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CLINICAL AND LABORATORY PROCEDURES INCONSTRUCTION OF

COMPLETE DENTURES

Dr Ziad AL-Dwairi BDS, PhD(UK), FIADFEAssociate Professor of Prosthodontics

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Complete Denture

A dental prosthesis that replaces all of

the natural dentition and associated

structures of maxilla and mandible. It

may be supported by mucosa or

sometimes by dental implants.

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Esthetic.

Improve mastication.

Improve speech.

Function withoutinterferences.

Preservation of oralstructures.

Maintenance of health &

comfort.

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Clinical examination

Tray selection

Primary impression

Primary cast

Secondary impression Secondary cast

Denture base fabrication and Occlusal

rim

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Setting of teeth

Flasking ,dewaxing

And curing

Trimming and polishing

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HISTORY ANDEXAMINATION FOR

EDENTULOUS PATIENTS

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Objectives

Recognition of relevant anatomical,

physiological and psychologicalconditions

Understand significance of medical

status Development of treatment plan

(prescription of prosthesis)

Assessment of existing dentures

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Extra-oral

examination The extra-oral examination should look for :

– Temporo mandibular joint( TMJ):palpate externally and from inside the

ear: pain, clicking, limitation of movement, extreme deviation

– The patients face height,

– Any facial asymmetry including – The centre line;

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Extra-oral examination

– The lip line including the smile line as allthese features will need to be transferred

to the patients dentures. –

– The degree of overclosure will also needto be assessed and this will help withdeciding on how you want to make thedenture

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Intra-oral Examination

Soft tissue

Salivary flow

Sulcus depth Ridge anatomy: height, depth and form

(firm or flabby)

Inter-ridge relationships If already wearing dentures: denture

assessment – fit, retention, stability andocclusion. Can you copy this if it is

already satisfactory?

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Maxillary arch

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Mandibular Arch

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IMPRESSIONS FOR

COMPLETE DENTURES

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IMPRESSIONS

Definition: A negative likeness of thetissues so that a model can be madefrom which a denture can be

constructed. The impression material is held against

the tissues and is supported by animpression tray. The material shows

plastic flow in the initial stages and thenhardens.

A model is then formed using modelstone or plaster. For maximum accuracy

a 2 stage impression procedure is

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IMPRESSIONS

Impression witha stock tray is

first taken – called a primaryor preliminary

impression

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Preliminary

Impressions Impression compound (Modeling

compound

– Thermoplastic Material – - Greatest pressure asserted to the center

of its mass

– Can be softened in wet heat for over- all

adaptation, or it can be softened in small areas by dry heat for localized modifications

– Softening not > 60 C

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Preliminary


compound

– Tray selection (cover anatomicallandmarks)

– Kneading of compound to obtain auniform consistency( rope or ball)

– Warming of tray – Adaptation to tray with grooving to

receive crest of ridge( the lingual aspect3mm deeper than labial anteriorly and

6mm posteriorly)

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Preliminary


compound

– Can be added and re-adapted

– Used in combination with other materials

– Pouring of impression may be delayed

– Does nor reproduce fine surface details – Should not be used in undercuts

– Re-softening-unhygienic

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IMPRESSION TRAYS

Two types of impressions trays are used – stock and special trays

Properties:

Must be clean and smooth Must be rigid and strong Should permit correct thickness of impression

material to be used (3mm)

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STOCK TRAYS

Box trays: RPD

Trays for edentulous arches

Combination trays: Distal extensionbase

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STOCK TRAYS

Handle must be shaped andattached to the tray so that it

doesn’t displace the lip when theimpression is taken Must hold the impression material in

the correct position in the mouth

and consequently must cover thewhole area of the jaw required inthe impression.

Must prevent distortion of theimpression material during setting

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STOCK TRAYS

Variation inthickness of

impressionmaterial

Localised pressure

on oral tissues Incomplete

coverage of oraltissues

Distortion of

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Tray Selection

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Primary Impression

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Preliminary

Impressions Corrective alginate wash

– To obtain greater surface details the

initial compound impression is used as atray to record a further impression inalginate

– Shake alginate tin to avoid condensing??

– Powder or water first??

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Preliminary

Impressions Alginate

– Sodium alginate, calcium sulphate,

trisodium phosphate – Perforated trays, adhesive( polyamide in

isoprpyl alcohol)

– Impression poured immediately(imbibition and syneresis): 30 minutes

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Preliminary

Impressions Alginates

– Record good surface detail with a

minimum of tissue displacement – Accuracy depends upon the accuracy of

the tray

– Easily distorted

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Preliminary

Impressions Alginates

– Excellent surface details

– Elastic---undercuts

– Different viscosities

– Not flow in areas not supported by tray

– Cannot be added – Liable to distortion at laboratory

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Preliminary

Impressions Maxillary or mandibular impression

first???

– Increase salivation-----Maxillary – Retching reflex---------Maxillary

– Chocking by impression----Maxillary

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Preliminary

Impressions Common faults: (lower impression)

– Edge of the tray showing:

Incorrect centring of the tray Use of too large or too small tray

Forward thrust of tongue not been counteredby backward pressure on the tray in the

anterior region

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Preliminary

Impressions Common faults: (lower impression)

– Insufficient depth at lingual pouch:

Short flange Lack of compound

Too little force applied

Tongue trapped

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Preliminary

Impressions Common faults: (Upper impression)

– Deficiency in midline of palate

Insufficient compound Insufficient pressure

Compound cold

Trapped air

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Lab forms

Special trays

– Tray Material

– Amount of spacer and location of tissuestops

– Tray perforations

– Tray handle

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DIAGNOSTIC CASTS

Analyse feasibility of various treatmentmeasures

Foundation forspecial trays

Help the dentist to

discuss possibletreatment forms withpatient orTECHNICIAN

Analyse occlusion

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CASTS MATERIAL

Compatible with all types of impression materials

Reasonable setting and working time

Reproduce surface details

Exhibit surface hardness

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EDENTULOUS CASTS

Posterior border of caststops 8 mm from

maxillary tuberosity orretromolar pad

The outer surface of

the cast is trimmed toabout 3mm from themaximum convexity (

Land area)

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Custom Trays

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Soak in water

Draw the outline on

the cast.

Block out the

undercuts using wax.

Place the wax spacer on the cast.

Conditioning the primary cast

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SPECIAL TRAYS

The special tray can be either spaced orclose fitting.

Spaced trays are used with impressionplaster and alginate. The mould iscovered with a wax spacer and an acrylicsheet of at least 2mm thickness is then

used to construct the tray. If the sheetis too thin, there will be no rigidity thuscausing distortion of the impression.

Close fitting trays are constructed with

the undercuts blocked out on the cast.

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record tissues in a state of anatomical rest.

Stability during impressionmaking.

Relief the non stressbearing areas .

2 mm thick.

modelling wax ,

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SPECIAL TRAYS

Special tray is made suchthat in the mouth itsperiphery liesapproximately 2 mm short

of the reflection of themucosa when the tissuesare at rest.

Upper tray is extended1mm distal to thehamular notch and 2mmdistal to the fovea

palatini. The tray should

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SPECIAL TRAYS

Lower tray isextended 1mmlateral to the externaloblique ridge. Thearea overlying themylohyoid muscle iscoated with wax

(2mm) so that itallows for contractionof the muscle duringimpression taking.

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SPECIAL TRAYS

Materials used to construct the trays:

Acrylic resins – can be cold cured or heat

cured. Tray handle position is importantand depending on the impressionmaterial to be used a spacer isincorporated. In addition to the trayhandle finger rests can be incorporatedespecially in the lower and should be1cm long by 1cm high and 4mm wide.

These are usually placed in the lower

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SPECIAL TRAYS

To provide the space in the tray for thematerial, the model is covered first with

2 layers of wax and then the trayadapted to the surface.

When alginate is used, holes can bedrilled through the tray to providemechanical retention.

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SPECIAL TRAYS

Outlined on diagnostic cast with frenal relief

Tissue stops to ensure even thickness of impression material

Stubs to avoid interference with peripheriesof impression

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Border Molding

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Secondary impressions

A more accurateworking

impression (calleda working orsecondaryimpression) is

taken usingspecial trayswhich is made for

a particular

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Impression plaster( with anti-expansion liquid)

Zinc-oxide eugenol impression paste(most commonly used)

Alginate

Elastomers (Polysulphides andSilicons)

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Secondary Impression

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Zinc-oxide eugenol impression paste

– Composition: Zinc-oxide, white

powdered resin, eugenol, natural oils,fillers.

– Patient lips and nearby skin should belightly covered with facer cream or

petroleum jelly.

– Orange oil or chloroform to remove pastefrom patient or operator skin

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Muscle trimming( border moulding).

Aim: to record functional depth and

width of sulcus Using tracing compound-related to--

impression compound???

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Elastomers

– Polysulphides :

base (polysulphide, titanium dioxide filler) andactivator ( lead dioxide)

Medium body viscosity is used for impression

Hydrophobic material

Prolonged setting time Strong odor of rubber

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IMPRESSION Techniques

Anatomic or arbitrary - Based onlandmarks.

Open or closed mouth - Based on themouth position.

Pressure - Pressure, nonpressure,

negative pressure or selected pressure

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IMPRESSION Techniques

Mucocompressive: Displace oraltissues because pressure is needed to

seat the material Mucostatic: No displacement: good

flow properties

Functional: Taken during musclecontraction

Special

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Maintains the width and

height of the sulcus

Mainly preserves

mucobuccal and mucolingualborders.

Materials used

beading: utility wax

boxing : boxing wax

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Master Casts

D b

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Denture bases

Requirements

– Easy to handle

– Capable of reproducing details from cast – Should not distort at mouth temperature

– Capable of being modified at chairside

Made of: wax, shellac, acrylic resinand impression compound

D b

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Denture bases

Acrylic resin (heat cure, self-cured, lightcured) bases have superior fit and stability

Wax bases tend to distort if left in mouth orif subjected to heavy occlusal forces

Shellac is more stable than wax but difficultto adjust at the chairside

Compound bases may be used in caseswhere the rim is to be made of the samematerial

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Record Blocks

Record base

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Record base

Base of denture Support wax occlusal rims.

Requirements :

Well adapted to the final cast . Dimensionally stable.

Retentive .

1mm thick on the crest andfacial slope of the ridge .

2mm thick in the palatal andlingual flange.

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Occlusal rims

Occluding surfaces built on temporaryor permanent denture bases for the

purpose of making maxillo-

mandibular relation records andarranging teeth.

o Primarily serves as gingivao Done mainly to arrange teeth

A t i l i f ti

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Anatomical information:Maxilla

The labial surface of anterior teethsupport the lips and is between 10 -12mm labial to incisive papilla

The centre of the last molar is nearlyopposite the centre of the tuberosity andits buccal surface is 3-5mm buccal to

centre of tuberosity On average, the distance from the

functional sulcus to incisal edge of centrals is about 20mm and to the

occlusal surface of first molar is about

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22mm high from the depth of thesulcus.

Ant region should be 8mm away from

incisive papilla .

4 – 6 mm wide in ant region.

Occlusal table should be 18mm high

from the depth of sulcus.

Occlusal table should be 8 –

12 mmwide posterior.

Occlusal table should be 10 – 12 mm

above the crest of alveolar ridge

anteriorly.

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A t i l i f ti

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Anatomical information:Mandible

The centre of the last molar is buccalto retromolar pad by 3mm

The occlusal surface of posterior teethcorresponds with the centre of retromolar pad

Mandibular occlusal rim

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6 -8mm high from the crest of the ridgeanteriorly

18mm high from depth of the sulcus in the

canine eminence region

3 –

6mm high from the crest of the ridgeposteriorly

The occlusal plate should extend to 2/3rd ht of

the retromolar pad posteriorly

Width

anteriorly 4 – 6mm

posteriorly 8 – 12mm

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JAW RELATIONS AND ARRANGEMENT OF ARTIFICIAL TEETH FOR

COMPLETE DENTURES

Jaw relations

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Jaw relations

A cast records details of natural dentition andalveolar ridges but we need to know the

following information before denture constructionso that the patient can get the maximum benefitfrom the complete denture:

– Centric occlusion: Static tooth contacts inmaximum intercuspation (termination of masticatory closure).

Jaw relations

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Jaw relations

– Centric relation: most retruded position of mandibleto maxilla from which lateral movement can be

made at a given degree of jaw separation.

– Vertical dimension: the distance between alveolarprocess of maxilla and mandible in centric relation

– Occlusal plane: the position and angle of a plane towhich the occlusal surfaces of teeth relate

Jaw relations

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Jaw relations

When teeth are missing, theirpositions are taken by record blocks

and these information recorded onthem

The blocks are attached to a base

constructed to accurately fit themouth

Registration blocks( base and wax

rim)

Jaw relations

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Jaw relations

Orientation relation: relation to the cranium

Vertical relation: amount of jaw separation

Horizontal relation: antero-posterior andlateral relations

These relations are transferred from patient tocasts (replica of edentulous ridges) throughthe use of: – Face bow( Orientation relation)

– Record blocks( Vertical and Horizontal relations)

Jaw relations

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Jaw relations

The established recorded jaw relationsare transferred to a mechanical

instrument that represents TMJ andJaws to which the maxillary andmandibular casts are attached. This isthe articulator which aims to simulatesome or all mandibular movements

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The articulator

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Jaw relations

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Jaw relations

– Assess lip support and notice vermillionborder and naso-labial groove

– Check height and orientation of occlusalplane( anterior and antero-posterior): thelower border of the maxillary rim represents thelevel at which the incisive edge of the upper

central incisors will be set and decides howmuch of the incisal edge will be seen below themargin of upper lip( 1mm average)

Jaw relations

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Jaw relations

Jaw relations

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Jaw relations

Maxillary rim

– Check height and orientation of

occlusal plane( anterior and antero-posterior

– the anterior occlusal plane is trimmedparallel to the inter-pupillary line while

the patient is in rest

– The antero-posterior plane is parallel toCamper’s line( ala-tragus line)

Inter-pupillary line

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Inter-pupillary line

O i i f l l l

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Orientation of occlusal plane

using Fox plane

Orientation of occlusal plane

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Orientation of occlusal planeusing Fox plane

Jaw relations

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Jaw relations

Maxillary rim

– Check height and orientation of

occlusal plane( anterior and antero-posterior :Mark centre line on labialsurface of upper rim which shouldcorrespond to the centre line of the whole

face and is not necessarily the centre of lips, nose , or any other individual facialstructure

Jaw relations

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Jaw relations

Maxillary rim

– Canine lines: better to indicate distal

surfaces of canines – High lip line:

indicates the position of maximum elevation of upper lip when smiling

Assist in selecting length of upper anteriors

Jaw relations

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Jaw relations

Jaw relations

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Jaw relations

Maxillary rim

– Measure rest vertical dimension

– Patient seated upright with Frankfurtplane horizontal (lowest point in marginof orbit to highest margin of externalauditory meatus).

– Ask patient to relax:

Swallow and relax

Pronounce ‘em’ and relax

Moisten lips with tip of the tongue and relax

Jaw relations

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Jaw relations

Maxillary rim

– Measure rest vertical dimension

(VDR) – The VDR is measured using

Willis gauge: separation between lower borderof nasal septum and lower border of chin (

pressure applied and angulations of gaugemay differ

2-dot technique: most common: tip of the

nose and non-movable part of chin)

2-dot technique

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2 dot technique

Jaw relations

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Jaw relations

Measure Occlusal verticaldimension (VDO):

– Insert lower base plate and wax rim – Ensure even contact between wax rims

– At this stage, the heals of acrylic basesmay touch, the interference may betrimmed but not to affect retention of bases

– Reduce lower occlusal rim so that the

VDO( between 2-dots) is 2-4 mm less

Interocclusal space

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Interocclusal space

Jaw relations

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Jaw relations

Arch form

– Posterior height of lower wax rim should

be 2/3 level up of retromolar pad – There should be 8-10mm from centre of

incisive papilla to labial surface of maxillary rim

Jaw relations

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Jaw relations

Record horizontal jaw relations

Retruded contact position: jaw

relationships in the horizontal plane atwhich the location of the occlusal rimswill be registered

Jaw relations

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Jaw relations

Record horizontal jaw relations

– when the condyles are in most retruded

position in the fossa and the jaw musclesare relaxed, the mandible can be movedin a simple hinge like manner and the jawmust be in most retruded position

– Swallowing and closure – Tip of the tongue against posterior border

of upper base plate

Jaw relations

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Jaw relations

Measure Occlusal verticaldimension (VDO):

– This space is interocclusal spaceexisting between upper and lowerteeth when mandible in physiologicrest position

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