Microsoft Word - 94 2020.docx Vol 8, No 1 (2020) ISSN 2167-8677 (online) DOI 10.5195/d3000.2020.94 http://dentistry3000.pitt.edu New articles in this journal are licensed under a Creative Commons Attribution 4.0 United States License. Comparative evaluation of retentive strength of polyvinyl siloxane im- pression materials to custom tray using different tray adhesives: An in vitro study Jinsa P Devassy1, Nishna Pradeep2, A V Sreekumar2, Jimmy George1, Jittin James3, Jacob George1 1. Department of Prosthodontics, Mar Baselios Dental College, Kerala, India 2. Department of Prosthodontics, Kannur Dental College, Kerala, India 3. Department of Prosthodontics, Indira Gandhi Dental College, Kerala, India Abstract The reten(ve strength of the impression material to the impression tray is an important factor that can affect the quality of the final impression. Separa(on of the impression from the tray or tearing of the im- pression while removing from the mouth could be one of the reasons for distor(on. It is impera(ve to know the most effec(ve tray adhesive which can be used with different brands of rubber-based impression ma- terial. So, this study was directed to compare the different tray adhesives that can be effec(vely used in our day-to-day clinical prac(ce. Keywords: Tray adhesive, Polyvinyl siloxane impression material, Reten(ve strength. Cita/on: Devassy JP, et al. (2020) Compara've evalua'on of reten've strength of polyvinyl silox- ane impression materials to custom tray using dif- ferent tray adhesives: An in vitro study. Den(stry 3000. 1:a001 doi:10.5195/d3000.2020.94 Received: March 25, 2020 Accepted: April 25, 2020 Published: May 4, 2020 Copyright: ©2020 Devassy JP, et al. This is an open access ar(cle licensed under a Crea(ve Commons AVribu(on Work 4.0 United States Li- cense. Email: jinsa.pd@gmail.com Introduction The bond strength of an impres- sion material to tray is essential and in case of rubber-based im- pression materials the retention is mainly achieved via chemical ad- hesion. To obtain an accurate im- pression, the impression material must be securely attached to the tray. If the material is not secured to tray firmly while retrieving from the mouth, it will result in im- proper impression and therefore cause distorted die, wax pattern and casting. [1,2] The polyvinyl siloxane impression materials are addition reaction sili- cone elastomers which were first introduced in the 1970s. [3] In the past decade, these materials have occupied a large share of the im- pression material market. They possess good physical properties and handling characteristics. They have achieved a high level of den- tist and patient acceptance as they are clean, odorless and tasteless. [3] An effective adhesive is especially indicated when the impression material has a high tear resistance, so that it can effectively be re- moved from undercuts. The chem- istry of the adhesives usually are polydimethyl siloxane and ethylsil- icate. The adhesive reacts with the surface of the tray material and forms a chemical bond to the tray and to the impression material. It is usually recommended to wait Compara(ve evalua(on of reten(ve strength of polyvinyl siloxane impression materials to custom tray using different tray adhesives: An in vitro study Vol 8 No 1 (2020) DOI 10.5195/d3000.2020.94 http://dentistry3000.pitt.edu for ten to fifteen minutes after ap- plication of the adhesive before making the impression. This allows time for the solvent to react with the tray material. Sulong and Setchell [4] demonstrated that roughening the surface of the im- pression tray will significantly im- prove the effectiveness of polyvi- nyl siloxane adhesives. Impression tray adhesives are ap- plied as a spray, or are manually applied using a brush. Prior to tray loading, the adhesive requires a lengthy drying time. Suggested drying times for adhesives vary widely among manufacturers. Also, adhesive strength of differ- ent tray adhesive varies considera- bly and hence in our clinical prac- tice the knowledge of adhesive strength of various impression ma- terials with certain adhesive is of utmost important for the success of the impression and final result. Permanent distortion occurs when the impression material does not adhere to the tray. Ideally, the im- pression material tears instead of undergoing considerable distor- tion before it is released from the undercut. If the material is not ad- equately retained in the impres- sion tray when it is removed from the mouth, it may be a potential source of error. The most consist- ently accurate impression is ob- tained with the adhesive lined resin custom tray. Each class of elastomeric impression material has its own specific adhesive. Metal and plastic stock trays are used routinely for dental impres- sions, especially with the putty- wash systems. However, heat- acrylic cured trays with an adhe- sive is recommended for addi- tional silicones [4]. The purpose of this study is to compare the retentive bond strength of the three commonly available brands of poly vinyl silox- ane impression materials (Aquasil, Virtual and ExpressTM) to acrylic tray using universal tray adhesive (Zhermarck) and adhesives sup- plied by the respective manufac- tures using the universal testing machine. Materials Figure 1. Armamentarium. Armamentarium (Fig.1): • Acrylic discs IMPRESSION MATERIAL: • Virtual Heavy Body Impres- sion Material-Regular Set (Vivadent) • Aquasil Ultra Heavy (Dentsply) • Express TM XT PentaTM H (3M ESPE) TRAY ADHESIVES: Brand specific tray adhesives: • Virtual • Aquasil • 3M ESPE • Universal tray adhesives (Zhermarck) Methods The polyvinyl siloxane heavy body impression materials selected were Aquasil, Virtual, ExpressTM and these formed the groups I, II and III. Group I: Aquasil impression mate- rial. Group II: Virtual impression mate- rial. Group III: Express TM impression material. The tray adhesives selected were universal tray adhesives (Zher- marck) & adhesives of respective impression materials. The main groups were further subdivided based on the adhesives used. Total sample size used were 135. The procedures were divided into five steps: Step 1: Preparation of the acrylic discs. Step 2: Application of adhesives. Step 3: Placement of disc on uni- versal testing machine. Step 4: Injection of heavy body material to acrylic disc. Step 5: Checking the retentive strength of impression material. Compara(ve evalua(on of reten(ve strength of polyvinyl siloxane impression materials to custom tray using different tray adhesives: An in vitro study Vol 8 No 1 (2020) DOI 10.5195/d3000.2020.94 http://dentistry3000.pitt.edu Step 1: Preparation of acrylic disc For preparing the acrylic disc a wax pattern of diameter of 64mm and height 9mm was made using modeling wax. Simultaneously another cylin- drical wax pattern of diameter 28mm height and 12mm diam- eter was made for perpendicu- lar shaft. The wax pattern was invested and acrylisation was done using compression mold- ing technique. Then heat cured acrylic disc and shaft thus ob- tained were finished and smoothed using 320-grit sili- cone-carbide paper to stand- ardize surface roughness. The heat cured acrylic cylinder shaft was attached to center of the heat cure acrylic disc using self-cure acrylic. Three pairs of same kind were fabricated for convenience purpose. For each time after the loading, ethanol was used for cleaning the acrylic disc as recommended by the manufacturers of tray adhesives. Step 2: Application of adhe- sives on disc Based on the adhesives used the main group was divided into subdivisions A, B and C [Table 1]. Subdivision A of main Groups I, II and III was kept as control group. The adhesive was not applied to all the samples tested in this subdivision. In subdivision B of Group I, Caulk tray adhesives [brand specific] was applied on the disc. The adhesive was applied using a brush as thin as possi- ble [Fig.2]. Only a single coat was applied and it allowed to dry for 5 minutes*. In Group II subdivision B, Vir- tual tray adhesives was applied using brush as thin as possible and allowed to dry for 3 minutes*. In Group III subdivison B, 3M ESPE tray adhesive was applied as thin as possible and allowed to dry for 5 minutes*. In subdivision C of all Groups, the universal tray adhesive (Zhermarck) was applied on the acrylic disc in the same manner. It was allowed to dry for 2 minutes*. *Time as recommended by the manufacturer. Figure 2. Applica3on of adhesives. Placement of disc on universal testing machine Universal testing machine Universal testing machine (model LR5K plus) consists of upper compartment and lower compartment. It is an auto- matic computerized machine for high accuracy load meas- urements with LCD display [Fig. 3]. It is also connected to a personal computer for pro- gramming and data collection. It is operated using software called Nexygen. Once loaded this machine itself will auto- matically align the disc for measurements. After the application of tray adhesives, the acrylic disc was placed on lower compartment and another acrylic disc was placed on upper compartment. Then ensured the acrylic disc aligned properly. Figure 3. Universal Tes3ng Machine [LR5K PLUS]. Injection of heavy body mate- rial Heavy body material was in- jected [Fig. 4] on the lower disc and then upper disc low- ered until a space of 4mm [Fig. 5]. Care was taken to ensure that the heavy body material completely occupied in this 4mm space between the Compara(ve evalua(on of reten(ve strength of polyvinyl siloxane impression materials to custom tray using different tray adhesives: An in vitro study Vol 8 No 1 (2020) DOI 10.5195/d3000.2020.94 http://dentistry3000.pitt.edu acrylic discs [Fig. 6]. Impres- sion material used was differ- ent for each group [Table 1]. Figure 4. Injec3on of heavy body mate- rial. Figure 6. Penta mix dispenser. In Group I the Aquasil impres- sion material injected using mixing gun and the material was allowed to polymerize for 5 minutes*. In Group II, Virtual impression material dispensed using mix- ing gun and allowed to set for 4.30 minutes*. Table 1. Grouping of selected impression materials with its subdivisions based on tray adhesives used. In case of Group III for ExpressTM, pentamix dispenser [Fig. 6] was used and allowed to set for 3.30 minutes* * Time as recommended by the manufacturer. Checking the retentive strength The test specimens were tested in tensile mode at a cross- head speed of 6mm/min until separation failure [Fig. 7] occurred and maxi- mum force of separation is auto- matically recorded and saved to the computer both numerically and graphically [Fig.8]. The study was conducted on re- maining samples in a similar man- ner and results were statistically analyzed using One Way ANOVA and Tukey Post-Hoc test. Figure 7. Impression material separa3on at maximum load. GROUP I 1. AQUASIL [45 samples] 2. SUB DIV A 3. WITHOUT TRAY ADHESIVE 4. 15 samples 5. SUB DIV B 6. CAULK TRAY ADHESIVE 7. 15 samples 8. SUB DIV C 9. ZHERMARCK TRAY ADHESIVE 10. 15 samples GROUP II VIRTUAL [45 samples] 11. 12. SUB DIV A 13. WITHOUT TRAY ADHESIVE 14. 15 samples 15. SUB DIV B 16. VIRTUAL TRAY ADHESIVE 17. 15 samples 18. SUB DIV C 19. ZHERMARCK TRAY ADHESIVE 20. 15 samples 21. GROUP III 22. EXPRESS T M [45 samples] 23. SUB DIV A 24. WITHOUT TRAY ADHESIVE 25. 15 samples 26. SUB DIV B 27. 3M ESPE TRAY ADHESIVE 28. 15 samples 29. SUB DIV C 30. ZHERMARCK TRAY ADHESIVE 31. 15 samples Figure 5. Heavy body material between the acrylic discs. Figure 8. Computer generated graph according to the maximum force of separa3on failure. Compara(ve evalua(on of reten(ve strength of polyvinyl siloxane impression materials to custom tray using different tray adhesives: An in vitro study Vol 8 No 1 (2020) DOI 10.5195/d3000.2020.94 http://dentistry3000.pitt.edu Results On comparison Aquasil with uni- versal tray adhesive showed greater retentive strength than Aquasil with brand specific tray adhesive and Aquasil without tray adhesive [Table 2]. On comparison Virtual with uni- versal tray adhesive showed greater retentive strength than Virtual with brand specific tray ad- hesive and Virtual without tray ad- hesive [Table 3]. On comparison ExpressTM with universal tray adhesive showed greater retentive strength than Ex- pressTM with brand specific tray adhesive and ExpressTM without tray adhesive [Table 4]. On applying One Way ANOVA, it was found that there was signifi- cant difference [p-value<0.001] in mean retentive strength between the study subgroups. The mean value of the retentive strength is highest for Virtual with universal tray adhesive and lowest for Aqua- sil without tray adhesive [Table 5]. Table 6 shows the summary of in- teractions of sub groups with each other. Comparing subdivisions A, B and C of Group I, II and III, the sub- division C showed the greatest re- tentive values than subdivision B and subdivision A. When compar- ing Group I, II, and III, the Group II showed the greatest retentive val- ues than Group I and Group III. Table 2. Maximum force of separa6on failure in group I in Newton [N] Table 3. Maximum force of separa6on failure in group II in Newton [N] Table 4. Maximum force of separa6on failure in group III in Newton [N] Compara(ve evalua(on of reten(ve strength of polyvinyl siloxane impression materials to custom tray using different tray adhesives: An in vitro study Vol 8 No 1 (2020) DOI 10.5195/d3000.2020.94 http://dentistry3000.pitt.edu Table 5. One way anova test to compare the reten6ve strength of the subdivisions. Discussion The impression adhesives used for silicone impression materials con- tain polydimethyl-siloxane or a similar reactive silicone, and ethyl silicate. Polymethylsiloxane of adhesives bonds to the silicone impression material whereas ethylsilicate forms a hydrated sil- ica that bonds to the impression tray material physically. The vola- tile solvent in the form of ethyl ac- etate reacts with the acrylic tray material to create microporosities on the tray material so that the adhesive physically and mechani- cally bonds with it. Sulong and Setchell [3] studied the properties of tray adhesives of ad- dition polymerizing silicones to im- pression tray materials. They Number of values Mean Std. Deviation Lower 95% CI Upper 95% CI F p value Grp I Subdiv A Aquasil without tray adhe- sive 15 250.6 15.85 241.9 259.4 1166 <0.001 Subdiv B Aquasil brand specific tray adhesive 15 704.2 26.41 689.6 718.9 Subdiv C Aquasil universal tray ad- hesive 15 887.5 12 880.9 894.2 Grp II Subdiv A Virtual without tray adhe- sive 15 501.6 48.34 474.8 528.3 Subdiv B Virtual brand tray adhesive 15 805 21.43 793.2 816.9 Subdiv C Virtual universal tray adhe- sive 15 891.3 8.801 886.4 896.2 Grp III Subdiv A Express tm without tray adhesive 15 351.7 20.47 340.3 363 Subdiv B Express tm brand tray ad- hesive 15 511.3 11.74 504.8 517.8 Subdiv C Express tm universal tray adhesive 15 710.4 41.03 687.7 733.1 Compara(ve evalua(on of reten(ve strength of polyvinyl siloxane impression materials to custom tray using different tray adhesives: An in vitro study Vol 8 No 1 (2020) DOI 10.5195/d3000.2020.94 http://dentistry3000.pitt.edu reported that acrylic resin trays roughened with eighty grit sili- cone-carbide created highest strength and they also concluded that adhesives did not adhere well to chromium plated metal or plas- tic stock tray material. Samman [5] studied about impres- sion tray adhesives and reported that tray adhesives definitely improve the bonding of impres- sion material to the tray. Table 6. A cross table showing interaction of subgroups with each other by post-hoc tukey test p value. (*Significant P values). VS GROUP I GROUP II GROUP III SUB DIV A SUB DIV B SUB DIV C SUB DIV A SUB DIV B SUB DIV C SUB DIV A SUB DIV B SUB DIV C GROUP I SUB DIV A <0.001* <0.001* <0.001* <0.001* <0.001* <0.001* <0.001* <0.001* SUB DIV B <0.001* <0.001* <0.001* <0.001* <0.001* <0.001* <0.001* 0.999 SUB DIV C <0.001* <0.001* <0.001* <0.001* 0.999 <0.001* <0.001* <0.001* GROUP II SUB DIV A <0.001* <0.001* <0.001* <0.001* <0.001* <0.001* 0.984 <0.001* SUB DIV B <0.001* <0.001* <0.001* <0.001* <0.001* <0.001* <0.001* <0.001* SUB DIV C <0.001* <0.001* 0.999 <0.001* <0.001* <0.001* <0.001* <0.001* GROUP III SUB DIV A <0.001* <0.001* <0.001* 0.984 <0.001* <0.001* <0.001* <0.001* SUB DIV B <0.001* <0.001* <0.001* <0.001* <0.001* <0.001* <0.001* <0.001* SUB DIV C <0.001* 0.999 <0.001* <0.001* <0.001* <0.001* <0.001* <0.001* Compara(ve evalua(on of reten(ve strength of polyvinyl siloxane impression materials to custom tray using different tray adhesives: An in vitro study Vol 8 No 1 (2020) DOI 10.5195/d3000.2020.94 http://dentistry3000.pitt.edu Tjan and Sung [6] reported the sig- nificance of tray adhesives in case where the impressions were poured repeatedly, to minimize accidental separation of the im- pression from the tray. Though manufacturers have come out with its own tray adhesives for particular rubber-based impres- sion materials, previous literature [1,7] has reported that it might not be the best. Paint-on adhesive on medium body VPS is found to be effective. [5,7] Considering the above facts, the study was done to compare the ef- fectiveness of the universal tray adhesive, Zhermarck with the three commonly available medium consistency VPS impression mate- rials, Aquasil, Virtual and Ex- pressTM with their respective tray adhesives, Caulk, Virtual and 3M ESPE. Among the different groups stud- ied, heavy body impression mate- rial with universal tray adhesives [subdivision C] showed the highest value. In subdivision C, the tray ad- hesive used was Zhermarck tray adhesive. The results of the study agree with the findings of study done by Land7 et al. and Ashiwini et al. [1] In their study, they evalu- ated the bond strength of the three polyvinyl siloxane materials with a methacyrlate autopolymer- izing and light polymerizing tray material, using the adhesives rec- ommended by the manufactures of the impression materials and two universal adhesives (paint on and spray on). They reached the conclusion that paint on universal tray adhesives offers the ad- vantage of providing equal or su- perior adhesive bond strength for the three VPS impression materi- als to the autopolymerizing and light polymerizing tray materials tested, compared to the manufac- tures recommended adhesives. When comparing subdivision A [without tray adhesives] of all groups, group II [Virtual heavy body impression material] showed the greatest bond strength and it is statistically significant [Table 6, Graph 1]. Without using any tray adhesives retentive bond strength of Virtual heavy body impression material to acrylic resin tray mate- rial which was roughened by 320 grit silicon carbide was compara- tively higher than group I [Aquasil heavy body impression material] and group III [ExpressTM heavy body impression material]. When comparing the subdivision B [brand specific] of all groups, group II [Virtual heavy body im- pression material] showed the greatest bond strength than group I Aquasil heavy body impression material and Group III ExpressTM heavy body impression material [Table 6, Graph 1 ]. When compar- ing the subdivision C of all groups, there is no significant difference observed [Table 6]. As already stated, on comparison of the sub- divisions A, B and C, the subdivi- sion C [with universal tray adhe- sives] showed the greatest bond strength and is statistically signifi- cant [Table 6]. Variations in bond strength of im- pression material, adhesive agent GROUP I AQUASIL GROUP II VIRTUAL GROUP III EXPRESSTM 25 0. 6 50 1. 6 35 1. 7 70 4. 2 80 5 51 1. 3 88 7. 5 89 1. 3 71 0. 4 WITHOUT TRAY ADHESIVE BRAND SPECIFIC TRAY ADHESIVE UNIVERSAL TRAY ADHESIVE Graph 1. Bar diagram showing comparison of groups and subdivisions. Compara(ve evalua(on of reten(ve strength of polyvinyl siloxane impression materials to custom tray using different tray adhesives: An in vitro study Vol 8 No 1 (2020) DOI 10.5195/d3000.2020.94 http://dentistry3000.pitt.edu and custom tray material combi- nation is related to 1. The chemis- try of the adhesive agents 2. The surface chemistry of the resin tray material. [8] The significantly greater bond strengths of Zhermarck universal tray adhesive were probably at- tributable to the higher adhesive capability of these adhesives. The adhesion of the tray adhesives is achieved because of chemical ad- hesion between the impression material and methyl methacrylate tray material. Upon application of the tray adhesive, the carrier sol- vent present in the adhesive causes swelling of the outermost surface of the tray, thereby allow- ing the adhesive to penetrate and interact intimately with the im- pression material. The solvent then evaporates, leaving the en- tire tray surface covered with the adhesive, which is retained within the molecular network of the im- pression material. The retention of impression mate- rials to acrylic resin tray material ultimately depends on the ability of the solvent in the adhesive to dissolve the resin tray material. Thus solvent evaporation is con- sidered as the “setting” of the ad- hesive and is dependent on time, temperature and relative humidity [9]. It is generally recommended to wait for a few minutes after ap- plication of the adhesive before making the impression. This allows time for the solvent to react with the tray material. Therefore, in this present study, the better adhesive bond strength of Zhermarck universal tray adhe- sive in comparison with brand spe- cific tray adhesives may be at- tributed to the difference in the solubility of the tray material by the solvent present in the tray ad- hesive. From the results obtained in this study, Zhermarck universal tray adhesive with addition silicone im- pression material could be recom- mended as an ideal tray adhesive- impression material combination using acrylic resin tray material. When comparing among the heavy body impression materials selected, Aquasil, Virtual and Ex- pressTM, the Virtual heavy body im- pression material showed the greatest retentive strength to cus- tom tray with both brand specific tray adhesive and universal tray adhesive. Clinical Implications From the results of this study, it can be concluded that the univer- sal tray adhesive can be used in our clinical practice with most of the elastomeric impression mate- rials to attain maximum results without the need of the adhesive supplied by the respective manu- facturer. Acknowledgements Mr. Binish Jacob, Mr. Arun, Assistant Managers and Mr. Abilash, engineer in US based amphenol fci-oen Connentors Ernakulam, India. Dr. Sreekanth, Research Investigator, Manipal Institute of Medical Science, India. Dr. Imad Muhammed Ismail, Assistant Professor in Kannur Dental College, India. Dr. Shahanaz Hamza, Dr. Harsha Gangadharan, Dr. Navaz, House Surgeons Anjarakandy Dental College, India. Mr. Satheesh, Lab Assistant in Kannur Dental College, India. References 1. The bond strength of dif- ferent tray adhesives on vi- nyl polysiloxane to two tray materials: an in vitro study. Ashwini BL, Manju- nath S, Mathew KX. 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