normal development of the dentition by almuzian ok ok

UNIVERSITY OF GLASGOW

Normal Development of the Dentition

Mohammed Almuzian

1/1/2013

Normal Development of the Dentition

Chronology of development of the primary dentition, (Foster & Hamilton, 1969)

Teeth Crown Complete

(months)

Calcification

(weeks IU)

Eruption

(months)

A 1.5-3 13-15 6-9

B 1.5-3 13-15 6-9

D 6 14-17 12-15

C 9 15-18 18-20

E 10-11 16-23 21-35

Root development complete 1-1.5 years after tooth eruption

Mohammed Almuzian, University of Glasgow, 2014 Page 1

Chronology of development of the permanent teeth, (Foster & Hamilton, 1969)

Teeth Calcification

begins

(months)

Crown

Complete

(year)

Eruption

(year)

First molars Birth 2.3-3 6

Mandibular Central Incisors 3-4 4-56-7

Mandibular Lateral Incisors 3-4 4-5 7-8

Mandibular Canine 4-5 6-7 9-10

Mandibular First premolar 21-26 5-6 11-12

Mandibular Second

Premolar27-30 15-7 12-13

Second Molars 30-36 7-8 12-13

Third Molars 7-10 12-16 16-21

Root development complete 3 years after eruption

Teeth Calcification Crown Eruption

Mohammed Almuzian, University of Glasgow, 2014 Page 2

begins

(months)

Complete

(year)

(year)

First molars Birth 2.3-3 6

Maxillary Central Incisors 3-4 4-5 7-8

Maxillary Lateral Incisors 10-12 4-5 8-9

Maxillary Carnine 4-5 6-7 11-12

Maxillary First Premolar 15-21 5-6 10-11

Maxillary Second Premolar 24-27 6-7 11-12

Second Molars 30-36 7-8 12-13

Third Molars 7-10 12-16 16-21

Root development complete 3 years after eruption

Postnatal development of the dentition

According to Richardson 1999 he divided it into 5 stages

1. Edentulous stage

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2. Eruption of deciduous dentition (Early primary dentition)

3. Functional deciduous dentition (Full primary dentition)

4. Eruption of permanent dentition (Mixed dentition)

5. Functional permanent dentition (Full primary dentition)

Edentulous stage

At birth the usual findings with regard to the future dentition are maxillary and

mandibular gum pads, which are approximately without teeth for the first six months.

The gum pads are covered with a dense fibrous periostium and divided into segmental

elevations representing the teeth forming below. The maxillary gum pad is horse shoe

shaped and the palatal vault is almost flat, it is wider and longer than the underlying

mandibular U shaped gum pad. In both arches well developed grooves are noted distal

to the canine segments called lateral sulci. The alveolar processes are separated on the

palatal side by a horizontal groove known as the dental or gingival groove. The frenum

or the upper lip is attached to the crest of the gum pad and there is a fibrous continuum

to the incisive papilla.

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Abnormality during edentulous stage:

1. At birth there is considerable variation in the antero-posterior relationships of the

jaws but in general the mandibular gum pad lie distal to the maxillary, assessment is

difficult as temperomandibular joints are not fully formed yet. Any parental concern

regarding jaw relationships should be pacified as the neonatal position is no way

predictive of future relationship.

2. Occasionally on the alveolar mucosa small whitish nodules may appear, these are

gingival cysts of infancy, often called Epstein’s pearls or Bohn’s nodules. They are

about 2-3 mms in diametrer and contain keratin, they tend occur on the midline of the

palate and on the alveolar gum pads. Parents should not be concerned about gingival

cysts of infancy and should be reassured that they will spontaneously burst and resolve

within the first three months of life.

3. Occasionally natal teeth can form that are present in the mouth at birth

Parents may express concern or pride that their child has his first tooth and should be

reassured that management is only required if the problems occur. Natal teeth should

only be extracted if so loose they may be inhaled or causing nipple trauma during

breast feeding or soft tissue ulceration in the infants mouth. If the natal tooth is the

mandibular incisor and part of the primary dentition, its removal will have negligible

effects on the permanent dentition.

The deciduous dentition (ABDCE sequence)

At approximately six months, on the whole, the first tooth to erupt is the mandibular

central primary incisor. Prior to this tooth’s eruption and before any tooth eruption a

translucent bluish cyst may rarely appear, this is an eruption cyst; they most commonly

occur over primary molars and are formed by an accumulation of tissue fluid within the

dental follicle. Parents may voice concern, especially if it becomes enlarged and

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erythematous, the cyst may be painful to bite upon. The cyst may spontaneously burst on

eruption of the tooth, or it may be necessary to incise the cyst if it is painful.

Average ages for eruption of deciduous teeth have been calculated; generally they

erupt between 6 months and 2 years. However, all the deciduous teeth should be erupted

at 3 years.

The conventional orders of eruption are first incisors, lateral incisors, first molars,

canines and finally second molars. Mandibular teeth tend to erupt before maxillary

teeth.

There is no sex difference for primary tooth eruption dates and times can vary up to six

months.

Root formation is complete 12-18 months after eruption.

During eruption the alveolar bone becomes progressively more developed, there is a

small increase in vertical dimensions, antero-posterior and transverse dimensions as the

teeth progressively erupt, after eruption the arches change very little until eruption of

the permanent teeth.

An Ideal deciduous dentition

1. The arches are semi-circular in shape;

2. positive overjet and overbite;

3. The molar relationship is class I

4. The canine relationship is class I

5. Mesial step or flush terminal plane molar relationship.

6. Incisor spacing. Spacing is important in the incisor region.

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Parents expressing concern about spacing should be reassured that this feature is not

only developmentally correct but also important to accommodate the permanent teeth.

Leighton 1971 estimated that if there is no space in the incisor region there is a 70%

chance of crowding, if less than 3mm space a 50% chance of crowding and if there is

6mms or more there is little chance of crowding

7. Anthropoid (Primate) spaces. These spaces are located mesial to the maxillary canine

and distal to the mandibular canine, they are important for the accommodation of

permanent teeth and parents should be informed of this if concerned.

Functional deciduous dentition

1. Once the primary dentition is complete, between the ages of three and six two

changes occur, there is attrition (wear due to tooth to tooth contact) and erosion (wear

due to food and drinks abrasiveness on the tooth surface) which has the effect of

shortening the heights of the incisors and a forward movement of the mandible. The net

result is worn teeth that occlude edge to edge. Parents may be concerned about this but

should be reassured of its normality.

2. Occlusal changes take place between the ages of 3 - 6 yrs with an increase in

intercanine width with either incisor spacing developing or increasing

Does a normal deciduous dentition exist?

Foster and Hamilton studied the complete deciduous dentitions of 100 children aged 3

years. There was not a single child within this sample that had incisor spacing, primate

spaces, upright incisors and flush terminal molars all present within the same dentition.

Amongst these occlusal features, the presence of primate spaces was the most constant

finding. Approximately one-third of the sample had spacing between all the incisor

teeth, but the majority only had spacing between some of these teeth. Around half of the

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children had second deciduous molars that were flush in the terminal plane. The greatest

variation was seen in the incisor relationship, with only a fifth of children having a

normal overbite and almost three-quarters having some increase in the overjet

Can a future malocclusion be predicted from the deciduous dentition?

1. There is wide individual variation in occlusal development and predicting a

malocclusion in the permanent dentition based upon an established deciduous dentition

is difficult.

2. Unilateral crossbite, anterior open bite and an increased overjet associated with a

digit-sucking habit will usually spontaneously improve, if cessation of the habit occurs

before the mixed dentition is established.

3. However, in the absence of a digit-sucking habit, a markedly increased or reverse

overjet will give a fairly accurate prognosis for the incisor relationship in the permanent

dentition.

Little predictive information regarding the potential for crowding in the permanent

dentition is obtained from measuring the size of the deciduous teeth or the arch length.

However, alignment of the incisor dentition can give a good indication of the potential

for future crowding. If any incisor crowding exists in the deciduous dentition then this

almost certainly means there will be crowding of the permanent teeth. Leighton 1971

estimated that if there is no space in the incisor region there is a 70% chance of

crowding, if less than 3mm space a 50% chance of crowding and if there is 6mms or

more there is little chance of crowding.

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The permanent dentition

Mixed dentition to permanent dentition

The eruption sequence can be variable, however in the upper jaw the normal sequence

of eruption is 61243578. In the lower jaw 16234578. Considerable variation exists for

eruption dates and a variation of about 1 year.

First permanent molar eruption.

This tooth erupts without displacing a primary tooth and parents occasionally must be

reminded that this is a permanent tooth. The development of class I molars according to

Baume 1950 occurs by three methods

1. Primary dentitions with a mesial step: the

permanent molars erupt straight into a class I molar

relationship

2. Primary dentitions with a flush terminal step. In

this case, there will be two scenarios:

A. ‘’ early mechanism’’ In spaced dentitions with flush

terminal planes, eruption of the 1st molars pushes the

mandibular primary molars forward to occupy the

space of the primate space. A class I molar relationship is

created. The upper 6 cannot push the UE or UD into

primate space because it is mesial to C which is locked in by

the occlusion.

B. ‘’ late mechanism’’In primary dentitions with no spaces mesial movement of the

primary molars cannot occur and the permanent molars erupt in a ½ class II

relationship. The normal class I relationship is achieved when the primary molars are

shed and there is utilisation of the leeway space.

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Mandibular incisors

At approximately 6 years when the 1st incisors erupt, they essentially use up all the

spacing between the primary incisors, with the eruption of the lateral incisors at the age

of 7-8 years there is an average of 5 mm less space available than would be required to

perfectly align them. The deficit of space at this developmental stage is called the

incisor liability and results in crowding in the lower labial segment in children of the

age 8-9.

Parents should be reassured that this crowding will generally improve in a well

proportioned jaws and the temptation to extract to make space is to be avoided.

The extra space comes from three sources. Moorrees 1965

A slight width of the dental arch, increasing the intercanine width due to transverse

growth. This can contribute up to 1-2 mms of space.

Labial position of the permanent incisors that are more proclined than the deciduous

predecessors, the result is a larger arch circumference and about 1-2 mms of extra

space.

Repositioning of the canines into the primate space, this will occur in the mandibular

arch where the space is distal to the canine. If this occurs there is less space for mesial

movement of buccal segments later and may produce a buccal space deficit or a ½ class

II molar relationship.

Maxillary incisors

Maxillary incisors often erupt with a distal inclination and with a diastema between the

central incisors. This stage of development at about the age of 8–9 years is called the

ugly duck phase, so called because like the ugly duck the situation improves as the child

develops. The diastema is caused by pressure from the developing permanent canines,

pushing on the lateral incisor roots. Parents should be reassured that this situation

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generally self corrects. Edwards 1977 suggested as a guideline that a diastema greater

than 2mms is unlikely to fully close.

As in the mandibular arch there is an increase in intercanine width due to transverse

growth and the permanent incisors are more proclined and erupt in a more labial

position, thereby increasing the arch perimeter and space for tooth alignment.

Canines and premolars

Favourable development of these teeth depends upon the following.

Favourable eruption sequence.

Good tooth arch size ratio.

Attainment of a class I molar relationship with minimal loss of space for canines.

A favourable transverse relationship between the maxillary and mandibular alveolar

processes.

The differing size between the primary molars and the premolars

Unlike the anterior teeth the permanent premolars are smaller than the primary teeth

they replace. This extra space known as the leeway space.

The sequence of eruption is variable. In the lower buccal segment the first tooth to erupt

is either the lower 1st premolar, or canine. The lower 2nd premolar usually erupts next

but occasionally this erupts after the 2nd permanent molar. In the maxillary buccal

segments the 1st premolar erupts first followed by the canine and 2nd premolar.

The maxillary canine has the longest eruption pathway and potentially has more

eruptive problems associated with it; Ericson and Kurol recommend annual inspection

and palpation of maxillary canines from the age of 8 years, in order to intercept if

necessary.

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Buccal teeth tend to erupt earlier if the deciduous molars are removed earlier, providing

space loss is not so great to have caused an impaction.

Second and third molars

The 2nd molars erupt usually between 12-14 years and the third molar eruption is highly

variable but is quoted to erupt between 16-20 years.

Summary

1. The lower incisors erupt before the upper teeth and lingual to their predecessors.

2. The collective mesiodistal dimensions of the permanent incisor tooth crowns are

larger than their deciduous predecessors by approximately 5-mm in the mandible and

7-mm in the maxilla, a deficit known as the incisor liability. This increased space

requirement for the permanent incisor teeth is gained from the following:

• Spacing present between the deciduous incisors;

• Labial eruption (particularly in the maxilla) than their deciduous predecessors and

therefore occupying a greater arch perimeter;

• Primate space

• Part of Lee way space;

• Transverse increase in the intercanine arch width.

3. It is common for the upper incisors to be distally inclined and a midline maxillary

diastema to be present. This stage of development used to be described as the 'ugly

ducking' or 'Broadbent' stage and should be considered as normal

4. A transient anterior open bite can be associated with eruption of the incisors as

they approach the occlusal plane and this invariably improves with time.

5. The first permanent molars should be guided into occlusion by the distal surfaces

of the second deciduous molars. If these surfaces are flush as previously described the

teeth should come into a cusp-to-cusp relationship, which is normal for the mixed

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dentition. So they are in half unit class II. The transition to the stepped Class I molar

relationship occurs during the mixed dentition as a result of

• differential mandibular growth

• or the leeway space produced by the replacement of the deciduous molars by the

premolars

• or by the use of primate space.

6. The upper canines develop palatally, but migrate buccally to lie slightly labial and

distal to the root apex of the lateral incisors. In normal development they can be

palpated buccally from as young as 8 years of age in some children

7. For the first and second premolars, there is extra space when thy replace their

predecessors which called Lee way space (2mm in the LA and 1.5mm in the UA). This

space helps to allow correction of molar relationship and to provide space for canine

and incisor alignment. However, successful alignment of the canine and premolar teeth

within each quadrant relies upon a number of factors:

• The size of the leeway space;

• Previous encroachment by the incisors into the canine region;

• The mechanism of molar relationship correction.

8. The second permanent molars should be guided directly into the correct

relationship by the distal aspect of the first permanent molars. The third molars should

follow the same pattern but space is often not available leading to impaction

Full permanent dentition

1. In the full dentition the upper buccal segments are tilted slightly outwards and the

lower buccal segments slightly lingually (curve of Monson).

2. The occlusal plane has a distinct upward curve anteriorly (curve of Spee).

3. The maxillary teeth are half a cusp to the buccal of the mandibular teeth and the

mesiobuccal cusp of the upper first permanent molar occlude with the anterior buccal

groove of the lower first permanent molar.

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4. The upper canine occludes in the embrasure between the lower permanent canine

and the first premolar.

5. The lower incisors should occlude with the cingulum plateau of the upper incisors

6. The overbite is about a third of the height of the lower incisor crowns

7. The overjet is approximately 2mm.

Growth changes

A. Arch width

1. The arch width at intercanine increased after eruption of primary teeth (1-2mm)

followed by a period of little changes then another increase during mixed dentition

(3mm) followed by small increase in intercanine width during permanent dentition.

1. Growth posteriorly provides space for the permanent molars, and considerable

appositional vertical growth occurs to maintain the relationship of the arches during

vertical facial growth.

2. However regarding the arch width measured at intermolar are, between the ages

of 3 and 18 years an increase of 2 in LA and 4 in UA mm takes place but for clinical

purposes arch width is largely established by the late mixed dentition.

B. Arch circumference

1. It 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.

2. There is little change in the maxillary arch with growth

3. The mandibular circumference decreases by about 4mm because of the leeway space. In

individuals with crowded mouths a greater reduction may be seen.

4. Late changes in the dentition with growth - Apart from third molar development the

most noticeable change is an increase in crowding between the ages of 15 - 20 years.

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This is most noticeable in the lower incisors possibly as a result of a change in

interincisal angle under the influence of soft tissue maturation and differential growth of

the mandible and maxilla with a tendency to prognathism and forward mandibular

rotation. The other factors often discussed in relation to late lower incisor crowding is

mesial drift of buccal teeth and the eruption of third molars

Changes in the permanent dentition into adulthood

Slight increase in mandibular prognathism.

Late lower incisor crowding.

Overbite tends to reduce with age.

Increase in interincisal angle and uprighting of incisors.

Understanding the causes of late lower incisor crowding

Crowding of the mandibular incisors is one of the most common problems encountered

in the permanent dentition and lower incisor alignment is one of the most likely things

to relapse after orthodontic treatment. Richardson, 2000:

1. Primary crowding refers to a discrepancy of tooth dimension and jaw size, mainly

determined genetically.

2. Secondary crowding is caused by environmental factors, including local space

conditions in the dental arches and the position and function of the tongue, the lips and

the buccal musculature.

3. Tertiary crowding occurs during adolescence and post-adolescence with a

predilection for the lower labial segment.

4. Factors contributing to late lower incisor crowding may include:

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Mandibular growth rotations;

Anterior component of occlusal force;

Degenerative periodontal changes allowing teeth to drift under light pressures;

Change in diet and lack of interproximal wear;

Soft tissue maturation;

Mandibular third molars–presence and position.

Mutual protection is thought to be achieved in the presence of:

a. ICP (or centric occlusion, CO) coincident with the retruded contact position

(RCP) (or centric relation, CR) but with some limited freedom for the mandible to move

slightly forwards in the sagittal and horizontal planes from ICP.

b. An immediate and permanent posterior dis-occlusion in lateral and protrusive

contact with no associated non-working side interferences (tooth contacts); this is

achieved by the presence of canine guidance or group function in lateral excursion and

incisal guidance in protrusion. Thus, the anterior teeth protect the posteriors;

c. Multiple, simultaneous and bilateral contacts of the posterior teeth in intercuspal

position (ICP) with the incisor teeth slightly out of contact; thus, the posterior teeth

protect the anterior.

Functional Occlusal Goals

1. CO = CR

2. Anterior guidance & gently posterior disclusion

3. Canine guidance, minimal posterior disclusion

4. Cusp/ embrasure buccally

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5. Cusp/fossa lingually

6. Posterior forces along LA

7. Lower 4s contact 3s in protrusion

8. Absence of non-working contact

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