A 36-month randomized trial in Clinical Oral Investigations found that placing a glass ionomer cement (GIC) liner under composite, after selective caries removal to soft dentin, did not improve restoration survival. Pulp vitality was preserved more often in teeth restored without the liner. The authors suggest routine liner placement in this situation may not be necessary.
Whether to place a liner in a deep cavity is one of the most routine decisions in restorative dentistry, and after selective caries removal it is still an open question. As of November 2026, a new randomized controlled trial adds 30- to 36-month clinical data to that question. It was published online on November 5, 2026 in Clinical Oral Investigations (volume 30, issue 11, article 556), and it tested the liner directly in deep lesions managed with selective caries removal.
What Did the Trial Test?
The study is titled "Clinical outcomes of composite restorations with or without a glass ionomer liner after selective caries removal to soft dentin: a 36-month randomized controlled trial." Its authors are C. Muñoz-Sandoval, J.J. Jardim, K. Gambetta-Tessini, R.A. Giacaman and M. Maltz. They are affiliated with the Cariology Unit at the University of Talca's Faculty of Dentistry in Chile and the Faculty of Odontology at the Federal University of Rio Grande do Sul in Porto Alegre, Brazil.
The authors frame the problem this way: selective caries removal to soft dentin (SCR-SD) is currently recommended for deep dentine caries lesions in permanent teeth. Whether a pulp-protective liner is needed after SCR-SD, they write, "remains uncertain."
To test it, the team treated 144 deep dentin caries lesions in permanent posterior teeth. The lesions came from 98 participants aged 9 to 55 years. After SCR-SD, each lesion was randomly allocated to one of two restorative strategies:
- SE (no liner): a universal adhesive applied in selective enamel etching mode, then composite resin.
- GIC + SE: a conventional glass ionomer cement liner, then the same universal adhesive in selective enamel etching mode, then composite resin.
Restorations were followed for 30 to 36 months. The primary outcome was restoration survival, assessed using selected FDI criteria. The secondary outcome was preservation of pulp vitality. The authors analysed survival with Weibull regression models. The trial is registered at ClinicalTrials.gov as NCT04250142.
What Did the Trial Find?
Of the 144 treated lesions, 117 were evaluated at 30 to 36 months. Only one of the two outcomes differed significantly between groups.
Restoration survival: no significant difference
Survival was 96.0% in the SE group and 92.4% in the GIC + SE group. The difference was not statistically significant (p = 0.37).
Pulp vitality: better without the liner
Pulp vitality was preserved in 97.5% of the SE group and 87.3% of the GIC + SE group, a statistically significant difference (p = 0.01). In the adjusted Weibull model, the SE strategy was associated with a lower risk of pulp vitality failure than GIC + SE. The authors also report that restorative failure was strongly associated with pulp vitality failure.
What Do the Authors Conclude?
The authors conclude that using a GIC liner after SCR-SD did not improve restoration survival and was not associated with better pulp vitality preservation. They report that composite restorations bonded with a universal adhesive in selective enamel etching mode, placed directly over the remaining dentin, showed favourable restorative and biological outcomes after 30 to 36 months.
Their clinical significance statement goes a step further. It attributes effective sealing to a universal adhesive in selective enamel etching mode combined with nanofilled composite resin, and says these simple procedures maintained restoration integrity and pulp vitality. Their bottom line is that routine liner placement after SCR-SD "may not be necessary."
Notice how carefully that is worded. The trial does not say liners are harmful in every situation, and it does not test every liner material or every adhesive. It compared one specific protocol with and without a conventional GIC liner, in deep lesions in permanent posterior teeth that were managed with selective caries removal to soft dentin.
Why Does This Matter for Canadian Practices?
For dental professionals in Toronto, the GTA and across Canada, the trial is most useful as a prompt to look again at habit. If your habit is to place a liner whenever a preparation gets deep, this study is a reason to revisit it. It suggests that, at least with the protocol tested, the extra step did not buy better restoration survival over about three years.
The pulp vitality result deserves a close read. Preservation was lower in the liner group, and the adjusted model associated the no-liner strategy with a lower risk of vitality failure. The abstract reports that association but does not offer a mechanism, so be wary of anyone who explains exactly why the liner group did worse. That explanation is not in the published summary.
Pro Tip: Before changing a protocol based on one trial, read the full text, not only the abstract. The article is published open access, so your whole team can review the methods, including how lesions were selected and how vitality was assessed, at your next clinical meeting.
Questions to ask before you change your protocol
- Does your caries management match the trial? The findings apply to deep lesions managed with selective caries removal to soft dentin. A different excavation approach may not give the same result.
- Does your adhesive strategy match? The no-liner arm used a universal adhesive in selective enamel etching mode. If you bond differently, the trial does not directly test your technique.
- Which patients does it cover? Participants were 9 to 55 years old and the teeth were permanent posterior teeth. Primary teeth and anterior restorations were outside the trial.
- How long is the follow-up? Thirty to 36 months is meaningful for a restorative trial, but it is not lifetime data.
Pro Tip: If you decide to drop routine liners for SCR-SD cases, record that decision and the rationale in your clinical protocol so associates and hygienists explaining treatment to patients are working from the same playbook.
Limits of the Evidence
This is a single randomized trial with 144 lesions at the start, and 27 lesions were not evaluated at follow-up. The two groups differed significantly on the secondary outcome, not on the primary outcome. Treat that as a signal worth watching rather than a final verdict. Clinical judgment, the specific lesion, and your patient's history still decide the right restoration, and evidence-based guidance from Canadian and international bodies should be weighed alongside any single study.
EBIKO Dental will continue monitoring restorative dentistry research and will report follow-up studies on liner use as they are published. For restorative supplies and Canadian dental news, visit ebiko.ca.
Sources
- Muñoz-Sandoval C, Jardim JJ, Gambetta-Tessini K, Giacaman RA, Maltz M. Clinical outcomes of composite restorations with or without a glass ionomer liner after selective caries removal to soft dentin: a 36-month randomized controlled trial. Clin Oral Investig. 2026;30(11):556 (PubMed record)
- Article DOI: 10.1007/s00784-026-07209-8
- ClinicalTrials.gov registration NCT04250142
Frequently Asked Questions
Q: Do you need a glass ionomer liner under composite after selective caries removal?
A 2026 randomized trial suggests routine use may not be necessary. After selective caries removal to soft dentin, restoration survival was 96.0% without a liner and 92.4% with a GIC liner (not significant) at 30 to 36 months. The authors concluded that routine liner placement in this situation may not be necessary.
Q: Did the liner protect the pulp in the 2026 trial?
Not in this trial. Pulp vitality was preserved in 97.5% of teeth restored without a liner and 87.3% of teeth with a GIC liner, a significant difference (p = 0.01). The authors reported that the liner was not associated with better pulp vitality preservation.
Q: Which teeth and patients did the liner trial include?
The trial treated 144 deep dentin caries lesions in permanent posterior teeth from 98 participants aged 9 to 55 years. Only permanent molars and premolars were included, so the results do not directly address primary teeth.