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GOOD MORNING



Journal of Prosthodontics, Vol 12, No 3 (September), 2003: pp 192-197

A Retrospective Comparison ofTwo Definitive Impression

Techniques and TheirAssociated Postinsertion

Adjustments in Complete

Denture ProsthodonticsCarl J. Drago, DDS, MS



Treatment of edentulous patients with completedentures is a technically demanding task.

Making a definitive impression is one of themost critical steps that a clinician performs in the

process of fabricating complete dentures. The objective of the complete denture definitive

impression is to accurately record the entiredenture-bearing area to produce a stable and

retentive prosthesis while maintaining patientcomfort and aesthetics and preserving theremaining tissues.



Most U.S. dental schools teach complete denturedefinitive impression techniques consisting of secondary impressions in border-molded customimpression trays.

Even though the materials used in definitive

denture impressions varied among the reportingdental schools, the techniques used wereremarkably similar among the schools.

However, a significant number of dentistsreported that they abandoned the procedures

that they were taught in the complete denturecurriculum and made definitive dentureimpressions in their private practices withtechniques they considered simpler.



Clinicians in the United Kingdom reportedthat they did not always use the techniquesthat were taught to them as dental students.

A survey was conducted in the United

Kingdom asking about the types of impression materials and techniques used formaking definitive denture impressions incomplete denture prosthodontics.

A questionnaire containing 12 questions wasmailedto 905 general practitioners.



The response rate was 50%; 74% used custom trays for definitive

impressions; and

•

94% used irreversible hydrocolloid impressionmaterial for the definitive impressions;

• with 29% using zinc oxide/ eugenol and 13%using vinyl polysiloxane.

Irreversible hydrocolloid is not consideredthe material of choice for definitive dentureimpressions in U.K.dental schools.



Definitive impressions for complete dentureshave been identified as a difficult technique tomaster for dental students with limitedexperience.

Students generally scheduled between two and

four appointments to complete the definitiveimpressions. The definitive impression technique is reportedly

one of the more critical elements in completedenture prosthodontics.

The objective in definitive impressions is forclinicians to obtain accurate impressions of thedenture-bearing areas of the edentulous jaws.



Accurate impressions are important in fabricatingstable and retentive prostheses with optimalesthetics and function and a comfortable fit foredentulous patients.

Definitive denture impressions may be made withvarious materials: impression plaster, zincoxide/eugenol, polysulfide rubber, irreversiblehydrocolloid, vinyl polysiloxane, or polyether.

The techniques for definitive denture

impressions canbe classified as mucostatic, maximumdisplacement, functional,or selective pressure.



It has been acknowledged that a single techniquecannot be used for all clinical situations.

Textbooks in complete denture prosthodonticsdescribe numerous theories and techniques formaking definitive denture impressions.

These have been identified as traditional orconventional techniques. McGregor and Fen described four materials for

definitive impressions and five specializedtechniques.

Duncan described a modified definitive impressiontechnique taught to predoctoral dental studentscomprising deliberately overextended irreversiblehydrocolloid impressions for fabrication of mastercasts.



Chaffee et al reported a definitive dentureimpression technique that illustrated the use of aselective pressure placement technique.

in that Vinyl polysiloxane impression materialwas used to border- mold custom impression

trays. The authors believed that using this material for

border molding in a conventional fashion andusing the selective pressure placementimpression technique could yield predictable

results in making properly extended,accurate,definitive impressions. Evidence was not presented to justify the

technique, however.



Due to the complexities involved in complete denturetreatment, patients generally experience anadjustment phase after the dentures are inserted.

Postinsertion adjustments and/or scheduled follow-up appointments are necessary to ensure proper fit

of the dentures to the soft tissues and optimalocclusion, and also to monitor the patients’ overallresponse to treatment.

Multiple unscheduled postinsertion adjustmentappointments can be costly and frustrating toclinicians and patients alike.

Seiffert et alsuggested that patients’ personalitiesand their relationships with dentists play substantialroles in the overall successful adaptation to completedentures.



They found psychological attributes to be asimportant to successful adaptation as a patient’sanatomical features and the clinician’s skills infabricating complete dentures.

Davis et al examined the clinical dilemma of

providing dentures to patients with unrealisticexpectations for new complete dentures, and foundthat a patient’s pre-treatment expectations mightinfluence treatment outcomes;

treatment failures may result from mismatchedperceptions and expectations of the patient and the

dentist. Lamb and Ellis found that post insertion adjustments

may be related to poor patientcompliance/understanding.



Despite the large volume of literature regardingpatient satisfaction with complete denturetherapy, there is no consensus among authors asto reliable predictors of denture success.

If a definitive impression technique could bedeveloped that was easier to perform thanconventional border-molding techniques withmodeling plastic impression compound, tookless clinical time, and did not increase the

number of postinsertion visits to dental offices,then more dentists might elect to treat moreedentulous patients with complete dentures



The purpose of this study was to compare thenumber of postinsertion adjustments neededby edentulous patients who had completedentures fabricated using a traditional

technique versus those with completedentures fabricated using a modifiedtechnique in a retrospective analysis of patients in a private practice setting.



In this retrospective study, all patients were treatedby the author in a private practice setting within alarge multispecialty medical/dental group practice .

A group of 78 consecutive edentulous patients wastreated with the traditional technique involving

custom light-polymerized impression trays. The impression trays were border-molded with

modeling plastic impression compound.

Another group of 78 consecutive edentulous patientswas treated with a modified impression techniqueinvolving custom light-polymerized impression traysthat were border-molded with heavybody vinylpolysiloxane impression material.



The patients ranged in age from 18 to 75 years. Fifty-six males were treated, 26 with the

traditional technique and 30 with the modifiedtechnique.

One hundred females were treated, 52 with thetraditional technique and 48 with the modifiedtechnique.

All patients were edentulous and were treatedwith complete maxillary and mandibular

dentures. Patients were followed for 1 year after insertion

of the complete dentures.



Post insertion adjustments to the flanges of thecomplete dentures were quantified by thenumber of post insertion appointments requiredfor one year after insertion of the completedentures.

The data for this study were taken from clinicalpatient records.

Only those denture adjustments that involved theheight or thickness of the denture flanges were

quantified by the number of times that patientspresented to the dental office for dentureadjustments.



The number or locations of the dentureadjustments were not quantified, because thereis significant variability in the clinicalpresentations of denture irritations.

Immediate dentures were not included in the

study. All patients had been edentulous for at least one

year before the preliminary impressions and hadbeen wearing complete dentures for at least oneyear before definitive impressions for this study.

The complete dentures were fabricated accordingestablished prosthodontic principles. One dental laboratory technician accomplished

all of the laboratory procedures.



Custom denture impression trays were taken tothe mouth, and the tray borders were adjusted tohave approximately 2 mm of clearance betweenthe tray borders and the mucobuccal andmucolingual folds.

The frenum notches were adjusted to providesimilar clearances. The posterior extensions of maxillary trays

extended 3 to 5 mm beyond the vibrating line of the soft palates.

Border molding of the custom trays wasaccomplished with 1 of 2 impression materialsand techniques.



With the traditional technique, gray modeling plasticimpression compound was applied in incrementsaround the periphery of the impression trays.

The clinician border-molded each individualsegment; the patient accomplished tongue

movements and swallowing. The border-molding process required between 5 and

10 attempts in the maxillae and between 7 and 10attempts in the mandible.

The mouth was dried with gauze before the definitiveimpressions were made.

Tray adhesive was applied to the impression trays,and all definitive impressions were made with light-body vinyl polysiloxane impression material.



In the modified technique, tray adhesive was placedon the borders of the trays and allowed to dry. Heavy-body vinyl polysiloxane impression material

was applied to the borders of the impression trays,and border molding of the maxillary trays wasaccomplished with one application of the heavy-bodyimpression material.

Mandibular border molding was accomplished in asimilar fashion. After the labial and buccal bordermolding was completed, the patient was instructed toplace the tongue in contact with the anterior tray

handle after swallowing. The mouth was dried with gauze before the definitive

impressions were made.



Tray adhesive was applied to the impression trays, and alldefinitive impressions were made with light-body vinylpolysiloxane impression material .

Working time with this material was approximately 2minutes.

After the material had set, the impressions were removed. Master casts, occlusion rims, waxed dentures, and

definitive dentures were fabricated using conventionalprosthodontic techniques.

The author made the ultimate determination of thevertical dimension of occlusion.

The 3-dimensional orientation of the maxillary casts andtheir relationships to the cranial structures weretransferred to semi-adjustable articulators (Hanau H-2Articulator) with an arbitrary face bow (Hanau EarpieceFace Bow;).

The casts were mounted with mounting stone.



One dental laboratory technician set the denture teeth. All patients were treated with acrylic resin teeth. The anterior teeth were set in positions consistent with the

contours established by the maxillary occlusion rims. Posterior teeth were set in posterior balanced occlusion.

Patients, and the author evaluated the esthetics, lipsupport, occlusal vertical dimension, and rest verticaldimension of the wax dentures at the wax try-inappointment.

The author evaluated the accuracy of the jaw relationrecords in accordance with the foregoing parameters.

The dentures were deemed ready for processing only afterall steps had been completed.

All of the dentures were processedwith heatpolymerizedacrylic resin following the manufacturer’s instructions.



The dentures were inserted, and patientswere followed for at least 1 year.

The number of times that patients returnedfor adjustments relative to thickness and theheights of the denture flanges were recorded.

The severity of the denture adjustments wasnot qualified, because this parameter was

thought to be too subjective.



Denture adjustments (height or thickness of denture flanges) within the first 12 monthsafter the dentures were inserted ranged from0 (4 patients) to 8 (1 patient) with the

traditional technique and from 0 (6 patients)to 11 (1 patient) with the modified technique.

The average number of adjustment visits was2.68 for the patients treated with thetraditional technique and 2.68 for thosetreated with the modified technique .



The data were compared using the Student t test (Table 2).

There was no significant difference in thenumber of adjustments required for patientswhose dentures were made with eithertechnique (t 0.000, p 1.00).



Definitive complete denture impressions arebelieved to be 1 of the critical factors indetermining success or failure for patientswearing complete dentures.

The definitive impression appointment is

generally considered to be 1 of the more timeconsuming and technically difficult appointmentsin the traditional treatment sequence forcomplete dentures.

If modeling plastic impression compound is

used as the border molding material, thenclinicians must heat the compound, apply thesoftened material to the impression tray, temperthe tray, and place the tray into the patient’smouth.



Border molding is accomplished with the clinicianmoving the tissues in a manner consistent withfunction.

Modeling plastic impression compound presents theclinician with a finite working time to modify themodeling plastic impression compound before ithardens.

This procedure requires multiple attempts peredentulous jaw.

After the border molding has been completed,definitive impressions may be made.

Heavy-body vinyl polysiloxane may also be used toaccomplish border molding in complete denturedefinitive impression techniques.



Irreversible hydrocolloid may be used as the finalimpression material with or without bordermolding.

However, irreversible hydrocolloid impressionsare generally overextended.

Clinicians may realize a significant time savingswith the irreversible hydrocolloid impressiontechnique, because border molding isaccomplished at the same time as the definitiveimpression.

However, this may result in ill-fitting denturesthat need extensive modification after thedentures have been inserted



In this study, the level of denture experiencevaried from the second set of dentures for somepatients to the fourth set of dentures for others.

The amount of bone resorption of the edentulous jaws of the patients treated in this study rangedfrom mild to significant.

A larger number of patients would be requiredto adequately group patients with similar degreesof bone resorption and to evaluate any

correlation that may exist between boneresorption and the number of postinsertiondenture adjustments.



Denture adjustments are multifactorial, affected bythe amount of residual ridge resorption, health of thesoft tissues covering the edentulous jaws,adaptability of patients to complete dentures, skillsof the clinicians and dental laboratory techniciansinvolved in the treatment, jaw relationships, denture

occlusion, and other factors. There were no significant differences in terms of

postinsertion adjustments between the patientstreated with either impression technique in thisstudy.

However, this does not mean that either techniqueshould be taken as the definitive method of fabricating definitive complete denture impressions,because of several limitations in the design of thisstudy:



The total number of patients is too small to makeconclusions for all edentulous patients; somepatients can better adapt to dentures than otherpatients; and anatomical variations amongpatients and the author’s clinical experience may

not be representative of other clinicians. There were also differences among patients

relative to fit of the dentures, vertical dimensionof occlusion, and other factors.

Moreover, the relationships that existed between

the author and the patients may also have had abearing on an individual patient’s need to returnfor denture adjustments.



The number of postinsertion adjustments forcomplete denture patients is a complex phenomenon.

Certainly other factors (eg, occlusion, denture fit,diet) played important roles in the need forpostinsertion adjustment visits required by thispatient as compared with the number of visitsrequired by the other complete denture patients who

did not need to return for postinsertion adjustments. Although border-molding and definitive impression

techniques are important in fabricating successfulcomplete dentures for edentulous patients, it isunlikely that border-molding techniques andmaterials are solely responsible for the number of postinsertion adjustments in complete denturepatients.



Complete edentulous patients exhibit a broad rangeof physical and psychological variations. Physically, all of the patients in this study were

without teeth and merited complete denturetreatments.

Classifying all of the edentulous patients in this studyas being members of one diagnostic or experimentalgroup would be inaccurate and would not take intoaccount the multiple levels of physical variationspresent.

This study was retrospective, and although the author

has a standardized treatment protocol for thepatients in this study, this study could not take intoaccount the subtle differences in the proceduresneeded to complete the denture treatments for all of the patients.



The present study included 156 patients, withvarying amounts of bone resorption anddifferent levels of denture experience.

The conclusions from the present study

would have a greater degree of validity if there were more patients and if these patientshad been classified more specifically.



The definitive impression techniquedescribed in this study may not be applicablefor all clinicians.

Because complete denture prosthodontics is

both an art and a science, some of the resultsdescribed in this article may be attributed tothe clinical skills and knowledge of theauthor.



Further research with a larger group of patients is warranted to establish acorrelation between the modified impressiontechnique described in this study and the

number of post insertion adjustment visitsneeded by complete denture patients.



Within the limitations of this study, there wasno significant difference in the number of postinsertion appointments required forpatients with dentures fabricated using the

traditional technique (border-molding withmodeling plastic impression compound) andthose with dentures fabricated using themodified technique (border-molding with

heavy body vinyl polysiloxane) for definitiveimpressions.



Boucher -prosthodontic treatment foredentulous patient.11th edtn.

Heartwell- sylabous of complete denture,4th edtn.

JPD-1998.issue 8 page no-129.technique forborder moulding using poly vinyl silioxane.

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