Maxillo-Mandibular Relationships Occlusal Vertical Dimension And Hinge Axis Relation

Occlusal Vertical Dimension Amount of separation between mandible & maxilla when denture teeth contact

Hinge Axis Location Use earbow to record relationship of maxilla to transverse horizontal axis Locate anterior reference point

Centric Position Relationship of maxilla & mandible Anterior/posterior & medio-lateral) Maximum intercuspation of denture teeth

Programming the Articulator Protrusive Relationship Simulate relationship of maxilla to mandible in excursions Denture teeth set in harmonious relationship for function

Record Bases (Baseplates) and Occlusion Rims Used to relate casts on an articulator Record bases simulate the finished denture base

Record Bases and Occlusion Rims Wax occlusion rims simulate the position of the teeth

Occlusion Rim Dimensions Occlusion rims slightly bulkier Provide additional stability during record making

Record Base Retention Required for record making & phonetic tests Inaccurate if loose Use denture adhesive if slightly loose Pronounced looseness - REMAKE

Record Base Retention Causes of Poor Retention Poor adaptation of resin to cast Over- or under-extension Excessive block-out

Occlusal Vertical Dimension Video

Arbitrary Adjustment of Occlusion Rims Adjust separately using average dimensions: Maxillary - 23 mm Mandibular - 18 mm ‘Starting Point’ Fairly rapid adjustment ~ 15 minutes per arch

Use a Hot Scapel Blade

Use Hot Wax Former or Metal Spatula

Maxillary Occlusion Rim Adjustment Maxillary rim slightly facial to compensate for ridge resorption

Maxillary Occlusion Rim Adjustment Anterior height 1-2 mm below the lip at rest/when the patient slightly smiles

Wax rim/tooth display can be adjusted with sex, age, and lip length (Vig: JPD 1978). Incisal Display 10-20mm 3-4mm 20-25mm 2mm 26-30mm 1mm >30mm Sex & Age Female Male Young +2 +1 Middle +1 0 Old 0 -1

Position of Maxillary Incisal Edge Edge of rim touches wet line of lower lip when ‘F’ or ‘V’ sounds Count ‘50-60’

Lip Support Lips should be unstrained Naso-labial angle ≈ 90° Philtrum depressed Vermilion border showing

Occlusion Rim Angulation Occlusal plane parallel to the ala-tragus line

Occlusion Rim Occlusal Plane Mediolaterally, parallels the pupils Fox plane can be used

Fox Plane Helps orient occlusal plane

Centered Occlusion Rim Centered over ridge to maximize stability

Posterior Occlusion Rim Height Posteriorly, the occlusion rim intersects 1/2 - 2/3 up the retromolar pad

Mandibular Rim Height Anterior height even with the corners of mouth when lip is relaxed

Facial Occlusion Rim Relations 1-2 mm horizontal overlap in anterior & posterior in centric position

Proper Lip Support Unstrained lips Vermilion border showing

Occlusal Vertical Dimension (OVD) Distance between maxilla & mandible when teeth or wax rims contact in centric position

Physiologic Rest Position (PRP) At rest, lips barely touching Occlusion rims should not touch Intraorally no contact

Interocclusal Distance (ID) Space between wax rims at physiologic rest position Usually 2-4 mm

Establishing Occlusal Vertical Dimension PRP = ID + OVD

Establishing Occlusal Vertical Dimension 1. Measure difference between PRP & OVD 2. Feel to ensure movement of mandible 3. Phonetics tests ‘Closest Speaking Space’ Patient sitting bolt upright

Establishing Occlusal Vertical Dimension Check with three techniques to ensure acceptable OVD No one technique 100% correct

Patient Sits Bolt Upright Soft tissue position affected by posture

Measurements OVD & PRP Use external points for ease of measurement Small dots under columnella & mid-symphisis Use Boley Gauge, not ruler

Measuring Occlusal Vertical Dimension Measure the distance between dots At PRP At OVD Difference is ID Measurements change each day (position of dots)

Measuring Physiologic Rest Postion Open and close until lips barely touch - Physiologic Rest Position (PRP) Measure distance between dots

Measuring Occlusal Vertical Dimension Open and close until rims touch Measure distance between dots (OVD) Measurement will be different each appointment

Establishing OVD Feel for Interocclusal Distance Close until lips barely touch - PRP Place finger on chin Look away Patient closes until rims touch (OVD) Feel for movement of the mandible

Establishing OVD Phonetics Test Closest Speaking Space Confirms OVD Sibilant sounds ("s", "z", sh", ch") Rims should be at least 1 mm apart Don’t worry about sounds yet

Excessive OVD Wax Rims Too High Insufficient interocclusal distance Remove wax from one or both of the rims Use large wax formers #5 & #7 wax spatulas Red-handled knife Bunsen burner and torch

Wax Rim Adjustment at OVD Flat even contact along entire occlusal surface EXTREMELY CRITICAL If uneven contact, patient may be forced into eccentric position

Adjusting Wax Rim Height Scribe lines parallel to opposing occlusal rim Use as a guides during reduction

Eliminating Record Base or Wax Rim Interferences Patient in Centric Position Scribe three widely separated lines between maxillary & mandibular rims

Establishing OVD Remove, superimpose lines Eliminate contacts between record bases, record base/occlusion rims/casts Only contact should be rim to rim

Adjusting Occlusion Rims Continue to adjust the rims until: interocclusal distance is 2-4 mm even contact along rims in centric position.

Excessive Occlusal Vertical Dimension Sore muscles Soft tissue sore spots Rapid bone resorption Dentures click during speech

Inadequate Occlusal Vertical Dimension Collapsed Appearance - chin too close to the nose or protruding jaw Fatigue when chewing Sore muscles or joints

Hinge Axis Location Face-bow or ear-bow used Record relationship of maxilla to transverse horizontal hinge axis of mandible

Hinge Axis Transferred to the articulator Important to prevent occlusal errors, particularly when cusped teeth are used in dentures.

Facebow (Earbow) Transfer Mount Maxillary Cast 2 Video Clips

Attach cast with mounting plaster in two steps