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Registering Centric Relation position
Retruded Contact Position (RCP)Guided occlusal relationship occurring 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 (ICP)The complete inter-cuspation of the opposing teeth
independent of condylar position. Sometimes referred to as the best fit of the teeth regardless of the condylar position.
Centric Occlusion (CO)The occlusion of opposing teeth when the mandible is
in centric relation. This may or may not coincide with the inter-cuspal position.
Registering Centric Relation:Retruded Position (RP) / Retruded Contact Position (RCP):
- Agreed position for recording the A-P position of the:- mandible relative to the maxilla.
- Reproducible position in the edentulous patient. Occlusal rims with chosen OVD inserted into the mouth.Patient persuaded to close gently with mandible in RP..Do not use the word 'bite‘ as this tempts the patient to:
- forceful jaw closure resulting in protrusive jaw position.Why Register RP /RCP:Abnormal occlusal tooth contacts other than RP / RCP are:
- OIs (premature occlusal contacts causing CDs unstable. Articulator used for reproducing relevant jaw movements:
- operates from RP / RCP.- abnormal TMJ activity may result from attempting to:
- accommodate incorrect occlusal relations.
Methods for Registering RP / RCP / CRP:Many methods assist patient to achieve mandibular retrusion.Some patients able to relax mandibular muscles so the:
- operator moves patients’ mandible up and down as it:- rotates about the condyles & guided to close in RP.
Other patients able to retrude mandible when the:- tongue is curled back in the roof of mouth to:
- feel the posterior border of the upper base.- touch a shallow wax-ridge in palate of the base:
- placed posterior to the first molar region.Giving patient the feeling of protruding the upper jaw. Using Myo-monotor to get rest position so as to go to RP.Using Gothic-arch (or arrowhead) tracing:
- the most positive & successful method.- it readily identifies the most RP of the mandible.
RP / CRP a position from which lateral excursions are made.
Three Fingers Chin-point Method for Registering the RP of the Mandible
Chin Point Guidance of Mandible in RCP Closure
Bimanual Manipulation Method for Guiding Mandible to Close in CRP
Bimanual Manipulation Method for Guiding Mandible to Close in CRP
Lucia Jig on cast and in mouth helping deprogramming abnormal closure of mandible
A Book of multi-coloured leaves which can be selectively used as a leaf gauge (Panadent Corp., CA, USA).
Clinical View Showing the Graduated Acetate Ohio State University (OSU) Woelfel Gauge (Girrbach Dental GmbH, Germany).
Methods of RP / CRP Registration for Edentulous Patients:Upper & lower jaw relation registered with mandible in RP.Jaws separated by the established / chosen OVD.A variety of RP registrarion methods include:
- Wax squash bite (its predecessor, the T-block system).- Wax rims.- 'Manchester' blocks. - Gothic-arch tracing (Intra-oral & Extra-oral tracing).
Wax Squash Bite Registration of RP:Occlusal surface of Lower rim roughened & softened. Fixed / indexed to the upper with mandible kept in RP.
- difficulty of obtaining mandibular retrusion.- RP recorded during the act of mandibular closure. - surface of wax rim not uniformly softened throughout;
- its length, an unstable relation to underlying tissues is recorded.
Wax-Squash Bite: Insufficient Denture Geometry & Form Seen
T-Block Method of Registering RP /CRP:
An earlier version of Wax-squash method. A T-shaped wax form is used instead of horseshoe form.The 'horizontal' portion is placed b/w rims.The 'vertical' part that protrudes anteriorly is moulded to:
- contour the labial aspects of the rims.This method fell into disuse because of the:
- arbitrary nature of the moulding procedure that also:- induces patient to assume non-RCP posturing of:
- the jaw.- as well as the other problems with wax-
sqaush.
Wax Rims Fixation / Indexation Method of RP register:Wax interposed between the rims to secure a registration. Upper rim (ACB) formed, and prescribed to suit the patient.Lower rim exhibits even contacts in mouth at RCP.Achieving even contact not easy for some.Alternatively, use of Manchester Rim is easy & simple:
- several elements in it ensure OVD maintenance.- the bases are maintained in stable relationship.
Lower base has two pillars of wax situated in the region of:- the 2nd premolar/1st molar teeth positions.
Functional imp. & form of lower labial arch made in:- soft carding wax, Plaster of Paris or PVS putty:
Achieve even bilateral contacts at the selected OVD.Seal rims with registration paste / wax or staple pins.
Conventional upper and lower rims
'Manchester' rims - simplify complete denture registration technique
Gothic-Arch Tracing:Intra-oral tracing;Reliable method of obtaining a consistent RP. Also consider mandibular movements other than just closure.An intra-oral Gothic-Arch tracing device used. Method based on rotation about the condyles when lateral
mandibular excursions are made. Left-ward mandibular movement from CR occurs by:
- its inward rotation about the left condyle.A right lateral movement from CR causes:
- its outward rotation about the right condyle. Between each lateral excursion, the condyles assume their
most retruded (RP) or centric relation (CR) position.
Occlusal view of mandible and its arcs of movement about the condyles
Intra-oral Tracing Method:Uses two piece apparatus, one for each arch.Both mounted on rigid stable acrylic bases.Upper plate is a metallic plate spanning maxillary arch.Lower is a bar with adjustable central-bearing screw with:
-1mm thread mounted on wax or compo 'pivots' on base.The lower plate is on the most stable pivotal areas of arch. Central-bearing screw contacts upper plate at right angles and
at the selected OVD. Bases adjusted so that no contact between them can occur.Patient makes lateral mandibular excursions with contact of
the central-bearing pin on the upper plate only. Patient swallows, to indicate a 'central' (RCP) position.Then makes 3 protrusive movements before returning to RCP. From RCP, patient makes 3 left lateral excursions.And then returns to RCP.
Finally, 3 right & left lateral movements before return to RCP. The patient is made familiar with the two pieces of apparatus.Practitioner now proceed to record the tracing by:
- coating upper plate with, e.g ink from a felt tipped pen.- patient now replicates protrusive & lateral movements.
Alternate lateral jaw movements scribe on the upper plate:- two arcs of rotation intersecting in a position of RCP.
Clearly, it is from this point that an intersection (arrowhead) with the protrusive movement is also traced.
RCP validated by securing a perforated perspex cover slip:- with its perforation over the arrowhead on plate.
Patient swallows & RCP confirmed by the:- central bearing screw engaging the perforation.
Thus both OVD & RCP recorded. Plaster of Paris or PVS putty placed b/w bases & central-
bearing screws to ensure & secure correct relationship.
Extra-oral tracing:Similar to intra-oral, except tracing apparatus is attached to:
- plates that protrude from mouth.Not as accurate as intra-oral method for edentulous patients:
- because protrusion of recording apparatus is so far:- forward of the pivotal area that tilting and/or
- deflection of the bases is likely.A technique not universally taught worldwide.
Further considerations:Upon completion of OVD & CRP:
- OR / Face-bow Transfer Record made.All Records sent to lab including:
- the face bow transfer register for mounting in articulator.
Teeth have still to be selected. Also consider the type of articulator on which:
- the records & casts are to be mounted, as the proper:- adjustment of these may require additional records.
Articulators for complete denturesThe usage of articulators to enhance clinical practice.Articulators in common use for the production of complete
dentures comprise: - Simple hinge (plane line).- Moveable, fixed condylar path.- Semi-adjustable.- Fully Adjustable articulators not usually used for CD work.
Simple / Plane Line Articulator / Cast Holder / Occludator
