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Nano-Hydroxyapatite Beats CPP-ACP And Peptide Gel In 130 Extracted Primary Molars

Nano-Hydroxyapatite Wins130 Extracted MolarsSealant Bond StrengthLab Study Only

A laboratory comparison of four remineralizing treatments on 130 extracted primary molars found that 0.15% nano-hydroxyapatite produced the strongest bond between tooth enamel and dental sealant material, reaching a shear bond strength of 10.12 MPa, according to a study published in Photobiomodulation, Photomedicine, and Laser Surgery.

Researchers demineralized enamel on 130 caries-free primary molars, then split them into five groups of 26: an untreated control, CPP-ACP paste, CPP-ACP activated with a CO2 laser, 0.15% nano-hydroxyapatite, and Curodont Repair, a self-assembling peptide gel called P11-4. Eight teeth per group were tested for calcium-to-phosphate ratio, a marker of rebuilt mineral. After sealants were placed, researchers measured resin tag length -- how deeply the sealant penetrated the enamel -- in 8 teeth per group by electron microscope, and shear bond strength, the force needed to break the seal, in 10 teeth per group. The nano-hydroxyapatite group reached the highest calcium-to-phosphate ratio, 2.27, the longest resin tags, 54.22 micrometers, and the strongest bond, 10.12 MPa. Curodont Repair raised the mineral ratio but produced the shortest resin tags, 23.21 micrometers, and the weakest bond, 7.89 MPa.

Nano-Hydroxyapatite Reaches 10.12 MPa Sealant Bond Vs 7.89 MPa With Peptide Gel

Photobiomodulation, Photomedicine, and Laser Surgery, 2026

Nano-hydroxyapatite is a synthetic form of the mineral that makes up tooth enamel. The authors suggest its small particle size fills microscopic gaps left by acid damage, rebuilding a denser mineral surface that gives sealant resin more structure to grip. Curodont's peptide instead forms a scaffold that pulls calcium and phosphate from saliva, which raised the mineral ratio but left a surface less suited to sealant bonding.

This is a lab study on extracted teeth, not a test inside children's mouths, so it cannot show how these materials hold up under real chewing and saliva exposure over time. The control group's exact numbers were not given in the available record, and funding and conflicts of interest were not reported.

Data Panel

Who: 130 caries-free primary molars (extracted teeth), divided into 5 groups of 26
Design: Ex vivo lab study; groups: untreated control, CPP-ACP paste, CPP-ACP plus CO2 laser, 0.15% nano-hydroxyapatite, and Curodont Repair (self-assembling peptide P11-4); calcium-to-phosphate ratio measured in 8 teeth per group, resin tag length by electron microscope in 8 teeth per group, shear bond strength in 10 teeth per group after sealant placement
Dose: 0.15% nano-hydroxyapatite application; CPP-ACP paste; CO2 laser activation parameters not reported; Curodont Repair applied per manufacturer protocol, not detailed in the abstract
Primary result: Nano-hydroxyapatite group: calcium-to-phosphate ratio 2.27 ± 0.18 (highest of all groups), resin tag length 54.22 ± 2.45 micrometers (longest), shear bond strength 10.12 ± 0.21 MPa (highest)
Secondary: Curodont Repair: shortest resin tag length, 23.21 ± 1.43 micrometers, and weakest shear bond strength, 7.89 ± 0.14 MPa, though it raised the calcium-to-phosphate ratio above the untreated control (exact control value not reported)
Funding / conflicts: Not reported

Dr. Axe's Take

This lab study shows nano-hydroxyapatite's fine particle size fills demineralized enamel more completely than CPP-ACP or the peptide gel, giving sealant resin a denser, mineral-rich surface to bond to. That is a material-science finding on extracted teeth, not proof of how these treatments perform in a child's mouth over years of chewing and saliva exposure. Before a sealant appointment, I would ask the dentist which remineralizing step, if any, they use first, since bond strength depends heavily on the enamel surface underneath. Cutting back sugar and refined carbs in the weeks beforehand also protects that same enamel surface these treatments are trying to rebuild.

— Dr. Axe

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