Experimental hydrogel formed a remineralised layer of about 32 µm in 7 days
After seven days in artificial saliva, a hydrogel with amorphous fluorinated calcium phosphate formed a layer about 32 µm thick on enamel and completely occluded open dentinal tubules, more than fluoride and CPP-ACP.
A layer of about 32 µm outperformed fluoride and CPP-ACP
The idea is as old as remineralisation itself: bring calcium, phosphate and fluoride to a demineralised surface and keep them there long enough to convert into hydroxyapatite. The team around Z. Zhang built such a reservoir from a two-component hydrogel, of hydroxypropyl methylcellulose and carboxymethyl chitosan, in which the ions remain in a metastable amorphous state.
The resulting amorphous fluorinated calcium phosphate particles were 30 to 80 nm in size and in artificial saliva remained amorphous for more than two hours before crystallising into hydroxyapatite. The hydrogel showed negligible cytotoxicity and did not cause irritation of the oral mucosa.
Demineralised enamel and dentine samples, eight per group, were treated with deionised water, sodium fluoride with 2000 ppm fluoride, a preparation with 10 per cent CPP-ACP and 900 ppm fluoride, and the hydrogel under test, then immersed in artificial saliva for seven days. The hydrogel formed a dense mineral layer that completely occluded the open dentinal tubules, and on etched enamel formed a layer about 32 µm thick, more than fluoride and than CPP-ACP with fluoride. X-ray diffraction confirmed that the newly formed mineral resembles hydroxyapatite, and nanoindentation that the mechanical properties of enamel and dentine were restored close to physiological values, with the greatest recovery among the four groups (p < 0.05). The effect was also confirmed in vivo, in a rabbit model.
Limitations
This is an experimental material that is not on the market. Seven days in artificial saliva and a rabbit model do not reproduce diet, abrasion or the biofilm in the mouth, and eight samples per group is a small sample for conclusions about the size of the effect.
For your practice
- Nothing changes in the protocol: fluoride varnishes and CPP-ACP preparations remain what is available to you, and this hydrogel is still preclinical.
- If you follow materials for the early treatment of caries and dentine hypersensitivity, tubule occlusion without drilling is a direction worth keeping an eye on.
- For patients who arrive with a media story, it helps to explain the difference between a finding on eight laboratory samples and clinical confirmation in humans.