dr sasikumar university-synopsis presentation

8/8/2019 Dr Sasikumar University-synopsis Presentation

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Presented by,

DR. SASIKUMAR.T.P.

1ST YR PG STUDENT

DEPT OF PROSTHODONTICS


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A COMPARATIVE EVALUATION OF DIMENSIONAL

ACCURACY OF CASTS RESULTING FROM PUTTYWASH ADDITION

SILICONE IMPRESSIONS MADE USING DIFFERENT IMPRESSION

TECHNIQUES- AN INVITRO STUDY.

Guided by

DR.K. KAMALAKANTH SHENOY. M.D.S DR. SANATH SHETTY. M.D.S

PROFESSOR AND HEAD PROFFESSOR AND GUIDE

DEPT. OF PROSTHODONTICS DEPT. OF PROSTHODONTICS


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NEED FOR THE STUDY:

Accuracy of an impression is very critical for the success

of any prosthesis. This accuracy largely depends on the

impression techniques and also the inherent quality of the

impression material to record finer details. It is also a great

advantage if the impression maintains the accuracy for a

period of time.


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The addition silicone impression materials have been

reported to be the most accurate and dimensionally stablewith the combination of excellent physical properties and

handling characteristics.1

For the purpose of fabricating precise fitting prosthesis,

like cast partial dentures, fixed partial dentures, implant

prosthesis, etc, an accurate gypsum cast, reproduced from anaccurate and dimensionally stable impression is a basic

prerequisite.


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Accuracy of gypsum casts indirectly depends on factors

like - type of impression material, impression techniques,

thickness of wash material (light-body) and time of pour.

Putty-wash technique has been recommended for

addition silicone impression materials. It can be made as a

one-step or a two-step technique. Advantages of the one-step

technique include reduced chairside time and saving on the

consumption of lightbody. An advantage of the putty-wash

two-step impression technique is that the impression of the

teeth can be captured with the wash material (lightbody).


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Some researchers claim that impression materials have

improved to such an extent that accuracy may be

controlled more with technique than by the material itself.

Whereas others reported that impression technique does

not affect the accuracy2,3.

Undesirable dimensional changes and stone model

inaccuracies which resulted from excessive or uncontrolledthickness of the wash impression material have been

reported,4,5.


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Delay in the pour of impression is of interest clinically,

because delayed pouring of cast is often desired. Accuracy

of the gypsum casts are also influenced by the time of pour6.

A lot of research has gone into investigating, as to which

brand of impression material is the most accurate.


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Very little studies have been done to assess the accuracy

of the various techniques involved in making impressions

and also the ideal time interval after which casts could be

poured to achieve optimum accuracy.

So the evaluation of dimensional accuracy of cast made

form addition silicone impression using one step and two

step putty/wash technique with different wash (light-body)

thickness at different time intervals are subjected in this

study.


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6.2. REVIEW OF LITERATURE

In one study6, accuracy of four types of rubber impression materials compared

with time of pour and a repeat pour of models was done indirectly by measuring the

seven dimensions on the improved stone models recovered from the impression of

the master model. They reported that there was little change in dimensions among

abutment preparations for all materials, for all time of pour, with a repeat pouring.

The vertical dimensions of stone posts were, in general shorter than the standard for

all materials, with the addition silicone demonstrating the smallest changes. The

addition silicone and condensation silicone demonstrated the best recovery from

under cuts and the least change in dimensions between the initial and second pour ofan impression. The addition silicone and polyether were the least affected with

delays of 1, 4 and 24 hours in pouring the impression.


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A study7 was conducted on accuracy of addition silicones as a function of

technique. They investigated four addition silicone impression material and one

condensation impression material with 3 techniques, ie, putty wash, single mix and double

mix. They concluded that the same accuracy was achieved with all techniques (ie, putty

wash, single mix and double mix) when addition silicones were used, where as the putty

wash technique produced the most accurate results for the condensation silicone.

A study2

was done to compare the accuracy of one step putty wash with two

step putty wash impression techniques. Five addition silicone impression materials were

tested. A stainless steel model containing two full crown abutment preparations was used as

the positive control. Five replications of one-step and two- step putty- wash impression of

the master model were made for each test material. Accuracy of the material was assessedby measuring six dimensions on stone dies poured from impressions of the master model

and concluded that accuracy of addition silicone impression material is affected more by

material than technique.


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In another study3 putty-wash one-step and two-step techniques for making

addition silicone impression were carried out. The results indicated that the interabutment

distances increased slightly compared with the control for both the techniques. Though

statistically significant differences in accuracy can be found between the techniques, these

were not of sufficient magnitude to warrant the strong recommendation of one technique

over the other. Neither techniques resulted in dies that deviated sufficiently from the master

model to cause clinically important difficulties in the fit of castings.

A study4 was done on three puttywash impression techniques 1) one step putty-

wash impression 2) two-step with 2mm relief for wash material 3) two-step putty with poly

ethylene spacer. The accuracy was assessed by measuring the dimensions on stone dies

poured from impression of the master model. The study concluded that twostep 2mm

putty wash impression technique was most accurate in dimensions when compare to either

techniques because the controlled wash bulk compensates for the shrinkage of the putty

material.


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A study5 was carried out to determine effect of wash bulk on

the accuracy of polyvinyl siloxane putty-wash impressions.

Variations in the bulk of wash in a putty wash impression technique

can result in dimensional changes proportional to the thickness of

the wash material during setting. So to determine the amount of

wash necessary to achieve accurate stone models while using a

two-step putty- wash impression technique with poly vinyl siloxane

impression material, wash thickness of 1mm, 2mm and 3mm are

subjected to study. The conclusion of the study was, wash thickness

of 1 to 2mm are most accurate for fabrication of stone dies when

using polyvinyl siloxane impression material with the two step

putty-wash impression technique.


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AIM OF THE STUDY

To evaluate the dimensional accuracy of casts resulting

from addition silicone impressions made from 1 step

putty/wash and 2 step putty/wash impression techniques.


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SOURCE OF THE DATA

150 impressions of the stainless steel master

die will be made from EXPRESSTMXT (3M

ESPE) penta putty VPS impression material

using PENTAMIXTM ( 3 M ESPE ) automatic

mixing unit and EXPRESSTM XT (3M

ESPE) light body VPS impression material

using auto mix syringe.


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These 150 impressions will be poured with ELITE

ROCKTM Type IV die stone from ZhermackRto

procure 150 stone dies.

TRAVELING MICROSCOPE will be used for

measuring the interabutment distance and

occlusogingival distance on these 150 stone dies.


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METHOD OF COLLECTION OF DATA

Fabrication of stainless steel die :

A machined standard stainless steel die which

will be the control for all measurements will be

fabricated to simulate two full crown fixed partial

denture abutment preparations.


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The dimensional details6

are as follows :

1. Distance between the abutment preparations : 30 mm

2. Gingival diameter of the abutment preparations : 10 mm

3. Occlusogingival height of the abutment preparations : 10 mm

4. Occlusogingival taper of the abutment preparations : 60

5. Platform thickness : 5mm


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Reference lines will be inscribed on the occlusal

and axial surfaces of the abutment preparations for

the purpose of measurements. A cross marking will

be made at the centre of the occlusal surface of the

abutment preparations for the purpose of measuring

the interabutment distance of the stone dies.


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Circumferential reference lines will be made on

axial surface of abutment preparation 1mm short of

the occlusal surface and base. A vertical line will be

inscribed along occlusogingival direction joining

the two circumferential lines. This will be used for

assessing the occlusogingival dimension of the

stone dies.


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Fabrication of the impression tray:

A perforated stainless steel tray with a handle

will be fabricated of 2mm thickness. A clearance

of 4mm is provided for the putty material between

the abutment and the inner surface of the tray.8, 9


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Fabrication of spacers for the wash material :

a. Thickness of stainless steel spacer :2mm

b. Thickness of stainless steel spacer :1mm

c. Polyethylene spacer :50microns(approx)


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Impression making :

Group 1: One step putty/wash technique:

Perforated tray will be loaded with putty from the

PENTAMIXTM. Simultaneously the light body will

be injected onto the stainless steel dies using automix

syringe.


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30 impressions will be thus made using this technique.

These 30 impressions will again be subgrouped into 5,

each subgroup containing 6 impressions. Each subgroup

will be poured with Type IV die stone at 5 different timeintervals.

The tray will be seated onto the dies with a gentle finger

pressure. After the material has set, the impression will

be gently removed from the die.


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Group 2-A : Two step putty /wash technique

without spacer: Perforated tray will be loaded with putty from the

PENTAMIX.TM. Then the tray will be seated onto the die

with gentle finger pressure.

After the putty impression material sets, impression will

be carefully removed and loaded with the light body from

the automix syringe. The tray is again seated back onto

the die.


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After the set of the light body, the impression will be

gently removed from the die.




will be poured with Type IV die stone at 5 different time

intervals.


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Group 2-B: Two step putty/ wash technique using

polyethylene spacer: A polyethylene spacer will be closely adapted on the

abutment preparations.

Perforated tray will be loaded with the putty from the

PENTAMIXTM. Then the tray will be seated onto the die

with gentle finger pressure. After the material has set, the

impression will be removed from the die.


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Once the lightbody is set the impression will be gently

removed from the die.


These 30 impressions will again be subgrouped into 5,each subgroup containing 6 impressions. Each subgroup

will be poured with Type IV die stone at 5 different time

intervals.

The polyethylene spacer is then removed from the

impression and the light body from the automix syringe is

loaded in the impression. The tray will be then reinserted

onto the die.


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Group2-C: Two -step putty/wash technique using 1mm thick metal

spacer:

A 1mm thick metal spacer will be placed on the abutment

preparations.


PENTAMIXTM. This tray will then be seated onto the die with

gentle finger pressure. After the material has set, the impression

will be removed along with the metal spacer.

The metal spacer will be separated from the impression and

light body from the auto mix syringe will be loaded into the

tray. This tray will be then seated onto the die.


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Once the material has set, the impression will be gently

removed from the die. 30 impressions will be thus made

using this technique.



will be poured with Type IV

die stone at 5 different timeintervals.


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Group 2-D: Two step putty/wash technique using 2mm thick

metal spacer:

A 2mm thick metal spacer will be placed on the abutment

preparations.


PENTAMIXTM. This tray will be then seated onto the die with

gentle finger pressure. After the material has set, the impression

will be removed along with the metal spacer.

The metal spacer will be separated from the impression and light

body from the auto mix syringe will be loaded into the tray. This

tray will be then seated onto the die.


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Once the material has set, the impression will be gently

removed from the die. 30 impressions will be thus made

using this technique.



will be poured with Type IV

die stone at 5 different timeintervals.


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5) Preparation of stone dies :

The 5 subgroups(consisting of 6 impressions) of

Group 1, Group 2-A, Group 2-B, Group 2-C and Group

2-D will be poured with type IV dental stone at time

intervals of 0 hour, 1 hour, 6 hours, 24 hours and 48

hours respectively.


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The stone will be mixed initially with hand followed by

mechanical mixing under vacuum as recommended bythe manufacturer. (A ratio of 19-20 ml of water to 100 gm

ofELITE ROCKTM stone will be used).

The mix will be poured into the impression and will be

kept on vibrator to avoid air entrapment.

After 1 hr the stone dies will be recovered from theimpressions.

A total of 150 stone dies will be thus obtained.


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Assessment of accuracy :

The dimensional accuracy of impression will be determined by

measuring the

a) The interabutment dimension and

b) The occlusogingival dimension of the recovered stone dies usinga traveling microscope capable of measuring dimensions up to

0.001mm.

The results thus obtained will be compare with stainless steelmaster die and then tabulated and subjected to statistical analysis

using TWO WAY ANOVA test.


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LIST OF REFERENCES

1) Craig RG. Review of dental impression materials. Adv Dent Res 1988; 2:51-64.

2) Shirley H.hung, John H.Purk, Daniel E.Tira, J.David Eick. Accuracy of one step

versus two- step putty wash addition silicone impression technique.J PROSTHET DENT

.1992;67:583-58.

3) ) Badr Idris, Frank Houston ,and Noel Claffey. 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.

4) Joseph Nissan, Tamar Brosh, and David Assif. Accuracy of three polyvinyl siloxane

putty-wash impression techniques. J PROSTHET DENT. 2000;83:161-165.

5) J,Nissan,M.Gross, A.ahifman and A.Assif..Effect of wash bulk on the accuracy of

polyvinyl siloxne putty-wash impressions. Journal of oral rehabilitation 2002;29:357-361.


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6) Glen H.Johnson ,and Robert G.Craig .Accuracy of four types of

rubber impression materials compared with time of pour and a repeat pour of models. J PROSTHET DENT. 1985;53:484-490.

7) Glen H.Johnson ,and Robert G.Craig .Accuracy of addition

silicones as a function of technique. J PROSTHET

D

ENT.1986;55:197-203 8) Reisbick, M . H., and Matyas, J. The accuracy of highly filled

elastomeric impression materials. J PROSTHET DENT.1975; 33 : 67.

9) Asgar, K.: Elastic impressions materials. Dent Clin North Am .

1971;15: 81.


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