Ch 3 orthodontics

Management of

the developing

dentition

By : Cezar Edward

4 developing stages

1-Gum Pad Stage

2-Primary Dentition stage

3-Mixed Dentition stage

4-Prmanent Dentition stage

Normal dental development

Canine during erupting push the root of the lateral so the crown of lateral will

go anteriorly ….

This latter stage of development used to be described as the ‘ugly duckling’ stage

of development ( Fig. 3.3 ), although it is probably diplomatic to describe

it as normal dental development to concerned parents. As the canines

erupt, the lateral incisors usually upright themselves and the spaces close.

The combined width of the deciduous canine, fi rst molar, and second

molar is greater than that of their permanent successors, particularly in

the lower arch. This difference in widths is called the leeway space ( Fig.

3.4 ) and in general is of the order of 1–1.5 mm in the maxilla and 2–2.5

mm in the mandible (in Caucasians). This means that if the deciduous

buccal segment teeth are retained until their normal exfoliation time,

there will be sufficient space for the permanent canine and premolars.

The deciduous second molars usually erupt with their distal surfaces

flush anteroposteriorly. The transition to the stepped Class I molar

relationship occurs during the mixed dentition as a result of differential

mandibular growth and/or the leeway space.

Development of the dental

arches

Intercanine width is measured across the cusps of the deciduous/

permanent canines, and during the primary dentition an increase of

around 1–2 mm is seen. In the mixed dentition an increase of about 3

mm occurs, but this growth is largely completed around a developmental

stage of 9 years with some minimal increase up to age 13 years. After

this time a gradual decrease is the norm.

Arch width is measured across the arch between the lingual cusps of

the second deciduous molars or second premolars. Between the ages

of 3 and 18 years an increase of 2–3 mm occurs; however, for clinical

purposes arch width is largely established in the mixed dentition.

Arch circumference is determined by measuring around the buccal

cusps and incisal edges of the teeth to the distal aspect of the second

deciduous molars or second premolars. On average, there is little

change with age in the maxilla; however, in the mandible arch circumference

decreases by about 4 mm because of the leeway space. In individuals

with crowded mouths a greater reduction may be seen.

Abnormalities of eruption and

exfoliation

Screeningcareful observation of the developing dentition

for evidence of any problems, for example deviations from the

normal sequence of eruption.

Natal teethmost commonly arise anteriorly in the mandible

and are typically a lower primary incisor which has erupted

prematurely

Because root formation is not complete at this stage, natal

teeth can be quite mobile, but they usually become firmer

relatively quickly. If the tooth (or teeth) interferes with breast

feeding or is so mobile that there is a danger of inhalation,

removal is indicated

Eruption cyst

An eruption cyst is caused by an accumulation of fluid or blood in the

follicular space overlying the crown of an erupting tooth ( Fig. 3.7 ). They

usually rupture spontaneously, but very occasionally marsupialization

may be necessary.

Failure of/delayed eruption

Signs

• A disruption in the normal sequence of eruption.

• An asymmetry in eruption pattern between contralateral teeth

Mixed dentition problems

Premature loss of deciduous teeth

Deciduous incisor: premature loss of a

deciduous incisor has little

impact, mainly because they are shed

relatively early in the mixed

dentition.

Deciduous canine: unilateral loss of a

primary canine in a crowded

mouth will lead to a centreline shift ( Fig.

3.10 ). To avoid this when

unilateral premature loss of a deciduous

canine is necessary consideration

should be given to balancing with the

extraction of the contralateral

tooth.

Deciduous first molar: unilateral loss of this tooth may result in a

centreline shift. In most cases an automatic balancing extraction is

not necessary, but the centreline should be kept under observation

and, if indicated, a tooth on the opposite side of the arch removed.

Deciduous second molar: if a second primary molar is extracted

the fi rst permanent molar will drift forwards ( Fig. 3.11 ).

In most cases balancing or compensating extractions

of other sound second primary molars is not necessary unless they

are also of poor long-term prognosis.

Us space maintainer

Balancing and compensating extractions

Balancing extraction is the removal of the contralateral tooth –

rationale is to avoid centreline shift problems

Compensating extraction is the removal of the equivalent

opposing tooth – rationale is to maintain occlusal relationships

between the arches

Retained deciduous teeth

retained primary teeth should be

extracted, particularly if they are causing

deflection of the permanent tooth

Infra-occluded (submerged)

primarymolarstooth fails to achieve or maintain its occlusal relationship with

adjacent or opposing teeth.

Resorption of deciduous teeth is not a continuous process. In fact,

resorption is interchanged with periods of repair, although in most cases

the former prevails. If a temporary predominance of repair occurs, this

can result in ankylosis and infra-occlusion of the affected primary molar.

Impacted first permanent molars

Impaction of a first permanent molar tooth against the second deciduous

molar occurs in approximately 2–6 per cent of children and is indicative

of crowding. It most commonly occurs in the upper arch

Dilaceration

Dilaceration is a distortion or bend in the root of a tooth. It usually

aff ects the upper central and/or lateral incisor.

Causd by : 1-Developmental – this anomaly usually affects an isolated

central incisor

and occurs more often in females than males. The crown of the

affected tooth is turned upward and labially and no disturbance of

enamel and dentine

2-Tauma

Dilaceration usually results in failure of eruption.

In milder cases it may be possible to expose the crown surgically

and apply traction to align the tooth, provided that the root apex will

be sited within cancellous bone at the completion of crown alignment.

Supernumerary teeth

Supplemental: this type resembles a tooth and occurs at the end of a

tooth series

Conical: the conical or peg-shaped supernumerary most often

occurs between the upper central incisors

Tuberculate: this type is described as being barrel-shaped, but usually

any supernumerary which does not fall into the conical or supplemental

categories is included. Classically, this type is associated

with failure of eruption

Odontome: this variant is rare. Both compound and complex forms

Effects of supernumerary teeth

between the central incisors they are often described as a mesiodens

A supernumerary tooth distal to the arch is called a distomolar

one adjacent to the molars is known as a paramolar

Failure of eruption

Displacement

Crowding

No effect

Habits

The effect of a habit will depend upon the

frequency and intensity of indulgence.

Check for the presence of all permanent teeth. If any are absent, extraction

of the first permanent molar in that quadrant should be avoided.

If the dentition is uncrowded, extraction of first permanent molars

should be avoided as space closure will be difficult.

in the maxilla there is a greater tendency for mesial

drift and so the timing of the extraction of upper fi rst permanent

molars is less critical if aiming for space closure.

If space is needed anteriorly for the relief of labial segment crowding

or for retraction of incisors, then it may be prudent to delay extraction

of the first molar, if possible, until the second permanent molar

has erupted in that arch. The space can then be utilized for correction

of the labial segment.

Extraction of the first molars alone will relieve buccal segment crowding,

but will have little effect on a crowded labial segment.

Serious consideration should be given to extracting the opposing

upper first permanent molar, should extraction of a lower molar be

necessary. If the upper molar is not extracted it will over-erupt and

prevent forward drift of the lower second molar

Median diastema 98% of Childrens

Aetiology

• physiological (normal dental development)

• small teeth in large jaws (a spaced dentition)

• missing teeth

• midline supernumerary tooth/teeth

• proclination of the upper labial segment

• prominent fraenum

In the developing dentition a diastema of less than 3 mm rarely warrants

Intervention BUT if more than 3 mm need management after eruption of

central incisor “and still have primary lateral “ … we can use fixed

appliance on two central to reduce the space btw them and create space to

facilitate the eruption of permanent laterals and canines

Serial extractionThe deciduous canines are extracted at the age of 8–9 years to create space for

proper alignment of incisors, followed by extraction of deciduous first molars a year

later so that the eruption of first premolars is accelerated and lastly extraction of the

erupting first premolars to give space for the alignment of permanent canines. In

some cases a modified technique is followed in which the first premolars are

enucleated at the time of extraction of the deciduous first molar.

Reference