Plasma is the fourth form of matter after solid, liquid, and gas. Plasma refers to a gas that is heated or placed in a high-frequency and high-voltage electric field, forming a highly ionized gas cloud. The outer electrons of the gas cloud, which acquire enormous energy, break free from the constraints of the atomic nucleus and become free electrons. The positive charge carried by the atomic nucleus is equal to the total negative charge carried by the free electrons, presenting an electrically neutral state as a whole. Therefore, it is called plasma. 99.9% of matter in the universe is in a plasma state, such as stars, auroras, and candle flames. In recent years, with the continuous in-depth research of plasma technology, plasma has gradually become a comprehensive discipline.

Classification of Plasma

According to the temperature generated by plasma, plasma can be divided into two types: high-temperature plasma and low-temperature plasma. High temperature plasma refers to a plasma with a degree of ionization close to 1 produced by complete ionization at a temperature of 108-109K, and with high temperatures for heavy particles and electrons. Low temperature plasma is achieved at low temperatures (≤ 104K), with only a portion of the gas ionized (ionization degree of 10-7~10-4), while most gas molecules remain in an un ionized state. According to different thermodynamic states, low-temperature plasmas can be divided into thermal equilibrium plasmas (also known as hot plasmas) and non thermal equilibrium plasmas (also known as cold plasmas). In non thermal equilibrium plasmas, because the temperature of heavy ions is much lower than that of electrons, their temperature is relatively low. Therefore, such plasmas are very suitable for application in the medical field

Application of Low Temperature Plasma in Surface Modification of Oral Materials

Improving the mechanical and physical properties of the material itself to enhance its biocompatibility with the body is a very important purpose of material modification. Low temperature plasma can activate the surface of the material without changing its basic properties, thereby changing its wettability and cellular biocompatibility.

Surface modification of oral implant materials

The failure of implants to form a good osseointegration with the surrounding bone tissue after implantation is often an important reason for the failure of implant surgery. Changing the surface properties of implants, increasing the biocompatibility between implants and surrounding tissues, reducing post implantation infections, and improving implant success rates have always been the research direction of many scholars.

Using atmospheric pressure low-temperature plasma jet to treat the surface of titanium sheets for 10 seconds, it was found that plasma treatment can increase the wettability of the titanium sheet surface and promote the early adhesion of gingival fibroblasts on the titanium sheet surface, thereby enhancing the sealing effect between the implant and surrounding soft tissues, reducing the infection of pathogenic bacteria, and enhancing the ability of the implant to bond with surrounding tissues and bones.

Surface modification of oral restorative materials

The oral environment is relatively complex, and various factors constrain the restorative effect of oral materials. Plasma forms an inert surface protective layer on the material surface without affecting its basic properties, thereby improving the wettability, molecular polarity, adhesion, and biocompatibility of the material surface itself.

The bonding strength between zirconia and resin commonly used in repair materials is closely related to their hydrophilic properties. After treating zirconia with plasma, it was found that the surface morphology of the material did not change significantly, but the wettability of its surface increased, resulting in a significant improvement in the adhesive strength between the material and the resin.

Thermosetting acrylic resin is a commonly used material for making complete dentures and removable partial denture bases, but this material has low surface hydrophilicity, which often leads to poor adsorption effect of dentures in clinical practice. After treating the thermosetting denture base resin with low-temperature plasma, it was found that the active substance of the plasma can introduce oxygen polar groups on the material surface, significantly increasing the wettability of the material surface and enhancing the adsorption force between the denture base and the mucosa.

Surface modification of dental tissue

Plasma is rich in active particle components in ground or excited states, which can cause bombardment and thermal etching effects on the surface of biological materials. Through these effects, the physical, chemical, and biological properties of the dentin surface can be effectively changed, thereby improving the wettability of the dentin surface, increasing the grafting of oxygen-containing functional groups on the collagen fiber surface of the dentin, promoting the permeability of the adhesive resin, and forming a mixed layer structure with higher adhesive durability.

Plasma was used to treat dentin, and infrared spectroscopy analysis revealed that the secondary structure of collagen fibers in dentin changed before and after plasma treatment, and the bonding performance between dentin and composite resin was significantly enhanced after plasma treatment.

Plasma medicine is a comprehensive interdisciplinary field that combines physics, chemistry, life sciences, and clinical medicine, and has a wide range of application prospects in the medical field. In recent years, the application of plasma in the field of oral medicine has become increasingly widespread. Plasma can also modify the surface of commonly used materials in the oral cavity by grafting or introducing new chemical functional groups, without damaging the structure and morphology of the material itself, and without damaging oral tissue during use. It is precisely because plasma possesses these unique properties that its research in the field of oral medicine continues to expand.