Centric Records Dr. Muaiyed. Mahmoud. Buzayan, BDS MClinDent Malaysia AF AAMP USA

Occlusion the static relationship between the incising or masticating surfaces of the maxillary or mandibular teeth or tooth analogues Deals with the static relationship of the opposing teeth. Articulation Deals with the dynamic relationship of the opposing teeth. Protrusive and lateral movements

Centric Relation The maxillomandibular relationship in which the condyles articulate with the thinnest avascular portion (non innervated) of their respective disks with the complex in the anterior-superior position against the shapes of the articular eminencies. This position is independent of tooth contact. It is restricted to a purely rotary movement about the transverse horizontal axis

Centric Occlusion The occlusion of opposing teeth when the mandible is in centric relation. This may or may not coincide with the maximal intercuspal position. Maximal intercuspal position The complete intercuspation of the opposing teeth independent of condylar position, sometimes referred to as the best fit of the teeth regardless of the condylar position

1. Hapitual class III (ridge to ridge) 2. Edentulous patients have more difficulty determining where their denture teeth should contact (No periodontal membrane) 3. Record base fit (loose) and wax rim (dimensions) changes confuse some patients

Occlusal position to be acceptable, it should be: 1. Conducive to health Harmless to TMJ Painless 2. Relatively repeatable position can be checked and repeated, before dentures completed CR is not far from CO at same occlusal vertical dimension

Terminal Hinge axis An imaginary line around which the mandible may rotate within the sagittal plane Hinge Position is Repeatable (axis of circle) relatively centered patient can find stable occlusal contacts relatively easily allows change in vertical dimension Can be transferred to the articulator

1. When entire occlusion being restored (full mouth rehabilitation) No remaining posterior centric stops 2. When complete, or removable partial dentures involve the entire occlusion 3. Restoring/ Increasing of vertical dimension (OVD) Tooth surface loss (TSL) erosion, attrition and abrasion

1. Stable occlusion 2. Posterior centric stops present 3. No reason to change current occlusion Use maximal intercuspation

Occlusal Vertical Dimension

Plane of occlusion An imaginary surface which is related anatomically to the incisors and tips of the occluding surfaces of the posterior teeth. In complete denture prosthodontics, this plane is parallel to Camper's line. Camper's plane A plane established by the inferior border of the right or left ala of the nose and the superior border of the tragus of both ears.

Physiologic rest position The habitual postural position of the mandible when the patient is resting in an upright position and the condyles are in a neutral, unstrained position in the glenoid fossae. Vertical relation at rest position VDR The length of the face when the mandible is in the physiologic rest position. The wax rims should not touch. Vertical dimension of occlusion VDO The distance measured between two points when the occluding members (upper and lower Occlusion rims) are in contact. It is about 2-4mm less than Vertical Relation at Rest Position. Freeway Space (interoclusal distance) the difference between the vertical dimension of rest and the vertical dimension while in occlusion. (2- 4 mm) Freeway space= VDR- VDO Centric relation record A registration of the relationship of the maxilla and the mandible in centric relation made at the established vertical relation of occlusion.

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Amount of separation between mandible & maxilla when denture teeth are in contact Over closure VDO Restoring with prosthesis

Used to relate casts on an articulator Record bases simulate the finished denture base Wax occlusion rims simulate the position of the teeth Occlusion rims slightly bulkier, provide additional stability during record making

Required for record making and phonetic tests Centric relation record will be inaccurate if loose Use denture adhesive if slightly loose Much looseness REMAKE Causes of Poor Retention 1. Poor adaptation of resin to cast 2. Over- or under-extension 3. Excessive block-out of the cast before making the denture base Starting Point for VDO; adjust the height of the occlusal blocks separately using average dimensions: Maxillary - 23 mm Mandibular - 18 mm

Maxillary rim slightly facial to compensate for ridge resorption. (Incisal display) Anterior height 1-2 mm below the lip at rest/when the patient slightly smiles 10-20mm 3-4mm 20-25mm 2mm 26-30mm 1mm Lip Length Incisal Display

Horizental extension; Touches wet line of lower lip (the vermilion border) when F or V sounds (Count 50-60). The labial surface of the wax anterior to incisive papilla 8 10 mm Lips should be unstrained To confirm correct wax block dimensions: 1. Naso-labial angle 90 2. Philtrum depressed (not full) 3. Vermilion border showing (not invereted)

Frontal (Mediolaterally) the occlusal plane parallels the pupils (Fox plane can be used Anterio-posteriorly, The Maxillary denture occlusal plane should be parallel to the campers line

Extension: Posteriorly, the occlusion rim intersects 1/2 - 2/3 up the retromolar pad. Anterior height even with the corners of the mouth when the lip is relaxed (Buccal corridor 1-2 mm horizontal overjet Unstrained lips, Vermilion border showing

Amount of separation between mandible & maxilla when denture teeth or wax rims are in contact Over closure VDO Restoring with prosthesis

The target is to get unstrained Physiologic Rest Position (PRP) within the average 1. At rest, lips barely touching 2. Occlusion rims should not touch 3. With INTEROCLUSAL DISTANCE (ID) FWS between wax rims at physiologic rest position ( 2-4 mm) PRP (OVR) = ID (2- 4mm) + OVD

1. Measure difference between PRP & OVD to get the average ID 2. Feel to ensure smooth movement of mandible 3. Phonetics tests Closest Speaking Space 4. Face profile (not long/ short face) Check with all the previous techniques to ensure acceptable OVD. No one technique 100% correct.

1. place the maxillary record base in the patient's mouth. 2. Seat the patient in a comfortable upright position unsupported by a head rest. Soft tissue position affected by posture. Mark a small dot on on the nose and the chin to serve as reference points. Ask the patient to swallow and relax the jaw several times. 3. Use external points for ease of measurement Small dots under columnella (or on the nose tip) & mid-symphisis Use Boley Gauge or ruler 4. Measure the distance between dots At PRP and OVD, the difference is ID 5. the operator should adjust the wax rims until the ID is (2 4 mm)

Open and close until lips barely touch - Physiologic Rest Position (PRP). Measure distance between dots Open and close until rims touch without interference and uniformly. Measure distance between dots (OVD) These measurement will be different each appointment. However , the ID would be in the same range.

Closest Speaking Space Sibilant sounds ("s", "z", sh", ch") (,) Rims should be at least 1 mm apart No need to get clear sounds and pronunciation yet.

If there was no ID or ID less than 2mm Excessive OVD Wax Rims Too High. If there was insufficient interocclusal distance Remove wax from one or both of the rims Use large wax formers wax spatulas Bunsen burner and torch

Flat and even contact along entire occlusal surface If uneven contact, patient may be forced into eccentric position Scribe lines parallel to the opposing occlusal rim. Use as a guides during reduction

Making three marks on the wax rims, when the patient in Centric Position Scribe three widely separated lines between maxillary & mandibular rims Remove, superimpose the lines Eliminate contacts between record bases, record base/occlusion rims

Excessive Occlusal Vertical Dimension Inadequate Occlusal Vertical Dimension Sore muscles Collapsed Appearance Soft tissue sore spots chin too close to the nose or protruding jaw Rapid bone resorption Fatigue when chewing Dentures click during speech Sore muscles or joints Long face Short face

1. Bimanual manipulation 2. Chin point guidance

Generally 1. Patient sit in a slightly supine position 2. Occlusion rim notched to aid stabilizing the record bases 3. Index fingers on the rim, thumbs under symphysis (Chin point guidance) 4. Jiggle the mandible 5. Mandible should freely arc 6. Allow the patient to close into contact 7. Do NOT push the mandible or dislodge the record base 8. Medium (record material) must be soft 9. Minimal closing pressure

1. Place 3 widely separated lines between the rims in the centric position 2. CRITICAL! Check that record base heels/rims do not touch 3. Two sharp V-shaped notches in the molar/premolar area of each sided wax, depth 1-2 mm

1. Place occlusion rims intraorally 2. PVS registration material, over entire occlusal rim 3. Have patient close into record 4. Ensure smooth arc of closure, no horizontal deviations 5. Use index fingers to stabilize lower record base 6. Want flat record, no excess on sides of rims 7. Excess material recording of the sides of the rim can cause deflection when checking record

Ensure record is repeatable Increase the height of incisal pin 1 mm, invert articulator Place wax rims together, lute with sticky wax - 4 spots