Pr BENAOUF. S
Dr MOHAMED BAKIR FZ
TO: 2023/2024
Dysfunction of the masticatory system
I. History˸
In 1934, JAMES COSTEN described multiple disorders (vertigo, tinnitus, pain, headaches, etc.) found in partially edentulous patients; he explained these disorders by compression of the roof of the mandibular fossa. In 1948, SICHER refuted these arguments and demonstrated that these disorders were due to regional muscular dystonia and poor intermaxillary contacts. In 1956, SCHWARTZ precisely defined Dysfunctional Pain Syndrome and introduced the Neuromuscular Theory. Then in 1969, LASKIN proposed the psychophysiological theory. He emphasized the importance of muscular action on dynamic occlusion. It was ROZENCWEIG in 1970 who first proposed the name SADAM to designate all of these signs. This term was used for a long time by French speakers, while in the Anglo-Saxon literature we tend to find the term temporomandibular disorders. In 1995 ROZENCWEIG changed his vision and abandoned the term syndrome which implied a number of signs occurring at the same time when this was not the case. In 2000 the National College of Occlusodontics adopted the term dysfunctions of the masticatory apparatus (DAM).
II. Definition:
Masticatory system dysfunctions correspond to pain and dysfunction of the masticatory system related to a musculoskeletal abnormality.
With reference to the affected system, we speak of muscular or articular DAM, keeping in mind the uniqueness of the masticatory apparatus.
III. Etiology:
Recognizing the etiologies of DAM is a delicate undertaking due to the number and complexity of the intertwined factors and the very varied modes of reaction of the masticatory system.
GOLA and GOTHLIEB classify these etiologies into:
a. Predisposing factors:
Natural or acquired, they create the bed of disease;
1-Occlusion disorders:
- Occlusal prematurities:
These are occlusal contacts occurring before maximum intercuspation, during the closing movement.
These prematurities are avoided by a reflex deviation of the closing path, this deviation will produce an increase in activity of the propulsion muscles.
- Occlusal interferences:
- Loss of rear alignment:
Faced with insufficient molar support, 2 types of situations are possible:
– The remaining teeth provide sufficient support to prevent posterior movement of the mandible, a new support point appears in front of the molar area, the condyle being directed upwards and forwards. – The remaining teeth do not provide sufficient support to prevent posterior movement of the mandible, the upper incisor-canine block creates a sliding plane and the condyle is directed backwards, causing compression of the retrodiscal tissues. The upper head of the lateral pterygoid, the only stabilizing element of the condylar position, is rapidly spasmed.
- Changes to the vertical dimension of occlusion:
Changes in the DVO are generally well tolerated by the masticatory system when they are symmetrical.
• Only very significant, sudden and especially asymmetrical changes (even slight unilateral occlusal elevation) can cause DAM. Occlusal anomalies of skeletal origin:
Maxillomandibular and condylar dysmorphoses:
May be responsible for occlusal disturbances and DAM.
2- Ligament hyperlaxity:
– Congenital (MARFAN syndrome)
– Acquired (functional promandibulia)
3-The para functions:
Will develop exaggerated forces, static (tensing) or dynamic (bruxomania).
These parafunctions are symptomatic of psychological fragility or an occlusal anomaly.
4-The psychological terrain:
Anxiety and other psychological disorders would act as catalysts for temporomandibular dysfunctions, by lowering the resistance threshold of the masticatory system, and by aggravating muscle contracture and increasing parafunctions.
5-Physiopathy factors:
Vascular, rheumatological, metabolic, hormonal disorders, homeostasis disorders of nutritional, degenerative, infectious origin, etc.
Recent studies have shown the possible existence of a link between hormonal fluctuations (estrogen levels) during the ovarian cycle and the occurrence of DAM. This could explain the female predominance
Alpha and beta estrogen receptors in muscles, role of estrogen in collagen metabolism (capsule and articular disc)
b-Triggering factors:
They abruptly disrupt the homeostasis of the masticatory system.
A situation of imbalance, stabilized by a structural and functional adaptation due to its progressive installation, can be decompensated, and thus cause the appearance of symptoms and clinical signs;
1. Emotional shock: mourning…
2. Sudden change in occlusion: orthodontics, iatrogenic prosthesis, multiple extractions.
3. Behavioral modification: chewing gum, para function, nail biting, etc.
4. Trauma:
• Traumatic joint injuries
• Forced mouth opening (dental care or maxillofacial surgery under general anesthesia)
• Accidental trauma (whiplash)
• Professional malpositions causing repetitive microtraumas.
• Fractures of the condylar region
• Fractures of the jaws
c-Maintenance factors:
They perpetuate the pathology through secondary structural, functional or neuropsychiatric modifications:
Bad posture.
Secondary dental migrations.
Psychological fragility.
Age :
The high functional tolerance in children is more related to the possibilities of adaptive growth of the condyle, these possibilities of adaptation and the plasticity of the ATM gradually disappear with age. However, a Finnish study (VIEROLA et al 2012) conducted on 483 children aged 6-8 years shows that 35% of children have at least 1 sign of DAM
III – PATHOGENESIS:
Most of the clinical signs that characterize DAM can be explained
The lower bundle contracts during mouth opening, propulsion and on the non-working side during diduction movements
The upper bundle is activated mainly during mouth closing movements, retropulsion movements and more incidentally on the working side during diduction movements.
Its 2 heads (sup. & inf.) have globally antagonistic activities, and their functional deregulation would constitute a fundamental physiopathological element. It can be added that joint trauma, whatever its importance, due to its repetition, by the incessant capsulo-disco-ligamentous pulling that it causes, maintains a discreet but continuous irritation.
Not all subjects react equally to these tugging sensations; some patients who have tolerated them without harm for years may at some point become sensitized by psychological tension, and then the irritation becomes a source of problems.
IV- SYMPTOMATOLOGY:
The clinical manifestations of DAM are extremely polymorphic; some are suggestive and immediately point towards the masticatory system, while others are more equivocal and can lead to confusion.
1. Muscle manifestations:
They are induced by parafunctions, muscular compensations for occlusal instability and avoidance movements.
Most often linked to spasms, they result in pain, limited mouth opening and muscle hypertrophy.
a) Splinting reflex:
It is a protective reflex response induced by the CNS, resulting in muscle contraction and pain in order to protect an injured area from further trauma.
Agonist muscle CNS increases activity
contracted by an antagonist muscle
• The splinting reflex is not a pathological condition, but on the contrary a normal physiological response of the neuromuscular system
b) Muscle aches:
• Definition :
It is a primary, non-inflammatory muscle disorder, which usually represents the first response of muscle tissue to a prolonged splinting reflex.
• Clinically
– Slight decrease in the range of active movements
– Muscle weakness
– Slight pain at rest
– Pain accentuated by function
– Painful palpation
c) Spasm
Muscle spasm is a sudden, involuntary, violent muscle contraction induced by the CNS; a spasmed muscle is therefore shortened and painful.
It occurs after:
– Prolonged and excessive contraction of a muscle
– Excessive muscle stretching
Hyperfunction Ischemic Anoxia
Muscular
Spasm
Accumulation of toxins
d) Muscle hypertrophy:
Increase in muscle volume, unilateral or bilateral, symmetrical or not, and secondary to muscular hyperactivity.
e)-Myofacial pain:
Found in 84 of the cases at the level of the lateral pterygoid. Myofacial pain is characterized by a dull regional muscular pain and by the presence of muscular trigger points which, on palpation, produce referred pain.
f) Limitation of mouth opening: (trismus)
The trismus is intermittent and indicates a muscle contracture of the elevators.
– It is at its maximum upon waking and gradually subsides in the morning when it is caused by nocturnal bruxomania.
– Conversely, it will be at its maximum at the end of the day and will subside at the end of the night, if it is secondary to daytime tension.
• Origin of trismus:
– Limitation of mouth opening + propulsion and diduction preserved: Muscular origin.
– Limitation of mouth opening + impaired diduction: Articular origin.
2- Joint manifestations:
These manifestations tend to point more towards the temporomandibular joint.
a) Pain:
They are typically located at the joint or in the ear, and are unilateral or bilateral.
They are aggravated by:
– Chewing hard foods.
– Yawning or sneezing.
– Cold and humidity.
– Fatigue.
– Para functions
These pains can be spontaneous or caused by:
– Mouth opening movements.
– Diduction movements.
– Pressure at the joint.
b) Joint noises (gnathosonias):
These are objective signs that alert the patient and attract the practitioner’s attention.
They are of 3 types:
• Clicking:
A sharp, loud noise, comparable to a whip cracking.
Normally the disc is attached to the condyle.
If the disc is displaced (forward or inward) relative to the condyle during mandibular movements, it will manifest itself by a clicking sound (corresponding to the crossing of the posterior rim)
These constant or non-constant clicks appear when opening and closing the mouth.
• Cracking:
Short, loud noise, comparable to a branch breaking.
When sliding under the articular tubercle, the disc would be slowed down by irregularities at its level, when it crosses them a cracking sound occurs.
• Crepitations:
A series of low, repeated noises, similar to the sound of rasping or footsteps on gravel.
Perceptible at all degrees of mouth opening and closing, they correspond to the friction of the articular surfaces, often eroded. Raise suspicion of a more or less significant disc perforation.
c)-Dynamic disturbances:
• The jump:
Visual and tactile sign that gives the patient the sensation when opening the mouth that “the mandible is coming loose”. The opening then takes place in 2 stages
The bumps indicate a reducible anterior disc dislocation.
d) Synovial and ligamentous damage:
• Retro-discitis:
– The pain is located in the posterior part of the joint
– These pains are aggravated by mandibular movements and intra-articular pressure
– Biting a tongue depressor results in reduced pain
• Capsulitis:
– They are often secondary to trauma or joint overload.
– The pain is localized in the lateral part of the joint and caused by opening movements
– Palpation sometimes reveals a swelling next to the joint.
e) Damage to the disc apparatus:
- Reducible disc displacement (RDD):
The movement of the disc in front of the condylar head, with the mouth closed, is reduced during condylar translation movements, the condyle crosses the posterior rim (disc recoaptation with snap) during the return movement, the snap corresponds to condylar decoaptation.
- Irreducible disc displacement (IDD):
The disc moved in front of the condylar head is no longer supported by the condyle when the mouth opens.
Pain and limitation of mouth opening predominate at the beginning of the course.
- Hyper joint laxity:
Hyper laxity of the disc and capsulo-ligamentous apparatus combines an increase in the amplitude of mandibular movements, muscle pain, very intense joint clicking when opening, and signs of synovitis.
In advanced forms, mouth closure may be hampered by the disc and it is only after a few mandibular maneuvers that the patient will be able to close his mouth.
f)-Structural anomalies:
Movements of the condylo-discal complex can be disrupted by structural abnormalities;
- Disc apparatus abnormalities:
– Adhesions (essentially synovial neoformations, which unite the disc to the temporal surface)
– Disc perforations.
- Bone abnormalities:
– Temporomandibular osteoarthritis: occurs as a result of excessive friction of the joint tissues.
characterized anatomically by deterioration and abrasion of articular cartilage with concomitant formation of reactive bone on the articular surfaces.
Unlike osteoarthritis in the elderly, osteoarthritis of the DAM is more painful.
3. Alveolo-dental manifestations:
Apart from muscular and joint signs, patients suffering from DAM may complain of dental and periodontal disorders.
This could include:
– Dental manifestations:
• Abrasions
• Pain.
• Dental mobility
• Coronary fractures
• Dental migrations
4. Cranio-cervico-facial manifestations:
– Headaches
– Ear pain symptoms (tinnitus, etc.)
– Ocular manifestations (discomfort, pain, photophobia, tearing, etc.)
– Facial pain.
-Cervical myalgia: any contraction of the anterior muscles of the face is accompanied by a contraction of the muscles of the neck and nape of the neck to maintain the position of the head.
– Lingual manifestations (glossodynia)
– Cervical manifestations (pain and posture disorders)
V- DIFFERENTIAL DIAGNOSIS:
Despite its high frequency, DAM should not be an easy diagnosis but should remain a diagnosis of elimination.
It should only be retained after having eliminated:
1. Extra-manducative pathologies:
a) Pain:
– Muscle pain: craniofacial-cervical pain is discussed.
– Joint pain: otalgia and periauricular pain are discussed.
– Headaches or headaches:
Subjective painful phenomena, they accompany many pathological processes.
A neurological examination is sufficient to distinguish organic pathologies from chronic functional pathologies.
– Ear pain and periauricular pain:
External otitis.
Otitis media.
Lithiatic parotitis.
– Facial pain: it can develop in varying degrees:
Facial vascular pain
Facial neuralgia (essential or symptomatic)
Dental pain (pulpitis, desmodontitis, septum syndrome, etc.)
Pain of sinus origin (acute sinusitis, chronic sinusitis, sinus tumor)
Orbital pain (acute glaucoma attack, uveitis, vision problems, orbital tumor)
-Neck pain:
Neck pain from poor posture of professional origin.
Cervicalgia from a static disorder of the spine.
Cervical osteoarthritis.
Post-traumatic neck pain.
Symptomatic neck pain, revealing a tumor.
b-Limitation of mouth opening:
Local trismus:
– Peri coronaritis on wisdom tooth.
– Cellulitis and osteitis.
– Mandibular fracture (angle, ascending ramus, condylar region)
– Of tumor origin.
General cause of trismus:
– Tetanus.
– Of toxic and medicinal origin.
– Of metabolic and deficiency origin.
– Of neurological origin.
c- Joint noises:
Oto-neurological origin:
– Otitis media.
– Internal otitis.
Vascular origin
2- Other masticatory pathologies:
a) Joint damage:
Infectious and inflammatory conditions:
– Infectious diseases (septic arthritis)
– Rheumatic conditions.
– Rheumatoid arthritis.
Degenerative conditions:
– Temporomandibular osteoarthritis.
– Temporomandibular ankylosis.
– Synovial chondromatosis.
b) Bone damage:
– Congenital malformations of the temporomandibular joints.
c) Muscle damage:
– Myopathies.
– Myositis.
– Myasthenia.
VI – Treatment:
The DAM treatment aims to:
• sedation of painful phenomena,
• suppression of joint noises and restoration of function.
The treatment includes 3 components (symptomatic component, etiological component and physical component).
6.1 Emergency treatment:
Simple actions often bring about an improvement or even a resolution of symptoms;
a- Emergency occlusal splint: The anterior occlusal stop
It can be performed very quickly in the dental office to respond urgently to acute muscular symptoms.
This emergency splint will be replaced as quickly as possible by other types of splints made from casts mounted on an articulator.
Its use results in muscle relaxation and pain relief and should be limited to a few days because it presents a risk of egression for the posterior teeth and compression of the ATMs.
b- Drug treatment:
Depending on the predominance of painful, inflammatory or spastic problems, various therapies may be prescribed.
Analgesics
Non-steroidal anti-inflammatory drugs combine the anti-inflammatory effect with a significant analgesic effect.
Muscle relaxants: Muscle relaxants are substances used in the treatment of reflex contractures, particularly when these contractures are painful.
Botulinum toxins: recent experimental studies have shown that intramuscular injection of botulinum toxin type 2 BOTOX® Allergan would provide an analgesic effect on spasmed muscles. (C.DENGLEHEM 2012)
6.2. Dental treatment:
– Endodontic treatment.
– Treatment of caries.
– Removal of overflowing fillings.
– Extraction of irretrievable teeth.
6.3. Occlusal therapy:
The occlusal treatment itself aims to re-establish an occlusal confrontation without conflicts between antagonistic teeth, ensuring a balanced mandibular posture, allowing good functioning and rest of the masticatory system.
a) Occlusal splints:
The occlusal splint aims to prevent the subject from returning to his usual OIM and to force him to place his mandible in a new OIM, thus associated with a new muscular and articular balance.
a-1-Neuromuscular reconditioning gutters:
These are devices made of smooth, preferably transparent, acrylic resin, most often hard, covering the occlusal surface of an entire maxillary or mandibular arch.
Their indications are of 2 types:
– Obtain neuromuscular reconditioning which will allow to define an asymptomatic intermaxillary relationship.
– Protect teeth from excessive wear related to para functions.
a-2-Mandibular repositioning trays:
Indicated in joint problems, they present a repositioning wall and/or deep indentations which, when the masticatory muscles contract, necessarily reposition the mandible in a position such that the surfaces and articular discs are correctly coapted.
There are 3 types:
Reduction gutters:
The reduction splint, indicated in the DDR, aims to wedge the mandible in a position where opening and closing are achieved without clicking.
The therapeutic position is identified either:
– Radiologically.
– Clinical adjustment during mandibular movements.
This gutter:
– Must be worn continuously (24 hours a day) even during meals.
– Requires prolonged wear of 4 to 6 months
Decompression gutter:
It is indicated to decompress the joint, this therapeutic approach is recommended in the case of irreducible dislocation.
(The disc is confined in front of the condylar head which is in a posterior position that compresses the bilaminar area)
The practitioner’s intervention therefore aims to reposition, by manipulation of the mandible, the condylar head under the displaced disc and to maintain this clinical situation by an inter-occlusal device.
The goal is to reduce intra-articular pressure by lowering the condyle.
Joint decompression promotes thickening of the retrodiscal ligament which plays the role of a neodisc.
Stabilization gutter:
This device promotes the stabilization of the mandible in RC, and the protection of the teeth against abrasion.
For Orthlieb it is indicated after successful disc repositioning, in order to maintain the coaptation of the articular parts in the new reference position.
This gutter is indicated after:
– Manual disc reduction.
– Disc repositioning surgery.
b) Occlusal equilibration:
It is a procedure for reorganizing the dento-dental relationships, this balancing tends to correct the occlusal anomalies responsible for DAM.
The fundamental rule of occlusal equilibration lies in the search for and application of the most conservative therapeutic procedures possible.
- Orthodontic restoration:
Its aim is to correct malocclusions by moving the dental organs without altering them.
Orthodontics should not alter the mandibular position corrected by the initial repositioning treatments.
It must intervene to correct the dento-alveolar anomalies causing DAM (correction of a crossbite, an overbite, etc.)
- Prosthetic restoration:
Its aim is to restore missing teeth, it represents the most reliable therapy of occlusal treatment but the least conservative from a tissue point of view.
She has several roles:
– Increase the masticatory coefficient.
– Distribute the loads over all the teeth.
– Psycho-aesthetic role.
- Balancing grinding:
Occlusal adjustment by grinding represents a very delicate irreversible treatment phase, imperatively preceded by a study on an articulator.
This grinding has the following basic principles:
– A tissue economy.
– Correction of dental malpositions tending towards better dental alignment.
– Accentuation of occlusal reliefs.
A new OIM ensuring a new stable position of the mandible.
6.4/Adjuvant therapies:
The use of adjuvant therapies plays a complementary role to occlusal treatment.
These therapies allow the psychosomatic care of the patient and contribute to the improvement, or even the cure, of DAM.
a) Physiotherapy:
Application of dry heat: it is done on the joint and on the painful muscle, the indication is joint inflammation and possibly spasm.
Cryoanesthesia:
The cryoanesthetic should be sprayed along the axis of the muscle fibers, starting from the initial painful area and ending in the region of radiated pain.
Pressotherapy: applying pressure to the painful muscle area for one minute causes hypoesthesia which will allow the affected muscle to stretch.
Ultrasound: this technique uses acoustic waves, the effects are thermal, mechanical and analgesic, the sessions last 10 minutes and are daily.
Contact electrical stimulation: cutaneous electrical impulses inhibit the passage of nociceptive impulses coming from the masticatory system.
Percutaneous electrical stimulation: (subcutaneous nerve stimulation) two electrodes, passed through the skin, allow variable currents to be administered.
The athermic laser or “soft laser” or “low laser”
Low-level laser therapy has recently been used to relieve pain and manage TMJ and masticatory muscle disorders. Several authors have demonstrated the therapeutic efficacy of lasers, particularly in reducing inflammatory processes, alleviating acute and chronic pain, and improving local microcirculation.
Low-level laser therapy is generally considered a safe therapeutic procedure.
b) Infiltration:
By local anesthetics: local anesthetics without vasoconstrictor, can be injected around the joint, in the joint or in the muscles (lateral pterygoid)
By corticosteroids: intra-articular infiltration, based on intermediate or delayed action corticosteroids,
c) Massage and Physiotherapy:
These therapies are particularly beneficial in the treatment of orofacial pain.
– Massage:
Massage is used for myofascial pain to relieve pain and improve muscle length and flexibility. The frequency of massage sessions should be 30 minutes twice a week. The treatment should be applied with increasing force, in subsequent sessions.
– Physiotherapy:
It aims to eliminate the different components of muscular or joint DAM.
The objectives of these therapies are:
– Improve neuromuscular balance
– Participate in maintaining joint stability
– Eliminate primary and secondary etiologies by eliminating para-functional habits that overload the different components of the masticatory system.
* The exercises are performed with the physiotherapist
By the patient, for the first sessions, after warming up the muscles for around ten minutes using gloves or hot compresses.
6.5. Psychological treatment:
The psychological factor must be taken into account in the therapy of DAM, isolated dental treatment appears in fact less effective than dental treatment associated with psychological therapies.
a) Drug treatments:
These medications will only be prescribed by the specialist doctor;
– Tranquilizers; provide relaxation and sedation of anxiety.
– Hypnotics; restore the normal sleep cycle.
– Antidepressants; indicated in the case of depressive syndrome.
b) Psychotherapy:
Any consultation between the patient and their doctor has therapeutic value and these patients should be reassured that their condition is benign.
Other psychotherapies can be used (hypnotherapy, behavioral therapies, etc.) these therapies are centered on the patient’s acceptance of the painful experience.
The use of specific therapy such as relaxation, practiced by psychiatrists but also psychologists. There are, moreover, many related techniques such as self-relaxation or yoga.
6.6. Surgical treatment:
Surgical treatment of the temporomandibular joint is intended for patients with irreversible lesions,
This treatment should aim above all to restore joint function.
It primarily targets the disc apparatus and can also affect the articular bone surfaces.
The interventions are performed by arthroscopy or by conventional surgery;
a) Arthroscopy:
Conducted under general anesthesia, it allows:
– To confirm the diagnosis before performing any possible open surgery.
– To remove disco-temporal adhesions by washing or sweeping
– To limit the amplitude of antero-internal movements of the condyle.
– To remove certain small temporal exostoses .
b) Open ATM surgery:
This intervention is heavy, but it is indicated for all major intra-articular problems (ankylosis, painful non-reducible anterior dislocations)
There are multiple therapies:
Disc repositioning; the disc is replaced and fixed posteriorly with sutures.
Disc perforation
Discectomy; degenerated discs are removed and replaced either by part of the temporal fascia or by silicone implants.
-Bone surgery: mandibular advancement by retrocondylar cartilaginous wedge