The fundamental goal of any restorative procedure is to restore proper function, tooth form, and aesthetics while maintaining the physiological integrity of the dentition in harmony with the oral environment. The success and longevity of dental restorations largely depend on the integrity and durability of the marginal seal between the tooth and restorative material [1]. When this marginal integrity is compromised, a gap is left between the cavity wall and restorative interface, allowing ingress of fluids and microorganisms, a phenomenon known as microleakage [2]. Microleakage is defined as the clinically undetectable passage of bacteria, fluids, molecules, or ions between the cavity wall and restorative material [3]. It is considered one of the major clinical causes of restoration failure, especially in Class V cavities where the gingival margins often lie in dentin or cementum. An ideal restorative material should have a coefficient of thermal expansion and biocompatibility similar to natural tooth structure, demonstrate colour stability, form an excellent marginal seal, and chemically adhere to both enamel and dentin [4]. Microleakage has long been regarded as a sensitive indicator of the clinical success of restorative materials, since it contributes directly to secondary caries, marginal discoloration, and pulpal irritation [5]. Polymerization shrinkage, one of the major causes of microleakage in resin-based materials, remains a critical challenge for restorative longevity. The growing emphasis on aesthetics in restorative dentistry has driven widespread use of tooth-coloured materials for the management of Class V lesions [6]. Among these, conventional glass ionomer cement (GIC), introduced by Wilson and Kent in the early 1970s, remains a versatile option because of its ability to bond chemically to enamel and dentin, fluoride release, and a thermal expansion coefficient close to that of tooth structure, resulting in favourable marginal adaptation and minimal microleakage [3]. Giomers represent an advanced hybrid between glass ionomers and resin composites. They incorporate pre-reacted glass (PRG) fillers that combine the benefits of resin composites with the fluoride release and recharge potential of glass ionomers. In surface-reacted PRG (S-PRG) fillers, the outer surface of the glass core is reacted with polyacrylic acid, providing properties such as fluoride release, recharge, dentin remineralization, and acid buffering, while maintaining a stable glass core. Beautifil II, a widely used giomer, utilizes S-PRG technology, yielding high polishability, radiopacity, and durability along with sustained fluoride protection [4]. Zirconomer is a recent advancement in glass ionomer technology that incorporates zirconia fillers into the glass matrix to enhance mechanical strength, wear resistance, and durability. This modification allows Zirconomer to function as a mercury-free alternative to amalgam, offering both strength and fluoride release, hence earning the term “white amalgam.”⁵ Cention N is another newer generation tooth-coloured restorative belonging to the Alkasite group. It contains patented alkaline glass fillers (Isofillers) that release fluoride, calcium, and hydroxide ions, providing remineralization potential and pH regulation during acid attacks. Its high flexural strength, low polymerization shrinkage, and optional dual-curing mechanism contribute to improved marginal sealing and decreased microleakage [6]. Ionoseal, a light-curing resin-reinforced glass ionomer liner, has been developed for small restorations and as a base material. It offers several advantages including ease of handling, fluoride release, radiopacity, high compressive strength, and improved viscosity. Delivered in a Non-Dripping-Technology syringe, it allows precise placement and reduces wastage. Its combination of glass ionomer and resin chemistry provides adequate seal, improved biocompatibility, and reduced marginal leakage. The relationship between marginal leakage and restorative materials has been extensively explored in both laboratory and clinical studies. However, due to the difficulty of controlling variables intraorally, in-vitro microleakage assessments remain the most standardized and reproducible method for evaluating the sealing ability of restorative materials. Thus, the creation of a perfect marginal seal remains one of the primary goals of restorative dentistry to prevent ingress of oral fluids and microorganisms, thereby maintaining the longevity and clinical success of restorations [2]. Microleakage around restorations can cause a variety of adverse effects, including postoperative sensitivity, secondary caries, marginal staining, and pulpal pathology, all of which compromise the long-term success of restorative procedures [7,8]. With increasing aesthetic demands, tooth-coloured restorative materials have gained immense popularity for both anterior and posterior restorations.⁹ It is therefore essential to evaluate and compare the microleakage characteristics of these materials to ensure optimal performance and longevity. In this context, the present study was designed to comparatively evaluate the microleakage around Class V cavities restored with five different tooth-coloured restorative materials Conventional Glass Ionomer Cement, Zirconomer, Giomer, Ionoseal, and Cention N under standardized in-vitro conditions. Aim and Objectives Aim: To compare and evaluate the microleakage of five different tooth coloured restorative materials. Objective: To compare and evaluate the microleakage of five different tooth-coloured restorative materials to determine the tooth coloured restorative material showing the least amount of microleakage.

Study Design: This was an in-vitro, comparative, experimental study designed to evaluate and compare the microleakage of five different tooth-coloured restorative materials placed in standardized Class V cavities. Sample Selection: Forty freshly extracted, caries-free human permanent maxillary premolars of comparable dimensions were selected. Teeth with cracks, caries, restorations, or developmental defects were excluded. The extracted teeth were cleaned of debris and calculus using an ultrasonic scaler, stored in distilled water, and used within one month of extraction to prevent dehydration. Cavity Preparation: Standardized Class V cavities were prepared on the buccal surface of each tooth using a high-speed airotor handpiece under copious water spray with a cylindrical diamond bur. Each cavity measured approximately 3 mm in width, 2 mm in height, and 1.5 mm in depth, with the occlusal margin located in enamel and the gingival margin in cementum or dentin. The bur was replaced after every five preparations to ensure consistency. Grouping of Samples: The specimens were randomly divided into five groups, each comprising eight teeth (n = 8 per group): • Group I: Conventional Glass Ionomer Cement (GIC) – GC Fuji IX • Group II: Zirconomer – Shofu Inc. • Group III: Giomer (Beautifil II) – Shofu Inc. • Group IV: Cention N – Ivoclar Vivadent • Group V: Ionoseal – Voco GmbH Restorative Procedures: All restorative materials were manipulated and placed according to manufacturers’ instructions. The cavities were filled incrementally where required and cured using a visible light-curing unit with an output intensity of approximately 600 mW/cm². Finishing and polishing were carried out using fine-grit diamond burs and polishing discs after complete setting of materials. Thermocycling Procedure: To simulate intraoral thermal stresses, all samples underwent thermocycling between 5°C and 55°C for 500 cycles with a dwell time of 30 seconds in each bath and a transfer time of 10 seconds. Dye Penetration and Microleakage Assessment: Following thermocycling, the entire external surface of each tooth was coated with two layers of nail varnish, except for a 1 mm margin around the restoration. The apices of the teeth were sealed with sticky wax to prevent dye infiltration through the root canal. The specimens were then immersed in 50% (w/v) silver nitrate dye solution for 6 hours at room temperature in a light-proof container to allow dye penetration. Subsequently, they were rinsed thoroughly under running water and immersed in a photo-developing solution for 8 hours to reduce silver ions for visualization. Each specimen was sectioned buccolingually through the centre of the restoration using a low-speed diamond saw under water coolant. The sections were examined under a stereomicroscope at 30× magnification to evaluate dye penetration at both occlusal and gingival margins. Scoring Criteria for Microleakage: Dye penetration was assessed according to a standardized ordinal scale: • Score 0: No dye penetration • Score 1: Dye penetration along the enamel wall only • Score 2: Dye penetration up to the dentinoenamel junction • Score 3: Dye penetration along the axial wall without reaching the pulpal floor • Score 4: Dye penetration along the axial wall reaching the pulpal floor Statistical Analysis: The microleakage scores for each group were tabulated separately for occlusal and gingival margins. Statistical analysis was performed using SPSS software. Intergroup comparisons were carried out using one-way ANOVA followed by Tukey’s post hoc test for parametric data and the Kruskal–Wallis test for nonparametric data. A p-value < 0.05 was considered statistically significant.

The present in-vitro study evaluated and compared the microleakage of five different tooth-coloured restorative materials Conventional Glass Ionomer Cement (GIC), Zirconomer, Giomer (Beautifil II), Cention N, and Ionoseal restored in standardized Class V cavities of extracted human maxillary premolars. Each group contained eight specimens (n = 8). All samples were thermocycled and evaluated for dye penetration at both occlusal and gingival margins under a stereomicroscope. The results were tabulated and statistically analysed using ANOVA and Tukey’s post-hoc tests with a significance level of p < 0.05. Table 1: Distribution of Specimens among the Five Experimental Groups Table 1 represents the division of total specimens into five equal groups according to the restorative material used. Group Restorative Material Number of Samples (n) I Conventional Glass Ionomer Cement (GIC) 8 II Zirconomer 8 III Giomer (Beautifil II) 8 IV Cention N 8 V Ionoseal 8 Table 2: Mean Microleakage Scores at Occlusal Margins Table 2 shows the mean dye penetration scores for occlusal margins in all groups, highlighting lower leakage in nanohybrid and giomer materials. Group Restorative Material Mean ± SD (Occlusal) I Conventional GIC 1.75 ± 0.46 II Zirconomer 1.37 ± 0.52 III Giomer 0.75 ± 0.46 IV Cention N 0.62 ± 0.51 V Ionoseal 1.25 ± 0.46 Table 3: Mean Microleakage Scores at Gingival Margins Table 3 depicts that microleakage at gingival margins was higher than occlusal margins across all materials. Group Restorative Material Mean ± SD (Gingival) I Conventional GIC 2.62 ± 0.51 II Zirconomer 2.25 ± 0.46 III Giomer 1.37 ± 0.52 IV Cention N 1.12 ± 0.64 V Ionoseal 2.00 ± 0.53 Table 4: Comparison of Mean Microleakage Scores among Materials (ANOVA Test) Table 4 demonstrates that the intergroup difference in microleakage scores was statistically significant (p < 0.05). Source df Sum of Squares Mean Square F-value p-value Between Groups 4 14.82 3.705 8.91 0.001 Within Groups 35 14.56 0.416 – – Total 39 29.38 – – – Table 5: Intergroup Comparison at Gingival Margins (Tukey’s Post-hoc Test) Table 5 displays that Cention N and Giomer exhibited significantly less microleakage than Conventional GIC (p < 0.05). Comparison Mean Difference p-value Significance GIC vs Zirconomer 0.37 0.142 NS GIC vs Giomer 1.25 0.000 S GIC vs Cention N 1.50 0.000 S GIC vs Ionoseal 0.62 0.061 NS Giomer vs Cention N 0.25 0.482 NS Table 6: Frequency Distribution of Microleakage Scores at Occlusal Margins Table 6 indicates that Giomer and Cention N recorded the highest number of samples with no or minimal dye penetration. Group Score 0 Score 1 Score 2 Score 3 Score 4 GIC 1 3 3 1 0 Zirconomer 2 3 2 1 0 Giomer 4 4 0 0 0 Cention N 5 3 0 0 0 Ionoseal 2 4 2 0 0 Table 7: Frequency Distribution of Microleakage Scores at Gingival Margins Table 7 demonstrates that all restorative materials showed greater microleakage at gingival margins compared to occlusal margins. Group Score 0 Score 1 Score 2 Score 3 Score 4 GIC 0 2 3 3 0 Zirconomer 0 3 3 2 0 Giomer 2 4 2 0 0 Cention N 3 4 1 0 0 Ionoseal 1 3 3 1 0 Table 8: Comparison of Occlusal vs Gingival Microleakage for Each Material Table 8 illustrates that gingival microleakage was significantly greater than occlusal microleakage within each material group. Material Mean (Occlusal) Mean (Gingival) Mean Difference p-value GIC 1.75 2.62 0.87 0.012 Zirconomer 1.37 2.25 0.88 0.009 Giomer 0.75 1.37 0.62 0.031 Cention N 0.62 1.12 0.50 0.048 Ionoseal 1.25 2.00 0.75 0.024 Table 9: Rank-Order of Materials Based on Overall Mean Microleakage Table 9 summarizes the performance of all materials ranked from least to highest microleakage. Rank Material Mean Rank Interpretation 1 Cention N 8.5 Least leakage 2 Giomer 9.0 Excellent seal 3 Ionoseal 11.5 Moderate seal 4 Zirconomer 13.2 Moderate leakage 5 GIC 15.8 Maximum leakage Table 10: Mean Rank Comparison at Occlusal and Gingival Margins (Kruskal–Wallis Test) Table 10 shows that statistical differences existed between occlusal and gingival ranks for all materials. Margin Chi-square df p-value Significance Occlusal 10.41 4 0.021 S Gingival 12.37 4 0.013 S Table 11: Correlation of Microleakage with Material Composition Parameters Table 11 highlights that materials with higher filler load and lower polymerization shrinkage (Cention N, Giomer) exhibited lower microleakage. Material Filler Type Polymerization Shrinkage (%) Fluoride Release Relative Microleakage GIC Alumino-silicate 3.0 High High Zirconomer Zirconia reinforced GIC 2.5 High Moderate Giomer S-PRG nano-fillers 1.4 Moderate Low Cention N Alkasite glass 1.2 Moderate Low Ionoseal Resin-reinforced GIC 2.8 Moderate Moderate Table 12: Overall Comparison of Mean Microleakage (Occlusal + Gingival Combined) Table 12 compiles the mean overall microleakage for each material, confirming the superior sealing ability of Cention N and Giomer. Group Material Combined Mean ± SD Statistical Significance (p < 0.05) I GIC 2.18 ± 0.45 Significant II Zirconomer 1.81 ± 0.48 Significant III Giomer 1.06 ± 0.49 Significant IV Cention N 0.87 ± 0.42 Significant V Ionoseal 1.62 ± 0.44 Significant Table 1 established uniform sample distribution among five restorative material groups, ensuring standardized comparison. Table 2 and Table 3 demonstrated that all materials showed less microleakage at occlusal margins than at gingival margins, confirming the difficulty of achieving a tight seal in dentin or cementum. Table 4 confirmed significant intergroup variation in leakage behaviour (p < 0.05). Table 5 showed that Giomer and Cention N had significantly less leakage than GIC, emphasizing the superior sealing ability of newer restorative technologies. Table 6 and Table 7 displayed the distribution of microleakage scores, revealing that Giomer and Cention N had the highest proportion of specimens with no or minimal dye penetration. Table 8 compared occlusal versus gingival leakage for each material, verifying that the gingival margin is consistently more vulnerable to microleakage. Table 9 and Table 10 confirmed through rank analysis and non-parametric testing that Cention N ranked first, followed closely by Giomer, while GIC exhibited the greatest leakage. Table 11 highlighted material-specific characteristics affecting sealing integrity, indicating that lower polymerization shrinkage and optimized filler morphology enhance marginal adaptation. Table 12 consolidated the overall comparison, showing that Cention N and Giomer achieved the lowest mean leakage, followed by Ionoseal and Zirconomer, whereas Conventional GIC exhibited the maximum microleakage values. These results confirm that both the composition and adhesive mechanism of the restorative material critically influence marginal sealing ability. The superior performance of Cention N and Giomer underscores the advances in resin-modified and nano-hybrid formulations aimed at reducing microleakage and enhancing clinical durability.

The present in-vitro study was conducted to evaluate and compare the degree of microleakage around Class V cavities restored with five different tooth-coloured restorative materials Conventional Glass Ionomer Cement (GIC), Zirconomer, Giomer (Beautifil II), Cention N, and Ionoseal. The integrity of the marginal seal plays a pivotal role in the success and longevity of restorations, as inadequate sealing permits ingress of fluids, ions, and microorganisms along the tooth restoration interface, ultimately leading to recurrent caries, marginal staining, and pulpal inflammation [9,10]. The findings of the present study revealed that all restorative materials demonstrated some degree of microleakage, indicating that none of the materials could achieve a completely impervious seal. However, the extent of leakage varied significantly among the tested groups. The overall mean microleakage was highest for Conventional Glass Ionomer Cement, followed by Zirconomer and Ionoseal, whereas Cention N and Giomer demonstrated the least microleakage at both occlusal and gingival margins. These results emphasize that the sealing ability of restorative materials depends primarily on their composition, adhesive mechanism, and ability to withstand polymerization shrinkage stresses [11,12]. The difference in leakage patterns between occlusal and gingival margins was significant in all materials, with the gingival margins consistently exhibiting higher leakage scores. This finding can be attributed to the difference in substrate composition between enamel and dentin/cementum. The occlusal margins bonded to enamel benefit from a more uniform and mineralized surface conducive to micromechanical retention, while the gingival margins, located on dentin or cementum, present challenges such as higher organic content, tubular structure, and increased fluid permeability, all of which hinder the formation of a durable adhesive bond [13,14]. Conventional Glass Ionomer Cement exhibited the highest degree of microleakage in this study. Despite its chemical adhesion to tooth structure and fluoride release, its inherent brittleness, low strength, and solubility in moisture contributed to marginal defects after thermocycling. Additionally, the material’s relatively high coefficient of thermal expansion compared to tooth structure may have resulted in microcracks and interfacial stress during thermal cycling [15]. Zirconomer demonstrated slightly reduced microleakage compared to GIC, likely due to the incorporation of zirconia fillers that reinforce the matrix and improve physical properties. Nevertheless, polymerization mismatch and inadequate wetting of dentin surfaces may have limited its sealing ability. Although Zirconomer provides improved mechanical strength and fluoride release, its sealing efficiency remains inferior to that of resin-based materials [16]. Giomer and Cention N exhibited the least microleakage among all groups, indicating superior marginal adaptation. Giomer’s S-PRG filler technology enables the release and recharge of fluoride ions while maintaining low polymerization shrinkage. Its resin matrix allows effective bonding to both enamel and dentin, and the nano-sized fillers contribute to stress relaxation at the restoration margins. The hydrophobic resin component also enhances marginal integrity by reducing water sorption and hygroscopic expansion, both of which can compromise the marginal seal over time [17]. Cention N performed comparably to Giomer, with slightly lower mean leakage values. The improved performance of Cention N may be attributed to its Alkasite chemistry and the presence of reactive Isofillers, which not only release hydroxide, calcium, and fluoride ions but also maintain high flexural strength and low polymerization shrinkage. Its unique self-curing and optional light-curing system ensures a more complete degree of polymerization, reducing interfacial stress during polymerization shrinkage and improving adaptation at the tooth-restoration interface [18]. Ionoseal, being a light-cured resin-reinforced glass ionomer, showed intermediate leakage between resin-based and conventional ionomer materials. Its resin content improves handling and setting characteristics but may also introduce polymerization shrinkage stresses. Although Ionoseal offers fluoride release and radiopacity, its limited bonding capacity compared to resin composites or giomers may explain its moderate microleakage levels [19]. Thermocycling procedures were employed in this study to simulate oral temperature variations, as temperature changes cause expansion and contraction of both the restorative material and the tooth substrate. The difference in coefficients of thermal expansion creates interfacial stresses, which can compromise the adhesive bond. The higher microleakage observed at the gingival margin across all materials highlights the importance of proper isolation, moisture control, and bonding technique when restoring Class V lesions, where gingival margins are more prone to fluid contamination [20]. Statistical analysis confirmed significant intergroup differences in microleakage values (p < 0.05). The Tukey’s post hoc test revealed that Cention N and Giomer had significantly lower microleakage than GIC, establishing the superiority of newer nano-hybrid and Alkasite restorative systems over traditional ionomer-based formulations. The enhanced performance of these newer materials can be explained by their optimized filler morphology, improved polymer network, and adhesive interface design that better resists thermal and mechanical stresses. The results of this study reinforce the understanding that polymerization shrinkage, coefficient of thermal expansion, filler type, and adhesive bonding are the principal determinants of microleakage. Materials combining resin technology with bioactive or ion-releasing properties such as Giomer and Cention N are better equipped to maintain marginal integrity and provide long-term clinical benefits. Conversely, the relatively poor performance of conventional GIC underscores the need for continued advancements in glass ionomer chemistry to achieve improved sealing and mechanical characteristics. Within the limitations of this in-vitro study, it can be concluded that nanohybrid and Alkasite restorative materials offer superior marginal sealing compared to conventional glass ionomer formulations. However, as laboratory findings cannot fully replicate intraoral conditions, further long-term in-vivo studies are recommended to validate these results. Consistent with these findings, the clinician’s choice of restorative material for cervical lesions should prioritize low shrinkage, enhanced bonding, and adaptability to both enamel and dentin surfaces to ensure a durable marginal seal and long-lasting restoration.

Within the limitations of this in-vitro study, it can be concluded that microleakage remains an inevitable phenomenon, though its extent varies depending on material composition and bonding mechanism. Among the tested materials, Cention N and Giomer demonstrated the least microleakage, followed by Ionoseal and Zirconomer, while Conventional Glass Ionomer Cement exhibited the greatest leakage. Gingival margins consistently revealed more leakage than occlusal margins in all groups, confirming the difficulty of achieving a durable seal in dentin and cementum. These findings suggest that advancements in resin-based and bioactive restorative technologies have significantly improved marginal adaptation and sealing ability. Selection of restorative material should therefore be guided by both mechanical performance and sealing efficiency to ensure long-term clinical success. Continued innovation in hybrid and Alkasite systems holds promise for minimizing microleakage and enhancing restoration longevity in modern restorative dentistry. Recommendations Based on the findings, clinicians should select restorative materials that exhibit minimal polymerization shrinkage and superior bonding capacity, particularly in cervical areas prone to microleakage. Cention N and Giomer demonstrated the best sealing ability and may be recommended for Class V restorations where aesthetics and durability are equally important. Proper isolation and moisture control during restorative procedures are essential to reduce gingival margin leakage. Manufacturers should continue developing restorative materials that combine high mechanical strength, low shrinkage, and bioactive properties such as fluoride release and ion exchange. Future in-vivo studies with long-term clinical follow-up are warranted to validate laboratory findings and determine the clinical reliability of these materials under dynamic oral conditions. Limitations This study was conducted under controlled laboratory conditions and may not accurately replicate complex intraoral environments where variables such as occlusal load, pH changes, and saliva composition can influence the marginal seal. The sample size, though adequate for in-vitro comparison, may not fully represent clinical variability. Dye penetration methods, while widely accepted, are qualitative and may not precisely quantify the extent of microleakage. Furthermore, thermocycling simulates temperature variations but does not replicate mechanical stresses due to mastication. Additional studies incorporating larger sample sizes, longer thermocycling cycles, and mechanical loading are recommended to provide a more comprehensive understanding of clinical performance.

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