Summary of "محاضرة ماجستير دفعة 2025 - TMD part 1"

Summary of “محاضرة ماجستير دفعة 2025 - TMD part 1”

This lecture provides an in-depth overview of the temporomandibular system (TMD), focusing on the anatomy, biomechanics, neuromuscular control, and functional movements of the mandible and temporomandibular joint (TMJ). It also covers clinical considerations related to occlusion, joint disorders, and implant dentistry.

Main Ideas and Concepts

1. Anatomy and Structure of the Temporomandibular System

The maxillary teeth are fixed to the maxilla (part of the cranium), while mandibular teeth are attached to the mandible, a free-moving bone suspended by ligaments and muscles.
The mandible moves in two main parts:
- At the temporomandibular joint (TMJ) (posterior movement limiter)
- At the teeth (anterior movement limiter)
The TMJ consists of bony components (condyle, glenoid fossa), soft tissues (capsule, ligaments), and the articular disc.
The articular disc acts as a cushion and allows adaptive movement between the condyle and the temporal bone; it is attached posteriorly but loosely anteriorly to allow rotation and translation.
Ligaments (sphenomandibular, stylohyoid, temporomandibular ligaments) restrict excessive mandibular movements.
Muscles involved include the temporalis, masseter, medial and lateral pterygoids, and suprahyoid muscles, each contributing to mandibular movement and stabilization.

2. Mandibular Movements and Border Movements

Border Movements: The extreme limits of mandibular motion, analogous to the boundary defined by a tethered pen’s chain.
- These are reproducible, controlled, and occur in three dimensions but are often studied in single planes.
Intra-Border Movements: Movements within the border, including functional activities like chewing and speaking.
Enveloping Motion: The combined 3D movement field created by multiple border movements.
Functional movements are limited by teeth contact and joint anatomy.
Parafunctional movements (e.g., bruxism) are considered but are less relevant for normal function.

3. Neuromuscular Control

Neuromuscular control regulates mandibular movement, muscle tone, and position.
Sensory receptors in teeth, bone, joint capsules, and oral mucosa provide feedback to maintain equilibrium.
This control maintains balance between joint position and tooth contact, influencing mandibular posture and function.

4. Occlusion and Mandibular Position

Centric Relation: The position where the condyles are in their most superior and anterior position against the articular eminence with the disc properly interposed.
Centric Occlusion: The tooth contact position when the mandible is in centric relation.
Centric relation and maximum intercuspation (maximum tooth contact) often do not coincide; in 80-85% of people, condyles are not in centric relation during habitual occlusion.
Deflective contacts can cause mandibular shifts and occlusal instability.
The mandible may be displaced due to occlusal interferences, causing joint and muscle issues.

5. TMJ Disorders and Disc Displacement

Disc displacement, especially anterior displacement, is common and can be:
- With reduction: The disc returns to its normal position upon mouth opening, causing clicking sounds.
- Without reduction: The disc remains displaced, limiting movement.
Muscle dysfunction, occlusal trauma, and parafunctional habits contribute to TMJ disorders.
Adaptive changes like fibrosis can reduce symptoms but do not restore normal anatomy.
Importance of avoiding excessive forces (e.g., cracking seeds) to protect the joint.

6. Implant Dentistry Considerations

Implants lack periodontal ligament proprioception and have different biomechanical properties compared to natural teeth.
Implant-supported prostheses require precise occlusal schemes aligned with centric relation and border movements to avoid overload.
The absence of normal joint and bone proprioception in implants necessitates careful treatment planning.

7. Muscle Function and Testing

Muscles like the temporalis and masseter have specific fiber orientations affecting mandibular movements.
The lateral pterygoid muscle has two heads, with the upper head attached to the disc, playing a role in disc displacement when overactive.
Muscle tone and reflexes can be tested clinically to assess mandibular position and function.

Detailed Methodology / Instructional Points

Border Movement Assessment:
- Ask the patient to perform maximum mandibular excursions within physiological limits.
- Observe reproducibility and shape of border movements.
Occlusal Analysis:
- Identify maximum intercuspation and centric relation.
- Detect deflective contacts and their influence on mandibular shifts.
Neuromuscular Testing:
- Palpate temporalis muscle during clenching to assess centric relation return.
- Evaluate lateral pterygoid muscle function and tone.
TMJ Evaluation:
- Use imaging (MRI) to detect disc displacement.
- Listen for reciprocal clicking indicative of disc displacement with reduction.
Implant Occlusion Planning:
- Ensure occlusal contacts do not force mandible out of centric relation.
- Design occlusion to accommodate limited proprioception and joint feedback.

Key Terminology

Temporomandibular Joint (TMJ)
Mandible
Maxilla
Articular Disc
Centric Relation
Centric Occlusion
Border Movements
Intra-Border Movements
Neuromuscular Control
Disc Displacement (with/without reduction)
Parafunctional Movements
Maximum Intercuspation
Deflective Contact
Implant Occlusion

Speakers / Sources Featured

Primary Speaker: Unnamed lecturer delivering the master’s level lecture on temporomandibular disorders (TMD).
Referenced Expert: Dr. Reem (mentioned in relation to joint disorders explanation).
Additional Mentions: No other specific speakers identified.

This summary encapsulates the lecture’s comprehensive exploration of TMJ anatomy, mandibular biomechanics, neuromuscular coordination, occlusal relationships, TMJ pathology, and clinical implications for dental treatment and implantology.