Combining Novel Multifunctional Dental Composite/Poly(amido Amine) for Tooth Root Dentin Remineralization

Objectives: The objective of this study was to investigate the effects of the combination of poly (amido amine) (PAMAM) and a novel multifunctional composite (NMDC) containing nanoparticles of amorphous calcium phosphate (NACP), 2-methacryloyloxyethyl phosphorylcholine (MPC), dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of silver (NAg) on the remineralization of root dentin in a cyclic artificial saliva/lactic acid environment for the first time.
Methods: Root dentin specimens were prepared and demineralized with 37% phosphoric acid. Four groups were tested: (1) dentin control, (2) dentin coated with PAMAM, (3) dentin with NMDC, (4) dentin with PAMAM+NMDC. Specimens were treated with a cyclic artificial saliva/lactic acid regimen for 21 days. Acid neutralization and calcium (Ca) and phosphate (P) ion concentrations were determined. The remineralized root dentin was examined via scanning electron microscopy (SEM) and hardness testing.
Results: Flexural strength of NMDC was similar to two commercial control composites (p>0.1), which were (70.3±10.7), (76.7±7.0) and (69.3±5.8) MPa, respectively. NMDC showed substantial acid-neutralization and Ca and P ion release, while control composites had none (p<0.05). NMDC+PAMAM achieved the greatest mineral regeneration and the greatest hardness increase in the demineralized root dentin among all groups tested (p<0.05). NMDC+PAMAM successfully remineralized the pre-demineralized root dentin and achieved a dentin hardness of (0.53±0.03) GPa, which approached the hardness of (0.55±0.04) GPa for healthy root dentin (p>0.1).
Conclusions: Superior remineralization efficacy of the novel NMDC+PAMAM method on demineralized root dentin was demonstrated for the first time. NMDC+PAMAM induced nearly-complete remineralization of demineralized root dentin in acid challenge when conventional remineralization methods such as PAMAM alone did not work well. While DMAHDM, MPC and NAg inhibited cariogenic/periodontal pathogens as shown previously, the new NMDC+PAMAM strategy is promising for class V restorations especislly those with subgingival margins to achieve both antimicrobial and root dentin remineralization capabilities.