Effectiveness of Low-Level Laser Therapy in Anterior Disc Displacement Without Reduction of Temporomandivular Joint

The temporomandibular joint (TMJ) is a synovial joint located between the mandible and the temporal bone, playing a critical role in daily functions such as chewing, speaking, and swallowing (1). This joint requires considerable flexibility and durability during movement; however, when biomechanical balance is disrupted, various temporomandibular joint disorders (TMDs) can develop (2). Proper functioning of the TMJ depends on the harmonious interaction of muscles, ligaments, the articular disc, and bone structures. Dysfunction in any of these components can lead to temporomandibular disorders (2). Among TMJ disorders, anterior disc displacement without reduction (ADDwoR) is a common condition that significantly affects patients' quality of life (3). ADDwoR is characterized by the loss of the normal anatomical relationship between the articular disc and the mandibular condyle, with the disc failing to return to its original position during movement. This results in restricted mouth opening, joint pain, and impaired mandibular function (4).

The etiology of ADDwoR is multifactorial, including a wide range of factors such as genetic predisposition, trauma, parafunctional habits like bruxism, and intra-articular inflammation (4). Clinically, the most frequently observed symptoms include limited mandibular movement, pain, and functional difficulties during mastication. Mouth opening is often reduced to less than 30 mm, and the characteristic "click" sound during mandibular movement is typically absent (5). As a subtype of TMD, anterior disc displacement without reduction (ADDwoR) is characterized by the disc losing its normal position and failing to coordinate with the mandibular condyle during joint movement (3). In ADDwoR, the disc becomes locked anterior to the condyle, leading to pain and restricted mouth opening. This condition can negatively impact patients' daily life due to its effect on jaw function (6).

The etiology of ADDwoR is multifactorial, involving genetic predisposition, trauma, parafunctional habits (e.g., bruxism), intra-articular inflammation, and ligament laxity (7). In addition, psychological factors such as stress and anxiety have also been reported to contribute to this disorder (5). Pathophysiologically, weakening of the posterior ligaments of the disc allows the condyle to shift anteriorly to the disc, and this mechanical imbalance eventually results in chronic pain and limited movement (8). Clinically, ADDwoR typically presents with restricted mandibular motion, pain during mastication, and functional impairment. Magnetic resonance imaging (MRI) is considered the gold standard in the diagnosis of ADDwoR, as it allows for precise assessment of disc position and intra-articular inflammation (9).

This article provides a comprehensive overview of the pathophysiological mechanisms, diagnostic methods, and current treatment approaches for ADDwoR. The aim is to offer an in-depth perspective for both healthcare professionals and researchers, thereby contributing to the development of effective interventions that enhance patient quality of life.

Pathophysiology
In anterior disc displacement without reduction (ADDwoR), the articular disc loses its normal position and fails to return to its place during condylar movements. As a result, joint range of motion decreases, and pain occurs during mandibular movement. Disc displacement is commonly associated with trauma, parafunctional habits, or structural abnormalities (10). The pathophysiology of ADDwoR is often linked to weakening of the posterior ligaments of the disc and excessive mechanical loading. This condition leads to anterior displacement of the condyle relative to the disc.

Clinical Findings
Patients typically present with limited mouth opening (<35 mm), deviation during mandibular movement, and tenderness in the joint region. The absence of disc reduction may result in the disappearance of the clicking sound commonly heard during chewing (11).

Diagnosis
Diagnosis is generally made through a detailed medical history, physical examination, and imaging methods (MRI or ultrasonography). MRI is considered the gold standard for evaluating disc position and intra-articular structures (12). Patients commonly present with restricted jaw movements, difficulty in chewing, and pain. The jaw opening is typically reduced to less than 30 mm, and no clicking sound is heard during chewing (1). Diagnosis is usually established through clinical examination and imaging techniques. Magnetic resonance imaging (MRI) is the most reliable method for assessing the position of the disc and other intra-articular structures (6).

Treatment

The primary goal in the treatment of temporomandibular joint disc displacement without reduction (DDNR) is to reduce pain, improve jaw function, and enhance quality of life. Treatment is divided into two main categories: conservative approaches and surgical methods. The treatment plan is developed by considering the severity and duration of the patient's symptoms, as well as their individual needs.

Conservative Treatment

Conservative treatment is the first step in the management of DDNR and is generally applied to control symptoms.

Splint Therapy: Stabilization splints help relieve pain and support jaw functions by reducing the mechanical load on the joint (13). They are particularly useful in managing parafunctional habits such as bruxism or teeth clenching. Stabilization splints are effective in reducing pressure on the joint (14). Splints are particularly beneficial in managing parafunctional habits such as bruxism or teeth clenching. Stabilization splints are effective in reducing pressure on the joint (1).

Physical Therapy:Physical therapy exercises aimed at strengthening the jaw muscles and improving mobility are effective in the treatment of DDNR. Commonly used methods include ultrasound therapy, transcutaneous electrical nerve stimulation (TENS), and manual therapy techniques. Jaw exercises and hot/cold applications may also be used to alleviate symptoms. Ultrasound therapy, transcutaneous electrical nerve stimulation (TENS), and manual therapy techniques are frequently used. Jaw exercises and hot/cold applications can be used to alleviate symptoms. (15).

Low-Level Laser Therapy (LLLT): Low-Level Laser Therapy (LLLT) has become an increasingly common method in the treatment of temporomandibular joint (TMJ) dysfunctions. This technique reduces pain and controls inflammation by creating a biostimulatory effect in the tissues (16). Laser energy accelerates the healing process by enhancing cellular metabolism. Studies have shown that LLLT is effective in relieving pain and improving jaw mobility. This method is particularly recommended for patients who do not respond to other conservative treatment options (17).

Pharmacological Treatment: Nonsteroidal anti-inflammatory drugs (NSAIDs), muscle relaxants, and analgesics are commonly used to alleviate acute symptoms (18). In some cases, corticosteroid injections may be preferred to reduce inflammation. NSAIDs and muscle relaxants are used to relieve pain. In some cases, corticosteroid injections may be preferred to reduce inflammation. Nonsteroidal anti-inflammatory drugs (NSAIDs) and muscle relaxants are used to relieve pain (19).

Behavioral Therapy: Stress management, relaxation techniques, and controlling parafunctional habits (such as teeth clenching) support conservative treatment (5).

Surgical Treatment: Surgical intervention is considered when conservative methods are insufficient or when symptoms are severe.

Arthrocentesis: Arthrocentesis is a minimally invasive procedure in which fluid is injected into the joint to flush out inflammatory mediators. This method helps reduce pain and improve joint mobility. It is a minimally invasive technique used to decrease intra-articular inflammation (20).

Arthroscopy: Arthroscopy is used to directly visualize intra-articular structures and, if necessary, perform surgical interventions. As both a diagnostic and therapeutic method, arthroscopy has shown successful outcomes in the treatment of DDNR (21).

Disk Reposition Surgery: This surgical method aims to return the joint disc to its anatomical position and is generally preferred for young and active patients (22). Surgeries targeting the restoration of the disc to its anatomical position can be performed (23).

Discectomy: This procedure involves the complete removal of the joint disc and may be used in severe and chronic cases. After the disc is removed, graft material is usually placed in the area (24).

Combined Treatment Approaches

In some cases, a combination of conservative and surgical methods may be necessary. For example, applying arthrocentesis alongside physical therapy and splint therapy can lead to faster symptom relief.

Novel and Experimental Methods

In recent years, studies have focused on innovative methods such as stem cell therapy and the use of biological agents. These approaches aim to reduce intra-articular inflammation and repair damaged tissues (25).

Application Protocol and Device Types for Low-Level Laser Therapy

Low-Level Laser Therapy (LLLT) is considered an effective conservative treatment method for temporomandibular joint (TMJ) dysfunctions. For successful outcomes, the appropriate treatment protocol and device selection are critically important.

Application Protocol

Important parameters to consider in the application of Low-Level Laser Therapy (LLLT) include the following:

Type of Laser: Low-energy lasers (typically diode lasers operating in the 600–1000 nm wavelength range) are commonly used. This wavelength range allows for deeper tissue penetration and creates a biostimulatory effect (26).

Energy Density (Dose): Most studies suggest that laser energy should be within the range of 4–8 J/cm² for effective results. Higher energy densities should be avoided, as they may cause thermal damage to biological tissues (27).

Treatment Duration:
A laser is applied to each treatment point for 1–3 minutes. The total duration of treatment varies depending on the patient's symptoms and is generally administered 2–3 times per week for 4–8 weeks (28).

Application Points:

• • Temporomandibular joint area
  • Trigger points of the masseter and temporalis muscles
  • Other regions where pain radiates

Therapeutic Effects: LLLT reduces inflammation, controls pain, and accelerates tissue healing. The effectiveness of the treatment varies depending on factors such as the patient's age, the severity of the dysfunction, and adherence to the therapy protocol (29).

Device Types: LLLT devices vary in their usage depending on their specifications. The commonly used device types in TMJ treatment include:

Diode Lasers: The most frequently used type of laser

Models operating at a wavelength of 808 nm are ideal for deep tissue biostimulation (30).

He-Ne (Helium-Neon) Lasers:

• Effective on superficial tissues
• Operate at a wavelength of 632 nm, but have limited penetration into deeper tissues (31).

Infrared Lasers:

• Among the most effective types for reaching deep tissues (800–1000 nm)
• Commonly preferred for controlling pain in TMJ dysfunctions (32)

Portable Laser Devices:

• Designed for use outside of clinical settings
• Suitable for mild cases or home-based treatment (33).

Advantages of LLLT

• It is a non-invasive and painless method.
• It has minimal to no side effects.
• Compared to pharmacological treatments, it provides longer-lasting symptom control (28).

Limitations of LLLT

• The effectiveness may be limited if the application protocol is not followed correctly.
• It may not be sufficient on its own in cases with severe structural abnormalities (28,30).

Comparison of Low-Level Laser Therapy with Other Treatment Methods

Low-Level Laser Therapy (LLLT) is increasingly being preferred as a conservative treatment option for temporomandibular joint dysfunctions (TMD). This section will address the comparative effectiveness of LLLT in relation to other commonly used treatment modalities.

LLLT vs. Splint Therapy

• Splint therapy is one of the most commonly used conservative treatment methods for TMD patients. Stabilization splints help reduce inflammation by decreasing the mechanical load on the joint. However, splints generally require long-term use to achieve symptom relief (13).
• In contrast, LLLT provides rapid pain relief with shorter treatment sessions. One study reported that LLLT was more effective than splint therapy in reducing pain in the short term (34).
• Nonetheless, splint therapy may yield better results in managing bruxism or other parafunctional habits. Therefore, in certain patients, the combined use of LLLT and splint therapy is recommended.

LLLT vs. Physical Therapy

• Physical therapy techniques are frequently used to increase jaw mobility and alleviate muscle pain. Methods such as ultrasound, TENS, and manual therapy can be highly effective in specific patient groups (26).
• Compared to physical therapy, LLLT has the advantage of being non-invasive and causing minimal discomfort to the patient. Moreover, LLLT's direct anti-inflammatory and tissue-healing effects may lead to faster results (18).
• However, physical therapy is generally more effective than LLLT in improving jaw range of motion. Therefore, in patients with limited jaw opening, the combined use of physical therapy and LLLT is recommended.

LLLT vs. Pharmacological Treatment

• Pharmacological agents such as NSAIDs and muscle relaxants are commonly used for the acute management of pain and inflammation. However, their long-term use is limited due to potential side effects.
• The greatest advantage of LLLT compared to pharmacological treatment is its lack of side effects. Laser therapy offers an effective alternative, especially for patients who are resistant to medications.
• Studies have shown that LLLT can be as effective as NSAIDs and may play a complementary role in pain reduction alongside drug therapy (18).

LLLT vs. Surgical Treatment

• Surgical interventions are performed in severe DDNR cases where conservative methods have failed. Minimally invasive procedures such as arthrocentesis and arthroscopy are highly effective in reducing pain and inflammation (21).
• LLLT is considered a method that may reduce the need for surgical treatment. It helps control symptoms without surgery, especially in mild to moderate cases. However, in cases with severe structural abnormalities, the effectiveness of LLLT is limited, and surgical treatment may be necessary (35).