RECORDING THE RETRUDED CONTACT POSITION:RECORDING THE RETRUDED CONTACT POSITION:A REVIEW OF CLINICAL TECHNIQUESA REVIEW OF CLINICAL TECHNIQUES

BDJ 2004;196:395-402

P.H.R.WILSON AND A.BANERJEE

• The retruded contact position is an important maxillomandibular relation in restorative dentistry. This review article will describe the RCP , consider its importance and use in prosthodontics.

• RCP also known as premature contact in centric relation, centric relation contact position, retruded axis position, terminal hinge position, & ligamentous position.

Terminology ImportanceUsesMethodsComparisonSummary

TerminologyTerminologycentric relationcentric relation

The maxillomandibular relationship in which the condyles articulate with the thinnest avascular portion of their respective disks with the complex in the anterior-superior position against the shapes of the articular eminencies.This position is independent of tooth contact. This position is clinically discernible when the mandible is directed superior and anteriorly. It is restricted to a purely rotary movement about the transverse horizontal axis (GPT-5)

Term Abbreviation Definition

Retruded contact position RCP

Guided occlusal relationship occuring at the most retruded position of the condyles in the joint cavities.a position that may be more retruded than the centric relation position.

Intercuspal position

ICPThe complete intercuspation of the opposing teeth independent of condylar postion.

Centric occlusion CO

The occlusion of opposing teeth when the mandible is in centric relation.

Importance of RCPImportance of RCP

• Relative reproducibility

• Stability of denture bases in conjunction with a lack of interfering contacts in eccentric mandibular positions.

• Contribute in TMJ health.

• Fenlon et al demonstrated positive correlation between CD usage & accuracy of CR registration.

Uses of RCPUses of RCP

• Mounting Models On An Articulator

• Reorganising a Patients Occlusion At A New Occlusal Vertical Dimension.

• Occlusal Analysis.

• Occlusal Splint Therapy.

• Determining The Magnitude & direction Of RCP to ICP.

• Distalising the mandible to create palatal space for anterior restorations.

• Restoring the tooth which involved in determining the RCP

Factors affecting RCPFactors affecting RCP

• Patient

• Operators experience.

• Registration material.

• Recording method.

• Neuromuscular condition

• Record handling & storage.

• Time of recording

PATIENT GUIDED RECORDING OF RCPPATIENT GUIDED RECORDING OF RCP

METHODS OF RECORDING

schuyler techniqueschuyler technique

• This technique involves the patient placing the tip of the tongue to the back of the palate and closing in to a horse shoe of softened wax with light pressure.

• In edentulous patients this technique can be used with wax rims.

Drawbacks:• There is no way of verifying the nature of any

unwanted tooth contact or the retrusion of the mandible.

• The wax may not be uniformly softened which can lead to inaccuracies in the recording.

Physiological techniquePhysiological technique

• Appropriate for edentulous patients.

• Cones of soft wax placed posteriorly.

• Patients swallows several times, simultaneously mandible

• Retrudes and recording is made.

Draw backs

• No control over mandibular retrusion nor tooth contact.

Gothic arch tracing(arrow point Gothic arch tracing(arrow point tracing)tracing)

• Used in both edentulous & dentate patients.• used intra-orally or extra-orally • Based on tracing movement of mandible.• Metal plates are added to upper and lower wax rims.• The lower plate has a central pin, which can be adjusted

to the desired occlusal facial height and at right angles to the opposing plate.

• Pin is the only point of contact between maxilla and mandible.

• The patient practices mandibular excursions then fine spray of occlude is added to maxillary plate.

• Patient replicates the excursive movements & mandibular pins scribe an arrow head tracing on the maxillary plate. The three lines intersects indicates the retruded mandibular relation.

Draw backs

• Time consuming • Requires well defined non

displaceable upper and lower alveolar ridges to allow stable & retentive acrylic bases.

• Large tongue movements also cause base movements during the tracing.

• Recently gnathometer M consists of wax rims with tracing plates.

• Pantograhs are mechanical or electronic device which trace mandibular movements similar to gothic arch tracer.

• Digital pantograph machines have an electronic facebow & lower incisal plate, which are linked remotely to the computer and relation to each other is measured and calculated by specialised software.

Myo-monitorMyo-monitor

It is an electrical device which is reputed to achieve muscle relaxation & produce a neuromuscular mandibular position.

It produces pulsed ultra low frequency stimulation of facial and masticatory muscles.

Stimulating electrodes are placed over the coronoid notches and a common electrode is located at the nape of the neck.

OPERATOR GUIDED RECORDING OF RCPOPERATOR GUIDED RECORDING OF RCP

Chin-guided recording methodChin-guided recording method

• Patient is seated upright position and relaxed, with clinician in front.

• A softened two layer wax wafer [1.4mm thick] is gently pushed against the cusps of the maxillary teeth with just enough force to make to make cuspal indentations.

• The wafer is removed, chilled & reseated in order to check fit & stability.

• A registration medium is applied to the mandibular surface of the wax wafer & the patients mandible is guided in to a hinge closure by thumb & index finger of the operator.

• After several smooth movements the hinge closure is completed when the mandibular teeth just indent the registration material.

Draw backs:

• It can be over retruded.

Three finger chin-point guidance Three finger chin-point guidance methodmethod

•Not recommended for edentulous patients

•A tripod is created at the chin-point & lower border of the mandible on both sides by the thumb, index finger & third finger.

•Gentle guidance in all three digits in a mid sagittal plane.

•This encourage anterior–superior placement of condyles.

Draw backs

•Easy to deflect mandible to one side

Bimanual manipulation methodBimanual manipulation method

This technique is carried out with the patient supine & operator seated behind.

By opening & closing a few times on the hinge Axis, the patient will relax & registration can be made.

Alternative methodAlternative method

• Operator seated in front of the patient is to use the index fingers to stabilize the lower record base and guidance is from the thumbs on the chin.

• Smith has described a modification where one hand can stabilize both upper & lower denture bases.

Anterior guidance by lucia jigAnterior guidance by lucia jig

• The basics is to provide an anterior reference point.

• Lucia jig is made of self curing resin either in the study cast or in the mouth.

• The palatal acrylic is manipulated to just cover the palatal soft tissues.

• The lingual aspect should slope posteriorly & superiorly at an angle of 40-60 degree.

• After setting the jig is adjusted using articulating paper placed on the palatal aspect while the patient performs lateral & antero-posterior or excursive movements.

A selected lower incisor scribes an arrow–head pattern, can be ground of leaving the apex.

This is the area of the retruded position of the mandible and vertical height is then adjusted until the posterior teeth are just out of contact.

Then the record is made at this position.

Anterior guidance by tongue Anterior guidance by tongue bladeblade

The tongue blade method uses wooden spatula instead of custom made lucia jig.The degree of tooth separation is altered by number of spatulas used

The patients teeth must be discluded for a period of time, [10-20min]prior to registration, in order of proprioceptive input to be lost.

Once the correct anterior spatula guidance is achieved registration material is used to record the relative position of the mandibular & maxillary teeth.

Anterior guidance by leaf gaugeAnterior guidance by leaf gauge

The leaves provide the anterior reference point & the degree of tooth separation can be altered until the teeth achieve disclusion.

A registration support wafer permits the registration of the inter-dental record.

originally a book of ten acetate leaves were used.

Now disposable paper versions are also available.

Anterior guidance by osu woelfel Anterior guidance by osu woelfel gaugegauge

• Developed by woelfel.

• The specially designed device has a graduated acteate bite platform, the position of which is adjusted antero-posteriorly until the teeth are minimally out of contact.

• A registration support wafer can then be added & the inter–dental record made.

Power-centric registration Power-centric registration methodmethod

• Dentist standing in front and right of the supine patient ,left thump & fore fingers placed over upper teeth.

• Right thump is placed on superior aspect of the chin,while second & third fingers along the inferior border of the mandible.

• Right arm is stiffened ,pressure is applied from shoulder by leaning.

• Reflex muscle shortened and retrudes the mandible.

Drawbacks

• Mandible may be pushed too posteriorly

comparisoncomparison

• It is reported that guided mandibular closure gave more reproducible RCP recordings than no guidance.

• The most consistent guidance method were the lucia jig, bilateral manipulation which have been demonstrated by electromyographic studies to produce the least temporalis & masseter activity.

• Wise classified patients in to1. Easy

2. Manipulation with slight difficulty

3. Manipulation with more difficulty.

• For easy patients he suggested bimanual manipulation.

• Anterior guidance from tongue blade followed by bimanual manipulation for manipulation with slight difficulty.

• manipulation with more difficulty patients need jucia jig to be left in situ for 30 min to disrupt proprioception.

• For some very difficult patients proprioceptive deprogramming may need to be accomplished using an occlusal splint for an extended period.

summarysummary

• As a reproducible position, it is useful in the restorative management of dentate & edentulous patients.

• Reference point for the registration of transfer records.

• It is unknown whether one registration method is better than other, but it is the accuracy & reproducibility of achieving the retruded position of the mandible is in the hands of operator