Jaw relations in removable partial denture

Purpose of jaw relation Methods of recording jaw relation Try in appointment Recording of jaw relations in special conditions

Purpose of Recording the Jaw Relations To establish and maintain a harmonious relationship To ensure that all the effects of occlusal loading be distributed To best control the undesirable effects of rotational or torquing forces on the prosthesis. To prevent any deflective contacts of the teeth during centric or eccentric closures

The fourth phase* in the treatment of patients with removable partial dentures is the establishment of a functional and harmonious occlusion. To establish and maintain a harmonious relationship with all oral structures and to provide a masticatory apparatus that is efficient and esthetically acceptable. 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. (3) an unacceptable occlusal plane.

Recording Jaw relation Before construction of framework - mounted on an articulator Definitive jaw relation – after functional impression and altered cast

Methods of recording Jaw relation  Direct apposition of cast. This should not influence the path of closure of mandible

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.

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 record like using metallic oxide paste, interocclusal wax record,..etc. The least accurate of these methods is the interocclusal wax record. The bulk, consistency, and accuracy of the wax will influence the successful recording of centric relation with an interocclusal wax record after chilling. Excess wax that contacts the mucosal surfaces may distort soft tissue, thereby preventing accurate seating of the wax record onto the stone casts. Distortion of wax during or after removal from the mouth may also interfere with accurate seating.

Some of the advantages of using a metallic oxide paste over wax as a recording medium for occlusal records include: (1) uniformity of consistency. (2) ease of displacement on closure. (3) accuracy of occlusal surface reproduction. (4) dimensional stability. (5) the possibility of some modification., in occlusal relationship after closure, if it is made before the material sets. (6) reduced likelihood of distortion during mounting procedures.

Occlusal relations using occlusion rims on record base one or more distal extension areas are present a tooth supported edentulous space is large when opposing teeth do not meet

A third method is used when one or more distal extension areas are present, when a tooth-supported edentulous space is large, or when opposing teeth do not meet. In these instances, occlusion rims on accurate jaw relation record bases must be used. Simple wax records of edentulous areas are never acceptable. Any wax, however soft, will displace soft tissue. It is impossible to accurately seat such a wax record on a stone cast of the arch. With this method, the recording proceeds much the same as with the second method, except that occlusion rims are substituted for missing teeth.

Jaw Relations Records Made Entirely on Occlusion Rims when either arch has only anterior teeth present opposing posterior teeth do not meet #

The fourth method is used when no occlusal contact occurs between the remaining natural teeth, such as when an opposing maxillary complete denture is to be made concurrently with a mandibular removable partial denture. It may also be used in those rare situations in which the few remaining teeth do not occlude and will not influence eccentric jaw movements. Jaw relation records are made entirely on occlusion rims when either arch has only anterior teeth present (Figure #). In any of these situations, jaw relation records are made entirely on occlusion rims. The occlusion rims must be supported by accurate jaw relation record bases. Here, the choice of method for recording jaw relations is much the same as that for complete dentures. Either some direct interocclusal method or a stylus tracing may be used. As with complete denture fabrication, the use of a facebow, the choice of articulator, the choice of method for recording jaw relations, and the use of eccentric positional records are optional, based on the training, ability, and desires of the individual dentist.

Establishing Occlusion by the Recording of Occlusal Pathways Support the wax occlusion rim with a denture base occlusion rim must be worn for 24 hours or longer After 24 hours, the occlusal surface of the wax rim should show a continuous gloss, which indicates functional contact with the opposing teeth in all extremes of movement. After a second 24- to 48-hour period of wear, the registration should be complete and acceptable

Vertical Dimension VDR VDO Freeway space

Altering the existing vertical dimension of occlusion Normally the VDO of a partially edentulous patient is provided by the opposing natural teeth contact if they have normal shape, size and position and it should not be changed unless: Symptoms of diminished OVD exist such as tired aching muscles, unexplained pain in the head and neck region, shortened nose-chin distance (appearance of premature aging). Excessive Free way Space or ‘over-closure’ of the jaws. Confirmation of decrease in VD can be seen with severe tooth wear, intrusion and greater than 4 mm free way. Temp. removable device in form of acrylic resin overlay. This device must be worn for 24 hrs. If the pt can tolerate this for 3- 4 mths then definitive correction should be instituted.

Symptoms of diminished VDO like tired aching muscles unexplained pain in the head and neck region shortened nose-chin distance (appearance of premature aging) Excessive Free way Space or ‘over-closure’ of the jaws

Wearing of the teeth does not mean that VDO should be increased – unless the free-way space is greater than 4mm. the fact that the occlusal surfaces have worn out does not indicate that the VDO has been decreased. Under certain conditions continuous eruption of the teeth can maintain the vertical dimension.Wearing of the teeth will increase the free way space.

How to alter the existing VDO 1. Confirm the loss of VD by taking history, cephalometric examination, and the presence of excessive free-way space. 2. Increase the existing VDO temporarily by fabricating an acrylic resin occlusal overlay appliance in maximum intercuspation, ensuring that 4mm of freeway space must exist. in case there is reduced vertical dimension of occlusion.Anything grter than 4 mm.

3. Restore the desired VDO permanently with the help of fixed or removable prosthesis only after the physiologic response of the patient to this appliance is positive. Restorartion of the VDO permanently can be done with the help of overlay. This device must be worn for 24 hrs. If the pt can tolerate this for 3- 4 months then definitive correction should be instituted.

this is a patients cast with kennedy class II in max and kennedy class I in the mandible.This is a pt cast with reduced VDO. V r reducing the teeth to get it to the desired occ. plane.

Facebow transfer To relate (record relation) the maxillary cast to the condylar elements of the articulator at the same orientation that the maxillary teeth have to the mandibular condyles of the patient. Facebow transfer in case of Rpd is done to… after the desired vertical dimension has been recorded. bite registration material is placed on the bite fork and the maxillary cast is placed over it. Care should be taken that the midline of the teeth coincide with the this midline.

The bite fork is then placed in the patients mouth and the thumb screws are tightened.

Horizontal jaw relation centric relation centric occlusion

centric relation or centric occlusion ? The most delicate proprioception in your body is between the upper and lower teeth.

In more than 90% of people, C.O is 0.5 - 2mm in front of the CR Centric occlusion Centric relation

C.O should be recorded when there are cusps on remaining natural teeth that can guide the mandible back to its position. C.R should be recorded for distal extension RPD, or when the opposing arch is edentulous.

When Not to Use Centric Relation Stable occlusion Posterior centric stops present No valid reason to change Use maximum intercuspation

Try In Appointment if the RPD opposes a complete denture all posterior teeth in both arches are being replaced if no opposing natural teeth are in contact Provides verification of the jaw relation recorded provides an, opportunity to view and approve the esthetic size, color, and arrangement of the anterior teeth Phonetic inspection

Desirable occlusal contact relationship for removable partial dentures Simultaneous bilateral contact – centric occlusion Tooth supported partial denture – occlusion as in natural dentition Maxillary complete denture opposes partial denture - bilateral balanced occlusion in eccentric positions

Bilateral upper distal extension base - simultaneous working and balancing side contact Only working contacts need to be formulated for the maxillary or mandibular unilateral distal extension removable partial denture

Bilateral distal extension mandibular RPD opposed by natural dentition in the maxillary arch - Working contacts are achieved Artificial posterior teeth should not be arranged on the sharp upward incline of the mandibular residual ridge or over the retro molar pad

Three possible sequelae of occlusal error If the premature contact is on a natural tooth, damage to the tooth or its periodontal ligament may occur. If the saddle bears the brunt of the force of closure, there will be localized mucosal inflammation and resorption of the underlying bone. If the patient attempts to steer the mandible around the premature contact until a more comfortable occlusal position is found, this abnormal closing pattern throws increased demands on certain muscles of mastication, which may result in the patient complaining of facial pain.

Maxillary complete denture opposing a RPD make a record base and wax occlusal rim for the maxillary cast. The record base and wax occlusal rim will allow us to secure jaw relationship records from our patient. now try the wax rim in the patient and assess facial support, tooth display and occlusal vertical dimension. Adjustments will be made as necessary to the wax rim. This is then placed in the pt's mouth opposing the rpd.

to make a temporary base on the partial denture framework to make a temporary base on the partial denture framework. This will allow the occlusal registration to be taken. The temporary base will have an occlusal rim in the posterior area to compensate for the lack of teeth here. Grooves will be placed in the occlusal rim prior to securing the occlusal registration.

show the creation of an index on the bite fork for the maxillary record base and wax occlusal rim. Remember that you could use blue-bite on the bite fork instead of wax . All we need is an index for the maxillary occlusal rim.

Occlusal consideration in implant retained partial denture  Axial displacement of teeth in the socket are 25-100 μm, while that of the osseointegrated dental implants has been reported approximately 3-5 μm.  Natural tooth moves 56-108 μm and rotates at the apical third of the root upon a lateral load, while dental implant moves 10-50 μm under a similar lateral load. An ‘ideal occlusion’ in removable prosthodontics is one which reduced de-stabilisating forces to a level that is within the denture’s retentive capacity

References Carr AB, Brown DT, McCracken’s Removable Partial Prosthodontics, 12th edition, Canada, Elsevier Publishers, 2011, pp:242-252 Stewart, Rudd, Kuebkar, Clinical Removable Partial Prosthodontics, 2nd edition, India, All India Publishers and Distributors, 2001, pp:367- 396 Jones DJ,Gracia LT, Removable Partial Dentures : A Clinician’s guide, 1st edition, Singapore, Wiley-Blackwell, 2009, pp : 90-94 Jacobs, R. and Van Steenberghe D. (2006), From osseoperception to implant-mediated sensory-motor interactions and related clinical implications. Journal of Oral Rehabilitation, 33: 282–292. Davies S.J, Gray .R and McCord J.F, Good occlusal practice in removable prosthodontics British Dental Journal 2001; 191: 491–502 Davenport .J.C etal The removable partial denture equation, British Dental Journal 2000; 189: 414–424 Vinay pavan kumar