This lecture provides an in-depth continuation of craniomandibular dysfunction (CMD) analysis, focusing on instrumental recording techniques for establishing the maxillomandibular relationship, particularly concerning the vertical dimension of occlusion (VDO). The speaker outlines the challenges in standardizing VDO measurement due to numerous techniques and the lack of a universal gold standard. A critical comparison is made between various techniques for finding centric relation (CR), including manipulated, leaf gauge, and neuromuscular methods, concluding that forceful retrusion should be avoided due to the risk of compressing the TMJ's stress-absorbing bilaminar zone. The video stresses the importance of using the physiological rest position as a reference and details the use of the intraoral needle point tracing device (Gothic Arch) to locate a reproducible CR, recommending the functional position be set 0.5–1 mm anterior to the Gothic Arch tip. Finally, static and dynamic occlusal concepts are reviewed, emphasizing that different biodynamic principles apply to natural dentition (anterior/canine guidance) versus complete dentures (balanced occlusion for stabilization).
Cranium Mandibular Dysfunction: Instrumental Analysis and Occlusal Concepts
0:05 Last Lecture Recap: Physiological craniomandibular function is characterized by pain-free movement and unrestricted mandibular mobility. The physiological mandibular position (MIP) is slightly anterior to the Centric Relation (CR).
3:04 Vertical Dimension of Occlusion (VDO): VDO is crucial, especially in cases of abrasion or tooth loss. A review of techniques shows there is currently no single "gold standard" for determining VDO.
4:51 VDO and Rest Position: Using Posselt's diagram, the rest position is typically 3 mm below the Physiological Intercuspal Position (MIP) in natural dentition. This difference (2–3 mm) is the crucial value used as a reference when reconstructing VDO.
15:12 VDO and Articulator Use: If a device (like a Luchia jig) is used to temporarily raise the VDO for recording, a facebow is mandatory to transfer the patient's anatomical hinge axis to the articulator. This preserves the possibility of rotational movement to correctly reset the VDO.
19:00 VDO Takeaway: Clear guidelines for VDO determination and alteration are still lacking. Increasing VDO by more than 6.0 mm is highly recommended to be checked first using an interocclusal splint.
20:33 Maxillomandibular Recording Techniques: Techniques to find the ideal relationship include using the existing MIP, manipulated records (CR), central bearing tracing (Gothic Arch), and neuromuscular registration (e.g., electronic methods).
24:49 Critique of Registrations: Manipulated CR records are often less retruded than those achieved by leaf gauge techniques. Neuromuscular positions (using electric stimulation) often result in a position that is significantly anterior to the patient's physiological centric occlusion, making it doubtful for use in definite reconstruction.
32:42 TMJ Anatomy Warning: Forceful retrusion of the mandible should be avoided for permanent positions, as it compresses the bilaminar zone—a tissue complex containing vascular spaces that function as a crucial stress absorber.
37:11 Intraoral Needle Point Tracing (Gothic Arch): This method registers the rearmost position (CR) at the arch's tip. The physiological intercuspal position should be placed 0.5 to 1 mm anterior to the tip of the Gothic arch to prevent overloading the joint.
43:10 Deprogramming Time: Short-term devices like the Luchia jig (up to 30 minutes) eliminate occlusal contacts but do not provide true neuromuscular deprogrammation. Long-term muscle adaptation and stability require a splint in place for approximately three months.
46:06 Deflective Contacts: A deflective occlusal contact displaces a tooth or diverts the mandible from its intended movement. Instrumental analysis is not always necessary for TMD diagnosis but can be helpful in complex cases.
48:51 Dynamic Occlusion (Natural Dentition): The recommendation for natural teeth and fixed partial dentures is anterior guidance or canine guidance. Group function is typically estimated as physiological.
49:48 Dynamic Occlusion (Complete Dentures): Due to the viscoelastic connection of the denture base, the goal is stabilization, not protection (as with natural teeth). The recommended concept is Balanced Occlusion, which ensures contacts on both the working and balancing sides during eccentric movements to prevent the denture from lifting.