Enamel restoring Properties of Hydroxyapatite-Protein-Composites in Human Saliva

Objectives: Recent in vitro studies which were based on artificial saliva and profilometry, have demonstrated the surface restorative properties of toothpastes containing a Hydroxyapatite-Protein-Composite (HPC). In those studies the HPC pastes led to the formation of stable mineralized layers on enamel which compensated a previously inflicted erosive loss. Objective of this study was to verify these findings by shifting to the more complex human saliva.

Methods: An HPC containing toothpaste served as test (TP), an HPC free paste as control (CP), both containing 1450ppm Fluoride. 18 bovine enamel specimens were mounted in cold cure epoxy resin, polished flat and eroded (30sec, 5% citric acid, RT). The amount of eroded enamel (wear in µm) was analyzed at three positions per specimen using a Scantron Proscan 3D Profilometer and customized software. Specimens were divided randomly into 6 groups of 3, brushed with 1:1 slurries of either TP or CP in water (1min, 150g load, twice daily, 15d). In between treatments specimens were stored in non-pooled human saliva of 3 volunteers. During erosion and treatment reference areas were covered by adhesive tape. After rescanning the treated surfaces, the difference between the post- and pre-treatment wear indicates the amount of restoration.

Results: The average wear after erosion was -2.49±0.72µm

Post treatment restorations were:

 

	Restoration (MW±SD)/saliva of volunteer
Paste	Volunteer 1	Volunteer 2	Volunteer 3	mean
TP	3.55±0.98µm	5.39±0.55µm	9.96±2.22µm	6.30
CP	0.12±0.85µm	-0.26±0.22µm	4.05±1.79µm	1.30

Conclusion: Also with human saliva the HPC paste led to a clear restoration of the eroded surface which was greater than the applied erosive loss of approx. 2.5µm. The fluoride control paste showed only minor restorative effects. The salivary conditions of the individual strongly influence the strength of the effects.