This document summarizes the 4 stages of dental development: gum pad, primary dentition, mixed dentition, and permanent dentition. It describes normal sequences of eruption and development as well as some abnormalities that can occur such as natal teeth, eruption cysts, delayed or failed eruption, premature loss of primary teeth, retained primary teeth, impacted permanent molars, dilaceration, supernumerary teeth, and habits affecting development. It provides guidance on management of space issues and timing of extractions in the mixed dentition to facilitate proper alignment of permanent teeth.

1. Ch 3 orthodontics
Management of
the developing
dentition
By : Cezar Edward

2. 4 developing stages
 1-Gum Pad Stage
 2-Primary Dentition stage
 3-Mixed Dentition stage
 4-Prmanent Dentition stage

3. Normal dental development

6. 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.

7. 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.

8. 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.

9. 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.

10. Abnormalities of eruption and
exfoliation
Screening
careful observation of the developing dentition
for evidence of any problems, for example deviations from the
normal sequence of eruption.
Natal teeth
most 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

11. 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.

12. Failure of/delayed eruption
Signs
• A disruption in the normal sequence of eruption.
• An asymmetry in eruption pattern between contralateral teeth

13. 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.

14. 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

15. 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

16. Retained deciduous teeth
retained primary teeth should be
extracted, particularly if they are causing
deflection of the permanent tooth

17. Infra-occluded (submerged)
primarymolars
tooth 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.

18. 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.

19. 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

20. 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

21. Habits
The effect of a habit will depend upon the
frequency and intensity of indulgence.

22. 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.

23. 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

24. 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

25. 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.

26. Reference