New clinical guidelines aim to ensure safer dental implant procedures for patients on dialysis for kidney failure. Chronic kidney disease is becoming more common, and 90% of patients experience oral symptoms that lead to early tooth loss. Dental implants can greatly improve quality of life, but carry increased risk of infections for dialysis patients because of their compromised immune systems. Dr. Yuan at Sichuan University, Chengdu, China, and experts from other 4 countries have produced comprehensive clinical guidelines for installing dental implants in dialysis patients. They stress that dentists should consult kidney specialists early in the process, systematically review patient history and perform extensive blood tests prior to surgery. The procedure itself should be as simple and non-invasive as possible, and prophylactic antibiotics should be taken post-operation to minimize infection risk and complications with dialysis.

Coating titanium implants with calcium carbonate (CC) may improve their integration with the surrounding bone tissue. Yining Wang of China’s Wuhan University and colleagues tested a new method to prepare CC coatings for titanium implants. CC is resorbable, that is, it is absorbed by the body after a period of time. Current implants coated with non-resorbable materials show decreasing success rates several years after implantation. CC-coated and control implants were embedded in the legs of rabbits and extracted one, two, four, eight and 12 weeks after surgery. The CC-coated implants integrated earlier with the surrounding bone tissue than the controls. The method needs improvement due to incomplete coating of the titanium surface but the team believes CC-coating of titanium implants could reduce healing times and lead to higher implant success rates.

Images of the jaw joint in 3D from pre- and post-operative CT scans can help doctors assess bone loss after jaw surgery. Laura Ferreira Pinheiro Nicolielo of UZ Leuven in Belgium and colleagues rendered 3D images from multi-slice and cone-beam computed tomography scans taken from 20 patients before and after jaw surgery. An algorithm was used to analyze the images and calculate bone loss in the condyles, the rounded tips at the back of the jaw that form part of the temperomandibular joint (TMJ). The condyles in all but one patient showed up to 46% bone loss. Jaw surgery can change the location of the TMJ, leading to stress on the condyles and joint dysfunction. This method could help oral surgeons assess condylar bone loss after surgery to optimize patient treatment.

A bacterium living in the mouth facilitates oral wound healing by activating a protein involved in immune and inflammatory responses. Stian Engen and colleagues from the University of Oslo in Norway cultured human oral epithelial cells with Streptococcus mitis, a bacterium that colonizes surfaces in healthy peoples’ mouths. Its presence altered the activity of 29 proteins involved in transcribing RNA from DNA. Further analyses were conducted on one of these “transcription factors”, the aryl hydrocarbon receptor, which is known to have a role in immune and inflammatory responses. The researchers found that its activation by S. mitis helps heal oral wounds by stimulating the generation of molecules that attract white blood cells to the area to regulate inflammation. This is followed by the release of a lipid that helps in wound repair.

German and Swiss scientists have used computerized scanning techniques to map the root tips of molars to better inform dental practitioners. This research is highly applicable to clinical practice, as proper treatment of the root tips is a determining factor of root canal surgery success. Thomas Wolf of Germany’s Johannes Gutenberg University of Mainz led a team to analyze 516 first and second human molars, scanning both upper (maxillary) and lower (mandibular) teeth to elucidate the anatomy of the root apex, the junction between the tooth and its surrounding tissue. This work allows scientists to provide recommendations on how dentists can best shape root canals during therapy. As well as a better understanding of tooth anatomy, this study presents the first fine-detail measurements of the root apex geometry of the first and second mandibular and maxillary molar.

An antibiotic commonly used to treat bacterial infections helps promote healing in the jawbones of rats. Glauce Viana and colleagues from the Federal University of Ceará in Fortaleza, Brazil, extracted upper molar teeth from rats and then treated the animals with either the antibiotic drug doxycycline or a saline control. After seven days, the rats that received doxycycline had less inflammation in their tooth sockets than the controls, and after 14 days, more signs of successful wound closure. Looking closely at the cells in the repaired bone in the antibiotic-treated rats, the researchers saw more bone-forming osteoblast cells, fewer bone-resorbing osteoclast cells and greater activity of a signaling pathway known to improve bone healing. The authors suggest the drug should now be tested in people suffering from periodontal disease.

A modified antibiotic has been shown to effectively get inside cells and kill bacteria that can cause gum disease to return after treatment. The bacterium Porphyromonas gingivalis is a cause of gum disease, and treatment with the antibiotic metronidazole is not completely effective. Metronidazole kills P. gingivalis but, unlike the bacteria, cannot get inside cells. P. gingivalis that consequently persists inside cells in the mouth after treatment is thought to contribute to recurrence of gum disease. In their new study, Ping Ye from the University of Sydney, Australia, and colleagues modified metronidazole with porphyrin, a molecule that enabled the antibiotic to enter cultured human mouth cells and target the bacteria. The modified antibiotic killed bacteria inside cells effectively, indicating that it could treat gum disease and prevent its recurrence.

Exposure to nicotine can strongly affect both the movement of teeth and the surrounding bone over the course of an orthodontic procedure. The deleterious dental effects of smoking are well understood, but little is known about how nicotine affects the changes that take place when wearing an orthodontic appliance. Researchers led by Christian Kirschneck at Germany’s University Medical Centre of Regensburg have now determined that regular nicotine exposure exerts both positive and negative influences in rats during a multi-week orthodontic treatment. On the one hand, nicotine markedly accelerated the intended goal of tooth movement and reorganization. However, it was also associated with inflammation and bone loss at the roots of the teeth. Accordingly, the researchers conclude that orthodontists should caution their patients regarding the added risks of using tobacco during treatment.