1Primary and secondary Primary and secondary

(definitive) impressions (definitive) impressions

for complete denturesfor complete dentures

Dr David C. Attrill

d.c.attrill@bham.ac.uk

RecapRecap

History and examination performedHistory and examination performed

Special tests (i.e. radiographs, haematology Special tests (i.e. radiographs, haematology etc.) performed if indicatedetc.) performed if indicated

Diagnosis and treatment plan formulatedDiagnosis and treatment plan formulated

NO DIAGNOSIS, NO TREATMENTNO DIAGNOSIS, NO TREATMENT

Preliminary impressions need to be made Preliminary impressions need to be made (impression compound)(impression compound)

Preliminary impressionsPreliminary impressions

Impression compoundImpression compound

Softened to 55Softened to 55OOCC

Range of stock trays availableRange of stock trays available

Shaped to tray prior to insertion in the Shaped to tray prior to insertion in the mouthmouth

MakeMake an impression, dont an impression, dont taketake an an impressionimpression

2Next stagesNext stages

Technical (lab)Technical (lab)

Request casting of preliminary impressionsRequest casting of preliminary impressions

Request construction of special impression Request construction of special impression

trays (upper and lower)trays (upper and lower)

ClinicalClinical

Make definitive impressions using special Make definitive impressions using special

trays and appropriate impression materials. trays and appropriate impression materials.

Typical prescription at Typical prescription at

preliminary impression stagepreliminary impression stage

Upper Upper

(alginate 2(alginate 2O O imp) imp)

Please cast upper impression in Please cast upper impression in

plaster of plaster of parisparis, and construct , and construct

3mm spaced tray3mm spaced tray

nonnon--perforatedperforated

anterior L shapedanterior L shaped

VLC acry licVLC acry lic

Depends on what sort of materials you are goingDepends on what sort of materials you are going

to use for definitive impressionsto use for definitive impressions

LowerLower

((ZnOZnO/Eugenol 2/Eugenol 2O O imp) imp)

Please cast lower impression in Please cast lower impression in plaster of plaster of parisparis, and construct, and construct

0.5mm spaced tray**0.5mm spaced tray**

nonnon--perforatedperforated

3 stub3 stub--handleshandles

VLC acrylicVLC acrylic

Prescription variables for Prescription variables for

special traysspecial trays

MaterialsMaterials PMMA (VLC/SC/HC)PMMA (VLC/SC/HC)

Shellac/thermoplastic materialsShellac/thermoplastic materials

(Metal)(Metal)

SpacingSpacing 0.50.5--3mm, dependent on impression material3mm, dependent on impression material

PerforationsPerforations Non perforated/Perforations/selectively perforatedNon perforated/Perforations/selectively perforated

Handle design & numberHandle design & number Stub/L shape/No handlesStub/L shape/No handles

Extension into Extension into sulcussulcus Generally, 2mm short of Generally, 2mm short of suclussuclus

3Secondary (definitive) Secondary (definitive)

impressionsimpressions

Definitive impressionsDefinitive impressions

Enable dentist and technician to fabricate an Enable dentist and technician to fabricate an accurate replica of denture bearing areaaccurate replica of denture bearing area

More accurate than preliminary impressionMore accurate than preliminary impression

Even spacing of impression materialsEven spacing of impression materials

Customised impression trayCustomised impression tray

Define support for dentureDefine support for denture

Record available Record available functionalfunctional depth and width depth and width of of sulcussulcus

Spacing of impression traysSpacing of impression trays

Dependent on impression material to be usedDependent on impression material to be used

3mm alginate3mm alginate

2mm Plaster of 2mm Plaster of parisparis

2mm PVS/Polyether2mm PVS/Polyether

0.5mm 0.5mm 1mm close fitting 1mm close fitting ZnOEZnOE

Allows for even layer of impression materialAllows for even layer of impression material

Amount of spacing for each impression material is a Amount of spacing for each impression material is a

function of their inherent properties i.e. alginate does function of their inherent properties i.e. alginate does

not perform well in thin sectionnot perform well in thin section

Methods of restoring spacing Methods of restoring spacing

or modifying extensionsor modifying extensions

=1 Greenstick tracing compound (Dr. =1 Greenstick tracing compound (Dr. Attrills Attrills favourite!)favourite!)

=1 Cold cure acrylic i.e. Total (Professor =1 Cold cure acrylic i.e. Total (Professor Walmsleys Walmsleys favourite!)favourite!)

Red carding wax Red carding wax better than nothing but can better than nothing but can distort. Good to use with POP but can distort. Good to use with POP but can compromise alginate/ZOE impressionscompromise alginate/ZOE impressions

4Greenstick

Thermoplastic material

High over bunsen

Hot water

Upper alginate Upper alginate

impressionimpression

Sequence for upper definitive Sequence for upper definitive

alginate impression alginate impression

Assess tray on model (adjust)Assess tray on model (adjust)

DecontaminateDecontaminate

Assessment in mouthAssessment in mouth

Init ia l adjustmentsInit ia l adjustments

Greenstick for underGreenstick for under--extensionextension

Remove areas of overRemove areas of over--extensionextension

Develop periphera l sea l/restore spacingDevelop periphera l sea l/restore spacing

Greenst ick applicationGreenst ick application

Posterior borderPosterior border

Lateral aspects of tuberosities (width of Lateral aspects of tuberosities (width of sulcussulcus))

Anterior stops (single anterior stop or canine Anterior stops (single anterior stop or canine stops)stops)

Reassess extension and adjust as Reassess extension and adjust as necessarynecessary

Adhesive (FIX Adhesive (FIX TMTM) & dry) & dry

Mix alginate (2 scoops usually Mix alginate (2 scoops usually

sufficient)sufficient)

Make impression, incorporat ing Make impression, incorporat ing

border mouldingborder moulding

Trim excess out of mouthTrim excess out of mouth

DecontaminateDecontaminate

(Prescript ion)(Prescript ion)

5Upper plaster of Upper plaster of

paris paris impressionimpression

Lower ZincLower Zinc--Oxide Oxide

Eugenol impression Eugenol impression

((ZnOEZnOE))

Sequence for lower definitive Sequence for lower definitive ZnOEZnOE

impressionimpression

Assess tray on model (adjust)Assess tray on model (adjust)

DecontaminateDecontaminate

Assessment in mouthAssessment in mouth

Init ia l adjustmentsInit ia l adjustments

Remove areas of overRemove areas of over--extensionextension

Restore spacing (develop peripheral sea l)Restore spacing (develop peripheral sea l)

Greenst ick applicationGreenst ick application

Retromolar Retromolar pads & premolar stopspads & premolar stops

Lingual Lingual sulcussulcus

Buccal Buccal sulcussulcus

Dry tray (a ir)Dry tray (a ir)

Vaseline around mouthVaseline around mouth

Mix Mix ZnOE ZnOE & load tray& load tray

Make impression, incorporat ing Make impression, incorporat ing

border mouldingborder moulding

Trim excess out of mouthTrim excess out of mouth

DecontaminateDecontaminate

(Prescript ion)(Prescript ion)

6Whats next?Whats next?

TechnicalTechnical

Production of appropriate occlusal rimsProduction of appropriate occlusal rims

ClinicalClinical

Perform jaw registration procedurePerform jaw registration procedure

Typical laboratory prescriptionTypical laboratory prescription

Please cast upper and lower Please cast upper and lower impressions in 100% dental stone impressions in 100% dental stone

(50/50)(50/50)

Upper occlusal rim, thermoplastic base Upper occlusal rim, thermoplastic base

wax rimwax rim

Lower occlusal rim, acrylic base, Lower occlusal rim, acrylic base, Manchester rimManchester rim

Variables to consider when Variables to consider when

requesting rim constructionrequesting rim construction

Baseplate materialsBaseplate materials

Acrylics (PMMA) usually VLCAcrylics (PMMA) usually VLC

thermoplastic base (formerly shellac)thermoplastic base (formerly shellac)

Wax with wire Wax with wire strengthener strengthener (usually lower only)(usually lower only)

Rim materialsRim materials

WaxWax

Others (i.e. plaster/pumice)Others (i.e. plaster/pumice)

Rim designRim design

Complete rimComplete rim

Partial rim i.e. Manchester rimPartial rim i.e. Manchester rim