This document summarizes local and general complications that can occur from local anesthesia in dentistry. For local complications, it discusses failure to obtain anesthesia, pain during/after injection, hematoma formation, intravascular injection, blanching, trismus, facial paralysis, lip trauma, prolonged impairment of sensation, broken needles, and infection. For general complications, it mentions fainting, drug interactions, homologous serum jaundice, sensitivity reactions, occupational dermatitis, and cardio-respiratory emergencies. Causes and treatments are provided for many of the complications.

1. Complications of local anasthesia
in dentistry (part I)
Dr.Mohamed Rhael Ali
2016 - 2017

2. I. Local complications :
1. Failure to obtain anasthesia
2. Pain during and after injection
3. Hematoma formation at the site of injection
4. Intravascular injection
5. Blanching
6. Trismus
7. Facial paralysis
8. Lip trauma
9. Prolonged impairment of sensation
10. Broken needle
11. Infection
12. Visual disturbance
II. General complications :
1. Fainting
2. Drug interactions
3. Homologous serum jaundice
4. Sensetivity reaction
5. Occupational dermatitis
6. Cardio- respiratory emergencies

3. Local complications

4. Failure to obtain anasthesia
It may be complete or partial
Causes :
Operator experience
Inadequate amount of the local anasthesia
Injection in to the blood vessel
Presence of infection
Expire date of local anasthesia solution
Patient response to drugs

5. pain during and after injection
Suggested causes :
a. Injection of either non isotonic or contaminated
solutions .
b. Neurological pain during injection due to
penetration of nerve sheath by the needle
c. Use of excessive force during deposition of
anasthesia solution

6. Hematoma formation
Bleeding in the tissue due to injury to blood vessels during
injection

9. Hematoma formation
Mainly occure with block injection
• Mostly superior posterior block injection
• Less common inferior alveolar and infa-orbital block
injection
• Bleeding from pterygoid venous plexus clinically appear as
swelling in the cheek followed by discoloration of the
overlying skin due to break down of the blood within 24 -48
hours .
• Bleeding from the infraorbital vessels appear as above with
black eye
• Bleeding in to the pterygo-mandibular space not show any
swelling in the cheek but it may show trismus

10.  Management :
• Reassurance of the patient
• Antibiotic to avoid infections
• Follow - up
Hematoma formation

11. Intra – vascular injection
• Result in Increase the toxicity of
local anasthetic solution or
vasoconstrictor in the blood .
• Clinically patient may show
fainting , pale,clammy skin and
even decrease in the level of
consciousness .
• Can be avoided by using
aspiration injection technique

12. Blanching at the site of injection
Ischemia of the area as aresult of decrease in
blood supply

13. Causes :
• Increase tissue tension due to the deposition
of fluid .
• Local effect of local anasthesia
Blanching at the site of injection

14. Blanching at the site remote from
that of injection

15. Blanching at the site remote from
that of injection
Causes :
• Intra-vascular injection
• Interferance with the autonomic nerve supply of
the blood vessels
Treatment :
• No treatment is needed just reassurance to the
patient . Its usually transit

16. Trismus
Difficulty in opening of the mouth due to muscle
spasm

17. Causes :
 Injection in to the medial pterygoid muscle may cause injury to
the blood vessels inside the muscle and hematoma formation or
infection
 Inflamation in the pterygomandibular space
 Blood that escape during injection in the pterygomandibular
space may cause irritation to the muscle and produce trismus
• Note : if trismus associated with pain ,fever so its due to
infection and should treated by drainage of pus , antibiotic , and
mouth wash by warm saline
Trismus

18. Facial paralysis
May be partial or complete

19. Causes :
Due to deposition of anasthetica solution in the
parotid which occure when the tip of needle
inserted too far back and behind the ramus
Facial paralysis

20. Facial paralysis
Treatment
• Reassurance , and if
eyelids envolved than
eye protection is
necessary (protective
pad or eye shade)

21. Prolonged impairment of sensation
Occure due to nerve injury
Main causes :
Direct trauma from the nerve
Injection of a solution contaminated with a
neurotoxic substances as alcohol
Hemorrhage and infection near the nerve
Surgery near the nerve fibers as mental nerve

22. Prolonged impairment of sensation
• Testing the degree and extent of parasthesia or
anasthesia can done by measuring the reactions to pin –
prinks and passing of cotton wall wisps over the skin

23. Prolonged impairment of sensation
Treatment :
In case of infection .. Drainage of pus and
anti-biotic coverage
Follow up to check the improvement
If no improvement then refer the patient to a
specialist

24. Broken needles
Prevention
• The needle must kept straight during injection .
• If resistance is encounterd , force must not be
applied to overcome it .
• The direction of the needle should not changed
within the tissue .
• Bending of the needle should be avoided .
• The needle should never embeded completely
within the tissue , at least 5 mm must project from
the mucosal surface .

25. Broken needles
Treatment
• If fracture occure the patient should told to stop any
movment to prevent displacemnt of needle within
the tissue .
• The needle graspes by artery forceps or pleir and
withdrawn .
• If the needle displaced within the tissue then its
position must determined radiographically ( two x-
ray films must be taken one perpendicular to other )
to confirm the exact position of needle and then
removed it surgically by dental surgeon .

26. infection
• Use of contaninated needle may cause infection
especially in pterygomandibular space during inferior
alveolar nerve block

27. Lip trauma
• Anasthetised lip after injection may suffer
from trauma by chewing it espcially in
children or thermal injury by hot drink or
cigarrete in adult .

28. Visual disturbance
• Rare complication of unknown causes but
suspected to be due to vascular spasm or
accidental intra-arterial injection
Treatment
• Reassurance , usually normal vision retained
within 30 minute

29. Thank you for listening ….