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9 • Orthodontics I: Development, Assessment and Treatment Planning
237
quality of life. This may be linked to personal differences
regarding coping strategies, personality, values and
societal issues. Additionally, occlusal status in adulthood
appears to have limited association with psychological
factors and quality of life.
Summary
Dental health is likely to benefit long term where any of the
following exist: impacted teeth with a risk of resorption, increased overjet with a trauma risk, mandibular displacement in the presence of a crossbite, traumatic overbite and
crossbite or crowding associated with gingival recession.
Psychosocial wellbeing/quality of life is also likely to improve with early treatment for increased overjet. The impact
of orthodontic treatment on long-term social/psychological
wellbeing appears limited.
Limitations of Orthodontic Treatment
Orthodontic treatment, like all forms of dental treatment, has
some limitations, and these should be borne in mind when
the aims of treatment and treatment plan are being devised.
n
Tooth movement is confined to cancellous bone.
n
Limited differential eruption of anterior or posterior
teeth may be used successfully to aid correction of malocclusion, but there is limited evidence on the permanency of any alteration in vertical skeletal pattern.
n
Some small restraint or redirection of maxillary and/or
mandibular growth is possible with headgear or functional appliance therapy; with rapid maxillary expansion, some orthopaedic increase in maxillary dental base
width is possible.
n
The effect of tooth movement on the facial profile is modest, with the growth of the nose and chin having a
greater effect.
n
Tooth movement is generally more efficient in a growing
child but may still be undertaken in the adult.
n
Growth may aid or hinder correction of a malocclusion
and attempts to modify its expression, even though this
is limited, may be considered on occasion in the early
mixed dentition.
n
Removable appliances tip teeth, whereas fixed appliances
may bodily move, tip, intrude, extrude, rotate or torque
teeth.
n
Functional appliances alter arch relations through a
combination of actions that involves tipping of teeth,
differential eruption and possibly some restraint or
stimulation of maxillary and/or mandibular growth,
depending on the specifics of the design.
n
Headgear restrains or redirects growth of the maxillary
complex depending on the force magnitude and direction employed.
n
Treatment success is dependent on:
n
correct diagnosis, treatment planning including assessment of anchorage, and proficiency in whatever
appliance system is selected on the part of the operator
n
regular attendance, compliance with all instructions
regarding appliance wear and maintenance of a high
standard of oral hygiene by the patient
n
a stable result is only possible if the forces from the
soft tissues, occlusion and periodontium are in equilibrium and facial growth is favourable.
Aims of Treatment
The aims of treatment should arise from the problem list
arranged in the order of priority and outlines in a logical
sequence the steps required to achieve the desired outcome.
For example, in a patient with a class II division 1 malocclusion with moderate upper and lower arch crowding as well
as a half unit class II molar relationship, these would often
be as follows:
n
Relief of crowding.
n
Alignment within the arches.
n
Overbite reduction.
n
Overjet correction.
n
Closure of residual spacing and correction of molar relationship to class I.
One should always aim for the ideal plan initially but
keep an open mind, as sometimes this plan may require
alteration (e.g. if the patient does not wish to wear a particular type of appliance). Importantly, where a limited
objective plan is proposed, the patient must still benefit and
not be compromised in the long term.
TREATMENT PLANNING
All pathological problems (e.g. caries and periodontal
disease) must be addressed before any orthodontic treatment is considered. Treatment success requires a highly
motivated patient and must satisfy the patients’ concerns
and expectations provided the latter are realistic.
In broad terms, the following series of steps will be useful
for treatment-planning purposes in most malocclusions
(refer to the sections covering management of each malocclusion).
Consider the Profile and Smile
While the influences of orthodontic treatment on the facial
profile may be variable, nonetheless, upper lip support
should not be compromised by incisor retraction which
may increase an already obtuse nasolabial angle. Additionally, treatment mechanics that would extrude the upper labial segment and worsen smile aesthetics should be avoided
in the presence of a gummy smile.
Plan the Lower Arch
In general, the lower arch form is to be accepted, particularly the anteroposterior position of the lower labial segment, which lies in a narrow zone of balance between the
lips and tongue. Movement beyond this narrow zone is
likely to lead to an unstable result apart from in certain
circumstances (where thumb sucking has retroclined the
lower incisors, class II division 2 malocclusion, class III
camouflage treatment and bimaxillary proclination); these
invariably require specialist management. In some cases
where the lower incisors are mildly crowded, proclination
may be apposite but this is often undertaken in combination with limited interproximal reduction (IPR). The general and local factors that govern the need for and choice of
any extractions are described below.
Imagine the lower canine repositioned for alignment of
the lower labial segment. If the canine is mesially angulated
in a crowded arch, it will upright spontaneously following
238
Master Dentistry
the extraction of a first premolar, thereby providing space
for alignment of the lower labial segment. Most improvement occurs within the first 6 months following extraction,
and if the premolars are removed as the canines are erupting. If the canine is upright or distally angulated, a fixed
appliance will be necessary for its retraction.
Plan the Upper Arch
Mentally correct 3 position to a class I relationship
with the aligned lower canine. This is done assuming that
the lower labial segment is not spaced and that the upper
incisor teeth are all of proportional size and not retroclined.
The space needed may come from extractions, arch expansion or distal movement of the buccal segment. Importantly,
if all of an extraction space is required to achieve a class I
canine relationship, anchorage will need to be reinforced.
The appliance type needed to achieve the desired canine relationship may be assessed also.
Consideration should be given as well to relief of upper
labial segment crowding, reduction of the overjet and/
or overbite and the appliance type necessary to achieve
correction.
Plan the Final Buccal Segment Relationship and the Need for Closure of Any Residual Spaces
In most cases, if corresponding teeth have been extracted in
each quadrant, the final buccal segment relationship
should be class I; however, if only upper arch extractions or
lower arch extractions have been undertaken, the final relationship will be class II or class III, respectively. The potential for spontaneous space closure depends on:
n
the degree of initial crowding
n
the age of the patient
n
the vertical pattern of facial growth (space closure
tends to occur more rapidly in patients with increased
Frankfort–mandibular planes angle compared to those
with a reduced angle).
Alternatively, space closure may be produced mechanically by applying intramaxillary (from within the same
arch), intermaxillary (from the opposing arch) or extraoral
traction.
Plan the Mechanics and Consider the Anchorage Demands
Removable appliances are limited to tipping movements,
whereas bodily movement is possible with fixed appliances.
Functional appliances are generally confined to correction
of class II malocclusion in growing children and mostly
produce tipping rather than bodily movement of teeth.
Tipping movements make only modest demands on the
balance between the desired tooth movements and the
space available (i.e. anchorage), whereas bodily movements
place greater strain on anchorage. Where all the space
available from extractions is required to relieve crowding,
reduce an overjet or both, anchorage is at a premium and
will need reinforcement.
Treatment Timing
Intervention in the mixed dentition is advisable in some circumstances (Section 9.3). Certain orthodontic treatments
rely on growth for success. For example, overbite reduction
and functional appliance therapy and treatment are usually
best started in the late mixed dentition. However, where a
severe skeletal problem exists that is likely to be exacerbated
by growth, treatment is best deferred until the late teens
when a combined orthodontic surgical approach can be
considered.
Retention
A phase of retention is usually required following tooth
movement with appliance therapy to allow consolidation of
the new tooth positions through adaptation of the alveolar
bone, gingival and periodontal tissues. Planning the retention phase of treatment requires an appraisal of the original features of the malocclusion as well as:
n
the skeletal pattern and growth pattern
n
soft tissue and periodontal factors
n
the type and duration of treatment.
The likely retention regimen should be individualised for
each patient, taking these factors into account, and must be
explained to the patient before treatment starts. Specific
guidelines in relation to retention are included in the management of each malocclusion type and appliance treatments (Section 11.4).
Final Presentation
Where two or more options exist with regard to treatment,
these must be talked over thoroughly with the patient, parent
and clinician so that an informed decision is arrived at steered
by the patient’s values, likes and dislikes. The ‘pros’ and ‘cons’
of each treatment option should be explained and the objectives of each stage of treatment clearly outlined in a form that
is understandable to the patient and/or parent or guardian.
Good colour photographs of any appliance to be used are very
helpful. If anchorage reinforcement by headgear or temporary anchorage devices (TADs) is required, this must be explained. An outline of the likely appointment intervals and
their length, together with an estimate of the overall duration
of treatment and likely cost, is also necessary.
The commitment to maintenance of a high standard of
oral hygiene, importance of regular dental attendance for
routine dental care and level of compliance expected with
treatment must be emphasised. The potential risks of treatment (Table 9.6) should be explained along with the benefits. When there is a risk with no treatment, this must also
be highlighted.
Valid (voluntary and informed) consent individually
adapted to each patient should then be obtained making
certain there is an accurate grasp of all aspects mentioned
above (details of treatment, risks and benefits, expected
duration, commitment and cost). Written consent should
be obtained acknowledging that this may require updating
as treatment proceeds; the patient/parent/guardian should
also be provided with a copy.
CREATING SPACE FOR DESIRED TOOTH MOVEMENT
Space Assessment
This entails evaluating the space required and space to be
created during treatment; for the latter, the treatment aims
9 • Orthodontics I: Development, Assessment and Treatment Planning
Table 9.6 Risks of Orthodontic Treatment.
RISKS
Root resorption 0.5–1 mm loss of root length common, but large individual variation
Suggested risk factors are force magnitude and method of application, length of treatment, appliance
type (more with fixed than removable appliances), history of trauma, previous root resorption, blunt or
pipette-shaped roots
Current evidence indicates heavy forces and comprehensive treatment with fixed appliances increase
incidence and severity; previous trauma and unusual root shape unlikely causes
Demineralisation/enamel damage Greater risk with fixed than removable appliances; risk increases with poor oral hygiene and frequent
intake of sugary foods/drinks
Risk if occlusal contact with ceramic brackets and lack of care at debonding
Periodontal disease Palatal gingival inflammation common with removable appliances if oral hygiene poor
Marginal gingivitis common with fixed appliances; tends to resolve on appliance removal
Occasionally 1 mm loss of attachment and 0.25–0.5 mm loss of alveolar bone adjacent to extraction sites
Pulpal/soft tissue damage Loss of pulpal vitality, particularly if overactivation of appliance and previous history of trauma
Abrasion/ulceration of mucosa more common with fixed than removable appliances
Relapse More likely if teeth moved into unstable positions, retention regime inappropriate or not adhered to by
the patient (see Section 11.4)
Iatrogenic Greater risk with inexperienced operator (e.g. anchorage loss, inappropriate treatment mechanics)
Facial profile/ocular damage Likely if poor diagnosis and treatment (see Limitations of Orthodontic Treatment and Profile Considerations
under General Factors, Extractions)
Headgear safety mechanisms not attached and patient carelessness with appliance (see Section 11.1,
Headgear Safety)
239
need to be finalised. The following require space: relief of
crowding; overbite reduction; overjet correction; centreline
correction; contracting the arch width; adjusting incisor tip
or torque. The mesiodistal width of the misaligned teeth
compared to the space available in the arch allows the magnitude of crowding to be assessed and classified (see Section
9.3). Where the depth of the curve of Spee is 3 mm, 1 mm
of space is estimated to be required for correction; more
space will be required where the curve is deeper. Each mm
of overjet reduction is reckoned to require 2 mm of space.
Proclination of incisors will create space (2 mm gain for
each mm). Space required for changes in incisor angulation
or inclination is generally small.
Extractions
Extraction of teeth is required to provide space for either
relief of crowding or to camouflage a class II or class III
skeletal discrepancy. In general, to preserve symmetry, teeth
are usually extracted from both sides of the same arch. The
decision to extract teeth is governed by:
n
general factors:
n
profile considerations
n
incisor relationship
n
appliance to be used
n
anchorage requirements.
n
local factors:
n
the condition of the teeth
n
the site of crowding
n
the degree of crowding
n
the position of individual teeth.
General Factors
Profile considerations. Attempts to expand the arches
anteroposteriorly to relieve crowding and improve facial
aesthetics are unlikely to be inherently stable over the
long term. Indeed, the extraction of premolars rather
than second permanent molars may produce only 1–2
mm of retraction of the lips. Differences in lip thickness
and growth pattern between individuals are likely to
have greater bearing on the soft tissue profile than
whether or not extractions are undertaken as part of
treatment. However, where there is a marked class II skeletal discrepancy, retraction of the incisors is likely to
produce a very unsatisfactory facial profile, and specialist
advice should be sought.
Incisor relationships. In class I or class II, it is usual to
extract at least as far forward in the upper arch as in the
lower, but the opposite holds true in class III. Where the
overbite is deep with a curve of Spee 5 mm or more,
about 2 mm of space will be required for its reduction
whereas 1.5 mm is likely to be required where the
curve of Spee is 4 mm. Centreline discrepancies require
greater space on one side of the arch than on the other
to facilitate correction. To camouflage a moderate class
II or class III skeletal problem, extraction of only upper
first or lower first premolars, respectively, may be
indicated.
Appliance to be employed. In crowded mouths, extraction
of the same tooth from each quadrant encourages mesial
drift and spontaneous space closure, but the choice of
extraction is not so critical if fixed appliances are to be
used for correction of the malocclusion.
Anchorage requirements. Bodily movement of teeth,
particularly apical torque, is more demanding on anchorage than tipping movement, so space near to the
site of the intended tooth movement is desirable. In addition, the anchorage balance (best thought of in terms of
the combined root surface area posterior and anterior to
the extraction site) is unfavourable for aligning crowded
incisors the further posterior in the arch extractions are
undertaken.
240
Master Dentistry
Local Factors
The condition of the teeth. Teeth with poor long-term
prognosis should be considered for extraction even if
treatment is made more difficult or prolonged as a result.
Site of crowding. Crowding in one part of the arch is more
easily corrected if extractions are carried out in, or close
to, that location. This is not true for the incisor areas:
extraction of an incisor is not usually undertaken for relief of crowding because of the poor appearance that
would result. First premolars, located midway between
the front and back of the arches, often provide space for
relief of crowding in both locations, whereas second permanent molars may be extracted for crowding confined
to the posterior regions.
Degree of crowding. In the mixed dentition, mild crowding
may resolve with the leeway space, but after this stage has
passed, appliance therapy to either expand the arches or
to move the buccal segments distally will be required to
provide space. Where space shortage is of the order of
4 mm per quadrant, it may be dealt with in some instances without extractions, but extractions are more
likely to be necessary for more severe crowding.
The position of individual teeth. Teeth that are grossly
malpositioned and that would be difficult to align are often the choice for extraction. The position of the apex of
the tooth must be considered as it is usually more difficult
to move the apex than the crown.
Extraction of Teeth in the Buccal Segment
First premolars. These teeth are most commonly ex-
tracted for relief of moderate-to-severe crowding. Maximum spontaneous labial segment alignment is likely if
the first premolars are extracted as the canines are erupting, provided they are mesially angulated, and is greatest
in the first 6 months following extractions.
Second premolars. Extraction of these teeth is indicated in
the following situations:
n
Mild to moderate crowding, as the anchorage balance
favours space closure by mesial movement of the molars; fixed appliances will be required for this.
n
When the teeth are hypoplastic (usually as a result of
extensive caries and pulpal pathology affecting the
overlying second primary molar; Turner’s hypoplasia), carious or absent.
n
Where one or more second premolar is absent and
crowding is mild to moderate, the second premolar
may be extracted in the other quadrant(s), thereby
balancing and/or compensating for the extractions;
fixed appliances will be required to align the remaining teeth and close any residual spacing.
n
One or more second premolar excluded from the arch
either palatally or lingually following early loss of the
second primary molar; the contact between the first
permanent molar and the first premolar should be acceptable.
First permanent molars. See Section 10.1.
Second permanent molars. Extraction of lower second
permanent molars may be considered for relief of slight
premolar crowding or to compensate for upper second
permanent molar extractions, being undertaken to facilitate distal movement of the buccal segments. First permanent molars must have a good prognosis. The best
chance of providing space to disimpact a lower third
molar successfully occurs when:
n
it overlaps the distal of 7
n
it makes ,30° angulation to the long axis of 7
n
bifurcation is calcified.
Even when these criteria are met, the final position of 8 is
unpredictable.
Third molars. Guidelines for removal are issued by The
National Institute for Health and Care Excellence (NICE)
and removal cannot be justified as a means of preventing
or ameliorating late lower incisor crowding.
Extraction of Teeth in the Labial Segment
Lower incisors. Rarely, extraction of a lower incisor pro-
duces an acceptable solution for crowded incisors. Crowd-
ing of three lower incisors may occur due to a reduction
in the lower intercanine width and a tendency for the la-
bial segment to move lingually. Fitting six upper anterior
teeth around five lower anteriors may lead to a reduction
in the upper intercanine width and upper labial segment
crowding. Therefore, extraction of a lower incisor is usu-
ally best considered only in the following situations:
n
Poor prognosis due to caries, trauma or gingival
recession.
n
Severe crowding with one incisor excluded from the
arch.
n
Distally angulated canines with fanning of the lower
incisors.
n
Mild class III malocclusion in an adult with aligned
buccal segments.
n
Class I buccal and incisor relationships with severe
lower incisor crowding; here subsequent changes in
arch dimensions are likely to be minimal.
n
Tooth-size discrepancy in the upper labial segment
(i.e. small upper lateral incisors).
When extraction of a lower incisor is an option, it is wise
to see what the final result is likely to be by carrying
out a diagnostic set-up on a set of working casts. In
each case, a lower fixed appliance is usually required to
align and approximate the remaining teeth.
Upper incisors. A permanent central incisor is never a
tooth of choice for extraction but may be considered if
dilacerated or of poor prognosis due to trauma. Extrac-
tion of an upper lateral incisor is not recommended
except in the following circumstances:
n
2 abnormally formed
n
2 on opposite side of the arch absent or abnormally
formed
n
2 bodily excluded palatally with 1 and 3 in contact
n
moderate crowding with 3 distally angulated.
The canine should be of good size, shape and colour to
allow optimal dental aesthetics in the upper labial segment.
Canines
Lower canines. These should only be removed if the tooth
is severely displaced or ectopic with good contact
between first premolar and lateral incisor.
Upper canines. See Section 10.1.
Interproximal Reduction (IPR)
Using abrasive strips, discs or burs 0.25 mm of enamel can
be removed from each proximal surface of the anterior
9 • Orthodontics I: Development, Assessment and Treatment Planning
teeth to give 2 mm of space. An extra 3–6 mm is possible
per arch through enamel removal from the buccal segment
teeth using fine tapered burs in a high-speed handpiece; the
teeth should preferably be fairly well aligned with space
created between them before this is carried out and fluoride
applied after all enamel removal. IPR also flattens the contact points, re-shapes fan-shaped teeth and possibly reduces
the chance of relapse.
Arch Expansion (Lateral or Anteroposterior)
Provided care is taken to limit lateral expansion to the confines of the supporting alveolar bone, lateral expansion in the
upper arch may obviate the need for extractions (,0.5 mm
per 1 mm of expansion). Expanding the lower intercanine
distance should be avoided due to the propensity to relapse,
but correction of a lingual crossbite in the premolar/molar
areas by lower arch expansion is possible in some cases. For
each mm of incisor proclination (anteroposterior arch expansion), ,2 mm of space is obtained in the arch.
Distal Movement of the Upper Molars
Space lost to unilateral mesial drift of the first permanent
molar following early loss of a primary molar may be regained by use of a removable appliance with a screw and
headgear support (Fig. 9.15). Bilateral distal movement
of the upper first permanent molars by 2–3 mm is possible in well-motivated individuals and requires excellent
co-operation with headgear wear or may be undertaken
241
Fig. 9.15 An upper removable appliance (
gear support to regain space lost to unilateral mesial drift. URA to
move |56 distally. Screw section to |56; single Adams’ clasp 6/ and
double Adams’ clasp |56 (both 0.7 mm SS wire); tubes for headgear
soldered to clasp bridges; labial bow 2 1 | 1 2 (0.7 mm wire).
URA
) with screw and head-
in conjunction with a fixed appliance attached to TADs.
This may suffice to relieve a small amount of crowding or
to reduce a small overjet but where space demands are
greater, extractions in conjunction with distal molar
movement will be necessary.
Combination of Means
In some circumstances, a combination of any or all of the
methods listed may be appropriate to create space.
Self-Assessment: Questions
MULTIPLE CHOICE QUESTIONS (TRUE/FALSE)
1. The maxilla:
a. Is derived from the second pharyngeal arch
b. Completes growth in length before growth in width
c. Grows partly by passive displacement of its articula-
tion with the cranial base
d. Is translated downwards and forwards by the condy-
lar cartilage
e. On average completes growth by 15 years in males
2. The mandible:
a. Is derived from the first pharyngeal arch
b. Ossifies medial to Meckel’s cartilage
c. Has a predictable pattern of growth in each individual
d. On average follows the growth pattern of the maxilla
e. Does not grow after age 18 years in males
3. Marked anterior mandibular growth rotation:
a. Occurs when growth in posterior face height is less
than in anterior face height
b. Is more common than backward growth rotation
c. Is often associated with a deep overbite
d. Is associated with an increased maxillary/mandibular
plane angle
e. Is associated with a concave lower mandibular border
4. In the dental development of the ‘average’ child:
a. Calcification of the primary incisors commences
6–8 months in utero
b. Root calcification of the primary teeth completes
2–2.5 years after eruption
c. Primary incisors erupt in contact and proclined
d. Calcification of the first permanent molars com-
mences at 8–10 months after birth
e. The ‘leeway space’ is greater in the upper than in the
lower arch
5. Space for the permanent upper incisors:
a. Is obtained mostly by eruption palatal to their prede-
cessors
b. Is obtained by use of existing primary labial segments
spacing
c. Is obtained by intercanine width growth
d. Is likely to be adequate where the primary incisors
are crowded
e. Is affected by the overbite
6. Expected maturational changes in the dentition include:
a. A reduction in lower labial segment crowding
b. An increase in upper labial segment crowding
c. A reduction in lower intercanine width
d. Increase in overjet
e. An increase in interincisal angle
7. Clinical assessment of the anteroposterior dental base
relationship:
a. Is undertaken by viewing the patient from in front
b. Should be undertaken with the teeth just out of
occlusion
c. Is best carried out with the patient supine
d. Is reflected by the maxillary/mandibular planes angle
e. Depends on the upper incisor angulation
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Master Dentistry
8. A class II skeletal pattern:
a. Is present when the mandible is protruded relative
to the maxilla
b. Can be assessed from the SNB angle
c. Is usually associated with a retrognathic maxilla
d. Can be assessed from the first permanent molar
relationship
e. Depends on the incisor relationship
9. The maxillary/mandibular planes angle (MMPA):
a. Can be assessed clinically
b. Reflects the anteroposterior skeletal pattern
c. Indicates the vertical skeletal pattern
d. Reflects posterior lower facial height and anterior
lower facial height
e. Is affected by lower incisor position
10. Class II division 2 malocclusion:
a. Is defined by a half unit class II buccal segment
relationship
b. Exists when the lower incisor edges occlude anterior
to the cingulum of the upper incisors
c. Is characterised by retroclined upper central incisors
d. Is usually associated with a minimal overjet
e. May be associated with an increased overjet
11. A lateral cephalometric radiograph:
a. Is taken with the head tilted up
b. Is recorded with tube-to-midsagittal plane distance
typically of about 15 cm
c. Is an exact record of facial dimensions
d. Is essential for orthodontic diagnosis
e. May be useful in localising the position of an
unerupted tooth
12. Cephalometrically:
a. SNA (sella–nasion A point) angle describes the
relationship of the mandible to the cranial base
b. ANB angle is obtained by subtracting angle SNA
from SNB (sella–nasion B point)
c. Frankfort plane joins porion and nasion
d. Mandibular plane joins gonion and menton
e. Sella is the most anterior point on the cranial base
13. The ANB angle:
a. Indicates the vertical relationships of the face
b. Describes the anteroposterior skeletal pattern
c. Tells about the relationship of the maxilla to the
cranial base
d. Is influenced by variation in the vertical position of
nasion
e. Is affected directly by the position of porion
EXTENDED MATCHING ITEMS QUESTIONS
Theme: Cephalometrics
For each of the clinical problems (a–e), select from the list
below (1–25) the most appropriate cephalometric input to
assist in your assessment (more than one may be correct).
Each variable can be used once, more than once or not at all.
1. Nasion.
2. Porion.
3. Lower incisor angulation to mandibular plane.
4. Superimposition on Bjork’s structures.
5. Orbitale.
6. ANB angle.
7. PNS.
8. Upper incisor angulation to maxillary plane.
9. MMPA.
10. Gonion.
11. ANS.
12. Interincisal angle.
13. Lower incisor tip to A–pogonion line.
14. Superimposition on S–N, holding at S.
15. Lower incisor tip.
16. Frankfort plane.
17. S–N line.
18. Maxillary plane.
19. No cephalometric assessment.
20. Prognosis tracing.
21. Mandibular plane.
22. Superimposition on anterior vault of the palate.
23. SNA angle.
24. SNB angle.
25. Menton.
a. A 12-year-old girl presenting for treatment plan-
ning of her moderately severe class II division 2
malocclusion; you are asked to give priority to planning the lower labial segment position.
b. An 18-year-old male patient on review for his wors-
ening class III malocclusion, where an overall
assessment is required of facial changes which
have occurred in the 2 years since he was last seen
(a cephalometric film is available from that time).
c. A 14-year-old girl with a class II division 1 maloc-
clusion seen for treatment planning, where it is
necessary to evaluate upper incisor angulation and
decide between tipping or bodily tooth movement
for overjet correction.
d. A 13-year-old male patient presenting for assess-
ment of his class I malocclusion who indicates no
desire to undertake orthodontic treatment.
e. A 20-year-old female patient with an anterior open
bite, class I skeletal and incisor relationships.
CASE HISTORY QUESTION
A 13-year-old female patient presents with a class I malocclusion with moderate upper and lower midarch crowding
on a class I dental base with average FMPA. There is a history of recurrent oral ulceration.
1. What are the priorities in the management of this case?
2. Outline how you would go about orthodontic treatment
planning for this patient.
3. What orthodontic treatment possibilities may exist?
PICTURE QUESTIONS
Picture 1
Examine the records in Fig. 9.16.
1. Classify the incisor relationship.
2. Classify the right and left molar relationships.
3. Classify the degree of crowding in the maxillary and
mandibular arches (all permanent teeth are present).
4. What are the likely causes of this malocclusion?
5. What is the IOTN (DHC) score? (Additional information:
no mandibular displacement associated with the crossbite; overjet 6 mm; lips competent.)
9 • Orthodontics I: Development, Assessment and Treatment Planning
243
Fig. 9.16 Records for Picture question 1.
Picture 2
Examine the records in Fig. 9.17.
1. Classify the incisor relationship.
2. Classify the right and left molar relationships.
3. Assess the degree of crowding in the upper and lower
arches.
4. What is the most likely cause of the upper arch crowding?
5. What is the IOTN (DHC) score? (Additional information:
no mandibular displacement associated with |2 or |7
crossbites.)
Fig. 9.17 Records for Picture question 2.
DATA INTERPRETATION QUESTION
Given the following cephalometric values: SNA 5 78°; SNB
5 85°; SN to maxillary plane 7°; MMPA 5 30°; 1 to maxil-
lary plane 5 130°; 1 to mandibular plane 5 75°; answer
the following questions, explaining your reasoning.
1. What is the anteroposterior skeletal pattern?
2. Classify the maxillary–mandibular planes angle. Explain
your classification.
3. What feature of the malocclusion is expressed by the
incisor angulation?
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SHORT NOTE QUESTIONS
Write short notes on:
1. Angle’s classification of malocclusion
2. The dental health component of the Index of Orthodontic Treatment Need (IOTN)
3. The aesthetic component of IOTN
4. Methods of creating space for relief of crowding other
than by extraction.
VIVA QUESTIONS
1. What are the potential benefits/risks of orthodontic
treatment? How would you assess the need for treatment?
2. Describe the occlusion of an average primary dentition
in a child aged 5 years. What changes occur up to the age
of 14 years leading to the establishment of a idealised
permanent occlusion?
3. What factors should be considered when obtaining
informed consent from a patient prior to orthodontic
treatment?
SINGLE BEST ANSWER QUESTIONS
1. Postnatal maxillary growth is more akin to that of the
following body tissue type:
A. Cartilage
B. Genital
C. Lymphoid
D. Neural
E. Somatic
2. Anterior mandibular growth rotation is associated
with:
A. Concave lower mandibular border
B. Increased Frankfort–mandibular plane angle
C. Minimal overbite
D. Pronounced antegonial notch
E. Reduced lower facial height
3. Postnatal growth of the cranial vault is usually complete by:
A. 7 years
B. 10 years
C. 12 years
D. 15 years
E. 18 years
4. The leeway space on each side of the lower arch is
typically:
A. 0.5 mm
B. 1.5 mm
C. 2.5 mm
D. 3.5 mm
E. 4.5 mm
5. The IOTN DHC Grade for an overjet of 9 mm is:
A. 1a
B. 2a
C. 3a
D. 4a
E. 5a
6. The Zero-meridian line is a:
A. Line perpendicular to the maxillary plane
B. Measure of facial asymmetry
C. Parallel to the occlusal plane
D. Plane joining the condylar axes
E. True vertical dropped from soft tissue nasion
7. The Zero-meridian line is used to assess the:
A. Anteroposterior skeletal pattern
B. Incisor inclinations to the lips
C. Maxillary plane cant
D. Tempero-mandibular joint axis
E. Smile aesthetics
8. In an idealised smile the upper incisor edges:
A. Are not visible
B. Lie 1 mm below the upper lip
C. Parallel the lower lip
D. Touch the lower lip
E. Are in line with the canine tips
9. Rotations are described by the tooth surface:
A. Easiest to see from the line of the arch
B. Furthest away from the line of the arch
C. In the line of the arch
D. Nearest to the line of the arch
E. With the broadest tooth contact in the line of the
arch
10. The Eastman standard cephalometric norm for the
maxilla–mandibular planes angle is:
A. 21° SD 1°
B. 23° SD 2°
C. 25° SD 3°
D. 27° SD 4°
E. 29° SD 5°
11. The mandibular plane joins the following cephalometric
landmarks:
A. ANS to PNS
B. B point to pogonion
C. Gonion to menton
D. Porion to orbitale
E. Sella to nasion
12. Orthodontic treatment has potential long-term benefits
to dental health for:
A. Completely lingually displaced erupted lower second
premolar
B. Increased complete non-traumatic overbite
C. Mild crowded lower incisors
D. Overjet of 10 mm with trauma risk
E. Reverse overjet of 3 mm with no mandibular dis-
placement
13. A reasonable estimate of the space required to reduce
a 4-mm curve of Spee would be:
A. 0.5 mm
B. 1 mm
C. 1.5 mm
D. 2 mm
E. 2.5 mm
14. Typically enamel removal by interproximal reduction
from each proximal surface is:
A. 0.1 mm
B. 0.25 mm
C. 0.5 mm
D. 0.75 mm
E. 1 mm
Self-Assessment: Answers
9 • Orthodontics I: Development, Assessment and Treatment Planning
245
MULTIPLE CHOICE ANSWERS
1. a. False. Derived partially from first pharyngeal arch.
b. False. Completes growth in width before growth in
length.
c. True.
d. False. Condylar cartilage directs mandibular growth.
e. False. In males, maxillary growth is complete, on
average, by age 17 years; it is true in females.
2. a. True.
b. False. It ossifies lateral to Meckel’s cartilage.
c. False. Pattern of growth is not predictable.
d. False. Growth pattern is independent of maxillary
growth pattern.
e. False. Although, on average, mandibular growth will
complete by 18–19 years in males, the mandible continues to grow, albeit at a considerably reduced rate,
throughout the next three decades.
3. a. False. It occurs when growth in posterior facial height
exceeds that in anterior facial height.
b. True. A mild forward growth rotation is expected to
produce a well-balanced facial appearance.
c. True. The reduction in the anterior vertical facial
proportions will promote overbite increase.
d. False. Reduced maxillary/mandibular planes angle
will result from marked anterior mandibular growth
rotation, leading to increased overbite; see (c) above.
e. False. It is associated with a convex lower mandibular
border.
4. a. False. Typically at 3–4 months.
b. False. Typically 1–1.5 years after eruption.
c. False. Typically they are upright and spaced.
d. False. Typically at birth.
e. False. Greater in the lower than in the upper arch.
5. a. False. It is provided by their eruption in a more pro-
clined angulation labial to the primary predecessors.
b. True. This will help space requirements.
c. True. Tends to be about 1–2 mm in primary dentition
and 2–3 mm in mixed dentition.
d. False. Crowding of the primary incisors is likely to
provide insufficient space for the permanent incisors.
e. False. Overbite will have no effect on potential space
for the upper permanent incisors.
6. a. False. An increase in lower labial segment crowding
is expected.
b. False. An increase in lower labial segment crowding
is expected.
c. True. This will contribute to lower labial segment
crowding.
d. False. This is not a an expected finding.
e. True. With uprighting of the lower incisors in response
to facial growth changes, the tendency is for the interincisal angle to increase.
7. a. False. For anteroposterior assessment of the dental
bases, the patient should be observed from the side.
b. False. The teeth should be in maximum indigitation,
ensuring that the mandible is not postured forward.
c. False. The patient should be seated upright with the
Frankfort plane horizontal.
d. False. This assesses vertical dental base relationship
cephalometrically and not clinical anteroposterior
dental base relationship.
e. False. Dental base relationship is not influenced by
the upper incisor angulation.
8. a. False. This represents class III skeletal pattern; class
II is present when the mandible is retruded relative
to the maxilla.
b. False. SNB angle tells about the relationship of
the mandible to the cranial base; ANB angle tells the
relationship of the mandible to the maxilla (i.e. the
skeletal pattern).
c. False. Class II is usually associated with a an as ex-
pected or prognathic maxilla.
d. False. The anteroposterior skeletal pattern cannot
be assessed by examination of the first permanent
molar relationship, although Angle believed incorrectly that this was possible. It is possible for the first
permanent molar relationship to be class II and the
skeletal pattern to be also class II, but where early
loss of primary teeth has occurred or if significant
hypodontia is present, this will be altered.
e. False. Incisor relationship does not influence the
skeletal pattern. A class II skeletal pattern may be
associated with a class II incisor relationship, but the
latter does not have a direct bearing on the former.
9. a. False. The maxillary plane cannot be assessed clinically so this angle cannot be calculated. Frankfort–
mandibular planes angle is assessed clinically.
b. False. It reflects the vertical skeletal pattern. Antero-
posterior skeletal pattern is reflected by the ANB angle.
c. True. See (b) above.
d. True. As it is an angular assessment of vertical skel-
etal pattern.
e. False. It is not affected by lower incisor position but
MMPA has an inverse relationship with lower incisor angulation. As MMPA increases, lower incisor
angulation reduces and the converse is also True.
10. a. False. Class II division 2 is an incisor classification
and is, therefore, not defined by the buccal segment
relationship.
b. False. This would be present in a class III incisor
relationship. For class II malocclusion, the lower
incisor edges lie posterior to the cingulum plateau
of the upper incisors.
c. True. This is a characteristic of this malocclusion
type.
d. True. This feature is also part of the British Stan-
dards Institute definition of this incisor relationship,
although the overjet may also be increased.
e. True. See (d) above.
11. a. False. The radiograph is taken with the Frankfort
plane horizontal or the patient in natural head
posture.
b. False. The tube-to-midsagittal plane distance is usu-
ally standardised at the order of about 150 cm.
c. False. Because of the magnification factor (which is
in the range 8–12%), it is not an exact record of
facial dimensions.
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Master Dentistry
d. False. It is not essential for orthodontic diagnosis,
although it may be of benefit in gaining an insight
as to the cause of a malocclusion and in treatment
planning.
e. True. It would not, however, be taken solely for this
purpose.
12. a. False. It describes the maxillary relationship as ‘A’
point is on the maxilla.
b. False. The ANB angle is obtained by subtracting
SNB from SNA.
c. False. It joins porion and orbitale.
d. True.
e. False. It is the midpoint of the sella turcica.
13. a. False. It indicates the anteroposterior skeletal pattern.
b. True. See (a) above.
c. False. This is reflected in the SNA angle.
d. True. This affects the angles SNA and SNB, and
hence their difference ANB.
e. False. The position of porion does not affect the
ANB angle.
EXTENDED MATCHING ITEMS ANSWERS
a. 3, 6, 9. Lower incisor angulation should be assessed in
conjunction with ANB and MMPA, observing any dentoalveolar compensation that has occurred for the anteroposterior and vertical skeletal discrepancies respectively.
Lower incisor position to A–pogonion line (13) might
also be assessed, but for treatment-planning purposes,
priority should not be attributed to this parameter.
b. 14. Superimposition of the two cephalometric tracings
or digitisations on the S–N line holding at S will allow
evaluation of facial changes.
c. 8, 20. These will provide the information sought.
d. 19. As the patient is not interested in pursuing orth-
odontic treatment, a cephalometric assessment is not
indicated.
e. 9, 12. The interincisal angle is directly related to the
vertical relationship of the incisors, which may also be
affected by MMPA.
cephalometric film may be required if comprehensive
treatment with upper/lower fixed appliances is likely).
Decide on aims of treatment: aim for the ideal outcome
but bear in mind the medical history; a plan that avoids
the wearing of an orthodontic appliance would be optimal if the ulceration does not resolve. Plan the lower
arch first: consider crowding (in this case moderate and
midarch), canine inclination, overbite, centreline as well
as anchorage requirements for all intended tooth movements. Then proceed to the upper arch and assess
crowding, canine inclination, incisor angulation (anchorage requirements). Decide on the type of appliance
required to effect tooth movements required and appropriate retention plan.
3. If the ulceration does not resolve, and appliance therapy
is still warranted, consider fitting an upper removable
appliance and monitor the oral reaction to wear before
considering any likely extractions. If the ulceration
resolves, upper removable appliance therapy alone or
upper/lower fixed appliances may be justified, based on
the assessment of the occlusal features.
PICTURE ANSWERS
Picture 1
1. Class II division 1.
2. Almost class II half unit on the right (mesiobuccal cusp
of 6 occludes in a cusp-to-cusp relationship with 6);
class I on the left.
3. Lower arch has mild crowding (note spacing); upper
arch has moderate crowding (note spacing).
4. Possible causes are:
n
overjet, possibly mild class II skeletal discrepancy
n
lower arch crowding: early loss of primary molars:
note tilting of 6s and distal drifting and rotation of 4s
n
upper arch crowding: inherent dento-alveolar disproportion most likely; early loss of primary teeth unlikely (observe the reasonably good alignment of the
premolars).
5. 5i because of impaction of lower 5s.
CASE HISTORY ANSWERS
1. As with all orthodontic referrals, the patient’s concern
regarding appearance of her teeth as well as willingness
to wear any likely appliances should be recorded. Medical history should be checked and a detailed history of
the nature of the recurrent oral ulceration should be
taken. The patient should be made aware that satisfactory wear of an orthodontic appliance may prove impossible depending on the nature and frequency of the
recurrent oral ulceration. Thorough investigation of
the ulcers should be undertaken, including referral to a
consultant in oral medicine for blood tests if these are
deemed necessary. If a systemic cause is identified, orthodontic treatment should be delayed until it is treated as
the recurrent ulceration may resolve and allow comprehensive treatment with appliance therapy. If the ulceration is particularly severe, appliance therapy will
need to be avoided.
2. Obtain all necessary records – study models recorded in
centric occlusion and relevant radiographs (a lateral
Picture 2
1. Class I: the lower incisors occlude opposite the cingulum
plateau of the upper central incisors.
2. Right is class I; left is half unit class II.
3. Lower arch has moderate crowding; upper arch has
moderate crowding.
4. Inherent dento-alveolar disproportion.
5. 4d due to contact point displacement between |2 and |3.
DATA INTERPRETATION ANSWER
1. Class III. Subtracting SNB from SNA gives the ANB angle, a measure of the anteroposterior skeletal pattern.
An ANB value of –5.5° after Eastman correction indicates a marked class III skeletal discrepancy.
2. This angle is average. The maxillary–mandibular planes
angle may be classified as average (27 6 4°); high
(.31°) or low (,23°).
3. The upper incisors are very proclined (average angulation 109 6 6°) while the lower incisors are very
retroclined (average angulation 93 6 6°), indicating