Physiologic Tooth Movement: Eruption and Shedding

TOOTH ERUPTION

The jaws of an infant can only accommodate a few small teeth. Since teeth, once formed

cannot increase in size, the larger jaws of an adult require not only more but bigger teeth. This

accommodation is accomplished in humans by having two dentitions. The first is known as the

deciduous teeth (primary teeth), and the second is the permanent teeth (secondary teeth).

The early development of teeth develops within the tissues of the jaw thus for teeth to

become functional, considerable movement is required to bring them into the occlusal plane.

The movements teeth make are complex and may be described as:

1. Preeruptive tooth movement. Made by deciduous and permanent tooth germs within

tissues of the jaw before they begin to erupt

2. Eruptive tooth movement. Made by a tooth to move from its position within the bone

of the jaw to its functional position in the occlusion

3. Posteruptive tooth movement. Maintaining the osition of the erupted tooth in

occlusion while the jaw continues to grow and compensate for occlusal and proximal

tooth wear.

TOOTH MOVEMENT

I. Preeruptive Tooth Movement

When the deciduous tooth germs first differentiate, they are extremely small and

there is a good deal of space for them in the developing jaw. Because they grow rapidly,

however, they become crowded together. The crowding Is gradually alleviated by a lengthening

of the jaws which permits the deciduous second molar tooth germs to move backward and

anterior germs to move forward. At the same time the tooth germs are moving bodily outward

and upward with the increasing length as well as width and height of the jaws.

The origin of the successional permanent teeth develops on the lingual aspect of

their deciduoud predecessors, in the same bony crypt. From this position they shift considerably

as the jaws develop. The successional anterior teeth eventually come to occupy on the lingual

of the roots of their deciduous teeth and the posterior premolar tooth gers are finally positioned

between the divergent roots of the deciduous molars.

The permanent molar tooth germs without predecessors develop from the backward

extension of the dental lamina. At first there is a litter room in the jaws to accommodate these

tooth germs so that in the upper jaw the molar tooth germs develop first with their oclusal

surfaces facing distally and swinginto position only when the maxilla has grown sufficiently to

provide room for such movement. It is almost the same with the permanent molars in the

mandible but instead of a distal inclination, there is a mesial inclination prior to the development

of the jaw.

Analysis has shown that these preeruptive movement of teeth are a combination of

two factors: total bodily movement and growth in which one part of the tooth germ remains fixed

while the rest continues to grow.

II. Eruptive Tooth Movement

During the phase of eruptive tooth movement the tooth moves from its position within

the bone of the jaw to its functional position in occlusion, and the principal direction of

movement is occlusal or axial.The mechanisms of eruption for deciduous and permanent teeth

are similar, resulting in axial or occlusal movement of the tooth from its developmental position

within the jaw to its final functional position in the occlusal plane.

A. Eruptive Phase (Prefunctional Phase)

Begins when the root starts to form and ends when the tooth reaches the occlusal

plane. The PDL develops only after root formation has been initiated; once established, the PDL

must be remodeled to accommodate continued eruptive tooth movement. Tooth germ

undergoes intraosseous stage and supraosseous stage.During the intraosseous stage, the

tooth moves out of its bony crypt to pierce the gingival. During the supraosseous stage, the

tooth moves into its final occlusal plane.

A specialized feature associated with the erupting permanent tooth is the presence

of a gubernacular canal. This canal occurs where the roof of the alveolar crypt of the permanent

tooth is not complete. The canal enables the dental follicle of the tooth germ to communicate

with, and be attached to, the overlying oral mucosa. The gubernacular canal contains the

gubernacular cord, composed of a central strand of epithelium derived from dental lamina. As

the successional tooth erupts, its gubernacular canal is widened rapidly by local osteoclastic

activity, delineating the eruptive pathway for the tooth.

Reduced enamel epithelium unites with the oral epithelium. It will migrate occlusally

or incisally until surface is reached, preventing the gingiva to bleed during the crown eruption.

The crown breaks the double layer epithelium overlying it and enters the oral cavity.

The rate of eruption depends on the phase of movement.When the erupting tooth

appears in the oral cavity, it is subjected to environmental factors that help determine its final

position in the dental arch. Muscle forces from the tongue, cheeks and lips play on the tooth, as

do the forces of contact of the erupting tooth with other erupted teeth. A sustained muscular

force of only 4 to 5 grams is sufficient to move a tooth. The childhood habit of thumb-sucking is

an obvious example of environmental destruction of tooth position.

B. Functional Phase

- Begins when the tooth reaches the occlusal plane and continues its functions as

long as the tooth remains in the oral cavity. As the teeth meet their antagonists, the bone is

stimulated and the periodontal ligament strengthens. There is a continuous vertical eruption

mesially and occlusally but the process may decrease because it is supposed by their

antagonist teeth.

-

Mechanisms of Tooth Movement Currently Favored

These mechanisms are still debatable and are likely to be a combination of a

number of factors. Eruptive mechanisms are not understood fully yet, and most reviews on this

subject have concluded that eruption is a multifactorial process in which cause and effect are

difficult to separate.

1. Root Formation

The root growth theory supposes that the proliferating root impinges on a fixed

case, thus converting an apically directed force of the tooth into occlusal movement. Root

formation should be an obvious cause of tooth eruption because it causes an overall increase in

the length of the tooth. But it produces enough forces that lead to the resorption of the bone.

Rootless tooth still erupts. Some teeth erupt more than the total length of the roots. And the

teeth still erupt after the complete formation of the root. Therefore root formation is

accommodated during tooth eruption and is a consequence, not a cause, of the eruption

process.

Hammock Ligament Theory

According to Sicher, a band of fibrous tissue exists below the root apex spanning

from one side of alveolar wall to another. This fibrous tissue appears to form a network below

the developing root and is rich in fluid droplets. The developing root forces itself against this

band of tissue, which in turn applies an oclusally directed force on tooth.

2. Bone Remodeling

Bone remodeling theory supposes that selective formation and resorption of

bone brings about eruption.The bone at the base of the socket cannot act as a fixed base

because pressure on bone results in its resorption.

3. Periodontal Ligament

The ligament traction theory supposes that cells and fibers of the ligament push

the tooth into occlusion.PDL is rich in fibroblasts that contain contractile tissue. The contraction

of these PDL fibers mainly the oblique group of fibers result in axial movement of the teeth.

4. Vascular Pressure

The vascular pressure theory supposes that a local increase in tissue fluid

pressure in the periapical region is sufficient to move the tooth.The tissue around the developing

end of the root is highly vascular. This vascular pressure is believed to cause the axial

movement of the teeth.It is known that teeth move in synchrony with the arterial pulse, so local

volume changes can produce limited tooth movement.

III. Post Eruptive phase

Posteruptive tooth movements are those made by the tooth after it ahs reached

its functional position in the occlusal plane. It includes three categories: (1) movements to

accommodate the growing jaws, (2) those to compensate for continued occlusal wear, (3) those

to accommodate interproximal wear.

1. Accommodation of Growth

Accommodating the growth of the jaws are completed toward the end of the

second decade, when jaw growth ceases. Readjustment of the position of the tooth socket is

achieved by the formation of new bone at the alveolar crest and on the socket floor to keep

pace with the increasing height of the jaws. This readjustment usually occurs between the ages

14 to 18 years, when active movement of the tooth takes place. The apices of the teeth move 2

to 3 mm away from the inferior dental canal. This occurs earlier in girls than in boys and is

related to the bust of the condylar growth that separates the jaws and the teeth.

2. Compensation for Occlusal Wear

This is achieved by the continued cementum deposition around the apex of the

tooth; however, the deposition of cementum in this location occurs only after the tooth has

moved. This emphasizes the role of the periodontal ligament. Axial movement that a tooth

makes in most likely achieved by the same mechanism as eruptive tooth movement.

3. Accomodation for Interproximal Wear

Wear also occurs at the contact points between teeth, on their proximal surfaces

and its extent can be considerable (more than 7 mm in the mandible). Mesial or approximal

drifting compensates for the interproximal wear.

This is important in the practice of Orthodontics because the maintenance of

tooth position after treatment depends on the extent of such drift. Mesial drift is multifactorial

and include: (A) anterior component of occlusal force, (B) contraction of the transseptal ligament

between teeth and (C) soft tissue pressure.

A. Anterior component of occlusal force

When teeth are brought into contact, like during clenching of the jaws, and

anteriorly directed force is generated.It is the result of the mesial inclination of most teeth and

the summation of intercuspal planes.When cusps are selectively ground, the direction of

occlusal force can be enhanced or reversed

When opposing teeth were removed, thereby eliminating the biting force, the

mesial migration of the teeth was slowed but not halted.

B. Contraction of the Transseptal Ligament between Teeth

The Peridontal ligament plays an important role in maintaining tooth position.

Transseptial fibers draw neighboring teeth together and mainten them in contact; there are also

capable of adaptation.For example, relapse of orthodontically removed teeth is reduced if a

gingivectomy removing the transseptal ligament is performed.

*Grinding away of proximal contacts provides room for a tooth to move, after which teeth move

to reestablish contact.

C. Soft Tissue Pressures

The pressures generated by the cheeks and tongue may push teeth mesially.Soft

tissue pressure does influence tooth position even if it does not cause tooth movement. It does

not play a major role in creating mesial drift.

CAUSES OF TOOTH ERUPTION (THEORIES)

1. Growth of Root

Root formation undoubtfully causes an overall increase in the length of the tooth that

must be accommodated by the growth of the root into the bone of the jaw, by an increase in jaw

height or by the occlusal movement of the crown. Root growth produces a force that is

sufficient to produce bone resorption. Pressure applied to bone normally result in the removal

of osteoclasts. Though root formation can produce a force, it cannot translate into eruptive

tooth movement unless some structure exists at the base of the tooth capable of withstanding

this force. Since this structure does not exist, some other mechanisms must move the tooth to

accommodate root growth.

The Root Growth theory supposes the proliferating root impinges on a fixed case thus

converting an apically directed force into occlusal movement. Some facts proving this statement

include the fact that rootless teeth erupt, that some teeth erupt a greater distance than the total

length of their roots and the teeth still will erupt after the completion of root formation or when

the tissue forming the root are removed surgically.

Root growth is not required but it may accelerate tooth eruption. Depending on the rte at

which the root elongates, the basal bone will resorb or form to maintain a proper relationship

between the root and bone.

2. Vascular Pressure

Vascular Pressure and blood vessel thrust. It is known that the teeth move in their

sockets in synchrony with the arterial pulse, so local volume changes can produce limited tooth

movement. Furthermore, spontaneous changes in blood pressure have been shown to influence

eruptive behavior. Ground substance can swell from 30% to 50% by retaining additional water,

so this to could create pressure. But since surgical excision of the growing root and associated

tissues eliminates the periapical vasculature without stopping eruption, this means that the local

vessels are not absolutely necessary for tooth eruption.

The Vascular Pressure theory supposes that a local increase of in tissue fluid pressure

in the periapical region is sufficient to move the tooth.

3. Bone Remodeling (Apposition and Resorption of bone)

Bone Remodeling is important to permit tooth movmement. If the tooth germ is removed

and the dental follicle left intact, an eruptive pathway forms in the overlying bone. If Silicone

Replica is substituted for the tooth germ, it also erupts. But, if the dental follicle is removed, no

eruptive pathway will form.

The follicle provides the source for new bone-forming cells and the conduit for

osteoclasts derived from monocytes through the vascular supply. Control may reside with the

bone-lining cells, the osteoblasts. These cells secrete collagenase and other proteolytic

enzymes to remove the osteoid layer. In so doing these cells round up and expose the newly

denuded mineralized bone surface, providing the stimulus to attract osteoclasts to the site.

4. Periodontal Ligament Traction

Periodontal Ligament Traction. Eruptive force resides in the dental follicle-periodontal

ligament complex. Formation and renewal of the PDL has been considered a factor in tooth

eruption because of the traction power that fibroblasts have and because of the experimental

results using the continuously erupting rat incisor.

Periodontal Ligament Traction. Eruptive force resides in the dental follicle-periodontal

ligament complex. Formation and renewal of the PDL has been considered a factor in tooth

eruption because of the traction power that fibroblasts have and because of the experimental

results using the continuously erupting rat incisor.

5. Control of Endocrine Glands

6. Pressure from muscular action

7. Effect of Nutrition

8. Inherent tendency of teeth to erupt

SEQUENCE AND CHRONOLOGY OF TOOTH ERUPTION

Humans have two sets of teeth in their lifetime. The first set of teeth to be seen in the

mouth is the primary or deciduous dentition which will remain intact until the child is about 6

years of age. At about that time the first permanent or succedaneous teeth begin to emerge into

the mouth. The emergence of these teeth begins the transition or mixed dentition period in

which there is a mixture of deciduous and succedaneous teeth present. The transition period

lasts from about 6 to 12 years of age and ends when all deciduous teeth have been shed. At

that time, the permanent dentition period begins.

Usually at birth, no teeth are visible in the mouth; however, occasionally, infants are born

with erupted mandibular incisors. The development of both primary and permanent teeth

continues in this period and jaw growth follows for the needed additional space for posterior

teeth. Alveolar bone height also increases, accommodating the increasing length of the teeth.

Primary teeth emerge in children between the ages of 6 moths and 2 years. They play a

role in “reserving” space for the permanent teeth. At about 6 months of age, the mandibular

central incisors emerge through the alveolar gingival followed by other anterior teeth. By about

13 to 16 months, all the eight primary incisors have erupted. The first primary molars emerge by

about 16 months of age. By about 19 months the primary maxillary canines erupt while the

primary mandibular canines erupt at 20 months. The primary second mandibular molar erupts at

a mean of age 27 months and primary maxillary second molar follows at a mean age of 29

months. The primary dentition is considered to be completed by about 30 months when the

second primary molars are in occlusion.

TABLE 1.1 Chronology of Primary TeethDENTITIO TOOTH FIRST EVIDENCE CROWN ERUPTION ERUPTION ROOT

N

OF CALCIFICATION

(WEEKS IN UTERO)

COMPLETED (MONTHS)

(MONTHS) SEQUENCECOMPLETED

(YEARS)

Primary (upper)

Central incisor

14 1.5 7.5 3 1.5

Lateral Incisor 16 2.5 9 4 2Canine 17 9 18 8 3.25

First Molar 12.5 - 15.5 6 14 6 2.5Second Molar 12.5 - 19 11 24 10 3

Primary (lower)

Central incisor

18 2.5 6 1 1.5

Lateral Incisor 18 3 7 2 1.5Canine 20 9 16 7 3.25

First Molar 12 - 15.5 5.5 12 5 2.25Second Molar 12.5 - 18 10 20 9 3

The transition or mixed dentition period begins with the emergence and eruption of the

mandibular first permanent molar and ends with the loss of the last primary tooth which usually

occurs at 11 to 12 years of age. The initial phase of transition period lasts about 2 years, during

which time the permanent first molars erupt, the primary incisors are shed, and the permanent

incisors emerge and erupt into position.

Permanent dentition consists of 32 teeth and is completed 18 to 25 years of age. At 6

years of age, the first molars emerge in the oral cavity followed by the central incisor at 6 to 8

years of age. Mandibular lateral incisor erupts at about 1 year later or soon after the central

incisors. When the child is about 10 years old, the first premolars and the mandibular canines

erupt. Second premolars follow during the next year then the maxillary canines. Usually second

molars come in when the individual is 12 years of age. Third molars do not come until the age of

17 or later. Considerable posterior jaw growth is required after the age of 12 to allow room for

these teeth.

TABLE 1.2 Chronology of Permanent TeethDENTITIO TOOTH FIRST CROWN ERUPTIO ERUPTION ROOT

N

EVIDENCE OF CALCIFICATION (WEEKS IN

UTERO)

COMPLETED (MONTHS)

N (YEARS)

SEQUENCE

COMPLETED (YEARS)

Permanent (upper)

Central incisor 3 - 4 4 - 5 7 - 8 5 10

  Lateral Incisor 10 - 12 4 - 5 8 - 9 6 11  Canine 4 - 5 6 - 7 11 - 12 8 13 - 15  First Premolar 1.5 - 1.75 5 - 6 10 - 11 9 12 - 13

 Second

Premolar2 - 2.25 6 - 7 10 - 12 11 12 - 14

  First Molar At birth 2.5 - 3 6 - 7 3 9 - 10  Second Molar 2.5 - 3 7 -8 12 - 13 13 14 - 16  Third Molar 7 - 9 12 - 16 17 - 21 16 18 - 25

Permanent (lower)

Central incisor 3 - 4 4 - 5 6 - 7 1 9

  Lateral Incisor 3 - 4 4 - 5 7 - 8 4 10  Canine 4 - 5 6 - 7 9 - 10 7 12 - 14  First Premolar 1.75 - 2 5 - 6 10 - 12 10 12 - 13

 Second

Premolar2.25 - 2.5 6 - 7 11 - 12 12 13 - 14

  First Molar At birth 2.5 - 3 6 - 7 2 9 - 10  Second Molar 2.5 - 3 7 - 8 11 - 13 14 14 - 15  Third Molar 8 - 10 12 - 16 17 - 21 15 18 - 25

SHEDDING OR EXFOLIATION

Shedding or Exfoliation is the physiologic process resulting in the elimination of the

deciduous dentition. It is the result of the gradual resorption of their roots and the consequent

loss of periodontal ligament attached. Resorptions and shedding occurs to enable eruption of

permanent tooth (excluding the permanent molars

To understand the process of shedding or exfoliation of deciduous teeth, we must first

remember that we have two sets of dentition. Mammals are described as being diphydont, with

two successive sets of teeth, first the "deciduous" set and later the "permanent" set. Our

deciduous teeth, or our primary teeth consist of 20 teeth, and is later replaced by our 32

permanent teeth.

The fewer deciduous teeth have importance by:

Help provide nutrition

Help make speech possible

Aid in the normal development of the jaw bones and facial muscles

Add to an attractive appearance

Reserve space for the permanent teeth and help guide them into position

Because the jaw is smaller in younger people, the 20 deciduous teeth accommodate the

space, but as the person grows, so does the jaw, allowing for the additional 12 teeth in the

permanent set. Teeth in the permanent dentition are also larger to accommodate the larger jaw.

The replacement of the deciduous teeth with its permanent successor is known as

shedding or exfoliation. Shedding is the physiological process that permanent teeth influence

resorption until elimination of deciduous teeth. Resorption of the tooth is the breakdown of hard

tissue and its release of its minerals. This resorption is achieved by cells with a histologic

nature similar to osteoclasts called odontoclasts. Odontoclasts derive from the monocyte and

migrate from blood vessels to the resorption site, where they fuse to form the characteristic

multinucleated odontoclast with a clear attachment zone and ruffled border.

Less is known about the resorption of the soft tissues of the tooth as it sheds. Although

active root resorption is taking place, coronal pulp appears normal and odontoblasts still line the

surface of the predentin. When root resorption is almost complete, these odontoblasts

degenerate, and mononuclear cells emerge from the pulpal vessels and migrate to the

predentin surface, where they fuse with other mononuclear cells to form odontoclast actively

engaged in the removal of predentin and dentin. Just before exfoliation, the resorption process

stops. Tooth then sheds with pulpal tissue intact.

There are at least two ways of the resorption of cells or “cell death”. Through studies

and observations show that its abrupt and yet no inflammation occurs. The two forms are as

follows:

1. Fibroblast is a type of cell that synthesizes the extracellular matrix and collagen,

the structural framework (stroma) for tissues. The main function of fibroblasts is to maintain the

structural integrity of connective tissues by continuously secreting precursors of the extracellular

matrix. Fibroblasts secrete the precursors of all the components of the extracellular matrix,

primarily the ground substance and a variety of fibers. But the fibroblasts are interrupted and

their normal cellular processes such as secreting the precursors and cytotoxic alterations that

eventually lead to cell death.

2. Apoptosis, form of cell death in which a programmed sequence of events leads

to the elimination of cells without releasing harmful substances into the surrounding area.

Apoptosis plays a crucial role in developing and maintaining health by eliminating old cells,

unnecessary cells, and unhealthy cells. Ligament fibroblasts have the same features of apoptic

cell death. Apoptosis produces cell fragments called apoptotic bodies that phagocytic cells are

able to engulf and quickly remove.

With further reading, pressure can also play a factor in exfoliation. Reason may

be because if a successional tooth is missing, the normal time period for exfoliation is delayed.

Some say that the force applied to a deciduous tooth can initiate resorption. Pressure from an

erupting permanent tooth results in some root loss, which in turn means a loss of supporting

tissue structures. So if the structures are lost, then its inevitable that the process of shedding is

accelerated.

Mechanism Of Shedding

A. Resorption Period

In the case of Bone resorption, it is thought that the osteoblast must must first degrade

the osteoid, exposing the mineralized bone to which osteoclast can attach. Osteoblast may also

resorbs the dentin .Hard tissues resorption occurs in two phases: the extracellular during which

the matrix fragments and dissolution begins and intracellular during which complete digestion of

the products of resorption occurs . Resorption of intraradicular dentin takes place in some

resorption of the pulp chamber, coronal dentin and sometimes enamel. Resorption of the

periodontal ligament involves apoptopic cell. This form of cell death involves shrinkage of the

cells so that they can be phagocytosed be neighboring cells. Apoptotic cell death is

programmed so that cells die at a specific tmes to permit orderly development . Occurrence of

the apoptotic cell death together with periodontal ligament resorption and with the observation

that in monozygotic twins the eruption pattern is largely (80%) determined by genetic factor

suggest that shedding is a programmed developmental event influenced by local factors

Whatever the preliminary steps in hard tissue resorption , it is clear that the odontoclast

attaches to the hard tissue surface peripherally through the clear zone creating a sealed space

is created lined with ruffled border of the cell, that acts like a proton pump adding hydrogen ions

to the extracellular environment and acidifying it so that dissolution occurs and primary

lysozymes are secreted to degrade the organic matrix .

Factors that may Initiate or affect tooth resorption :

1. Pressure

Pressure from erupting permanent tooth may cause some root loss that will

decrease tooth support therefoe the tooth is less able to withstand the increasing masticatory

forces thereby the process of exfoliation is accelerated. As resoption of the roots initiated by

pressure of the underlying tooth occurs , there is a progressive loss of surface area for

attachment of the periodontal ligament fiber bundles. This weakening of the tooth support

occurs because it has to withstand increasingly greater occlusal forces generated by the

growing muscles of mastication

Mesial Drift is the lateral bodily movement of the teeth on both sides of the mouth

toward the midline of the arch.One condition that leads to mesial drift is when the teeth is in

function producing a rubbing of cotact areas making the transseptal fibers of the periodontal

ligament to maintain a tooth contact. Pressure on the periodontal ligament fibers results in

resorption of bone , whereas pull on fibers results in bone apposition(formation) .As the contact

areas of the crowns wear, the teeth tend to move mesially to maintain contact . The slight

pressure on the mesial side of the socket results in the slow resorption of the lamina dura while

the accompanying tension on the distal side induces appositional lamina dura bone in this area.

2. When Succesional tooth germ is missing

It will delayed the shedding of deciduous teeth

3. Forces of masticatory applied to deciduous teeth

As an individual grows the mastication increases in size and exert effort on tooth

more than the periodontal ligament can stand that leads to trauma to the ligament and the

initiation of resoption.

B. Rest Period and Repair Period

Resorption of deciduous teeth is not continuous process, During rest periods, reparative

tissue may be formed , leading to reattachment of the periodontal ligament. The areas of early

resorption are repaired by the deposition of the cementum like tissue which lay down a

collagenous ns showing small foci of mineralization which helps in repair

As the tooth continue to resorbs, the tooth loosens. Eventually, all the periodontal

ligament attachment is lost and the rootless crown of the primary tooth literally falls off the jaw

If the repair process prevail over the resoption , the tooth may become anykylose to the

surrounding bone, with the loss of the periodontal ligament.

Pattern of Shedding

Pressure generated by the growing and erupting permanent tooth dictates the pattern of

deciduous tooth resorption. Because of the developmental position of the permanent incisors

and canine tooth germs their subsequent movement in an occlusal and vestibular direction ,

resorption of the incisors and canines begins on their lingual surfaces and later occupy directly

apical to the primary tooth .In mandibular incisors the apical positioning of the tooth germ does

not occur and permanent tooth erupt lingually

Resorption occurs on the lingual aspect of the deciduous canine , and the tooth often shed with much of its lingual root intact

For deciduous molar, root resorption commences on the inner surfaces where the

permanent premolars initially develop . Premolars later lie beneath the roots of the deciduous

molars. However, as a result of continuous growth of the jaws and occlusal movement of the

deciduous molars, the successional tooth germs come to lie apical to the deciduous teeth. This

change in position provides the growing bi-cuspids with adequate space for their continued

development.

Sequence of Shedding in the mandible follows an anterior to posterior order of the in the

jaw while for the maxilla the first molar exfoliate before the canine disrupts this sequence.

CLINICAL CONSIDERATIONS

1. Enamel hypoplasia is caused by the disturbance in the development of the enamel

during matrix formation. This results to deficiency in the quantity of enamel. The matrix formed

is defective but calcification is normal The enamel is irregular, often pitted or thin fissures or

grooves but otherwise it has normal hardness and translucency.

2. Eruption of tooth is frequently accompanied by pain and fever. This is due to trauma

initiating an inflammatory response. Adding up to the inflammation is the attack of microbial

infections.

3. Retained deciduous teeth are usually caused by failure of the succedaneous tooth to

form or the corresponding succedaneous tooth is impacted. Retained deciduous teeth are most

often are the upper lateral incisor, less frequently to the second permanent premolar. If the

permanent tooth is ankylosed or impacted, its deciduous predecessor may also be retained.

This is most frequently seen with the deciduous and permanent canine teeth.

4. Premature loss of primary teeth can cause early eruption of its permanent successor.

It can also cause a loss of arch length with a consequent tendency for crowding of the

permanent dentition. Increase chances for the adjacent teeth to mesial migrate resulting to

blockage of the path of eruption of the succedaneous tooth.

5. Delayed eruption of teeth are common and may be caused by congenital, systemic,

or local factors

Congenital absence most commonly occurs with the permanent third molars.

Systemic factors may be caused by endocrine deficiencies, nutritional

deficiencies, systemic lesion, and some genetic factors.

Local factors: early loss of deciduous teeth, with consequent drifting of the

adjacent teeth to block the eruptive pathway, eruption cysts

6. Remnants of deciduous teeth consist of dentin and cementum. They may remain

embedded in the jaw for a considerable amount of time. This are most frequently found

associated with lower second premolars. Root remnants are also may be found deep in the

bone, completely surrounded by and ankylosed to the bone.

7. Submerged deciduous teeth are due to trauma resulting to the damage of either

the dental follicle or the developing periodontal ligament. If this happens, the eruption of the

tooth ceases, and it becomes ankylosed to the bone of the jaw. Due to the continued eruption of

the adjacent teeth and increased in height of the alveolar bone, the ankylosed tooth may be

shortened or submerged in the alveolar bone it prevents eruption of their permanent successors

due to crowding or tipping of the adjacent teeth onto the space created by missing tooth.

SOURCES

Berkovitz, Bary K: Master Dentistry: Oral Biology . Elsevier Ltd.2011 p 113-121

Melfi, Rudy C: Permar’s Oral Embroyology and Microscopic Anatomy. Lippincott Williams &

Wilkins .2000 p 265-279

Ten Cate A. R: Oral Histology –Development , Structure, and Function , 6th Edition , Mosby.

2008

Bhaskar , S.N : Orban’s Oral Histology and Embryology , 11 edition , Mosby Inc. 1991

Osborn, J.W : Advance Dental Histology p 135-140