Mini-implants provide stable anchorage for orthodontics, despite secondary movement over time, report dental researchers in Germany. When teeth are damaged due to misalignment, they must be rebuilt and carefully anchored to the jaw. Recently, developed mini-implants are useful for such anchorage, but they may move over time with use. Manuel Nienkemper and colleagues at Heinrich-Heine University in Düsseldorf reviewed 27 recent research studies about the displacement of mini-implants. They found that movement during the initial placement was insignificant, but secondary movement caused by dental forces over time could cause problems for the patient. The team emphasizes that mini-implants require a suitable bone site with a thin mucosal covering. They also suggest that implant failure could be avoided by inserting the implant slightly off-centre, leaving space in the opposite direction from the main orthodontic forces.
Antibiotics alone are often ineffective in the treatment of bacterial biofilm infections and new strategies are needed. Once bacteria shift from their free-swimming state to the structured community of a biofilm, they become much harder to kill with conventional antibiotic regimens. A review by Zhi-Jun Song and colleagues at Denmark’s University Hospital of Copenhagen explores the challenges of diagnosing and eliminating biofilms that form on the surface of implanted medical devices. At present, the best solution is early detection followed by aggressive treatment with multiple antibiotics and removal of the device in question. However, recent research suggests other possible solutions, including drugs that interfere with communication between bacteria or disrupt their ability to anchor to surfaces, and viruses that specifically infect and kill biofilm-forming microbes.
The bacterium Staphylococcus aureus is more sensitive than Escherichia coli to disruption by low-voltage currents, researchers in Germany have found. Dental restorations made of different alloys can generate a direct, or galvanic, current in the mouth that is conducted through saliva. Typically, bacteria are negatively charged, so galvanic currents can alter their growth and behavior. Dunya Zituni and co-workers at Cologne University investigated the effect of low-voltage currents with electrical field strength of 2–27 V⋅m−1 on cultures of the common oral microbe S. aureus and the model organism E. coli. In solid medium, the currents inhibited larger zones of S. aureus than E. coli; and, in liquid culture, they ruptured a larger percentage of S. aureus’s cells. The researchers conclude that dental restorations should consist of one alloy only to avoid altering oral microbial communities.
The timing of hard palate closure is important for preserving the normal growth of the upper jaw (maxilla) and palate after cleft surgery. Cleft surgeons are concerned surgery will restrict growth of the maxilla. Led by Shi Bing from the West China School of Stomatology in Sichuan, the researchers reviewed studies on surgically related growth inhibition among cleft patients. The extent of growth restriction in cleft lip repair is related to the severity of the original deformity, whereas in palate repair it is related to early reconstruction. A 25-year follow-up study found that 60% of patients had normal maxillary growth when their soft palate was repaired at 4–6 months and hard palate closure was delayed until 18–24 months. Another study by the review authors found the timing of hard palate closure affects post-operative growth.
An extract from the tropical vine plant Piper betle can combat Candida yeast infections, according to researchers in Malaysia. Candida species are natural components of the flora in the oral cavity, but may cause infections when the immune system fails. Also, some Candida strains have become resistant to antifungal medicines. Inspired by the effectiveness of some popular natural medicines, Mohd-Al-Faisal Nordin and co-workers at the University of Malaya in Kuala Lumpur tested the antifungal properties of Piper betle, a member of the pepper family that is used to treat asthma, halitosis and other conditions. After adding Piper betle extract to Candida cell cultures, the researchers saw strongly reduced Candida populations and damaged Candida cells. These results point to the potential use of Piper betle in future oral healthcare products.
Viruses that have been linked with various cancers of the head and neck do not appear to play a role in salivary gland tumors. Certain subtypes of human papilloma virus (HPV), Epstein-Barr virus (EBV) and cytomegalovirus (CMV) can disrupt cellular signaling in a way that promotes uncontrolled growth. Infections with these viruses are common in certain tumors of the mouth, nose and throat. Kais Hussein’s team at Hannover Medical School in Germany searched for viruses in tissue samples of salivary gland tumors from 77 patients. HPV, EBV and CMV were not present in any of the samples, regardless of tumor type and whether a tumor was benign or malignant. The researchers observed abnormal activity in the signaling pathways normally affected by these viruses but concluded that these changes arose from other physiological disruptions.
A study in China that dissected the underlying immune processes of an oral inflammatory disease could lead to effective diagnostic strategies. The pathology of many diseases is affected by the activity of two distinct populations of helper T cells, TH1 and TH2, which coordinate distinct immune pathways. Hongxia Dan and colleagues at Sichuan University examined the physiological signatures of immune activity in patients with oral lichen planus (OLP) in an effort to resolve a debate regarding the relative contribution of TH1 and TH2 processes in this mucosal disorder. By comparing saliva and serum from patients versus controls, the researchers determined that TH2 plays a dominant role in OLP and identified a biochemical signature that might offer a useful prognostic biomarker. Their experiments also show that salivary analysis may offer a simple mechanism for OLP diagnosis.
Children undergoing treatment for leukaemia may benefit from a drug that prevents mucositis, or injury to the cells that line the mouth. A team led by Dorina Lauritano from the University of Milan Bicocca, Italy, tested a drug called palifermin in 20 patients under 16 years of age who received high doses of chemotherapy and radiation, followed by stem cell transplantations to treat acute lymphoblastic leukaemia. Palifermin is a modified version of a naturally occurring human protein called keratinocyte growth factor. It is marketed as Kepivance for the prevention of oral mucositis for all age groups. However, information on the safety and efficacy of the drug in paediatric populations was limited. Lauritano and her colleagues found that Palifermin significantly reduced the severity of mucositis compared to a control group that did not receive the drug.
The timing and site of action of two key enzymes help regulate the formation of cementum, one of the mineralized substances of teeth. An international team led by Brian Foster from the US National Institute of Arthritis and Musculoskeletal and Skin Diseases considered the roles of two enzymes — tissue non-specific phosphatase (TNAP) and ectonucleotide pyrophosphatase/phosphodiesterase 1 (NPP1) — in cementum development. They showed in mice that early TNAP expression created a particular environment in teeth with low levels of pyrophosphate, a mineral inhibitor. This promoted the creation of a type of cementum that does not incorporate cells into its structure. Later on in development, the expression of NPP1 boosted levels of pyrophosphate, which restricted this type of cementum. These enzymes had little effect on cementum containing cells. The researchers confirmed these patterns in extracted human teeth.
Gene expression profiling reveals how surrounding tissues may the promote growth of a benign but aggressive class of oral tumor. The process by which keratocystic odontogenic tumors (KCOT) develop is poorly understood, but evidence suggests that KCOT cells receive important cues from the stromal cells that surround the tumor. Researchers led by Tie-Jun Li and Feng Chen of China’s Peking University School and Hospital of Stomatology analyzed and compared the gene activity in KCOT stromal tissue with healthy samples. They identified a secreted protein, LOXL4, which is produced at considerably elevated levels in KCOT samples. Preliminary functional analysis suggests that LOXL4 can stimulate blood vessel growth, and may also promote proliferation and invasive growth in endothelial cells. These findings thus illustrate one possible mechanism by which cells in the tumor environment could stimulate KCOT formation and expansion.
Better education and awareness campaigns are needed to encourage people who notice symptoms of oral cancer to quickly have their lesions inspected by medical or dental professionals. Led by Giuseppe Colella and Giuseppina Campisi, a research team from the Universities of Palermo and Naples in Italy interviewed 156 people with squamous cell carcinoma of the oral cavity to determine the time taken between patients first noticing signs of cancer and then consulting physicians or dentists. People with knowledge or personal experience with cancer tended to seek medical assistance much earlier than people who were in denial or were unaware of the problem, the researchers found. Older patients showed a shorter delay than younger patients. The team calls for educational interventions to encourage early diagnosis and treatment of oral cancer, a disease responsible for an estimated 130 000 deaths worldwide each year.
Cleaning root canals with chlorhexidine antiseptic leaves a sustained residual antimicrobial effect, research from Spain shows. Root canal surgery carries a high risk of infection: the bacteria Enterococcus faecalis is commonly found following the procedure. Effective irrigation of root canals during root canal treatment disinfects the area and can provide a barrier to future infection by leaving an antimicrobial residue to attack remaining bacteria. To verify the most effective treatment, Carmen Maria Ferrer-Luque and colleagues at the University of Granada compared three irrigation solutions on root canals infected with E. faecalis. After 50 days, the team found significant bacterial growth on 69% of roots treated with weak solutions (0.2%) of cetrimide and chlorhexidine. A more potent chlorhexidine solution (2%), however, indicated a longer-lasting residual effect, with E. faecalis growth on less than 35% of roots.
Researchers in China and Belgium show that immediate implant placement and loading favours sensory nerve regrowth in dogs. Tooth extraction can damage nerve endings that signal information about tooth loads and which are essential for chewing but little is known about the influence of implant loading on their recovery. A randomized study led by Xin Liang at Dalian Medical University, China, examined the effects of immediate and delayed implant placement and loading on sensory reinnervation in six dogs. They found that compared with control (natural socket healing after extraction) and delayed implant placement (eight weeks after tooth extraction), immediate implant placement and loading led to the highest nerve density and largest nerve fiber diameters 16 weeks after surgery. These findings highlight the importance of timely implant placing and loading in optimizing nerve recovery.
A comprehensive survey of six orthodontic treatment centers in China indicates a high level of consistency with which Chinese orthodontic specialists assess treatment outcomes. The study, led by Tian-Min Xu of Peking University, is the first of its kind to compare the values of different combinations of methods for such assessments. The three most commonly used approaches to evaluate the success of orthodontic procedures are: study, or plaster, casts; cephalometric films, or head images (traditionally x-rays); and facial photographs. Previous studies examined the predictive potential of each of these methods in isolation. Xu and colleagues showed that study casts were the most reliable predictors of successful treatment. The additional use of cephalometric films and facial photographs increased the likelihood of a reliable assessment. More than 300, 000 Chinese patients undergo orthodontic procedures annually.
Sandblasting of glass fiber posts could enhance resin cement adhesion during tooth restoration, as scientists in China suggest. During endodontic treatment, such as root canal surgery, teeth must be hollowed out and rebuilt. Glass fiber posts and resin cements can replace lost structural support, but weak bonding between them can lead to restoration failure. In a study using human teeth, Chang Liu and co-workers at Jilin University in China analyzed the bonding of four different resin cements under different conditions. The type of resin cement significantly affected bonding to the posts regardless of pre-treatment, with two cements outperforming the others. However, one type of cement, called DMG Luxacore, adhered far better to the post following small-scale sandblasting. The sandblasting roughens the glass surface, increasing both the bonding area and interlocking between post and cement.
The ability of root canal sealers to flow into and seal a root canal can best be measured with a strain-controlled rheometer. Researchers usually measure sealer viscosity using the simple press method, that is, by pressing the material between two glass plates and measuring the diameter of the resulting disc. Rheometers, however, can measure the viscosity of a complex fluid as it changes with strain, time and temperature. Kwang Shik Bae of the Seoul National University School of Dentistry, Korea, and colleagues tested four sealers (Capseal, AH Plus, Sealapex, and Pulp Canal Sealer EWT) using both methods. The rheometer measured sealer viscosity more sensitively than the simple press method. The rheometer data also showed how the viscosity of sealers changed as they set, indicating effective working times, and how increased temperature affected their chemical properties.