Oral Surgery II Flashcards
1
Q
What are TDIs?
A
Traumatic dento-alveolar injuries
2
Q
Clinically identifiable dental concussions are most commonly associated with?
A
Discolouration of the
crown
3
Q
Why does concussion cause discoloration of the tooth?
A
This may be complete or partial and is often seen as pink initially then degrading to brown and
finally grey/ loss of the natural pearlescent lustre of the normal tooth. The discolouration is associated
with bleeding from the pulp and movement of haemoglobin and its breakdown products through the
dentinal tubules.
4
Q
Irreversible pulpitis or pulp necrosis is reported in what percentage of teeth with generalised crown discolouration, sometimes referred to as intrinsic staining?
A
93%
5
Q
It should also be noted
that cessation of dentin deposition is not the only indicator of pulp health compromise and what else is?
A
Increased dentin deposition and canal obliteration can be seen in cases of chronic, irreversible,
pulpitis.
6
Q
What has a craved paving appearance and what causes it?
A
Enamel infraction is seen as a “crazed paving” appearance of the crown of teeth. This is especially
common in dogs where high masticatory forces are inflicted on teeth. In the authors experience this is
most coolly seen affecting the canine teeth. Micro-fractures radiate across the enamel surface but the
adhesion of the enamel to the underlying dentin is not lost. Enamel thickness in cats and dogs is
reported to be 0.1-1mm which is considerable thinner than in humans. In general, enamel infractions
do not require treatment or intervention
7
Q
What is the approach to enamel dentin fractures (EDF)?
A
There is no clear evidence base for therapeutic options in management of EDF. It is good practice to
perform dental radiographs of teeth affected by EDF to assess for the presence of pulpitis or apical
periodontitis. The author routinely advises simple unfilled resin sealing of freshly fractured teeth
especially in younger patients. Deeper injuries may benefit from restoration with composite or
prosthodontics, especially if there has been loss of the buccal bulge, present in premolar and molar
teeth. Loss of buccal bulge is likely to increase the risk of periodontitis as periodontal trauma will
occur during normal mastication.
8
Q
Enamel-dentin-pulp (EDP) fractures always require?
A
Treatment, be that extraction or preservation
through endodontic treatments.
9
Q
Why do Enamel-dentin-pulp (EDP) fractures always require treatment?
A
The pulp is not able to persevere in the harsh oral environment when
exposed and bacterial colonisation and pulp necrosis is inevitable. Apical periodontitis, granuloma,
abscess, cyst or sclerosing osteitis are expected sequelae.
10
Q
What should be done with near pulp exposure?
A
Near pulp exposure, where the pulp is less
than 0.5mm from the dentin surface should be considered to be the same as pulp exposure
physiologically. Near pulp exposure can be evaluated radiographically but clinical examinations
revealing pink blush of the pulp through dentin is also considered pathognomonic.
11
Q
It should be noted that EDP fractures are common in primary/ deciduous teeth. What should be done with them?
A
Unless rotation of the
tooth is imminent, and appropriate pain management is instituted until the injured tooth is lost, the
author would advise extraction of the injured tooth. Prompt action will alleviate pain and prevent
apical pathology causing damage to the developing tooth bud of the permanent dentition.
12
Q
What Endodontic therapy is most commonly performed on teeth affected by EDP (enamel dentine pulp) fractures is?
A
Root canal
treatment.
13
Q
Conventional root canal treatment can only be effectively performed on?
A
Teeth with a fully
formed root apex (tooth maturation).
14
Q
When does apical maturation occur in cats and dogs?
A
Apical maturation occurs between 10 and 14 months of age in
cats and dogs.
15
Q
Immature teeth with EDP (enamel dentine pulp) fractures require urgent intervention if preservation is
desired, treatment of choice is?
A
Partial pulpotomy and direct pulp capping often called vital pulp
therapy (VPT). The success of VPT decreases significantly after 72 hours of pulpal exposure and is
unlikely to be successful after 7 days of exposure.
16
Q
A crown root fracture of a single rooted tooth where the root fracture is relatively shallow may be
managed by?
A
Performing crown lengthening procedures with the aim of achieving a supra-gingival
position of the fracture extent.
17
Q
What different classes of crown lengthening are there?
A
Class 1 crown lengthening refers to simple gingivectomy and may be
performed where there is sufficient attached gingiva to maintain biologic width greater than 2mm.
Class 2 crown lengthen may be performed where the depth of the fracture is deeper than the attached
4
gingiva. Class 2 lengthening involves the creation of buccal and palatal/ lingual pedal flaps,
alveolectomy and alveoplasty and subsequent apical repositioning of the flaps. Alveolectmoy/
alveoplasty is commonly performed with a combination of water cooled rotary diamond burs (the
author prefers medium grit egg shape no:368,369, 379). Class 2 crown lengthen has a number of
significant clinical challenges and requires a high degree of skill with regards to tissue handling and
tension management and should not be undertaken without practice.
18
Q
How can sticks create root fractures?
A
The author has also seen numerous cases of root fracture in
dogs that suffer from trans-palatal stick injuries. The author suspects that forces exerted on the palatal
roots of the 4th premolar tooth when the stick is cut results in extreme tension and a fracture occurs in
the coronal 1/3 of the palatal root.
19
Q
How should different root fractures be treated/managed?
A
Not all root fractures will require extraction of the tooth. If the crown is unstable or the fracture is in
the coronal third of the root extraction is required. If in the apical or middle third and the crown is
stable and no periodontal compromise is detected radiographic monitoring is advised at 6 and 19
months after diagnosis and extraction only performed if apical periodontitis etc develops.
20
Q
Extrusive luxation and avulsion result in partial or complete movement of the tooth out of the alveolus.
Both are considered?
A
An emergency of veterinary dentistry if preservation of the tooth is desired. The
urgency originates with the need to maintain the viability of the fibroblasts on the root surface that will be responsible for reattachment of the periodontal ligament after replantation of the tooth.
21
Q
After avulsion of a tooth what is the best transport media?
A
Although there is little evidence from the animal population there is a great deal of evidence from
human medicine indicating that rapid replantation, within a few hours, is the only option for
management of these injuries. If the tooth is avulsed that addition of a transport media is required.
Historically, the most commonly recommended easily found transport medium was milk. Milk will
preserve fibroblasts for unto 2 hours. Current recommendation is use of egg white as a transport
medium as this extends the window of opportunity up to 6 hours after avulsion before re-implantation
is likely to be unsuccessful.
22
Q
After reimplantation of a tooth what should be done?
A
Once a tooth is replanted stability must be provided to allow for regrowth of the periodontal ligament.
Multiple human studies have indicated that profoundly rigid stabilisation and prolonged stabilisation
increases the risk of post-replantation complications. The greatest complication, other than failure of
replantation, is ankylosis and subsequent tooth resorption. The use of lightweight splints which allow
for some movement of the tooth under normal, but cautious, loading forces reduces the risk of
resorption. Splints should be maintained for not more than 2 weeks and the vast majority of teeth will
require root canal treatment at the time of splint removal. This results from irreversibly compromise
to the vessels of the apical delta and avascular necrosis of the pulp. In rare circumstances of luxation
or avulsion in immature teeth with open apices, re-vascularisation has been reported. This in turn has
led to the development of regenerative endodontic treatments, although this technique is still in its
relative infancy in animal patients.
23
Q
Lateral luxation and alveolar fracture are similar in many ways to extrusive luxation and avulsion with
the addition of a bone fracture. Similar treatment is recommended but common practice is to?
A
Prolong the duration of maintenance of the splint for 6 to 8 weeks to allow for bone union. Some authors would
advocate performing root canal treatment of the injured tooth or teeth after 2 weeks as there is a risk
of impairment of healing by the release of degradation products of the pulp as it undergoes necrosis. In the author’s experience, lateral luxation of the canine tooth and alveolar fracture involving the
adjacent incisor teeth is often seen simultaneously. If this involves the mandibular canine tooth careful
assessment of the mandible lingual to the apex of the canine tooth is appropriate as fracture of the mandible may also occur.
24
Q
Even if definitive treatment of luxated or avulsed teeth are not going to be undertaken in primary care
setting there is likely to be benefit from?
A
Simple replantation of the tooth and closure of the gingival
tissues, with sling sutures, prior to referral for splint placement. Any delay in replantation could
adversely effect fibroblast health.
25
TDI (traumatic dento-alveolar injury) are seen most commonly in?
Middle aged groups with patients that are less than 3 or older than 10 years of age having less TDI. Luxation injuries, especially lateral luxations, were identified most
frequently in patients less than 3 years of age.
26
What are the most commonly reported TDIs (traumatic dento-alveolar injuries)?
The most commonly identified TDI were enamel-dentin-pulp fractures (49.6%). Concussive injuries
had a reported frequency of 14%, enamel- dentin fractures 12%, crown root fractures with pulp
involvement 10% and all other injuries less than 5% frequency. The least frequently identified the
intrusive laxations and subluxations.
27
Where are the majority of TDI's likely to occur?
The majority of TDIs are reported to occur in the maxilla (70%) with the majority of those affecting the
rostral oral cavity; canines and incisor teeth. The canine teeth were the single tooth most commonly
fractured, concussed or luxated.
28
Jaw fractures account for what percentage of all fractures in dogs and cats?
Jaw fractures account for 1.5-3% of all fractures in dogs and 15-23% of fractures in cats.
29
The lower jaw consists of 2 mandibles, in cats and dogs, as the fibrous synchondrosis between the
roughened end of the incisive processes of the mandibles remain and imparts and degree of flexibility
throughout life. Symphyseal laxity is?
Not uncommon and in some patients can be relatively extreme, it
is the authors experience that this is unlikely to effect functioning is almost never associated with
clinical impact on a patient (symphyseal laxity has been considered as part of the mechanism of open
mouth locking in some individuals).
30
The non-dentate mandible consists of?
The ramus, angular process, articular process and coronoid process
31
What is the first most important step in evaluation of maxillofacial and mandibular injuries?
Maxillofacial and mandibular injuries are, alone, rarely life-threatening. Although these injuries may
be very evident on presentation of patients that have suffered head injuries it should be stressed that
evaluation of the whole patient with focus on cardio-respiratory stabilisation and assessment of
central nervous function should be the initial focus. Even with severe maxillofacial and mandibular
trauma it is often appropriate to fully stabilise a patient prior to in-depth evaluation of their injuries.
Hypotension, hypoxaemia and hypercapnia can all have significant impact on the traumatised brain
and result in irreversible secondary brain injuries. This is of especial concern in high force injuries
such as road traffic collisions.
32
Statistically CT will identify, in dogs, and cats, how many more maxillofacial
injuries as plain radiography?
Statistically CT will identify, in dogs, 1.6 times and, in cats, twice as many maxillofacial
injuries as plain radiography. Fractures of the dentate mandible and maxilla can be assessed with
dental radiography but plain radiographic evaluation of the non-dentate structures, especially the
caudal mandible and temporomandibular joints, is exceedingly challenging, due primarily to
superimposition.
33
As the majority of jaw fractures will be contaminated or infected urgent administration of what is required?
Antibiotics is
recommended. The author prefers to use intravenously administer antibiotics, such as potentiated
amoxycillin or cefuroxime, up to completion of the definitive repair then transition to oral
medicaments usually for a 5 days post operative period.
34
What are the four primary principles of fracture repair?
1. Fracture reduction to restore anatomical relationship. Especially important as previously
noted to achieve an atraumatic and function dental occlusion.
2. Fracture fixation providing absolute or relative stability as the “personality” of the fracture,
patient and injury requires. As a rule, the more complex a fracture is and the less stable the
greater the level of stability is required to achieve bone healing.
3. Preservation of blood supply to soft tissues (including periosteum) and bone.
4. Early and safe mobilisation of the injured part and the patient as a whole. Wolf’s law indicates
that bone remodelling will adapt to loading forces therefore if a bone is not loaded this may result in atrophy or affect long term healing.
35
What does bone healing result from?
Bone healing results from the interaction between osteoblasts and osteoclasts. Osteoblasts are able to
produce 1µm of osteoid daily which undergoes maturation and calcification over a further 10 day
period. Osteoclasts are multinucleate giant cells derived from mononuclear macrophages which
breakdown bone prior to formation of new bone.
36
What are the 2 subsets of bone healing?
Direct and Indirect. Indirect relies upon the formation of a callous
and results from mechanical instability. Where indirect healing is expected the preservation of the
fracture capsule has increased importance.
37
What is the process of indirect bone healing?
The fracture capsule is formed the degradation products of
the fracture margins and blood clot and results in an optimal healing environment. Close to the bone
ends, assuming sufficient vascularity, osteoblasts secrete osteoid which is directly calcified. Further
from the bone ends osteoclasts transform into chondroblasts which secrete fibrocartilage. This
fibrocartilage increases the tissue stiffness and then is subsequently mineralised. This mineralised
fibrocartilage is finally removed before being replaced by osteoid and woven bone.
38
Discuss how direct bone healing occurs in the jaw?
Direct bone healing seen where the only bone forms between the fragment ends and does not involve
formation of a callous. Direct bone healing is subdivided into contact healing where the bone ends are
in direct contact, usually requiring compressive forces to achieve, and gap healing where the gap
between the bone ends is less than 800µm. If the gap is greater than 800µm indirect bone healing will
occur. Contact healing is difficult to achieve in the jaws but gap healing is the desire in most
circumstances.
39
What muscles open and close the jaw?
The temporal, masseter and pterygoid muscles all act to close the mouth and
have the ability to generate tremendous force. The digastricus muscle is the primary jaw opening
muscle and is comparatively weak. The muscles all insert on the caudal aspect of the mandible.
40
In the lower jaw the majority of the muscle force is directed in a rostrodorsal direction. If a load is applied to the rostral mandible a
tensile force results. In response, there is a tendency for the rostral jaw to be displaced?
Caudoventrally. If a fracture has occurred rostral to the point of insertion the caudal fragment will be pulled
upwards and the rostral fragment displaced downwards opening the fracture line and resulting in
mobility.
41
Where is the best place for fixation devices to be placed?
Along the length of the fracture there will be a continuum of tensile to compresses stress. The
compressive stress is greatest at the ventral margin and tension greatest at he dorsal margin of the
mandible. All fixation methods function best under tension and so it is preferable to place fixation
devices as close to the dorsal surface as possible. This may not always be practicable and further
review will be made later. Tension and compression forces only form where the is load sharing along
the feature line.
42
The tendencies for mandibular fracture fragments to be pulled apart can be exaggerated in?
in certain
fracture orientations.
43
Comminuted fractures and fractures of atrophic mandibles will result in?
Minimal
or no load sharing across the fracture line or force concentration.
44
Discuss favourable and unfavourable fractures?
Oblique fractures that
course in a caudoventral to rostrodorsal direction, called unfavourable fractures, will have an
increased tendency for retraction of fracture ends. Favourable fractures, rostroventral to caudodorsal
will have a tendency for the fracture ends to be compressed and as such may require less rigid fixation
to achieve healing.
45
How are different head on forces distributed across the jaw?
Rostral force
loading, as seen in a head on collision, will be distributed across the small bones and result in
“crumpling” and force dissipation (presumably to protect the vital structures found behind the
maxillofacial tissues). In contrast, a rostral force applied to the mandible will result in a significant
shearing force at the junction of the mandibular body and the ramus.
46
The maxillofacial bones act as a frame to link the dentition to the skull base. The support of the facial
region can be considered to be provided by 3 separate buttresses. these buttresses are defined as:
Rostral - nasomaxillary buttress
Lateral - zygomaticomaxillary buttress
Caudal - pterygomaxillary buttress
47
Destabilisation of the facial frame will only occur if the 3 facial butresses are compromised and the butresses
correspond to anatomically thicker bone and act in unison in a triangular formation to stabilise in 3-
dimensions. The facial frame can be reconstructed to relative rigidity by reconstruction of?
two of the
three buttresses, the caudal buttress is not easily accessed surgically and so is rarely repaired.
48
A tooth present in the fracture line should not be extracted unless it is?
Mobile, has a significant
crown/root fracture or has significant periodontitis. Extraction of teeth in the fracture line may cause
further iatrogenic damage, displace fracture fragments and create large bony defects. Extraction also
removes teeth that may be useful in the fracture stabilisation.
49
What is one of the primary goals of jaw fracture management?
Preservation of patient specific normal occlusion or at least avoidance of a
traumatic occlusion is one of the primary goals of jaw fracture management.
50
It should be common place to use
alternate methods of placement of endotracheal tubes when managing?
complex maxillofacial and
mandibular injuries.
51
How is Pharyngostomy intubation (PI) performed:
Normal placement of a trans-oral tube
Intra-pharyngeal digital palpation of the “gap” between the angular process and hyoid apparatus.
Insertion of using curved forceps (such as Mixter forceps) through the oral cavity in to the identified
“gap”
Tensioning of the overlying tissues by means of exteriorisation of the forceps’ tip
Incision over the tip of the forceps through the skin, carefully avoiding the bifurcating jugular vein.
Blunt dissection through the underlying soft tissues to fully exteriorise the tip of the forceps.
Grasping a second endotracheal tube (ideally armoured) and pulling through into the oral cavity by
use of the forceps.
Removal of the existing tube
Retroflexion of the pharyngostomy tube and subsequent re-intubaiton.
The tube can be held in place by means of a tie or Chinese finger trap suture. removal too the tube is by
simple exteriorisation trough the stoma and the stoma is not surgically closed,
The author finds PI challenging and can be somewhat stressful especially in smaller patients. It is also
the the author’s opinion that post operative morbidity is significant after pharyngostomy.
52
What is a safer alternative to Pharyngostomy intubation (PI)?
An alterante to PI is trans-mylohyoid intubation. The author feels that this allows all of the benefits of
PI without as many post operative complications and is significantly easier to perform.
53
How is trans-mylohyoid intubation performed?
Prior to anaesthesia the selected tube should have the end connector loosened/ freed to allow simple removal.
Normal placement of a trans-oral tube (ideally armoured).
The patient is placed in lateral or dorsal recumbency.
A sharp incision is made over the ventral border of the mandible through the skin and platysma at the level of the mandibular 1st molar tooth. The incision should be longer than the diameter of the
selected endotracheal tube.
Straight artery forceps are directed through the incision into the oral cavity staying close to the lingual aspect of the mandibular body as possible until the tip is visualised submucosally in the oral cavity.
The mucosa overlying the forceps tip is incised and the forceps advanced.
The trans-orally placed ET tube is decuffed and the connector removed.
The tube is advanced or curved to allow the end of the tube to be grasped by the forceps and then pulled through the created stoma and exteriorised.
The tube is reconnected and tied in place using a Chinese finger trap suture.
At the end of surgery the tube is reversed back into a normal trans-oral position and the stoma is closed in 3 layers.
54
How many teeth do you need for Intraoral wire and acrylic splints (IWAS)?
IWAS depends upon teeth for anchorage of the splint used for fracture stabilisation. The teeth used for splint anchorage need to be periodontally sound, stable and sufficient in number and size to provide secure fixation, common wisdom suggest a minimum of 2 large teeth on either side of the fracture are appropriate.
55
Why does andrew perry not like Cerclage or circum-mandibular wiring to fix symphyseal fractures?
The author has a number of reservations regarding this technique. Cross-section of the rostral mandibles reveal that they are an inverted egg shape. When a wire is tightened around the mandible at this
position the ventral borders can be rotated towards the midline and as a result the crowns of the canine teeth tipped laterally which may result in malocclusion. The author’s main concern is that even with exceedingly careful positioning of the wire and appropriate tensioning soft tissues are invariably trapped between the wire and mandible. These soft tissues undergo avascular necrosis and as a result within 2 weeks of application it is common for circus-mandibular wires to loosen. This may not
compromise restoration of function, increased laxity of the symphysis is unlikely to result in post
operative complications but it is undesirable.
56
What is the authors preferred method for fixing symphyseal fractures?
The use of an Intraoral wire and acrylic splints (IWAS) for symphyseal separation may neutralise the rotational forces that act on the
rostral mandibles more effectively, eliminate the risk of lateral tipping of the canine teeth, does not
loosen and avoids the need to place surgical implants into traumatised, possibly infected, tissues. IWAS
are placed between the mandibular canine teeth (an exception to the rule of requiring 2 teevthnon
either side of the fracture). If canine teeth are missing or injured it is possible to fabricate an anchor
point using an endodontic file anchored into the root canal or an orthopaedic screw inserted into the
bone.
57
The simplest form of non-invasive repair is?
Applications of a tape muzzle. The level of rigidity of this
construct is low and may be only appropriate as a means of temporary support prior to repair. It
should be noted that most animals with head trauma will have had blood clots form in the nasal
passages preventing nasal breathing and may find muzzles distressing. Very young puppies with
minimally displaced fractures may be related effectively with tape muzzles alone due to rapidity of
healing.
58
What is MMF?
maxillomandibular fixation
59
What is MMF (maxillomandibular fixation) used for?
MMF uses canine teeth for bonding and requires at least two ipsilateral canine teeth for fixation,
though four canine teeth are better. The most commonly used maxillomandibular fixation technique
involves bonding the maxillary to the mandibular canine teeth which immobilises the mandible
relative to the maxilla thus promoting secondary bone healing. This technique is particularly useful in
cases of complex maxillofacial fractures which are not amenable to other fixation techniques. It can
also be useful for short term stabilisation of temporomandibular joints following reduction of luxation.
60
How is MMF (maxillomandibular fixation) done?
The canine teeth are cleaned, acid etched and the etched surface primed for bonding. Most comply
spot bonding is advocated as it reduced the risk of iatrogenic tooth injury during removal. The canine
teeth are then placed in occlusion along with visual confirmation that the mandibular and maxillary
arches are correctly aligned. Crown overlap (commonly 1/3 crown height) is achieved so that there is
an opening of approximately 10mm between the opposing incisal arches allowing enough space for
lapping of water and liquid food. Light cured composite is applied in 2mm thick layers,
circumferentially around the teeth forming two pillars of splinting material. Alternatively, composite
can be placed into cut down clear drinking straws and the teeth inserted then the composite cured.
61
What are the dangers of MMF (maxillomandibular fixation)?
MMF is often associated with significant post operative morbidity and placement of a feeding tube preoperatively is strongly recommended. Many patients will adapt to be able to eat and drink with time
but not all, eating is always very messy. Additionally, MMF is contraindicated in patients where
pharyngeal or significant sublingual swelling is present or that have an increased risk of vomiting or
regurgitation due to increased risk of airway obstruction and aspiration pneumonia. It is common to
have a pair of extraction forceps or nail clippers with patients who have had MMF at all times. If these
patients are observed to be having difficulties that may risk their life it is better to break the bonding
(and possibly the teeth) than to allow a patient to succumb. Where possible the author will try to avoid
use of permanent MMF.
62
Intra-oral wire and acrylic splints can be utilised in?
Intra-oral wire and acrylic splints can be utilised in definitive repair of both mandibular or
maxillary fractures. There are a variety of wiring techniques that are used in providing stability to
maxillofacial fractures in dogs and cats.
63
What is the commonest Intra-oral wire and acrylic splints technique?
The commonest technique is the Stout multiple loop technique
where multiple loops of wire are passed between adjacent teeth and twisted to secure a second strand
of wire that is passed through the preformed interdental loop. The twisted loops can be placed on
either the buccal or lingual aspect of the dental arcade depending on the surface which is least likely to
cause malocclusion. In order to help retain the wire in the correct position it is often passed sub
gingivally. As with other uses of surgical wire, during twisting consistent traction should be applied to
the wire. this will prevent one wire twisting around the other and allow for the formation of a helical
twist which is considerably more resistant to tension forces.
64
Look at the Ivy loop wiring technique?
65
Look at the Stout multiple loop wiring technique?
66
Look at the Essig wiring technique?
67
Look at the Risdon wiring technique?
68
Though it is possible to stabilise some fractures with interdental wiring techniques alone usually wire
is reinforced with?
Acrylic.
Acrylic doesn’t adhere well to metal but conforms to crown shape and
interdigitates with the wire loops and twists and the resulting construct is stronger than either wire or
acrylic alone. Edentulous regions or areas where encircling teeth is not possible (mandibular 1st
premolar) the use of circus-mandibular wires can be used to increase construct rigidity.
69
What should application of wire and acrylic not do?
Application of wire and acrylic should not interfere with a patient’s normal occlusion. Where
premolars don’t occlude directly with each other, acrylic can be applied to both the buccal and lingual
surfaces of the teeth. In the caudal and rostral aspects of the oral cavity where teeth occlude directly or
move in close proximity with their opposite number, acrylic can only be applied to certain tooth
surfaces. For example acrylic cannot be applied to the palatal aspect of the maxillary fourth premolar
or the buccal aspect of the mandibular molar in dogs in order to prevent malocclusion and the
application of direct and significant forces to the splint during mastication.
70
What do Inter-fragmentary wiring techniques rely on to work?
The forces generated by the tension of the wire and by
the frictional forces between the corresponding bone fragments.
71
What is required for Inter-fragmentary wiring to work?
adequate stability for
healing requires accurate anatomic reduction and sufficient neutralization of two broad, opposing
bone fragments. Comminution or bone loss prevents precise anatomic apposition of the bone
fragments and/or the continuous interfragmentary compression across each/all bone fragments.
Inter-fragmentary wires only provide two-dimensional stability as rotation can occur around the
wires as they are passed through holes of slightly greater diameter than the wire.
72
What type of equipment is needed for Inter-fragmentary wiring?
Generally 1.0 - 1.25-mm orthopaedic wire (18 - 20 gauge) is used most often; using wire <1.0 mm (<20 gauge) is of insufficient strength to maintain the fracture reduction, even in small patients. Although the larger wire is more difficult to pass into the appropriate position, it results in a more
secure fixation. Excessive manipulation and kinking of the wire should be avoided as kinked wire is
difficult to pass through the drill holes and makes it impossible to maintain even tension.
73
For Inter-fragmentary wiring where should the drill holes be placed?
Drill holes for the wires are placed so that they cross perpendicular to the fracture line so that as the wire is tightened there is no shearing movement when stress is applied. In most fractures in order to
also to neutralise all shear and rotational forces across the fracture two wires should be placed, the
second is placed parallel to the first one. With less stable oblique fractures, the second wire should be
placed at an angle to the first wire. The divergent fixation prevents overriding or rotation of the
opposing bone fragments.
Drill holes need to be 5-10 mm away from the fracture in order to prevent an additional fracture the
possibility of pulling the wire through the bone and into the fracture site as the wire is tightened. Drill
holes placed too far from the fracture line produce insufficient tension and the wires will become
loose when placed under stress. Orienting the drill holes towards the fracture site results in a sloping
hole that facilitates both positioning of the orthopaedic wire and subsequent tightening.
74
How are Inter-fragmentary wires tightened?
Inter-fragmentary wires are tightened with a twist knot. As the twist knot is tightened,
tension must be applied by pulling up on the wire ensuring that the wire slides through the angled
drill holes. It is essential to apply wires tightly in order to compress the bone fragments. The wire is
bent over against the bone (perpendicular to both arms of the wire) away from the gingival margin
and cut to maintain at least three twists.
75
What is the post op care inter-fragmentary wiring?
If good fixation stability has been achieved patients can eat and drink soft food within 24 hours of
surgery. Chewing on hard objects and playing with toys is not permitted for the first 4-6 weeks
postoperatively
76
What are complications usually associated with for inter-fragmentary wiring?
Complications are usually associated with inadequate fracture reduction or wire tightening allowing
movement at the fracture site and progressive wire loosening. Fracture fixation instability will
predispose to post-operative infection, dehiscence of the soft tissue surgical wound and delayed or
non-union of the fracture. Loose implants will interfere with re-vascularisation, and also act as a
foreign body, both of which predispose to bone infection.
77
What does plate fixation provide?
Plate fixation provides three-dimensional rigidity of all bone fragments, can act as a buttress device to
support multiple comminuted bone fragments or span a gap.
78
What is the preferred metal for plates?
Titanium.
It is less
resistant to cyclic bending and care must be taken whilst performing plate contouring not to bend and then bend back repeatedly.
79
The design of plates used for maxillofacial repair are ideally?
Low profile (generally 0.7mm to 1.0mm
thick) and come in a wide variety of designs.
80
Application of plates along the tension surface of the mandible is highly challenging due
to?
The presence of the tooth roots and high risk of mucosal erosion and plate exposure post operatively.
81
It is recommended that non-locking constructs should have a minimum of 6 cortices engaged by
screws on either side of the fracture line. When using locking constructs this number may be reduced
to?
A minimum of 4 cortices.
82
How can the maxilla and mandible be approached for surgery?
A separate ventral surgical approach is made to each mandible though for bilateral mandibular body
fractures a single midline incision can be made. The mandibular ramus can be accessed through a
ventral or lateral approach depending on the location of the fracture. The maxilla can be approached
by an intra-oral exposure reflecting the gingiva and alveolar mucosa away from the alveolar bone or
via a dorsal mid-line approach. The zygomatic arch can be approached directly as can the lateral
aspect of the frontal bone and orbit.
83
How should the sequence of fracture repairs be addressed?
The sequence of repair of fractures should be considered carefully. Simple fractures are
reconstructed anatomically. Highly comminuted fractures, or fractures with gaps, should be
reconstructed using the patient’s normal occlusion to determine the accuracy of the reduction and
temporary MMF should be strongly considered as a method to ensure that adequate reduction is
obtained. Reconstruction should start with reduction of the more straightforward fracture first,
building toward the more comminuted fractures. It is the authors’ preference to begin caudally and
work rostrally where multiple fractures exist. For the maxilla, the lateral buttresses are reduced first
followed by the medial buttresses (the caudal buttress need not be addressed as reconstruction of two
of the three buttresses ensures that the remaining buttress will be reduced).
84
How should Fractures Involving the Zygomatic Arch be repaired/approached?
Fractures of the zygomatic bone can be associated with trauma to the eye and orbit. A direct approach
to the zygomatic arch is performed and for simple fractures the arch is reconstructed either with a
single plate that spans the arch or reconstructed with smaller plates across the individual fracture
lines and then additionally spanned over the entire distance. The zygomatic branch of the facial nerve, which passes over the caudodorsal aspect of the zygomatic arch should be preserved. Caudal fractures of the zygomatic arch must be approached with great caution due to the proximity of the facial nerve and maxillary artery.
85
Fractures Involving the Maxillary (Medial and Lateral) Buttresses
Approach to the medial and lateral buttresses can be obtained from what approach?
A dorsal midline approach with
lateral soft tissue elevation in order to adequately expose the fractures. The lateral buttress may be
approached separately, either directly over the rostral aspect of the zygomatic bone or intraorally by
elevating the alveolar mucosa apical to the fourth premolar. Reconstruction should commence with
the lateral buttress to re-establish continuity between the occlusal surfaces and the skull. Accurate
reduction of the lateral and medial buttresses will automatically result in reposition of the caudal
buttress.
86
Complications associated with plate fixation can occur even if the principles of rigid skeletal fixation
are followed and include:
* The use of a plate that is too short, too thin and with screws placed too close to the fracture
site, is one of the most common causes of failure of this method of internal fixation for
mandibular fractures.
* A poor result for maxillary fractures is often the result of not restoring the three-dimensional
anatomy and not placing the plates along the maxillary buttresses, where the thicker bone
enhances screw purchase.
* If the plate is poorly contoured the underlying bone will be pulled toward the plate, causing a
corresponding shift at the occlusal level.
* Accurate and atraumatic drill-hole placement must be performed in order to prevent bone
necrosis, which will result in premature screw loosening. In thin bone drilling should be a at
less than 1000 rpm. It also is essential that all drilling occur along a single axis. If any doubt
exists regarding screw purchase, an emergency screw should be used to replace the
questionable screw.
15
* Failure to bridge a fracture gap will predispose to implant failure as the plate will have to take
the forces of mastication. Bridging the gap with a bone graft will allow the bone to share the
torsion, bending and shear loads resulting in a more stable fixation. The use of a locking plate
system in this situation produces a more stable construct.
* Malocclusion can result in increased leverage on the fracture site and implant failure. Accurate
restoration of occlusion is vital.
* Plate exposure can occur if the implant loosens and in this situation plate removal is necessary.
If plate exposure isn’t related to loosening it can be maintained in place until healing occurs
and then removed or covered using a mucosal transposition flap.
* Infection is rarely a complication of internal rigid fixation but can occur if the implant loosens
for any of the reasons listed above.
* Delayed or non-union is again a result of implant loosening and can be prevented by good
fracture fixation technique.
* Perforation of tooth roots can result in pulp necrosis. Treatment consists of either endodontic
procedures, or tooth extraction. Extraction should wait until after fracture healing if possible,
in order to avoid creating a significant bone defect.
87
The introduction of non-invasive fixation techniques and advances in bone plating systems have
limited the indications for?
External skeletal fixators (ESF) in veterinary patients, and even
comminuted fractures are often treated with reconstruction plates and screws.
88
Why might External skeletal fixators (ESF) be indicated?
Most maxillofacial fractures are grossly contaminated fractures that are directly exposed to the
external environment through the skin, mucosa or periodontal ligament. Diffuse infection of the bone
at the fracture site is a possible contraindication for open fracture reduction and is an example where
ESF may be the treatment of choice. ESF may also be considered in management of fractures of
atrophic edentulous jaws and severely comminuted fractures with a tenuous blood supply. External
skeletal fixation devices can also useful for the treatment of non-union fractures where bone grafting
is necessary although large reconstruction plates and specialist gifting techniques have been more
commonly utilised in recent years. ESF can be used as a method of interim stabilisation before
definitive jaw reconstruction where soft tissues have been compromised or not declared their level of
vascular compromise.
89
TMJ trauma is particularly common in?
cats following head injury
90
What are common injuries of the TMJ?
Injuries include luxation and fracture
of the mandibular condyle and fossa.
91
How can TMJ fractures be visualised?
Complete radiographic assessment, by plain radiography, of the
TMJ is exceedingly challenging and is likely to only detect the most severe of fractures , although has a
higher degree of sensitivity for TMJ luxation. CT is particularly useful in assessing TMJ injuries and
should be the modality of choice when available. If conventional radiography is used, useful views
include ventrodorsal or dorsoventral and right and left lateral oblique projections are to isolate each
TMJ.
92
TMJ fractures and luxations commonly occur with?
Other maxillofacial injuries, especially in the cat.
93
How does TMJ damage present?
The most common finding with TMJ luxation or fracture is an inability to completely close the mouth.
Unilateral rostral luxation results in shifting of the mandible toward the side opposite the luxation,
caudal luxation results in shifting of the mandible toward the side of luxation and bilateral rostral
luxation results in slight rostral protrusion of the mandible. A fracture involving the TMJ may or may not result in malocclusion depending on the degree of displacement.
94
What is the treatment of Subluxation of the TMJ? (which may show no radiographic evidence of TMJ pathology)
Requires no
specific treatment other than soft foods and restriction of oral activity during healing.
Reduction of TMJ luxations is attempted using closed techniques.
95
Reduction of a chronic luxation is difficult or impossible due to?
Formation of an organised blood clot and fibrous tissue that fills the joint space.
Therefore, closed reduction should be attempted as soon as possible after the injury occurred.
96
How is closed reduction of TMJ luxation done?
Closed reduction is most commonly performed using a pencil placed between the mandibular 1st molar and maxillary 4th premolar only on the side of the luxation. The mouth is the forcibly closed on the pencil (which acts and as fulcrum) and the pencil relocated whilst applying rostrodorsal (ventral luxation) or
caudoventral (dorsal luxation) force. Repeat imaging is appropriate to asses reduction. Soft food and withdrawal of chew toys for six weeks is indicated. Additional support may be given using a tape muzzle or temporary MMF.
97
The most common direction of TMJ luxation is?
Rostrodorsal.
98
Rostrodorsal
luxations have a greater propensity to stability after reduction, conversely ventrocaudal luxation islikely to result in injury to the retroarticular process and resulting instability after reduction. Why?
The retroarticular process, which
forms the most caudal and ventral portion of the TMJ, is delicate and easily damaged.
99
If, after reduction, the TMJ is felt to be unstable the use of short term (2 weeks) MMF may provide
sufficient fibrous stabilisation of the TMJ to avoid?
Chronic luxation formation.
100
What is the treatment for non reducible TMJ luxations?
Open reduction or
condylectomy is considered for non-reducible luxation and recurrent luxation.
101
The treatment of TMJ fractures will vary, depending on the degree of displacement of the fracture, but may include:
Conservative treatment with soft diets and the use of a muzzle (in dogs), MMF in dogs and
cats and partial or total condylectomy.
102
Conservative treatment of minimally-displaced condylar, subcondylar and pericondylar fractures without significant joint surface involvement is usually?
successful
103
When doing a condylectomy what must you be very careful of?
Where condylectomy is considered appropriate the site is identified at the base of the condylar process at the level of the mandibular notch. The ostectomy is most easily made using a piezotome or a
small sterile water-cooled bone bur. Care must be taken to avoid laceration of the maxillary and
external carotid arteries which course immediately medial and ventral to the condyle.
104
What are the indications for a condylectomy?
* Chronic luxation
* Acute luxation than can not be reduced
* Extensive comminuted fractures
* Septic arthritis
* Ankylosis
105
What is the approach to a condylectomy?
Approach to the condyle is made by performing a curvilinear incision along the ventral surface of the
caudal half of the zygomatic arch. The platysma, sphincter coli and zygomaticus muscles and
underlying fascia is incised and retracted avoiding the parotid duct and dorsal branch of the facial
nerve. revealing the insertion of the aster muscle on the ventral border of the zygomatic arch The
caudal half of the masseter muscle is subperiosteally elevated and the muscle retracted in a
caudorostral direction. Opening and closing of the mouth at this point will usually allow for visual or
digital identification of the joint. If needed, surgical incision into the joint can be performed. If the
cartilaginous disc is uninjured it can be left in situ and may reduced the incidence of pseudo ankylosis,
if damaged it should be removed. If possible interposing fat between the cut surface of the mandible
and the articular fossa may reduce pseudoankylosis
106
Malocclusion resulting from condylectomy, is usually minimal and of?
No functional importance. Guided
elastic traction may be used to assist the animal in closing the mouth in correct occlusion.
107
What is the post op care of a condylectomy?
Post operatively tape or nylon muzzles or MMF is applied for a limited period of up to two weeks.
Prolonged immobilisation of the TMJ is avoided as immobilisation may result in TMJ ankylosis and a
limited range of mouth opening. Feeding soft food and reduced oral activity is continued for an
additional 3-4 weeks during continued healing for luxation and until clinical healing of fractures.
Guided elastic traction using orthodontic buttons and power chains can also be used to prevent
malocclusion following condylectomy in cats.
108
Most reduced TMJ luxations and nondisplaced or minimally displaced TMJ fractures heal adequately
and provide normal oral function with conservative management. Poor functional results
(malocclusion, ankylosis, degenerative joint disease) can usually be corrected by?
mandibular
condylectomy
109
What is Temporomandibular joint ankylosis?
An intracapsular fibrous or bony union of the TMJ due to
disease, trauma or neoplasia. False ankylosis is caused fibrous adhesion between the zygomatic arch and mandible secondary to fracture, infection or neoplasia.
110
What are the clinical signs of Temporomandibular joint ankylosis?
Clinical findings include an inability to
completely open the mouth, weight loss and atrophy of the muscles of mastication.
111
What is the treatment for Temporomandibular joint ankylosis?
En bloc resection
of the involved bone and abnormal soft tissue is necessary to resolve the ankylosis. Resection may
include condylectomy or caudal mandibulectomy, including the condylar process, with removal of zygomatic arch and interposed affected soft tissues. These cases can be exceedingly challenging and 3-
dimensional modelling can be of significant benefit in surgical planning.
112
What is the anatomy of the TMJ?
Anatomy
* Synovial joint
* Condylar process (Head of mandible)
* Mandibular fossa originates squamous temporal bone
* Fibrocartilagenous disc
* Hinge joint (Cats esp) slight laterotrusion (Dogs)
113
What are the possible complications of Rigid Internal Fixation?
Complications
* Implant failure
* Malocclusion
* Screw loosening
* Plate exposure
* Infection
* Delayed union
* Iatrogenic tooth injury
114
What acrylic is used for Intra-oral wire and acrylic splints?
115
What materials are needed for Intra-oral wire and acrylic splints?
40 % phosphoric acid
* Gel
* 15-30 second application.
* Irrigate for same period as
application
* Selectively removed mineral content
and exposes collagen fibrils
Priming/ bonding agent
* Low viscosity methy-methacrylate monomers
* Consider hydrophobic
* Flow between collagen fibrils
* Micro-mechanical retention
* Light cured most commonly
* Use spot bonding technique
* Avoid risk of iatrogenic trauma during
removal
Flowable composite
* High rigidity
* Strong but brittle
* MM monomers with filler particles
* Light or chemical cure
Bis-acrylic temporisation material
* Less brittle
* High tensile strength
* Chemical cure
* Minimally exothermic
* Easily shaped with appropriate burrs
116
117
118
Show the caudal buttress?
119
Show the lateral buttress?
120
Show the rostral buttress?
121
Look at this diagram of a favourable fracture?
122
