oral surgery Flashcards
1
Q
What influences the rate of absorption of local anaesthetic?
A
Blood flow in the tissue Concentration of the anaesthetic Amount administered
2
Q
What is the onset time and duration time of Prilocaine?
A
Onset 3 minutes Duration 2 - 2 1/2 hours
3
Q
What is the onset time and duration time of Lidocaine?
A
Onset 5 minutes Duration 1/2 - 2 hours
4
Q
What is the onset time and duration time of Articaine?
A
Onset 5 minutes Duration 1 - 3 hours
5
Q
Give four factors that affect the intrinsic factors of local anaesthetic…
A
Pregnancy pH Vasodilation Vasoconstriction
6
Q
Explain how pregnancy can affect the intrinsic factors of local anaesthetic
A
progeserone can potentiate (increase) the nerve blocking effect of the LA therefore increasing its effectiveness
7
Q
Explain how an alteration in pH can affect the intrinsic factors of local anaesthetic…
A
Inflammation and uraemia lower the tissue pH. This reduces the percentage of the neutral base form. A pH alteration can affect the binding to plasma and tissue proteins and seems relevant for the rapid appearance of tolerance during a repeat injection
8
Q
Explain how vasodilation can affect the intrinsic factors of local anaesthetic…
A
intrinsic vasodilation (due to local processes in the surrounding tissue) causes rapid elimination from the area of injection. Eg, bupivaccain is a vasodilator
9
Q
Explain how vasoconstriction can affect the intrinsic factors of local anaesthetic…
A
A vasoconstrictor masks the inherent vasodilatory properties of the LA and causes an increased effect that also lasts longer
10
Q
What is the mode of action of local anaesthetics? ie how is anaesthesia achieved?
A
Local anaesthetics stop nerve conduction by blocking the voltage gated sodium channels. LA binds to a site in the sodium channel, blocks the channel and prevents sodium influx. This blocks action potential generation and propagation. Block persists so long as sufficient number of sodium channels are blocked.
11
Q
What are the three components of a local anaesthetic molecule?
A
Aromatic region (hydrophobic) Ester or amide bond Basic amine side chain (hydrophillic)
12
Q
Name four possible ingredients in a local anaesthetic solution
A
- a hydrochloride base to increase solubility in aqueous solution (2-4%) -Reducing agent - Preservative(s) and fungicide - +/- vasoconstictor
13
Q
Why are vasoconstrictors included in local anaesthetics?
A
most local anaesthetics are vasodilators, the increased blood flow will increase the ‘wash out’ of the LA. adding a vasoconstrictor will increase the duration of action (adrenaline or felypressin)
14
Q
What is the maximum dose of lignocaine?
A
5mg per kg body weight 44mg per cartridge therefore 7 cartridges (approx 1 per 10kg body weight)
15
Q
what is the maximum dose of articaine?
A
7mg per kg body weight 88mg in each cartridge therefore 5 cartridges
16
Q
what is the maximum dose of prilocaine?
A
8mg per kg body weight 66mg per cartridge therefore 8 cartridges
17
Q
Name 8 possible complications of local anaesthetic
A
-failure to achieve anaesthesia -prolonged anaesthesia -pain during or after injection -trismus -haematoma -intra-vascular injection -blanching -facial paresis -broken needle -infection -soft tissue damage -contamination
18
Q
Give reasons for prolonged anaesthesia
A
direct trauma from needle multiple passes with same needle chemical trauma from direct injection different results depending on LA used
19
Q
Describe and give causes of trismus
A
presentation within a few hours of IAN block, may severely restrict opening, may last for weeks or months. Caused probably by damage to medial ptterygoid. Injection too low? Too forceful? Management may include reassurance, muscle relaxant or anti-inflammatory
20
Q
Describe and give causes of facial palsy
A
Presentation usually complete (whole half of face paralysed) Unilateral motor nerve paralysis within minutes of block Confirm temporal branch affected ie lower motor neuron distribution Caused by LA into parotid gland, injection too far posteriorly Test branches of facial nerve Reassure patient and cover eye with pad until blink reflex returns
21
Q
What would be the signs/symptoms of an arterial injection with LA?
A
This is very rare skin blanching, visual and or aural disturbance
22
Q
What would be the signs/symptoms of an intravenous injection with LA?
A
Palpitations, anxiousness, restlessness, headache, sweating, pallor. can be avoided by using a careful technique and slow administration
23
Q
What post extraction advice should be given to a patient regarding pain?
A
-expect some post-op pain and that they will be sore when the LA wears off, but this is normal and varies person to person -painkillers can be taken prior to LA wearing off (paracetamol and ibuprofen best if possible), and should be taken for 1-3 days and then as and when required
24
Q
What post extraction advice should be given to a patient regarding prevention of bleeding?
A
- tell the patient that post op bleeding is unlikely but is a possibility - tell the patient not to explore the socket with their tongue, finger, toothbrush as this could dislodge the clot and result in bleeding - do not exercise that day and avoid strenuous activity that would increase BP - avoid very hot food - stick to a softer diet for a few days - avoid alcohol and smoking for at least 24 hours - gently rinse with warm salt water from the following day 4 x daily
25
what post extraction advice should be given to a patient regarding bleeding at home?
- roll up a damp tissue or gauze and bite firmly for 20-30 minutes - If bleeding persists, bite on a fresh tissue/gauze for an hour - if bleeding persists, contact the practice or out of hours - if bleeding will not stop and the patient is unable to get an emergency appointment, they should go to their nearest A&E
26
what post extraction advice should be given to a patient regarding sensitivity?
may experience sensitivity of the teeth on either side of the extraction site and if this happens they should avoid extreme hot and cold in that area until it settles, which could take a few days to two weeks
27
what post extraction advice should be given to a patient regarding other symptoms to maybe expect?
pain and stiffness of the TMJ and muscles with limited mouth opening which should settle over the course of a few days to a couple of weeks. If it affects eating or lasts longer than two weeks, further advice should be sought. Swelling can be especially evident two days after extraction. If it gets worse or there is concern of infection, further advice should be sought. Bruising can occur and varies from person to person, but this is normal
28
What is the correct term for a dry socket?
alveolar osteitis
29
What two types of haemmorhage can occur post extraction?
\*Immediate post operative period - reactionary and rebound bleeding which occurs within 48 hours of the extraction - caused by vessels opening up as the vasoconstrictive effects of the local anaesthetic wears off, sutures become loose/lost, or if the patient traumatises the socket \*Secondary bleeding - often due to infections, commonly occurring 3-7 days post extraction - usually a mild ooze but can occasionally cause a major bleed
30
How do you stop bleeding after an extraction?
-apply firm even pressure with damp gauze -local anaesthetic with a vasoconstrictor can be administered -haemostatic aids; \*surgical oxidised cellulose or gelatin sponge can be packed into the socket which acts as a framework for clot formation \* Whiteheads varnish pack which contains iodoform, gum benzoin, storax, balsam tolu and ethyl ether \*bone wax \* thrombin liquid and powder \*fibrin foam -surgical aids \*suture the socket with interrupted/horizontal mattress sutures \*ligation of vessels and diathermy may be used
31
What nerves are affected by an IDB?
\*inferior alveolar nerve \*lingual nerve \*some branches of incisive and mental nerve may also be affected
32
What is the aim of suturing?
\*to approximate and reposition the tissues \* to compress the blood vessels \*to cover the bone \*to prevent wound breakdown \*to achieve haemostasis \*to encourage healing by primary intention
33
What are the four different types of sutures?
\*Resorbable - monofilament (monocryl) - polyfilament (vicryl rapide) \*non-resorbable -monofilament (prolene) - polyfilament (mersilk)
34
What are the different type of flap design?
\*3 sided
\*envelope
\*rectangular
\*semilunar
35
What are the general principles that should be adhered to when carrying out flap surgery?
\*create maximal access with minimal trauma as larger flaps heal just as quickly as smaller ones
\*wide based incision should be used for circulation
\*use the scalpel in one firm continuous stroke
\*do not create any sharp angles
\*minimise trauma to dental papilla
\*flap reflection should be down to bone and done cleanly
\*avoid crushing the tissues
\*keep tissues moist
\*ensure the flap margins and sutures lie on sound bone
\*make sure wounds are not closed under tension
\*aim for healing by primary intention to avoid scarring
36
What handpiece and bur are used to cut bone and why?
\*straight electrical handpiece with saline cooled bur
- round or fissue tungsten carbide bur
- air driven handpiece may lead to surgical emphysema and embolisms to form
37
List the indications for extractions
- unrestorable teeth
- symptomatic partially erupted teeth
- traumatic position
- orthodontic indications
- interference with construction of dentures
38
What analgesics can be prescribed by a dentist?
\*aspirin (NSAID)
\*ibuprofen (NSAID)
\*diclofenac (NSAID)
\*paracetamol
\*dihydrocodeine (opioid)
\*carbamazepine
39
Describe the production of prostaglandins resulting in pain
- trauma and infection lead to the breakdown of membrane phospholipids producing arachidonic acid
- arachidonic acid can be broken down to form prostaglandins
- prostaglandins sensitise the tissue to other inlammatory products which results in pain
40
What are the three mechanical principles for tooth elevation
- wheel and axle (rotation
- lever
- wedge
- all three actions can be used in combination with each other
- excessive force should be avoided
41
What are the points of application for tooth elevation?
- mesial
- distal
- buccal
- inferior
- superior
42
List four peri-operative complications
\* difficulty gaining access
\* abnormal resistance
\* tooth fracture
\* fracture of maxillary tuberosity or alveolar plate
\* Jaw fracture
\* OAC
\* loss of tooth
\* soft tissue damage
\* haemorrhage
\* dislocation of TMJ
\* damage to adjacent teeth/restorations
\* extraction of permanent tooth germ
\* broken instruments
\* wrong tooth
43
What are the criteria for a dento-alveolar surgery flap?
must be full thickness base must be wider than incision site must not split interdental papilla avoid important structures
44
What do you use to remove bone and why?
Must use an electric drill rather than air turbine as air turbine driven instruments can force air into the cavity and cause a surgical emphysema the drill is cooled with sterile water to reduce heat (\>55\* will kill bone) and reduce infection, increase visibility
45
What is the difference between Asepsis, antisepsis sterilisation and disinfection?
asepsis - avoidance of pathogenic material - aseptic technique in surgery antisepsis - application of agent which inhibits growth of microorganisms when in contact with them sterilisation - destruction or removal of all forms of life disinfection - inhibition or destruction of all pathogens
46
What types of extraction forceps are used?
upper anteriors - straight and narrow upper molars - 90\* angle beak to cheek lower anteriors - 90\* angle and narrow lower molars - 90\* angle and two beaks cowhorns - for removal of teeth with splayed roots - penetrate bifurcation
47
What are elevators used for?
Elevators dilate the sockets. Always used to remove impacted teeth. Couplands, Cryers, Warick james
48
What periosteal elevators are used?
These pull back the periosteum from the bone, they are blunt, curved instruments Howarths periosteal elevator
49
What is the mitchells trimmer for?
this is a curette. this is used for finding a weak spot of bone overlying pathology to be removed
50
What are dissecting forceps for?
They hold soft tissue without damamging it, Gillies dissectors.
51
What order should you extract molar teeth (if all are going) and why?
Extract from the most posterior to the most anterior. Prevents a single standing tooth left in a weakened bone - reduces chance of alveolar or tuberosity fracture
52
what different types of post-op bleeding are there?
immediate (at surgery no haemostasis achieved) reactionary ( within 48 hours - rise in BP) secondary (~7 days post op. infection and destruction of clot)
53
If a patient comes in to your surgery the day after an Xn with bleeding, how would you deal with them?
Reassure the patient that it is ok and they wont bleed to death repeat a full Hx inc DH. Get pt to bite on gauze suction socket, clean pt identify source of bleeding - if coming from socket then squeeze the gingivaea of outer walls with finger and thumb. if stops, was gingival. if from bone vessels, needs packing can use bone wax, fibrin foam, sutures, collagen sponge, recall the next day
54
What suture would you use for an extraction socket?
Resorbable suture, monofilament, 18mm curved tapered needle simple interrupted suture knot is tied twice one way and once the other (two surgeons knot, one locking knot)
55
What is MRONJ and what can cause it?
medication related osteonecrosis of the jaw - non healing socket or wound \>8 weeks, bone seen, halitosis caused by monoclonal antibody medications, RANK-L inhibitors, bisphosphonates and anti-angiogenics (VEG-F inhibiotors)
56
What would you be looking for in someones history to see if they would be at riskof MRONJ?
A history of metastatic breast or bone cancer osteoporosis, Pagets disease
57
What increases a patients risk of MRONJ?
Hx of MRONJ If they on Antiresorbtive or Antiangiogenic drugs for management of cancer on BPs for \>5 years on denosumab in last 9 months + systemic glucocortioid or \<5years BPs + systemic glucocorticoid
58
What surgical options are there for impacted canines?
1. removal 2. surgical exposure and ortho alignment (attaching a bracket and gold chain to re-position) 3. auto transplantation
59
How would you distinguish a tooth with an apical abscess?
teeth with apical abscesses are TTP, non vital, discoloured, Hx of trauma or RCT. Radiograph shows well demarcated PA radiolucency with widening of the lamina dura
60
how would you distinguish dry socket?
pain 2-4 days post extraction worse than preceeding toothache exposed bone is visible - no clot in socket socket looks inflamed
61
How do you treat dry socket?
warm LA in socket so you can clean Alvogyl in socket CHX mw or hot salty MW, NSAIDs
62
What is ludwigs andgina?
Medical emergency abscess and cellulitits spreading throught he submandibular space and sublingual space patient might complain of tongue being pushed up or problems swallowing soft tissues of FOM and neck are hard, airway is at risk
63
What is denture hyperplasia?
non tumour soft tissue lump hyperplastic response to chronic trauma. rolls of tissue in the sulcus relating to denture flange. similar to FEP. complete excision, temporary removal of denture/relieve denture.
64
What are warts/squamous papillomata?
non tumour soft tissue lump HPV infection. multiple pappilated pink asymtomatic lumps. excise and Bx
65
What are Tori?
non tumour hard tissue lump bony exostoses. both jaws. developmental abnormality, not sinister
66
What is Pagets disease of bone?
non tumour hard tissue lump skull, pelvis, long bones and jaws. max\>mand hypercementosis of roots. replacement of bone abnormality. bone pain and cranial neuropathy occuts. Cotton wool appearance of bones. Avoid GA, treat with BPs
67
What are odontomes?
compound - denticles in a sac complex - irregular mass of dental tissues treat as malpositioned/impacted teeth
68
what is the difference betwen OAF and OAC?
OAC - oroantral communication. not lined by epithelium, can heal closed. acute OAF - fistula, lined by epithelium. needs removal of the lining and surgically closing. chronic
69
what teeth are most likely to give OAC?
max 6/7/8
70
How do you treat OAC
inform patient if small (\<2mm) - encourage clot, suture, if large - lift buccal advancement flap - parallel incisions - full thickness score periosteal layer so it becomes stretchy advance over defect and suture close give ABs - 7 days amoxicillin 500mg TID post op instructions: steam inhalations. no blowing nose/sneezing/playing wind instrument/using straw for 2 weeks/give decongestants review after 6 weeks
71
What does granulation tissue mean?
Granulation tissue is new connective tissue and microscopic blood vessels that form on the surfaces of a wound during the healing process. Granulation tissue typically grows from the base of a wound and is able to fill wounds of almost any size.
72
What nerves do you need to anaesthetise to extract a lower permanent molar?
inferior alveolar nerve, long buccal, lingual nerve
73
how to do check for IAN, long buccal and lingual nerve for anaesthesia?
check for altered sensation in the lower lip on that side, gingivae around the tooth (buccal and lingual side), altered sensation in that side of the tongue
74
What are different IDB techniques?
Halsteads technique Indirect technique Anterior ramus technique (limited mouth opening) Gow-gates technique (long buccal at same time) Akinosi (limited mouth opening and long buccal at the same time)
75
What principles of flap design should you adhere to when raising a mucoperiosteal flap?
Avoid vital structures full thickness of flap raised - not saw-toothed edges must close over bone base must be wider than the apex provide access to the surgical site be able to be closed at the end of surgery minimise trauma to papilla reflect flap clealy healing by primary intention
76
What guidelines can you follow for determining the removal of a wisdom tooth?
NICE (guidance on the extraction of wisdom teeth) SIGN 43
77
How would you judge the relationship of a root to the IAN?
Radiographically: 1. do the tramlines converge or disappear 2. is there a shadow across the root 3. loss of the cortical outline as it passes the root 4. deflection of the roots 5. bifid root apices 6. diversion of the canal 7. juxta apical area
78
What information is given for consent?
must be written and verbal description of procedure in patient friendly terms risks/warnings - pain, swelling, bruising, bleeding, infection, dry socket, jaw stiffness, damage to adjacent, potential damage to nerves (specifically - permanent risk, temporary risk, what it will feel like, distribution), jaw fracture, anesthetic
79
What are bisphosphonates and what are the risk categories?
anti resoptive drugs. If patient has Hx of MRONJ, on BPs for Tx of cancer, taken them \>5 years and concurrent Tx with glucocorticoid puts patient in high risk
80
When would you refer a patient at risk of MRONJ?
if an extraction socket has not healed within 8 weeks, or there is evidence of spontaneous MRONJ - refer to oral surgery/SCD
81
You have a patient who is about to start treatment with BPs, how would you manage them?
1. OH is imperative - consequences of not 2. examine dental tissues for evidence of active infection - Tx 3. examine prosthesis for trauma potential 4. teeth with poor prognoses/ poor long term retention XLa 5. educate pt on signs and symptoms of MRONJ 6. must be dentally fit before treatment starts
82
Patient on BPs at high risk needs XLA. How would you manage them?
pre-operative rinse with CHX, atruamatic surgical technique, primary closure of soft tissues without stripping periosteum post-operative CHX until mucosa has healed. review patient until socket has healed. do not attempt further XLA until socket has healed
83
How would you diagnose pt with MRONJ?
be on, or have been on, anti-resorptive medication exposed bone or probe bone through fistula of maxfacs region \>8 weeks no obvious metastatic disease to the jaws
84
Why might a patient be on anti-resorptive drugs?
osteoporosis prevention of skull fractures Paget's disease of the bone, metastatic bone disease multiple myeloma renal cell carcinoma
85
What radiographic views would you take to identify a root/tooth in the antrum?
OPT upper occlusal periapical
86
What dental causes can sinusitis mimic?
• Periapical abscess • Periodontal infection • Deep caries • Recent extraction socket • MFPDS (myofacial pain syndrome) • Neuralgia or atypical facial pain
87
What would you use to remove bone from a socket?
rongeurs (bone nibblers)
88
which nerves are at risk of damage form 8s removal?
lingual IAN mylohyoid long buccal
89
What would you use for soft tissue elevation and retraction?
Howarths periosteal elevator wards periosteal elevator buser periosteal elevator bowdler-henry rake retractor Lacks retractor minnesota retractor
90
List some uses of elevators
• To provide a point of application for forceps • To loosen teeth prior to using forceps • To extract a tooth without the use of forceps • Removal of multiple root stumps • Removal of retained roots • Removal of root apices
91
Where are the application points for an elevator and what actions would you use?
mesial, buccal and distal wheel and axle, wedge, lever
92
What instruments could be used to debride a socket after extraction?
bone file mitchells trimmer victoria curette irrigation suction
93
List post-op analgesia and doses
Ibuprofen – 200 or 400mg, 6 hourly or 3 times daily. Avoid in asthmatics, bleeding disorders/Warfarin, on other NSAIDs – see BNF. Note some asthmatics can take it but check, and if they’ve never had it don’t prescribe it. • Paracetamol 500mg tablets, 2 tabs 4-6 hourly, no more than 8 a day. Overdose serious. • Cocodamol – contains 8mg codeine and 500mg Paracetamol (stronger contains 30mg codeine/500mg Paracetamol). 2 Tabs 4-6 hourly, do not exceed 8 in a day.
94
list some perioperative complications of surgery
tooth/root/adjacent lingual plate/alveolus/mandible # max tuberosity # OAC/loss of tooth into sinus trauma to IAN bleeding crush/puncture/laceration injuries to soft tissue burns
95
list some postoperative complications of surgery
pain swelling bruising trismus para/ana/dysaesthesia altered taste infection dry socket port op bleeding haematoma osteomyelitis MRONJ/ORNJ actinomycosis
96
what are post operative techniques for controlling bleeding?
• Post-operative – Pressure (finger or via swab or pack) – LA with vasoconstrictor infiltration in soft tissues, inject into socket, or on a swab – Diathermy – Haemostatic Agents – Surgicel/Kaltostat – Sutures – Bone wax smeared on socket wall with blunt instrument – Haemostatic forceps/ artery clips
97
what are peri-operative techniques for controlling bleeding?
Peri-operative – Pressure – LA with vasoconstrictor – Artery forceps – Diathermy – Bone wax
98
what are symptoms of OAC?
hollow suction nasal sounding voice air coming through mouth bubbling of blood pt hold nose and breathe out when you look in mouth you can see air
99
what drugs can affect clot formation and how?
aspirin - prevents platelet aggregation warfarin - prevents formation of clotting factors herparin - reduces action of platelets NOACs; Dabigatran direct inhibitor of thrombin, apixaban/rivaroxaban direct factor Xa inhibitors
100
What are the clinical features of trigeminal neuralgia?
\*Severe spasms of pain 'electric shock' lasts seconds
\*Usually unilateral
\*More common in older age groups
\*Trigger spot identified
\*Females more than males
\*Periods of remission
\*Recurrences often greater severity
101
What drug is used to manage trigeminal neuralgia?
Carbamazepine
102
Name and describe the three types of debridement?
\*Physical; bone file or handpiece to remove sharp bony edges. Mitchells trimmer or victorial curette to remove soft tissue debris
\*Irrigation. Sterile saline/water into socket and under flap
\*Suction. Aspirate under flap to remove debris. Check socket for retained apices etc
103
Define anaesthesia
Numbness
104
Define parasthesia
tingling
105
Define dysaesthesia
unpleasant sensation/pain
106
Define hypoaesthesia
reduced sensation
107
Define hyperaesthesia
increased/heightened sensation
108
Name some haemostatic agents
\*LA with adrenaline
\*surgicel (oxidised regenerated celluslose
\*Gelatin sponge
\*thrombin liquid and powder
\*fibrin foam
109
What is alveolar osteitis?
A dry socket
110
What are some features of a dry socket?
Intense pain, keeping patient awake at night. Often starts 3-4 days post op and can take 7-14 days to resolve. It is inflammation affecting the lamina dura. The clot either fails to form or breaks down
111
What are some predisposing factors of a dry socket?
\*Risk increases from anterior to posterior
\*Mandible more common
\*smoking - reduced blood supply
\*Oral contraceptive pill
\*Excessive trauma during extraction
\*Excessive mouth rinsing
\*Family history/previous dry socket
112
How should a dry socket be managed?
\*Reassure patient
\*LA block
\*Irrigate socket with warm saline
\*Curettage/debridement to encourage bleeding and new clot formation
\*Antispetic pack eg BIP or alvogyl
113
Describe osteoradionecrosis
condition seen in patients who have had radiotherapy of the head and neck. Bone within radiation beam becomes virtually non vital. Turnover of any remaining vital bone is slow and repair is ineffective.
114
What is MRONJ?
Medication related osteonecrosis of the jaw.
Can be caused by bisphosphonates used to treat osteoperosis and malignant bone metastases. They inhibit osteoclast activity and so inhibit bone resorption and therefore bone renewal.
115
What is infective endocarditis
inflammation of the endocardium, particularly affecting the heart valves or CMP caused by bacteria. Antibiotic prophylaxis is not routinely recommended.
116
What is prescribed as a prophylaxis against infective endocarditis?
3g amoxicillin oral powder to be taken 60 minutes before treatment
117
Name two drugs in which care must be taken when carrying out an extraction and explain why
- Warfarin:
— If a patient taking warfarin INR is not within target
range if below \<4 there is an increased change of
bleeding as the drug is an anti-coagulant so it prevents
clots from forming and growing,
— It decreased blood clotting by blocking vitamin k
epoxied reductase that reactivates vitamin K1. Without
sufficient activation of this vitamin K, clotting factors II,
VII, IX and X have decrease clotting ability. The anticlotting
protein C and protein S are also inhibited.
— Due to the reduced clotting efficiency of the blood if
the INR is not in target range a blood clot cannot be
formed at the site of extraction which means the
socket will continue to bleed if there is not adequate
haemostasis.
- Clopidogrel:
— This is an anti-platelet prodrug where it’s active
metabolite then specifically and irreversibly inhibits the
P2Y12 subtype of the ADP receptor which is important
in the activation of platelet and the cross linking of
fibrin. Platelet inhibition therefore occurs and a fibrin
clot production is reduced.
— This reduces a clot being produced at the site of
extraction; however there is a less chance of
spontaneous bleed on patients on this drug alone
when compared with patients on dual therapy or
warfarin
