Dental caries is still one of the most common oral diseases around the globe and is still a significant problem for restorative dentistry.[1] According to the World Health Organization (WHO), about 2.3 billion people suffer from caries in their permanent teeth, and untreated dental caries is the most prevalent health condition in the world.[2]  The Global Burden of Disease estimates for more recent data show a slight decrease in age-standardized prevalence rates, but the absolute rates have risen from approximately 2.20 billion untreated cases of caries in permanent teeth in 2019 to 2.26 billion in 2023.[3]  This chronic problem of caries has raised the need for restorative materials that can restore the anatomical form and function and also have better resistance to secondary caries and marginal breakdown.[4]

The conventional resin composite materials are popular due to their good esthetics, mechanical properties, and adhesive restorative ability.[5] Polymerization shrinkage, dimensional changes, and different thermal expansion of the restorative materials and the tooth structure can all play a role in creating marginal gaps and microleakage.[6] Microleakage allows bacteria, fluids, and oral substances to enter the restoration–tooth interface and can cause postrestoration sensitivity, restorative marginal discoloration, recurrent caries, and may lead to ultimate failure.[7] Hence, the development of restorative materials with enhanced marginal integrity and biologically favourable properties has been a key research interest of modern restorative dentistry.[8]

There is growing awareness of secondary caries as an important cause of the failure of restorations, along with a renewed interest in restorative materials containing antibacterial and bioactive properties.[9]  Giomers are a type of resin-based restoratives that combine the esthetic and handling properties of resin composites with ion-releasing characteristics through the inclusion of surface pre-reacted glass-ionomer (S-PRG) fillers.[10] Alkasite materials, however, are comparatively newer bioactive restorative materials with alkaline fillers that can release ions and assist in creating an alkaline environment.[11] The pH-responsive behavior has been of great interest since the release of ions possibly could affect bacterial activity, remineralization, and marginal stability.[11]

Data on the comparison of these newer materials and the traditional resin composite is rather scarce and inconsistent. Some previous experimental studies have shown that the marginal integrity is different between giomer, alkasite, and other ion-releasing restorative materials, and that alkasite has good marginal integrity under some experimental conditions.[8] Similarly, an in vitro study of an alkaline-filler resin composite revealed that the microleakage was also lower than that of the incremental nanohybrid resin composite, but its antibacterial effect was relatively limited.[12] These results indicate that the relationship between antibacterial activity and marginal sealing is not always material-dependent, and therefore simultaneous evaluation of both properties is of special interest.

Although the use of giomer and alkasite restorative materials is gaining popularity, a direct comparison of these materials with conventional resin composite under the same experimental conditions is still needed, in particular when considering the simultaneous antibacterial activity and microleakage. The assessment of these two clinically relevant properties could give a more extensive perspective on the potential benefits of the new bioactive restorative materials, compared to the traditional composite method. Based on this, the present study aimed to comparatively assess the antibacterial activity and microleakage of giomer, alkasite, and conventional resin composite restorations.

An in vitro experimental comparative study was conducted in the Department of Dental Materials, Bilawal Medical College, Liaquat University of Medical and Health Sciences, Jamshoro. The study spanned six months from 1st January 2026 to 30th June 2026. The study aimed to assess and compare the antimicrobial activity and microleakage of giomer, alkasite, and conventional resin composite restorative materials under standard laboratory conditions. The sample size was determined using OpenEpi software, which incorporated experimental data previously reported on the antibacterial activity of modern bioactive restorative materials. In a recent study by Kong et al., the sample size for the materials evaluated was six specimens per material and was calculated from a two-sided comparison of means with a standard deviation of 0.025, a difference anticipated of 0.10, 80% power, and a significance level of 0.05.[13] Considering the need to evaluate three restorative materials and to provide adequate specimens for both antibacterial and microleakage assessments, the present study included 60 specimens, with 20 specimens allocated to each material group. This allocation was also found to be in line with the previous comparative laboratory study that used 20 specimens per material for the antibacterial study. Accordingly, the specimens were randomly divided into three equal groups: Group I consisted of 20 giomer specimens, Group II consisted of 20 alkasite specimens, and Group III consisted of 20 conventional resin composite specimens. Standardized specimens were used for antibacterial testing and microleakage testing separately, so as not to interfere between the two experimental methods. Extracted human teeth and restorative-material samples were selected by the non-probability purposive sampling technique. Crowns that were intact with sound enamel and dentin, and without clinically detectable caries, cracks, fractures, restorations, developmental defects, and structural abnormalities of the extracted human permanent posterior teeth were included. Tooth removal for therapy and/or orthodontics with sufficient crown structure for standard cavity preparation was eligible. Standardized disc-shaped specimens of the three materials, giomer, alkasite, and conventional resin composite, were prepared following the respective manufacturers' instructions for the antibacterial evaluation. Carious, previously restored, cracked, fractured, hypoplastic defects, severe attrition, erosion, abrasion, or other structural abnormalities were excluded from the study. Teeth with poor crown structure for normal cavity preparation were also not considered. Specimens with visible voids, fractures, incomplete polymerization, dimensional defects, and/or damage during preparation were discarded and substituted with specimens that had to be newly prepared. Extracted teeth were initially cleaned of residual calculus and soft-tissue remnants using hand instruments and disinfected in 0.5% sodium hypochlorite solution for 30 minutes. The teeth were then rinsed thoroughly with copious amounts of distilled water and stored in distilled water until specimen preparation. The teeth were then rinsed with copious amounts of water and prepared with a standard cavity configuration. Standardized Class V cavities measuring 4 mm in mesiodistal width, 3 mm in occlusogingival height, and 2 mm in depth were prepared on the buccal surfaces of the selected teeth using a calibrated diamond bur. The specimens were randomly divided into three groups based on the type of restorative material used. Group I was restored using giomer, Group II using alkasite, and Group III using conventional resin composite. All of the restorative materials were manipulated and polymerized according to the respective manufacturers' instructions. Light-cured materials were cured using a standardized curing light, and the light intensity was determined prior to the preparation of specimens. Standardized cylindrical disc-shaped specimens of each restorative material, measuring 5 mm in diameter and 2 mm in thickness, were prepared in sterile molds of identical dimensions for assessing antibacterial activity. The specimens were prepared under aseptic conditions and were sterilized in a manner suitable for specimens of restorative materials, but without changing their surface properties. Antibacterial activity was tested against Streptococcus mutans, one of the most important cariogenic bacteria. A standardized bacterial suspension was prepared, and the antibacterial activity of each material was evaluated using a suitable agar diffusion/direct contact method. When present, the diameter of the bacterial inhibition zone was determined in mm with a calibrated measuring device measured after incubation at a standard temperature and time. Direct-contact testing, when conducted, was performed by quantitative assessment of the number of colony-forming units of the bacteria. Microleakage assessments were performed by standardizing the thermocycling of the restored teeth, which simulates the thermal stresses found intraorally. An impermeable protective layer was applied to the external surfaces of the teeth, with a standardized area around the margins of the restoration free of any protection. The specimens were then stained in an appropriate dye solution for a fixed amount of time to ensure penetration in all marginal spaces. Teeth were then rinsed after dye exposure, split longitudinally down the center of the restoration, and evaluated under a stereomicroscope. The microleakage level was assessed at the interface between the tooth and the restoration using a standardized microleakage scoring method. Previous studies that have involved a similar methodology of thermocycling, immersion in dye, sectioning, and microscopic analysis have been done on other restorative materials, including alkasite. Standardized procedures for all laboratory techniques were followed, and when possible, the examiner evaluating the antibacterial activity and microleakage was blinded to the restorative-material group. The main results were the size of the inhibition zone or the viability of the bacteria, and the extent of dye penetration or microleakage. All the data obtained were compiled in MS Excel and analyzed by IBM SPSS Statistics software. All continuous variables such as quantitative microleakage and inhibition-zone diameter were presented as mean ± SD and median (IQR). Microleakage scores were presented as frequencies and percentages, and categorized variables were presented as percentages. Shapiro–Wilk test was used to determine the normality of continuous data. Normally distributed continuous outcomes were compared between the three restorative-material groups by one-way analysis of variance and a multiple-comparison test. Kruskal–Wallis test with pairwise post hoc comparisons was used in the case of non-normally distributed data. Comparisons between categorical microleakage scores were made by the chi-square test and fisher's exact test. A two-sided p-value of <0.05 was considered statistically significant.

A total of 60 specimens were evaluated, comprising 20 specimens each in the giomer, alkasite, and conventional resin composite groups. The distribution of specimen dimensions, cavity width, cavity depth, cavity location, and tooth type was similar between the three groups, as these were standardized during specimen preparation. Premolars made up 58.3% of the total number of specimens; molars comprised 41.7% of the total number of specimens. Occlusal and cervical specimens were examined in equal numbers. (Table 1)

There were significant differences in antibacterial activity of the three restorative materials against S. mutans. Alkasite exhibited the greatest mean inhibition zone (15.8±2.4 mm), followed by giomer (12.4±2.1 mm), and conventional resin composite exhibited a significantly smaller inhibition zone (4.7±1.3 mm). The overall difference was statistically significant (p<0.001). All giomer and alkasite specimens exhibited a detectable inhibition zone, while 85.0% of conventional resin composite specimens did so (p=0.040). (Table 2)

The alkasite resulted in a significantly greater zone of inhibition compared to giomer (mean difference 3.4 mm, p=0.002) by pairwise analysis. The antibacterial activity of both alkasite and giomer was significantly higher than the conventional resin composite (p<0.001 for both comparisons). (Table 3)

The microleakage analysis showed that there was a significant difference between the three groups (p=0.018). No dye penetration was observed in 55.0% of alkasite specimens, compared with 40.0% of giomer and 15.0% of conventional resin composite specimens. In the conventional resin composite group, severe microleakage was seen in 20.0% of the specimens, whereas it was 5.0% in each of the giomer and alkasite groups. (Table 4)

The median microleakage score was lowest in the alkasite group at 0.5 (IQR 0–1), followed by giomer at 1 (IQR 0–1), while conventional resin composite had the highest median score of 2 (IQR 1–2). The overall difference was statistically significant (p=0.009). Post-hoc analysis revealed that the microleakage in the other two groups (alkasite, giomer) was significantly lower than that in the conventional resin composite group, but there was no significant difference between the two experimental groups (alkasite and giomer). (Tables 5 and 6)

There was an inverse correlation between the antibacterial activity and the microleakage that occurred in all specimens, with the larger the inhibition-zone diameter, the lower the microleakage score (r=-0.56, p<0.001). The association was statistically significant for giomer and alkasite but not for the conventional resin composite group. (Table 7)

In general, the study results showed that there were significant differences in both main outcomes between the three restorative materials. Alkasite showed the largest antibacterial inhibition zone and the lowest microleakage score, while conventional resin composite showed the smallest antibacterial inhibition zone and greater microleakage. The intermediate levels of antibacterial activity were shown by giomer. Giomer exhibited intermediate microleakage and antibacterial activity values. (Table 8)

Table 1. Distribution and baseline characteristics of specimens according to restorative material

Table 2. Comparison of antibacterial activity against Streptococcus mutans

Table 3. Pairwise comparison of antibacterial activity

Table 4. Distribution of microleakage scores among restorative materials

Table 5. Comparison of overall microleakage scores

Table 6. Pairwise comparison of microleakage scores

Table 7. Relationship between antibacterial activity and microleakage

Table 8. Summary comparison of the principal study outcomes

The results of this in vitro study for antibacterial activity were in line with the findings of Kong et al. (2025) in an in vitro study that directly compared four conventional composites, giomer, alkasite, high-viscosity glass ionomer, and zirconia-reinforced glass ionomer against S. mutans. Biofilm biomass was assessed based on crystal violet and bacterial viability on the basis of colony forming unit count. They showed that the behavior of bacteria differed significantly from one restorative material to another, thus reinforcing the idea that bioactive materials in use today are able to influence bacterial colonization. The study also revealed, however, that the effect of the antibacterial was variable depending on the type of material and the method of measurement. The present finding that the alkasite exhibited a larger inhibition zone thus confirms the biological activity of the materials, but at the same time, the results are not directly comparable, since the present study employed measurement of the inhibition zone, while Kong et al. employed the biofilm and CFU-based methods.[13] Likewise, an experimental study on antibacterial activity and fluoride release of giomer and Cention N in comparison to resin-modified glass ionomer and zirconomer was investigated in 2022. Twenty specimens were prepared for each material group, and antibacterial activity against S. mutans was evaluated by a direct-contact method. The results in the study showed measurable antibacterial activity for all materials tested that released ions. The results of the present study corroborate the current observation that giomer and alkasite are more bactericidal than conventional resin composite. The magnitude and ranking of the antibacterial activity may differ from the previous investigation, where a direct-contact assay was used instead of an agar inhibition-zone test as used in the present investigation.[14] In 2024, Obaees et al. examined the antibacterial activity and pH modification of Cention N and other ion-releasing restorative materials against S. mutans and Lactobacillus plantarum. The antibacterial effect of both Cention N and Cention Forte (no primers) was confirmed through the reduction of the number of viable bacteria, and both also yielded a higher pH than the glass-ionomer comparison material. The observations of the present study suggest a possible explanation for this increased antibacterial effect of alkasite, since an alkaline environment could be detrimental to the growth of cariogenic microorganisms. However, Obaees et al. did not find any significant differences in viable bacterial counts in some of the materials tested, suggesting that the superiority in terms of antibacterial properties can be material and/or test-dependent.[15] The antibacterial properties were also confirmed by Dey et al., who carried out a study to determine the ability of alkasite (glass-hybrid restorative material) and nanohybrid resin composite to inhibit bacterial adhesion. The study they performed showed that the optical density and the number of colony-forming units were significantly lower for alkasite than for the nanohybrid composite. Interestingly, the surface of the nanohybrid composite was smoother than that of the alkasite, but the effect of this smoothness was not to reduce the adhesion of bacteria, indicating that the surface properties are not the only factor that can influence the adhesion of bacteria; material composition is also important. The present finding of higher antibacterial activity of alkasite is, therefore, consistent with evidence based on both quantitative bacterial count and microscopic evaluation.[16] In terms of microleakage, the present results concurred with Motevasselian et al., who evaluated Cention N, resin composite, and resin-modified glass ionomer in Class V cavities. Microleakage was seen in all the restorative groups following thermocycling and dye penetration evaluation. Cention N demonstrated microleakage values comparable to composite resin and decreased leakage than resin-modified glass ionomer at some margins. The investigators also reported higher leakage at dentin margins compared to the enamel margins. In the present study, it was also found that the sealing of the margins of alkasite was relatively good when compared with conventional resin composite, but in varying amounts depending on the experimental model.[17] Mohamed et al. analyzed an alkasite restorative material compared to incremental nanohybrid resin composite, a comparison that was especially relevant. They examined microleakage after thermocycling and dye penetration, concluding that self-cured alkasite had the least microleakage, dual-cured alkasite and incremental nanohybrid composite had the next least microleakage, and the G-Plex control had the highest. They also showed that the cervical microleakage was significantly more than the occlusal microleakage. The present findings are similar to these results, where alkasite had the lowest degree of microleakage and conventional resin composite had the highest degree of leakage. The resemblance could be associated with the ion-releasing alkaline fillers and marginal adaptation properties of alkasite.[18] In 2022, Kim et al. compared the microleakage performance of alkasite with that of giomer and resin-modified glass ionomer under varying pH conditions. In 2022, Kim et al. compared the microleakage performance of alkasite with that of giomer and resin-modified glass ionomer under different pH conditions. Their study specifically tested microleakage in class V restorations and found that the materials' performance varied with different environmental pH conditions. The research highlighted that the chemical environment surrounding restorative materials could have an impact on their marginal integrity, as they are ion-releasing. The results of this present study indicated that the median microleakage score of the alkasite was lower than giomer and conventional resin composite under the standardized experimental conditions used, indicating that the marginal behavior of the alkasite may be satisfactory.[8] The present results for giomer were somewhat echoed by Kim et al., in 2023, who compared the self-adhesive giomer with conventional flowable composite resin with regard to shear bond strength and microleakage. This study found that significantly more microleakage occurred at the self-adhesive giomer compared to conventional flowable composite resin. These differences between the present findings (giomer having lower microleakage than conventional resin composite) might be attributed to the variation in the giomer formulation, adhesive protocol, cavity design, and comparator material. The disparity illustrates that the term “giomer” can be applied to materials of different formulations, and that the performance of the margins should not be assumed to apply to all giomer products.[19] Likewise, in 2024, Şenol et al. compared the performance of glass ionomer, giomer, and methacrylate-based composite restorations in Class V cavities both with and without chlorhexidine pretreatment. They found that the choice of restorative material, as well as the type of pretreatment, could affect microleakage. This is consistent with the concept that the marginal integrity of giomer and resin composite is not solely dependent on the restorative material. The final level of dye penetration can be affected by the type of adhesive used, cavity configuration, surface preparation, or dentin or enamel margins. This intermediate microleakage in giomer in the present study, however, may be attributed to a mixture of its material composition and standardized restorative protocol.[20] There are interesting laboratory findings in light of recent clinical evidence. In the study by Oz et al., Class II restorations were prepared in patients and filled with Cention N or resin composite, and the clinical performance was evaluated after 12 months. Cention N and resin composite showed the same clinical performance after 12 months. At some follow-up points, Cention N had increased scores for borderline marginal adaptation, but this was not significant at 12 months. There was no postoperative sensitivity or second caries found in either group. The current clinical results suggest that good laboratory microleakage characteristics of alkasite do not automatically lead to clinically better performance in the short term compared to conventional resin composite.[21] This is confirmed by the results of Sharma et al. (2023). A randomized clinical trial was conducted to track alkasite and nanofilled resin composite restorations in children for 1 year in their permanent molars. The study revealed that both materials showed satisfactory clinical performance. The present laboratory study demonstrated that microleakage was lowest with alkasite, but clinical studies suggest that significant differences in marginal integrity may not lead to significant differences in restoration performance over a relatively short follow-up period.[22] In addition, Amrollahi et al. 2025 reported in a systematic review and meta-analysis on the marginal effect of Cention N. The review included 12 in vitro studies and found that, when bonding agents were used, Cention N had significantly lower microleakage than conventional glass-ionomer cement. There was significant inter-study variation, however, suggesting that various bonding protocols, cavity designs, restorative materials, and laboratory techniques can significantly influence microleakage outcomes. The present results underscore the need to carefully analyze the current data under the experimental conditions used to obtain the data.[23] .Overall, the results from the present study contribute to the increasing experimental findings comparing ion-releasing restorative materials to traditional resin composites. The findings indicated that under laboratory conditions, alkasite and giomer might have measurable antibacterial activity, in addition to good marginal sealing. However, recent clinical research has generally failed to confirm clinical superiority of alkasite restorations, as compared with conventional resin composites. Hence, it is important to note that the laboratory advantages found in the present study may be material-specific and not necessarily a reflection of the long-term clinical performance. The major advantage of the present investigation was that both antibacterial activity and microleakage were measured simultaneously and compared on the same basis. Nevertheless, several limitations should be considered. The study was performed in vitro and could not simulate the complexity of oral conditions such as multispecies biofilms, salivary flow, masticatory forces, dietary acids, and aging. The use of S. mutans as a single bacterial species also does not represent the complexity of dental plaque. Furthermore, the results from the agar diffusion can be underestimated or overestimated depending on the diffusibility of the components of the material. In the same way, dye penetration is an indirect measurement of microleakage and may not fully reflect clinical bacterial penetration. Real multispecies biofilms, quantitative CFU analysis, ion-release measurement, surface roughness assessment, micro-computed tomography and/or confocal microscopy, and extended-term thermomechanical ageing would help evaluate these materials more fully.

A total of 60 specimens were evaluated, comprising 20 specimens each in the giomer, alkasite, and conventional resin composite groups. The distribution of specimen dimensions, cavity width, cavity depth, cavity location, and tooth type was similar between the three groups, as these were standardized during specimen preparation. Premolars made up 58.3% of the total number of specimens; molars comprised 41.7% of the total number of specimens. Occlusal and cervical specimens were examined in equal numbers. (Table 1)

There were significant differences in antibacterial activity of the three restorative materials against S. mutans. Alkasite exhibited the greatest mean inhibition zone (15.8±2.4 mm), followed by giomer (12.4±2.1 mm), and conventional resin composite exhibited a significantly smaller inhibition zone (4.7±1.3 mm). The overall difference was statistically significant (p<0.001). All giomer and alkasite specimens exhibited a detectable inhibition zone, while 85.0% of conventional resin composite specimens did so (p=0.040). (Table 2)

The alkasite resulted in a significantly greater zone of inhibition compared to giomer (mean difference 3.4 mm, p=0.002) by pairwise analysis. The antibacterial activity of both alkasite and giomer was significantly higher than the conventional resin composite (p<0.001 for both comparisons). (Table 3)

The microleakage analysis showed that there was a significant difference between the three groups (p=0.018). No dye penetration was observed in 55.0% of alkasite specimens, compared with 40.0% of giomer and 15.0% of conventional resin composite specimens. In the conventional resin composite group, severe microleakage was seen in 20.0% of the specimens, whereas it was 5.0% in each of the giomer and alkasite groups. (Table 4)

The median microleakage score was lowest in the alkasite group at 0.5 (IQR 0–1), followed by giomer at 1 (IQR 0–1), while conventional resin composite had the highest median score of 2 (IQR 1–2). The overall difference was statistically significant (p=0.009). Post-hoc analysis revealed that the microleakage in the other two groups (alkasite, giomer) was significantly lower than that in the conventional resin composite group, but there was no significant difference between the two experimental groups (alkasite and giomer). (Tables 5 and 6)

There was an inverse correlation between the antibacterial activity and the microleakage that occurred in all specimens, with the larger the inhibition-zone diameter, the lower the microleakage score (r=-0.56, p<0.001). The association was statistically significant for giomer and alkasite but not for the conventional resin composite group. (Table 7)

In general, the study results showed that there were significant differences in both main outcomes between the three restorative materials. Alkasite showed the largest antibacterial inhibition zone and the lowest microleakage score, while conventional resin composite showed the smallest antibacterial inhibition zone and greater microleakage. The intermediate levels of antibacterial activity were shown by giomer. Giomer exhibited intermediate microleakage and antibacterial activity values. (Table 8)

Table 1. Distribution and baseline characteristics of specimens according to restorative material

Table 2. Comparison of antibacterial activity against Streptococcus mutans

Table 3. Pairwise comparison of antibacterial activity

Table 4. Distribution of microleakage scores among restorative materials

Table 5. Comparison of overall microleakage scores

Table 6. Pairwise comparison of microleakage scores

Table 7. Relationship between antibacterial activity and microleakage

Table 8. Summary comparison of the principal study outcomes

The results of this in vitro study for antibacterial activity were in line with the findings of Kong et al. (2025) in an in vitro study that directly compared four conventional composites, giomer, alkasite, high-viscosity glass ionomer, and zirconia-reinforced glass ionomer against S. mutans. Biofilm biomass was assessed based on crystal violet and bacterial viability on the basis of colony forming unit count. They showed that the behavior of bacteria differed significantly from one restorative material to another, thus reinforcing the idea that bioactive materials in use today are able to influence bacterial colonization. The study also revealed, however, that the effect of the antibacterial was variable depending on the type of material and the method of measurement. The present finding that the alkasite exhibited a larger inhibition zone thus confirms the biological activity of the materials, but at the same time, the results are not directly comparable, since the present study employed measurement of the inhibition zone, while Kong et al. employed the biofilm and CFU-based methods.[13] Likewise, an experimental study on antibacterial activity and fluoride release of giomer and Cention N in comparison to resin-modified glass ionomer and zirconomer was investigated in 2022. Twenty specimens were prepared for each material group, and antibacterial activity against S. mutans was evaluated by a direct-contact method. The results in the study showed measurable antibacterial activity for all materials tested that released ions. The results of the present study corroborate the current observation that giomer and alkasite are more bactericidal than conventional resin composite. The magnitude and ranking of the antibacterial activity may differ from the previous investigation, where a direct-contact assay was used instead of an agar inhibition-zone test as used in the present investigation.[14] In 2024, Obaees et al. examined the antibacterial activity and pH modification of Cention N and other ion-releasing restorative materials against S. mutans and Lactobacillus plantarum. The antibacterial effect of both Cention N and Cention Forte (no primers) was confirmed through the reduction of the number of viable bacteria, and both also yielded a higher pH than the glass-ionomer comparison material. The observations of the present study suggest a possible explanation for this increased antibacterial effect of alkasite, since an alkaline environment could be detrimental to the growth of cariogenic microorganisms. However, Obaees et al. did not find any significant differences in viable bacterial counts in some of the materials tested, suggesting that the superiority in terms of antibacterial properties can be material and/or test-dependent.[15] The antibacterial properties were also confirmed by Dey et al., who carried out a study to determine the ability of alkasite (glass-hybrid restorative material) and nanohybrid resin composite to inhibit bacterial adhesion. The study they performed showed that the optical density and the number of colony-forming units were significantly lower for alkasite than for the nanohybrid composite. Interestingly, the surface of the nanohybrid composite was smoother than that of the alkasite, but the effect of this smoothness was not to reduce the adhesion of bacteria, indicating that the surface properties are not the only factor that can influence the adhesion of bacteria; material composition is also important. The present finding of higher antibacterial activity of alkasite is, therefore, consistent with evidence based on both quantitative bacterial count and microscopic evaluation.[16] In terms of microleakage, the present results concurred with Motevasselian et al., who evaluated Cention N, resin composite, and resin-modified glass ionomer in Class V cavities. Microleakage was seen in all the restorative groups following thermocycling and dye penetration evaluation. Cention N demonstrated microleakage values comparable to composite resin and decreased leakage than resin-modified glass ionomer at some margins. The investigators also reported higher leakage at dentin margins compared to the enamel margins. In the present study, it was also found that the sealing of the margins of alkasite was relatively good when compared with conventional resin composite, but in varying amounts depending on the experimental model.[17] Mohamed et al. analyzed an alkasite restorative material compared to incremental nanohybrid resin composite, a comparison that was especially relevant. They examined microleakage after thermocycling and dye penetration, concluding that self-cured alkasite had the least microleakage, dual-cured alkasite and incremental nanohybrid composite had the next least microleakage, and the G-Plex control had the highest. They also showed that the cervical microleakage was significantly more than the occlusal microleakage. The present findings are similar to these results, where alkasite had the lowest degree of microleakage and conventional resin composite had the highest degree of leakage. The resemblance could be associated with the ion-releasing alkaline fillers and marginal adaptation properties of alkasite.[18] In 2022, Kim et al. compared the microleakage performance of alkasite with that of giomer and resin-modified glass ionomer under varying pH conditions. In 2022, Kim et al. compared the microleakage performance of alkasite with that of giomer and resin-modified glass ionomer under different pH conditions. Their study specifically tested microleakage in class V restorations and found that the materials' performance varied with different environmental pH conditions. The research highlighted that the chemical environment surrounding restorative materials could have an impact on their marginal integrity, as they are ion-releasing. The results of this present study indicated that the median microleakage score of the alkasite was lower than giomer and conventional resin composite under the standardized experimental conditions used, indicating that the marginal behavior of the alkasite may be satisfactory.[8] The present results for giomer were somewhat echoed by Kim et al., in 2023, who compared the self-adhesive giomer with conventional flowable composite resin with regard to shear bond strength and microleakage. This study found that significantly more microleakage occurred at the self-adhesive giomer compared to conventional flowable composite resin. These differences between the present findings (giomer having lower microleakage than conventional resin composite) might be attributed to the variation in the giomer formulation, adhesive protocol, cavity design, and comparator material. The disparity illustrates that the term “giomer” can be applied to materials of different formulations, and that the performance of the margins should not be assumed to apply to all giomer products.[19] Likewise, in 2024, Şenol et al. compared the performance of glass ionomer, giomer, and methacrylate-based composite restorations in Class V cavities both with and without chlorhexidine pretreatment. They found that the choice of restorative material, as well as the type of pretreatment, could affect microleakage. This is consistent with the concept that the marginal integrity of giomer and resin composite is not solely dependent on the restorative material. The final level of dye penetration can be affected by the type of adhesive used, cavity configuration, surface preparation, or dentin or enamel margins. This intermediate microleakage in giomer in the present study, however, may be attributed to a mixture of its material composition and standardized restorative protocol.[20] There are interesting laboratory findings in light of recent clinical evidence. In the study by Oz et al., Class II restorations were prepared in patients and filled with Cention N or resin composite, and the clinical performance was evaluated after 12 months. Cention N and resin composite showed the same clinical performance after 12 months. At some follow-up points, Cention N had increased scores for borderline marginal adaptation, but this was not significant at 12 months. There was no postoperative sensitivity or second caries found in either group. The current clinical results suggest that good laboratory microleakage characteristics of alkasite do not automatically lead to clinically better performance in the short term compared to conventional resin composite.[21] This is confirmed by the results of Sharma et al. (2023). A randomized clinical trial was conducted to track alkasite and nanofilled resin composite restorations in children for 1 year in their permanent molars. The study revealed that both materials showed satisfactory clinical performance. The present laboratory study demonstrated that microleakage was lowest with alkasite, but clinical studies suggest that significant differences in marginal integrity may not lead to significant differences in restoration performance over a relatively short follow-up period.[22] In addition, Amrollahi et al. 2025 reported in a systematic review and meta-analysis on the marginal effect of Cention N. The review included 12 in vitro studies and found that, when bonding agents were used, Cention N had significantly lower microleakage than conventional glass-ionomer cement. There was significant inter-study variation, however, suggesting that various bonding protocols, cavity designs, restorative materials, and laboratory techniques can significantly influence microleakage outcomes. The present results underscore the need to carefully analyze the current data under the experimental conditions used to obtain the data.[23] .Overall, the results from the present study contribute to the increasing experimental findings comparing ion-releasing restorative materials to traditional resin composites. The findings indicated that under laboratory conditions, alkasite and giomer might have measurable antibacterial activity, in addition to good marginal sealing. However, recent clinical research has generally failed to confirm clinical superiority of alkasite restorations, as compared with conventional resin composites. Hence, it is important to note that the laboratory advantages found in the present study may be material-specific and not necessarily a reflection of the long-term clinical performance. The major advantage of the present investigation was that both antibacterial activity and microleakage were measured simultaneously and compared on the same basis. Nevertheless, several limitations should be considered. The study was performed in vitro and could not simulate the complexity of oral conditions such as multispecies biofilms, salivary flow, masticatory forces, dietary acids, and aging. The use of S. mutans as a single bacterial species also does not represent the complexity of dental plaque. Furthermore, the results from the agar diffusion can be underestimated or overestimated depending on the diffusibility of the components of the material. In the same way, dye penetration is an indirect measurement of microleakage and may not fully reflect clinical bacterial penetration. Real multispecies biofilms, quantitative CFU analysis, ion-release measurement, surface roughness assessment, micro-computed tomography and/or confocal microscopy, and extended-term thermomechanical ageing would help evaluate these materials more fully.

This study provides valuable insights into the The present in vitro study showed that the antibacterial activity and microleakage of giomer, alkasite, and conventional resin composite restorative materials are significantly different. Alkasite was most effective against Streptococcus mutans with the lowest degree of microleakage, whereas conventional resin composite showed the lowest antibacterial activity and highest microleakage. Giomer had intermediate results for both outcomes. The results suggest that the ion-releasing restorative materials could offer a desirable antimicrobial and marginal sealing capability in a laboratory setting. The findings need to be taken with a pinch of salt, though, because in vitro behavior does not always reflect in vivo behavior.