Classification of the edentulous ridge allows clinicians to discuss cases without the patient being present.

Class I – Dentate

Class II – Immediately post extraction

Class III – Well rounded ridge form, adequate height and width

Class IV – Knife edge form, adequate in height but not in width

Class V – Flat ridge form, inadequate height and width

Class VI – Depressed ridge form with some basal bone loss shown

1. Primary impressions – request the lab make primary casts and special trays

2. Master impressions – request the lab make master casts and special trays

3. Jaw registration – request the lab make a wax try in denture

4. Wax try-in – request the lab make the finished completed dentures

5. Delivery of complete dentures

Stock Trays:

• These are a pre made impression tray used to obtain the impression by placing material into contact within the oral tissues.
• Different stock trays are available (metal, disposable, plastic, perforated). Perforated trays are present to provide a measure of mechanical retention which is required to secure impression materials in the tray.
• Stock trays are available in various sizes but rarely fit the mouth accurately.

The accuracy of the impression material depends on:

• “Thickness” of the mix (viscosity) 
• Ability to flow evenly over the area required  
• Adapt closely to the hard and soft structures incorporated within the denture bearing area (note: Some materials are hydrophobic (water repellent) and will not drive the water away from those areas. It is critical in these cases that a dry working area is generated in order to take an accurate impression)

Impression materials can be categorised in several ways:

1. Muco-static(alginate) or Muco-compressive(impression compound)– this describes whether the soft tissues of the dento-alveolar ridge have been displaced or not from their passive state during impression taking. 

Muco-static means that the impression is taken with the mucosa in its normal resting position e.g. alginate, zinc oxide eugenol 

Muco-compressive means that the impression is taken when the mucosa is subject to compression (Do not use with edentulous patients with undercuts as material will not come out once set)

2. Another way of classifying the materials is identifying the materials set properties 

e.g. Rigid (Plaster of Paris, impression compound, zinc oxide-eugenol),     Elastic Hydrocolloid (Alginate, agar), Elastomeric (Polysulphide, polyether, silicone)

FOR THE PATIENT	FOR THE CLINICIAN
Neutral taste	Easily mixed
Neutral odour	Not technique sensitive
Quick setting time	Quick setting time
Non-toxic	Records a high level of surface detail
Easily removed	Good flow properties
Minimal material required	Dimensionally stable
	Easily removed
	Low cost material
	Long shelf life

The impression materials that may be used in the production of primary models can be classified as muco-static or muco-compressive: 

• Impression compound is muco-compressive and is used for edentulous patients but should not be used for patients with large undercuts as it is rigid and will not withdraw once set in the mouth. 
• Alginate is used for partially dentate or fully dentate patients as alginate will withdraw from undercuts so is ideal for partially dentate patients and those edentulous patients with pronounced ridges and deep undercuts. However if undercuts are too deep the alginate may tear. 

With a full edentulous patient impression compound is the best material to use.

• Impression Compound when heated becomes viscous enabling it to flow into the sulci. It requires steaming hot water to soften. Ensure to use Vaseline to help prevent it becoming sticky.
• Ensure the use of an impression technique which captures the functional depth of the sulcus achieved by adequate border moulding
• Remember to disinfectant the impression after use:
  • Wash under running water 
  • 10 minutes in sodium hypochlorite (1000 part per million) 
  • Wash under running water 
  • Place in a gauze and wrap in a plastic bag 
  • Complete the labcard 

Please construct upper and lower impression in plaster of paris. Please construct non-perforated stub handled upper special tray with 3mm wax spacer for alginate and a lower close fitting tray (0.5 mm) non-perforated with 3 stub handles.

Example labcard

With a full/partial dentate patient alginate is used:

• A thin layer of adhesive is applied to the stock tray to improve the adhesion between the alginate and the stock tray reducing the risk of deformation when removing the impression tray from the mouth. (Use a thin layer as the cohesive properties of the adhesive is poor and will fail if too thick).
• Remember when taking the lower impression ensure the patient elevates and protrudes their tongue as this will ensure an accurate definition of the floor of the mouth. If not then every time the person speaks or eats and the muscles in the floor of the mouth are used it will displace the denture. 
• Remember to disinfectant the impression after use 
  • Wash under running water 
  • 10 minutes in sodium hypochlorite(1000 part per million) 
  • Wash under running water 
  • Place in a damp gauze to prevent syneresis (not placed in water which would cause imbibition-expansion) and wrap in a plastic bag      
• Complete the labcard  

How to take an impression

Upper impression

• The clinician should be positioned behind and to one side of the patient. 
• The tray is inserted posteriorly upwards and forwards to fill, firstly the left and right sulci before the palatal area, and then labial sulcus is pressed into position. 

Lower impression

• The clinician should be positioned in front and to one side of the patient. 
• The tray is held over the lower ridge and the loaded tray depressed, the labial, right and left sulci in turn being everted to permit the impression material to fill the functional width of the sulci. 

ADVANTAGES OF ALGINATE	DISADVANTAGES OF ALGINATE
Non-toxic	Poor dimensional stability – syneresis
Good surface detail	Incompatible with some dental stones
Was of use and mix	Setting time is dependent on operator handling
Cheap and good shelf life	Messy to work with

What factors affect the setting time of alginate? 

Setting time should be controlled by varying water temperature, and not the consistency of mix. The colder the water the longer it takes to set.

Primary models and special trays 

Pouring primary models:

• The Plaster of Paris (dental plaster) is mixed with water at the correct water/plaster ratio (100grams plaster powder to 50ml of water). 
• The plaster mix is carefully vibrated into the upturned impression. 
• The impression should be topped up until the mould is full and tends to overflow. 
• A mound of plaster is laid on the work bench. 
• The impression is carefully pressed into the mound. 
• When the plaster mix has set, the impression material is softened and removed and the dental primary model is trimmed. 

Special trays:

The following are the steps in the construction of special trays: 

• The upper and lower special trays wax spacers are muscle trimmed & contoured 2mm above the sulcus of the primary casts. This border is where the external border of the special tray will lie. 
• The trays are constructed in light cured acrylic 
• The tray design will depend on the impression material being used for master impressions. 
• Wax spacers laid down will simulate the required space taken up by the impression material. 
• Finger stops over the molar region of the lower model are added to the tray along with the handle. These are placed to allow the tray to be held in place without movement or sliding during the making of the master impression and to help judge the amount of pressure being applied. 
• Any wax spacer is removed before delivery to the clinic 

Special trays @prostesis_dentales_vzla

Why do we use wax spacer?

• Allows for even layer of impression material  
• Amount of spacing for each impression material is a function of their properties i.e. alginate does not perform well in thin section 

The thickness of the wax spacer is dependent on impression material to be used: 

• 3mm for alginate 
• 2mm for Plaster of Paris/PVS/ Polyether 
• 0.5mm – 1mm “close fitting” for ZnOE (or no spacer, just undercuts blocked out)

Customising the Special Trays

1. Disinfect in sodium hypochlorite for 10 minutes.

2. Try fit of tray in the mouth and adjust accordingly

3. Check trays have been designed the way you asked with no rough areas, correct handles etc.

4. Apply tracing compound to the posterior aspect of the upper tray to produce a posterior seal. The tracing compound should extend uninterrupted from one border of the tray to the other. This allows the creation of a post dam, facilitates the location of the tray posteriorly and, finally, serves as a spacer for the impression material. 

5. In the lower tray the tracing compound should be added to displace the retro-molar pad sufficiently to give a posterior seal. The lower tray may also need the periphery moulded with tracing compound. This is performed in a similar fashion to the upper tray. 

6. At this stage, the fully customised trays should exhibit good retention. 

7. Add a small amount of tracing compound or suitable material to the special tray in the area of the upper and lower canines and gently place into the mouth. This provides a similar effect as the posterior placement of the tracing compound. This will prevent the incorporation of support problems by avoiding undue and uneven displacement of the impression material. 

Impression

1. Apply tray adhesive, while it is drying mix the alginate. Alginate is an irreversible hydrocolloid and is mucostatic. It is used to take an impression of the upper arch.

2. Lower impression should be carried out using zinc oxide eugenol. Ensure good border moulding is performed with lateral and protrusive movements of the tongue to enable a functional impression to be taken

Preparing the laboratory prescription

Within the prescription you have to state the appropriate baseplate for the upper and lower wax occlusal rims. 

For the lower: 

• Normally a wax baseplate with wire strengthener or a light cured baseplate is suitable for the lower.  
• The other option would be to have a permanent clear acrylic baseplate. 

For the upper: 

The upper baseplate may be constructed from: 

• Heat cured acrylic  
• Light cured acrylic  
• Thermo-plastic 
• Shellac  
• Metal (Co Cr)  
• Wax (satisfactory in the lower with a wire strengthener, but never in the upper)

Please construct upper and lower impressions in dental stone. Please construct upper wax occlusal rim with thermoplastic baseplate and a lower wax occlusal rim with wax baseplate and wire strengthener.

Example labcard

Dental stone vs Dental plaster

The main ingredient of dental plaster and dental stone is calcium sulphate hemihydrate (CaSO4)2 + 2H2O. 

The main difference between Dental Plaster and Stone is in the manufacturing process of the material (CaSO4 + 2H2O) or calcium sulphate dihydrate which effects the base crystal size and shape. 

Dental Plaster, also known as β-hemihydrate is manufactured by heating in an open kiln to 110 – 120 degrees Celsius. The resulting material has irregular shaped crystals and a sponginess texture.

Dental Stone (α-hemihydrate) is manufactured by heating in a sealed kiln to 110 – 120 degrees Celsius. This produces a more regular rod like shaped crystal. 

Lab work

• The upper and lower master models are allowed to soak in cold water for approx. 4 minutes. 
• If requested and illustrated on the upper impression a post dam (see later) may be carved into the master model after which a baseplate is accurately adapted to the palate, posterior border and the palatal edge of the crest of the ridge.  
• The lower has a baseplate adapted over the ridge and approx. 2/5th of the way down off the ridge. 
• The baseplate will stop approx. ½ up the retro molar pad area. 
• Modelling wax is softened and carefully pressed and adapted into the area of the sulcus. Care being taken not to entrap any air in the wax. The wax is trimmed clear of the edge of the land area but conforming to the width of the sulcus. 
• It should look like this: 

• After making a baseplate which fills the sulcus and covers the palate, a solid wax block is softened in warm water, adapted to conform the shape of the ridge. 
• More wax is added to provide a smooth labial and palatal surface to the wax rim, care being taken not to incorporate any air. 
• When chilled the wax block is carved to give an occlusal surface parallel to the base of the cast and dimensions as shown in the diagram. 
• The rims should be checked to ensure they occlude evenly, if so they are ready for the 3rd clinical visit.

Wax occlusal rims @porlowska_dent.tech

What are wax occlusal rims used for? 

• Their purpose is to be trimmed to provide a 3D representation of the patient’s lost hard and soft tissues 
• Provide the dental technologist with a 3D prescription of the patient’s proposed complete dentures in shape for soft tissue support and in the relationship between the mandible and the maxilla 
• This process is called jaw registration.

Wax occlusal rims @laboratorio_j_g

Wax occlusal rims @prostesis_dentales_vzla

Jaw registration stages

First adjust the upper rim in the following order:

Nasio-labial angle 

• The trimming of the upper rim to provide a template for anterior tooth position thereby providing adequate lip support. 
• The rim should be adjusted to provide a Nasio-labial angle between 90 and 100 degrees. 
• What is required? 
• Preservation of the philtrum (vertical groove in the middle area of the upper lip) 
• Preservation of the vermilion boarder (the border between the lip and the adjacent normal skin) 
• Development of the appropriate Nasio-labial angle 

Incisal height/occlusal plane

• The next step in this clinical episode is to identify the incisal height/occlusal plane of the anterior teeth.  
• Scribe a line on the wax rim which should be approximately 1mm and1.5mm below the lips at rest. Then reduce the anterior height on the hot plate to the prescription line.  

Buccal corridors

• As you will probably see in your patient the areas around the posterior to the canines may look full or puffy. 
• This area is known as the buccal Corridors and when trimming to fit care must be taken not to damage the peripheral roll as this will have an adverse effect on the retentive qualities of the complete dentures.
• Be aware of a knife edge periphery, this will mean that you have accidentally melted away some of the peripheral roll when adjusting the rim, the same feature/fault can occur when adjusting the wax rim labial aspect. 

Incisal Occlusal Plane 

• Take the Fox Plane Guide to check the occlusal level of the incisors’ occlusal plane, this should be parallel to the Inter-papillary line (an imaginary horizontal line drawn between the centre’s of the pupils of the eyes).

Posterior Occlusal Plane 

• The posterior occlusal plane should be recorded on the wax rim using the Fox plane to check angulation when viewed from the side.
• After adjustment this should be parallel to the ala-tragus line. This is a line from the lower border of the ala of the nose to the upper border of the tragus of the ear.  
• This should mean we have now completed the adjustments of the upper rims vertical component to provide a correct incisal height and occlusal plane is correct (parallel to the inter-papillary lines) and the posterior occlusal plane is correct (parallel to ala-tragus line). 

Other Upper Wax Rim Prescription Lines and Guides

Centreline: The centre line is marked on the upper wax rim by a line running through the mid-line of the face. This marks the line of symmetry.

High smile line:Ask the patient for a big/wide smile and mark on the height of the upper lip while smiling in the area of the centre line. This is giving us the approximate length of tooth when measured.   

Canine lines: Before adjusting the lower rim to the appropriate width and height, guide lines should be marked on the rim to represent the canine position. The simplest way of reproducing this line and marking it on the wax rim is by using a piece of dental floss as illustrated. This gives us the length of the anterior portion of the arch, aiding in mould selection.

Now adjust the lower rim:

With only the lower rim in situ (mouth) check for stability of the rim getting the patient to raise the floor of the mouth. Adjust the lower rim to give appropriate lower lip and buccal mucosa support. 

Now we have to identify the patient’s vertical component. 

Insert lower occlusal rim without upper rim and establish resting face height.:

• Get the patient to slowly close until lips just contact
• This is the Resting Vertical Dimension (RVD) 
• Repeat this several times and see if the resting position is reproducible. 
• A Freeway Space (FWS) of 3mm is desired and so deduct 3mm from RVD 
• This measurement is the desired Occlusal Vertical Dimension (OVD) with both rims in place. 

Trim the lower rim to establish even bilateral contact with the upper at the retruded contact position. 

The patient should be asked to close until the rims first contact. 

We are now ready to relate the upper arch to the lower arch, we do this by asking the patient to go into retruded contact position. This is a reproducible position of the mandible in relation to the maxilla. 

• When you are satisfied that the patient is consistently occluding in the retruded contact position, make locating marks in the premolar regions with a cold wax knife. 
• Remove the rims and place them together outside the mouth using the locating marks. Check again that there are no posterior premature contacts between the baseplates. 
• Prior to final recording of the retruded contact position, cut small ‘V’ shaped notches bilaterally in the upper rim in the premolar region distal to the locating marks. Smear a thin film of petroleum jelly on the occlusal surface of the upper rim to act as a separating medium. 
• Remove sufficient material from the occlusal surface of the lower rim in the second premolar/first molar regions (distal to the locating marks), to provide adequate space for a layer of softened wax (1mm).
• This wax is re-softened with a hot wax knife, the rim reinserted in the mouth and the patient requested to close into the retruded contact position (check that the locating marks are coincident). 
• Once the wax has hardened sufficiently, remove the rims from the mouth and chill them.
• Remove excessive wax, separate the rims, ensure that they relocate accurately together, replace them in the mouth and check the registration for evenness of contact and accurate recording of the retruded contact position. 
• Note: You can also use VPS and Futar D material instead of wax.
•  If the wax becomes detached from the lower rim, the procedure must be repeated. 

Now you can take a mould and shade

Mould:

• Taking the arch length and high smile line into consideration this will give you the height of the teeth and with reference to the mould guide the width of the tooth. These records you have recorded on the upper wax rim. 
• Now we must choose the shape of the teeth. Look at the shape of your patient’s lower 2/3rds of facial height or from the brow to the chin, invert it and imagine the shape. This is a good indicator as to tooth shape.  
• Many clinicians describe the relationship between the anterior teeth in the arch as the Golden Proportion. 

Shade:

• All that remains is to choose a shade of tooth and complete the laboratory card. 
• This colour is selected to suit the patient using a shade guide. 

Post dam

This is also known as a posterior palatal seal. It’s function is to create a peripheral seal anterior to the vibrating line. This seal enhances the retention of the maxillary denture.

How to form a post dam?

1. Draw out the posterior border 
2. Cut a conventional post dam 
3. Draw in the Cupid’s Bow 
4. Cut the Bow 
5. Adapt baseplate….. Or ask the lab to do it!  

Lab card

Please articulate, set up the teeth selected and wax up for wax trial of teeth (remember to complete the shade and mould).

Example lab request

Relevance of previous dentures

Remember that previous dentures may provide information on the appropriate jaw relationship, occlusal plane, incisal level and the relationship of teeth to soft tissues.

The lab will return to you a wax trial of teeth for you to review the jaw registration.

This is done to confirm all the records taken with the wax rims in the previous appointment have been transferred to the wax trial dentures correctly.

Wax denture @dentures_by_sa

The jaw registration review should be done in the same order as the intial jaw registration, making sure nothing is missed. The order should be in the following way:

• Lip support (Nasio Labial Angle) 
• Buccal mucosa support (Buccal Corridor) 
• Shape and extension of the denture base and flanges 
• Incisal and posterior occlusal plane level and angle
• Anterior tooth position (Lips at rest, 1mm to 1.5mm, centre lines canine position and high smile line) 

Why is it important to make any adjustment before the final denture is cast in acrylic? 

Because once in acrylic it is more difficult and expensive to fix, also if certain areas of the denture are faulty then the denture may need to be totally remade.

How to check the wax dentures stability?

• Starting with the placement of the upper wax trial denture and check the denture extension into the buccal sulcus is not over extended. 
• Remember the depth needs to be a functional/working sulcus depth so there is a need to ensure that none of the muscle attachments are the cause of the instability. 
• For the lower remember to ask patient to protrude their tongue to check if displacement of the denture occurs. Also ask them to touch the roof of the mouth with their tongue to check the functional depth of the floor of the mouth 

Now you need to check adaptation of the denture base

We may have to carefully re-adapt the baseplate to the cast as there may be some distortion if the denture has been in the mouth for too long. 

Things to check with the denture base: 

• Adaptation of the denture base to the underlying tissues 
• Extension of the bases 
• Stability 
• Retention 
• Contour of the polished surfaces 

Occlusion

Things to check with occlusion:

Simultaneous, bilateral contact in RCP at the correct OVD :

• Examine the occlusal contacts when the patient closes and is guided into retrudedcontact position. 

FWS:

• Insert lower wax denture without upper wax trial and establish and check the resting face height.
• ‘Slowly close until lips just contact’- This is the RVD and should be measured with a Willis bite guage.
• Repeat this several times and see if the resting position is reproducible.
• This should match the record taken at Jaw Registration.
• A Freeway Space (FWS) of 3mm is desired and so deduct 3mm from RVD. This measurement is the desired Overall Vertical Dimension (OVD) with both wax trial dentures in place. 

Occlusal planes:

• Incisal occlusal plane (Fox plane should be parallel to inter papillary line) and posterior occlusal plane (Fox plane should be parallel to the ala-tragus line) 

Posterior tooth position:

• The first molar is positioned to occlude with the upper second premolar and first molar. 
• Check on the articulator (if provided) that the molar should move evenly into working, balancing and retrusive occlusal excursions without the articulating pin leaving the incisal guidance table. 
• When the patient moves into protruded occlusion, again there should be a smooth transition with minimal/no lower denture displacement.
• The palatal cusps of the upper posteriors should lie directly over the crest of the alveolar ridge of the mandible. With the upper posteriors in this position this will mean that the lower posteriors lie over the crest of the ridge. This is the area where the muscle forces from the buccal mucosa and the tongue cancel each other out, which should help to generate denture stability. This is known as the Neutral Zone.

Anterior tooth position:

• Incisal level 
• Location of the teeth relative to the ridge 
• Centre lines 
• Assess speech (count from 55-65, say ‘every Friday’) and observe if the denture is displaced

The Laboratory Prescription for Finishing the Dentures

Laboratory card should be completed stating wax trial is satisfactory and the technician can wax up the denture for finish. 

Waxing up is important as this refines the polished surfaces and means that minimal adjustments and polishing will be required when processed.

Please wax up and contour complete dentures for processing in heat cured acrylic

Example lab request

The wax trial complete dentures will then be processed in acrylic ready for delivery to the patient.

Final denture processed in acrylic @laboratorio_j_g

Refining the occlusion: 

The occlusion and OVD of the complete dentures will be slightly altered due to errors that occur during the flasking and pressing procedures. 

These processing errors must be eliminated via the use of articulating paper and the selective grinding of the various cusps of the posterior teeth until OVD, occlusion and balance have been restored. 

Lack of attention to detail executing these procedures will result in excessive grinding which destroys the occlusal forms of the teeth. 

This is done by using the BULL Rule- Adjust the Buccal of the Upper and Lingual of the Lower. 

• Adjust the slope of the Buccal cusp of the Upper molar
• Adjust the slope of the Lingual cusp of the Lower molar

The maxillary arch is wider than the mandibular and so supporting (functioning) cusps are the maxillary lingual cusps and mandibular buccal cusps. Therefore, the guiding cusps (non-functioning) cusps are the maxillary buccal and mandibular lingual cusps. 

If gaps between teeth exceeds 1.5 mm reset teeth or remake the complete dentures.
The denture and teeth should be carefully re-polished when all the
adjustments have been carried out.

Artificial teeth;  

• Require group function so that the occlusal load is dispersed across the teeth to prevent excess load on individual teeth. 
• Bilateral balanced occlusion is mandatory to produce stability of denture. 

Clinical visit

The technician will send you the polished dentures are placed in a Polygrip bag with a small amount of water in order to maintain their dimensional stability and to absorb any residual monomer. 

The delivery appointment is the last stage in denture fabrication, when the new dentures are inserted and adjusted for the first time. The fitting surface and periphery of each denture in turn is checked for any sharp areas and removed before insertion 

1. Identification of sore areas produced by denture

Upper denture is placed and patient is asked if they feel pain and where they feel it. Those areas are painted with pressure indicating paste (disclosing paste)and the denture is eased back into the mouth. On removal of the denture the disclosing paste area is re-examined, the areas where the paste has been displaced is carefully removed with a dental steel bur and handpiece. The whole procedure is repeated until the denture is pain free. 

2. Identification of muscles that may be causing instability

The upper denture is placed in the mouth and checked for stability. The denture may be unstable due to displaced muscle attachments or the denture base is over-extended in those areas. Again, disclosing paste is painted on the suspect area and replaced in the mouth. Denture put under some functional pressure and then checked. On removal of the denture the disclosing paste area is re-examined, the areas where the paste has been displaced is carefully removed with a dental steel bur and handpiece. The whole procedure is repeated until the denture is stable. Care should be used as we do not want to lose peripheral seal. A similar process is then followed for the lower 

3. Ensuring occlusion is correct 

The occlusion of all complete dentures must be checked before the patient is allowed to wear them. As already discussed the complete denture will have been set-up, removed from the articulator and processed using a split cast technique where the processed complete dentures and the master models will have be reattached to the articulating plaster. This will have allowed the technician to spot grind off any premature contact points using the BULL rule. This is now repeated at the chairside. 

The complete dentures are inserted then checked as follows: 

• The patient’s OVD, RVD and FWS are compared with the wax trial measurements.  
• Check occlusal planes.  
• Check the position of the teeth and the soft tissue support.  
• Stability in function  
• Speech  
• Finally, is the patient happy?!

Dover Dental labs inc.

In order to fully understand complete dentures there are certain key terms that need to be understood.

Centric relation and retruded contact position

Centric relation

Centric relation has 3 definitions:

1. Anatomical defintion – When the condyle of the mandible is in the most upper foremost position in the glenoid fossa (any point before translation starts). 

2. Geometric definition – In the terminal hinge axis position in Posselts envelope of motion

3. Physiological definition – The position in which the muscles are doing the least work 

All 3 of these definitions are true simultaneously.

Retruded contact position

This refers specifically to the tooth to tooth contact when the condyle is in the most superior anterior position.

Note: The only difference between centric relation and retruded contact position (RCP) is that centric relation refers to the position of the condyle, whereas RCP refers to the position of the teeth. This is why they are often used interchangeably.

Closing in centric relation is the same as closing in RCP (retruded contact position) 

Centric occlusion and intercuspal position (ICP)

Centric occlusion

Centric occlusion refers to the position of the condyle in the glenoid fossa when the teeth are in a state of maximum interdigitation (habitual bite). 

With centric occlusion the mandibular head can be in any position, but in centric relation it is fixed. 

However closing in RCP generally results in the teeth not coming together properly, the cusps aren’t in a point of maximum digitation. 

Intercuspal position (ICP)

ICP refers to the relationship between the maxilla and mandible when the teeth are in a state of maximum interdigitation.

Note: The difference between centric occlusion and ICP is that centric occlusion specifically refers to the position of the condyle, whereas ICP refers to the relationship between the maxilla and mandible. Centric occlusion and ICP are used interchangeably.

Other terms:

Eccentric position – This refers to any position other than centric position/relation.

Balanced occlusion – The bilateral simultaneous, anterior and posterior occlusal contact of teeth in excursive movements. So essentially there is contact on the working and non-working side on excursive movements.

Group function – When laterally a number of teeth on the working side are in contact at the same time all sharing the load. Complete denturesrequire group function so that the occlusal load is dispersed across the teeth, to prevent excessive load on individual teeth.

Working side – The side that the mandible moves toward during mastication.

Non-working side – The side the mandible moves away from during mastication.

An articulator is a device to which casts of the maxillary and mandibular teeth are fixed, reproducing positions of the mandible in relation to the maxilla. This will assist in complete dentures construction.

Types of articulators:  

1. Simple hinge

• The simplest type of articulator consisting of a simple hinge joint. No lateral or sliding movements are possible.

2. Average value (most common)

3. Semi adjustable 

• The condylar angle can be adjusted
• The bennet shift angle can be adjusted
• The local incisal guidacne table can be adjusted

4. Fully adjustable  

• The are capable of being adjusted to facilitate a more accurate representation of the patient’s condylar movement to assist the construction complete dentures.

5. Plasterless 

Average value articulator @laboratorio_j_g

Simple hinge articulator @laboratorio_j_g