Question

The growth and development of the face and occlusion from infancy to adolescence.


Q1/H1 Describe the features of the pre-dental period and the various
developmental abnormalities that may be seen in this period.
Q2/H2 Describe the transition from the mixed dentition to the permanent
dentition phase and the variations that may occur.
Q3/H3
Using five examples of self-correcting malocclusions present during the
development of the occlusion, describe the mechanisms of how each of
these takes place.
Q4/H4 Explain how the sequence of eruption of the permanent dentition plays a
role in the establishment of a normal occlusion.

Answer 1

Ans - predentate period.

Is the period soon after birth. There are gum pads and no teeth . The alveolar process at time of birth is called gum pads . The gum pads are horse shaped , pink . It is diviede into two parts labiobuccal and lingual by the dental groove . It is further divided into 10 segments by transcerse groove and each segment will have onw developing tooth sac. A lateral sulcus is seen between canine and 1st molar.

The various self forrecting anomalies in predentate period are-

1- retrognathic mandible

2- anterior open bite

3-infantile swallow .

2- transition from mixed dentition to permanent dentition occurs at 6 years of age and continues upto 12 years of age.

* First transitional period.

Eruption of 1st permanent molars occur at around 6 years of age ,guided by distal surface of primary second molar.  

So when 2nd deciduous molar is in flush terminal plane ,the permanent molars will also be in in flush terminal plane . For a cpass 1 relation to occyr the molar has to move 2-3 mm in anterior or mesial direction .

So , Early mesial shift- the eruptive forces of M1 permanent push the deciduous molars anteriorly in the arch and utilise the primate space to establish class 1 relation.

Late mesial shift- in children lacking primate space in deciduous dentition where earky mesial shift cannit occur . The molars establish class 1 relation by drifting mesially and utilising the leeway space after exfoliation of 2nd deciduous molar .

If second deciduous molar is is mesial step then permanent molar will be in class 1.

If 2nd deciduous molar is in distal step then permanent molar will be in class 2.

Exchange of incisors.

Deciduous incisors are reppaced by permanent incisors in this phase. Occurs between 6 and a half to 8and a half years of age.

Now incisor liability - it is the difference in space available and space required for permanent incisors to erupt is called incisor liability.

The space available is lesser than the space required as deciduous incisors are smaller in size than permanent.

The incisor liability will be 7mm for upper arch and 5 mm for lower arch .

Now how permanent incisors gain space in the arch-

1- by utilising interdental space of primary incisors

2- increase in intercanine arch width - occurs as the child grows ,in males 6mm - maxilla and 4mm - mandible and 4.5mm maxilla in females and 4mm in mandible.

Increase in intercanine arch length - due to growth of jaws .

Change in interincisal angle- the angle between upper and lower deciduous incisors is 150 degrees whereas the same is 123 degrees in permanent dentition.

*Intertransitional period-

The arches consisists if permanent incisors and permanent molars and deciduous canines and molars.

*Second transitional period .

1- replacement of deciduous molars and canine .

Leeway space of nance- combined mesiodistal width of permanent canine and premolars is less than that of deciduous canine and molars . So the extra space is leeway space of nance. It is utilised by mandibular molars to establush class 1 relationship through late mesial shift .

E- space - dimensions of deciduous 2nd molar is more than that of 2nd premolars ,this excess available space is called E- space.

2-Eruption of maxillary lateral incusors and canines ,creating the ugly duckling stage at around 8-11 years . When maxillary canines erupt they displace roots of maxillary lateral incisors and central incisors mesially . This causes midline spacing or diastema. This is ugly duckling stage.

This is forrected when canines fully erupt after eruotion the canines apply pressure on crowns of incisors and this cayses them to shift to original position.

Please post the rest of the questions individually . The answers are too long . Hope this helps. If it does please rate it positive.