Complete Denture Occlusion Lecture Handout

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					2ND YEAR COMPLETE DENTURE COURSE
RT432a
FALL QUARTER

COMPLETE DENTURE OCCLUSION:

Investigators have not shown one type of occlusion to be:
1.      superior in function
2.      safer to oral structures
3.      more acceptable to patients

Goal of artificial occlusion
1.      stability
2.      decrease trauma to supporting structures
3.      decrease rate of bone resorption

Reaction of bone to force
1.     pressure perpendicular or tangential to the long axis of the bone results in resorption
       due to osteoclasts and interruption of circulation resulting in necrosis
2.     tension in long axis results in apposition

Bone resorption
1.     most of resorption (20%)occurs during first year therefore recall is important
2.     maxillary loss is vertical and palatal (0.1 mm/year)
3.     mandibular loss is vertical and lingual (0.4 mm/year or 4X maxillary loss)

Difference bewteen natural and artificial teeth

               Natural                                           Artificial
1.   teeth retained in PDL                        1.   mobile bases on mucosa
2.   teeth move independently                     2.   teeth move as a unit
3.   malocclusion unev  entful for years          3.   malocclusion results in immediate response and
                                                             es
                                                       involv entire base
4.   nonvertical forces affect onlyteeth          4.   nonvertical forces affect all teeth and are
           ed
     involv and isusually well tolerated               traumatic
5.   incising with natural teeth does not         5.   incising affects all teeth of base
     affect posterior teeth
6.   bilateral balanced is rare and if found is   6.   bilateral balance is often considered necessary
     considered balancing side interference            for base stability
7.   natural teeth with proprioception thus       7.   no feedbacksignal system causing interferences
                   oid
     possible to av prematurities                      to shift base



Forces of mastication

1.      natural teeth can exert up to175 pounds of force during mastication
        artificial teeth can exert only 22 to 24 pounds of force in the molar and premolar region
        (10-15% that of natural teeth)
2.      second premolar carries heaviest load because it is the center of occlusal table and
        provides best balance in function
3.      size of the occlusal table and chewing showed that a broader table exerts more pressure

                                     RT432A FALL QUARTER
                          2ND YEAR COMPLETE DENTURE COURSE - HAMADA
                                                  1
        on the ridge but requires same number of chewing strokes
4.      during chewing little force until teeth were through the bolus and nearly in contact
5.      penetration of bolus depends on
        a.       adequate ridges
        b.       can ridges (mucosa and bone) tolerate amount of roce necessary to penetrate
                 the bolus (20 lbs for steak)
        c.       steep cusps penetrate bolus better but cusped teeth increase horizontal force
                 to tissues and actually result in denture base deformation
6.      control of horizontal force is important
                 forces perpendicular to ridge crest best tolerated
                 cusp teeth require accurate programming of articulator in harmony with teeth,
                          neuromuscular controls and TMJ
7.      summary
        a.       anatomic teeth are more efficient in chewing but result in greater horizontal
                 pressure
        b.       nonanatomic teeth cause less horizontal and more vertical force
        c.       goal is the health of the supporting structures

Tooth types
composed of spectrum including following general categories:
              anatomic:       33 degree
                              Pilkington-Turner 30 degree
                              Anatoline posteriors (IPN material)
              semianatomic: 20 degree (also available in IPN)
                                       milled Functional posteriors
                              Levin bladed teeth (metal inserts on lingual cusps)
              non-anatomic: Monoplane type teeth
                                       0 degree Rational posteriors
                                       Monoline posteriors (IPN material)
                                       Hardy cutters or "VO Posteriors" (Vitallium Occlusal
                                               inserts)
                              Other nonanatomic tooth forms

Occlusion of teeth and Mandiular position

1.      border movements of mandible have a posterior, anterior and lateral limit known as
        the envelope of motion
2.      border positions are not dependent on a fixed vertical dimension
3.      centric relation position is at the intersection of right and left border positions
4.      CR is reproducible
5.      CR has been attributed to the restraining action of the ligaments, muscels and meniscus
6.      CR has been referred to as retruded contact position, centric relation, hinge axis position
        and the retruded mandibular position
7.      when chewing and swallowing the mandible approaches the posterior border position

Clinical application
1.       CR is reporducible best when guided by the dentist
2.       Recording CR is only possible with stabel record bases without posterior interferences
         andequal pressure distributed to the bases
3.       CR is the only constant repeatable position at which to start construction of stable
         occlusion and a smooth gliding noninterfering movement from this point to a comfortable
         muscular position is possible



                                   RT432A FALL QUARTER
                        2ND YEAR COMPLETE DENTURE COURSE - HAMADA
                                                 2
Summary
1.   CR is learnable
2.   CR is repeatable
3.   CR is recordable
4.   CR is an unstrained position

Balanced occlusion

The term "balance" refers merely to a stable, paired simultaneous contact of opposing occluding
surfaces. Thus, we may have several types of balance including:
1.      cross arch balance - even simultaneous side to side (across the arch) contact
2.      balance in centric - even cross arch simultaneous contact in centric relation
3.      balance in excursives - even cross arch simultaneous contact in eccentric positions

A "balanced occlusion" generally refers to the stable simultaneous contact of opposing upper and
lower teeth in centric relation position and a smooth bilateral gliding contact to any eccentric
position within the normal range of mandibular function

factors affecting occlusal balance
1.       condylar guidance - path of the condyle in the TMJ
2.       incisal guidance - the effect the upper and lower anteriors have on the movement of the
         mandible is expressed in degrees of angulation from the horizontal by a line drawn in
         the sagittal plane between the incisal edges of the upper and lower incisor teeth when
         closed in centric occlusion
                   steep incisal guidance requires steep cusps, steep occlusal plane or steep
                   compensating curve to achieve occlusal balance
3.       inclination of the plane of occlusion
4.       compensating curve - determined by the inclination of posterior teeth and their vertical
         relationship to the occlusal plane so that their occlusal surface results in a curve that
         is in harmony with movement of the mandible as guided posteriorly by the condylar
         guidance
                   steep condylar path requires a steep compensating curve for occlusal balance
                   a lesser compensating curve would result in anterior interference due to a
                           loss of molar balancing contacts
5.       cuspal inclination - modifies the effect of the plane of occlusion and compensating curve

The above factors comprixe what is known as Hanau's Quint (five factors) and their relationship
can be described algebraically by Theilman's Formula :

        Constant    =    condylar inclination X incisal guidance______________
                         occlusal plane X cuspal inclination X compensating curve

Because condylar guidance is fixed (determined by patient) the dentist can control only
four factors:
1.       incisal guidance - can only be altered slightly due to esthetics and phonetics
2.       plane of occlusion - can only be altered slightly due to tongue function etc.
3.       compensating curve - one of the major factors under the control of the dentist
4.       cuspal inclination - one of the major factors under the control of the dentist

Clinical application
1.       steep cusps produce more denture base shifting
2.       forces of occlusion should be balanced from right to left and anterior to posterior
3.       steep incisal guide angle in complete dentures makes attaining balance more difficult


                                   RT432A FALL QUARTER
                        2ND YEAR COMPLETE DENTURE COURSE - HAMADA
                                                 3
        because it requires steeper cusps, and/or an increase in compensating curve and/or
        an increased occlusal plane angle, all of which compromises the stability of the
        denture base
4.      if phonetics and/or esthetics require a significant vertical overlap of the anterior
        teeth, then a compensating horizontal overlap is necessary to keep the incisal
        guidance from getting too steep

Schemes of occlusion
1.    Bilaterally balanced occlusion
      a.       in centric relation all posterior teeth in contact, no anterior contact
      b.       in excursions there are at least three stable contacts widely distributed
                around the arch (anteriorly and posteriorly on each side)
      examples:
               1.       anatomic tooth form - e.g. State Board setup
               2.       monoplane tooth form - utilizes 2 balancing ramps and simultaneous
                                 anterior contact in excursives
               3.       lingualized occlusion
                        a.       maxillary posterior palatal cusps (P-T 30 degree teeth) contact
                                 the central fossae of the mandibular posteriors (20 degree teeth)
                                 creating a mortar and pestle action
                        b.       The buccal cusps of the mandibular posteriors do
                                  not interdigitate with the maxillary teeth
                        c.       resultant force in centric occlusion and excursions is lingual to
                                 the ridge crest to encourage base stability

2.      Neutrocentric occlusion - Devan
        a.     Non-balanced occlusion in excursions
        b.     flat occlusal surfaces should have flat planes in all directions with no inclination
               at all with respect ot the underlying denture foundation
        c.     balanced occlusion in excursions is unnecessary and undesirable
               as resulting inclines causes horizontal forces
        d.     contact in centric only, no eccentric balance
        e.     theory is to modify the muscular pattern to centric only, so that patient      chews
               with a vertical pattern only, no horizontal component
        f.     forces of occlusion on posterior teeth as lingually as possible with a decreased
               buccal lingual width of teeth, decreased numbers of teeth resulting indecreased
               force
        g.     denture is made to "flip out" if patient attempts to incise
        h.     no vertical overlap of anteriors

3.      Organic occlusion
        a.     natural dentition
        b.     bilateral posterior and light anterior contact in centric relation
        c.     anterior guidance (incisal, canine or anterior group) in excursions with no
               posterior contact
        d.     a "mutually protective occlusion" in which the anterior guidance and
               proprioceptionprotects the posteriors from lateral forces in excursives and the
               posteriors protect the anteriors from excessive forces in centric relation.
        e.     not an appropriate occlusion for complete dentures because the decreased
               proprioception of the patient results in decreased muscular control of mandibular
               movement and thus causes increased tipping and horizontal forces to the
               residual alveolus



                                   RT432A FALL QUARTER
                        2ND YEAR COMPLETE DENTURE COURSE - HAMADA
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           RT432A FALL QUARTER
2ND YEAR COMPLETE DENTURE COURSE - HAMADA
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