Advanced Veterinary Dental Techniques (RCT) Flashcards
Define endodontics?
This name is derived from the Greek endo inside and odont tooth. It is therefore
the branch of dentistry involved in the diagnosis and treatment of diseases of the pulp-dentine complex
Describe the relationship between dentine and the pulp?
Dentine is the hard substance making up the bulk of the tooth. It appears solid,
but actually consists of thousands of microscopic dentinal tubules extending
from the dentino-enamel junction to the pulp (40-70 000/mm2
). Within the
tubules are cytoplasmic extensions from odontoblast cells lining the pulp space,
fluid and nerve fibre endings (the nociceptors Aδ and C fibres). This means
dentine is a sensitive structure. Odontoblasts are responsible for producing new
dentine throughout life, but can only function if the pulp is vital. Bacteria can
potentially invade the dentine via the tubules, and therefore infect the pulp. As
the dentine is intimately associated with the pulp, it is known as the pulp dentine complex.
When does primary dentine form?
Primary dentine forms before eruption of the tooth.
When does secondary dentine form?
Secondary dentine forms continually after tooth eruption as long as the pulp
remains vital. The odontoblast, which is at the outer periphery of the pulp
space, is the cell responsible for dentine production. A young animal therefore
has thin dentinal walls and a wide pulp space, which is a very delicate tooth. An
old animal conversely has thick dentinal walls and a small pulp space. The apex
is not fully formed immediately as the tooth erupts. This forms as the secondary
dentine is being laid down and is normally completed by 7-8 months of age. If
the pulp becomes necrotic (e.g. after dentinal fracture and pulp exposure) then
secondary dentine production becomes arrested.
When is tertiary dentine formed?
Tertiary dentine is formed as an attempt at tooth repair. If odontoblasts are
traumatised (e.g. by attrition or abrasion exposing dentine) they are stimulated
to produce more dentine. This tertiary dentine may be laid down rapidly and
haphazardly and therefore stains easily. This causes the brown staining seen
on many worn teeth. If the trauma is slow, the repair mechanism can cope and
protect the tooth. If the damage is rapid, the repair mechanism cannot cope and
the pulp may become exposed. Using a sharp dental explorer probe in the
anaesthetised patient will allow you to determine if pulp exposure has occurred.
Here, you will feel the probe ‘drop’ into the pulp space. With tertiary dentine it
will feel smooth like glass.
In the crown the pulp space is known as the …………….., and in the root the
pulp space is known as the ……………
In the crown the pulp space is known as the pulp chamber, and in the root the
pulp space is known as the root canal.
What does the pulp contain?
The pulp contains blood vessels,
lymphatic vessels, nerves, fibroblasts, collagen fibres, undifferentiated
mesenchymal cells and odontoblasts.
The predominant nerve fibres within the
pulp are?
nociceptors: i.e. they only transmit pain signals.
These are of the Aδ
(myelinated fast conduction, sharp pain) or C type (unmyelinated, slow
conduction, dull throbbing pain).
Pulp inflammation/infection can happen via a variety of routes:
- Via dentinal tubules (e.g. uncomplicated crown fracture, caries)
- Via an open cavity in the pulp chamber (complicated crown fracture,
abrasion) - Periodontal space- bone loss in periodontitis can allow bacteria to enter
the pulp via the apical delta, or lateral channels - Via the blood stream- bacteria in a transient bacteraemia can be
attracted to sites of inflammation (anachoresis) e.g. discoloured teeth - Via disruption to its blood supply (e.g. luxation, avulsion, jaw fracture)
What are Dentoalveolar injuries (DAI) ?
These describe any injury to the tooth, or tooth-supporting structure (periodontal
ligament, alveolar bone, gingiva). They are common in cats and dogs after
falling, fighting, being accidentally hit, catching/carrying stones and road traffic
accidents. It has been shown by Soukup et al (2013) that 72% of animals with a
maxillofacial fracture will also have a DAI- the most common type being root or
crown fractures of the incisors and canines.
Crown fractures can affect enamel, enamel & dentine or enamel, dentine and
pulp. Classification of tooth fractures has been performed by the AVDC:
In cases of concussion/intrinsic tooth staining what percentage of teeth are non-vital?
In a case
series of 84 entirely discoloured teeth in dogs (Hale 2001), 92% were found to
be necrotic and therefore treatment recommended (either extraction or root
canal therapy). Feigin et al (2022) found that 87% of 102 intrinsically stained teeth were non-vital, with only 57% showing radiographic signs of endodontic
disease.
What should you do if a tooth is only partially intrinsically stained?
Teeth with partial discolouration should be monitored radiographically.
These are tricky cases as we cannot ask the patient if they can feel hot/cold on
the tooth to ascertain vitality, nor can we assess response to percussion or
pressure. If the whole crown is entirely discoloured, it is likley that the pulp is
necrotic. However when only part of the crown is discoloured it is possible the
pulp is vital and non-inflamed. Radiography may tell us there is a necrotic pulp if
we can see a difference in pulp width compared to the contralateral side, but of
course this takes time to be visible. Acute pulpitis will not be visible. Any
periapical changes will also take time to occur (cyst, granuloma, abscess).
What is Subluxation?
Describes an injury to the tooth supporting structures resulting in
increased mobility, but without displacement. This is not often detected.
Luxations can be?
lateral, intrusive or extrusive.
Lateral luxations involve fracture of the?
Alveolar socket.
Intrusive luxations are
when the tooth is displaced into the?
Socket, compressing or fracturing the
alveolar bone.
Extrusive luxations are?
Partial displacements of the tooth out of
its socket, compared to a complete displacement seen with avulsion.
With luxations and avulsions what will inevitably occur?
Damage
will inevitably occur to the vascular supply to the tooth in the pulp and also the
periodontal ligament. Replacement of displaced teeth is possible, with treatment
consisting of placement of an acrylic splint for 4- 6weeks. Early referral is
advised.
In the case of complete avulsion what are the emergency measures?
In the case of complete avulsion, the following first aid measures
should be employed should the client wish to save the tooth:
* Tell the client to handle the tooth by the white crown only
* Wash briefly if it is dirty and re-position in the socket if possible
* Otherwise place the tooth into a suitable storage medium such as
pasteurised whole milk.
* Start the patient on penicillin antibiotics
* Provide analgesia
* Seek urgent referral- a dental emergency!
What is an enamel infarction?
This is a disruption of enamel without loss of tooth
substance. It is seen clinically as series of cracks in the
enamel, often on crowns that are subjected to high stresses
(e.g. dogs which carry heavy objects). It does not usually
require treatment.
What is an enamel fracture?
This is loss of tooth substance, which is confined to the
enamel. As enamel is a very thin layer in dogs and cats, this
is rarely seen and dentine is usually involved as well. Loss of
enamel can however expose dentinal tubules, and thus
requires treatment
What is a Enamel-dentine fracture/ uncomplicated crown fracture (UCF)?
This describes a fracture through enamel and dentine, but not directly exposing
the pulp. This is also referred to as an uncomplicated
crown fracture (UCF). However, this is a misleading name,
as these fractures can often lead to complications such as
endodontic compromise, pulpitis and even pulp necrosis and tooth root abscess. These are rare in cats as the pulp extends very close to
the tip of the crown, so a complicated crown fracture is much more likely.
What is the Treatment of fresh enamel-dentine fractures?
Exposed dentinal tubules are sensitive due to the connection to the pulp via
afferent nerve fibre extensions from the pulp into the tubules. The fast
myelinated Aδ fibres transmit sharp, localised pain, while the slower,
unmyelinated C fibres transmit dull, diffuse pain. There are an estimated 40-70
000 tubules per mm2
, which is more than humans. In addition, bacteria and/or
their toxins can enter the dentinal tubules and reach the pulp resulting in
pulpitis. Furthermore, rough enamel edges can lead to tongue trauma. These
injured teeth can be treated by the general practitioner, by applying bonding
agents and composite (filling) materials. Radiography is essential to ensure no
endodontic pathology.
What are Enamel-dentine-pulp fractures / complicated crown fracture (CCF)?
These are also referred to as complicated crown fractures when the pulp is
directly involved. These injuries should be treated without
delay. Pulp exposure is painful. The tooth should either
be extracted or treated by root canal therapy where the
entire pulp is removed and the pulp canal space
disinfected and then filled with an inert rubber-based material and sealer.
Immediate treatment should involve analgesia. Antibiotics are not indicated as
they will not stop the pulp from becoming inflamed and infected. Do provide
analgesia until treatment can take place.
What is the pulps response to trauma?
The pulp becomes inflamed typically via trauma or due to exposure either
directly or indirectly (abrasion, fractures, bone loss in periodontitis). Pulpitis is
either reversible or irreversible. Pulp necrosis is a sequel to untreated,
irreversible pulpitis and these teeth are known as non-vital.
The initial inflammation is known as acute pulpitis, which is painful- the Aδ fibres
send sharp, intense pain signals with the slower conducting C fibres
transmitting dull, throbbing pain signals. The acute pulpitis can become chronic,
with the immune system trying to resolve the problem. This leads to waves of
pain and then periods of quiescence, then waves of pain. The increase in
pressure within an enclosed space leads to necrosis of the pulp, as the inflamed
pressure is too high for the arterial supply into the tooth. At this point (necrosis),
the tooth becomes comfortable! However, if the pulp is already infected, there is
now a reservoir of necrotic, infected tissue within the tooth, which has effectively
been cut off from the immune system. In a discoloured tooth, the inflamed
tissue can become infected during a benign period of bacteraemia- a process
known as anachoresis. At this point a tooth root abscess can form, which is
extremely painful. This will be noted radiographically as an area of bone loss
around the apex of the root, known as a periapical lucency. If the pulp is
exposed due to a crown fracture, the infection is immediate. Antibiotics will not
stop the inevitable acute pulpitis→chronic pulpitis→ necrosis.
The three main differentials for the periapical lucency are:
What are the disadvantages of root canal treatment?
Root canal therapy is a very technique sensitive procedure, involving
investment in many different types of equipment and materials. Success rates
are highly dependent on the surgeon’s ability and experience, and most trainee
specialists will have practiced the procedure on many cadavers before
attempting the procedure in the live patient. Because success rates are not
100% it is vital to ensure ongoing success via periodic radiographic assessment
under general anaesthesia.
Outline in brief the root canal procedure and equipment?
- Access: in to RCT can be achieved via fracture site or by making an entrance using a small round size 2
or pear-shaped bur to provide straight-line access to the start of the root canal
space. - Endodontic files: shaping of the canal is then continued with
hand or rotary instruments. Engine-driven systems
are also available, which dramatically. A speeds up treatments and reduces hand
fatigue. A working length is established by an ISO sized 15mm file is
placed into the canal until it reaches the apex. The rubber
stop on the file is placed against the crown of the tooth in a
repeatable position. A radiograph confirms the file is at the apex. This length is then measured with an endodontic ruler, and the
measurement is known as the working length. Subsequent file placements
should not pass further than this measurement, otherwise there is a risk of
extending into the periapical tissues. - Cleaning, shaping and irrigation: Increasingly larger files are used to shape the canal. This is interspersed with
irrigation using a disinfectant to kill all microbes, and dissolve organic material.
The best solution for this is sodium hypochlorite (NaOCl) at 3-5 % solutions
(bleach) in contact with the pulp tissue for at least 30 minutes. Care should be taken to ensure bleach does not
touch the oral soft tissues, nor extend beyond the root apex, otherwise severe
complications can occur. Dentinal filings should come out cleaner and whiter. The final file able
to reach or worked to the apex is known as the master file. A radiograph
confirms this. The penultimate rinse is with a solution of EDTA to remove the
so-called smear layer. EDTA is left in the canal for 1 minute and then a final
rinse is performed with sterile saline or NaOCl. The smear layer is an ultrafine
layer of organic and inorganic debris plugging the dentinal tubules, and caused
by instrumentation. - Paper points are then used to dry the canal. These are
available in the same ISO sizes as files. These should come out clean, and
eventually dry. - Obturation: This is the process of three-dimensionally sealing the cleaned and shaped
canal and forming a hermetic seal from bacterial ingress. It is usually performed
with a combination of gutta-percha points and a sealer. The master guttapercha point (same size as the master file), is placed into the canal, and the
radiograph taken to ensure adequate fit at the apex. The point can then be
sterilised in bleach for 1 minute and rinsed in alcohol then dried. The sealer is
then applied into the canal using a syringe or Lentulo-spiral on a low-speed
handpiece. The master point is then coated in the sealer, and placed to the
apex before being condensed into position. The crown walls are then thoroughly
cleaned before a final restoration is placed. - Composite restoration: Once the canal is filled, the pulp chamber must be cleaned in order to place the
final composite filling. In some cases, an alloy metal crown can be placed over
the crown of the tooth, but in the majority of patients this is not performed. It can
be considered in working dogs that require strengthening of the tooth.
Restorative techniques and prosthodontics will be covered later on.
Taper describes the amount the file diameter increases each mm from the tip to the?
Handle.
ISO files increase in width by 0.02mm per mm of file length, so that a size #25 file would have a 0.27mm diameter 1mm from the tip, 0.29mm
diameter 2mm from the tip, etc. This is known as a 2% taper. Both K- and H type files are produced in human (21, 25 and 30mm) and veterinary lengths
(60 and 120mm). Human files are inadequate length for the majority of canine
teeth in dogs, requiring a veterinary length file to adequately instrument the
apex.
What are the three stages of RCT treatment?
What are Barbed Broaches?
- Remove pulp tissue
- Produced by making small incisions into smooth
metal shank forced open to produce barbs - Slow insertion into canal until contact with
debris/dentinal wall rotate 180° to entangle tissue
and withdraw - Care they can break
How should K files be used?
Used in a clockwise turning movement, carrying
dentinal filings to access in the flutes
How should H-files be used?
- Push-pull filing action
- Not designed to be rotated as prone to fracture
What does Sodium Hypochlorite/bleach do?
- Antimicrobial
- Dissolve necrotic organic debris
- 0.5-5.25%
What type of needle needs to be used with bleach/sodium hypochlorite?
- Side vented endodontic needle, luer lock syringe
- CARE do not allow onto soft tissues
- CARE do not allow beyond apex
- Use suction
What is the smear layer?
What is the penultimate rinse and what is it for?
What can sharpei’s get?
