|Year : 2015 | Volume
| Issue : 1 | Page : 1-5
Evaluation of effectiveness of intraoral delivery tip on single step impressions using monophase and two-phase impression materials: An in vivo study
S Gowri1, V Shenoy2, S Kannan3
1 Department of Prosthodontics, Subharti Dental College, Meerut, Uttar Pradesh, India
2 Department of Prosthodontics, AJ Institute of Dental Sciences, Mangalore, Karnataka, India
3 Department of Pharmacology, Subharti Medical College, Meerut, Uttar Pradesh, India
|Date of Web Publication||7-Jul-2015|
Department of Prosthodontics, Subharti Dental College, Meerut, Uttar Pradesh
Source of Support: None, Conflict of Interest: None
Background and Rationale: The precise fit of prosthesis depends on the impression materials and the technique used. Addition silicone impression materials being the user-friendly material are used in monophase and two-phase techniques. Considering the paucity of data on the effectiveness of intraoral delivery tip (IODT) on void, tear and bubble formation using monophase impression technique in stock tray and two-phase impression technique in custom tray the present study was initiated.
Materials and Methods: A total of 50 patients requiring single complete veneer crowns were enrolled. Monophase and two-phase impressions with and without IODT were made. Evaluation of the impression were made for tears, voids, and bubbles and alpha, beta, delta scores were given.
Results: A significant reduction in the total number of voids was observed with two-phase technique either with or without IODT. No significant differences were observed in the proportion of overall evaluation into alpha, beta and delta between monophase and two-phase with and without IODT. No significant association was seen in the overall evaluation between the two groups (monophase and two-phase) as compared using Chi-square test for independency and a trend in association between overall evaluation as tested using Chi-square for linear trend analysis.
Conclusion: Two-phase impression technique with the use of IODT produced decreased number of voids.
Keywords: Addition silicone, bubble, tear, void
|How to cite this article:|
Gowri S, Shenoy V, Kannan S. Evaluation of effectiveness of intraoral delivery tip on single step impressions using monophase and two-phase impression materials: An in vivo study. J Oral Res Rev 2015;7:1-5
|How to cite this URL:|
Gowri S, Shenoy V, Kannan S. Evaluation of effectiveness of intraoral delivery tip on single step impressions using monophase and two-phase impression materials: An in vivo study. J Oral Res Rev [serial online] 2015 [cited 2020 Dec 4];7:1-5. Available from: https://www.jorr.org/text.asp?2015/7/1/1/160152
| Introduction|| |
The precise fit of prosthesis depends on the impression materials and the technique used.  Obtaining an accurate replica along with the ability to identify and analyze an inaccurate impression is the key to success.  Greater emphasis is now being placed on the materials used in making impression especially addition polyvinyl siloxane and also the technique.  Addition silicone impression materials have high accuracy, little dimensional change after setting, moderately short working and setting time and excellent recovery from deformation on removal.  The two-phase impression technique is recorded using light body in syringe and medium, heavy or putty material used in custom tray. The introduction of single viscosity or monophase addition silicone, which can be used both as syringe and tray material avoids the need for double-mix.  Void formation and hydrophobicity remain an inherent problem in impression making. Because many impression materials lack the ability to wet oral tissues, this leads to void formation. , Though microscopic analysis of all impressions made day in and out is not possible, visible defects in impression have to be identified and analyzed. These visible defects include bubbles, voids and tears on critical areas like the finish line.  Intraoral delivery tips (IODT) attached to automatic mixing tips for ease of dispensing eliminates the need to load the material into an impression syringe, which theoretically will reduce the incorporation of air in the impression material.  Stackhouse inferred that tips with small diameter produced less number of voids compared to the ones with larger diameter.  Considering the paucity of data on the effectiveness of IODT on void, tear and bubble formation using single step impression technique using monophase impression material in stock tray and single step impression technique using two-phase impression material in custom tray, the present study was initiated.
| Materials and Methods|| |
Ethics and study participants
The study was conducted in the Department of Prosthodontics, Manipal College of Dental Sciences, Mangalore, after obtaining the Institutional Ethics Committee approval. Written informed consent was obtained from all the participants. Patients requiring complete veneer porcelain fused to metal crowns either in maxillary or mandibular, right and left posterior molar teeth, without any history of allergic reactions to materials used in the study were included.
A total of 50 participants were divided into two groups of 25 each. The first 25 belonged to group A in which Addition polyvinyl siloxane impressions (Aquasil™, Dentspy) were made without the use of IODT. In the second group B, addition polyvinyl siloxane impressions were made with the use of IODT. One impression with monophase material (group M) and one with two-phase materials (group T) utilizing heavy body on tray and light body syringed onto the preparation surface, was made for each subject in both the groups. Totally, 100 impressions were made, 25 monophase without IODT (MA), 25 two-phase without IODT (TA), 25 monophase with IODT (MB) and 25 two-phase with TODT (TB). A summary of the sample divisions has been mentioned in [Table 1].
Diagnostic casts were obtained from diagnostic impressions made with irreversible hydrocolloid (Tropicalgin™) material in a stock metal tray. Preoperative radiographs were taken for the tooth to be considered for the preparation, to rule out any pathology. Tooth preparation was done for a full coverage full veneer porcelain fused to metal crown with supragingival margin, and a well-defined shoulder finish line was obtained. After the preparation was completed isolation of prepared tooth using gingival retraction cord (UltraPak™) was done. The technique used was single cord technique impregnated with hemostatic solution containing tannic acid. Impression was made using a custom tray and stock metal tray on each subject. A custom tray was fabricated on the diagnostic cast with auto polymerizing acrylic resin (Rapid Repair™, Dentsply) with 2 mm wax spacer that provided space for the impression material. 
Single step impression using monophase and two-phase impression materials
Impression material was loaded into the automixing gun. If IODT was used, it was attached to the end of the mixing tip. The plastic disposable white/clear IODT of 5.2 mm in diameter was used to syringe material onto the prepared tooth. The impression tray was prepared by applying a thin layer of tray adhesive (Adhesive™, Coltene/Whaledent) 10 min before making the impression for adequate bonding. For the single step technique using monophase material, part of the material was syringed onto tooth, and part held on the tray. For the dual phase impressions, low-viscosity material was injected on the tooth surface, and high-viscosity material was placed in the impression tray. After injecting the low-viscosity material onto the tooth, the tray containing high-viscosity material was placed in the mouth and held with gentle pressure until the final set according to manufacturer's instructions. Tray must be seated within 1 min and 10 s and removed from the mouth in 5 min and this timing is provided by the manufacturer. The regular set material was used. The material was checked in mouth for firmness, resiliency and tackiness before removal. The tray was removed parallel to the preparation path of withdrawal and the impression was evaluated for parameters related to the study that are tears, voids and bubbles as was assessed in other studies with various other dental impression materials. ,,
Impressions were made by the same clinical evaluator to standardize the procedure and eliminate operator variability. The impressions were evaluated for tears, voids and bubbles on the finish line visibly by another clinical evaluator who was not involved in impression making process.
Tears described as "uneven unplanned breaking apart of some material," void as "the volume of space that is essentially empty of matter, open from one side" and bubble as "volume of space that is essentially empty of matter, closed from all sides" were looked for in the impressions.
The number of tears, voids and bubbles were counted visibly based on the above criteria and the impressions were classified into one of the following categories by the clinical evaluator: Alpha - No defects. Impression is usable;
Beta - defects like tears, voids and bubbles that do not affect finish line to prevent use of impressions. Impression is usable.
Delta - defects like tears, voids and bubbles present on the impression finish line, warrants remaking the impression.
Demographic details such as age, sex are represented by descriptive statistics. The number of tears, voids and bubbles in both monophase and two-phase with and without IODT were calculated for normality using Kolmogorov-Smirnov test. As these variables are not normally distributed, comparisons within each group (with IODT and without IODT) were performed using Wilcoxon-Signed matched pair test and between the groups by Mann-Whitney U-test. Since bubbles were not formed in any of the participants, it was not statistically analyzed. The overall evaluation (alpha, beta, delta) between monophase and two-phase in each group were analyzed by Chi-square for independence and Chi-square for trend analysis. The proportions of overall evaluation between both groups were represented with 95% confidence interval. All analysis was performed using GraphPad InStat 3.10 and Epi info Version 6 (CDC, Atlanta). All the statistical tests were two-tailed, and the significance level was kept at 5%. Sample size was calculated to be 50 impressions in each group (with and without IODT) taking into consideration, alpha error of 5%, power of 80% and proportion of defects in without and with IODT group, assumed to be 0.5 and 0.2 respectively.
| Result|| |
Of the 50 patients enrolled in the study, 25 patients were in each of the two groups - without IODT (group A) and with IODT (group B). The mean ± standard deviation of the age of study participants in each group and the sex ratio in each group are mentioned in [Table 1].
Tears, voids and bubbles
The median (range) of the number of tears, voids and bubbles in each of the impression technique (mono- and two-phase) in both the groups (with IODT and without IODT) are mentioned in the [Table 2] and [Table 3]. A significant reduction in the total number of voids was observed with two-phase technique either with or without IODT. Comparison between tears, voids and bubbles within monophase (with and without IODT) and two-phase technique (with and without IODT) are compared using Mann-Whitney U-test [Table 4]. No significant differences were observed in the proportion of overall evaluation into alpha, beta, and delta between monophase and two-phase with and without IODT [Table 5] and [Table 6]. No significant association was seen in the overall evaluation between the two groups (monophase and two-phase) as compared using Chi-square test for independency and a trend in association between overall evaluation as tested using Chi-square for linear trend analysis [Table 7] and [Table 8].
|Table 3: Tears, voids and bubbles in mono-and two-phase technique with IODT |
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|Table 5: Tears, voids and bubbles in mono- and two-phases in both with and without IODT |
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|Table 6: Proportion (with 95% CI) of overall evaluation in mono-and two-phases in with IODT |
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|Table 7: Proportion (with 95% CI) of overall evaluation in mono-and two-phases without IODT |
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|Table 8: Association of overall evaluation and trend analysis between the two groups |
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| Discussion|| |
The present study evaluated the effectiveness of single and two-phase techniques using both with and without IODT. We found that there was a significant decrease in the number of voids using two-phase technique as compared to the monophase. Reversible hydrocolloid materials had been used in the past for making impressions of prepared tooth, but they have some disadvantages like poor dimensional stability and low tear resistance. Monophase and two-phase addition polyvinyl siloxane impression materials are commonly used techniques of impression making for crowns and bridges, the advantages being high accuracy, little dimensional change after setting, moderately short working and setting time and excellent recovery from deformation on removal.  The findings in the present study may be attributed to the higher viscosity of monophase material that makes their injection more difficult causing the slumping of material, making placement less accurate that is the disadvantage of the technique.  Custom trays were used with two-phase and stock trays were used with monophase material. It is possible that this had an effect on the surface voids present because of the pressure exerted on the syringed material on the preparation from the material in the close fitting tray and also the amount of material to be used also increases when stock trays are used. This forms another disadvantage of the monophase technique.  However, the advantage of monophase material in stock trays is that the making of custom tray can be avoided and the technique is less time consuming as it is only a single mix.  As regards the two-phase technique, the main advantage is the consistencies of light and the heavy body used and also the amount of material used would be less as impressions are made on custom trays, the only disadvantage being the use of multiple-mix and it is a technique sensitive procedure warranting correct injection of the light body material onto the prepared tooth and also correct placement of the custom tray with the heavy body loaded.
With regards to the impressions made with and without the use of IODT, a trend is seen toward decrease in void formation with the use of IODT. This infers that there could be a slight decrease in the number of voids with the use of IODT. In the study conducted by Chong et al.,  tip and tip diameter has been identified as a factor that influences the number of voids present. It was identified that tips with smaller diameter produced fewer voids compared to tips with larger diameter. In the present study, same tip diameter was used to make all the impressions considering this factor. The present study also identifies intraoral tip as a factor reducing the number of voids. The use of automixing with IODT may safeguard against cross contamination and enables the clinician to dispense impression material directly onto the preparation without loading the material into a syringe saving time and eliminates the need for assistance.  The results of this study were limited to impressions of single units. Neither the operator nor the clinical evaluator who evaluated the impressions was blinded to the type of impression material used, due to the difference in color of the impression materials. The effect of salivary film on the surface may have had an effect on the number of voids present in impression. It has been evaluated that the adsorbed salivary film can cause an increase in surface tension, which will lead to formation of defects in elastomeric impressions  However, this factor was not evaluated in the present study. The scope of this present study is to emphasize the accuracy of two-phase impression technique using addition polyvinyl siloxane impression material, and this would even prove better success with the help of IODT. Further studies can be done to evaluate various other impression materials using IODT.
| Conclusion and Clinical Significance|| |
Comparing monophase and two-phase impressions in the present study, it was concluded that two-phase impression produced lesser defects especially as evaluated on the finish lines. The use of IODT significantly reduces the number of defects especially when used with the two-phase impression technique.
Financial support and sponsorship
Conflict of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8]