28 February 2023

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Remineralizing effect of contemporary ion-releasing materials in mineral-depleted dentin

By Lorenzo Breschi and Carlo D’Alessandro

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Introduction

The preservation of dental hard tissues represents the main principles of the minimal invasive dentistry. Nowadays, in case of intervention, several bioactive materials — such as glass-ionomer cements, GICs, calcium silicate cements, MTA, resin-modified calcium silicate cements, RMTA — are available to replace tooth substance loss after selective caries removal. Besides, bio-interactive materials also optimize tissue mineral recovery through remineralization properties when used in restorative dentistry. 

Despite the increasing interest for these materials, data comparing their remineralizing abilities under conditions similar to the clinical ones, are still insufficient and inconsistent.

In this regard, Maciel Pires et al. have conducted an in vitro study to evaluate the ability of current ion-releasing materials to remineralize bacteria-driven artificial caries lesions.

Materials and methods

Researchers obtained standardized class I cavities (4 mm length × 3 mm width) in 60 extracted sound human molars. Specimens underwent a microbiological cariogenic protocol (28 days) in order to generate artificial caries lesions and, subsequently, were randomly divided into four restorative groups (n=15): adhesive + composite (control), GIC, MTA and RMTA. 

After 24 hours, microhardness analysis (ΔKHN) was performed on 40 specimens (n=10) at baseline and after 30, 45 and 60 days of artificial storage. Micro-CT scans were acquired (3/group, t=0 days, 30 days and 90 days). Confocal microscopy was employed for interfacial ultra-morphology analysis (2/group, t=0 days and 60 days). 

Three additional specimens per group were prepared and processed for scanning electron microscopy (SEM) and FTIR to analyze the ability of the tested materials to induce apatite formation on totally demineralized dentin discs (60 days in artificial saliva). All data were statistically analyzed with a significance level of 5% (p<0.05).

Results

Control specimens showed the lowest ΔKHN values and the presence of gaps at the interface when assessed through micro-CT even after artificial storage. However, all the tested ion-releasing materials induced an overall increase of the ΔKHN after storage (p<0.05). MTA best reduced the demineralized artificial carious lesions gap at the interface. Moreover, MTA and RMTA showed apatite deposition on totally demineralized dentin surfaces though SEM and FTIR analyses.

Conclusions

All the tested ion-releasing materials can induce remineralization expressing mineral precipitation in artificial carious dentin. Furthermore, MTA showed enhanced ability of precipitation of hydroxyapatite and hardness recovery of in mineral-depleted dentin over time. RMTA and GIC may be more appropriate for preserving the demineralized collagen fibrils in the caries-affected tissues.

Maciel Pires P, Ionescu AC, Pérez-Gracia MT, Vezzoli E, Soares IPM, Brambilla E, de Almeida Neves A, Sauro S. “Assessment of the remineralisation induced by contemporary ion-releasing materials in mineral-depleted dentine.” Clin Oral Investig. 2022 Oct; 26(10):6195-6207. doi: 10.1007/s00784-022-04569-9. Epub 2022 Jun 7. PMID: 35670863.