The Influence of putty wash impression technique on dimensional accuracy of 2 commercially available vinyl poly siloxane impression materials - An Invitro study

Kanmani, M (2007) The Influence of putty wash impression technique on dimensional accuracy of 2 commercially available vinyl poly siloxane impression materials - An Invitro study. Masters thesis, Tamilnadu Government Dental College and Hospital, Chennai.

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Abstract

INTRODUCTION Impression is an imprint of the teeth and adjacent structures for uses in dentistry. Impression materials in one substance or combination of substances are used for making an impression or negative reproduction. Various impression techniques are used in making a negative likeness (GPT-4). History reveals that waxes were used as an Impression material during 18th & 19th century. Later in 19th century plaster and compound were used for making impression. But both plaster and compound do not have sufficient elastic property to register the undercut areas. In various stages Agar, Zinc Oxide Eugenol, alginate and elastomers were developed for impression making. These materials have been modified chemically and physically for use in dentistry. Initially elastomer group consisted exclusively of polysulfide & condensation silicone impression material. Polysulfide and condensation silicone impression materials sets by an condensation polymerization reaction leading to release of volatile by products which there by causes shrinkage. AIM OF THE STUDY : The aim of the study is to assess the 1. Accuracy of 2 commercially available vinyl poly siloxane impression materials. 2. Accuracy among one step putty wash and 2 step putty wash impression technique for the two impression materials. 3. Accuracy within 2 step putty wash impression technique employing various forms of spacers such as a. Polyethylene sheet, b. Scrapping, c. Coping. MATERIALS AND METHODS : The accuracy of the impression was evaluated indirectly by measuring several clinically relevant dimensions on gypsum casts recovered from impressions of a master model. A machined standard mild steel die was made to serve as a model, which simulating 3 unit fixed partial denture. Reference lines were inscribed on the top and axial surfaces of abutments, which are used to assess the dimensional changes with help of traveling microscope. A perforated tray was fabricated from the same mild steel. Orientation grooves were placed both on the tray and the metal model to ensure uniform seating for each-impression. SUMMARY : A precise impression is necessary for fabricating an accurately fitting cast restoration. This is one factor that determines the restorations longevity. In this study two commercially available poly vinyl siloxane impression materials were selected. Poly vinyl siloxane impression materials are extremely popular because of their combination of excellent physical properties, handling characteristics and dimensional stability. Its excellence clinical features remain unaffected if simple measures are guarded. This study presents several impression techniques using 2 commercial available PVS and recommends, the one technique that provides the most accurate impression, utilizing the superior qualities of the PVS. The 2 materials used were 3 m Poly vinyl siloxane and ivoclar vivadent PVS. The impression technique which was used to find the accuracy was one step putty wash simultaneous technique, 2 step putty wash scrapping technique, 2 step putty wash poly ethylene spacer technique, and 2 step putty wash 2 mm coping technique. The 2 PVS material was named as Group I and Group II. The technique were classified as Gr.IA, Gr.IB, Gr.IC, Gr.ID, Gr.IIA, Gr.IIB, Gr.IIC, Gr.IID. GroupI represents 3M PVS material. Similarly Gr.IA represents one step putty wash simultaneous impression technique. Gr.IB represents 2 step putty wash scrapping technique, Gr.IC represents 2 step putty wash polyethylene spacer technique, Gr.ID represents 2 step putty wash 2 mm coping technique as mentioned above with Ivoclar vivadent material. The accuracy of the impression technique was measured from the stone model using traveling microscope and compared with master model. One way analysis of variance (ANOVA) was used to compare the differences among the 4 putty wash impression techniques and the master model for each measurement. The results of the study showed that there was a significant difference between one step and 2 step putty wash impression technique. In the one step impression technique, where no control of wash bulk and thickness exists, is considered to be the least accurate impression method. Furthermore, the direct contact between the less refined putty material and the tooth preparation, as well as the high prevalence of air bubble entrapment, seriously compromises restoration longevity. The 2 stage impression technique has proved to produce the most accurate and reliable impression due to complete control of the wash bulk and thickness. Among the 2 step putty wash impression technique like 2 step scrapping, 2 step polyethylene spacer and 2 step 2 mm coping technique, 2 step putty wash coping technique was the most accurate for fabricating restorations since in this technique 2 mm coping uniform bulk size prevents differential setting contraction and uneven dimensional changes. Using a “putty tray” at the first stage with a predetermined Space encircling the abutment will allow the wash to flow to its ideal uniform size at the second stage. Among the 2 polyvinyl siloxane impression material 3 M polyvinyl siloxane material produced better results with 2 step technique is accurate.Virtual PVS material showed comparatively better results in 1 step technique. From this study it is concluded that the 2 step putty wash impression technique with controlled bulk wash is essential for fabricating accurate stone dies. CONCLUSION : Within the limitations of the study it can be concluded that; 1. There is significant difference existing between one step and 2 step putty wash impression technique.2 step putty wash method irrespective of spacer technique used produced more dimensionally stable dies than one step technique. 2. There is significant difference existing among two step putty wash impression technique when different spacers are used for wash material. 2 mm coping spacer for wash material produced stone dies with minimal dimensional change compared to other spacer technique. 3. Among the 2 PVS material 3M PVS material produced better results, with two step technique than virtual material. 4. Virtual PVS material showed comparatively better results in one step technique when compared to 3M PVS material.

Item Type: Thesis (Masters)
Uncontrolled Keywords: putty wash impression technique, dimensional accuracy, vinyl poly siloxane impression materials.
Subjects: DENTAL > Prosthodontics and Crown and Bridge
Depositing User: Kambaraman B
Date Deposited: 19 Jan 2018 01:26
Last Modified: 28 Oct 2018 16:14
URI: http://repository-tnmgrmu.ac.in/id/eprint/5487

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