There has been considerable debate over thedesired amount of pressure and the resultant tissue dis-placement that is required for complete dentureimpressions. Three basic but mutually exclusive con-cepts for impressions have been described: mucostatic,maximum displacement, and functional impressiontechniques. Addison1 credits Page2 with introducingthe mucostatic technique. Fournet and Tuller3 advo-cated a high-pressure technique, and Chase4 and Vig5

described the technique for functional impressions.Variations to these fundamental concepts have beendescribed that combine some of the useful aspects ofthe techniques. Klein and Broner6 offer a variation toadapt high-pressure areas by using a clear acrylic resintray before taking secondary impressions. Boucher etal7 recommend a modified pressure technique that usesa perforated close-fitting secondary tray and zincoxide–eugenol. Sharry8 recommended secondaryimpressions with zinc oxide–eugenol and a spaced tray.

Most standard textbooks recognize the variation inacademic opinion and each offers various materials andtechniques for different clinical situations. McGregor9

described both impression compound and irreversiblehydrocolloid (alginate) primary impressions and 4 basicmaterials for secondary impressions and an additional5 special techniques. Basker et al10 advocated a com-

pound and alginate primary impression with the samebasic materials as McGregor. Grant et al11 recommend-ed 3 primary impression materials and a total of7 techniques for definitive or secondary impressions.Each textbook gives useful advice on which clinicalsituation each technique is best suited and appropriatedetails for special trays. The variety of recommenda-tions in standard textbooks suggests no one techniqueis satisfactory for all clinical situations. Different clini-cians offer different solutions to the same problem.

Given the variety of recommendations from acade-mics, the general dental practitioner (GDP) is facedwith a choice of materials and techniques for impres-sions for complete dentures. The aim of this survey isto determine which material and which techniqueGDPs in the United Kingdom use to fabricate a clini-cally straightforward complete denture.

METHOD

A questionnaire was sent out to 905 dental practi-tioners in Manchester and the surrounding areas in theUnited Kingdom. The names and addresses of the den-tists were obtained from the local Family Health Ser-vice Agency (FHSA) lists. The aim of the questionnairewas to find out current clinical practice rather than totest textbook knowledge. To this end, an undertakingwas given that the replies would be anonymous. Thestudy was designed so that there was no way of tracingan individual reply to a specific practitioner. No

Survey of prosthodontic impression procedures for complete dentures ingeneral dental practice in the United Kingdom

T. Paul Hyde, BChD,a and J. Fraser McCord, BDS, DDSb

Turner Dental School, University Dental Hospital, Manchester, United Kingdom

Statement of problem. Anecdotal evidence suggests impression techniques used in general dental prac-tice may vary from those taught at dental schools. There is little published information on this topic.Purpose. This study identifies the materials and methods used by general dental practitioners for recordingimpressions for the provision of replacement of complete dentures. Methods. A total of 905 questionnaires were sent to general dental practitioners in the Greater Manches-ter area to identify current clinical practices.Results. The results revealed that 88% of respondents use only irreversible hydrocolloid for primaryimpressions. If multiple responses are included, 99% of respondents mentioned irreversible hydrocolloids asan option for primary impressions. In response to the same question for secondary impressions, 94% ofrespondents mentioned irreversible hydrocolloids as an option. Other material mentioned as an option forsecondary impressions included zinc oxide–eugenol (29%) and polyvinyl siloxane (13%). With regard to spe-cial trays, 75% of respondents routinely used laboratory constructed special trays to take definitive impres-sions. Questions on the requisite spacing, perforation, handle design of special trays, and on disinfectionshowed a diversity of opinion among practitionersConclusions. Although this survey reflected a diverse range of clinical preferences, it is clear that irre-versible hydrocolloid dominates the impression market for complete dentures. The use of special trays isnormal practice for complete dentures in general dental practice in the United Kingdom. (J Prosthet Dent1999;81:295-9.)

aLecturer in Prosthodontics Unit.bProfessor and Head of Unit of Prosthodontics.

MARCH 1999 THE JOURNAL OF PROSTHETIC DENTISTRY 295

reminders or follow-up letters were sent to practition-ers who did not reply.

The introduction to the questionnaire stated that allthe questions related to a straightforward completedenture case in which there were no bony undercuts orflabby edentulous ridges. The survey contained 12questions (Table I); where multiple answers werereceived, each one was counted.

RESULTS

A total of 456 (50%) responses were received. TwoGDPs (0.44%) returned the questionnaire but gave noresponse to the questions so they were eliminated fromthe study. Where multiple answers were received, each

answer was counted. The questions asked, and thereplies are as follows.

In response to question 1, 23 GDPs (5%) did notroutinely provide complete dentures, which includedthose practitioners who were in a specialist orthodonticpractice. It was assumed that 95% of GDPs routinelyprovide complete replacement dentures. For question2, the responses are illustrated in Figure 1, whichindicates the preference of GDPs for irreversible hydro-colloid. In response to question 3, 74% said theyroutinely used special trays for such a straightforwardcase (Fig. 2). The responses to question 4 are summa-rized in Figure 3. The graph illustrates the high use of

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Table I. The questions

Questionnumber Wording of question Answer options

1 Do you routinely provide Yes or Nocomplete (full) dentures inthe normal course of yourpractice?

2 Which of the following List of optionsmaterials would you routinelyuse for preliminaryimpressions?

3 Do you routinely use Yes or Nolaboratory constructed specialtrays to take definitiveimpressions?

4 If Yes, which of the following List of optionsmaterials would you use in aspecial tray for a definitiveimpression?

5 What type of special tray List of optionswould you normally askyour technician to construct?

6 In which of the following List of optionsmaterials would you normallyhave your special traysconstructed?

7 Do you specify to your Yes or Notechnician any detailsregarding the handles of yourspecial trays?

8 If Yes, do you routinely List of optionsask for…

9 Do you routinely disinfect Yes or Noyour impressions prior todispatch to the laboratory?

10 If yes, how? List of options11 What percentage of your List of options

practice is private?12 If you are in a mixed NHS Yes or No

and private practice, wouldyou use a differentimpression technique forNHS and private practice?

NHS = National Health Service.

Fig. 1. Histogram of practitioner replies on preferred choiceof material for primary impressions. 1, Irreversible hydrocol-loid; 2, impression compound; 3, irreversible hydrocolloidand impression compound; 4, condensation cured polyvinylsiloxane putty; 5, condensation cured polyvinyl siloxaneputty and wash; 6, addition cured polyvinyl siloxane putty;7, addition cured polyvinyl siloxane putty and wash; 8,impression plaster; 9, zinc oxide and eugenol; 10, other.

Fig. 2. Pie chart outlining percentage of practitioners whouse special trays. 1, Special tray used; 0, no special trayused.

irreversible hydrocolloids for secondary impressions.The silicone techniques are combined in 1 category, asare the variations involving impression compound. Theresponses to question 5 are presented in Table II. SomeGDPs gave multiple answers. All the options for spac-ing and perforation of special trays were represented inthe replies. In all cases, the GDPs preferred perforatedtrays.

For question 6, 231 GDPs use shellac and 222GDPs responded that they use autopolymerizingacrylic resin (Table III). The remaining GDPs uselight-curing resin or other materials. For question 7regarding specifications for technicians, 85% repliedthat they do not routinely specify the type of handlethey require to their technician. In response to ques-tion 8, intended for those GDPs who answered “yes”to question 7, multiple answers were given (Table IV),with the most frequent response being the L-shapedhandle.

The response to question 9, concerning impressiondisinfection, revealed that 49% of the GDPs do notdisinfect their impressions before dispatch to their tech-nician, and 51% said they do disinfect their impressions.For question 10, intended for those who replied “yes”to question 9, most GDPs stated that they rinse theimpression under tap water (Table V).

The response to question 11 indicated few GDPs inprivate practice only, and that the greatest number ofrespondents were affiliated with National Health Ser-vice (NHS) practice (Table VI). Responses to question12 indicated that 69% of respondents did not use dif-

ferent impression technique for NHS and privatepatients.

DISCUSSION

Although the percentage return of the question-naires was disappointing (50%), the replies of almost500 general dental practitioners, representing a broadrange of practices, revealed some interesting trends.

Regarding primary impressions, 88% cited irre-versible hydrocolloids as their only option, with 99%listing these materials as one of their options. ManyUnited Kingdom (UK) dental schools recommendimpression compound (that is option 2 on Fig. 1) forprimary impressions for conventional replacementcomplete dentures. If irreversible hydrocolloid is usedfor a primary impression, the conventional, UK teach-ing12 is that the material is supported by impressioncompound (that is option 3 on Fig. 1). Although onebrand of irreversible hydrocolloid impression material,which has both viscous and light-bodied phases, is soldin the UK (Accu-Dent, San Jose, Calif.), it does notenjoy universal usage. Therefore the ability of unsup-ported conventional irreversible hydrocolloid materialsto record the denture-bearing area of most edentulousridges in a satisfactory way must be questioned. Thereasons for this departure from conventional teachingwould merit further investigation.

An interesting finding in this study was that approx-imately 75% of the respondents use special trays in thefabrication of complete dentures. This is a sizableimprovement on the earlier study of Basker et al.13 Asthis sample represents almost 500 GDPs who work inboth private and NHS environments, it suggests anendorsement for the use of special trays. In UK law, thetest of competence for a practitioner is whether they

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MARCH 1999 297

Fig. 3. Preferred choice of materials for definitive impres-sions: 1, irreversible hydrocolloid; 2, all impression com-pound answers; 3, all polyvinyl siloxane materials and tech-niques; 4, plaster; 5, zinc oxide and eugenol; 6, other.

Table II. Question 5

1: Close fitting, nonperforated 772: Close fitting, perforated 873: 1.5 mm spaced, nonperforated 254: 1.5 mm spaced, perforated 1825: 3 mm spaced, nonperforated 186: 3 mm spaced, perforated 120

Table III. Question 6

1. Shellac 2312. Self-cured acrylic resin 2223. Light-cured acrylic resin 324. Other 6

Table IV. Question 7

1. “L” shaped 662. “Stub” shaped in center 233. “Stub” shaped in premolar 144. No handles 45. Other 1

carried out the treatment to the standard of the major-ity of their peers. This survey shows, for the first time,that the majority of UK practitioners use special traysfor the construction of complete dentures. It can there-fore be argued that a practitioner who does not usespecial trays may have to justify his/her action in anymedicolegal dispute.

How special trays are designed is obviously a productof practitioner experience and preference, in addition tosimilar preferences of laboratories. Given the obviouspreference, among the respondents in this study, forirreversible hydrocolloid as a material of choice fordefinitive impressions, it is surprising that all the optionsfor spacing of the trays were used (namely, close fitting,1.5, and 3 mm spaced); most textbooks recommend2 to 3 mm spacing for irreversible hydrocolloids.14

Of greater interest is the fact that 62.2% of practi-tioners requested perforated special trays. We wouldcontend that as no peripheral seal can be demonstratedwhen perforations are present in a tray, that the specialtrays should be returned from the laboratory nonper-forated.11 When a peripheral seal has to be demon-strated, the practitioner may then perforate the tray ifhe/she so prefers.

The responsibility of each clinician to recognize therequirements for special trays is fundamental to patientcare. Textbooks recommend prescription for specialtrays based on ridge form, mucosal status, and lipform.15 Technicians cannot determine such mattersfrom primary casts. For these reasons, we asked therespondents to describe the spacing requested for thespecial trays and details of the handles for the trays.Over 60% of respondents use L-shaped handles, which,according to some textbooks, can restrict the moldingof the labial sulci.8,11,15 Of respondents, 4% did not askfor handles. This might suggest that this matterrequires more attention by undergraduate and post-graduate educators.

Infection control is mandated for the day-to-daypractice of dentistry. It was disturbing that 49% ofrespondents did not routinely disinfect impressionsbefore dispatch to a dental laboratory. However, labo-ratories routinely disinfect impressions when they arereceived. Of greater concern was the apparent failure ofmany respondents to appreciate the appropriatemethod of disinfection, with 70% opting to just rinseimpressions in water.

The probity of the responses was confirmed by visit-ing 2 large laboratories that supply a service through-out the UK. This separate survey confirmed thepercentage of dentists who use special trays and followrequired disinfection preparation in the provision ofcomplete dentures. The results of this separate labora-tory survey were presented to the British Society forthe Study of Prosthetic Dentistry (BSSPD) for peerreview. A further separate laboratory survey16 hasrevealed that many impressions had not been disinfect-ed before receipt by the laboratory. Thus confirmingthe probity of the results of this survey.

Because the response rate was low, it is necessary tobe cautious when applying these results to all GDPs inthe UK. However, if it is assumed that this sample pop-ulation is not unique in the dental profession, theresults have to be viewed with concern. Perhaps thesegeneral practitioners are fabricating fewer completedentures than their colleagues of 20 or even 10 yearsago, but the responsibilities of quality of clinical careand infection control procedures are fundamental todental care. As the prevalence of edentulousness falls,the degree of difficulty of each edentulous case rises.

CONCLUSIONS

Within the limits of this study, the following conclu-sions were drawn:

1. Irreversible hydrocolloid (alginate) dominates themarket for impression materials for complete dentures.

2. The use of special trays is normal practice for com-plete dentures in General Dental Practice in the UK.

REFERENCES

1. Addison PI. Mucostatic impressions. J Am Dent Assoc 1944;31:941.2. Page HL. Mucostatics—a capsule explanation. Chron Omaba Dist D Soc

1951;14:195-6.3. Fournet SC, Tuller CS. A revolutionary mechanical principle utilized to

produce full lower dentures surpassing in stability the best modern upperdentures. J Am Dent Assoc 1936;23:1028-30.

4. Chase WW. Tissue conditioning utilizing dynamic adaptive stress. J Pros-thet Dent 1961;11:804-15.

5. Vig RG. A modified chew-in and functional impression technique. J Pros-thet Dent 1964;14:214-20.

6. Klein IE, Broner AS. Complete denture secondary impression technique tominimize distortion of ridge and border tissues. J Prosthet Dent1985;54:660-4.

7. Boucher CO, Hickey JC, Zarb GA. Prosthodontic treatment for edentulouspatients. 9th ed. St Louis: CV Mosby; 1990. p. 185-93, 229-42.

8. Sharry JH. Complete denture prosthodontics. 3rd ed. New York: McGraw-Hill; 1974. p. 191-211.

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Table V. Question 10

1. Rinse under tap water 1992. Bleach 183. Alcohol 584. Alcohol 225. Gluteraldehyde 416. Other 15

Table VI. Question 11

1. 100% Private 0% NHS 292. 75% Private 25% NHS 443. 50% Private 50% NHS 284. 25% Private 75% NHS 1265. 0% Private 100% NHS 199

NHS = National Health Service.

9. MacGregor AR, Fenn HRB. Fenn, Liddelow, and Gimson’s clinical dentalprosthetics. 3rd ed. London: Wright; 1989. p. 43-77.

10. Basker RM, Davenport JC, Tomlin HR. Prosthetic treatment of the edentu-lous patient. 3rd ed. London: Macmillan Press; 1976. p. 142-67.

11. Grant AA, Heath JR, McCord JF. Complete prosthodontics, problems diag-nosis and management. London: Wolfe; 1994. p. 89-92.

12. Grant AA, Johnson W. An introduction to removable denture prosthetics.London: Churchill Livingstone; 1983. p. 127.

13. Basker RM, Ogden AR, Ralph JP. Complete denture prescription—anaudit of performance. Br Dent J 1993;174:278-84.

14. Grant AA, Johnson W. Removable prosthodontics. 2nd ed. London:Churchill Livingstone; 1992. p. 194.

15. Hickey JC, Zarb GA, Bolender CL. Boucher’s prosthodontic treatment foredentulous patients. 9th ed. St Louis: CV Mosby; 1985. p. 119-230.

16. Verran J, Kosser S, McCord JF. Microbiological study of selected risk areasin dental technology laboratories. J Dent 1996;74:77-80.

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Histologic analysis of clinically retrieved titaniummicroimplants placed in conjunction with maxillary sinusfloor augmentationJensen OT, Sennerby L. Int J Oral Maxillofac Implants1998;13:513-32.

Purpose. Bone grafts in the maxillary sinus are used to increase the volume of load-bearing bone.Previous studies have not presented histologic evaluations from consecutively treated patients.This study used implants, to be retrieved at specific periods, to evaluate the histology at the tita-nium-graft interface.Material and methods. A series of 9 patients participated. Brånemark implants (Nobel Biocare)were placed in the residual maxilla with the implants extending into the maxillary sinus. Sixpatients had unilateral implant placement and 3 had bilateral implant placement. Grafting mate-rials consisted of autogenous bone from the iliac crest donor site or radiated mineralized cancel-lous allograft (RMCA) (Rocky Mountain Tissue Bank). Grafts were placed into all sinuses with 6of each type of grafting material used. Microimplants (2 mm wide and 6 mm long) were placedinto the lateral wall of the sinus and were removed through the use of a trephine bur at either 6or 12 months after implant placement. Histologic analysis was conducted on the retrieved speci-mens.Results. Normal bone morphology was observed in sites with autogenous grafts. This bone wasmore mature at the later retrieval date than at 6 months. Tissue structure of the allografted siteswas mixed with newly formed bone and nonviable allograft particles seen in a background of looseconnective tissue. Neither grafting material resulted in a high level of bone to implant contact atthe interface.Conclusions. Primary stability of the implants placed in this study was achieved through theresidual maxillary bone. Autogenous grafts were responsible for the formation of more normalbone histology than the allografts but neither graft provided a high level of bone to implant con-tact. 19 References. —SE Eckert

Noteworthy Abstractsof theCurrent Literature