The Occlusal Decision (SDF) MCQ

The Structural Decision Framework reads every occlusal case through four lenses: STRUCTURE (the tooth and joint anatomy and the remaining tooth structure), FORCE (the load path through the dentition), TIME (the longitudinal predictability of the bite), and STABILITY (the survivable system over years). The same four lenses decide whether to equilibrate or add, whether to rebuild anterior guidance, whether to raise the bite, which splint to choose, when to refer for TMD, and the equally important question of when NOT to change the occlusion at all.

Subtractive vs Additive: Equilibration vs Composite/Onlay

• Occlusal EQUILIBRATION removes interferences by selective grinding (subtractive); it uses the BULL rule for non-working and the MUDL rule for working interferences, preserving centric stops.
• Equilibration is conservative when the existing contacts are essentially correct but a few interferences must be removed; it does NOT add tooth structure.
• ADDITIVE restoration (direct composite or onlay/overlay) is used when worn or lost tooth structure must be replaced, when anterior guidance has flattened, or when VDO needs to be opened with restorative material rather than ground in.
• The SDF judgment: when the Structure has been lost (wear, fracture, attrition past enamel), additive restoration restores it; when the Structure is intact but the Force vector is wrong, equilibration corrects it. Avoid grinding healthy structure to fix a force problem you could solve restoratively.

Rebuilding Anterior Guidance

• Flattened anterior guidance (from attrition, palatal erosion, or restorative inattention) loses the protective disocclusion of posteriors in lateral and protrusive movement; group function or non-working interferences emerge.
• Restoring anterior guidance uses direct composite (palatal of upper anteriors) or ceramic (palatal veneers, onlays) to recreate the canine and incisal guidance surfaces; the lab fabricates from articulator-mounted casts at the patient-accepted provisional VDO.
• Provisional restorations at the planned new anterior guidance let the patient TEST the design (and let the dentist read fremitus, mobility, muscle response) before committing to definitive restorations.
• The SDF judgment: anterior guidance rebuild is justified when Force flattening is producing posterior interferences and accelerated posterior wear; Structure is restored, Force is redirected through canines, Time is bought, Stability is improved.

Bite Raising and VDO Change

• RAISING VDO restoratively is reserved for cases with substantial wear or restorative need; the change is tested through a provisional period (removable appliance or provisional restorations) for weeks to months before definitive restorations.
• Small VDO changes (about 1-2 mm) are generally well tolerated; larger changes need a deliberate provisional period; persistent symptoms (muscle pain, joint discomfort, lip-seal difficulty) during the provisional phase prompt VDO adjustment before definitive work.
• Lost VDO from severe attrition produces overclosure (perioral wrinkles, angular cheilitis, chewing inefficiency); raising VDO restoratively restores facial dimension, freeway space, and chewing function.
• The SDF judgment: bite raising is justified when Structure has been lost (worn dentition), Force redistribution is needed (concentrated wear), Time has shortened the dentition's lifespan, and Stability requires more vertical face height; raising VDO without these is unjustified.

Splint Therapy Decision: Stabilization vs Anterior Bite Plane

• STABILIZATION SPLINT (full-arch hard acrylic with centric stops + canine guidance + anterior guidance) is the workhorse for sleep bruxism and chronic myofascial TMD; it distributes load and protects teeth and joints; safe for long-term wear with adjustments.
• ANTERIOR BITE PLANE (NTI / Lucia jig) disengages the posteriors and deprograms muscles in the short term; useful for acute myofascial pain or diagnostic CR registration; LONG-TERM full-time wear risks posterior overeruption and anterior intrusion.
• SOFT (cushion) splints are inexpensive but compressible; they can encourage muscle activity in some patients; usually short-term protection (e.g., athletic mouthguards), not for chronic bruxism management.
• The SDF judgment: stabilization splint matches most Structure + Force + Time + Stability needs; NTI is reserved for short-term Force redirection in acute pain or for diagnostic CR; long-term posterior open bite from NTI overuse damages Stability.

TMD Treatment Ladder and Referral

• TMD pain management ladder is CONSERVATIVE FIRST: patient education + soft diet + jaw rest + heat/ice + jaw stretching + NSAIDs → occlusal appliance (stabilization splint) + physical therapy + relaxation techniques → low-dose tricyclic antidepressant (amitriptyline) for chronic pain → intra-articular injection or specialist referral → surgery in refractory severe cases (rare).
• Most TMD responds to the first three rungs; the ladder is climbed in order, not skipped.
• Persistent severe symptoms (limited opening, severe locking, refractory pain, signs of intra-articular destruction) prompt referral to a TMD / orofacial pain specialist; advanced imaging (MRI for soft tissue and disc, CT/CBCT for bony changes) is selected on findings.
• The SDF judgment: TMD is multifactorial; conservative care respects Structure and Stability while reducing Force and giving Time to heal. Surgery is the last resort precisely because it alters Structure irreversibly.

The Decision NOT to Change the Occlusion

• Many functional, asymptomatic dentitions HAVE small CR-CO slides, mild non-working contacts, or wear that LOOKS imperfect but causes no symptoms; the dentition is in equilibrium with the patient's masticatory system.
• Grinding or restoratively altering an asymptomatic functional occlusion creates Force imbalances, removes Structure unnecessarily, and risks pain, fracture, and the chronic dissatisfaction of a 'new bite' that the patient never asked for.
• The SDF judgment: when Structure is adequate, Force is balanced, Time is producing acceptable change, and Stability holds — DO NOT change the occlusion. Document the findings, monitor, and treat the actual chief complaint.
• Conversely, change the occlusion when Structure has been lost (wear, fracture), Force is causing damage (interferences, parafunction with pain), Time is producing accelerated decline, or Stability is failing (mobility, fremitus).

Full-Mouth Rehabilitation and the Four Lenses

• FULL-MOUTH REHABILITATION is the integrated case where many SDF decisions converge: lost Structure (wear), wrong Force (lost anterior guidance, non-working interferences), prolonged Time (chronic parafunction), failing Stability (mobility, fremitus, restoration failures).
• Sequence: comprehensive examination + records (facebow + CR + protrusive/lateral) + diagnostic wax-up on articulator-mounted casts + provisional restorations at the planned VDO and anterior guidance + adaptation period + definitive restorations.
• Anterior guidance reconstruction precedes posterior restorative work in many cases, because anterior guidance dictates posterior morphology (Hanau's quint inputs).
• Maintenance: the rehabilitated dentition needs lifelong stabilization splint wear in most parafunctional patients, regular recalls, and adjustment of restorations as the dentition ages.