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22 Indian Journal of Oral Sciences Vol. 6 Issue 1 Jan-Apr 2015

Introduction

Over the past four decades tremendous

progress has been made in procedures formaking impressions for fixed prosthodontics.

The quality of fit of dental restorations ismainly influenced by the accuracy of thedental impressions. There are various

techniques for making fixed partial denture(FPD) impressions.[1-6] These include the

following: (1) The single copper bandtechnique, (2) the monophase technique

(in which an impression material of only1 viscosity is used), (3) the single-step

technique (in which impression materials of2 viscosities are applied at the same time),

or (4) the double-step technique (in whichthe impression is made in two steps, using

material of different viscosity in each step).

Livaditis G [7] compared the methodsand effectiveness of traditional FPD

impression system which includes thematrix impression system in relation to

the registration of the finish lines and

sulci of the tooth preparations, very less

importance was given to the accuracy

of the occlusal plane and impression

techniques.

The putty reline methods have become more

popular among the dentists because of the

ease of handling when compared to custom

tray techniques. But due to the improper

seating of the tray and compressibility ofthe putty material can lead to the variation

in interocclusal relations registration within

the impression.[8]

Although the bite registration method is

commonly used to record and transfer the

occlusal relations to the articulator,[9] minor

variations in the occlusal plane occur due

to the faulty impression procedure that

Address for Correspondence:Dr. Roseline Meshramkar,Department of Prosthodontics, S.D.M.College of Dental Sciences and Hospital,Dharwad 580 009, Karnataka, India.Email: [email protected]

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www.indjos.comDOI:10.4103/0976-6944.154605

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A comparative study to evaluatedifferent impression technique inrelation to accuracy of the occlusal

plane in fxed partial dentureRoopa Kundur Thippanna, Roseline Meshramkar1, Suresh Sajjan2

Department of Prosthodontics, College of Dental Sciences, Davangere, 1Department of Prosthodontics, S.D.M.College of Dental Sciences and Hospital, Dharwad, Karnataka, 2Department of Prosthodontics, Vishnu DentalCollege, Bhimavaram, Andhra Pradesh, India

ABSTRACT

Introduction: The purpose of this study was to evaluate and compare different impression

techniques in relation to accuracy of the occlusal plane.

Materials and Methods:Twenty impressions were made with different techniques and casts

were fabricated and discrepancy in the occlusal plane was measured using microcator. Fiveimpressions for each of the technique were made using polyvinyl silicone and impression poured

with type IV die stone. The discrepancies in the occlusal plane were measured and compared.

Results:Casts poured with custom tray yielded the most accurate models from the impression

and the values were statistically significant.

Conclusion:Impression technique using custom tray yielded most accurate model from the

impressions. Among relining putty with spacer on the prepared area produced more variation

in occlusal plane.

Key words: Double mix impression, fixed partial denture, impression technique, occlusal plane, putty reline technique,single step technique

OriginalArticle

Date of Submission:11-03-2014Date of Acceptance:26-09-2014

[Downloaded free from http://www.indjos.com on Monday, October 26, 2015, IP: 114.125.12.137]


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Thippanna,et al.: Impression techniques and occlusal plane in FPD

23Indian Journal of Oral Sciences Vol. 6 Issue 1 Jan-Apr 2015

are often unnoticed. This results in a variation in occlusal

contacts while doing the clinical trials although it appearsto be acceptable in the articulator. The ability to identify

and analyze inaccurate impressions and to understand howto avoid them is key to successful restoration. Many studieson impression accuracy have been published. Only a few

studies reported on the quality of the impressions and its

relation to the occlusal plane. Therefore, the purpose ofthis study is to do a comparative evaluation of differentimpression techniques in relation to accuracy of the

occlusal plane.

Materials and Methods

In the present study, three putty-wash impression

techniques and single step impression technique usingcustom tray have been used.

Materials

Master model, containing three complete crown FPDabutment preparations

Six metal copings, three each of 1 and 2 mm thickness. Polyethylene separating sheets

Perforated metal tray Addition silicone impression material. (Flextime,

Heraeus Kulzer)(easy putty and light-bodied polyvinylsiloxane)

Tray adhesive (Heraeus Kulzer, universal adhesive)

Die stone (Kalrock, super hard die stone class IV,Kalabhai Karson, Mumbai)

Debubblizer (Dentofill).

Armamentarium

Vaccum mixer

Automatic mixing syringe and dispensing gun(Heraeus Kulzer)

Vibrator Rubber bowl Mixing spatula

Base former Microcator (Company name).

A frasco model of maxillary arch with typhodont teeth was

taken. The maxillary first molar right side was prepared fora full cast crown. A slot was prepared using sticky wax in

the palatal region to facilitate the placement of the metalblock. Thus the prepared model was used as a standardmodel. The impressions were made using the standard

model without the block.

Grouping of impressions

The impressions were categorized into four groups asfollows:Group I Putty impression with reline on prepared area:

First a preliminary impression was made with puttymaterial. Later the material was scooped off from theprepared tooth area to provide space for light body. Thefinal impression was made by injecting the light body overthe prepared tooth area and impression area. The puttyimpression was reseated on the model. The impressionwas removed after setting of the light body.

Group II Putty impression with complete reline:

This method was similar to above mentioned techniqueexcept that the relining was done throughout the arch.

Group III Putty impression with spacer on prepared areaand relining:

This was also similar to first technique but the space forlight body was gained by placing polythene spacer.

Group IV Single impression technique using custom tray:

Medium and light body materials were used. Both thematerials were mixed simultaneously on different paperpads. The medium body was loaded onto the tray andthe light body into the syringe. The syringe material wasinjected onto the area of preparation. The tray was thenseated over the model. Both the materials set together toproduce a single impression.

For each technique five impressions were made usinga polyvinyl siloxane (addition silicon material). Theimpressions were poured in die stone (type IV) with awater: Powder ratio as recommended by the manufacturer.

All of the variables involved in the impression techniquesand cast production were carefully standardized.

Method of evaluation

To assess the accuracy of the occlusal plane, die models werecompared to that of the standard frasaco model. Referencepoints were established on the buccal aspect of the firstmolar in between the cusp tips on both left and right side.The measurements were done by using MICROCATOR[Figure 1] instrument. The sensitivity of this instrumentis of 0.001mm. The metal block was inserted into the slotcreated in the model. All the measurements were done fromthe fixed point [Figures 2 and 3]. From this point the heightsonto the right and left side were measured [Figures 4and 5]. The difference between the right and left side onthe standard model was taken as standard reading to findthe discrepancy from each technique. All the measurementscarried out were in millimeters.

Results

The readings from the four experimental techniqueswere independently analyzed using analysis of variance



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24 Indian Journal of Oral Sciences Vol. 6 Issue 1 Jan-Apr 2015

(ANOVA). Differences between the different techniqueswere found out. Of all the techniques studied theocclusal plane was either elevated or depressed whichintern results in altered occlusal contacts. Figure 6 showsthe variation range, mean discrepancy of occlusal plane

and standard deviation of the different impressiontechniques. The values for impression techniques

Figure 1: Microcator Figure 2: Metal block placed on the die model

Figure 3: Instrument in position on the metal block Figure 4:Measurement of an unprepared tooth

Figure 5: Measurement of a prepared tooth

Figure 6: Discrepancy of range, mean and SD of different impression

techniques



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25Indian Journal of Oral Sciences Vol. 6 Issue 1 Jan-Apr 2015

I, II, III and IV were 0.831, 1.033, 1.085 and 0.598respectively.

Discussion

The science of occlusion encompasses more than mereinterrelationship of teeth. It involves the stomatognathic

system in health and disease.[10] Failure to restore toothanatomy can lead to disturbed occlusal function and painfulmuscles. If the restoration is to fit precisely the die on whichit is made must be accurate which requires an acceptableimpression.[8]A clinically acceptable impression technique isone according to Dr. Tjan et al.,[11]that produces an accuratedie which shows the least variation. In the present studyfour different commonly used elastomeric impressiontechniques (putty-reline and custom tray) were comparedin relation to the accuracy of the occlusal plane.

Addition silicon impression material was used to make

impression as this material was shown to be dimensionallystable with time, no reaction products are producedand polymerization is complete when the impression isremoved.[12]The impressions were poured with type IVdental stone as additional silicon (polyvinyl siloxane)material showed to have greater compatibility with type IVdental stone.[13]

Figure 6 shows the variation in the occlusal plane forthe impression techniques. Group III (space providedby polyethylene spacer) showed more variation (1.085)where as Group IV impression technique using customtray showed least variation (0.598). The present study isnot in accordance with Hung et al..[14] and Idris et al.,[6]who reported that impression accuracy is not techniquedependent.

Overall the relining technique showed more variation.This could be because of some errors during impressionprocedure as listed by (Barry Marshak) [15]which leadinaccurate impression: An excess bulk of wash material can result in dimensional

changes proportional to the thickness of the materialduring setting

Undercuts or projections into the putty affect the

accuracy of the impression.

Summary and Conclusion

This invitro study was conducted to evaluate and assess fourdifferent impression techniques in relation to the accuracyof the occlusal plane.

The following conclusions were drawn from this study: The single step technique using custom tray with 2

viscosities yielded the most accurate models from theimpressions

Among relining techniques the putty with spacer on theprepared area and relining produced more variations inocclusal plane.

However, the selection of a specific technique dependson evaluation of an individual patient and experience ofthe dentist.

References

1. Chee WW, Donovan E. Polyvinyl siloxane impression materials:

A review of properties and techniques. J Prosthet Dent 1992;68:728-32.

2. Millar B. How to make a good impression (crown and bridge). Br Dent

J 2001;191:402-5.

3. Messing JJ. Copper band technique. Br Dent J 1965;119:246-8.

4. Gelbard S, Aoskar Y, Zalkind M, Stern N. Effect of impression materials

and techniques on the marginal fit of metal castings. J Prosthet Dent

1994;71:1-6.

5. hongtham machat S, Moore BK, Barco M 2nd, Hovijitra S,

Brown D, Andres CJ. Dimensional accuracy of dental casts: Influence of

tray material, impression material, and time. J Prosthodont 2002;11:98-108.

6. Idris B, Houston F, Claffey N. Comparison of the dimensional accuracy

of one- and two-step techniques with the use of putty/wash addition

silicone impression materials. J Prosthet Dent 1995;74:535-41.

7. Haim M, Luthardt RG, Rudolph H, Koch R, Walter MH, Quaas S.

Randomized controlled clinical study on the accuracy of two-stage putty

and wash impression materials. J Prosthet Dent 2009;22:296-301.

8. Herbert SL. Fundamentals of fixed Prosthodontics. Illinois: Quintessence

Publishing. co. inc. 3rdEdition,1997; 281-304.

9. Livaditis GJ. Comparision of new matrix system with traditional fixed

prosthodontics impression procedures. J Prosthet Dent 1998;79:200-207.

10. Malone WF, ylman SD, Koth DL. ylmans Teory and pract ice offixed Prosthodontics. 8thed. Missouri: Ishiyaku Euro America; 1989.

p. 237-54.

11. jan AH, Whang B, jan AH. Clinically oriented assessment of the

accuracy of three putty-wash silicones impression techniques. J Am Dent

Assoc 1984;108:973-5.

12. Johnson GH, Craig RG. Accuracy of addition silicones as a function of

technique. J Prosthet Dent 1986;55:197-203.

13. Schelb E, Mazzocco CV, Jones JD, Prihoda . Compatibility of type IV

dental stones with polyvinyl siloxane impression materials. J Prosthet

Dent 1987;58:19-22.

14. Hung SH, Purk JH, ira DE, Eick JD. Accuracy of one-step versus two-

step putty-wash addition silicon impression technique. J Prosthet Dent

1992;67:583-9.

15. Marshak B, Assif D, Pilo R. A controlled putty- wash impression

technique. J Prosthet Dent 1990;64:635-6.

How to cite this article: Thippanna RK, Meshramkar R, Sajjan S.

A comparative study to evaluate different impression technique in

relation to accuracy of the occlusal plane in xed partial denture. Indian

J Oral Sci 2015;6:22-5.

Source of Support:Nil, Conict of Interest:None declared


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