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9 • Orthodontics I: Development, Assessment and Treatment Planning
247
dento-alveolar compensation for the class III skeletal
discrepancy.
SHORT NOTE ANSWERS
1. Angle’s classification is used nowadays to classify the
anteroposterior molar relationship, although it was
originally intended for classification of the anteroposterior dental arch relationship on the assumption that the
first permanent molar erupted into a consistently reliable position in the face.
Three molar relationships exist:
Class I: mesiobuccal cusp of the upper first permanent
molar occludes in the buccal groove of the lower first
permanent molar.
Class II: mesiobuccal cusp of the upper first permanent
molar occludes anterior to a class I relationship.
Class III: mesiobuccal cusp of the upper first permanent
molar occludes posterior to a class I relationship.
2. This records occlusal features of a malocclusion using
a MOCDO convention where M is missing teeth, O is
overjet, C is crossbite, D is displacement of contact
points and O is overbite. A specially designed ruler aids
the process. A malocclusion is then ascribed to one of
five categories of treatment need: Grades 1, 2, no/
slight need; grade 3, borderline; grades 4, 5, great/very
great need. Assessment by this means is objective,
reliable and rapid.
3. This scores the need for treatment of a malocclusion
based on the degree of aesthetic impairment of the anterior teeth. Assessment is made by viewing the anterior
occlusion either clinically or from study models and
comparing this with a set of 10 photographs of increasing aesthetic handicap. Treatment need is accorded as:
grades 1–4, no/slight need; grades 5–7, borderline need;
grades 8–10, definite need. The set of photographs does
not include a full range of malocclusion types and assessment is subjective.
4. Space may be created by each of the following means:
a. Arch expansion: only indicated where a unilateral
crossbite exists, especially if there is an associated
displacement.
b. Distal movement of the buccal segments: may be
undertaken in the lower arch if extraction of a lower
second permanent molar is considered, but rarely
adopted as an approach to relief of crowding. If undertaken, a fixed appliance is invariably required. In
the upper arch, bilateral distal movement of the buccal segments using headgear may be undertaken to
provide space for relief of mild upper arch crowding
or correction of a small overjet. In these patients, the
lower arch should be well aligned and the molar relationship no greater than half unit class II. Unilateral
distal movement may be undertaken when space is
required on one side of the arch only and may be
undertaken using a screw section in a removable appliance, although provision for incorporation of
headgear in the appliance is advisable. To remove the
need for headgear use, a TAD may be used instead in
combination with a fixed appliance to bring about
the desired movement. Consider extraction of upper
second permanent molar(s) to aid distal movement in
the upper arch provided third molars are present and
of good size and position.
c. Interdental stripping: only really a consideration in
adults where a small amount of space is required for
alignment. Usually confined to the lower labial segment. Involves the removal of ,0.25 mm from the
mesial and distal surfaces of each tooth.
d. Any combination of above.
VIVA ANSWERS
1. The potential benefits of orthodontic treatment to the
patient should outweigh the potential risks and sideeffects.
The potential benefits of orthodontic treatment are quite
limited. The relationship between dental caries and
malocclusion is unproven. Periodontal health can be
improved by orthodontic treatment of occlusal relationships traumatising the periodontal tissues, e.g. a
traumatic overbite or incisor crossbite with mandibular displacement leading to mobility with/without
gingival recession of a lower incisor. Where an impacted tooth is removed, the resorption risk to the
associated teeth is reduced; the risk of incisor trauma
may be reduced by overjet correction but the benefits
of early intervention indicate no significant gains in
this regard. Although TMD has been shown to be associated with crossbites, anterior open bite, class II
due to mandibular retrusion and asymmetry, this is
weak. Orthodontic treatment cannot be guaranteed
to cure TMD. There are psychological benefits accruing from correction of increased overjet or anterior
spacing which include improved self-concept and less
negative experiences.
The potential risks are failure to achieve the aims of treat-
ment; pulpal, gingival and mucosal damage; root resorption and loss of alveolar crestal height; and possibly
instigation or exacerbation of temporomandibular joint
dysfunction syndrome (see Section 9.4). With fixed appliances, the risk of decalcification is increased while
there is a small but significant risk of facial or ocular
damage from headgear.
The need for treatment may be assessed using the Index of
Orthodontic Treatment Need (see Section 9.2). This has
two components, but the dental health rather than the
aesthetic component can only be assessed reliably.
2. In the average primary dentition at age 5 years, abcde
have erupted in all quadrants. Although the ‘ideal’
features have been described as a generalised spaced
dentition with specific space mesial to the upper and
distal to the lower cs (anthropoid spaces), upright incisors with a relatively deep overbite and flush terminal
planes, these rarely occur and great individual variation
is encountered.
Where the overbite has been deep initially, it usually re-
duces by 5 years of age, and an edge-to-edge incisor
relationship with attrition is common. From about age
6 years onwards, the permanent dentition starts to
erupt, usually commencing with the eruption of the
lower incisors or of the lower first permanent molars
as growth posteriorly in the arch accommodates them.
As the permanent incisors erupt lingual to their
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Master Dentistry
predecessors, some incisor crowding is often seen, but
this generally resolves with growth in the intercanine
width.
Order and dates of eruption of permanent teeth are given in
Tables 7.1 and 7.2 (Chapter 7, p. 194).
Space for the upper incisors is provided by the primary inci-
sor spacing, intercanine growth (1–2 mm in the primary and ,3 mm in the mixed dentition) and the more
proclined inclination of the permanent incisors. Commonly, these teeth erupt spaced and distally
inclined but the spacing reduces as the permanent canines erupt. These should be palpable in the buccal sulcus at age 10 years and are guided into position by the
roots of the permanent lateral incisors.
Space for the premolars and permanent canines is provided
by intercanine growth and the ‘leeway space’, typically
1–1.5 mm and 2–2.5 mm in the upper and lower
arches, respectively. The greater space in the lower than
in the upper arch also may allow the molar relationship
to correct from a possible half a unit class II to a class I
relationship.
By 14 years of age, the permanent occlusion should be all
but complete apart from third molars, if present. The six
features of a good (‘ideal’) permanent occlusion are
given in Section 9.1.
3. All the points listed below should be gone through in a
systematic order in a format that is understandable to
the patient, with adequate time given to question any
item that is not entirely clear.
a. The diagnosis (problem list) should be outlined to the
patient and/or parent together with the dental health
component of IOTN. The significance of the latter
should be explained.
b. If there is more than one possible approach to treat-
ment, the various options should be explained together with the ‘pros’ and ‘cons’ of each. If there are
risks attached to undertaking no treatment, this
must be explained also.
c. Appliances to be used for treatment must be explained
and examples demonstrated – colour photographs are
a good means of doing this. If headgear is required,
this requires special consideration together with
an explanation of the specific care required in
its use. If a TAD is to be used, this should also be
explained.
d. Likely treatment intervals and an estimate of treat-
ment length should be given.
e. The compliance required from the patient during orth-
odontic treatment must also be emphasised: the need
for maintenance of a high standard of oral hygiene;
regular dental attendance for routine dental care; cooperation required with appliance wear, particularly if
headgear or intraoral elastic wear is prescribed; and
importance of attendance for appliance adjustment at
the appointed times. The retention regimen and its
importance should also be explained.
f. Importance of risks of each treatment plan (i.e. root
resorption, decalcification, alveolar bone loss, relapse
potential) should be explained to the patient and parent/guardian, taking care not to dramatise sequelae,
which are likely to be minor.
g. An information sheet may be useful for the patient to
take away to think over all the issues related to
treatment prior to giving consent for treatment at a
subsequent visit.
SINGLE BEST ANSWER QUESTION ANSWERS
Question 1: D
Question 2: E
Question 3: A.
Question 4: C.
Question 5: D.
Question 6: E
Question 7: A
Question 8: C
Question 9: B
Question 10: D
Question 11: C
Question 12: D
Question 13: C
Question 14: B
10
Orthodontics II: Management of Occlusal Problems
CHAPTER OUTLINE
Overview‚ 249
10.1 Problem Solving in the Developing
Dentition‚ 249
10.2 Class I Malocclusion‚ 257
10.3 Class II Malocclusion‚ 258
10.4 Class III Malocclusion‚ 262
Overview
The management of malocclusion comprises a substantial
part of orthodontic practice. It ranges from interception of
developing occlusal problems through to comprehensive
correction of established malocclusion in the adolescent
or adult. It also encompasses the special requirements in
orthodontic care of those with cleft lip and/or palate.
This chapter describes the management of the developing dentition and of all major anomalies of established
malocclusion, including surgical correction. The occlusal
problems particular to cleft lip and/or palate together with
their management are also outlined.
10.5 Open Bite and Crossbite‚ 264
10.6 Adult and Surgical–Orthodontic
Treatment‚ 267
10.7 Cleft Lip and Palate‚ 270
Self-Assessment: Questions‚ 272
Self-Assessment: Answers‚ 277
ANOMALIES OF ERUPTION AND EXFOLIATION
Both eruption and exfoliation of primary and permanent
teeth may be premature or delayed.
Natal Teeth
Natal teeth are usually lower incisors that are erupted at
birth or appear soon after. Removal is indicated only if they
interfere with suckling or if they are so mobile as to be at
risk of inhalation.
Eruption of Teeth
Other than natal teeth, the following points should be
borne in mind:
10.1 Problem Solving in the Developing Dentition
LEARNING OBJECTIVES
You should:
• know the problems which are best dealt with in the
developing dentition
• be able to classify supernumerary teeth
• know how to localise an unerupted tooth in the anterior
maxilla
• understand the principles of management of an
unerupted 1, ectopic 3 and first permanent molar
with poor long-term prognosis.
Although most orthodontic treatment is undertaken
when the permanent dentition is established, some aspects
of the developing occlusion may be better dealt with in the
mixed dentition. Such interception may eliminate the need
for, or simplify, later treatment. Systematic and regular
screening of the developing dentition is essential to this
process.
n
There is greater variation in the eruption sequence of
primary teeth between races than there is in eruption
times.
n
Poor diet and chronic ill-health in child populations may
alter eruption sequence.
n
Permanent teeth tend to erupt later in White European
people compared to people of East and South East Asia,
who in turn tend to have later eruption times than Black
Central and Southern African people.
n
Females tend to erupt their permanent teeth earlier than
males, particularly second and third molars.
Factors causing premature exfoliation or delay in the
eruption and exfoliation of primary or permanent teeth are
given in Table 10.1.
To ensure that any deviation in the typical eruption
sequence is detected early, clinical vigilance is required during the developing dentition, supported by radiographic
investigations where necessary. Particular attention should
be given to the permanent maxillary incisors and canines,
as early recognition of an anomaly in their eruption
improves the prognosis.
249
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Master Dentistry
Table 10.1 Causes of Premature or Delayed Eruption
of Primary or Permanent Teeth.
Causes
Premature
eruption
Delayed
eruption
Premature
exfoliation
Delayed
exfoliation
Familial tendency
Primary dentition: high birthweight
Permanent dentition: early-onset puberty, excess
growth or thyroid hormone secretion
Primary dentition: very low birthweight, premature
birth
General causes: Down or Turner syndromes, severe
nutritional deficiency, hypothyroidism/ hypopituitarism, cleidocranial dysplasia, hereditary gingival
hyperplasia, cleft lip and palate
Local causes: ectopic crypt position, supernumerary
or odontome, developmental absence, retention of
primary tooth, dilaceration, primary failure of eruption, crowding
Commonly caries or trauma
Rarely hereditary hypophosphatasia, developmental
neutropenia, cyclic neutropenia, Chediak–Higashi
syndrome, histiocytosis X
Developmental absence of permanent successor
Ectopic position of permanent successor
Trauma
Severe periradicular infection of primary tooth
Hypodontia
The most common missing teeth are:
n
third molars (25–35%)
n
upper lateral incisors (2%)
n
lower second premolars (3%)
n
lower incisors (0.5%).
Hypodontia affects females more than males with a ratio
of 3:2 and depending on the number of developmentally
absent teeth, excluding third molars, may be classified as
mild (1 or 2), moderate (3 – 6) or severe (greater than 6).
The aetiology may be non-syndromic or syndromic, the
former arising from a multifactorial interplay of environmental (systemic and local) and genetic (MSX1, PAX9,
AXIN2) factors. Premolar and molar agenesis is related
mostly to alterations in MSX1 and PAX9 respectively,
whereas agenesis affecting several tooth types is linked to
changes in AXIN2. With over a hundred syndromes associated with hypodontia, some of the more common are cleft
lip and/or palate where almost 75% may be affected,
Down syndrome, Ehlers–Danlos syndrome and ectodermal
dysplasia. Additional dental features commonly found include microdontia, hypoplastic enamel, abnormal crown
shape, infraoccluded primary molars and ectopic maxillary
canines. Lower face height is also often reduced with an
increase in overbite.
Absent Third Molars
Extraction of a second molar, either to facilitate distal
movement of the upper buccal segments or to relieve posterior crowding, should not be considered in the absence of a
third molar. These start to calcify any time between 8 and
14 years.
Absent Upper Lateral Incisors
Management options for the space created by absent upper
lateral incisors are:
n
space opening
n
space maintenance
n
space closure.
The final decision depends on:
n
the patient’s attitude to orthodontic treatment
n
the anteroposterior and vertical skeletal relationships
n
amount of exposure of the upper canines and incisors
on smiling
n
the colour, size, shape and inclination of the canine and
incisor teeth
n
whether the arches are spaced or crowded
n
the buccal segment occlusion.
The possible plans are best assessed by carrying out a
trial set-up of each on duplicate study models, followed by
joint consultation with a restorative colleague.
space opening. In uncrowded or mildly crowded arches,
when the buccal segment occlusion is class I or, at most,
half unit class II, or in class III where proclination of the
incisors is likely to correct an anterior crossbite, space
opening is best. In addition, in patients with low Frankfort-mandibular plane angle (FMPA) or where the maxillary canine is considerably darker than the incisors, it
may be best to open rather than close the anterior spaces.
A fixed appliance is required to localise space for the missing units, followed by at least 3–6 months of removable
appliance retention ensuring that the space is maintained
by placing wire spurs in contact with the adjoining teeth
in addition to prosthetic tooth replacements. Where artificial teeth are added to a vacuum-formed retainer rather
than to a Hawley retainer, the former must not be worn
while eating or drinking. In selected cases, autotransplantation of lower premolars (extracted for relief of
crowding) to the upper lateral incisor area may be possible but this may be difficult due to relative crown size
differences. Rarely has a lower incisor been autotransplanted to an upper lateral incisor space but only if a
satisfactory occlusal outcome is likely. More commonly,
the missing units may be replaced on resin-retained
bridgework, and occasionally by implants at a later date
provided in the latter case that there is adequate width
and height of alveolar bone along with root parallelism
of the abutment teeth. If bridge work is planned, it is important to ensure that sufficient interocclusal clearance
exists or has been created during appliance therapy for
placement of the metal framework or for the pontic in the
case of an implant. In the short term of 3–5 years, success rates of 85% and 95% have been reported with
resin-bonded bridges and single-tooth implant-supported
prostheses, respectively.
space closure. In crowded mouths, early extraction of the
primary canines should be carried out to encourage mesial
drift of the posterior teeth, but a later phase of fixed appliance therapy is usually needed to align and approximate
the upper anterior teeth, followed by bonded retention. Recontouring of the canines in addition to composite build-up
of their mesio-incisal aspects is advisable before treatment
10 • Orthodontics II: Management of Occlusal Problems
251
starts to assist with definitive tooth positioning; final restorations are placed following appliance removal. Bleaching
of the canines may also be required to enhance aesthetics.
Overjet reduction by space closure may be more favourable
than resorting to midarch extractions and space opening.
Space closure is likely to be facilitated in patients with
increased FMPA, crowding and where the buccal segment
relationship is a full unit class II.
Absent Second Premolars
The primary second molar should preferably be retained
where the arch is uncrowded or aligned. Prospects are
good long term if they survive to 20 years of age. If the
tooth starts to infraocclude, an occlusal onlay may be
placed to maintain it in function. Removal of the lower
second primary molar shortly after eruption of the lateral
incisors will encourage spontaneous space closure in
mildly crowded cases; in those with marked crowding, its
extraction should be delayed until orthodontic treatment
commences so that the resulting space may be used for
arch alignment. Where it is necessary to extract the second
primary molar and the resultant space is substantial, additional anchorage will need to be considered to move the
lower molars forward without the lower labial segment
being moved lingually. Alternatively acceptance of the
space as it is out of sight and if not compromising occlusal
function may be a possibility. In the upper arch, extraction
of the second primary molar is best deferred until orthodontic treatment is about to start. Rarely, a lower second
premolar develops late and necessitates an alteration in the
original treatment plan.
Absent Lower Central Incisors
In the absence of permanent lower central incisors, root resorption and progressive incisal wear may lead to loss of the
primary incisors in the late mixed dentition, although occasionally they can last longer. With one absent lower incisor,
space closure is likely to increase the overjet and overbite, favourable where these are minimal and for correction of a
class III incisor relationship; space opening is normally preferable in class II cases. Where both lower central incisors are
absent, confining spacing to the lateral incisor areas is usually
better due to the favourable characteristics afforded by the
lower canines to support resin-retained bridgework.
Supernumerary Teeth
Teeth additional to the usual number are termed ‘supernumerary’. Most common in the anterior maxilla (80%), they
may occur between the central incisors (mesiodens) but
often also develop distal to the last tooth in each dental series (lateral incisor, second premolar and third molar) as an
exuberant growth of the dental lamina. The exact aetiology
is not known but it seems genetic factors play a part. They
are more common:
n
in males than in females (relative reported frequency
approximately 2:1 in White European populations)
n
in the permanent than in the primary dentition (respective incidences around 2% and 1%)
n
in children with cleft of the lip and alveolus, cleidocranial dysplasia and Gardner syndrome.
Those in the anterior maxilla can be categorised into
three groups: conical, tuberculate and supplemental.
Conical Teeth
Conical teeth occur between the upper permanent central
incisors; they are often singular but can sometimes occur in
combination with others of similar form. They may have no
effect if they are well above the apices of the incisors. If
there is no risk of damage to adjacent teeth with tooth
movement, they can be left in place and observed. Often,
however, they may displace the adjacent teeth, perhaps
creating a large diastema, or they may delay eruption. In
these instances, removal is indicated. Occasionally, a conical supernumerary tooth erupts and can be extracted.
Tuberculate Teeth
Tuberculate teeth are the most common cause of an unerupted permanent maxillary central incisor. Suspicion
should be raised if the lateral incisors erupt in advance of
the centrals. In these cases, a radiograph of the premaxilla
should be taken to allow early detection and localisation of
any supernumerary, which should then be surgically removed. An attachment with gold chain should be bonded to
the unerupted incisor to allow provision for orthodontic
alignment if the tooth fails to erupt spontaneously within
12 months of surgery. In conjunction with surgery, space
to accommodate the unerupted tooth must be maintained
or opened by appliance therapy; the latter may entail extraction of the upper primary canines.
Supplemental Teeth
The supplemental tooth resembles the expected tooth in
morphology and commonly produces crowding or displacement of adjacent teeth. Usually, the tooth, which is similar to
the contralateral tooth, is better retained (provided it is not
severely malpositioned) and the other incisor is extracted.
ANOMALIES OF DEVELOPMENT
First Permanent Molars With Poor Long-Term Prognosis
The first permanent molar is never the extraction of choice
for orthodontic reasons but is invariably enforced because
of poor prognosis resulting from caries and/or enamel hypoplasia. Molar incisor hypoplasia (MIH) has an unknown
aetiology but is reckoned to be multifactorial with genetic
and systemic (acute and chronic illnesses) factors thought
to interact; it affects about one in seven children worldwide
with no gender bias. It may lead to marked enamel breakdown, associated dental caries and dental sensitivity.
Enamel demineralisation on the lingual aspect of lower first
permanent molars or on the buccal aspect of upper first
permanent molars should be treated seriously, as it is often
a hallmark of a high caries rate and possible limited lifespan
of these teeth. When a two-surface or deep occlusal restoration is indicated in one molar 2–3 years after eruption,
careful assessment of the malocclusion and the condition
of the other first permanent molars should be made. Timely
removal may lead to considerable spontaneous correction
of the malocclusion in certain patients but it does little for
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Master Dentistry
relief of incisor crowding or correction of an incisor relationship unless appliance therapy is instituted.
A ‘cook book’ approach to each patient with poor-quality
first permanent molars is not possible but some guidelines
are listed in Box 10.1.
Infraoccluded Primary Molars
Between 1% and 9% of children are likely to exhibit this
anomaly but estimates regarding its incidence vary. A genetic tendency has been suggested with absent premolars,
ectopic position of the first permanent molars and palatal
canine displacement identified as associated factors. Infraocclusion results from ankylosis of the tooth while alveolar
growth and eruption of the adjacent teeth continues. Provided the permanent successor is present, exfoliation will
occur eventually, but removal is indicated in its absence and
where the infraocclusion is marked, with the crown of the
tooth just visible, or where root development of the unerupted premolar is almost complete.
Impaction of the Maxillary First Permanent Molar
Impaction of the maxillary first permanent molar occurs in
2–6% of children. It may correct spontaneously (unlikely
after the upper lateral incisors erupt) or it may require disimpaction of the molar either by placing a brass wire separator
between the adjacent teeth (in mild cases) or by appliance
therapy (in more marked impaction). Extraction of the second primary molar is required if the impaction produces
symptomatic resorption with pulpal involvement or to facilitate restoration of the first permanent molar. Crowding is
Box 10.1 Guidelines for Management of First
Permanent Molars (FPM) With Poor Long-Term
Prognosis.
n
Institute preventive measures including oral hygiene motivation,
dietary advice and fluoride therapy.
n
Evaluate social circumstances, motivation for restorative and
orthodontic treatment, level of dental awareness, general
anaesthetic need, age and class of malocclusion.
n
Ensure (radiographically) that all permanent teeth, particularly
second premolars and third molars, are present and that all
others are of good prognosis. Avoid extraction of an FPM in a
quadrant with an absent tooth, or in uncrowded arches.
n
Assess the need to balance or compensate for extraction of
an FPM but balancing extraction of sound FPMs is seldomly
indicated. To avoid occlusal interference from overeruption
of 7, consider extraction of the upper FPM when extraction
of a lower FPM is required but the corollary does not apply.
n
Timing of extraction of lower FPM is best when the bifurcations
are calcifying (aged approximately 8.5–9.5 years) and moderate
premolar crowding is present.
n
Timing of extraction of upper FPM is less important because of
the distal tilt and downward and forward eruption path of 7.
n
Extraction of upper FPM is best delayed:
n
in Class III until the incisor crossbite is corrected
n
in Class II division 1 until 7s erupt
n
in severely crowded mouths until 7s erupt.
n
Extraction of lower FPM may be deferred in Class III with
marked incisor crowding until lower 7s erupt.
n
Monitor eruption of second and third molars.
exacerbated by the subsequent mesial drift of the first permanent molar, but this can be treated later.
Aberrant Position of Second Premolars
Occasionally, the second premolars appear in slightly
unfavourable positions when viewed on a radiograph,
but generally this is of no long-term consequence and
their final position is usually satisfactory. A grossly ectopic
second premolar is rare and may be observed or surgically
removed.
Posterior Crossbite With Mandibular Displacement
Sometimes, a unilateral crossbite of the buccal segment
teeth with mandibular displacement follows a prolonged
finger- or thumb-sucking habit. In some children, grinding
the primary canines can lead to correction and prevent
perpetuation of the crossbite from the mixed to the permanent dentition; where this is not effective, arch expansion
by using either a removable appliance and a midline screw
or a quadhelix is required to reduce the chance of the crossbite being present in the permanent dentition. The latter
treatment method is more efficient and cost-effective. Alternatively, correction may be deferred until the premolars
erupt (Fig. 10.1).
TREATMENT OF ANOMALIES BY SERIAL EXTRACTIONS
In 1948, Kjellgren, a Swedish orthodontist, ascribed the term
‘serial extractions’ to the following three-stage procedure:
n
Extraction of the primary canines at age 8.5–9.5 years
to encourage alignment of the permanent incisors.
n
Extraction of the first primary molars approximately
1 year later to encourage eruption of the first premolars.
n
Extraction of the first premolars as the permanent
canines are erupting.
The full extent of the original technique is never adopted
in contemporary orthodontic practice, as three episodes of
extractions are unpleasant for any child and may psychologically scar their attitude to subsequent dental treatment.
In addition, simultaneous intervention at a time when the
intercanine width is increasing makes gauging the extent
Fig. 10.1 Upper removable appliance to correct unilateral buccal
segment crossbite with associated mandibular displacement. • Midline
expansion screw; Adams’ clasps 64|46 (0.7 mm SS wire); buccal
capping.
10 • Orthodontics II: Management of Occlusal Problems
253
of crowding problematic. The process was originally intended to remove the need for appliance therapy but, in
practice, this is seldom the case. In children with class I
malocclusion, however, aged 10–12 years, with moderate
crowding, a full complement of teeth in favourable positions and no concern about the long-term prognosis of the
first permanent molars, a reasonable outcome may be
forthcoming from removal of the first premolars alone,
without recourse to the earlier extraction of primary teeth.
Planned extraction, however, of the primary canines is beneficial in the following instances:
n
To allow labial movement of a permanent upper lateral
incisor erupting palatal to the permanent upper central
incisors and in potential crossbite.
n
To create space in the upper labial segment for proclination of an instanding permanent lateral incisor or the
eruption of a permanent incisor, where a supernumerary tooth has delayed its appearance.
n
To promote alignment of a displaced permanent maxillary
canine; this is particularly beneficial where the canine is
displaced palatally.
n
To facilitate lingual movement of a labially placed permanent lower incisor with reduced periodontal support
or of the lower labial segment to aid anterior crossbite
correction in class III malocclusion.
OTHER DEVELOPMENTAL PROBLEMS
Early Loss of Primary Teeth
Early loss of primary teeth is most commonly caused by
caries but, occasionally, it results from premature exfoliation, often when there is severe crowding, or it may be
planned (e.g. to encourage space closure by mesial drift of
the buccal segments in children who are missing one or
more permanent teeth). In all cases, consideration should
be given to balancing (extraction of the same tooth on the
opposite side of the arch) or to compensating (extraction of
the equivalent opposing tooth) for an extraction, the respective justification being to avoid a shift of the midline or
to ensure that the occlusion is not compromised. Premature loss of a primary tooth does not inevitably lead to premature eruption of the permanent successor.
The effects of early loss of a primary tooth depend on
several factors including:
n
the patient’s age
n
the degree of crowding
n
the tooth extracted
n
the arch from which it is removed
n
the type of occlusion.
All of these influence the potential for crowding to be
concentrated at the extraction site. In general, this potential is greatest in a young child with pre-existing crowding
when a maxillary posterior tooth is removed with poor buccal segment intercuspation.
Incisors
Early loss of a primary incisor tends to have minimal effect
as it usually exfoliates in the early mixed dentition. Premature loss of a primary incisor through trauma may, however, lead to dilaceration of the permanent successor.
Canines
Unilateral loss of a primary canine invariably leads to
movement of the centreline and should be balanced to
prevent this occurring.
First Molars
Occasionally, displacement of the centreline follows early
extraction of a first primary molar, but the need for a balancing extraction is best assessed by checking the midlines
at subsequent reviews.
Second Primary Molars
Where the second primary molar is extracted, the first permanent molar migrates mesially and may lead to considerable space loss if the extraction is carried out before the
permanent molar erupts; hence, it is preferable to delay
extraction until the first permanent molar has erupted. Provided the prognosis of the other second primary molars is
favourable, in general, the need for a compensating or balancing extraction is unlikely but should be assessed on a
case-by-case basis.
Space Maintenance for Early Tooth Loss
Space maintenance is indicated:
n
when premature loss of a tooth promotes crowding in an
otherwise acceptable occlusion
n
in severely crowded mouths where all of the extraction
space is required for alignment of the remaining teeth
n
following traumatic loss of an upper permanent incisor.
A removable appliance will usually suffice in the upper
arch but a lingual arch soldered to bands cemented to molar teeth is best in the lower. The impact on dental health
and potential to strain co-operation with regard to further
comprehensive treatment should be borne in mind.
Upper Median Diastema
Upper median diastema is a typical phase of dental development and reduces as the permanent maxillary canines
erupt. It has a tendency to run in families or may be racial
in origin or result from:
n
a midline supernumerary tooth
n
missing or small upper lateral incisors
n
incisor proclination in class II division 1 malocclusion
(Section 10.3) or due to a digit-sucking habit
n
a more generalised spacing condition due to mismatch
in tooth/arch size (Section 10.2).
A radiograph of the upper incisor area should be taken
to exclude the presence of a supernumerary tooth in
those with a large midline diastema. Rarely, a low-lying
attachment of the labial frenum is a primary cause, as
the attachment usually recedes as the incisors approximate. In a spaced arch, this does not occur, indicating
that the frenum is associated with, but not causative of,
the diastema.
Where the frenum is implicated in causing a diastema,
blanching of the incisive papilla usually occurs when the lip
is pulled upwards or outwards, with characteristic V-shaped
notching of the alveolar bone between the two central incisors visible radiographically. The need for fraenectomy
should be assessed after eruption of the permanent canines
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and is preferably undertaken during space closure as the
scar tissue will aid approximation of the incisors. Treatment of the diastema in the early mixed dentition may be
necessary if there is insufficient space for the lateral incisors
and the diastema exceeds 3 mm but vigilance is needed to
ensure that the lateral incisor roots are not moved into the
path of the erupting canines. A fixed appliance is usually
required to close an upper midline space, with bodily
approximation of the incisors followed by palatal bonded
retention.
Dilaceration
Dilaceration is a sudden angular alteration in the long
axis of the crown or in the root of a tooth. Most commonly it results from intrusion of a primary incisor driving the crown of the permanent successor palatally, and
it leads to enamel and dentine hypoplasia. On occasion,
dilaceration is developmental in origin, more so in females and with a characteristic labial and superior coronal deflection of the tooth involved. Usually, a dilacerated
incisor remains unerupted and when markedly affected
requires surgical removal but, if the dilaceration is mild,
surgical exposure and orthodontic alignment may be feasible when the root apex is destined not to perforate the
cortical plate.
Traumatic Loss of an Upper Permanent Central Incisor
As the adjacent teeth tend to tilt towards the site of loss in
the first days following trauma, the space must be maintained, ideally by immediate reimplantation of the tooth
or by fitting a denture carrying a replacement tooth.
Later, autotransplantation of preferably a single-rooted
premolar (either upper second or a lower) with restorative
modification or prosthetic replacement by adhesive or
fixed bridgework or implant may be considered. This is
generally preferable to space closure, as a lateral incisor
rarely gives an optimum appearance in a central incisor
position, even with coronal build-up and gingival recontouring. Involvement of oral surgery, paediatric dental
and restorative colleagues is required for optimal treatment planning. Should autotransplantation be considered, provided that adequate space has been created and
the donor site carefully prepared, this is best undertaken
when two-thirds to three-quarters of the root is developed, ensuring an atraumatic technique and that the
tooth is positioned at gingival level before splinting for
7 – 10 days. This procedure has good success with failure
only reported in 10% – 15% of cases.
Incisors in Crossbite
Early correction of a crossbite involving a permanent incisor is essential to prevent displacing occlusal forces compromising the periodontal support of the lower anterior
teeth and to allow the occlusion to develop around an
undisplaced condylar position. Provided there is likely to be
adequate overbite of 2–3 mm, an upper removable appliance with a double-cantilever spring to procline the instanding incisor and posterior capping to disengage the
occlusion will usually suffice (see Section 10.5 and
Fig. 10.2); a screw section clasping the teeth in crossbite
d
e
Fig. 10.2 Upper removable appliance to procline 1|1 in the early mixed
dentition, assuming all primary teeth are in good condition. • Double-
cantilever springs 1|1 (0.5 mm SS wire); Adams’ clasps d|d (0.6 mm SS
wire) and 6|6 (0.7 mm SS wire); posterior capping 2–3 mm in height to
disengage the anterior occlusion.
d
e
will maintain appliance retention where two or more teeth
need to be moved anteriorly. It may be necessary to remove
the upper primary canines to facilitate crossbite correction
on a permanent upper lateral incisor or the lower primary
canines to allow alignment of a labially placed permanent
lower incisor.
Habits
Depending on the positioning of a finger(s) or thumb, the
frequency and intensity of a sucking habit may:
n
procline the upper incisors
n
retrocline the lower incisors
n
increase the overjet, often asymmetrically
n
reduce the overbite
n
lead to a crossbite tendency of the buccal segments.
Gentle persuasion to discontinue the habit should be
given and simple measures adopted to effect this. Fitting of
a fixed habit breaker (palatal crib or palatal arch) may be
considered if the child is eager to stop.
Increased Overjet
Where the overjet is greater than 3 mm, the risk of incisor
trauma is more than doubled; trauma is more common in
boys and the risk is greater with incompetent lips. An initial
phase of functional appliance treatment to retract the incisors may be beneficial in these children or where the malocclusion is associated with bullying. A second phase with
fixed appliances, however, is generally required to detail the
occlusion with possibly premolar extractions for relief of
crowding. As overall treatment time is increased and considerable demands placed on patient co-operation, the likely
benefits of such early intervention must be deemed to outweigh potential disadvantages including the risk of upper
incisor root resorption if these teeth are retracted into the
eruption path of the upper canines.
Results of a North American clinical trial found that
early skeletal effects produced by either functional or
headgear therapy in the preadolescent period were
not maintained long term. In addition, little or no differences existed following fixed appliance therapy in the
10 • Orthodontics II: Management of Occlusal Problems
255
permanent dentition between those who had been treated
earlier or who had been observed until the permanent
dentition erupted. Furthermore, a multicentre UK trial
established that functional appliance treatment at 8–10
years of age did not result in a better skeletal or occlusal
outcome. Consequently many clinicians now prefer to
wait until the permanent dentition before starting treatment in these cases. Functional appliance treatment in
the early mixed dentition, however, is indicated to reduce
the risk of incisor trauma or where a child is being teased
because of the malocclusion. The need for a custom-made
mouthguard for sports should also be emphasised for all
children with an increased overjet.
Ectopic Maxillary Canines
The maxillary canine is ectopic in approximately 2% of the
population, with 15% of these buccal and 85% palatal to
the arch. Development of the maxillary canine begins
about 4–5 months after birth, the crown is complete around
6–7 years and eruption is typically at 11–12 years. From an
initial position high in the maxilla, the tooth moves buccally downwards and forwards to be guided into its final
position by the distal aspect of the lateral incisor root. For
this reason, absence or diminution in the size of the lateral
incisor increases the incidence of displacement (32.4).
There also appears to be a greater incidence of palatal canine displacement where the maxillary arch is spaced or in
class II division 2 malocclusion; a polygenic multifactorial
aetiology has been suggested for palatal displacement.
With this, there is a familial and racial (more common in
Europeans) tendency, greater prevalence in females than
males and an increased bilateral occurrence than seems
likely. In addition, there is an association with absent or small
teeth, infraoccluded primary molars, impacted upper first
permanent molars and other ectopic teeth. The long eruption path and in the case of more pronounced displacement,
ectopic position of the tooth germ, are additional possible
aetiological factors. Buccal displacement is more common
in crowded arches. Where routine palpation of the buccal
sulcus at 10–11 years fails to detect a canine prominence,
the path of eruption is likely to deviate from the expected. In
addition, considerable delay in the eruption of a canine
compared with the opposite side of the arch points to canine displacement.
Transposition
Transposition occurs when the position of the canine is interchanged with that of an adjacent tooth. It has a prevalence of less than 1% and an aetiology involving genetic
and environmental factors. In the upper arch, the maxillary canine and first premolar, or the lateral incisor and
canine, are involved, although the former arrangement is
more common. In the lower arch, the lateral incisor and
canine teeth are solely affected.
Estimating the Maxillary Canine Position
clinical estimate. Buccal and palatal palpation along
with observation of the lateral incisor inclination give a
hint to the canine position. When it is lying low and palatal
or high and buccal, the lateral incisor is likely to be labially
inclined.
radiographic estimation. Although a dental panoramic
tomogram is helpful in the initial assessment of the canine
position, it underestimates its potential for alignment;
the tooth is actually closer to the midline and at a more
acute angle than it appears radiographically. Further radiographic views are needed to locate the position of the
tooth. Most commonly an upper anterior occlusal view,
preferably taken at 70 – 75°, or two periapical films taken
with a tube shift are needed to allow localisation, using
vertical or horizontal parallax respectively. The axial
inclination, apex location and the vertical and mesiodistal
position of the canine relative to the incisor roots should
be assessed. The permanent incisors should be checked
carefully to exclude resorption, and the root length of the
primary canine noted. Resorption of incisors is more common in females than males and there is a 50% greater risk
of its occurrence should the canine be at a greater than
25° angulation to the midline when viewed on a dental
panoramic tomogram. If incisor resorption is detected,
urgent treatment is indicated. Removal of the impacted
canine may arrest the resorption but extraction of the incisor may be required in those with severe resorption. Conebeam computed tomography (CBCT) can reveal the full
extent of resorption.
Management of Canine Displacement
The management of buccal or palatal maxillary canine
displacement including transposition is described in
Table 10.2.
ANOMALIES OF SIZE AND FORM
Size
Teeth of a size that is greater or less than the norms for
gender and for a given population are described as ‘megadont’ or ‘microdont’, respectively.
Megadontia has a prevalence of 1.1% in the permanent
dentition, with maxillary central incisors most frequently
affected, although lower second premolars are affected occasionally. The typical shape and absence of incisor notching distinguishes megadont maxillary incisors from ‘double
teeth’. Megadont teeth may be found unilaterally on the affected side in unilateral facial hyperplasia, but more generalised megadontia is associated with gigantism. A megadont
upper incisor may produce crowding, an increased overjet
or both. If the tooth is only slightly enlarged, removal of
about 1 mm of enamel from each proximal surface and appliance therapy to close the resultant space may suffice. In
gross enlargement, extraction of the affected tooth and
placement of a pontic following any appliance treatment
may be necessary.
Microdontia is frequently seen in association with hypodontia, in Down syndrome and in ectodermal dysplasia.
The prevalence is 0.2–0.5% in the primary dentition and
2.5% in the permanent dentition, with diminutive upper
lateral incisors accounting for 1–2% of the latter. Short
roots are often found on these teeth, which may be a factor
in the aetiology of palatally displaced canines. In crowded
mouths, where the lateral incisor is peg-shaped on one side
of the arch and of typical size on the opposite side, removal
of both lateral incisors may be optimal to achieve symmetry
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Table 10.2 Management of Maxillary Canine Displacement.
Treatment Options Indications Comments
Buccal
displacement
Palatal
displacement
Transposition Accept Transposition complete
a
In each case, the patient’s interest in orthodontic treatment, their level of dental awareness and general features of the malocclusion (including the degree of
crowding or spacing and the condition of the primary canine (if present) and adjacent teeth) must be assessed before the final treatment plan can be devised.
b
91% chance of normalisation of eruption path of 3 with extraction of c where 3 is mesially positioned and overlaps , half of root of 2; 64% chance of eruption
of 3 if . half of 2 root overlapped. Recent evidence shows significant improvement in success rate of eruption of 3 with the use of RME and headgear (or
headgear only) compared to untreated controls.
Early removal of
4 before 3 erupts
Exposure of 3 Delayed eruption of 3 Apically repositioned flap or replaced flap required at
Removal of 3 Severe crowding with 2 and 4 in contact 3
Early removal
b
of c
Exposure of 3 Well-disposed patient
Transplantation
Removal of 3 Hopeless prognosis for alignment of 3
Retain 3 Occasionally in a young patient who is
Extraction of the most
displaced tooth
Orthodontic Sufficient space in the arch Apical positions of the transposed teeth will determine
Moderate crowding May require removable or sectional fixed appliance to
severely displaced
Ectopic position of 3 detected at 10–13 years
of age
3 overlaps up to half width of 2
3 crown below the apical third of 2 root
3 long axis to midsagittal plane #30°
Ideally, crowding in arch no greater than mild
Good oral hygiene and dentition
3 overlaps less than half width of 1 and
below the apical third of 2 root
3 root apex is not distal to 5 and 3 long axis
#30° to midsagittal plane
Spaced arch or possible to create space
Hopeless prognosis for alignment of 3
Adequate space in arch for 3
Intact removal of 3 possible
Adequate buccal/palatal bone
Patient not keen for appliance therapy or
evidence of incisor resorption or dentigerous
cyst 2 and 4 in contact
Good root length on c and aesthetics of
c acceptable
uncertain about treatment at present
but may elect to proceed with alignment
of 3 later
If crowding present
a
align 3 depending on axial inclination
surgery
Bond bracket or gold chain to 3 to facilitate alignment
May require fixed appliance to detail the occlusion or
close any remaining space
Extract contralateral c to prevent centerline shift;
extraction of c may promote crowding
Failure of 3 to erupt will leave space
Bond bracket or gold chain to 3 at surgery
May commence alignment of 3 with removable appliance
but fixed appliance usually required to align apex of 3
Prospects for alignment reduced and treatment time
extended in adults
Prognosis improved if root of 3 is two-thirds to threequarters formed, minimal root handling at surgery, 3 not
in occlusion with 6 weeks of sectional archwire splint
Approximately 70% survival rate at 5 years
Prosthetic replacement of c required when lost
Periodic radiographic examination of incisors required
to exclude resorption
whether alignment is carried out in the transposed
positions or if these are corrected
in the upper labial segment. If the diminutive lateral incisor
is retained, orthodontic treatment should first create sufficient space to ensure that the tooth can be restored to ideal
anatomical dimensions. This space is maintained for at
least 3 months with metal spurs on a removable retainer
prior to final restoration.
Form
Double Teeth
n
Have a prevalence of 0.1–0.2% in the permanent
dentition.
n
Are equally common in males and females.
n
Affect incisors more frequently than other tooth types.
Clinical appearance can vary from an incisal notch in a
tooth of enlarged mesiodistal width to an anomaly resembling two separate crowns. Treatment is best delayed until
the pulp has receded. Separation may be possible if there
are two separate pulp chambers and root canals, but recontouring of the crown to resemble two separate teeth or reduction of its mesiodistal width may be possible where one
pulp chamber exists.
The reported Prevalence in the primary dentition is 0.5–
1.6% in White European populations and it affects teeth
mostly in the mandibular labial segment. In the presence of
hypodontia, double primary teeth are followed usually by
absence of permanent teeth, but supernumerary teeth are
more common in the permanent dentition if all of the