Performance of composite-reinforced glass ionomer liners in class V restorations

Abstract

Background:

Postoperative sensitivity (POS) and marginal integrity (MI) are common concerns in Class V restorations because of dentin exposure and polymerization shrinkage stress. Composite-reinforced glass ionomer liners have been introduced to improve stress absorption and marginal sealing.

Aim:

To clinically compare the POS and MI of Axioglass and Ionoseal liners in Class V restorations.

Materials and Methods:

In this randomized, single-blinded clinical study, 60 patients requiring Class V restorations were allocated into two groups: Axioglass (n = 30) and Ionoseal (n = 30). Restorations were placed using a self-etch adhesive system followed by the respective liner. POS was assessed using the Schiff Sensitivity Scale at baseline, 1 week, 1 month, 6 months, and 12 months. MI was evaluated using modified USPHS criteria at 12 months. Statistical analysis included repeated-measures analysis of variance, independent t-test, and Chi-square test (P < 0.05).

Results:

Both materials showed a significant reduction in POS over time (P < 0.001). Axioglass demonstrated significantly lower sensitivity at 6 and 12 months and superior MI compared with Ionoseal (P < 0.05).

Conclusion:

Axioglass demonstrated better long-term clinical performance than Ionoseal in Class V restorations.

INTRODUCTION

Class V restorations are considered highly technique-sensitive due to their cervical location, frequent involvement of dentin or cementum, and exposure to complex biomechanical stresses during function.[1,2] Bonding to cervical dentin is inherently challenging because of its structural characteristics and dentinal fluid movement, which often result in postoperative sensitivity (POS) and compromised marginal integrity (MI).[3,4] Polymerization shrinkage stress generated by resin-based restorative materials further contributes to marginal gap formation, microleakage, and pulpal irritation.[5,6,7] Composite-reinforced glass ionomer (CRGI) liners were introduced to improve stress distribution, enhance marginal sealing, and reduce POS by combining the benefits of resin composites and glass ionomer cements.[8,9,10,11] These materials have been advocated for cervical restorations due to their stress-absorbing capacity and fluoride-releasing properties.[12,13,14,15] Ionoseal and Axioglass are commonly used composite-containing glass ionomer liners; however, limited clinical evidence exists comparing their performance in Class V restorations. CRGI liners combine the fluoride release and chemical bonding of glass ionomer cements with improved mechanical properties derived from resin components. Their stress-absorbing capacity may reduce polymerization shrinkage stress in overlying composite restorations, thereby improving marginal sealing and decreasing POS. These properties make CRGI liners particularly beneficial in Class V restorations where dentin bonding is challenging and cervical stress concentration is high.

MATERIALS AND METHODS

This randomized, single-blinded clinical study was conducted in accordance with the Declaration of Helsinki following institutional ethical approval and written informed consent from all participants. The study protocol was reviewed and approved by the Institutional Ethics Committee (IEC Approval No: 3677/2024). The trial was conducted according to the Declaration of Helsinki guidelines. Written informed consent was obtained from all participants prior to inclusion. The clinical trial was registered in the Clinical Trial Registry of India (CTRI No: CTRI/2024/1899). Sixty patients aged 20–45 years requiring a single Class V restoration were enrolled and randomly allocated into two groups (n = 30): Group A – Axioglass and Group B – Ionoseal. Sample size was calculated using G*Power Software (Franz Faul et al., Heinrich Heine University Düsseldorf, Düsseldorf, North Rhine-Westphalia, Germany) based on an expected medium effect size (0.5), power of 80%, and significance level of 5%. The minimum sample size required was 52 restorations; however, to compensate for possible dropouts, 60 restorations were included in the study. Patients between 20 and 45 years were selected because this age group commonly presents with noncarious cervical lesions and maintains good pulpal vitality, minimizing age-related dentin sclerosis that could influence sensitivity outcomes. Vital teeth with noncarious or shallow carious Class V lesions not exceeding 2 mm in depth were included. Teeth with pulpal or periapical pathology, previous restorations, cracks, parafunctional habits, or patients with systemic contraindications were excluded. All restorations were placed by a single operator to minimize variability. Standard Class V cavities were prepared using a high-speed handpiece with a cylindrical diamond bur (#1092, Mani Inc., Japan) under water coolant. The cavities were standardized to approximately 3 mm mesiodistal width, 2 mm occlusogingival height, and 2 mm depth. Depth was measured using a calibrated periodontal probe to ensure uniformity across samples. A self-etch adhesive system (Axio Bond 7, Axiodent) was applied according to manufacturer instructions: Agitation for 20 s, gentle air thinning, and light curing for 10 s using an LED curing unit with intensity of approximately 1000 mW/cm². Assigned liner material was applied and light-cured for 20 s. Finishing and polishing were performed using SofLex discs (3M ESPE) after 24 h. Axioglass Axiodent Inc and Ionoseal (VOCO) were used in the present study according to manufacturer recommendations. Axioglass and Ionoseal were selected because they are widely used CRGI liners with reported stress-absorbing properties and fluoride release. Their ability to act as an intermediate liner beneath adhesive restorations may reduce dentinal sensitivity and improve marginal adaptation in cervical restorations. POS was assessed using the Schiff Sensitivity Scale at baseline, 1 week, 1 month, 6 months, and 12 months. MI was evaluated at 12 months using modified USPHS criteria. The scoring criteria for the Schiff analog scale are the following: Grade 0 if the subject does not respond to the air blast stimulus, Grade 1 if the subject responded to the air blast stimulus but did not request to discontinue the stimulation, Grade 2 if the subject responded to the air blast stimulus and asked to discontinue the stimulation or moved away from the stimulation and Grade 3 is subject responded to air blast stimulus, considers it as painful and ask to discontinue the stimulation. MI was evaluated at the 12-month recall using modified USPHS criteria. The margins were examined using an explorer and mirror under adequate illumination, and restorations were rated as Alpha, Bravo, or Charlie.

Statistical analysis

Data were analyzed using IBM SPSS Software Statistics 30. Repeatedmeasures analysis of variance (ANOVA) was used for intragroup comparison of sensitivity scores over time, while independent t-tests were used for intergroup comparisons. MI scores were analyzed using the Chi-square test. The level of statistical significance was set at P < 0.05.

RESULTS

A total of 60 Class V restorations were evaluated in 60 patients, with 30 restorations in each group. All participants completed the 12-month follow-up period, and no dropouts were recorded. None of the restorations in either group showed complete loss, secondary caries, or pulpal complications during the evaluation period. Both groups demonstrated progressive reduction in sensitivity scores over time. Intragroup comparison using repeated measures ANOVA showed a statistically significant reduction from baseline to 12 months in both groups (P < 0.001). Intergroup comparison showed no significant difference at baseline, 1 week, or 1 month. However, at 6 and 12 months, the Axioglass group showed significantly lower Schiff scores compared with Ionoseal (P < 0.05) [Table 1]. For MI, the majority of restorations in the Axioglass group received Alpha scores (96.7%), while Ionoseal showed 86.7% Alpha ratings [Tables 2 and 3]. Chi-square analysis revealed a statistically significant difference favoring Axioglass (P < 0.05).

Table 1.

Mean Schiff sensitivity scores at different time intervals

Group	Baseline	1 week	1 month	6 months	12 months
Axioglass	2.6±0.6	1.8±0.5	1.2±0.4	0.6±0.3	0.3±0.2
Ionoseal	2.7±0.5	2.1±0.6	1.6±0.5	1.1±0.4	0.7±0.3

Table 2.

Marginal integrity assessment using modified USPHS criteria at 12 months

Group	Alpha, n (%)	Bravo, n (%)	Charlie, n (%)
Axioglass	29 (96.7)	1 (3.3)	0
Ionoseal	26 (86.7)	4 (13.3)	0

Table 3.

Clinical evaluation criteria-modified-USPHS rating

Criteria	Alpha (A)	Bravo (B)	Charlie (C)
Color match	The restoration appears to match the shade and translucency of adjacent tooth tissue	The restoration does not match the shade and translucency of adjacent tooth tissue, but the match is within the normal range of tooth shades	The restoration does not match the shade and translucency of adjacent tooth structure, and the mismatch is outside the normal range of tooth shades and translucency
Bubble formation	No bubble formation visible on the applied surface with intact restoration	Restoration depicts slight bubble formation on the surface	Majority of the surface is covered with bubbles
Marginal integrity	The explorer does not catch when drawn across the surface of the restoration toward the tooth, and there is no visible crevice along the periphery	The explorer catches with visible evidence of a crevice; dentin/base not exposed, and restoration not mobile	The explorer penetrates a crevice defect extending to the dento-enamel junction
Surface texture	Surface texture similar to polished enamel as determined by a sharp explorer	Surface texture is gritty or similar to a surface subjected to a white stone or composite with super mirror-sized particles	Surface pitting is sufficiently coarse to inhibit continuous movement of an explorer across the surface
Gross fracture	Restoration is intact and fully retained	Restoration is partially retained with some portion still intact	Restoration is completely missing

Baseline characteristics

The distribution of restorations with respect to patient age, sex, and tooth type was comparable between the two groups, with no statistically significant differences observed (P > 0.05). The majority of restorations were placed in premolars, followed by anterior teeth. The mean cavity depth and cervical lesion dimensions were standardized and showed no significant intergroup differences, ensuring baseline homogeneity.

Postoperative sensitivity

At baseline, all teeth in both groups exhibited varying degrees of sensitivity to air stimulus prior to restoration placement. The mean Schiff sensitivity scores were comparable between the Axioglass and Ionoseal groups, with no statistically significant difference (P > 0.05). At the 1-week evaluation, both groups demonstrated a marked reduction in POS compared to baseline values. However, the reduction in mean Schiff scores was greater in the Ionoseal group, although this difference was not statistically significant (P > 0.05). At the 1-month follow-up, continued reduction in sensitivity scores was observed in both groups. The Axioglass group demonstrated lower mean Schiff scores compared to the Ionoseal group, indicating improved patient comfort, though the difference remained statistically nonsignificant (P > 0.05). At the 6-month evaluation, the Axioglass group showed significantly lower mean Schiff sensitivity scores compared to the Ionoseal group (P < 0.05). A greater proportion of restorations in the Axioglass group were completely asymptomatic, whereas a small percentage of patients in the Ionoseal group continued to report mild sensitivity to air stimulus. At the 12-month follow-up, POS was minimal in both groups. However, the Axioglass group demonstrated significantly lower mean Schiff scores and a lower prevalence of residual sensitivity compared to the Ionoseal group (P < 0.05). These findings indicate superior long-term desensitizing performance of Axioglass in Class V restorations. Overall, repeated-measures analysis revealed a statistically significant reduction in POS over time within both groups (P < 0.001). Intergroup comparison demonstrated that Axioglass was significantly more effective than Ionoseal in reducing POS at later follow-up periods.

Marginal integrity

MI was assessed at the 12-month recall using modified USPHS criteria. In the Axioglass group, the majority of restorations (96.7%) received an Alpha rating, indicating excellent marginal adaptation with no detectable crevice at the restoration margins. Only a small percentage (3.3%) of restorations was rated as Bravo, with no Charlie scores recorded. In the Ionoseal group, 86.7% of restorations achieved an Alpha rating, while 13.3% were rated as Bravo due to detectable marginal discrepancies without dentin exposure. No restorations in either group demonstrated gross marginal failure or required replacement during the study period. Statistical analysis revealed a significant difference in MI between the two groups, with the Axioglass group demonstrating superior marginal adaptation compared to the Ionoseal group (P < 0.05).

Restoration survival

All restorations in both groups remained clinically intact and functional throughout the 12-month evaluation period, resulting in a 100% survival rate for both materials. No fractures, debonding, or loss of retention were observed.

DISCUSSION

The present randomized clinical study evaluated POS and MI of Class V restorations restored using Axioglass and Ionoseal over 12 months. Both materials demonstrated satisfactory clinical performance; however, Axioglass showed superior long-term reduction in POS and improved MI. Class V restorations are inherently technique-sensitive because they are often located in areas with thin or absent enamel and are subjected to complex biomechanical stresses such as tensile and flexural forces during function.[1] Bonding to cervical dentin is further complicated by its structural characteristics and dentinal fluid movement, increasing the risk of POS and marginal failure.[2] According to the hydrodynamic theory, sensitivity occurs due to fluid movement within dentinal tubules in response to external stimuli, which may be intensified by polymerization shrinkage stress and marginal gap formation.[3,4,5,6] In the present study, both materials exhibited a significant reduction in POS over time, which is consistent with previous reports emphasizing the role of liners and adhesive protocols in minimizing dentin hypersensitivity in cervical restorations.[7,8,16] However, Axioglass demonstrated significantly lower sensitivity scores at 6 and 12 months compared to Ionoseal. This finding may be attributed to the lower elastic modulus and stress-absorbing capacity of CRGI liners, which can reduce stress transmission to dentin and limit dentinal fluid movement.[14,15] MI is a key determinant of restoration longevity, as marginal discrepancies can promote microleakage, bacterial penetration, and pulpal irritation.[9,10,12] In the present study, Axioglass exhibited a higher percentage of alpha ratings according to modified USPHS criteria compared to Ionoseal at the 12-month evaluation. Improved marginal adaptation with Axioglass may be related to better wettability, stress accommodation, and interaction with the adhesive system, which are critical factors in cervical restorations where enamel support is limited.[13,17,18,19,20,21] Although Ionoseal demonstrated acceptable clinical outcomes, a higher proportion of Bravo ratings suggests slightly inferior marginal sealing over time. Recent clinical studies have highlighted the role of intermediate liners in reducing POS in cervical restorations. Somani et al.[16] reported a significant reduction in dentin hypersensitivity when desensitizing liners were used beneath adhesive restorations. Similarly, George et al.[22] demonstrated improved patient comfort and marginal adaptation when stress-absorbing materials were incorporated in cervical restorations. Recent randomized clinical trials evaluating restorative materials in Class V lesions have also emphasized the importance of material elasticity and bonding performance in maintaining MI over time (Hendam and Mosallam, 2025).[20] The present findings are consistent with these reports and further support the use of CRGI liners to improve long-term clinical outcomes. Variations in clinical performance among glass ionomer–composite hybrid materials have been associated with differences in resin content, filler characteristics, and polymerization behavior.[13,14,22] The 100% survival rate observed in both groups is consistent with earlier studies reporting favorable short-term survival of Class V restorations when appropriate restorative protocols are followed.[15,18] However, restoration survival alone does not fully reflect clinical success, as marginal degradation and sensitivity may precede overt failure.[23,24] The limitations of this study include the relatively short follow-up period and the absence of supporting laboratory evaluations. Long-term clinical studies with extended follow-up and combined in vitro analyses are recommended to further validate these findings and better understand material behavior in cervical restorations.[25,26,27,28,29,30]

CONCLUSION

Within the limitations of this randomized clinical study, both Axioglass and Ionoseal demonstrated satisfactory clinical performance in Class V restorations. However, Axioglass showed superior outcomes, with significantly greater reduction in POS and better MI over the 12-month follow-up period. These findings suggest that Axioglass may provide a more stable tooth–restoration interface in cervical restorations subjected to functional stresses. Further long-term clinical studies are recommended to confirm these results and evaluate their impact on restoration longevity.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.