Occlusal relationships for removable partial dentures

Occlusal Relationships for Removable Partial
Dentures
Chapter Outline
Desirable Occlusal Contact Relationships for Removable Partial
Dentures
Methods for Establishing Occlusal Relationships
Direct apposition of casts
Interocclusal records with posterior teeth remaining
Occlusal relations using occlusion rims on record bases
Jaw relation records made entirely on occlusion rims
Establishing occlusion by the recording of occlusal pathways
Materials for Artificial Posterior Teeth
Arranging teeth to an occluding template
Establishing Jaw Relations for a Mandibular Removable Partial Denture
Opposing a Maxillary Complete Denture
The fourth phase* in the treatment of patients with removable partial dentures
is the establishment of a functional and harmonious occlusion. Occlusal harmony
between a removable partial denture and the remaining natural teeth is a major
factor in the preservation of the health of their surrounding structures. In the
treatment of patients with complete dentures, the inclination of the condyle
path is the only factor not within the control of the dentist. All other factors may
be altered to obtain occlusal balance and harmony in eccentric positions to
conform to a particular concept and philosophy of occlusion.
Balanced occlusion is desirable with complete dentures because unbalanced
occlusal stresses may cause instability of the dentures and trauma to the
supporting structures. These stresses can reach a point that causes movement
of the denture bases. In removable partial dentures, however, because of the
attachment of the removable partial denture to the abutment teeth, occlusal
stresses can be transmitted directly to the abutment teeth and other supporting
structures, resulting in sustained stresses that may be more damaging than
those transient stresses found in complete dentures. Failure to provide and

maintain adequate occlusion on the removable partial denture is primarily a
result of (1) lack of support for the denture base, (2) the fallacy of establishing
occlusion to a single static jaw relation record, and (3) an unacceptable occlusal
plane.
In establishing occlusion on a removable partial denture, the influence of the
remaining natural teeth is usually such that the occlusal forms of the teeth on
the removable partial denture must be made to conform to an already
established occlusal pattern. Occlusal adjustment or restoration may have
altered this pattern. However, the pattern present at the time the removable


partial denture is made dictates the occlusion on the removable partial denture.
The only exceptions are those in which an opposing complete denture can be
made to function harmoniously with the removable partial denture, or in which
only anterior teeth remain in both arches and the incisal relationship can be
made so that tooth contacts do not disturb denture stability or retention. In
these situations, jaw relation records and the arrangement of the teeth may
proceed in the same manner as with complete dentures, and the same general
principles apply.
With all other types of removable partial dentures, the remaining teeth dictate
the occlusion. The dentist should strive for planned contacts in centric occlusion
and no interferences in lateral excursions. Although a functional relationship of
the removable partial denture to the natural dentition sometimes may be
adjusted satisfactorily in the mouth, extraoral adjustment is often easier for both
dentist and patient, is more accurate, and can be accomplished in a more
comprehensive manner.
Establishment of a satisfactory occlusion for the removable partial denture
patient should include the following: (1) analysis of the existing occlusion; (2)
correction of existing occlusal disharmony; (3) recording of centric relation or an
adjusted centric occlusion; (4) harmonizing of eccentric jaw movements for a

functional eccentric occlusion; and (5) correction of occlusal discrepancies
created by the fit of the framework and during processing of the removable
partial denture.

Desirable Occlusal Contact Relationships for Removable Partial Dentures
The following occlusal arrangements are recommended to develop a harmonious
occlusal relationship among removable partial dentures and to enhance stability
of the removable partial dentures:
1. Simultaneous bilateral contacts of opposing posterior teeth must occur in
centric occlusion.
2. Occlusion for tooth-supported removable partial dentures may be arranged
similarly to the occlusion seen in a harmonious natural dentition, because
stability of such removable partial dentures results from the effects of direct
retainers at both ends of the denture base.
3. Bilateral balanced occlusion in eccentric positions should be formulated when
a maxillary complete denture (Figure 17-1) opposes the removable partial
denture. This is accomplished primarily to promote the stability of the complete
denture. However, simultaneous contacts in a protrusive relationship do not
receive priority over appearance, phonetics, and/or a favorable occlusal plane.
4. Working side contacts should be obtained for the mandibular distal extension
denture (Figure 17-2). These contacts should occur simultaneously with working
side contacts of the natural teeth to distribute the stress over the greatest
possible area. Masticatory function of the denture is improved by such an
arrangement.
5. Simultaneous working and balancing contacts should be formulated for the
maxillary bilateral distal extension removable partial denture whenever possible


(Figure 17-3). Such an arrangement will compensate in part for the unfavorable
position the maxillary artificial teeth must occupy in relation to the residual

ridge, which is usually lateral to the crest of the ridge. However, this desirable
relationship often must be compromised when the patient’s anterior teeth have
an excessively steep vertical overlap with little or no horizontal overlap. Even in
this situation, working side contacts can be obtained without resorting to
excessively steep cuspal inclinations.
6. Only working contacts need to be formulated for the maxillary or mandibular
unilateral distal extension removable partial denture (Figure 17-4). Balancing
side contacts would not enhance the stability of the denture because it is
entirely tooth supported by the framework on the balancing side.
7. In the Kennedy Class IV removable partial denture configuration, contact of
opposing anterior teeth in the planned intercuspal position is desired to prevent
continuous eruption of the opposing natural incisors, unless they are otherwise
prevented from extrusion by means of a lingual plate or auxiliary bar, or by
splinting. Contact of the opposing anterior teeth in eccentric positions can be
developed to enhance incisive function but should be arranged to permit
balanced occlusion without excursive interferences.
8. Artificial posterior teeth should not be arranged farther distally than the
beginning of a sharp upward incline of the mandibular residual ridge or over the
retromolar pad (Figure 17-5). To do so would have the effect of shunting the
denture anteriorly.

Figure 17-1 Posterior occlusion of a maxillary complete denture opposing a Class I
mandibular removable partial denture. The stability of the maxillary complete denture can
be promoted by developing balanced occlusion as shown.


Figure 17-2 Bilateral distal extension mandibular removable partial denture opposed by
natural dentition in the maxillary arch. Working contacts are achieved, balancing contacts
are purposefully avoided because they would not enhance the stability of the restoration,
and protrusive balance is avoided in favor of an acceptable appearance and a favorable

occlusal plane.

Figure 17-3 Opposing Class I partially edentulous arches arranged to allow working side
contacts of opposing posterior teeth with balancing contact arranged to minimize tipping of


the maxillary removable partial denture and to broadly distribute forces accruing to its
supporting structures (abutments and residual ridges).

Figure 17-4 When occlusion is developed for a Class II removable partial denture
(maxillary or mandibular), only working side contacts are necessary, as the cross-arch
framework stability gained from tooth engagement provides resistance to movement.
Balancing side contacts do not enhance stability beyond that provided by the contralateral
teeth.

Figure 17-5 Mandibular posterior teeth should not be arranged distal to the upward incline
(ascending ramus) of the residual ridge. The molar tooth has been placed just anterior to a
mark on the cast land area designating the beginning incline.

A harmonious relationship of opposing occlusal and incisal surfaces alone is
not adequate to ensure stability of distal extension removable partial dentures.
In addition, the relationship of the teeth to the residual ridges must be
considered. Bilateral eccentric contact of the mandibular distal extension
removable partial denture need not be formulated to stabilize the denture. The
buccal cusps, however, must be favorably placed to direct stress toward the
buccal shelf, which is the primary support area in the mandibular arch. In such


positions, the denture is not subjected to excessive tilting forces (Figure 17-6).
On the other hand, the artificial teeth of the bilateral, distal extension, maxillary

removable partial denture often must be placed lateral to the crest of the
residual ridge (Figure 17-7). Such an unfavorable position can cause tipping of
the denture, which is restrained only by direct retainer action on the balancing
side. To enhance the stability of the denture, it seems logical to provide
simultaneous working and balancing contacts in these situations if possible.

Figure 17-6 The posterior teeth in this distal extension with a narrower buccal-lingual
width than the original teeth have been selected, and they are placed relative to the primary
support (buccal shelf) to distribute the functional load to the most anatomically favorable
location in a manner that reduces leverage effects.


Figure 17-7 A, Maxillary molar occluded in a normal horizontal relationship to the
opposing molar. B, The resultant position is lateral to the supporting crest of the residual
ridge. This position is functionally unfavorable because of the potentially unstable leverage
effects; however, stability can be improved by arranging simultaneous working and
balancing contacts in the occlusal scheme.

Methods for Establishing Occlusal Relationships
Five methods of establishing interocclusal relations for removable partial
dentures will be briefly described. Before any of these is described, it is
necessary that the use of a facebow mounting of the maxillary cast and
pertinent factors in removable partial denture occlusion be considered. The
technique for applying the facebow has been described briefly in Chapter 12.
Although a hinge axis mounting may be desirable for complete oral
rehabilitation procedures, any of the common types of facebow will facilitate
mounting of the maxillary cast in relation to the condylar axis in the articulating
instrument with reasonable accuracy and are acceptable for a removable partial
denture. As was suggested in Chapter 12, it is still better that the plane of
occlusion be related to the axis-orbital plane. Because the dominant factor in

removable partial denture occlusion is the remaining natural teeth and their
proprioceptive influence on occlusion, a comparable radius at the oriented plane
of occlusion in an acceptable instrument will allow reasonably valid mandibular
movements to be reproduced.
Semiadjustable articulators can simulate but not duplicate jaw movement.
Realization of the limitations of a specific instrument and knowledge of the
procedures that can overcome these limitations are necessary if an adequate
occlusion is to be created.
The recording of occlusal relationships for the partially edentulous arch may
vary from the simple apposition of opposing casts (by occluding sufficient
remaining natural teeth) to the recording of jaw relations in the same manner as
for a completely edentulous patient. As long as some natural teeth remain in
contact, however, the cuspal influence that those teeth will have on functional
jaw movements dictates the placement of the artificial teeth and the occlusal
scheme.
The horizontal jaw relation (planned intercuspal position or centric relation) in
which the restoration is to be fabricated should have been determined during
diagnosis and treatment planning. Mouth preparations also should have been
accomplished in keeping with this determination, including occlusal adjustment
of the natural dentition, if such was indicated. Therefore one of the following
conditions should exist: (1) centric relation and planned intercuspal position
coincide with no evidence of occlusal pathologic conditions, therefore the
decision should be to fabricate the restoration in centric relation; (2) centric
relation and the planned intercuspal position do not coincide, but the planned
intercuspal position is clearly defined and the decision has been made to
fabricate the restoration in the planned intercuspal position; (3) centric relation


and the planned intercuspal position do not coincide and the intercuspal position
is not clearly defined, therefore the decision should be made to fabricate the

restoration in centric relation; and (4) posterior teeth are not present in one or
both arches, and the denture will be fabricated in centric relation.
Occlusal relationships may be established by using the most appropriate of
the following methods to fit a particular partially edentulous situation.

Direct Apposition of Casts
The first method is used when sufficient opposing teeth remain in contact to
make the existing jaw relationship obvious, or when only a few teeth are to be
replaced on short denture bases and no evidence of occlusal abnormalities is
found. With this method, opposing casts may be occluded by hand. The
occluded casts should be held in apposition with rigid supports attached with
sticky wax to the bases of the casts until they are securely mounted in the
articulator.
At best, this method can only perpetuate the existing occlusal vertical
dimension and any existing occlusal disharmony present between the natural
dentition. Occlusal analysis and the correction of any existing occlusal
disharmony should precede the acceptance of such a jaw relation record. The
limitations of such a method should be obvious. Yet, such a jaw relation record is
better than an inaccurate interocclusal record between the remaining natural
teeth. Unless a record is made that does not influence the closing path of the
mandible because of its bulk and/or the consistency of the recording medium,
direct apposition of opposing casts at least eliminates the possibility that the
patient may have a faulty jaw relationship.

Interocclusal Records With Posterior Teeth Remaining
A second method, which is a modification of the first, is used when sufficient
natural teeth remain to support the removable partial denture (Kennedy Class III
or IV) but the relation of opposing natural teeth does not permit the occluding of
casts by hand. In such situations, jaw relations must be established as for fixed
restorations with some type of interocclusal/>