Nanoparticles and Cold Plasma Join Forces to Rebuild Tooth Enamel at the Atomic Level

Dental enamel is the hardest substance in the human body, yet it faces a relentless daily assault. Every sugary snack, every acidic drink, and every colony of cavity-causing bacteria strips away the minerals that give teeth their strength. Once enamel is lost, the body cannot grow it back, which is why dentists have long searched for ways to reverse the earliest stages of decay before a drill becomes necessary. Now, a team of researchers from Iraq has reported that a combination of two cutting-edge technologies — biodegradable nanoparticles loaded with xylitol and a jet of cold atmospheric plasma — can measurably restore the chemical building blocks of damaged enamel in the laboratory.

The study, published in the Journal of Medical and Biological Engineering, focused on the three elements that define healthy enamel chemistry: calcium, phosphorus, and oxygen. Enamel is composed almost entirely of hydroxyapatite, a crystalline mineral built from calcium and phosphate ions arranged in a tight lattice, with oxygen bound within the phosphate groups. When acids dissolve this lattice, calcium and phosphorus leach out of the crystal structure in a process called demineralization, leaving behind a weakened, porous surface that bacteria can penetrate. Reversing that loss — restoring calcium and phosphorus while managing the oxygen signature of the surface — is the central goal of remineralization therapy.

To test whether their dual approach could accomplish this, Ghada A. Ibrahim of Osol AL-ELM University College and Al-Baladiyat Specialized Dental Centre, together with Eaman A. Al-Rubaee of the University of Baghdad, Maha J. Abbas of Mustansiriyah University, and Nisreen Kh. Abdalameer of the University of Baghdad, collected fifty human maxillary first premolars. The teeth were divided into five groups of ten: four experimental groups and one control. On each tooth, the researchers prepared a round window on the buccal, or cheek-facing, surface to serve as a standardized test site. They then induced artificial caries-like lesions using a pH cycling method, a laboratory technique that alternates the teeth between acidic and neutral environments to mimic the repeated acid attacks that occur in the mouth.

The experimental treatments were deliberately simple in concept but sophisticated in execution. One group received PLGA/xylitol nanoparticles at a concentration of 5 percent. PLGA, short for poly(lactic-co-glycolic acid), is a biodegradable polymer widely used in medicine to deliver drugs safely into tissues; embedding xylitol — a sugar alcohol known to interfere with the metabolism of cavity-causing Streptococcus mutans — inside these nanoparticles allows the compound to penetrate deep into bacterial biofilms and linger on the enamel surface. Other groups received cold atmospheric plasma, a partially ionized gas that operates near room temperature and generates a cocktail of reactive oxygen and nitrogen species, charged particles, and ultraviolet photons capable of killing bacteria without damaging surrounding tissue. Two groups combined the two therapies, applying them in different sequences: nanoparticles followed by plasma, or plasma followed by nanoparticles.

The researchers tracked the elemental composition of the enamel at three stages — sound, demineralized, and treated — using energy dispersive spectroscopy, or EDS. This analytical technique, typically paired with a scanning electron microscope, bombards the sample with an electron beam and reads the characteristic X-rays emitted by each element, allowing precise quantification of the surface chemistry without destroying the specimen. The results revealed a clear pattern. After treatment, every experimental group showed an increase in calcium except the plasma-only group and the control group, and every experimental group showed an increase in phosphorus except the control. Oxygen, by contrast, decreased after treatment in all groups except the PLGA/xylitol nanoparticle group — a shift the researchers interpret as evidence of mineral redeposition, since newly formed hydroxyapatite incorporates oxygen into its phosphate lattice while displacing surface oxygen associated with demineralized, oxidized tissue.

The most striking numbers came from the combined-therapy groups. EDS analysis showed that the greatest difference in mean calcium and phosphorus values between the demineralization and remineralization stages occurred in the group that received nanoparticles first and plasma second, followed closely by the group treated with plasma before nanoparticles, with statistically significant differences. The plasma-plus-nanoparticles group achieved the highest calcium and phosphorus readings of all, at 34.520 ± 6.382 and 14.860 ± 0.757 respectively, while the nanoparticles-plus-plasma group followed at 33.420 ± 1.878 and 14.560 ± 0.704. These values approach the composition of sound enamel, suggesting that the combined treatment did not merely halt demineralization but actively drove the surface back toward its original mineral density.

The researchers conclude that the enamel surface treated with cold atmospheric plasma and PLGA/xylitol nanoparticles produced favourable results in increasing the microhardness of the tooth through its chemical elements, implying that this therapy might be recommended as a method of preventing dental cavities. Microhardness — the resistance of the enamel surface to localized indentation — is a well-established proxy for mineral content, and its recovery alongside calcium and phosphorus restoration indicates that the treated enamel regained genuine structural integrity rather than a superficial coating.

The mechanisms behind the synergy are plausible and physically grounded. Cold plasma is known to alter the surface energy and wettability of enamel, creating reactive sites that can bind mineral ions more readily; previous studies have shown that plasma pretreatment increases fluoride uptake from varnishes and modifies enamel and dentin surfaces in ways that favour remineralization. Meanwhile, the PLGA carrier degrades slowly into lactic acid and glycolic acid — metabolites the body already processes — releasing xylitol gradually at the tooth surface while its nanoscale dimensions allow penetration into the extracellular polymeric substances of bacterial biofilms, disrupting the communities that produce the very acids causing demineralization. Applied in sequence, the plasma may prime the enamel surface for mineral binding while the nanoparticles suppress the bacterial acid production that would otherwise undo the gains.

The study carries important caveats. It was conducted entirely in vitro, on extracted teeth in a laboratory setting, where the complex environment of the human mouth — saliva, dietary variation, plaque dynamics, and individual differences in oral hygiene — is absent. The sample size of ten teeth per group is modest, and the pH cycling model, while widely accepted, cannot fully replicate the years-long progression of natural caries. Ethical approval was granted by the Ethical Committee of the College of Dentistry at the University of Baghdad in accordance with the Helsinki Declaration, and the authors affirm no conflicts of interest, but clinical translation will require in vivo studies and, ultimately, randomized controlled trials before dentists can reach for a plasma jet and a vial of nanoparticles in everyday practice.

Nevertheless, the findings add to a growing body of evidence that the future of dentistry may lie less in repairing damage and more in preventing it at the molecular scale. Nanohydroxyapatite pastes, bioactive glasses, and antimicrobial nanoparticles are already being explored as remineralization agents, and cold plasma has demonstrated antibacterial effects against the microorganisms responsible for dental caries in earlier work by some of the same research groups. By quantifying exactly how calcium, phosphorus, and oxygen shift across the demineralization-remineralization boundary under combined nanoparticle and plasma treatment, this study provides a chemical fingerprint that future therapies can be measured against. If subsequent research confirms these results in living teeth, the humble filling — the defining symbol of dental care for over a century — may one day share the clinic with a technology that stops cavities before they begin.

Subject of Research: The Impact of PLGA/ Xylitol Nanoparticles and Cold Atmospheric Plasma on the Chemical Element(Calcium (Ca), Phosphorus (P), Oxygen (O)) of the Dental Enamel (in Vitro Study)

Article Title: The Impact of PLGA/ Xylitol Nanoparticles and Cold Atmospheric Plasma on the Chemical Element(Calcium (Ca), Phosphorus (P), Oxygen (O)) of the Dental Enamel (in Vitro Study)

Article References: Ibrahim, G. A., Al-Rubaee, E. A., Abbas, M. J., & Abdalameer, N. K. (2026). The Impact of PLGA/ Xylitol Nanoparticles and Cold Atmospheric Plasma on the Chemical Element(Calcium (Ca), Phosphorus (P), Oxygen (O)) of the Dental Enamel (in Vitro Study). Journal of Medical and Biological Engineering. https://doi.org/10.1007/s40846-026-01057-3

Image Credits: AI Generated

DOI: 10.1007/s40846-026-01057-3

Keywords: Impact, PLGA, Xylitol, Nanoparticles, Cold, Atmospheric, Plasma, Chemical, Element, Calcium, Phosphorus, Oxygen