Effect of hydroxyapatite nanoparticles on enamel remineralization and estimation of fissure sealant bond strength to remineralized tooth surfaces: an in vitro study

Abstract

Background The management of noncavitated caries lesions before sealant therapy is a clinical challenge when the tooth needs sealant application. Sealing noncavitated carious lesions in pits and fissures may lead to failure of the fissure sealant (FS) due to incomplete sealing. Therefore the use of remineralizing agents such as nanoparticles has been suggested. This study investigated the ability of hydroxyapatite nanoparticles (nano-HA) to remineralize enamel, and their effect on sealant microleakage and shear bond strength (SBS). Methods A total of 192 third molars were demineralized and pretreated with two concentrations of nano-HA with and without sodium hexametaphosphate (SHMP), followed by phosphoric acid etching and resin FS application. The study groups were 1) etching + FS, 2) etching + nano-HA 0.15% + FS, 3) etching + nano-HA 0.03% + FS, 4) etching + mixture of nano-HA 0.15% and SHMP 0.05% + FS, 5) etching + mixture of nano-HA 0.03% + SHMP 0.01% + FS. The laboratory tests included microleakage in 50 teeth, scanning electron microscopy (SEM) evaluation in 10 samples, and SBS in 100 samples. Enamel remineralization changes were evaluated in 32 teeth with energy-dispersive X-ray spectroscopy (EDS) and field emission scanning electron microscope (FESEM). Results Nano-HA enhanced the SBS to remineralized enamel in a large percentage of nanoparticles. Mean SBS in group 2 was significantly greater than in groups 1, 3 and 4 (all P < 0.05). SBS was related to nano-HA concentration: nano-HA 0.15% yielded greater SBS (16.8 ± 2.7) than the 0.03% concentration (14.2 ± 2.1). However, its effect on microleakage was not significant. Nano-HA with or without SHMP led to enhanced enamel remineralization; however, the Calcium (Ca)/Phosphate (P) weight percent values did not differ significantly between the groups ( P > 0.05). SEM images showed that SHMP did not affect sealant penetration into the deeper parts of fissures. FESEM images showed that adding SHMP led to increased nanoparticle dispersal on the tooth surface and less cluster formation. Conclusions The ultraconservative approach (combining nano-HA 0.15% and SHMP) and FS may be considered a minimal intervention in dentistry to seal demineralized enamel pits and fissures.

Effect of Actilux - Activated Whitening Toothpaste and Marine Salts on Color Change and Microhardness of Bovine Enamel

“…This increase in enamel microhardness could be attributed to hydroxyapatite contents in Blanx White shock toothpaste that have similar structure to the main mineral component of teeth and bone. Moreover, it provides a source of calcium and phosphate ions that enhance enamel remineralization (24) .…”

Biomimetic Effect of Nano-Hydroxyapatite in Demineralized Enamel before Orthodontic Bonding of Brackets and Attachments: Visual, Adhesion Strength, and Hardness in In Vitro Tests

“…is property can be modulated by ion substitution and crystallinity degree achieved implementing innovative synthesis with nanosized crystal control [1].…”

“…Dental erosion is a process consisting in the loss of hard substance of the tooth as a consequence of frequent and prolonged exposure to acidic agents [1]. Assuming that the solubility of hydroxyapatite is low (pH of 5.5), it tends to increase as the oral pH decreases [2].…”

Enamel Conditioning by Phosphoric Acid and Er.Cr: YSGG Laser Irradiation - EDS and SEM Studies

“…The more or less clear emphasis of the interpersonal structure directs us to apply 35% orthophosphoric acid for at least 30 s if a good complication of material is desired in the substructure [21]. Otherwise any demineralization of the substrate and laser treatment favor material retention more in the surface.…”