Disturbances in Size.

Microdontia  smaller than
normal Teeth . Generalized microdontia is a rare condition associated with
uncommon conditions such as pituitary dwarfism. More often, microdontia is
limited to just one or two teeth  "Peg-shaped" upper lateral incisors and
small third molars are seen.

Macrodontia : larger than
normal teeth . Generalized macrodontia is rare, seen infrequently in conditions
such as pituitary gigantism. It can be localized involving just one or a few
teeth.

Disturbances in Number.

Anodontia is the congenital
absense of all teeth.  (Edentulous means the clinical absence of teeth.
Anodontia means the failure of teeth to form at all.) In
true (or complete) anodontia, all teeth fail to develop. True anodontia is an extremely
rare occurrence. Occurs in  generalized disorder ectodermal dysplasia, an
inherited defect of all ectodermally derived structures.

Partial anodontia is the failure
of one or more teeth to develop. It is much more common than complete anodontia.
Third molars, lower second premolars, and upper lateral incisors  are the
most common congenitally absent teeth. In Primary Dentition most often the upper lateral
incisor that is absent. When a deciduous tooth is absent, its permanent
successor is usually missing also.)

Supernumerary teeth are 'extra'
teeth. Most (90%) occur in the maxilla. Their presence in the deciduous
dentition is quite rare. The most common of all supernumerary teeth is the mesiodens which is a supernumerary that forms in the midline between and lingual
to the roots of the maxillary central incisors. Most supernumerary teeth do not
erupt; they often are unknown until detected on X-ray films. Fourth molars,
themselves a rare occurrence are infrequently called 'paramolars' or 'distomolars.'
Supernumerary teeth occur less often than do missing teeth.

Disturbances in Eruption.

Premature eruption of all of the teeth, either
deciduous or permanent, may suggest an underlying endocrine dysfunction such as
hyperthyroidism.

Delayed eruption can be due to local or systemic
factors. For one or a few teeth, surgical exposure and--if needed--orthodontic
guidance can bring the tooth into its proper place. X-ray films are useful in
evaluating early or late eruption of teeth.

Impacted teeth are those that have failed to erupt and
remain buried in the alveolar bone. Usually, some barrier to eruption will be
seen on the X-ray film. Other  term for unerupted teeth is embedded
teeth. The third molars and maxillary canine are the most frequently impacted
teeth, followed by premolars and supernumerary teeth.

Ectopic eruption is another type of eruption
disturbance; this occurs when a tooth cannot complete its eruption because it is
blocked by an adjacent tooth or by a misplaced orthodontic band--usually on a
first molar tooth.

Disturbances in Shape

Dilaceration is a severe bend in
the long axis of the tooth. The bend it located at the junction between the
crown and the root. The bend can be as much as 90 degrees. Dilaceration usually
results from trauma to the unfinished tooth when development is in progress.
Also called a 'hawk billed tooth'.

Taurodontism  means
'bull-like teeth'. Taurodont teeth are usually molars. They have an abnormally
long pulpal chamber and shortened roots. The pulp chamber has no constriction
near the CEJ as do normal teeth. Clinically these teeth appear normal.

Dens in dente literally means
'tooth within a tooth'. It is an uncommon developmental abnormality that
primarily affects maxillary lateral incisors. It is in fact a deeply invaginated
lingual pit with an important clinical implication: these are very susceptible
to caries and they ought to be restored promptly. Left unattended, these teeth
tend to decay very rapidly. Also this condition is called as
dens invaginatus.

Supernumerary cusps, or as they
are often called, extra cusps are occasionally found on teeth.

The most common one is the Carabelli
Cusp which is found on the mesiolingual aspect (on the mesiolingual cusp)
of maxillary first molars AND maxillary second deciduous molars.

A talon cusp is an extra cusp
that resembles an eagle's talon, These can interfere with occlusion, Talon cusps
often contain a prominent pulp horn which is very susceptible to exposure in the
younger people. Projection of enamel can occur on the occlusal surface
of the premolar teeth. It forms a tubercle called a dens
evaginatus

Peg-shaped lateral incisors

Fusion is the union of two teeth
by dentin and enamel , This condition can be differentiated from gemination 
by counting the teeth

Gemination is the development of
two crowns from a single tooth germ. It is an incomplete twinning of the gooth
germ. In gemination, there is a shared pulp and root.

Concrescence is the joining of
tooth roots by cementum. It occurs after tooth formation is complete, Missed
diagnosis is serious in case of extractions

Disturbances in Formation

Enamel pearls (enamelomas) are
small nodules of enamel found on the root of the tooth close to or at the
cemento-enamel junction

Hutchinson's incisors or
mulberry molars are developmental anomalies that result from congenital
syphilis. Clinically, the incisor teeth are, on occasion called 'screwdriver
teeth' due to their distinctive shape

Enamel hypoplasia can be
localized or generalized, It is an indicator of severe sickness or nutritional
deprivation, it can be detected histologically in the enamel as a Wilson line