This online lecture by Dr. Kristoff Hunter provides a comprehensive overview of Craniomandibular Dysfunction (CMD), challenging traditional mechanistic views of the stomatognathic system. Hunter begins by tracing the biological evolution of jaws and teeth, demonstrating that "ideal occlusion" with numerous contact points is exceedingly rare and that redundancy and wear are physiological adaptations. The lecture then addresses the medical perspective, advocating for the bio-psychosocial model and emphasizing the critical role of standardized, validated diagnostic tools, specifically the Diagnostic Criteria for Temporomandibular Disorders (DC/RDC-TMD), which covers both physical and psychosocial axes. Finally, Hunter discusses therapeutic goals, stressing the importance of careful diagnosis before irreversible treatment, defining physiological occlusion based on subjective stability, and defending the mathematical necessity of the hinge axis concept for accurate prosthodontic procedures, particularly when changing the vertical dimension of occlusion.
Cranio Mandibular Dysfunction: A Biological and Medical Perspective
0:04 CMD: A Complex and Evolving Topic: The lecture, delivered by Kristoff Hunter, focuses on Craniomandibular Dysfunction (CMD). Early 20th-century views treated the system mechanistically (Alfred Gizy’s gear wheels, requirement for 30+ occlusal contact points).
2:55 Shift to Biopsychosocial Model: Since the late 1970s, the understanding of CMD has evolved into a more complex bio-psychosocial approach, recognizing that mechanical occlusion is not the sole factor.
4:26 Biological Function of Teeth: Teeth evolved independently of jaws (seen in lampreys). Their function extends beyond chewing to include holding, compression, penetration, scraping, tearing, signaling, and speech sound formation in humans.
11:36 Evolution of Occlusion: Complex dental occlusion, capable of grinding (tribosphenic form), is a late mammalian specialty. The lecture notes that in animals like dogs, guidance comes from posterior teeth (carnassial), not necessarily the canines.
18:41 Tooth Wear is Physiological: Attrition and wear are common in natural history (e.g., Neanderthals) and should not be inherently regarded as pathological unless it exceeds a painful or functionally problematic degree.
27:53 Rarity of Ideal Occlusion: Hunter cites a study finding that "ideal occlusion" (e.g., 20 contacts) exists in only 0.3% of the population, concluding that a high number of contacts is not necessary to maintain a physiological situation.
46:01 Static Occlusion and TMD (Controversy): Early systematic reviews (Cochran 2004) showed an absence of evidence that occlusal adjustment treats or prevents TMD. This suggests that mechanical occlusion alone is rarely the primary cause or cure for CMD pain, although poor restorations can cause discomfort.
49:45 Defining Physiological Occlusion: Physiological occlusion is best defined as the state where a patient experiences subjective occlusial stability and satisfactory masticatory, phonetic, and aesthetic function, irrespective of the exact number of contact points.
51:00 Centric Relation vs. Physiological Position: The lecture reviews changing, often contradictory, definitions of Centric Relation (CR). Key Takeaway: CR (the rearmost position) is not the ideal physiological position; the most stable physiological mandibular position is slightly anterior to CR and should coincide with Maximum Intercuspal Position (MIP).
1:17:02 Use of Validated Diagnostic Tools (DC/RDC-TMD): To make a correct diagnosis, a thorough history and specific findings are mandatory. The Diagnostic Criteria for TMD (DC-TMD) is recommended as an internationally accepted and scientifically validated two-axis tool (physical diagnosis and psychosocial status).
1:24:03 Joint Pathologies: Common disc disorders include anterior disc dislocation with reduction (clicking) and without reduction (closed locking). Other pathologies requiring management include subluxation, hypermobility, arthritis, and local/myofacial pain.
1:41:48 Treatment Goals: Irreversible Caution: Dentists should be cautious with irreversible treatment (e.g., adjustment with a bur). Reversible tools like occlusal splints are recommended first to test and establish a stable, comfortable balance.
1:45:01 The Hinge Axis Concept is Valid: Despite criticisms, the hinge axis concept is mathematically essential for describing and understanding mandibular movement (rotation and translation). Neglecting it prevents proper understanding of joint function.
1:53:08 Instrumentation for Vertical Dimension: A face bow (even an arbitrary/average axis face bow) is crucial when increasing or decreasing the vertical dimension of occlusion (VDO). Failure to use a face bow when altering VDO results in incorrect representation of occlusal interaction in the articulator.
2:04:40 Increasing VDO: If increasing the VDO by more than 6 mm, preceding splint therapy is advisable. A face bow should be used to ensure the anatomical hinge axis is represented correctly in the articulator.