced
face, the face can be divided into equal thirds. The dis-
tance from the hairline to the mid-eyebrow height should
be equal to that of the upper facial height (the mid-
eyebrow level to the base of the nose) and the lower facial
height (base of the nose to the inferior aspect of the
chin). The lower facial height may, therefore, be assessed
as average when the upper and lower facial heights are
228
Master Dentistry
Class I Class II Class III
Fig. 9.7 Classification of the anteroposterior skeletal pattern.
FMPA
Fig. 9.8 Assessment of the vertical facial relationships. Lower facial height (
planes angle (
FMPA
).
equal, reduced (when lower facial height is less than upper facial height) or increased (when lower facial height
is greater than upper facial height).
Assessment of the Frankfort–mandibular planes angle
(FMPA). With one hand, or the handle of a dental mirror,
along the inferior aspect of the mandible and another
hand along the Frankfort plane, these two lines can be
projected backward in the imagination to give an estimate
of the FMPA. Where the vertical dimensions of the face
are as expected, both lines should meet at the back of the
skull (occiput) and the FMPA is regarded as average. If
the FMPA is reduced, the lines will meet beyond occiput,
and if the FMPA is increased, they will meet anterior to it.
Transverse Plane
Obvious facial asymmetry may be assessed first from in front
of the patient and then, if present, by standing directly behind
UFH
L FH
LFH
) compared with upper facial height (
UFH
) and Frankfort–mandibular
the patient and looking down across the face, checking the
coincidence of the midlines of the nose, upper and lower lips
and midpoint of the chin. In most people, some degree of facial
asymmetry is present and may be regarded as what is expected. Marked asymmetries, however, require further investigation. The location and extent of any marked asymmetry
(e.g. upper, middle or lower facial third) should be recorded. As
a general guide, eye width is a fifth of the facial width.
Soft Tissue Assessment
The following should be evaluated:
n
Naso-labial angle: this may be classified as high, average
(90–110°) or low and is affected by upper incisor inclination.
n
Lip protrusion: using a line joining soft tissue chin and
the upper lip (Rickett’s E plane) as a reference, the lower
9 • Orthodontics I: Development, Assessment and Treatment Planning
lip sits 2 mm (62 mm) ahead of this with the upper lip
slightly behind, but it is important to acknowledge differences, seen in diverse populations of people of colour
and who are white. In the majority of people, some vermillion is visible and the lips everted at rest.
n
Whether the lips are together (competent) or apart (incompetent) at rest: if lips are apart, it should be noted if
they are slightly (potentially competent so capable of
being brought together if required but incisor position
stops this) or wide apart; markedly incompetent lips
confer a poor prospect for stability of overjet correction
with class II division 1 malocclusion.
n
Lower lip position and coverage in relation to the upper
incisors: the upper incisors may lie behind, on, or in
front of the lower lip. At rest, on average, the lower lip
should cover at least one-third to one-half of the upper
incisor teeth.
n
Upper lip level in relation to the upper incisors: the length
of the upper lip and amount of exposure of the upper
incisors at rest should be assessed; in males 1–2 mm
display of the incisors is average, with slightly more in
females.
n
Tongue position at rest, during swallowing and speech:
throughout the examination tongue position should be
observed and particular note made if it lies in contact
with the lower lip as this is likely to contribute to an
incomplete overbite. How an anterior oral seal is
achieved and atypical tongue activity on swallowing,
or marked hyperactivity of the lower lip, should be
noted. A tongue thrust may be adaptive especially
where a thumb-sucking habit (see later) has produced
an anterior open bite but in rare instances may be endogenous, the latter associated with an interincisal
forward resting tongue position, marked circumoral
contraction of the lips on swallowing, a lisp and proclined labial segments.
n
Smiling: Typically a smile has the following components:
symmetrical, upper dental midline in line with the facial
midline, minimal buccal corridors (space between the
furthest visible tooth and the corner of the mouth), full
crown length of the upper incisors and related interproximal gingivae shown, gingival margins of the central incisors and canines level but lateral incisors about
1 mm more incisal, curvature of the upper incisors
matches but does not touch the lower lip. In general,
maxillary incisor exposure on smiling is greater in females than in males by about 1–2 mm.
Speech
Obvious impacts such as a lisp will be noticed during general questioning of the patient, and specific assessment by a
speech therapist is rarely indicated in patients referred for
orthodontic advice.
Habits
The tell-tale signs of finger- or digit-sucking habits are
generally easy to ascertain:
n
Proclination of maxillary incisors
n
Retroclination of mandibular incisors
n
Incomplete overbite or open bite, often asymmetric
n
Increase in overjet
229
n
Tendency to bilateral buccal segment crossbite, often
resulting in a unilateral crossbite with displacement.
Effects vary depending on whether the finger or thumb is
placed in a median or paramedian position and on whether
one or more digits are sucked. An adaptive tongue thrust is
common. Inspection of the hands will usually identify the
offender. The patient and parent should be made aware of
the effects of the habit on the dentition and occlusion. Note
also if the patient is a nail biter or bruxist.
Temporomandibular Joints
Opening and lateral mandibular movements should be assessed by first observing the patient from in front and, second,
by palpation of the condylar heads while listening for the
presence of crepitus, or a joint click. Expected findings should
be recorded as a baseline for future reference. Palpation of the
masticatory muscles is not required unless symptoms are
present. Referral to a specialist may be required in advance of
any orthodontic treatment.
Mandibular Path of Closure
The path of closure from rest position to maximum interdigitation should be assessed, noting any anterior or lateral
mandibular displacement. This may be difficult to detect in
a young and anxious patient where a habitual posture has
developed to avoid a premature contact, often from an instanding incisor. Applying gentle backward and upward
pressure to the chin while instructing the patient to touch
the back of the mouth with the tip of the tongue usually
addresses this.
Intraoral Examination
The soft tissues of the buccal mucosa, floor of the mouth,
tongue and the attachment of the maxillary labial frenum
should be observed and any abnormality noted. A general
dental examination should be carried out prior to assessing
the individual arches of teeth and the occlusal relationships. The following should be charted:
n
Standard of oral hygiene and caries rate.
n
Gingival condition, paying particular attention to any
area of gingival recession or attachment loss.
n
All erupted teeth, noting those with atypical shape or
size. A quick way to assess if an anterior tooth-size discrepancy exists is to compare the mesiodistal widths of
the upper and lower lateral incisors. The upper laterals
should be larger than the lower incisors, but only discrepancies of greater than 1.5 mm should be recorded as
these are likely to affect treatment planning.
n
Teeth with untreated caries, hypoplasia, large restorations or previous trauma. The condition of the first permanent molars should be examined, in particular, and a
record made of any cervical decalcification (buccally on
the uppers or lingually on the lowers), or large areas of
hypoplasia, which may indicate a poor prognosis.
n
The presence of erosion on the palatal surfaces of
the upper incisors. In these cases, the patient should
be questioned about frequency of intake of acidic or
carbonated drinks.
n
Marked attrition of the dentition. If present, enquiry
should be made regarding bruxism.
230
Master Dentistry
The lower arch followed by the upper arch should then be
assessed independently.
Assessment of the Upper and Lower Arches
lower arch
Symmetry and overall alignment. Include here the pres-
ence of rotations (classified by the surface furthest from
the line of the arch).
Inclination of the lower labial segment to the man-
dibular plane. By placing the index finger of the right
hand along the mandibular body and gently everting the
lower lip, the inclination of the lower incisors may be assessed as average (if they appear to make almost a 90°
angle with the mandibular plane), retroclined or proclined.
Angulation of the canines. These may be described as
upright, mesially inclined or distally angulated.
Depth of curve of Spee. Measure the distance from the
premolar cusps to a line joining the distal cusps of the
first permanent molars and the tips of the incisors.
Presence and site of spacing or crowding including the
magnitude of each. The degree of spacing/crowding
may be assessed by performing a space analysis on the
study models. This only takes account of any space discrepancy anterior to the first permanent molars and is
usually carried out as described later.
For each quadrant. Measure with dividers the distance
from the mesial surface of the first permanent molar to
the distal surface of the permanent lateral incisor, and
from there to the midline. Add these measurements for
each arch to give the space available.
Measure the mesiodistal width of each tooth and add
these together to calculate the space required. Where
the canines and premolars have not erupted, on average 21 mm in each lower quadrant and 22 mm per
quadrant in the upper arch is an estimate of their space
requirements.
Quantify any surplus or deficit. Subtract the space
available from the space required. Individual arches
may then be classified as uncrowded, mildly crowded
(,4 mm), moderately crowded (4–8 mm) or severely
crowded (.8 mm).
from the mesial of the upper central incisors to the lower
incisors. If there is a marked difference for each upper
central incisor, both measurements should be noted.
Overbite (vertical overlap of the upper over the lower
incisors). This is measured (in millimetres) – an indica-
tion should be given as to whether it is complete, incomplete or if there is an anterior open bite or traumatic
overbite. The overbite is complete when the lower incisors
occlude with the opposing maxillary teeth or with the
palatal mucosa; it is incomplete if there is no contact
with the opposing surfaces. The extent (in millimetres)
of an anterior open bite should be noted and the site of
mucosal ulceration recorded (either palatal to the upper
incisors, labial to the lower incisors or in both locations)
in the presence of a traumatic overbite.
Centrelines. Upper and lower centrelines should be coinci-
dent with the midline of the face and in line with each
other; any centreline shift should be recorded (in millimetres) with a note to indicate the direction of the shift.
Molar relationship. Providing a corresponding molar is
present in the opposing arch, the molar relationship
may be categorised according to Angle’s classification
(see Section 9.2).
Where the first permanent molar is missing in either arch,
the premolar or canine relationship may be assessed.
Canine relationship. This should be recorded in addition
to the molar relationship, as although they are often the
same, on occasion discrepancies are present.
The presence of anterior or posterior crossbite (bucco-
lingual discrepancy in arch relationship). Is the
crossbite buccal or lingual, bilateral or unilateral, anterior or posterior (Fig. 9.9)? For the premolar and/or molar
teeth, a buccal crossbite exists when the buccal cusps of
the lower tooth occlude buccally to the buccal cusps of
the upper teeth. A lingual crossbite exists when the buccal
cusps of the lower tooth occlude lingually to the palatal
upper arch
Symmetry and overall alignment. (As for the lower arch.)
Inclination of the upper incisors relative to the Frank-
fort plane. With the patient sitting upright and a finger
or ruler placed along the Frankfort plane, the angulation
of the upper incisors may be assessed as retroclined, average or proclined.
Angulation of the canines and presence and site of
spacing or crowding including the magnitude of
each. Assessed as for the lower arch.
Assessments With the Teeth in Occlusion
With the teeth in maximum intercuspation, the remaining
aspects should be recorded.
Incisor relationship. This may be categorised accord-
ing to the British Standards Institute classification (see
Section 9.2).
Overjet (the horizontal overlap of the upper over the
lower incisors). This is usually measured (in millimetres)
A
B
Fig. 9.9 Bucco-lingual discrepancies. (A) Bilateral buccal crossbite.
(B) Bilateral lingual crossbite.
9 • Orthodontics I: Development, Assessment and Treatment Planning
231
cusps of the upper teeth. A unilateral crossbite affects
teeth on one side of the arch while teeth on both sides of
the arch are affected with a bilateral crossbite. Often a
unilateral crossbite is associated with an anterior or
lateral mandibular displacement (Fig. 9.10).
Diagnostic Records
Study Models
These provide a record of the starting malocclusion and
should include all erupted teeth and supporting areas. They
may be produced traditionally in dental stone from alginate
impressions or from intraoral scans of the arches or of the
impressions, all of which may then be stored digitally.
Extra- and Intraoral Photographs
Facial views at rest and on smiling, as well as right and left
buccal and occlusal views should be recorded. These may
act as an incentive during treatment. Localised gingival recession, enamel defects or traumatised teeth may warrant a
separate view.
Special Investigations
Sensibility Tests
Traumatised incisors or other teeth with suspect vitality
should be sensibility tested, the most accurate of which is
probably electric pulp testing, and their status recorded.
Radiography – Conventional or Digital
All radiographs should be justified on clinical grounds.
Radiographs forwarded by a referring practitioner may
provide sufficient information to supplement the clinical
findings but often the following views are needed.
views of the incisors are often required for those. Although
large carious lesions will be obvious on a panoramic film, a
more thorough assessment should be made from bitewing
or periapical radiographs if required.
Upper Anterior Occlusal
This provides a good view of the upper anterior teeth and is
useful to check root lengths of the incisors or to exclude the
presence of a supernumerary or other pathology. Additionally, it may be used to locate ectopic maxillary canines when
used in conjunction with another film taken at a different
angle employing the parallax technique.
Periapical and Bitewing Radiographs
The former are indicated to check the position of unerupted
teeth, root anatomy and pulpal pathology, whereas the latter are used for assessment of caries and restoration status.
Cone Beam Computed Tomography (CBCT)
Only where standard radiographs have not or are doubtful
to provide sufficient information for diagnosis, should this
be requested. It is particularly indicated with unerupted
teeth to exclude resorption of adjacent teeth but is also indicated in cases requiring combined surgical-orthodontic
management, cleft lip and palate cases particularly prior
to alveolar bone grafting, and for implant planning with
regard to width and volume of alveolar bone.
Lateral Cephalometric Radiograph
This film is indicated in the presence of anteroposterior
and/or vertical skeletal discrepancies, particularly when
incisor movement anteroposteriorly is planned.
Dental Panoramic Tomograph (DPT)
The bony architecture of the maxillary and mandibular
bases as well as that of the mandibular condyles (if included) should be checked first to exclude any dentally related, or other, pathology. All teeth should be identified and
counted. It is a good routine to start in one area (e.g. upper
right third molar area) and follow systematically through
the upper left, lower left and finally lower right quadrants to
ensure that nothing is missed. Then the condition of each
tooth should be checked for caries, hypoplasia or resorption.
All unerupted teeth should be charted, noting their developmental stage and position. Teeth previously extracted, those
developmentally absent and any pathology should be recorded. Due to the narrow focal trough anteriorly, other
A
Fig. 9.10 Unilateral buccal crossbite with mandibular displacement and associated lower centreline shift. (A) Initial cusp-to-cusp molar contact.
(B) Maximum intercuspal position.
CEPHALOMETRIC ANALYSIS
Cephalometric analysis involves the evaluation and subsequent interpretation of both lateral and posteroanterior
views of the skull although, in practice, it is usually confined to the former because of difficulty in interpreting the
posteroanterior view.
To allow comparison of measurements recorded for the
same patient at different times, or between patients, a
standardised technique is used. Originally developed by
Broadbent and Hofrath independently in 1931, the radiograph is taken with the Frankfort plane horizontal or in
natural head position, the latter achieved by looking
straight ahead at the eyes in a mirror placed slightly
B
232
Master Dentistry
further away. The ear posts are located in the external
auditory meati and the teeth in centric occlusion. The
central ray should pass through the ear posts. Importantly, the X-ray source to midsagittal plane distance (typically 150–180 cm) and the midsagittal plane-to-film distance (about 30 cm) should be standardised to facilitate
reproducibility and to minimise magnification (7–8%). To
allow accurate calculation of magnification, a steel rule of
known length should be placed at the midsagittal plane
and recorded on each film.
It is now common practice to collimate the X-ray beam,
thereby avoiding radiation exposure to areas of the head
not required for lateral cephalometric analysis. To enhance
the soft tissue profile, the beam intensity can be reduced by
placing an aluminium filter between the X-ray source and
the patient, but this is less necessary with digital technology. Digital radiographs, whether taken using photostimulable phosphor plates or solid-state sensors, eliminate the
need for developing and allow immediate viewing, rapid
transfer and facilitate storage of images.
Uses of Lateral Cephalometric Analysis
Lateral cephalometric analysis is used:
n
as a diagnostic aid and pre-treatment reference
n
to check treatment progress
n
to assess treatment and growth changes
n
for dentofacial research.
A Diagnostic Aid and Pre-Treatment Reference
Lateral cephalometric analysis sheds light on the dental
and skeletal characteristics of a malocclusion, thereby assisting in determining its aetiology and in planning correction. In some patients, particularly those with class III
skeletal pattern, growth may be checked from serial radiographs and treatment considered at the appropriate time.
Assessment of skeletal age, based on the characteristics of
cervical vertebral maturation, has also been developed
which indicates where an individual is with regard to
the peak growth at adolescence. The image may also assist
in identifying the position of unerupted teeth as well as soft
or hard tissue pathology, including upper incisor root resorption. It provides a useful reference of pre-treatment
incisor position, especially if anteroposterior movement
is intended.
A Means of Checking Treatment Progress
During treatment with fixed or functional appliances, it is
customary to check incisor inclinations and anchorage
considerations. Any change in the position of unerupted
teeth may be checked also.
A Means of Assessing Treatment and Growth Changes
A near end of treatment radiograph is useful to check that
the treatment objectives have been achieved and to assist in
planning retention. Where concern exists regarding the
stability of treatment or unfavourable growth, a radiograph
may be taken after treatment although this is rare.
If films are to be compared, they must be superimposed
on some stable area or points. As orthodontic treatment is
generally carried out during the growth period, no natural
fixed points or planes exist. The following, however, are
reasonably stable areas and are used commonly for superimposition:
n
Cranial base: after 7 years of age, the anterior cranial
base is found to be relatively stable. The S–N (sella–
nasion) line is a close approximation to the anterior
cranial base (N is not on the anterior cranial base), and
holding at sella allows the general pattern of facial
growth to be assessed; superimposition on de Coster’s
line (the anatomical outline of the anterior cranial base)
reflects more accurately changes in facial pattern but
requires greater skill to carry out.
n
Maxilla: superimposition on the anterior vault of the palate, or on the easier recognised maxillary plane at posterior nasal spine (PNS), shows changes in maxillary tooth
position.
n
Mandible: changes in mandibular tooth position may be
assessed by superimposition on Bjork’s structures. These
are the inner cortex of the symphysis, the tip of the chin,
the mandibular canal outline and the third molar tooth
germ before root development.
Dentofacial Research
The taking of serial images to assess longitudinal dentofacial growth changes, although practised formerly as part
of data collection in several growth studies, is no longer
ethical. Nonetheless, if ethically approved and informed
consent obtained, growth and treatment data gleaned
from radiographs routinely taken for diagnostic and treatment purposes may be used for research purposes.
Aim and Objective of Cephalometric Analysis
The aim of cephalometric analysis is to assess the anteroposterior and vertical relationships of the upper and lower
teeth with supporting alveolar bone to their respective
maxillary and mandibular bases, and to the cranial base.
The objective is to compare the patient with expected population standards appropriate for his/her racial group, identifying any differences between the two. The technique used
is outlined in Box 9.1.
It is important, however, to remember that irrespective of
whether cephalometric measurements are made directly
from a digitiser or indirectly from a tracing, the cephalometric technique and its subsequent analysis are open to error
of projection, landmark identification and measurement.
The technique relies on reducing the three-dimensional
(3D) facial skeleton to a two-dimensional X-ray film. Bilateral landmarks, therefore, are superimposed. The validity of
the analysis depends upon the ability of the operator to identify points accurately and reproducibly and make measurements which in turn is dependent on the film quality and
operator experience.
Three-dimensional (3D) analysis of facial form is now
possible with CBCT, having its greatest value in planning
combined surgical-orthodontic management notably of
asymmetry, but at present, no uniform means exists for 3D
cephalometric analysis.
Cephalometric Interpretation
The following aspects may be assessed from the cephalometric analysis.
9 • Orthodontics I: Development, Assessment and Treatment Planning
233
Box 9.1 Technique for Cephalometric Analysis.
1. First check the radiograph to ensure that the teeth are in
occlusion and that the patient is not postured forward. It may
be necessary to refer to clinical measurements to verify the
overjet. It is advisable to scan the film for any pathology
including resorption of the upper incisor roots, enlarged
adenoids or degenerative changes in the cervical spine.
2. In a darkened room, attach tracing paper or tracing acetate
(preferable due to better transparency) to the X-ray film and
secure both to an illuminated viewer ensuring that the
Frankfort plane is horizontal and parallel to the edge of the
viewing screen.
3. With a sharp 4H pencil, identify the points (Fig. 9.11) and planes,
the definitions of which are listed in Table 9.4. By convention,
the most prominent incisor is traced and, for structures with
two shadows (e.g. the mandibular outline), the average is
selected for analyses. Alternatively, landmarks may be digitised
using a cursor linked to a computer program that allocates
and
y
co-ordinates to each point. Angular and linear measurements are calculated automatically. A piece of cardboard with a
cut-out area of about 5 cm 3 5 cm is helpful in blocking out
background light and aiding landmark identification.
4. Record the values for the measurements listed in Table 9.5.
Anteroposterior Skeletal Pattern
ANB (A point, nasion, B point) angle. This is determined
by the difference between SNA (sella–nasion A) and SNB
(sella–nasion B; the relative positions of the maxilla and
mandible to the cranial base, respectively) and allows the
following broad classification:
Class I skeletal pattern: 2° # ANB # 4°
Class II skeletal pattern: ANB . 4°
Class III skeletal pattern: ANB , 2°
The ANB value should be considered along with the mea-
surement for SNA, as ANB is affected by variation in the
x
Table 9.4 Definition of Commonly Used Cephalometric
Points and Planes (Fig. 9.11).
Points
and Planes Definition
S sella: midpoint of sella turcica
N nasion: most anterior point of the fronto-
Po porion: uppermost, outermost point on the
Or orbitale: most inferior anterior point on the
ANS tip of the anterior nasal spine
PNS tip of the posterior nasal spine (pterygo-
A A point: most posterior point of the concavity
B B point: most posterior point of the concavity
Pog pogonion: most anterior point on the bony
Me menton: lowermost point on mandibular
Go gonion: most posteroinferior point at the angle
S–N line line drawn through S and N
Frankfort plane line connecting Po and Or
Maxillary plane line joining PNS and ANS
Mandibular plane line joining Go to Me
Functional
occlusal plane
nasal suture (may use the deepest point at the
junction of the frontal and nasal bones instead)
bony external auditory meatus (upper border
of the condylar head is at the same level, which
helps location)
margin of the orbit (use average of the left and
right orbital shadows)
maxillary fissure is directly above, which helps
location)
on the anterior surface of the premaxilla in the
midline below ANS
on the anterior surface of the mandible in the
midline above pogonion
chin
symphysis in the midline
of the mandible (bisect the angle between
tangent to the posterior ramus and inferior
body of the mandible to locate)
line drawn between the cusp tips of the first
permanent molars and premolars/primary
molars
Po
N
S
O
PNS
Go
Fig. 9.11 Standard cephalometric points.
B
Me
A
Pog
ANS
Table 9.5 Eastman Cephalometric Values for
White (Caucasian) populations.
Parameter Value (6SD)
SNA 81 6 3°
SNB 78 6 3°
ANB 3 6 2°
S–N/Max 8 6 3°
1 to maxillary PL 109 6 6°
1 to mandibular PL 93 6 6°
Interincisal angle 135 6 10°
MMPA 27 6 4°
Facial proportion 55 6 2%
SD
point nasion, B point; PL, plane,
angle.
SNA
, sella-nasion A;
SNB
MMPA
, sella-nasion B;
, maxillary/mandibular planes
ANB
, A
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position of nasion. In cases where the SNA value is above
or below the average value of 81° and provided the S–N/
maxillary plane angle is within 8 6 3°, a correction may
be employed to the ANB value as follows: for every degree
SNA is greater than 81°, subtract 0.5° from the ANB,
and vice versa.
The Wits analysis and Ballard conversion. This is an al-
ternative means of assessing the skeletal pattern in which
the distance (in mm) is measured between perpendiculars
from A and B point to the functional occlusal plane (a line
joining the cusp tips of the permanent molars and premolars or primary molars). The average values for males and
females are 1 6 1.9 mm and 0 6 1.77 mm, respectively.
No indication is given, however, of the relation of the
dental bases to the cranial base and the functional occlusal plane is difficult to locate. In some cases, however, it
may be a useful check to complement that made from the
ANB value.
With the Ballard conversion, the angles made by the upper
and lower incisors to the maxillary and mandibular
planes, respectively, are normalised by rotating around
their centroids (one-third of the root length from the
apex) taking into account any compensation necessary
(for the lower incisor angle (LIA) with the maxillary/
mandibular planes angle (MMPA); see later). The overjet
is then measured as an indicator of the anteroposterior
skeletal pattern.
Nasion perpendicular. Relative to a perpendicular to the
Frankfort plane from nasion, A point should be 0–1 mm
and pogonion –2 mm to 4 mm when assessed at 90° to
this line.
Vertical Skeletal Pattern (MMPA and Facial Proportion) (Fig. 9.12)
Both anterior and posterior lower facial heights are considered in the MMPA whereas facial proportion assesses the
contribution of lower anterior facial height to total facial
height. The facial proportion should lend support to the
value obtained for the MMPA; a reduced facial proportion is
usually consistent with a low MMPA and vice versa. Where
there is disagreement between these two assessments, the
tracing should be checked to identify the cause.
Incisor Position
Angle of the upper incisor to the maxillary plane. The
mean value for this angle is 109 6 6°; the incisors may
be classified as retroclined or proclined relative to the
mean value. In class II division 1, it is often helpful to
carry out a ‘prognosis tracing’ to indicate if correction of
the incisor relationship may be undertaken by tipping or
bodily movement (Fig. 9.13). An alternative method is to
apply the following rule of thumb: for every 1 mm of
overjet reduction, subtract 2.5° from the upper incisor to
maxillary plane angle. Provided the final upper incisor
angle is not likely to be less than 95° to the maxillary
plane, tipping rather than bodily movement may be
acceptable.
Angle of the lower incisor to the mandibular plane.
This must be looked at in conjunction with the ANB
and MMPA angles as the lower incisor angulation may
compensate for discrepancies in the anteroposterior
and vertical skeletal pattern. Under the influence of the
soft tissues, the lower incisors may procline in class II
malocclusion or retrocline in class III malocclusion.
There is also an inverse relationship between the MMPA
and the lower incisor angle (LIA); for every degree
MMPA is greater than average (27°), the LIA is 1° less
than the average (93°); the opposite holds true when
the MMPA is less than average. Alternatively, the lower
incisor angle is determined by subtracting the MMPA
from 120°.
Lower incisor to A–pogonion line. This has been used as
an aesthetic reference line for lower incisor positioning
(average 0–2 mm) but it is unwise to lend too much
credence to this measurement for treatment-planning
purposes. Both point A and pogonion may shift with
treatment or growth, and orientating the lower incisors
correctly with respect to the A–pogonion line does not
improve the prospect of a stable result.
Analysis of Soft Tissues
Various reference lines, regarded as indicators of pleasing
facial appearance, have been suggested to assess the relationship of the soft tissues of the nose, lips and chin. These
lines are more helpful in orthognathic surgical planning
than in planning conventional orthodontic treatment.
Aside from the facial plane which intersects the Frankfort
plane at about 86°, joins soft tissue nasion and soft tissue
chin, with A point lying on it, two other commonly used
lines are shown in Fig. 9.14.
n
Holdaway line: joins the upper lip and chin and, when
extended, should bisect the nose if facial proportions are
correct.
n
Rickett’s E plane: joins the nasal tip to the chin such that
the lower lip is positioned 2 mm (62 mm) in front of the
E plane, the upper lip lying slightly further behind.
9.4 Principles of Orthodontic Treatment Planning
LEARNING OBJECTIVES
You should:
• know the potential benefits and limitations of orth-
odontic treatment
• know and understand the steps generally adopted in
treatment planning
• know what factors should be considered in presentation
of the final treatment plan
• know how space requirements may be assessed
and how space may be created for desired tooth
movement.
PROBLEM LIST AND TREATMENT NEED
The first stage in treatment planning is to summarise the
features of a patient’s malocclusion to produce a problem
list of the pathological and developmental (orthodontic)
problems; the latter should document what troubles the
patient regarding their dentofacial appearance and level of
enthusiasm for treatment, skeletal and dental relationships
(anteroposterior, vertical and lateral) including appraisal of
9 • Orthodontics I: Development, Assessment and Treatment Planning
235
FMPA
MMPA
Frankfort plane
Maxillary plane
Mandibular plane
Po
O
PNS
Go
Although measurement of FMPA is favoured by some analyses,
MMPA is preferable due to easier and more accurate location of
the maxillary plane.
x
ANS
Me
N
Fig. 9.12 Maxillary–mandibular planes angle (
the smile and profile, followed by the degree of upper and
lower arch crowding and centreline discrepancies. The
need for treatment on dental health and aesthetic grounds
should then be considered (see Section 9.2). Only if appliance therapy and/or extractions can confer significant benefit to dental health and/or appearance of the dentition,
should treatment be undertaken. If there is any doubt,
treatment is best withheld.
PNS
y
y
Facial proportion =
(y = perpendicular distance from maxillary plane to Me
x = perpendicular distance from maxillary plane to N)
MMPA
) and facial proportion.
x + y
× 100
ANS
Me
Potential Benefits and Limitations of Orthodontic
Treatment
Dental Health and Function
Overall, the oral health-related benefits of orthodontic
treatment are rather limited.
Caries. No significant relationship has been found between
dental caries experience and malocclusion. Orthodontic
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Holdaway line
Master Dentistry
a
Centroid
Fig. 9.13 Prognosis tracing to assess if correction of the incisor relationship can be achieved by tipping or bodily movement. a 5 presenting
angle of 1 to maxillary plane; b 5 angulation of 1 to maxillary plane following rotation around the centroid to simulate tipping movement.
Fig. 9.14 Soft tissue planes.
b
Rickett’s E plane
treatment could not be claimed to prevent caries but
in selected cases, extractions alone may allow greater
access for tooth cleaning and potentially reduce the
caries risk.
Periodontal disease. In general, crowding is weakly asso-
ciated with periodontal disease and improvement in oral
hygiene techniques/motivation are more likely than
orthodontic treatment to reduce susceptibility to periodontal disease. Where an occlusal relationship is causing periodontal trauma, e.g. displacing occlusal contacts
leading to gingival recession and mobility where one
lower incisor or all of the lower incisors are in crossbite,
or where a deep overbite produces palatal or labial gingival trauma, periodontal health is improved by corrective
orthodontic treatment. Similarly, gingival recession may
arise where teeth are markedly displaced from the arch
due to crowding and orthodontic alignment may confer
benefits to periodontal health.
Incisor trauma. The risk of trauma to the upper anterior
teeth is twice as great when the overjet is increased more
than 3 mm. Although trauma is more widespread in
boys and when the lips are incompetent, of note is that
overjet has a greater impact on girls. Where a higher
propensity to upper incisor trauma is considered likely
due to their prominence in the presence of markedly incompetent lips and particularly when previous trauma
has occurred, early orthodontic treatment aimed at overjet reduction may be justified.
Tooth impaction. Unerupted teeth may cause resorption
of the adjacent teeth or dentigerous cyst formation. In
the case of a maxillary canine, timely surgical exposure
and orthodontic traction may reduce the risk of resorption or arrest it by moving the tooth away from the adjacent incisors/premolars. Removal of supernumerary
teeth may allow eruption of the related permanent
tooth/teeth but surgical exposure is often required in
advance of successful orthodontic alignment of maxillary incisors.
Speech. Speech is a complex process involving mutual
compensation between the contributing organs (brain,
lips, tongue and laryngeal muscles) so drawing firm conclusions regarding the correlation between a speech
disorder and malocclusion is difficult although hypernasal speech is associated with a cleft of the soft palate. No
guarantee could be made that correction of malocclusion (e.g. severe class II or class III malocclusion or anterior open bite which may be associated with lisping)
would improve a speech impediment without accompanying speech therapy.
Masticatory function. In those with marked anterior
open bite, increased or reverse overjet, incising food may
be difficult or even impossible while marked hypodontia
may compromise eating; each of these clinical features
may impact quality of life. However, minimal evidence
exists that dental health and masticatory function will be
compromised long term if ideal occlusion is not achieved.
Temporomandibular joint dysfunction syndrome
(TMJDS). Research has linked, although weakly, crossbites,
class III malocclusion, asymmetry, class II mandibular
retrusion and open bite with TMJDS. Orthodontic treatment, with or without extractions, will not lead to or
resolve TMJDS. Due to the multifactorial aetiology, any initial treatment should be conventional and not irrevocable,
but all symptoms should be addressed before starting any
orthodontic treatment.
Social/psychological wellbeing. Malocclusion may have
a negative impact on self-confidence and self-esteem
resulting in poorer oral health-related quality of life
(OHRQoL). The severity of malocclusion is not always
commensurate with the psychosocial effect. In a UK
study where almost 13% of adolescents reported being
bullied, this was significantly associated with increased
overjet and low self-esteem. Interceptive orthodontic
treatment reduced the frequency of bullying and significantly improved OHRQoL but interestingly had no effect
on self-esteem. In contrast, compared to controls, a North
American study found short-term gain in self-concept
with early treatment at 8–10 years for children with
class II division 1 malocclusion. Could self-esteem perhaps be a factor influencing how one responds to malocclusion, rather than an effect? Furthermore, long-term
longitudinal assessment in adulthood of orthodontic
treatment undertaken during childhood has indicated
only limited positive impact on psychological health or