Providing minimally invasive restorative care can be difficult for many clinicians. Not only is there the challenge of choosing the most apt solution for the clinical problem faced, but working with the dentition to treat it in a manner that preserves the natural tissues is key.
When treating dental caries, this creates interesting challenges and requirements of a restoration. Often, the optimal approach to a carious lesion on a tooth will be to remove the decay, before providing an additive restoration to protect healthy tissue and reinstate optimal aesthetics and function.
The infection impact parts of the tooth differently to others, meaning both healthy and severely impacted tissue surround caries-affected dentine and enamel. As such, there is a grey area that must be addressed. Bonding to or building restorations directly upon affected tissue may present challenges, but it is not impossible. When successful, we can expect long-term viability.
Break it down
Break it downThe bond strengths to caries-affected dentine are typically lower than those to normal dentine in the literature.[i] This can severely compromise treatment success in the short- and long-term. Various properties within caries-affected tissue led to this result.
The smear layer in dentine, which is formed after instrumentation, is inherently weak and can interfere with good adhesion.[ii] The smear layer of caries-affected dentine has differing aspects and chemical characteristics compared to the smear layer of natural, healthy dentine due to the change in organic composition after infection – it is typically richer in organic components and is thicker, with a highly disorganised collagen material.ii The smear layer can also accumulate in the orifices of dentinal tubules, which reduces the dentine’s permeability.i
The mineral content of healthy dentine must also be considered in modern adhesive approaches. It is typically made up of 50% mineral phase, 30% collagen and 20% water. [iii] When carious tissues develop, however, dentine undergoes a significant change in demineralisation, which is substituted for additional water content – the literature notes this could make up 53% of the volume of the tissue.iii The moisture can make the saturation of hydrophobic resins more difficult.ii Such a radical change in structure means it is no surprise that a clinician can encounter difficulties without an altered approach.
When taking a minimally invasive approach, it may not simply be acceptable to remove caries-affected tissue until healthy dentine is reached. Instead, strategies such as diet modification and biofilm disruption can be implemented by a patient whilst this still-viable tissue remains. In the intervention of the dental professional, a selective approach can be adequate without having to eradicate the entire presence of harmful bacteria. This has benefits: over-treatment can damage the dentine-pulp complex in the short-term, and compromise the mechanical integrity of the tooth structure in the long-term, which facilitates the development of cracks and fractures[iv] that require invasive treatment.
Approach compromises
Approach compromisesDespite the aforementioned issues, the literature provides some hope for predictable outcomes. The adhesion to caries-affected dentine, whilst weaker, may be clinically insignificant in the case that the surrounding structure is appropriately prepared.iv There must be adequate sound enamel and dentine which can ensure high bond strengths are achieved at other points of the restoration, and a hermetic seal is achieved in order to deprive biofilm of its nutrient supply.iv
It’s important to choose an adhesive solution that can adapt to the caries-affected dentine with success. Etch and rinse adhesive systems will remove the smear layer completely, demineralising the dentinal sub-surfaces and exposing the collagen fibrils.i Penetration into these areas is necessary for optimal adhesion, but will be compromised in caries-affected tissue due to the high water content.i
Self-etch adhesive solutions may have fewer discrepancies between the depths of the demineralised zone and resin monomer penetration, as demineralisation and resin monomer penetration will occur simultaneously.i Studies have, however, seen that self-etch adhesives may not fully infiltrate adhesive monomers into the demineralised zone in caries-affected dentine, but this is most likely due to penetration being compromised by a slightly lower acidity.i
Choose your solutions
To maximise longevity of a restoration, it may not be a case of deciding between etching approach, but rather it is essential to choose reliable adhesive solutions that are designed to optimise clinical intervention. Clinicians could turn to the Scotchbond Universal Plus Adhesive from Solventum, formerly 3M Health Care, as an ideal award-winning* solution. The one-bottle system is optimised to offer the same high-bond strength to caries-affected dentine as it does to sound dentine, for maximum confidence. As well as this, the radiopaque solution forms a well-defined, void-free hybrid layer to seal the treatment site.
Optimising success in minimally invasive care is key. Clinicians must assess the viability of caries-affected dentine, taking care to recognise when the tissue could remain in the dentition without creating further issues, and how restorations can be crafted around them.
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[i] Nakajima, M., Kunawarote, S., Prasansuttiporn, T., & Tagami, J. (2011). Bonding to caries-affected dentin. Japanese Dental Science Review, 47(2), 102-114.
[ii] Pinna, R., Maioli, M., Eramo, S., Mura, I., & Milia, E. (2015). Carious affected dentine: its behaviour in adhesive bonding. Australian dental journal, 60(3), 276-293.
[iii] Mohanty, P. R., Mishra, L., Saczuk, K., & Lapinska, B. (2023). Optimizing Adhesive Bonding to Caries affected dentin: a comprehensive systematic review and Meta-analysis of Dental Adhesive Strategies following chemo-mechanical caries removal. Applied Sciences, 13(12), 7295.
[iv] Lim, Z. E., Duncan, H. F., Moorthy, A., & McReynolds, D. (2023). Minimally invasive selective caries removal: a clinical guide. British Dental Journal, 234(4), 233-240.
