The pulp will usually respond to noxious stimuli by
becoming inflamed, but it may also respond by
degeneration which includes atrophy and fibrosis,
calcification, root resorption, or hyperplasia.
Atrophy
Atrophy is a normal physiologic process that occurs
with age and is asymptomatic. Pulp sensibility tests
responses may be normal or delayed. No significant
radiographic or clinical signs are present. As the pulp
atrophies, there will also likely be fibrosis of the pulp
tissue and the extent of this will be largely determined
by the number of irritant episodes suffered by that
particular pulp throughout its history. The size of the
pulp chamber may be reduced. No treatment is
required.
Pulp canal calcification
Teeth with pulp canal calcification (commonly
referred to as pulp canal obliteration or PCO) may or
may not have any symptoms – if the pulp tissue within
the calcified or calcifying canal is normal then there will
be no symptoms (Fig 7a); on the other hand, however,
if the canal is pulpless and infected, then this will cause
apical periodontitis with symptoms eventually
developing as the apical periodontitis progresses
(Fig 7b). There are usually no responses to thermal tests
(e.g., heat, cold) but an electrical test may elicit a
normal or delayed response. Radiographically, there is
no evidence of the usual pulp chamber outline and the
root canal may appear narrow or it may not be evident
at all. Pulp canal calcification may appear radio-graphically
to be partial or complete but it is not
possible to assess the extent of calcification from a
clinical or radiographic examination. It is feasible, and
likely, that the canal may only be a few cells wide and
therefore will not be evident radiographically, but may
still contain viable and healthy tissue. Hence, the term
“obliteration” is not ideal since this term implies that
there is no canal remaining and instead the term
“calcification” is preferred.
Hyperplasia
Hyperplasia of the pulp occurs almost exclusively in
young teeth with an abundant blood supply and a large
carious lesion. It is essentially an overgrowth of
granulation tissue and may result in the development of
a pulp polyp. The hyperplasic tissue is relatively
insensitive to touch due to having only a few nerves
present. It may bleed easily depending on the degree of
the tissue vascularization and the degree of ulceration.
Occasionally it may cause mild discomfort during
mastication. It has been suggested that the inflammation
may be limited to the pulp chamber and that the apical
pulp tissues may be normal, except for some
vasodilation and minimal chronic inflammation. The
tooth will respond to pulp sensibility testing but often
with an exaggerated response to cold tests. No
significant radiographic changes (except for the cause
of the problem – for example, caries, fractured
restoration, etc.) are evident unless there is also
periapical involvement presenting as a radiolucency or
radiopacity.
Sometimes, the gingival tissues may grow into the
carious lesion and this may be suggestive of a hyper-plasic pulpitis (Fig 8b).
In these cases the distinction
may be made by careful examination of the tissue mass,
so as to determine if it is connected to the pulp or to the
gingivae.
Internal resorption
There are three forms of internal resorption –
surface, inflammatory and replacement. Internal
surfaceresorption is unlikely to ever be diagnosed since
it is defined as minor areas of resorption of the surface
of the root canal wall. It is unlikely to be noticed
radiographically and there will be no clinical signs or
symptoms. No treatment is required, which is fortunate
since it cannot be clinically or radiographically
diagnosed.
Internal inflammatory resorption can occur at any
point along the length of the pulp space – that is,
coronally within the pulp chamber or within the root
canal. It is believed to occur in teeth with necrobiosis
and it is probably due to a metaplastic change or
activation of dentinoclasts within the inflamed pulp
tissue that is in contact with the coronal pulp which is
necrotic and infected. This condition is usually
asymptomatic and often only recognized during a
routine radiographic examination. If symptoms are pre-sent,
they are usually indicative of acute apical
periodontitis due to an infected canal, or pain when
perforation of the crown occurs and the metaplastic
tissue is exposed to oral fluid and bacteria. Initially,
part of the pulp (i.e., the apical portion) is alive and still
contains nerve fibres so a response to pulp sensibility
testing is possible. However, as the lesion progresses,
the entire pulp becomes necrotic and infected, and over
time the canal will become pulpless and infected –
hence there will be no response to pulp sensibility test-ing.
Radiographically, internal inflammatory resorption
will have an oval-shaped increase in the size of part of
the root canal system. Periapical changes may be noted
after the canal has become infected and apical
periodontitis develops (Fig 9a).
Internal replacement resorption is an uncommon
condition that occurs when the pulp undergoes
metaplastic changes and the dentine is resorbed and
replaced by bone-like hard tissue. The cause of internal
replacement resorption is usually unknown but is not
due to the presence of bacteria in the pulp. This
condition is asymptomatic, and usually only recognized
during routine radiographic examination. Radio-graphically,
internal replacement resorption will have
an irregular enlargement of the pulp space that is filled
with bone-like hard tissue (Fig 9b). Periapical changes
do not usually occur with internal replacement
resorption.