Performance of an alkasite restorative material under acidic conditions: surface roughness, gloss and hardness

Abstract

In this study, the effects of acidic environments on the surface integrity of an alkasite-based resin composite (Cention Forte, CF) were compared with those of a nanohybrid composite (Z250 XT) and a resin-modified glass ionomer (Fuji II LC, FLC). The samples (n = 6) were immersed for 96 h at 37 °C in Coca-Cola (CC, pH 2.6), simulated gastric acid (SGA, pH 1.2) or artificial saliva (pH 6.5). Surface roughness (Ra and Rz), gloss, and microhardness were measured, and morphology was examined using scanning electron microscopy (SEM). Significant effects of material, solution and their interaction were observed (p < 0.001). In artificial saliva, CF exhibited Ra and Rz values (0.34 ± 0.03 and 2.39 ± 0.33 μm, respectively) comparable to those of FLC, intermediate gloss (46.30 ± 1.47 GU), and the lowest microhardness (59.01 ± 2.57 VHN). In CC and SGA, CF had higher roughness (Ra: 0.52 ± 0.10 and 0.71 ± 0.12 μm; Rz: 3.16 ± 0.78 and 4.05 ± 0.74 μm, respectively), lower gloss (32.72 ± 1.13 and 23.47 ± 1.18 GU), and lower microhardness (51.99 ± 3.15 and 42.70 ± 3.59 VHN) than FLC. SEM analysis confirmed these findings, showing matrix erosion and filler loss in CF. Z250 XT consistently maintained superior integrity. Clinically, these findings suggest that alkasite-based restorations may be less durable in patients with frequent dietary acid exposure or gastric reflux.

Introduction

Erosive tooth wear has become an increasingly common concern in modern dentistry and is influenced significantly by evolving lifestyles and dietary patterns as well as medical conditions such as gastroesophageal reflux disease (GERD)¹. Frequent consumption of acidic food and beverages can progressively demineralize enamel and dentin, leading to dietary erosion^1,2. On the other hand, endogenous erosion results from internal acids reaching the oral cavity through conditions such as GERD or recurrent vomiting². Regardless of the cause, both types of erosion ultimately lead to progressive loss of hard dental tissue, compromising structural integrity, function and aesthetics³.

The management of erosive tooth wear necessitates timely diagnosis, preventive strategies, and careful selection of restorative materials capable of withstanding the acidic oral environment. With respect to moderate wear lesions, resin-based composites (RBCs) offer a minimally invasive approach along with excellent aesthetics and favorable mechanical properties³. Nevertheless, their inability to promote remineralization remains a limitation.

Consequently, bioactive RBCs have attracted considerable attention, as they are designed not only to restore tooth structure but also to release ions that buffer acidic conditions, enhance remineralization, and inhibit cariogenic activity^4–6. Although resin-modified glass ionomers (RMGICs) have traditionally served as the primary representatives of this class, their mechanical properties remain inferior to those of conventional RBCs, with reported flexural strengths of 40–80 MPa and Vickers hardness values of 30–50 VHN compared to 100–160 MPa and 60–90 VHN for modern nanohybrid RBCs^7–9.

Recently, an innovative class of restorative materials known as alkasites has emerged, represented by Cention N and Cention Forte. Alkasites are bulk-fill RBCs enriched with alkaline calcium-fluoro-silicate glass fillers capable of releasing hydroxide, calcium, and fluoride ions¹⁰. The release of these ions enables the material to function as a pH-responsive or “smart” material that actively neutralizes acidic environments, maintaining a favorable mineral balance at the tooth–restoration interface⁶. These materials are presented as tooth-colored, mechanically durable alternatives to amalgam in stress-bearing posterior restorations^11,12.

Previous research has highlighted the promising bioactive properties of alkasites, demonstrating their ability to effectively seal restoration margins, reduce mineral loss in adjacent tissues, and exert antibacterial effects against Streptococcus mutans^13–16. Moreover, recent studies have reported mechanical properties similar to those of conventional and bulk-fill RBCs^17,18. However, a critical gap exists in the literature regarding their surface stability under clinically relevant acidic challenges. Evidence addressing the effects of both dietary and gastric acids on key surface characteristics, such as microhardness, roughness, and gloss, remains limited^19,20. These properties are clinically relevant, as they directly influence the longevity, aesthetic outcomes, and biological performance of restorative materials. Surface roughness values exceeding 0.2 μm are considered plaque-retentive and may promote staining and secondary caries^21,22. For gloss, values within the range of 40–60 gloss units (GU) are regarded as clinically acceptable, with variations as small as 6.4 GU being perceptible and differences approaching 35.7 GU often judged clinically unacceptable^23,24. Accordingly, evaluating the behavior of alkasite materials under different acidic environments is essential to better understand their resistance to acidic degradation and to optimize their clinical use, particularly in patients at increased risk of erosion.

This study aimed to investigate the effects of acidic conditions on the surface roughness, gloss, and hardness of alkasite restorative material in comparison to those of conventional RBCs and RMGICs. The null hypotheses for this study were that (I) there are no significant differences in surface roughness, gloss, or hardness among the restorative materials after immersion in artificial saliva, Coca-Cola or simulated gastric acid; (II) the immersion solution does not significantly affect these properties for any material; and (III) there is no significant interaction between the restorative material and immersion solution for the measured surface properties.

Materials and methods

Three restorative materials were selected for evaluation: Cention Forte (CF; Ivoclar Vivadent, Schaan, Lichtenstein), Z250 XT Nanohybrid Universal Restorative (Z250 XT; 3M ESPE, St. Paul, MN, USA) and Fuji II LC (FLC; GC, Tokyo, Japan). Eighteen samples of each material were prepared in the form of disks measuring 6 mm in diameter and 1.5 mm in height²⁵. The material was introduced as a single layer into a polyethylene mold positioned on a glass slide, covered by a second glass slide, and manually pressed to squeeze out excess material. To ensure a smooth, uniform surface, a cellulose strip was positioned at the interface between the material and the glass slides. Polymerization was performed using an LED light-curing unit (Elipar; 3M ESPE) according to the manufacturers’ instructions (Table 1). Light curing was applied from both the top and bottom surfaces through the glass plates, with the light guide positioned perpendicular and in direct contact with the glass surface. The irradiation time was 15 s for CF and 20 s for Z250 XT and FLC. After polymerization, the samples were removed from the molds and stored at 37 °C for 24 h. Subsequently, the upper surface of the sample was polished using composite polishing discs (Sof-Lex Fine and Superfine; 3M ESPE) mounted in a straight handpiece set to 30,000 rpm. Ten linear strokes were applied per sample with the handpiece held perpendicular to the surface. Between grits, the samples were rinsed and air-dried for 5 s. A new disc was used for each sample at each step to ensure uniform surface characteristics.

Table 1.

Manufacturer-reported composition and application techniques of the investigated restorative materials.

Material Manufacturer	Application method	Composition	Mean filler wt%, size
Cention Forte Ivoclar Vivadent, Schaan, Lichtenstein	Capsule activated and mixed for 13 s, dispensed into mold, then light-cured for 15 s	UDMA, Aromatic aliphatic-UDMA, DCP, PEG-400 DMA, barium aluminium silicate glass, calcium fluorosilicate glass, calcium barium aluminium fluorosilicate glass, ytterbium trifluoride, isofiller, initiator, stabilizers, pigments	78.4, 0.1–35 μm
Filtek Z250 XT Nanohybrid Universal Restorative 3 M ESPE, St. Paul, MN, USA	Dispensed into the mold and light-cured for 20 s	Bis-GMA, TEGDMA, UDMA, BIS-EMA, PEGDMA, silica and zirconia/silica cluster fillers, stabilizers, catalysts	82%, silica fillers: 20 nm zirconia/silica cluster fillers: 0.1–10 μm
GC Fuji II LC GC, Tokyo, Japan	Capsule activated and mixed at high speed for 10 s, dispensed into the mold, and light-cured for 20 s	Aluminofluorosilicate glass, 2-HEMA, polyacrylic acid, polybasic carboxylic acid, dimethacrylate, water, photoinitiator	58%, 5.9 μm

UDMA urethane dimethacrylate, DCP tricyclodecan-dimethanol dimethacrylate, PEG-400 DMA polyethylene glycol 400 dimethacrylate, Bis-GMA bisphenol A-glycidyl methacrylate, TEGDMA tetraethyleneglycol dimethacrylate, Bis-EMA bisphenol A ethoxylated dimethacrylate, 2-HEMA 2-hydroxyethyl methacrylate.

The samples of each material were then randomly allocated into three experimental groups (n = 6) on the basis of the immersion solution: simulated gastric acid (SGA; 0.01 M HCl with 2 g/L NaCl, pH 1.2) to simulate gastric reflux, Coca-Cola (CC; Coca-Cola Bottling Company of Saudi Arabia, Riyadh, Saudi Arabia, pH 2.6) to represent dietary acid exposure, and artificial saliva as a neutral control (pH 6.5)²⁶. The artificial saliva was prepared by dissolving 1 mM CaCl₂, 3 mM NaH₂PO₄, and 100 mM NaCl in distilled water, and the pH was adjusted to 6.5 using 0.1 M NaOH. The pH values of the solutions were measured using a pH meter (AD11; Adwa Instruments, Szeged, Hungary). Each sample was individually immersed in 1 mL of the respective solution in a sealed glass vial for 96 h at 37 °C, following protocols reported in prior investigations simulating prolonged acid exposure²⁷. The immersion solution was refreshed daily to maintain consistent conditions. At the end of the storage period, the samples were rinsed with distilled water, cleaned in an ultrasonic bath (Shenzhen Leadsonic Co.; Shenzhen, China) and gently dried before measurement.

Surface profilometry

Surface roughness was evaluated by measuring the arithmetic mean roughness (Ra, µm) and the maximum height of the profile (Rz, µm) using a contact profilometer (Surftest SJ-210; Mitutoyo, Kawasaki, Japan) equipped with a 2-µm-radius diamond stylus²². Measurements were performed using a Gaussian filter with a cutoff length (λc) of 0.8 mm, in accordance with ISO 4288:1996²⁸. Prior to testing, the device was calibrated according to the manufacturer’s instructions using a certified reference standard to ensure measurement accuracy and reliability. During measurement, each sample was securely fixed on a stable platform, and the stylus was oriented perpendicular to the surface. For each sample, three parallel traces were recorded at different locations in the central area, and the mean Ra and Rz values were calculated for statistical analysis. The parameters were determined according to ISO 4287:1997 and are defined below²⁹.

Ra represents the average deviation of the surface profile from the mean line over the evaluation length and reflects the overall surface roughness:

where z(x) is the deviation of the profile from the mean line over the measurement length l.

Rz represents the average maximum height of the surface profile, calculated as the mean of the five greatest peak-to-valley distances within the evaluation length, and reflects the severity of extreme surface irregularities:

where p_i is the maximum peak height and V_i is the maximum valley depth within the sampling length³⁰.

Surface gloss

The surface gloss of each sample was measured under standardized conditions using a gloss meter (IGB-331 Gloss Checker; Horiba Instruments, Kyoto, Japan), which features an oval measurement area of 6 × 3 mm and operates at light incidence and reflection angles of 60°. Before starting the measurements, the device was calibrated using the supplied calibration jig with a reference value of 90 gloss units (GU). Gloss readings were taken at a 60° angle, and each sample was measured six times, with the sample rotated 90° between measurements. The average GU value was then calculated.

Surface microhardness testing

The samples were polished to obtain a standardized surface finish and then ultrasonically cleaned in distilled water to remove any residual debris. Vickers microhardness was measured on the top surface using a microhardness tester (HMV-2T; Shimadzu, Kyoto, Japan) with a 50-gf load applied for 15 s. The Vickers hardness number (VHN) is defined as follows:

where F is the applied load in kilogram force (kgf), and d is the mean length of the indentation diagonal (mm)²⁷.

For each sample, three non-overlapping indentations were made at random locations, and the average of the three readings was taken as the sample’s VHN.

Morphological analysis

A scanning electron microscope (AURA100, Seron Technologies, Uiwang-si, Republic of Korea) was used to examine the surface morphology of one sample from each group. The samples were fixed on aluminum stubs using double-sided adhesive and then were sputter-coated with gold. SEM images were captured at magnifications of ×500 and ×1000, an accelerating voltage of 15 kV and a working distance of 9.2.

Statistical analysis

Numerical data are presented as the mean and standard deviation. Two-way ANOVA was used to assess the effects of the tested variables and their interaction on the measured outcomes. Model assumptions, including normality and homogeneity of variance, were evaluated through visual inspection and statistical tests. Since violations of homogeneity and heteroscedasticity were detected, a Box–Cox transformation was applied, after which the assumptions were confirmed.

Post hoc comparisons were conducted using the model’s error term, with p values adjusted using the false discovery rate (FDR) method. Correlation analysis was performed using Spearman’s rank-order correlation coefficient. A significance level of α = 0.05 was used for all tests. Statistical analysis was conducted using R software (version 4.4.2 for Windows; R Foundation for Statistical Computing, Vienna, Austria).

Results

Two-way ANOVA revealed significant effects of material type and immersion solution for all the measured parameters (p < 0.001). Additionally, the interactions among these factors were significant for Ra (p < 0.001), Rz (p = 0.009), surface gloss (p = 0.002), and microhardness (p = 0.009). Simple effects analysis further identified specific trends within the tested variable, as detailed in Table 2.

Table 2.

Descriptive statistics and two-way ANOVA results for Ra, Rz, surface gloss, and microhardness, showing the main effects of material, solution and their interaction (p < 0.05).

Parameter	Source of variation	Sum of squares	df	Mean square	F-value	p-value	95% CI for effect
Ra	Material	0.11	2	0.06	143.19	< 0.001	0.86 (0.79–0.89)
	Solution	0.03	2	0.01	31.63	< 0.001	0.58 (0.40–0.68)
	Material × Solution	0.01	4	0.00	5.86	< 0.001	0.34 (0.11–0.45)
Rz	Material	0.09	2	0.05	106.87	< 0.001	0.83 (0.73–0.87)
	Solution	0.02	2	0.01	20.20	< 0.001	0.47 (0.27–0.59)
	Material × Solution	0.01	4	0.00	3.87	0.009	0.26 (0.04–0.37)
Surface gloss	Material	9.89 × 10⁴	2	4.95 × 10⁴	408.99	< 0.001	0.98 (0.97–0.99)
	Solution	9.89 × 10⁴	2	4.94 × 10⁴	469.38	< 0.001	0.98 (0.97–0.99)
	Material × Solution	741.47	4	185.37	5.13	0.002	0.31 (0.09–0.42)
Microhardness	Material	1.50 × 10¹⁰	2	7.52 × 10⁹	2154.17	< 0.001	0.99 (0.98–0.99)
	Solution	8.91 × 10⁸	2	4.46 × 10⁸	127.72	< 0.001	0.85 (0.77–0.88)
	Material × Solution	1.47 × 10⁸	4	3.66 × 107	10.50	< 0.001	0.48 (0.26–0.58)

df degrees of freedom, CI confidence interval.

Surface profilometry

Ra and Rz followed similar trends across all immersion conditions, with Z250 XT exhibiting the lowest values (p < 0.001). Comparisons between CF and FLC in artificial saliva revealed no significant differences in Ra or Rz (p > 0.05). However, when immersed in CC, the Ra of the CF was significantly greater than that of FLC (p < 0.001), whereas the difference in Rz remained nonsignificant (p > 0.05). Under SGA immersion, CF exhibited significantly greater Ra and Rz than FLC (p < 0.001). Within-material comparisons revealed that, for both Z250 XT and CF, SGA immersion resulted in significantly higher Ra and Rz values than the other solutions (p < 0.001). Additionally, CF exhibited significantly greater Ra and Rz in CC than in artificial saliva (p < 0.001). In contrast, FLC showed no significant differences in Ra or Rz among the immersion conditions (p = 0.141 and p = 0.107, respectively) (Tables 3, 4).

Table 3.

Mean surface roughness (Ra, µm) values with standard deviation (SD) of the restorative material across immersion media.

Solution	Ra (µm) (Mean ± SD)
	Z250 XT	FLC	CF
Artificial saliva	0.16 ± 0.02Bb	0.39 ± 0.06Aa	0.34 ± 0.03Ac
CC	0.13 ± 0.01Cb	0.41 ± 0.08Ba	0.52 ± 0.10Ab
SGA	0.29 ± 0.12Ca	0.49 ± 0.09Ba	0.71 ± 0.12Aa

Values marked with different uppercase letters in the same row and different lowercase letters in the same column indicate statistically significant differences (p < 0.05).

Table 4.

Mean (± SD) maximum profile height (Rz, µm) of the restorative materials under different immersion conditions.

Solution	Rz (µm) (Mean ± SD)
	Z250 XT	FLC	CF
Artificial saliva	1.06 ± 0.15Bb	2.42 ± 0.43Aa	2.39 ± 0.33Ac
CC	0.92 ± 0.18Bb	2.98 ± 0.69Aa	3.16 ± 0.78Ab
SGA	1.88 ± 0.68Ca	3.20 ± 0.75Ba	4.05 ± 0.74Aa

Different uppercase superscripts within a row and different lowercase superscripts within a column indicate statistically significant differences (p < 0.05).

Surface gloss

The GU values decreased significantly across all the materials upon exposure to acidic solutions, with SGA having the most pronounced effect (p < 0.001). In artificial saliva, Z250 XT demonstrated the greatest gloss, followed by CF, whereas FLC had the lowest values (p < 0.001). In CC and SGA, Z250 XT maintained the highest GU values. However, compared with FLC, CF had lower values in both solutions (p < 0.001) (Table 5).

Table 5.

Simple effects comparisons for surface gloss values between restorative materials across immersion media. Different uppercase letters within rows indicate significant differences between materials within the same medium (p < 0.05). Different lowercase letters within columns indicate significant differences between immersion media for the same material (p < 0.05).

Solution	Surface Gloss (GU) (Mean ± SD)
	Z250 XT	FLC	CF
Artificial saliva	60.11 ± 0.53Aa	44.86 ± 1.64Ca	46.30 ± 1.47Ba
CC	50.61 ± 0.48Ab	34.66 ± 1.54Bb	32.72 ± 1.13Cb
SGA	43.33 ± 0.70Ac	25.20 ± 1.04Bc	23.47 ± 1.18Cc

Surface microhardness

In terms of microhardness, Z250 XT resulted in the highest hardness in artificial saliva, followed by FLC, with CF resulting in the lowest values (p < 0.001). Under acidic conditions, compared with the other materials, Z250 XT remained significantly harder (p < 0.001). The difference in microhardness between the CF and FLC groups was not statistically significant in either CC or SGA (p > 0.05). For all the materials, the immersion solution significantly affected the microhardness (p < 0.001). The highest hardness was observed in artificial saliva, followed by CC, and the lowest was noted in SGA. Specifically, for Z250 XT, compared with artificial saliva exposure, SGA exposure resulted in significantly lower hardness (p < 0.001). For CF and FLC, all pairwise comparisons across solutions were statistically significant, following the same decreasing trend from artificial saliva to CC to SGA (p < 0.001) (Table 6, Fig. 1).

Table 6.

Surface microhardness (Vickers hardness number, VHN) of the tested restorative materials following immersion in different media. Values with different upper and lowercase superscripts within the same row and column, respectively, are significantly different (p < 0.05).

Solution	VHN (Mean ± SD)
	Z250 XT	FLC	CF
Artificial saliva	93.24 ± 1.47Aa	65.84 ± 3.24Ba	59.01 ± 2.57Ca
CC	90.98 ± 1.09Aab	54.12 ± 2.51Bb	51.99 ± 3.15Bb
SGA	89.08 ± 1.29Ab	41.30 ± 4.53Bc	42.70 ± 3.59Bc

Fig. 1.

Bar charts showing the mean and standard deviation values for Ra (a), Rz (b), surface gloss (c) and microhardness (d).

Morphological analysis

Representative SEM images are shown in Fig. 2. Z250 XT displayed a smooth, homogeneous surface in artificial saliva, with only fine polishing scratches and no evidence of matrix or filler degradation. After CC exposure, no surface changes were detected, whereas SGA produced only occasional filler protrusion. FLC exhibited mild surface texturing and localized filler exposure in artificial saliva, progressing to roughening and pitting after CC and more evident matrix dissolution with frequent filler protrusion after SGA. CF showed a roughened but intact surface with scattered microdefects in artificial saliva, whereas CC exposure led to the detachment of porous areas, voids, and filler particles. Following SGA immersion, the CF surfaces became irregular and cratered with matrix erosion, filler–resin separation, and the protrusion of large filler particles.

Fig. 2.

Representative SEM images of the three restorative materials after immersion in artificial saliva, CC, and SGA (from left to right). Magnification: ×1000. Scale bar = 50 μm.

Discussion

In the present study, the effects of acidic environments on the surface integrity of an alkasite restorative material were investigated and compared to those of a conventional RBC and an RMGI. Statistically significant differences were observed for all surface properties, with material type, immersion condition, and their interaction exerting significant effects. Accordingly, all three null hypotheses were rejected.

Surface characterization in the present study was primarily based on quantitative measurements of surface roughness, gloss, and microhardness, while SEM was used to provide qualitative visualization of general surface morphological changes following acidic exposure. Surface roughness was evaluated using contact profilometry, a widely used method in dental research with reported agreement with optical techniques for detecting surface changes in restorative materials^22,31–34.

The acidic solutions CC and SGA were selected to simulate the effects of intrinsic and extrinsic acids on restorative dental materials. Both solutions significantly impaired the surface properties, with SGA consistently producing the most severe degradation. Overall, increased roughness, reduced gloss, and hardness loss were observed, primarily due to acid-induced hydrolysis of the organic matrix and weakening of the filler–matrix interface^35,36. These processes were particularly pronounced in the ion-releasing materials FLC and CF, where filler dissolution and ion exchange further destabilized the matrix³⁷.

Among materials, the nanohybrid RBC Z250 XT consistently exhibited superior performance across all immersion conditions. Its highly cross-linked resin network composed of bisphenol A-glycidyl methacrylate (Bis-GMA), tetraethyleneglycol dimethacrylate (TEGDMA), and the more hydrophobic monomers urethane dimethacrylate (UDMA) and bisphenol A ethoxylated dimethacrylate (Bis-EMA) limits water sorption and hydrolytic breakdown^38,39. In addition, its densely packed filler system of silica nanoparticles and zirconia–silica clusters (82 wt%, 68 vol%) enhances surface stability, whereas silane-treated fillers strengthen the filler–matrix interface^36,40,41. SEM observations supported these findings, revealing smooth surfaces with only minimal changes following acid immersion.

Under neutral conditions, CF exhibited significantly higher gloss but lower microhardness than FLC. Gloss in RBCs is influenced by the filler loading, filler distribution, and refractive index compatibility between the resin matrix and fillers²⁴. Clinically, this may provide CF with an initial aesthetic advantage. However, its lower microhardness may be attributed to the presence of polyethylene glycol 400 dimethacrylate (PEG-400 DMA), a hydrophilic monomer prone to water sorption and hydrolytic degradation, which reduces the crosslink density and surface hardness despite the presence of UDMA^42,43. These findings align with studies reporting that RMGICs have significantly higher microhardness than Cention N⁴⁴.

When subjected to acidic immersion, CF degradation was pronounced, especially in SGA. This can be attributed to its alkaline calcium fluorosilicate fillers, which are highly reactive at low pH¹⁹. Their rapid degradation produces voids and crater-like defects, with large particle size further accentuating the surface irregularities observed using SEM. Both calcium fluorosilicate and ionomer-type glasses in Cention N undergo marked surface degradation under acidic conditions, leaving only the inert barium alumino-silicate fillers visible on exposed surfaces⁴⁵. In addition, the hydrophilicity of PEG-400 DMA promotes acid penetration, further accelerating matrix breakdown^43,46.

In contrast, FLC showed more uniform but still substantial degradation. Its hydrophilic resin matrix promotes water sorption and softening, while low pH disrupts ionic crosslinks and accelerates ion leaching, resulting in significant reductions in gloss and hardness^38,47. However, compared with CF, its finer and more homogeneously dispersed aluminofluorosilicate glass fillers may have contributed to the relative stability of Ra and Rz values by promoting more uniform degradation rather than localized pitting. Clinically, FLC may undergo gradual rather than abrupt surface deterioration; however, the loss of gloss and hardness still limits its longevity in erosive environments.

The surface degradation of the alkasite material observed in the present study is consistent with previous reports. The significant increase in surface roughness following exposure to CC and SGA agrees with the findings of Karakaş and Küden (2022), who reported similar roughness changes after cola immersion, supported by SEM/EDS evidence of compositional alterations¹⁹. Similarly, exposure to acidic beverages, including cola and energy drinks, has been shown to result in progressive surface deterioration and reduced microhardness of Cention N²⁰. The wear pattern identified in the present study is also consistent with reports of greater material loss in bioactive bulk-fill RBCs, including earlier Cention formulations, under thermomechanical loading⁴⁸. In addition, Daabash et al. (2022) demonstrated that alkasite material exhibited greater wear than conventional RBCs and RMGICs⁷. Furthermore, previous investigations have shown that nanohybrid RBCs exhibit higher hardness, whereas alkasites demonstrate greater solubility than RMGICs, supporting the overall performance trend observed in the present study⁴².

From a clinical perspective, these changes have important implications, particularly in patients at high risk of erosion. The increased surface roughness observed in CF exceeds the threshold associated with plaque retention, potentially increasing the risk of staining, secondary caries, and gingival inflammation²¹. In addition, the reduction in gloss may compromise aesthetic outcomes, especially in restorations located in visible areas^23,24. The decrease in microhardness, together with SEM evidence of matrix degradation and filler loss, further indicates a greater susceptibility to functional wear and toothbrushing abrasion over time²². Accordingly, for patients with frequent exposure to dietary or gastric acids, materials with greater resistance to surface degradation, such as nanohybrid RBCs, may represent a more suitable clinical choice.

Nevertheless, the limitations of the present study should be acknowledged. The in vitro design cannot fully replicate the complex oral environment, including fluctuating pH, salivary buffering, and mechanical stresses from mastication and oral hygiene procedures. In addition, the pH of the immersion media was not monitored, which may be particularly relevant for CF, a material designed to exhibit acid-neutralizing potential. Future studies should incorporate more clinically relevant aging conditions, including mechanical loading and dynamic acid challenges. Furthermore, evaluating protective approaches, such as surface coatings or composite overlays, may provide valuable insights into strategies to enhance the long-term durability of bioactive materials in patients prone to erosive wear.

Conclusion

Within the limits of this study, CF exhibited greater susceptibility to acidic degradation, with decreased gloss and microhardness and surface roughness exceeding the clinically relevant threshold. These changes may compromise aesthetics and reduce restoration longevity. Clinically, alkasite materials may be considered suitable for patients with low erosive risk. However, in individuals with frequent acid exposure, conventional RBCs may be preferred.

Author contributions

The author conceived and designed the study, performed the experiments, analyzed the data, interpreted the results, and wrote the manuscript.

Funding

This Project was funded by the Deanship of Scientific Research (DSR) at King Abdulaziz University, Jeddah, under grant no. (PIP: 693-165-2025).

Data availability

The datasets used and/or analyzed during the current study are available from the author on reasonable request.

Declarations

Competing interests

The authors declare no competing interests.