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Complete Removable Prosthodontics9-5-2009

Complete Denture OcclusionComplete Denture Articulation

1. Definitionsa. Occlusion is the relationship of the teeth in one position, static relationship when they are in that

one positionb. Articulation are when these teeth move across each other, like when you protrude, retrude, and do

excursive movementsi. Talks about the entire spectrum of functional movement

2. Natural Teeth vs. Artificial Occlusionsa. Natural dentition’s periodontal tissues are innervatedb. Natural teeth receive individual pressures of occlusion and can move independently

i. Artificial teeth move as a unit on a basec. Non-vertical forces on natural teeth affect only the teeth involved.

i. Artificial teeth – the effect involved all teeth on the based. Incising with natural teeth doesn’t affect the posterior teeth. e. Proprioception found in natural teeth allows patient to avoid prematurities and interferences.

i. In artificial teeth, lack of proprioception means prematurities would cause the bases to shift on the foundation tissue

f. The differences make the CD occlusion a unique problem. The occlusion must function in the compromised situation of the edentulous mouth. It must be designed to redress the unequal stability of the upper and lower denture bases. Lower dentures are almost always less stable, so the occlusal design and position of lower teeth are usually given priority in approaching a solution to the problem of CD occlusion.

i. We don’t want cusp over cusp or incline contacting incline or long axis over long axis in the dentures

ii. Or between a maxillary denture and mandibular natural teeth3. Axioms for Denture Occlusion (Sears VH, J. Prosthet Dent, 1952)

a. The smaller the area of occlusal surface acting on food, the smaller will be the crushing force (on food) transmitted to the supporting structures

b. Vertical force applied to an inclined occlusal surface causes non-vertical force on the denture basec. Vertical force applied outside (lateral to) the ridge crest creates tipping forces on the denture based. Vertical forces applied to inclined supporting tissue will cause non-vertical forces on the denture

base4. Dentures are subject to the principles of physics – the inclined plane and the lever. The forces operate

whether we recognize them or note. Controlling these forces generated by the occlusion will enhance function, stability, comfort, and longevity of the dentures.

5. There are numerous concepts, techniques, and philosophies of complete denture occlusion6. Metal Inserts

a. Metal on occlusal surface of the posterior teeth with a plus sign on it that is raised up; these are called Sosan Blades

b. Hardy Cutters are a three tooth block with acrylic resin teeth that have a metallic blade sticking up out of the resin

c. These are extremely efficient at chewing, they will chew up cheek and tongue and anything else that gets in the way

i. Among the things dentures have to do is chew up food, these are top of the line at chewing7. One philosophy: Posterior denture teeth should have cusps which function in harmony with mandibular

movementsa. Ideal occlusion in the natural teeth doesn’t involve the posterior teeth contacting in excursive

movementsb. This is completely different than natural teeth

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c. Mutually Protected Occlusion = Canine guidance = when the pt slides to the right the only teeth that are touching are the canines, everything else is separated. When you protrude the anterior teeth cause the posterior teeth to disclude. It is the opposite situation here.

d. Setting posterior teeth like this is placing them in Balanced Occlusione. This is a very hard scheme to do

8. A philosophy: Posterior denture teeth should not have cusps because cusps create lateral forces which are hard to control

a. So the form of the tooth is non-anatomic and the arrangement of the teeth is non-balancedb. There is no contact of anterior teeth and no vertical overlapc. The posterior teeth do not slope up as they go to the posterior

9. Common Occlusal Schemesa. Form of the posterior teeth and their arrangementb. Types:

i. Anatomic, balanced occlusion (BO)ii. Non-anatomic, (balanced or non-balanced)

iii. Lingualized (balance or non-balanced)10. Anatomic, Balanced Occlusion

a. Introduction i. Definition: Stable, simultaneous contact of opposing

maxillary and mandibular posterior teeth in CR position and continuous, smooth bilateral gliding contacts from this position to any eccentric position within the normal range of mandibular function (usually not beyond edge-to-edge position of anterior teeth)

ii. If you have BO and slide your teeth to the left all of the teeth on the WS stay in contact, and all of the teeth on the NWS except one stay in contact

iii. In protrusion all of the anterior teeth contact and there are posterior teeth contacting

iv. Balanced Occlusion refers to what happens when the pt moves into eccentric movement, there are contacts on both sides

b. Specificsi. Teeth glide evenly over each other from the central incisor through the second molar on the

working side of the archii. Contacts on the non-working side should exist and must not interfere with the smooth

gliding movement of the working sideiii. No single tooth can interfere and cause the others to life or separate from their opponentiv. Posterior contacts must exist simultaneously with contacts on the anterior teeth in

protrusive movementsv. May use anatomical or zero-degree teeth

vi. Requires precise jaw relation records – so it is technically challengingvii. Results may be short lived

c. Advantagesi. More esthetics, natural appearance – because they look like natural teeth

ii. Penetrate bolus better – because it isn’t a flat surfaceiii. Greater denture stability in eccentric movements – because the teeth remain in contactiv. Often times referred to cross-tooth and cross-arch balance

d. Disadvantagesi. Precise, accurate records required

1. Have to pick your patient, they have to be able to do the excursive movements in the direction you tell them to

ii. More time-consuming to developiii. Function against inclines -> greater lateral forces placed on alveolar ridges

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iv. Articulator precision not duplicated in mouthv. Difficult in Class II, Class III, and crossbites – so Class I only

vi. Results are short-lived – because there is resorption under the denturee. Indications

i. Young, healthy alveolar ridges1. Not for people with extreme resorption of their ridges

ii. Good neuromuscular control to allow precise records1. Not for people with Parkinson’s or bad muscular control

iii. Skeletal Class I patientiv. Balanced occlusion in old denturesv. Vertical overlap of anterior teeth

11. Rudolph Hanau, 1925 – ON NBDE ----- For Balanced Occlusiona. Paper titled “Articulation: Defined, analyzed, and formulated”b. Hanau’s “factors governing articulation”c. Hanau’s Quint

i. Incisal guidanceii. Condylar guidance – this one cannot be changed on the patient

iii. Cusp heightiv. Plane of occlusionv. Compensating curve

1. If these 5 things are correct you will have balanced occlusiond. Incisal Guidance

i. Horizontal Overlapii. Vertical Overlap – some patient’s will demand this, it is permissible with this scheme

iii. The influence of the contacting surfaces of the maxillary and mandibular anterior teeth on mandibular movement

iv. Definition: the influence of the contacting surfaces of the maxillary and mandibular anterior teeth on mandibular movement

e. Condylar Guidancei. The influence of the contours/slope of the glenoid fossae on mandibular movement

1. Definition: mandibular guidance generated by the condyles transversing the contours of the glenoid fossa

2. When a pt protrudes this slope causes the posterior teeth to separate3. The teeth cannot be on a flat plane and get balanced occlusion – the posterior teeth

will separate in protrusionii. Christensen’s Phenomenon

1. Separation of posterior teeth during mandibular protrusion caused by the slope of the articular eminence

f. Cusp height/anglei. 0, 10, 15, 20, 33, 45 all in degrees

1. In our kit we have 0 degree and 15 degree teethg. Plane of occlusion

i. The average plane established by the incisal and occlusal surfaces of the teethii. You can raise it a little bit but not much, there are some guidelines

1. You can’t be above the retromolar pad or above the tongueh. Compensating curve

i. Definition: the A-P and M-L curvature of occluding surfaces and incisal edges of artificial teeth used to develop balanced occlusion

1. In the lab we will be setting non-balanced occlusion so our teeth will be on a flat plane

2. A-P curved called the Curve of Spee3. M-L curve called the Curve of Wilson

a. In dentures they combine those two and call it the Compensating curve

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4. Curvature allows mandibular 2nd molar to be lower than the mandibular 1st molar – this causes the maxillary 2nd molar to be up higher than the maxillary 1st molar (allowing for contact)

i. Thielemann’s Formula (NTK – ON EXAM)i. Balanced Occlusion = (IGxCG)/(CHxCCxPO)

ii. IGxCG = CHxCCxPO1. If you move the anterior teeth to get more vertical overlap you have increased the

incisal guidance2. What do you do to put it back in balanced occlusion?3. You could decrease the condylar guidance but we can’t do that4. So you will have to increase CH, CC, or PO5. On NBDE they changed the IG and asked what you needed to do to put it back into

Balanced Occlusion12. Non-Anatomic, Balanced Occlusion

a. Definition: teeth are arranged on a single plane, condylar and incisal inclinations are set at 0°. No attempt is made to eliminate deflective occlusal contacts in protrusive or lateral movements.

b. Posterior teeth are non-anatomic (0 degree cusps) and are arranged with a curve or a ramp in the occlusal plane to give some protrusive and lateral balance

c. Uses the Pleasure curve which incorporates a reverse curve on the premolars and first molars and a compensating curve on the second molars (also called a balancing ramp)

i. Distal part of 2nd molar maintains contact with maxillary tooth, all other teeth separate1. Not as hard to set

13. Non-Anatomic, Non-Balanced Occlusion – “Neutrocentric” a. Specifics

i. Non-anatomic teeth arranged on a flat plane which evenly divides the space between the upper and lower ridges. No occlusion over incline/slope of mandibular ridge. Occlusal plane height should be 2/3 up the RM pad.

1. Non-anatomic because teeth have no cuspsa. This is what we will be setting this

week and is easier to setii. Plane of occlusion parallels the mean denture base

foundationiii. Posterior teeth positioned over the crest of the mandibular ridge to centralize the forcesiv. Often eliminate one posterior tooth from the arrangementv. No effort is made to achieve “gliding contacts” in eccentric movements

b. Monoplane Occlusioni. Two key objectives (MM DeVan, 1954)

1. Neutralize the inclinesa. Put the occlusal plane parallel to the crest of the ridgeb. No inclination relative to the crest of the ridgec. Flatten the occlusal inclines of the teeth

2. Centralize occlusal forces over ridgesa. No vertical overlap - NONE

c. Advantagesi. Simple technique, requiring less precise recores

ii. Lateral forces…iii. “Area of Closure” – a CR to MI discrepancy is less destructiveiv. Good for skeletal Class II, III, and crossbites

d. Disadvantagesi. The least esthetic scheme – ugly!

ii. Lingual positioning of posterior teeth may crowd the tongue

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e. Indicationsi. Excessive inter-ridge distance (interarch distance)

ii. Skeletal class II, class III jaw relationships (no cusp-fossa relationships), and crossbitesiii. Successful previous dentures were monoplane/nonbalancediv. Limited oral dexterity – poor neuromuscular controlv. Severely resorbed ridges

vi. No vertical overlap of anterior teeth14. Lingualized, Balanced or Non-Balanced Occlusion

a. Introduction - We will be doing one like thisi. “Articulates the maxillary lingual cusps with the

mandibular occlusal surfaces in centric, working and non-working mandibular positions” GPT, 7th edition

1. 1927 Gysi, 1929 Garmer, 1930 Payneii. Maxillary lingual cusps are the major functioning

occlusal elementiii. Cusps oppose mandibular cuspless teeth or shallow

cusp (10 degree) teethiv. Can be (maxillary/mandibular) = 10°/0° or 30°/10° or 30°/0°

b. Specificsi. Maxillary posterior teeth are anatomic cusp form teeth

ii. Mandibular posterior teeth are zero degree of shallow cusp (10°) teethiii. Teeth may be set on a flat plane (non-balanced) or set to a compensating curve (for

balanced scheme)iv. Buccal cusps of maxillary teeth are raised up off the occlusal plane and do not contact the

mandibular teeth in centric occlusion or in eccentric movementsv. Theoretically combines the advantages of cusp form teeth with the advantages of zero

degree teethc. Advantages

i. More centralized forcesii. Creates only one contact point

1. Only palatal cusp will be in contactiii. Minimizes frictional contactsiv. Simplifies the working and non-working contactsv. Can be used with all ridge contours

vi. Esthetics – cusps look more naturalvii. Area of closure = easier accommodation to unpredictable changes

viii. Better penetrating = less vertical force requiredix. May be used in Class II, Class III, and crossbite relationships

1. “—has most of the advantages of other schemes while eliminating or minimizing the disadvantages” Parr and Ivanhoe, DCNA 1996

d. Indicationsi. Class I, II, II jaw relationships, and crossbites

ii. Where esthetics are paramount iii. Can be justified for most situations

15. A Philosophy of Occlusiona. Simultaneous, bilateral contact of all posterior teeth when the mandible is in centric jaw relation to

the maxillaeb. Absence of contact of maxillary and mandibular anterior teeth when the posterior teeth are in

centric occlusion (i.e. mandible is in centric relation)c. Absense of deflective occlusal contacts between opposing teeth during eccentric jaw movementsd. Form, contour, and positions of anterior and posterior teeth create a natural and pleasing

appearance16. Summary

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a. All occlusal forms may be arranged with or without bilateral balance. No scientific data are available to identify a superior tooth form or a superior arrangement. Advantages of one occlusal scheme or concept are often cited as disadvantages by advocates of another scheme. The least complicated approach that fulfills the requirements of the patient may have much to recommend it as the denture occlusion for that patient.