What is the role of glass-ionomer cements in the preservation of tooth structures against caries?

This summary is based on the article published in the British Dental Journal: Minimal intervention dentistry II: part 7. Minimal intervention in cariology: the role of glass-ionomer cements in the preservation of tooth structures against caries (May 2014)

H. Ngo and S. Opsahl-Vital

 

 

Context

Glass-ionomer cements (GICs) are essential materials in clinical practice because of their versatility, self-adhesion to enamel and dentine, and good biocompatibility.

In addition, being chemically cured, with no shrinkage stress, makes them well suited for minimally invasive restorative techniques.

Purpose of the Article

This article looks at some of the clinical situations where the chemical adhesion and high biocompatibility of GIC are important for clinical success: excavation of deep carious lesions, fissure sealing and protection of root surfaces against caries.

Key Messages

• GICs setting involves complex chemical reactions that can be separated into two distinct stages:

1. First stage: Immediately after mixing: cross-linking of the poly-acid chains by either free calcium or strontium ions. Cross-linking is not stable and can be easily affected by excessive water loss or too much moisture contamination, due to poor isolation technique, during placement.
2. Second stage: the chains of poly-acid are further cross-linked by trivalent aluminium ions. This stage brings both an increase in mechanical properties, a reduction in solubility and improved aesthetic.

• GICs can be divided into two groups:
  • Conventional: auto-cured, with self-adhesion to dentine and enamel, (1) provide a long lasting seal, which is due to their adhesion property and dimensional stability. However, they required careful maintenance of water balance immediately after placement.
  • Resin-modified-glass-ionomer cements (RMGIC): have similar components of conventional glass-ionomer cements plus a small quantity of resin hydroxyethylmethacrylate (HEMA) and bisphenol A glycidyl dimethacrylate (BisGMA) and both photo and chemical initiators. RMGICs eventually set completely even when there is inadequate light activation.
• The current literature suggests that for most clinical cases the re-entry step can be eliminated, so a final restoration can be placed at the initial visit then the vitality of the tooth monitored. (2, 3, 4) The use of GIC is essential in this technique, because there is a suggestion that the demineralised dentine can be remineralised through an ion exchange process with GIC. This process was described as ‘internal remineralisation.’ (5, 6)
• In the ‘open-sandwich’ technique, GIC is used as a base that is exposed to the oral cavity. The rationale for using a GIC base is to provide a seal at the gingival dentinal margin when enamel is missing and to reduce the depth of the proximal box so that light curing can be reliably achieved. It also reduces the number of increments of composite resin. (7, 8)
• GIC can be used as a pit and fissure sealant, the key advantage is that it offers a dual, mechanical and chemical protection with long-term fluoride release.

References

1. Attal J. Les ciments verres ionomères. In Matériaux alternatifs à l’amalgame. pp 12–20. Paris: ADF, 2002.
2. Ricketts D N, Kidd E A, Innes N, Clarkson J. Complete or ultraconservative removal of decayed tissue in unfilled teeth. Cochrane Database Syst Rev 2006; 3: CD003808.
3. Maltz M, Oliveira E F, Fontanella V, Carminatti G. Deep caries lesions after incomplete dentine caries removal: 40-month follow-up study. Caries Res 2007; 41: 493–496.
4. Gruythuysen R J, van Strijp A J, Wu M K. Long-term survival of indirect pulp treatment performed in primary and permanent teeth with clinically diagnosed deep carious lesions. J Endod 2010; 36: 1490–1493.
5. Ngo H C, Mount G, Mc Intyre J, Tuisuva J, Von Doussa R J. Chemical exchange between glass-ionomer restorations and residual carious dentine in permanent molars: an in vivo study. J Dent 2006; 34: 608–613.
6. Ngo H. Glass-ionomer cements as restorative and preventive materials. Dent Clin North Am 2010; 54: 551–563.
7. Andersson-Wenckert I E, van Dijken J W, Kieri C. Durability of extensive Class II open-sandwich restorations with a resin-modified glass ionomer cement after 6 years. Am J Dent 2004; 17: 43–50.
8. Andersson-Wenckert I E, van Dijken J W, Horstedt P. Modified Class II open sandwich restorations: evaluation of interfacial adaptation and influence of different restorative techniques. Eur J Oral Sci 2002; 110: 270–275.

 

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