SHEDDING OF THE DECIDUOUS
Presented by: Hossam Abd el-Mohsen El- saidy
CAUSES OF Shedding
Histology of shedding
Mechanism of shedding
Resorbtion pattern of the anterior teeth
Resorption pattern of posterior teeth
Pattern of shedding
• HUMANS LIKE MOST MAMMALS ARE DIPHYODONT, HAVE TWO SETS OF TEETH
DECIDUOUS AND PERMENANAT.
• DECIDUOUS teeth are the temporary first teeth of young that fall of to be replaced by the
Because teeth can not increase in size so at first it’s small in size and number to fit the small
jaws of infants .
• The process of turning from deciduous into permanent is know as shedding .
Shedding: is the exfoliation of the deciduous teeth as a result of physiologic resorbtion of
their roots prior to clinical eruption of the permanent successors.
• Loss of root ; due to present of osteoclasts which results in resorption of the
deciduous roots and loss of attachment fibers of PDL.
• Loss of bone ; due to weaken of the supporting tissues of the deciduous teeth
cause of root loss and facial growth of the alveolar bone.
• Increase masticatory forces ; due to muscular growth.
• Odntoclasts (dental osteoclasts ) originate from circulating blood monocytes ,
generally large and multinucleated cells that appear in cup shaped depression of
the resorbing hard tissue called “howship’s lacunae”.
• Light microscope : appears as large cell containing 6 to 12 nuclei , vacuolated
cytoplasm and striated (brush like) border close to resorbing hard tissue.
• Electron microscope :
cell membrane ruffled borders consist of deep invaginations forming numerous
intermingled villus-like processes which differ in diameter along
the course of individual villi .
cytoplasm in the ruffled borders almost devoid of organelles.
peripheral to the ruffled borders devoid of organelles but
rich in contractile filaments (actin & myosin ) forming a
clear zone (for odontoclasts attachment).
between the ruffled borders and nuclei is extremely rich in
Mitochondria , and Golgi apparatus SURROUNDED BY
rounded electron dense granules with central core which
is surrounded by a pale halo , too.
nuclei young : ovoid , pale and with smooth membrane.
old : pyknotic , dark and wrinkled outlines.
• Odontoclasts are able to resorb all hard dental tissue including enamel.
• The process of shedding is not continuous (resorption periods and rest periods)
• It seems that the pressure of successional tooth plays an important role CUZ.
Odontoclasts appear at sites of pressure
• In case of bone osteoclasts play a key-role by secreting MMPs .
• There is an evidence that MMPs are also secreted to remove cementoid tissue which
is the first to be removed .
• Current info. Say that it happens in two phases
1. Extracellular phase :
minerals is separated from collagen , happens at the
ruffled borders by secreting citric and lactic acids .
2. Intracellular phase :
uptake of free crystals within the cell , digestion by
acid phosphatase enzyme , the organic matrix is also
Little is knows about soft tissue resorption however macrophages and fibroblasts
seem to be implicated in the process.
• It begins at 4 to 5 years for incisors and at 6 to 8 years for canines , at this times the
crowns of permanents are completed and situated in their own crypts
• Pressure first is directed to the bone to separate the crypt and the alveoli then to
the deciduous roots , after the permanent crown lies directly apical to the deciduous
root resorption take a horizontal direction.
Sometimes for mandibular incisors the labial movement of permanent teeth does
not cause complete loss of deciduous teeth so they appear lingual to the deciduous
• The premolars crown are located between the deciduous roots it takes the usual
sequence first the supporting bone then to the roots .
• Shedding is 80% genetically determined .
• Pattern of exfoliation is symmetrical for right and left sides , except for second
• The mandibular teeth shed before their maxillary counter .
• The sequence of shedding in mandible follows the anterior to posterior order of the
• In maxilla the first molar exfoliate before the canine.
• Exfoliation occurs in girls before boys.
I. Retained deciduous tooth :
absence or impaction of the permanent teeth
most often in the upper lateral incisors then
the second molars and the least one are
the lower central incisors.
It remain in function for many years till they lost by resorption and heavy
• Due to ankylosis teeth are prevented from active eruption .
• It leads to inclination of the adjacent teeth .
• It should be removed as soon as possible specially when the permanent tooth is
• Parts of the deciduous roots escaped from resorption .
• they remain embedded in jaw mainly found in the region of the lower second
• they may exfoliate if are near to the surface or undergo resorption and be replaced
• Appear in the oral cavity of the new porn mainly on mandible .
• The fall of during the early weeks if not they should be removed to prevent
discomfort to both mother and baby in breast feeding .
• It does not affect the deciduous teeth .
• It may happen that they will not be replaced till the permanent come out .