This document outlines the etiology and management of trismus. It defines trismus as restricted mouth opening and describes normal ranges of opening. Common causes of trismus include infections, trauma, surgery, tumors, radiation, TMJ disorders, and drugs. Management involves thorough history and examination, investigations to diagnose the underlying cause, and various treatment approaches depending on the etiology such as heat therapy, medical management, physiotherapy, surgery, and appliances.

1. BY
DR. HOPE INEGBENOSUN
AETIOLOGY AND MANAGEMENT OF
TRISMUS

2. OUTLINE
 Introduction
 Normal mouth opening
 Measurement of mouth opening
 Classification of trismus
 Aetiology of trismus
 Management of trismus
 History taking
 Examination
 Investigations
 Diagnosis
 Treatment
 Heat therapy
 Medical management
 Physiotherapy
 Surgery
 Trismus appliances
 Conclusion
 References

3. INTRODUCTION
 Trismus refers to a sustained, tonic spasm of the masticatory muscles,
particularly the masseter and temporalis, which results in forced jaw closure
[Lai MM, Howard RS, 1994]
 Trismus is derived from the greek word ‘trismos’ meaning gnashing
 More recently, the term “trismus” has been used to describe any restrictions
to mouth opening including restrictions caused by infection, trauma, surgery
or radiation [Johnson J., et al, 2010].
 This limitation in the ability to open the mouth can have serious health
implications, including reduced nutrition due to impaired mastication,
difficulty in speaking and compromised oral hygiene.

4. NORMAL MOUTH OPENING
 The normal range of mouth opening varies from patient to patient, within a
range of 40– 60 mm, although some authors place the lower limit at 35
mm.
 The width of the index finger at the nail bed is between 17 and 19 mm.
Thus, two fingers’ breadth (40 mm) up to three fingers’ breadth (54–57 mm)
is the usual width of opening.
 Evidence suggests that gender may be a factor in vertical mandibular
opening. In general, males display greater mouth opening [Dwarkins SF, et al, 1990)
 Lateral movement is 8–12 mm [Scully C, 2008], and normal protrusive movement
is approximately 10mm [Hupp JR, et al., 2008].

5. MEASUREMENT OF MOUTH OPENING
 Screening
“Three finger test”
 Measurement tools
 Boley gauge
 Manufacturers scale
• Dynasplint
• Therabite
 Influencing factors
 Dental alignment
 Age
 Gender
 Ramus length
 Gonial angle

6. CLASSIFICATION OF TRISMUS
A. BASED ON RANGE OF MOUTH OPENING
 Mild trismus = 30 – 40mm
 Moderate trismus = 15 – 30mm
 Severe trismus = ≤15
B. BASED ON DURATION
 Acute trismus
 Subacute trismus
 Chronic trismus
C. BASED ON AETIOLOGY
 Intra-articular
 Extra-articular

7. AETIOLOGY OF TRISMUS
A. ACUTE TRISMUS
 INFECTIONS
 Pericoronitis
 Odontogenic infection with spread involving masticatory muscles, TMJ,
bone or fascial spaces
 Tonsillar or pharyngeal infections
 Parotitis
 Otitis
 Tetanus

8.  TRAUMA
 Jaws
 Soft tissues
 POSTOPERATIVE
 Third molar teeth removal
 Other jaw and oral surgeries
 Associated with haematoma
 Local anaesthetic injection trauma to pterygoid muscles
 DRUG RELATED
 Psychotomimetics such as ecstasy
 Extra-pyramidal reaction to anti-emetics (e.g metoclopramide)
 Malignant hyperthermia
 Temporomandibular joint disease (e.g gout, rheumatoid arthritis) and
pain dysfunction syndrome

9. B. SUB-ACUTE TRISMUS
 Tumour infiltration of muscles or joint
 Chronic infection
 TMJ disease and pain dysfunction syndrome
C. CHRONIC TRISMUS
 Soft tissue scar formation or TMJ damage after surgery, trauma, radiation or
burns
 Submucous fibrosis
 Scleroderma
 Rheumatoid arthritis
 TMJ disease and pain dysfunction syndrome
 TMJ ankylosis
 Masticatory muscle disorders (e.g myotonia, myositis ossificans,
fibrodysplasia ossificans, fibroslerosis)
 Pseudobulbar palsy [reported by Lai MM, Howard RS, 1994]

11. INFECTIONS
 The hallmark of a masticatory space infection is limited jaw opening.
 Infections causing trismus may be of an odontogenic or non-odontogenic
nature.
 Odontogenic infections have three major origins: pulpal, periodontal and
pericoronal.
 The presence of an oral infection, particularly around an erupting mandibular
third molar, is the most common cause of trismus [Nitzam DW, Shteyer A, 1986].
 Severe odontogenic infections involving the muscles of mastication are often
accompanied by trismus at initial presentation.
 Non-odontogenic infections such as tonsillitis, tetanus, and parotid abscess
may also cause trismus [Backland LK, et al, 1988].

12. TRAUMA
 Fractures, particularly those of the mandible, may cause limited jaw opening.
 Depending upon the type of injury and the direction of the traumatic force,
fractures of the mandible may occur in different locations, producing
mandibular hypomobility.
 Another cause of trismus seen is trauma of the zygomatic arch and
zygomaticomaxillary complex (ZMC), which interferes with the movement of the
coronoid process [Azaz B et al, 1994].

13. TRISMUS RELATED TO DENTAL PROCEDURES
 Trismus may occur after any oral surgery that involves the pterygoid muscles
or after which there is disuse of the TMJ.
 Maxillectomy is the classical example of an oral operation that will lead to
trismus
 The extraction of teeth may cause trismus as a result either of inflammation
involving the muscles of mastication or direct trauma to the TMJ.
 Occasionally, the medial pterygoid muscle is accidentally penetrated or a
vessel is punctured during an IAN block and a small bleed follows: a
haematoma can occur in the muscle bed and subsequently organize, causing
a fibrosis.
 Hot packs, stretching exercises using wooden spatulas and reassurance are
usually sufficient for this condition, although sometimes the haematoma
becomes infected and requires surgical evacuation.

14. TEMPOROMANDIBULAR JOINT DISORDERS
 There are numerous subcategories of TMD, a number of which may
be associated with trismus.
 TMDs may be divided into extracapsular (mainly myofascial) and
intracapsular problems (including disc displacement, arthritis, fibrosis,
etc.).
 Intracapsular problems are often caused by trauma.
 Pain upon palpation, lateral to the joint capsule, is a significant finding.
Clicking may indicate anterior disc displacement.
 Painless clicking alone does not require treatment.
 Conditions such as fibrosis or unilateral condylar hyperplasia require
surgical consultation and treatment.

15.  Suspicion of TMJ trauma or dislocation should be considered in young
patients who have dysphagia and trismus but who do not have a
serious infectious aetiology.
 Acute closed-lock conditions may occur when the meniscus becomes
displaced anteromedial to the condyle.
 In such instances, the patient usually has a history of paroxysmal
clicking and some discomfort.
 In closed-lock conditions of a mechanical nature, the patient can often
open his or her jaw 20–25 mm.
 If the opening is significantly less than this the practitioner should
suspect a closed lock of muscular origin.

16. TUMOURS AND ORAL MALIGNANCIES
 Trismus is a common complication of oncology
 Tumours involving the mandible, muscles of mastication and
associated structures can cause limitation of mandibular movement
 Also primary tumours occurring in any parts of the body could
metastasize to the epipharyngeal region, parotid, mandible or TMJ
and cause trismus

17. DRUG THERAPY
 Some drugs are capable of causing trismus as a secondary effect,
succinylcholine, phenothiazines and tricyclic antidepressants being
among the most common [Cunningham PA, Kendrick RW, 1988].
 It has also been reported that MDMA abusers are prone to clenching,
bruxism and/or trismus and TMJ dysfunction [Baylen CA et al, 2006].

18. RADIOTHERAPY
 Radiotherapy is commonly used to treat squamous cell carcinoma of the
head and neck and regional lymphomas.
 Complications may develop from its use, depending upon which healthy
tissues are in the path of the radiation beam, the amount of radiation
given and the course of treatment.
 When the muscles of mastication are within the field of radiation,
radiation induced fibrosis may result and lead to trismus, reducing the
range of movement.

19.  Fibrosis and trismus have been attributed to the ischaemia caused by
endarteritis obliterans.
 Trismus complicates post-radiation dental care.
 The recommendation to minimize the effects of radiation on the facial
and masticatory muscles include the use of protective stents, jaw
exercises and hyperbaric oxygen to increase neovascularization.
 Results from a pilot study suggested that pentoxifyline may be
effective in treating radiation-induced trismus [Chua DT et al, 2001]

20. CONGENITAL/DEVELOPMENTAL CAUSES
 There has been a report of trismus as a result of hypertrophy of the
coronoid process causing interference of the coronoids against the
anteromedial margin of the zygomatic arch [Daniele A, 1994].
 Trismus pseudo-camptodactyly syndrome is a rare combination of
hand, foot and mouth abnormalities and trismus.

21. MANAGEMENT OF TRISMUS
HISTORY TAKING
Thoroughly review the patient’s dental and medical history
o Ask about onset, nature, progression, aggravation, radiation of pain
and relieving factors
o Ask about any dental treatment, joint clicking and locking, trauma,
infections, medical conditions, radiotherapy or drug intake.
o Inquire about pain in neck, shoulder and back muscles and joints.
o Inquire about sleep bruxism (clenching, grinding, tooth tapping) or
daytime parafunction (clenching, gum chewing, fingernail biting)

22. EXAMINATION
Perform a complete extraoral and intraoral examination
 Check for facial asymmetry
 Measure maximum mouth opening (check for interincisal distance) and
lateral range of jaw motion
 Palpate the masticatory muscles in the jaw and check for tenderness
 Check for visible muscle fasciculation, pathognomic for myospasm/trismus
diagnosis
 Examine the TMJ (check for any tenderness, uncoordinated movement,
clicking sounds and crepitus)
 Look for partially erupting third molars, carious teeth and gingival
inflammation
 Check teeth for any wear facets and/or occlusal disharmony

23. INVESTIGATIONS
 Periapical radiograph
 To rule out caries in the teeth
 Panoramic radiograph
 Confirms degenerative joint diseases
 Quantify levels of asymmetrty
 CT
 MRI
 Casting
 Axiography
 Evaluates trajectory

24. OTHER DIAGNOSTIC AIDS
 Nasendoscopy
 Ultrasound
 Biopsy
 Microscopy, culture and sensitivity
 Full blood picture
 ESR
 Serum uric acid
 Antinuclear antibodies (ANA)
 Anti-topoisomerase 1 antibodies (ATA or anti-Scl-70)
 Anticentromere antibodies (ACA)
 Rheumatoid factors (RF)
 Psychological assessment

25. DIAGNOSIS

26. TREATMENT
 Treatment of trismus varies depending on the aetiological factor.
 The degree of discomfort and dysfunction varies, but is usually mild.
 When a patient reports mild pain and dysfunction, the practitioner should
prescribe the following to manage the initial phase of muscle spasm.
 Heat therapy;
 Analgesics;
 Soft diet; and
 Muscle relaxants (if necessary)

27. HEAT THERAPY
 Heat therapy consists of placing moist hot towels on the affected area
for 15–20 minutes every hour.
 Heat increases the extensibility of collagen tissue, decreases joint
stiffness, relieve pain and muscle spasm, increase blood flow and
helps to resolve inflammatory infiltrates and oedema [Lund TW, et al, 1993]

28. MEDICAL MANAGEMENT
 Aspirin is usually adequate in managing the pain associated with
trismus; its anti-inflammatory properties are also beneficial.
 A narcotic analgesic may be required if the discomfort is more intense.
 If necessary, diazepam (2.5–5 mg three times daily) or other
benzodiazepine may be prescribed for muscle relaxation.

29.  One of the latest treatment modalities is the use of botulinum
treatment injections.
 Its site of action is predominantly the synaptic terminal of the
cholinergic lower motor neurone.
 This toxin causes flaccid paralysis due to neuroexocytosis block, i.e
acethycholine release, especially at the lower motor neurone terminal
presynaptically.
 The dose recommended is 25IU injected into each masseter and 10IU
into the temporalis muscle.
 The onset of action is somewhat delayed, hence it is desirable to start
the therapy early [Herrman H et al, 2008].

30.  If further dental care is needed, as with a painful infected tooth,
access for local anaesthesia may be difficult when trismus is present.
 The closed mouth nerve block usually provides relief of the motor
dysfunction, permitting the patient to open and allowing the
practitioner to provide the appropriate treatment.
 If trismus is suspected to be associated with infection, appropriate
antibiotics should be prescribed.

31. PHYSIOTHERAPY
 When the acute phase is over the patient should be advised to initiate
physiotherapy for opening and closing the jaws.
 A good starting regimen for most patients is the ‘7-7-7’, which involves
opening and closing the mouth with assisted opening seven times.
 Then holding the open position to the maximum opening that can be
sustained without pain for seven seconds.
 They are to perform this exercise seven times a day.
 Sugarless chewing gum is another means of providing lateral
movement of the TMJ.
 Soft diet is prescribed if necessary

32. SURGERY
 Surgical management in the case of trismus is rare.
 Cases involving intracapsular TMJ pathosis, bony interferences from
styloid or coronoid processes, the presence of a foreign body or
restrictive maxillomandibular bands or dense scar tissues may require
surgical intervention.
 If trismus is caused due to fibrotic band formation in the submucosa,
lysis of these bands can be done using laser.
 Myotomy of the masseteric muscle helps in certain cases.
 Treatment should be directed toward the aetiology.

33. TRISMUS APPLIANCES
 Various appliances have been described for treating trismus.
 Ideally they are used in combination with physical therapy.
 According to their design, they act externally or internally.

34. EXTERNALLY ACTIVATED APPLIANCES
 This appliances apply some mechanical means of forces stretching
the elevator muscles by depressing the mandible.
 They impact forces that can be continuous or intermittent, light or
heavy, and elastic or inelastic.
 Such appliances include the following:
 Dynamic bite opener
 Threaded tapered screw
 Screw type mouth gag
 Fingers
 Tongue blades
 Continuous dynamic jaw extension apparatus
 Therabite jaw motion rehabilitation system

35. A. DYNAMIC BITE OPENER
 This provides continuous elastic force to depress the mandible,
thereby the amount and direction of the force can be controlled

36. B. THREADED TAPERED SCREW
 This appliance is commonly constructed with acrylic resin and is
usually placed between the posterior teeth.
 With gradual turns of screw, the mandible is depressed and both
maxillary and mandibular teeth are forced apart.

37. C. SCREW TYPE MOUTH GAG
 It employs a screw type component similar to the type incorporated
into orthodontic palatal extension appliances.
 It provides a continuous unilateral and inelastic force.

38. D. FINGERS
 Patient should use fingers to depress the mandible, stretch the
musculature to the maximum, and them maintained the position for a
slow count of 10.
 This exercise is repeated by patient throughout the day.

39. E. TONGUE BLADES
 Tongue blades have been used as a wedge or as a mouth prop to
sustain maximal opening

40. F. CONTINUOUS DYNAMIC JAW EXTENSION
APPARATUS
 This appliance consists of a contra rotating extending screw attached
to the maxillary and mandibular arches by two resilient stainless steel
wire arms that are connected to acrylic resin splints.
 The apparatus distributes the forces generated by the screw over the
entire dental arch covered by the splints.
 The force provided is continuous, bilateral and elastic.

41. G. THERABITE JAW MOTION REHABILITATION
SYSTEM
 The therabite system is a patient operated device used for passive
rehabilitation therapy of the TMJ
 The TheraBite appliance has shown greater efficacy than any other
treatments [Buchbinder D, et al, 1993]
 It is a useful appliance for patients with sustained trismus particularly
for those having undergone treatment for head and neck cancers.

42. INTERNALLY ACTIVATED APPLIANCES
 These appliances rely on the patient’s depressor muscles to stretch
the elevator muscles, since the elevator muscles can generate forces
that are 10 times generated by the depressor muscles.
 The amount of force delivered depends on the strength and motivation
of the patient, as do the frequency and duration of stretching.
 Such appliances include the following:
 Tongue blades
 Plastic tapered cylinder

43. A. TONGUE BLADES
 Tongue blades can be employed so that the force delivered is
imparted by the depressor muscle alone and thus the tongue blade
are not used as a wedge.

44. B. PLASTIC TAPERED CYLINDER
 It is simple carrot shaped appliance which allows the patient to easily
identify the maximal maxillomandibular distance on initial stretching by
noting which ring on the taper is reached when both the maxillary and
mandibular teeth come into contact with the tapered cylinder.
 This appliance relies on the patient depressor muscle to depress the
mandible.

45. CONCLUSION
 Successful treatment depend on prompt recognition of its cause and
initiation of appropriate management, otherwise trismus may lead to
permanent functional imapairment

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