Tyrosine kinases and phosphatases are enzymes that regulate many bacterial proteins involved in promoting infection. Tyrosine kinases work by tacking phosphate molecules onto specific amino acids, while phosphatases take them off. Sarah Whitmore and Richard Lamont of the University of Louisville in Kentucky, USA, have now reviewed the structure and function of these enzymes, which contribute to bacterial virulence, including that of Porphyromonas gingivalis and Streptococcus gordonii. They explain that tyrosine kinases help regulate the production of specialized sugars that bacteria use to interact with target cells; many bacterial phosphatases, however, actively sabotage host cell signaling processes. The authors conclude that future work will provide a better understanding of these important enzymes and should help guide development of more effective antibacterial drugs.

Meticulous laser excision of oral tissues has enabled researchers from the US and China to identify genes involved in tooth-root development. Better understanding of the spatial and temporal regulation of these genes could open the way for gum and tooth regenerative therapies. Led by Hai Zhang from the University of Washington,Seattle,the researchers used two complementary gene profiling approaches to identify genes that were differentially expressed in pure samples of five cell- and tissue-types excised from one- and two-week-old mice using the technique known as laser capture microdissection. The findings will help scientists to elucidate the carefully orchestrated molecular interactions between the epidermal and mesenchymal cell layers that control root formation,including the dramatic differentiation of soft tissues into enamel—the body's hardest tissue.

To keep bacteria at bay, oral devices made from ethylene vinyl acetate (EVA) should be cleaned and then stored under ventilated conditions. This plastic is widely used in mouthguards as well as medical and dental devices, but clear guidelines on hygienic storage were lacking since little was known about the bacteria that survive on EVA surfaces or the conditions under which they may thrive. Taiji Ogawa and colleagues at the Osaka University Graduate School of Dentistry, Japan, profiled bacterial growth on EVA sheets subjected to different cleaning and storage regimens following exposure to patients' saliva. Storage in closed environments favored bacterial growth. However, washing the sheets with sterilized water or mechanical brushing reduced bacteria populations, as did ventilated storage conditions. The authors recommend a combination of both strategies to maintain hygienic use of EVA-based devices in real-world conditions.

Pathogenic bacteria in the saliva, including Enterococcus faecalis, can colonize imperfectly sealed root canals, research from China shows. E. faecalis is associated with chronic periodontitis and often found in the mouths of patients who have undergone root canal or other endodontic procedures. From a study of 54 patients with periodontitis and root canals requiring retreatment, a research team led by Cheng-Fei Zhang of the University of Hong Kong observed a significant association between E. faecalis in the saliva and the presence of this species within root canals. However, the researchers generally detected these bacteria more at root canal sites than in saliva. They also found that poorly sealed canals generally contained more diverse populations of bacteria, highlighting that greater care should be taken in performing this procedure.

Anesthetized patients can experience potentially serious physiological responses to physical stimuli. For example, animal studies have revealed a ‘trigeminal depressor response’ (TDR), wherein stimulation of facial nerves under anesthesia triggers a marked decrease in blood pressure and heart rate. Since these studies have not considered the impact of depth of anesthesia, Hiroshi Hanamoto and colleagues at Japan’s Osaka University Graduate School of Dentistry examined the importance of this factor. They found that in lightly anesthetized cats, electrical stimulation of the lingual nerve actually led to increased heart rate and blood pressure; only under heavier anesthesia did such stimuli trigger TDR. This suggests that dental patients who faint during procedures could do so in response to pain, or fear of pain, rather than physiological changes induced by TDR, as was previously speculated.

Ameloblastomas are tumors that typically form in the lower jaw and leave patients and doctors with difficult choices. Although benign, ameloblastomas can grow aggressively. Clinicians must therefore choose between a conservative excision—and risk recurrence—or radical jaw surgery likely to reduce a patient’s quality of life. Long-jiang Li and colleagues at China’s Sichuan University have found that X-ray imaging can offer useful guidance. On reviewing 178 ameloblastoma cases, they determined that growths with poorly defined edges were more than twice as likely to recur following conservative surgery relative to ameloblastomas with clear boundaries. Cells in the former group of tumors also expressed higher levels of a genetic marker associated with cellular proliferation, further supporting the use of radical surgery to address such growths.

A method for imaging facial structures in 3D, without harmful X-rays, has been successfully demonstrated by researchers in Italy. By merging data from stereophotographic images of individual faces with laser scanning information from dental casts, Chiarella Sforza and colleagues at the Universita` degli Studi di Milano accurately determined the orientation of the occlusal plane—where the upper and lower teeth make contact. Two different operators repeated the process in 20 adult volunteers with errors generally less than 1 millimeter. This non-invasive type of imaging, although still technical and expensive, avoids the potential dangers of radiographic techniques such as X-rays and CT scanning. The technique could eventually prove useful for basic dental diagnoses and treatments, monitoring growth in children or even researching healthy volunteers to assess biological variability among populations.

Two researchers in Greece have identified reasons why ‘miniscrew’ dental implants may succeed or fail. They monitored 34 patients with a total of 82 miniscrews implanted in their mouths, and analyzed the factors that might contribute to miniscrews becoming infected or dislodged. They found that the length and diameter of the miniscrews, the site and method of miniscrew placement and, most importantly, the number of miniscrews implanted, showed significant correlations with success rates. Overall, the miniscrews had a success rate of 90.2%. Miniscrews are the preferred method of anchorage for many dental procedures, as they avoid the social stigma of external devices such as headgear, or the expensive surgery involved in osseo‐integration, where implants make direct functional connections to bone.

Granular cell ameloblastoma is a rare, benign neoplasm of the odontogenic epithelium. A case of massive granular cell ameloblastoma in a 44-year-old Thai female is reported. Histopathological features displayed a follicular type of ameloblastoma with an accumulation of granular cells residing within the tumor follicles. After treatment by partial mandibulectomy, the patient showed a good prognosis without recurrence in a 2-year follow-up. To characterize the granular cells in ameloblastoma, we examined the expression of basement membrane (BM) proteins, including collagen type IV, laminins 1 and 5 and fibronectin using immunohistochemistry. Except for the granular cells, the tumor cells demonstrated a similar expression of BM proteins compared to follicular and plexiform ameloblastomas in our previous study, whereas the granular cells showed strong positivity to laminins 1 and 5 and fibronectin. The increased fibronectin expression in granular cells suggests a possibility of age-related transformation of granular cells in ameloblastoma.

We report a case of carcinoma ex pleomorphic adenoma of a sublingual gland in a 70-year-old man. Under a clinical diagnosis of benign salivary gland tumor, excision of the mass with the sublingual salivary gland in an en bloc fashion via an intraoral approach was performed. Histopathologically, there was a rupture of the fibrous capsule and diffuse cell-rich sheets composed of myoepithelial cells with round nuclei were also seen. Immunohistochemically, the cells that composed of cell rich sheets were positive to smooth muscle actin. Final diagnosis of myoepithelial carcinoma ex pleomorphic adenoma was made.