Saliva has the potential to be used for diagnosis of a wide range of diseases. Xue-Dong Zhou and colleagues from China’s Sichuan University reviewed recent literature on the prospects of using saliva in the early diagnosis of diseases and in translational and precision medicine. They conclude that saliva can be used instead of blood to diagnose a variety of diseases. Saliva is simple and non-invasive to collect, and convenient to store. As well as containing high-quality DNA, it contains biomarkers that can be used to detect early stages of oral diseases, such as caries, gum disease, and oral cancer, in addition to pancreatic, breast, prostate and lung cancers and a variety of other conditions. Research in this area is still in its early stages and means of evaluating salivary content need to be standardized.

Different strains of pathogenic bacteria rely on distinct interactions to anchor themselves firmly into oral ‘biofilm’ communities. The microbe Fusobacterium nucleatum is a major component of these densely populated bacterial societies. This species is not harmful, but can mediate recruitment of disease-causing Porphyromonas gingivalis bacteria into biofilms. Renate Lux and colleagues at the University of California at Los Angeles have demonstrated that various strains of P. gingivalis apparently latch onto different proteins on the surface of F. nucleatum. Previous studiesidentified the protein Fap2 as a binding target for P. gingivalis, but Lux and colleagues found at least one strain that relies on a different protein and found evidence for other as yet unidentified protein ‘anchors’. Identifying the proteins recognized by the most virulent P. gingivalis strains could lead to therapeutics that selectively block these interactions.

Laboratory-made sheets of the cells from the inside of the mouth could help treat oral muscular defects. Shigeki Yamane and colleagues from Tokyo Dental College, Japan, isolated different kinds of rabbit cells from the mucous membrane that lines the mouth. They then fabricated layered sheets that contained all three cell types: epithelial, mesenchymal, and muscular. The researchers studied the expression of proteins that are essential for maintaining this structure and found that, on a molecular level, the tissues of the engineered sheets closely resembled those found inside the oral cavity. The cells also had the capacity to proliferate after grafting. Similar constructs made of human cells could offer a path toward regenerative therapies for people with muscle problems in the tongue or pharynx who have trouble swallowing or chewing.

Silver-palladium-gold and gold-platinium alloys used as magnets for dental prostheses resist corrosion more than cobalt-chromium alloys. In removable prostheses, such magnets are attracted to a keeper, which is placed either on a treated root or a metal framework fixed in the mouth, enabling the prostheses to remain fixed. In the oral environment, the function of these attachment systems declines due to corrosion. Jie-Fei Shen at Sichuan University, Chengdu, China, and colleagues compared the corrosion resistance of three alloys and two common methods (casting or laser-welding) for fabricating the alloy-keeper complex. Microscopy revealed the structure of the corroded surfaces, indicating that the cobalt-chromium alloy is more prone to corrosion than the other alloys tested. The laser-welded cobalt-chromium and silver-palladium-gold alloys were shown to be more resistant to corrosion than equivalent samples made by the casting technique.

Sturdier implant–porcelain bonds are now accessible thanks to new insight into the impact of restorative procedures on veneered ceramics. Zirconia has emerged as a dental ceramic of choice due to its favorable integration into the existing bone, and high toughness and thermal expansion, which are needed for durable implant–porcelain bonds. However, these bonds tend to chip and peel. To uncover the root of these failures, Tariq Alghazzawi and Gregg Janowski from The University of Alabama at Birmingham assessed the contribution of liner and porcelain applications to zirconia surfaces under various veneering conditions. Liners and layered porcelain altered the zirconia composition and microstructure to a greater extent than pressed porcelain. These changes facilitated material diffusion at the zirconiaŐporcelain interface, promoting bond failure, especially with ageing of the implant.

Antibacterial properties of dental restorations improve on addition of nano-silver and an ammonium compound. Amorphous calcium phosphate is widely used for restoration because of its biocompatibility and similar composition to minerals in hard tissues. However, the detrimental formation of biofilms on dental resins and hence, the promotion of secondary caries, are problems. Hockin Xu at the University of Maryland, US, and Xuedong Zhou at Sichuan University, China, monitored the mechanical and antibacterial properties of a range of calcium phosphate composites to assess the effects of adding nano-silver and quaternary ammonium dimethylacrylate. Both additives decreased the formation of biofilms as well as lactic acid production over one year. Moreover, composites that incorporated both additives showed significantly enhanced antibacterial properties compared to those with a single additive. The composites’ mechanical properties were not compromised by additive incorporation.

Daily use of a mouth rinse can effectively treat the gum disease gingivitis by reducing oral bacterial diversity and plaque formation. Dental plaque is a biofilm formed from multiple bacteria that can cause gingivitis and other infections if it is allowed to mature. Rui Li at Procter & Gamble International Operations in Singapore, and coworkers across China conducted a randomized trial on 91 adults to clarify the response of oral bacteria to treatment with cetylpyridinium chloride-based (CPC) mouth rinse. After intensive oral hygiene treatment for 21 days, the participants were split into a control group (given only water) and a CPC rinse group. Both groups followed a daily rinsing routine for three weeks. The team found the CPC rinse inhibited 17 gingivitisassociated bacteria, and significantly reduced plaque formation by disrupting bacterial interactions.

Scientists from the Netherlands have identified a type of white blood cell as a potential component of oral health. Elena Nicu of the Academic Centre for Dentistry Amsterdam and her collaborators collected oral rinse and blood samples from 268 healthy volunteers. Cell count, cycle stage, reactive oxygen species (ROS) and cellular activation levels of oral polymorphonuclear neutrophils (oPMNs) were obtained and compared to those of circulatory PMNs (cPMNs), known facilitators of systemic immunity. They discovered that despite a higher number of aging cells among the oPMNs, their cellular activation and ROS production levels were comparable to those of cPMNs taken from the same volunteers and exposed to bacteria in the laboratory. This indicates that oPMNs are responsive to bacterial infections and potentially contribute to a healthy oral ecoystem.