Mmr 566k4g

Maxillo-Mandibular Relation (MMR) & occlusion in complete dentures Dr Mandakini Mohan Dr.Omar H. Bayati International Medical University (IMU)

Learning objectives: to understand what is the component parts of the maxillo-mandibular relation and it is role in the success of the complete denture treatment. to understand the clinical steps of maxillo-mandibular relation in complete denture treatment. to uderstand the theory of the face-bow transfer , it‘s indication & clinical application procedure. To undertand the difference of occlusal concept in dentate & edentulous patients & appreciate the role of occlusion in the success of complete denture treatment. to understand the theoretical principles & concepts of occlusion in complete denture treatment.

Maxillo-Mandibular Relation (MMR) in complete dentures

Part 1

MMR is The clinical stage following the visit where Definitive (final impressions) are recorded. Occlusal rims should be ready to accomplish the MMR record.

MMR stage is composed of three component parts: Creating and outlining the form of the dentures Recording of intermaxillary relations Selection of teeth.

Creating and outlining the form of the dentures: Objective: • to design and orient the polished surface of the denture to be in harmony with the physiological function of the Tongue, lips and cheeks. • the polished surface should occupy a position of equilibrium among these groups of muscles and it is frequently referred to as the neutral zone.

Clinical steps in Creating and outlining the form of the maxillary denture:

prior to inserting the rim into the mouth, ensure that the rim is well adapted to the master cast

that the technician constructed the occlusal rims based on average values and it is the role of the dentist to create & outline the form of the denture by adding or removing wax for each individual patient.

Clinical steps in Creating and outlining the form of the maxillary denture: First clinical step is to ensure that the infra-nasal tissues are harmonious with the soft tissues of the middle third of the face. Failure to do this may affect the form and length of the upper lip, by raising the lip inappropriately.

Clinical steps in Creating and outlining the form of the maxillary denture:

Confirm that the upper lip is adequately ed. This should result in restoration of the - vermilion border - the philtrum

Vertical Naso-labial angle is 90º

Horizontal labial angle varies from 90º to 120º

determine the position of the incisal point relative to the resting lip: the incisal level of the upper rim is 2 mm inferior to the resting upper lip.

Younger patients may reasonably be expected to show 4–5 mm of tooth beneath the resting lip. In contrast, a 70-year-old patient might be best suited by having the incisal point level with the resting lip

Antero-posterior verification of the placement of the incisal point may be achieved by asking the patient to say a word containing a labiodental sound eg ‗fish‘ . in general , the incisal point should correspond to the vermilion border of the lower lip

Determine the upper anterior plane. ‗Fox Plane‘ device placed against the maxillary occlusion rim. This should be parallel to the interpupillary line.

Determine the posterior occlusal plane. Fox‘s plane device used The posterior occlusal plane should be parallel to the alatragus line (Camper‘s Plane).

Determine the position of the mid points of the upper canine teeth using one of 2 methods:

extend dental floss from the inner canthus of the eye, via the lateral border of the alar cartilage (with the patient smiling) onto the incisal edge of the upper rim

use a photograph of the patient when the patient was dentate. Using the pupils as stable reference points, the clinician may determine the relative position of the upper canine teeth using the ratio

Using the canine tips as a reference point, the buccal form of the upper rim may be moulded by reducing the inferior borders of the posterior rims by 3° to 5°. This procedure creates what are known as the buccal corridors and creates a more natural smile

the following should be scribed clearly on the anterior aspect of the rim:

High smile line Canine points.

Centre line

Recording of intermaxillary relations: JAW RELATIONSHIPS: Vertical Relationships Horizontal Relationships Orientation of the occlusal plane in relation to the condyler axis.

Vertical Relation Important Vertical dimension of rest: (RVD) also known as Physiologic rest position Vertical Dimension of Occlusion: (OVD) Interocclusal Distance Formerly known as ― freeway space‖

Vertical Dimension of Occlusion: The position of the jaws when the natural teeth are in maximum intercuspation. May become ―less‖ (nose closer to chin) if posterior is lost or natural teeth wear quickly. With complete dentures VDO ―lost‖ as denture teeth wear and ridges resorbs.

Vertical Dimension of Rest Position of jaws when ―All muscles that open and close the jaw are in a state of minimal tonic contraction‖. • VDO is usually about 2-4mm less than VDR • Difference (VDR-VDO) is the interocclusal distance (free way space) • This space between the teeth is necessary for comfort • This is the best starting point in establishing the correct VDO for a new set of dentures

Vertical Relation

RVD

OVD

Increase in OVD ―patient mouth is opened excessively‖ Loss of interocclusal distance Denture teeth in at rest Soreness of mucosa over ridges Potential for accelerated resorption Soreness of facial muscles : ―Tired face‖ Soreness of TMJ Difficulty with eating and speech Clicking dentures, no room to chew

Decrease in OVD ―patient‘s mouth has over closure‖ Collapsed Appearance - chin too close to the nose or protruding jaw Fatigue when chewing Sore muscles or ts

Establishing Occlusal Vertical Dimension 1. Measure difference between RVD & OVD 2. Tactile sense and patient-perceived comfort. 3. Phonetics tests “Closest Speaking Space”

Patient sitting upright

Patient sitting upright Soft tissue position affected by posture

Measure difference between RVD & OVD:

Tactile sense and patient-perceived comfort:

Phonetics tests ―Closest Speaking Space‖: Closest Speaking Space confirms OVD Sibilant sounds ("s", "z", sh", ch") Rims should be at least 1 mm apart. Don‘t worry about sounds quality yet.

Horizontal Relationships The generally agreed position for recording the antero-posterior position of the mandible relative to the maxilla is that of the retruded position (R). R=CR (centric relation).

Centric relation: The most posterior relation of the lower to the upper jaw from which lateral movements can be made at a given vertical dimension.

Centric relation: the maxillomandibular relationship in which the condyles articulate with the thinnest avascular portion of their respective disks with the complex in the anteriorsuperior position against the slopes of the articular eminencies.

Why centric relation ...? it is the only repeatable , recordable & reproducible position in the edentulous patient. abnormal between opposing dentures when set up in other than the retruded relationship results in denture instability. the apparatus used for reproducing relevant jaw movements (the articulator) operates from the retruded position.

Registration of the centric relation: Guiding the patient into retruded position: Ask the patient to relax and guide the mandible into the centric relation.

Guiding the patient into retruded position:

Ask patient to curl back the tongue to touch the posterior border of the palatal baseplate and then close together (swallow).

Guiding the patient into retruded position: Ask the patient to push the mandible forward while applying gentle counter resistance to the chin.

Train the patient to bite into retruded position prior to registration. Draw a check marks on the occlusal rims to ensure reproducibility of the mandibular closure pattern.

Registration of the centric relation: Make a 3mm notches into the maxillary occlusal rims at about the 2nd premolar region bilaterally . 2 mm of wax are removed from the mandibular occlusal rims at the opposing region. the centric relation using a bite registration material.

Registration of the centric relation: Gothic arch tracing : This trace is made on a ‗central bearing apparatus‘. This comprises upper and lower acrylic plates onto which is mounted centrally, a stylus and a platform.

Gothic arch tracing : These will record a ‗map‘ of the patient‘s range of movements, by asking the patient to go into: • Protrusive • Right lateral • Left lateral excursions.

Orientation of the occlusal plane: The use of a face bow registration fixes the maxillary cast in the same three-dimensional plane in relation to the condyles as exists in the patient and thereby reproduces the patient's arc of closure. Capturing the correct mandibular arc of closure is probably the most compelling rationale for the use of a semi-adjustable articulator.

A facebow relates the maxillary arch to the axis of the condylar hinge using tripod localisation: 1. Two posterior references approximating each of the TMJ (external auditary meatus) 2. An anterior reference point to relate the maxilllary cast vertically to the selected horizontal reference plane.

What is the hinge axis ? The frame of reference common to the articulator and patient. It is determined : i) Mechanically with a device called a (Kinematic facebow). ii) Arbitrarily or automatic measurement 12 to 13 mm anterior to the tragus (Arbitrary Facebow). • When facebow is not used to relate the maxillary cast to the approximated starting positions of the condyles, the resulting arcs of movement may differ from the patient to the articulator. • This may cause restorations fabricated on the articulators to have potential occlusal errors.

Facebow Transfer Record using arbitrary facebow:

Edentulous Bite Fork: Allows patient to close against the opposing rim to stabilize the record bases

Heat bite fork and imbed it centered and parallel the occlusal plane

Finger cots can be used over ear pieces for infection control

Patient can assist with placement and orientation in external auditory meatus

Orient in external auditory meatus

Slide facebow onto bitefork

Extend nasion & tighten

Tighten all facebow wrenches

Loosen these tighteners. Release the recordbase by breaking the seal, and removing the facebow.

Loosen and remove the transfer jig from the earbow

Place facebow on transfer jig and attach to indirect mount. Don’t use direct method with indirect mount.

Remove incisal pin and set the centric latch

Transfer jig with record base on articulator

Place cast and maxillary mounting plate

Attach cast with mounting plaster

TEETH SELECTION

Selection of upper anterior teeth. Selection of lower anterior teeth. Selection of posterior teeth types and moulds. Selection of shade(s) of the anterior and posterior teeth.

Selection of upper anterior teeth: Pre-extraction record: Photograph. Relate canine points to pupils. Relate canine points to inter-alar width. Relate six anterior teeth to smile line.

Radiograph Cast of arch Relative of similar facial appearance.

Pre-extraction record: Photograph Radiograph Cast of arch Relative of similar facial appearance.

Pre-extraction record: Photograph Radiograph Cast of arch Relative of similar facial appearance.

Pre-extraction record: Photograph Radiograph Cast of arch Relative of similar facial appearance.

Post-extraction record: Central Incisor restore philtrum Central incisor restore vermillion Border Incisal point and smile line determine height of tooth Position of canine points. Relate to inner canthus of the eyes and inter-alar width (smiling).

Selection of lower anterior teeth Lower anterior teeth selected to be harmonious with upper teeth.

Selection of posterior teeth types and moulds. Posterior tooth moulds are of three types: a) Posterior teeth which have cusps. b) Posterior teeth which have no cusps. c) Hybrid mould ie teeth which are modified to obtain the benefits of a) and b)

Selection of teeth shade(s) that patient acceptance is the main factor.

Complete dentures‘ occlusion

Part 2

The design of an occlusion in complete dentures is different from that of the dentate patient…? The absence of direct attachment between the dentures and the patient‘s musculoskeletal system requires a different set of guidelines of good occlusal practice. occlusion is considered a major factor governing stability…?

The minimal level of occlusion that should be achieved in complete dentures..? Balanced occlusion: is ‗even, harmonious bilateral between teeth or tooth analogues in retruded position (R)‘. This is a ‗static occlusion‘ concept

Balanced articulation: In which the teeth of the maxillary denture must maintain harmonious sliding s with the teeth of the mandibular denture in all excursive (Protrusive & lateral) movements.

‗Dynamic occlusal‘ concept.

If balanced articulation is required : Use a facebow transfer. Accurately determining condylar angles. Harmonise the occlusion to match mandibular movements.

The biomechanics of functional occlusal s Two determinants of Protrusive movement: The incisal guidance angle (IGA).

The sagittal condylar guidance angle (SCGA).

―Christensen phenomenon‖ in which the mandibular path in a forwards direction produces a downward displacement of the mandible. This means that record blocks, for instance, set on a flat plane will separate when the mandible moves forwards.

Setting of 20º teeth in flat occlusal plane: The mandible's path is an arc which is steeper posteriorly than anteriorly. The only teeth that will remain in are those mid-way between the 30° movement posteriorly and the 10° movement anteriorly, i.e. whose cusp angles are 20° at the midpoint of the arc (30+10=40; half of 40=20).

Setting of 20º teeth in a compensating curve (curve of Spee):

The steepness of the compensating curve (curve of Spee)varies according to the condylar guidance angle as the incisal guidance angle remains the same.

The biomechanics of functional occlusal s Two determinants of Lateral movement: The Canine guidance angle (CGA).

The Medial condylar guidance angle (MCGA).

Setting of 20º teeth in a compensating curve (curve of Monson):

Lingualized articulation: this form of denture occlusion articulates the maxillary palatal cusps with the mandibular occlusal surfaces in centric, working and nonworking mandibular positions.

Centric occlusion in a lingualised articulation. The upper palatal cusps the central fossae of their opposing mandibular teeth, and the buccal cusps have been adjusted to just raise them sufficiently so that they do not take part in the articulation.

The teeth set in (curve of Spee) in a same way as in balanced articulation.

The teeth set in (curve of Monson). Excluding the buccal cusps (simplified the setting by eliminating it‘s influence on the working side ).

References: Davies SJ, Gray RM, McCord JF. Good occlusal practice in removable prosthodontics (2001).Br Dent J.10;191(9):491-4, 497-502. Grant A. A., Heath J. R. & McCord J. F. (1994). Complete prosthodontics problems diagnosis and management. Mosby. Mc Cord J F, Grant AA(2000).Registration: stage I--creating and outlining the form of the upper denture. Br Dent J. 27;188(10):529-36.

Mc Cord J F, Grant AA(2000). Registration: stage II--intermaxillary relations. Mc Cord J F, Grant AA(2000). Registration: stage III—selection of teeth. The glossary of prosthodontic (2005) J Prosthet Dent ;94(1):10-92. Zarb Bolender (2004) Prosthodontic treatment for edentulous patients. Complete dentures and implant-ed prostheses. Mosby. Twelfth Edition. Br Dent J. 24;188(12):660-6.