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СпутникиРНSpaceXРоскосмосNASAAbstract* Background Alginate is a widely used irreversible hydrocolloid impression material in dentistry because of its ease of use, affordability, and acceptable clinical performance. Modification of alginate with additives may alter its physical and mechanical properties. This study evaluated the effect of incorporating vanillin at different concentrations into two alginate impression materials, Zelgan and Neocolloid. Methods Vanillin was incorporated into Zelgan and Neocolloid alginate impression materials at concentrations of 0.5% and 1%. The materials were mixed with deionized water using a figure-of-8 motion for 1 minute and moulded in polyvinyl chloride moulds to prepare specimens. Gel strength, permanent deformation, gelation time, flow, and tear strength were evaluated using standardized methods. Data were analyzed using the Shapiro–Wilk test for normality, followed by ANOVA or Kruskal–Wallis tests with appropriate post-hoc analyses. Between-group comparisons were performed using the independent-samples t-test or Mann–Whitney U test. Statistical significance was set at P
Research Article
[version 1; peer review: awaiting peer review]
https://orcid.org/0009-0003-9925-3525
1, Nayana Prabhuhttps://orcid.org/0009-0002-1450-2717
2, Kishore Ginjupalli3, [...] Runki Saran4, P Kalyan Chakravarthyhttps://orcid.org/0000-0002-5462-5677
5, Disha Prabhu6, Veena Hedge7, Pradeep S8https://orcid.org/0009-0003-9925-3525
1, Nayana Prabhuhttps://orcid.org/0009-0002-1450-2717
2, [...] Kishore Ginjupalli3, Runki Saran4, P Kalyan Chakravarthyhttps://orcid.org/0000-0002-5462-5677
5, Disha Prabhu6, Veena Hedge7, Pradeep S81 Manipal College of Dental Sciences ,Department of Prosthodontics and Crown & Bridge, Manipal Academy of Higher Education, Manipal, Karnataka, 576104, India
2 Manipal College of Dental Sciences,Department of Prosthodontics and Crown & Bridge, Manipal Academy of Higher Education, Manipal, Karnataka, 576104, India
3 Manipal College of Dental Sciences ,Department of Dental Materials, Manipal Academy of Higher Education, Manipal, Karnataka, 576104, India
4 Manipal College of Dental Sciences, Department of Dental Materials, Manipal Academy of Higher Education, Manipal, Karnataka, 576104, India
5 Manipal College of Dental Sciences, Department of Public Health Dentistry, Manipal Academy of Higher Education, Manipal, Karnataka, 576104, India
6 Manipal College of Dental Sciences, Department of Conservative Dentistry & Endodontics, Manipal Academy of Higher Education, Manipal, Karnataka, 576104, India
7 Department of Prosthodontics and Crown & Bridge, Manipal College of Dental Sciences, Manipal Academy of Higher Education, Manipal, Karnataka, India
8 Department of Prosthodontics and Crown & Bridge, Manipal College of Dental Sciences, Manipal Academy of Higher Education, Manipal, Karnataka, India
Sai Surya Sameehan Adavi
Roles: Conceptualization, Data Curation, Formal Analysis, Funding Acquisition, Investigation, Methodology, Resources, Software, Validation, Visualization, Writing – Original Draft Preparation, Writing – Review & Editing
Nayana Prabhu
Roles: Project Administration, Supervision, Writing – Original Draft Preparation, Writing – Review & Editing
Kishore Ginjupalli
Roles: Methodology, Project Administration, Validation, Writing – Original Draft Preparation, Writing – Review & Editing
Runki Saran
Roles: Investigation, Methodology, Project Administration, Validation, Visualization, Writing – Original Draft Preparation, Writing – Review & Editing
P Kalyan Chakravarthy
Roles: Formal Analysis, Validation, Writing – Original Draft Preparation, Writing – Review & Editing
Disha Prabhu
Roles: Visualization, Writing – Original Draft Preparation, Writing – Review & Editing
Veena Hedge
Roles: Supervision, Visualization, Writing – Review & Editing
Pradeep S
Roles: Supervision, Visualization, Writing – Review & Editing
OPEN PEER REVIEW
REVIEWER STATUS AWAITING PEER REVIEW
Alginate impression material, Irreversible hydrocolloid, Vanillin, Gel strength, Gelation time, Permanent deformation, Flow, Tear strength
Corresponding author: Nayana Prabhu Competing interests: No competing interests were disclosed.
Grant information: The author(s) declared that no grants were involved in supporting this work.
Copyright: © 2026 Adavi SSS et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. How to cite: Adavi SSS, Prabhu N, Ginjupalli K et al. Influence of Vanillin at different concentrations on the properties of commercial alginate impression materials: An in-vitro study. [version 1; peer review: awaiting peer review]. F1000Research 2026, 15:1224 (https://doi.org/10.12688/f1000research.184245.1) First published: 27 Jul 2026, 15:1224 (https://doi.org/10.12688/f1000research.184245.1) Latest published: 27 Jul 2026, 15:1224 (https://doi.org/10.12688/f1000research.184245.1)
Irreversible hydrocolloid impression materials, widely known as Alginates, are widely used for recording preliminary impressions of dentulous and partially dentulous mouths. It is supplied as a powder containing sodium alginate, calcium sulfate, trisodium phosphate, and fillers that form a gel upon mixing with water through a chemical reaction regulated by trisodium phosphate.1,2 Alginate is known for its ability to record fine details due to its hydrophilic nature and good flow and is a cost-effective material with a relatively simple manipulative technique. However, its use is limited due to poor dimensional stability, lower tear strength and lack of antimicrobial action. Dimensional changes arise from imbibition, which occurs during conventional immersion or spray disinfection of impression and may compromise accuracy due to the material’s hydrophilic nature.3
As alginate lacks antimicrobial activity, cross-infection between the clinic and the laboratory, or among patients, is a concern. To address this, self-disinfecting alginates incorporating antimicrobial agents have been developed. Various antimicrobial additives, including chlorhexidine, quaternary ammonium compounds such as didecyldimethyl ammonium chloride, fluoride, silver nanoparticles, magnesium oxide nanoparticles, and titanium dioxide nanoparticles, have been investigated for incorporation into impression materials to impart self-disinfecting properties and reduce the risk of cross-contamination.3–7 The incorporation of antimicrobial additives alters the alginate-to-water ratio, directly affecting the properties of the resultant formulations. In this regard, it is pertinent to select an additive that imparts superior antimicrobial activity at lower concentrations without significantly altering the properties of alginate.8,9
Vanillin (4-hydroxy-3-methoxybenzaldehyde), a naturally occurring phenolic compound derived from vanilla, exhibits broad-spectrum antimicrobial activity by disrupting bacterial cell membranes and inhibiting essential enzymes.10 It has been investigated as a constituent of mouthrinses, as a reducing agent for the synthesis of antimicrobial silver nanoparticles.11 Vanillin has recently been added as an antimicrobial additive to alginates. However, its effects on the physical properties of alginate at various concentrations have not been investigated.
The present in vitro study aimed to evaluate the physical properties of two commercially available irreversible hydrocolloid impression materials- Zelgan (Dentsply Sirona) and Neocolloid (Zhermack) – incorporated with vanillin at 0.5% and 1% concentrations.
Two commercially available irreversible hydrocolloid materials- Zelgan (Dentsply Sirona) and Neocolloid (Zhermack) were selected as shown in Table 1.
Vanillin (4-hydroxy-3-methoxybenzaldehyde) purity-99.5%, quantity- 100gms was procured from Nano Research Lab, Jharkhand, India, Catalogue number-NRL0219042/215. Vanillin at 0.5% and 1% (w/w) concentration was incorporated into alginate impression materials. The sample size was estimated using G*power (v3.1.9.7). Based on an effect size of 0.63, with 80% power and 95% confidence, a minimum of 9 samples per group was required. Study design is depicted in Table 2.
A precisely measured quantity of alginate impression material was blended with vanillin at either 0.5% or 1% by weight by transferring both into a container and mixing thoroughly to achieve homogeneous distribution. Unmodified alginate powder served as the control group. Test specimens were fabricated by combining a weighed quantity of alginate (with or without vanillin) with a measured volume of deionised water following the respective manufacturer’s instructions. The powder and water were placed into a rubber mixing bowl and spatulated for 45 seconds in a figure-of-8 motion by a single operator to minimise variability in manipulation. Mixing was continued until a smooth, homogeneous consistency was obtained. For specimen fabrication, the resulting mix was packed into a polyvinyl chloride (PVC) cylindrical mould (internal diameter: 30 mm; height: 16 mm) resting on a glass slab. A smaller secondary mould (internal diameter: 15 mm; height: 19 mm) was then inserted into the first mould until the material was expressed from the top, ensuring complete mould filling and eliminating air entrapment. A flat glass plate was subsequently pressed over the second mould to remove any excess material, and the assembly was left undisturbed for 5 minutes to allow complete gelation. Specimens were then carefully removed and subjected to testing. All specimens were fabricated in strict accordance with ADA Specification No. 18/ISO 1563.
Gelation time was assessed using a method adapted from Lemon et al. (2003).12 Beginning 60 seconds after the initiation of mixing, a cylindrical polymethyl methacrylate (PMMA) rod (diameter: 6 mm; length: 10 cm) with a flat, polished tip was gently brought into contact with the surface of the alginate mix and lifted away. This contact-and-withdrawal procedure was carried out at 5-second intervals. The endpoint was identified as the moment when the material ceased to adhere to the rod tip. Gelation time was recorded as the total elapsed time from the commencement of mixing to this endpoint.
Flow was assessed following the method outlined by Wang et al. (2007).13 A 0.5 mL volume of freshly mixed alginate was dispensed onto a glass plate via a disposable syringe. A second glass plate was positioned over the material, and a 1 kg weight was applied to the upper plate for a duration of 5 seconds. The resulting disc of material was measured at three equidistant points, and the mean diameter (in mm) was recorded as the flow value.
Compressive gel strength was evaluated using a technique adapted from MacPherson et al. (1967).14 Six minutes after the start of mixing, specimens were removed from their moulds and positioned on the lower plate of a universal testing machine (Instron Model 3366, Instron Corporation, United Kingdom). A compressive load was applied at a crosshead speed of 10 mm/minute. The peak load recorded at the point of material failure — identified by a marked and sudden drop in the load–displacement curve — was taken as the gel strength value.
Permanent deformation was determined using a previously established protocol with minor modifications. At 6 minutes from the start of mixing, each specimen was subjected to a compressive load sufficient to reduce its height by 10% of its original dimension. This deformation was sustained for 15 seconds, after which the load was released, and the specimen was allowed to recover freely for 30 seconds. The final height was then recorded, and permanent deformation was calculated as follows:
Permanent Deformation(%)=(Change in Length/Original Length)×100
Tear strength specimens were prepared by packing freshly mixed alginate into a rectangular mould (70 × 25 × 1.5 mm). A cellophane sheet was placed over the mould surface to prevent adhesion, followed by a glass plate on top, upon which a load was applied to ensure complete and uniform mould filling. Once gelation was complete, specimens were carefully retrieved and trimmed of excess flash material using a surgical blade. Each specimen was then split longitudinally for 50 mm of its length, leaving the remaining 20 mm intact for gripping. The two resulting flanges were clamped into the tensile jigs of a universal testing machine (Instron Model 3366, UK), and a tensile force was applied at a rate of 50 mm/minute until complete separation occurred. Tear strength was calculated by dividing the maximum recorded load by the specimen thickness, and results were expressed in N/mm.
Data were analysed using SPSS v26. Normality was assessed by the Shapiro-Wilk test. Within-group comparisons were performed using one-way ANOVA with post-hoc Tukey’s test, or Kruskal-Wallis ANOVA with Bonferroni correction based on the distribution of data. Comparison of mean values between groups was performed using the independent samples t-test or the Mann-Whitney U test, depending on the data distribution. P < 0.05 was considered statistically significant.
The physical properties of Zelgan and Neocolloid alginate impression materials incorporated with vanillin at 0%, 0.5% and 1% concentrations were evaluated and are presented in Tables 3.1-3.5.
Gel Strength: Intra-group analysis revealed a significant reduction in gel strength within Zelgan upon vanillin incorporation (P = 0.002), whereas Neocolloid showed no significant change (P = 0.439). Inter-group comparison demonstrated that Zelgan exhibited consistently and significantly higher gel strength than Neocolloid across all concentrations (P < 0.001).
Permanent Deformation: Neither material showed significant intra-group variation (Zelgan- P = 0.780; Neocolloid- P = 0.792), and no significant inter-group difference was observed at any concentration.
Gelation Time: Both materials showed a highly significant intra-group reduction in gelation time with vanillin (P < 0.001). Inter-group comparison confirmed that Zelgan elated significantly faster than Neocolloid at all concentrations (P < 0.001).
Flow: Significant intra-group reductions were noted in both materials (P < 0.001). Inter-group analysis revealed no significant difference at 0% vanillin (P = 0.497), but Neocolloid demonstrated significantly higher flow at 0.5% and 1% concentrations (P < 0.001).
Tear Strength: Zelgan showed no intra-group variation (P = 0.293), while Neocolloid demonstrated a significant increase at 1% vanillin (P < 0.001). Inter-group comparison showed Zelgan had significantly higher tear strength at 0% and 0.5% vanillin, with no significant difference at 1% (P = 0.121).
The findings of the present study revealed changes in the physical properties of Zelgan and Neocolloid alginate impression materials after incorporating vanillin at concentrations of 0%,0.5%, and 1%. The incorporation of vanillin resulted in noticeable changes in the tested properties of both materials, with some parameters increasing and others decreasing. The magnitude and nature of these changes varied with the type of alginate, indicating that the interaction between vanillin and the alginate matrix is material-dependent.
Disinfection of alginate impression material is commonly performed by spraying or immersion, but because of syneresis and imbibition, these methods are not recommended. Additives like vanillin can be incorporated into alginate impression material, as it is known for its antimicrobial activity and can be an effective way to promote self-disinfection.
Gel strength in the present study decreased after the incorporation of vanillin into both Zelgan and Neocolloid. Any additive capable of influencing the rate or extent of cross-linking is expected to produce corresponding alterations in gel strength.15 The incorporation of vanillin partially replaces alginate in the formulation, thereby reducing the amount of alginate powder available for interaction with a given quantity of water compared to the control group.16 This reduction may decrease the degree of crosslinking, ultimately leading to lower gel strength. Furthermore, variations in the magnitude of gel strength reduction were observed between the two commercial alginate materials, Zelgan & Neocolloid, which may be attributed to differences in their respective compositions.
In the present study, vanillin incorporation significantly reduced gelation time in both alginate impression materials, with the greatest reduction observed at 0.5% concentration. This effect may be attributed to the presence of vanillin particles, which could facilitate localized calcium–alginate crosslinking by providing additional surfaces for interaction, thereby accelerating gel network formation.17 In addition, vanillin may interfere with the action of trisodium phosphate, the retarder component, reducing its effectiveness in delaying calcium alginate formation. The present findings corroborate those of Leelapong et al. (2024),18 who reported a significant reduction in the setting time of alginate impression materials following the incorporation of vanillin at concentrations ranging from 0.1% to 1% (w/w). In agreement with these observations, the present study demonstrated a significant reduction in gelation time after vanillin incorporation. Notably, statistical significance was observed at 0.5% and 1% (w/w) concentrations, indicating that the accelerating effect of vanillin on alginate gelation becomes more pronounced at higher concentrations. This may be attributed to enhanced interactions between vanillin particles and the alginate crosslinking system, leading to accelerated gel formation.
The incorporation of vanillin did not result in a significant alteration in permanent deformation in either Zelgan (P = 0.780) or Neocolloid (P = 0.792), indicating that the elastic recovery of both materials remained unaffected. Since permanent deformation reflects the ability of the calcium alginate gel network to recover following deformation, the present findings suggest that vanillin did not compromise the integrity of the cross-linked polymer matrix. The maintenance of this property implies that the concentration of vanillin incorporated was insufficient to disrupt the network architecture responsible for elastic behaviour.19 From a clinical perspective, the preservation of elastic recovery is desirable, as it ensures accurate reproduction of oral structures, particularly in undercut regions, while minimising the risk of permanent distortion during impression removal. These results therefore demonstrate that vanillin can be incorporated into alginate impression materials without adversely affecting their elastic recovery characteristics.
The present study found that incorporating vanillin did not significantly affect the tear strength of either alginate material, indicating that the additive did not adversely alter the structural integrity of the calcium alginate gel network. This suggests that the incorporated vanillin concentration was insufficient to disrupt the intermolecular interactions responsible for resistance to tensile stress.20
Interestingly, a significant increase in tear strength was observed in Neocolloid at a 1% vanillin concentration, whereas Zelgan showed a non-significant upward trend. The observed improvement in tear strength may be attributed to the uniform dispersion of vanillin particles within the alginate matrix, where they potentially act as reinforcing micro-fillers. The incorporation of such particulate additives may enhance the structural cohesion of the gel network by facilitating a more homogeneous distribution of applied stresses throughout the cross-linked matrix. Consequently, the material may exhibit increased resistance to crack initiation and propagation under tensile loading. In addition, vanillin particles may promote physical interactions with the surrounding polymer network, thereby improving filler–matrix interfacial adhesion and contributing to localised reinforcement of the calcium alginate structure. These effects may collectively enhance the mechanical integrity of the gel, thereby improving its resistance to tearing.20
From a clinical perspective, preserving or enhancing tear strength is advantageous, as it reduces the likelihood of impression tearing during removal, thereby improving the accuracy and completeness of impressions obtained from regions with deep embrasures or undercut anatomical structures. These findings indicate that vanillin incorporation, particularly at a concentration of 1%, may provide additional reinforcement to the alginate matrix without compromising its mechanical performance.
Although the present study’s findings suggest that vanillin can be incorporated into alginate impression materials without adversely affecting key physical properties, additional investigations are needed to comprehensively evaluate its effects on other clinically relevant characteristics. In particular, further studies should assess the effects of vanillin incorporation on detail reproduction and dimensional stability, as these properties are critical determinants of impression accuracy and the subsequent fabrication of precise dental casts. Such investigations would provide a more comprehensive understanding of the suitability of vanillin as an antimicrobial additive in irreversible hydrocolloid impression materials.
The incorporation of vanillin at concentrations of 0.5% and 1.0% modified the physicochemical properties of the alginate impression materials. However, the magnitude of these changes remained within clinically acceptable limits, indicating that vanillin incorporation does not adversely affect the functional performance of the materials. The observed variations were dependent on the specific alginate formulation, suggesting that the interaction between vanillin and the alginate matrix is material-specific.
We acknowledge the use of ChatGPT v4.0(OpenAI) to assist with proof reading and language editing of this manuscript.
The author(s) declared that no grants were involved in supporting this work.
© 2026 Adavi SSS et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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