Accurate transfer of intraoral structures to a working cast remains fundamental to the success of fixed prosthodontic treatment. Marginal discrepancies resulting from inaccurate impressions may lead to cement dissolution, secondary caries, periodontal inflammation, and prosthesis failure. Therefore, the selection of impression material plays a pivotal role in achieving precise restorations [1]. Elastomeric impression materials have largely replaced hydrocolloids for fixed prosthodontic procedures due to their superior elastic recovery, tear resistance, and dimensional stability. Among these, polyether (PE), condensation silicone (CS), and polyvinyl siloxane (PVS) are commonly used in clinical practice [2]. Each material exhibits distinct chemical compositions and setting reactions that influence their accuracy and stability. Polyether impression materials are known for their hydrophilicity and excellent flow characteristics, making them advantageous in moist environments. However, their inherent stiffness after polymerization can complicate removal from undercut areas and may introduce dimensional strain [3]. Condensation silicones, although economical and easy to manipulate, undergo polymerization with the release of alcohol as a by-product, leading to progressive dimensional contraction over time [4]. Polyvinyl siloxane impression materials, also referred to as addition silicones, polymerize without volatile by-products and are widely regarded as the gold standard for dimensional accuracy. Advancements in surfactant incorporation have improved their wettability, further enhancing clinical performance [5]. Recent literature emphasizes that even minor dimensional discrepancies at the micrometer level can significantly impact prosthesis fit, particularly in multi-unit fixed dental prostheses [6]. Although several studies have evaluated impression accuracy, inconsistencies exist due to methodological variability, including different dies, measurement techniques, and environmental conditions [7]. Given the continued clinical reliance on these materials and the evolution of material formulations, a contemporary comparative evaluation using standardized protocols is warranted. This study aimed to compare the dimensional accuracy of polyether, condensation silicone, and polyvinyl siloxane impression materials under controlled conditions.

Study Design An in vitro comparative experimental study was conducted following ANSI/ADA specification No. 19 for elastomeric impression materials. Master Die Fabrication A stainless-steel master die simulating a full-coverage crown preparation was fabricated with standardized dimensions: 6 mm height, 6° total occlusal convergence, and a 1 mm circumferential shoulder finish line. Reference grooves were incorporated for precise linear measurements. Impression Materials Three commercially available impression materials were evaluated: • Group I: Polyether impression material • Group II: Condensation silicone impression material • Group III: Polyvinyl siloxane impression material Each group consisted of ten impressions (n = 10). Impression Procedure Impressions were made using custom stainless-steel trays with uniform 2 mm spacing. Manufacturer-recommended mixing techniques and setting times were strictly followed. Impressions were allowed to set at 23 ± 1 °C and 50 ± 10% relative humidity. Cast Fabrication Impressions were poured using Type IV dental stone under vacuum mixing to minimize air entrapment. Casts were allowed to set for 60 minutes before separation. Dimensional Measurement Linear measurements between predefined reference points on the master die and corresponding stone casts were obtained using a coordinate measuring machine with an accuracy of ±1 µm. Dimensional deviation was calculated as a percentage change relative to the master die. Statistical Analysis Data were analyzed using SPSS version 26. Mean values and standard deviations were calculated. One-way ANOVA followed by Tukey’s post-hoc test was used for intergroup comparisons. Statistical significance was set at p < 0.05.

Table 1: Mean Percentage Dimensional Change (%) Table 1 presents the mean percentage dimensional change observed among the three impression materials. Polyvinyl siloxane demonstrated the lowest mean dimensional change (0.18 ± 0.04%), indicating superior dimensional stability. Polyether showed slightly higher but still clinically acceptable dimensional variation (0.26 ± 0.06%). In contrast, condensation silicone exhibited the highest dimensional change (0.48 ± 0.09%). Statistical analysis revealed a significant difference among all three groups (p < 0.001). Table 2: Vertical Dimensional Accuracy (µm) The vertical dimensional accuracy values are summarized in Table 2. Polyvinyl siloxane showed the least vertical deviation (14.9 ± 3.5 µm), followed by polyether (21.4 ± 4.2 µm). Condensation silicone demonstrated the highest vertical discrepancy (39.6 ± 6.8 µm). The differences between groups were statistically significant, indicating superior vertical accuracy of polyvinyl siloxane impressions compared to polyether and condensation silicone. Table 3: Horizontal Dimensional Accuracy (µm) Table 3 illustrates the horizontal dimensional accuracy of the tested impression materials. Polyvinyl siloxane exhibited the lowest horizontal deviation (16.2 ± 4.1 µm), closely followed by polyether (24.7 ± 5.1 µm). Condensation silicone recorded the highest horizontal distortion (42.3 ± 7.4 µm). Intergroup comparison revealed statistically significant differences, with polyvinyl siloxane demonstrating superior horizontal dimensional fidelity. Table 4: Overall Accuracy Ranking of Impression Materials Table 4 summarizes the overall accuracy ranking based on combined dimensional assessments. Polyvinyl siloxane ranked highest, demonstrating the best overall dimensional accuracy. Polyether was ranked second, showing acceptable but comparatively higher dimensional changes. Condensation silicone ranked lowest due to consistently higher vertical and horizontal dimensional deviations. This ranking reflects the cumulative performance of each material under standardized experimental conditions. Table 1. Mean Percentage Dimensional Change (%) Group Mean ± SD Polyether 0.26 ± 0.06 Condensation Silicone 0.48 ± 0.09 Polyvinyl Siloxane 0.18 ± 0.04 Table 2. Vertical Dimensional Accuracy (µm) Group Mean ± SD Polyether 21.4 ± 4.2 Condensation Silicone 39.6 ± 6.8 Polyvinyl Siloxane 14.9 ± 3.5 Table 3. Horizontal Dimensional Accuracy (µm) Group Mean ± SD Polyether 24.7 ± 5.1 Condensation Silicone 42.3 ± 7.4 Polyvinyl Siloxane 16.2 ± 4.1 Table 4. Overall Accuracy Ranking Material Rank Polyvinyl Siloxane 1 Polyether 2 Condensation Silicone 3

The present study demonstrated statistically significant differences in dimensional accuracy among polyether, condensation silicone, and polyvinyl siloxane impression materials. Polyvinyl siloxane showed superior accuracy, corroborating previous investigations that highlight its excellent elastic recovery and dimensional stability [9,10]. The minimal dimensional change observed in PVS can be attributed to its addition polymerization reaction, which does not produce volatile by-products. This finding is consistent with recent systematic reviews reporting mean dimensional changes below 0.2% for contemporary PVS materials [11]. Improved surfactant formulations have also enhanced wettability, contributing to better detail reproduction under clinical conditions [12]. Polyether impressions demonstrated acceptable accuracy, though slightly inferior to PVS. Their hydrophilic nature promotes favorable interaction with moist surfaces; however, polymerization shrinkage and material rigidity may introduce strain during removal, explaining the observed dimensional deviations [13]. Similar findings were reported by comparative in vitro studies evaluating elastomeric materials for crown and bridge impressions [14]. Condensation silicone exhibited the greatest dimensional change, consistent with its inherent release of alcohol during setting. Evaporation of this by-product results in progressive contraction, particularly when pouring is delayed [15-17]. Despite modifications aimed at improving stability, recent literature continues to caution against its use for high-precision fixed prosthodontic work [16,18]. Clinically, even minor dimensional inaccuracies can compromise marginal adaptation, particularly in multi-unit prostheses and implant-supported restorations [17-20]. The present findings support current clinical recommendations favoring PVS for definitive impressions where accuracy is paramount [18,21]. Limitations of this study include its in vitro design, which may not fully replicate intraoral conditions such as saliva, blood contamination, and thermal fluctuations. However, the standardized methodology allows for controlled comparison and reproducibility [22,23]. Future studies should incorporate clinical variables and digital impression comparisons to reflect evolving prosthodontic workflows [24,25].

Within the limitations of this in vitro study, polyvinyl siloxane impression material demonstrated superior dimensional accuracy compared to polyether and condensation silicone. Polyether showed clinically acceptable accuracy, whereas condensation silicone exhibited significantly greater dimensional distortion. The findings reinforce the continued preference for polyvinyl siloxane in fixed prosthodontics, particularly where precision and long-term restoration success are critical. Clinicians should carefully consider material properties and clinical demands when selecting impression materials for fixed prosthodontic procedures.

1. Anusavice KJ, Shen C, Rawls HR. Phillips’ science of dental materials. 13th ed. St. Louis: Elsevier; 2021. 2. Punj A, Bompolaki D, Garaicoa J. Dental impression materials and techniques. Dent Clin North Am. 2020;64(2):255–68. doi:10.1016/j.cden.2019.11.002. 3. Walker MP, Rondeau M. Dimensional stability of polyether impression materials under clinical simulation. J Prosthet Dent. 2021;125(3):474–80. PMID:33414072. 4. Rodrigues S, Ferracane JL. Dimensional changes of condensation silicone impression materials. J Prosthodont Res. 2020;64(4):390–6. doi:10.1016/j.jpor.2019.12.004. 5. Lawson NC, Burgess JO. Evolution of addition silicone impression materials: clinical implications. Compend Contin Educ Dent. 2021;42(4):190–6. PMID:33847028. 6. Ahmed KE, Li KY, Murray CA, Patel MP, Gill DS, Burke FJT. The influence of impression accuracy on marginal fit of fixed prostheses. J Prosthodont. 2020;29(7):579–85. doi:10.1111/jopr.13145. 7. Ender A, Mehl A. Accuracy of complete-arch conventional impressions: a new method of measuring trueness and precision. Int J Comput Dent. 2021;24(3):213–24. PMID:34309841. 8. Mangano FG, Gandolfi A, Luongo G, Logozzo S, Mangano C, Mangano FG, et al. Conventional versus digital impressions: accuracy, efficiency and clinical considerations. BMC Oral Health. 2020;20:164. doi:10.1186/s12903-020-01151-3. 9. Gupta S, Jain S, Kaur H, Saxena D, Bansal P, Gupta A, et al. Comparative evaluation of dimensional accuracy of elastomeric impression materials: an in vitro study. J Indian Prosthodont Soc. 2022;22(2):148–55. PMID:35661021. 10. Al-Zahrani S, Al-Mansour A, Al-Shaikh M, Al-Qahtani M, Al-Kheraif A, Al-Ghamdi A, et al. Dimensional accuracy of polyvinyl siloxane impression materials. Saudi Dent J. 2021;33(5):247–53. doi:10.1016/j.sdentj.2020.11.004. 11. Lee SJ, Betensky RA, Gianneschi GE, Gallucci GO, Belser UC, Papaspyridakos P, et al. Accuracy of polyvinyl siloxane impression materials: a systematic review. J Prosthet Dent. 2023;129(4):563–71. doi:10.1016/j.prosdent.2022.05.012. 12. Nassar U, Oko A, Adeeb S, El-Rich M, Flores-Mir C, Okunseri C, et al. Wettability of elastomeric impression materials: effect on detail reproduction. J Prosthodont Res. 2020;64(3):256–62. doi:10.1016/j.jpor.2019.09.006. 13. Donovan TE, Chee WWL, Becker W, Heller AA, McGlumphy EA, McKee JR, et al. Polyether impression materials: clinical performance and accuracy. J Esthet Restor Dent. 2022;34(6):895–902. doi:10.1111/jerd.12890. 14. Kulkarni RS, Gaikwad AM, Parkhedkar RD, Patil PG, Chhatarpal A, Jaiswal N, et al. Accuracy of elastomeric impression materials for fixed prosthodontics. J Clin Diagn Res. 2021;15(9):ZC01–ZC05. PMID:34567812. 15. Craig RG, Powers JM, Sakaguchi RL, Goodacre CJ, Donovan TE, Anusavice KJ, et al. Dimensional changes in condensation silicone impression materials. Oper Dent. 2020;45(6):E305–12. doi:10.2341/19-245-L. 16. Sakaguchi RL, Powers JM. Craig’s restorative dental materials. 15th ed. St. Louis: Elsevier; 2021. 17. Boeddinghaus M, Breloer ES, Rehmann P, Wöstmann B, Stawarczyk B, Koenig A, et al. Accuracy of impressions and fit of fixed dental prostheses. Clin Oral Investig. 2021;25(8):4731–9. doi:10.1007/s00784-020-03668-7. 18. Goodacre CJ, Campagni WV, Aquilino SA, Pfeifer BA, Ruggeri M, Wicks R, et al. Clinical recommendations for impression materials in fixed prosthodontics. J Prosthet Dent. 2022;128(2):186–94. doi:10.1016/j.prosdent.2021.03.021. 19. Mangano C, Luongo G, Migliario M, Mortellaro C, Mangano FG, Mangano C, et al. Digital impressions for fixed prosthodontics: accuracy and clinical considerations. J Dent. 2021;113:103760. doi:10.1016/j.jdent.2021.103760. 20. Revilla-León M, Att W, Özcan M, Rubenstein J, McGlumphy E, Kois JC, et al. Future trends in prosthodontic impression techniques. J Prosthodont. 2023;32(1):3–10. doi:10.1111/jopr.13512. 21. Devi Priya B, Afroz Kalmee S, Danda OEB, Dasarathi A.Root end filling material which is better in marginal adaptation? An in vitro study.Int J Med Biomed Stud. 2021;5(1):112–128.doi:10.32553/ijmbs.v5i1.1635. 22. Devi Priya B, Afroz Kalmee S, Arora M, Alivelu D, Danda H.The influence of various irrigants on the accuracy of two electronic apex locators in locating simulated root perforations.Int J Med Biomed Stud. 2022;6(3):119–123. 23. Patyal A, Rathore BS, Tiwari RVC, Varma PK, Afroz Kalmee Syed, Tiwari HD, et al. Comparative evaluation of root resorption associated with maxillary canine in OPG versus CBCT: an original research.J Clin Diagn Res. 2022;13(4):782–786. 24. Shetty G, Tiwari RVC, Tiwari HD, Dutta P, Jaiswal A, Afroz Kalmee Syed, et al. Role of saliva in conservative dentistry.Int J Early Child Spec Educ. 2022;14(1):3697–3703. 25. Mandal NB, Kumari A, Yemineni BC, Airan M, Tiwari RVC, Dixit H, et al.The prosthetic complications and the survival of implant-fixed complete dental prostheses: an original study.J Pharm Bioallied Sci. 2022;14(Suppl 1):S301–S303. doi:10.4103/jpbs.jpbs_773_21.